Objectives: Organ-based tube current modulation aims to reduce exposure to radiosensitive organs like the breasts by considering their anatomical location and altering tube current during rotation. Former phantom studies demonstrated a dose reduction of 20-37 %. Our study aimed to estimate the potential of dose reduction with this technique in relation to the actual location of breast tissue in a large clinical cohort.
Methods: A 1-year cohort of chest CTs of females (N=1,263) was retrospectively evaluated. To estimate the relative dose effect, breast location was analysed by measuring the angle range of glandular tissue within the different dose zones. Relative exposure compared with constant tube current was calculated. Descriptive statistics and Wilcoxon-test were applied.
Results: Only 63 % of angle range of glandular breast tissue was found inside the reduced dose zone. The estimated mean relative dose reduction was lower than observed in former phantom studies(16 % vs. 20-37 %) but still significant compared to constant tube current (p<0.0001).
Conclusions: Although organ-based tube current modulation results in a significant reduction of breast exposure compared to non-modulated irradiation, the technique cannot unfold its full potential, because breast tissue is often located outside the reduced dose zone, resulting in significantly lower dose reduction than expected.
Key points: • OBTCM results in significant dose reduction compared to constant tube current scans. • A substantial portion of glandular tissue lies outside the reduced dose zone. • Potential dose reduction using organ-based tube current modulation may be overestimated.
Keywords: Breast; Chest CT; Computed tomography; Radiation dosage; Radiation protection.