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High dose rate (HDR) brachytherapy treatment planning usually involves optimization methods to deliver uniform dose to the target volume and minimize dose to the healthy tissues. Four optimizations were used to evaluate the high-risk clinical target volume (HRCTV) coverage and organ at risk (OAR). Dose-volume histogram (DVH) and dosimetric parameters were analyzed and evaluated. Better coverage was achieved with PGO (mean CI = 0.95), but there were no significant mean CI differences than GrO (p = 0.03322). Mean EQD2 doses to HRCTV (D90) were also superior for PGO with no significant mean EQD2 doses than GrO (p = 0.9410). The mean EQD2 doses to bladder, rectum, and sigmoid were significantly higher for NO plan than PO, GrO, and PGO. PO significantly reduced the mean EQD2 doses to bladder, rectum, and sigmoid but compromising the conformity index to HRCTV. PGO was superior in conformity index (CI) and mean EQD2 doses to HRCTV compared with the GrO plan but not statistically significant. The mean EQD2 doses to the rectum by PGO plan slightly exceeded the limit from ABS recommendation (mean EQD2 dose = 78.08 Gy EQD2). However, PGO can shorten the treatment planning process without compromising the CI and keeping the OARs dose below the tolerance limit.

Ultra-high dose rate "FLASH" radiotherapy has been shown to drastically reduce normal tissue toxicities while being as efficacious as conventional dose rate radiotherapy to treat tumors. A large number of preclinical studies describing this so-called FLASH effect have led to the clinical translation of FLASH-RT using ultra-high dose rate electron and proton beams. Although the vast majority of radiation therapy treatments are delivered using x-rays, few preclinical data using ultra-high dose rate x-ray irradiation have been published. This review focuses on different methods that can be used to generate ultra-high dose rate x-rays and their beam characteristics along with their effect on the biological tissues and the perspectives for the development of FLASH-RT with x-rays. This article is protected by copyright. All rights reserved.

PURPOSE Intracavitary brachytherapy using High-Dose-Rate (HDR) and Low-dose-rate (LDR) in cervical cancer has been utilized. We report the long-term final results of a large randomized trial in terms of toxicities and efficacy. METHODS AND MATERIALS Between 1996 to 2005, 816 patients were randomized to LDR (n = 441 patients) or HDR brachytherapy (n = 369 patients) stratified by FIGO Stage grouping. Patients with Stage I-II received external irradiation of 40 Gy in 20 fractions (with midline block (MLB)) followed by either 2 LDR Intracavitary applications of 30 Gy to point A (2–3 weeks apart) or 5 HDR Intracavitary applications of 7 Gy to point A once weekly. Patients with Stage III received 50 Gy in 25 fractions (with MLB after 40 Gy) followed by either one application of LDR 30 Gy to point A or three applications of HDR 7 Gy to point A once weekly. RESULTS With a median follow-up was 64 months (interquartile range [IQR]: 21 - 111), moderate to severe rectal and bladder complications were higher in LDR arm as compared to HDR arm (9.7% vs. 3.6%; p = 0.02) and (10.5% vs. 5.5%; p = 0.06) for Stage I-II. No difference in rectal or bladder complications for Stage III patients. Disease free and overall survivals were similar in both the arms for all stages. CONCLUSIONS HDR intracavitary brachytherapy with 7 Gy per fraction weekly is superior to LDR in terms of late rectal and bladder complications. Local control rates and survivals are similar irrespective of stages.

Purpose To establish and investigate the effects of dose, linear energy transfer (LET), and O2 concentration on biologic response to ultrahigh dose rate (uHDR; FLASH) helium ion beams compared with standard dose rate (SDR) irradiation. Methods and Materials Beam delivery settings for raster-scanned helium ions at both uHDR and SDR were tuned to achieve >100 Gy/s and ∼0.1 Gy/s, respectively. For both SDR and uHDR, plan optimization and calibration for 10 × 10-mm 2 fields were performed to assess in vitro response at an LET range of 4.5 to 16 keV/µm. Clonogenic survival assay was conducted at doses ranging from 2 to 12 Gy in 2 human lung epithelial cell lines (A549 and H1437). Radiation-induced nuclear γH2AX foci (RIF) were assessed in both epithelial cell lines and primary human pulmonary fibroblasts. Results Average dose rates achieved were 185 Gy/s and 0.12 Gy/s for uHDR and SDR, respectively. No differences in cellular response to SDR versus uHDR were observed for all tested doses at 21% O2, and at 2 and 4 Gy at 1% O2. In contrast, at 1% O2 and a dose threshold of ≳8 Gy cell survival was higher and correlated with reduced nuclear γH2AX RIF signal, indicating FLASH sparing effect in the investigated cell lines irradiated with uHDR compared with SDR. Conclusions The first uHDR delivery of raster-scanned particle beams was achieved using helium ions, reaching FLASH-level dose-rates of >100 Gy/s. Baseline oxygen levels and delivered dose (≳8 Gy) play a pivotal role, irrespective of the studied cell lines, for observation of a sparing effect for helium ions.

In recent decades, eye plaques of brachytherapy have been extensively used as primary treatment as well as a complementary treatment for ocular cancer. The purpose of this study is the development of the eye plaque brachytherapy throughout a new design of eye plaque by combining the COMS plaque and the CCB BEBIG plaque loaded by IRA1-103Pd and 106Ru, respectively. A new dual-core plaque with a diameter of 20 mm was designed in the way that the BEBIG plaque with a diameter of 20 mm loaded by 106Ru plate is attached to the COMS plaque with a diameter of 20 mm loaded by 24 of IRA1-103Pd seeds. Dose calculations for the new plaque were performed by using the MCNP5 code. Dose calculations of dual-core plaque including 103Pd seeds (gamma) and 106Ru plate (beta) were separately done for the sake of MCNP constraints in gamma and beta particle transfer simultaneously. The new dual-core plaque delivers a much higher dose rate to the tumor compared with every single plaque, while the dose rate reached to healthy tissues is slightly higher than each plaque separately. Of course, this is acceptable because the treatment time reduces and subsequently the error in radiation therapy reduces.

PURPOSE In this article, we investigate the feasibility of magnetic resonance (MR)-only imaging for high-dose-rate (HDR) surface brachytherapy (SABT). We examined whether a standard CT-based planning can be replaced with an MR-only planning. For this purpose, the MRI digitization and plan quality check processes were compared against the standard CT-based processes. A prospective clinical implementation of the MR-only planning was evaluated on a clinical data set. METHODS A pointwise encoding time reduction with radial acquisition (PETRA) sequence was optimized for visualization of Freiburg flap (FF) on MR images. MR and conventional CT images were acquired with a FF applicator (Elekta, Stockholm, Sweden) placed on the following phantoms: (1) flat styrofoam (FST), FF locked-in placed with supporting structure; (2) cast-made facemask, and (3) porcine leg (PL). Catheters were digitized and activated with 10 mm step size on Oncentra Brachy 4.5.3 Treatment Planning System. The CT-only and MR-only treatment plans were generated by optimizing the dose to the target defined as volume at 3 mm skin depth. To compare the plans, the MRI-to-CT alignment was performed via rigid registration. Positional displacements of dwell positions between CT and MR plans were compared on the FST phantom and the relative percent dose difference in 2210 different points from CT or MR-only plans was compared. For all three phantoms, the comparabilities between CT and MR-only plans were assessed by calculating dice similarity coefficient (DSC) for volumes enclosing 150%, 125%, 100%, 95%, 90%, 80%, and 65% isodose lines (V150 -V65 ). The MR images of FF placed on the forearm of a healthy subject were acquired with this optimized PETRA sequence and used for treatment planning. The relative percent dose was calculated on 140 representative points placed at 3 mm skin depth to evaluate the dose to the skin. RESULTS Using the optimized PETRA sequence, MRTP digitization accuracy was

PURPOSE To quantitatively evaluate through automated simulations the clinical significance of potential high-dose rate (HDR) prostate brachytherapy (HDRPB) physics errors selected from our internal failure-modes and effect analysis (FMEA). METHODS AND MATERIALS A list of failure modes was compiled and scored independently by 8 brachytherapy physicists on a one-to-ten scale for severity (S), occurrence (O), and detectability (D), with risk priority number (RPN) = SxOxD. Variability of RPNs across observers (standard deviation/average) was calculated. Six idealized HDRPB plans were generated, and error simulations were performed: single (N = 1722) and systematic (N = 126) catheter shifts (craniocaudal; -1cm:1 cm); single catheter digitization errors (tip and connector needle-tips displaced independently in random directions; 0.1 cm:0.5 cm; N = 44,318); and swaps (two catheters swapped during digitization or connection; N = 528). The deviations due to each error in prostate D90%, urethra D20%, and rectum D1cm3 were analyzed using two thresholds: 5–20% (possible clinical impact) and >20% (potentially reportable events). RESULTS Twenty-nine relevant failure modes were described. Overall, RPNs ranged from 6 to 108 (average ± 1 standard deviation, 46 ± 23), with responder variability ranging from 19% to 184% (average 75% ± 30%). Potentially reportable events were observed in the simulations for systematic shifts >0.4 cm for prostate and digitization errors >0.3 cm for the urethra and >0.4 cm for rectum. Possible clinical impact was observed for catheter swaps (all organs), systematic shifts >0.2 cm for prostate and >0.4 cm for rectum, and digitization errors >0.2 cm for prostate and >0.1 cm for urethra and rectum. CONCLUSIONS A high variability in RPN scores was observed. Systematic simulations can provide insight in the severity scoring of multiple failure modes, supplementing typical FMEA approaches.

The objective of this study was to identify occupational exposure in the work process of nursing professionals, with radiopharmaceuticals marked with 68 Ga in a nuclear medicine service in municipality in the south of Brazil. Nursing professionals who work exclusively in the positron emission tomography/computed tomography participated in the study. The professionals were identified with the pseudonyms alpha and beta. Data collection took place through observation and prescribed documents in national and international regulatory standards, which were defined in four consecutive moments: observation of professionals during the procedure with the radionuclide 68 Ga, application of scripts related to the observed process, occupational dosimetry, and verification of the dose rate in the period from May to August 2019. Exposure increased by 20% with noted decreases in distance between the sources and radiosensitive structures (i.e., the eye lens and thyroid gland), increased exposure time, and improper use of available shielding. After evaluating the routine of nursing professionals and considering the high-energy parameters of 68 Ga, time, distance, shielding, and the high dose rate, it is suggested that the work process should be reevaluated and standardized, paying attention to critical points, as well as not having only the dosimetric reading as an evaluation parameter.

Objective: To investigate patient-specific radioprotection methods for people in close contact with cancer patients treated by 125I-seed implantation. Methods: The initial dose rates (Ḋ0) at distances of 30 and 100 ​cm from 80 patients who had undergone 125I-seed implantation were measured within 24 ​h of the procedure. The dose rate at t (Ḋt) and effective dose (E) were calculated according to the measured values of Ḋ0. The appropriate precaution times for general adult family members, spouses, coworkers, and children or pregnant women were determined, and the relationships between Ḋ0 and precaution time for different close-contact groups were derived by curve-fitting the corresponding data. Results: The mean Ḋ0 values of 80 patients at distances of 30 and 100 ​cm were (15.24 ​± ​11.25) μSv/h and (1.96 ​± ​2.63) μSv/h, respectively (P ​

Aim Aim of the study was to determine the effects of the β--emitter 186Re and 662 keV photon radiation in order to compare the biological effects of low dose rate (186Re) to high dose rate irradiation. Methods Prae-B-lymphocytes were exposed to 662 keV photon radiation or incubated with a liquid solution of 186Re. Cell count and viability were compared over the observation period of seven days, survival curves constructed and analysed at time of lowest cell-viability. Results Biphasic cell survival curves resulted for both radiation types. Survival curves were obtained at 24 h for photon radiation and 72 h for 186Re. The biphasic survival curve after photon radiation exposure can be explained by radiation hypersensitivity at doses below 1 Gy resulting in a D0 of 3.3 Gy. Doses exceeding 1.0 Gy showed a D0 of 10 Gy. The biphasic survival curve in case of 186Re incubation represents repair of sub lethal damage in the first section of the curve (D0 11.1 Gy) – in this case, biological effects of the β--emitter are attenuated by repair. Beyond an accumulated dose of 1.6 Gy, 186Re showed a steeper slope with a D0 of 4 Gy, corresponding to 2.5 times higher biological effects compared to acute photon irradiation (10 Gy). Conclusion Low dose rate radiation resulted in low biological effects at low doses. There is a threshold of accumulated dose above which biological effects of 186Re-incubation exceed those of photon irradiation.

Tin-117 m (Sn-117m) is used to treat dogs with osteoarthritic joints by radiosynoviorthesis. The decay process for Sn-117m is internal conversion wherein IC electrons and auger electrons provide the therapeutic effect. Additionally, the most prominent gamma emission is 158.6 keV. The effective dose rate received by a person interacting at close distances with a treated dog is needed to determine the person's total dose and thus regulatory compliance. Simple measurement of the dose rate at a given distance does not provide an accurate measurement of the effective dose to a person due to the non-uniform nature of the radiation field at close distances. MNCP models of the interactions of five ages of humans at three distances were created to determine the effective dose rates using the methodology from NRC Regulatory Guide 8.40. Ratios of the effective dose rate to the person to the measured dose rate at 1 m from the same source were calculated.

PURPOSE Implanted fiducial markers are a commonly used tool in delineating the CTV in high-dose-rate interstitial brachytherapy (HDR-ISBT) for gynecologic malignancy, but their reliability in gynacological sites is not well understood. These markers and interstitial applicators can experience interfractional motion due to organ swelling or other anatomical changes. The purpose of this study was to evaluate the spatial variation of these features. METHODS AND MATERIALS The spatial positions of 50 implanted markers and 202 needles were tracked in 15 patients treated over 70 fractions of HDR brachytherapy. Marker and/or needle coordinates were extracted from CT images with contours and dose distributions. Automated analysis determined marker self-consistency and displacements between various elements of the implant. RESULTS From start to end fraction, the relative positions of the markers experienced an average magnitude displacement of 4.5 ± 3.0 mm while the average displacement of the applicator tips was 11 ± 8 mm, relative to their respective centers of mass (CM). CONCLUSIONS Markers implanted lateral and superior to the CTV experience greater drift than other implant locations.

Only scarce data are available on the possibility to reduce rectal dose by controlling rectum filling before HDR (high dose rate) IGABT (image-guided adaptive brachytherapy) in LACC (locally advanced cervical carcinoma) patients. We compared dosimetric outcomes before and after the evacuation of gasses using a rectum emptying tube.Sixty CT (computed tomography) scans from 30 consecutive patients with cancer of the cervix undergoing HDR IGABT after EBRT were reviewed. Patients who underwent at least one gas evacuation were included in the analysis. The three-dimensional dosimetric data of the dosimetric plan performed before and after gas evacuation were compared. Primary endpoint was the difference between D2cc of the rectum before and after the procedure. Expected probability of grade 2-4 overall rectum morbidity was assessed using a probit model from the prospective multicenter EMBRACE study.Thirty five (58.3%) CT scans from 23 patients (76.7%) requiring gas evacuation were analysed. The mean rectum volume, before and after gas evacuation, was 123.1 cc (sd, ± 60.4) and 66.4 cc (sd, ± 34.8), respectively. For each patient, the volume of the rectum after gas evacuation was lower than before. No major complication occurred during and after the procedure. After gas evacuation, a significant reduction in rectal dose per fraction was observed, on average -4.3 Gy (-38.4%, p0.001) for D0.1cc and -1.9 Gy (-30.6%, p0.001) for D2cc. Estimated mean probability to develop a grade 2-4 rectum morbidity was significantly lower after gas evacuation, 6.9% (sd,± 1.94) versus 9.5% (sd,± 3.17), p0.001.Gas evacuation using a rectal emptying tube in selected LACC patients treated with HDR BT after chemoradiotherapy, allowed a substantial reduction in the dose to the rectum. Such procedure could be of particular interest when a dose escalation strategy is being considered.

Background In unresectable hepatocellular carcinoma several local ablative treatments are available. Among others, radiation based treatments such as stereotactic body radiotherapy (SBRT) and high-dose rate interstitial brachytherapy (HDR BT) have shown good local control rates. Methods We conducted a dose comparison between actually performed HDR BT versus virtually planned SBRT to evaluate the respective clinically relevant radiation exposure to uninvolved liver tissue. Moreover, dose coverage and conformity indices were assessed. Results Overall, 46 treatment sessions (71 lesions, 38 patients) were evaluated. HDR BT was applied in a single fraction with a dose prescription of 1 × 15 Gy. D98 was 17.9 ± 1.3 Gy, D50 was 41.8 ± 8.1 Gy. The SBRT was planned with a prescribed dose of 3 × 12.5 Gy (65%-Isodose), D98 was 50.7 ± 3.1 Gy, D2 was 57.0 ± 2.3 Gy, and D50 was 55.2 ± 2.3 Gy. Regarding liver exposure Vliver10GyBT was compared to Vliver15.9GySBRT, Vliver16.2GySBRT (EQD2 equivalent doses), and Vliver20GySBRT (clinically relevant dose), all results showed significant differences (p BT was smaller than Vliver20GySBRT in 38/46 cases (83%). Dmean of the liver was significantly smaller in BT compared to SBRT (p GTV volume was correlated to the liver exposure and showed an advantage of HDR BT over SBRT in comparison of clinically relevant doses, and for EQD2 equivalent doses. The advantage was more pronounced for greater liver lesions The Conformity Index (CI) was significantly better for BT, while Healthy Tissue Conformity Index (HTCI) and Conformation Number (CN) showed an advantage for SBRT (p Conclusion HDR BT can be advantageous in respect of sparing of normal liver tissue as compared to SBRT, while providing excellent target conformity.

The purpose of this study was to evaluate the effect of dose rate to the rectum on late rectal complications in patients treated with computed tomography (CT)-based image-guided brachytherapy (IGBT) for cervical cancer. The subjects were 142 patients with cervical cancer who underwent Ir-192 high-dose-rate (HDR)-IGBT between March 2012 and January 2018. The dose rate to the rectum was calculated using in-house software. The minimum, mean and maximum effective dose rate (EDR) was calculated for voxels of the rectal volume covered by cumulative doses >D0.1cc, >D2cc, and > D5cc. The average EDR of three to four brachytherapy sessions was calculated (EDR for patients; EDRp). The total dose of the rectum was calculated as the biologically equivalent dose in 2-Gy fractions (EQD2). The associations between EDRp for D0.1cc, D2cc, and D5cc and the respective rectal EQD2 values with late rectal complications were then analyzed. The median follow-up period was 40 months. Patients with rectal complications of ≥Grade 1 received a significantly higher mean EDRp for D0.1cc–5cc and had a greater EQD2 for D0.1cc–5cc. Multivariate analysis was performed using the mean EDRp for D2cc, EQD2 for D2cc, heavy smoking and BMI. Of these four variables, mean EDRp for D2cc (HR = 3.38, p = 0.004) and EQD2 for D2cc (HR = 2.59, p = 0.045) emerged as independent predictors for late rectal complications. In conclusion, mean EDRp and EQD2 were associated with late rectal complications in patients treated with HDR CT-based IGBT for cervical cancer.

Purpose The in vivo dosimetric monitoring in HDR brachytherapy is important for improving patient safety. However, there are very limited options available for clinical application. In this study, we present a new in vivo dose measurement system with a plastic scintillating detector (PSD) for GYN HDR brachytherapy. Methods An FDA approved PSD system, called OARtrac (AngioDynamics, Latham, NY), was used with various applicators for in vivo dose measurements for GYN patients. An institutional workflow was established for the clinical implementation of the dosimetric system. Action levels were proposed based on the measurement and system uncertainty for measurement deviations. From October 2018 to September 2019, a total of 75 measurements (48 fractions) were acquired from 14 patients who underwent HDR brachytherapy using either a multichannel cylinder, Venezia applicator, or Syed-Neblett template. The PSDs were placed in predetermined catheters/channels. A planning CT was acquired for treatment planning in Oncentra (Elekta, Version-4.5.2) TPS. The PSDs were contoured on the CT images, and the PSD D90% values were used as the expected doses for comparison with the measured doses. Results The mean difference from patient measurements was −0.22% ± 5.98%, with 26% being the largest deviation from the expected value (Syed case). Large deviations were observed when detectors were placed in the area where dose rates were less than 1 cGy/s. Conclusions The establishment of clinical workflow for the in vivo dosimetry for both the intracavitary and interstitial GYN HDR brachytherapy will potentially improve the safety of the patient treatment.

This article presents nuclide-specific organ dose rate coefficients for environmental external exposures due to soil contamination assumed as a planar source at a depth of 0.5 g cm−2in the soil and submersion to contaminated air, for a pregnant female and its fetus at the 24th week of gestation. Furthermore, air kerma free-in-air coefficient rates are listed. The coefficients relate the organ equivalent dose rates (Sv s−1) to the activity concentration of environmental sources, in Bq m−2or Bq m−3, allowing to time-integrate over a particular exposure period. The environmental radiation fields were simulated with the Monte Carlo radiation transport codes PHITS and YURI. Monoenergetic organ dose rate coefficients were calculated employing the Monte Carlo code EGSnrc simulating the photon transport in the voxel phantom of a pregnant female and fetus. Photons of initial energies of 0.015–10 MeV were considered including bremsstrahlung. By folding the monoenergetic dose coefficients with the nuclide decay data, nuclide-specific organ doses were obtained. The results of this work can be employed for estimating the doses from external exposures to pregnant women and their fetus, until more precise data are available which include coefficients obtained for phantoms at different stages of pregnancy.

In this work, the use of gold and gold alloy plaques is proposed for the first time, to reduce the dose to healthy organs in brachytherapy with Ir-192 sources. For dose simulations in tumour and healthy tissue, the MCNPX Monte Carlo code was used. The radiation source implemented in those simulations was benchmarked with well-known TG-43 criteria of dose rate constant, air-kerma strength, radial dose function, and 2D anisotropy function. For various arrangements of iridium sources and plaques of gold and gold alloy of various thicknesses, the dose distributions in an esophagus tumour and in surrounding healthy organs were simulated. The results showed that while the dose to the tumour is not much affected by the presence of gold plaques with a thickness of 3.5 mm in an optimized 192Ir sources’ configuration, a relative reduction in average organ dose of 64%, 65%, 73%, 67%, and 35% was observed, for esophagus, thyroid, heart, stomach, and liver, respectively. Moreover, it was found that a gold plaque leads to smaller doses to healthy organs than a gold alloy plaque. It is concluded that gold plaques can be used to improve the treatment of esophageal cancer by HDR brachytherapy and to protect surrounding non-target organs.

Purpose To document time analysis of detailed workflow steps for the online adaptive magnetic resonance–guided radiation therapy treatments (MRgRT) with the ViewRay MRIdian system and to identify the barriers to and solutions for shorter treatment times. Methods and Materials A total of 154 patients were treated with the ViewRay MRIdian system between September 2018 and October 2019. The time process of MRgRT workflow steps of 962 fractions for 166 treatment sites was analyzed in terms of patient and online adaptive treatment (ART) characteristics. Results Overall, 774 of 962 fractions were treated with online ART, and 83.2% of adaptive fractions were completed in less than 60 minutes. Sixty-three percent, 50.3%, and 4.2% of fractions were completed in less than 50 minutes, 45 minutes, and 30 minutes, respectively. Eight-point-three percent and 3% of fractions were completed in more than 70 minutes and 80 minutes, respectively. The median time (tmed) for ART workflow steps were as follows: (1) setup tmed: 5.0 minutes, (2) low-resolution scanning tmed: 1 minute, (3) high-resolution scanning tmed: 3 minutes, (4) online contouring tmed: 9 minutes, (5) reoptimization with online quality assurance tmed: 5 minutes, (6) real targeting tmed: 3 minutes, (7) beam delivery with gating tmed: 17 minutes, and (8) net total treatment time tmed: 45 minutes. The shortest and longest tmean rates of net total treatment time were 41.59 minutes and 64.43 minutes for upper-lung-lobe-located thoracic tumors and ultracentrally located thoracic tumors, respectively. Conclusions To our knowledge, this is the first broad treatment-time analysis for online ART in the literature. Although treatment times are long due to human- and technology-related limitations, benefits offered by MRgRT might be clinically important. In the future, implementation of artificial intelligence segmentation, an increase in dose rate, and faster multileaf collimator and gantry speeds may lead to achieving shorter MRgRT treatments.

The purpose of this study was to educate operators regarding cardiac catheterization using radiation protection slides prepared for this study and to consider whether or not this radiation protection education contributes to reducing the exposure of the operator's ocular lens. Thermoluminescent dosimeter (TLD) was installed at the outside left, inside left, outside right, and inside right of the X-ray protective eyewear of the operators performing the cardiac catheterization. The exposure dose rate before and after radiation protection education for 3 operators performing cardiac catheterization was compared. The exposure dose ratio was defined by dividing the TLD measurement value, which is the air kerma calculated by the X-ray diagnosis apparatus for the angiography. In other words, this can calculate the ratio of how much the operators are exposed to radiation from the dose of the patient per examination. When comparing the radiation dose ratio obtained from the dosimeter installed on the right outer side before and after education, p-value was

Aim:To study the feasibility of constant dose rate volumetric modulated arc therapy (CDR-VMAT) in radiotherapy for gallbladder cancer by comparing dosimetric parameter suggested by International Commission on Radiation Units and Measurements-83 (ICRU-83) with step and shoot intensity-modulated radiation therapy (SS IMRT).Methods:For this study, we selected 21 post-operative gallbladder cancer patients, which were treated with the IMRT technique from 2016 to 2019. For each patient, we generated SS IMRT plan and CDR-VMAT plan and were dosimetrically compared by parameters suggested by ICRU-83 for PTV. Homogeneity Index (HI) and Conformity Index (CI) were also calculated. For evaluation of Organ at Risk (OAR), we compared the mean doses, volume doses to the right kidney, left kidney, both kidneys combined, liver and max dose to the spinal cord. Monitor units (MUs) and treatment delivery time were also compared.Results:On comparing, we found that CDR-VMAT plans were highly conformed as CI and PCI (CI define by Paddick) were found more (0·98 ± 0·01 vs. 0·97 ± 0·03 and 0·86 ± 0·05 vs. 0·85 ± 0·05) than IMRT plans but not statistically significant. Better dose HI was found for IMRT plans with statistical significant difference (p < 0·001). The tumour coverage was found similar 98·24% and 97·83% for SS IMRT and CDR-VMAT, respectively. For D2%, the maximum dose to PTV was significantly lower in IMRT (p = 0·001). D50% and mean dose to PTV were also comparable to IMRT with no statistically significant difference. The OAR parameters were comparable in both the techniques. The mean doses and volume doses V10, V20 and V30 to the right kidney, left kidney and liver were also comparable with no significant difference (p > 0·05) was noted among them. However, the maximum dose to the spinal cord was significantly less in CDR-VMAT (21·1 Gy vs. 25·1Gy) than SS IMRT with p = 0·006. More MUs were associated with the CDR-VMAT technique, but shorter treatment delivery time than the IMRT technique.Conclusions:On dosimetric comparison of two treatment techniques, we conclude that CDR-VMAT can be a valid option in radiotherapy as it achieved highly conformed dose distribution, comparable tumour coverage and OAR sparing as IMRT technique for gallbladder cancer.

The aim is to make an adequate estimate of the ambient equivalent dose received by the groups closest to the patient, once the patient has the radiological and clinical discharge. As a first step, a patient's daily life pattern with its closest environment has been modelled. A maximum dose rate of 40 μSv/h at 1 meter has been set to give the patient the radiological discharge. Secondly, a fitting equation that gives us the evolution of the dose rate with distance has been formulated. How the function fits to the experimental points after measuring 45 patients at the distances between 0.4 and 2 meters was verified obtaining R2 ≥ 0.98 for 75.55% of the cases. Besides, a smaller error is made than using the equation of the Radiological Protection in the Healthcare Enviroment in 93.33% of cases. When models are simulated, modes of the dose distributions do not exceed the dose restriction, namely, 3 mSv per treatment when partner is under 60 years old and 15 mSv when companion is over 60 years old. Finally, an experimental elimination time is obtained, being this less than the given in the Forum document, reducing the mode of distributions between a half and one tenth.

The article presents the first data on EK-164ID steel swelling after operational irradiation in a fast nuclear reactor in the temperature range of 370–630 °C and maximum damaging doses of 66–77 dpa. The dose accumulation rate along the cladding tubes made of this material was 1×10-8–1.6×10-6 dpa/s. The swelling was determined by the hydrostatic weighing method with an error of no more than 0.5%. The results obtained were analyzed depending on the irradiation parameters and in comparison with the 16Cr-15Ni grade material. The objectives of the study were to estimate the characteristic values of the maximum swelling temperature and dose as well as to calculate the average material swelling rate at the working temperature of irradiation, the incubation period for the onset of swelling, and the stationary swelling rate. It was found that the tube samples, characterized with austenite grain sizes of 9–12 µm before irradiation, have an average swelling rate of 0.035–0.05 %/dpa after reaching the maximum damaging doses of 66–77 dpa (at a rate of (1–1.5)×10-6 dpa/s) and not more than 0.035%/dpa at doses less than 20 dpa (at a rate of 5×10-7 dpa/s). The characteristic maximum swelling temperature of the studied material is in the range of 430–500 °C. The characteristic maximum swelling dose is in the range of 61–72.5 dpa or 70–80% of the maximum accumulated dose. The incubation stationary swelling period for the material is 30 dpa. The stationary swelling rate is 0.1% /dpa. The radiation resistance characteristics of the studied material have an advantage over those for 16Cr-15Ni grade cladding materials under similar irradiation conditions and a similar structural state, which inherits grain sizes of 9–14 μm during the tube processing.

Purpose To evaluate (a) the effects of megavoltage (MV)‐scatter on concurrent kilovoltage (kV) projections (P MVkV) acquired during rotational delivery, and (b) the image quality of intra‐irradiation cone‐beam computed tomography (ii‐CBCT) images acquired during prostate volumetric‐modulated arc therapy (VMAT) delivery. Methods Experiment (1): P MVkVs were acquired with various MV beam parameters using a cylindrical phantom: field size (FS), MV energy (6 or 15 MV), dose rate (DR), and gantry speed. The average pixel values were calculated in a region on each P MVkV which were extracted at eight equally spaced gantry angles. Experiment (2): 11 one‐arc and seven two‐arc 15 MV prostate VMAT plans were used along with a pelvis phantom. One plan was selected from each of arc plans and its MV energy was changed to 6 MV. After P MVkVs were acquired, projections consisting of MV‐scatter only (P MVS) were acquired with closing kV blades and subtracted from P MVkV (P MVScorr). Projections by kV beams only were acquired (P kV). The corresponding CBCT images were reconstructed (CBCTMVkV, CBCTMVScorr, and CBCTkV). The root‐mean‐square errors (RMSEs) were calculated in prostate region and 3D gamma analysis was conducted, in which the CBCT‐number was used instead of doses between ii‐CBCT images and CBCTkV (30 HU/1 mm). Results Experiment (1): The MV‐scatters were dependent on the FSs, MV energies, and DRs. Experiment (2): The median RMSEs for CBCTMVScorr were decreased by 107.5 HU (1‐arc) and 42.9 HU (2‐arc) compared to those for CBCTMVkV. The median GPRs for CBCTMVScorr were 94.7% (1‐arc) and 93.4% (2‐arc), while those for CBCTMVkV were 61.1% and 79.9%, respectively. GPRs for 6 MV plans were smaller than those for 15 MV plans. Conclusions The number of MV‐scatters increased with larger FSs and DRs, and smaller MV energy. The MV‐scatters were corrected on the CBCTMVScorr regardless of the number of arcs.

In this study, a method was developed for delivering high dose rate (HDR) brachytherapy treatments to basal cell carcinomas (BCCs) as well as squamous cell carcinomas (SCCs) of the lower eyelid via superficial catheters. Clinically-realistic BCC/SCC treatment areas were marked in the lower-eyelid region on a head phantom and several arrangements of catheters and bolus were trialled for treating those areas. The use of one or two catheters of different types was evaluated, and sources of dosimetric uncertainty (including air gaps) were evaluated and mitigated. Test treatments were planned for delivery with an iridium-192 source, using the Oncentra Brachy treatment planning system (Elekta AB, Stockholm, Sweden). Dose distributions were evaluated using radiochromic film. The proposed method was shown to be clinically viable, for using superficial HDR brachytherapy to overcome anatomical difficulties and create non-surgical treatments for BCC and SCC of the lower eyelid.

Diagnostic x-radiation is an essential part of present-day medical practice being the largest contributor of irradiation to the general population. Therefore, routine checking of x-ray tubes leakage is very important to ensure that leakage radiation at a one-meter distance from focus is less than 1mR/h. The measurement of background radiation was performed during normal departmental working hours: early in the morning before the machines were switched on, and after the machines were switched on. Exposures were performed using different exposure factors and the fall out radiation in both control and uncontrolled areas were also recorded. The highest equivalent dose rate was recorded in the uncontrolled area of room 2, where the mean dose rate was 26.21 μSv/h (in changing room) and 11.67 μSv/h (behind the door), respectively. It follows the dose rate measured in the uncontrolled area of room 1, where the mean dose rate was 6.33 μSv/h (behind the door), 2.96 μSv/h (in changing room B), and 1.56 μSv/h (in changing room A), respectively. The lowest radiation dose was measured in both controlled and uncontrolled areas of CT-scan, where the mean dose rate was 0.17 μSv/h and 0.16 μSv/h, respectively, simply because the room doors and wall are adequately lead-lined and protected. All values obtained in this study are within the permissible limit, except that for uncontrolled areas in x-ray rooms 1 and 2, where radiation dose rates were higher than the reference limit for public exposure.

Background: In recent years, the incidence of prostate cancer (PCa) is increasing. Advanced PCa has a poor prognosis and high cost, which seriously affects the quality of life of patients. Therefore, how to improve the diagnosis rate and prognosis of early PCa is the focus of clinical research. This paper aims to investigate the value of P504s, 34βE12, Ki-67 and prostate-specific antigen (PSA) in the diagnosis and prognosis of PCa. Objective: To investigate the expression of P504s, 34βE12, Ki67 and PSA in prostate tissues and their clinical significance. Methods: Twenty four cases in the study group were selected from PCa confirmed by pathology in the urology department of Chengde Affiliated Hospital from October 2018 to August 2020, and 33 cases of Benign Prostate Hyperplasia (BPH) confirmed by pathology in the same period were selected as the control group. The expression of P504s, 34βE12 and Ki-67 in prostate tissues were determined by immunohistochemistry. Results: The positive expression rates of P504s, 34βE12 and TPSA or F/TPSA in PCa patients were 95.8%, 12.5%and 87.5%, respectively. The positive rates in BPH patients were 9.1%, 93.9% and 27.3%, The difference between the two groups was statistically significant (p

Purpose To compare the dose measured by MOSkin dosimeters coupled to a trans-rectal ultrasound (TRUS) probe to the dose predicted by the brachytherapy treatment planning system (BTPS) during high dose rate (HDR) prostate brachytherapy (pBT), and to examine the feasibility of performing real-time catheter-by-catheter analysis of in-vivo rectal dosimetry during TRUS based HDR pBT. Method Four MOSkin dosimeters were coupled to a TRUS probe during 20 TRUS-based HDR pBT treatment fractions. The measured MOSkin doses were retrospectively compared to those predicted by the BTPS for the total treatment fraction, as well as on a per catheter basis. Results The average relative percentage difference between MOSkin measured and BTPS predicted doses for a total treatment fraction was 0.3% ± 11.6% (k = 1), with a maximum of 23.2% and a minimum of −29.0%. The average relative percentage difference per catheter was +2.5% ± 16.9% (k = 1). The majority (64%) of per catheter MOSkin measured doses agreed with the treatment planning system within the calculated uncertainty budget of 12.3%. Conclusion The results of the study agreed well with previously published data, despite differences in clinical workflows. To improve the redundancy to potential dosimeter errors, a minimum of 4 MOSkin dosimeters should be used when performing real-time in-vivo rectal dosimetry for HDR pBT, and error thresholds should be based off the total combined uncertainty estimate of measurement. ‘Real time’ error thresholds can be more confidently applied in the future through enhanced integration between IVD systems with both the imaging device and the BTPS/afterloader.

Purpose Dark current radiation produced during linac beam‐hold has the potential to lead to unplanned dose delivered to the patient. With the increased usage of motion management and step‐and‐shoot IMRT deliveries for MR‐guided systems leading to increased beam‐hold time, it is necessary to consider the impact of dark current radiation on patient treatments. Methods The relative dose rate due to dark current for the ViewRay MRIdian linac was measured longitudinally over 15 months (June 2018‐August 2019). Ion chamber measurements were acquired with the linac in the beam‐hold state and the beam‐on state, with the ratio representing the relative dark current dose rate. The potential contribution of the dark current dose to the overall prescription was retrospectively analyzed for 972 fractions from 83 patients over the same time period. The amount of time spent in the beam‐hold state was combined with the monthly measured relative dark current dose rate to estimate the dark current dose contribution. Results The relative dark current dose rate compared to the beam‐on dose rate was 0.12% ± 0.027%. In a near worst‐case estimation, the dark current dose contribution accounted for 0.90% ± 0.67% of the prescription dose across all fractions (3.61% maximum). Gantry and MLC motion between segments accounted for 87% of the dark current contribution, with the remaining 13% attributable to gating during segment delivery. The largest dark current contributions were associated with plans delivering a small dose per treatment segment. Conclusions The dark current associated with new clinical treatment units should be considered prior to treatment delivery to ensure it will not lead to dosimetric inaccuracies. For the MRIdian linac system investigated in this work, the contribution from dark current remained relatively low, though users should be cognizant of the larger potential dosimetric contribution for plans with small doses per segment.

Purpose To develop an alternative method for summing biologically effective doses of external beam radiotherapy (EBRT) with interstitial high-dose-rate (HDR) brachytherapy (BT) boost in breast cancer. The total doses using EBRT boost were compared with BT boost using our method. Material and methods Twenty-four EBRT plus interstitial HDR-BT plans were selected, and additional plans using EBRT boost were created. The prescribed dose was 2.67/40.05 Gy to whole breast and 4.75/14.25 Gy BT or 2.67/10.7 Gy EBRT to planning target volume (PTV) boost. EBRT and BT computed tomography (CT) were registered twice, including fitting the target volumes and using the lung, and the most exposed volume of critical organs in BT were identified on EBRT CT images. The minimal dose of these from EBRT was summed with their BT dose, and these EQD2 doses were compared using BT vs. EBRT boost. This method was compared with uniform dose conception (UDC). Results D90 of PTV boost was significantly higher with BT than with EBRT boost: 67.1 Gy vs. 56.7 Gy, p = 0.0001. There was no significant difference in the dose of non-target and contralateral breast using BT and EBRT boost. D1 to skin, lung, and D0.1 to heart were 58.6 Gy vs. 66.7 Gy (p = 0.0025), 32.6 Gy vs. 50.6 Gy (p = 0.0002), and 52.2 Gy vs. 58.1 Gy (p = 0.0009), respectively, while D0.1 to ribs was 44.3 Gy vs. 37.7 Gy (p = 0.0062). UDC overestimated D1 (lung) by 54% (p = 0.0001) and D1 (ribs) by 28% (p = 0.0003). Conclusions Based on our biological dose summation method, the total dose of PTV in the breast is higher using BT boost than with EBRT. BT boost yields lower skin, lung, and heart doses, but higher dose to ribs. UDC overestimates lung and ribs doses.

In recent years, 3D printing technology has received significant research attention. Additionally, 3D printing technology is being applied to study radiation dosimeters of various materials. In this study, a plastic scintillator for 3D printing was developed in a laboratory and used to manufacture a plastic scintillation dosimeter (PSD) with a shape identical to that of the ionization chamber PTW31010. The 16-mm beam of Gamma Knife® Perfexion™ was irradiated to derive the absorbed dose rates of the PSD and PTW31010; they were subsequently compared with the dose rates of the treatment plan. The differences in the dose rates of the Gamma Knife treatment plan and the absorbed dose rates of PTW31010 were within 0.87%. The difference between the dose rates of the Gamma Knife treatment plan and the absorbed dose rates of the PSD were within 4.1%. A linear fit of the absorbed dose rates of four shots involving different dose rates and irradiation angles yielded an adjusted R-square value exceeding 0.9999. A total of 10 repeated measurements were conducted for the same shot to confirm its reproducibility, with a relative error of 0.56%.

Objective: The aims of this study were to estimate the instantaneous dose rate(IDR) and annual dose rate (ADR) to radiation staff and the general public withinthe controlled and supervised areas, respectively, to determine the shieldingdesign goals (P) of the 2 CT facilities and to determine the average annual dose(AD) to radiographer/operator in the control console during CT scans. Materials and Methods: The equipment used in this study consisted of twonewly installed General Electric (GE) Revolution ACTs CT machines. Technicalparameters used were a thoracic/dorsal spine scan, which was rarely done in both facilities. A calibrated Inspector USB (S.E. International, Inc.) survey meter was positioned < 50 cm from each barrier at various points to determine the average shielded air kerma Results: The average background radiation in the 2 facilities was 0.11 ?Sv/hr. The average ADR to the controlled and supervised areas in CT1 was 0.563±0.25 and 0.369±0.11 mSv/yr, respectively. Also, the average ADR to the controlled and supervised areas in CT2 were 0.410±0.28 and 0.354±0.04 mSv/yr, respectively. The average shielding design goal to the controlled and supervised areas for CT1 was 0.00898±0.0041 and 0.0059±0.0028 mSv/Week, respectively. Similarly, the average shielding design goal for the controlled and supervised areas for CT2 was 0.0066±0.0044 and 0.0057±0.0019 mSv/Week respectively. The estimated average AD to the operator in CT1 and CT2 was 2.5 and 1.3 ?Sv, respectively. Conclusion: The average ADR and shielding design goals in the controlled and supervised areas from both CTs were within acceptable limits for radiation staff and the public.

The objective of this study was to establish radiation dose-response calibration curves using automated dicentric scoring to support rapid and accurate cytogenetic triage dose-assessment. Blood was drawn from healthy human volunteers and exposed to Co gamma rays at several dose rates (i.e., 1.0, 0.6, and 0.1 Gy min). After radiation, the blood was placed for 2 h in a 37 °C incubator for repair. Blood was then cultured in complete media to which a mitogen (i.e., phytoghemagglutinin, concentration 4%) was added for 48 h. Colcemid was added to the culture at a final concentration of 0.2 μg mL after 24 h for the purpose of arresting first-division metaphase mitotics. Cells were harvested at the end of 48 h. Samples were processed using an automated metaphase harvester and automated microscope metaphase finder equipped with a suite of software including a specialized automated dicentric scoring application. The data obtained were used to create dose-response tables of dicentric yields. The null hypothesis that the data is Poisson-distributed could not be rejected at the significance level of α = 0.05 using results from a Shiny R Studio application (goodness-of-fit Poisson). Calibration curves based on linear-quadratic fits for Co gamma rays at the three different dose rates were generated using these data. The calibration curves were used to detect blind test cases. In conclusion, using the automated harvester and automated microscope metaphase finder with associated automated dicentric scoring software demonstrates high-throughput with suitable accuracy for triage radiation dose assessment.

Aim The aim is a dosimetric comparison of dynamic conformal arc integrated with the segment shape optimization and variable dose rate (DCA_SSO_VDR) versus VMAT for liver SBRT and interaction of various treatment plan quality indices with PTV and degree of modulation (DoM) for both techniques. Background The DCA is the state-of-the-art technique but overall inferior to VMAT, and the DCA_SSO_VDR technique was not studied for liver SBRT. Materials and methods Twenty-five patients of liver SBRT treated using the VMAT technique were selected. DCA_SSO_VDR treatment plans were also generated for all patients in Monaco TPS using the same objective constraint template and treatment planning parameters as used for the VMAT technique. For comparison purpose, organs at risk (OARs) doses and treatment plans quality indices, such as maximum dose of PTV (D max %), mean dose of PTV (D mean %), maximum dose at 2 cm in any direction from the PTV (D 2cm %), total monitor units (MU’s), gradient index R 50% , degree of modulation (DoM), conformity index (CI), homogeneity index (HI), and healthy tissue mean dose (HTMD) were compared. Results Significant dosimetric differences were observed in several OARs doses and lowered in VMAT plans. The D 2cm %, R 50% , CI, HI and HTMD are dosimetrically inferior in DCA_SSO_VDR plans. The higher DoM results in poor dose gradient and better dose gradient for DCA_SSO_VDR and VMAT treatment plans, respectively. Conclusions For liver SBRT, DCA_SSO_VDR treatment plans are neither dosimetrically superior nor better alternative to the VMAT delivery technique. A reduction of 69.75% MU was observed in DCA_SSO_VDR treatment plans. For the large size of PTV and high DoM, DCA_SSO_VDR treatment plans result in poorer quality.

Background In the case of extravasation of radioactive drugs used in peptide-receptor radionuclide therapy of neuroendocrine tumors, or in radionuclide therapy in general, rapid action is important to reduce or avoid complications. The literature on extravasation of drugs for radionuclide therapy is sparse. Based on the present case, we discuss handling and consequences of extravasation. Further, we demonstrate that dosimetry can aid in judging if the treatment of neuroendocrine tumors is satisfactory even after extravasation. Case presentation A case of extravasation of [177Lu]Lu-DOTATOC with a treatment strategy involving exercise and elevation of the affected arm and application of a compression bandage and heating is reported. Redistribution of the drug is verified and quantified by whole-body imaging and quantitative SPECT/CT and measurements of the dose rate at contact with the injection site. [177Lu]Lu-DOTATOC was redistributed to tumors and organs within 1 day. The patient did not report any discomfort during or after hospitalization, and no side effects related to extravasation were observed. Quantitative SPECT/CT scans at the subsequent treatment cycle of the same patient were analyzed for a comparison between the treatments. Dosimetry showed the treatments were similar with respect to the kidney and tumor absorbed doses. The radiation dose to the epidermal basal layer near the injection site was estimated and found to be consistent with the lack of side effects. Conclusions The treatment of extravasation was successful, and the redistribution of the drug can be easily verified through measurement of the dose rate at contact with the skin. From the results of dosimetry, it was assessed that no change of the treatment course was necessary to compensate for a possibly incomplete treatment as a result of the extravasation.

3D imaging devices, when coupled to an image guided surgery system, allow for a more precise surgical approach than classical C-arms. Nevertheless, the exposure to radiation of both patient and staff remains a concern and therefore the choice of imaging device plays an important role. Two 3D imaging systems, an imaging mobile device with an O-ring geometry and an imaging mobile device with a C-arm geometry, have been compared in terms of absorbed doses to organs as well as ambient dose equivalent. Absorbed organ doses were evaluated for thoracic and pelvic examinations using TLDs placed within a CIRS anthropomorphic phantom representing an adult woman. Equivalent ambient dose measurements were performed at various positions in the room around the X-ray system using a calibrated dose rate meter. Results suggest that the O-ring system exposes both patient and staff to higher levels of radiation than the C-arm system. Indeed, organ absorbed doses were found to be 3.5 and 1.7 higher for the O-ring system than for the C-arm system for the same thoracic and pelvic explorations respectively. Concerning the ambient dose equivalent, it was found that for a single 3D image acquisition at a radial distance of one meter from the isocentre, measurements for the O-ring system were approximately 30% larger than the C-arm system.

Direct irradiation may cause malfunctioning of cardiac implantable electronic devices (CIEDs). Therefore, a treatment plan that does not involve direct irradiation of CIEDs should be formulated. However, CIEDs may be directly exposed to radiation because of the sudden intrafractional movement of the patient. The probability of CIED malfunction reportedly depends on the dose rate; however, reports are only limited to dose rates ≤8 Gy/min. The purpose of this study was to investigate the effect of X-ray dose rates >8 Gy/min on CIED function. Four CIEDs were placed at the center of the radiation field and irradiated using 6 MV X-ray with flattening filter free (6 MV FFF) and 10 MV X-ray with flattening filter free (10 MV FFF). The dose rate was 4–14 Gy/min for the 6 MV FFF and 4–24 Gy/min for 10 MV FFF beams. CIED operation was evaluated with an electrocardiogram during each irradiation. Three CIEDs malfunctioned in the 6 MV FFF condition, and all four CIEDs malfunctioned in the 10 MV FFF condition, when the dose rate was >8 Gy/min. Pacing inhibition was the malfunction observed in all four CIEDs. Malfunction occurred simultaneously along with irradiation and simultaneously returned to normal function on stopping the irradiation. An X-ray dose rate >8 Gy/min caused a temporary malfunction due to interference. Therefore, clinicians should be aware of the risk of malfunction and manage patient movement when an X-ray dose rate >8 Gy/min is used for patients with CIEDs.

The present study aimed to report the efficacy and toxicity of our high-dose-rate (HDR) brachytherapy for early stage lip cancer (LC) using customized dental spacers. A retrospective analysis was performed among six patients with early stage LC treated with HDR interstitial brachytherapy between April 2015 and August 2019 using customized dental spacers. The total treatment dose was 49 Gy/7 fractions or 54 Gy/9 fractions. The median follow-up duration for the patients was 13 (range: 2–52) months. All patients completed the entire brachytherapy protocol safely and have experienced no local recurrence thus far. The CTV D100 and D90 values per fraction were median 100 (range: 98.3–100) % prescribed dose (PD) and median 133.4 (range: 129.3–138.9) % PD, respectively. The D2cc and D0.1cc values per fraction for the mandible were median 1.07 (range, 0.79–1.88) Gy and median 1.65 (range: 1.21–2.83) Gy, D2cc and D0.1cc values per fraction for oral cavity were median 1.48 (range, 1.31–1.72) Gy and median 2.73 (range: 1.79–2.88) Gy, respectively. Acute toxicities encountered were mucositis and lip edema limited to the irradiated area; none of them was beyond grade 2 and all were resolved within 1–2 months after treatment. We did not observe any late grade 2 adverse events or worse. This study shows that the adverse effects of HDR brachytherapy for early stage LC can be minimized using a dental spacer. Cooperation with the dentistry department is essential to make spacers that are individually customized for each patient.

Purpose To assess the capability of an intracavitary 169 Yb-based helical multishield rotating shield brachytherapy (RSBT) delivery system to treat cervical cancer. The proposed RSBT delivery system contains a pair of 1.25 mm thick platinum partial shields with 45° and 180° emission angles, which travel in a helical pattern within the applicator. Methods A helically threaded tandem applicator with a 45° tandem curvature containing a helically threaded catheter was designed. A 0.6 mm diameter 169 Yb source with a length of 10.5 mm was simulated. A 37-patient treatment planning study, based on Monte Carlo dose calculations using MCNP5, was conducted with high-risk clinical target volumes (HR-CTVs) of 41.2-192.8 cm3 (average ± standard deviation of 79.9 ± 35.8 cm3 ). All patients were assumed to receive 25 fractions of 1.8 Gy of external beam radiation therapy (EBRT) before receiving 5 fractions of high-dose-rate brachytherapy (HDR-BT). For each patient, 192 Ir-based intracavitary (IC) HDR-BT, 192 Ir-based intracavitary/interstitial (IC/IS) HDR-BT using a hybrid applicator with eight IS needles, and 169 Yb-based RSBT plans were generated. Results For the IC, IC/IS, and RSBT treatment plans, 38%, 84%, and 86% of the plans, respectively, met the planning goal of an HR-CTV D90 (minimum dose to hottest 90%) of 85 GyEQD2 (α/β = 10 Gy). Median (25th percentile, 75th percentile) treatment times for IC, IC/IS, and RSBT were 11.71 (6.62, 15.40) min, 68.00 (45.02, 80.02) min, and 25.30 (13.87, 35.39) min, respectively. 192 Ir activities ranging from 159.1-370 GBq (4.3-10 Ci) and 169 Yb activities ranging from 429.2-999 GBq (11.6-27 Ci) were used, which correspond to the same clinical ranges of dose rates at 1 cm off-source-axis in water. Extra needle insertion and planning time beyond that needed for intracavitary-only approaches was accounted for in the IC/IS treatment time calculations. Conclusion 169 Yb-based RSBT for cervical cancer met the HR-CTV D90 goal of 85 Gy in a greater percentage of the patients considered than IC/IS (86% vs 84%, respectively) and can reduce overall treatment time relative to IC/IS. 169 Yb-based RSBT could be used to replace IC/IS in instances where IC/IS treatment is not available, especially in instances when HR-CTV volumes are ≥30 cm3 .

The effects of different doses of irradiation, including gamma and electron irradiation, on viability of saw-toothed grain beetles (Oryzaephilus surinamensis) have been studied. Barley grains infested with the pests were irradiated with a GUR-120 unit in a dose range of 150–1000 Gray (Gy) (treatment at doses of 100–120 Gy/h and 1800–2000 Gy/h) and with a “Duet” electron accelerator in a dose range of 200–1000 Gy (at a dose rate of 100 Gy/imp.). It is ascertained that gamma irradiation of saw-toothed grain beetles (imago stage) in a dose range of 170–1000 Gy at a dose rate of 100Gy/h and in a dose range of 150–600 Gy at the dose rate of 1800 Gy/h results in absolute pest death 15 days after irradiation. Under electron irradiation, the absolute death of pests at the imago stage occurred 15 days after irradiation at all the studied doses and the irradiation dose rate of 100 Gy/imp. The death rate for the saw-toothed grain beetles after irradiation depended on the dose and the dose rate of irradiation. It was ascertained that, with irradiation at 250 Gy, 400–550 Gy (at a dose rate of 100 Gy/h), and 900–1400 Gy (at a dose rate of 1800 Gy/h), the pest’s death occurred 15 days, 9 days, and 6 days later, respectively. However, absolute pest death was recorded at 1200 Gy. A qualitative analysis of the irradiated spring barley grain of the Nur and Vladimir varieties was performed. Thus, gamma irradiation in a dose range of 200–600 Gy (at a dose rate of 1800 Gy/h) caused a significant increase, by 4–6%, in the ash content in the Nur variety, while a 5.3% decrease in this parameter was recorded at a dose of 800 Gy. Application of electron irradiation in the analyzed range of doses generally had no effect on the barley grain quality of the indicated variety.

In breast‐targeted intraoperative radiotherapy (TARGIT) clinical trials (TARGIT‐B, TARGIT‐E, TARGIT‐US), a single fraction of radiation is delivered to the tumor bed during surgery with 1.5‐ to 5.0‐cm diameter spherical applicators and an INTRABEAM x‐ray source (XRS). This factory‐calibrated XRS is characterized by two depth‐dose curves (DDCs) named "TARGIT" and "V4.0.” Presently, the TARGIT DDC is used to treat patients enrolled in clinical trials; however, the V4.0 DDC is shown to better represent the delivered dose. Therefore, we reevaluate the delivered prescriptions under the TARGIT protocols using the V4.0 DDC. A 20‐Gy dose was prescribed to the surface of the spherical applicator, and the TARGIT DDC was used to calculate the treatment time. For a constant treatment time, the V4.0 DDC was used to recalculate the dosimetry to evaluate differences in dose rate, dose, and equivalent dose in 2‐Gy fractions (EQD2) for an α/β = 3.5 Gy (endpoint of locoregional relapse). At the surface of the tumor bed (i.e., spherical applicator surface), the calculations using the V4.0 DDC predicted increased values for dose rate (43–16%), dose (28.6–23.2 Gy), and EQD2 (95–31%) for the 1.5‐ to 5.0‐cm diameter spherical applicator sizes, respectively. In general, dosimetric differences are greatest for the 1.5‐cm diameter spherical applicator. The results from this study can be interpreted as a reevaluation of dosimetry or the dangers of underdosage, which can occur if the V4.0 DDC is inadvertently used for TARGIT clinical trial patients. Because the INTRABEAM system is used in TARGIT clinical trials, accurate knowledge about absorbed dose is essential for making meaningful comparisons between radiation treatment modalities, and reproducible treatment delivery is imperative. The results of this study shed light on these concerns.

Purpose To evaluate the electromagnetic (EM) tracking of endoscopes and applicators as a method of positioning a high dose rate (HDR) luminal applicator. Method An anatomical phantom consisting of a rigid trachea and flexible esophagus was used to compare applicator placement measurements using EM tracking vs the traditional method using two-dimensional (2D) fluoroscopy and surface skin markers. The phantom included a tumor in the esophagus and several pairs of optically visible points inside the lumen that were used to simulate proximal and distal ends of tumors of varying lengths. The esophagus tumor and lung points were visible on a computed tomography (CT) image of the phantom, which was used as ground truth for the measurements. The EM tracking system was registered to the CT image using fiducial markers. A flexible endoscope was tracked using the EM system and the locations of the proximal and distal ends of the tumor identified and this position recorded. An EM-tracked applicator was then inserted and positioned relative to the tumor markings. The applicator path was mapped using the EM tracking. The gross tumor length (GTL) and the distance between the first dwell position and distal edge of tumor (offset) were measured using the EM tracking and 2D fluoroscopy methods and compared to the same measurements on the CT image. Results The errors in GTL using EM tracking were on average -0.5 ± 1.7 mm and 0.7 ± 3.6 mm for esophagus and lung measurements, similar to errors measured using the 2D fluoroscopy method of -0.9 ± 1.2 mm and 3.4 ± 4.4 mm. Offset measurements were slightly larger while using EM tracking relative to the fluoroscopy method but these were not statistically significant. Conclusions Electromagnetic tracking for placement of lumen applicators is feasible and accurate. Tracking of the endoscope that is used to identify the proximal and distal ends of the tumor and of the applicator during insertion generates accurate three-dimensional measurements of the applicator path, GTL and offset. Guiding the placement of intraluminal applicators using EM navigation is potentially attractive for cases with complex insertions, such as those with nonlinear paths or multiple applicator insertions.

Purpose:The objective of this article is to evaluate the dosimetric efficacy of volumetric modulated arc therapy (VMAT) in comparison to dynamic conformal arc therapy (DCAT) and 3D conformal radiotherapy (3DCRT) for very small volume (≤1 cc) and small volume (≤3 cc) tumours for flattened (FF) and unflattened (FFF) 6 MV beams.Materials and methods:A total of 21 patients who were treated with single-fraction stereotactic radiosurgery, using either VMAT, DCAT or 3DCRT, were included in this study. The volume categorisation was seven patients each in 12 Gy dose, dose to the organ at risk (OAR), beam ON time and dose received by 12 cc of the brain.Result:The average target coverage for all plans, all tumour volumes (TVs) and delivery techniques is 96·4 ± 4·5 (range 95·7 ± 6·1–97·5 ± 2·9%). The conformity index averaged over all volume ranges varies between 0·55 ± 0·08 and 0·68 ± 0·04 with minimum and maximum being exhibited by DCA_FFF for 1 cc and Static_FFF/RA_FFF for 3 cc tumours, respectively. Mean IMRT factor averaged over all volume ranges for RA_FF, DCA_FF and Static_FF are 3·5 ± 0·8, 2·0 ± 0·2 and 2·0 ± 0·2, respectively; 50% dose fall-off gradient varies in the range of 0·33–0·42, 0·35–0·40 and 0·38–0·45 for 1, 2 and 3 cc tumours, respectively.Conclusion:This study establishes the equivalence between the FF and FFF beam models and different delivery techniques for stereotactic radiosurgery in small TVs in the range of ≤1 to ≤3 cc. Dose conformity, heterogeneity, dose fall-off characteristics and OAR doses show no or very little variation. FFF could offer only limited time advantage due to excess dose rate over an FF beam.