No abstract available

[en] Attenuation correction method by a cylinder phantom was evaluated using simulated phantoms. A circular phantom (r = 10cm) with uniform activity and attenuation coefficient μ₀ = 0.088 cm^-1) was used for calculation of attenuation correction factor. Three types of objects were estimated. (1) Two size of circles (r = 10 and 7.5cm) and two size of ellipsoids (19 x 16cm and 15 x 12cm). Assuming uniform μ in four objects. (2) A circular phantom (r = 9cm) with uniform activity and nonuniform μ (= μ₀, 1.05μ₀, 1.10μ₀ and 1.20μ₀). (3) A brain slice with nonuniform value (μ value in skull is 1,05μ₀). In a case of same size and same μ value of a object with the circular phantom for correction, a reconstructed image with uniform activity was obtained by this method. For a smaller size of objects, however, a nonuniform image with higher activity at the edge was reconstructed due to over estimation of absorption correction. Nonuniform activity due to variable absorption were clearly seen in reconstructed image by assuming a uniform μ value of correction phantom. (author)

[en] Three-dimensional data processing was developed for single photon computed tomographic imaging of the multigated blood pool with Tc-99m labelled red blood cells. A gamma camera was rotated from the left posterior oblique to the right anterior oblique projections at intervals of 180 deg/32. Data were collected at each part for one to two minutes, and the number of gates per beat was 12 to 20, depending on the patient. Three-dimensional transaxial images of the heart were reconstructed by the filtered back projection method without attenuation correction. A Shepp and Logan filter was used for the convolution filter. Short-axial images were reconstructed from the transaxial images. Using the equicount level method, the contours of both ventricles at each short-axial cross-section image were determined automatically with 50 % levels of the maximum counts. Each contour line was smoothed to the fifth order of Fourier function after conversion from (x-y) coordinates to (r-θ) polar coordinates with respect to the center of the area. Each contour line, converted again into (x-y) coordinates, was drawn successively on a color CRT at constant intervals and inclinations in order to display the ventricles three-dimensionally. It is possible to display simultaneously on a CRT the right and left ventricles or two types of cardiac disease. It is also possible to depict superimposed images of end-diastolic and end-systolic ventricles. The length of the long axis at end-systole in the normal case became less than half the length of the one at end-diastole. In the case of inferior infarction, the length of the left ventricular long axis did not change according to contraction, and akinesis at the inferior wall was clearly imaged. In the case of hypertrophic cardiomyopathy, the thickness of the interventricular septum was markedly increased compared to that of the normal. (J.P.N.)

[en] Published in summary form only

[en] Analytical method of the movement of left ventricular wall using a coordinate system fixed to the left ventricle was developed by transforming the left ventricular margin obtained from the x-y coordinate fixed in the space into the γ-theta coordinate of fixed center of area. This method was applied to two- and three-dimentional multigated image analysis, thereby making it possible to visualize the spacial movement. In particular, it is considered useful in three-dimentional image analysis with SPECT. (Namekawa, K.)

[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] Currently available advanced methods of cardiovascular nuclear medicine for the diagnosis of ischemic heart disease were studied. The methods included the multigate method by a large capacity gamma camera-computer (128 KW memory with multilayer disc) system which made it possible to acquire the data of either the first pass study or the equilibrium study in ''image mode''. Analyzed data were displayed on a color CRT using our moving image system (MIS) and dynamic image thus obtained serve to help for the high sensitive observation of the regional wall motion as well as the global function of the ventricles. Myocardial tomography by a 7 pinhole collimator designed by us was also reported. The myocardial tomogram obtained was proven to show more sensitivity than two dimensional myocardial scan by the conventional collimator to detect smaller lesion and the lesions at the inferior or posterior wall of the left ventricle. The cardiovascular nuclear medicine with recent advanced technologies was thought to be sensitive and useful method for the diagnosis of the ventricular performance and the myocardial ischemia. (author)

[en] We have developed two kinds of data processing methods for co-registered PET and MR images. The 3D-brain surface, representing the cortical rim in the transaxial images, was projected on a 2D-plane by utilizing Mollweide projection, which is an area-conserving method of displaying the globe as a world map. A quantitative ROI analysis on the brain surface and 3D superimposed surface display were performed by means of the 2D projection image. A clustered brain image was created by referring to the clustered 3D correlation map of resting CBF, the acetazolamide response and the hyperventilatory response, where each pixel in the brain was labeled with the color representing its cluster number. With this method, the stage of hemodynamic deficiency was evaluated in a patient with the occlusion of internal carotid artery. The differences in the brain images obtained before and after revascularized surgery was also evaluated. (author)

[en] Contraction patterns between left and right ventricles were evaluated using phase analysis in the patients with right ventricular endocardial pacing (RVEP). Phase images were compared between 11 cases of RVEP, 10 cases of normal control (NC) and 7 cases of left bundle branch block (LBBB). NC group showed nearly simultaneous contraction between both ventricles although contraction of right ventricular outflow tract was slightly delayed. LBBB group showed markedly delayed contraction of the whole LV compared with the contraction of RV. On the other hand, all cases of RVEP group showed initial contraction at apex of RV and then wavelike spread of contraction to the basal portions of both ventricles. Thus, three groups were clearly separated on the phase image. QRS wave forms of the electrocardiogram at pacing were classified into 4 types (RBBB, RS, S and LBBB) and phase difference was compared between each type. Several cases of RS type showed little phase difference between LV and RV, however, there was no significant difference between LBBB and RS type. Phase difference between LV and RV was studied at various pacing rates in 9 cases. In 6 out of 9 cases, phase of the left ventricle was delayed in proportion to increasing the pacing rate. Phase analysis was useful to evaluate the ventricular contraction pattern in the patients with RVEP. (author)

[en] The effects of the non-uniform attenuators on the cardiac SPECT (Single Photon Emission Computed Tomography) have been evaluated by using the computer simulation technique. The models with realistic structures were created by tracing the outline of attenuators and the activity distributions on the gated MRI images. Fifteen slices in three normal volunteers were used to generate the SPECT images with 64 linear samplings and 64 views over 360 degree. Two types of the models, the uniform attenuator model (UAM) and the non-uniform attenuator model (NUAM), were generated simulating both the Tc-99 m blood pool SPECT (TC) and Tl-201 myocardial SPECT (TL). Images were then reconstructed with the various attenuation correction techniques including the pre-correction (PRE), the post-correction (POST), the Weighted Backprojection (WBP), and the Radial Post Correction method (RPC). The results were compared with the true images reconstructed from a model without assuming no attenuators and a relative percent error (% ERROR) was calculated in the cardiac region. The RPC has shown lowest % ERROR in UAM (11 %). However twenty to thirty percent % ERROR increase has been observed for NUAM reconstructed with the RPC, WBP, and POST method. They were considered to be caused by larger attenuation coefficient used in the reconstruction. Introducing of an average attenuation coefficient (0.12/cm for Tc-99 m and 0.14/cm for Tl-201) in the RPC method decreased % ERROR to the levels of UAM. (author)