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Introduction: According to the American Urological Association imaging guidelines, patients presenting with renal colic should undergo low-dose (LD) rather than standard-dose (SD) noncontrast CT. The aim of the present study was to assess how often physicians ordered LD CT scans and to calculate mean effective radiation exposure (ERE) from CT scans from dose length products, and determine mean cumulative ERE over 1-year follow-up period. Methods: After obtaining ethics approval, a retrospective chart review was conducted for patients with renal colic presenting to the emergency department between August 1, 2015 and July 31, 2016 (Phase I) and between April 1, 2019 and October 1, 2019 (Phase II). All imaging studies performed within 1-year of initial presentation were cataloged. Results: In Phase I, 146 patients, with mean age of 51 years and mean body mass index (BMI) of 28.6 kg/m 2 , underwent 220 CT scans. In Phase II, 225 patients, with mean age of 55 years and mean BMI of 26.7 kg/m 2 , underwent 273 CT scans. Urologists were the only physicians ordering LD CT scans and they ordered significantly more LD than SD CT scans (71.3% vs 28.7%, p  < 0.001). In Phase II, after revision of LD CT scan protocol in March 2019, the mean ERE per LD CT significantly decreased (6.5 vs 1.6 mSv, p  < 0.001). In addition, there were significant differences in mean ERE from LD CT scans between two hospitals in the same health system (1.6 vs 7.8 mSv, p  < 0.001). The mean cumulative ERE in Phase II over the 1-year period was 19.3 mSv, with 6.9% of patients exceeding 50 mSv. Conclusions: Although LD CT scans are being ordered, a small percentage of patients continue to exceed the 50 mSv annual threshold. It is important to keep track of mean ERE of LD CT scans and collaborate with medical physicists and the diagnostic imaging department to further refine LD CT scan protocols since not every low-dose is low-dose.

Purpose: To evaluate the performance of the EBT3 radiochromic film dosimetry system using reflection measurements and to suggest a calibration protocol for precise and accurate reflection film dosimetry., Methods: A set of 14 Gafchromic EBT3 film pieces were irradiated to various doses ranging from 0 to 8 Gy and subsequently scanned using both the reflection and transmission mode. Scanning resolution varied from 50 to 508 dpi (0.5-0.05 mm/pixel). Both the red and green color channels of scanned images were used to relate the film response to the dose. A sensitivity, uncertainty, and accuracy analysis was performed for all scanning modes and color channels. The total uncertainty, along with the fitting and experimental uncertainty components, was identified and analyzed. A microscope resolution target was used to evaluate possible resolution losses under reflection scanning. The calibration range was optimized for reflection scanning in the low (<2 Gy) and high (>2 Gy) dose regions based on the reported results., Results: Reflection scanning using the red channel exhibited the highest sensitivity among all modes, being up to 150% higher than transmission mode in the red channel for the lowest dose level. Furthermore, there was no apparent loss in resolution between the two modes. However, higher uncertainties and reduced accuracy were observed for the red channel under reflection mode, especially at dose levels higher than 2 Gy. These uncertainties were mainly attributed to saturation effects which were translated in poor fitting results. By restricting the calibration to the 0-2 Gy dose range, the situation is reversed and the red reflection mode was superior to the transmission mode. For higher doses, the green channel in reflection mode presented comparable results to the red transmission., Conclusions: A two-color reflection scanning protocol can be suggested for EBT3 radiochromic film dosimetry using the red channel for doses less than 2 Gy and the green channel for higher doses. The precision and accuracy are significantly improved in the low dose region following such a protocol.

Two recently introduced GafChromic film models, HS and XR-T, have been developed as more sensitive and uniform alternatives to GafChromic MD-55-2 film. The HS model has been specifically designed for measurement of absorbed dose in high-energy photon beams (above 1 MeV), while the XR-T model has been introduced for dose measurements of low energy (0.1 MeV) photons. The goal of this study is to compare the sensitometric curves and estimated dosimetric uncertainties associated with seven different GafChromic film dosimetry systems for the two new film models. The densitometers tested are: LKB Pharmacia UltroScan XL, Molecular Dynamics Personal Densitometer, Nuclear Associates Radiochromic Densitometer Model 37-443, Photoelectron Corporation CMR-604, Laser Pro 16, Vidar VXR-16, and AGFA Arcus II document scanner. Pieces of film were exposed to different doses in a dose range from 0.5 to 50 Gy using 6 MV photon beam. Functional forms for dose vs net optical density have been determined for each of the GafChromic film-dosimetry systems used in this comparison. Two sources of uncertainties in dose measurements, governed by the experimental measurement and calibration curve fit procedure, have been compared for the densitometers used. Among the densitometers tested, it is found that for the HS film type the uncertainty caused by the experimental measurement varies from 1% to 3% while the calibration fit uncertainty ranges from 2% to 4% for doses above 5 Gy. Corresponding uncertainties for XR-T film model are somewhat higher and range from 1% to 5% for experimental and from 2% to 7% for the fit uncertainty estimates. Notwithstanding the significant variations in sensitivity, the studied densitometers exhibit very similar precision for GafChromic film based dose measurements above 5 Gy.

The subject of this work was to compare the effect of Conventional and Conformal techniques, used for anal canal cancer treatments, on the skin dose deposition. Skin dose was measured on a Rando phantom using XR-T GAFCHROMIC film. A skin surface dose histogram was constructed and a skin dose profile in the sagittal direction of the perineal region was measured, for both techniques. The measured skin dose in the anterior and posterior region of the skin exposed to radiation is from two to ten times higher when using a conventional technique. In the perineal region, an 85% of the prescription isodose line spreads over 25% of the perineum for conformal technique as compared to 65% with conventional techniques. In addition, conformal technique dose profiles confine better the anatomical position of the anal verge than conventional techniques. Results presented in this work confirm clinically observed improvement in the radiation-induced dermatitis when using the conformal technique.

Purpose: To evaluate the feasibility of delivering conformal radiotherapy (RT) and concurrent chemotherapy without a mandatory break in patients with anal canal carcinoma., Methods and Materials: Thirty patients with T2-T4 tumors were treated with a combination of 54 Gy in 30 fractions and two cycles of 5-fluorouracil and mitomycin C. Dose-volume histograms were obtained for bone marrow, small bowel, and skin to compare the conventional technique using the Radiation Therapy Oncology Group standard with our conformal technique., Results: The mean dose ratio of the conventional compared with the conformal technique for bone marrow, small bowel, and skin was, respectively, 2.1-2.7, 3.0, and 2.0, in favor of the conformal technique. All patients completed their treatment without a treatment break. An incidence of Grade 3 toxicity for bone marrow, bowel, and skin of 13.3%, 3.3%, and 20%, respectively, was observed. With a median follow-up of 33 months, a 4-year local recurrence-free survival rate of 91% was observed., Conclusion: The results of this study have shown that conformal RT leads to a well-tolerated treatment. The treatment time is shortened to 6 weeks. A significant decrease in the acute toxicity rate suggests that by decreasing the "volume factor," conformal RT improves the therapeutic index in patients treated with combined chemotherapy and RT.