Evaluating a low-dose protocol for computed tomography (CT) pulmonary angiography: combining reduced contrast medium,...

The aim of this study was to evaluate a comprehensive low-dose computed tomography pulmonary angiography (CTPA) protocol combining low tube voltage, iterative reconstruction (sinogram-affirmed iterative reconstruction [SAFIRE]), and nonlinear blending and assess the feasibility of reducing contrast medium (CM) volume.

In this retrospective study, 166 patients were divided into four groups. Group A (conventional) received 120-kVp, 50 mL CM, filtered back projection, and linear blending. Groups B, C, and D (low-dose) underwent 80-kV/Sn140-kV dual-source scanning with SAFIRE and nonlinear blending and received 20, 30, and 50 mL CM, respectively. Objective image quality (attenuation, noise, contrast-to-noise ratio [CNR], and signal-to-noise ratio [SNR]), subjective scores, and radiation dose (volume computed tomography dose index [CTDIvol], dose-length product [DLP], and effective dose [ED]) were compared.

The low-dose groups achieved approximately 63% radiation reduction versus group A (all P<0.05). Objective image quality was superior in groups C and D compared to that in groups A and B. Subjective image quality was diagnostic and comparable across all groups (κ>0.73). A 30-mL CM volume yielded objective and subjective image quality comparable to the 50-mL volume; the 20-mL volume remained diagnostic but with lower objective metrics.

This synergistic low-dose protocol enables substantial reductions in both radiation and CM dose. Reducing CM to 30 mL yields image quality comparable to the conventional protocol, supporting its feasibility in a safer, patient-centred CTPA strategy.