Evaluation of adaptation strengths of CARE Dose 4D in pediatric CT

The motivation of this study is the general lack of knowledge regarding the efficiency and the appropriate use of the adaptation strengths of Siemens automatic exposure control system CARE Dose 4D. The purpose was to evaluate the effect on radiation absorbed dose using different adaptation strengths of CARE Dose 4D in three routine pediatric CT protocols. A pediatric anthropomorphic whole body phantom was used to simulate a 4 year old patient. CT scans were performed with a Siemens SOMATOM Definition Flash using three different pediatric protocols: neck, thorax, and abdomen. The characteristic of the tube current modulation was similar for all adaptation strengths. The difference is the extent of decrease in tube current. The degree of dose reduction using CARE Dose 4D and CARE kV compared using a fix effective mAs was 34-57%, 51-88%, and 56-91% for neck, thorax, and abdomen protocol, respectively. Accordingly, there is a large difference in radiation dose dependent on the adaptation strength: a factor of 1.5, 4.5, and 4.6 for neck, thorax, and abdomen protocol, respectively. The adaptation strengths can be used to obtain user-specified modifications of image quality or radiation dose to the patient. Radiologists and medical physicists need to be aware of the large differences between the adaptation strengths, and such differences are useful when attempting strategies to optimize CT radiation dose.