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Radiation Protection Dosimetry Oct 2023In this study, in some neighborhoods in Kahramanmaraş province of Turkey, indoors and outdoors direct gamma dose rate measurements have been done. All of the gamma dose...
In this study, in some neighborhoods in Kahramanmaraş province of Turkey, indoors and outdoors direct gamma dose rate measurements have been done. All of the gamma dose rate measurements have been made at ground level and at the height of 1 m from the ground. The median values of the gamma dose rates on the ground and 1 m above the ground indoors are 70.34 ± 7.74 and 49.53 ± 5.39 nGy h-1, respectively. Outdoor measurements have been carried out on both soil and asphalt floors. The average values of gamma dose rate on the ground and at a height of 1 m outdoors (soil floor) are 68.16 ± 7.49 and 53.50 ± 5.88 nGy h-1, respectively. The mean values of gamma dose rate on the ground and 1 m above the ground outdoors (asphalt floor) are 61.63 ± 6.77 and 48.69 ± 5.35 nGy h-1, respectively. Indoor and outdoor average gamma dose rates are below the mean world. In addition, using the measured gamma dose rate values, annual effective dose equivalent (AEDE) and excess lifetime cancer risk (ELCR) for adults have been calculated. The total AEDE and ELCR (on soil floors and indoors at 1 m above ground level) are 0.31 ± 0.03 mSv y-1 and 1.08 ± 0.10 × 10-3, respectively. The total AEDE and ELCR (on asphalt floors and indoors at 1 m above ground level) are 0.30 ± 0.03 mSv y-1 and 1.06 ± 0.10 × 10-3, respectively. The AEDE and ELCR for adults living in the neighborhoods within the scope of the study in Kahramanmaraş city center within 1 y are lower than the average world.
PubMed: 37587689
DOI: 10.1093/rpd/ncad223 -
World Journal of Urology Jan 2023To identify the relationship between fluoroscopy pulse rate and absorbed radiation dose. We compared absorbed radiation dose with common proxy measurements such as...
PURPOSE
To identify the relationship between fluoroscopy pulse rate and absorbed radiation dose. We compared absorbed radiation dose with common proxy measurements such as fluoroscopy time and C-arm reported dose.
METHODS
Using a simulated patient model, 60 s fluoroscopy exposures were performed using pulse rates of 30, 8, 4, 2, and 1 pulse(s) per second. Each experiment was performed with both standard and low-dose settings using a GE OEC 9800 plus C-arm. Landauer nanoDot™ OSL dosimeters were used to measure the absorbed radiation dose.
RESULTS
Fluoroscopy pulse rate and absorbed radiation dose demonstrated a linear correlation for both standard (R = 0.995, p < 0.001) and low-dose (R = 0.998, p < 0.001) settings. For any given pulse rate, using the low-dose setting reduced absorbed radiation dose by 58 ± 2.8%. Fluoroscopy time demonstrated a linear relationship with absorbed radiation dose for both standard (R = 0.996, p < 0.001) and low-dose (R = 0.991, p < 0.001) settings, but did not change with use of the low-dose setting. C-arm reported radiation dose correlated linearly with absorbed dose (R = 0.999) but consistently under-estimated measured values by an average of 49 ± 3.5%. Using a combination of 1 pulse-per-second and low-dose fluoroscopy, absorbed dose was reduced by 97.7 ± 0.1% compared to standard dose and 30 pulse-per-second settings.
CONCLUSION
Absorbed radiation dose decreases linearly with fluoroscopy pulse rate during equivalent exposure times. Adjusting fluoroscopy pulse rate and utilizing low-dose settings significantly reduces overall absorbed radiation exposure by up to 98%.
Topics: Humans; Radiation Dosage; Heart Rate; Radiation Exposure; Fluoroscopy; Patients
PubMed: 36525105
DOI: 10.1007/s00345-022-04238-2 -
World Journal of Plastic Surgery Jan 2021Radiotherapy as an adjuvant therapy to surgical resection has shown variable rates of recurrence treating earlobe keloids. The purpose of this study was to describe our...
BACKGROUND
Radiotherapy as an adjuvant therapy to surgical resection has shown variable rates of recurrence treating earlobe keloids. The purpose of this study was to describe our experience with surgical excision followed by high-dose-rate brachytherapy and present our outcomes after 24 months of follow-up.
METHODS
Retrospective chart of 14 patients with 14 earlobe keloids treated with surgical excision followed by high-dose-rate brachytherapy, between January 2015 and May 2016 were enrolled. Database included demographics, Fitzpatrick skin type, laterality, lesion size, and follow-up visits information. Outcomes were assessed in terms of keloid recurrence rates, complications, and patient subjective aesthetical result satisfaction after 24 months of follow-up.
RESULTS
All procedures were completed without complications. Three patients experienced keloid recurrence after 6 (14.28%) and 12 months (7.14%). Three patients experienced mild signs of self-limited post-radiation dermatitis. Self-assessment of aesthetical result was considered "very good" in 71.43% of patients.
CONCLUSION
Surgical excision followed by high-dose-rate brachytherapy is secure and effective to treat earlobe keloids, and can be considered a first line combined treatment. Larger clinical trials comparing different irradiation protocols are still needed.
PubMed: 33833958
DOI: 10.29252/wjps.10.1.78 -
Medical Physics Dec 2020FLASH radiotherapy (RT) can potentially reduce normal tissue toxicity while preserving tumoricidal effectiveness to improve the therapeutic ratio. The key of FLASH for...
PURPOSE
FLASH radiotherapy (RT) can potentially reduce normal tissue toxicity while preserving tumoricidal effectiveness to improve the therapeutic ratio. The key of FLASH for sparing normal tissues is to irradiate tissues with an ultra-high dose rate (i.e., ≥40 Gy/s), for which proton RT can be used. However, currently available treatment plan optimization method only optimizes the dose distribution and does not directly optimize the dose rate. The contribution of this work to FLASH proton RT is the development of a novel treatment optimization method, that is, simultaneous dose and dose rate optimization (SDDRO), to optimize tissue-receiving dose rate distribution as well as dose distribution.
METHODS
Distinguished from existing methods, SDDRO accounts for dose rate constraint and optimizes dose rate distribution. In terms of mathematical formulation, SDDRO is a constrained optimization problem with dose-volume constraint on dose distribution, minimum dose rate constraint on dose-averaged tissue-receiving dose rates, minimum monitor unit constraint on spot weight, and maximum intensity constraint on beam intensity. In terms of optimization algorithm, SDDRO is solved by iterative convex relaxation and alternating direction method of multipliers. SDDRO algorithms are presented for both scenarios with either constant or variable beam intensity.
RESULTS
SDDRO was compared with intensity modulated proton therapy (IMPT) (dose optimization alone, and no dose rate optimization) using three lung cases. SDDRO substantially improved the dose rate distribution compared to IMPT, for example, increasing of the region-of-interest (ROI) volume (ROI = CTV_10mm: the ring sandwiched by 10 mm outer and inner expansion of CTV boundary) receiving at least 40 Gy/s from ~30-50% to at least 98%, and the lung volume receiving at least 40 Gy/s from ~30-40% to ~70-90%. Moreover, both dose and dose rate distributions from SDDRO were further considerably improved via the combined use of hypofractionation and multiple beams.
CONCLUSIONS
We have developed a joint dose and dose rate optimization method for FLASH proton RT, namely SDDRO, which is first-of-its-kind to the best of our knowledge. The results suggest that (a) SDDRO can substantially improve the FLASH-dose rate coverage (e.g., in terms of dose rate volume histogram) compared to IMPT for the purpose of normal tissue sparing while preserving the dose distribution and (b) the combination of hypofractionation and multiple beams can further considerably improve the SDDRO plan quality in terms of both dose and dose rate distribution.
Topics: Algorithms; Proton Therapy; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Radiotherapy, Intensity-Modulated
PubMed: 33068294
DOI: 10.1002/mp.14531 -
Medical Physics Mar 2022Compared to CONV-RT (with conventional dose rate), FLASH-RT (with ultra-high dose rate) can provide biological dose sparing for organs-at-risk (OARs) via the so-called...
PURPOSE
Compared to CONV-RT (with conventional dose rate), FLASH-RT (with ultra-high dose rate) can provide biological dose sparing for organs-at-risk (OARs) via the so-called FLASH effect, in addition to physical dose sparing. However, the FLASH effect only occurs, when both dose and dose rate meet certain minimum thresholds. This work will develop a simultaneous dose and dose rate optimization (SDDRO) method accounting for both FLASH dose and dose rate constraints during treatment planning for pencil-beam-scanning proton therapy.
METHODS
SDDRO optimizes the FLASH effect (specific to FLASH-RT) as well as the dose distribution (similar to CONV-RT). The nonlinear dose rate constraint is linearized, and the reformulated optimization problem is efficiently solved via iterative convex relaxation powered by alternating direction method of multipliers. To resolve and quantify the generic tradeoff of FLASH-RT between FLASH and dose optimization, we propose the use of FLASH effective dose based on dose modifying factor (DMF) owing to the FLASH effect.
RESULTS
FLASH-RT via transmission beams (TB) (IMPT-TB or SDDRO) and CONV-RT via Bragg peaks (BP) (IMPT-BP) were evaluated for clinical prostate, lung, head-and-neck (HN), and brain cases. Despite the use of TB, which is generally suboptimal to BP for normal tissue sparing, FLASH-RT via SDDRO considerably reduced FLASH effective dose for high-dose OAR adjacent to the target. For example, in the lung SBRT case, the max esophageal dose constraint 27 Gy was only met by SDDRO (24.8 Gy), compared to IMPT-BP (35.3 Gy) or IMPT-TB (36.6 Gy); in the brain SRS case, the brain constraint V12Gy≤15cc was also only met by SDDRO (13.7cc), compared to IMPT-BP (43.9cc) or IMPT-TB (18.4cc). In addition, SDDRO substantially improved the FLASH coverage from IMPT-TB, e.g., an increase from 37.2% to 67.1% for lung, from 39.1% to 58.3% for prostate, from 65.4% to 82.1% for HN, from 50.8% to 73.3% for the brain.
CONCLUSIONS
Both FLASH dose and dose rate constraints are incorporated into SDDRO for FLASH-RT that jointly optimizes the FLASH effect and physical dose distribution. FLASH effective dose via FLASH DMF is introduced to reconcile the tradeoff between physical dose sparing and FLASH sparing, and quantify the net effective gain from CONV-RT to FLASH-RT.
Topics: Humans; Male; Organs at Risk; Proton Therapy; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Radiotherapy, Intensity-Modulated
PubMed: 34800301
DOI: 10.1002/mp.15356 -
Brachytherapy 2019The purpose of this study was to analyze and compare clinical outcomes of low-dose-rate (LDR) and high-dose-rate (HDR) interstitial brachytherapy boost (ISBT) after EBRT...
PURPOSE
The purpose of this study was to analyze and compare clinical outcomes of low-dose-rate (LDR) and high-dose-rate (HDR) interstitial brachytherapy boost (ISBT) after EBRT or radio chemotherapy for the treatment of anal canal cancers.
METHODS AND MATERIALS
One hundred patients with anal canal cancers were treated at our institution by ISBT [LDR (n = 50); HDR (n = 50)]. Chronic toxicity rates, local control, disease-free survival, overall survival, and colostomy-free survival of the two different dose-rate brachytherapy modalities were analyzed and compared.
RESULTS
With a median followup of 42.2 months (95% CI, [34.5-48.8]), 9 (9% [4.8-16.2%]) local recurrences were observed, 4 (8% [3.2-18.8%]) in LDR vs. 5 (10% [4.4-21.4%]) in HDR group (odds ratio [OR] = 1.28 [0.32-5.07], p = 0.73). The 5-year rate of local control for the entire population was 90% [81-95%], 93% [79-98%] vs. 86% [69-94%] for LDR and HDR, respectively (p = 0.38). The 5-year disease-free survival rate for all patients was 82% [71-90%], 88% [73-95%] vs. 72% [44-88%] for LDR and HDR, respectively (p = 0.21). The 5-year overall survival rate for global population was 94% [84-98%], with no significant differences between LDR (97% [79-100%]) and HDR (93% [80-98%]) (p = 0.27). The 5-year colostomy-free survival rate was 92% [83-96%], respectively, 95% [83-99%] vs. 86% [69-94%] for LDR and HDR (p = 0.21). Significant differences were found in terms of chronic toxicity rates, with 28 (56% [42.3-68.8%]) patients concerned in low-dose-rate brachytherapy vs. 17 (34% [22.4-47.9%]) in high-dose-rate brachytherapy (OR = 0.40 [0.18-0.91], p = 0.03).
CONCLUSIONS
Local recurrence rates were comparable between both groups; HDR brachytherapy seem to have a better toxicity profile. Our data confirmed the finding that HDR can be used to safely administer ISBT without increasing chronic toxicity.
Topics: Adult; Aged; Anal Canal; Anus Neoplasms; Brachytherapy; Dose-Response Relationship, Radiation; Female; Follow-Up Studies; France; Humans; Male; Middle Aged; Neoplasm Staging; Radiotherapy Dosage; Survival Rate; Time Factors
PubMed: 31515067
DOI: 10.1016/j.brachy.2019.08.005 -
International Journal of Radiation... 2021Carcinogenic effects of radiation are often assumed to be universally understood, more often than, for example, carcinogenic effects of many different chemicals. This... (Review)
Review
Carcinogenic effects of radiation are often assumed to be universally understood, more often than, for example, carcinogenic effects of many different chemicals. This in turn leads to an assumption that any dose of radiation, delivered at any dose rate, poses a serious health challenge. This remains an issue of dispute and low dose radiation research is focused on understanding whether these exposures contribute to cancer incidence. This review is focused on the low linear energy transfer (low LET) radiation exposures for which the data is the most abundant in recent years. Review of the literature between 2008 and today, highlighting some of the most diverse studies in low dose research. Low dose and low dose rate, low LET ionizing radiation animal studies suggest that the effects of exposure very much depend on animal genotype and health status. Only the integration of all of the data from different models and studies will lead to a fuller understanding of low dose radiation effects. Therefore, we hope to see an increase in international archival efforts and exchange of raw data information opening the possibilities for new types of meta analyses.
Topics: Animals; Carcinogenesis; Dose-Response Relationship, Radiation; Humans; Linear Energy Transfer; Neoplasms, Radiation-Induced
PubMed: 33289582
DOI: 10.1080/09553002.2020.1859155 -
International Journal of Molecular... Jun 2022Accurate knowledge of the relative biological effectiveness (RBE) and its dependencies is crucial to support modern ion beam therapy and its further development....
Accurate knowledge of the relative biological effectiveness (RBE) and its dependencies is crucial to support modern ion beam therapy and its further development. However, the influence of different dose rates of the reference radiation and ion beam are rarely considered. The ion beam RBE-model within our "UNIfied and VERSatile bio response Engine" (UNIVERSE) is extended by including DNA damage repair kinetics to investigate the impact of dose-rate effects on the predicted RBE. It was found that dose-rate effects increase with dose and biological effects saturate at high dose-rates, which is consistent with data- and model-based studies in the literature. In a comparison with RBE measurements from a high dose in-vivo study, the predictions of the presented modification were found to be improved in comparison to the previous version of UNIVERSE and existing clinical approaches that disregard dose-rate effects. Consequently, DNA repair kinetics and the different dose rates applied by the reference and ion beams might need to be considered in biophysical models to accurately predict the RBE. Additionally, this study marks an important step in the further development of UNIVERSE, extending its capabilities in giving theoretical guidance to support progress in ion beam therapy.
Topics: DNA Repair; Kinetics; Relative Biological Effectiveness
PubMed: 35682947
DOI: 10.3390/ijms23116268 -
International Journal of Urology :... Jan 2020The history of prostate brachytherapy has passed one century. In 1983, modern low-dose-rate prostate brachytherapy using a transrectal ultrasound-guided procedure was... (Review)
Review
The history of prostate brachytherapy has passed one century. In 1983, modern low-dose-rate prostate brachytherapy using a transrectal ultrasound-guided procedure was introduced. In the early 1990s, low-dose-rate brachytherapy was introduced and rapidly spread across the USA due to its excellent oncological control, cost-effectiveness and technically easy procedure. Since low-dose-rate brachytherapy was introduced in Japan (2003), over 15 years have passed. More than 43 000 patients have undergone low-dose-rate brachytherapy. Japanese urologists and radiation oncologists are on course with leading brachytherapists in the USA. A nationwide prospective cohort study, J-POPS, was initiated in 2005. The J-POPS group also provides educational programs including an annual novel training course in low-dose-rate brachytherapy to familiarize urologists, radiation oncologists and pathologists with the procedure. Important information on Japanese patients has accumulated, especially by the J-POPS study group. The Japanese investigators reported excellent oncological outcomes of low-dose-rate brachytherapy, showing equivalent or superior efficacy to surgery in low- to intermediate-risk patients, and superior efficacy in high-risk patients using the surgery biochemical recurrence definition (prostate-specific antigen cut-off value of 0.2 ng/mL). Two randomized controlled studies (SHIP study: intermediate risk, and TRIP study: high risk) carried out by the J-POPS group are ongoing, and an additional follow-up study (J-POPS 2 study) has been started to evaluate survival outcomes over longer follow-up periods. Low-dose-rate brachytherapy is expected to provide a survival benefit, which must be confirmed by further studies with longer follow-up periods in the future.
Topics: Brachytherapy; Humans; Japan; Male; Prostatic Neoplasms; Radiotherapy Dosage; Time Factors; Treatment Outcome
PubMed: 31549770
DOI: 10.1111/iju.14098 -
The Science of the Total Environment Jul 2021After the 2011 Fukushima Dai-ichi Nuclear Power Station (FDNPS) accident, wild populations of animals and plants living in the evacuation zone received additional...
After the 2011 Fukushima Dai-ichi Nuclear Power Station (FDNPS) accident, wild populations of animals and plants living in the evacuation zone received additional ionizing radiation of both internal and external radiation doses. Morphological abnormalities of pine and fir trees near the FDNPS were reported. In order to evaluate dose-effect relationships, it is necessary to quantify the radiation doses to trees and plants. In this study, the internal and external dose rates to Japanese cedar and plants collected at three sites in Okuma, approximately 4 km southwest of FDNPS were estimated applying the ERICA Assessment Tool. The activity concentrations of Cs and Cs in soils, cedar trunks, and plants were determined. The total dose rates to cedar ranged from 2.2 ± 1.2 to 6.1 ± 2.2 μGy h. These rates were within the derived consideration reference levels (DCRLs) reported by ICRP 108 as 4-40 μGy h for pine trees. The highest estimate for plants was 7.1 ± 2.7 μGy h, much smaller than the DCRLs reported for grasses and herbs (40-400 μGy h). On average, the internal radiation dose rates to cedars at the two sites accounted for 5% and 29% of the external dose rates, respectively, while the value in another site was only 0.4% for cedar. This was attributed to differences in the crown area between the three sites. The trunk diameter of cedars shows a positive correlation with the ratio of internal to external radiation dose rates. It indicates that the total dose rate to cedars is easily estimated with the soil radiocaesium inventory and trunk diameter. The internal radiation dose rate to the plant varied depending on the plant species. This variation was considerably large in plants due to the presence of two species, including Solidago altissima and Artemisia indica var. maximowiczii.
Topics: Animals; Cesium Radioisotopes; Cryptomeria; Fukushima Nuclear Accident; Japan; Nuclear Power Plants; Radiation Dosage; Radiation Monitoring; Soil Pollutants, Radioactive
PubMed: 33744576
DOI: 10.1016/j.scitotenv.2021.146350