Dose profiles for lung and breast regions at prospective and retrospective CT coronary angiography using optically stimulated luminescence dosimeters on a 64-detector CT scanner

APPLICATIONS OF OPTICALLY STIMULATED LUMINESCENCE IN MEDICAL DOSIMETRY

If the first decade of the new millennium saw the establishment of a more solid foundation for the use of the Optically Stimulated Luminescence (OSL) in medical dosimetry, the second decade saw the technique take root and become more widely used in clinical studies. Recent publications report not only characterization and feasibility studies of the OSL technique for various applications in radiotherapy and radiology, but also the practical use of OSL for postal audits, estimation of staff dose, in vivo dosimetry, dose verification and dose mapping studies. This review complements previous review papers and reports on the topic, providing a panorama of the new advances and applications in the last decade. Attention is also dedicated to potential future applications, such as LET dosimetry, 2D/3D dosimetry using OSL, dosimetry in magnetic resonance imaging-guided radiotherapy (MRIgRT) and dosimetry of extremely high dose rates (FLASH therapy).

Calibration strategies for use of the nanoDot OSLD in CT applications

Aluminum oxide based optically stimulated luminescent dosimeters (OSLD) have been recognized as a useful dosimeter for measuring CT dose, particularly for patient dose measurements. Despite the increasing use of this dosimeter, appropriate dosimeter calibration techniques have not been established in the literature; while the manufacturer offers a calibration procedure, it is known to have relatively large uncertainties. The purpose of this work was to evaluate two clinical approaches for calibrating these dosimeters for CT applications, and to determine the uncertainty associated with measurements using these techniques. Three unique calibration procedures were used to calculate dose for a range of CT conditions using a commercially available OSLD and reader. The three calibration procedures included calibration (a) using the vendor-provided method, (b) relative to a 120 kVp CT spectrum in air, and (c) relative to a megavoltage beam (implemented with 60 Co). The dose measured using each of these approaches was compared to dose measured using a calibrated farmer-type ion chamber. Finally, the uncertainty in the dose measured using each approach was determined. For the CT and megavoltage calibration methods, the dose measured using the OSLD nanoDot was within 5% of the dose measured using an ion chamber for a wide range of different CT scan parameters (80-140 kVp, and with measurements at a range of positions). When calibrated using the vendor-recommended protocol, the OSLD measured doses were on average 15.5% lower than ion chamber doses. Two clinical calibration techniques have been evaluated and are presented in this work as alternatives to the vendor-provided calibration approach. These techniques provide high precision for OSLD-based measurements in a CT environment.

Patient understanding of radiation risk from medical computed tomography-A comparison of Hispanic vs. non-Hispanic emergency department populations

Background. Cultural differences and language barriers may adversely impact patients with respect to understanding the risks/benefits of medical testing.

Objective. We hypothesized that there would be no difference in Hispanic vs. non-Hispanic patients’ knowledge of radiation risk that results from CT of the abdomen/pelvis (CTAP).

Methods. We enrolled a convenience sample of adults at an inner-city emergency department (ED). Patients provided written answers to rate agreement on a 10-point scale for two correct statements comparing radiation exposure equality between: CTAP and 5 years of background radiation (question 1); CTAP and 200 chest x-rays (question 3). Patients also rated their agreement that multiple CT scans increase the lifetime cancer risk (question 2). Scores of >8 were considered good knowledge. Multivariate logistic regression analyses were performed to estimate the independent effect of the Hispanic variable.

Results. 600 patients in the study group; 63% Hispanic, mean age 39.2 ± 13.9 years. Hispanics and non-Hispanics whites were similar with respect to good knowledge-level answers to question 1 (17.3 vs. 15.1%; OR = 1.2; 95% CI [0.74–2.0]), question 2 (31.2 vs. 39.3%; OR = 0.76; 95% CI [0.54–1.1]), and question 3 (15.2 vs. 16.5%; OR = 1.1; 95% CI [0.66–1.8]). Compared to patients who earned <20,000, patients with income >40,000 were more likely to answer question 2 with good knowledge (OR = 1.96; 95% CI [1.2–3.1]).

Conclusion. The study group’s overall knowledge of radiation risk was poor, but we did not find significant differences between Hispanic vs. non-Hispanic patients.