Feasibility of Using Iterative Reconstruction to Reduce Radiation Dose for Computed Tomography Pulmonary Angiograms

The purpose of this study was to assess the potential for iterative reconstruction algorithms to be used to reduce patient radiation dose for computed tomography pulmonary angiography examinations while maintaining diagnostic image quality.

This two-stage study first considered current computed tomography pulmonary angiography image quality through an audit of current practice. Secondly, an experimental design was adopted using an anthropomorphic phantom with the addition of contrast-enhanced tubes to mimic pulmonary arteries. The radiation dose was reduced by incrementally reducing the milliampere seconds value from the standard institutional protocol, and subjective and objective (contrast-to-noise ratio [CNR] and signal-to-noise ratio [SNR]) quality measures were recorded for each exposure and reconstruction.

A sample of 10 patients met the inclusion criteria for the audit, and a mean CNR of 44.2 and an SNR of 47.9 were established as baseline quality. A clear positive correlation was identified between the number of iterations and objective quality measures (CNR [r = 0.78, P < .001] and SNR [r = 0.78, P < .001]). No relationship was identified between the subjective measures and either radiation exposure (milliampere seconds) or the number of iterations. Findings suggest that a potential reduction in effective dose of 1.46 mSv (57.0%) is possible with no associated loss of image quality with the use of iterative reconstruction.

Findings suggest that the potential dose reduction may be as great as 57%; however, further work is required to confirm this in a patient population.