The Stereotactic Body Frame, which was devised as a fastening unit for the irradiation of various truncal lesions, has obtained a good reputation for its high-precision reproductivity. This device is accessorized with ‘Diaphragm Control’, which can reduce the respiratory movement of intra-thoracic organs. In this study, to investigate the possibility of a respiratory monitor using our device, we try to clarify the relationship between the pressure against the abdominal board of ‘Diaphragm Control’ and each constrained tidal respiratory movement. Our original software was programmed to detect and analyze these data with our personal computer from some ready-made highly sensitive pressure detectors. In any fundamental performance of this system, response time is less than 1 msec at 115,200 bps, minimum detectable weight is 420 g, linearity correlation between loading weight and pressure index value is seen from 1000 g to 6000 g loading, and reproducibility of measurement is evaluated by coefficient of variation (CV=0.95% at 3000 g loading). It has sufficient capability to be used as a respiratory monitoring device during radiation therapy. In an experiment with three volunteers, the results revealed a positive correlation between pressure index value and ventilation air volume by spirometer. The decision coefficients (R2) were 0.7717, 0.7995, and, 0.8684, respectively. Our original respiratory monitoring device can be used for quantitative respiratory suppression and unexpected breathing detection without loading additional stress on the patient.
Some cases have been reported in which an optical illusion of lightness perception influences the detectability in diagnosis of low-density hematoma in head CT images in addition to the visual impression of the photographic density of the brain. Therefore, in this study, the author attempted to compare the detectability in diagnosis for chest images with pneumothorax using visual subjective evaluation, and investigated the influence of optical illusion on that detectability in diagnosis. Results indicated that in the window setting of lung, on such an occasion when the low-absorption free space with pneumothorax forms a crescent or the reduced lung borders on the chest-wall, an optical illusion in which the visual impression on the difference of the film contrast between the lung and the low-absorption free space with pneumothorax was psychologically emphasized when contrast was observed. In all cases the detectability in diagnosis for original images with the white thorax and mediastinum was superior to virtual images. Further, in case of the virtual double window setting of lung, thorax, and mediastinum, under the influence of the difference in the radiological anatomy of thorax and mediastinum as a result of the grouping theories of lightness computation, an optical illusion different from the original images was observed.
We estimated collimator scatter factor, Sc, of symmetric rectangular fields of any size by applying a two-component scatter model to measured in-air output data in width and length directions of measured rectangles. The in-air output was measured for symmetric rectangles with combined width and length sizes of 7 × 7 and 6 × 6 using 10 MV and 4 MV X-rays of Varian’s Clinac 2100 C/D, respectively. The model consists of scatter components from the primary collimator and flattening filter and from the collimator jaws: the former shows a saturation curve and the latter increases linearly with enlarging field size. This model was fitted to the measured dataset firstly in the width and secondly in the length directions of rectangles; then, by compiling interpolated matrix data, the Sc table of symmetric rectangles was constructed. In addition, using this Sc table, values of Sc were calculated for a few asymmetric rectangles by Day’s method, and were in good agreement with measured values. Therefore, we think that our method is practical and precise for constructing the Sc table of symmetric rectangles from measured data, and that using this table, the Sc of any asymmetric rectangles may be calculated.
Purpose: Positron emission tomography (PET) is a powerful tool for measuring in vivo functions such as blood flow, metabolism, enzyme activity, receptors, and transporters. However, plural measuring instruments (i.e., the dose-calibrator, the auto well gamma counter, the continuous blood sampling system) are necessary for the quantitative PET measurement as well as the PET scanner. The purpose of this study was to investigate the reliability of plural measuring instruments from the maintenance data for 6 years. Methods: Four kinds of measuring instrument were evaluated: a dose-calibrator (CAPINTEC, CRC-15R), an auto well gamma counter (ALOKA, ARC-400), a continuous blood sampling system (ESPEC Techno, PH type), and a dedicated PET scanner (Siemens, ECAT EXACT HR+). We examined whether the initial performance for system sensitivity is maintained. The reliability of the PET scanner was evaluated from the value of mean time between failures (MTBF) for each part of the system obtained from the maintenance data for 6 years. Results: The sensitivity of a dose-calibrator and an auto well gamma counter were maintained virtually constant during the 6 years, but the sensitivity of a continuous blood sampling system was 0.1±3.2%. The sensitivity of a PET scanner was decreased to 92.3% of the initial value. Fifty-one percent of the problems with the PET scanner were for detector block (DB) and analog processor (AP) board. The MTBF of DB and AP board module were 199 and 244 days, respectively. The MTBF of the PET scanner was 56 days. Conclusion: The performance of three measuring instruments, excepting the PET scanner, was relatively stable. The reliability of the PET scanner strongly depends on the MTBF of the DB and AP board. For quantitative PET measurement, it is effective to evaluate the reliability of the system and to make it known to the users.
In non-vascular interventional radiology (IVR) such as percutaneous transhepatic cholangio-drainage (PTCD) and nerve block, the operator’s hands are irradiated in primary x-ray field. In Over-table tube fluoroscopy system, operator’s hands inevitably are exposed excessively to intensive primary radiation, whereas in the Under-table tube fluoroscopy system, they are irradiated weakly by attenuated radiation through the patient’s body. For this reason, the dose to the operator’s hands in Under-table tube fluoroscopy is less than in Over-table tube fluoroscopy. This paper proposes general formulas for estimating the absorbed dose on the operator’s hands in two types of fluoroscopy. The formulas include factors affecting the absorbed dose on the operator’s hand; distance from source to the operator’s hands, x-ray transmittance of the patient and patient’s bed, and back-scatter factor of the patient. Absorbed dose to imitated operator’s hand was measured and estimated by formulas in two types of fluoroscopy for various phantom thicknesses and two field sizes using an ionization chamber. The difference between estimated absorbed dose and measured absorbed dose was less than 10%.
It has been noted that the manual settings of region of interest (ROI) to the single-photon-emission-computed-tomography (SPECT) slice lacked objectivity when the fixed quantity value of regional cerebral blood flow (rCBF) was measured previously. Therefore, we jointly developed software “Brain ROI” with Daiichi Radioisotope Laboratories, Ltd. (Present name: FUJIFILM RI Pharma Co., Ltd.) The software normalized an individual brain to a standard brain template by using Statistical Parametric Mapping 2 (SPM 2) of the easy Z-score Imaging System ver. 3.0 (eZIS Ver. 3.0), and the ROI template was set to a specific slice. In this study, we evaluated the accuracy of this software with an ROI template that we made of useful size and shape, in some clinical samples. The method of automatic setting of ROI was the objective. However, we felt that we should use the shape of the ROI template without the influence of brain atrophy. Moreover, we should see normalization of the individual brain and confirm the accuracy of normalization. When normalization failed, we should partially correct the ROI or set everything by manual operation for the operator. However, it was thought that this software was useful if the tendency was understood because examples of failure were few.
Pediatric patients are especially sensitive to radiation, and when scanning their heads with CT, it is necessary to do so with a low dose and pay very close attention. However, there are many problems when scanning pediatric patients, and it is often confusing to set the conditions for scanning. To do a survey and comparison, we issued a questionnaire to 23 pediatric hospitals and 89 university hospitals, asking about their usage of sedation, studied disorders, as well as how and under what conditions they scan their patients. The percentage of response was 40% in total. Based on the questionnaire results, we could not see much difference in the conditions for scanning. However, there was a significant difference in the usage of sedation and studied disorders between pediatric hospitals and university hospitals. The most studied disorders at pediatric hospitals were convulsion and consciousness disorders, and low-contrast areas such as the albocinereous, which requires images without movement artifacts. In order to obtain clear images, the patient was put under sedation. On the other hand, university hospitals often deal with external injuries, which usually involve danger in using sedation, and patients are usually examined without it. In addition, the usage of sedation is rare because bleeding brings up high-contrast images, and it is easy to make a diagnosis even if there is some movement artifact. Also to aim at setting a standard for medical technology, from here on, guidelines of examining methods and setting conditions should be made depending on how the different disorders should be treated.