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Title: Quality Control of High-Dose-Rate Brachytherapy: Treatment Delivery Analysis Using Statistical Process Control

Abstract

Purpose: Statistical process control (SPC) is a quality control method used to ensure that a process is well controlled and operates with little variation. This study determined whether SPC was a viable technique for evaluating the proper operation of a high-dose-rate (HDR) brachytherapy treatment delivery system. Methods and Materials: A surrogate prostate patient was developed using Vyse ordnance gelatin. A total of 10 metal oxide semiconductor field-effect transistors (MOSFETs) were placed from prostate base to apex. Computed tomography guidance was used to accurately position the first detector in each train at the base. The plan consisted of 12 needles with 129 dwell positions delivering a prescribed peripheral dose of 200 cGy. Sixteen accurate treatment trials were delivered as planned. Subsequently, a number of treatments were delivered with errors introduced, including wrong patient, wrong source calibration, wrong connection sequence, single needle displaced inferiorly 5 mm, and entire implant displaced 2 mm and 4 mm inferiorly. Two process behavior charts (PBC), an individual and a moving range chart, were developed for each dosimeter location. Results: There were 4 false positives resulting from 160 measurements from 16 accurately delivered treatments. For the inaccurately delivered treatments, the PBC indicated that measurements made at themore » periphery and apex (regions of high-dose gradient) were much more sensitive to treatment delivery errors. All errors introduced were correctly identified by either the individual or the moving range PBC in the apex region. Measurements at the urethra and base were less sensitive to errors. Conclusions: SPC is a viable method for assessing the quality of HDR treatment delivery. Further development is necessary to determine the most effective dose sampling, to ensure reproducible evaluation of treatment delivery accuracy.« less

Authors:
 [1]; ;  [1]
  1. Department of Radiation Oncology, Wake Forest School of Medicine, Winston-Salem, North Carolina (United States)
Publication Date:
OSTI Identifier:
22224388
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 85; Journal Issue: 3; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; ACCURACY; BRACHYTHERAPY; CALIBRATION; COMPUTERIZED TOMOGRAPHY; DOSE RATES; DOSEMETERS; ERRORS; GELATIN; MOSFET; OXIDES; PROCESS CONTROL; PROSTATE; QUALITY CONTROL; RADIATION DOSES; RADIATION SOURCE IMPLANTS; SEMICONDUCTOR MATERIALS; URINARY TRACT

Citation Formats

Able, Charles M., E-mail: cable@wfubmc.edu, Bright, Megan, and Frizzell, Bart. Quality Control of High-Dose-Rate Brachytherapy: Treatment Delivery Analysis Using Statistical Process Control. United States: N. p., 2013. Web. doi:10.1016/J.IJROBP.2012.05.016.
Able, Charles M., E-mail: cable@wfubmc.edu, Bright, Megan, & Frizzell, Bart. Quality Control of High-Dose-Rate Brachytherapy: Treatment Delivery Analysis Using Statistical Process Control. United States. doi:10.1016/J.IJROBP.2012.05.016.
Able, Charles M., E-mail: cable@wfubmc.edu, Bright, Megan, and Frizzell, Bart. 2013. "Quality Control of High-Dose-Rate Brachytherapy: Treatment Delivery Analysis Using Statistical Process Control". United States. doi:10.1016/J.IJROBP.2012.05.016.
@article{osti_22224388,
title = {Quality Control of High-Dose-Rate Brachytherapy: Treatment Delivery Analysis Using Statistical Process Control},
author = {Able, Charles M., E-mail: cable@wfubmc.edu and Bright, Megan and Frizzell, Bart},
abstractNote = {Purpose: Statistical process control (SPC) is a quality control method used to ensure that a process is well controlled and operates with little variation. This study determined whether SPC was a viable technique for evaluating the proper operation of a high-dose-rate (HDR) brachytherapy treatment delivery system. Methods and Materials: A surrogate prostate patient was developed using Vyse ordnance gelatin. A total of 10 metal oxide semiconductor field-effect transistors (MOSFETs) were placed from prostate base to apex. Computed tomography guidance was used to accurately position the first detector in each train at the base. The plan consisted of 12 needles with 129 dwell positions delivering a prescribed peripheral dose of 200 cGy. Sixteen accurate treatment trials were delivered as planned. Subsequently, a number of treatments were delivered with errors introduced, including wrong patient, wrong source calibration, wrong connection sequence, single needle displaced inferiorly 5 mm, and entire implant displaced 2 mm and 4 mm inferiorly. Two process behavior charts (PBC), an individual and a moving range chart, were developed for each dosimeter location. Results: There were 4 false positives resulting from 160 measurements from 16 accurately delivered treatments. For the inaccurately delivered treatments, the PBC indicated that measurements made at the periphery and apex (regions of high-dose gradient) were much more sensitive to treatment delivery errors. All errors introduced were correctly identified by either the individual or the moving range PBC in the apex region. Measurements at the urethra and base were less sensitive to errors. Conclusions: SPC is a viable method for assessing the quality of HDR treatment delivery. Further development is necessary to determine the most effective dose sampling, to ensure reproducible evaluation of treatment delivery accuracy.},
doi = {10.1016/J.IJROBP.2012.05.016},
journal = {International Journal of Radiation Oncology, Biology and Physics},
number = 3,
volume = 85,
place = {United States},
year = 2013,
month = 3
}
  • The aim of this study is to introduce tools to improve the security of each IMRT patient treatment by determining action levels for the dose delivery process. To achieve this, the patient-specific quality control results performed with an ionization chamber--and which characterize the dose delivery process--have been retrospectively analyzed using a method borrowed from industry: Statistical process control (SPC). The latter consisted in fulfilling four principal well-structured steps. The authors first quantified the short term variability of ionization chamber measurements regarding the clinical tolerances used in the cancer center ({+-}4% of deviation between the calculated and measured doses) by calculatingmore » a control process capability (C{sub pc}) index. The C{sub pc} index was found superior to 4, which implies that the observed variability of the dose delivery process is not biased by the short term variability of the measurement. Then, the authors demonstrated using a normality test that the quality control results could be approximated by a normal distribution with two parameters (mean and standard deviation). Finally, the authors used two complementary tools--control charts and performance indices--to thoroughly analyze the IMRT dose delivery process. Control charts aim at monitoring the process over time using statistical control limits to distinguish random (natural) variations from significant changes in the process, whereas performance indices aim at quantifying the ability of the process to produce data that are within the clinical tolerances, at a precise moment. The authors retrospectively showed that the analysis of three selected control charts (individual value, moving-range, and EWMA control charts) allowed efficient drift detection of the dose delivery process for prostate and head-and-neck treatments before the quality controls were outside the clinical tolerances. Therefore, when analyzed in real time, during quality controls, they should improve the security of treatments. They also showed that the dose delivery processes in the cancer center were in control for prostate and head-and-neck treatments. In parallel, long term process performance indices (P{sub p}, P{sub pk}, and P{sub pm}) have been analyzed. Their analysis helped defining which actions should be undertaken in order to improve the performance of the process. The prostate dose delivery process has been shown statistically capable (0.08% of the results is expected to be outside the clinical tolerances) contrary to the head-and-neck dose delivery process (5.76% of the results are expected to be outside the clinical tolerances).« less
  • Purpose: The aim of this study was to evaluate dose distribution within uterus (clinical target volume [CTV]) and tumor (gross tumor volume [GTV]) and the resulting clinical outcome based on systematic three-dimensional treatment planning with dose-volume adaptation. Dose-volume assessment and adaptation in organs at risk and its impact on side effects were investigated in parallel. Methods and Materials: Sixteen patients with either locally confined endometrial carcinoma (n = 15) or adenocarcinoma of uterus and ovaries after bilateral salpingo-oophorectomy (n = 1) were included. Heyman packing was performed with mean 11 Norman-Simon applicators (3-18). Three-dimensional treatment planning based on computed tomographymore » (n = 29) or magnetic resonance imaging (n = 18) was done in all patients with contouring of CTV, GTV, and organs at risk. Dose-volume adaptation was achieved by dwell location and time variation (intensity modulation). Twelve patients treated with curative intent received five to seven fractions of high-dose-rate brachytherapy (7 Gy per fraction) corresponding to a total dose of 60 Gy (2 Gy per fraction and {alpha}/{beta} of 10 Gy) to the CTV. Four patients had additional external beam radiotherapy (range, 10-40 Gy). One patient had salvage brachytherapy and 3 patients were treated with palliative intent. A dose-volume histogram analysis was performed in all patients. On average, 68% of the CTV and 92% of the GTV were encompassed by the 60 Gy reference volume. Median minimum dose to 90% of CTV and GTV (D90) was 35.3 Gy and 74 Gy, respectively. Results: All patients treated with curative intent had complete remission (12/12). After a median follow-up of 47 months, 5 patients are alive without tumor. Seven patients died without tumor from intercurrent disease after median 22 months. The patient with salvage treatment had a second local recurrence after 27 months and died of endometrial carcinoma after 57 months. In patients treated with palliative intent, symptom relief was achieved. No severe acute and late side effects (Grade 3/4) were observed. Conclusions: Sectional image-based three-dimensional treatment planning on computed tomography and magnetic resonance imaging is feasible in definitive brachytherapy of endometrial carcinoma and enables by the use of dwell time and location adaptation a sufficient coverage of GTV and major parts of CTV. Local control in this limited number of patients is excellent and rate of side effects minimal.« less
  • Purpose: Despite improvements of HDR brachytherapy delivery systems, verification of source position is still typically based on the length of the wire reeled out relative to the parked position. Yet, the majority of errors leading to medical events in HDR treatments continue to be classified as missed targets or wrong treatment sites. We investigate the feasibility of using dose maps acquired with a two-dimensional diode array to independently verify the source locations, dwell times, and dose during an HDR treatment. Methods: Custom correction factors were integrated into frame-by-frame raw counts recorded for a Varian VariSource™ HDR afterloader Ir-192 source locatedmore » at various distances in air and in solid water from a MapCHECK2™ diode array. The resultant corrected counts were analyzed to determine the dwell position locations and doses delivered. The local maxima of polynomial equations fitted to the extracted dwell dose profiles provided the X and Y coordinates while the distance to the source was determined from evaluation of the full width at half maximum (FWHM). To verify the approach, the experiment was repeated as the source was moved through dwell positions at various distances along an inclined plane, mimicking a vaginal cylinder treatment. Results: Dose map analysis was utilized to provide the coordinates of the source and dose delivered over each dwell position. The accuracy in determining source dwell positions was found to be +/−1.0 mm of the preset values, and doses within +/−3% of those calculated by the BrachyVision™ treatment planning system for all measured distances. Conclusion: Frame-by-frame data furnished by a 2 -D diode array can be used to verify the dwell positions and doses delivered by the HDR source over the course of treatment. Our studies have verified that measurements provided by the MapCHECK2™ can be used as a routine QA tool for HDR treatment delivery verification.« less
  • Purpose: For tandem and ovoid (T&O) HDR brachytherapy in our clinic, it is required that the planning physicist manually capture ∼10 images during planning, perform a secondary dose calculation and generate a report, combine them into a single PDF document, and upload it to a record- and-verify system to prove to an independent plan checker that the case was planned correctly. Not only does this slow down the already time-consuming clinical workflow, the PDF document also limits the number of parameters that can be checked. To solve these problems, we have developed a web-based automatic quality assurance (QA) program. Methods:more » We set up a QA server accessible through a web- interface. A T&O plan and CT images are exported as DICOMRT files and uploaded to the server. The software checks 13 geometric features, e.g. if the dwell positions are reasonable, and 10 dosimetric features, e.g. secondary dose calculations via TG43 formalism and D2cc to critical structures. A PDF report is automatically generated with errors and potential issues highlighted. It also contains images showing important geometric and dosimetric aspects to prove the plan was created following standard guidelines. Results: The program has been clinically implemented in our clinic. In each of the 58 T&O plans we tested, a 14- page QA report was automatically generated. It took ∼45 sec to export the plan and CT images and ∼30 sec to perform the QA tests and generate the report. In contrast, our manual QA document preparation tooks on average ∼7 minutes under optimal conditions and up to 20 minutes when mistakes were made during the document assembly. Conclusion: We have tested the efficiency and effectiveness of an automated process for treatment plan QA of HDR T&O cases. This software was shown to improve the workflow compared to our conventional manual approach.« less
  • Purpose: Plan specific quality assurance (QA) is an important step in high dose rate (HDR) brachytherapy to ensure the integrity of a treatment plan. The conventional approach is to assemble a set of plan screen-captures in a document and have an independent plan-checker to verify it. Not only is this approach cumbersome and time-consuming, using a document also limits the items that can be verified, hindering plan quality and patient safety. We have initiated efforts to develop a web-based HDR brachytherapy QA system called AutoBrachy QA, for comprehensive and efficient QA. This abstract reports a new plugin in this systemmore » for the QA of a cylinder HDR brachytherapy treatment. Methods: A cylinder plan QA module was developed using Python. It was plugged into our AutoBrachy QA system. This module extracted information from CT images and treatment plan. Image processing techniques were employed to obtain geometric parameters, e.g. cylinder diameter. A comprehensive set of eight geometrical and eight dosimetric features of the plan were validated against user specified planning parameter, such as prescription value, treatment depth and length, etc. A PDF document was generated, consisting of a summary QA sheet with all the QA results, as well as images showing plan details. Results: The cylinder QA program has been implemented in our clinic. To date, it has been used in 11 patient cases and was able to successfully perform QA tests in all of them. The QA program reduced the average plan QA time from 7 min using conventional manual approach to 0.5 min. Conclusion: Being a new module in our AutoBrachy QA system, an automated treatment plan QA module for cylinder HDR brachytherapy has been successfully developed and clinically implemented. This module improved clinical workflow and plan integrity compared to the conventional manual approach.« less