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Die Cone-Beam-Computertomographie in der Diagnostik der Skaphoidfraktur
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BACKGROUND About 2 000 patients annually incur a fractured scaphoid in Norway. Assessment and diagnosis can be difficult, and fractures are overlooked. Scaphoid fractures have traditionally been cast-immobilised, but for the last decade screw fixing has been used
increasingly, and offers hope of a higher healing frequency and improved function. Some scaphoid fractures are not diagnosed in the acute phase and some do not heal after treatment. Patients may then end up with painful pseudarthrosis. The purpose of this article is to provide an overview of the assessment, treatment and outcomes of scaphoid fractures.
METHOD The article is based on literature searches in PubMed and the authors' own clinical
experience.
RESULTS Primary diagnosis of scaphoid fractures and subsequent plaster cast immobilisation yield very good clinical results. Surgery should be limited to displaced fractures, fractures forming part of more extensive wrist injuries and exceptional other cases. Results comparable a quality equivalent to cast immobilisation are achieved by experienced surgeons in this area. Untreated scaphoid fractures often result in painful pseudarthrosis with subsequent abnormal
position of the carpal bones and secondary arthrosis. This outcome can be counteracted by surgery on old fractures with bone grafting, internal fixation and cast immobilisation.
INTERPRETATION Norwegian procedures for treating scaphoid
fractures/pseudarthrosis are consistent with internationally documented good practice. Assessment of wrist pain following falls can be improved by conducting clinical tests for scaphoid fracture and radiology with four wrist projections. In the event of clinical suspicion, but no X-ray findings, the patient should be referred for a CT or MRI scan.
Objective
Evaluate the diagnostic value of cone beam computed tomography (CBCT) for scaphoid and wrist fractures that are missed on standard radiographs.
Materials and methods
Between September 2014 and October 2015, we prospectively enrolled 49 patients with a clinically suspected scaphoid fracture following an acute injury but had normal radiographs. Each patients underwent radiographs, CBCT and (magnetic resonance imaging) MRI within 7 days of the initial injury event. Both exam were evaluated independently by two radiologists.
Results
For scaphoid cortical fractures CBCT sensitivity is 100% (95% CI: 75%–100%), specificity 97% (95% CI: 83%–100%). CBCT diagnosed all 24 corticals wrist fractures, corresponding to a sensitivity of 100% (95% CI: 83%–100%), specificity of 95% (95% CI: 75%–100%). Kappa agreement rate between the two radiologists was K = 0.95 (95% CI: 0.85–1) for scaphoid fractures and K = 0.87 (95% CI: 0.73–1) for wrist fractures.
Conclusions
CBCT is superior to radiographs for diagnosing occult cortical fractures. Because of its low radiation dose, we believe that CBCT can be used in current practice as a replacement or supplement to radiographs to detect these fractures and optimize the cost-effectiveness ratio by limiting the number of needless immobilizations.
Objective:
To evaluate the effect of cone-beam computed tomography (CBCT) image acquisition protocols on image quality, lesion detection, delineation, and patient dose.
Methods:
100-patients and a CTDI phantom combined with an electron density phantom were examined using four different CBCT-image acquisition protocols during image-guided transarterial chemoembolization (TACE). Protocol-1 (time: 6s, tube rotation: 360°), protocol-2 (5s, 300°), protocol-3 (4s, 240°) and protocol-4 (3s, 180°) were used. The protocols were first investigated using a phantom. The protocols that were found to be clinically appropriate in terms of image quality and radiation dose were then assessed on patients. A higher radiation dose and/or a poor image quality were inappropriate for the patient imaging. Patient dose (patient-entrance dose and dose-area product), image quality (Hounsfield Unit, noise, signal-to-noise ratio and contrast-to-noise ratio), and lesion delineation (tumor-liver contrast) were assessed and compared using appropriate statistical tests. Lesion detectability, sensitivity, and predictive values were estimated for CBCT-image data using pre-treatment patient magnetic resonance imaging.
Results:
The estimated patient dose showed no statistical significance (p>0.05) between protocols-2 and -3; the assessed image quality between these protocols manifested insignificant difference (p>0.05). Two other phantom protocols were not considered for patient imaging due to significantly higher dose (protocols-1) and poor image quality (protocol-4). Lesion delineation and detection were insignificant (p>0.05) between protocols-2 and -3. Lesion sensitivities generated were 81-89% (protocol-2) and 81-85% (protocol-3) for different lesion types.
Conclusion:
Data acquisition using protocols-2 and -3 provided good image quality, lesion detection and delineation with acceptable patient dose during CBCT-imaging mainly due to similar frame numbers acquired.
Purpose
To compare the diagnostic accuracy of radiography, to radiography equivalent dose multidetector computed tomography (RED-MDCT) and to radiography equivalent dose cone beam computed tomography (RED-CBCT) for wrist fractures.
Methods
As study subjects we obtained 10 cadaveric human hands from body donors. Distal radius, distal ulna and carpal bones (n = 100) were artificially fractured in random order in a controlled experimental setting. We performed radiation dose equivalent radiography (settings as in standard clinical care), RED-MDCT in a 320 row MDCT with single shot mode and RED-CBCT in a device dedicated to musculoskeletal imaging. Three raters independently evaluated the resulting images for fractures and the level of confidence for each finding. Gold standard was evaluated by consensus reading of a high-dose MDCT.
Results
Pooled sensitivity was higher in RED-MDCT with 0.89 and RED-MDCT with 0.81 compared to radiography with 0.54 (P = < .004). No significant differences were detected concerning the modalities’ specificities (with values between P = .98). Raters' confidence was higher in RED-MDCT and RED-CBCT compared to radiography (P < .001).
Conclusion
The diagnostic accuracy of RED-MDCT and RED-CBCT for wrist fractures proved to be similar and in some parts even higher compared to radiography. Readers are more confident in their reporting with the cross sectional modalities. Dose equivalent cross sectional computed tomography of the wrist could replace plain radiography for fracture diagnosis in the long run.
Purpose:
The best diagnostic modality for confirmation of the diagnosis of a scaphoid fracture that is not visible on the initial radiograph (occult scaphoid fracture) is still subject of debate. The aim of this study was to compare the accuracy of magnetic resonance imaging (MRI), computed tomography (CT) and bone scintigraphy (BS) for the diagnosis of these occult scaphoid fractures.
Patients and methods:
In a study period of 12 months, 33 consecutive patients with a clinically suspected scaphoid fracture without a fracture on the scaphoid radiographs were evaluated with MRI, CT and BS. In case of a discrepancy between the diagnostic modalities, the final diagnosis was based on standardised follow-up with clinical examination and a repeated radiograph.
Results:
Three of the 33 patients had a scaphoid fracture. MRI missed one scaphoid fracture and did not over-diagnose. CT missed two scaphoid fractures and did not over-diagnose. BS missed no scaphoid fractures and over-diagnosed one scaphoid fracture in a patient with a fracture of the trapezium.
Conclusion:
This study shows that neither MRI, nor CT and BS are 100 % accurate in diagnosing occult scaphoid fractures. MRI and CT miss fractures, and BS tends to over-diagnose. The specific advantages and limitations of each diagnostic modality should be familiar to the treating physicians and taken into consideration during the diagnostic process.
To determine the diagnostic accuracy and radiation dose of conventional radiography and multidetector computed tomography (MDCT) in suspected scaphoid fractures.
One hundred twenty-four consecutive patients were enrolled in our study who had suffered from a wrist trauma and showed typical clinical symptoms suspicious of an acute scaphoid fracture. All patients had initially undergone conventional radiography. Subsequent MDCT was performed within 10 d because of persisting clinical symptoms. Using the MDCT data as the reference standard, a fourfold table was used to classify the test results. The effective dose and impaired energy were assessed in order to compare the radiation burden of the two techniques. The Wilcoxon test was performed to compare the two diagnostic modalities.
Conventional radiography showed 34 acute fractures of the scaphoid in 124 patients (42.2%). Subsequent MDCT revealed a total of 42 scaphoid fractures. The sensitivity of conventional radiography for scaphoid fracture detection was 42.8% and its specificity was 80% resulting in an overall accuracy of 59.6%. Conventional radiography was significantly inferior to MDCT (P < 0.01) concerning scaphoid fracture detection. The mean effective dose of MDCT was 0.1 mSv compared to 0.002 mSv of conventional radiography.
Conventional radiography is insufficient for accurate scaphoid fracture detection. Regarding the almost negligible effective dose, MDCT should serve as the first imaging modality in wrist trauma.
Cone-beam computed tomography (CBCT) is a relatively new technique for imaging of extremities. It provides high-resolution images with lower effective dose compared to conventional CT. However following the ALARA principle, CBCT-imaging protocols and practices must also be optimised to minimize the dose absorbed by the patient as well as personnel. The aim of this study is to evaluate the effect of a novel scanner-attached radiation shield on the dose absorbed by the patient and on the amount of scattered radiation around the scanner.
The objective of this study was to assess and compare the organ and effective doses in the knee area resulting from different commercially available multislice computed tomography devices (MSCT), one cone beam computed tomography device (CBCT) and one conventional X-ray radiography device using MOSFET dosemeters and an anthropomorphic RANDO knee phantom. Measurements of the MSCT devices resulted in effective doses ranging between 27 and 48 µSv. The CBCT measurements resulted in an effective dose of 12.6 µSv. The effective doses attained using the conventional radiography device were 1.8 µSv for lateral and 1.2 µSv for anterior-posterior projections. The effective dose resulting from conventional radiography was considerably lower than those recorded for the CBCT and MSCT devices. The MSCT effective dose results were two to four times higher than those measured on the CBCT device. This study demonstrates that CBCT can be regarded as a potential low-dose 3D imaging technique for knee examinations.
Objectives:
Evaluation and reduction of dose are important issues. Since cone beam CT (CBCT) has been established now not just in dentistry, the number of acquired examinations continues to rise. Unfortunately, it is very difficult to compare the doses of available devices on the market owing to different exposition parameters, volumes and geometries. The aim of this study was to evaluate the spans of effective doses (EDs) of ten different CBCT devices.
Methods:
48 thermoluminescent dosemeters were placed in 24 sites in a RANDO(®) head phantom. Protocols with lowest exposition parameters and protocols with highest exposition parameters were performed for each of the ten devices. The ED was calculated from the measured energy doses according to the International Commission on Radiological Protection 2007 recommendations for each protocol and device, and the statistical values were evaluated afterwards.
Results:
The calculation of the ED resulted in values between 17.2 µSv and 396 µSv for the ten devices. The mean values for protocols with lowest and highest exposition parameters were 31.6 µSv and 209 µSv, respectively.
Conclusions:
It was not the aim of this study to evaluate the image quality depending on different exposition parameters but to define the spans of EDs in which different CBCT devices work. There is a wide span of ED for different CBCT devices depending on the selected exposition parameters, required spatial resolution and many other factors.
The fractured scaphoid remains challenging with regard to diagnosis and treatment. Nowadays we still notice quite a huge number of complications like nonunion or even late stages with carpal collapse. Therefore we need precise diagnostics in case of suspected fractures. Initially standardized radiographs and additionally a computed tomograph (CT) longitudinal to the axis of the scaphoid should be done. The CT allows to diagnose or exclude occult fractures and to assess fractures concerning dislocation and stability. Waist fractures with dislocation as well as all fractures at the proximal third should be fixed as they demonstrate decreased healing rates. Waist fractures without dislocation might be treated conservatively in an upper arm cast. If early mobilisation is needed they can be fixed minimal invasively. Fracture in the distal part can be treated conservatively and only in case of severe dislocation they should be fixed.
Artefacts are common in today's cone beam CT (CBCT). They are induced by discrepancies between the mathematical modelling and the actual physical imaging process. Since artefacts may interfere with the diagnostic process performed on CBCT data sets, every user should be aware of their presence. This article aims to discuss the most prominent artefacts identified in the scientific literature and review the existing knowledge on these artefacts. We also briefly review the basic three-dimensional (3D) reconstruction concept applied by today's CBCT scanners, as all artefacts are more or less directly related to it.
The aim of this prospective study was to evaluate the diagnostic accuracy of multidetector computed tomography (MDCT) in detecting occult scaphoid fractures.
A total of 54 patients with a clinically suspected scaphoid fracture and negative initial conventional radiographs were evaluated with 64-row MDCT wrist examinations within 1 week of the trauma. The gold standard used was the diagnosis on MRI done within 1 week after MDCT. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MDCT were calculated.
MRI showed a total of 22 fractures in 20 of 55 (36%) wrists. Fractures included 14 scaphoid and 8 other carpal bones. MDCT showed a total of 19 fractures in 17 of 55 (30%) wrists. Two isolated scaphoid fractures and one trapezium fracture were missed on MDCT. The sensitivity, specificity, PPV, and NPV of MDCT were 86%, 100%, 100%, and 91%, respectively.
MDCT offers highly accurate results, especially concerning cortical involvement, and is a useful alternative in facilities lacking MRI.
To compare the diagnostic accuracy and radiation exposure of cone beam computed tomography (CBCT) and multislice computed tomography (MSCT) in the evaluation of finger fractures.
In a 3-year period, 57 consecutive patients with post-traumatic fractures of the metacarpal-phalangeal (MCP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints with involvement of the articular surface were studied by means of CBCT and MSCT. Student's t test was used to compare CBCT and MSCT accuracy in evaluating the percentage of joint surface involvement and in detecting bone fragments. The average tissue-absorbed doses of CBCT and MSCT were also compared. A value of p < 0.05 was considered statistically significant. Inter-observer agreement was calculated.
In all cases, CBCT allowed the percentage of articular involvement to be correctly depicted compared with MSCT, showing 100% sensitivity and specificity (p < 0.001). A total of 103 bone fragments were depicted on MSCT (mean 3.8 per patient, range 1-23). CBCT indicated 92 out of 103 fragments (89.3%) compared with MSCT (mean diameter of missed fragments 0.9 mm, range 0.6-1.3 mm), with no statistically significant difference between CBCT and MSCT (p < 0.025). Multislice CT radiation exposure was significantly higher than that of CBCT (0.18 mSv vs 0.06 mSv, p < 0.0025). Inter-observer agreement was good (overall κ = 0.89-0.96).
Cone beam CT may be considered a valuable imaging tool in the preoperative assessment of finger fractures, when MSCT is not available.
We evaluated 100 consecutive patients with a suspected scaphoid fracture but without evidence of a fracture on plain radiographs using MRI within 24 hours of injury, and bone scintigraphy three to five days after injury. The reference standard for a true radiologically-occult scaphoid fracture was either a diagnosis of fracture on both MRI and bone scintigraphy, or, in the case of discrepancy, clinical and/or radiological evidence of a fracture.
MRI revealed 16 scaphoid and 24 other fractures. Bone scintigraphy showed 28 scaphoid and 40 other fractures. According to the reference standard there were 20 scaphoid fractures. MRI was falsely negative for scaphoid fracture in four patients and bone scintigraphy falsely positive in eight. MRI had a sensitivity of 80% and a specificity of 100%. Bone scintigraphy had a sensitivity of 100% and a specificity of 90%.
This study did not confirm that early, short-sequence MRI was superior to bone scintigraphy for the diagnosis of a suspected scaphoid fracture. Bone scintigraphy remains a highly sensitive and reasonably specific investigation for the diagnosis of an occult scaphoid fracture.
Twenty observers reported independently on the presence or absence of a fracture of the scaphoid on 60 sets of radiographs; these included initial and 2- to 3-week views in patients in whom the outcome was known, normal scaphoids and random copies of these. Analysis of variance of the accuracy of observations revealed that the 2- to 3-week radiographs did not improve diagnostic ability and that this was independent of the experience or seniority of the observer. For normal radiographs, 20% of the observations reported a fracture. Reproducibility of opinion improved with experience but this did not help with accuracy. Radiographs without accurate clinical observation should not determine the management of the suspected scaphoid fracture.
Up to 30 % of acute scaphoid fractures are missed in conventional radiography. CT and MRI should be early performed in the diagnostic workflow, when radiograms (dorsopalmar, lateral and Stecher’s views) are negative or inconclusive in fracture detection. Significance of CT is different from that of MRI: Sensitivity of CT imaging (85 to 95 %) is superior to conventional radiography (about 70 %), but inferior to MRI (almost 100 %). However, CT (specificity 95 to 100 %) is able to provide more detailed anatomic information of the fracture pattern when compared to MRI (specificity 80 to 90 %). Particularly, differentiation of bone contusion (“bone bruise”) and non-displaced fracture can be difficult in MRI. Thus, CT indication is not only given for fracture detection, but also for assessing the morphology in scaphoid fractures (localization, fragment dislocation, comminuted zones) and the fragment instability, too. MRI should be limited to equivocal trauma cases presenting pain in the snuff box, but with inconclusive CT findings. In CT and MRI of scaphoid fractures, image display must be aligned along the longitudinal extension of the scaphoid, either by acquiring or reformatting oblique-sagittal and oblique-coronal planes.
Key points
• Radiography can be limited to the dorsopalmar, lateral and Stecher’s views in scaphoid fractures.
• In CT and MR imaging, the dedicated anatomy of the scaphoid has to be covered with oblique-sagittal and oblique-coronal images.
• CT provides most detailed information of scaphoid fractures (localization, fragment dislocation and instability pattern). However, its capability in detecting non-displaced fractures is inferior to MRI.
• All scaphoid fractures are seen in MRI. But differentiation of bone contusion (bone bruise) and a non-displaced fracture can be crucial.
• This order is recommended in the diagnostic algorithm of scaphoid fractures: 1. radiography, 2. CT, and 3. MRI.
Citation Format:
• Schmitt R, Rosenthal H. Imaging of Scaphoid Fractures According to the New S3 Guidelines. Fortschr Röntgenstr 2016; 188: 459 – 469
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.
Objective
To compare image quality and diagnostic validity of CBCT and MSCT for distal radius fractures. Methods35 CBCT and 33 MSCT scans were retrospectively reviewed with a visual grading scale regarding the depiction of cortical bone, trabecular bone, articular surfaces, and soft tissue. The extent and type of artefacts was analyzed. Agreement on AO classification and measurement of cortical disruption and length of the fracture gap was determined. Fracture reduction was evaluated in post-treatment x-rays. Statistical analysis was performed with visual grading characteristics (VGC), chi square tests, and Kendall’s coefficient of concordance. ResultsCBCT performed significantly worse for cortical bone, articular surfaces, and especially soft tissue. Trabecular bone showed no significant difference. Significantly more CBCT images showed artefacts. Physics-based artefacts were the most common. CBCT scans also showed motion artefacts. There was no significant difference in agreement on AO classification. The agreement on measurements was substantial for both modalities. Slightly more fractures that had undergone MSCT imaging showed adequate reduction. Conclusion
This initial study of an orthopaedic extremity CBCT scanner showed that the image quality of a CBCT scanner remains inferior for most structures at standard settings. Diagnostic validity of both modalities for distal radius fractures seems similar. Key Points• Subjectively, CBCT remains inferior to MSCT in depicting most structures.• Similar diagnostic validity for CBCT and MSCT imaging of distal radius fractures.• CBCT is a possible alternative to MSCT in musculoskeletal imaging.• Visual grading characteristics (VGC) analysis proves useful in analyzing visual grading scales.
Purpose: Comparison of radiation dose of cone beam computed tomography (CBCT) and multidetector computed tomography (MDCT) in examinations of the hand. Materials and Methods: Dose calculations were carried out by means of Monte Carlo simulations in MDCT and CBCT. A corpse hand was examined in a 320-row MDCT scanner and a dedicated extremities CBCT scanner with standard protocols and multiple low-dose protocols. The image quality of the examinations was evaluated by 5 investigators using a Likert scale from 1 (very good) to 5 (very poor) regarding depiction of cortical bone, cancellous bone, joint surfaces, soft tissues and artifacts. For a sum of ratings of all structures < 50 a good overall image quality was expected. The studies with at least good overall image quality were compared with respect to the dose. Results: The dose of the standard examination was 13.21 (12.96 to 13.46 CI) mGy in MDCT and 7.15 (6.99 to 7.30 CI) mGy in CBCT. The lowest dose in a study with good overall image quality was 4.54 (4.43 to 4.64 CI) mGy in MDCT and 5.72 (5.59 to 5.85 CI) mGy in CBCT. Conclusion: Although the dose of the standard protocols in the CBCT is lower than in the MDCT, the MDCT can realize a good overall image quality at a lower dose than the CBCT. Dose optimization of CT examination protocols for the hand is useful in both modalities, the MDCT has an even greater potential for optimization. Key points: • Low dose examinations of the hand are feasible in CBCT and MDCT.• In default settings CBCT has a lower dose than MDCT.• MDCT enables a good image quality at a lower dose than CBCT. Citation Format: • Neubauer J, Neubauer C, Gerstmair A et al. Comparison of the Radiation Dose from Cone Beam Computed Tomography and Multidetector Computed Tomography in Examinations of the Hand. Fortschr Röntgenstr 2016; 188: 488 - 493.
© Georg Thieme Verlag KG Stuttgart · New York.
Background:
Scaphoid fractures are common but may be missed on initial radiographs. Advanced imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI) have improved diagnostic accuracy, but at an increased initial cost. The purpose of this study was to evaluate the cost-effectiveness of immediate advanced imaging for suspected occult scaphoid fractures.
Methods:
A decision analysis model was created to evaluate three diagnostic strategies for patients with concerning history and examination but negative radiographs: (1) empiric cast immobilization with orthopaedic follow-up and repeat radiography at two weeks post-injury, (2) immediate CT scanning, or (3) immediate MRI. Prevalence of occult scaphoid fracture, sensitivity and specificity of CT and MRI, and risks and outcomes of a missed fracture were derived from published clinical trials. Costs of imaging, lost worker productivity, and surgical costs of nonunion surgery were estimated on the basis of the literature.
Results:
Advanced imaging was dominant over empiric cast immobilization; advanced imaging had lower costs and its health outcomes were projected to be better than those of empiric cast immobilization. MRI was slightly more cost-effective than CT on the basis of the mean published diagnostic performance, but was highly sensitive to test performance characteristics. Advanced imaging would have to increase in cost to more than $2000 or decrease in sensitivity to <25% for CT or <32% for MRI for empiric cast immobilization to be cost-effective.
Conclusions:
Given its relatively low cost and high diagnostic accuracy, advanced imaging for suspected scaphoid fractures in the setting of negative radiographs represents a cost-effective strategy for reducing both costs and morbidity. The decision to use CT compared with MRI is a function of individual institutional costs and local test performance characteristics.
A dedicated extremity cone-beam computed tomography (CBCT) was introduced recently, rapidly becoming an attractive modality for extremity imaging. This study aimed at evaluating the effectiveness of a curtain shaped lead shielding in reducing the exposure of patients to scattered radiation in dedicated extremity CBCT.
A dedicated extremity CBCT scanner was used. The lead shielding curtain was 42 cm x 60 cm with 0.5 mm lead equivalent. Scattered radiation dose from CBCT was measured using thermoluminescence dosimetry chips at 20 points, at different distance and direction from CT gantry. Two sets of scattered radiation dose measurements were performed before and after installation of curtain-shaped lead shield, and percentage reduction in dose in air was calculated.
Mean radiation exposure dose at measured points was 34.46 ± 48.40 μGy without curtains, and 9.67 ± 4.53 μGy with curtains, exhibiting 71.94% reduction (p = 0.000). The use of lead shielding curtains significantly reduced scattered radiation at 0.5 m, 1.0 m, and 1.5 m from CT gantry, with percent reduction of 84.8%, 58.0% and 35.5%, respectively (p = 0.000, 0.000, 0.002). The percent reduction in the diagonal (+45°, -45°) and vertical forward (0°) directions were 86.3%, 83.1%, and 77.7%, respectively, and were statistically significant (p = 0.029, 0.020, 0.041).
Shielding with lead curtains suggests an easy and effective method for reducing patient exposure to radiation in extremity CBCT imaging. Advances in knowledge: Lead shielding curtains are an effective technique to reduce scattered radiation dose in dedicated extremity CBCT, with higher dose reduction closer to the gantry opening.
To compare the diagnostic value of cone-beam computed tomography (CBCT) and conventional radiography (CR) after acute small bone or joint trauma.
Between March 2013 and January 2014, 231 patients with recent small bone or joint trauma underwent CR and subsequent CBCT. CR and CBCT examinations were independently assessed by two readers, blinded to the result of the other modality. The total number of fractures as well as the number of complex fractures were compared, and inter- and intraobserver agreement for CBCT was calculated. In addition, radiation doses and evaluation times for both modalities were noted and statistically compared.
Fracture detection on CBCT increased by 35 % and 37 % for reader 1 and reader 2, respectively, and identification of complex fractures increased by 236 % and 185 %. Interobserver agreement for CBCT was almost perfect, as was intraobserver agreement for reader 1. The intraobserver agreement for reader 2 was substantial. Radiation doses and evaluation time were significantly higher for CBCT.
CBCT detects significantly more small bone and joint fractures, in particular complex fractures, than CR. In the majority of cases, the clinical implication of the additionally detected fractures is limited, but in some patients (e.g., fracture-dislocations), the management is significantly influenced by these findings. As the radiation dose for CBCT substantially exceeds that of CR, we suggest adhering to CR as the first-line examination after small bone and joint trauma and keeping CBCT for patients with clinical-radiographic discordance or suspected complex fractures in need of further (preoperative) assessment.
During the last decade, DVT (digital volume tomography) imaging has become a widely used standard technique in head and neck imaging. Lower radiation exposure compared to conventional computed tomography (MDCT) has been described. Recently, DVT has been developed as an extremity scanner and as such represents a new imaging technique for hand surgery. We here describe the first 24 months experience with this new imaging modality in hand and wrist imaging by presenting representative cases and by describing the technical background. Furthermore, the method's advantages and disadvantages are discussed with reference to the given literature.
© Georg Thieme Verlag KG Stuttgart · New York.
The aims of this study are to evaluate diagnostic performance of conventional radiographs for wrist fractures using multidetector computerized tomography (MDCT) as a reference standard, to determine prevalence, demographic risk factors including age and sex, and associations among various wrist fractures. A retrospective study was performed, finding a total 455 patients (457 wrists) who had wrist trauma and who had undergone a radiography and subsequent MDCT examination during a 45-month period. The MDCT and radiographs of the patients were reviewed by two radiologists, and a consensus was obtained for the presence of fracture. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of radiographs were calculated using MDCT findings as reference standard. The correlation of both age and sex between the presence of fracture was also analyzed. Of the 455 patients, 223 (49.0 %) had one or more fractures in wrist. A total of 302 (160 patients had one, 50 had two, 10 had three, and 3 had four) fractures were diagnosed in the wrist region. In 457 wrists, MDCT revealed 128 occult fractures missed by radiography. The overall sensitivity, specificity, PPV, and NPV of radiography for the detection of all wrist fractures were 57.8, 99.5, 87.4, and 97.4 %, respectively. The sensitivities of radiography ranged 0-41.2 % for other carpal bone except scaphoid (66 %) fractures and 66.7-80 % for the proximal metacarpus, distal ulna, and radius fractures. Wrist fractures appear to be overlooked on radiography. Further imaging should be warranted for patients who are clinically suspicious for wrist fracture in emergency rooms.
The aim of this study was to compare the image quality of a compact mobile flat-panel computed tomography (FPCT) capable of extremity imaging and a multidetector computed tomography (MDCT) in examinations with the same radiation dose.
Imaging with the FPCT was performed with default settings. Monte Carlo simulations were used to calculate equivalent dose settings for the 320-row MDCT. Simulations were based on and validated by dose measurements. Homogeneity, geometric distortion, artifacts, accuracy of Hounsfield values, contrast, and spatial resolution were evaluated in different imaging phantoms. Whitney-Mann U Test and Spearman ρ were used for statistical analysis.
Homogeneity reached 2.5% for the FPCT and 0.5% for the MDCT. Hounsfield values were more accurate and contrast to noise ratios were higher for the MDCT than the FPCT (P ≤ 0.001). The MDCT depicted more rod inserts than the FPCT did. No significant geometric distortion was detected in either modality. The FPCT was more prone to artifacts around Krischner wires with a diameter of 2 mm (P = 0.05-0.001), whereas the MDCT showed a higher amount of artifacts around wires with a diameter of 0.8 mm (P ≤ 0.001). Spatial resolution was 1 lp/mm (xy), 1.7 lp/mm (z) for the FPCT and 1 lp/mm (xy), less than 1 lp/mm (z) for the MDCT.
We compared a mobile FPCT and a 320-row MDCT by using the same radiation dose for scans. We found the spatial resolution to be higher in the FPCT. Hounsfield units were more accurate and homogeneity and contrast resolution were better in MDCT. The MDCT was also less prone to artifacts from thick Kirschner wires but showed comparably more artifacts around thin wires.
This paper reports on the design and initial imaging performance of a dedicated cone-beam CT (CBCT) system for musculoskeletal (MSK) extremities. The system complements conventional CT and MR and offers a variety of potential clinical and logistical advantages that are likely to be of benefit to diagnosis, treatment planning, and assessment of therapy response in MSK radiology, orthopaedic surgery, and rheumatology.
The scanner design incorporated a host of clinical requirements (e.g., ability to scan the weight-bearing knee in a natural stance) and was guided by theoretical and experimental analysis of image quality and dose. Such criteria identified the following basic scanner components and system configuration: a flat-panel detector (FPD, Varian 3030+, 0.194 mm pixels); and a low-power, fixed anode x-ray source with 0.5 mm focal spot (SourceRay XRS-125-7K-P, 0.875 kW) mounted on a retractable C-arm allowing for two scanning orientations with the capability for side entry, viz. a standing configuration for imaging of weight-bearing lower extremities and a sitting configuration for imaging of tensioned upper extremity and unloaded lower extremity. Theoretical modeling employed cascaded systems analysis of modulation transfer function (MTF) and detective quantum efficiency (DQE) computed as a function of system geometry, kVp and filtration, dose, source power, etc. Physical experimentation utilized an imaging bench simulating the scanner geometry for verification of theoretical results and investigation of other factors, such as antiscatter grid selection and 3D image quality in phantom and cadaver, including qualitative comparison to conventional CT.
Theoretical modeling and benchtop experimentation confirmed the basic suitability of the FPD and x-ray source mentioned above. Clinical requirements combined with analysis of MTF and DQE yielded the following system geometry: a -55 cm source-to-detector distance; 1.3 magnification; a 20 cm diameter bore (20 x 20 x 20 cm3 field of view); total acquisition arc of -240 degrees. The system MTF declines to 50% at -1.3 mm(-1) and to 10% at -2.7 mm(-1), consistent with sub-millimeter spatial resolution. Analysis of DQE suggested a nominal technique of 90 kVp (+0.3 mm Cu added filtration) to provide high imaging performance from -500 projections at less than -0.5 kW power, implying -6.4 mGy (0.064 mSv) for low-dose protocols and -15 mGy (0.15 mSv) for high-quality protocols. The experimental studies show improved image uniformity and contrast-to-noise ratio (without increase in dose) through incorporation of a custom 10:1 GR antiscatter grid. Cadaver images demonstrate exquisite bone detail, visualization of articular morphology, and soft-tissue visibility comparable to diagnostic CT (10-20 HU contrast resolution).
The results indicate that the proposed system will deliver volumetric images of the extremities with soft-tissue contrast resolution comparable to diagnostic CT and improved spatial resolution at potentially reduced dose. Cascaded systems analysis provided a useful basis for system design and optimization without costly repeated experimentation. A combined process of design specification, image quality analysis, clinical feedback, and revision yielded a prototype that is now awaiting clinical pilot studies. Potential advantages of the proposed system include reduced space and cost, imaging of load-bearing extremities, and combined volumetric imaging with real-time fluoroscopy and digital radiography.
To compare the effective dose levels of cone beam computed tomography (CBCT) for maxillofacial applications with those of multi-slice computed tomography (MSCT).
The effective doses of 3 CBCT scanners were estimated (Accuitomo 3D, i-CAT, and NewTom 3G) and compared to the dose levels for corresponding image acquisition protocols for 3 MSCT scanners (Somatom VolumeZoom 4, Somatom Sensation 16 and Mx8000 IDT). The effective dose was calculated using thermoluminescent dosimeters (TLDs), placed in a Rando Alderson phantom, and expressed according to the ICRP 103 (2007) guidelines (including a separate tissue weighting factor for the salivary glands, as opposed to former ICRP guidelines).
Effective dose values ranged from 13 to 82 microSv for CBCT and from 474 to 1160 microSv for MSCT. CBCT dose levels were the lowest for the Accuitomo 3D, and highest for the i-CAT.
Dose levels for CBCT imaging remained far below those of clinical MSCT protocols, even when a mandibular protocol was applied for the latter, resulting in a smaller field of view compared to various CBCT protocols. Considering this wide dose span, it is of outmost importance to justify the selection of each of the aforementioned techniques, and to optimise the radiation dose while achieving a sufficient image quality. When comparing these results to previous dosimetric studies, a conversion needs to be made using the latest ICRP recommendations.
This study assessed whether nonunion of displaced scaphoid waist fractures with nonoperative treatment could be predicted from 4 week CT scans. Thirty-one patients with unilateral displaced scaphoid waist fractures and adequate follow-up were included. CT scans in the longitudinal axis of the scaphoid with sagittal and coronal slices were done 4 weeks after the index injury. The effects of fracture gap, sclerosis and bone resorption on union were assessed. Fracture union was observed in all 13 displaced fractures with a < 2 mm gap, four of the seven with a gap of 2-3 mm and only four of the 11 with a gap > 3 mm (p = 0.01). Bone resorption involving more than 50% of the fracture cross-section was also associated with nonunion, but sclerosis was not.
There is no consensus on the optimum imaging method to use to confirm the diagnosis of true scaphoid fractures among patients with suspected scaphoid fractures. This study tested the null hypothesis that computed tomography (CT) and magnetic resonance imaging (MRI) have the same diagnostic performance characteristics for the diagnosis of scaphoid fractures.
Thirty-four consecutive patients with a suspected scaphoid fracture (tenderness of the scaphoid and normal radiographic findings after a fall on the outstretched hand) underwent CT and MRI within ten days after a wrist injury. The reference standard for a true fracture of the scaphoid was six-week follow-up radiographs in four views. A panel including surgeons and radiologists came to a consensus diagnosis for each type of imaging. The images were considered in a randomly ordered, blinded fashion, independent of the other types of imaging. We calculated sensitivity, specificity, and accuracy as well as positive and negative predictive values.
The reference standard revealed six true fractures of the scaphoid (prevalence, 18%). CT demonstrated a fracture in five patients (15%), with one false-positive, two false-negative, and four true-positive results. MRI demonstrated a fracture in seven patients (21%), with three false-positive, two false-negative, and four true-positive results. The sensitivity, specificity, and accuracy were 67%, 96%, and 91%, respectively, for CT and 67%, 89%, and 85%, respectively, for MRI. According to the McNemar test for paired binary data, these differences were not significant. The positive predictive value with use of the Bayes formula was 0.76 for CT and 0.54 for MRI. The negative predictive value was 0.94 for CT and 0.93 for MRI.
CT and MRI had comparable diagnostic characteristics. Both were better at excluding scaphoid fractures than they were at confirming them, and both were subject to false-positive and false-negative interpretations. The best reference standard is debatable, but it is now unclear whether or not bone edema on MRI and small unicortical lines on CT represent a true fracture.
This study examined whether multidetector computed tomography (CT) is superior to bone scintigraphy for diagnosis of an occult scaphoid fracture.
In a study period of 22 months, 100 consecutive patients with a clinically suspected scaphoid fracture and no fracture on scaphoid radiographs, were evaluated with CT within 24 hours after injury and bone scintigraphy between 3 and 5 days after injury. The reference standard for a true (radiographic occult) scaphoid fracture was either (1) diagnosis of fracture on both CT and bone scintigraphy or (2) in case of discrepancy, clinical and/or radiographic evidence of a fracture during follow-up.
CT showed 10 scaphoid and 18 other fractures. Bone scintigraphy showed 21 scaphoid and 36 other fractures. According to the reference standard, there were 14 scaphoid fractures. CT had a sensitivity of 64%, specificity of 99%, accuracy of 94%, a positive predictive value of 90%, and a negative predictive value of 94%. Bone scintigraphy had a sensitivity of 93%, specificity of 91%, accuracy of 91%, a positive predictive value of 62%, and a negative predictive value of 99%.
This study could not confirm that early CT imaging is superior to bone scintigraphy for suspected scaphoid fractures.
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.
Scaphoid fractures are the most common fractures of the carpus, accounting for 79% of all carpal fractures. Early diagnosis of scaphoid fractures is imperative owing to potential complications following the fracture, including non-union, avascular necrosis, carpal instability and osteoarthritis. Plain radiography remains the initial imaging modality to assess scaphoid fractures. Magnetic resonance imaging (MRI) is excellent in the detection of clinically suspected, but initially radiographically negative, scaphoid fractures. Cost-effectiveness analysis studies have demonstrated MRI is effective in this setting. Gadolinium enhanced MRI has been shown to be superior to unenhanced MRI in the detection of avascular necrosis. Computerized tomography scan is the preferred modality to assess the intricacies of scaphoid fracture, including fracture location and deformity, as well as union status. This review paper explores the recent advances in imaging of the scaphoid, with reference also to avascular necrosis and non-union following a scaphoid fracture.
Imaging protocols for suspected scaphoid fractures among investigators and hospitals are markedly inconsistent. We performed a systematic review and meta-analysis to assess and compare the diagnostic performance of bone scintigraphy, MRI, and CT for diagnosing suspected scaphoid fractures. Twenty-six studies were included. Sensitivity, specificity, and diagnostic odds ratio were pooled separately and summary receiver operating characteristic curves were fitted for each modality. Meta-regression analyses were performed to compare these modalities. We obtained likelihood ratios derived from the pooled sensitivity and specificity and, using Bayes’ theorem, calculated the posttest probability by application of the tests. The pooled sensitivity, specificity, natural logarithm of the diagnostic odds ratio, and the positive and negative likelihood ratios were, respectively, 97%, 89%, 4.78, 8.82, and 0.03 for bone scintigraphy; 96%, 99%, 6.60, 96, and 0.04 for MRI; and 93%, 99%, 6.11, 93, and 0.07 for CT. Bone scintigraphy and MRI have equally high sensitivity and high diagnostic value for excluding scaphoid fracture; however, MRI is more specific and better for confirming scaphoid fracture. We believe additional studies are needed to assess diagnostic performance of CT, especially paired design studies or randomized controlled trials to compare CT with MRI or bone scintigraphy.
Level of Evidence: Level III, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.
Computerized tomographic scans are routinely obtained to evaluate a number of musculoskeletal conditions. However, since computerized tomographic scans expose patients to the greatest amounts of radiation of all imaging modalities, the physician must be cognizant of the effective doses of radiation that are administered. This investigation was performed to quantify the effective doses of computerized tomographic scans that are performed for various musculoskeletal applications.
The digital imaging archive of a single institution was retrospectively reviewed to identify helical computerized tomographic scans that were completed to visualize the extremities or spine. Imaging parameters were recorded for each examination, and dosimetry calculator software was used to calculate the effective dose values according to a modified protocol derived from publication SR250 of the National Radiological Protection Board of the United Kingdom. Computerized tomographic scans of the chest, abdomen, and pelvis were also collected, and the effective doses were compared with those reported by prior groups in order to validate the results of the current study.
The mean effective doses for computerized tomographic scans of the chest, abdomen, and pelvis (5.27, 4.95, and 4.85 mSv, respectively) were consistent with those of previous investigations. The highest mean effective doses were recorded for studies evaluating the spine (4.36, 17.99, and 19.15 mSv for the cervical, thoracic, and lumbar spines, respectively). In the upper extremity, the effective dose of a computerized tomographic scan of the shoulder (2.06 mSv) was higher than those of the elbow (0.14 mSv) and wrist (0.03 mSv). Similarly, the effective dose of a hip scan (3.09 mSv) was significantly higher than those observed with knee (0.16 mSv) and ankle (0.07 mSv) scans.
Computerized tomographic scans of the axial and appendicular skeleton are associated with substantially elevated radiation exposures, but the effective dose declines substantially for anatomic structures that are further away from the torso.
In this work, a Monte Carlo code was constructed taking into account all the relevant photon interactions, including the multiple scattering and interference due to the liquid structure to calculate the secondary to primary ratio for large water samples in radiological conditions. The simulation results were compared to former results and some discrepancies were found mainly for low energies where the elastic scattering plays a major role.
This article on x-ray cone-beam CT (CBCT) acquisition provides an overview of the fundamental principles of operation of this technology and the influence of geometric and software parameters on image quality and patient radiation dose. Advantages of the CBCT system and a summary of the uses and limitations of the images produced are discussed. All current generations of CBCT systems provide useful diagnostic images. Future enhancements most likely will be directed toward reducing scan time; providing multimodal imaging; improving image fidelity, including soft tissue contrast; and incorporating task-specific protocols to minimize patient dose.
Radiographic wrist relationships are reviewed emphasizing the posteroanterior view, and analyzing the three normal arcs, principles of parallelism, and overlapping articular surfaces. Use of these concepts, which are not stressed in the literature, enables the radiographic interpreter to easily arrive at a definitive diagnosis and to detect and interpret subtle and complex abnormalities. Case material is included to emphasize major different diagnostic points.
The incidence, location, and type of scaphoid fractures found in a well-defined population is described. Fractures of the carpal scaphoid (n = 442) were identified during an eight-year period, of which 19 (5%) were nonunions. At the initial radiographic examination the fractures were visible on PA views in 70% of the cases (true lateral 10%, scaphoid view neutral 77%, scaphoid view ulnar deviated 73%, and scaphoid view with the X-ray tube tilted 30 degrees distally 71%). Among inhabitants living in the Odense Municipality (population at risk 170648 in 1983 to 174948 in 1989) 222 males and 51 females (age range 9-87 year) sustaining scaphoid fractures during a seven-year were period used for computation of incidences. During the survey, there was an average annual incidence of scaphoid fracture of 8 per 100000 females, and 38 per 100000 males. All patients (except a 9-year-old male) were aged 10 years or over. In the age-group 10-14 years there was an average annual incidence of 3 per 100000 females, and 39 per 100000 males. Average annual incidence per 100000 inhabitants of carpal scaphoid fractures according to the location was proximal 6, middle 15, and distal (fractures of the tuberosity included) 2. Average annual incidence per 100000 inhabitants of carpal scaphoid fractures according to type was transverse 7, horizontal oblique 9, vertical oblique 1, avulsion/fracture of the tuberosity 5, and not stated 1.
Since 1981, I treated 81 scaphoid fractures: 14 wrists (group A) with acute unstable fracture, 37 (B) with ununited fracture accompanied by dorsiflexed intercalated segment instability (DISI), and 30 (C) with ununited fracture without DISI. The methods and results were evaluated retrospectively. Bone union occurred in 100% of group A wrists, 92% of group B, and 90% of group C. By a modification of Cooney's clinical scoring chart, mean scores were 91 in group A, 84 in group B, and 87 in group C. In 43% of group A, a scapholunate gap remained after surgery. Of 21 wrists in group B treated by bone graft and screw fixation, union was not achieved in one; in another 13, the R-L angle was corrected to within 10 degrees of the unaffected side. In group C, DISI did not develop if bone union occurred. There was correlation between shortness of the scaphoid and DISI remaining. The clinical scores of wrists with and without DISI were not different, except for patients who did hard manual labor, in half of whom the score was poor when DISI remained. Cineradiography of ununited fractures was done before and after surgery. For three wrists in group B, plain X-ray films showed that DISI improved, but cineradiography showed that DISI was present; even without static DISI, there may be dynamic DISI. Treatment of acute unstable fractures of the scaphoid by reduction and internal fixation generally gave satisfactory results. Perhaps when ligament injury may have caused instability, ligament repair or reconstruction is needed. For ununited fractures with DISI, correction of the DISI was needed as well as bone union. If union occurred with the scaphoid shorter than normal, DISI was present, so restoration of the length of the scaphoid during surgery is mandatory.
To evaluate the reproducibility of the interpretation of radiographs for the diagnosis of scaphoid fractures, 134 radiographs (60 consecutive patients) were blindly observed by a resident radiologist, consultant radiologist, resident trauma surgeon and consultant trauma surgeon. The results of radiographs were analysed using kappa (kappa) statistics and stratified according to the results of the corresponding bone scan. In 23 patients the bone scan was positive for fracture of the scaphoid. Irrespective of training and experience, the kappa of the comparison of the scores of the radiographs between any two observers did not exceed 40 per cent. After stratification of the outcome of the bone scan, the kappa did not increase significantly. A panel of three experienced observers gave their opinion of all radiographs. The results were compared with the bone scan results. We conclude that radiographs in suspected scaphoid fracture cannot be used as a reliable diagnostic approach because of the low inter-observer agreement in the interpretation, irrespective of the experience and training of the observer.
Pain or tenderness in the anatomical snuff-box following trauma suggests an injury to the scaphoid or surrounding soft tissues. It is often difficult to make a definite diagnosis since normal bone markings across the scaphoid can be misinterpreted as a fracture. To clarify whether a fracture is present or not, an X-ray of the uninjured scaphoid is taken in a comparable position to the most suspicious view. If bone markings are similar on both views, then a fracture can be excluded. Conversely, if the bone markings differ, then suspicion of a fracture may be confirmed. In combination with the clinical features, a more accurate diagnosis can be made and unnecessary out-patient and X-ray reviews can be avoided.
Some scatter studies have previously been conducted using film as a detector. The serious limitations caused by the narrow latitude, the non-linear density response, and the required optical densitometric measurements of film can be avoided by computed radiography (CR) which provides linear numeric data over a wide dynamic range. The imaging plate is used as a large-area detector and the data is analyzed from the computer memory. Variation in the scatter-to-primary ratio within an image caused by absorption differences was simulated in a water-aluminum phantom. The measurement technique showed repeatable results, being comparable to the values expected on the basis of previous studies. A multiple pencil-beam (MPB) imaging device was also compared to a standard 1:12 grid by this technique. The maximal scatter-to-primary ratio in our model was up to 7.9 with no scatter reduction, 1.5 with grid, and 0.4 with the MPB device. The variation caused by the absorption of primary radiation was much less in the MPB modality, and the MPB system was also less sensitive to an increase in the used tube voltage from 60 to 120 kVp. The benefits of multiple pencil-beam imaging in scatter reduction are briefly discussed.
Degenerative arthritis of the wrist follows very specific patterns from onset to terminal severe bone and joint destruction. About 95% of them occur as periscaphoid area problems: SLAC (scapholunate advanced collapse pattern) wrist (55%), triscaphe arthritis (26%), and a combination of the two (14%). In SLAC wrist, the repeating sequence of degenerative change is based on and caused by articular alignment problems between the scaphoid and the radius. Changes then progress between the capitate and the lunate that are secondary to carpal collapse. In triscaphe arthritis, the degenerative change is limited to between the trapezium, trapezoid, and distal scaphoid. SLAC procedure (fusion of the capitate, lunate, hamate, and triquetrum along with silastic scaphoid implant) for SLAC wrists and triscaphe arthrodesis (fusion of the scaphoid, trapezium, and trapezoid) for triscaphe arthritis, are designed to make maximum use of undamaged structures and to maintain full-power, painless, mobile human wrists.
This article describes a technique in which X ray transmission readings are taken through the head at a multitude of angles: from these data, absorption values of the material contained within the head are calculated on a computer and presented as a series of pictures of slices of the cranium. The system is approximately 100 times more sensitive than conventional X ray systems to such an extent that variations in soft tissues of nearly similar density can be displayed.
The author reviews the anatomy of the transverse volar carpal ligament. The division of this ligament results in a decrease on the carpal concavity and the distance between the two crests can increase by 3 mm on the average.
A new and simple operative technique has been developed to provide rigid internal fixation for all types of fractures of the scaphoid. This involves the use of a double-threaded bone screw which provides such good fixation that, after operation, a plaster cast is rarely required and most patients are able to return to work within a few weeks. A classification of scaphoid fractures is proposed. The indications for operation included not only acute unstable fractures, but also fractures with delayed healing and those with established non-union; screw fixation was combined with bone grafting to treat non-union. In a prospective trial, 158 operations using this technique were carried out between 1977 and 1981. The rate of union was 100 per cent for acute fractures and 83 per cent overall. This method of treatment appears to offer significant advantages over conventional techniques in the management of the fractured scaphoid.