Biomedical subjects

Yasuyuki Yamashita

Publications and source records attributed to Yasuyuki Yamashita.

At least 19 recordsLinked to original sources

PubMed2007

Prediction of aortic peak enhancement in monophasic contrast injection protocols at multidetector CT: phantom and patient studies.

PURPOSE: The aim of this study was to investigate whether it is possible to predict aortic peak enhancement (APE) from the contrast dose and injection rate. MATERIALS AND METHODS: We first undertook an experimental study using a flow phantom that simulates the human circulation. We delivered 90-150 ml of iomeprol-350 at various injection rates and measured the APE values of the simulated aorta. In our clinical study we randomized 20 patients into four groups. In groups A, B, and C the iodine dose per kilogram of body weight (BW) ranged from 450 to 600 mg, and the injection duration was fixed at 30 s; group D received 450 mg/kg over 25 s. We then measured APE in all patients at the whole aorta, averaged the three highest values, and took the result as APE. RESULTS: In the phantom study, the decision coefficient for the best-fit equation obtained by multiple regression analysis of the relation between the iodine dose and injection rate and the simulated APE was high (0.93). In the patient study, the predicted APE values almost corresponded with the averaged APE values when we applied the fitness equation. CONCLUSION: Using our fitness equation, APE on contrast-enhanced computed tomography can be predicted from the iodine dose and the contrast injection rate per patient weight.

Adult↗

PubMed2006

In vitro evaluation of metallic coronary artery stents with sub-millimeter multi-slice computed tomography using an ECG-gated cardiac phantom: relationship between in-stent visualization and stent type.

The aim of this experimental study was to investigate visualization of various coronary artery stents with sub-millimeter multi-slice spiral computed tomography (MSCT) using a cardiac physical phantom. Four 3-mm stents of various designs were implanted in tubes with an inner diameter of 3 mm to simulate coronary artery. Stents were placed on a cardiac phantom and scanned at different heart rates. Retrospective ECG-gated adaptive segmental reconstruction technique was employed. Profile curves across longitudinal curved planar reconstruction images of the stents were generated. From the profile curve, the full width at half maximum was defined as the stent lumen index. The effect of heart rate and stent type on the stent lumen index was evaluated. Visual evaluation for each stent at various heart rates was also performed. The heart rate had no significant effect on in-stent visualization. However, in-stent visualization differed significantly for the various stent types for both profile curve analysis and visual evaluation (the Tukey-Kramer multiple comparisons test). Multiple regression analysis indicated that strut thickness, especially minimal strut thickness, was the significant influencing factor for the in-stent visualization. On the basis of four stent models examined it would appear that visualization of the coronary stent lumen varies depending on the stent type, but not on the heart rate. Stents with slim struts are preferable for in-stent evaluation with multi-slice spiral computed tomography.

Biocompatible Materials↗

PubMed2006

Hemorrhage into pancreatic pseudocyst.

We report a patient whose upper abdominal pain was due to an alcoholic pancreatic pseudocyst with hemorrhage. CT showed a gradually enhancing pancreatic pseudocyst about 6 cm in diameter. It exhibited hyposignal intensity on T2-weighted images and hypersignal intensity on T1-weighted images. Enlargement of the pancreatic pseudocyst was thought to be attributable to hemorrhage into the pancreatic pseudocyst. Angiography revealed a pseudoaneurysm in the anterior superior pancreaticoduodenal (ASPD) artery. Selective transcatheter arterial embolization (TAE) of the ASPD artery stopped the bleeding and his abdominal pain lessened. After 1 month, the diameter of the pseudocyst was reduced to about 3 cm and it showed hypersignal intensity on T2-weighted images and hyposignal intensity on T1-weighted images. TAE was considered to be a minimally invasive, highly effective treatment in this patient with hemorrhage into a pancreatic pseudocyst.

Aneurysm, False↗

PubMed2006

Acute adrenal hemorrhage after blunt trauma.

OBJECTIVE: To determine the appropriate management of adrenal hemorrhage in patients with severe chest and upper abdominal blunt trauma. MATERIALS AND METHODS: We reviewed 7 patients who suffered from severe traumatic adrenal hemorrhage after a traffic accident (n = 4) or fall (n = 3). Contrast-enhanced CT images were analyzed for multi-organ traumatic injury, hematoma size, extravasation, and pseudoaneurysm formation. We also report their management including transarterial embolization (TAE) and follow-up findings. RESULTS: All 7 patients manifested multi-organ traumatic injury and hemothorax; 5 also had rib fractures, 5 had abdominal organ injuries (liver, n = 3; kidneys, n = 2; pancreas, n = 1); 2 had dorsal fractures, and 1 had a traumatic aortic aneurysm. On CT images, unilateral right adrenal hematomas ranging from 20 to 50 mm (mean 26 mm) in length and from 15 to 50 mm (mean 23 mm) in width were seen. In 6 patients these were localized, and they were followed without any intervention. The other patient had a massive hematoma with pseudoaneurysm and extravasation, who subsequently received TAE. At 3-month follow-up all patients were doing well. CONCLUSION: Information regarding the size of the hematoma and the presence of extravasation helps to select the appropriate management of patients with traumatic adrenal hemorrhage. TAE appears to be useful for treating patients with massive adrenal hemorrhage.

Accidents, Traffic↗

PubMed2006

Monitoring therapeutic responses of primary bone tumors by diffusion-weighted image: Initial results.

The purpose of our study was to investigate whether quantitative diffusion-weighted images (DWI) were useful for monitoring the therapeutic response of primary bone tumors. We encountered 18 osteogenic and Ewing sarcomas. Magnetic resonance (MR) images were performed in all patients before and after therapy. We measured the apparent diffusion coefficient (ADC) values, contrast-to-noise ratio (CNR), and tumor volume of the bone tumors pre- and posttreatment. We determined change in ADC value, change in CNR on T2-weighted images (T2WI), change in CNR on gadopentetate dimeglumine (Gd)-T1-weighted images (Gd-T1WI), and change in tumor volume. The bone tumors were divided into two groups: group A was comprised of tumors with less than 90% necrosis after treatment and group B of tumors at least with 90%. Changes in ADC value, tumor volume, and CNR were compared between the groups. Change in the ADC value was statistically greater in group B than that in the group A (p = 0.003). There was no significant difference in the changes in CNR on T2WI (p = 0.683), in CNR on Gd-T1WI (p = 0.763), and tumor volume (p = 0.065). The ADC value on DWI is a promising tool for monitoring the therapeutic response of primary bone sarcomas.

Adolescent↗

PubMed2006

Automated hepatic volumetry for living related liver transplantation at multisection CT.

PURPOSE: To prospectively compare in vivo hepatic automated volumetry with manual volumetry and measured liver volume. MATERIALS AND METHODS: The study was conducted in accordance with the guidelines of the Institutional Review Board of Kumamoto University (Japan). Patient informed consent was obtained. Preoperative multisection computed tomography (CT) was performed in 35 consecutive patients (21 men, 14 women; mean age, 42.8 years; range, 28-72 years) with hepatic disease awaiting living related liver transplantation. The CT scans covered the entire liver at a section thickness of 2.5 mm. Liver volume was estimated by using both the automated and the manual methods. Actual liver weight was obtained for all patients and was converted to hepatic volume on the basis of a predetermined relationship between actual liver weight and volume. Processing time required for both methods was also recorded. Two-tailed paired t test, correlation coefficient, and Bland-Altman tests were used for statistical analyses. RESULTS: Mean liver weight was 881.7 g +/- 249.8 (standard deviation), and mean measured liver volume was 956.00 cm(3) +/- 280.10. Volumetry performed with the automated and manual methods provided liver volumes of 982.99 cm(3) +/- 301.98 and 937.10 cm(3) +/- 301.31, respectively. There was good correlation between measured and estimated volumes obtained with the automated method (r = 0.792, P < .01). The manual and automated methods required 32.8 minutes +/- 6.9 and 4.4 minutes +/- 1.9, respectively. CONCLUSION: The automated method reduced the time required for volumetry of the liver and provided acceptable measurements.

Adult↗

PubMed2006

[Comparison of LCD and CRT monitors for detection of pulmonary nodules and interstitial lung diseases on digital chest radiographs by using receiver operating characteristic analysis].

Soft copy reading of digital images has been practiced commonly in the PACS environment. In this study, we compared liquid-crystal display (LCD) and cathode-ray tube (CRT) monitors for detection of pulmonary nodules and interstitial lung diseases on digital chest radiographs by using receiver operating characteristic (ROC) analysis. Digital chest images with a 1000x1000 matrix size and a 8 bit grayscale were displayed on LCD/CRT monitor with 2M pixels in each observer test. Eight and ten radiologists participated in the observer tests for detection of nodules and interstitial diseases, respectively. In each observer test, radiologists marked their confidence levels for diagnosis of pulmonary nodules or interstitial diseases. The detection performance of radiologists was evaluated by ROC analyses. The average Az values (area under the ROC curve) in detecting pulmonary nodules with LCD and CRT monitors were 0.792 and 0.814, respectively. In addition, the average Az values in detecting interstitial diseases with LCD and CRT monitors were 0.951 and 0.953, respectively. There was no statistically significant difference between LCD and CRT for both detection of pulmonary nodules (P=0.522) and interstitial lung diseases (P=0.869). Therefore, we believe that the LCD monitor instead of the CRT monitor can be used for the diagnosis of pulmonary nodules and interstitial lung diseases in digital chest images.

Data Display↗

PubMed2006

Multi-slice CT demonstration of sinus of Valsalva rupture.

Aneurysms of the sinus of Valsalva are rare. We report here the case of a 56-year-old man with a ruptured aneurysm of sinus of Valsalva with flow into the right ventricle which was diagnosed non-invasively by 64-row multi-slice computed tomographic (CT) imaging. The right sinus of Valsalva aneurysm rupturing into the right ventricular outflow region might be silent or symptomless in many cases. The patient also had mild symptom. For anatomical demonstration, contrast-enhanced CT was performed. Although the ruptured sinus of Valsalva was initially diagnosed by echocardiography, CT images did give our surgeons a better three-dimensional appreciation when surgical repair was performed. Multi-slice CT imaging should be considered the technique of choice for both diagnosis and follow-up examination of the aneurysm of sinus of Valsalva and its rupture.

Aortic Rupture↗

PubMed2006

Coronary arterial malformation depicted at multi-slice CT angiography.

We present a case of a 57-year-old woman with an unremarkable medical history except for a continuous cardiac murmur at the left second and third interspaces. Transthoracic echocardiography revealed an unusual chamber in front of the heart. To evaluate the precise anatomy of this abnormality, multi-slice computed tomographic (MSCT) imaging was performed. MSCT angiography with retrospective ECG gating showed a coronary arterial malformation with fistulous communications to the coronary artery, pulmonary artery and the root of aorta. Images from MSCT coronary angiography can be helpful in understanding the tortuous configuration of the coronary arterial malformation.

Aorta↗

PubMed2006

Pulmonary nodules: estimation of malignancy at thin-section helical CT--effect of computer-aided diagnosis on performance of radiologists.

PURPOSE: To evaluate the effect of a computer-aided diagnosis (CAD) system on the diagnostic performance of radiologists for the estimation of the malignancy of pulmonary nodules on thin-section helical computed tomographic (CT) scans. MATERIALS AND METHODS: The institutional review board approved use of the CT database; informed specific study-related consent was waived. The institutional review board approved participation of radiologists; informed consent was obtained from all observers. Thirty-three (18 malignant, 15 benign) pulmonary nodules of less than 3.0 cm in maximal diameter were evaluated. Receiver operating characteristic (ROC) analysis with a continuous rating scale was used to compare observer performance for the estimation of the likelihood of malignancy first without and then with the CAD system. The participants were 10 board-certified radiologists and nine radiology residents. RESULTS: For all 19 participants, the mean area under the best-fit ROC curve (A(z)) values achieved without and with the CAD system were 0.843 +/- 0.097 (standard deviation) and 0.924 +/- 0.043, respectively. The difference was significant (P = .021). The mean A(z) values achieved without and with the CAD system were 0.910 +/- 0.052 and 0.944 +/- 0.040, respectively, for the 10 board-certified radiologists (P = .190) and 0.768 +/- 0.078 and 0.901 +/- 0.036, respectively, for the nine radiology residents (P = .009). CONCLUSION: Use of the CAD system significantly (P = .009) improved the diagnostic performance of radiology residents for assessment of the malignancy of pulmonary nodules; however, it did not improve that of board-certified radiologists.

Adenocarcinoma↗

PubMed2006

Signal intensity of the normal pontine tegmentum on T2-weighted MR imaging.

On T2-weighted MR images, the pontine tegmentum frequently shows a signal of high intensity in neurologically healthy individuals. We examined whether the signal intensity of the pontine tegmentum normally differs from that of the pontine base. We evaluated the signal intensity of the pontine tegmentum and pontine base on T2-weighted images from 38 neurologically healthy subjects. The subjects included 29 adults (16 males and 13 females, age range 23-48 years, mean age 39.5 years) and 9 children (4 boys and 5 girls (age range 4-9 years mean age 6.5 years). We compared the contrast-to-noise ratio (CNR) between the tegmentum and the base in the upper pons, midpons and lower pons, and evaluated the signal intensity ratio of the tegmentum to the base. The CNR was significantly higher for the tegmentum than the base at each level of the pons (P<0.0001), and the signal intensity ratio of the tegmentum to the base in the upper pons was significantly higher in children than in adults (P<0.005). On T2-weighted images, a high signal intensity of the pontine tegmentum is frequently seen in neurologically healthy subjects. This finding should not be considered abnormal, particularly in children.

Adult↗

PubMed2006

Mutidetector-row CT and quantitative gated SPECT for the assessment of left ventricular function in small hearts: the cardiac physical phantom study using a combined SPECT/CT system.

UNLABELLED: The aim of this study was to compare results of left ventricular (LV) function obtained by quantitative gated single-photon emission tomography (QGS) and multidetector-row spiral computed tomography (MDCT) with reference parameters using an electrocardiogram-gated cardiac physical phantom. The phantom study was performed using a combined SPECT/CT system. Flexible membranes formed the inner and outer walls of the simulated LV. The stroke volume was adjusted (45 mL or 58 mL) and the fixed 42-mL end-systolic volume (ESV) produced two different volume combinations. The LV function parameters were estimated by means of MDCT and QGS. Differences in true and measured volumes were compared among CT with a reconstructed image thickness of 2.5 mm and 5.0 mm and QGS volumetric values. Each scan was repeated three-times. The estimation of LV volumes using both QGS and MDCT analyses were reproducible very well. QGS overestimated ejection fraction (EF) by approximately 20%; MDCT volumetry overestimated EF by approximately 5% in each volume setting. The differences in true and measured values for EF and ESV obtained with QGS were significantly greater than obtained with MDCT. CONCLUSION: MDCT provides a reliable estimation of functional LV parameters, whereas QGS tends to significantly overestimate the EF in small hearts.

Analysis of Variance↗

PubMed2006

Evaluation of diffusion-weighted imaging for the differential diagnosis of poorly contrast-enhanced and T2-prolonged bone masses: Initial experience.

PURPOSE: To determine whether quantitative diffusion-weighted imaging (DWI) is useful for characterizing poorly contrast-enhanced and T2-prolonged bone masses. MATERIALS AND METHODS: We studied 20 bone masses that showed high signal intensity on T2-weighted images and poor enhancement on contrast-enhanced T1-weighted images. These included eight solitary bone cysts, five fibrous dysplasias, and seven chondrosarcomas. To analyze diffusion changes we calculated the apparent diffusion coefficient (ADC) for each lesion. RESULTS: The ADC values of the two types of benign lesions and chondrosarcomas were not significantly different. However, the mean ADC value of solitary bone cysts (mean +/-SD, 2.57 +/- 0.13 x 10(-3) mm(2)/second) was significantly higher than that of fibrous dysplasias and chondrosarcomas (2.0 +/- 0.21 x 10(-3) mm(2)/second and 2.29 +/- 0.14 x 10(-3) mm(2)/second, respectively, P < 0.05). None of the lesions with ADC values lower than 2.0 x 10(-3) mm(2)/second were chondrosarcomas. CONCLUSION: Although there was some overlapping in the ADC values of chondrosarcomas, solitary bone cyst, and fibrous dysplasia, quantitative DWI may aid in the differential diagnosis of poorly contrast-enhanced and T2-prolonged bone masses.

Adolescent↗

PubMed2006

The diagnostic efficacy of FDG-PET in the local recurrence of hilar bile duct cancer.

BACKGROUND/PURPOSE: It is frequently difficult to make an accurate diagnosis of the local recurrence of hilar bile duct cancer (HBC). We assessed the efficacy of fluorodeoxyglucose-positron emission tomography (FDG-PET) in diagnosing the local recurrence of HBC. METHODS: Among 18 patients who had previously undergone resection of HBC, 5 were suspected of having a recurrence. These 5 patients were examined for recurrence by computed tomography (CT) and FDG-PET. A definitive diagnosis was determined either by pathological studies or by clinical follow-up. RESULTS: Whereas CT showed a recurrent mass in only 1 patient, FDG-PET revealed the high uptake of FDG in all patients. Histopathological and/or cytological examinations confirmed the local recurrence of HBC in 4 patients. One false-positive result occurred in a patient with reflux cholangitis. One patient with a recurrent tumor was followed by FDG-PET after irradiation therapy. The high level of FDG uptake, which had been seen in that patient before irradiation, completely disappeared after treatment. CONCLUSIONS: When used in combination with other modalities, FDG-PET offered useful information for the diagnosis of a local recurrence of HBC. This highly sensitive imaging approach also appeared to be useful for follow-up examination after irradiation therapy.

Aged↗

PubMed2006

Management of sentinel lymph nodes in malignant skin tumors using dynamic lymphoscintigraphy and the single-photon-emission computed tomography/computed tomography combined system.

BACKGROUND: The differentiation of true sentinel lymph nodes from nonsentinel lymph nodes is difficult in cases of multiple radiolabeled or dyed lymph nodes. METHODS: We examined the locations of sentinel lymph nodes in melanoma and other malignant skin tumors by using dynamic lymphoscintigraphy and the single-photon-emission computed tomography/computed tomography (SPECT/CT) combined system. RESULTS: Sentinel lymph nodes were detected in 45 of the 53 patients examined using only the ordinary blue dye method (85%), and were detected in all 35 patients examined using the SPECT/CT method (100%). Twenty of the 35 patients mentioned above had one sentinel lymph node. Multiple sentinel lymph nodes were demonstrated in the head and neck areas using the SPECT/CT method. Significant differences (P=0.0015) in the numbers of sentinel lymph nodes were found between the blue dye method only and the SPECT/CT method in the neck area. Popliteal sentinel lymph nodes were recognized in three patients, and cubital sentinel lymph nodes were recognized in two patients. Two patients had plural regional lymph nodes: one had popliteal and groin sentinel lymph nodes, while the other had cubital and axillary sentinel lymph nodes. The probe counts of the popliteus and cubitus were significantly lower (P=0.0241) than the counts in the groin, axilla, and neck areas. Micrometastatic sentinel lymph nodes were recognized in four patients, and two patients had metastases in both sentinel and nonsentinel lymph nodes. CONCLUSIONS: Dynamic lymphoscintigraphy was useful when we were concerned about cubital and popliteal lymph nodes. The SPECT/CT combined system was useful in recognizing the anatomical location of sentinel lymph nodes before biopsy. The detection rate of sentinel lymph nodes using the SPECT/CT method was always better than that with the blue dye method (P=0.0197).

Adult↗

PubMed2006

Ectopic cervical thymus in an infant.

We report a case of accessory cervical thymus presenting as a unilateral neck mass in a 2-month-old boy. Ultrasonography (US) showed a mass isoechogenic to muscle in the left neck. Computed tomography (CT) revealed a well-defined, mildly enhanced mass located anterior to the sternocleidomastoid muscle, anterolateral to the carotid sheath, and posterior to the submandibular gland. On magnetic resonance imaging (MRI), the mass was isointense to muscle on T1-weighted images and hyperintense to muscle on T2-weighted images. Diffusion-weighted images showed relatively low apparent diffusion coefficient (ADC) values, and the mass was slightly enhanced after administration of contrast material. We suspected ectopic thymus, but we could not exclude the possibility of a malignant lesion. Therefore, the tumor was surgically resected. The histological diagnosis was ectopic cervical thymus. Ectopic thymus should be included in the differential diagnosis of a submandibular or cervical mass in infants. US and MRI can provide useful information for the diagnosis of ectopic cervical thymus.

Biomarkers, Tumor↗

PubMed2006

Concurrent chemoradiation therapy with low-dose CDDP and UFT for glottic carcinomas: evaluation using the sixth edition of the UICC TNM staging system.

We evaluated whether low-dose chemotherapy could improve effects of radiation therapy for glottic carcinoma with different prognostic factor based on the UICC 6th edition. Fifty-one patients with T2N0 glottic carcinoma classified by the UICC 5th edition underwent chemoradiation therapy with low-dose CDDP (4 mg/m(2)) and oral UFT (450 mg of tegafur) continuing for four weeks (CRT group). The historical control consisted of 49 patients treated with radiation therapy alone (RT group). Forty-six tumors with the adjacent sign, i.e. tumors located adjacent to the thyroid cartilage on radiological examinations, were classified as T3 according to the 6(th) edition. The 5-year local control and laryngeal preservation rates of the T2 (n=54) vs. T3 (n=46) lesions were 87% vs. 50% (p<0.0001) and 94% vs. 61% (p<0.0001), respectively. Among the T3 lesions, CRT (n=24) yielded significantly higher laryngeal preservation rates than did RT alone (n=22) (83% vs. 40%, p=0.0063), and the local control rates were higher in the CRT- than the RT group (62% vs. 36%, p=0.0882). While such benefits of CRT were not observed in patients with T2 lesions.

Adult↗

PubMed2006

Improvement of low-contrast detectability in low-dose hepatic multidetector computed tomography using a novel adaptive filter: evaluation with a computer-simulated liver including tumors.

PURPOSE: The purpose of this study was to investigate how much radiation dose can be reduced without loss of low-contrast detectability with a newly developed adaptive noise reduction filter in hepatic multidetector computed tomography (MDCT) scans by using a computer-simulated liver phantom. MATERIALS AND METHODS: Simulated CT images, including liver and intrahepatic tumors, were mathematically constructed using a computer workstation to evaluate low-contrast detectability by the observer performance test. Milliampere second for construction of simulated images were 60, 80, 100, and 120 mAs (low dose) and 160 mAs (standard dose) at 120 kVp. Images with 60, 80, 100, and 120 mAs were postprocessed with the adaptive noise reduction filter. A total of 432 images were prepared and receiver operating characteristic (ROC) analysis was performed by 5 radiologists. The detectability of simulated tumor by radiologists was estimated with the area under the ROC curves (Az values). In addition, we visually evaluated CT images of 15 patients with chronic liver damage for graininess of the liver parenchyma, sharpness of the liver contour, conspicuity and marginal sharpness of the liver tumors, and overall image quality. RESULTS: The mean Az value at 0.777 (60 mAs), 0.828 (80 mAs), and 0.844 (100 mAs) without filter was significantly lower than that of 160 mAs without filter (P < 0.001, 60 mAs; P = 0.010, 80 mAs; P = 0.040, 100 mAs). There was no statistical difference between the mean Az value at 80 mAs with and 160 mAs without the adaptive noise reduction filter (P = 0.220) and 100 mAs with and 160 mAs without the adaptive noise reduction filter (P = 0.979). In the visual evaluation of patient livers, there was no statistical difference in the graininess and sharpness of the liver, the conspicuity and marginal sharpness of the tumor, and the overall image quality between standard-dose and filtered low-dose images (Wilcoxon signed rank test, P > 0.05). CONCLUSION: The radiation dose can be reduced by 50% without loss of nodule detectability by applying the adaptive noise reduction filter to simulated and patient liver images obtained at MDCT.

Aged↗