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Biomedical subjects

Kazuo Miyasaka

Publications and source records attributed to Kazuo Miyasaka.

At least 19 recordsLinked to original sources
PubMed2006

Uncertainty in treatment of head-and-neck tumors by use of intraoral mouthpiece and embedded fiducials.

PURPOSE: To reduce setup error and intrafractional movement in head-and-neck treatment, a real-time tumor tracking radiotherapy (RTRT) system was used with the aid of gold markers implanted in a mouthpiece. METHODS AND MATERIALS: Three 2-mm gold markers were implanted into a mouthpiece that had been custom made for each patient before the treatment planning process. Setup errors in the conventional immobilization system using the shell (manual setup) and in the RTRT system (RTRT setup) were compared. Eight patients with pharyngeal tumors were enrolled. RESULTS: The systematic setup errors were 1.8, 1.6, and 1.1 mm in the manual setup and 0.2, 0.3, and 0.3 mm in the RTRT setup in right-left, craniocaudal, and AP directions, respectively. Statistically significant differences were observed with respect to the variances in setup error (p <0.001). The systematic and random intrafractional errors were maintained within the ranges of 0.2-0.6 mm and 1.0-2.0 mm, respectively. The rotational systematic and random intrafractional errors were estimated to be 2.2-3.2 degrees and 1.5-1.6 degrees , respectively. CONCLUSIONS: The setup error and planning target volume margin can be significantly reduced using an RTRT system with a mouthpiece and three gold markers.

Adult↗
PubMed2006

Speed and amplitude of lung tumor motion precisely detected in four-dimensional setup and in real-time tumor-tracking radiotherapy.

BACKGROUND: To reduce the uncertainty of registration for lung tumors, we have developed a four-dimensional (4D) setup system using a real-time tumor-tracking radiotherapy system. METHODS AND MATERIALS: During treatment planning and daily setup in the treatment room, the trajectory of the internal fiducial marker was recorded for 1 to 2 min at the rate of 30 times per second by the real-time tumor-tracking radiotherapy system. To maximize gating efficiency, the patient's position on the treatment couch was adjusted using the 4D setup system with fine on-line remote control of the treatment couch. RESULTS: The trajectory of the marker detected in the 4D setup system was well visualized and used for daily setup. Various degrees of interfractional and intrafractional changes in the absolute amplitude and speed of the internal marker were detected. Readjustments were necessary during each treatment session, prompted by baseline shifting of the tumor position. CONCLUSION: The 4D setup system was shown to be useful for reducing the uncertainty of tumor motion and for increasing the efficiency of gated irradiation. Considering the interfractional and intrafractional changes in speed and amplitude detected in this study, intercepting radiotherapy is the safe and cost-effective method for 4D radiotherapy using real-time tracking technology.

Dose Fractionation, Radiation↗
PubMed2006

Percutaneous transluminal angioplasty for hepatic artery stenosis after living donor liver transplantation.

The purpose of this study was to evaluate the efficacy of percutaneous transluminal angioplasty (PTA) for treatment of hepatic artery stenosis after living donor liver transplantation. Eighteen patients with hepatic artery stenosis after living donor liver transplantation were included in this study. The success rate and complications of PTA and recurrent stenosis of the hepatic artery were evaluated. Seventeen of 18 patients (94.4%) were successfully treated without complication by a first PTA procedure. Recurrence of hepatic artery stenosis occurred in 6 patients (33.3%). Repeated PTA was performed 12 times for the 6 patients. Two complications occurred as arterial dissection and perforation. As a consequence, the complication rate was 6.7%, involving 2 of 30 procedures in total. In conclusion, PTA is effective for treatment of hepatic artery stenosis after living donor liver transplantation without an increase in the complication rate.

Adult↗
PubMed2006

Magnetic resonance imaging findings and histopathological observations after percutaneous renal cryoablation in the rabbit model.

PURPOSE: We investigated sequential changes in MRI and relevant histopathological findings after PRC. MATERIALS AND METHODS: A total of 15 rabbits were examined with MRI and sacrificed immediately (3), and 7 (4), 45 (4) and 90 (4) days after PRC. MRI studies were reviewed for the signal intensity of cryolesions and correlated with pathological findings. MRI and pathological measurements of cryolesion sizes were compared using the paired t test. RESULTS: CCN was produced in central areas of cryolesions and associated with hemorrhage, hemolysis, fibrous granulation and fibrosis that was orderly through days 1 to 90. Signal intensity was slightly hyperintense on T1-weighted spin-echo images immediately after PRC, and hyperintense on T1 and T2-weighted fast spin-echo images at 7 days. On T2-weighted fast spin-echo images there was a hypointense zone in peripheral areas between the central area and renal parenchyma at the prior 2 stages, which was consistent with PCN histologically. It was enhanced at 7 days. At 45 and 90 days the signal intensity of cryolesions was isointense or hypointense on the 2 sequences. Parenchymal injury adjacent to cryolesions was histologically recognized and visible as a hyperintense zone in 2 lesions at 45 days. This zone was enhanced in 2 lesions at 45 and 90 days. No statistical significance was apparent between the 2 measurements of cryolesions and CCN sizes (p <0.05). CONCLUSIONS: The MRI appearance of cryolesions reflects orderly histopathological findings. MRI distinguishes CCN from PCN, reveals injury to the renal parenchyma outside of cryolesions and accurately estimates the size of cryolesions and CCN.

Animals↗
PubMed2005

Hypofractionated radiotherapy boost for dose escalation as a treatment option for high-grade spinal cord astrocytic tumor.

PURPOSE: To retrospectively analyze the outcome of post-operative radiotherapy for spinal cord glioma with the emphasis on the hypofractionated radiotherapy boost for dose escalation as a treatment option for high-grade spinal cord astrocytic tumors. MATERIALS AND METHODS: Forty-one patients with spinal cord glioma received post-operative radiotherapy between 1979 and 2003. The median age was 34 years (range, 10-66 years). Median follow-up was 49 months (range, 5-291 months). There were 12 low-grade astrocytic tumors, 11 high-grade astrocytic tumors, 16 low-grade ependymal tumors and 2 high-grade ependymal tumors. Among 11 patients with high-grade astrocytic tumors, 5 with anaplastic astrocytoma and 1 with glioblastoma received hypofractionated radiotherapy boost for dose escalation. The median total dose of the conventional radiotherapy was 45.5 Gy in 19 fractions (range, 30.0-60.0 Gy). The median normalized total dose (using daily dose of 2.0 Gy and an alpha/ per thousandbeta ratio of 2.0) of the hypofractionated radiotherapy boost was 131 Gy2 (range, 85-249). RESULTS: The Kaplan-Meier survival rates at 10 years from the date of the first surgery were 64% for the entire group, 47% for the astrocytic tumors and 84% for the ependymal tumors, respectively (P=0.009). Among 11 patients with high-grade astrocytic tumors, the actuarial survival rate at 10 years was 35%. The actuarial survival rates at 10 years were 67% for those who received hypofractionated radiotherapy boost for dose escalation, and 20% for those who did not (P=0.47). DISCUSSION: The results for ependymal tumors and low-grade astrocytic tumors were comparable to those reported in the literature. Hypofractionated radiotherapy boost for dose escalation may help to prolong the survival of patients with high-grade astrocytic tumors.

Adolescent↗
PubMed2005

The effect of tumor location and respiratory function on tumor movement estimated by real-time tracking radiotherapy (RTRT) system.

PURPOSE: The effects of tumor location and pulmonary function on the motion of fiducial markers near lung tumors were evaluated to deduce simple guidelines for determining the internal margin in radiotherapy without fiducial markers. METHODS AND MATERIALS: Pooled data collected by a real-time tumor-tracking radiotherapy system on 42 markers in 39 patients were analyzed. The pulmonary functions of all patients were assessed before radiotherapy. Using chest X-ray film, the position of the marker was expressed relative to the geometry of the unilateral lung. Posterior location meant the area of the posterior half of the lung in a lateral chest X-ray film, and caudal location meant the caudal half of the chest X-ray film; these categories were determined by measuring the distance between the marker and anatomic landmarks, including the apex, costophrenic angle, midline of spinal canal, lateral, anterior, and posterior boundary of the lung. RESULTS: Before the radiotherapy, 18 patients had obstructive respiratory dysfunction (ratio of forced expiratory volume in 1 s to forced vital capacity [FEV1.0/FVC] <70), 5 patients had constrictive dysfunction (percent vital capacity [%VC] <80), and 3 had mixed dysfunction. Means of FEV1.0/FVC and %VC were 97.0% and 66.5%, respectively. Median tumor movements in the x (left-right), y (anteroposterior), and z (craniocaudal) directions were 1.1 mm, 2.3 mm, and 5.4 mm, respectively. There was no significant correlation between respiratory function and magnitude of marker movement in any direction. Median marker movement in the z direction was 2.6 mm for the cranial location and 11.8 mm for the caudal location, respectively (p < 0.001). Median movement in the z direction was 11.8 mm for posterior location and 3.4 mm for anterior location, respectively (p < 0.01). CONCLUSIONS: Simple measurement of the relative location on plain chest X-ray film was related, but respiratory function test was not related, to the craniocaudal amplitude of the motion of the fiducial marker near lung tumors.

Adult↗
PubMed2005

Insertion and fixation of fiducial markers for setup and tracking of lung tumors in radiotherapy.

PURPOSE: Internal 1.5-mm fiducial markers were used in real-time tumor-tracking radiotherapy (RT) for lung cancer. The fixation rate of the markers using the bronchial insertion technique, reliability of the setup using markers around the target volume, dislocation of the markers after real-time tumor-tracking RT, and long-term toxicity of marker insertion were investigated. METHODS AND MATERIALS: Between July 2000 and April 2004, 154 gold markers were inserted into 57 patients with peripheral lung cancer. The distances between the implanted markers in 198 measurements in 71 set-ups in 11 patients were measured using two sets of orthogonal diagnostic X-ray images of the real-time tumor-tracking RT system. The distance between the markers and the chest wall was also measured in a transaxial CT image on 186 occasions in 48 patients during treatment planning and during follow-up. The median treatment time was 6 days (range, 4-14 days). RESULTS: In 115 (75%) of the 154 inserted markers, the gold marker was detected throughout the treatment period. In 122 markers detected at CT planning, 115 (94%) were detected until the end of treatment. The variation in the distances between the implanted markers was within +/-2 mm in 95% and +/-1 mm in 80% during treatment. The variation in the distances between the implanted markers was >2 mm in at least one direction in 9% of the setups for which reexamination with a CT scan was indicated. The fixation rate in the left upper lobe was lower than in the other lobes. A statistically significant relationship was found between a shorter distance between the markers and the chest wall and the fixation rate, suggesting that the markers in the smaller bronchial lumens fixed better than those in the larger lumens. A learning curve among the endoscopists was suggested in the fixation rate. The distance between the markers and the chest wall changed significantly within a median of 44 days (range, 16-181 days) after treatment. CONCLUSION: The fixation of markers into the bronchial tree was useful for the setup for peripheral lung cancer and had an accuracy of +/-2 mm during the 1-2-week treatment period. The relationship between the markers and tumor can change significantly after 2 weeks, suggesting that adaptive four-dimensional RT is required.

Adult↗
PubMed2005

Comparison of imaging modalities for the accurate delineation of arteriovenous malformation, with reference to stereotactic radiosurgery.

PURPOSE: To investigate the discrepancy between the arteriovenous malformations seen on magnetic resonance angiography (MRA) and on stereotactic digital subtracted angiography (DSA). METHODS AND MATERIALS: The target volume on stereotactic DSA (V(DSA)) and the target volume on MRA (V(MRA)) were separately delineated in 28 intracranial arteriovenous malformations. The coordinates of the center and the outer edges of V(DSA) and V(MRA) were calculated and used for the analyses. RESULTS: The standard deviations (mean value) of the displacement of centers of V(MRA) from V(DSA) were 2.67 mm (-1.82 mm) in the left-right direction, 3.23 mm (-0.08 mm) in the anterior-posterior direction, and 2.16 mm (0.91 mm) in the craniocaudal direction. V(MRA) covered less than 80% of V(DSA) in any dimensions in 9 cases (32%), although no significant difference was seen in the target volume between each method, with a mean value of 11.9 cc for V(DSA) and 12.3 cc for V(MRA) (p = 0.948). CONCLUSION: The shift of centers between each modality is not negligible. Considering no significant difference between V(DSA) and V(MRA), but inadequate coverage of the V(DSA) by V(MRA), it is reasonable to consider that the target on MRA might include the feeding artery and draining vein and possibly miss a portion of the nidus.

Adolescent↗
PubMed2005

Real-time monitoring of a digestive tract marker to reduce adverse effects of moving organs at risk (OAR) in radiotherapy for thoracic and abdominal tumors.

PURPOSE: To evaluate the feasibility of real-time monitoring of a fiducial marker in/near the digestive tract and to analyze the motion of organs at risk to determine a reasonable internal margin. METHODS AND MATERIALS: We developed two methods to insert a fiducial marker into/near the digestive tract adjacent to the target volume. One method involves an intraoperative insertion technique, and the other involves endoscopic insertion into the submucosal layer of the normal digestive tract. A fluoroscopic real-time tumor-tracking radiotherapy system was used to monitor the marker. RESULTS: Fourteen markers (2 in the mediastinum and 12 in the abdomen) were implanted intraoperatively in 14 patients with no apparent migration. Seventeen of 20 markers (13/14 in the esophagus, 1/2 in the stomach, and 3/4 in the duodenum) in 18 patients were implanted using endoscopy without dropping. No symptomatic adverse effects related to insertion were observed. The mean/standard deviation of the range of motion of the esophagus was 3.5/1.8, 8.3/3.8, and 4.0/2.6 mm for lateral, craniocaudal and anteroposterior directions, respectively, in patients with intrafractional tumor motion less than 1.0 cm. CONCLUSION: Both intraoperative and endoscopic insertions of a fiducial marker into/near the digestive tract for monitoring of organs at risk were feasible. The margin for internal motion can be individualized using this system.

Abdominal Neoplasms↗
PubMed2005

The role of tumor lysis in reversible posterior leukoencephalopathy syndrome.

We report on a child with B-cell lymphoma who developed hypertension and reversible posterior leukoencephalopathy syndrome (RPLS) after chemotherapy conducted during recovery from tumor lysis syndrome. After recovery from RPLS, the patient received further combination chemotherapy without recurrence of the neurological signs or symptoms suggestive of RPLS. Many etiological factors have been reported in the development of RPLS; however, little attention has been paid to tumor lysis syndrome as a contributory factor for RPLS. Tumor lysis syndrome can precipitate the development of RPLS in patients with hematological malignancies who are undergoing chemotherapy. Knowledge and awareness would help facilitate immediate management such as normalization of blood pressure and temporary cessation of chemotherapy, helping to avoid irreversible brain damage.

Acute Kidney Injury↗
PubMed2005

Detection of amiodarone-induced pulmonary toxicity in supine and prone positions: high-resolution computed tomography study.

BACKGROUND: The aim of the present study was to describe the effectiveness and feasibility of high-resolution computed tomography (HRCT) in patients in supine and prone positions to detect amiodarone-induced pulmonary toxicity (APT). With regard to the possible differential diagnosis, our second goal was to emphasize the clinical value of HRCT with the patients in supine and prone positions compared with other paraclinical tests. METHODS AND RESULTS: Thoracic HRCT taken in both positions for 23 patients who were administrated amiodarone were prospectively evaluated in the current study. High-resolution computed tomography scans obtained with the patient in a prone position were helpful in differentiating dependent opacity from lung disease in 11 out of 23 patients. In another 4 patients, HRCT scans obtained with the patient in a prone position were useful in confirming the presence of subtle ground-glass opacities, considered as APT. Combination of HRCT in supine and prone positions provided a more reproducible method for evaluating the global extent of APT than other paraclinical tests. CONCLUSIONS: High-resolution computed tomography used in prone positions as well as a supine position could be an effective technique for reducing false-positive results in detection of APT and preventing the clinically serious pulmonary adverse effects by amiodanone.

Adult↗
PubMed2005

[Rapidly increasing allergic diseases].

It is well known that allergic diseases, such as allergic rhinitis, asthma, atopic dermatitis, and food allergy, are increasing in prevalence. Epidemiological studies show that the prevalence of allergic diseases is approximately 40% in children and 30% in adult. Thus allergic diseases are global health problem in Japan. Changes in environment or lifestyle may be one of the causes of the increase in allergic diseases. Therefore it may be a great concern for many people how they prevent the diseases or how they manage allergic symptoms. The major purpose of this citizen joint symposium was to broaden citizen's knowledge on the mechanism, epidemiology, and appropriate management of allergic diseases. We hope that this symposium provided useful information to the participants about the current trends in the management of allergic diseases.

Adult↗
PubMed2005

Bilateral germinoma involving the basal ganglia and cerebral white matter.

We describe radiologic findings of germinoma involving bilateral basal ganglia and cerebral white matter. In the early stage, T1-weighted MR images showed hyperintense areas in the bilateral globi pallidi. Later, T2-weighted images showed hyperintense areas involving bilateral white matter. The MR imaging findings reported here could help facilitate the early diagnosis of germ cell tumors in young patients.

Basal Ganglia Diseases↗
PubMed2005

[A case report of spinal dural AV fistula which showed drastic recovery].

Spinal dural AVF is the most common type of spinal AVMs. It affects especially old male with slowly progressive paraparesis in most cases. We have experienced a rare case of a middle aged male with spinal dural AVF who showed rapid deterioration in its course. The patient was treated with surgical interruption of AVF after transarterial embolization with NBCA. The patient improved well after the treatment, and intramedullary lesion on MRI disappeared after 4 years. The authors would like to stress the importance of early diagnosis and proper treatment for spinal dural AVFs.

Adult↗
PubMed2005

MR-guided percutaneous cryoablation for bilateral multiple renal cell carcinomas.

A 35-year-old woman with five renal cell carcinomas (RCCs) was treated by percutaneous cryoablation. She had two RCCs in the left kidney and three in the right. Cryoablation was performed using a high-pressure argon-based system with 2- or 3-mm cryoprobes under magnetic resonance (MR) guidance. Three tumors were completely ablated. Two tumors were residual, as they were so close to nearby organs that we were forced to stop the freezing to avoid complications. No complications were encountered, and renal function was preserved. In conclusion, MR-guided cryoablation is a safe procedure even when RCCs are bilateral and multiple.

Adult↗
PubMed2005

[Diagnostic imaging of spinal diseases].

With the advent of magnetic resonance imaging, diagnostic accuracy of spinal disorders has been much improved regarding their localization and histological prediction. The location of herniated disc materials is well appreciated on MR images without using contrast materials. MRI can predict the posterior longitudinal ligament is perforated or not. Kinematics of the spinal axis and CSF flow movement is evaluated on MRI with fast imaging. MR angiography with 3D reconstruction depicts the Adamkiewicz's artery and anterior spinal artery. Neuritis and neuropathy can be diagnosed by post-contrast T1 weighted image since inflammatory nerves are thick and enhance. Some intramedullary deseases tend to involve the peripheral area of the spinal cord; others are central. Edema extends longitudinally within the spinal cord by sparing the peripheral margin of the spinal cord and it is well appreciated with the T2- and proton- weighted images. The lateral and posterior funiculi are more frequently involved in multiple sclerosis.

Diffusion Magnetic Resonance Imaging↗
PubMed2004

Computed tomography and magnetic resonance imaging of the pericardium: anatomy and pathology.

The purpose of this article is to review the characteristics of computed tomography (CT) and magnetic resonance imaging (MRI) of the pericardium and pericardial diseases. Because patients with pericardial diseases usually present with nonspecific symptoms, these diseases may not be detected until they have reached an advanced stage. It is therefore important to distinguish between normal pericardial structure and disease. Multiplanar reconstruction images of CT and MRI are useful for evaluating faint changes of the pericardium. The specific pericardial diseases described in this article include pericardial cyst, constrictive pericarditis, pericarditis with radiation pericarditis, postoperative pericardial hematoma, and cardiac tamponade due to a paracardiac mass (lymphoma).

Heart Diseases↗