Lena Gordon Murkes MD, Presenter: Nothing to Disclose

Marika Gullberg Lidegran MD, PhD, Abstract Co-Author: Nothing to Disclose

Bolus tracking (BT) in pediatric CTA is associated with non-negligible contributions to the patient’s radiation dose. To mitigate radiation dose, a fixed scan delay for the timing of iodinated contrast medium (ICM) has been recommended by other institutions, in place of BT. The aim of this study was to minimize the radiation dose contribution from BT while preserving optimal ICM timing, for pediatric cardiac CTA.

The BT was optimized (from scanner default) by setting the tube parameters to 80 kV/10 mAs, postponing the start of BT to 10 seconds after the start of the bolus injection, and decreasing the BT monitoring frequency to 1.43 s. The DLP was used to compare the radiation dose from BT prior to and after optimization. The study included 118 children (2 days-3 years old) examined with a cardiac CTA protocol, over a 3-year period. The ICM (2 ml/kg, 320 mgI/ml) bolus was administered with a dual power injector followed by the double amount of saline chaser. Depending on the vessels of interest, the ICM injection time varied between 12-15 seconds. The diagnostic scans were triggered manually using BT as a reference for the arrival of ICM. The feasibility of using fixed scan delays for ICM timing was investigated by studying the time between the start of the bolus injection and the start of the diagnostic scan.

All 118 examinations provided CTA images of diagnostic value and the majority of the scans had excellent ICM timing. Prior to optimization, the DLP for BT varied from 1-15 (mean 7.9) mGycm. After optimization, the DLP for BT decreased to 1-2 (mean 1.4) mGycm. As a comparison, the mean DLP for the diagnostic scans was 16 mGycm. The time from bolus injection start to diagnostic scan varied between 18 and 32 seconds, making a fixed scan delay for ICM timing elusive.

BT is an important tool to achieve a well-timed CTA examination, with respect to ICM. Excellent ICM timing can be preserved with an optimized BT, which only contributes a fraction of the radiation dose compared to non-optimized BT. Furthermore, optimal ICM timing is paramount to allow for further dose optimization in pediatric CTA.

The use of bolus tracking is recommended to achieve a well-timed CTA examination and with optimized settings  the dose contribution will be negligible.

Gordon Murkes, L, Gullberg Lidegran, M, Dose-optimized Bolus Tracking in Pediatric Cardiac CT Angiography.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14004412.html