Complete Remission of Mouse Melanoma after Temporally Fractionated Microbeam Radiotherapy

Background: Synchrotron Microbeam Radiotherapy (MRT) significantly improves local tumour control with minimal normal tissue toxicity. MRT delivers orthovoltage X-rays at an ultra-high “FLASH” dose rate in spatially fractionated beams, typically only few tens of micrometres wide. One of the biggest challenges in translating MRT to the clinic is its use of high peak doses, of around 300–600 Gy, which can currently only be delivered by synchrotron facilities. Therefore, in an effort to improve the translation of MRT to the clinic, this work studied whether the temporal fractionation of traditional MRT into several sessions with lower, more clinically feasible, peak doses could still maintain local tumour control. Methods: Two groups of twelve C57Bl/6J female mice harbouring B16-F10 melanomas in their ears were treated with microbeams of 50 µm in width spaced by 200 µm from their centres. The treatment modality was either (i) a single MRT session of 401.23 Gy peak dose (7.40 Gy valley dose, i.e., dose between beams), or (ii) three MRT sessions of 133.41 Gy peak dose (2.46 Gy valley dose) delivered over 3 days in different anatomical planes, which intersected at 45 degrees. The mean dose rate was 12,750 Gy/s, with exposure times between 34.2 and 11.4 ms, respectively. Results: Temporally fractionated MRT ablated 50% of B16-F10 mouse melanomas, preventing organ metastases and local tumour recurrence for 18 months. In the rest of the animals, the median survival increased by 2.5-fold in comparison to the single MRT session and by 4.1-fold with respect to untreated mice. Conclusions: Temporally fractionating MRT with lower peak doses not only maintained tumour control, but also increased the efficacy of this technique. These results demonstrate that the solution to making MRT more clinically feasible is to irradiate with several fractions of intersecting arrays with lower peak doses. This provides alternatives to synchrotron sources where future microbeam radiotherapy could be delivered with less intense radiation sources.

Integrity test of lead apron and its effect on personnel and carer

<p class="Abstract">The use of lead apron is known to protect radiation workers and carers (patient relatives) from the scatter radiation. The study intends to assess the integrity of lead apron by checking for defects and to estimate the mean dose rate to personnel and carers and also to compare the percentage mean absorbance of the apron with the related studies. Ten lead aprons were used involving three vendors. A fluoroscopy unit, floor mounted X-ray unit, survey meter, lead aprons and meter rule were used. Crack and tear were identified with some areas close to the critical organ site. Eighty percent of the aprons showed signs that they were defective. Correlation of the lead aprons mean age and the total number of defective lead aprons were not significant (p=0.866). The mean thickness of the aprons for the three brands affected the percentage absorbance (p&lt;0.001). The mean dose rate was above 20 mSv recommended for radiation workers averaged over a single year. It is recommended that the defective apron close to the critical organ be replaced and those in areas distal from the critical organs be further evaluated using the rejection criteria test before they are replaced.</p>

Assessment of Environmental Gamma Radiation (Outdoor and Indoor Spaces) in the Region of Bandar Abbas Gachine

Background: Ionizing radiation is present in all environment of the Earth’s surface, beneath the Earth and in the atmosphere. Human beings are exposed to external radiation from their surroundings naturally and also to internal radiation from food, water and air they consume. Then, it is important to measure and develop knowledge about radiation.Objective: This study is designed to evaluate the risks of radiation outdoors and indoors and in hot spring in Gachine area of Bandar Abbas.Materials and Methods: The device used in this study was environmental radiation surveymeter. Indoor gamma radiation in Gachine area was carried out inside 115 dwellings. Measurement for hot spring waters was carried out at one meter above water level. Dose rates were recorded for an hour.Results: Our results indicate the outdoor dose rate gamma radiation in Gachine area is higher than the global mean dose rate. Moreover, Gachine Bala has the highest outdoor gamma radiation (78.87 nGy/h) and Gachine Paien has the lowest gamma background radiation (71.62 nGy/h).Discussion: This study demonstrates that indoor mean dose rate of gamma radiation in this area is higher than the global mean dose rate. Estimated indoor mean dose rates were for Gachine Paien (110.58 nGy/h), Gachine Bala (111.83 nGy/h), Ship industry dwelling (109.30 nGy/h) and Jamal Ahmad (107.84 nGy/h). The highest dose rate above hot spring was obtained from Chostaneh (1320 nGy/h).

Delivery Parameter Variations and Early Clinical Outcomes of Volumetric Modulated Arc Therapy for 31 Prostate Cancer Patients: An Intercomparison of Three Treatment Planning Systems

We created volumetric modulated arc therapy (VMAT) plans for 31 prostate cancer patients using one of three treatment planning systems (TPSs)—ERGO++, Monaco, or Pinnacle—and then treated those patients. A dose of 74 Gy was prescribed to the planning target volume (PTV). The rectum, bladder, and femur were chosen as organs at risk (OARs) with specified dose-volume constraints. Dose volume histograms (DVHs), the mean dose rate, the beam-on time, and early treatment outcomes were evaluated and compared. The DVHs calculated for the three TPSs were comparable. The mean dose rates and beam-on times for Ergo++, Monaco, and SmartArc were, respectively, 174.3 ± 17.7, 149.7 ± 8.4, and 185.8 ± 15.6 MU/min and 132.7 ± 8.4, 217.6 ± 13.1, and 127.5 ± 27.1 sec. During a follow-up period of 486.2 ± 289.9 days, local recurrence was not observed, but distant metastasis was observed in a single patient. Adverse events of grade 3 to grade 4 were not observed. The mean dose rate for Monaco was significantly lower than that for ERGO++ and SmartArc (P<0.0001), and the beam-on time for Monaco was significantly longer than that for ERGO++ and SmartArc (P<0.0001). Each TPS was successfully used for prostate VMAT planning without significant differences in early clinical outcomes despite significant TPS-specific delivery parameter variations.