A study of the dependence of the dose measurement and image assessment on the variations in the patient’s position and the exposure conditions for CT mammography

This study compared and analyzed the variation in the image quality with changes in the positions of breast cancer patients during imaging, and examined acrylic and breast phantoms. In the phantom study, the kilo-voltage-peak (kVp) and the milliampere-second (mAs) for the acrylic phantom was changed from (A) 120 kVp/100 mAs to (B) 100 kVp/100 mAs, (C) 120 kVP/70 mAs, (D) 100 kVp/70mAs, (E) 120 kVp/50 mAs, (F) 100 kVp/50 mAs, (G) 120 kVp/30 mAs, and (H) 100 kVp/30 mAs in order to conduct scanning before the exposure dose measurement. Under the same scanning conditions for the target patients, we used images of the arterial phase in the supine position, which had been obtained most recently, and a breast holder for the prone position, which had been manufactured for this study. This was done to conduct a qualitative assessment based on CT (computed tomography) mammography images that were taken with the patients in the prone position to ensure that the breasts were not pressed but spread downward as much as possible. The exposure doses were measured during scanning at 120 kVp/100 mAs, which is currently applied to the clinical stage and used for the phantom study, and at 100 kVp/70 mAs, which was used for this study, before being compared and recorded. Based on the study results, it was possible to establish the standard for determining the optimum dose without any change in the amount of clinical information by conducting CT mammography scanning with 100 kVp/70 mAs and with the patient in the prone position.