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Xiao Q, Li G. Application and Challenges of Statistical Process Control in Radiation Therapy Quality Assurance. Int J Radiat Oncol Biol Phys 2024; 118:295-305. [PMID: 37604239 DOI: 10.1016/j.ijrobp.2023.08.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 07/21/2023] [Accepted: 08/08/2023] [Indexed: 08/23/2023]
Abstract
Quality assurance (QA) is important for ensuring precision in radiation therapy. The complexity and resource-intensive nature of QA has increased with the continual evolution of equipment and techniques. An effective approach is to improve the process control technology and resource optimization. Statistical process control is an economical and efficient tool that has been widely used to monitor, control, and improve quality management processes and is now being increasingly used for radiation therapy QA. This article reviews the development and methodology of statistical process control technology, evaluates its suitability in radiation therapy QA practices, and assesses its importance and challenges in optimizing radiation therapy QA processes.
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Affiliation(s)
- Qing Xiao
- Department of Radiation Oncology, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China; Department of Radiotherapy Physics & Technology, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Guangjun Li
- Department of Radiation Oncology, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China; Department of Radiotherapy Physics & Technology, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
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Raveendran V, R GR, P T A, Bhasi S, C P R, Kinhikar RA. Moving towards process-based radiotherapy quality assurance using statistical process control. Phys Med 2023; 112:102651. [PMID: 37562233 DOI: 10.1016/j.ejmp.2023.102651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 07/16/2023] [Accepted: 08/01/2023] [Indexed: 08/12/2023] Open
Abstract
Monitoring Radiotherapy Quality Assurance (QA) using Statistical Process Control (SPC) methods has gained wide acceptance. The significance of understanding the SPC methodologies has increased among the medical physics community with the release of Task Group (TG) reports from the American Association of Physicists in Medicine (AAPM) on patient-specific QA (PSQA) (TG-218) and Proton therapy QA (TG-224). Even though these reports recommend using SPC for QA analysis, physicists have ambiguities and doubts in choosing proper SPC tools and methodologies. This review article summarises the utilisation of SPC methods for different Radiotherapy QAs published in the literature, such as PSQA, routine Linac QA and patient positional verification. QA analysis using SPC could assist the user in distinguishing between 'special' and 'routine' sources of variations in the QA, which can aid in reducing actions on false positive QA results. For improved PSQA monitoring, machine-specific, site-specific, and technique-specific Tolerance Limits and Action Limits derived from a two-stage SPC-based approach can be used. Adopting a combination of Shewhart's control charts and time-weighted control charts for routine Linac QA monitoring could add more insights to the QA process. Incorporating SPC tools into existing image review modules or introducing new SPC software packages specifically designed for clinical use can significantly enhance the image review process. Proper selection and having adequate knowledge of SPC tools are essential for efficient QA monitoring, which is a function of the type of QA data available, and the magnitude of process drift to be monitored.
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Affiliation(s)
- Vysakh Raveendran
- Department of Radiation Oncology, Advanced Centre for Treatment Research and Education in Cancer, Tata Memorial Centre, Homi Bhabha National Institute, Navi Mumbai, Maharashtra, India.; Department of Physics, Noorul Islam Centre for Higher Education, Kumaracoil, Kanyakumari District, Tamil Nadu, India..
| | - Ganapathi Raman R
- Department of Physics, Saveetha Engineering College (Autonomous), Chennai, Tamil Nadu, India
| | - Anjana P T
- Department of Radiation Oncology, Advanced Centre for Treatment Research and Education in Cancer, Tata Memorial Centre, Homi Bhabha National Institute, Navi Mumbai, Maharashtra, India
| | - Saju Bhasi
- Division of Radiation Physics, Regional Cancer Centre, Trivandrum, India
| | - Ranjith C P
- Department of Radiation Oncology, Advanced Centre for Treatment Research and Education in Cancer, Tata Memorial Centre, Homi Bhabha National Institute, Navi Mumbai, Maharashtra, India
| | - Rajesh Ashok Kinhikar
- Department of Medical Physics, Tata Memorial Centre, Homi Bhabha National Institute Parel, Mumbai, India
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Li G, Xiao Q, Dai G, Wang Q, Bai L, Zhang X, Zhang X, Duan L, Zhong R, Bai S. Guaranteed performance of individual control chart used in gamma passing rate-based patient-specific quality assurance. Phys Med 2023; 109:102581. [PMID: 37084678 DOI: 10.1016/j.ejmp.2023.102581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 03/20/2023] [Accepted: 04/06/2023] [Indexed: 04/23/2023] Open
Abstract
PURPOSE To assess the effect of sampling variability on the performance of individual charts (I-charts) for PSQA and provide a robust and reliable method for unknown PSQA processes. MATERIALS AND METHODS A total of 1327 pretreatment PSQAs were analyzed. Different datasets with samples in the range of 20-1000 were used to estimate the lower control limit (LCL). Based on the iterative "Identify-Eliminate-Recalculate" and direct calculation without any outlier filtering procedures, five I-charts methods, namely the Shewhart, quantile, scaled weighted variance (SWV), weighted standard deviation (WSD), and skewness correction (SC) method, were used to compute the LCL. The average run length (ARL0) and false alarm rate (FAR0) were calculated to evaluate the performance of LCL. RESULTS The ground truth of the values of LCL, FAR0, and ARL0 obtained via in-control PSQAs were 92.31%, 0.135%, and 740.7, respectively. Further, for in-control PSQAs, the width of the 95% confidence interval of LCL values for all methods tended to decrease with the increase in sample size. In all sample ranges of in-control PSQAs, only the median LCL and ARL0 values obtained via WSD and SWV methods were close to the ground truth. For the actual unknown PSQAs, based on the "Identify-Eliminate-Recalculate" procedure, only the median LCL values obtained by the WSD method were closest to the ground truth. CONCLUSIONS Sampling variability seriously affected the I-chart performance in PSQA processes, particularly for small samples. For unknown PSQAs, the WSD method based on the implementation of the iterative "Identify-Eliminate-Recalculate" procedure exhibited sufficient robustness and reliability.
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Affiliation(s)
- Guangjun Li
- Radiotherapy Physics & Technology Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Qing Xiao
- Radiotherapy Physics & Technology Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Guyu Dai
- Radiotherapy Physics & Technology Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Qiang Wang
- Radiotherapy Physics & Technology Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Long Bai
- Radiotherapy Physics & Technology Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Xiangbin Zhang
- Radiotherapy Physics & Technology Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Xiangyu Zhang
- Radiotherapy Physics & Technology Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Lian Duan
- Department of Radiation Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia 19104, United States
| | - Renming Zhong
- Radiotherapy Physics & Technology Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Sen Bai
- Radiotherapy Physics & Technology Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China; Department of Radiation Oncology, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China.
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Jiménez-Melguizo M, Espinosa M, Montes J, Guirado D, Lallena AM. Response of the ArcCHECK® device at 6 MV and 15 MV for VMAT and IMRT quality control. Phys Med 2020; 80:373-382. [PMID: 33310373 DOI: 10.1016/j.ejmp.2020.11.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 11/10/2020] [Accepted: 11/14/2020] [Indexed: 10/22/2022] Open
Abstract
PURPOSE To study the response of the ArcCHECK® device as VMAT and IMRT verification system. METHODS Various tests analyzing the linearity, the repeatability and the angular dependence of the device response, its dependence with the pulse repetition rate and the leakage losses were performed. The long-term response in dose measurements and the uniformity of the detectors conforming the system were controlled using a statistical process control program. The Elekta Infinity™ 6 and 15MV photon beams were used. RESULTS The device showed excellent repeatability and linearity. The differences between the responses obtained for any pair of angular incidences were less than 2%. The absorbed dose increased by 3% when the pulse repetition rate varied from 50 to 600MU/min. Results are in overall agreement with those found in previous works for the ArcCHECK®, in which a reduced number of the device diodes were analyzed, and for the MapCheck®, an older 2D device that used the same diodes. Charge losses were found to be negligible except for some of the diodes of the device. The statistical process control program is a very useful tool to control the correct functioning of the device in the long term. CONCLUSIONS The results of the analysis carried out indicate that the working and stability conditions of the ArcCHECK® device are adequate for its purpose. The dependence with the pulse repetition rate should be considered when VMAT or similar treatments are evaluated. A control program for the statistical monitoring of the device would be desirable and useful.
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Affiliation(s)
- Miguel Jiménez-Melguizo
- Servicio de Radiofísica y Protección Radiológica, Hospital Universitario "Virgen de las Nieves", E-18014 Granada, Spain; Unidad de Radiofísica, Hospital Universitario Clínico "San Cecilio", E-18016 Granada, Spain
| | - Miguel Espinosa
- Unidad de Radiofísica, Hospital Universitario Clínico "San Cecilio", E-18016 Granada, Spain
| | - Joaquín Montes
- Unidad de Radiofísica, Hospital Universitario Clínico "San Cecilio", E-18016 Granada, Spain
| | - Damián Guirado
- Unidad de Radiofísica, Hospital Universitario Clínico "San Cecilio", E-18016 Granada, Spain; Instituto de Investigación Biosanitaria (ibs.GRANADA), Complejo Hospitalario Universitario de Granada/Universidad de Granada, E-18016 Granada, Spain; CIBER de Epidemiología y Salud Pública (CIBERESP), Granada, Spain
| | - Antonio M Lallena
- Instituto de Investigación Biosanitaria (ibs.GRANADA), Complejo Hospitalario Universitario de Granada/Universidad de Granada, E-18016 Granada, Spain; Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada, Spain
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Tiplica T, Dufreneix S, Legrand C. A Bayesian control chart based on the beta distribution for monitoring the two-dimensional gamma index pass rate in the context of patient-specific quality assurance. Med Phys 2020; 47:5408-5418. [PMID: 32970863 DOI: 10.1002/mp.14472] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 09/01/2020] [Accepted: 09/03/2020] [Indexed: 11/06/2022] Open
Abstract
PURPOSE In the context of quality assurance in intensity modulated radiation therapy (IMRT), the aim of this work was two-fold: (a) to show that the beta distribution characterizes the two-dimensional gamma index pass rate (GIPR), and that the quantiles of the distribution should be used in order to compute the control limit (CL) for the detection of abnormally low GIPR, and (b) to introduce a Bayesian control chart that allows calculation of CLs from the first measurement. METHODS In order to enable monitoring of the GIPR from the first measurement, we developed a Bayesian control chart based on the beta distribution, elaborated according to the following two steps: (a) an iterative bayesian inference approach without any prior information on the GIPR distribution was used at the start of monitoring and the CL was progressively updated; and (b) when sufficient in-control arcs had been recorded and the estimators of the parameters of the beta distribution were sufficiently accurate, the CL of the chart was fixed to a constant value corresponding to the quantile of the beta distribution. The clinical utility of this approach is illustrated through a real data case study: monitoring the GIPR of patients treated with a moving gantry IMRT technique RapidArcTM on a Novalis TrueBeam STx (Varian Medical Systems) linear accelerator equipped with an aS1200 electronic portal imager device. RESULTS We showed that some commonly used distributions for monitoring GIPR in the literature, such as normal or logarithm transformation, are not appropriate. We compared the CLs of those solutions with the CL of our chart based on the BD (CL = 95.14%). The comparison revealed that the CL for the normal law (CL = 97.62%) generated too many false positives, and that the CL of the Logarithm transformation (CL = 83.74%) could fail to efficiently detect (i.e., sufficiently early on or faster) changes in the process. CONCLUSIONS Successful GIPR monitoring requires careful and rigorous application of well-established statistical concepts in the field of statistical process control. In this paper, we stress the importance of carefully analyzing the distribution of the monitored characteristic that is plotted on the control chart. We propose a Bayesian control chart that can be viewed as a practical solution for early implementation of GIPR monitoring, starting from the first arc. We demonstrate that beta distribution is a better method for characterizing the GIPR, and thus, the use of this approach is expected to improve patient-specific quality assurance plans in radiotherapy.
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Affiliation(s)
- Teodor Tiplica
- LARIS Systems Engineering Research Laboratory, University of Angers, Angers, France
| | - Stéphane Dufreneix
- Department of Medical Physics, Institut de Cancérologie de l'Ouest, Angers, France
| | - Christophe Legrand
- Department of Medical Physics, Institut de Cancérologie de l'Ouest, Angers, France
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Meyers SM, Balderson MJ, Létourneau D. Evaluation of Elekta Agility multi-leaf collimator performance using statistical process control tools. J Appl Clin Med Phys 2019; 20:100-108. [PMID: 31199568 PMCID: PMC6612682 DOI: 10.1002/acm2.12660] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 05/03/2019] [Accepted: 05/23/2019] [Indexed: 12/15/2022] Open
Abstract
Purpose To evaluate the performance and stability of Elekta Agility multi‐leaf collimator (MLC) leaf positioning using a daily, automated quality control (QC) test based on megavoltage (MV) images in combination with statistical process control tools, and identify special causes of variations in performance. Methods Leaf positions were collected daily for 13 Elekta linear accelerators over 11‐37 months using the automated QC test, which analyzes 23 MV images to determine the location of MLC leaves relative to radiation isocenter. Leaf positioning stability was assessed using individual and moving range control charts. Specification levels of ±0.5, ±1, and ±1.5 mm were tested to determine positional accuracy. The durations between out‐of‐control and out‐of‐specification events were determined. Peaks in out‐of‐control leaf positions were identified and correlated to servicing events recorded for the whole duration of data collection. Results Mean leaf position error was −0.01 mm (range −1.3–1.6). Data stayed within ±1 mm specification for 457 days on average (range 3–838) and within ±1.5 mm for the entire date range. Measurements stayed within ±0.5 mm for 1 day on average (range 0–17); however, our MLC leaves were not calibrated to this level of accuracy. Leaf position varied little over time, as confirmed by tight individual (mean ±0.19 mm, range 0.09–0.43) and moving range (mean 0.23 mm, range 0.10–0.53) control limits. Due to sporadic out‐of‐control events, the mean in‐control duration was 2.8 days (range 1–28.5). A number of factors were found to contribute to leaf position errors and out‐of‐control behavior, including servicing events, beam spot motion, and image artifacts. Conclusions The Elekta Agility MLC model was found to perform with high stability, as evidenced by the tight control limits. The in‐specification durations support the current recommendation of monthly MLC QC tests with a ±1 mm tolerance. Future work is on‐going to determine if performance can be optimized further using high‐frequency QC test results to drive recalibration frequency.
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Affiliation(s)
- Sandra M Meyers
- Radiation Medicine Program, Princess Margaret Cancer Center, Toronto, Ontario, Canada.,Department of Radiation Medicine and Applied Sciences, Moores Cancer Center, University of California, San Diego, La Jolla, California
| | - Michael J Balderson
- Radiation Medicine Program, Princess Margaret Cancer Center, Toronto, Ontario, Canada
| | - Daniel Létourneau
- Radiation Medicine Program, Princess Margaret Cancer Center, Toronto, Ontario, Canada.,Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
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Meyer J, Nyflot MJ, Smith WP, Wottoon LS, Young L, Yang F, Kim M, Hendrickson KRG, Ford E, Kalet AM, Cao N, Dempsey C, Sandison GA. Electron beam energy QA - a note on measurement tolerances. J Appl Clin Med Phys 2016; 17:249-257. [PMID: 27074488 PMCID: PMC5875568 DOI: 10.1120/jacmp.v17i2.6049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2015] [Revised: 11/24/2015] [Accepted: 11/17/2015] [Indexed: 11/29/2022] Open
Abstract
Monthly QA is recommended to verify the constancy of high‐energy electron beams generated for clinical use by linear accelerators. The tolerances are defined as 2%/2 mm in beam penetration according to AAPM task group report 142. The practical implementation is typically achieved by measuring the ratio of readings at two different depths, preferably near the depth of maximum dose and at the depth corresponding to half the dose maximum. Based on beam commissioning data, we show that the relationship between the ranges of energy ratios for different electron energies is highly nonlinear. We provide a formalism that translates measurement deviations in the reference ratios into change in beam penetration for electron energies for six Elekta (6‐18 MeV) and eight Varian (6‐22 MeV) electron beams. Experimental checks were conducted for each Elekta energy to compare calculated values with measurements, and it was shown that they are in agreement. For example, for a 6 MeV beam a deviation in the measured ionization ratio of ±15% might still be acceptable (i.e., be within ±2 mm), whereas for an 18 MeV beam the corresponding tolerance might be ±6%. These values strongly depend on the initial ratio chosen. In summary, the relationship between differences of the ionization ratio and the corresponding beam energy are derived. The findings can be translated into acceptable tolerance values for monthly QA of electron beam energies. PACS number(s): 87.55, 87.56
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López-Tarjuelo J, Quirós-Higueras JD, Bonaque-Alandí J, Luquero-Llopis N, García-Mollá R, Juan-Senabre XJ, de Marco-Blancas N, Ferrer-Albiach C, Santos-Serra A. What can statistical process control show us about ionization chamber stability? RADIAT MEAS 2016. [DOI: 10.1016/j.radmeas.2015.12.041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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López-Tarjuelo J, Luquero-Llopis N, García-Mollá R, Quirós-Higueras JD, Bouché-Babiloni A, Juan-Senabre XJ, de Marco-Blancas N, Ferrer-Albiach C, Santos-Serra A. Statistical process control for electron beam monitoring. Phys Med 2015; 31:493-500. [PMID: 26032002 DOI: 10.1016/j.ejmp.2015.05.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 04/28/2015] [Accepted: 05/12/2015] [Indexed: 11/16/2022] Open
Abstract
PURPOSE To assess the electron beam monitoring statistical process control (SPC) in linear accelerator (linac) daily quality control. We present a long-term record of our measurements and evaluate which SPC-led conditions are feasible for maintaining control. METHODS We retrieved our linac beam calibration, symmetry, and flatness daily records for all electron beam energies from January 2008 to December 2013, and retrospectively studied how SPC could have been applied and which of its features could be used in the future. A set of adjustment interventions designed to maintain these parameters under control was also simulated. RESULTS All phase I data was under control. The dose plots were characterized by rising trends followed by steep drops caused by our attempts to re-center the linac beam calibration. Where flatness and symmetry trends were detected they were less-well defined. The process capability ratios ranged from 1.6 to 9.3 at a 2% specification level. Simulated interventions ranged from 2% to 34% of the total number of measurement sessions. We also noted that if prospective SPC had been applied it would have met quality control specifications. CONCLUSIONS SPC can be used to assess the inherent variability of our electron beam monitoring system. It can also indicate whether a process is capable of maintaining electron parameters under control with respect to established specifications by using a daily checking device, but this is not practical unless a method to establish direct feedback from the device to the linac can be devised.
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Affiliation(s)
- Juan López-Tarjuelo
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Avda. Dr. Clará 19, Castellón de la Plana 12002, Castellón, Spain.
| | - Naika Luquero-Llopis
- Fundación Hospital Provincial de Castellón, Avda. Dr. Clará 19, Castellón de la Plana 12002, Castellón, Spain
| | - Rafael García-Mollá
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Avda. Dr. Clará 19, Castellón de la Plana 12002, Castellón, Spain
| | - Juan David Quirós-Higueras
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Avda. Dr. Clará 19, Castellón de la Plana 12002, Castellón, Spain
| | - Ana Bouché-Babiloni
- Servicio de Oncología Radioterápica, Consorcio Hospitalario Provincial de Castellón, Avda. Dr. Clará 19, Castellón de la Plana 12002, Castellón, Spain
| | - Xavier Jordi Juan-Senabre
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Avda. Dr. Clará 19, Castellón de la Plana 12002, Castellón, Spain
| | - Noelia de Marco-Blancas
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Avda. Dr. Clará 19, Castellón de la Plana 12002, Castellón, Spain
| | - Carlos Ferrer-Albiach
- Servicio de Oncología Radioterápica, Consorcio Hospitalario Provincial de Castellón, Avda. Dr. Clará 19, Castellón de la Plana 12002, Castellón, Spain; Facultad de Medicina, Universidad Cardenal Herrera-CEU, C/ Grecia 31, Castellón de la Plana 12006, Castellón, Spain
| | - Agustín Santos-Serra
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Avda. Dr. Clará 19, Castellón de la Plana 12002, Castellón, Spain
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de la Vega JM, Ruiz-Arrebola S, Tornero-López AM, Vilches M, Guerrero R, Guirado D, Lallena AM. A method to relate StarTrack(®) measurements to R50 variations in clinical linacs. Phys Med 2014; 30:827-32. [PMID: 24735905 DOI: 10.1016/j.ejmp.2014.03.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 03/18/2014] [Accepted: 03/19/2014] [Indexed: 11/16/2022] Open
Abstract
The relation between the data recorded with any device for the daily checking of the behavior of a clinical linac and the reference magnitudes to be monitored may be unknown. An experimental method relating the energy stability of the electron beam measured with StarTrack(®) to the R50 beam quality index is proposed. The bending magnet current is varied producing a change in the exit energy window and, therefore, a modification of the R50 value. For different values of this current, the output data of StarTrack(®) and the R50, obtained from depth doses measured in a water phantom are determined. A linear fit between both sets of data allows the identification of the StarTrack(®) output that provides the best way to obtain the quality index R50, for each beam nominal energy. Using these fits, an historical datum series is used to analyze the method proposed in the daily quality control. The ouput data of the StarTrack(®) and the R50 values show a good linear correlation. It is possible to establish a methodology that allows the monitoring of R50 by direct use of the daily quality control data measured with StarTrack(®). A method to monitor R50 in the daily quality control using the StarTrack(®) device has been developed. The method may be applied to similar devices in which the statistical control variable does not show a linear behavior with R50.
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Affiliation(s)
- J M de la Vega
- Servicio de Radiofísica, Hosp. Univ. "San Cecilio", Avda Dr. Olóriz, 16, E-18012 Granada, Spain.
| | - S Ruiz-Arrebola
- Departamento de Oncología Radioterápica, Clínica Santa María, Avda Santa María, 0500, 7520378 Santiago de Chile, Chile
| | - A M Tornero-López
- Servicio de Radiofísica, Hosp. Univ. "San Cecilio", Avda Dr. Olóriz, 16, E-18012 Granada, Spain
| | - M Vilches
- Unidad de Radiofísica, IMOMA (Instituto de Medicina Oncológica y Molecular de Asturias), Avda Richard Gangrio, s/n, E-33193 Oviedo, Spain
| | - R Guerrero
- Servicio de Radiofísica, Hosp. Univ. "San Cecilio", Avda Dr. Olóriz, 16, E-18012 Granada, Spain
| | - D Guirado
- Servicio de Radiofísica, Hosp. Univ. "San Cecilio", Avda Dr. Olóriz, 16, E-18012 Granada, Spain
| | - A M Lallena
- Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada, Spain
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Nordström F, af Wetterstedt S, Johnsson S, Ceberg C, Bäck SJ. Control chart analysis of data from a multicenter monitor unit verification study. Radiother Oncol 2012; 102:364-70. [PMID: 22239866 DOI: 10.1016/j.radonc.2011.11.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Revised: 11/10/2011] [Accepted: 11/28/2011] [Indexed: 11/25/2022]
Abstract
BACKGROUND AND PURPOSE This study aims to investigate the process of monitor unit verification using control charts. Control charts is a key tool within statistical process control (SPC), through which process characteristics can be visualized, usually chronologically with statistically determined limits. MATERIAL AND METHODS Our group has developed a monitor unit verification software that has been adopted at several Swedish institutions for pre-treatment verification of radiotherapy treatments. Deviations between point dose calculations using the treatment planning systems and using the independent monitor unit verification software from 9219 treatment plans and five different institutions were included in this multicenter study. The process of monitor unit verification was divided into subprocesses. Each subprocess was analyzed using probability plots and control charts. RESULTS Differences in control chart parameters for the investigated subprocesses were found between different treatment sites and different institutions, as well as between different treatment techniques. 19 of 37 subprocesses met the clinical specification (± 5%), i.e. process capability index was equal to or above one. CONCLUSIONS Control charts were found to be a useful tool for continuous analysis of data from the monitor unit verification software for patient specific quality control, as well as for comparisons between different institutions and treatment sites. The derived control chart limits were in agreement with AAPM TG114 guidelines on action levels.
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Affiliation(s)
- Fredrik Nordström
- Department of Medical Radiation Physics, Lund University, Malmö, Sweden.
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