No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
[Visualization of subtle temporal bone structures : Comparison of cone beam CT and MDCT.]
Abstract
The purpose of this study was to compare the visualization of subtle, non-pathological temporal bone structures on cone beam computed tomography (CBCT) and multi-detector computed tomography (MDCT) in vivo.
Temporal bone studies of images from 38 patients archived in the picture archiving and communication system (PACS) were analyzed (slice thickness MDCT 0.6 mm and CBCT 0.125 mm) of which 23 were imaged by MDCT and 15 by CBCT using optimized standard protocols. Inclusion criteria were normal radiological findings, absence of previous surgery and anatomical variants. Images were evaluated blind by three trained observers. Using a five-point scale the visualization of ten subtle structures of the temporal bone was analyzed.
Subtle middle ear structures showed a tendency to be more easily distinguishable by CBCT with significantly better visualization of the tendon of the stapedius muscle and the crura of the stapes on CBCT (p = 0.003 and p = 0.033, respectively). In contrast, inner ear components, such as the osseus spiral lamina and the modiolus tended to be better detectable on MDCT, showing significant differences for the osseous spiral lamina (p = 0.001). The interrater reliability was 0.73 (Cohen's kappa coefficient) and intraobserver reliability was 0.89.
The use of CBCT and MDCT allows equivalent and excellent imaging results if optimized protocols are chosen. With both imaging techniques subtle temporal bone structures could be visualized with a similar degree of definition. In vivo differences do not seem to be as large as suggested in several previous studies.
... However, these studies compared images of cadaver heads and are thus free of reallife motion artifacts. In-vivo comparisons of the modalities find that the images are equivalent, although MSCT is better for imaging inner ear structures and CBCT produces better images of the ossicles [9]. Another study state that MSCT is equal or better; CBCT producing adequate or very good images for 75-85% of the evaluated structures [10]. ...
... Repetitive imaging without changes in pathology or anatomy is essential for comparing imaging modalities. There are only few clinical studies comparing the use of MSCT and CBCT to temporal bone imaging: Redfors et al. [10] were the first to evaluated the anatomical structures of the temporal bones of 20 post-stapedectomy patients (otosclerosis), and Pein et al. [9] compared images of 38 patients without pathology, but most of the compared images were from different patients. Some additional studies comparing imaging modalities have a narrow scope, such as imaging post-operative implant position or pre-operative imaging of otosclerosis. ...
... The meningoencephalocele protrudes through the tegmen tympani and is in contract with the incus and the malleus provides crisp, clear images of the bony structure with radiation doses ranging from 1.6 mSv for adults to 7.1 mSv for new-borns, an amount equivalent to 6-24 months of background radiation [8,12]. CBCT can produce images that are as good or even better [5][6][7]9]. However, the hypernym CBCT includes a variety of hardware, software and setting combinations, our combinations in this article are named as HR CBCT and ULD CBCT. ...
Purpose
This study will evaluate the clinical quality and usability of peripheral image data from the temporal bone area obtained using a sinonasal ultra-low-dose (ULD) cone-beam computed tomography (CBCT) scan and compare them to those obtained using a high-resolution (HR) CBCT.
Methods
The population consisted of 66 anatomical sites (ears of 33 subjects) imaged using two modalities: an HR CBCT (Scanora 3Dx scanner; Soredex, Tuusula, Finland) and a ULD CBCT (Promax 3D Mid scanner; Plandent, Helsinki, Finland). The image quality (IQ) for every anatomical site in each image was rated using a Likert scale from 0 to 5.
Results
The quality of ULD CBCT scans was clinically sufficient in over 95% of the assessed images of the sigmoid sinus, jugular bulb, epitympanum and mastoid antrum as well as external acoustic meatus (all p > 0.05 compared to HR CBCT). The IQ was clinically sufficient in 75–94% of the assessed images of the scutum, mastoid segment of the facial nerve, cochlea and semicircular canals (all p < 0.05 compared to HR CBCT). The overall IQ of the HR CBCT scans was good or excellent.
Conclusion
CBCT imaging and the data at image margins are underutilized. CBCT can produce excellent structural resolu- tion with conventional imaging parameters, even with off-focus images. Using ultra-low doses of radiation, the produced IQ is clinically sufficient. We encourage ear surgeons to check the patients’ imaging history and to consider the use of imaging modalities that involve lower radiation doses especially when conducting repetitive investigations and with children.
... The following ten anatomical structures were assessed using a 5-point scale similar to one applied by Pein and coworkers [23]: 1-not visible, 2-faintly visible, 3-visible, 4-well visible, and 5-very well visible. The visibility of the following structures was rated: the tendon of the m. ...
... Inner ear structures such as the modiolus and the lamina spiralis ossea were more clearly defined in CT images with optimized protocols (p = 0.001). These authors concluded that optimized CT and CBCT protocols were a prerequisite for the equal visualization of temporal bone structures [23]. Interestingly, the lamina spiralis ossea was not visible in any imaging mode in this study. ...
... CT and CBCT have been directly compared in many studies, resulting in contradictory results in terms of resolution and radiation dose [29][30][31][32][33]. Due to the inhomogeneous image quality of different scanners and increased susceptibility to motion artifacts, CBCT should not be generally seen as a replacement for the CT [23]. Radiation exposure is lower in CBCT in the high-contrast range and it was described to be superior to CT in terms of the resolution of high-contrast structures [34]. ...
Objective:
Repeated computed tomography (CT) is essential for diagnosis, surgical planning and follow-up in patients with middle and inner ear pathology. Dose reduction to "as low as diagnostically acceptable" (ALADA) is preferable but challenging. We aimed to compare the diagnostic quality of images of subtle temporal bone structures produced with low doses (LD) and reference protocols (RP).
Methods:
Two formalin-fixed human cadaver heads were scanned using a 64-slice CT scanner and cone-beam CT (CBCT). The protocols were: RP (120 kV, 250 mA, CTDIvol 83.72 mGy), LD1 (100 kV, 80 mA, CTDIvol 26.79 mGy), LD2 (100 kV, 35 mA, CTDIvol 7.66 mGy), LD3 (80 kV, 40 mA, CTDIvol 4.82 mGy), and CBCT standard protocol. Temporal bone structures were assessed using a 5-point scale.
Results:
A median score of ≥2 was achieved with protocols such as the tendons of m. tensor tympani (RP/LD1/LD2/CBCT) and m. stapedius (CBCT), the incudostapedial joint (RP/LD1/CBCT), the incudomalleolar joint (RP/LD1/LD2/CBCT), the stapes feet (RP/LD1/CBCT), the stapes head (RP/LD1/LD2/CBCT), the tympanic membrane (RP/LD1/LD2/CBCT), the lamina spiralis ossea (none), the chorda tympani (RP/LD1/CBCT), and the modiolus (RP/LD1/LD2/CBCT). Adaptive statistical iterative reconstructions did not show advantages over the filtered back projection.
Conclusions:
LD protocols using a CTDIvol of 7.66 mGy may be sufficient for the identification of temporal bone structures.
... However, few comparative clinical studies have been conducted [5,13,15,16] and little research has specifically focused on the potential role of CBCT in assessing anatomic structures related to the ossicular chain or causes of conductive hearing loss. ...
... Some middle ears were still filled with fluid despite paracentesis of the eardrum of all formalin-fixed human cadaver heads, which made assessing visibility of some clinically important structures more difficult. Another factor is that normal temporal bones were assessed in this study, although it has been specifically reported that CBCT can be limited in the assessment of pathology of the middle ear [16] . ...
... Despite promising results [16] and expert remarks [4] about the potential of CBCT as an alternative diagnostic tool for patients with conductive hearing loss, additional research will be needed for more conclusive results. ...
Objectives:
Multislice computed tomography (MSCT) is commonly used as a diagnostic tool for patients with a conductive hearing loss. Recent studies indicate that cone-beam computed tomography (CBCT) may be used as a low-radiation dose alternative for temporal bone imaging. This study compares image quality and radiation dose between CBCT and MSCT when assessing anatomical landmarks related to conductive hearing loss.
Materials and methods:
Five human cadaver heads (10 ears) were imaged on the NewTom 5G CBCT and the Discovery CT750 HD MSCT. Visibility of 16 anatomical landmarks of the middle and inner ear was assessed by two observers on a 4-point Likert scale. Furthermore, effective radiation dose was compared, and contrast-to-noise ratio and spatial resolution were measured with a phantom head.
Results:
Image quality of CBCT was assessed as superior to MSCT. Effective radiation dose of the high-resolution CBCT protocol was 30.5% of the clinical MSCT dose. High-resolution CBCT was reported as having a higher spatial resolution and superior contrast-to-noise perception in comparison with MSCT.
Conclusion:
High-resolution CBCT was evaluated as superior to MSCT in the assessment of structures related to conductive hearing loss. Furthermore, CBCT imaging resulted in a considerably lower effective radiation dose.
... The image quality was grouped into note 1-completely visible, 2-partial visible, and 3-not visible. The following bony anatomic structures were determined: (1) mastoid part of facial nerve; (2) middle ear part of facial nerve; (3) inner ear part of facial nerve; (4) joint between malleolus and incus; (5) joint between incus and stapes; (6) head of stapes; (7) posterior crus of the stapes; (8) anterior crus of the stapes; (9) long process of incus; (10) round window niche; (11) oval window niche; (12) horizontal semicircular canal; (13) superior semicircular canal; (14) posterior semicircular canal; (15) jugular bulb; (16) bony canal of sigmoid sinus; (17) bony skull base at middle ear (so called tegmen tympani); (18) bony skull base at the mastoid. Of course, only the bony canals could be evaluated and not the soft tissue structures themselves. ...
... To visualize soft tissue, especially in diagnostics of chronic otitis media epitympanalis/cholesteatoma, the MRI is the method of choice [11][12][13]. In visualization of bony structures, conventional CT has become the gold standard [14,15]. Conventional X-ray examination (Schueller/Stenvers) is still used, but limitations in visualization of the detailed anatomy of the dedicated middle and inner ear structures exist [1,2]. ...
... Because of additional irradiation in performing more than one X-ray-dependent diagnostic tool, an intra-individual analysis of several radiologic techniques (CT, radiography) is ethically impossible. Pein et al. tried to compare CT and CBCT (N = 38) and demonstrated a minor advantage of CBCT [14]. Studies with higher patient numbers with a focus on visualization of the temporal bone anatomy in real daily usage do not exist. ...
Cone beam computed tomography (CBCT, syn. digital volume tomography = DVT) was introduced into ENT imaging more than 10 years ago. The main focus was on imaging of the paranasal sinuses and traumatology of the mid face. In recent years, it has also been used in imaging of chronic ear diseases (especially in visualizing middle and inner ear implants), but an exact description of the advantages and limitations of visualizing precise anatomy in a relevant number of patients is still missing. The data sets of CBCT imaging of the middle and inner ear of 204 patients were analyzed regarding the visualization of 18 different anatomic structures. A three-step scale (excellent visible, partial visible, not visible) was taken. All analyses were performed by two surgeons experienced in otology and imaging. The indications for imaging were chronic middle ear disease or conductive hearing loss. Previously operated patients were excluded to rule out possible confounders. In dependence of a radiological pathology/opacity of the middle ear, two groups (with and without pathology) were built. Regarding the possibility of excellent visualization, significant differences were only found for small bony structures: incu-stapedial joint (25.8 vs. 63.5 %), long process of incus (42.7 vs. 88.8 %), head of stapes (27.0 vs. 62.6 %), anterior crus of stapes (16.9 vs. 40.9 %) and posterior crus of stapes (19.1 vs. 42.6 %). The other structures (semicircular canals, skull base at mastoid and middle ear, jugular bulb, sinus sigmoideus, facial nerve) could be visualized well in both groups with rates around 85–100 %. Even CBCT shows little limitations in visualization of the small structures of the middle and inner ear. Big bony structures can be visualized in normal as well as in pathologic ears. Overall, due to pathology of middle ear, an additional limitation of evaluation of the ossicular chain exists. In future, studies should focus on comparative evaluation of different diseases and different radiological modalities and be performed by radiologists and otologists together to improve the quality of reports and to answer clinical questions more satisfactorily.
... However, few comparative clinical studies have been conducted [5,13,15,16] and little research has specifically focused on the potential role of CBCT in assessing anatomic structures related to the ossicular chain or causes of conductive hearing loss. ...
... Some middle ears were still filled with fluid despite paracentesis of the eardrum of all formalin-fixed human cadaver heads, which made assessing visibility of some clinically important structures more difficult. Another factor is that normal temporal bones were assessed in this study, although it has been specifically reported that CBCT can be limited in the assessment of pathology of the middle ear [16] . ...
... Despite promising results [16] and expert remarks [4] about the potential of CBCT as an alternative diagnostic tool for patients with conductive hearing loss, additional research will be needed for more conclusive results. ...
Cone-Beam CT compared to Multi-slice CT for the diagnostic analysis of conductive hearing loss, a pilot study - Volume 130 Issue S3 - Pieter Kemp, Jiska van Stralen, Pim de Graaf, Erwin Berkhout, Jan Wolff, Pepijn van Horssen, Paul Merkus
... The aim in developing FPCT was to have a higher isotropic spatial resolution compared to MDCT. While earlier studies in explanted temporal bone preparations showed better image quality of FPCT compared to MDCT [12,14] other studies comparing MDCT versus FPCT in whole-skull preparations did not show significant differences in image quality for temporal bone imaging [12,15,16]. Pein et al. [16] reported, in line with our results, that the identification of the spiral lamina of the cochlea was even better in MDCT compared to FPCT. ...
... While earlier studies in explanted temporal bone preparations showed better image quality of FPCT compared to MDCT [12,14] other studies comparing MDCT versus FPCT in whole-skull preparations did not show significant differences in image quality for temporal bone imaging [12,15,16]. Pein et al. [16] reported, in line with our results, that the identification of the spiral lamina of the cochlea was even better in MDCT compared to FPCT. This is confirmed by Saeed et al., who reported difficulties in visualizing the osseous spiral lamina in cone beam computed tomography after cochlear implant surgery [17]. ...
Purpose
Imaging of temporal bone and skull base acquire high resolution due to the small anatomic structures with high clinical relevance. The purpose of this study was to compare image quality of the temporal bone in standard 20 s protocol flat-panel computed tomography (FPCT) with the new time- and dose improved 10 s protocol as well as with 128 slice multidetector computed tomography (MDCT). The aim was to evaluate the new time- and dose improved 10 s protocol.
Methods
10 whole-skull preparations—20 temporal bones—were scanned with either 128 slice MDCT CT (SOMATOM Definition AS + , Siemens, Erlangen) or FPCT (AXIOM-Artis, Siemens, Erlangen) using 10 s or 20 s protocol.
Results
We show here that overall FPCT provides significantly better image quality and improved delimitation of clinically relevant structures in the temporal bone compared to 128 slice MDCT. Especially the shorter, dose saving 10 s protocol of the FPCT is still superior to 128 slice MDCT. The 20 s FPCT protocol was only significantly superior in identification of the cochlear apical turn and can thereby be used specifically in clinical cases with pathologies in this area.
Conclusions
The 10 s FPCT protocol yields a significantly better image quality than MDCT in imaging finer structures of the temporal bone.
... One example is in the case of chronic kidney diseases (CKD), that affect about 10% in a general population, and often lead to severe secondary osteoporosis. CKD patients seem predisposed for fractures that are linked to much higher morbidity and mortality rates than fractures observed in the normal population [60,61]. ...
... Although their heads and cheeks are fixated with straps, this position may increase the risk of motion artefacts. However, a recent clinical study demonstrated that the small middle ear structures could easily be demonstrated by CBCT(A) when used clinically [60]. Further clinical studies are necessary to investigate the possibility of imaging the trabecular bone structure in vivo. ...
... While image quality of flat panel CT and multidetector-CT in temporal bone imaging has already been compared in various publications, showing an advantage for flat panel CT [3,22,24,25], there are several publications regarding the use of cone beam CT and assessing its accuracy for intraoperative navigation [19,21]. Comparison between MDCT and Cone beam CT in skull base imaging on phantom and human dry skull showed no significant differences between the 2 CT systems [6]. ...
Background
Purpose of this study was to compare image quality of the skull base in standard 20s protocol flat panel computed tomography (FPCT) with the new time and dose improved 10s protocol as well as with 128 slice multidetector computed tomography (MDCT).
Methods
10 whole skull preparations were scanned with either 128 slice MDCT(SOMATOM Definition AS+, Siemens, Erlangen) or FPCT (AXIOM-Artis, Siemens, Erlangen) using 10s or 20s protocol.
Results
FPCT provides significantly better image quality and improved delimitation of clinically relevant structures in the anterior, temporal and posterior skull base compared to 128 slice MDCT. The 20s FPCT protocol yielded best delimitability of evaluated skull base structures. However, the shorter, dose saving 10s FPCT protocol was still significantly superior to 128 slice MDCT regarding delimitability of skull base structures and additionally showed no significant inferiority compared with the 20s FPCT protocol.
Conclusions
The 10s FPCT protocol yields a significantly better image quality at a comparable radiation dose exposure in imaging skull base structures compared to MDCT.
Trial registration
371/2017BO2.
... often includes areas outside of the field of interest [6]. Cone beam computed tomography has shown that it can detect delicate structures which is comparable to multi-detector computed tomography (MDCT) [7]. ...
Background
Stroke is the second leading cause of death globally and account for 25,000 deaths annually in South Africa. Both medial and intimal located intracranial internal carotid artery (iICA) calcifications are associated with stroke. Cone beam computed tomography (CBCT) is commonly used where advanced dental imaging of the skull is required and often includes areas outside of the field of interest. Modalities such as CBCT have great potential to identify and provide early detection of calcifications during imaging for dental purposes. The aim of the study was to investigate the presence, distribution and extent of iICA calcifications in a South African population using CBCT images. Retrospectively collected CBCT data sets of 582 patients were evaluated. All data sets were evaluated for the presence, location and severity of calcifications within the course of the internal carotid artery.
Results
Age was associated with a higher prevalence of internal carotid artery (ICA) calcifications, but sex was not. Individuals older than 61 years presented with a high number of calcifications. In total, the presence of calcifications was found in 199 patients (i.e. 34.19% of the patients). White South African individuals showed the highest prevalence. A higher degree of calcifications was also present within the C4, C5 and C6 ICA segments.
Conclusions
Detection of calcifications along the course of the ICA was possible using CBCT images taken for dental treatment purposes. Early detection of calcifications allows for appropriated referral and assessment which will be beneficial to the patient presenting with ICA calcifications.
... The recently developed modality known as cone-beam CT provides higher resolution in temporal bone examinations and exposes patients to less radiation, although its indications are quite limited, as is its availability in Brazil. However, it has been used for monitoring the evolution of alterations already identified on multidetector CT and for the diagnosis of pathologies in children, as well as for the evaluation of ossicular prostheses, cochlear implants, malformations, and otosclerosis (4,5) . ...
... Patient movement may be an issue, but studies performed with HR-pQCT have shown that it is possible to measure the biomechanical performance of bone in vivo. 43 The tiny middle ear structures can be visualized by using in vivo imaging with CBCT, 44,45 which suggests the possibility of imaging other minute structures, such as trabecular bone, in vivo. ...
Objectives
The aim of this study was to evaluate the possibility of estimating biomechanical properties of trabecular bone through finite element (FE) simulations using dental cone beam computed tomography (CBCT) data.
Study design
Fourteen human radius specimens were scanned in three CBCT devices: 3D Accuitomo 80, NewTom 5G, and Verity. The imaging data was segmented using two different methods. Stiffness (Young's modulus), shear moduli, and the size and shape of the stiffness tensor were studied. Corresponding evaluations using micro-CT were regarded as the reference standard.
Results
The 3D Accuitomo 80 showed good performance in estimating stiffness and shear moduli, but was sensitive to the choice of segmentation method. NewTom 5G and Verity yielded good correlations, but they were not as strong as the Accuitomo. The CBCT devices overestimated both stiffness and shear compared to the micro-CT estimations.
Conclusions
FE-based calculations of biomechanics from CBCT data are feasible, with strong correlations for the Accuitomo 80 scanner combined with an appropriate segmentation method. Such measurements might be useful for predicting implant survival by in vivo estimations of bone properties.
... CBCT has been analyzed in regards to electrode position (scala tympani versus scala vestibuli insertion, intracochlear dislocation, and insertion angle) and cochlear size (diameters and height). As determined by Pein et al. [15], the use of CBCT and HRCT allows equivalent imaging results; and with both imaging techniques, temporal bone structures can be visualized in detail, so that the solitary evaluation by CBCT is valid and sufficient. The position of the electrode array was determined by two physicians; the measurements of the cochlea were performed independently. ...
Objective:
Preoperative information about cochlear morphology and size increasingly seems to be a defining factor of electrode choice in cochlear implant surgery. Different types of electrodes differ in length and diameter to accommodate individual cochlear anatomy. Smaller cochlear size results in increased insertion depth with a higher risk to dislocate and causes cochlear trauma with reduced postoperative outcome. The objective of the current study is to describe the three-dimensional size of the cochlea, to compare interindividual differences, to determine the relationship between cochlear size and insertion angle, and to define risk factors for dislocation during insertion.
Design:
Four hundred and three patients implanted between 2003 and 2010 inserted via cochleostomy with a perimodiolar electrode array (Cochlear™ Contour Advance® electrode array) have been compared. CBCT (Cone beam computed tomography) was used to determine electrode array position (scala tympani versus scala vestibuli insertion, intracochlear dislocation, and insertion angle) and cochlear size (diameters and height). The trajectory of the electrode array and the lateral wall have been measured, and the position of the electrode array has been estimated.
Results:
The mean value of the largest diameter was 9.95 mm and that of the perpendicular distance was 6.54 mm. There was a statistically significant correlation between those values. Mean height was 3.85 mm. The intracochlear relation of the electrode array and the modiolus showed a statistically significant relationship with the cochlear expanse. The electrode array was more likely to dislocate in cochleae with a smaller diameter and a lower height. Cochleae with insertions into scala vestibuli exhibited a smaller height compared to scala tympani insertions with statistical significance.
Conclusion:
Cochlear size and shape is variable, and the measured data of this study confirm the finding of other researchers. This study established two heights by two different planes to achieve a three-dimensional understanding of the cochlea. The electrode array was more likely to dislocate in cochleae with smaller diameter and smaller height. It can be assumed that the height established in this study seems to be a new preoperative parameter to underline the risk of scalar dislocation and not favored scala vestibuli insertion if using a cochleostomy approach. In conclusion, cochlear size, especially the height, is influencing the final position of the electrode array. Using preoperative scans of the cochlear diameters and cochlear height, a next step to custom-sized arrays is available.
... Although their heads and cheeks are fixated with straps, this position may increase the risk of motion artefacts. However, a recent clinical study demonstrated that the small middle ear structures could easily be demonstrated by CBCT(A) when used clinically [60]. Further clinical studies are necessary to investigate the possibility of imaging the trabecular bone structure in vivo. ...
Stiffness and shear moduli of human trabecular bone may be analyzed in vivo by finite element (FE) analysis from image data obtained by clinical imaging equipment such as high resolution peripheral quantitative computed tomography (HR-pQCT). In clinical practice today, this is done in the peripheral skeleton like the wrist and heel. In this cadaveric bone study, fourteen bone specimens from the wrist were imaged by two dental cone beam computed tomography (CBCT) devices and one HR-pQCT device as well as by dual energy X-ray absorptiometry (DXA). Histomorphometric measurements from micro-CT data were used as gold standard. The image processing was done with an in-house developed code based on the automated region growing (ARG) algorithm. Evaluation of how well stiffness (Young’s modulus E3) and minimum shear modulus from the 12, 13, or 23 could be predicted from the CBCT and HR-pQCT imaging data was studied and compared to FE analysis from the micro-CT imaging data. Strong correlations were found between the clinical machines and micro-CT regarding trabecular bone structure parameters, such as bone volume over total volume, trabecular thickness, trabecular number and trabecular nodes (varying from 0.79 to 0.96). The two CBCT devices as well as the HR-pQCT showed the ability to predict stiffness and shear, with adjusted R2-values between 0.78 and 0.92, based on data derived through our in-house developed code based on the ARG algorithm. These findings indicate that clinically used CBCT may be a feasible method for clinical studies of bone structure and mechanical properties in future osteoporosis research.
OBJECTIVE. The purpose of this article is to evaluate subjective image quality and diagnostic accuracy to determine cochlear implant (CI) electrode position in a temporal bone (TB) specimen on cone-beam CT (CBCT) versus MDCT. MATERIALS AND METHODS. In this retrospective study, two radiologists independently reviewed CBCT (96-kV and 120-kV settings) and MDCT images of 20 TB specimens after electrode implantation. Qualitative evaluation of bone structures of the otic capsule, inner and outer cochlear wall, osseous spiral lamina, electrode position relative to the osseous spiral lamina, visualization of single electrode contacts on the array, metal artifacts, and overall image quality was performed using a five-point scale. Intracochlear electrode position was subsequently correlated with histologic examination. RESULTS. Radiologic assessment of bone structures of the otic capsule, the cochlear wall (except the outer part), osseous spiral lamina, electrode position, visualization of single electrode contacts on the array, metal artifacts, and overall image quality were significantly higher in CBCT compared with MDCT (maximum p = .04). No significant differences were found between CBCT at 96 kV and 120 kV (minimum p = .21). The intracochlear electrode position with histologic correlation was correctly diagnosed in 100% and 97.5% of specimens on 120-kV and 96-kV CBCT, respectively, whereas 77.5% were correctly assessed using MDCT. CONCLUSION. The data suggest that CBCT shows a higher diagnostic accuracy in TB specimen imaging after CI compared with MDCT, in particular to determine the intracochlear localization of the implant.
Hypothesis: Before modern imaging was introduced, revision surgery was the only way to evaluate possible reasons for inadequate improvement in hearing after ossicular replacement during reconstructive middle ear surgery.
Background: The aim of this study was to evaluate freely navigable virtual tympanoscopy using different computed tomographic modalities. We compared cone-beam computed tomography (CBCT), flat panel computed tomography (FPCT), and conventional computed tomography in helical mode (CTH), volume mode (CTV), and ultra high resolution mode (CTD).
Methods: Four temporal bone specimens were reconstructed with partial or total ossicular replacement prostheses. The best functional results for prosthetic coupling were achieved under the control of laser Doppler vibrometry (LDV). Afterward, a progressive step-by-step decoupling of the prostheses was carried out. Different prosthesis positions were evaluated by LDV as well as different computed tomographic modalities with 3D reconstruction of each dataset.
Results: Anatomical structures were better depicted and the best position and coupling of inserted prostheses were achieved using CBCT. All imaging techniques could be used to control the position of middle ear prostheses, but CBCT provided the highest resolution and the best image quality in both 2D and 3D reformations and in 3D-animated video representation.
Conclusion: Compared with several other imaging modalities, CBCT was best at depicting miscellaneous coupling problems. Noninvasive detection of coupling problems caused by minimal loss of contact between prostheses and middle ear ossicles will influence the clinical outcome. This early detection will help to determine whether revision surgery is needed.
Einfluss der cochleären Morphologie auf die Dislokationswahrscheinlichkeit des Elektrodenträgers des Cochlea Implantates
Objective:
Navigation systems create a connection between imaging data and intraoperative situs, allowing the surgeon to consistently determine the location of instruments and patient anatomy during the surgical procedure. The best results regarding the target registration error (measurement uncertainty) are normally demonstrated using fiducials. This study aimed at investigating a new registration strategy for an electromagnetic navigation device.
Methods:
For evaluation of an electromagnetic navigation system and comparison of registration with screw markers and automatic registration, we are calculating the target registration error in the region of the paranasal sinuses/anterior and lateral skull base with the use of an electromagnetic navigation system and intraoperative digital volume tomography (cone-beam computed tomography). We carried out 10 registrations on a head model (total n = 150 measurements) and 10 registrations on 4 temporal bone specimens (total n = 160 measurements).
Results:
All in all, the automatic registration was easy to perform. For the models that were used, a significant difference between an automatic registration and the registration on fiducials was evident for just a limited number of screws. Furthermore, the observed differences varied in terms of the preferential registration procedure.
Conclusion:
The automatic registration strategy seems to be an alternative to the established methods in artificial and cadaver models of intraoperative scenarios. Using intraoperative imaging, there is an option to resort to this kind of registration as needed.
Objective:
Computed tomography (CT) is the imaging tool of choice in the diagnosis of temporal bone lesions. With the recent progress in imaging technology, CT with higher spatial resolution (Ultra-high resolution CT) has become available in the clinical setting. The purpose of this study is to evaluate the visibility of small temporal bone structures using ultra-high resolution CT.
Material and methods:
The visibility of 27 minute temporal bone structures on ultra-high resolution CT images was evaluated. Non-helical axial scans were performed in 18 normal hearing ears without previous otologic diseases. Visibility was scored by an experienced radiologist and otologist.
Results:
Minute temporal bone structures including the ossicular chain, the crus of the stapes, the greater superficial petrosal nerve, and the anterior malleolar ligament were clearly visualized on ultra-high resolution CT. The stapedius muscle tendon and the chorda tympani exiting the posterior canaliculus and coursing medial to the malleus could be visualized.
Conclusion:
Ultra-high resolution CT provides good visualization of small temporal bone structures in normal subjects.
The utility of high-resolution computed tomography (HRCT) has been to a certain extent neglected in order to investigate on acquired cochleo-vestibular disorders of uncertain origin until the wide range of labyrinthine dehiscences has been discovered. In the last decade both the technical progress, that has permitted a diagnostic refinement in general terms, and the better definition of the width of the dehiscence syndromes, that proved larger than previously expected, has restored CT to its crucial role in detecting inner ear affections. Despite its evidence, this statement has not uniformly entered the habit of clinical practice. For this reason, a review of the literature of the last years, aimed at underlying the real significance of this tool for the otologist, appears of some utility in order to contribute to eliminate deep-rooted diagnostic incongruities.
In diesem Beitrag wird der gegenwärtige Stellenwert von Computertomographie (CT), Magnetresonanztomographie (MRT), digitaler Volumentomographie (DVT), digitaler Subtraktionsangiographie (DSA) und Röntgenspezialaufnahmen in der Diagnostik von Schläfenbeinerkrankungen dargelegt, wobei Letztere für diagnostische Zwecke obsolet sind. Möglichkeiten und Grenzen der Schnittbildverfahren beim Erkennen und/oder der Darstellung des Ausmaßes von entzündlichen, traumatischen und tumorösen Erkrankungen bzw. postoperativer Pathologien werden erörtert. Wichtig für die Wahl der im Einzelnen einzusetzenden Methode sind eine konkrete Fragestellung und die Übermittlung klinischer Befunde. Nur durch die CT oder DVT können Mittelohrfehlbildungen nichtinvasiv aufgedeckt werden. Es sind auch die Methoden, mit denen in unklaren Fällen die Diagnose einer Otosklerose untermauert werden kann. Die MRT ist Methode der Wahl bei Erkrankungen des Innenohrs und des inneren Gehörgangs inklusive Innenohrfehlbildungen. Die Endolymphhydrops-Visualisierung bei der Menière-Erkrankung wird derzeit nur in wenigen Einrichtungen erfolgreich realisiert.
Isolated fracture of the handle of the malleus is a rare cause of conductive hearing loss and represents a challenge for the otolaryngologist in terms of past medical history, diagnostics, and therapy.
Objectives
Modern passive middle ear titanium prostheses are filigree structures, resulting in poorer depiction on CT compared to prostheses used in the past. We compared the visibility of newer prostheses on cone beam CT (CBCT) to multi-detector CT (MDCT) with standard and lower dose in vitro, and analysed image noise and metal artefacts. Methods
Six different titanium middle ear prostheses (three partial and one total ossicular replacement prostheses, two stapes prostheses) were implanted twice in formalin-fixed head specimens—first correctly and then with displacement. Imaging was performed using standard CBCT and MDCT as well as MDCT with lower dose (36 single imaging investigations). Images were analysed with knowledge of the used types of middle ear prostheses, but blinded with respect to the positioning in the specific case. ResultsOn all images the type of prostheses and their positions could be clearly recognized. Their identifiability including their details was rated as statistically significantly higher for all CBCT investigations than for MDCT. MDCT with lower dose showed the worst results. No statistical differences were found in image noise and metal artefacts. Conclusions
If available, CBCT should be preferred over MDCT in diagnostic evaluation of passive middle ear prostheses. Key Points• Middle ear prostheses became more filigree, leading to poorer visibility on CT.• High spatial resolution and paraxial reconstructions are necessary requirements for imaging evaluation.• CBCT and MDCT can identify type and positioning of titanium prostheses.• Metal artefacts play a minor part in filigree titanium prostheses.• Regarding visualisation of prostheses details, cone beam CT aids the evaluation.
Objectives:
The aim was to compare the accuracy of linear bone measurements of cone beam CT (CBCT) with multidetector CT (MDCT) and validate intraoral soft-tissue measurements in CBCT.
Methods:
Comparable views of CBCT and MDCT were obtained from eight intact cadaveric heads. The anatomical positions of the gingival margin and the buccal alveolar bone ridge were determined. Image measurements (CBCT/MDCT) were performed upon multiplanar reformatted data sets and compared with the anatomical measurements; the number of non-assessable sites (NASs) was evaluated.
Results:
Radiological measurements were accurate with a mean difference from anatomical measurements of 0.14 mm (CBCT) and 0.23 mm (MDCT). These differences were statistically not significant, but the limits of agreement for bone measurements were broader in MDCT (-1.35 mm; 1.82 mm) than in CBCT (-0.93 mm; 1.21 mm). The limits of agreement for soft-tissue measurements in CBCT were smaller (-0.77 mm; 1.07 mm), indicating a slightly higher accuracy. More NASs occurred in MDCT (14.5%) than in CBCT (8.3%).
Conclusions:
CBCT is slightly more reliable for linear measurements than MDCT and less affected by metal artefacts. CBCT accuracy of linear intraoral soft-tissue measurements is similar to the accuracy of bone measurements.
A recent development in radiology is the use of flat panel detectors in CT to obtain higher-resolution images. This technique is known as flat panel volume CT (fpVCT). We sought to compare the image quality and diagnostic value of 2 different flat panel detector-equipped scanners: one is a prototype fpVCT scanner, and the other is a so-called flat panel digital volume tomography (fpDVT) scanner, which is routinely used in clinical setup with current state-of-the-art multisection CT (MSCT) scanners.
Five explanted temporal bones and 2 whole-head cadaveric specimens were scanned with fpVCT, fpDVT, and MSCT scanners. The image series were blindly evaluated by 3 trained observers who rated 38 anatomic structures with regard to their delineation/appearance.
Although the image quality obtained with fpVCT and fpDVT was rated significantly better compared with MSCT on isolated temporal bones, the differences were not significant when whole cadaveric heads were scanned.
Theoretic and practical advantages exist for flat panel detector-equipped scanners, including improved image quality. However, when imaging whole cadaveric heads, no significant difference could be demonstrated between them and standard-of-care MSCT.
To evaluate image quality by examining segmentation accuracy and assess radiation dose for cone beam CT (CBCT) scanners.
A skull phantom, scanned by a laser scanner, and a contrast phantom were used to evaluate segmentation accuracy. The contrast phantom consisted of a polymethyl methacrylate (PMMA) cylinder with cylindrical inserts of air, bone and PMMA. The phantoms were scanned on the (1) Accuitomo 3D, (2) MercuRay, (3) NewTom 3G, (4) i-CAT and (5) Sensation 16. The structures were segmented with an optimal threshold. Thicknesses of the bone of the mandible and the diameter of the cylinders in the contrast phantom were measured across lines at corresponding places in the CT image vs a ground truth. The accuracy was in the 95th percentile of the difference between corresponding measurements. The correlation between accuracy in skull and contrast phantom was calculated. The radiation dose was assessed by DPI(100,c) (dose profile integral (100,c)) at the central hole of a CT dose index (CTDI) phantom.
The results for the DPI(100,c) were 107 mGy mm for (1), 1569 mGy mm for (2), 446 mGy mm for (3), 249 mGy mm for (4) and 1090 mGy mm for (5). The segmentations in the contrast phantom were submillimeter accurate in all scanners. The segmentation accuracy of the mandible was 2.9 mm for (1), 4.2 mm for (2), 3.4 mm for (3), 1.0 mm for (4) and 1.2 mm for (5). The correlation between measurements in the contrast and skull phantom was below 0.37 mm.
The best radiation dose vs image quality was found for the i-CAT.
Three-dimensional cochlear canal lengths, electrode array intracochlear insertion depths, and characteristic frequency ranges were estimated for 20 Nucleus implant recipients on the basis of in vivo computed tomography (CT) scans. Ultra-high resolution images were reconstructed from spiral CT data with 0.1-mm slicing and expanded attenuation scales. Canal length estimates (mean 33.01 mm; SD 2.31) were consistent with previous findings for normal human temporal bones. Intracochlear array insertion depths estimated by 3-dimensional (3-D) spiral calculations (mean 20.19 mm; SD 2.86) and by a computerized array tracking algorithm (mean 20.36 mm; SD 2.66) were not significantly different. Estimates from surgical observations were significantly longer (mean 21.03 mm; SD 2.31) because array compressions were not detectable. Characteristic frequencies at apical electrodes estimated from Greenwood's equations ranged from 387 Hz to 2,596 Hz. The results show that significant variations in cochlear anatomy and array distribution among implant patients that may impact implant performance can be reliably detected and quantified by using in vivo high-resolution CT and 3-D reconstructions.
Ziel: Vergleich von Dosis und Bildauflösungsvermögen von 3D-fähigen digitalen Röntgenanlagen in der HNO-Diagnostik.
Material und Methoden: Verglichen wurden 3 hauseigene Röntgengeräte (CT, DVT, DSA) identischer Generation. Zur Anwendung kamen dabei Protokolle für Nasennebenhöhlen- (NNH) und Schläfenbeinuntersuchungen. Die Strahlenexposition wurde sowohl mit einer Punktionsmesskammer an einem CTDI-Kopfphantom als auch mittels Chipstrate-Dosimeter an einem Alderson-Kopfphantom im Augen- und Schilddrüsenbereich gemessen. Am Alderson-Kopfphantom wurde zudem die protokollspezifische, geräteeigene Dosisanzeige erfasst. Die Bestimmung des Auflösungsvermögens im Hochkontrastbereich erfolgte qualitativ anhand von Aufnahmen eines speziell angefertigten Strukturphantoms durch 6 Auswerter.
Ergebnisse: Je nach Protokollart und/oder Gerätemodus zeigten die 3 Geräte deutlich unterschiedliche Werte sowohl für die Strahlenexposition als auch das Auflösungsvermögen. Für Routineprotokolle wies die DVT in der Kombination beider Bewertungskriterien gegenüber der CT und DSA Vorteile auf, wobei der Unterschied für NNH-Untersuchungen weniger deutlich ausfiel.
Schlussfolgerung: Im Hochkontrastbereich stellt die DVT bei Einsatz moderner Geräte eine zu beachtende Alternative in der Kopf-Hals-Radiologie dar.
Purpose:
Comparison of dosage and spatial resolution of digital X-Ray devices with 3D-capability in head and neck imaging.
Materials and methods:
Three on-site X-Ray devices, a general purpose multi-slice CT (CT), a dedicated cone-beam CT (CBCT) and the CT-mode of a device for digital angiography (DSA) of the same generation were compared using paranasal sinus (PNS) and temporal bone imaging protocols. The radiation exposure was measured with a puncture measuring chamber on a CTDI head phantom as well as with chip-strate-dosimeters on an Alderson head phantom in the regions of the eyes and thyroid gland. By using the Alderson head phantom, the specific dosage of the X-Ray device with regard to different protocols was read out. For the assessment of the high-contrast resolution of the devices, images of a self-made phantom were qualitatively analysed by six observers.
Results:
The three devices showed marked variations in the dosage and spatial resolution depending on the protocol and/or modus. In both parameters, CBCT was superior to CT and DSA using standard protocols, with the difference being less obvious for the investigation with PNS.
Conclusion:
For high-contrast investigations CBCT CT is a remarkable option in head and neck radiology.
Der Beitrag gibt einen Überblick über Erkrankungen des Schläfenbeins, die für den Radiologen relevant sind. Zunächst werden die dominierenden bildgebenden Methoden unter Berücksichtigung des aktuellen Stands kurz zusammengefasst. Zudem werden die wesentlichen Aspekte der Schnittbildanatomie des Schläfenbeins erläutert. Darauf folgt die Vorstellung verschiedener entzündlicher Erkrankungen. Im Rahmen der Verletzungen am Os temporale werden Frakturen (Längs-, Quer- und gemischte Frakturen), Gehörknöchelchenläsionen und die Contusio labyrinthi besprochen. Auch Tumoren und tumorähnliche Läsionen, das Krankheitsbild der Otosklerose und Fehlbildungen werden abgehandelt. Schließlich wird auf die Anwendung der Bildgebung nach Operationen eingegangen.
Besonderer Wert wird darauf gelegt, die Stellung der Bildgebung innerhalb der Diagnosekette zu verdeutlichen. Zudem werden die möglichen Aussagewerte abgeleitet. Spezielle bildmorphologische Charakteristika und differenzialdiagnostische Aspekte ergänzen die Übersicht.
Anatomical information of the middle and inner ear is becoming increasingly important in post-operative evaluation especially after stapesplasty with unsuccessful improvement of the air-bone gap (ABG). So far computed tomography (CT) has been the first choice for detection of reasons for recurrent hearing loss. CT has the disadvantage of metal-induced artefacts after insertion of middle ear implants and of a relatively high irradiation dose.
Flat panel CT (fpCT) was performed in three temporal bone specimen after experimental insertion of different stapes prostheses, aiming to validate the accuracy of fpCT of the middle and inner ear. Additionally, 28 consecutive patients, supplied with different stapes prostheses underwent post-operative fpCT to compare the pre- and post-operative hearing results with the determined prosthesis position in the middle and inner ear.
In all cases, fpCT showed a statistically significant correlation between hearing improvement and prosthesis position. This technique provided detailed post-operative information of the implant position in patients and temporal bone specimen.
The new imaging technique of fpCT allows the immediate and almost artefact-free evaluation of surgical results following stapesplasty. Further benefits are a lower irradiation dose and higher isovolumetric resolution compared with standard CT.
Flat panel computed tomography (fpCT) helps otosurgeons design precise stapes protheses. fpCT allows a prediction of the postoperative hearing outcome in patients. fpCT is an adequate imaging technique for immediate postoperative quality control. Postoperative management of patients with prosthesis-related complications is more appropriate.
In the last five years digital volume tomographs (DVT) have found their way into the diagnostic imaging of the facial skull. In this study both the image quality and dose of DVT and multislice spiral CT (MSCT) in this field of application were investigated using established physical methods for CT.
Measurements on DVT scanners of various manufacturers and on a modern MSCT scanner were performed. The investigation was based on equivalent dose levels for both modalities (CT dose index, CTDI). For this purpose, the dose was measured with an ionization chamber in a cylindrical PMMA phantom. For the evaluation of image quality, the spatial resolution, contrast and noise were investigated with phantoms established for CT.
MSCT exhibited spatial resolution values of 1.0 to 1.6 lp/mm, while DVT provided resolution between 0.6 and 1.0 lp/mm only. Thus, MSCT offered similar or better resolution at an equivalent dose. For soft tissue resolution, DVT showed significant image artifacts. MSCT yielded higher homogeneity and no significant artifacts, and the contrast steps of the phantom were more verifiable. The different DVT devices, from image intensifiers to modern flat-detector (FD) devices, showed significant differences in favor of the FD devices.
For medium and high contrast applications (teeth/bones), DVT scanners can be an alternative to MSCT at comparable radiation exposure. However, MSCT offers advantages in terms of constantly good and controlled image quality with significantly more flexible scan parameters at a constant or lower dose and should therefore be given preference.
This article presents a review of diseases of the temporal bone which are relevant for radiologists in routine clinical practice. First the most prominent imaging methods will be briefly summarized with respect to the current state of the art and the most important aspects of cross-sectional anatomy of the temporal bone will be presented. This is followed by the presentation of various inflammatory diseases. Fractures (longitudinal, transverse and mixed fractures), auditory ossicle lesions and contusions of the labyrinth will be discussed in connection with injuries of the temporal bone. Tumors and tumor-like lesions and the clinical symptoms of otosclerosis and malformations will also be discussed. Finally the postoperative use of imaging methods will be presented. Special importance is given to the position of imaging techniques in the diagnostic chain and their evidential value. This is supplemented by special morphological imaging characteristics and aspects of differential diagnostics.
The aim of the present study was to analyze the diagnostic value of some temporal bone structures, e.g., ossicular chain, with digital volume tomography (DVT) compared with computed tomography (CT).
Radiological imaging for presentation structures of the temporal bone were performed by DVT and CT. Axial and coronal scans in vitro examinations were performed in 38 human temporal bones. 43 structures were defined. The frequency of visualization of these anatomic structures were studied and statistically analyzed.
In the present study there was a higher significance of identified structures in DVT. In 15 (34.9%) temporal bone specimens defined structures were found equally in DVT and CT scans of axial images and 12 (27.9%) of coronal images. However, 9 structures (20.1%) of axial scans and 5 structures (11.6%) of coronal scans could be identified statistically significantly (P < 0.05) more often in DVT than in CT.
Anatomical structures of the temporal bone can be identified in higher significance in DVT than in CT scans.
Radiological evaluation of the position of cochlear implant (CI) devices is an upcoming method for quality control after CI surgery. First, results of imaging of the middle and inner ear with digital volume tomography (DVT) show considerable advantages such as exceptional image quality, thin slice thickness, and low radiation dose. The aim of this study was to evaluate whether DVT is an appropriate method for postoperative imaging of CI patients and to identify the exact position of the implant array within the cochlear by multiple measurements.
Thirteen formalin-fixed temporal bone specimens were implanted with a CI array and scanned in DVT. To determine the exact electrode position, these specimens were ground and stained for microscopic measurements. The measurements on grindings acted as a referee and were compared with the measurements in DVT scans. The statistical analysis between the two measurement protocols was performed using the Bland-Altman method.
Best achievable agreement between DVT scans and histological reference was shown. Mean differences between DVT and grindings from -1.55 to -65.40 microm were calculated. All means are within the region of accuracy. General positioning of the implant into the cochlea could be verified in all specimens. The exact position of the implanted array within the cochlear scalae could be recognized correctly in 11 of 13 cases in DVT. It was possible to identify shiftings between the tympanic and vestibular scalae in all cases.
DVT seems to be a convenient technique for postoperative position control after cochlear implantation.
Bionic ear implants provide a solution for deafness. Patients treated with these hearing devices are often children who require close follow-up with frequent functional and radiological examinations; in particular, multislice computed tomography (MSCT). Dental volumetric cone-beam CT (CBCT) has been reported as a reliable technique for acquiring images of the temporal bone while delivering low radiation doses and containing costs. The aim of this study was to assess, in terms of radiation dose and image quality, the possibility of using CBCT as an alternative to MSCT in patients with bionic ear implants.
One hundred patients (mean age 26 years, range 7-43) with Vibrant SoundBridge implants on the round window underwent follow-up: 85 with CBCT and 15 with MSCT. We measured the average tissue-absorbed doses during both MSCT and CBCT scans. Each scan was focused on the temporal bone with the smallest field of view and a low-dose protocol. In order to estimate image quality, we obtained data about slice thickness, high- and low-contrast resolution, uniformity and noise by using an AAPM CT performance phantom.
Although the CBCT images were qualitatively inferior to those of MSCT, they were sufficiently diagnostic to allow evaluation of the position of the implants. The effective dose of MSCT was almost three times higher than that of CBCT.
Owing to low radiation dose and sufficient image quality, CBCT could be considered an adequate technique for postoperative imaging and follow-up of patients with bionic ear implants.
Conebeam x-ray CT (CBCT) is being increasingly used for point-of-service head and neck and dentomaxillofacial imaging. This technique provides relatively high isotropic spatial resolution of osseous structures with a reduced radiation dose compared with conventional CT scans. In this second installment in a 2-part review, the clinical applications in the dentomaxillofacial and head and neck regions will be explored, with particular emphasis on diagnostic imaging of the sinuses, temporal bone, and craniofacial structures. Several controversies surrounding the emergence of CBCT technology will also be addressed.
To compare image quality and visibility of anatomical structures in the mandible between five Cone Beam Computed Tomography (CBCT) scanners and one Multi-Slice CT (MSCT) system.
One dry mandible was scanned with five CBCT scanners (Accuitomo 3D, i-CAT, NewTom 3G, Galileos, Scanora 3D) and one MSCT system (Somatom Sensation 16) using 13 different scan protocols. Visibility of 11 anatomical structures and overall image noise were compared between CBCT and MSCT. Five independent observers reviewed the CBCT and the MSCT images in the three orthographic planes (axial, sagittal and coronal) and assessed image quality on a five-point scale.
Significant differences were found in the visibility of the different anatomical structures and image noise level between MSCT and CBCT and among the five CBCT systems (p=0.0001). Delicate structures such as trabecular bone and periodontal ligament were significantly less visible and more variable among the systems in comparison with other anatomical structures (p=0.0001). Visibility of relatively large structures such as mandibular canal and mental foramen was satisfactory for all devices. The Accuitomo system was superior to MSCT and all other CBCT systems in depicting anatomical structures while MSCT was superior to all other CBCT systems in terms of reduced image noise.
CBCT image quality is comparable or even superior to MSCT even though some variability exists among the different CBCT systems in depicting delicate structures. Considering the low radiation dose and high-resolution imaging, CBCT could be beneficial for dentomaxillofacial radiology.
Cone beam computed tomography (CBCT) has become an extremely useful technique for dentomaxillofacial imaging because it provides clear images of highly contrasted structures. Previous studies evaluating the applicability of this technique in otologic imaging were very encouraging but were only performed in vitro on temporal bone specimens. The intracochlear positioning of the individual electrodes after cochlear implantation by means of CBCT has not yet been shown in vivo.
We describe a protocol for in vivo postoperative imaging of cochlear implants by CBCT. Moreover, the effective dose was measured and compared with the effective dose used on 4- and 16-slice multislice computed tomography (MSCT) by using a RANDO-phantom.
Developing a protocol for in vivo postoperative imaging of cochlear implants by CBCT.
CBCT provides high-resolution and almost artifact-free multiplanar reconstruction images allowing assessment of the precise intracochlear position of the electrode and visualization of each of the individual contacts. The calculated effective dose of the used CBCT and MSCT acquisitions is 80 musv for the CBCT, 3,600 musv for the 16-slice computed tomography, and 4,800 musv for the 4-slice computed tomography.
These preliminary results suggests that, for in vivo postoperative evaluation of cochlear implants, CBCT can provide at least the same information as conventional radiography, digital radiograph, and MSCT but in a more comfortable and a much more safer way.
Because of high resolution and the relatively lower costs in comparison with modern helical CT scanners, digital volume tomography (DVT) can be recommended in the diagnosis of the nasal cavity and paranasal sinuses.
DVT is an advancement of panoramic tomography and is based on the principles of rotational tomography. It enables high resolution visualization of osseous structures. The slices can be displayed in three orthogonal planes that can be changed in angle arbitrarily. Data volumes of up to 12×17 cm can be examined with a new generation of the DVT. The aim of this study was to point out the potential of DVT in the anterior skull base.
DVT scans with a cylindrical size of 10 cm in diameter and 10 cm in height were performed in 23 patients. The identification of surgical key landmarks (uncinate process, middle turbinate, ethmoidal bulla, agger nasi cells, Haller cells, frontal recess, anterior ethmoidal artery in its relationship to the skull base, the cribiform plate of the sphenoidal sinus in relation to the optic nerve, and the internal carotid artery) was evaluated.
Display of the essential surgical key landmarks was possible in all patients.
To propose a nondestructive method for three-dimensional analysis of inner ear morphology after cochlear implantation for isolated petrous bones.
After implantation of cochlear implant electrode arrays, fresh temporal bones were investigated on a new C-arm-based radiographic device permitting the generation of cross-sectional images and of three-dimensional models from multiple two-dimensional radiographic images taken under different projections (cone-beam computed tomography). Cross-sectional images and multiplanar reformations with a slice thickness of 0.15 mm were acquired. The relationship of the electrode to the modiolus was analyzed (distance between electrode and the modiolus; position of the electrode inside the tympanic or vestibular scale). Histologic preparation was used as a gold standard.
In all cases, cone-beam computed tomography gave similar information concerning the position of the electrode compared with histologic analysis (tympanic scale versus vestibular scale, proximity versus distance to the modiolus). Perforation of the electrode from the tympanic to the vestibular scale could be assessed three-dimensionally in the cross-sectional images. In contrast to histology, cross-sectional imaging based on radiography is performed in less than 10 minutes and needs no preparation of the object. Because it is nondestructive, it can be repeated and used as a control after position-correcting maneuvers.
Cross-sectional imaging based on radiography is a valuable tool for the analysis of the electrode-modiolus relationship after cochlear implantation in isolated temporal bones, which may confirm histologic analysis.
The purpose of this study was to evaluate the feasibility and usability of different radiologic methods (single-slice computed tomography (CT), multi-slice CT and rotational tomography (RT)) for assessment of the position of cochlear implant electrodes. Cochlear implants in an isolated human temporal bone and in a complete formalin-fixed cadaver head were examined and the electrode position was determined. Subsequently, the labyrinth bone was isolated out of the cadaver head and histologically examined to compare the results of histology with imaging. Single-slice CT reliably identifies the electrode inside the human cochlea; however, due to the technically based large electrode artifact its position inside the cochlear spaces (e.g. electrode position in scala tympani or scala vestibuli) cannot be detected. Multi-slice CT of the cadaver head also showed artifacts that complicate the assessment of electrode position. Using RT the electrode artifact is small and therefore the electrode position within the cochlear spaces, scala tympani versus scala vestibuli, can be assessed. This technique was also applicable in a complete cadaver head, which is in contrast with former studies. In conclusion, CT allows the identification of electrode arrays inside the human cochlea. Multi-slice CT permits a much more precise depiction of the electrode inside the cochlea. RT alone has minimized electrode artifacts to a high extent and permits the assessment of the electrode position within the scala tympani or scala vestibuli. As RT was performed successfully in a complete cadaver head, further studies for evaluation of the intracochlear electrode position can now be performed in patients.
Subtle bony structures, small canals and fine sutures cause sometimes problems in the analysis of CTs of the temporal bone. The aim of this study was: to analyze the visibility of subtle structures and to estimate the incidence of vascular anomalies.
We retrospectively analyzed axial scans of 223 high-resolution CTs of the temporal bone obtained as single slice or spiral CT with 1mm slice thickness. All CTs had clinical indications. Two experienced radiologists studied CTs regarding the visibility of the fine sutures, fissures and small canals and the occurrence of vascular anomalies.
The following structures were seen commonly: sphenosquamosal suture (76%), arcuate artery canal (93%), vestibular aqueduct (89%), mastoid emissary vein (82%), singular canal (56%). Not so commonly were observed: tympanosquamosal suture (31%), mastoid canaliculus (28%), lateral sigmoid sinus (28%), petrotympanic fissure (24%), tympanomastoid suture (10%). Seldom we identified: the inferior tympanic canaliculus (6%), high jugular bulb (6%), anterior sigmoid sinus (5%), dehiscent internal carotid artery canal (2%), persistent petrosquamosal sinus (1%), dehiscent jugular bulb (1%). Persistent stapedial artery, aberrant internal carotid artery, dehiscent jugular bulb, high jugular bulb with diverticulum, anterior and dehiscent sigmoid sinus were detected in below 1% of the analyzed temporal bones. The frequency of asymmetry of the jugular foramen, which varied between 3% and 42%, depended on different criterions of size.
A profound knowledge of normal anatomy and anomalies of the temporal bone avoids misinterpretation as pathological lesions and iatrogenic bleedings.
We evaluated the clinical applicability and the value of digital volume tomography for visualization of the lateral skull base using temporal bone specimens.
Twelve temporal bone specimens were used to evaluate digital volume tomography on the lateral skull base. Aside from the initial examination of the temporal bones, radiologic control examinations were performed after insertion of titanium, gold, and platinum middle-ear implants and a cochlear implant.
With high-resolution and almost artifact-free visualization of alloplastic middle-ear implants of titanium, gold, or platinum, it was possible to define the smallest bone structures or position of the prosthesis with high precision. Furthermore, the examination proved that digital volume tomography is useful in assessing the normal position of a cochlear implant.
Digital volume tomography expands the application of diagnostic possibilities in the lateral skull base. Therefore, we believe improved preoperative diagnosis can be achieved along with more accurate planning of the surgical procedure. Digital volume tomography delivers a small radiation dose and a high resolution coupled with a low purchase price for the equipment.
The aim of this study was to examine beam hardening artefacts of the NewTom 9000 cone-beam computed tomography (CBCT) device compared with the Philips MX 8000 (4-row multidetector CT (MDCT)).
We modified a SawBone skull to become a standardized model for our study. The skull was used for scans with the NewTom 9000 CBCT device and a standard dental multi-detector CT (MDCT) at a comparable reconstruction resolution with a standard Straumann ITI 4.1 mm implant in four implant positions in the maxilla (first permanent premolar in the right maxilla region, second permanent molar in the right maxilla region, first permanent premolar in the left maxilla region and second permanent molar in the left maxilla region). Results were compared with construction data of the dental implant. An image quality assessment of the images from both devices was performed with four experienced physicians and statistically analysed with the two-tailed Wilcoxon test.
Scans with the NewTom 9000 CBCT showed strong beam hardening artefacts in the form of a radiation beam shadow in all reconstructions compared with the MDCT. These imaging artefacts became stronger with greater distance from the centre of the scanned volume. These differences in the imaging quality were proved as significant in a quality evaluation by four experienced physicians (P<0.05).
Visual spatial resolution of the NewTom 9000 CBCT was less accurate than the Philips MX 8000 MDCT in the imaging of metallic dental implants.
To compare the accuracy of cone-beam computerized tomography (CBCT) and multislice CT (MSCT) for linear jaw bone measurements.
An ex vivo formalin-fixed human maxilla was imaged with both CBCT (Accuitomo 3D; Morita, Kyoto, Japan) and MSCT (4-slice Somatom VolumeZoom and 16-slice Somatom Sensation 16; Siemens, Erlangen, Germany). The MSCT images were reconstructed using different reconstruction filters to optimize bone visualization (U70u and U90u for VolumeZoom, H30s and H60s for Sensation 16). Before scanning, triplets of small gutta-percha markers were glued onto the soft tissues overlying the maxillary bone on the top and on both sides of the alveolar ridge to define a set of reproducible linear measurements in 11 planes. Image measurements were performed by 2 observers. The gold standard was determined by means of physical measurements with a caliper by 3 observers.
The accuracy of the linear measurements was 0.35 +/- 1.31 mm (U70u) and 0.06 +/- 1.23 mm (U90u) for the Somatom VolumeZoom, 0.24 +/- 1.20 mm (H60s) and 0.54 +/- 1.14 mm (H30s) for the Sensation 16, and -0.09 +/- 1.64 mm for the Accuitomo 3D. Statistical analysis with 2-way analysis of variance showed no significant inter- or intraobserver disagreement for the physical or the radiologic measurements. There was also no significant difference for the measurements on the different reconstruction filters.
Both CBCT and MSCT yield submillimeter accuracy for linear measurements on an ex vivo specimen.
To evaluate and compare the image validity of a cone beam CT machine for dental use (3DX) and the latest medical CT system, multidetector row helical CT (MDCT).
A dried right maxilla of an Asian adult was used as a phantom. It was cut from the zygomatic process towards the midline, parallel to the midline plane, into eight slices of 2 mm thickness. This phantom was imaged with the 3DX and MDCT machines. Images were evaluated by comparing them with one selected bone slice from the phantom. In this comparison, two types of MDCT images were used: one with the window level (WL) and window width (WW) suitable for observing teeth (MDCT tooth image), and the other appropriate for observing bone (MDCT bone image). Three dentists and one radiographer then used our reported subjective five-level scale to evaluate and compare images generated by the two systems in terms of validity. Cancellous bone as well as enamel, dentin, pulp cavity, periodontal ligament space, lamina dura and overall impression were evaluated.
Statistically significant differences (P<0.05) were found for almost all observation items. Our subjective evaluation clarified that 3DX was superior to MDCT in terms of image validity. Few significant intra- or interevaluator errors were found.
Our subjective evaluation of image validity clarified 3DX as being superior to MDCT. Taken together with the low skin dose we previously reported for 3DX, the results demonstrate 3DX to be beneficial for imaging diagnosis of hard tissues in the maxillofacial region.
Rotational tomography in cochlear implant patients: a new tool for quality control of the electrode position
- A Aschendorff
- R Kubalek
- A Bink
- Aschendorff
In vivo measures of cochlear length and insertion depth of nucleus cochlear implant electrode arrays
- D R Ketten
- M W Skinner
- G Wang
- Ketten
Comparative localized linear accuracy of small-field cone-beam CT and multislice CT for alveolar bone measurements. Oral Surg Oral Med Oral Pathol Oral Radiol Endod
- M Loubele
- N Van Assche
- K Carpentier
- Loubele
Temporal bone imaging using digital volume tomography and computed tomography: a comparative cadaveric radiological study
- A Teymoortash
- S Hamzei
- T Murthum
- Teymoortash
Flat panel CT following stapes prosthesis insertion: an experimental and clinical study
- K Zaoui
- J Kromeier
- M Neudert
- Zaoui
Digitale Volumen Tomografie (DVT) und Mehrschicht-Spiral-CT (MSCT): eine objektive Untersuchung von Dosis und Bildqualität
- Y Kyriakou
- D Kolditz
- O Langner
- Kyriakou