Optimization of the Non-Contrast CT Chest-Abdomen-Pelvis Protocol to Reduce Radiation Dose and Improve Acquisition Efficiency: Single-Pass Versus Two-Pass
Abstract
Purpose
The CT CAP W/O CONT protocol (Computed tomography for chest, abdomen, and pelvis without contrast) is routinely scanned in patients for assessment of systemic disease, oncologic surveillance and staging. Traditionally, this protocol is performed with a two-pass protocol (chest then abdomen/pelvis with different noise indexes (NI)) which has concerns of radiation dose and acquisition efficiency. We hypothesize using a single-pass continuous acquisition with unified noise index will have equivalent image quality as two-pass acquisition while improving efficiency and reducing radiation dose to patients. This study compares patient dose, image quality, and acquisition time between these two protocols.
Methods
Retrospective analysis was performed on the acquired routine CT CAP W/O CONT images with the two protocols in patients (group1: two-pass, NI=19.5 (chest) and 22.6 (abdomen/pelvis), 01/01/2005~ 09/01/2025, 618 patients; group2: single-pass, NI=19.5 (chest-abdomen-pelvis), 12/01/2005~ 1/8/2026, 54 patients). For each exam, images, data acquisition time, DLP (mGy*cm) and effective dose (ICRP103, mSv) were extracted from image archive and dose tracking systems. Group differences were analyzed statistically using a two-sample Weltch’s t-test with non-equal variance.
Results
The single-pass protocol significantly reduced radiation dose compared with the two-pass protocol by an average of 358 mGy-cm(DLP) and 10.1 mSv(ICRP130) (DLP: 1269±542 vs 1627±817 mGy*cm, p=3.64e-4; ICRP103: 24.6±13.6 vs 34.5±23.6 mSv, p=4.14e-6). The single-pass protocol was 1.7 times faster than the two-pass protocol (6.35±0.42 s vs 11.00±3.56 s, p=0.003). There is no image quality difference between the two protocols from radiologist’s assessment.
Conclusion
The single-pass non-contrast CT chest–abdomen–pelvis (CT CAP W/O CONT) protocol achieves comparable image quality while significantly reducing radiation dose and scan time compared with the conventional two-pass protocol. Adoption of a single-pass protocol with a unified noise index offers a straightforward strategy to optimize radiation dose and improve scan efficiency in routine clinical imaging, particularly for patients requiring repeated examinations