Dataset Information

Dosimetric evaluation of multilumen intracavitary balloon applicator rotation in high-dose-rate brachytherapy for breast cancer.

ABSTRACT: The objective of this work is to evaluate dosimetric impact of multilumen balloon applicator rotation in high-dose-rate (HDR) brachytherapy for breast cancer. Highly asymmetrical dose distribution was generated for patients A and B, depending upon applicator proximity to skin and rib. Both skin and rib spacing was ? 0.7 cm for A; only rib spacing was ? 0.7 cm for B. Thirty-five rotation scenarios were simulated for each patient by rotating outer lumens every 10° over ± 180° range with respect to central lumen using mathematically calculated rotational matrix. Thirty-five rotated plans were compared with three plans: 1) original multidwell multilumen (MDML) plan, 2) multidwell single-lumen (MDSL) plan, and 3) single-dwell single-lumen (SDSL) plan. For plan comparison, planning target volume for evaluation (PTV_EVAL) coverage (dose to 95% and 90% volume of PTV_EVAL) (D95 and D90), skin and rib maximal dose (Dmax), and normal breast tissue volume receiving 150% (V150) and 200% (V200) of prescribed dose (PD) were evaluated. Dose variation due to device rotation ranged from -5.6% to 0.8% (A) and -6.5% to 0.2% (B) for PTV_EVAL D95; -5.2% to 0.4% (A) and -4.1% to 0.7% (B) for PTV_EVAL D90; -2.0 to 18.4% (A) and -7.8 to 17.5% (B) for skin Dmax; -11.1 to 22.8% (A) and -4.7 to 55.1% (B) of PD for rib Dmax, respectively. Normal breast tissue V150 and V200 variation was < 1.0 cc, except for -0.1 to 2.5cc (B) of V200. Furthermore, 30° device rotation increased rib Dmax over 145% of PD: 152.9% (A) by clockwise 30° rotation and 152.5% (B) by counterclockwise 30° rotation. For a highly asymmetric dose distribution, device rotation can outweigh the potential benefit of improved dose shaping capability afforded by multilumen and make dosimetric data worse than single-lumen plans unless it is properly corrected.

SUBMITTER: Kim Y

PROVIDER: S-EPMC5711249 | biostudies-other | 2014 Jan

REPOSITORIES: biostudies-other

ACCESS DATA

Publications

Dosimetric evaluation of multilumen intracavitary balloon applicator rotation in high-dose-rate brachytherapy for breast cancer.

Kim Yongbok Y Trombetta Mark G MG

Journal of applied clinical medical physics 20140106 1

The objective of this work is to evaluate dosimetric impact of multilumen balloon applicator rotation in high-dose-rate (HDR) brachytherapy for breast cancer. Highly asymmetrical dose distribution was generated for patients A and B, depending upon applicator proximity to skin and rib. Both skin and rib spacing was ≤ 0.7 cm for A; only rib spacing was ≤ 0.7 cm for B. Thirty-five rotation scenarios were simulated for each patient by rotating outer lumens every 10° over ± 180° range with respect to ...[more]

PMID: 24423837

Similar Datasets

Project description:Background and purposeTo assess the dosimetric flexibility of a dual balloon brachytherapy applicator developed for the treatment of anorectal lesions.Materials and methodsDifferent amounts of water were infused into the inner and outer balloon separately to study the asymmetrical distribution of the catheter, the radial distance of the active source channel to the inner surface of the global target volume , the space between the active source channels, and their dosimetric impact to target tissues and uninvolved rectum.ResultsIncreasing inner balloon volume directly increased both the space between the active source channels and the radial distance of the active source channel to the inner surface of the global target volume. The space between the active source channels and the percentage of global target volume received 150% or more of the prescribed dose to target had a strong inverse correlation (-0.881/P = .007, -0.976/P = .001, respectively) with the radial distance of the active source channel to the inner surface of the global target volume. Conformity index, dose to 2 cm3 of rectum, and total reference air kerma were strongly correlated with the radial distance of the active source channel to the inner surface of the global target volume, with values of 0.952 (P = .001), 0.833 (P = .015), and 0.922 (P = .002), respectively. Percentage of global target volume received 150% or more of the prescribed dose was significantly correlated with the space between the active source channels (0.81/P = .022), and conformity index was strongly inversely correlated with the space between the active source channels (-0.833/P = .015).ConclusionThe dual balloon-constructed Anorectal Applicator offers a flexible way to adjust the distances of the active source positions to the target in relation to uninvolved rectal wall. This flexibility simplifies planning which results in a highly conformal dose distribution to the target lesion while minimizing dose to normal rectal tissue.

Project description:PurposeTo develop and validate a preliminary machine learning (ML) model aiding in the selection of intracavitary (IC) versus hybrid interstitial (IS) applicators for high-dose-rate (HDR) cervical brachytherapy.MethodsFrom a dataset of 233 treatments using IC or IS applicators, a set of geometric features of the structure set were extracted, including the volumes of OARs (bladder, rectum, sigmoid colon) and HR-CTV, proximity of OARs to the HR-CTV, mean and maximum lateral and vertical HR-CTV extent, and offset of the HR-CTV centre-of-mass from the applicator tandem axis. Feature selection using an ANOVA F-test and mutual information removed uninformative features from this set. Twelve classification algorithms were trained and tested over 100 iterations to determine the highest performing individual models through nested 5-fold cross-validation. Three models with the highest accuracy were combined using soft voting to form the final model. This model was trained and tested over 1,000 iterations, during which the relative importance of each feature in the applicator selection process was determined.ResultsFeature selection indicated that the mean and maximum lateral and vertical extent, volume, and axis offset of the HR-CTV were the most informative features and were thus provided to the ML models. Relative feature importances indicated that the HR-CTV volume and mean lateral extent were most important for applicator selection. From the comparison of the individual classification algorithms, it was found that the highest performing algorithms were tree-based ensemble methods - AdaBoost Classifier (ABC), Gradient Boosting Classifier (GBC), and Random Forest Classifier (RFC). The accuracy of the individual models was compared to the voting model for 100 iterations (ABC = 91.6 ± 3.1%, GBC = 90.4 ± 4.1%, RFC = 89.5 ± 4.0%, Voting Model = 92.2 ± 1.8%) and the voting model was found to have superior accuracy. Over the final 1,000 evaluation iterations, the final voting model demonstrated a high predictive accuracy (91.5 ± 0.9%) and F1 Score (90.6 ± 1.1%).ConclusionThe presented model demonstrates high discriminative performance, highlighting the potential for utilization in informing applicator selection prospectively following further clinical validation.

Project description:CivaTech Oncology Inc. (Durham, NC) has developed a novel low-dose rate (LDR) brachytherapy source called the CivaSheet.TM The source is a planar array of discrete elements ("CivaDots") which are directional in nature. The CivaDot geometry and design are considerably different than conventional LDR cylindrically symmetric sources. Thus, a thorough investigation is required to ascertain the dosimetric characteristics of the source. This work investigates the repeatability and reproducibility of a primary source strength standard for the CivaDot and characterizes the CivaDot dose distribution by performing in-phantom measurements and Monte Carlo (MC) simulations. Existing dosimetric formalisms were adapted to accommodate a directional source, and other distinguishing characteristics including the presence of gold shield x-ray fluorescence were addressed in this investigation. Primary air-kerma strength (SK ) measurements of the CivaDots were performed using two free-air chambers namely, the Variable-Aperture Free-Air Chamber (VAFAC) at the University of Wisconsin Medical Radiation Research Center (UWMRRC) and the National Institute of Standards and Technology (NIST) Wide-Angle Free-Air Chamber (WAFAC). An intercomparison of the two free-air chamber measurements was performed along with a comparison of the different assumed CivaDot energy spectra and associated correction factors. Dose distribution measurements of the source were performed in a custom polymethylmethacrylate (PMMA) phantom using GafchromicTM EBT3 film and thermoluminescent dosimeter (TLD) microcubes. Monte Carlo simulations of the source and the measurement setup were performed using MCNP6 radiation transport code. The CivaDot SK was determined using the two free-air chambers for eight sources with an agreement of better than 1.1% for all sources. The NIST measured CivaDot energy spectrum intensity peaks were within 1.8% of the MC-predicted spectrum intensity peaks. The difference in the net source-specific correction factor determined for the CivaDot free-air chamber measurements for the NIST WAFAC and UW VAFAC was 0.7%. The dose-rate constant analog was determined to be 0.555 cGy h-1 U-1 . The average difference observed in the estimated CivaDot dose-rate constant analog using measurements and MCNP6-predicted value (0.558 cGy h-1 U-1 ) was 0.6% ± 2.3% for eight CivaDot sources using EBT3 film, and -2.6% ± 1.7% using TLD microcube measurements. The CivaDot two-dimensional dose-to-water distribution measured in phantom was compared to the corresponding MC predictions at six depths. The observed difference using a pixel-by-pixel subtraction map of the measured and the predicted dose-to-water distribution was generally within 2-3%, with maximum differences up to 5% of the dose prescribed at the depth of 1 cm. Primary SK measurements of the CivaDot demonstrated good repeatability and reproducibility of the free-air chamber measurements. Measurements of the CivaDot dose distribution using the EBT3 film stack phantom and its subsequent comparison to Monte Carlo-predicted dose distributions were encouraging, given the overall uncertainties. This work will aid in the eventual realization of a clinically viable dosimetric framework for the CivaSheet based on the CivaDot dose distribution.

Project description:Historically, treatment of malignant surface lesions has been achieved with linear accelerator based electron beams or superficial x-ray beams. Recent developments in the field of brachytherapy now allow for the treatment of surface lesions with specialized conical applicators placed directly on the lesion. Applicators are available for use with high dose rate (HDR)(192)Ir sources, as well as electronic brachytherapy sources. Part I of this paper discussed the applicators used with electronic brachytherapy sources. Part II will discuss those used with HDR (192)Ir sources. Although the use of these applicators has gained in popularity, the dosimetric characteristics have not been independently verified. Additionally, there is no recognized method of output verification for quality assurance procedures with applicators like these.This work aims to create a cohesive method of output verification that can be used to determine the dose at the treatment surface as part of a quality assurance/commissioning process for surface applicators used with HDR electronic brachytherapy sources (Part I) and(192)Ir sources (Part II). Air-kerma rate measurements for the (192)Ir sources were completed with several models of small-volume ionization chambers to obtain an air-kerma rate at the treatment surface for each applicator. Correction factors were calculated using MCNP5 and EGSnrc Monte Carlo codes in order to determine an applicator-specific absorbed dose to water at the treatment surface from the measured air-kerma rate. Additionally, relative dose measurements of the surface dose distributions and characteristic depth dose curves were completed in-phantom.Theoretical dose distributions and depth dose curves were generated for each applicator and agreed well with the measured values. A method of output verification was created that allows users to determine the applicator-specific dose to water at the treatment surface based on a measured air-kerma rate.The novel output verification methods described in this work will reduce uncertainties in dose delivery for treatments with these kinds of surface applicators, ultimately improving patient care.

Dataset Information

Dosimetric evaluation of multilumen intracavitary balloon applicator rotation in high-dose-rate brachytherapy for breast cancer.

Publications

Dosimetric evaluation of multilumen intracavitary balloon applicator rotation in high-dose-rate brachytherapy for breast cancer.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets