[show abstract][hide abstract] ABSTRACT: Our aim in this study was to determine an optimal delay time of hepatic arterial phase (HAP) imaging of hypervascular hepatocellular carcinomas (HCCs) in dynamic contrast-enhanced MDCT (DCE-CT) by use of the bolus-tracking method. The time-enhancement curves (TECs) of the aorta and the contrast of the hepatic arterial and portal system (APC) in the pharmacokinetic analysis were calculated. The clinical study included 41 patients with known or suspected HCC who underwent DCE-CT. The TECs of the aorta and the tumor-liver contrast (TLC) in the clinical study were calculated. On pharmacokinetic analysis, the peak aortic enhancement and the peak APC simulated under conditions of an injection duration of 30 s and an iodine load of 500 mg I/kg body weight were observed 18.5 and 22.5 s, respectively, after the trigger threshold (increased CT value 100 Hounsfield units), respectively. In the clinical study, the peak aortic enhancement and the peak TLC were observed 17.2 and 24.8 s after the trigger threshold, respectively. The optimal delay times until peak aortic enhancement and peak HAP were 15-17 and 19-21 s after the trigger threshold, respectively, under the following conditions: injection dose, 500 mg I/kg body weight; injection duration, 30 s; acquisition time, 5 s; and the trigger threshold. In addition, the peak TLC was achieved 4-7 s after the time to peak aortic enhancement.
Radiological Physics and Technology 01/2011; 4(1):43-52.
[show abstract][hide abstract] ABSTRACT: Misregistration errors occur at the periphery of the hepatic region due to respiratory- and interval-related changes in hepatic shape. To reduce these misregistration errors, we developed a temporal and dynamic subtraction technique to enhance small hepatocellular carcinoma (HCC) by using a 3D nonlinear image-warping technique. The study population consisted of 21 patients with HCC. We registered the present and previous arterial-phase CT images or the present nonenhanced and arterial-phase CT images obtained in the same position by 3D global-matching plus 3D nonlinear image-warping. Temporal subtraction images were obtained by subtraction of the previous arterial-phase CT image from the warped present arterial-phase CT image. Dynamic subtraction images were obtained by subtraction of the present nonenhanced CT image from the warped present arterial-phase CT image. When we used this new technique, the number of good or excellent cases increased from 14.2% (3/21 cases) to 71.4% (15/21 cases) on temporal subtraction images. With this technique, subjective rating scores for image quality improved in 57.1% of cases (12/21 cases) on temporal subtraction images and 81.0% of cases (17/21 cases) on dynamic subtraction images. The results indicated that the new subtraction images were greatly improved by use of the 3D nonlinear image-warping technique.
Radiological Physics and Technology 01/2011; 4(2):109-20.
[show abstract][hide abstract] ABSTRACT: To investigate the correlation between the peripheral hyperintense pattern of breast carcinoma on T2-weighted images (T2WI) and the early peripheral enhancement (EPE) on dynamic magnetic resonance imaging (MRI) and to examine the histological characteristics involved in the causes thereof.
The signal intensity of 131 breast carcinomas of common type on T2WI was classified into four types and the correlations between the signal intensity and the histopathological subtypes were evaluated. We investigated correlation with the peripheral hyperintense pattern on a T2WI and other findings on MR images including EPE. In addition, we also investigated the histopathological characteristics in the lesions with a peripheral hyperintense pattern.
The signal intensities of the lesions on T2WI demonstrated hyperintensity, isointensity, hypointensity, and a peripheral hyperintense pattern in 26 (20%), 66 (50%), 19 (15%), and 20 (15%) lesions, respectively. A peripheral hyperintense pattern correlated with the appearance of EPE (P < 0.0001) and the degree of central fibrosis (P < 0.0001).
A peripheral hyperintense pattern on T2WI is a characteristic finding observed in breast carcinomas and correlated with the appearance of EPE. The appearance of a peripheral hyperintense pattern was affected by various histopathological features in the same manner as that observed for the formation of EPE.
Journal of Magnetic Resonance Imaging 11/2010; 32(5):1117-23. · 2.57 Impact Factor
[show abstract][hide abstract] ABSTRACT: Magnetic resonance imaging (MRI) is useful in the quantitative evaluation of brain atrophy, because the superior contrast resolution facilitates separation of the gray and white matter. Quantitative assessment of brain atrophy has mainly been performed by manual measurement, which requires considerable time and effort to determine the brain volume. Therefore, computer-aided quantitative measurement methods for the diagnosis of brain atrophy are required. We have developed a method of segmenting the cerebrum, cerebellum-brainstem, and temporal lobe simultaneously on MR images obtained in a single sequence. It is important to measure the volume of not only these regions but also the frontal lobe in clinical use. However, for segmenting the frontal lobe, it is necessary to identify the Sylvian fissure and the central sulcus, which represent boundaries. Here, we developed a method of identifying the central sulcus from MR images obtained with a 1.5 T MRI scanner. The brain and the cerebrospinal fluid (CSF) regions were segmented using semiautomated segmentation method on MR images. The central sulcus shows an oblique line from the inside to the outside on the convexity view. The almost straight appearance of the central sulcus was used for segmentation of the central sulcus from the segmented CSF images. The central sulcus was identified with this technique in 77% of the images obtained by all sequences. This technique for identifying the central sulcus is very important not only for volumetry, but also for clinical diagnosis.
Radiological Physics and Technology 09/2010; 4(1):53-60.
[show abstract][hide abstract] ABSTRACT: Gd-EOB-DTPA is a new liver specific MRI contrast media. In the hepatobiliary phase, contrast media is trapped in normal liver tissue, a normal liver shows high intensity, tumor/liver contrast becomes high, and diagnostic ability improves. In order to indicate the degree of uptake of the contrast media, the enhancement ratio (ER) is calculated. The ER is obtained by calculating (signal intensity (SI) after injection-SI before injection) / SI before injection. However, because there is no linearity between contrast media concentration and SI, ER is not correctly estimated by this method. We discuss a method of measuring ER based on SI and T(1) values using the phantom. We used a column phantom, with an internal diameter of 3 cm, that was filled with Gd-EOB-DTPA diluted solution. Moreover, measurement of the T(1) value by the IR method was also performed. The ER measuring method of this technique consists of the following three components: 1) Measurement of ER based on differences in 1/T(1) values using the variable flip angle (FA) method, 2) Measurement of differences in SI, and 3) Measurement of differences in 1/T(1) values using the IR method. ER values calculated by these three methods were compared. In measurement made using the variable FA method and the IR method, linearity was found between contrast media concentration and ER. On the other hand, linearity was not found between contrast media concentration and SI. For calculation of ER using Gd-EOB-DTPA, a more correct ER is obtained by measuring the T(1) value using the variable FA method.
[show abstract][hide abstract] ABSTRACT: True tracheal bronchus (TTB) is a rare anomaly in which a lobar or segmental ectopic bronchus arises from the trachea. We examined the frequency and multidetector computed tomography (MDCT) appearances of TTB.
We retrospectively analyzed 9781 chest MDCT examinations. In cases in which there was an abnormal bronchus suggesting TTB on axial CT images, the following imaging of the abnormal bronchi was undertaken: multiplanar reformation (MPR), multiprojection volume reconstruction (MPVR), volume rendering (VR), and virtual endoscopy (VE).
Of 9781 MDCT examinations, 30 TTBs were observed in 10 females and 20 males. The frequency of TTB was 0.21% among 4622 females, 0.39% among 5159 males (0.31 % in the overall patient population). TTBs arose from the right lateral wall of the trachea; 17 TTBs were of the displaced type and 13 of the supernumerary type. With the displaced type, all segments of the right upper lobe were supplied by the TTB in 8 patients, and the apical segment was supplied in 8 patients. With the supernumerary type, TTBs showed blind termination in 10 patients, and the TTB had a small lobule in 3 patients. All TTBs were clearly visualized on MPR, MPVR, VR, and VE.
TTB was identified by MDCT with an incidence of 0.31%.
Japanese journal of radiology 04/2010; 28(3):188-92. · 0.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: In cases of suspected cranial trauma, cranial CT examinations should be performed to rule out pathology. There are some methods available for reducing intraocular doses; however, it is difficult for the operators to conduct the necessary measurements because of restrictions in time and patient mobility, especially in high-energy trauma cases. Therefore, we performed a head phantom study for intraocular dose evaluation of 64-slice multidetector CT examination in patients with suspected cranial trauma.
Assuming that the orbitomeatal (OM) line and bed were vertical, a head phantom was tilted from 10 degrees caudally to 25 degrees cranially at 5-degree intervals. At each tilted position, the phantom was examined using a 64-section multidetector CT device using three acquisition protocols. Intraocular doses during each examination were measured using small dosimeters.
Assuming that the OM line and bed were vertical, intraocular doses varied between 52 and 140%, 17-138%, and 90-142% during helical, non-helical, and helical CT angiographic examinations, respectively. Intraocular doses increased when the phantom was tilted cranially.
If possible, the best way to reduce the intraocular dose is by angling the gantry cranially, tilting the head of each patient caudally and adopting a non-helical acquisition method. During procedure, the acquisition angle should be angled cranially more than 0 degrees based on the OM line. The estimation of intraocular dose using the acquisition angle and displayed volumetric CT dose index might be useful to evaluate the deterministic effect risks and to inform patients about the associated risks.
European journal of radiology 02/2010; 79(2):283-7. · 2.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: The effectiveness of a positioning doll for radiography training (XPD) and acquiring the techniques of radiography was evaluated through performing radiography practice for the students in our school of radiological technologists and a questionnaire for radiological technologists. We made a ranking test composed of a five-grade evaluation system of the 39 students for the techniques of radiography before and after the practice, and questionnaires about the XPD were given to the same students after the practice. The questionnaires about affinities between human bodies and the XPD and effectiveness of the XPD for the education of students were also carried out in six radiological technologists to examine the effectiveness of the practice of radiography by using the XPD. The rankings of the students after the practice were significantly higher than those before the practice (p <0.01), and 85% of the students rated the practice using the XPD as useful for them in acquiring the techniques of radiography. Seventy-eight percent of the radiological technologists rated it useful for student education in radiography. In conclusion, it was suggested that practice using the XPD was effective in helping students to acquire the techniques of radiography. We would like to develop supplementary tools for fixing the XPD and using the practice of radiography in many ways and in new directions in the future.
[show abstract][hide abstract] ABSTRACT: We compared effective doses for recent computed tomography (CT) examinations calculated based on International Commission on Radiological Protection publication number 103 (ICRP 103) with those calculated based on ICRP publication number 60 (ICRP 60), and considered the usefulness of the effective dose in CT dose evaluation. After placing radiophotoluminescence glass dosimeters (RPLDs) inside or outside an anthropomorphic phantom, we examined from the chest to the pelvis, cardiac, and cranial regions of the phantom. The absorbed dose was calculated by multiplying calibrated dose values of RPLD by the mass energy coefficient ratio. The effective dose was calculated as the sum total of the value for each tissue, which was multiplied by the equivalent dose according to the tissue weighting factor recommended in ICRP 103 and ICRP 60. Calculated effective doses based on ICRP 103 were different by –11% to +82% compared with those based on ICRP 60. The values of absorbed doses for selective tissues were relatively higher than the values for the effective dose. The effective dose represents only a mean dose value for an average human. Therefore, assessing the absolute dose of particular individuals in CT examinations based exclusively on the effective dose is not recommended.
European Radiology 08/2009; 19(12):2855-61. · 3.55 Impact Factor
[show abstract][hide abstract] ABSTRACT: Recent linear accelerators can perform cone-beam computed tomography to correct setup errors immediately before dose delivery. We calculated the dose distribution with setup errors acquired from cone-beam computed tomography to determine a more realistic and individual effect of setup errors. The differences in dose distribution were analyzed. The setup errors of three patients who were irradiated in the neck, esophagus, and pelvic area were obtained retrospectively. We found that the maximum dose variances for the three cases were 19.9-35.9%. The maximum dose variance points were relatively far from the isocenter. The volume of the 10% dose difference had widths of 1.3-1.85 cm around the beam edges. The V95 and mean doses at the clinical target volume were mostly unchanged. Doses around the beam edges were more varied than those around the isocenter for every case. The dose on the spinal cord located near the beam edges varied by 5-10% compared with the dose of the radiotherapy plan in two of the cases. We demonstrated the individual dose distributions of the cases affected by daily setup errors for all fractions.
Radiological Physics and Technology 07/2009; 2(2):151-8.
[show abstract][hide abstract] ABSTRACT: Recently, several types of post-processing image filter which was designed to reduce noise allowing a corresponding dose reduction in CT images have been proposed and these were reported to be useful for noise reduction of CT images of adult patients. However, these have not been reported on adaptation for pediatric patients. Because they are not very effective with small (<20 cm) display fields of view, they could not be used for pediatric (e.g., premature babies and infants) body CT images. In order to solve this restriction, we have developed a new noise reduction filter algorithm which can be applicable for pediatric body CT images. This algorithm is based on a three-dimensional post processing, in which output pixel values are calculated by multi-directional, one-dimensional median filters on original volumetric datasets. The processed directions were selected except in in-plane (axial plane) direction, and consequently the in-plane spatial resolution was not affected by the filter. Also, in other directions, the spatial resolutions including slice thickness were almost maintained due to a characteristic of non-linear filtering of the median filter. From the results of phantom studies, the proposed algorithm could reduce standard deviation values as a noise index by up to 30% without affecting the spatial resolution of all directions, and therefore, contrast-to-noise ratio was improved by up to 30%. This newly developed filter algorithm will be useful for the diagnosis and radiation dose reduction of pediatric body CT images.
Journal of Digital Imaging 06/2009; 23(6):806-18. · 1.10 Impact Factor
[show abstract][hide abstract] ABSTRACT: Inappropriate patient centering on the gantry changes the size of the localizer radiographs used for CT examinations, influencing the operation of CT automatic tube current modulation because tube current is controlled with information from localizer radiographs. The purpose of this study was to examine the influence of inappropriate patient centering on the gantry isocenter on automatic tube current modulation.
An elliptical phantom was scanned with four automatic tube current modulation techniques after acquisition of localizer radiographs in the horizontal and vertical directions with the phantom center shifted from the gantry isocenter in the vertical direction. After scanning, the magnification rate of the frontal localizer radiographs, tube current-time product, and image noise were examined.
On phantom studies, the magnification rate of localizer radiographs showed a linear relation to the vertical deviation of the phantom from the gantry isocenter. From 50 mm above to 50 mm below the gantry isocenter, tube current-time products ranged from 75% to 141% compared with those at the gantry isocenter. In addition, increases and decreases in the amount of image noise related to changes in tube current-time product were confirmed.
Inappropriate patient centering causes misoperation of automatic tube current modulation systems, in which tube current is controlled with information from localizer radiographs, and thus causes increases in tube current or image noise.
American Journal of Roentgenology 05/2009; 192(4):862-5. · 2.90 Impact Factor
[show abstract][hide abstract] ABSTRACT: Preoperative evaluation of bronchovascular structures is useful for prevention of accidents in pulmonary lobectomy. The purpose of this study was to examine the frequency and multidetector computed tomographic (CT) appearances of bronchovascular anomalies between the right middle and lower lobes.
A total of 1116 consecutive chest CT examinations were analyzed in the present study. On display, the bronchovascular anomalies between the right middle and lower lobes were searched. When anomalous structures were observed, 3-dimensional images were reconstructed.
Sixty-seven cases (6.0%) with anomalous findings were observed. In 20 cases (1.79%), the right middle lobe bronchus and artery supplied the lower lobe, whereas the lower lobe artery supplied the right middle lobe in 46 cases (4.12%). In 1 case (0.09%), the 2 patterns previously mentioned were observed concomitantly.
Anomalous bronchovascular structures between the right middle and lower lobes were identified by a multidetector CT with an incidence of 6.0%. Knowledge of the frequency and CT features is useful for preoperative CT evaluation.
[show abstract][hide abstract] ABSTRACT: The present study was performed to find the required volume of physiological saline for flushing that will allow the most efficient use of contrast medium during the early phase of dynamic CT. We calculated contrast medium aortic arrival time (AT), time to peak aortic enhancement (TPAE) and the elapsed time to TPAE from AT (rise time) from the TECs of pharmacokinetic analysis and clinical study. The rise time determined in the clinical study was 6.2s, which was shorter than that in the simulation study. In the present study, an appropriate volume for saline flush was estimated to be about 18 ml.
Computerized medical imaging and graphics: the official journal of the Computerized Medical Imaging Society 12/2008; 33(1):23-8. · 1.04 Impact Factor
[show abstract][hide abstract] ABSTRACT: To describe two different types of "ring-like enhancement" seen on dynamic magnetic resonance imaging (MRI) of breast cancer, and compare their histopathological features.
A total of 326 breast carcinomas in 311 patients were evaluated regarding the existence and appearance of "ring-like enhancement" in comparison to other MR imaging and histopathological findings.
Early peripheral enhancement (EPE) was observed in 81 of 326 lesions (24.8%) and delayed rim enhancement (DRE) in 110 (33.7%). Spiculated mass, invasive ductal carcinoma with abundant stroma, central fibrosis/necrosis, and a higher degree of fat invasion correlated with EPE (P < 0.001). DRE correlated with lobulated or round mass with a smooth border, invasive ductal carcinoma with scanty stroma, higher degrees of inflammatory change and surrounding compressed tissue, and less fat invasion (P <0.001). EPE correlated with the ratio of the peripheral to central blood vessel density (P = 0.0036) and DRE with the ratio of the peritumoral to peripheral lymph vessel density (P = 0.0298).
The appearance of two different types of ring-like enhancement on dynamic MRI in breast cancers was affected by the morphologic features, various histological factors reflecting the growth pattern of the mass, and angiogenesis and lymphangiogenesis.
Journal of Magnetic Resonance Imaging 12/2008; 28(6):1435-43. · 2.57 Impact Factor
[show abstract][hide abstract] ABSTRACT: MR imaging (MRI) is an important method for the diagnosis of abnormalities of the brain. In the present report, a semi-automated method is presented to segment the brain and CSF region on brain MR images. MR images were obtained from 6 subjects by SE sequence and 8 subjects by GRE sequence. The semi-automated method consisted of the following three steps: (1) segmentation of the intracranial region using the region-growing technique, (2) segmentation of the brain region using histogram analysis and mathematical morphology, and (3) segmentation of the CSF region using the top-hat transformation technique. The average ratio of a correctly recognized region (CRR) between the semi-automated method and manual method was 87.9%, 85.1% for the intracranial region (IRR), and 94.8% and 86.8% for the brain region in the SE and GRE sequences.
[show abstract][hide abstract] ABSTRACT: In this study, we analyzed the respiratory motion of the upper abdominal arteries preliminary to developing a method of respiratory motion correction for the roadmap technique used in vascular interventions. We retrospectively obtained six digital angiography sequences taken during respiration. The levels of the right and left hemidiaphragms and the positions of artery bifurcation points were measured manually through each sequence. Artery bifurcation points were classified as the hepatic artery group (HAG), splenic artery group (SAG), and celiac group (CG). Correlations between the motions of each hemidiaphragm and of the artery bifurcation points in each group were determined. We found that the vertical motion of the HAG and CG matched that of the right hemidiaphragm (r = 0.924 and r = 0.888, respectively). The vertical motion of the SAG matched that of the left hemidiaphragm (r = 0.949). The mean horizontal movements for all groups were up to 1.90 mm. The vertical motion for each group matched that of the right or the left hemidiaphragm. These findings will facilitate the development of a method of respiratory motion correction for the roadmap technique.
Radiological Physics and Technology 07/2008; 1(2):178-82.
[show abstract][hide abstract] ABSTRACT: The present study was performed for determining the optimal timing of MR sialography by use of the Japanese pickled plum (umeboshi) for promoting secretion by the salivary glands. MR sialography was performed in four healthy male volunteers. The four volunteers were examined before and 10 min after stimulation with umeboshi. On the next examination, three volunteers were examined before and after umeboshi stimulation every 1 min up to 5 min to allow assessment of the temporal changes in duct visualization. Dilatation of the salivary gland ducts and improvement of the visualization of the ducts were obtained after stimulation with umeboshi. The difference in the dilatation of the parotid duct was statistically significant. In the temporal study, the salivary gland ducts were shown to be dilated at 2 min after stimulation. As a result, 2 min after stimulation is the optimal timing for MR sialography by use of umeboshi as a stimulator of salivary secretion.
Radiological Physics and Technology 07/2008; 1(2):208-13.
[show abstract][hide abstract] ABSTRACT: The present study was performed to identify the theoretical background for optimal use of the bolus tracking system by analyzing the changes in the initial slope of the aortic time-enhancement curve (TEC).
We calculated the contrast medium aortic arrival time (TAR), the time to reach the trigger threshold (effective TAR), the slope of the linear equation of the enhancement unit (enhancement rate), and the time to peak aortic enhancement from the TECs of the pharmacokinetic analysis and retrospective clinical study.
In the pharmacokinetic analysis, the enhancement rate-simulated under conditions of injection duration 30 s and iodine load per body weight 500 mg/kg-was 27.1 HU/s. In the clinical study, the enhancement rate was 27.9 +/- 3.0 HU/s. A correlation was found between the TAR and the enhancement rate, indicating that enhancement rates decrease with increasing TAR. It took 22.7 +/- 0.5 s to reach maximum enhancement of the aorta from the trigger threshold of an increase of 100 HU and injection duration at 30 s.
We found that cardiac output differences are strongly dependent on the TAR and that most of the differences disappeared during the phase until effective TAR.
[show abstract][hide abstract] ABSTRACT: Currently, a large number of endovascular interventions are performed for treatment of intracranial aneurysms. For these treatments, correct positioning of microcatheter tips, microguide wire tips, or coils is essential. Techniques to detect such devices may facilitate endovascular interventions. In this paper, we describe an algorithm for tracking of microcatheter tips during fluoroscopically guided neuroendovascular interventions. A sequence of fluoroscopic images (1,024 x 1,024 x 12 bits) was acquired using a C-arm angiography system as a microcatheter was passed through a carotid phantom which was on top of a head phantom. The carotid phantom was a silicone cylinder containing a simulated vessel with the shape and curvatures of the internal carotid artery. The head phantom consisted of a human skull and tissue-equivalent material. To detect the microcatheter in a given fluoroscopic frame, a background image consisting of an average of the four previous frames is subtracted from the current frame, the resulting image is filtered using a matched filter, and the position of maximum intensity in the filtered image is taken as the catheter tip position in the current frame. The distance between the tracked position and the correct position (error distance) was measured in each of the fluoroscopic images. The mean and standard deviation of the error distance values were 0.277 mm (1.59 pixels) and 0.26 mm (1.5 pixels), respectively. The error distance was less than 3 pixels in the 93.0% frames. Although the algorithm intermittently failed to correctly detect the catheter, the algorithm recovered the catheter in subsequent frames.
Journal of Digital Imaging 04/2008; 21(1):99-108. · 1.10 Impact Factor