Laura Tamiko Meyer MD, Presenter: Nothing to Disclose

Caroline Laurens Hollingsworth MD, Abstract Co-Author: Nothing to Disclose

Catherine Luden Benton Lerner MD, Abstract Co-Author: Nothing to Disclose

Terry T. Yoshizumi PhD, Abstract Co-Author: Research support, General Electric Company

Greta Toncheva BS, Abstract Co-Author: Nothing to Disclose

Carolyn R. Lowry BS, Abstract Co-Author: Nothing to Disclose

Donald P. Frush MD, Abstract Co-Author: Research funded, General Electric Company

Daniel Tobias Boll MD, Abstract Co-Author: Nothing to Disclose

et al, Abstract Co-Author: Nothing to Disclose

To establish a range of radiation doses for pediatric dual source gated modulated cardiac CTA.

Cardiac CTA was performed with a dual source scanner (Siemens Somatom Definition) on an anthropomorphic phantom of a 5 yr old (CIRS). Timing bolus (80 kVp, 100 mA) and 3 protocols with retrospective gating were performed at low (80kVp, 200 mA), medium (120 kVp, 200 mA) and high (120 kVp, 350 mA) doses; all protocols used ECG modulation (reported mA is maximum effective mA), 64 x 0.6 mm, rotation time 0.33sec, 0.5 pitch, 100 mm FOV, 3.71 second scan time. Scan parameters were based on institutional experience with gated CTA in the pediatric age range. Organ doses were measured with high sensitivity MOSFET technology (2 runs/protocol, averaged). Effective dose (ED) was calculated (ICRP 60) from organ dose measurements. An age-specific conversion factor was calculated using the recorded DLP and measured ED.

ED was 0.9 mSv for the timing bolus, and 2.52, 8.31 and 18.31 mSv for low, medium, and high technique protocols. The highest doses were in the heart. No dose was detected in the ovaries for any protocol. Organ doses for low, medium and high technique protocols respectively were: thyroid, 0.09, 0.28 and 0.50 cGy; breasts, 0.63, 2.41, and 5.50 cGy; lungs, 0.91, 3.00, and 6.03 cGy; heart, 0.95, 3.95 and 8.28 cGy and bone marrow 0.48, 1.10, and 2.55 cGy. The age-specific dose coefficient was 0.064.

ED from 64-channel dual source gated cardiac CTA for a 5 yr-old ranges from 3.42 to 19.21 mSv, lower than those for 16-slice non modulated gated CTA, which were as high as 25.7 mSv. The measured doses do not increase as would be predicted based solely on adjustments to maximum kVp and mA, possibly due to scanner changes which are not user-specified. CTA performed with adult parameters may impart 560% greater dose than an exam with settings appropriate for young children. MOSFET allows determination of previously unavailable DLP conversion factors for pediatric gated CTA. For a 5 yr old, the gated CTA conversion factor is 3 times that for chest CT (0.018; Shrimpton et al). Further work assessing image quality is necessary to optimize protocols for pediatric gated cardiac CTA.

Radiation doses to children from 64-channel dual source gated cardiac CTA range from 3.42 to 19.21 mSv depending on scanning protocols, which is less than previously reported with 16-slice scanners.

Meyer, L, Hollingsworth, C, Lerner, C, Yoshizumi, T, Toncheva, G, Lowry, C, Frush, D, Boll, D, et al, , Radiation Dose in Contemporary Pediatric Dual Source ECG-gated Cardiac CTA.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6007022.html