Brachytherapy Dose Distributions Research Articles

SU‐E‐T‐635: Volumetric Modulated Arc Therapy for the Treatment of Cervical Cancer in Lieu of HDR Brachytherapy

Purpose: To investigate the use of VMAT to deliver the following conceptual GYN brachytherapy (BT) dose distributions: 1. traditional pear‐shaped dose distribution with substantial dose gradients, 2. homogeneous dose distribution throughout PTV (BT prescription volume), and 3. increased dose to PTV without OAR overdose. Methods: A tandem and ovoid BT treatment plan, with the prescription dose of 6 Gy to point A was exported into the VMAT treatment planning system (TPS) and became the baseline for further comparative analysis. The 200%, 150%, 130% 100%, 75% and 50% dose volumes were converted into structures for optimization and evaluation purposes. The 100% dose volume was chosen to be the PTV. Five VMAT plans were created to duplicate the Ir‐192 tandem and ovoid inhomogeneous dose distribution. Another five VMAT plans were generated to deliver a homogeneous dose of 6 Gy to the PTV. An additional five VMAT plans were created to increase the dose to the PTV with a homogeneous dose distribution. All plans used BT dose constraints. Results: On average in the first set of plans, the dose given to 99% of the 200‐100% dose volumes agreed within 2% of the BT plan, the 75% dose volumes were within 5% and the 50% dose volumes were within 6.4%. In the second set, the 100% dose volume was within 1% of the original plan. In the last set the maximum increase of dose to the PTV was 8 Gy with similar doses to OARs as the other VMAT plans. The maximum increase of dose was 2.50 Gy to the rectum. The maximum decrease of dose was 0.70 Gy to the bladder. Conclusion: VMAT was successful at reproducing brachytherapy dose distributions. Alternative dose distributions have the potential to be used in lieu of brachytherapy. However, differences in radiobiology need to be further investigated.

MO‐D‐108‐08: Fast Monte Carlo Electron‐Photon Transport Code Using Hardware Accelerators: Preliminary Results for Brachytherapy and Radionuclide Therapy Cases

Purpose: Although Monte Carlo methods provide the most accurate radiation dose calculation for medical physics applications, long simulation time remains an impediment for its routine utilization. An electron‐photon coupled Monte Carlo code ARCHER ‐ Accelerated Radiation‐transport Computations in Heterogeneous EnviRonments ‐ is being developed at Rensselaer Polytechnic Institute as a software testbed for emerging heterogeneous high performance computers that utilize accelerators such as GPUs. This paper describes the development of ARCHER and demonstrates its preliminary applications involving brachytherapy and radionuclide therapy. Methods: In ARCHER code electron transport was modeled by mixed condensed history method. Photon transport was simulated in analog. The energy range handled was from 10 keV to 30 MeV. The hardware platform involved a desktop with Intel Xeon X5660 CPU and six NVIDIA Tesla™ M2090 GPUs. ARCHER was benchmarked against MCNPX and EGSnrc on slab geometry. In addition, we used ARCHER to calculate Ir‐192 brachytherapy dose distribution and to evaluate Y‐90 beta SAF in radionuclide therapy. Results: The depth dose and lateral dose at different depth were tallied and compared with results from MCNPX and EGSnrc. For 99.1% of all tested voxels, the dose difference between ARCHER and EGSnrc was within 2% of the dose maximum. In the brachytherapy calculation, all the major organ doses from ARCHER matched those from MCNPX within statistical error. In the Y‐90 internal source case, ARCHER gave similar SAF value with MCNPX. Meanwhile the simulation speed was 2∼3 orders faster than MCNPX and EGS using single GPU. With multiple GPUs, the simulation time can be decreased almost linearly. Conclusion: We developed an electron photon coupled Monte Carlo code ARCHER. Preliminary testing showed good agreement with prevailing general purpose codes, while its speed was hundreds even thousands times faster. We are working on applying ARCHER to Brachytherapy and radionuclide therapy and have encouraging preparatory Result.

SU‐E‐T‐583: Optimizing Dosimetric Indices for HDR Brachytherapy Using CVaR

Purpose: To develop a new model for automated optimization of HDR brachytherapy (BT) dose distributions that operates on the dose volume indices used in plan evaluation. The model can be solved to optimality, with constraints that are easy to interpret and modify for the clinical user. Recent research has shown that the optimization model hitherto used corresponds only weakly to such dosimetric indices. Alternative models that include such dosimetric indices have been presented; however, the explicit inclusion of dosimetric indices yields intractable models. Methods: An approach for optimizing HDR BT dose distributions is presented where dosimetric indices are taken into account through surrogates based on the conditional value‐at‐risk concept (CVaR). This yields a linear optimization model that is easy to solve, and has the additional advantage that the constraints are easy to interpret and modify to obtain satisfactory dose distributions. Results: Experimental comparisons have shown that our proposed model corresponds well with constraining dosimetric indices. All modifications of the parameters in our model yield the expected Result. Both our approach and those presented earlier for optimization of dosimetric indices include an approximation, earlier models solve the models approximately, and we use a model based on an approximation. This gives us better control of the optimization. The dose distributions generated by the proposed optimization model are comparable to those generated by the standard model with respect to dosimetric indices. Conclusion: Our new model is a viable surrogate to optimizing BT dosimetric indices that quickly and easily yield high‐quality dose distributions. New optimization models that are capable of optimizing dosimetric indices will become of increasing importance in new applications involving more degrees of freedom than conventional HDR 192Ir BT such as electronic BT.

Comparison of methods for the measurement of radiation dose distributions in high dose rate (HDR) brachytherapy: Ge‐doped optical fiber, EBT3 Gafchromic film, and PRESAGE® radiochromic plastic

Dose distribution measurement in clinical high dose rate (HDR) brachytherapy is challenging, because of the high dose gradients, large dose variations, and small scale, but it is essential to verify accurate treatment planning and treatment equipment performance. The authors compare and evaluate three dosimetry systems for potential use in brachytherapy dose distribution measurement: Ge-doped optical fibers, EBT3 Gafchromic film with multichannel analysis, and the radiochromic material PRESAGE(®) with optical-CT readout. Ge-doped SiO2 fibers with 6 μm active core and 5.0 mm length were sensitivity-batched and their thermoluminescent properties used via conventional heating and annealing cycles. EBT3 Gafchromic film of 30 μm active thickness was calibrated in three color channels using a nominal 6 MV linear accelerator. A 48-bit transmission scanner and advanced multichannel analysis method were utilized to derive dose measurements. Samples of the solid radiochromic polymer PRESAGE(®), 60 mm diameter and 100 mm height, were analyzed with a parallel beam optical CT scanner. Each dosimetry system was used to measure the dose as a function of radial distance from a Co-60 HDR source, with results compared to Monte Carlo TG-43 model data. Each system was then used to measure the dose distribution along one or more lines through typical clinical dose distributions for cervix brachytherapy, with results compared to treatment planning system (TPS) calculations. Purpose-designed test objects constructed of Solid Water and held within a full-scatter water tank were utilized. All three dosimetry systems reproduced the general shape of the isolated source radial dose function and the TPS dose distribution. However, the dynamic range of EBT3 exceeded those of doped optical fibers and PRESAGE(®), and the latter two suffered from unacceptable noise and artifact. For the experimental conditions used in this study, the useful range from an isolated HDR source was 5-40 mm for fibers, 3-50 mm for EBT3, and 4-21 mm for PRESAGE(®). Fibers demonstrated some over-response at very low dose levels, suffered from volume averaging effects in the dose distribution measurement, and exhibited up to 9% repeatability variation over three repeated measurements. EBT3 demonstrated excellent agreement with Monte Carlo and TPS dose distributions, with up to 3% repeatability over three measurements. PRESAGE(®) gave promising results, being the only true 3D dosimeter, but artifacts and noise were apparent. The comparative response of three emerging dosimetry systems for clinical brachytherapy dose distribution measurement has been investigated. Ge-doped optical fibers have excellent spatial resolution for single-direction measurement but are currently too large for complex dose distribution assessment. The use of PRESAGE(®) with optical-CT readout gave promising results in the measurement of true 3D dose distributions but further development work is required to reduce noise and improve dynamic range for brachytherapy dose distribution measurements. EBT3 Gafchromic film with multichannel analysis demonstrated accurate and reproducible measurement of dose distributions in HDR brachytherapy. Calibrated dose measurements were possible with agreement within 1.5% of TPS dose calculations. The suitability of EBT3 as a dosimeter for 2D quality control or commissioning work has been demonstrated.

COMS eye plaque brachytherapy dosimetric sensitivity to source photon energy and seed design

This study explores the influence of source photon energy on eye plaque brachytherapy dose distributions for a 16mm COMS plaque filled with 103Pd, 125I, or 131Cs sources or monoenergetic photon emissions ranging from 12keV to 100keV. Dose distributions were similarly created for all permutations of three common brachytherapy seed designs. Within this range, sources with average energy ≤22keV may reduce dose to the opposite eye wall by more than a factor of 2 while maintaining tolerable proximal sclera doses when prescribing to depths of 9mm or less. Current commercially-available brachytherapy sources can exhibit up to 15% relative dosimetric sensitivity to seed design at regions within the eye.

Measurement verification of dose distributions in pulsed-dose rate brachytherapy in breast cancer

AimThe aim of the study was to verify the dose distribution optimisation method in pulsed brachytherapy. BackgroundThe pulsed-dose rate brachytherapy is a very important method of breast tumour treatment using a standard brachytheraphy equipment. The appropriate dose distribution round an implant is an important issue in treatment planning. Advanced computer systems of treatment planning are equipped with algorithms optimising dose distribution. Materials and methodsThe wax-paraffin phantom was constructed and seven applicators were placed within it. Two treatment plans (non-optimised, optimised) were prepared. The reference points were located at a distance of 5mm from the applicators’ axis. Thermoluminescent detectors were placed in the phantom at suitable 35 chosen reference points. ResultsThe dosimetry verification was carried out in 35 reference points for the plans before and after optimisation. Percentage difference for the plan without optimisation ranged from −8.5% to 1.4% and after optimisation from −8.3% to 0.01%. In 16 reference points, the calculated percentage difference was negative (from −8.5% to 1.3% for the plan without optimisation and from −8.3% to 0.8% for the optimised plan). In the remaining 19 points percentage difference was from 9.1% to 1.4% for the plan without optimisation and from 7.5% to 0.01% for the optimised plan.No statistically significant differences were found between calculated doses and doses measured at reference points in both dose distribution non-optimised treatment plans and optimised treatment plans. ConclusionsNo statistically significant differences were found in dose values at reference points between doses calculated by the treatment planning system and those measured by TLDs. This proves the consistency between the measurements and the calculations.

Calcul de la distribution de dose en curiethérapie

Brachytherapy dose distribution calculation has evolved from the simple use of charts to the TG-43 formalism. It depends on the physical and geometrical characteristics of each source, the position of the source relatively to the calculation point and on the medium composition. Its principles and limitations are presented as well as the different dosimetric systems associated with implementing rules and the definition of the prescribed dose. The new generation of algorithms and their contributions are discussed.

Comparison of intracavitary brachytherapy and stereotactic body radiotherapy dose distribution for cervical cancer: In regard to Cengiz et al.

Comparison of intracavitary brachytherapy and stereotactic body radiotherapy dose distribution for cervical cancer: In regard to Cengiz et al.

Verification of high dose rate brachytherapy dose distributions with EBT3 Gafchromic film quality control techniques

It is essential that quality control (QC) techniques are developed to keep pace with modern high dose rate (HDR) brachytherapy. Current QC methods may be insufficient to fully assure the accuracy of 3D-optimized dose delivery. This work presents an evaluation of Gafchromic EBT3 film, with multi-channel analysis, in HDR dose environments for advanced QC and commissioning. ‘Film-array in water’ and ‘three-channel Solid Water block’ purpose-designed phantoms are utilized. Dose and dose-rate dependency and practical film usage has been evaluated. EBT3 measurements of dose with radial distance from a HDR source are compared to Monte Carlo data. Semi-3D dose distributions around clinical HDR applicators are compared to treatment plans. The measurement of delivery accuracy for inverse-planned pseudo-clinical test cases, with correct delivery and simulated treatment errors, has also been investigated. Local gamma criteria of 3%, 3 mm is recommended with passing rates of at least 96% typically achieved. The system is sensitive to simulated errors in HDR delivery, with significant reductions of passing rate. It has been demonstrated that EBT3 Gafchromic film, in combination with multi-channel analysis, is appropriate for applicator, treatment unit and planning system commissioning measurements as well as practical routine QC to confirm agreement of planned and delivered complex HDR brachytherapy dose distributions.

Optimizing parametrial aperture design utilizing HDR brachytherapy isodose distribution

Treatment of cervical cancer includes combination of external beam radiation therapy (EBRT) and brachytherapy (BRT). Traditionally, coronal images displaying dose distribution from a ring and tandem (R&T) implant aid in construction of parametrial boost fields. This research aimed to evaluate a method of shaping parametrial fields utilizing contours created from the high-dose-rate (HDR) BRT dose distribution.Eleven patients receiving HDR-BRT via R&T were identified. The BRT and EBRT CT scans were sent to FocalSim (v4.62)® and fused based on bony anatomy. The contour of the HDR isodose line was transferred to the EBRT scan. The EBRT scan was sent to CMS-XIO (v4.62)® for planning. This process provides an automated, potentially more accurate method of matching the medial parametrial border to the HDR dose distribution. This allows for a 3D-view of dose from HDR-BRT for clinical decision-making, utilizes a paperless process and saves time over the traditional technique.

Prospective Evaluation of Stereotactic Body Radiation Therapy for Low- and Intermediate-risk Prostate Cancer: Emulating High-dose-rate Brachytherapy Dose Distribution

Prospective Evaluation of Stereotactic Body Radiation Therapy for Low- and Intermediate-risk Prostate Cancer: Emulating High-dose-rate Brachytherapy Dose Distribution

Feasibility of radiochromic gels for 3D dosimetry of brachytherapy sources

Two radiochromic gel dosimeters, Fricke-xylenol orange (FXO) gel and Turnbull Blue (TB) gel, were studied in the scope of the iMERA+ project ‘Increasing cancer treatment efficacy using 3D brachytherapy’ for their feasibility for the determination of relative 3D dose distribution of brachytherapy (BT) sources. Initially, the dose, dose rate and energy dependence of the gels were investigated. Subsequently, the gels were irradiated by a point low-dose-rate source IsoSeed I25.S16 (125I) and a high-dose-rate source GammaMed+ (192Ir) and scanned using optical computed tomography. Optical transmission images of irradiated gels were processed to obtain detailed 3D optical density maps inside the gels with voxel dimensions of 0.25 × 0.25 × 0.25 mm3. The radial dose function between 1.5 mm and 35 mm from the source and the anisotropy function at 10 mm radius were determined and compared with Monte Carlo calculations and TG-43 data, showing agreement mostly within the measurement uncertainty. Results revealed that the TB gel is feasible for measurements of the relative 3D dose distributions very close to the point BT source because it conserves sharp dose gradients as this gel does not suffer diffusion of dye created upon irradiation. On the other hand, FXO gel underestimates doses closer than 5 mm from the source due to diffusion effects, but it has a significantly higher sensitivity which enables convenient measurement of relative doses up to 35 mm from the source. Further development, especially on gel composition and corrections to optical CT images, is desirable.

Overview on the dosimetric uncertainty analysis for photon-emitting brachytherapy sources, in the light of the AAPM Task Group No 138 and GEC-ESTRO report

In 2011, the American Association of Physicists in Medicine (AAPM) and the Groupe Européen de Curiethérapie–European Society for Radiotherapy and Oncology (GEC-ESTRO) published a report pertaining to uncertainties in brachytherapy single-source dosimetry preceding clinical use. The International Organization for Standardization's Guide to the Expression of Uncertainty in Measurement and Technical Note 1297 by the National Institute of Standards and Technology are taken as reference standards for uncertainty formalism. Uncertainties involved in measurements or Monte Carlo methods to estimate brachytherapy dose distributions are provided with discussion of the components intrinsic to the overall dosimetric assessment. The uncertainty propagation from the primary calibration standard through transfer to the clinic for air-kerma strength is given with uncertainties in each of the brachytherapy dosimetry parameters of the AAPM TG-43 dose-calculation formalism. For low-energy and high-energy brachytherapy sources of low dose-rate and high dose-rate, a combined dosimetric uncertainty <5% (k = 1) is estimated, which is consistent with prior literature estimates. Recommendations are provided for clinical medical physicists, dosimetry investigators, and manufacturers of brachytherapy sources and treatment planning systems. These recommendations reflect the guidance of the AAPM and GEC-ESTRO for their members, and may also be used as guidance to manufacturers and regulatory agencies in developing good manufacturing practices for conventional brachytherapy sources used in routine clinical treatments.

SU‐E‐T‐323: A CT‐Based Monte Carlo Dose Calculation for Correction of Metal Artifacts Due to the Henschke Applicator

Purpose: Monte Carlo method is the most accurate dose calculation system in the modern world. And we use it to evaluate the influence of computed tomography (CT) metal artifacts resulted from the Henschke applicator in intracavitary brachytherapy dose distribution. Methods: The CT images of the Plastic Water® phantom with Henschke applicator and the applicator associated metal artifacts are applied to the Monte Carlo N‐Particle Transport Code X (MCNPX) for dose calculation. The accuracy of the CT images input is assessed by the phantom dose simulation with and without CT images based on our previous Monte Carlo parameters optimization. To reduce the effect of artifacts, the HU number of metal artifacts and metal materials in CT images are replaced by phantom HU number according to the redefined HU density table. Then the Henschke applicator geometry is superimposed on the corrected CT image. This corrected CT images are applied to MCNPX for dose calculation. The dose calculation with and without metal artifacts can be analyzed for the impact of metal artifacts. Results: This system can be implemented because the dose discrepancy with and without CT images is below 0.05%. We analyze the dose distribution with corrected CT‐based phantom for the impact of metal artifacts. The dose distribution shows the largest dose discrepancy is 8–9% and which is located at the region above 2cm distal to ovoid edge. Conclusions: In this study, the dose at the region above 2cm distal to ovoid edge is significantly under prescription dose. The artifacts resulted from Henschke applicator leads to a certainly inaccurate dose calculation in the planning system. Thus, dose distribution must be evaluated before using new applicator. The CT‐based Monte Carlo method can be used to evaluate the influence of CT metal artifacts in intracavity brachytherapy.

Correlation Between Bladder Volume and Irradiated Dose of Small Bowel in CT-based Planning of Intracavitary Brachytherapy for Cervical Cancer

To quantify the effect of bladder volume on the dose distribution of intracavitary brachytherapy in computed tomography-based treatment planning for cervical cancer. Ten patients with cervical cancer were treated with high-dose rate radiation brachytherapy. For the three-dimensional analysis, pelvic computed tomographic scans were obtained from patients with indwelling catheters in place and from patients who received 50, 100, 150 and 200 cc injections of sterile water into their bladders ('200 cc' was defined as a full bladder). Additionally, scans were made in the prone position with the full bladder. Bladder fullness significantly affected the dose to the small bowel and bladder. The median of maximal doses to the small bowel was significantly greater with an empty bladder in all factors of hot spot (480 vs. 256 cGy on D-2cc). Although dosimetry revealed lower doses for larger volumes of bladder (D-50 and V-25%), the median maximal dose to the bladder was significantly greater with a full bladder (420 vs. 775 cGy on D-2cc). The rectosigmoid doses were not affected by bladder distension (476 vs. 467 cGy on D-2cc). After changing to the prone position, the hot spot dose of small bowel did not change but that of the bladder significantly decreased, although this procedure was very difficult. An increase in bladder volume resulted in a significant reduction in the hot spot dose of the small bowel at the expense of an increase in that of the bladder without changing the dose distribution of the rectosigmoid.

Establishment of Ge-doped optical fibres as thermoluminescence dosimeters for brachytherapy

This study aims to establish the sensitive, ∼120μm high spatial resolution, high dynamic range Ge-doped optical fibres as thermoluminescence (TL) dosimeters for brachytherapy dose distribution. This requires investigation to accommodate sensitivity of detection, both for the possibility of short range dose deposition from beta components as well as gamma/x-mediated dose. In-air measurements are made at distances close to radionuclide sources, evaluating the fall off in dose along the transverse axis of 133Ba and 60Co radioactive sources, at distances from 2mm up to 20mm from their midpoints. Measurements have been compared with Monte Carlo code DOSRZnrc simulations for photon-mediated dose only, agreement being obtained to within 3% and 1% for the 133Ba and 60Co sources, respectively. As such, in both cases it is determined that as intended, beta dose has been filtered out by source encapsulation.

Verification of LDR brachytherapy dose distributions for different source geometries by Monte Carlo method

Verification of LDR brachytherapy dose distributions for different source geometries by Monte Carlo method

20 Gy Versus 44 Gy of Supplemental External Beam Radiotherapy With Palladium-103 for Patients With Greater Risk Disease: Results of a Prospective Randomized Trial

The necessity of external beam radiotherapy (EBRT) as a supplement to prostate brachytherapy remains unknown. We report brachytherapy outcomes for patients with higher risk features randomized to substantially different supplemental EBRT regimens. Between December 1999 and June 2004, 247 patients were randomized to 20 Gy vs. 44 Gy EBRT followed by a palladium-103 boost (115 Gy vs. 90 Gy). The eligibility criteria included clinically organ-confined disease with Gleason score 7-10 and/or pretreatment prostate-specific antigen (PSA) level 10-20 ng/mL. The median follow-up period was 9.0 years. Biochemical progression-free survival (bPFS) was defined as a PSA level of ≤0.40 ng/mL after nadir. The median day 0 prescribed dose covering 90% of the target volume was 125.7%; 80 men received androgen deprivation therapy (median, 4 months). Multiple parameters were evaluated for their effect on bPFS. For the entire cohort, the cause-specific survival, bPFS, and overall survival rates were 97.7%, 93.2%, and 80.8% at 8 years and 96.9%, 93.2%, and 75.4% at 10 years, respectively. The bPFS rate was 93.1% and 93.4% for the 20-Gy and 44-Gy arms, respectively (p = .994). However, no statistically significant differences were found in cause-specific survival or overall survival were identified. When stratified by PSA level of ≤10 ng/mL vs. >10 ng/mL, Gleason score, or androgen deprivation therapy, no statistically significant differences in bPFS were discerned between the two EBRT regimens. On multivariate analysis, bPFS was most closely related to the preimplant PSA and clinical stage. For patients with biochemically controlled disease, the median PSA level was <0.02 ng/mL. The results of the present trial strongly suggest that two markedly different supplemental EBRT regimens result in equivalent cause-specific survival, bPFS, and overall survival. It is probable that the lack of benefit for a higher supplemental EBRT dose is the result of the high-quality brachytherapy dose distributions.

Comparison of intracavitary brachytherapy and stereotactic body radiotherapy dose distribution for cervical cancer

PurposeTo compare the dose distribution characteristics of stereotactic body radiotherapy (SBRT) with intracavitary high-dose-rate (HDR) brachytherapy in patients with cervical carcinoma. Methods and MaterialsHDR intracavitary brachytherapy treatment plans for 11 women with cervical carcinoma were evaluated in this analysis. The total HDR brachytherapy dose was 28Gy given in four fractions. HDR brachytherapy was delivered with the microSelectron HDR therapy unit (Nucletron B. V., Veenendaal, The Netherlands). SBRT plans for each patient were generated with MultiPlan for CyberKnife Robotic Radiosurgery System (Accuray Inc., Sunnyvale, CA). The dose distributions, dose–volume histograms, and maximum dose points of the target and critical organs were recorded for both plans. ResultsSBRT yielded significantly better target coverage; the median target coverage for the 100% isodose line was 50.7% for HDR brachytherapy plans, whereas it was 99.1% for SBRT plans. The dose distributions for critical organs were similar in both types of plans. The exceptions were the 25% isodose being significantly better in brachytherapy plans for rectum, and the 100% isodose exposure being higher in brachytherapy plans for rectum, bladder, and sigmoid colon. Some significant differences were also found in maximum doses received by a 2-cc volume of bladder in favor of SBRT plans. In addition, maximum bone marrow doses were significantly higher in SBRT plans. ConclusionSBRT plans achieved better target coverage and better dose distributions to critical organs except bone marrow compared with HDR brachytherapy plans in patients with locally advanced cervical cancer.

WE‐A‐BRB‐08: Comparison of Brachytherapy Dose Distribution Using the Gamma‐Index Method

Purpose: The gamma‐index method was developed to quantitatively compare treatment planning system (TPS)‐derived dose distributions for external‐beam radiotherapy with measured dose distributions. However, the clinical medical physicist does not measure brachytherapy dose distributions and the use of this method for brachytherapy appears novel. The purpose of this study was to evaluate the accuracy of several TPS‐derived brachytherapy dose distributions in comparison to reference brachytherapy dose distributions, and suggest dose and distance criteria such as those recommended in the AAPM Task Group 56 report. Methods: Reference brachytherapy dose distributions from Monte Carlo (MC) simulations were commissioned into the Pinnacle TPS. MC and TPS dose distributions for several HDR and LDR sources were imported into the OmniPro IˈmRT software and compared. Sensitivity of distance‐to‐agreement for 1 mm =&lt; delta(d) =&lt; 5 mm and dose difference for 1% =&lt; delta(D) =&lt; 10% were investigated. TPS dose characterization was considered successful when at least 98% of all pixels examined satisfied a pass tolerance r =&lt;1.00. Results: At least 98% pixels passed for delta(d) = 2 mm and delta(D) = 2%. For delta(d) &gt;= 3 mm and delta(D) &gt;= 3% criteria, r =&lt; 1.00 for all pixels. Failure regions were located within the brachytherapy source, near the brachytherapy source surface, or in high dose‐gradient regions (&gt;50%/mm). A potentially useful standard is delta(d) = 2 mm and delta(D) = 2%. Conclusions: The gamma‐index method was used to evaluate brachytherapy dose distribution comparisons, and agreement criteria were proposed. The medical physics community may further investigate this method and consider standardized criteria for brachytherapy dosimetry.