Shigetaka Suzuki

Dose evaluation for foetal computed tomography with a 320-row unit in wide-volume mode and an 80-row unit in helical scanning mode: a phantom study

The purpose of this study was to evaluate the maternal and foetal effective doses during foetal computed tomography (CT) and to compare the radiation dose, dose profile and image noise on 80-row CT in helical scanning mode and 320-row CT in wide-volume scanning mode. The radiation doses were measured using thermoluminescent dosemeters implanted at various organ sites of an anthropomorphic pregnant phantom. The foetal doses in the 320-row multi-detector CT (MDCT) and 80-row MDCT units were higher than the volume CT dose index (CTDIvol). The dose profile in the 320-row MDCT overlapped in two places but showed no overlap in the 80-row MDCT. There were no significant differences in image noise between the two scanning modes. The foetal dose evaluation by CTDIvol may underestimate the foetal radiation risk. When using the wide-volume mode, operators must take into account the number of scans and overlap between volumetric sections.

The utility of an amorphous model in computer simulation of myocardial propagation

Previously carried out simulation of myocardial exciting propagation used lattice structure models composed of square units or hexagonal units. These models were planar, and problematic in that the front of the excitement-propagating waveform became polygonal rather than circular. This problem cannot be resolved even by increased unit numbers. To solve this problem, the authors created an amorphous model. Nearly circular exciting wavefronts were successfully obtained in this amorphous model. In addition, when multiple (3) stimuli were applied to the two types of model simultaneously, in lattice-structured models, continued shifting of the three stimuli locations by 90 degrees provoked noticeable differences in the residual form of exciting waves, but in the amorphous model no such illogical phenomena were noted. Furthermore, when an area with an abnormal excitement propagation was established in a region of the models, simulated propagation brought about a different outcome between the lattice model and the amorphous model. A reentry mechanism could be shown in the amorphous model, but not on the previous lattice model. Further trials are continuing. Based on the foregoing information, the authors have confirmed the utility of an amorphous model.