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Andersen CE. Magnetic field influence on the light yield from fiber-coupled BCF-60 plastic scintillators of relevance for output factor dosimetry in MR-linacs. Biomed Phys Eng Express 2023; 10:015016. [PMID: 38064731 DOI: 10.1088/2057-1976/ad13aa] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Accepted: 12/08/2023] [Indexed: 12/20/2023]
Abstract
Organic plastic scintillators are of interest for ionizing radiation dosimetry in megavoltage photon beams because plastic scintillators have a mass density very similar to that of water. This leads to insignificant perturbation of the electron fluence at the point of measurement in a water phantom. This feature is a benefit for dosimetry in strong magnetic fields (e.g., 1.5 T) as found in linacs with magnetic resonance imaging. The objective of this work was to quantify if the light yield per dose for the scintillating fiber BCF-60 material from Saint-Gobain Ceramics and Plastics Inc. is constant regardless of the magnetic flux density. This question is of importance for establishing traceable measurement in MR linacs using this detector type. Experiments were carried out using an accelerator combined with an electromagnet (max 0.7 T). Scintillator probes were read out using chromatic stem-removal techniques based on two optical channels or full spectral information. Reference dosimetry was carried out with PTW31010 and PTW31021 ionization chambers. TOPAS/GEANT4 was used for modelling. The light yield per dose for the BCF-60 was found to be strongly influenced by the magnitude of the magnetic field from about 1 mT to 0.7 T. The light yield per dose increased (1.3 ± 0.2)% (k = 1) from 1 mT to 10 mT and it increased (4.5 ± 0.9)% (k = 1) from 0 T to 0.7 T. Previous studies of the influence of magnetic fields on medical scintillator dosimetry have been unable to clearly identify if observed changes in scintillator response with magnetic field strength were related to changes in dose, stem signal removal, or scintillator light yield. In the current study of BCF-60, we see a clear change in light yield with magnetic field, and none of the other effects.
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Affiliation(s)
- Claus E Andersen
- DTU Health Tech, Technical University of Denmark, 4000 Roskilde, Denmark
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2
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Tho D, Lavallée M, Beaulieu L. A scintillation dosimeter with real-time positional tracking information for in vivo dosimetry error detection in HDR brachytherapy. J Appl Clin Med Phys 2023; 24:e14150. [PMID: 37731203 PMCID: PMC10691625 DOI: 10.1002/acm2.14150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 07/26/2023] [Accepted: 08/09/2023] [Indexed: 09/22/2023] Open
Abstract
PURPOSE To evaluate the performance of an electromagnetic (EM)-tracked scintillation dosimeter in detecting source positional errors of IVD in HDR brachytherapy treatment. MATERIALS AND METHODS Two different scintillator dosimeter prototypes were coupled to 5 degrees-of-freedom (DOF) EM sensors read by an Aurora V3 system. The scintillators used were a 0.3 × 0.4 × 0.4 mm3 ZnSe:O and a BCF-60 plastic scintillator of 0.5 mm diameter and 2.0 mm in length (Saint-Gobain Crystals). The sensors were placed at the dosimeter's tip at 20.0 mm from the scintillator. The EM sampling rate was 40/s while the scintillator signal was sampled at 100 000/s using two photomultiplier tubes from Hamamatsu (series H10722) connected to a data acquisition board. A high-pass filter and a low-pass filter were used to separate the light signal into two different channels. All measurements were performed with an afterloader unit (Flexitron-Elekta AB, Sweden) in full-scattered (TG43) conditions. EM tracking was further used to provide distance/angle-dependent energy correction for the ZnSe:O inorganic scintillator. For the error detection part, lateral shifts of 0.5 to 3 mm were induced by moving the source away from its planned position. Indexer length (longitudinal) errors between 0.5 to 10 mm were also introduced. The measured dose rate difference was converted to a shift distance, with and without using the positional information from the EM sensor. RESULTS The inorganic scintillator had both a signal-to-noise-ratio (SNR) and signal-to-background-ratio (SBR) close to 70 times higher than those of the plastic scintillator. The mean absolute difference from the dose measurement to the dose calculated with TG-43U1 was 1.5% ±0.7%. The mean absolute error for BCF-60 detector was 1.7%± 1.2 % $\pm 1.2\%$ when compared to TG-43 calculations formalism. With the inorganic scintillator and EM tracking, a maximum area under the curve (AUC) gain of 24.0% was obtained for a 0.5-mm lateral shift when using the EMT data with the ZnSe:O. Lower AUC gains were obtained for a 3-mm lateral shifts with both scintillators. For the plastic scintillator, the highest gain from using EM tracking information occurred for a 0.5-mm lateral shift at 20 mm from the source. The maximal gain (17.4%) for longitudinal errors was found at the smallest shifts (0.5 mm). CONCLUSIONS This work demonstrates that integrating EM tracking to in vivo scintillation dosimeters enables the detection of smaller shifts, by decreasing the dosimeter positioning uncertainty. It also serves to perform position-dependent energy correction for the inorganic scintillator,providing better SNR and SBR, allowing detection of errors at greater distances from the source.
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Affiliation(s)
- Daline Tho
- Department of Radiation OncologyThe University of Texas MD Anderson Cancer CenterHoustonTexasUSA
| | - Marie‐Claude Lavallée
- Département de physique, de génie physique et d'optique, et Centre de recherche sur le cancerUniversité LavalQuébecQuébecCanada
- Service de physique médicale et de radioprotection, Centre intégré de cancérologieCHU de Québec‐Université Laval et Centre de recherche du CHU de QuébecQuébecCanada
| | - Luc Beaulieu
- Département de physique, de génie physique et d'optique, et Centre de recherche sur le cancerUniversité LavalQuébecQuébecCanada
- Service de physique médicale et de radioprotection, Centre intégré de cancérologieCHU de Québec‐Université Laval et Centre de recherche du CHU de QuébecQuébecCanada
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Klavsen MF, Ankjærgaard C, Boye K, Behrens CP, Vogelius IR, Ehrbar S, Baumgartl M, Rippke C, Buchele C, Renkamp CK, Santurio GV, Andersen CE. Accumulated dose implications from systematic dose-rate transients in gated treatments with Viewray MRIdian accelerators. Biomed Phys Eng Express 2023; 9:065001. [PMID: 37591227 DOI: 10.1088/2057-1976/acf138] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 08/17/2023] [Indexed: 08/19/2023]
Abstract
The combination of magnetic resonance (MR) imaging and linear accelerators (linacs) into MR-Linacs enables continuous MR imaging and advanced gated treatments of patients. Previously, a dose-rate transient (∼8% reduced dose rate during the initial 0.5 s of each beam) was identified for a Viewray MRIdian MR-Linac (Klavsenet al2022Radiation Measurement106759). Here, the dose-rate transient is studied in more detail at four linacs of the same type at different hospitals. The implications of dose-rate transients were examined for gated treatments. The dose-rate transients were investigated using dose-per pulse measurements with organic plastic scintillators in three experiments: (i) A gated treatment with the scintillator placed in a moving target in a dynamic phantom, (ii) a gated treatment with the same dynamic conditions but with the scintillator placed in a stationary target, and (iii) measurements in a water-equivalent material to examine beam quality deviations at a dose-per-pulse basis. Gated treatments (i) compared with non-gated treatments with a static target in the same setup showed a broadening of accumulated dose profiles due to motion (dose smearing). The linac with the largest dose-rate transient had a reduced accumulated dose of up to (3.1 ± 0.65) % in the center of the PTV due to the combined dose smearing and dose-rate transient effect. Dose-rate transients were found to vary between different machines. Two MR-Linacs showed initial dose-rate transients that could not be identified from conventional linearity tests. The source of the transients includes an initial change in photon fluence rate and an initial change in x-ray beam quality. For gated treatments, this caused a reduction of more than 1% dose delivered at the central part of the beam for the studied, cyclic-motion treatment plan. Quality assurance of this effect should be considered when gated treatment with the Viewray MRIdian is implemented clinically.
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Affiliation(s)
- M F Klavsen
- DTU Health Tech, Technical University of Denmark, Roskilde, Denmark
| | - C Ankjærgaard
- DTU Health Tech, Technical University of Denmark, Roskilde, Denmark
| | - K Boye
- Dept. of Oncology, Copenhagen University Hospital-Rigshospitalet, Copenhagen, Denmark
| | - C P Behrens
- DTU Health Tech, Technical University of Denmark, Roskilde, Denmark
- Dept. of Oncology, Copenhagen University Hospital-Herlev and Gentofte, Copenhagen, Denmark
| | - I R Vogelius
- Dept. of Oncology, Copenhagen University Hospital-Rigshospitalet, Copenhagen, Denmark
- Faculty of Health and Medical Sciences, University of Copenhagen- Copenhagen, Denmark
| | - S Ehrbar
- Dept. of Radiation Oncology, University Hospital Zürich and University of Zürich, Zürich, Switzerland
| | - M Baumgartl
- Dept. of Radiation Oncology, University Hospital Zürich and University of Zürich, Zürich, Switzerland
| | - C Rippke
- Dept. of Oncology, University Hospital Heidelberg, Heidelberg, Germany
| | - C Buchele
- Dept. of Oncology, University Hospital Heidelberg, Heidelberg, Germany
| | - C K Renkamp
- Dept. of Oncology, University Hospital Heidelberg, Heidelberg, Germany
| | - G V Santurio
- Dept. of Oncology, Copenhagen University Hospital-Herlev and Gentofte, Copenhagen, Denmark
| | - C E Andersen
- DTU Health Tech, Technical University of Denmark, Roskilde, Denmark
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Jeong S, An S, Kwon YC, Pak SI, Cheon W, Shin D, Lim YK, Jeong JH, Kim H, Lee SB. Development of a real-time in vivo dosimetry tool for electron beam therapy using a flexible thin film solar cell coated with scintillator powder. Med Phys 2023; 50:557-569. [PMID: 35993665 DOI: 10.1002/mp.15947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 08/12/2022] [Accepted: 08/15/2022] [Indexed: 01/25/2023] Open
Abstract
PURPOSE A real-time solar cell based in vivo dosimetry system (SC-IVD) was developed using a flexible thin film solar cell and scintillating powder. The present study evaluated the clinical feasibility of the SC-IVD in electron beam therapy. METHODS A thin film solar cell was coated with 100 mg of scintillating powder using an optical adhesive to enhance the sensitivity of the SC-IVD. Calibration factors were obtained by dividing the dose, measured at a reference depth for 6-20 MeV electron beam energy, by the signal obtained using the SC-IVD. Dosimetric characteristics of SC-IVDs containing variable quantities of scintillating powder (0-500 mg) were evaluated, including energy, dose rate, and beam angle dependencies, as well as dose linearity. To determine the extent to which the SC-IVD affected the dose to the medium, doses at R90 were compared depending on whether the SC-IVD was on the surface. Finally, the accuracy of surface doses measured using the SC-IVD was evaluated by comparison with surface doses measured using a Markus chamber. RESULTS Charge measured using the SC-IVD increased linearly with dose and was within 1% of the average signal according to the dose rate. The signal generated by the SC-IVD increased as the beam angle increased. The presence of the SC-IVD on the surface of a phantom resulted in a 0.5%-2.2% reduction in dose at R90 for 6-20 MeV electron beams compared with the bare phantom. Surface doses measured using the SC-IVD system and Markus chamber differed by less than 5%. CONCLUSIONS The dosimetric characteristics of the SC-IVD were evaluated in this study. The results showed that it accurately measured the surface dose without a significant difference of dose in the medium when compared with the Markus chamber. The flexibility of the SC-IVD allows it to be attached to a patient's skin, enabling real-time and cost-effective measurement.
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Affiliation(s)
- Seonghoon Jeong
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Seohyeon An
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea.,Department of Physics, Hanyang University, Seoul, Republic of Korea
| | - Yong-Cheol Kwon
- Department of Radiation Oncology, Samsung Medical Center, Seoul, Republic of Korea
| | - Sang-Il Pak
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Wonjoong Cheon
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Dongho Shin
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Young Kyung Lim
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Jong Hwi Jeong
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Haksoo Kim
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
| | - Se Byeong Lee
- Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea
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In Vivo Verification of Treatment Source Dwell Times in Brachytherapy of Postoperative Endometrial Carcinoma: A Feasibility Study. J Pers Med 2022; 12:jpm12060911. [PMID: 35743696 PMCID: PMC9224704 DOI: 10.3390/jpm12060911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 05/24/2022] [Accepted: 05/28/2022] [Indexed: 11/17/2022] Open
Abstract
(1) Background: In brachytherapy, there are still many manual procedures that can cause adverse events which can be detected with in vivo dosimetry systems. Plastic scintillator dosimeters (PSD) have interesting properties to achieve this objective such as real-time reading, linearity, repeatability, and small size to fit inside brachytherapy catheters. The purpose of this study was to evaluate the performance of a PSD in postoperative endometrial brachytherapy in terms of source dwell time accuracy. (2) Methods: Measurements were carried out in a PMMA phantom to characterise the PSD. Patient measurements in 121 dwell positions were analysed to obtain the differences between planned and measured dwell times. (3) Results: The repeatability test showed a relative standard deviation below 1% for the measured dwell times. The relative standard deviation of the PSD sensitivity with accumulated absorbed dose was lower than 1.2%. The equipment operated linearly in total counts with respect to absorbed dose and also in count rate versus absorbed dose rate. The mean (standard deviation) of the absolute differences between planned and measured dwell times in patient treatments was 0.0 (0.2) seconds. (4) Conclusions: The PSD system is useful as a quality assurance tool for brachytherapy treatments.
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Time-resolved plastic scintillator dosimetry in MR linear accelerators without image distortion. RADIAT MEAS 2022. [DOI: 10.1016/j.radmeas.2022.106759] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Schoepper I, Dieterich S, Trestrail EA, Kent MS. Pre‐clinical and clinical evaluation of the HYPERSCINT plastic scintillation dosimetry research platform for in vivo dosimetry during radiotherapy. J Appl Clin Med Phys 2022; 23:e13551. [PMID: 35188331 PMCID: PMC8992935 DOI: 10.1002/acm2.13551] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Revised: 01/02/2022] [Accepted: 01/13/2022] [Indexed: 11/30/2022] Open
Abstract
Purpose The purpose of this work is to evaluate the Hyperscint‐RP100 scintillation dosimetry research platform (Hyperscint‐RP100, Medscint Inc., Quebec, QC, Canada) designed for clinical quality assurance (QA) for use in in vivo dosimetry measurements. Methods The pre‐clinical evaluation of the scintillator was performed using a Varian TrueBeam linear accelerator. Dependency on field size, depth, dose, dose rate, and temperature were evaluated in a water tank and compared to calibration data from commissioning and annual QA. Angularity was evaluated with a 3D printed phantom. The clinical evaluation was first performed in two cadaver dogs, and then in three companion animal dogs receiving radiation therapy for nasal tumors. A treatment planning CT scan was performed for cadavers and clinical patients. Prior to treatment, the probe was inserted into the radiation field. Radiation was then delivered and measured with the scintillator. For cadavers, the treatment was repeated after making an intentional shift in patient position to simulate a treatment error. Results In the preclinical measurements the dose differed from annual measurements as follows: field size −0.77 to 0.43%, depth dose −0.36 to 1.14%, dose −0.54 to 2.93%, dose rate 0.3 to 3.6%, and angularity −1.18 to 0.01%. Temperature dependency required a correction factor of 0.11%/°C. In the two cadavers, the dose differed by −1.17 to 0.91%. The device correctly detected the treatment error when the heads were intentionally laterally shifted. In three canine clinical patients treated in multiple fractions, the detected dose ranged from 98.33 to 103.15%. Conclusion Results of this new device are promising although more work is necessary to fully validate it for clinical dosimetry.
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Affiliation(s)
- Imke Schoepper
- Department of Radiation Oncology University of California Davis School of Veterinary Medicine Davis California USA
| | - Sonja Dieterich
- Department of Radiation Oncology University of California Davis Medical Center Sacramento California USA
| | | | - Michael Sean Kent
- Department of Radiation Oncology University of California Davis School of Veterinary Medicine Davis California USA
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Linares Rosales HM, Couture G, Archambault L, Beddar S, Després P, Beaulieu L. On the use of machine learning methods for mPSD calibration in HDR brachytherapy. Phys Med 2021; 91:73-79. [PMID: 34717139 DOI: 10.1016/j.ejmp.2021.10.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Revised: 07/15/2021] [Accepted: 10/02/2021] [Indexed: 11/17/2022] Open
Abstract
We sought to evaluate the feasibility of using machine learning (ML) algorithms for multipoint plastic scintillator detector (mPSD) calibration in high-dose-rate (HDR) brachytherapy. Dose measurements were conducted under HDR brachytherapy conditions. 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 192Ir source was remotely controlled and sent to various positions in a homemade PMMA holder, ensuring 0.1-mm positional accuracy. Dose measurements covering a range of 0.5 to 12 cm of source displacement were carried out according to TG-43 U1 recommendations. Individual scintillator doses were decoupled using a linear regression model, a random forest estimator, and artificial neural network algorithms. The dose predicted by the TG-43U1 formalism was used as the reference for system calibration and ML algorithm training. The performance of the different algorithms was evaluated using different sample sizes and distances to the source for the mPSD system calibration. We found that the calibration conditions influenced the accuracy in predicting the measured dose. The decoupling methods' deviations from the expected TG-43 U1 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 U1 formalism when measurements were performed in the same range of distances used for calibration. In such cases, the predictions with random forest exhibited minimal deviations (<2%). However, the performance random forest was compromised when the predictions were done beyond the range of distances used for calibration. Because the linear regression algorithm can extrapolate the data, the dose prediction by the linear regression was less influenced by the calibration conditions than random forest. The linear regression algorithm's behavior along the distances to the source was smoother than those for the random forest and neural network algorithms, but the observed deviations were more significant than those for the neural network and random forest algorithms. 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. In performing HDR brachytherapy dose measurements with an optimized mPSD system, ML algorithms are good alternatives for precise dose reporting and treatment assessment during this kind of cancer treatment.
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Affiliation(s)
- Haydee M Linares Rosales
- Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec, Canada; Département de radio-oncologie et Axe Oncologie du CRCHU de Québec, CHU de Québec - Université Laval, QC, Canada.
| | - Gabriel Couture
- Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec, Canada; Département de radio-oncologie et Axe Oncologie du CRCHU de Québec, CHU de Québec - Université Laval, QC, Canada
| | - Louis Archambault
- Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec, Canada; Département de radio-oncologie et Axe Oncologie du CRCHU de Québec, CHU de Québec - Université Laval, QC, Canada
| | - Sam Beddar
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States; The University of Texas MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
| | - Philippe Després
- Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec, Canada; Département de radio-oncologie et Axe Oncologie du CRCHU de Québec, CHU de Québec - Université Laval, QC, Canada
| | - Luc Beaulieu
- Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec, Canada; Département de radio-oncologie et Axe Oncologie du CRCHU de Québec, CHU de Québec - Université Laval, QC, Canada
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Jørgensen EB, Johansen JG, Overgaard J, Piché-Meunier D, Tho D, Rosales HML, Tanderup K, Beaulieu L, Kertzscher G, Beddar S. A high-Z inorganic scintillator-based detector for time-resolved in vivo dosimetry during brachytherapy. Med Phys 2021; 48:7382-7398. [PMID: 34586641 DOI: 10.1002/mp.15257] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 08/08/2021] [Accepted: 09/09/2021] [Indexed: 11/11/2022] Open
Abstract
PURPOSE High-dose rate (HDR) and pulsed-dose rate (PDR) brachytherapy would benefit from an independent treatment verification system to monitor treatment delivery and to detect errors in real time. This paper characterizes and provides an uncertainty budget for a detector based on a fiber-coupled high-Z inorganic scintillator capable of performing time-resolved in vivo dosimetry during HDR and PDR brachytherapy. METHOD The detector was composed of a detector probe and an optical reader. The detector probe consisted of either a 0.5 × 0.4 × 0.4 mm3 (HDR) or a 1.0 × 0.4 × 0.4 mm3 (PDR) cuboid ZnSe:O crystal glued onto an optical-fiber cable. The outer diameter of the detector probes was 1 mm, and fit inside standard brachytherapy catheters. The signal from the detector probe was read out at 20 Hz by a photodiode and a data acquisition device inside the optical reader. In order to construct an uncertainty budget for the detector, six characteristics were determined: (1) temperature dependence of the detector probe, (2) energy dependence as a function of the probe-to-source position in 2D (determined with 2 mm resolution using a robotic arm), (3) the signal-to-noise ratio (SNR), (4) short-term stability over 8 h, and (5) long-term stability of three optical readers and four probes used for in vivo monitoring in HDR and PDR treatments over 21 months (196 treatments and 189 detector calibrations, and (6) dose-rate dependence. RESULTS The total uncertainty of the detector at a 20 mm probe-to-source distance was < 5.1% and < 5.8% for the HDR and PDR versions, respectively. Regarding the above characteristics, (1) the sensitivity of the detector decreased by an average of 1.4%/°C for detector probe temperatures varying from 22 to 37°C; (2) the energy dependence of the detector was nonlinear and depended on both probe-to-source distance and the angle between the probe and the brachytherapy source; (3) the median SNRs were 187 and 34 at a 20 mm probe-to-source distance for the HDR and PDR versions, respectively (corresponding median source activities of 4.8 and 0.56 Ci, respectively); (4) the detector response varied by 0.6% in 11 identical irradiations over 8 h; (5) the sensitivity of the four detector probes decreased systematically by 0-1.2%/100 Gy of dose delivered to the probes, and random fluctuations of 4.8% in the sensitivity were observed for the three probes used in PDR and 1.9% for the probe used in HDR; and (6) the detector response was linear with dose rate. CONCLUSION ZnSe:O detectors can be used effectively for in vivo dosimetry and with high accuracy for HDR and PDR brachytherapy applications.
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Affiliation(s)
- Erik B Jørgensen
- Health Graduate School, Aarhus University, Aarhus, Denmark.,Department of Oncology, Aarhus University Hospital, Aarhus, Denmark
| | - Jacob G Johansen
- Department of Oncology, Aarhus University Hospital, Aarhus, Denmark
| | | | - Dominique Piché-Meunier
- Département de physique-de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec City, Quebec, Canada.,Département de radio-oncologie et Axe Oncologie, CHU de Québec-Université Laval, Québec City, Quebec, Canada
| | - Daline Tho
- Département de physique-de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec City, Quebec, Canada.,Département de radio-oncologie et Axe Oncologie, CHU de Québec-Université Laval, Québec City, Quebec, Canada
| | - Haydee M L Rosales
- Département de physique-de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec City, Quebec, Canada.,Département de radio-oncologie et Axe Oncologie, CHU de Québec-Université Laval, Québec City, Quebec, Canada
| | - Kari Tanderup
- Department of Oncology, Aarhus University Hospital, Aarhus, Denmark
| | - Luc Beaulieu
- Département de physique-de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec City, Quebec, Canada.,Département de radio-oncologie et Axe Oncologie, CHU de Québec-Université Laval, Québec City, Quebec, Canada
| | - Gustavo Kertzscher
- Department of Oncology, Aarhus University Hospital, Aarhus, Denmark.,Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Sam Beddar
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
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10
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Debnath SBC, Ferre M, Tonneau D, Fauquet C, Tallet A, Goncalves A, Darreon J. High resolution small-scale inorganic scintillator detector: HDR brachytherapy application. Med Phys 2021; 48:1485-1496. [PMID: 33476399 DOI: 10.1002/mp.14727] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 12/21/2020] [Accepted: 01/07/2021] [Indexed: 12/15/2022] Open
Abstract
PURPOSE Brachytherapy (BT) deals with high gradient internal dose irradiation made up of a complex system where the source is placed nearby the tumor to destroy cancerous cells. A primary concern of clinical safety in BT is quality assurance to ensure the best matches between the delivered and prescribed doses targeting small volume tumors and sparing surrounding healthy tissues. Hence, the purpose of this study is to evaluate the performance of a point size inorganic scintillator detector (ISD) in terms of high dose rate brachytherapy (HDR-BT) treatment. METHODS A prototype of the dose verification system has been developed based on scintillating dosimetry to measure a high dose rate while using an 192 Ir BT source. The associated dose rate is measured in photons/s employing a highly sensitive photon counter (design data: 20 photons/s). Dose measurement was performed as a function of source-to-detector distance according to TG43U1 recommendations. Overall measurements were carried out inside water phantoms keeping the ISD along the BT needle; a minimum of 0.1 cm distance was maintained between each measurement point. The planned dwell times were measured accurately from the difference of two adjacent times of transit. The ISD system performances were also evaluated in terms of dose linearity, energy dependency, scintillation stability, signal-to-noise ratio (SNR), and signal-to-background ratio (SBR). Finally, a comparison was presented between the ISD measurements and results obtained from TG43 reference dataset. RESULTS The detection efficiency of the ISD was verified by measuring the planned dwell times at different dwell positions. Measurements demonstrated that the ISD has a perfectly linear behavior with dose rate (R2 = 1) and shows high SNR (>35) and SBR (>36) values even at the lowest dose rate investigated at around 10 cm from the source. Standard deviation (1σ) remains within 0.03% of signal magnitude, and less than 0.01% STEM signal was monitored at 0.1 cm source-to-detector distance. Stability of 0.54% is achieved, and afterglow stays less than 1% of the total signal in all the irradiations. Excellent symmetrical behavior of the dose rate regarding source position was observed at different radiation planes. Finally, a comparison with TG-43 reference dataset shows that corrected measurements agreed with simulation data within 1.2% and 1.3%, and valid for the source-to-detector distance greater than 0.25 cm. CONCLUSION The proposed ISD in this study anticipated that the system could be promoted to validate with further clinical investigations. It allows an appropriate dose verification with dwell time estimation during source tracking and suitable dose measurement with a high spatial resolution both nearby (high dose gradient) and far (low dose gradient) from the source position.
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Affiliation(s)
| | | | - Didier Tonneau
- Aix Marseille Université, CNRS, CINaM UMR 7325, Marseille, 13288, France
| | - Carole Fauquet
- Aix Marseille Université, CNRS, CINaM UMR 7325, Marseille, 13288, France
| | - Agnes Tallet
- Institut Paoli-Calmettes, Marseille, 13009, France
| | - Anthony Goncalves
- Institut Paoli-Calmettes, Marseille, 13009, France.,Aix Marseille Université, CNRS UMR 7258, INSERM UMR 1068, CRCM, Marseille, 13009, France
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Yada R, Maenaka K, Miyamoto S, Okada G, Sasakura A, Ashida M, Adachi M, Sato T, Wang T, Akasaka H, Mukumoto N, Shimizu Y, Sasaki R. Real-time in vivo dosimetry system based on an optical fiber-coupled microsized photostimulable phosphor for stereotactic body radiation therapy. Med Phys 2020; 47:5235-5249. [PMID: 32654194 DOI: 10.1002/mp.14383] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 06/21/2020] [Accepted: 06/30/2020] [Indexed: 12/11/2022] Open
Abstract
PURPOSE To develop an in vivo dosimeter system for stereotactic body radiation therapy (SBRT) that can perform accurate and precise real-time measurements, using a microsized amount of a photostimulable phosphor (PSP), BaFBr:Eu2+ . METHODS The sensitive volume of the PSP was 1.26 × 10-5 cm3 . The dosimeter system was designed to apply photostimulation to the PSP after the decay of noise signals, in synchronization with the photon beam pulse of a linear accelerator (LINAC), to eliminate the noise signals completely using a time separation technique. The noise signals included stem signals, and radioluminescence signals generated by the PSP. In addition, the dosimeter system was built on a storage-type dosimeter that could read out a signal after an arbitrary preset number of photon beam pulses were incident. First, the noise and photostimulated luminescence (PSL) signal decay times were measured. Subsequently, we confirmed that the PSL signals could be exclusively read out within the photon beam pulse interval. Finally, using a water phantom, the basic characteristics of the dosimeter system were demonstrated under SBRT conditions, and the feasibility for clinical application was investigated. The reproducibility, dose linearity, dose-rate dependence, temperature dependence, and angular dependence were evaluated. The feasibility was confirmed by measurements at various dose gradients and using a representative treatment plan for a metastatic liver tumor. A clinical plan was created with a two-arc beam volumetric modulated arc therapy using a 10 MV flattening filter-free photon beam. For the water phantom measurements, the clinical plan was compiled into a plan with a fixed gantry angle of 0°. To evaluate the energy dependence during SBRT, the percent depth dose (PDD) was measured and compared with those calculated via Monte Carlo (MC) simulations. RESULTS All the PSL signals could be read out while eliminating the noise signals within the minimum pulse interval of the LINAC. Stable real-time measurements could be performed with a time resolution of 56 ms (i.e., number of pulses = 20). The dose linearity was good in the dose range of 0.01-100 Gy. The measurements agreed within 1% at dose rates of 40-2400 cGy/min. The temperature and angular dependence were also acceptable since these dependencies had only a negligible effect on the measurements in SBRT. At a dose gradient of 2.21 Gy/mm, the measured dose agreed with that calculated using a treatment planning system (TPS) within the measurement uncertainties due to the probe position. For measurements using a representative treatment plan, the measured dose agreed with that calculated using the TPS within 0.5% at the center of the beam axis. The PDD measurements agreed with the MC calculations to within 1% for field sizes <5 × 5 cm2 . CONCLUSION The in vivo dosimeter system developed using BaFBr:Eu2+ is capable of real-time, accurate, and precise measurement under SBRT conditions. The probe is smaller than a conventional dosimeter, has excellent spatial resolution, and can be valuable in SBRT with a steep dose distribution over a small field. The developed PSP dosimeter system appears to be suitable for in vivo SBRT dosimetry.
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Affiliation(s)
- Ryuichi Yada
- Division of Radiation Oncology, Kobe University Graduate School of Medicine, 7-5-2 Kusunokicho, Chuouku, Kobe, Hyogo, 650-0017, Japan
| | - Kazusuke Maenaka
- Department of Electrical Engineering and Computer Science, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo, 671-2280, Japan
| | - Shuji Miyamoto
- Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Kouto, Kamigoricho, Akogun, Hyogo, 678-1205, Japan
| | - Go Okada
- Co-creative Research Center of Industrial Science and Technology, Kanazawa Institute of Technology, 3-1 Yatsukaho, Hakusan, Ishikawa, 924-0838, Japan
| | - Aki Sasakura
- Meisyo Kiko Co., Ltd, 148 Numa, Hikamicho, Tamba, Hyogo, 669-3634, Japan
| | - Motoi Ashida
- Meisyo Kiko Co., Ltd, 148 Numa, Hikamicho, Tamba, Hyogo, 669-3634, Japan
| | - Masashi Adachi
- Meisyo Kiko Co., Ltd, 148 Numa, Hikamicho, Tamba, Hyogo, 669-3634, Japan
| | - Tatsuhiko Sato
- Nuclear Science and Engineering Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai, Ibaraki, 319-1195, Japan
| | - Tianyuan Wang
- Division of Radiation Oncology, Kobe University Graduate School of Medicine, 7-5-2 Kusunokicho, Chuouku, Kobe, Hyogo, 650-0017, Japan
| | - Hiroaki Akasaka
- Division of Radiation Oncology, Kobe University Graduate School of Medicine, 7-5-2 Kusunokicho, Chuouku, Kobe, Hyogo, 650-0017, Japan
| | - Naritoshi Mukumoto
- Division of Radiation Oncology, Kobe University Graduate School of Medicine, 7-5-2 Kusunokicho, Chuouku, Kobe, Hyogo, 650-0017, Japan
| | - Yasuyuki Shimizu
- Division of Radiation Oncology, Kobe University Graduate School of Medicine, 7-5-2 Kusunokicho, Chuouku, Kobe, Hyogo, 650-0017, Japan
| | - Ryohei Sasaki
- Division of Radiation Oncology, Kobe University Graduate School of Medicine, 7-5-2 Kusunokicho, Chuouku, Kobe, Hyogo, 650-0017, Japan
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Linares Rosales HM, Archambault L, Beddar S, Beaulieu L. Dosimetric performance of a multipoint plastic scintillator dosimeter as a tool for real‐time source tracking in high dose rate Ir brachytherapy. Med Phys 2020; 47:4477-4490. [DOI: 10.1002/mp.14246] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 04/03/2020] [Accepted: 05/11/2020] [Indexed: 11/08/2022] Open
Affiliation(s)
- Haydee M. Linares Rosales
- Département de physique de génie physique et d’optique et Centre de recherche sur le cancer Université Laval Québec Canada
- Département de radio‐oncologie et Axe Oncologie du CRCHU de Québec CHU de Québec ‐ Université Laval Québec QC Canada
| | - Louis Archambault
- Département de physique de génie physique et d’optique et Centre de recherche sur le cancer Université Laval Québec Canada
- Département de radio‐oncologie et Axe Oncologie du CRCHU de Québec CHU de Québec ‐ Université Laval Québec QC Canada
| | - Sam Beddar
- Department of Radiation Physics The University of Texas MD Anderson Cancer Center Houston TX USA
- The University of Texas MD Anderson UTHealth Graduate School of Biomedical Sciences Houston TX USA
| | - Luc Beaulieu
- Département de physique de génie physique et d’optique et Centre de recherche sur le cancer Université Laval Québec Canada
- Département de radio‐oncologie et Axe Oncologie du CRCHU de Québec CHU de Québec ‐ Université Laval Québec QC Canada
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Madden L, Archer J, Li E, Jelen U, Dong B, Holloway L, Rosenfeld A. MRI-LINAC beam profile measurements using a plastic scintillation dosimeter. Phys Med 2020; 73:111-116. [PMID: 32361155 DOI: 10.1016/j.ejmp.2020.04.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 04/14/2020] [Accepted: 04/16/2020] [Indexed: 10/24/2022] Open
Abstract
Plastic scintillation dosimeters (PSDs) possess many desirable qualities for dosimetry with LINACs. These qualities are expected to make PSDs effective for MRI-LINAC dosimetry, however little research has been conducted investigating their dosimetric performance with MRI-LINACs. In this work, an in-house PSD was used to measure 8 beam profiles with an in-line MRI-LINAC, compared with film measurements. One dimensional global gamma indices (γ) and corresponding γ pass rates were calculated to compare PSD and film profiles for the 1%/1 mm, 2%/2 mm and 3%/3 mm criterion. The mean global pass rates were 85.8%, 97.5% and 99.4% for the 1%/1 mm, 2%/2 mm and 3%/3 mm criteria, respectively. The majority of the γ failures occurred in the penumbral regions. Penumbra widths were measured to be slightly narrower with the PSD compared to film, however, the uncertainties in the measured penumbra widths brought the PSD and film penumbra widths into agreement. Differences in dose were calculated between the PSD and film, and remained within 2.2% global agreement for the central regions and 1.5% global agreement for out of field regions. These values for range of agreement were similar to the those reported in the literature for other dosimeters which are trusted for relative MRI-LINAC dosimetry.
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Affiliation(s)
- Levi Madden
- Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia; Ingham Institute for Applied Medical Research, Liverpool, NSW 2170, Australia
| | - James Archer
- Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia
| | - Enbang Li
- Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia.
| | - Urszula Jelen
- Ingham Institute for Applied Medical Research, Liverpool, NSW 2170, Australia
| | - Bin Dong
- Ingham Institute for Applied Medical Research, Liverpool, NSW 2170, Australia
| | - Lois Holloway
- Ingham Institute for Applied Medical Research, Liverpool, NSW 2170, Australia
| | - Anatoly Rosenfeld
- Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia; Illawarra Medical and Health Research Institute, University of Wollongong, NSW 2522, Australia
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Abstract
Many brachytherapy (BT) errors could be detected with real-time in vivo dosimetry technology. Inorganic scintillation detectors (ISDs) have demonstrated promising capabilities for BT, because some ISD materials can generate scintillation signals large enough that (a) the background signal emitted in the fiber-optic cable (stem signal) is insignificant, and (b) small detector volumes can be used to avoid volume averaging effects in steep dose gradients near BT sources. We investigated the characteristics of five ISD materials to identify one that is appropriate for BT. ISDs consisting of a 0.26 to 1.0 mm3 volume of ruby (Al2O3:Cr), a mixture of Y2O3:Eu and YVO4:Eu, ZnSe:O, or CsI:Tl coupled to a fiber-optic cable were irradiated in a water-equivalent phantom using a high-dose-rate 192Ir BT source. Detectors based on plastic scintillators BCF-12 and BCF-60 (0.8 mm3 volume) were used as a reference. Measurements demonstrated that the ruby, Y2O3:Eu+YVO4:Eu, ZnSe:O, and CsI:Tl ISDs emitted scintillation signals that were up to 19, 19, 250, and 880 times greater, respectively, than that of the BCF-12 detector. While the total signals of the plastic scintillation detectors were dominated by the stem signal for source positions 0.5 cm from the fiber-optic cable and >3.5 cm from the scintillator volume, the stem signal for the ruby and Y2O3:Eu+YVO4:Eu ISDs were <1% of the total signal for source positions <3.4 and <4.4 cm from the scintillator, respectively, and <0.7% and <0.5% for the ZnSe:O and CsI:Tl ISDs, respectively, for positions ⩽8.0 cm. In contrast to the other ISDs, the Y2O3:Eu+YVO4:Eu ISD exhibited unstable scintillation and significant afterglow. All ISDs exhibited significant energy dependence, i.e. their dose response to distance-dependent 192Ir energy spectra differed significantly from the absorbed dose in water. Provided that energy dependence is accounted for, ZnSe:O ISDs are promising for use in error detection and patient safety monitoring during BT.
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Affiliation(s)
- Gustavo Kertzscher
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States of America
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Santurio GV, Andersen CE. Quantifying the ionization quenching effect in organic plastic scintillators used in MV photon dosimetry. RADIAT MEAS 2019. [DOI: 10.1016/j.radmeas.2019.106200] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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16
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Qin Z, Xie T, Dai X, Zhang B, Ma Y, Khan IU, Zhang X, Li H, Yan Y, Zhao W, Li S, Chen Z, Zhang D, Xu J, Hu X, Xing L, Feng K, Lewis E, Sun W. New model for explaining the over-response phenomenon in percentage of depth dose curve measured using inorganic scintillating materials for optical fiber radiation sensors. OPTICS EXPRESS 2019; 27:23693-23706. [PMID: 31510270 DOI: 10.1364/oe.27.023693] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 07/23/2019] [Indexed: 06/10/2023]
Abstract
Inorganic scintillating material used in optical fibre sensors (OFS) when used as dosimeters for measuring percentage depth dose (PDD) characteristics have exhibited significant differences when compared to those measured using an ionization chamber (IC), which is the clinical gold standard for quality assurance (QA) assessments. The percentage difference between the two measurements is as high as 16.5% for a 10 × 10 cm2 field at 10 cm depth below the surface. Two reasons have been suggested for this: the presence of an energy effect and Cerenkov radiation. These two factors are analysed in detail and evaluated quantitatively. It is established that the influence of the energy effect is only a maximum of 2.5% difference for a beam size 10 × 10 cm2 compared with the measured ionization chamber values. And the influence of the Cerenkov radiation is less than 0.14% in an inorganic scintillating material in the case of OFS when using Gd2O2S:Tb as the luminescent material. Therefore, there must be other mechanisms leading to over-response. The luminescence mechanism of inorganic scintillating material is theoretically analysed and a new model is proposed and validated that helps explain the over-response phenomenon.
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17
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Galavis PE, Hu L, Holmes S, Das IJ. Characterization of the plastic scintillation detector Exradin W2 for small field dosimetry. Med Phys 2019; 46:2468-2476. [DOI: 10.1002/mp.13501] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 03/11/2019] [Accepted: 03/11/2019] [Indexed: 11/10/2022] Open
Affiliation(s)
- Paulina E. Galavis
- Department of Radiation Oncology New York University, Langone Medical Center & Laura and Issac Perlmutter Cancer Center New York NY 10016USA
| | - Lei Hu
- Department of Radiation Oncology New York University, Langone Medical Center & Laura and Issac Perlmutter Cancer Center New York NY 10016USA
| | | | - Indra J. Das
- Department of Radiation Oncology New York University, Langone Medical Center & Laura and Issac Perlmutter Cancer Center New York NY 10016USA
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18
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Linares Rosales HM, Duguay-Drouin P, Archambault L, Beddar S, Beaulieu L. Optimization of a multipoint plastic scintillator dosimeter for high dose rate brachytherapy. Med Phys 2019; 46:2412-2421. [PMID: 30891803 DOI: 10.1002/mp.13498] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 01/16/2019] [Accepted: 02/18/2019] [Indexed: 11/08/2022] Open
Abstract
PURPOSE This study is devoted to optimizing and characterizing the response of a multipoint plastic scintillator detector (mPSD) for application to in vivo dosimetry in high dose rate (HDR) brachytherapy. METHODS An exhaustive analysis was carried out in order to obtain an optimized mPSD design that maximizes the scintillation light collection produced by the interaction of ionizing photons. More than 20 prototypes of mPSD were built and tested in order to determine the appropriate order of scintillators relative to the photodetector (distal, center, or proximal) as well as their length as a function of the scintillation light emitted. The available detecting elements are the BCF-60, BCF-12, and BCF-10 scintillators (Saint Gobain Crystals, Hiram, OH, USA), separated from each other by segments of Eska GH-4001 clear optical fibers (Mitsubishi Rayon Co., Ltd., Tokyo, Japan). The contribution of each scintillator to the total spectrum was determined by irradiations in the low energy range (<120 keV). For the best mPSD design, a numerical optimization was done in order to select the optical components [dichroic mirrors, filters, and photomultipliers tubes (PMTs)] that best match the light emission profile. Calculations were performed taking into account the measured scintillation spectrum and light yield, the manufacturer-reported transmission and attenuation of the optical components, and the experimentally characterized PMT noise. The optimized dosimetric system was used for HDR brachytherapy measurements. The system was independently controlled from the 192 Ir source via LabVIEW and read simultaneously using an NI-DAQ board. Dose measurements as a function of distance from the source were carried out according to TG-43U1 recommendations. The system performance was quantified in terms of signal to noise ratio (SNR) and signal to background ratio (SBR). RESULTS For best overall light-yield emission, it was determined that BCF-60 should be placed at the distal position, BCF-12 in the center, and BCF-10 at the proximal position with respect to the photodetector. This configuration allowed for optimized light transmission through the collecting fiber and avoided inter-scintillator excitation and self-absorption effects. The optimal scintillator length found was of 3, 6, and 7 mm for BCF-10, BCF- 12, and BCF-60, respectively. The optimized luminescence system allowed for signal deconvolution using a multispectral approach, extracting the dose to each element while taking into account the Cerenkov stem effect. Differences between the mPSD measurements and TG-43U1 remain below 5% in the range of 0.5 to 6.5 cm from the source. The dosimetric system can properly differentiate the scintillation signal from the background for a wide range of dose rate conditions; the SNR was found to be above 5 for dose rates above 22 mGy/s while the minimum SBR measured was 1.8 at 6 mGy/s. CONCLUSION Based on the spectral response at different conditions, an mPSD was constructed and optimized for HDR brachytherapy dosimetry. It is sensitive enough to allow multiple simultaneous measurements over a clinically useful distance range, up to 6.5 cm from the source. This study constitutes a baseline for future applications enabling real-time dose measurements and source position reporting over a wide range of dose rate conditions.
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Affiliation(s)
- Haydee M Linares Rosales
- Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec City, QC, Canada.,Département de radio-oncologie et Axe Oncologie du CRCHU de Québec, CHU de Québec - Université Laval, Québec City, QC, Canada
| | - Patricia Duguay-Drouin
- Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec City, QC, Canada.,Département de radio-oncologie et Axe Oncologie du CRCHU de Québec, CHU de Québec - Université Laval, Québec City, QC, Canada
| | - Louis Archambault
- Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec City, QC, Canada.,Département de radio-oncologie et Axe Oncologie du CRCHU de Québec, CHU de Québec - Université Laval, Québec City, QC, Canada
| | - Sam Beddar
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, 77003, USA
| | - Luc Beaulieu
- Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec City, QC, Canada.,Département de radio-oncologie et Axe Oncologie du CRCHU de Québec, CHU de Québec - Université Laval, Québec City, QC, Canada
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Christensen JB, Andersen CE. Relating ionization quenching in organic plastic scintillators to basic material properties by modelling excitation density transport and amorphous track structure during proton irradiation. Phys Med Biol 2018; 63:195010. [PMID: 30183687 DOI: 10.1088/1361-6560/aadf2d] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Ionization quenching in organic scintillators is usually corrected with methods that require careful assessment of the response relative to that of an ionization chamber. Here, we present a framework to compute ionization quenching correction factors (QCFs) from first principles for organic plastic scintillators exposed to ions. The tool solves the kinetic Blanc equation, of which the Birks model is a simplified solution, based on amorphous track structures models. As a consequence, ionization quenching correction factors can be calculated relying only on standard, tabulated scintillator material properties such as the density, light yield, and decay time. The tool is validated against experimentally obtained QCFs for two different organic plastic scintillators irradiated with protons with linear energy transfers (LETs) between 5-[Formula: see text]. The QCFs computed from amorphous track structure models and the BC-400 scintillator properties deviate less than 3% from the Birks model for LETs below [Formula: see text] and less than 5% for higher LETs. The agreement between experiments and the software for the BCF-12 scintillator is within 2% for LETs below [Formula: see text] and within 10% for LETs above, comparable to the experimental uncertainties. The framework is compiled into the open source software [Formula: see text] available for download. [Formula: see text] enables computations of QCFs in organic plastic scintillators exposed to ions independently of experimentally based quenching parameters in contrast to the Birks model. [Formula: see text] can improve the accuracy of correction factors and understanding of ionization quenching in scintillator dosimetry.
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Affiliation(s)
- Jeppe Brage Christensen
- Center for Nuclear Technologies, Technical University of Denmark, Frederiksborgvej 399, 4000 Roskilde, Denmark
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Brage Christensen J, Almhagen E, Nyström H, Andersen CE. Quenching-free fluorescence signal from plastic-fibres in proton dosimetry: understanding the influence of Čerenkov radiation. ACTA ACUST UNITED AC 2018; 63:065001. [DOI: 10.1088/1361-6560/aaafad] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Alsanea F, Wootton L, Sahoo N, Kudchadker R, Mahmood U, Beddar S. Exradin W1 plastic scintillation detector for in vivo skin dosimetry in passive scattering proton therapy. Phys Med 2018; 47:58-63. [PMID: 29609819 DOI: 10.1016/j.ejmp.2018.02.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 01/23/2018] [Accepted: 02/16/2018] [Indexed: 01/30/2023] Open
Abstract
In vivo skin dosimetry is desirable in passive scattering proton therapy because of the possibility of high entrance dose with a small number of fields. However, suitable detectors are needed to determine skin dose in proton therapy. Plastic scintillation detectors (PSDs) are particularly well suited for applications in proton therapy because of their water equivalence, small size, and ease of use. We investigated the utility of the Exradin W1, a commercially available PSD, for in vivo skin dosimetry during passive scattering proton therapy. We evaluated the accuracy of the Exradin W1 in six patients undergoing proton therapy for prostate cancer, as part of an Institutional Review Board-approved protocol. Over 22 weeks, we compared in vivo PSD measurements with in-phantom ionization chamber measurements and doses from the treatment planning system, resulting in 96 in vivo measurements. Temperature and ionization quenching correction factors were applied on the basis of the dose response of the PSD in a phantom. The calibrated PSD exhibited an average 7.8% under-response (±1% standard deviation) owing to ionization quenching. We observed 4% under-response at 37 °C relative to the calibration-temperature response. After temperature and quenching corrections were applied, the overall PSD dose response was within ±1% of the expected dose for all patients. The dose differences between the PSD and ionization chamber measurements for all treatment fields were within ±2% (standard deviation 0.67%). The PSD was highly accurate for in vivo skin dosimetry in passively scattered proton beams and could be useful in verifying proton therapy delivery.
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Affiliation(s)
- Fahed Alsanea
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA; The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX 77030, USA
| | - Landon Wootton
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA; Department of Radiation Oncology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Narayan Sahoo
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA; The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX 77030, USA
| | - Rajat Kudchadker
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA; The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX 77030, USA
| | - Usama Mahmood
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Sam Beddar
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA; The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX 77030, USA.
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Validation of plastic scintillation detectors for applications in low-dose-rate brachytherapy. Brachytherapy 2017; 16:903-909. [DOI: 10.1016/j.brachy.2017.04.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 03/29/2017] [Accepted: 04/04/2017] [Indexed: 11/23/2022]
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Kertzscher G, Beddar S. Inorganic scintillation detectors based on Eu-activated phosphors for 192Ir brachytherapy. Phys Med Biol 2017; 62:5046-5075. [PMID: 28475494 DOI: 10.1088/1361-6560/aa716e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The availability of real-time treatment verification during high-dose-rate (HDR) brachytherapy is currently limited. Therefore, we studied the luminescence properties of the widely commercially available scintillators using the inorganic materials Eu-activated phosphors Y2O3:Eu, YVO4:Eu, Y2O2S:Eu, and Gd2O2S:Eu to determine whether they could be used to accurately and precisely verify HDR brachytherapy doses in real time. The suitability for HDR brachytherapy of inorganic scintillation detectors (ISDs) based on the 4 Eu-activated phosphors in powder form was determined based on experiments with a 192Ir HDR brachytherapy source. The scintillation intensities of the phosphors were 16-134 times greater than that of the commonly used organic plastic scintillator BCF-12. High signal intensities were achieved with an optimized packing density of the phosphor mixture and with a shortened fiber-optic cable. The influence of contaminating Cerenkov and fluorescence light induced in the fiber-optic cable (stem signal) was adequately suppressed by inserting between the fiber-optic cable and the photodetector a 25 nm band-pass filter centered at the emission peak. The spurious photoluminescence signal induced by the stem signal was suppressed by placing a long-pass filter between the scintillation detector volume and the fiber-optic cable. The time-dependent luminescence properties of the phosphors were quantified by measuring the non-constant scintillation during irradiation and the afterglow after the brachytherapy source had retracted. We demonstrated that a mixture of Y2O3:Eu and YVO4:Eu suppressed the time-dependence of the ISDs and that the time-dependence of Y2O2S:Eu and Gd2O2S:Eu introduced large measurement inaccuracies. We conclude that ISDs based on a mixture of Y2O3:Eu and YVO4:Eu are promising candidates for accurate and precise real-time verification technology for HDR BT that is cost effective and straightforward to manufacture. Widespread dissemination of this technology could lead to an improved understanding of error types and frequencies during BT and to improved patient safety during treatment.
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Affiliation(s)
- Gustavo Kertzscher
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States of America
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Veronese I, Chiodini N, Cialdi S, d’Ippolito E, Fasoli M, Gallo S, La Torre S, Mones E, Vedda A, Loi G. Real-time dosimetry with Yb-doped silica optical fibres. Phys Med Biol 2017; 62:4218-4236. [DOI: 10.1088/1361-6560/aa642f] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Cantley JL, Cheng CW, Jesseph FB, Podder TK, Colussi VC, Traughber BJ, Ponsky LE, Ellis RJ. Real-time in vivo dosimetry for SBRT prostate treatment using plastic scintillating dosimetry embedded in a rectal balloon: a case study. J Appl Clin Med Phys 2016; 17:305-311. [PMID: 27929503 PMCID: PMC5690496 DOI: 10.1120/jacmp.v17i6.6508] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 08/30/2016] [Accepted: 08/30/2016] [Indexed: 12/04/2022] Open
Abstract
A novel FDA approved in vivo dosimetry device system using plastic scintillating detectors placed in an endorectal balloon to provide real‐time in vivo dosimetry for prostatic rectal interface was tested for use with stereotactic body radiotherapy (SBRT). The system was used for the first time ever to measure dose during linear accelerator based SBRT. A single patient was treated with a total dose of 36.25 Gy given in 5 fractions. Delivered dose was measured for each treatment with the detectors placed against the anterior rectal wall near the prostate rectal interface. Measured doses showed varying degrees of agreement with computed/ planned doses, with average combined dose found to be within 6% of the expected dose. The variance between measurements is most likely due to uncertainty of the detector location, as well as variation in the placement of a new balloon prior to each fraction. Distance to agreement for the detectors was generally found to be within a few millimeters, which also suggested that the differences in measured and calculated doses were due to positional uncertainty of the detectors during the SBRT, which had sharp dose falloff near the penumbra along the rectal wall. Overall, the use of a real time in vivo dosimeter provided a level of safety and improved confidence in treatment delivery. We are evaluating the device further in an IRB‐approved prospective partial prostate SBRT trial, and believe further clinical investigations are warranted. PACS number(s): 87.53.Bn, 87.53.Ly, 87.55.km
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Kertzscher G, Beddar S. Ruby-based inorganic scintillation detectors for 192Ir brachytherapy. Phys Med Biol 2016; 61:7744-7764. [PMID: 27740947 DOI: 10.1088/0031-9155/61/21/7744] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We tested the potential of ruby inorganic scintillation detectors (ISDs) for use in brachytherapy and investigated various unwanted luminescence properties that may compromise their accuracy. The ISDs were composed of a ruby crystal coupled to a poly(methyl methacrylate) fiber-optic cable and a charge-coupled device camera. The ISD also included a long-pass filter that was sandwiched between the ruby crystal and the fiber-optic cable. The long-pass filter prevented the Cerenkov and fluorescence background light (stem signal) induced in the fiber-optic cable from striking the ruby crystal, which generates unwanted photoluminescence rather than the desired radioluminescence. The relative contributions of the radioluminescence signal and the stem signal were quantified by exposing the ruby detectors to a high-dose-rate brachytherapy source. The photoluminescence signal was quantified by irradiating the fiber-optic cable with the detector volume shielded. Other experiments addressed time-dependent luminescence properties and compared the ISDs to commonly used organic scintillator detectors (BCF-12, BCF-60). When the brachytherapy source dwelled 0.5 cm away from the fiber-optic cable, the unwanted photoluminescence was reduced from >5% to <1% of the total signal as long as the ISD incorporated the long-pass filter. The stem signal was suppressed with a band-pass filter and was <3% as long as the source distance from the scintillator was <7 cm. Some ruby crystals exhibited time-dependent luminescence properties that altered the ruby signal by >5% within 10 s from the onset of irradiation and after the source had retracted. The ruby-based ISDs generated signals of up to 20 times that of BCF-12-based detectors. The study presents solutions to unwanted luminescence properties of ruby-based ISDs for high-dose-rate brachytherapy. An optic filter should be sandwiched between the ruby crystal and the fiber-optic cable to suppress the photoluminescence. Furthermore, we recommend avoiding ruby crystals that exhibit significant time-dependent luminescence.
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Affiliation(s)
- Gustavo Kertzscher
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
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Beaulieu L, Beddar S. Review of plastic and liquid scintillation dosimetry for photon, electron, and proton therapy. Phys Med Biol 2016; 61:R305-R343. [DOI: 10.1088/0031-9155/61/20/r305] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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28
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Le Deroff C, Frelin-Labalme AM, Ledoux X. Characterization of a scintillating fibre detector for small animal imaging and irradiation dosimetry. Br J Radiol 2016; 90:20160454. [PMID: 27556813 DOI: 10.1259/bjr.20160454] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE Small animal image-guided irradiators have recently been developed to mimic the delivery techniques of clinical radiotherapy. A dosemeter adapted to millimetric beams of medium-energy X-rays is then required. This work presents the characterization of a dosemeter prototype for this particular application. METHODS A scintillating optical fibre dosemeter (called DosiRat) has been implemented to perform real-time dose measurements with the dedicated small animal X-RAD® 225Cx (Precision X-Ray, Inc., North Branford, CT) irradiator. Its sensitivity, stem effect, stability, linearity and measurement precision were determined in large field conditions for three different beam qualities, consistent with small animal irradiation and imaging parameters. RESULTS DosiRat demonstrates good sensitivity and stability; excellent air kerma and air kerma rate linearity; and a good repeatability for air kerma rates >1 mGy s-1. The stem effect was found to be negligible. DosiRat showed limited precision for low air kerma rate measurements (<1 mGy s-1), typically for imaging protocols. A positive energy dependence was found that can be accounted for by calibrating the dosemeter at the needed beam qualities. CONCLUSION The dosimetric performances of DosiRat are very promising. Extensive studies of DosiRat energy dependence are still required. Further developments will allow to reduce the dosemeter size to ensure millimetric beams dosimetry and perform small animal in vivo dosimetry. Advances in knowledge: Among existing point dosemeters, very few are dedicated to both medium-energy X-rays and millimetric beams. Our work demonstrated that scintillating fibre dosemeters are suitable and promising tools for real-time dose measurements in the small animal field of interest.
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Affiliation(s)
- Coralie Le Deroff
- 1 Grand Accélérateur National d'Ions Lourds (GANIL), CEA/DRF-CNRS/IN2P3, Boulevard Henri Becquerel, 14076 Caen, France
| | - Anne-Marie Frelin-Labalme
- 1 Grand Accélérateur National d'Ions Lourds (GANIL), CEA/DRF-CNRS/IN2P3, Boulevard Henri Becquerel, 14076 Caen, France.,2 Advanced Resource Centre for HADrontherapy in Europe (ARCHADE) Program, Caen, France
| | - Xavier Ledoux
- 1 Grand Accélérateur National d'Ions Lourds (GANIL), CEA/DRF-CNRS/IN2P3, Boulevard Henri Becquerel, 14076 Caen, France
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Scintillation properties of the YVO4:Eu3+ compound in powder form: its application to dosimetry in radiation fields produced by pulsed mega-voltage photon beams. Z Med Phys 2015; 25:368-374. [DOI: 10.1016/j.zemedi.2015.04.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 04/01/2015] [Accepted: 04/04/2015] [Indexed: 11/23/2022]
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Therriault-Proulx F, Wootton L, Beddar S. A method to correct for temperature dependence and measure simultaneously dose and temperature using a plastic scintillation detector. Phys Med Biol 2015; 60:7927-39. [PMID: 26407188 PMCID: PMC4613770 DOI: 10.1088/0031-9155/60/20/7927] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Plastic scintillation detectors (PSDs) work well for radiation dosimetry. However, they show some temperature dependence, and a priori knowledge of the temperature surrounding the PSD is required to correct for this dependence. We present a novel approach to correct PSD response values for temperature changes instantaneously and without the need for prior knowledge of the temperature value. In addition to rendering the detector temperature-independent, this approach allows for actual temperature measurement using solely the PSD apparatus. With a temperature-controlled water tank, the temperature was varied from room temperature to more than 40 °C and the PSD was used to measure the dose delivered from a cobalt-60 photon beam unit to within an average of 0.72% from the expected value. The temperature was measured during each acquisition with the PSD and a thermocouple and values were within 1 °C of each other. The depth-dose curve of a 6 MV photon beam was also measured under warm non-stable conditions and this curve agreed to within an average of -0.98% from the curve obtained at room temperature. The feasibility of rendering PSDs temperature-independent was demonstrated with our approach, which also enabled simultaneous measurement of both dose and temperature. This novel approach improves both the robustness and versatility of PSDs.
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Affiliation(s)
- Francois Therriault-Proulx
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
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Effects of Temperature and X-rays on Plastic Scintillating Fiber and Infrared Optical Fiber. SENSORS 2015; 15:11012-26. [PMID: 25970257 PMCID: PMC4481907 DOI: 10.3390/s150511012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 05/04/2015] [Accepted: 05/06/2015] [Indexed: 11/24/2022]
Abstract
In this study, we have studied the effects of temperature and X-ray energy variations on the light output signals from two different fiber-optic sensors, a fiber-optic dosimeter (FOD) based on a BCF-12 as a plastic scintillating fiber (PSF) and a fiber-optic thermometer (FOT) using a silver halide optical fiber as an infrared optical fiber (IR fiber). During X-ray beam irradiation, the scintillating light and IR signals were measured simultaneously using a dosimeter probe of the FOD and a thermometer probe of the FOT. The probes were placed in a beaker with water on the center of a hotplate, under variation of the tube potential of a digital radiography system or the temperature of the water in the beaker. From the experimental results, in the case of the PSF, the scintillator light output at the given tube potential decreased as the temperature increased in the temperature range from 25 to 60 °C. We demonstrated that commonly used BCF-12 has a significant temperature dependence of −0.263 ± 0.028%/°C in the clinical temperature range. Next, in the case of the IR fiber, the intensity of the IR signal was almost uniform at each temperature regardless of the tube potential range from 50 to 150 kVp. Therefore, we also demonstrated that the X-ray beam with an energy range used in diagnostic radiology does not affect the IR signals transmitted via a silver halide optical fiber.
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Carrasco P, Jornet N, Jordi O, Lizondo M, Latorre-Musoll A, Eudaldo T, Ruiz A, Ribas M. Characterization of the Exradin W1 scintillator for use in radiotherapy. Med Phys 2014; 42:297-304. [DOI: 10.1118/1.4903757] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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33
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Carrara M, Tenconi C, Rossi G, Guilizzoni R, Borroni M, Cerrotta A, Fallai C, Gambarini G, Vedda A, Pignoli E. Temperature dependence of a Ce3+ doped SiO2 radioluminescent dosimeter for in vivo dose measurements in HDR brachytherapy. RADIAT MEAS 2014. [DOI: 10.1016/j.radmeas.2014.06.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Abstract
Diagnostic radiology typically uses x-ray beams between 25 and 150 kVp. Plastic scintillation detectors (PSDs) are potentially successful candidates as field dosimeters but careful selection of the scintillator is crucial. It has been demonstrated that they can suffer from energy dependence in the low-energy region, an undesirable dosimeter characteristic. This dependence is partially due to the nonlinear light yield of the scintillator to the low-energy electrons set in motion by the photon beam. In this work, PSDs made of PMMA, PVT or polystyrene were studied for the x-ray beam range 25 to 100 kVp. For each kVp data has been acquired for additional aluminium filtrations of 0.5, 1.0, 2.0 and 4.0 mm. Absolute dose in the point of measurement was obtained with an ionization chamber calibrated to dose in water. From the collected data, detector sensitivities were obtained as function of the beam kVp and additional filtration. Using Monte Carlo simulations relative scintillator sensitivities were computed. For some of the scintillators these sensitivities show strong energy-dependence for beam average energy below 35 keV for each additional filtration but fair constancy above. One of the scintillators (BC-404) has smaller energy-dependence at low photon average energy and could be considered a candidate for applications (like mammography) where beam energy has small span.
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Affiliation(s)
- Luis Peralta
- Laboratório de Instrumentação e Física Experimental de Partículas, Lisboa, Portugal. Universidade de Lisboa, Faculdade de Ciências, Departamento de Física, Portugal and Laboratório de Instrumentação e Física Experimental de Partículas, Lisboa, Portugal
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Kertzscher G, Rosenfeld A, Beddar S, Tanderup K, Cygler JE. In vivo dosimetry: trends and prospects for brachytherapy. Br J Radiol 2014; 87:20140206. [PMID: 25007037 DOI: 10.1259/bjr.20140206] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The error types during brachytherapy (BT) treatments and their occurrence rates are not well known. The limited knowledge is partly attributed to the lack of independent verification systems of the treatment progression in the clinical workflow routine. Within the field of in vivo dosimetry (IVD), it is established that real-time IVD can provide efficient error detection and treatment verification. However, it is also recognized that widespread implementations are hampered by the lack of available high-accuracy IVD systems that are straightforward for the clinical staff to use. This article highlights the capabilities of the state-of-the-art IVD technology in the context of error detection and quality assurance (QA) and discusses related prospects of the latest developments within the field. The article emphasizes the main challenges responsible for the limited practice of IVD and provides descriptions on how they can be overcome. Finally, the article suggests a framework for collaborations between BT clinics that implemented IVD on a routine basis and postulates that such collaborations could improve BT QA measures and the knowledge about BT error types and their occurrence rates.
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Affiliation(s)
- G Kertzscher
- 1 Centre for Nuclear Technologies, Technical University of Denmark, Roskilde, Denmark
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Klawikowski SJ, Zeringue C, Wootton LS, Ibbott GS, Beddar S. Preliminary evaluation of the dosimetric accuracy of the in vivo plastic scintillation detector OARtrac system for prostate cancer treatments. Phys Med Biol 2014; 59:N27-36. [PMID: 24732073 PMCID: PMC4083835 DOI: 10.1088/0031-9155/59/9/n27] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A promising, new, in vivo prostate dosimetry system has been developed for clinical radiation therapy. This work outlines the preliminary end-to-end testing of the accuracy and precision of the new OARtrac scintillation dosimetry system. We tested 94 calibrated plastic scintillation detector (PSD) probes before their final integration into endorectal balloon assemblies. These probes had been calibrated at The University of Texas MD Anderson Cancer Center Dosimetry Laboratory. We used a complete clinical OARtrac system including the PSD probes, charge coupled device camera monitoring system, and the manufacturer's integrated software package. The PSD probes were irradiated at 6 MV in a Solid Water® phantom. Irradiations were performed with a 6 MV linear accelerator using anterior-posterior/posterior-anterior matched fields to a maximum dose of 200 cGy in a 100 cm source-axis distance geometry. As a whole, the OARtrac system has good accuracy with a mean error of 0.01% and an error spread of ±5.4% at the 95% confidence interval. These results reflect the PSD probes' accuracy before their final insertion into endorectal balloons. Future work will test the dosimetric effects of mounting the PSD probes within the endorectal balloon assemblies.
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Affiliation(s)
- Slade J. Klawikowski
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030
| | - Clint Zeringue
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030
| | - Landon S. Wootton
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030
- The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030
| | - Geoffrey S. Ibbott
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030
- The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030
| | - Sam Beddar
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030
- The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030
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Kertzscher G, Andersen CE, Tanderup K. Adaptive error detection for HDR/PDR brachytherapy: Guidance for decision making during real-time in vivo
point dosimetry. Med Phys 2014; 41:052102. [DOI: 10.1118/1.4870438] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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38
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Wootton L, Kudchadker R, Lee A, Beddar S. Real-time in vivo rectal wall dosimetry using plastic scintillation detectors for patients with prostate cancer. Phys Med Biol 2014; 59:647-60. [PMID: 24434775 DOI: 10.1088/0031-9155/59/3/647] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We designed and constructed an in vivo dosimetry system using plastic scintillation detectors (PSDs) to monitor dose to the rectal wall in patients undergoing intensity-modulated radiation therapy for prostate cancer. Five patients were enrolled in an Institutional Review Board-approved protocol for twice weekly in vivo dose monitoring with our system, resulting in a total of 142 in vivo dose measurements. PSDs were attached to the surface of endorectal balloons used for prostate immobilization to place the PSDs in contact with the rectal wall. Absorbed dose was measured in real time and the total measured dose was compared with the dose calculated by the treatment planning system on the daily computed tomographic image dataset. The mean difference between measured and calculated doses for the entire patient population was -0.4% (standard deviation 2.8%). The mean difference between daily measured and calculated doses for each patient ranged from -3.3% to 3.3% (standard deviation ranged from 5.6% to 7.1% for four patients and was 14.0% for the last, for whom optimal positioning of the detector was difficult owing to the patient's large size). Patients tolerated the detectors well and the treatment workflow was not compromised. Overall, PSDs performed well as in vivo dosimeters, providing excellent accuracy, real-time measurement and reusability.
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Affiliation(s)
- Landon Wootton
- Department of Radiation Physics, The University of Texas M D Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX, USA
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