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

Abstract

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.

The impact of pediatric-specific dose modulation curves on radiation dose and image quality in head computed tomography

“…Whilst there are numerous publications related to tube voltage reduction and recommendations for this during pediatric CT examination, especially for newborn patients [14,29], only a limited number of studies have tested the impact of tube voltage and tube current modulation combined in pediatric CT practice. Tube current modulation is, however, a tool readily available on the majority of CT scanners and there have been numerous papers related to this single form of modulation [30,31]. This technique was available at the participating clinical center; however, its application was not used as increased radiation dose had resulted once employed in practice as the modulation curves were not tailored to children.…”

The establishment of computed tomography diagnostic reference levels in Portugal

“…Therefore, young children will be exposed to less mA s reference value and older children will exceed the reference value (5,38,39) . Other studies indicate that modulation has more impact on adult dose reduction than that on children (40) with one study reporting that automatic tube current modulation whilst decreasing adult dose negatively increased paediatric dose in specific circumstances (41) . In Portugal, only centre B employs automated tube current modulation for paediatric patients and this is reflected in the lower mean dose findings.…”