Consensus Datasets Research Articles

RapidBrachyTG43: A Geant4-based TG-43 parameter and dose calculation module for brachytherapy dosimetry.

The AAPM TG-43U1 formalism remains the clinical standard for dosimetry of low- and high-energy -emitting brachytherapy sources. TG-43U1 and related reports provide consensus datasets of TG-43 parameters derived from various published measured data and Monte Carlo simulations. These data are used to perform standardized and fast dose calculations for brachytherapy treatmentplanning. Monte Carlo TG-43 dosimetry parameters are commonly derived to characterize novel brachytherapy sources. RapidBrachyTG43 is a module of RapidBrachyMCTPS, a Monte Carlo-based treatment planning system, designed to automate this process, requiring minimal user input to prepare Geant4-based Monte Carlo simulations for a source. RapidBrachyTG43 may also perform a TG-43 dose to water-in-water calculation for a plan, substantially accelerating the same calculation performed using RapidBrachyMCTPS's Monte Carlo dose calculationengine. TG-43 parameters , , , and were calculated using three commercial source models, one each of I, Ir, and Co, and were benchmarked to published data. TG-43 dose to water was calculated for a clinical breast brachytherapy plan and was compared to a Monte Carlo dose calculation with all patient tissues, air, and catheters set towater. TG-43 parameters for the three simulated sources agreed with benchmark datasets within tolerances specified by the High Energy Brachytherapy Dosimetry working group. A gamma index comparison between the TG-43 and Monte Carlo dose-to-water calculations with a dose difference and difference to agreement criterion of 1%/1 mm yielded a 98.9% pass rate, with all relevant dose volume histogram metrics for the plan agreeing within 1%. Performing a TG-43-based dose calculation provided an acceleration of dose-to-water calculation by a factor of165. Determination of TG-43 parameter data for novel brachytherapy sources may now be facilitated by RapidBrachyMCTPS. These parameter datasets and existing consensus or published datasets may also be used to determine the TG-43 dose for a plan inRapidBrachyMCTPS.

First Report On Physician Assessment and Clinical Acceptability of Custom-Retrained Artificial Intelligence Models for Clinical Target Volume and Organs-at-Risk Auto-Delineation for Postprostatectomy Patients

To assess the clinical acceptability of a commercial deep-learning-based auto-segmentation (DLAS) prostate model that was retrained using institutional data for delineation of the clinical target volume (CTV) and organs-at-risk (OARs) for postprostatectomy patients, accounting for clinical and imaging protocol variations. CTV and OARs of 109 prostate-bed patients were used to evaluate the performance of the vendor-trained model and custom retrained DLAS models using different training quantities. Two new models for OAR structures were retrained (n=30, 60 data sets), while separate models were trained for a new CTV structure (n=30, 60, 90 data sets), with the remaining data sets used for testing (n=49, 19). The dice similarity coefficient (DSC), Hausdorff distance, and mean surface distance were evaluated. Six radiation oncologists performed a qualitative evaluation scoring both preference and clinical utility for blinded structure sets. Physician consensus data sets identified from the qualitative evaluation were used toward a separate CTV model. Both the 30- and 60-case retrained OAR models had median DSC values between 0.91 to 0.97, improving significantly over the vendor-trained model for all OARs except the penile bulb. The brand new 60-case CTV model had a median DSC of 0.70 improving significantly over the 30-case model. DLAS (60-case model) and manual contours were blinded and evaluated by physicians with contours deemed acceptable or precise for 87% and 94% of cases for DLAS and manual delineations, respectively. DLAS-generated CTVs were scored precise or acceptable in 54% of cases, compared with the manual delineation value of 73%. The 30-case physician consensus CTV model did not show a significant difference compared with the randomly selected models. Custom retraining using institutional data leads to performance improvement in the clinical utility and accuracy of DLAS for postprostatectomy patients. A small number of data sets are sufficient for building an institutional site-specific DLAS OAR model, as well as for training new structures. Data indicates the workload for identifying training data sets could be shared among groups for the male pelvic region, making it accessible to clinics of all sizes.

Current and future regulatory and financial challenges in vascularized composite allotransplantation.

To discuss current and future regulatory and financial issues affecting the field of vascularized composite allotransplantation (VCA). Vascularized composite allografts are regulated by the US Department of Health and Human Services Organ Procurement and Transplantation Network Final Rule (42 CFR part 121) in the United States and Directive 2010/53/EU of the European Parliament and the Council of 7 July 2010 in the European Union (EU). However, in the United States and most of the EU, VCA is not yet paid for by insurance or third-party payers and many centers depend upon grant funding, philanthropic gifts, and/or supplemental hospital/institutional funding strategies to pay for the transplants and postoperative care. In the absence of randomized clinical trial data, which is infeasible for studying VCA outcomes, consensus data sets are needed to document these procedures' value proposition and have them accepted as part of the standard of care. Procedure and immunosuppression protocol variability applied to a small patient cohort necessitates collaborative efforts by field experts to devise creative approaches, such as determining return-on-investment for anatomical subunits, to better understand these transplants' value and impact on patient quality-of-life.

A revised dosimetric characterization of 60Co BEBIG source: From single-source data to clinical dose distribution

PurposeAlthough the dosimetric characterization of 60Co BEBIG source can be found in several literature studies, the data sets show major discrepancies and the lack of uncertainty analyses. This study tried to determine an accurate dosimetric data set for this source using Monte Carlo (MC) simulations along with detailed uncertainty analysis. To explore how different dosimetric data sets can make changes in practical situations, clinical dose distributions based on our results were compared with the dose distributions derived from Granero et al. and consensus data sets. Methods and MaterialsThe MC simulations were performed with Monte Carlo N-Particle eXtended code (MCNPX) version 2.6.0 and the TG-43 parameters were estimated adhering to the American Association of Physicists in Medicine (AAPM) and European SocieTy for Radiotherapy and Oncology (ESTRO) 229 report. The dose rate distributions for single-source and two typical clinical cases, including one intracavitary and one interstitial, were calculated using an in-house code on the basis of the TG-43 formalism. ResultsThe total uncertainties for water dose rate on source transverse axis at 1 cm and 5 cm, air kerma strength, and dose rate constant were evaluated to be 0.10%, 0.09%, 0.04%, and 0.11%, respectively. Meaningful differences were found for the interstitial case in which 22% of clinical target volume (CTV) showed differences from ±1% to ±10% or even larger. ConclusionsThe MC uncertainty was derived about 16 times smaller than the typical MC component stated in TG-138, partly because of large number of histories and partly because the spectra of 60Co and also its photons' attenuation coefficients are adequately accurate. The results showed that in the clinical situations, the applicator geometry and the superposition of single-source dose distributions can reduce the differences observed between several data sets.

Supplement 2 for the 2004 update of the AAPM Task Group No. 43 Report: Joint recommendations by the AAPM and GEC-ESTRO.

Since the publication of the 2004 update to the American Association of Physicists in Medicine (AAPM) Task Group No. 43 Report (TG-43U1) and its 2007 supplement (TG-43U1S1), several new low-energy photon-emitting brachytherapy sources have become available. Many of these sources have satisfied the AAPM prerequisites for routine clinical purposes and are posted on the Brachytherapy Source Registry managed jointly by the AAPM and the Imaging and Radiation Oncology Core Houston Quality Assurance Center (IROC Houston). Given increasingly closer interactions among physicists in North America and Europe, the AAPM and the Groupe Européen de Curiethérapie-European Society for Radiotherapy & Oncology (GEC-ESTRO) have prepared another supplement containing recommended brachytherapy dosimetry parameters for eleven low-energy photon-emitting brachytherapy sources. The current report presents consensus datasets approved by the AAPM and GEC-ESTRO. The following sources are included: 125 I sources (BEBIG model I25.S17, BEBIG model I25.S17plus, BEBIG model I25.S18, Elekta model 130.002, Oncura model 9011, and Theragenics model AgX100); 103 Pd sources (CivaTech Oncology model CS10, IBt model 1031L, IBt model 1032P, and IsoAid model IAPd-103A); and 131 Cs (IsoRay Medical model CS-1 Rev2). Observations are included on the behavior of these dosimetry parameters as a function of radionuclide. Recommendations are presented on the selection of dosimetry parameters, such as from societal reports issuing consensus datasets (e.g., TG-43U1, AAPM Report #229), the joint AAPM/IROC Houston Registry, the GEC-ESTRO website, the Carleton University website, and those included in software releases from vendors of treatment planning systems. Aspects such as timeliness, maintenance, and rigor of these resources are discussed. Links to reference data are provided for radionuclides (radiation spectra and half-lives) and dose scoring materials (compositions and mass densities). The recent literature is examined on photon energy response corrections for thermoluminescent dosimetry of low-energy photon-emitting brachytherapy sources. Depending upon the dosimetry parameters currently used by individual physicists, use of these recommended consensus datasets may result in changes to patient dose calculations. These changes must be carefully evaluated and reviewed with the radiation oncologist prior to their implementation.

A simple analytical method for heterogeneity corrections in low dose rate prostate brachytherapy

In low energy brachytherapy, the presence of tissue heterogeneities contributes significantly to the discrepancies observed between treatment plan and delivered dose. In this work, we present a simplified analytical dose calculation algorithm for heterogeneous tissue. We compare it with Monte Carlo computations and assess its suitability for integration in clinical treatment planning systems. The algorithm, named as RayStretch, is based on the classic equivalent path length method and TG-43 reference data. Analytical and Monte Carlo dose calculations using Penelope2008 are compared for a benchmark case: a prostate patient with calcifications. The results show a remarkable agreement between simulation and algorithm, the latter having, in addition, a high calculation speed. The proposed analytical model is compatible with clinical real-time treatment planning systems based on TG-43 consensus datasets for improving dose calculation and treatment quality in heterogeneous tissue. Moreover, the algorithm is applicable for any type of heterogeneities.

Could We Improve the Quality of Superficial Brachytherapy in the Head and Neck Region Using Image-Based Treatment Planning?

This value is equivalent to the mean value of L 5 1.112 0.002 cGy/(h U) for the ten HDR Ir sources for which consensus datasets have obtained by the HEBD-WG. The radial dose function for the generic source was also similar to the mean of the ten sources. Conclusions: Dosimetric data for a generic HDR Ir source model are provided by the MBDCA-WG. The AAPM-WG recommend that these data should be integrated into all clinical TPSs to support the use of the test plans to be developed by the MBDCA-WG in comparisons and QA tests. A generic source of identical design integrated into all TPSs will further support direct comparisons between different TPSs.

TU‐A‐213AB‐01: Dosimetry for Ir‐192 HDR Brachytherapy ‐ Present Status and Future Direction

Reference dosimetry for high doserate 192Ir brachytherapy in North America is based on an interpolated air kerma standard maintained at the U.S. ADCLs. Clinical well‐chambers are calibrated in terms of air kerma and the AAPM TG‐43 protocol is used to obtain absorbed dose to water.This first part of the presentation will review:i. The calibration chain for the dissemination of the quantity air kerma strength for 192Ir, from the primary standards maintained by NIST, through the intermediate realization at the ADCLs, to the calibration of clinical well‐type ionization chambers.ii. How the accuracy of dose measurements may be affected in situations where the source design differs for calibration and use.iii. What uncertainty components contribute to the overall uncertainty in the measurement of air kerma strength in the clinical situation, focusing on the recently published AAPM/ESTRO TG‐138 report.There are significant developments worldwide focused on moving to an absorbed dose‐to‐water basis for HDR 192Ir dosimetry. Various techniques have been proposed — water and graphite calorimetry, Fricke dosimetry, and ionization chambers — and all offer the potential for increased accuracy and a simpler protocol for users. The second part of the presentation will:i. Outline how absorbed dose standards provide a potential improvement in dosimetry for HDR 192Ir. An absorbed dose standard would mean that the calibration the clinical physicist obtains for their well chamber would be much closer to what they need, thereby potentially reducing the uncertainty on the clinical reference dose.ii. Review the new approaches for direct absorbed dose to water realization in detail. Water calorimetry would seem to be the most direct option for a primary standard but other approaches under investigation may ultimately offer a lower uncertainty.The AAPM TG‐43 protocol is the standard dosimetry protocol used worldwide for brachytherapy clinical dose calculations. While there have been a number of updates refining the approach, the basic formalism based on superposition of single‐source dose distributions in a fixed water sphere has remained. The joint AAPM/ESTRO HEBD report on high‐energy (> 50 keV) photon‐emitting brachytherapy source dosimetry further refines the basic TG‐43 formalism. Specific to high‐energy radionuclide sources such as 192Ir, the report includes the following:a) consensus datasets of brachytherapy dosimetry parameters and recommended methods for evaluating these consensus datasets,b) recommendations on dosimetry methods to characterize the source dose distribution (based on experimental procedures and Monte Carlo methods), andc) interpolation/extrapolation techniques for the 2D anisotropy function and radial dose function, specific to high‐energy sources, which differ from the low‐energy techniques in the 2004 and 2007 AAPM updates.In addition to explaining this report, the final part of the presentation will discuss other advances such as using model‐based dose calculation algorithms (AAPM/ESTRO/ABG TG‐186 report) and clinical implementation of primary HDR 192Ir dose rate‐to‐water calibrations.Learning Objectives:1. Understand the present basis for HDR 192Ir dosimetry in North America2. Understand how proposed standards of absorbed dose will benefit clinical dosimetry3. Understand how the TG‐43 protocol is being refined through joint AAPM/ESTRO activities.

Dose calculation for photon‐emitting brachytherapy sources with average energy higher than 50 keV: Report of the AAPM and ESTRO

Recommendations of the American Association of Physicists in Medicine (AAPM) and the European Society for Radiotherapy and Oncology (ESTRO) on dose calculations for high-energy (average energy higher than 50 keV) photon-emitting brachytherapy sources are presented, including the physical characteristics of specific (192)Ir, (137)Cs, and (60)Co source models. This report has been prepared by the High Energy Brachytherapy Source Dosimetry (HEBD) Working Group. This report includes considerations in the application of the TG-43U1 formalism to high-energy photon-emitting sources with particular attention to phantom size effects, interpolation accuracy dependence on dose calculation grid size, and dosimetry parameter dependence on source active length. Consensus datasets for commercially available high-energy photon sources are provided, along with recommended methods for evaluating these datasets. Recommendations on dosimetry characterization methods, mainly using experimental procedures and Monte Carlo, are established and discussed. Also included are methodological recommendations on detector choice, detector energy response characterization and phantom materials, and measurement specification methodology. Uncertainty analyses are discussed and recommendations for high-energy sources without consensus datasets are given. Recommended consensus datasets for high-energy sources have been derived for sources that were commercially available as of January 2010. Data are presented according to the AAPM TG-43U1 formalism, with modified interpolation and extrapolation techniques of the AAPM TG-43U1S1 report for the 2D anisotropy function and radial dose function.

Supplement to the 2004 update of the AAPM Task Group No. 43 Report

Since publication of the 2004 update to the American Association of Physicists in Medicine (AAPM) Task Group No. 43 Report (TG-43U1), several new low-energy photon-emitting brachytherapy sources have become available. Many of these sources have satisfied the AAPM prerequisites for routine clinical use as of January 10, 2005, and are posted on the Joint AAPM/RPC Brachytherapy Seed Registry. Consequently, the AAPM has prepared this supplement to the 2004 AAPM TG-43 update. This paper presents the AAPM-approved consensus datasets for these sources, and includes the following 125I sources: Amersham model 6733, Draximage model LS-1, Implant Sciences model 3500, IBt model 1251L, IsoAid model IAI-125A, Mentor model SL-125/ SH-125, and SourceTech Medical model STM1251. The Best Medical model 2335 103Pd source is also included. While the methodology used to determine these data sets is identical to that published in the AAPM TG-43U1 report, additional information and discussion are presented here on some questions that arose since the publication of the TG-43U1 report. Specifically, details of interpolation and extrapolation methods are described further, new methodologies are recommended, and example calculations are provided. Despite these changes, additions, and clarifications, the overall methodology, the procedures for developing consensus data sets, and the dose calculation formalism largely remain the same as in the TG-43U1 report. Thus, the AAPM recommends that the consensus data sets and resultant source-specific dose-rate distributions included in this supplement be adopted by all end users for clinical treatment planning of low-energy photon-emitting brachytherapy sources. Adoption of these recommendations may result in changes to patient dose calculations, and these changes should be carefully evaluated and reviewed with the radiation oncologist prior to implementation of the current protocol.

MO‐B‐230A‐01: AAPM TG‐43 Update for 2004 and Beyond

Since publication of the 2004 update to the American Association of Physicists in Medicine (AAPM) Task Group No. 43 Report (AAPM TG‐ 43U1), several new low‐energy photon‐emitting brachytherapy sources have become available. Many of these sources have satisfied the AAPM prerequisites for routine clinical use as of January 10th, 2005, and are posted on the Joint AAPM/RPC Brachytherapy Seed Registry. Consequently, the AAPM has prepared this supplement to the 2004 AAPM TG‐43 update. This paper presents the AAPM‐approved consensus datasets for these sources, and includes the following 125I sources: Amersham model 6733, Draximage model LS‐1, Implant Sciences model 3500, IBt model 1251L, IsoAid model IAI‐125A, Mentor model SL‐125/SH‐125, and SourceTech Medical model STM1251. The Best Medical model 2335 103Pd source is also included. While the methodology used to determine these datasets is identical to that published in the AAPM TG‐ 43U1 report, additional information and discussion are presented here on some questions that arose since the publication of the TG‐43U1 report. Specifically details of interpolation and extrapolation methods are described further. Despite these small changes, additions, and clarifications, the overall methodology, the procedures for developing consensus datasets and the dose calculation formalism remain the same as in the TG‐43U1 report. Thus, the AAPM recommends that the consensus datasets and resultant source‐specific dose‐rate distributions included in this supplement be adopted by all end users for clinical treatment planning of low‐energy photon‐emitting brachytherapy sources. Adoption of these recommendations may result in changes to patient dose calculations, and these changes should be carefully evaluated and reviewed with the radiation oncologist prior to implementation of the current protocol.

Update of AAPM Task Group No. 43 Report: A revised AAPM protocol for brachytherapy dose calculations

Since publication of the American Association of Physicists in Medicine (AAPM) Task Group No. 43 Report in 1995 (TG-43), both the utilization of permanent source implantation and the number of low-energy interstitial brachytherapy source models commercially available have dramatically increased. In addition, the National Institute of Standards and Technology has introduced a new primary standard of air-kerma strength, and the brachytherapy dosimetry literature has grown substantially, documenting both improved dosimetry methodologies and dosimetric characterization of particular source models. In response to these advances, the AAPM Low-energy Interstitial Brachytherapy Dosimetry subcommittee (LIBD) herein presents an update of the TG-43 protocol for calculation of dose-rate distributions around photon-emitting brachytherapy sources. The updated protocol (TG-43U1) includes (a) a revised definition of air-kerma strength; (b) elimination of apparent activity for specification of source strength; (c) elimination of the anisotropy constant in favor of the distance-dependent one-dimensional anisotropy function; (d) guidance on extrapolating tabulated TG-43 parameters to longer and shorter distances; and (e) correction for minor inconsistencies and omissions in the original protocol and its implementation. Among the corrections are consistent guidelines for use of point- and line-source geometry functions. In addition, this report recommends a unified approach to comparing reference dose distributions derived from different investigators to develop a single critically evaluated consensus dataset as well as guidelines for performing and describing future theoretical and experimental single-source dosimetry studies. Finally, the report includes consensus datasets, in the form of dose-rate constants, radial dose functions, and one-dimensional (1D) and two-dimensional (2D) anisotropy functions, for all low-energy brachytherapy source models that met the AAPM dosimetric prerequisites [Med. Phys. 25, 2269 (1998)] as of July 15, 2001. These include the following 125I sources: Amersham Health models 6702 and 6711, Best Medical model 2301, North American Scientific Inc. (NASI) model MED3631-A/M, Bebig/Theragenics model I25.S06, and the Imagyn Medical Technologies Inc. isostar model IS-12501. The 103Pd sources included are the Theragenics Corporation model 200 and NASI model MED3633. The AAPM recommends that the revised dose-calculation protocol and revised source-specific dose-rate distributions be adopted by all end users for clinical treatment planning of low energy brachytherapy interstitial sources. Depending upon the dose-calculation protocol and parameters currently used by individual physicists, adoption of this protocol may result in changes to patient dose calculations. These changes should be carefully evaluated and reviewed with the radiation oncologist preceding implementation of the current protocol.