[OA081] Patient-specific dose and risk estimation for organ-based tube-current modulation in chest CT. (August 2018)

• Record Type: Journal Article
• Authors: Franck, Caro; Smeets, Peter; Lapeire, Lore; Achten, Eric; Bacher, Klaus
• Is Part Of: Physica medica. Volume 52(2018)Supplement 1
• Page Start: 32
• Publication Date: 2018-08
• Subjects: Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2018.06.153
• Languages: English
• ISSNs: 1120-1797

Abstract

Abstract : Purpose: To assess the potential dose reduction to the thyroid and breasts in chest CT, using organ-based tube-current modulation (OBTCM). Posterior organs in the field of view were analyzed and overall lifetime attributable risk (LAR) of cancer induction and mortality was evaluated. Methods: With OBTCM, the exposure is lower when the X-ray tube passes over the anterior surface of the patient. In this way, the breast doses can be limited. However, to preserve image quality, the total exposure during one rotation has to be equal to the exposure of scans without OBTCM enabled. Therefore, the tube-current is higher during posterior projections. In this study (Jan 2015–Dec 2016), the location of the breasts with respect to the reduced tube-current zone was determined. Using Monte-Carlo simulations, patient-specific dose distributions of chest CT scans were calculated for 50 female patients (mean age 53.7 y ± 17.5, range 20–80 y). The potential dose reduction of OBTCM was assessed. In addition, simulations of clinical OBTCM scans were made for 17 female patients (mean age 43.8 y ± 17.1 y, range 20–69 y). LAR of cancer incidence and mortality was estimated according to BEIR-VII. Image quality (IQ) between standard and OBTCM scans was compared. Results: No women had all breast tissue within the reduced tube-current zone. Clinical observed dose reductions were 18% (thyroid) and 9% (breasts) whereas lung, liver and kidney doses were 17%, 11% and 26% higher. Overall, LAR for cancer incidence was not significantly different (p = .06) between conventional and OBTCM scanning. IQ improved with OBTCM (p < .002). Conclusions: The potential benefit of OBTCM to the female breast in chest CT is overestimated due to a limited reduced tube-current zone; despite a 9% dose reduction to the female breast, posterior organs will absorb up to 26% more radiation, resulting in no reduction of radiation induced malignancies.