Diagnosing lung cancer invading the pulmonary artery using ultra-low-dose CT pulmonary angiography: a feasibility...

Computed tomography pulmonary angiography (CTPA) is widely used for evaluating pulmonary artery invasion (PAI) in lung cancer, but conventional protocols involve relatively high radiation dose and contrast medium usage. The feasibility of a 60-kVp "triple-low" protocol combining low tube voltage, reduced contrast volume, and reduced injection rate in preserving image quality and diagnostic performance remains to be determined. Therefore, this study aimed to evaluate the feasibility of a 60-kVp "triple-low" CTPA protocol for assessing pulmonary artery invasion in patients with lung cancer.

In this prospective randomized study, 90 patients were assigned to routine dose (RD) CTPA (120 kVp, 50 mL, 4.5 mL/s; n=45) or ultra-low-dose (ULD) CTPA (60 kVp, 35 mL, 3.5 mL/s; n=45). Two senior thoracic radiologists established the reference standard by consensus after reviewing available pathological, imaging, and clinical records. Subjective image quality was evaluated using a 5-point Likert scale across multiple parameters, including enhancement homogeneity and vascular sharpness. Radiation dose was recorded, and the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured at the main, right, and left pulmonary arteries. Two additional readers independently assessed PAI; receiver operating characteristic (ROC) analysis against the reference standard yielded the area under the ROC curve (AUC), sensitivity, specificity, and accuracy.

ULD reduced effective dose (ED) from 3.59 to 0.72 mSv (~80%). Subjective scores were comparable between protocols for enhancement homogeneity, vascular sharpness, and diagnostic confidence (all P>0.05). SNR and CNR were similar overall, with a small decrease at the left pulmonary artery in the ULD group. Diagnostic performance for PAI was comparable between ULD and RD for both readers (reader 1: AUC 0.936 vs. 0.940; reader 2: 0.936 vs. 0.925; both P>0.05).

A 60-kVp triple-low CTPA protocol achieved ~80% dose reduction while maintaining image quality and diagnostic accuracy for evaluating PAI, supporting clinical implementation.