Study: Pediatric CCTA nudges toward sub-mSv levels
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Two primary barriers have hindered adoption of pediatric CCTA: higher heart rates that might compromise scan quality and concerns about radiation exposure. B. Kelly Han, MD, of Children’s Heart Clinic in Minneapolis, and colleagues sought to determine the impact of dual-source CT, retrospective and prospective electrocardiogram (ECG) gating and high-pitch scans on heart rate control, image quality, diagnostic confidence and radiation exposure among pediatric patients.
Han and colleagues retrospectively reviewed 71 CCTA studies acquired in 70 patients younger than 18 years old from June 2007 through February 2011 and graded diagnostic quality. Two experienced radiologists independently determined the diagnosis and compared results.
A total of 66 patients were premedicated to decrease their heart rates.
Of the 71 studies, 20 were performed with retrospective ECG gating (group 1), 33 were performed with prospective ECG triggering (group 2) and 18 were performed with a prospective ECG-triggered high-pitch spiral scan mode (group 3). The prospective ECG-triggered high-pitch spiral scan mode delivered the greatest reduction in dose.
The researchers reported a median effective dose of 1.71 mSv for group 1, 0.83 mSv for group 2 and 0.24 mSv for group 3. Signal-to-noise ratio, contrast-to-noise ratio and image quality were similar among the three groups. Both radiologists agreed on all diagnoses.
Han and colleagues noted that these dose estimates are lower than invasive coronary angiography, which is associated with dose estimates ranging from 3.5 to 5.6 mSv. “Although catheter-based angiography is the historical standard for pediatric coronary imaging, the comparatively high radiation doses, the invasive nature of the procedure, and the need for sedation in all age groups may make it less desirable than current noninvasive imaging techniques for many indications,” they wrote.
They also noted MR imaging has improved, particularly for visualization of proximal coronary artery segments, but is associated with other difficulties such as visualization of distal segments, a longer scan time and lower spatial resolution. Children’s Heart Clinic prefers MRI for patients referred for angiography who have a low likelihood of coronary artery disease. However, the authors noted that pediatric cardiac MRI expertise is not widely available.
“Our study shows [CCTA] maintained image quality and diagnostic confidence for multiple indications in a pediatric population with a high prevalence of pathology, while further decreasing the radiation dose over previous generation CT scanners,” wrote Han et al.
The researchers concluded by recommending CCTA for certain pediatric patients with a high likelihood of coronary disease, while adding that physician presence and meticulous attention to detail are needed to achieve optimal image quality at low dose.