Purpose: We sought to evaluate the feasibility of using machine learning algorithms for multipoint plastic scintillator detector calibration in high-dose-rate brachytherapy. Methods: The dosimetry system consisted of an optimized 1-mm-core mPSD and a compact assembly of photomultiplier tubes coupled with dichroic mirrors and filters. An $^{192}$Ir source was remotely controlled and sent to various positions in a homemade PMMA holder. Dose measurements covering a range of 0.5 to 12 cm of source displacement were carried out according to TG-43 recommendations. Individual scintillator doses were decoupled using a linear regression model, a random forest estimator, and artificial neural network algorithms. The performance of the different algorithms was evaluated using different sample sizes and distances to the source for the mPSD system calibration. Results: The decoupling methods' deviations from the expected TG-43 dose generally remained below 20%. However, the dose prediction with the three algorithms was accurate to within 7% relative to the dose predicted by the TG-43 formalism for measurements performed in the same range of distances used for calibration. The performance random forest was compromised when the predictions were done beyond the range of distances used for calibration. The dose prediction by the linear regression was less influenced by the calibration conditions than random forest, but with more significant deviations. The number of available measurements for training purposes influenced the random forest and neural network models the most. Their accuracy tended to converge toward deviation values close to 1% from a number of dwell positions greater than 100. Conclusions: In performing HDR brachytherapy dose measurements with an optimized mPSD system, ML algorithms are good alternatives for precise dose reporting and treatment assessment.
Purpose: This study aims to optimize and characterize the response of a mPSD for in vivo dosimetry in HDR brachytherapy. Methods: An exhaustive analysis was carried out in order to obtain an optimized mPSD design that maximize the scintillation light collection produced by the interaction of ionizing photons. Several mPSD prototypes were built and tested in order to determine the appropriate order of scintillators relative to the photodetector, as well as their length as a function of the scintillation light emitted. Scintillators BCF-60, BCF-12 and BCF-10 constituted the mPSD sensitive volume…
The $^{192}$Ir sources are widely used for high dose rate (HDR) brachytherapy treatments. The aim of this study is to simulate $^{192}$Ir MicroSelectron v2 HDR brachytherapy source and calculate the air kerma strength, dose rate constant, radial dose function and anisotropy function established in the updated AAPM Task Group 43 protocol. The EGSnrc Monte Carlo (MC) code package is used to calculate these dosimetric parameters, including dose contribution from secondary electron source and also contribution of bremsstrahlung photons to air kerma strength. The Air kerma strength, dose rate const…
Purpose: Many planning methods for high dose rate (HDR) brachytherapy treatment planning require an iterative approach. A set of computational parameters are hypothesized that will give a dose plan that meets dosimetric criteria. A dose plan is computed using these parameters, and if any dosimetric criteria are not met, the process is iterated until a suitable dose plan is found. In this way, the dose distribution is controlled by abstract parameters. The purpose of this study is to improve HDR brachytherapy planning by developing a new approach that directly optimizes the dose distribution ba…
Currently in HDR brachytherapy planning, a manual fine-tuning of an objective function is necessary to obtain case-specific valid plans. This study intends to facilitate this process by proposing a patient-specific inverse planning algorithm for HDR prostate brachytherapy: GPU-based multi-criteria optimization (gMCO). Two GPU-based optimization engines including simulated annealing (gSA) and a quasi-Newton optimizer (gL-BFGS) were implemented to compute multiple plans in parallel. After evaluating the equivalence and the computation performance of these two optimization engines, one preferred …
Most commercially available treatment planning systems for brachytherapy operate based on physical dose and do not incorporate fractionation or tissue-specific response. The purpose of this study is to investigate the potential for hypofractionation in HDR brachytherapy, thereby reducing the number of implants required. A new treatment planning algorithm was built in order to optimize based on tissue and fractionation specific parameters. Different fractionation schemes were considered for 6 patients, and plans were created using the new algorithm. A baseline fractionation scheme consisting of…
This study aims to introduce IViST (In Vivo Source Tracking), a novel multi-sensors dosimetry platform for real-time treatment monitoring in HDR brachytherapy. IViST is a platform that comprises 3 parts: 1) an optimized and characterized multi-point plastic scintillator dosimeter (3 points mPSD; using BCF-60, BCF-12, and BCF-10 scintillators), 2) a compact assembly of photomultiplier tubes (PMTs) coupled to dichroic mirrors and filters for high-sensitivity scintillation light collection, and 3) a Python-based graphical user interface used for system management and signal processing. IViST can …
Purpose: To determine whether alternative HDR prostate brachytherapy catheter patterns can result in improved dose distributions while providing better access and reducing trauma. Methods: Prostate HDR brachytherapy uses a grid of parallel needle positions to guide the catheter insertion. This geometry does not easily allow the physician to avoid piercing the critical structures near the penile bulb nor does it provide position flexibility in the case of pubic arch interference. On CT data from ten previously-treated patients new catheters were digitized following three catheter patterns: coni…
Purpose: To present the performance of a multi-point plastic scintillation detector (mPSD) as a tool in vivo dosimetry in brachytherapy. Methods: A previously optimized three-point sensor system was used for in vivo HDR brachytherapy measurements (using the scintillators BCF-60, BCF-12, and BCF-10). The light detection system of the mPSD consisted of compactly assembled photomultiplier tubes (PMTs) and dichroic mirrors and filters to achieve a highly sensitive scintillation light collection. The PMT signals were recorded using a NI-DAQ board at a rate of 100 kHz. Dose measurements covering a r…
Clinical test cases for commissioning, QA, and benchmarking of model-based dose calculation algorithms in 192Ir HDR gynecologic tandem and ring brachytherapy
National and Kapodistrian University of Athens（雅典国立卡波季斯里安大学）；General Hospital of Athens Alexandra（亚历山德拉雅典综合医院）；McGill University（麦吉尔大学）；Carleton University（卡尔顿大学）；Thomas Jefferson University（托马斯杰斐逊大学）；Maastricht University Medical Centre+（马斯特里赫特大学医学中心+）
Inverse planning algorithms for dwell time optimisation in interstitial high-dose-rate (HDR) brachytherapy may produce solutions with large dwell time variations within catheters, which may result in undesirable selective high-dose subvolumes. Extending the optimisation model with a dwell time modulation restriction (DTMR) that limits dwell time differences between neighboring dwell positions has been suggested to eliminate this issue. DTMRs may additionally reduce the sensitivity for uncertainties in dwell positions that result from catheter reconstruction errors and source positioning inaccu…
Current inverse treatment planning methods that optimize both catheter positions and dwell times in prostate HDR brachytherapy use surrogate linear or quadratic objective functions that have no direct interpretation in terms of dose-volume histogram (DVH) criteria, do not result in an optimum or have long solution times. We decrease the solution time of existing linear and quadratic dose-based programming models (LP and QP, respectively) to allow optimizing over potential catheter positions using mixed integer programming. An additional average speed-up of 75% can be obtained by stopping the s…
The high dose gradients near the source characteristics of brachytherapy are equivalent to nefarious effects if unnoticed errors take place during the patient treatment. In vivo dosimetry is the only method to quantify the delivered dose. Previous studies to this one, have characterized potential detectors that can be used as in vivo dosimeter. Some of them have focused on the source tracking topic in HDR brachytherapy. The aim of this study is to perform 3D source position reconstruction by combining in vivo dosimetry measurements from two independent detector systems. The first was based on …
Since large dose are administrated to the patient in brachytherapy treatment, ensuring the right dose is delivered is highly critical. This study presents a first step in solving the standing issue of accurately knowing the dosimeter position at all time during in vivo dosimetry. In this work, an energy independent dosimeter, namely plastic scintillation detector, is coupled to an electromagnetic (EM) sensor having sub-mm positional accuracy for real-time tracking of the dosimeter position. However, adding an EM sensor adds materials in the path to the scintillator and thus could potentially p…
Purpose: To present an efficient NEEdle Position Optimization (NEEPO) algorithm for prostate rotating shield brachytherapy (RSBT). With RSBT, the increased flexibility beyond conventional high-dose-rate brachytherapy (HDR-BT) due to the partially shielded radiation source has been shown by Adams et al. in 2020 to enable improved urethra sparing (23.1%), enhanced dose escalation (29.9%), or both, with 20 needles without NEEPO-optimized positions. Within this regime of improved dosimetry, we propose in this work that the benefits of RSBT can be maintained while also reducing the number of needle…
Automated Treatment Planning for Interstitial HDR Brachytherapy for Locally Advanced Cervical Cancer using Deep Reinforcement Learning
Department of Radiation & Cellular Oncology, University of Chicago（芝加哥大学辐射与细胞肿瘤学系）；Department of Physics, University of Chicago（芝加哥大学物理系）；Department of Radiation Oncology, Emory University（埃默里大学放射肿瘤学系）
High dose-rate brachytherapy (HDRBT) is widely used for gynecological cancer treatment. Although commercial treatment planning systems (TPSs) have inverse optimization modules, it takes several iterations to adjust planning objectives to achieve a satisfactory plan. Interactive plan-modification modules enable modifying the plan and visualizing results in real time, but they update plans based on simple geometrical or heuristic algorithms, which cannot ensure resulting plan optimality. This project develops an interactive plan optimization module for HDRBT of gynecological cancer. By efficient…
Automatic Treatment Planning using Reinforcement Learning for High-dose-rate Prostate Brachytherapy
Department of Medical Physics, Memorial Sloan Kettering Cancer Center（医学物理系，纪念斯隆-凯特琳癌症中心）；Department of Radiation Oncology and Winship Cancer Institute, Emory University（放射肿瘤学系和Winship癌症研究所，埃默里大学）；Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine（Wallace H. Coulter生物医学工程系，佐治亚理工学院和埃默里大学医学院）；Department of Biomedical Informatics, Emory University（生物医学信息学系，埃默里大学）
Purpose: To provide a fast computational method, based on the proximal graph solver (POGS) - a convex optimization solver using the alternating direction method of multipliers (ADMM), for calculating an optimal treatment plan in rotating shield brachytherapy (RSBT). RSBT treatment planning has more degrees of freedom than conventional high-dose-rate brachytherapy (HDR-BT) due to the addition of emission direction, and this necessitates a fast optimization technique to enable clinical usage. // Methods: The multi-helix RSBT (H-RSBT) delivery technique was considered with five representative cer…
