SU‐GG‐I‐04: Effect of CT Scan Parameters on Adult and Pediatric CT Dose When Using Automatic Tube Current Modulation

Purpose: To develop pediatric CT protocols by characterizing effects of CT parameters on adult and pediatric CT dose using automatic tube‐current modulation (ATCM). Method and Materials: Adult and 10‐year‐old (10yo) ATOM (CIRS) phantoms were scanned on a 16‐channel CT system (Emotion 16, Siemens) using ATCM (CareDose4D) to characterize the relationships between CT scan parameters and patient dose. The scan parameters investigated include scan‐kVp, reference‐mAs, scout‐kVp, patient‐size selection (adult/pediatric), and rotation‐time. Effective‐mAs delivered by ATCM was extracted from the DICOM header of each CT image. Results: Effective‐mAs delivered by ATCM varied with patient‐size selection, relative to reference‐mAs, it decreased for adult but increased for pediatric. Using ATCM the average effective‐mAs for 80, 100, 130 scan‐kVp changed by 81%&124%, 61%&110%, 55%&103% relative to reference‐mAs for the adult&10yo phantoms. However, when the 10yo was selected as adult, the average effective‐mAs decreased to 34%, 29%, and 26% of reference‐mAs. When selected as adult, dose decreased for all anatomical regions but when selected as pediatric, dose increase was observed for abdomen and pelvis (120–155%). ATCM effective‐mAs per slice scaled linearly (1±0.06) with input reference‐mAs. However, the minimum mA limited the modulation of effective‐mAs at low reference‐mAs. For both phantoms, 80 kVp scouts reduced the effective‐mAs by 5–7% on average (up to 20% for thorax) compared to 130 kVp scouts. For identical reference‐mAs, ATCM increased effective‐mAs for lower scan‐kVp; however, patient dose also decreased for lower scan‐kVp. For the adult&10yo phantoms, average dose at 80 and 110 scan‐kVp was 42%&39% and 72%&72% of that at 130 scan‐kVp, respectively. Conclusion: Patient dose with ATCM decreased for adult and increased for pediatric patients. The scout‐kVp affects ATCM schema with lower effective‐mAs for lower scout‐kVp. ATCM effective‐mAs is linear with input reference‐mAs. Net patient dose is reduced despite increased effective‐mAs at lower scan‐kVp using ATCM.