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Biomedical subjects

E Kunieda

Publications and source records attributed to E Kunieda.

At least 19 recordsLinked to original sources
PubMed2000

Indications of stereotactic irradiation for brain lesions.

Stereotactic radiosurgery (SRS: single-fraction stereotactic irradiation) was originally developed to treat benign lesions in the brain, and has been adopted for the treatment of small primary or metastatic brain tumours. It has recently been recommended that stereotactic radiotherapy (SRT: fractionated stereotactic irradiation) be applied to the treatment of brain tumours; however, it requires much more time and work than SRS, and sufficient radiobiological evaluations of these techniques have never been carried out. Biologically effective doses were calculated to determine the indications for SRS and SRT, and to decide on an effective SRT schedule, incorporating the factors of 'repair' and 'cell proliferation'. The results suggest that SRS would be recommended for arteriovenous malformations and benign tumours that have distinct margins separating them from surrounding normal tissue and SRT would be recommended for benign or malignant brain tumours without clearly defined boundaries. The recommended SRT schedules would be 7 Gy x 7 fractions every other day for malignant tumours and 3.5 Gy x 12 fractions every other day for benign tumours. However, clinically, these schedules should be modified according to many other factors in individual cases.

Brain Neoplasms↗
PubMed1999

Scintigraphic evaluation of myocardial ischaemia using a new fatty acid analogue: iodine-123-labelled 15-(p-iodophenyl)-9-(R, S)-methylpentadecanoic acid (9MPA).

Iodine-123-labelled 15-(p-iodophenyl)-9-(R,S)-methylpentadecanoic acid (9MPA) is a branched fatty acid analogue for myocardial imaging, which has been recently designed for medium washout rates from the myocardium. The purpose of this study was to assess the clinical feasibility of use of 9MPA for the evaluation of myocardial ischaemia. Twenty-one patients were injected with 9MPA at rest, and sequential single-photon emission tomography (SPET) acquisitions were performed 5, 45 and 240 min after administration to calculate washout rates from the myocardium. The findings of 9MPA images were analysed in comparison with those of perfusion images with thallium-201 or sestamibi, coronary angiography and left venticulography. In general, reduction of 9MPA uptake was more remarkable than that of perfusion tracers. The findings of 9MPA early images correlated better with those of exercise perfusion images than with the rest images. Measured washout rates of 9MPA from ischaemic myocardium were significantly slower than those from normal myocardium. The majority of areas with abnormal 9MPA distribution manifested wall motion abnormality, while all areas with normal tracer distribution presented normal wall motion. The detectability of myocardial ischaemia was improved by adding mid and delayed images in six cases. However, both washout and fill-in patterns were encountered in ischaemic lesions, rendering the interpretation of images difficult. In conclusion, the results of this study indicated that 9MPA has acceptable myocardial uptake, that its use is feasible for the detection of ischaemia and that the abnormal distribution of the tracer correlates well with wall motion abnormality reflecting metabolic disorders.

Fatty Acids↗
PubMed1999

[Evaluation of parathyroid imaging methods with 99mTc-MIBI--the comparison of planar images obtained using a pinhole collimator and a parallel-hole collimator].

Parathyroid scintigraphy with 99mTc-MIBI was performed using two kinds of collimators, namely, a pinhole one and a parallel-hole one, to evaluate which one was more suitable for the detection of hyperfunctioning parathyroid lesions. In the studies using 99mTc source, the pinhole collimator showed better efficiency and spatial resolution in the distance where the parathyroid scan are actually performed. In the phantom study, the nodular activities modeling parathyroid lesions were visualized better on the images obtained using the pinhole collimator. In clinical studies for 30 patients suspicious of hyperparathyroidism, hyperfunctioning parathyroid nodules were better detected when the pinhole collimator was used. In conclusion, the pinhole collimator was thought to be more suitable for parathyroid scintigraphy with 99mTc-MIBI than the parallel-hole collimator.

Aged↗
PubMed1999

[Hard-copy (film) versus soft-copy (CRT) reading performance between compressed and uncompressed images: SOLs in abdominal CT images].

The objective of this study was to examine the feasibility of soft-copy (CRT) reading and suitable compression. Forty abdominal CT images with a space-occupying lesion (SOL) in liver and 40 normal images were selected for receiver-operating-curve (ROC) analysis. Each image was compressed by JPEG extended mode into 1/10 its original capacity, and then an expanded image was printed on film. Ten radiologists evaluated the presence of liver SOLs (primary and secondary tumors) on soft-copy (CRT) and hard-copy (film) images. Each radiologist reviewed four types of images (original and compressed hard-copy and original and compressed soft-copy images). Values of the area under the curve in the various ROC analyses were 0.858 (FILM) and 0.842 (CRT) for original images and 0.879 (FILM) and 0.846 (CRT) for compressed images. The results of ROC analysis showed better reading performance with hard-copy than soft-copy images, but the difference was not statistically significant. Compressed images showed a higher value (0.879) than original images (0.858), a difference that was statistically significant (p < 0.029) by the paired t-test but not by the jackknife method. The results indicate that soft-copy reading is a clinically acceptable alternative to hard-copy reading. We have had no difficulty in reading abdominal CT images compressed to 1/10 of the original size by the JPEG method. This study was supported in part by a grant from the Japanese Ministry of Health and Welfare.

Humans↗
PubMed1998

New system for linear accelerator radiosurgery with a gantry-mounted video camera.

PURPOSE: We developed a positioning method that does not depend on the positioning mechanism originally annexed to the linac and investigated the positioning errors of the system. METHODS AND MATERIALS: A small video camera was placed at a location optically identical to the linac x-ray source. A target pointer comprising a convex lens and bull's eye was attached to the arc of the Leksell stereotactic system so that the lens would form a virtual image of the bull's eye (virtual target) at the position of the center of the arc. The linac gantry and target pointer were placed at the side and top to adjust the arc center to the isocenter by referring the virtual target. Coincidence of the target and the isocenter could be confirmed in any combination of the couch and gantry rotation. In order to evaluate the accuracy of the positioning, a tungsten ball was attached to the stereotactic frame as a simulated target, which was repeatedly localized and repositioned to estimate the magnitude of the error. The center of the circular field defined by the collimator was marked on the film. RESULTS: The differences between the marked centers of the circular field and the centers of the shadow of the simulated target were less than 0.3 mm.

Computer Terminals↗
PubMed1998

[Is medical linac suitable for high-precision stereotactic irradiation?: investigations in geometrical accuracies of gantry and couch].

Linac-based radiosurgery has many advantages over the gamma knife, including low initial cost and no need of source replacement. On the other hand, most of the medical linacs currently in use were not originally designed to be applied for radiosurgery, and, therefore, careful quality assurance programs are required. In the gantry-head of a linac, a small CCD video camera is mounted in a position optically identical to that of the x-ray source. The video signal from the camera was digitalized to be evaluated for geometrical errors. A metal ball fixed to the stereotactic base frame via XYZ-sliding rods was used as a simulated target. Displacements of the target from the isocenter were measured during rotation of the gantry. Displacements in the gantry-rotation plane were satisfactorily small, while those perpendicular to it were maximal at gantry position angles of 0 degree and 180 degrees. This error night be caused by gravitational vending of the heavy gantry head. Although other major errors of the linac were within one millimeter, the center of coach rotation around the isocenter did not coincide with the center of gantry rotation, probably owing to gravitational vending. Special care should be taken when very small collimators are employed.

Quality Control↗
PubMed1998

[Radiobiological considerations for stereotactic irradiation].

Stereotactic radiosurgery (SRS: stereotactic irradiation [STI] delivered in a single high dose) was initially developed by Leksell for non-malignant brain lesions, but there has been increasing interest in using it to treat small primary brain tumors or metastases. In more recent years, stereotactic radiotherapy (SRT: fractionated STI) has been developed, but radiobiological factors have not been sufficiently evaluated in relation to these techniques. Larson classified potential STI targets into four categories according to whether the target tissue is early- or late-responding and whether it is embedded within or only surrounded by normal tissue. We have actually calculated biologically effective doses for these categories to determine the indications for SRS and SRT, and to be able to choose suitable SRT schedules. Based on our calculations, theoretically SRS would be recommended for AVMs and benign tumors having distinct margins separating them from surrounding normal tissue and SRT would be recommended for low or high grade astrocytomas without clearly defined boundaries and metastasis. Recommended SRT schedules would be 49 Gy/7 fractions, 52 Gy/8 fractions or 54.9 Gy/9 fractions completed within 2 weeks. However, clinically, these indications and SRT schedules should be modified according to the many other factors involved in individual cases, such as tumor size, presence of tumor necrosis, the patient's general condition, prognosis, and so on.

Brain↗
PubMed1998

[Schedule of stereotactic radiotherapy: a study considering the factors of repair and cell proliferation].

Stereotactic radiosurgery (SRS: stereotactic irradiation [STI] delivered in a single high dose) was initially developed by Leksell for non-malignant brain lesions, but there has been increasing interest in using it to treat small primary brain tumors or metastases. Recently, stereotactic radiotherapy (SRT: fractionated STI) has been recommended on the basis of radiobiological considerations for tumors in which both normal glial cells and tumor cells reside within the tumor margin. Strangely, the factors 'repair' and 'cell proliferation' have been neglected in the radiobiological evaluations of STI reported so far, mainly because of the complexity of the calculations. 'Half-time repair' which is the key value in the 'repair' factor may be larger for nervous tissue than for many other normal tissues because nerve cells have decreased ability to recover from damage. 'Cell proliferation' should be an important factor when the total radiation period is extended by applying SRT. In this study, we created models based on estimated 'half-time repair' and 'cell doubling time' and attempted to determine optimal SRT schedules. When repair and cell proliferation factors are also taken into consideration, the recommended SRT schedules would be 7 Gy x 7 fractions every other day for malignant tumors and 3.5 Gy x 12 fractions every other day for benign tumors. However, clinically, these schedules should be modified according to factors in individual cases, e. g., tumor size, presence of tumor necrosis, the patient's general condition, prognosis, and so on.

Brain↗
PubMed1998

[IS&C image viewing and conversion software for Macintosh computer].

Although standardized data-transmission protocols such as DICOM are very beneficial, on-line transmission on images is often difficult to establish because of cost or security concerns. On the other hand, media-based data exchange is simple and adequate for the private use of medical images. We developed a viewing software program for medical images stored in magneto-optical disks with IS&C standard format. It displays images with gray-scale tone and stores them in Macintosh PICT format. The software is available for personal use from the first author.

Diagnostic Imaging↗
PubMed1995

[Evaluation of renal function using 99mTc-MAG3 comparison with 131I-OIH by simultaneous dual energy peak acquisition method].

A newly developed 99mTc-labeled renal scintigraphic and renographic agent, 99mTc-mercaptoacetyltriglycine (99mTc-MAG3) was studied clinically and compared with 131I-OIH in 16 patients with various renal and urinary tract disorders. The abdominal aorta and the common iliac artery were clearly visualized in the vascular phase. The renogram patterns showed the same pattern in all cases. The parameters on the renogram such as Tmax, T2/3, T1/2 were compared. The highly significant correlations of Tmax, T2/3 and T1/2 were observed between 99mTc-MAG3 and 131I-OIH with correlation coefficient of 0.982, 0.907, 0.990, respectively. In all cases, excretion of 99mTc-MAG3 was slower than that of 131I-OIH and the ratios of Tmax, T2/3 and T1/2 between 99mTc-MAG3 and 131I-OIH were 1.113 +/- 0.121, 1.277 +/- 0.247, 1.179 +/- 0.075, respectively. It is concluded that 99mTc-MAG3 is useful renal imaging agent as an alternative to 131I or 123I-OIH.

Adolescent↗
PubMed1995

[Dose-volume histogram comparison among techniques of linac stereotactic radiosurgery].

The aim of this study was to analyze the three-dimensional dose distributions produced by various techniques used in current radiosurgery treatments by means of dose-volume histograms (DVH). Off-center ratio and tissue-peak ratio from 6-MV X-rays through additional cylindrical collimators were measured in advance for dose calculation. The use of the diamond detector and beam profile film dosimetry in small fields were certified. The impact of arc number, arc geometry, and field size on the dose distribution in a spherical phantom was evaluated through the use of DVH. These were calculated for a) four arc irradiations with collimator sizes of 5, 10, 20 and 30 mm in diameter, and b) for single-plane rotation, four or eleven multiple non-coplanar convergent arcs, dynamic rotation and precessional converging radio-therapy (PCR) with a field size of 20 mm. PCR is performed in the sitting position with the patient seated on a special treatment chair, which is rotating continuously while the gantry moves from the top to the center of the chair rotation. Most of the differences between techniques were found in a range of less than 40% of the maximum dose. Multiple non-coplanar convergent arcs with four or eleven arcs and PCR performed similar result in DVH, while single-plane rotation revealed almost unacceptably shallow dose falloffs. The DVH of dynamic rotation was between that of single-plane rotation and the other three methods.

Humans↗
PubMed1995

Evaluation of bi-level image converting methods for nuclear medicine image database stored in the IS&C magneto-optical disk.

1. INTRODUCTION. We have developed a report and imaging management system for nuclear medicine. The report and image data are stored in the IS&C magneto-optical disk (IS&C MOD). Nuclear medicine image data are relatively small, but they are large enough to create problems when being transported over a low-speed Hospital Information System (HIS) network. Moreover, gray scale image output devices (i.e., high-resolution displays, sonoprinters) are expensive. If high quality bi-level (black and white) images were available, images could be transferred through low-speed network with inexpensive bi-level terminals or conventional page-printers. We examined images using several bi-level image conversion techniques [1, 2] in order to determine how useful the bi-level images are and to assess their suitability for use in nuclear medicine. The images were compared with original film images by ROC analysis. The modified minimized average error method was found to be superior to other methods in bone and gallium images. Its A-values are 0.83 in gallium scan and 0.85 in bone scan. 2. MATERIALS AND METHODS. Our system consists of three digital gamma cameras, a nuclear medicine data processing unit, two UNIX stations, and two personal computers. The computers and the data processing unit are connected via Ethernet and each computer has an IS&C MOD unit. Image and report data are stored in the IS&C MOD. The computers are also connected off-line through the IS&C MOD. To evaluate image quality, bone scan images and gallium scan images (1024x512, 2048x1024 pixels and 16 bits depth) were converted to bi-level images (same pixels and one bit depth) using four methods: dither method, minimized average error method (MAE)[1], modified regional adaptation method, and constrained average method. For the dither methods, three sets of dither matrix (Fatting's, Bayer's and our original matrix) were employed. The computer images were compared with original film images by ROC analysis. 3. RESULTS. The converted bi-level images were 1/16 the size of the originals. They were transferred via Ethernet, displayed on the monochrome display, and printed using a conventional page-printer (240 dpi or 300 dpi). The A-values of the original gallium and bone images on the films were 0.89 and 0.94. Modified MAE method gave better results than other methods tested, with the gallium image using this technique reading 0.83 on the A-scale; and the bone images were 0.85. 4. DISCUSSION. Generally, nuclear medicine images require lower spatial and gray level resolution than other computer imaging techniques. We compared four bi-level image conversion methods in order to know which methods are suitable to nuclear medicine images. The ROC analysis was employed to evaluate these image qualities. The MAE methods made particular texture pattern as artifacts in the intermediate gray level area. But it can express homogeneity the neutral level. The dither method images are coarse texture. It affects detectabilities of subtle abnormal findings. 5. CONCLUSIONS. The A-z values of the modified MAE images were comparable to those of original film images. Although bone images give slightly lower values, many abnormal findings can be ascertained on bi-level images. High quality bi-level image techniques are considered to be useful for nuclear medicine image database systems.

Japan↗
PubMed1995

Development of a personal computer's viewing station for the IS&C magneto-optical disk.

We developed a display station for the medical images stored in the IS&C (Image Save and Carry) magneto-optical disk. This station consisted of the personal computer and the magneto-optical disk drive. The performance of this system was evaluated and was compared with the Unix workstations. We found that the personal computer system had an adequate ability to display medical images. It provided, moreover, for portability and practical use of medical information.

Data Display↗
PubMed1994

[Parallel processing of dose calculation for external photon beam therapy].

We implemented external photon beam dose calculation programs into a parallel processor system consisting of Transputers, 32-bit processors especially suitable for multi-processor configuration. Two network conformations, binary-tree and pipeline, were evaluated for rectangular and irregular field dose calculation algorithms. Although computation speed increased in proportion to the number of CPU, substantial overhead caused by inter-processor communication occurred when a smaller computation load was delivered to each processor. On the other hand, for irregular field calculation, which requires more computation capability for each calculation point, the communication overhead was still less even when more than 50 processors were involved. Real-time responses could be expected for more complex algorithms by increasing the number of processors.

Mathematical Computing↗
PubMed1990

Bone scanning in patients with pleural effusion--experience in 76 cases.

Seventy-six patients with malignant or benign pleural effusion were studied to determine the incidence of accumulation of 99mTc-MDP in relation to effusion, and reveal the mechanism. Of 76 patients, 46 (61%) were found to have diffuse uptake of 99mTc-MDP in the hemithorax, with almost the same positive rate in malignant and benign effusions, i.e. 62% and 57%, respectively. Of 46 patients, 32 (70%) showed diffuse, slight accumulation in the hemithorax, and the positive rate had a tendency to be higher with the increase in the effusion volume. We are convinced that the major mechanism of unilateral intrathoracic accumulation of 99mTc-MDP in pleural effusion is a passive transudation.

Adult↗
PubMed1989

[Left ventricular function in right ventricular overload: asymmetry of the left ventricular ejection].

This study clarified regional and global functions of the distorted left ventricle due to right ventricular overload by means of gated radionuclide ventriculography (RNV). Cardiac catheterization and RNV were performed in 13 cases of atrial septal defect (ASD), 13 of pure mitral stenosis (MS), 10 of primary pulmonary hypertension (PPH), and 10 of normal subjects (NL). Right ventricular systolic pressure (RVSP) was 32.9 +/- 13.9, 45.0 +/- 12.2, 88.3 +/- 17.1, and 21.2 +/- 4.5 mmHg, respectively. RNV was performed with a 99mTc-red blood cell in a vivo labeling technique. The end-systolic LAO view of the left ventricle was halved into septal and free-wall sides. The end-diastolic halves were determined in the same plane. Ejection fractions of the global left ventricle (LVEF), global right ventricle (RVEF), the septal half of the left ventricle (SEPEF), and the free-wall half of the left ventricle (FWEF) were obtained. LVEF was 56.8 +/- 9.8% in NL, 52.8 +/- 10.5% in ASD, and 49.5 +/- 12.9% in PPH. In MS, LVEF (47.0 +/- 13.0%) was smaller than those in the other groups. RVEF was 37.0 +/- 5.2% in NL, 43.7 +/- 15.5% in ASD, and 32.8 +/- 11.5% in MS. In PPH, RVEF (25.0 +/- 10.6%) was smaller than those in the other groups. SEPEF was smaller in AS D (42.5 +/- 13.2%), MS (40.4 +/- 13.1%), PPH (40.5 +/- 12.5%) than in NL (53.5 +/- 8.5%). Systolic function of the septal half of the left ventricle was disturbed by right ventricular overload. RVEF (r = -0.35, p less than 0.05) and SEPEF (r = -0.51, p less than 0.01) had negative correlations with RVSP. As RVSP rose, systolic function of the septal half of the left ventricle was more severely disturbed. FWEF was the same among the four groups; NL (57.0 +/- 12.6%), ASD (48.6 +/- 15.2%), MS (50.5 +/- 12.0%), and PPH (51.1 +/- 12.3%). Right ventricular overload does not affect systolic function of FWLV. There was a good correlation between SEPEF and LVEF in NL (r = 0.81), though in PPH this correlation was poor (r = 0.64). In patients with PPH the septal side of the left ventricle does not act as a part of the global left ventricle. Systolic function of the septal side of the left ventricle is disturbed due to the distortion of the ventricular septum, but systolic function of the free-wall side is maintained within a normal range, when the left ventricular myocardium is kept normal.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗