Feasibility of using micro silica bead TLDs for in-Vivo dosimetry of CT-based HDR prostate brachytherapy: An experimental and simulation study.

PURPOSE: Feasibility of silica-based dosimeters for IVD of HDR prostate brachytherapy. MATERIAL AND METHODS: Plastic dosimeter holders and a water-fillable prostate phantom were built in-house. Interstitial prostate brachytherapy and Monte Carlo simulations were performed. The treatment planning, Monte-Carlo simulation, and dosimetry results were compared. RESULTS: The relative differences between TLD-TPS, TLD-MCNP, and TPS-MCNP were 0.2-6.9 %, 0.5-6.5 %, and 0.6-6.3 %, respectively. CONCLUSION: Micro-silica bead dosimeters can perform offline in situ quality assurance in HDR prostate brachytherapy.

Pulmonary fibrosis prevalence after adjuvant radiotherapy of Iranian patients with breast cancer: A single-center cross-sectional study.

AIMS: This study aims to investigate the incidence rate of pulmonary fibrosis as a late radiotherapy complication and identify the associated dosimetric and demographic factors using radiological findings between Iranian patients with breast cancer. METHODS AND MATERIAL: Breast cancer patients treated at the education hospital of Shohada-e Tajrish Hospital, Tehran, Iran, from 2017 to 2021 were considered. Patients have included for whom a secondary chest CT scan was available at least six months after radiotherapy. Dose-volume histogram (DVH) parameters of three-dimensional conformal radiotherapy (3D-CRT) treatment plans were exported. Demographic features and data on underlying lung diseases, diabetes, and smoking history were extracted. RESULTS: A total of 250 patients were included in the study with a mean age of 46.1 ± 7.5 yrs and a mean body mass index (BMI) of 24.5 ± 4.2 kg/m2. Pulmonary fibrosis was detected for sixty-two cases. A significant relationship was obtained between the ipsilateral lung DVH parameters of patients with pulmonary fibrosis (P value < 0.05). The V5Gy, V10Gy, V13Gy, V20Gy, V30Gy, MLD, and DMax for individuals with pulmonary fibrosis were significantly higher than those without this injury. CONCLUSIONS: Pulmonary fibrosis was distinguished for 25% of the breast cancer cases at least six months after adjuvant radiotherapy. A significant relationship between the DVH parameters, underlying lung disease, diabetes, radiotherapy fields (i.e., Breast + LN + SC or Breast/Chest-wall only), age, and BMI with the frequency of the ipsilateral pulmonary fibrosis was obtained. V13Gy and V30Gy of the ipsilateral lung may be the most predictor of pulmonary fibrosis incidence.

Predicting severe radiation-induced oral mucositis in head and neck cancer patients using integrated baseline CT radiomic, dosimetry, and clinical features: A machine learning approach.

Purpose: To establish the early prediction models of radiation-induced oral mucositis (RIOM) based on baseline CT-based radiomic features (RFs), dosimetric data, and clinical features by machine learning models for head and neck cancer (HNC) patients. Methods: In this single-center prospective study, 49 HNCs treated with curative intensity modulated radiotherapy (IMRT) were enrolled. Baseline CT images (i.e., CT simulation), dosimetric, and clinical features were collected. RIOM was assessed using CTCAE v.5.0. RFs were extracted from manually-contoured oral mucosa structures. Minimum-redundancy-maximum-relevance (mRMR) method was applied to select the most informative radiomics, dosimetric, and clinical features. Then, binary prediction models were constructed for predicting acute RIOM based on the top mRMR-ranked radiomics, dosimetric, and clinical features alone or in combination, using random forest classifier algorithm. The predictive performance of models was assessed using the area under the receiver operating curve (AUC), accuracy, weighted-average based sensitivity, precision, and F1-measure. Results: Among extracted features, the top 10 RFs, the top 5 dose-volume features, and the top 5 clinical features were selected using mRMR method. The model exploiting the integrated features (10-radiomics + 5-dosimetric + 5-clinical) achieved the best prediction with AUC, accuracy, sensitivity, precision, and F1-measure values of 91.7 %, 90.0 %, 83.0 % 100.0 %, and 91.0 %, respectively. The model developed using baseline CT RFs alone provided the best performance compared to dose-volume features or clinical features alone, with an AUC of 87.0 %. Conclusion: Our results suggest that the integration of baseline CT radiomic features with dosimetric and clinical features showed promising potential to improve the performance of machine learning models in early prediction of RIOM. The ultimate goal is to personalize radiotherapy for HNC patients.

Evaluating dose distributions of high dose rate 60Co brachytherapy in an asymmetric tumor: A comparison of different designs of vaginal cylindrical applicators.

The aim of this study is to evaluate organ-at-risk (OAR) doses obtained from different designs of intracavitary cylinder applicators during high-dose-rate (HDR) brachytherapy of an asymmetric vaginal tumor. Dose distributions around five cylinder applicators were obtained using the Geant4 toolkit. Three of these applicators are commercially available: single-channel, multi-channel, and shielded. Additionally, two proposed sub-configurations were evaluated: (I) a combination of the multichannel applicator with a central shield and (II) a dynamically modulated cylinder (DMC). The dose distributions of the proposed applicators were compared to those of the single-channel cylinder applicator. The results showed that using a cylindrical applicator with a higher degree of freedom in plan optimization can improve OAR, sparing up to 60% for the rectum and 20% for the bladder. In conclusion, this work suggests using a new design of a cylindrical applicator to enhance the therapeutic ratio of brachytherapy for asymmetric and irregularly shaped vaginal tumors.

Hydrogen nanobubbles: A novel approach toward radio-sensitization agents.

BACKGROUND: Ocular melanoma is a rare kind of eye malignancy that threatens the patient's eyesight. Radiotherapy and surgical removal are the most commonly used therapeutic modalities, and nanomedicine has lately entered this field. Brachytherapy using Ruthenium-106 (106 Ru) ophthalmic plaques has been used for decades to treat ocular melanoma, with the applicator placed on the patient's eyes until the prescribed dose reaches the tumor apex. PURPOSE: To investigate the efficiency of hydrogen nanobubbles (H2 -NBs) employment during intraocular melanoma brachytherapy using a 106 Ru electron emitter plaque. METHODS: The Monte Carlo (MC) simulation and experimental investigation using a 3D-designed phantom and thermoluminescence dosimetry (TLD) were employed. Various concentrations of H2 -NBs with a diameter of 100 nm were simulated inside tumor tissue. The results were presented as deposited energy and dose enhancement factor (DEF). An equivalent Resin phantom of the human eyeball was made using AutoCAD and 3D-Printer technologies. The glass-bead TLDs dosimeter were employed and placed inside the phantom. RESULTS: Using a 1% concentration of H2 -NBs, a DEF of 93% and 98% were achieved at the tumor apex of 10 mm from the experimental setup and MC simulation, respectively. For simulated concentrations of 0.1%, 0.3%, 0.5%, 1%, and 4% H2 -NBs, a maximum dose enhancement of 154%, 174%, 188%, 200%, and 300% were achieved, respectively, and a dose reduction was seen at about 3 mm from the plaque surface. CONCLUSION: H2 -NBs can be used as an absorbed dose enhancer in 106 Ru eye brachytherapy because of their unique physical characteristics. Reducing plaque implantation time on the patient's eye, reducing sclera absorbed dose, and decreasing the risk of patients' healthy organs irradiation are reported as some of the potential benefits of using H2-NBs.

Top cited publications for treatment of keloid with radiotherapy: A Bibliometric analysis.

ABSTRACTS: The use of radiation to treat keloid scars has gained popularity during the last few decades. However, few bibliometric analyses have been performed on the published articles. This research aimed to demonstrate and evaluate the trends, top-cited articles, and frontier areas. In this cross-sectional study, Web of Science (WOS) and Scopus database literature was searched for all MESH terms related to "keloid" and "radiotherapy." The bibliometric analysis was carried out by VOSviewer 1.6.15. Articles with Web of Science-based citations of ≥20 were included. The citation per year index (CPYI) of articles was calculated for further inclusion of papers if they had CPYI higher than the mean value. There were 95 papers on keloid radiation that satisfied the inclusion criteria and were published between 1942 and 2019. The CPYI ranged from 0.38 to 11.3. Most studies were published in the "International Journal of Radiation Oncology, Biology, and Physics" (9 papers). The United States has the most papers (14), followed by Japan (9), the Netherlands (7), and Germany (5). To the best of our knowledge, this is the first bibliometric analysis of top-cited papers on keloid radiotherapy. From 2014 to the present, it seems that this title has resurfaced as a popular topic, with radiotherapy within 24 h of surgery being the most commonly recommended treatment plan. Since around 2011, high-dose-rate brachytherapy (HDR-BT) has been used as an effective treatment for keloid control. Individualization of therapy and dose/technique based on the location is strongly suggested.

Evaluating the relationship between dosimetric parameters and esophagitis in patients who experienced radiotherapy in the cervicothoracic region.

Purpose: Prescribing radiotherapy or concurrent chemoradiation for cervicothoracic cancers inevitably leads to esophagitis. The purpose of the current study was to evaluate the correlation between the dose-volume parameters and the esophagitis in patients who received radiotherapy in the cervicothoracic region. Materials and Methods: Forty cancerous patients whose radiotherapy fields were in the cervicothoracic region have been rolled. The correlation between the dosimetric and clinical factors with esophagitis was analyzed through binary logistic regression model and Pearson correlation tests and was quantified with receiver operating characteristic curve. Results: The patients participating in the study were selected from breast (6 cases), lymphoma (7 cases), and head-neck (27 cases) patients with prescription doses of 36-72 Gy. Increasing esophagus mean dose resulted in an increase of acute esophagitis significantly (P = 0.05). Furthermore, by one-gray increase in the esophagus median dose, the possibility of esophagitis increased by 9.3% (P = 0.02). To prevent acute esophagitis (Grade ≥2), D50 should be kept below 7 Gy. To limit acute esophagitis, V40 should be kept below 19% (P = 0.04). Conclusions: Based on the correlation analysis of the current study, concurrent chemoradiotherapy, DMean, D50, D80, and V40 are known as reliable predictive dosimetric parameters of acute esophagitis incidence in patients who experienced radiotherapy in the cervicothoracic region.

3D in vivo dosimetry of HDR gynecological brachytherapy using micro silica bead TLDs.

PURPOSE: This study aimed to evaluate the feasibility of defining an in vivo dosimetry (IVD) protocol as a patient-specific quality assurance (PSQA) using the bead thermoluminescent dosimeters (TLDs) for point and 3D IVD during brachytherapy (BT) of gynecological (GYN) cancer using 60 Co high-dose-rate (HDR) source. METHODS: The 3D in vivo absorbed dose verification within the rectum and bladder as organs-at-risk was performed by bead TLDs for 30 GYN cancer patients. For rectal wall dosimetry, 80 TLDs were placed in axial arrangements around a rectal tube covered with a layer of gel. Ten beads were placed inside the Foley catheter to get the bladder-absorbed dose. Beads TLDs were localized and defined as control points in the treatment planning system (TPS) using CT images of the patients. Patients were planned and treated using the routine BT protocol. The experimentally obtained absorbed dose map of the rectal wall and the point dose of the bladder were compared to the TPSs predicted absorbed dose at these control points. RESULTS: Relative difference between TPS and TLDs results were -8.3% ± 19.5% and -7.2% ± 14.6% (1SD) for rectum- and bladder-absorbed dose, respectively. Gamma analysis was used to compare the calculated with the measured absorbed dose maps. Mean gamma passing rates of 84.1%, 90.8%, and 92.5% using the criteria of 3%/2 mm, 3%/3 mm, and 4%/2 mm were obtained, respectively. Eventually, a "considering level" of at least 85% as pass rate with 4%/2-mm criteria was recommended. CONCLUSIONS: A 3D IVD protocol employing bead TLDs was presented to measure absorbed doses delivered to the rectum and bladder during GYN HDR-BT as a reliable PSQA method. 3D rectal absorbed dose measurements were performed. Differences between experimentally measured and planned absorbed dose maps were presented in the form of a gamma index, which may be used as a warning for corrective action.

Dose to pelvic lymph nodes in locally advanced cervical cancer during high-dose-rate brachytherapy with tandem-ring applicators.

Purpose: The present study aimed to assess the correlation between dose to pelvic lymph nodes and to point B with tandem-ring (TR) applicators for intra-cavitary brachytherapy treatment of locally advanced cervical cancer. Material and methods: Cervical cancer patients treated at brachytherapy department of Lucien Neuwirth Cancer Center, from 2015 to 2018, were included. Target delineation was performed in compliance with GEC-ESTRO guidelines. Revised American Brachytherapy Society (ABS) point A was determined (ARN (right) and ALN (left)) as well as Manchester point B. Prescription dose was 25-35 Gy in 5 fractions. Pelvic lymph nodes were delineated, then dose to points A and B, and dose-volume histogram (DVH) parameters of delineated lymph nodes were extracted. Significant relationships or correlations between lymph nodes reference points, dosage to points B, and their DVH parameters were investigated. Results: The mean dose and mean percentage of the prescription dose to the left and right points B were 4.6 ±0.18 Gy and 82.08 ±0.72%, respectively. Pearson correlation coefficient R = 0.81 (p-value = 0.00) between dose to ARN and ALN points and prescription dose was obtained. Negative correlation between CTVHR volume and difference between French and ABS prescription points was found. Conclusions: Dose to point B can be a moderate surrogate for maximum, minimum, and median dose to the internal iliac and presacral lymph node, but cannot be for maximum dose to the obturator lymph node. Points B cannot be a reliable substitute for common and external iliac chains.

Dose to pelvic lymph nodes during brachytherapy of locally advanced cervical cancer with 60Co HDR source.

PURPOSE: This study investigated the correlation between the prescription dose and dose to the Manchester and International Commission on Radiation Units and Measurements-report 38 (ICRU-38) lymphatic trapezoid points during high-dose-rate (HDR) brachytherapy of locally advanced cervical cancer with (Cobalt-60) 60Co . METHODS AND MATERIALS: A retrospective study was designed for; patients with locally advanced cervical cancer, treated by external beam radiotherapy and concurrent weekly Cisplatin-based chemotherapy, had no extended parametrial invasion and was treated by tandem-ovoid set, from 2017 to 2020. Groupe Européen de Curiethérapie-European Society for Radiotherapy and Oncology (GEC-ESTRO) based target's volume, ICRU-89 revised version of Manchester points A and B, and ICRU-38 lymph node surrogate points were determined, and their dose was recorded. Paired sample t-test, linear regression analysis, and Pearson correlation analyses were done considering a statistical significance level of 0.05 and using IBM SPSS statistics (Version 23, IBM Crop.). RESULTS: Seventy-four brachytherapy cases were included. A positive and strong correlation was observed between D90 of clinical target volume (CTVHR) and points A and B dose for CTVHR〈 15 cc and 〉 35 cc. Strong and significant (p < 0.05) correlations were achieved between pelvic wall points dose and D90 and D100 of the obturator and between D50 and hot points of internal iliac lymph nodes. A strong correlation was obtained between D50 and D90 of external iliac lymph nodes and their ICRU points. CONCLUSIONS: Strong correlations were obtained between dose to the pelvic lymphatic chains and their historical ICRU-38 surrogate points during HDR brachytherapy of locally advanced cervical cancer patients with 60Co tandem-ovoid applicator sets. The correlation strength between point A and prescription dose highly depends on the CTVHR volume.

Validation of an individualized home-made superficial brachytherapy mold applied for deep nonmelanoma skin cancer.

Background: This study was conducted to evaluate the effect of brachytherapy (BT) customized mold [Condensation silicone elastomer (ProtesilTM)] and its thickness on the dose distribution pattern of deep nonmelanoma skin cancers (NMSC). Materials and methods: Four blocks of mold material were constructed in 5, 10, 15, and 20 mm thickness and 100 × 100 mm2 area by a plastic cast. The high dose rate (HDR) plus treatment planning system (TPS) (Version 3, Eckert & Ziegler BEBIG Gmbh, Berlin, Germany) with a 60Co source (model: Co0.A86, EZAG BEBIG, Berlin, Germany) as an high dose rate brachytherapy (HDR-BT) source was used. Solid phantom and MOSFETTM and GAFCHROMICTM EBT3 film dosimeters were used for experimental dosimetry of the different thicknesses (up to 20 mm) of BT customized mold. Skin dose and dose to different depths were evaluated. Result: The TPS overestimated the calculated dose to the surface. Skin dose can be reduced from 250% to 150% of the prescription dose by increasing mold thickness from 5 mm to 20 mm. There was a 7.7% difference in the calculated dose by TPS and the measured dose by MOSFET. There was a good agreement between film dosimetry, MOSFET detector, and TPS' results in depths less than 5 mm. Conclusion: Each BT department should validate any individualized material chosen to construct the customized surface BT mold. Increasing the mold thickness can treat lesions without overexposing the skin surface. Superficial BT can be recommended as an appropriate treatment option for some deep NMSC lesions (up to 20 mm) with pre-planning considerations employing thicker molds.

Correlation between gastric volume and organs at risk dose in adjuvant radiotherapy for left breast cancer.

BACKGROUND: The role of the gastric volume on the dose-effect relationship for these organs has not been investigated. The aim of the study was to evaluate the correlation between gastric volume and dose-volume histogram (DVH) parameters of the heart, left lung and stomach during left breast cancer radiotherapy (RT). MATERIALS AND METHODS: Ninety-nine left breast cancer patients who got adjuvant radiotherapy were included. Study was classified into two groups based on treatment field arrangements: 1) breast tangential fields only (T) and 2) breast tangential and supraclavicular fields (TS). Organs DVHs were extracted. Descriptive statistics, Pearson correlation, linear regression analyses, and receiver operating characteristic (ROC) analyses were performed. RESULTS: There is a direct but not significant correlation between the gastric volume and doses to the stomach and left lung. For a 100-cc increase in the gastric volume, the stomach maximum dose and the V50 increased by 3 Gy and 4%, respectively. For the left lung, V4 and V5 increased by 1% for TS cases. Considering ROC analysis results, one can make a decision for about 74% of patients due to their left lung DVH parameters, using gastric volume as a known input data. The correlation between gastric volume and heart dose was not significant. CONCLUSIONS: The gastric volume of about 170 cc or less can result in lower dose to the stomach and ipsilateral lung during left breast cancer radiotherapy, especially for TS cases. To reach this gastric volume threshold, patients should be fast for 2 hours before the procedure of CT simulation and treatment.

A rapid review of influential factors and appraised solutions on organ delineation uncertainties reduction in radiotherapy.

Background and purpose.Accurate volume delineation plays an essential role in radiotherapy. Contouring is a potential source of uncertainties in radiotherapy treatment planning that could affect treatment outcomes. Therefore, reducing the degree of contouring uncertainties is crucial. The role of utilized imaging modality in the organ delineation uncertainties has been investigated. This systematic review explores the influential factors on inter-and intra-observer uncertainties of target volume and organs at risk (OARs) delineation focusing on the used imaging modality for these uncertainties reduction and the reported subsequent histopathology and follow-up assessment.Methods and materials.An inclusive search strategy has been conducted to query the available online databases (Scopus, Google Scholar, PubMed, and Medline). 'Organ at risk', 'target', 'delineation', 'uncertainties', 'radiotherapy' and their relevant terms were utilized using every database searching syntax. Final article extraction was performed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. Included studies were limited to the ones published in English between 1995 and 2020 and that just deal with computed tomography (CT) and magnetic resonance imaging (MRI) modalities.Results.A total of 923 studies were screened and 78 were included of which 31 related to the prostate 20 to the breast, 18 to the head and neck, and 9 to the brain tumor site. 98% of the extracted studies performed volumetric analysis. Only 24% of the publications reported the dose deviations resulted from variation in volume delineation Also, heterogeneity in studied populations and reported geometric and volumetric parameters were identified such that quantitative synthesis was not appropriate.Conclusion.This review highlightes the inter- and intra-observer variations that could lead to contouring uncertainties and impede tumor control in radiotherapy. For improving volume delineation and reducing inter-observer variability, the implementation of well structured training programs, homogeneity in following consensus and guidelines, reliable ground truth selection, and proper imaging modality utilization could be clinically beneficial.

Radiotherapy based management during Covid-19 pandemic - A systematic review of presented consensus and guidelines.

Treatment management of cancer patients in the radiation oncology departments during the current COVID-19 pandemic is challenging. A systematic review of published consensus/guidelines on the role of radiotherapy prioritization, suggested treatment protocols, and set up management was undertaken based on the PRISMA protocol and through PubMed/PMC, Scopus, Google Scholar, Web of Science databases until 01/20/2021. One hundred and sixty-eight publications or regional consensus were included. Summary of recommendations contained: (1) using hypo-fractionated (Hypo-F) regimens for therapeutic/palliative indications, (2) delaying radiotherapy for several weeks or until pandemic over, (3) omitting radiotherapy by replacement of alternative therapies or active surveillance, (4) applying safer patients' setup and preparation protocols, (5) developing telemedicine/telehealth service. To conclude, it is essential to carefully weigh the risk of exposure to COVID-19 infection and the benefit of treating cancer patients during the pandemic. Trying to have a global guideline facing this or any other probable crisis is crucial for health care service.

Efficacy and complications of ruthenium-106 brachytherapy for uveal melanoma: a systematic review and meta-analysis.

PURPOSE: The aim of this study was to evaluate the efficacy and vision-threatening complications of brachytherapy with ruthenium-106 (106Ru) plaque to treat uveal melanoma. MATERIAL AND METHODS: A literature review was performed based on results from searching PubMed, Embase, Web of Science, Scopus, and Cochrane databases, using the following key words: "choroidal melanoma", "uveal melanoma", "brachytherapy", and "ruthenium-106". We included studies performed on more than 30 patients since 1986, reporting on local control rate, complications rate, mean radiation dose, and mean tumor thickness. The cumulative analysis was performed using Metaprop command of Stata v.16, and meta-regression was conducted based on mean tumor thickness and mean radiation dose to tumor's apex. RESULTS: Twenty-one retrospective studies were selected, involving 3,913 patients treated primarily with 106Ru plaque brachytherapy. The range of radiation dose to tumor apex was from 70 Gy to 250 Gy. The local control rate following brachytherapy ranged from 59% to 98%, and the overall weighted mean of local control was 84%. However, the heterogeneity between studies' reports was remarkable (I 2 = 95.40%). Meta-regression based on tumor thickness and mean dose of radiation to the apex showed that the studies' heterogeneity was minimally related to the difference in mean tumor size (I 2 = 92%). The correlation between larger tumor size and lower local control rate was statistically significant (p-value = 0.024). There was no significant correlation between the mean radiation dose and local control rate (p-value = 0.679). The most commonly reported complications were cataract and radiation-related retinopathy. CONCLUSIONS: Although the studies' heterogeneity was high, in a prescription dose ranging from 70 Gy to 250 Gy to the tumor apex, 106Ru brachytherapy seems to be successful in local control of uveal melanoma. The efficacy of 106Ru in controlling uveal melanomas decreased with the increase in tumor thickness. However, these outcomes should be verified in randomized comparative studies.

Manufacturing and evaluation of multi-channel cylinder applicator with 3D printing technology.

PURPOSE: This study was designed to assess dosimetric characteristics of 3D-printed personalized multi-channel cylinder applicator (MCCA). MATERIAL AND METHODS: UnionTech RS Pro 600 (UnionTech, Inc., Shanghai, China) 3D printer was used for manufacturing MCCA. The geometry of MCCA was designed with Fusion 360 v.2.0.5827 (Autodesk, Inc.) software. The designed file was exported to Meshmixer v.3.5 (Autodesk, Inc.) to create three-dimensional model in stereolithography (STL) file format, which is the common file format for inputting data to 3D printers. We used high-temp resin, FLHTAM02 model (Formlabs Inc., MA, USA), as material in 3D printing process. This resin model has good resistance to high temperature and compatibility with various solvents. We created a simple cubic shape phantom for dosimetric evaluation of the applicator with Gafchromic EBT3 films. Also, Monte Carlo method was applied to simulate MCCA in the same configuration as in experimental test. RESULTS: The mean ± standard deviation (SD) difference between measured and calculated doses in treatment planning system (TPS) for all control points was 0.0860 ±0.0393 Gy, corresponding to 4.01 ±1.21%. The mean ±SD difference between doses calculated by Monte Carlo simulation and TPS for all control points was 0.0996 ±0.0471 Gy, corresponding to 4.58 ±1.05%. The mean ±SD of dose difference between film measurement and Monte Carlo simulation for all control points was 0.0136 ±0.0200 Gy, corresponding to 0.60 ±0.69%. P-value for dose difference between film measurement and TPS, Monte Carlo and TPS, and film measurement and Monte Carlo were 0.7, 0.66, and 0.95, respectively. CONCLUSIONS: Dosimetric results and mechanical accuracy of MCCA show that high-temp resin with SLA 3D printing technique can be used for producing patient-specific MCCA in brachytherapy.

An in silico study on the effect of host tissue at brachytherapy dose enhancement by gold nanoparticles.

PURPOSE: Iridium-192 brachytherapy dose enhancement by gold nanoparticles was investigated in five different tumor tissues to observe the tissue-related differences as an effective environmental factor in the applications of nanoparticles as radio-enhancer agents. METHODS AND MATERIALS: The brachytherapy high-dose-rate source of BEBIG Ir-192, a tumor volume with five different tissues including water, Plexiglas, soft tissue, adipose, and bone with and without a uniform distribution of gold nanoparticles were mimicked by MCNPX Monte Carlo simulation code using lattice feature. Dose enhancement factors in the tumor volume were measured separately regarding the types of tissue, and a previous study using GEometry ANd Tracking 4 simulation was used for result validation. RESULTS: The results demonstrated that various types of tissue, as the host of gold nanoparticles, lead to different dose enhancement level, so that the bone and adipose have the lowest and the highest amount of dose enhancement factor with values 20.8% and 39.75%, respectively. The maximum difference of 4.8% was achieved from data benchmarking. CONCLUSIONS: The results of this study indicate that the MCNPX code can be used as a valid tool for dose measurement in the presence of nanoparticles. Moreover, tissue types of tumor as an environmental feature, alongside with the nanoparticle's size and concentration as well as the conditions of radiotherapy, should be considered in the dose calculation.

Recommendations on Management of Locally Advanced Rectal Cancer During the COVID-19 Pandemic: an Iranian Consensus.

PURPOSE: Today, the rapid outbreak of COVID-19 is the leading health issue. Patients with cancer are at high risk for the development of morbidities of COVID-19. Hence, oncology centers need to provide organ-based recommendations for optimal management of cancer in the COVID-19 era. METHODS: In this article, we have provided the recommendations on management of locally advanced rectal cancer during the COVID-19 pandemic based on our experience in Shohada-e Tajrish Hospital, Iran. RESULTS: We recommend that patients with locally advanced rectal cancer should be managed in an individualized manner in combination with local conditions related to COVID-19. CONCLUSION: Our recommendation may provide a guide for oncology centers of developing countries for better management of locally advanced rectal cancer.

Evaluation of deformable image registration algorithm for determination of accumulated dose for brachytherapy of cervical cancer patients.

PURPOSE: This study was designed to assess the dose accumulation (DA) of bladder and rectum between brachytherapy fractions using hybrid-based deformable image registration (DIR) and compare it with the simple summation (SS) approach of GEC-ESTRO in cervical cancer patients. MATERIAL AND METHODS: Patients (n = 137) with cervical cancer treated with 3D conformal radiotherapy and three fractions of high-dose-rate brachytherapy were selected. CT images were acquired to delineate organs at risk and targets according to GEC-ESTRO recommendations. In order to determine the DA for the bladder and rectum, hybrid-based DIR was done for three different fractions of brachytherapy and the results were compared with the standard GEC-ESTRO method. Also, we performed a phantom study to calculate the uncertainty of the hybrid-based DIR algorithm for contour matching and dose mapping. RESULTS: The mean ± standard deviation (SD) of the Dice similarity coefficient (DICE), Jaccard, Hausdorff distance (HD) and mean distance to agreement (MDA) in the DIR process were 0.94 ±0.02, 0.89 ±0.03, 8.44 ±3.56 and 0.72 ±0.22 for bladder and 0.89 ±0.05, 0.80 ±0.07, 15.46 ±10.14 and 1.19 ±0.59 for rectum, respectively. The median (Q1, Q3; maximum) GyEQD2 differences of total D2cc between DIR-based and SS methods for the bladder and rectum were reduced by -1.53 (-0.86, -2.98; -9.17) and -1.38 (-0.80, -2.14; -7.11), respectively. The mean ± SD of DICE, Jaccard, HD, and MDA for contour matching were 0.98 ±0.008, 0.97 ±0.01, 2.00 ±0.70 and 0.20 ±0.04, respectively for large deformation. Maximum uncertainty of dose mapping was about 3.58%. CONCLUSIONS: The hybrid-based DIR algorithm demonstrated low registration uncertainty for both contour matching and dose mapping. The DA difference between DIR-based and SS approaches was statistically significant for both bladder and rectum and hybrid-based DIR showed potential to assess DA between brachytherapy fractions.

Artificial neural network based gynaecological image-guided adaptive brachytherapy treatment planning correction of intra-fractional organs at risk dose variation.

PURPOSE: Intra-fractional organs at risk (OARs) deformations can lead to dose variation during image-guided adaptive brachytherapy (IGABT). The aim of this study was to modify the final accepted brachytherapy treatment plan to dosimetrically compensate for these intra-fractional organs-applicators position variations and, at the same time, fulfilling the dosimetric criteria. MATERIAL AND METHODS: Thirty patients with locally advanced cervical cancer, after external beam radiotherapy (EBRT) of 45-50 Gy over five to six weeks with concomitant weekly chemotherapy, and qualified for intracavitary high-dose-rate (HDR) brachytherapy with tandem-ovoid applicators were selected for this study. Second computed tomography scan was done for each patient after finishing brachytherapy treatment with applicators in situ. Artificial neural networks (ANNs) based models were used to predict intra-fractional OARs dose-volume histogram parameters variations and propose a new final plan. RESULTS: A model was developed to estimate the intra-fractional organs dose variations during gynaecological intracavitary brachytherapy. Also, ANNs were used to modify the final brachytherapy treatment plan to compensate dosimetrically for changes in 'organs-applicators', while maintaining target dose at the original level. CONCLUSIONS: There are semi-automatic and fast responding models that can be used in the routine clinical workflow to reduce individually IGABT uncertainties. These models can be more validated by more patients' plans to be able to serve as a clinical tool.