Comparison of Diagnostic Quality and Radiation Dose between Test Bolus and Bolus Tracking protocols for Computed Tomography Pulmonary Angiography (CTPA) among Pregnant Women in Two Tertiary Centres

Abstract

Introduction: Computed Tomography Pulmonary Angiography (CTPA) among pregnant women is often non-diagnostic and may need the repetition of CTPA. This study aims to compare the test bolus and the bolus tracking protocols for CTPA among pregnant women by analysing the mean contrast enhancement of the pulmonary artery, diagnostic quality and radiation dosage, as well as the outcome of repeated CTPA among pregnant women due to initial non-diagnostic CTPA. Methods: This retrospective study from two tertiary centres included pregnant women who underwent CTPA using test bolus and bolus tracking protocols. CTPA quality, mean pulmonary artery enhancement and dose length product (DLP) were collected and compared between both protocols. The frequency and outcome of CTPA repetition due to suboptimal quality were analysed. Results: Test bolus protocol yields a slightly higher number of diagnostic qualities CTPA than bolus tracking protocol; however not statistically significant. The bolus tracking protocol had significantly better acceptable CTPA quality than the test bolus protocol. Test bolus protocol had significantly lower mean DLP, 220 mGy.cm ± 69, than bolus tracking protocol, 323 mGy.cm ± 34, p-value <0.001. Half of the repeated CTPA did not show significantly better CTPA quality on repetition. Conclusion: No significant difference between test bolus and bolus tracking protocol in CTPA among pregnant women, but the bolus tracking protocol had better overall CTPA quality with higher radiation dose. Repetition of CTPA studies for poor CTPA quality may not always benefit. Hence, we advise weighing the risk and benefits of study repetition.