DEVELOPMENT OF RADIATION DOSE CALCULATION SOFTWARE USING THE SIZE-SPECIFIC DOSE ESTIMATE.

We aimed to develop a software for facilitating absorbed dose per pixel (pixel dose) calculation using a size-specific dose estimate (SSDE). We calculated the pixel dose at nine equal points inserted into the radiophotoluminescence glass dosemeter (RPLD) and compared the pixel dose with the measured doses using RPLD. With this method, the relative errors of average pixel dose was -0.1% for adults and 2.86, 3.36 and 1.17% for those aged 10, 5 and 1 years without tube current modulation, respectively. In contrast, the relative error of SSDE was 17.37% for adults and 20.38, 20.73 and 19.20% for those aged 10, 5 and 1 years, respectively. In other words, the pixel dose was almost equal to the measured doses. Therefore, our software can be useful for determining arbitrary point.

[Usefulness of criterion on which to operate coronary computed tomography angiography used dual source computed tomography comparisons with exposure dose of prospective electrocardiogram high-pitch spiral mode, low-pitch spiral mode, and step and shoot mode].

We believe that the patient exposure dose differs by heart rate for a coronary computed tomography angiography (CCTA), and we attempted to reduce patient exposure dose of the CCTA. Specifically, we made a clear difference of exposure dose between heart rate and optimal cardiac phase or some imaging methods. Next, we established criterion of the CCTA in our hospital, and usefulness was discussed. For examination methods, patients with a heart rate below 60 beats per minute (bpm) received a high-pitch spiral scan (Flash Spiral mode), those between 61 to 70 bpm received a step and shoot scan (SAS mode), and those of >70 bpm or an irregular heart rate received low-pitch spiral scan (Helical mode). The results of the clinical study showed that patient exposure dose reduced 87% in Flash Spiral mode (1.93±0.26 mSv) and 66% in SAS mode (4.88±1.24 mSv) compared with Helical mode (14.35±3.42 mSv). In our present study, we proved the usefulness of our criteria using CCTA. If the results of our present study become guidelines of CCTA users, we suggest that total patient exposure dose can be reduced.

[Evaluation of low dose chest expiratory high resolution computed tomography for diagnosis of air trapping].

In our hospital, expiratory high resolution computed tomography (HRCT) is being performed in patients with chronic obstructive pulmonary disease (COPD). Because expiratory HRCT is used in combination with inspiratory HRCT, it can provide less exposure according to diagnostic purposes. In the present study, we tried low-dose expiratory HRCT in terms of visual assessment and analysis software of phantom experiments. As a result, visual assessment in the dose reduction rate was about 50% to 75% against conventional exposure doses. Thoracic examinations are common in organs with high tissue weighting factors, and the present study shows a very effective means for medical exposure reduction.