[en] This invention concerns a radiation monitor for measuring the amount of radiaiton contaminations in nuclear reactor structural materials and classfying them depending on the degree of contamination upon reactor dismantling. The monitor has a wall surface adsorbing device for causing the monitor to be adsorbed on the wall surface and a driving mechanism for driving the monitor both front-to-back and right-to-left directions. Radioactive rays on the vertical wall surfaces or ceiling wall surfaces are measured by remote control operation for an analyzer for analyzing the measuring data from the radiation monitor. According to the present invention, it is possible to surely and safety measure the radiation rays at the vertical wall surfaces or top plates (inner wall surface of ceiling) difficult to be measured or at the inner wall surfaces of pipes in such a size that an operator can not enter. (I.S.)

[en] The circumstances of the development from longitudinal to transverse tomography of the SPECT method and their respective features are described. This SPECT imaging is influenced by various factors, and this can be responsible for image differences among institutions. Image-modifying factors for the SPECT method are verified in terms of 1) the system performance for measurement, 2) image techniques, and 3) the system performance for CRT indication and record, respectively. Beside, the author proposes optimal density and gradation for CRT image toward the standardization of digital images. (J.P.N.)

[en] The single photon emission CT method (SPECT) using a rotating scintillation camera has rapidly been spreading because of its handiness and usefulness. However, it has some questions theoretically. We studied the quantative capability of SPECT by phantom experiments. Although the ECT values in the reconstructed image were highly quantitative compared with algorithm in the planar image, it was imposible to estimate absolute activities from the ECT values because of theoretical difficulty in corrections of scattering and absorption. We attempted, on some assumptions, a simultaneous correction for scattering and absorption using an interactive convolution counts by Walter et al., considering elimination of scattering and improved the quality of the image. The distribution of absorption coefficients in the tomographic plane was obtained by the transmission CT data using sup(99m)Tc flood source, and corrected, assuming that these data are associated with compton scattering less than 90 deg. It reduced the scattering and improved the reliability of ECT values. As clinical applications, we have reported on the measurements of organ volumes, the ECT method for cerebral blood flow distribution by continuous sup(81m)Kr infusion, the functional ECT image in hepatobiliary scintigraphy, and the gated cardiac blood pool ECT method. We have further suggested that an application for dynamic study will increase in conjunction with the spread of the ring type SPECT equipment. (author)

[en] Maximum likelihood expectation maximization (ML-EM) image quality is sensitive to the number of iterations, because a large number of iterations leads to images with checkerboard noise. The use of median filtering in the reconstruction process allows both noise reduction and edge preservation. We examined the value of median filtering after reconstruction with ML-EM by comparing filtered back projection (FBP) with a ramp filter or ML-EM without filtering. SPECT images were obtained with a dual-head gamma camera. The acquisition time was changed from 10 to 200 (seconds/frame) to examine the effect of the count statistics on the quality of the reconstructed images. First, images were reconstructed with ML-EM by changing the number of iterations from 1 to 150 in each study. Additionally, median filtering was applied following reconstruction with ML-EM. The quality of the reconstructed images was evaluated in terms of normalized mean square error (NMSE) values and two-dimensional power spectrum analysis. Median filtering after reconstruction by the ML-EM method provided stable NMSE values even when the number of iterations was increased. The signal element of the image was close to the reference image for any repetition number of iterations. Median filtering after reconstruction with ML-EM was useful in reducing noise, with a similar resolution achieved by reconstruction with FBP and a ramp filter. Especially in images with poor count statistics, median filtering after reconstruction with ML-EM is effective as a simple, widely available method. (author)

[en] Both in post injection transmission method (PITM) and segmented attenuation correction (SAC) method are useful for clinical FDG-PET studies. The PITM, however, makes image noise bigger than conventional method because of the raw data subtraction to calculate transmission data. In this study, quantitative accuracy of PITM was evaluated in 2D and 3D FDG static images. A dedicated 3D PET scanner, GE Advance, was used to scan FDG images of phantoms, a Heart-Liver phantom (Kyoto Kagaku, type HL) and a cylindrical phantom (20 cm diameter), and human brain. Emission scans using 2D and 3D modes and transmission scan using conventional method and PITM was performed. The transmission data was processed with and without SAC method. PITM estimated the phantom activity 2% smaller than the conventional transmission method both in 2D and 3D modes. Visual inspection by nuclear medicine doctors found no change of the image qualities. In the chest imaging using both PITM and SAC method, the transmission scan time should be longer than 2 min. for its quantitative accuracy. PITM had high quantitative accuracy and clinical advantage to make total scan time shorter without deterioration of the image quality. (author)

[en] The comparison of the experimental data obtained at Mt. Chacaltaya (C-jet) and that of electron-positron annihilation experiment at DESY was made. The data obtained at Mt. Chacaltaya were the multiple meson production by superhigh energy particles of more than 100 TeV. Eighty C-jet phenomena with the observed energy more than 20 TeV were used for the analysis. The data of electron-positron annihilation were obtained by using the electron- positron colliding machine at DESY. The comparison of the data of C-jet and e⁺-e^- converted to the stationary system of all forward gamma-ray components, and H quanta and SH quanta was made. The comparison of particle multiplicity was carried out. It is considered that the number of the particles of C-jet is larger than that of e⁺-e^- collision. The transverse momenta were compared. In the energy region less than 15 GeV, both results of momentum measurement were in good agreement, and in energy region above 15 GeV, the average momentum of C-jet was larger than that obtained by e⁺-e^- collision. The distribution of thrust axis and the angular distribution of event plane were obtained. The shape parameters were compared. In the energy region below 10 GeV, both data were in good agreement. Discussions concerning the H quanta and SH quanta are presented. (Kato, T.)

[en] Concerning the integrated body imaging, an optimization of technical aspect in each modarities, such as radiation burden, labour turnover and cost effectiveness should also be considered, in diagnostic process. After investigation on these items, we decided to recommend that imagings of Ultrasound, radionuclide and plain X-ray film should be the first choice for screening, then, CT and X-ray contrast study be the second selected choice and lastly, elaborated contrast angiography be the last one to be selected, if it is necessary. As the increase of information dimension is appeared to be accompanied by the increasing burden in various technical aspect, technical effort to extract more information than those at present at the same burden should be worthwise in future. (author)

[en] In the quantitative analysis of SPECT images, it is necessary to correct for attenuation, scatter, and partial volume effect. Attenuation correction of a non-uniform body was possible with a simultaneous transmission-emission protocol (STEP). Scatter correction was also possible with the triple energy window (TEW) method. We evaluated the quantitative distribution of a Pei phantom and a cardiac-thoracic phantom using STEP and the TEW method. This system consists of a Tc-99m line source assembly and triple-head SPECT system (PRISM3000, Picker Int.) with cardio fan beam collimators. The uniformity of the tracer distribution on a Bull's-eye map was quantitatively evaluated as C.V. value in non-correction, STEP, and the combined correction protocol. Without activity in the liver, the C.V. value was improved from 8.9% to 5.58% with STEP. When liver activity was set beneath the cardiac phantom, the activity was not uniform with STEP, but it became uniform with the combined correction protocol. In conclusion, accurate correction of attenuation and scatter can be performed with the combined correction protocol. This protocol holds promise for the quantitative measurement of tracer concentration on SPECT images. (author)

[en] In order to delineate the hyperfunctioning parathyroid gland, a ²⁰¹Tl-chloride scan was performed on two cases with primary hyperparathyroidism. After the injection of ²⁰¹Tl-chloride of 2mCi, the serial scintiphoto on the neck and mediastinum were obtained. On the both cases, the abnormal accumulation of the tracer was obtained in the region of the right lower pole of the thyroid. Simultaneously the thyroid scan with ¹²³I or sup(99m)TO₄^- was done to eliminate the possibility of the uptake by the thyroid. These abnormal accumulations, extrathyroidal, of ²⁰¹Tl-chloride were confirmed to be the parathyroid adenoma by the neck surgery. The imaging of the hyperfunctioning parathyroid gland by ²⁰¹Tl-chloride was thought to be useful for the detection of the localization of parathyroid adenoma. (author)

No abstract available