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Decker SM, Bruza P, Zhang R, Williams BB, Jarvis LA, Pogue BW, Gladstone DJ. Technical note: Visual, rapid, scintillation point dosimetry for in vivo MV photon beam radiotherapy treatments. Med Phys 2024. [PMID: 38598093 DOI: 10.1002/mp.17071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 03/07/2024] [Accepted: 03/26/2024] [Indexed: 04/11/2024] Open
Abstract
BACKGROUND While careful planning and pre-treatment checks are performed to ensure patient safety during external beam radiation therapy (EBRT), inevitable daily variations mean that in vivo dosimetry (IVD) is the only way to attain the true delivered dose. Several countries outside the US require daily IVD for quality assurance. However, elsewhere, the manual labor and time considerations of traditional in vivo dosimeters may be preventing frequent use of IVD in the clinic. PURPOSE This study expands upon previous research using plastic scintillator discs for optical dosimetry for electron therapy treatments. We present the characterization of scintillator discs for in vivo x-ray dosimetry and describe additional considerations due to geometric complexities. METHODS Plastic scintillator discs were coated with reflective white paint on all sides but the front surface. An anti-reflective, matte coating was applied to the transparent face to minimize specular reflection. A time-gated iCMOS camera imaged the discs under various irradiation conditions. In post-processing, background-subtracted images of the scintillators were fit with Gaussian-convolved ellipses to extract several parameters, including integral output, and observation angle. RESULTS Dose linearity and x-ray energy independence were observed, consistent with ideal characteristics for a dosimeter. Dose measurements exhibited less than 5% variation for incident beam angles between 0° and 75° at the anterior surface and 0-60∘ $^\circ $ at the posterior surface for exit beam dosimetry. Varying the angle between the disc surface and the camera lens did not impact the integral output for the same dose up to 55°. Past this point, up to 75°, there is a sharp falloff in response; however, a correction can be used based on the detected width of the disc. The reproducibility of the integral output for a single disc is 2%, and combined with variations from the gantry angle, we report the accuracy of the proposed scintillator disc dosimeters as ±5.4%. CONCLUSIONS Plastic scintillator discs have characteristics that are well-suited for in vivo optical dosimetry for x-ray radiotherapy treatments. Unlike typical point dosimeters, there is no inherent readout time delay, and an optical recording of the measurement is saved after treatment for future reference. While several factors influence the integral output for the same dose, they have been quantified here and may be corrected in post-processing.
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Affiliation(s)
- Savannah M Decker
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Rongxiao Zhang
- Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA
| | | | - Lesley A Jarvis
- Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA
- Dartmouth Cancer Center, Dartmouth Health, Lebanon, New Hampshire, USA
| | - Brian W Pogue
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - David J Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA
- Dartmouth Cancer Center, Dartmouth Health, Lebanon, New Hampshire, USA
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Alexander DA, Majji S, Jermyn M, Byrd BK, Bruza P, Li T, Zhu TC. Characterization of Cherenkov imaging parameters and positional constraints on an O-ring linear accelerator. Phys Med Biol 2023; 68:10.1088/1361-6560/acfdf2. [PMID: 37757840 PMCID: PMC10693929 DOI: 10.1088/1361-6560/acfdf2] [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: 06/19/2023] [Accepted: 09/27/2023] [Indexed: 09/29/2023]
Abstract
Objective. With the introduction of Cherenkov imaging technology on the Halcyon O-ring linear accelerator platform, we seek to demonstrate the imaging feasibility and optimize camera placement.Approach. Imaging parameters were probed by acquiring triggering data Cherenkov image frames for simplistic beams on the Halcyon and comparing the analyzed metrics with those from the TrueBeam platform. Camera position was analyzed by performing 3D rendering of patient treatment plans for various sites and iterating over camera positions to assess treatment area visibility.Main results. Commercial Cherenkov imaging systems are compatible with the pulse timing of the Halcyon, and this platform design favorably impacts signal to noise in Cherenkov image frames. Additionally, ideal camera placement is treatment site dependent and is always within a biconical zone of visibility centered on the isocenter. Visibility data is provided for four treatment sites, with suggestions for camera placement based on room dimensions. Median visibility values were highest for right breast plans, with values of 80.33% and 68.49% for the front and rear views respectively. Head and neck plans presented with the lowest values at 26.44% and 38.18% respectively.Significance. This work presents the first formal camera positional analysis for Cherenkov imaging on any platform and serves as a template for performing similar work for other irradiation platforms. Additionally, this study confirms the Cherenkov imaging parameters do not need to be changed for optimal imaging on the Halcyon. Lastly, the presented methodology provides a framework which could be further expanded to other optical imaging systems which rely on line of sight visibility to the patient.
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Affiliation(s)
- Daniel A. Alexander
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia PA
| | | | - Michael Jermyn
- DoseOptics LLC, Lebanon NH
- Thayer School of Engineering, Dartmouth College, Hanover NH
| | - Brook K. Byrd
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia PA
| | - Petr Bruza
- DoseOptics LLC, Lebanon NH
- Thayer School of Engineering, Dartmouth College, Hanover NH
| | - Taoran Li
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia PA
| | - Timothy C. Zhu
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia PA
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3
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Lynch N, Robar JL, Monajemi T. Camera-based radiotherapy dosimetry using dual-material 3D printed scintillator arrays. Med Phys 2023; 50:1824-1842. [PMID: 36546558 DOI: 10.1002/mp.16167] [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: 05/18/2022] [Revised: 11/23/2022] [Accepted: 12/07/2022] [Indexed: 12/24/2022] Open
Abstract
PURPOSE AND OBJECTIVE To describe a methodology for the dual-material fused deposition modeling (FDM) 3D printing of plastic scintillator arrays, to characterize their light output under irradiation using an sCMOS camera, and to establish a methodology for the dosimetric calibration of planar array geometries. MATERIALS AND METHODS We have published an investigation into the fabrication and characterization of single element FDM printed scintillators intending to produce customizable dosimeters for radiation therapy applications. 1 This work builds on previous investigations by extending the concept to the production of a high-resolution (scintillating element size 3 × 3 × 3 mm3 ) planar scintillator array. The array was fabricated using a BCN3D Epsilon W27 3D printer and composed of polylactic acid (PLA) filament and BCF-10 plastic scintillator. The array's response was initially characterized using a 20 × 20 cm2 6 MV photon field with a source-to-surface (SSD) distance of 100 cm and the beam incident on the top of the array. The light signals emitted under irradiation were imaged using 200 ms exposures from a sCMOS camera positioned at the foot of the treatment couch (210 cm from the array). The collected images were then processed using a purpose-built software to correct known optical artefacts and determine the light output for each scintillating element. The light output was then corrected for element sensitivity and calibrated to dose using Monte Carlo simulations of the array and irradiation geometry based on the array's digital 3D print model. To assess the accuracy of the array calibration both a 3D beam and a clinical VMAT plan were delivered. Dose measurements using the calibrated array were then compared to EBT3 GAFChromic film and OSLD measurements, as well as Monte Carlo simulations and TPS calculations. RESULTS Our results establish the feasibility of dual-material 3D printing for the fabrication of custom plastic scintillator arrays. Assessment of the 3D printed scintillators response across each row of the array demonstrated a nonuniform response with an average percentage deviation from the mean of 2.1% ± 2.8%. This remains consistent with our previous work on individual 3D printed scintillators which showed an average difference of 2.3% and a maximum of 4.0% between identically printed scintillators.1 Array dose measurements performed following calibration indicate difficulty in differentiating the scintillator response from ambient background light contamination at low doses (<20-25 cGy) and dose rates (≤100 MU/min). However, when analysis was restricted to exclude dose values less than 10% of the Monte Carlo simulated max dose the average absolute percentage dose difference between Monte Carlo simulation and array measurement was 5.3% ± 4.8% for the fixed beam delivery and 5.4% ± 5.2% for the VMAT delivery CONCLUSION: In this study, we developed and characterized a 3D printed array of plastic scintillators and demonstrated a methodology for the dosimetric calibration of a simple array geometry.
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Affiliation(s)
- Nicholas Lynch
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada
| | - James L Robar
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada
- Department of Medical Physics, Nova Scotia Health, Halifax, NS, Canada
- Department of Radiation Oncology, Dalhousie University, Halifax, NS, Canada
| | - Thalat Monajemi
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada
- Department of Medical Physics, Nova Scotia Health, Halifax, NS, Canada
- Department of Radiation Oncology, Dalhousie University, Halifax, NS, Canada
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Wickramasinghe VA, Decker SM, Streeter SS, Sloop AM, Petusseau AF, Alexander DA, Bruza P, Gladstone DJ, Zhang R, Pogue BW. Color-resolved Cherenkov imaging allows for differential signal detection in blood and melanin content. JOURNAL OF BIOMEDICAL OPTICS 2023; 28:036005. [PMID: 36923987 PMCID: PMC10008915 DOI: 10.1117/1.jbo.28.3.036005] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 02/15/2023] [Indexed: 06/18/2023]
Abstract
Significance High-energy x-ray delivery from a linear accelerator results in the production of spectrally continuous broadband Cherenkov light inside tissue. In the absence of attenuation, there is a linear relationship between Cherenkov emission and deposited dose; however, scattering and absorption result in the distortion of this linear relationship. As Cherenkov emission exits the absorption by tissue dominates the observed Cherenkov emission spectrum. Spectroscopic interpretation of this effects may help to better relate Cherenkov emission to ionizing radiation dose delivered during radiotherapy. Aim In this study, we examined how color Cherenkov imaging intensity variations are caused by absorption from both melanin and hemoglobin level variations, so that future Cherenkov emission imaging might be corrected for linearity to delivered dose. Approach A custom, time-gated, three-channel intensified camera was used to image the red, green, and blue wavelengths of Cherenkov emission from tissue phantoms with synthetic melanin layers and varying blood concentrations. Our hypothesis was that spectroscopic separation of Cherenkov emission would allow for the identification of attenuated signals that varied in response to changes in blood content versus melanin content, because of their different characteristic absorption spectra. Results Cherenkov emission scaled with dose linearly in all channels. Absorption in the blue and green channels increased with increasing oxy-hemoglobin in the blood to a greater extent than in the red channel. Melanin was found to absorb with only slight differences between all channels. These spectral differences can be used to derive dose from measured Cherenkov emission. Conclusions Color Cherenkov emission imaging may be used to improve the optical measurement and determination of dose delivered in tissues. Calibration for these factors to minimize the influence of the tissue types and skin tones may be possible using color camera system information based upon the linearity of the observed signals.
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Affiliation(s)
| | - Savannah M. Decker
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
| | - Samuel S. Streeter
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
| | - Austin M. Sloop
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
| | - Arthur F. Petusseau
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
| | - Daniel A. Alexander
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
| | - Petr Bruza
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
| | - David J. Gladstone
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
- Dartmouth College, Geisel School of Medicine, Department of Medicine, Hanover, New Hampshire, United States
| | - Rongxiao Zhang
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
- Dartmouth College, Geisel School of Medicine, Department of Medicine, Hanover, New Hampshire, United States
| | - Brian W. Pogue
- Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States
- University of Wisconsin–Madison, Department of Medical Physics, Madison, Wisconsin, United States
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Di X, Geng C, Guo C, Shang Y, Fu H, Han H, Tang X. Enhanced Cherenkov imaging for real-time beam visualization by applying a novel carbon quantum dot sheeting in radiotherapy. Med Phys 2023; 50:1215-1227. [PMID: 36433734 DOI: 10.1002/mp.16121] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 11/10/2022] [Accepted: 11/10/2022] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND Cherenkov imaging can be used to visualize the placement of the beam directly on the patient's surface tissue and evaluate the accuracy of treatment planning. However, Cherenkov emission intensity is lower than ambient light. At present, time gating is the only way to realize Cherenkov imaging with ambient light. PURPOSE This study proposes preparing a novel carbon quantum dot (cQD) sheeting to adjust the wavelength of Cherenkov emission to obtain the optimal wavelength meeting the sensitive detection region of the camera, meanwhile the total optical signal is also increased. By combining a specific filter, this approach might help in using lower-cost camera systems without intensifier-coupled to accomplish in vivo monitoring of the surface beam profile on patients with ambient light. METHODS The cQD sheetings were prepared by spin coating and UV curing with different concentrations. All experiments were performed on the Varian VitalBeam system and optical emission was captured using an electron multiplying charge-coupled device (EMCCD) camera. To quantify the optical characteristics and certify the improvement of light intensity as well as signal-to-noise ratio (SNR) of cQD sheeting, the first part of the study was carried out on solid water with 6 and 10 MV photon beams. The second part was carried out on an anthropomorphic phantom to explore the applicability of sheeting when using different radiotherapy materials and the imaging effect of sheeting with the impact of ambient light sources. Additionally, thanks to the narrow emission spectrum of the cQD, a band-pass filter was tested to reduce the effect from environmental lights. RESULTS The experimental results show that the optical intensity collected with sheeting has an excellent linear relationship (R2 > 0.99) with the dose for 6 and 10 MV photons. The full-width half maximum (FWHM) in x and y axis matched with the measured EBT film image, with accuracy in the range of ±1.2 and ±2.7 mm standard deviation, respectively. CQD sheeting can significantly improve the light intensity and SNR of optical images. Using 0.1 mg/ml sheeting as an example, the signal intensity is increased by 209%, and the SNR is increased by 147.71% at 6 MV photons. The imaging on the anthropomorphic phantom verified that cQD sheeting could be applied to different radiotherapy materials. The average optical intensity increased by about 69.25%, 63.72%, and 61.78%, respectively, after adding cQD sheeting to bolus, mask sample and the combination of bolus and mask. Corresponding SNR is improved by about 62.78%, 56.77%, and 68.80%, respectively. Through the sheeting, optical images with SNR > 5 can be obtained in the presence of ambient light and it can be improved through combining with a band-pass filter. When red ambient lights are on, the SNR is increased by about 98.85% after adding a specific filter. CONCLUSION Through a combination of cQD sheeting and corresponding filter, light intensity and SNR of optical images can be increased significantly, and it shed new light on the promotion of the clinical application of optical imaging to visualize the beam in radiotherapy.
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Affiliation(s)
- Xing Di
- Department of Nuclear Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, People's Republic of China
| | - Changran Geng
- Department of Nuclear Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, People's Republic of China.,Joint International Research Laboratory on Advanced Particle Therapy, Nanjing University of Aeronautics and Astronautics, Nanjing, People's Republic of China
| | - Chang Guo
- Department of Radiation Oncology, Jiangsu Cancer Hospital, Nanjing, People's Republic of China
| | - Yufen Shang
- Department of Radiation Physics, Dezhou Second People's Hospital, Dezhou, People's Republic of China
| | - Hongtao Fu
- Department of Radiation Physics, Dezhou Second People's Hospital, Dezhou, People's Republic of China
| | - Haonan Han
- Department of Nuclear Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, People's Republic of China
| | - Xiaobin Tang
- Department of Nuclear Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, People's Republic of China.,Joint International Research Laboratory on Advanced Particle Therapy, Nanjing University of Aeronautics and Astronautics, Nanjing, People's Republic of China
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6
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Alexander DA, Decker SM, Jermyn M, Bruza P, Zhang R, Chen E, McGlynn TL, Rosselot RA, Lee J, Rose ML, Williams BB, Pogue BW, Gladstone DJ, Jarvis LA. One Year of Clinic-Wide Cherenkov Imaging for Discovery of Quality Improvement Opportunities in Radiation Therapy. Pract Radiat Oncol 2023; 13:71-81. [PMID: 35777728 PMCID: PMC10984217 DOI: 10.1016/j.prro.2022.06.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 05/20/2022] [Accepted: 06/07/2022] [Indexed: 01/10/2023]
Abstract
PURPOSE Cherenkov imaging is clinically available as a radiation therapy treatment verification tool. The aim of this work was to discover the benefits of always-on Cherenkov imaging as a novel incident detection and quality improvement system through review of all imaging at our center. METHODS AND MATERIALS Multicamera Cherenkov imaging systems were permanently installed in 3 treatment bunkers, imaging continuously over a year. Images were acquired as part of normal treatment procedures and reviewed for potential treatment delivery anomalies. RESULTS In total, 622 unique patients were evaluated for this study. We identified 9 patients with treatment anomalies occurring over their course of treatment, which were only detected with Cherenkov imaging. Categorizing each event indicated issues arising in simulation, planning, pretreatment review, and treatment delivery, and none of the incidents were detected before this review by conventional measures. The incidents identified in this study included dose to unintended areas in planning, dose to unintended areas due to positioning at treatment, and nonideal bolus placement during setup. CONCLUSIONS Cherenkov imaging was shown to provide a unique method of detecting radiation therapy incidents that would have otherwise gone undetected. Although none of the events detected in this study reached the threshold of reporting, they identified opportunities for practice improvement and demonstrated added value of Cherenkov imaging in quality assurance programs.
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Affiliation(s)
- Daniel A Alexander
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire.
| | - Savannah M Decker
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Dose Optics LLC, Lebanon, New Hampshire
| | - Michael Jermyn
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Dose Optics LLC, Lebanon, New Hampshire
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Dose Optics LLC, Lebanon, New Hampshire
| | - Rongxiao Zhang
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire; Dartmouth Cancer Center, Lebanon, New Hampshire
| | - Erli Chen
- Cheshire Medical Center, Keene, New Hampshire
| | | | | | - Jae Lee
- Dartmouth Cancer Center, Lebanon, New Hampshire
| | | | - Benjamin B Williams
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire; Dartmouth Cancer Center, Lebanon, New Hampshire
| | - Brian W Pogue
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Dose Optics LLC, Lebanon, New Hampshire; Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin
| | - David J Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire
| | - Lesley A Jarvis
- Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire; Dartmouth Cancer Center, Lebanon, New Hampshire
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Decker SM, Alexander DA, Bruza P, Zhang R, Chen E, Jarvis LA, Gladstone DJ, Pogue BW. Performance comparison of quantitative metrics for analysis of in vivo Cherenkov imaging incident detection during radiotherapy. Br J Radiol 2022; 95:20211346. [PMID: 35834415 PMCID: PMC10996952 DOI: 10.1259/bjr.20211346] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 06/06/2022] [Accepted: 06/10/2022] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVES Examine the responses of multiple image similarity metrics to detect patient positioning errors in radiotherapy observed through Cherenkov imaging, which may be used to optimize automated incident detection. METHODS An anthropomorphic phantom mimicking patient vasculature, a biological marker seen in Cherenkov images, was simulated for a breast radiotherapy treatment. The phantom was systematically shifted in each translational direction, and Cherenkov images were captured during treatment delivery at each step. The responses of mutual information (MI) and the γ passing rate (%GP) were compared to that of existing field-shape matching image metrics, the Dice coefficient, and mean distance to conformity (MDC). Patient images containing other incidents were analyzed to verify the best detection algorithm for different incident types. RESULTS Positional shifts in all directions were registered by both MI and %GP, degrading monotonically as the shifts increased. Shifts in intensity, which may result from erythema or bolus-tissue air gaps, were detected most by %GP. However, neither metric detected beam-shape misalignment, such as that caused by dose to unintended areas, as well as currently employed metrics (Dice and MDC). CONCLUSIONS This study indicates that different radiotherapy incidents may be detected by comparing both inter- and intrafractional Cherenkov images with a corresponding image similarity metric, varying with the type of incident. Future work will involve determining appropriate thresholds per metric for automatic flagging. ADVANCES IN KNOWLEDGE Classifying different algorithms for the detection of various radiotherapy incidents allows for the development of an automatic flagging system, eliminating the burden of manual review of Cherenkov images.
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Affiliation(s)
- Savannah M Decker
- Thayer School of Engineering, Dartmouth College,
Hanover, New Hampshire, United
States
| | - Daniel A Alexander
- Thayer School of Engineering, Dartmouth College,
Hanover, New Hampshire, United
States
- DoseOptics LLC, Lebanon, New
Hampshire, United States
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College,
Hanover, New Hampshire, United
States
- DoseOptics LLC, Lebanon, New
Hampshire, United States
| | - Rongxiao Zhang
- Thayer School of Engineering, Dartmouth College,
Hanover, New Hampshire, United
States
- Geisel School of Medicine, Dartmouth College,
Hanover, New Hampshire, United
States
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical
Center, Lebanon, New Hampshire,
United States
| | - Erli Chen
- Cheshire Medical Center, Keene
NH, United States
| | - Lesley A Jarvis
- Geisel School of Medicine, Dartmouth College,
Hanover, New Hampshire, United
States
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical
Center, Lebanon, New Hampshire,
United States
| | - David J Gladstone
- Thayer School of Engineering, Dartmouth College,
Hanover, New Hampshire, United
States
| | - Brian W Pogue
- Thayer School of Engineering, Dartmouth College,
Hanover, New Hampshire, United
States
- DoseOptics LLC, Lebanon, New
Hampshire, United States
- Department of Medical Physics, University of
Wisconsin-Madison, Madison,
Wisconsin, United States
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8
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Toyonaga C, Yamamoto S, Yabe T, Okudaira K, Yogo K, Hirano Y, Kataoka J. Correcting angular dependencies using non-polarized components of Cherenkov light in water during high-energy X-ray irradiation. Med Phys 2022; 49:5409-5416. [PMID: 35670250 DOI: 10.1002/mp.15794] [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: 08/18/2021] [Revised: 05/26/2022] [Accepted: 05/29/2022] [Indexed: 11/08/2022] Open
Abstract
OBJECTIVE Dose distribution measurements of high-energy X-rays from medical linear accelerators (LINAC) in water are important for quality control (QC) of the system. Although Cherenkov-light imaging is a useful method for measuring the high-energy X-ray dose distribution, depth profiles have an underestimated dose at increased depths due to the angular dependency of the Cherenkov light generated in water. In this study, we use a linear polarizer to separate the majority of polarized components from the majority of unpolarized components of Cherenkov-light images in water and then use this information to correct for angular dependencies. METHODS A water phantom, a cooled charge-coupled device (CCD) camera, and a polarizer were installed in a black box. Then, the water phantom was irradiated from the upper side with 6 MV or 10 MV X-rays, and the Cherenkov light generated in water was imaged with the polarizer axis at both parallel and perpendicular orientations to the beam. By using these images from the two orientations relative to the beam, we corrected the angular dependency of the Cherenkov light. RESULTS By subtracting the images measured with the polarizer perpendicular to the beams from the images measured with the polarizer parallel to the beams, we could obtain images with only the polarized components. Using these images, we could calculate the images with non-polarized components that had similar depth profiles to those calculated with a planning system. The average difference between corrected depth profiles and those calculated with the planning system was less than 1%, while that between uncorrected depth profiles and the planning system was more than 8.3% in depths of water from 20 mm to 100 mm. CONCLUSION We conclude that use of the polarizer has the potential to improve the accuracy of dose distribution in Cherenkov-light imaging of water using high-energy X-rays. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Chihiro Toyonaga
- Department of Integrated Health Science, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Seiichi Yamamoto
- Faculty of Science and Engineering, Waseda University, Tokyo, Japan
| | - Takuya Yabe
- Department of Integrated Health Science, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Kuniyasu Okudaira
- Department of Radiological Technology, Nagoya University Hospital, Nagoya, Japan
| | - Katsunori Yogo
- Department of Integrated Health Science, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yoshiyuki Hirano
- Department of Integrated Health Science, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Jun Kataoka
- Faculty of Science and Engineering, Waseda University, Tokyo, Japan
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Ashraf MR, Rahman M, Cao X, Duval K, Williams BB, Hoopes PJ, Gladstone DJ, Pogue BW, Zhang R, Bruza P. Individual pulse monitoring and dose control system for pre-clinical implementation of FLASH-RT. Phys Med Biol 2022; 67:10.1088/1361-6560/ac5f6f. [PMID: 35313290 PMCID: PMC10305796 DOI: 10.1088/1361-6560/ac5f6f] [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: 06/29/2021] [Accepted: 03/21/2022] [Indexed: 11/11/2022]
Abstract
Objective.Existing ultra-high dose rate (UHDR) electron sources lack dose rate independent dosimeters and a calibrated dose control system for accurate delivery. In this study, we aim to develop a custom single-pulse dose monitoring and a real-time dose-based control system for a FLASH enabled clinical linear accelerator (Linac).Approach.A commercially available point scintillator detector was coupled to a gated integrating amplifier and a real-time controller for dose monitoring and feedback control loop. The controller was programmed to integrate dose for each radiation pulse and stop the radiation beam when the prescribed dose was delivered. Additionally, the scintillator was mounted in a solid water phantom and placed underneath mice skin forin vivodose monitoring. The scintillator was characterized in terms of its radiation stability, mean dose-rate (Ḋm), and dose per pulse (Dp) dependence.Main results.TheDpexhibited a consistent ramp-up period across ∼4-5 pulse. The plastic scintillator was shown to be linear withḊm(40-380 Gy s-1) andDp(0.3-1.3 Gy Pulse-1) to within +/- 3%. However, the plastic scintillator was subject to significant radiation damage (16%/kGy) for the initial 1 kGy and would need to be calibrated frequently. Pulse-counting control was accurately implemented with one-to-one correspondence between the intended and the actual delivered pulses. The dose-based control was sufficient to gate on any pulse of the Linac.In vivodosimetry monitoring with a 1 cm circular cut-out revealed that during the ramp-up period, the averageDpwas ∼0.045 ± 0.004 Gy Pulse-1, whereas after the ramp-up it stabilized at 0.65 ± 0.01 Gy Pulse-1.Significance.The tools presented in this study can be used to determine the beam parameter space pertinent to the FLASH effect. Additionally, this study is the first instance of real-time dose-based control for a modified Linac at ultra-high dose rates, which provides insight into the tool required for future clinical translation of FLASH-RT.
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Affiliation(s)
- M. Ramish Ashraf
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
| | - Mahbubur Rahman
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
| | - Xu Cao
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
| | - Kayla Duval
- Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover NH 03755 USA
| | - Benjamin B. Williams
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover NH 03755 USA
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
| | - P. Jack Hoopes
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
- Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover NH 03755 USA
| | - David J. Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover NH 03755 USA
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
| | - Brian W. Pogue
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
- Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover NH 03755 USA
| | - Rongxiao Zhang
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover NH 03755 USA
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
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Alexander DA, Nomezine A, Jarvis LA, Gladstone DJ, Pogue BW, Bruza P. Color Cherenkov imaging of clinical radiation therapy. LIGHT, SCIENCE & APPLICATIONS 2021; 10:226. [PMID: 34737264 PMCID: PMC8569159 DOI: 10.1038/s41377-021-00660-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 10/01/2021] [Accepted: 10/08/2021] [Indexed: 05/08/2023]
Abstract
Color vision is used throughout medicine to interpret the health and status of tissue. Ionizing radiation used in radiation therapy produces broadband white light inside tissue through the Cherenkov effect, and this light is attenuated by tissue features as it leaves the body. In this study, a novel time-gated three-channel camera was developed for the first time and was used to image color Cherenkov emission coming from patients during treatment. The spectral content was interpreted by comparison with imaging calibrated tissue phantoms. Color shades of Cherenkov emission in radiotherapy can be used to interpret tissue blood volume, oxygen saturation and major vessels within the body.
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Affiliation(s)
- Daniel A Alexander
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
- DoseOptics LLC, Lebanon, NH, USA
| | - Anthony Nomezine
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
| | - Lesley A Jarvis
- Geisel School of Medicine, Dartmouth College, Hanover, NH, USA
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA
| | - David J Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
- Geisel School of Medicine, Dartmouth College, Hanover, NH, USA
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA
| | - Brian W Pogue
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
- DoseOptics LLC, Lebanon, NH, USA
- Geisel School of Medicine, Dartmouth College, Hanover, NH, USA
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.
- DoseOptics LLC, Lebanon, NH, USA.
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11
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Rahman M, Ashraf MR, Zhang R, Bruza P, Dexter CA, Thompson L, Cao X, Williams BB, Hoopes PJ, Pogue BW, Gladstone DJ. Electron FLASH Delivery at Treatment Room Isocenter for Efficient Reversible Conversion of a Clinical LINAC. Int J Radiat Oncol Biol Phys 2021; 110:872-882. [PMID: 33444695 PMCID: PMC10416223 DOI: 10.1016/j.ijrobp.2021.01.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 12/02/2020] [Accepted: 01/07/2021] [Indexed: 12/21/2022]
Abstract
PURPOSE In this study, procedures were developed to achieve efficient reversible conversion of a clinical linear accelerator (LINAC) and deliver ultrahigh-dose-rate (UHDR) electron or conventional beams to the treatment room isocenter for FLASH radiation therapy. METHODS AND MATERIALS The LINAC was converted to deliver UHDR beam within 20 minutes by retracting the x-ray target from the beam's path, positioning the carousel on an empty port, and selecting 10 MV photon beam energy in the treatment console. Dose rate surface and depth dose profiles were measured in solid water phantom at different field sizes with Gafchromic film and an optically stimulated luminescent dosimeter (OSLD). A pulse controller counted the pulses via scattered radiation signal and gated the delivery for a preset pulse count. A fast photomultiplier tube-based Cherenkov detector measured the per pulse beam output at a 2-ns sampling rate. After conversion back to clinical mode, conventional beam output, flatness, symmetry, field size, and energy were measured for all clinically commissioned energies. RESULTS The surface average dose rates at the isocenter for 1-cm diameter and 1.5-in diameter circular fields and for a jaws-wide-open field were 238 ± 5 Gy/s, 262 ± 5 Gy/s, and 290 ± 5 Gy/s, respectively. The radial symmetry of the beams was within 2.4%, 0.5%, and 0.2%, respectively. The doses from simultaneous irradiation of film and OSLD were within 1%. The photomultiplier tube showed the LINAC required ramp up time in the first 4 to 6 pulses before the output stabilized, after which its stability was within 3%. CONCLUSIONS At the isocenter of the treatment room, 10 MeV UHDR beams were achieved. The beam output was reproducible but requires further investigation of the ramp up time, equivalent to ∼1 Gy, requiring dose monitoring. The UHDR beam can irradiate both small and large subjects to investigate potential FLASH radiobiological effects in minimally modified clinical settings, and the dose rate can be further increased by reducing the source-to-surface distance.
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Affiliation(s)
- Mahbubur Rahman
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire.
| | - M Ramish Ashraf
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire
| | - Rongxiao Zhang
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire; Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire
| | - Chad A Dexter
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire
| | - Lawrence Thompson
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire
| | - Xu Cao
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire
| | - Benjamin B Williams
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire; Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire
| | - P Jack Hoopes
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire; Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire
| | - Brian W Pogue
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire; Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire
| | - David J Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire; Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire
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12
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Rahman M, Ashraf MR, Zhang R, Gladstone DJ, Cao X, Williams BB, Hoopes PJ, Pogue BW, Bruza P. Spatial and temporal dosimetry of individual electron FLASH beam pulses using radioluminescence imaging. Phys Med Biol 2021; 66:10.1088/1361-6560/ac0390. [PMID: 34015774 PMCID: PMC10468779 DOI: 10.1088/1361-6560/ac0390] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 05/20/2021] [Indexed: 11/11/2022]
Abstract
Purpose.In this study, spatio-temporal beam profiling for electron ultra-high dose rate (UHDR; >40 Gy s-1) radiation via Cherenkov emission and radioluminescence imaging was investigated using intensified complementary metal-oxide-semiconductor cameras.Methods.The cameras, gated to FLASH optimized linear accelerator pulses, imaged radioluminescence and Cherenkov emission incited by single pulses of a UHDR (>40 Gy s-1) 10 MeV electron beam delivered to the isocenter. Surface dosimetry was investigated via imaging Cherenkov emission or scintillation from a solid water phantom or Gd2O2S:Tb screen positioned on top of the phantom, respectively. Projected depth-dose profiles were imaged from a tank filled with water (Cherenkov emission) and a 1 g l-1quinine sulfate solution (scintillation). These optical results were compared with projected lateral dose profiles measured by Gafchromic film at different depths, including the surface.Results.The per-pulse beam output from Cherenkov imaging agreed with the photomultiplier tube Cherenkov output to within 3% after about the first five to seven ramp-up pulses. Cherenkov emission and scintillation were linear with dose (R2 = 0.987 and 0.995, respectively) and independent of dose rate from ∼50 to 300 Gy s-1(0.18-0.91 Gy/pulse). The surface dose distribution from film agreed better with scintillation than with Cherenkov emission imaging (3%/3 mm gamma pass rates of 98.9% and 88.8%, respectively). Using a 450 nm bandpass filter, the quinine sulfate-based water imaging of the projected depth optical profiles agreed with the projected film dose to within 5%.Conclusion.The agreement of surface dosimetry using scintillation screen imaging and Gafchromic film suggests it can verify the consistency of daily beam quality assurance parameters with an accuracy of around 2% or 2 mm. Cherenkov-based surface dosimetry was affected by the target's optical properties, prompting additional calibration. In projected depth-dose profiling, scintillation imaging via spectral suppression of Cherenkov emission provided the best match to film. Both camera-based imaging modalities resolved dose from single UHDR beam pulses of up to 60 Hz repetition rate and 1 mm spatial resolution.
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Affiliation(s)
- Mahbubur Rahman
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
| | - M. Ramish Ashraf
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
| | - Rongxiao Zhang
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Department of Medicine, Radiation Oncology, Geisel School of Medicine, Dartmouth College Hanover NH 03755 USA
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
| | - David J. Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Department of Medicine, Radiation Oncology, Geisel School of Medicine, Dartmouth College Hanover NH 03755 USA
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
| | - Xu Cao
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
| | - Benjamin B. Williams
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Department of Medicine, Radiation Oncology, Geisel School of Medicine, Dartmouth College Hanover NH 03755 USA
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
| | - P. Jack Hoopes
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Department of Medicine, Radiation Oncology, Geisel School of Medicine, Dartmouth College Hanover NH 03755 USA
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
- Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover NH 03755 USA
| | - Brian W. Pogue
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA
- Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover NH 03755 USA
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover NH 03755, US
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13
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Hachadorian R, Farwell JC, Bruza P, Jermyn M, Gladstone DJ, Pogue BW, Jarvis LA. Verification of field match lines in whole breast radiation therapy using Cherenkov imaging. Radiother Oncol 2021; 160:90-96. [PMID: 33892022 DOI: 10.1016/j.radonc.2021.04.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 03/17/2021] [Accepted: 04/09/2021] [Indexed: 01/05/2023]
Abstract
PURPOSE In mono-isocentric radiation therapy treatment plans designed to treat the whole breast and supraclavicular lymph nodes, the fields meet at isocenter, forming the match line. Insufficient coverage at the match line can lead to recurrence, and overlap over weeks of treatment can lead to increased risk of healthy tissue toxicity. Cherenkov imaging was used to assess the accuracy of delivery at the match line and identify potential incidents during patient treatments. METHODS AND MATERIALS A controlled calibration was constructed from the deconvolved Cherenkov images from the delivery of a modified patient treatment plan to an anthropomorphic phantom with introduced separation and overlap. The trend from this calibration was then used to evaluate the field match line for accuracy and inter-fraction consistency for two patients. RESULTS The intersection point between matching field profiles was directly correlated to the distance (gap/overlap) between the fields (anthropomorphic phantom R2 = 0.994 "breath hold" and R2 = 0.990 "free breathing"). The profile intersection points from two patients' imaging sessions yielded an average of +1.40 mm offset (overlap) and -1.32 mm offset (gap), thereby introducing roughly a 25.0% over-dose and a -23.6% under-dose (R2 = 0.994). CONCLUSIONS This study shows that field match regions can be detected and quantified by taking deconvolved Cherenkov images and using their product image to create steep intensity gradients, causing match lines to stand out. These regions can then be quantitatively translated into a dose consequence. This approach offers a high sensitivity detection method which can quantify match line variability and errors in vivo.
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Affiliation(s)
| | | | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover, United States
| | - Michael Jermyn
- Thayer School of Engineering, Dartmouth College, Hanover, United States; DoseOptics LLC, Lebanon, United States
| | - David J Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover, United States; Norris Cotton Cancer Center at Dartmouth Hitchcock Medical Center, Lebanon, United States; Geisel School of Medicine, Dartmouth College, Hanover, United States
| | - Brian W Pogue
- Thayer School of Engineering, Dartmouth College, Hanover, United States; DoseOptics LLC, Lebanon, United States; Norris Cotton Cancer Center at Dartmouth Hitchcock Medical Center, Lebanon, United States; Geisel School of Medicine, Dartmouth College, Hanover, United States
| | - Lesley A Jarvis
- Norris Cotton Cancer Center at Dartmouth Hitchcock Medical Center, Lebanon, United States; Geisel School of Medicine, Dartmouth College, Hanover, United States.
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14
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Tendler II, Bruza P, Jermyn M, Soter J, Sharp G, Williams B, Jarvis LA, Pogue B, Gladstone DJ. Technical Note: A novel dosimeter improves total skin electron therapy surface dosimetry workflow. J Appl Clin Med Phys 2020; 21:158-162. [PMID: 32306551 PMCID: PMC7324701 DOI: 10.1002/acm2.12880] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 03/11/2020] [Accepted: 03/13/2020] [Indexed: 01/15/2023] Open
Abstract
PURPOSE The novel scintillator-based system described in this study is capable of accurately and remotely measuring surface dose during Total Skin Electron Therapy (TSET); this dosimeter does not require post-exposure processing or annealing and has been shown to be re-usable, resistant to radiation damage, have minimal impact on surface dose, and reduce chances of operator error compared to existing technologies e.g. optically stimulated luminescence detector (OSLD). The purpose of this study was to quantitatively analyze the workflow required to measure surface dose using this new scintillator dosimeter and compare it to that of standard OSLDs. METHODS Disc-shaped scintillators were attached to a flat-faced phantom and a patient undergoing TSET. Light emission from these plastic discs was captured using a time-gated, intensified, camera during irradiation and converted to dose using an external calibration factor. Time required to complete each step (daily QA, dosimeter preparation, attachment, removal, registration, and readout) of the scintillator and OSLD surface dosimetry workflows was tracked. RESULTS In phantoms, scintillators and OSLDs surface doses agreed within 3% for all data points. During patient imaging it was found that surface dose measured by OSLD and scintillator agreed within 5% and 3% for 35/35 and 32/35 dosimetry sites, respectively. The end-to-end time required to measure surface dose during phantom experiments for a single dosimeter was 78 and 202 sec for scintillator and OSL dosimeters, respectively. During patient treatment, surface dose was assessed at 7 different body locations by scintillator and OSL dosimeters in 386 and 754 sec, respectively. CONCLUSION Scintillators have been shown to report dose nearly twice as fast as OSLDs with substantially less manual work and reduced chances of human error. Scintillator dose measurements are automatically saved to an electronic patient file and images contain a permanent record of the dose delivered during treatment.
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Affiliation(s)
| | - Petr Bruza
- Thayer School of EngineeringDartmouth CollegeHanoverNHUSA
| | - Michael Jermyn
- Thayer School of EngineeringDartmouth CollegeHanoverNHUSA
- DoseOptics LLCLebanonNHUSA
| | - Jennifer Soter
- Thayer School of EngineeringDartmouth CollegeHanoverNHUSA
| | - Gregory Sharp
- Department of Radiation OncologyMassachusetts General HospitalBostonMAUSA
| | - Benjamin Williams
- Department of MedicineGeisel School of MedicineDartmouth CollegeHanoverNHUSA
- Norris Cotton Cancer CenterDartmouth‐Hitchcock Medical CenterLebanonNHUSA
| | - Lesley A. Jarvis
- Department of MedicineGeisel School of MedicineDartmouth CollegeHanoverNHUSA
- Norris Cotton Cancer CenterDartmouth‐Hitchcock Medical CenterLebanonNHUSA
| | - Brian Pogue
- Thayer School of EngineeringDartmouth CollegeHanoverNHUSA
- DoseOptics LLCLebanonNHUSA
| | - David J. Gladstone
- Thayer School of EngineeringDartmouth CollegeHanoverNHUSA
- Department of MedicineGeisel School of MedicineDartmouth CollegeHanoverNHUSA
- Norris Cotton Cancer CenterDartmouth‐Hitchcock Medical CenterLebanonNHUSA
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15
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Andreozzi JM, Brůža P, Cammin J, Pogue BW, Gladstone DJ, Green O. Optical imaging method to quantify spatial dose variation due to the electron return effect in an MR-linac. Med Phys 2020; 47:1258-1267. [PMID: 31821573 PMCID: PMC7112467 DOI: 10.1002/mp.13954] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 11/21/2019] [Accepted: 11/26/2019] [Indexed: 11/12/2022] Open
Abstract
PURPOSE Treatment planning systems (TPSs) for MR-linacs must employ Monte Carlo-based simulations of dose deposition to model the effects of the primary magnetic field on dose. However, the accuracy of these simulations, especially for areas of tissue-air interfaces where the electron return effect (ERE) is expected, is difficult to validate due to physical constraints and magnetic field compatibility of available detectors. This study employs a novel dosimetric method based on remotely captured, real-time optical Cherenkov and scintillation imaging to visualize and quantify the ERE. METHODS An intensified CMOS camera was used to image two phantoms with designed ERE cavities. Phantom A was a 40 cm × 10 cm × 10 cm clear acrylic block drilled with five holes of increasing diameters (0.5, 1, 2, 3, 4 cm). Phantom B was a clear acrylic block (25 cm × 20 cm × 5 cm) with three cavities of increasing diameter (3, 2, 1 cm) split into two halves in the transverse plane to accommodate radiochromic film. Both phantoms were imaged while being irradiated by 6 MV flattening filter free (FFF) beams within a MRIdian Viewray (Viewray, Cleveland, OH) MR-linac (0.34 T primary field). Phantom A was imaged while being irradiated by 6 MV FFF beams on a conventional linac (TrueBeam, Varian Medical Systems, San Jose, CA) to serve as a control. Images were post processed in Matlab (Mathworks Inc., Natick, MA) and compared to TPS dose volumes. RESULTS Control imaging of Phantom A without the presence of a magnetic field supports the validity of the optical image data to a depth of 6 cm. In the presence of the magnetic field, the optical data shows deviations from the commissioned TPS dose in both intensity and localization. The largest air cavity examined (3 cm) indicated the largest dose differences, which were above 20% at some locations. Experiments with Phantom B illustrated similar agreement between optical and film dosimetry comparisons with TPS data in areas not affected by ERE. CONCLUSION There are some appreciable differences in dose intensity and spatial dose distribution observed between the novel experimental data set and the dose models produced by the current clinically implemented MR-IGRT TPS.
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Affiliation(s)
- Jacqueline M. Andreozzi
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA
- Current: Department of Radiation Oncology, University of Florida, Gainesville, Florida 32608
| | - Petr Brůža
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA
| | - Jochen Cammin
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Brian W. Pogue
- Thayer School of Engineering and Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755, USA
| | - David J. Gladstone
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03756, Geisel School of Medicine and Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA
| | - Olga Green
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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16
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Tendler II, Hartford A, Jermyn M, LaRochelle E, Cao X, Borza V, Alexander D, Bruza P, Hoopes J, Moodie K, Marr BP, Williams BB, Pogue BW, Gladstone DJ, Jarvis LA. Experimentally Observed Cherenkov Light Generation in the Eye During Radiation Therapy. Int J Radiat Oncol Biol Phys 2019; 106:422-429. [PMID: 31669563 DOI: 10.1016/j.ijrobp.2019.10.031] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 10/10/2019] [Accepted: 10/18/2019] [Indexed: 12/29/2022]
Abstract
PURPOSE Patients have reported sensations of seeing light flashes during radiation therapy, even with their eyes closed. These observations have been attributed to either direct excitation of retinal pigments or generation of Cherenkov light inside the eye. Both in vivo human and ex vivo animal eye imaging was used to confirm light intensity and spectra to determine its origin and overall observability. METHODS AND MATERIALS A time-gated and intensified camera was used to capture light exiting the eye of a patient undergoing stereotactic radiosurgery in real time, thereby verifying the detectability of light through the pupil. These data were compared with follow-up mechanistic imaging of ex vivo animal eyes with thin radiation beams to evaluate emission spectra and signal intensity variation with anatomic depth. Angular dependency of light emission from the eye was also measured. RESULTS Patient imaging showed that light generation in the eye during radiation therapy can be captured with a signal-to-noise ratio of 68. Irradiation of ex vivo eye samples confirmed that the spectrum matched that of Cherenkov emission and that signal intensity was largely homogeneous throughout the entire eye, from the cornea to the retina, with a slight maximum near 10 mm depth. Observation of the signal external to the eye was possible through the pupil from 0° to 90°, with a detected emission near 2500 photons per millisecond (during peak emission of the ON cycle of the pulsed delivery), which is over 2 orders of magnitude higher than the visible detection threshold. CONCLUSIONS By quantifying the spectra and magnitude of the signal, we now have direct experimental observations that Cherenkov light is generated in the eye during radiation therapy and can contribute to perceived light flashes. Furthermore, this technique can be used to further study and measure phosphenes in the radiation therapy clinic.
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Affiliation(s)
- Irwin I Tendler
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire
| | - Alan Hartford
- Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire; Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire
| | - Michael Jermyn
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; DoseOptics LLC, Lebanon, New Hampshire
| | - Ethan LaRochelle
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire
| | - Xu Cao
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire
| | - Victor Borza
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire
| | - Daniel Alexander
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire
| | - Jack Hoopes
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire; Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire
| | - Karen Moodie
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire
| | - Brian P Marr
- Department of Ophthalmic Oncology, Columbia University Medical Center, New York, New York
| | - Benjamin B Williams
- Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire; Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire
| | - Brian W Pogue
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; DoseOptics LLC, Lebanon, New Hampshire; Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire
| | - David J Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire; Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire; Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire
| | - Lesley A Jarvis
- Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire; Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire.
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Ashraf MR, Bruza P, Pogue BW, Nelson N, Williams BB, Jarvis LA, Gladstone DJ. Optical imaging provides rapid verification of static small beams, radiosurgery, and VMAT plans with millimeter resolution. Med Phys 2019; 46:5227-5237. [PMID: 31472093 DOI: 10.1002/mp.13797] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 08/09/2019] [Accepted: 08/10/2019] [Indexed: 11/07/2022] Open
Abstract
PURPOSE We demonstrate the feasibility of optical imaging as a quality assurance tool for static small beamlets, and pretreatment verification tool for radiosurgery and volumetric-modulated arc therapy (VMAT) plans. METHODS Small static beams and clinical VMAT plans were simulated in a treatment planning system (TPS) and delivered to a cylindrical tank filled with water-based liquid scintillator. Emission was imaged using a blue-sensitive, intensified CMOS camera time-gated to the linac pulses. For static beams, percentage depth and cross beam profiles of projected intensity distribution were compared to TPS data. Two-dimensional (2D) gamma analysis was performed on all clinical plans, and the technique was tested for sensitivity against common errors (multileaf collimator position, gantry angle) by inducing deliberate errors in the VMAT plans control points. The technique's detection limits for spatial resolution and the smallest number of control points that could be imaged reliably were also tested. The sensitivity to common delivery errors was also compared against a commercial 2.5D diode array dosimeter. RESULTS A spatial resolution of 1 mm was achieved with our imaging setup. The optical projected percentage depth intensity profiles agreed to within 2% relative to the TPS data for small static square beams (5, 10, and 50 mm2 ). For projected cross beam profiles, a gamma pass rate >99% was achieved for a 3%/1 mm criteria. All clinical plans passed the 3%/3 mm criteria with >95% passing rate. A static 5 mm beam with 20 Monitor Units could be measured with an average percent difference of 5.5 ± 3% relative to the TPS. The technique was sensitive to multileaf collimator errors down to 1 mm and gantry angle errors of 1°. CONCLUSIONS Optical imaging provides ample spatial resolution for imaging small beams. The ability to faithfully image down to 20 MU of 5 mm, 6 MV beamlets prove the ability to perform quality assurance for each control point within dynamic plans. The technique is sensitive to small offset errors in gantry angles and multileaf collimator (MLC) leaf positions, and at certain scenario, it exhibits higher sensitivity than a commercial 2.5D diode array.
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Affiliation(s)
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College Hanover, Hanover, NH, 03755, USA
| | - Brian W Pogue
- Thayer School of Engineering, Dartmouth College Hanover, Hanover, NH, 03755, USA.,Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH, 03756, USA
| | - Nathan Nelson
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH, 03756, USA
| | - Benjamin B Williams
- Thayer School of Engineering, Dartmouth College Hanover, Hanover, NH, 03755, USA.,Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH, 03756, USA.,Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover, Hanover, NH, 03755, USA
| | - Lesley A Jarvis
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH, 03756, USA.,Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover, Hanover, NH, 03755, USA
| | - David J Gladstone
- Thayer School of Engineering, Dartmouth College Hanover, Hanover, NH, 03755, USA.,Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH, 03756, USA.,Department of Medicine, Geisel School of Medicine, Dartmouth College Hanover, Hanover, NH, 03755, USA
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Alexander DA, Tendler II, Bruza P, Cao X, Schaner PE, Marshall BS, Jarvis LA, Gladstone DJ, Pogue BW. Assessment of imaging Cherenkov and scintillation signals in head and neck radiotherapy. Phys Med Biol 2019; 64:145021. [PMID: 31146269 DOI: 10.1088/1361-6560/ab25a3] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The goal of this study was to test the utility of time-gated optical imaging of head and neck (HN) radiotherapy treatments to measure surface dosimetry in real-time and inform possible interfraction replanning decisions. The benefit of both Cherenkov and scintillator imaging in HN treatments is direct daily feedback on dose, with no change to the clinical workflow. Emission from treatment materials was characterized by measuring radioluminescence spectra during irradiation and comparing emission intensities relative to Cherenkov emission produced in phantoms and scintillation from small plastic targets. HN treatment plans were delivered to a phantom with bolus and mask present to measure impact on signal quality. Interfraction superficial tumor reduction was simulated on a HN phantom, and cumulative Cherenkov images were analyzed in the region of interest (ROI). HN human patient treatment was imaged through the mask and compared with the dose distribution calculated by the treatment planning system. The relative intensity of radioluminescence from the mask was found to be within 30% of the Cherenkov emission intensity from tissue-colored clay. A strong linear relationship between normalized cumulative Cherenkov intensity and tumor size was established ([Formula: see text]). The presence of a mask above a scintillator ROI was found to decrease mean pixel intensity by >40% and increase distribution spread. Cherenkov imaging through mask material is shown to have potential for surface field verification and tracking of superficial anatomy changes between treatment fractions. Imaging of scintillating targets provides a direct imaging of surface dose on the patient and through transparent bolus material. The first imaging of a patient receiving HN radiotherapy was achieved with a signal map which qualitatively matches the surface dose plan.
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Affiliation(s)
- Daniel A Alexander
- Thayer School of Engineering, Dartmouth College, Hanover, NH, United States of America. Author to whom any correspondence should be addressed
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