[en] Weighted mean survival time was estimated by platelet method (P-M), plasma radioactivity corrected whole blood method (CWB-M) and noncorrected whole blood method (NWB-M). Platelets were labeled with In-111 tropolone. In normal platelet survival group, mean survival time by P-M, CWB-M and NWB-M were 8.68 ± 0.43 (mean ± 1 SD), 8.80 ± 0.37 and 8.94 ± 0.39, respectively. In short survival group, no significant difference in weighted mean survival time was observed among three methods. In some cases, weighted mean survival time by platelet method was shorter than those by whole blood methods due to the scattering of platelet radioactivity caused by handling of the platelets and/or platelet counting. In the case with smaller erythrocytes contamination during In-111 labeling, the whole blood method especially noncorrected one was useful because it enables easy and precise measurement. (author)

[en] An attempt was made to measure In-111 labeled platelet survival time rapidly in a total of 31 patients with thrombopenia or thromboembolism. Mean platelet survival time and maximum platelet recovery were obtained when platelet radioactivity decreased by 10-19% (L-method), by 20-39% (M-method), and by 40-59% (S-method). Using the conventional L-method as standard, mean platelet survival time was classified as normal (8 days or more), slightly shortened (4-7 days), or extremely shortened (less than 4 days). In the normal group, mean platelet survival time obtained by S-method significantly differed from that by L-method, although there was no difference between M- and L-methods. In the other slightly shortened and extremely shortened groups, there was no significant difference in survival time among the three measurement methods. Regarding maximum platelet recovery and measured maximum, there was no difference among the three measurement methods. It appeared that the S-method is feasible when platelet radioactivity decreases by less than 70% on the 2nd day of measurement; and that the M-method is feasible in the other cases. In measuring platelet survival time, it seemed possible to reduce the measurement days by 1-2 days for the normal group, 1-4 days for the slightly shortened group, and 2-4 days for the extremely shortened group. (N.K.)

[en] Regional cerebral blood flow (rCBF) values obtained by the TLU method with two ¹²³I-IMP SPECT scans and one point arterial blood sampling and rCBF obtained by the ARG method with one ¹²³I-IMP SPECT scan and fixed distribution volume (Vd) values were compared in 17 cases. A case with post ischemic hyperperfusion or luxury perfusion was not observed in our cases. The correlation coefficients between rCBF values and Vd values obtained by the TLU method were 0.49 (p<0.001) in 184 ROI without hypoactive areas on the early image, and 0.61 (p<0.001) in 207 ROI with hypoactive areas, respectively. A high rCBF value with a low Vd value was not observed in any region. Mean Vd value was 44.0±7.0 (mean±SD) in all regions. The correlation coefficients between rCBF values using the TLU method and those using the ARG method with Vd fixed at 44 and 50 were also 0.98. Error of the rCBF value was larger in the region of high rCBF, however, noticeable error of the rCBF value was not observed in the ARG method. The ARG method is more convenient for quantifying rCBF. Venous blood radioactivity at 10 min after ¹²³I-IMP infusion was smaller than arterial blood radioactivity, and the blood activity in the distal vein was larger than that in the proximal vein. The ratio of venous blood activity to arterial blood activity was 0.92±0.04 (mean±SD) at the back of the hand, however, the ratio was a variant in each case. Arterial sampling was thought to be a reliable method to obtain more stable and precise rCBF. (author)

[en] Reproducibility of regional cerebral blood flow (rCBF) values obtained by the autoradiography (ARG) method with one SPECT scan and one point arterial blood sampling at 10 min after ¹²³I-N-isopropyl-p-iodoamphetamine (IMP) infusion was evaluated. The variation in the cross calibration factor between SPECT counts and well-type scintillation counts remained 2.2% for 13 months. The error in rCBF by sampling time difference was less than 3% when sampling time was within 10 min±30 sec after infusion. There was a favorable correlation between the rCBF values in two separate resting scans measured by the ARG method in 10 patients (r=0.907). And the mean ratio of rCBF values by the second study to those by the first study in the cerebellum and cerebral lobes in 10 patients was 0.989±0.056 (mean±SD). There was no significant difference in rCBF values between two separate studies. Reproducibility of rCBF with the ARG method was proved to be good. The ARG method was thought to be useful for the assessment of treatment effects and clinical courses. (author)

[en] The thyroid uptake of ¹²³I and ¹³¹I is generally measured by a gamma camera system. We evaluated the error in determining thyroid uptake caused by different methods of calculation among four gamma camera systems with various collimators. We first designed an original thyroid phantom that consisted of the thyroid and a body containing various levels of radioiodine activity. The applications for thyroid uptake equipped in two gamma camera systems performed calculations by the automatic method with background counts not subtracted from the capsule counts. When the size of the rectangular region of interest (ROI) for the capsule was set at 10 x 8 cm (a typical ROI size for the thyroid), percentages of thyroid uptake as calculated by the manual method with background counts subtracted from the capsule counts and thyroid counts were 52% to 57% when the value was set at 55% for ¹²³I; and 54.2% and 58.7%, respectively, when the value was set at 60% for ¹³¹I. On the other hand, the percentages of thyroid uptake calculated by the automatic method with the application using two gamma camera systems with non-subtraction of background counts from the capsule counts were 46% and 50.5% when the value was set at 55%; and 49.6% when the value was set at 60%. The values calculated by the automatic method were underestimated as a result of background counts that were not subtracted from the capsule counts. When ROI size for the capsule was set at 4 x 4 cm, which is slightly larger than the capsule size, even thyroid uptake as determined by the automatic method using the application showed a difference of less 2% from the set values. There was no difference in thyroid uptake among the various kinds of collimators, high-resolution collimators, all-purpose collimators, and a suitable collimator for gamma-ray energy of ¹²³I. (author)

[en] First-pass radionuclide ventriculography (FRNV) followed by myocardial SPECT with ^99mTc-MIBI was performed on 9 patients with coronary artery disease at rest and ATP infusion. When ^99mTc-MIBI (740 MBq) was injected, FRNV was simultaneously performed and left ventricular function was evaluated. One hour after the injection of ^99mTc-MIBI, myocardial SPECT was performed. Agreements in findings with regard to the presence or absence of myocardial ischemia or infarction were 19 out of 27 (70%) segments. Left ventricular ejection fraction (LVEF) decreased (p<0.01) in the patients with multi vessel disease during ATP infusion. The wall motion abnormality during ATP infusion showed improvement after coronary bypass surgery (CABG). Improvement of regional wall motion or LVEF (regional EF) may reflect post CABG improvement. (author)

[en] In conventional three-dimensional (3D)-CT image processing, the images are influenced by subjective threshold settings. The purpose of this study was to evaluate an objective threshold setting technique based on the discriminant analysis method. The concentration of contrast medium in a joint of a simulated upper cervical spine phantom was changed, and its threshold was measured from scanned data by using the discriminant analysis method, and mean CT attenuation was measured. On the other hand, an accurate image of the corresponding joint in the phantom was made, and its minimum threshold was measured. Regression analysis between the adjusted minimum threshold and mean CT attenuation of the region of contrast medium was performed. The obtained linear regression formula was applied to the threshold settings in five cases for atlanto-axial 3D-CT facet arthrogram (3D-CTF), and the accuracy of the images was examined. There was a strong correlation between the adjusted threshold and mean CT attenuation, and the obtained linear regression formula was y=0.625x-141 (r²=0.991, p<0.01). This equation could be used clinically for correction of the threshold settings. We propose the following method for threshold setting of 3D-CTF: the threshold of the region of contrast medium is measured using the discriminant analysis method, then the adjusted minimum threshold for the threshold settings of 3D-CTF is calculated from mean CT attenuation. The method described herein is an objective, general-purpose methodology that is applicable to various types of 3D-CT. (author)

[en] We made a detailed study on the course of study in radiation safety control prescribed on March 28, 2003. Questionnaires were sent to 39 training schools for radiological technology, to which 66.7% replied (26/39). Subjects on radiation safety control must include knowledge and technology in both radiation control and medical safety. The contents for instruction of radiation control were in accordance with those given in the traditional program; however, some discrepancies were found in the contents of medical safety. As medical safety, emphasized by the revised Medical Service Law, is regarded as very important by many hospitals, safety control education that include medical ethics should be required as part of the curriculum in the training schools for radiological technologists. (author)

[en] To evaluate the usefulness for the detection of ischemic heart disease (IHD), ATP first pass radionuclide ventriculography (RVG) was performed in 10 patients. Coronary angiography was performed in all patients. Among these patients, 2 had single vessel disease, 2 had double vessel disease, 3 had triple vessel disease, and 3 had normal coronary arteries. RVG was performed at rest, then, ATP was infused at the rate of 0.16 mg/kg/min and ATP-RVG was done 4 minutes later. The left ventricular ejection fraction (LVEF) was calculated, and the regional wall motion (RWM) was graded as normal, hypokinesis, akinesis, and dyskinesis. In the patients with coronary artery disease, RWM decreased in 5 of 7 patients and LVEF decreased in 6 of 7 patients by ATP. However, RWM and LVEF did not decrease in the patients with normal coronary arteries. These results suggested that ATP-RVG might provide useful information for the evaluation of IHD. (author)

[en] Based on the new amendment of the Medical Service Law and the Pharmaceutical Affairs Law, the safety control for the medical equipments and devices was strengthened; and a radiological technologist should be stipulated as a safety control manager for the medical equipments and devices. Although it is thought that Start-up check is important for the safety assurance, the enforcement situation is not clear until now. In this report, on the occasion of the start-up of the new Law, questionnaire about the start up check (time and a check items) were investigated from 56 hospitals applying the visit interview. Modality by modality check up time was obtained from 261 institutions by the descriptive study paper type. Start-up check and arming up were applied for almost all modalities about 30 minutes before start of the clinical tests. The check up items for the medical equipments and devices depended on each hospital. Therefore, safety assurance should be established, cooperating with the medical equipment distributors, the hospital sharing the checked results for the patients' safety. (author)