Abstract:
Objective: To investigate the effect of using organ dose modulation (ODM) technology at different tube voltages on image quality and eye lens radiation dose in brain perfusion CT (CTP). Methods: Based on a clinical CTP scanning protocol, five tube voltages (70, 80, 100, 120, and 140 kV) were used to scan a Catphan phantom and a fresh, isolated human head specimen with three tube current modulation modes: without dose modulation technology (Manual mode), with smart tube current modulation technology (Smart mA mode), and with organ dose modulation technology (ODM mode). A long rod ionization chamber was fixed at a consistent position in front of the right eye lens. Each parameter combination was scanned nine times, and the average eye lens dose (Dav) was recorded. The modulation transfer function (MTF) of the CTP528 high-contrast resolution module in the Catphan phantom was measured. In the images of the head specimen, the heads of the caudate nucleus, lenticular nucleus, and thalamus were selected as signal regions at the basal ganglia level, and the lateral ventricle, anterior limb of the internal capsule, and posterior limb of the internal capsule were selected as respective background regions to measure the contrast-to-noise ratio (CNR). The same level of brain tissue was segmented to measure three texture feature parameters: contrast, correlation, and difference variance. Two-factor analysis of variance was used to compare MTF and CNR, and multi-factor non-parametric analysis of variance was used to compare eye lens dose and texture parameters. Results: The differences in MTF across the different tube voltages were statistically significant , with MTF values positively correlated with tube voltage above 80 kV. However, there was no significant difference between different tube-current modulation modes. The CNR of each signal and background region showed significant differences among different tube voltages. The CNR for the caudate nucleus head to lateral ventricle was the largest, at 120 kV. The CNR for the lenticular nucleus/thalamus were negatively correlated with tube voltage. There were no significant differences in CNR among different tube-current modulation modes. No texture parameter was significantly associated with the tube current modulation mode. There were significant differences in Dav values with respect to both different tube voltages and tube current modulation modes. When the tube voltage was below 120 kV, the eye lens dose was negatively correlated with tube voltage, and the ODM technology reduced the eye lens dose by approximately 20% at each tube voltage. Conclusion: Employing 80–100 kV CTP scanning with organ dose modulation technology can balance image parameters and reduce radiation dose to the eye lens while ensuring adequate image quality, as recommended for clinical use.