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Lall R, Lee K, Chopra S, Kandala A, Evans M, Seo Y, Niknejad A, Anwar M. Low cost, high temporal resolution optical fiber-based γ-photon sensor for real-time pre-clinical evaluation of cancer-targeting radiopharmaceuticals. Biosens Bioelectron 2024; 247:115956. [PMID: 38145595 DOI: 10.1016/j.bios.2023.115956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 12/17/2023] [Accepted: 12/20/2023] [Indexed: 12/27/2023]
Abstract
Cancer radiopharmaceutical therapies (RPTs) have demonstrated great promise in the treatment of neuroendocrine and prostate cancer, giving hope to late-stage metastatic cancer patients with currently very few treatment options. These therapies have sparked a large amount of interest in pre-clinical research due to their ability to target metastatic disease, with many research efforts focused towards developing and evaluating targeted RPTs for different cancer types in in vivo models. Here we describe a method for monitoring real-time in vivo binding kinetics for the pre-clinical evaluation of cancer RPTs. Recognizing the significant heterogeneity in biodistribution of RPTs among even genetically identical animal models, this approach offers long-term monitoring of the same in vivo organism without euthanasia in contrast to ex vivo tissue dosimetry, while providing high temporal resolution with a low-cost, easily assembled platform, that is not present in small-animal SPECT/CTs. The method utilizes the developed optical fiber-based γ-photon biosensor, characterized to have a wide linear dynamic range with Lutetium-177 (177Lu) activity (0.5-500 μCi/mL), a common radioisotope used in cancer RPT. The probe's ability to track in vivo uptake relative to SPECT/CT and ex vivo dosimetry techniques was verified by administering 177Lu-PSMA-617 to mouse models bearing human prostate cancer tumors (PC3-PIP, PC3-flu). With this method for monitoring RPT uptake, it is possible to evaluate changes in tissue uptake at temporal resolutions <1 min to determine RPT biodistribution in pre-clinical models and better understand dose relationships with tumor ablation, toxicity, and recurrence when attempting to move therapies towards clinical trial validation.
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Affiliation(s)
- Rahul Lall
- Department of Electrical Engineering and Computer Science, University of California, Berkeley, Berkeley, CA, 94720, USA.
| | - Kyoungtae Lee
- Department of Radiation Oncology, University of California, San Francisco, San Francisco, CA, 94107, USA
| | - Shalini Chopra
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, 94107, USA
| | - Averal Kandala
- Department of Electrical Engineering and Computer Science, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Michael Evans
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, 94107, USA
| | - Youngho Seo
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, 94107, USA
| | - Ali Niknejad
- Department of Electrical Engineering and Computer Science, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Mekhail Anwar
- Department of Electrical Engineering and Computer Science, University of California, Berkeley, Berkeley, CA, 94720, USA; Department of Radiation Oncology, University of California, San Francisco, San Francisco, CA, 94107, USA
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Loignon-Houle F, Toussaint M, Bertrand É, Lemyre FC, Lecomte R. Timing Estimation and Limits in TOF-PET Detectors Producing Prompt Photons. IEEE Trans Radiat Plasma Med Sci 2023; 7:692-703. [PMID: 38156329 PMCID: PMC10751813 DOI: 10.1109/trpms.2023.3279455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2023]
Abstract
The production of prompt photons providing high photon time densities is a promising avenue to reach ultrahigh coincidence time resolution (CTR) in time-of-flight PET. Detectors producing prompt photons are receiving high interest experimentally, ignited by past exploratory theoretical studies that have anchored some guiding principles. Here, we aim to consolidate and extend the foundations for the analytical modeling of prompt generating detectors. We extend the current models to a larger range of prompt emission kinetics where more stringent requirements on the prompt photon yield rapidly emerge as a limiting factor. Lower bound and estimator evaluations are investigated with different underlying models, notably by merging or keeping separate the prompt and scintillation photon populations. We further show the potential benefits of knowing the proportion of prompt photons within a detection set to improve the CTR by mitigating the detrimental effect of population (prompt vs scintillation) mixing. Taking into account the fluctuations on the average number of detected prompt photons in the model reveals a limited influence when prompt photons are accompanied by fast scintillation (e.g., LSO:Ce:Ca) but a more significant effect when accompanied by slower scintillation (e.g., BGO). Establishing performance characteristics and limitations of prompt generating detectors is paramount to gauging and targeting the best possible timing capabilities they can offer.
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Affiliation(s)
- Francis Loignon-Houle
- Sherbrooke Molecular Imaging Center of CRCHUS and with the Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada, currently with Instituto de Instrumentación para Imagen Molecular, Centro Mixto CSIC-Universitat Politècnica de València, 46022 Valencia, Spain
| | - Maxime Toussaint
- Sherbrooke Molecular Imaging Center of CRCHUS and with the Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - Émilie Bertrand
- CRCHUS and with the Department of Mathematics, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - Félix Camirand Lemyre
- CRCHUS and with the Department of Mathematics, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - Roger Lecomte
- Sherbrooke Molecular Imaging Center of CRCHUS and with the Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada, and also with IR&T Inc., Sherbrooke, QC, Canada
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Raylman RR, Johnson MB, Bintrim J, Dewasurendra V, Crawford K, Jaliparthi G, Martone P, Mantz P. Evaluation of advanced methods and materials for construction of scintillation detector light guides. Appl Radiat Isot 2022; 179:109979. [PMID: 34715460 DOI: 10.1016/j.apradiso.2021.109979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 08/09/2021] [Accepted: 10/05/2021] [Indexed: 01/03/2023]
Abstract
New techniques for fabrication of optically clear structures (3D printing and casting) can be applied to fabrication of light guides, especially complex -shaped ones, for scintillation detectors. In this investigation, we explored the spectral transmissivity of sample light guides created with different fabrication methods and materials. A spectrophotometer was used to measure the transmissivity of the samples to determine their compatibility with a number of commonly used inorganic scintillators (NaI(Tl), BGO, LaBr3, LaCr3, CSI(Tl) and LYSO). These measurements showed that stereolithography with a Stratasys 3D printer using Somos WaterClear Ultra 10122® produced the most compatible light guide with common organic scintillators, especially LYSO (peak emission λ=420 nm) (a scintillator commonly used in positron emission tomography (PET) imaging). Additionally, Polytek Poly-Optic® 1730 clear urethane produced a cast light guide that was the most optically compatible with these scintillators. To demonstrate the ability to create a unique shaped scintillation detector using 3D-printing and casting methods, a small arc-shaped piece of LYSO was coupled to a 4 × 4 array of 4 mm2 silicon photomultipliers (SiPM) using light guides made from these materials. For comparative purposes, a light guide was also fabricated using standard acrylic, a material often used in current light guides. All detectors produced similar event position maps. The energy resolution for 18F (511 keV photopeak) was 13% for the acrylic light-guide-based detector, while it was 18% for the printed light-guide-based detector and 20% for the cast light-guide-based detector. Results from this study demonstrate that advanced fabrication methods have the potential to facilitate creation of light guides for scintillation detectors. Continued advancements in materials and methods will likely result in improved optical performance for 3D-printed structures.
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Abstract
There have been significant recent advances in single photon emission computed tomography (SPECT) and positron emission tomography (PET) hardware. Novel collimator designs, such as multi-pinhole and locally focusing collimators arranged in geometries that are optimized for cardiac imaging have been implemented to reduce imaging time and radiation dose. These new collimators have been coupled with solid state photon detectors to further improve image quality and reduce scanner size. The new SPECT scanners demonstrate up to a 7-fold increase in photon sensitivity and up to 2 times improvement in image resolution. Although PET scanners are used primarily for oncological imaging, cardiac imaging can benefit from the improved PET sensitivity of 3D systems without inter-plane septa and implementation of the time-of-flight reconstruction. Additionally, resolution recovery techniques are now implemented by all major PET vendors. These new methods improve image contrast, image resolution, and reduce image noise. Simultaneous PET/magnetic resonance (MR) hybrid systems have been developed. Solid state detectors with avalanche photodiodes or digital silicon photomultipliers have also been utilized in PET. These new detectors allow improved image resolution, higher count rate, as well as a reduced sensitivity to electromagnetic MR fields.
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Affiliation(s)
- Piotr J Slomka
- Artificial Intelligence Program, Cedars-Sinai Medical Center, Los Angeles, California, 90048; UCLA School of Medicine, Los Angeles, California, 90048.
| | - Tinsu Pan
- University of Texas, MD Anderson Cancer Center, Houston, TX, 77030.
| | - Daniel S Berman
- Cardiac Imaging, Cedars-Sinai Medical Center, Los Angeles, California, 90048; UCLA School of Medicine, Los Angeles, California, 90048.
| | - Guido Germano
- Artificial Intelligence Program, Cedars-Sinai Medical Center, Los Angeles, California, 90048; UCLA School of Medicine, Los Angeles, California, 90048.
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Goertzen AL, Zhang X, Liu CY, Kozlowski P, Retière F, Ryner L, Sossi V, Stortz G, Thompson CJ. Sci-Fri AM: Imaging - 03: Temperature dependence of a SiPM detector for an MR compatible PET system. Med Phys 2012; 39:4640. [PMID: 28516645 DOI: 10.1118/1.4740189] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Silicon photomultiplier (SiPM) detectors are rapidly becoming the detector of choice for research and development of new detectors for positron emission tomography (PET) due to their combination of high gain, fast timing, compact form factor and ability to function in a magnetic field. We are investigating using SiPM based detectors in a compact PET system designed to be inserted into a 7T animal MRI system and enable simultaneous PET/MRI imaging. In order to understand the level of thermal stability required for this PET system, we examined the stability of a prototype SiPM detector vs. temperature. A detector was constructed using a SensL SPMArray4 SiPM array coupled to a LYSO scintillator crystal array. The temperature of the detector was varied between 23 and 60°C in 5°C steps. At each temperature setting data were collected to characterize the detector flood histogram, photopeak amplitude and energy resolution at 511 keV, timing resolution and signal arrival time. While the flood image showed no noticeable changes with temperature, the 511 keV photopeak amplitude showed a linear decrease of 1.5%/°C and the energy resolution degraded by 0.08%/°C. The timing resolution degraded by 1.5 ns, from 3.5 ns to 5 ns when the temperature changed from 23 to 60°C. Over this temperature range there was a shift in the signal arrival time of approximately 3 ns. These results demonstrate that the detector can be operated over a wide range of temperature, giving a large degree of flexibility in choosing an operating temperature set-point for our PET system.
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Affiliation(s)
- A L Goertzen
- Department of Radiology, University of Manitoba, Winnipeg, MB, Canada.,Department of Physics & Astronomy, University of Manitoba, Winnipeg, MB, Canada
| | - X Zhang
- Department of Radiology, University of Manitoba, Winnipeg, MB, Canada
| | - C-Y Liu
- Department of Physics & Astronomy, University of Manitoba, Winnipeg, MB, Canada
| | - P Kozlowski
- Department of Radiology, University of British Columbia, Vancouver, BC, Canada
| | - F Retière
- Detector Development Group, TRIUMF, Vancouver, BC, Canada
| | - L Ryner
- Magnetic Resonance Research and Development, Institute for Biodiagnostics, National Research Council Canada, Winnipeg, MB, Canada
| | - V Sossi
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada
| | - G Stortz
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada
| | - C J Thompson
- McConnell Brain Imaging Centre, Montreal Neurological Institute, Montréal, QC, Canada
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Therriault-Proulx F, Beddar S, Archambault L, Beaulieu L. Sci-Thur PM: YIS - 10: A new optically encoded single-fiber plastic scintillation detector for multi-point radiation dosimetry. Med Phys 2012; 39:4623-4624. [PMID: 28516538 DOI: 10.1118/1.4740107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To develop a new multi-point plastic scintillation detector (mPSD) that allows for simultaneous dose measurements at multiple points and uses a single optical guide. MATERIALS AND METHODS Two different prototypes were built. A two-point mPSD was built and light discrimination was based on the use of multiple color filters at the outputs of a network of optical fiber splitters. Light intensity was measured by an EMCCD camera. For the three-point mPSD, the light discrimination setup was replaced by a low-noise spectrometer. Depth-dose and profiles measurements were obtained on a 6 MV photon beam with the mPSDs inside a water phantom. An ion chamber was also used for comparison purpose. Finally, the three-point mPSD was tested under an Ir-192 high-dose-rate (HDR) brachytherapy dose delivery and compared to the treatment planning system. RESULTS A good agreement was found between the measured and expected dose for both mPSDs. The average relative differences to the ion chamber measurement for the two-point mPSD were of (2.4 ± 1.6)% and (1.3 ± 0.8)%. For the three-point mPSD, these differences were of (2.3±1.1)%, (1.6±0.4)% and (0.32±0.19)%. The latter mPSD was shown very versatile, being able to measure dose from HDR brachytherapy with an average accuracy of (2.3±1.0)% per catheter. CONCLUSIONS The practical feasibility of mPSDs using a single optical guide has been demonstrated under irradiation from a 6 MV photon beam and an Ir-192 HDR brachytherapy source. Their application for pre-treatment quality assurance and in vivo dosimetry will be various.
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Affiliation(s)
- F Therriault-Proulx
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.,Département de Physique, de Génie Physique et d'Optique, Université Laval, Québec, QC, Canada
| | - S Beddar
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - L Archambault
- Département de Physique, de Génie Physique et d'Optique, Université Laval, Québec, QC, Canada.,Département de Radio-Oncologie, Hôtel-Dieu de Québec, CHUQ, Québec, QC, Canada
| | - L Beaulieu
- Département de Physique, de Génie Physique et d'Optique, Université Laval, Québec, QC, Canada.,Département de Radio-Oncologie, Hôtel-Dieu de Québec, CHUQ, Québec, QC, Canada
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Shao Y, Sun X, Lan K, Bircher C. WE-C-217BCD-10: Development of High Performance PET for Animal Imaging and Therapy Applications. Med Phys 2012; 39:3951. [PMID: 28520023 DOI: 10.1118/1.4736126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE A prototype small animal PET is developed with several novel technologies to measure 3D gamma-interaction positions and to substantially improve imaging performance. METHODS Each new detector has an 8×8 array of 1.95×1.95×30 mm̂3 LYSO scintillators, with each end optically connected to a solid-state photo multiplier (SSPM) array through a light guide. This dual-ended-readout enables the depth-of-interaction (DOI) measurement. Each SSPM array has 16 SSPMs arranged in a 4×4 matrix. Each SSPM has active area about 3×3 mm̂2, with its output read by an ASIC electronics that directly converts analog signals to digital timing pulses which encode the interaction information for energy, timing, crystal of interaction, and DOI calculations. These digital pulses are transferred to and decoded by FPGA-based TDC for coincident event selection and data acquisition. This independent readout of each SSPM and parallel signal process significantly improve signal-to-noise ratio and permit applying flexible data processing algorithms. The current prototype system consists of two rotating detector panels on a portable gantry, with 4 detectors linearly packed together in each panel to provide ∼16 mm axial and variable trans- axial FOV with adjustable panel-to-panel distance. List-mode OSEM-based image reconstruction with resolution modeling was implemented. Both Na- 22 point source and phantom were used to evaluate the system performance. RESULTS The measured energy, timing, spatial and DOI resolutions for each crystal were around 16%, 2.6 ns, 2.0 mm and 5.0 mm, respectively. The measured spatial resolutions with DOI were ∼1.7 mm across the entire FOV in all direction, while those without DOI were much worse and non-uniform across the FOV, in the range predominately around 3.0 to 4.0 mm. In addition, images from a F-18 hot-rod phantom with DOI show significantly improved quality compared to those without DOI. CONCLUSIONS DOI- measurable PET shows substantially improved image performance for a compact system. National Institute of Health. University of Texas MD Anderson Cancer Center.
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Affiliation(s)
- Y Shao
- The University of Texas M.D. Anderson Cancer Ctr., Houston, TX
| | - X Sun
- The University of Texas M.D. Anderson Cancer Ctr., Houston, TX
| | - K Lan
- The University of Texas M.D. Anderson Cancer Ctr., Houston, TX
| | - C Bircher
- The University of Texas M.D. Anderson Cancer Ctr., Houston, TX
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Sinn D, Mackenzie M. SU-E-T-168: Development of a Liquid Scintillation Detector for External Beam Dosimetry. Med Phys 2012; 39:3741-3742. [PMID: 28517819 DOI: 10.1118/1.4735226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The goal of this research was to design a liquid scintillation dosimeter that could be used forrelative dosimetry of linear accelerator fields. The project emphasized minimization of cost and ease of use. METHODS The scintillator that was used in this research was BETAMAX- ES scintillation cocktail from MPBiomedical. This particular scintillator was selected due to its relatively high scintillation yield and lowcost. The entirety of the scintillator used the measurements was supplied free of cost. The housing for the liquid was constructed from PVC and is cylindrical with one tapered end. One fiber of the dual optical fibers transmits the generated photons to the CCD while the other fiber is used for Cerenkovsubtraction.The detector used comes from a Philips SPC880NC webcam. The plastic casing of the webcamwas removed so that only the printed circuit board, USB cable and lens eyepiece holder remained. Thesensor employed is the Sony ICX098QB CCD, which is 3.2mm by 2.4mm and each pixel is 5.6mm by 5.6mm. A small cylindrical insert was manufactured that was inserted into the lens eyepiece holder to get adequate mechanical coupling of the fibers to the CCD face. Images were acquired with a freeware image acquisition tool, SharpCap, and analyzed with theMatlab commercial math package from Mathworks. RESULTS Measurements have been performed that show that the detector is able to accurately measuretissue maximum ratio and the relative dose factor. The detector was able to accurately measurephysical wedge factors and made good predictions of the modulation factor for a patient's 7-field IMRT plan. CONCLUSIONS This work has shown that relative dosimetry can be performed using an inexpensive liquidscintillation detector. This could be expanded to include an array of liquid scintillator cells formeasurement of beam profiles and other more complex problems.
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Affiliation(s)
- D Sinn
- Cross Cancer Institute, Edmonton, Alberta
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Constantin D, Sun M, Abel E, Star-Lack J, Fahrig R. WE-C-217BCD-11: Coupled Radiative and Optical Geant4 Simulation of MV EPIDs Based on Thick Pixelated Scintillating Crystals. Med Phys 2012; 39:3951-3952. [PMID: 28520011 DOI: 10.1118/1.4736127] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE One way to greatly reduce the incidence of metal artifacts produced in kilovoltage (kV) CT images is by using megavoltage (MV) photons that penetrate high-Z objects, thus providing a measurable signal. For do se-efficient imaging, a high detective quantum efficiency (DQE) MV detector is desired. This study validates the coupled radiation and optical Geant4 simulation results against experimental data from various prototype pixelated scintillator MV detectors and determines the essential optical parameters which control the detector performance. METHODS Experimental data obtained with a 6MV radiation source from 8 different detectors was considered. The detectors used CsI, CdW and BGO as scintillating crystals and polystyrene septal wall material. Accurate Geant4 models of the detectors were implemented and coupled radiation and optical simulations were performed. The unknown optical properties of the models were determined by minimizing the difference between the modulation transfer functions (MTF) of the simulated data obtained with the slanted slit technique and the experimental MTFs. With the set of optical properties fixed, further simulation validation was performed against the experimental normalized noise power spectrum (NNPS(f)) and the experimental DQE(f) curves for each detector. All the simulations were performed on a computer cluster deployed on the Amazon EC2 platform. RESULTS The optimal values for the free optical parameters are 10%, 95% and 90% for the top surface reflectivity, the crystal-sept a surface reflectivity, and the Lambertian component contribution to the reflected beam from the crystal-septa interface respectively. The absolute difference between experimental and simulated data was below 10% for all the data sets. CONCLUSIONS To our knowledge this study is the first to present a full optical and radiative DQE(f) model using Geant4 that shows an excellent match with experimental data. The model indicates that improved performance can be obtained using more specular septa which are optically opaque. Support: NIH-T32-CA09695, NIH-1R01CA138426 NIH T32-CA09695, NIH R01- CA138426, Several authors work for Varian Medical Systems.
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Affiliation(s)
- D Constantin
- Stanford University, Stanford, CA.,Varian Medical Systems, Palo Alto, CA
| | - M Sun
- Stanford University, Stanford, CA.,Varian Medical Systems, Palo Alto, CA
| | - E Abel
- Stanford University, Stanford, CA.,Varian Medical Systems, Palo Alto, CA
| | - J Star-Lack
- Stanford University, Stanford, CA.,Varian Medical Systems, Palo Alto, CA
| | - R Fahrig
- Stanford University, Stanford, CA.,Varian Medical Systems, Palo Alto, CA
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Jozsef G, Pagliazzi M, Saxena I, DeWyngaert J. SU-E-T-111: Single Line Multi-Detector Scintillation Dosimetry: Demonstration of Feasibility. Med Phys 2012; 39:3728. [PMID: 28517135 DOI: 10.1118/1.4735169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Obtain feasibility data on the use of multiple scintillators on a single optical line for dose measurements. METHODS A CsI (Tl doped) crystal and a plastic (Rexon Inc, Rp-408) scintillator detectors, both transparent, were attached to the end of a fiberoptic line and connected to an Ocean Optics USB-2000 spectrometer. After baseline spectra, spectra with the two scintillators adjacent to each other and then separated by a 7.6 cm plexiglass spacer were obtained. Irradiations were performed using 6 MV X-ray beam from a Varian EX linear accelerator. Utilizing the baseline spectra the dose received by each scintillator were calculated from the measured spectral peaks of the linear scintillator assemblies. Linearity tests were performed by varying dose and the dose rate in a homogeneous radiation field covering both scintillators. Unequal doses were delivered to the scintillator by gradually closing the collimator from one direction, blocking one detector at a time. Doses to the scintillators were modulated by different amount of solid water placed over the two detectors, as well. RESULTS Measured scintillation spectra agreed with the published spectra. The spectra did not change with depth in the phantom. The multi-scintillator system response was strictly linear between 1.67 and 40 MUs, (approx. 1.3 to 31 cGy) and dose rate independent between 100 to 600 MU/min. The profile curves obtained by closing the collimator agreed with qualitatively expected curves. Doses measured under different phantom thicknesses were in good agreement with ion chamber measurements on the same locations (+/- 3%). The linearity and dose rate independence allow absolute dose calibration for given beam energies and scintillator arrangement. CONCLUSIONS Multi-probe scintillation dosimetry along a single optical fiber is possible in therapeutic irradiation conditions. This is feasible by using signals from multiple select scintillators with distinct spectroscopic responses arranged along an optical fiber.
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Affiliation(s)
- G Jozsef
- NYU Medical Center, New York, NY.,University of Pisa, Pisa, Italy.,Present contact: Paulsson, Inc., Van Nuys, CA.,NYU Medical Center, New York, NY
| | - M Pagliazzi
- NYU Medical Center, New York, NY.,University of Pisa, Pisa, Italy.,Present contact: Paulsson, Inc., Van Nuys, CA.,NYU Medical Center, New York, NY
| | - I Saxena
- NYU Medical Center, New York, NY.,University of Pisa, Pisa, Italy.,Present contact: Paulsson, Inc., Van Nuys, CA.,NYU Medical Center, New York, NY
| | - J DeWyngaert
- NYU Medical Center, New York, NY.,University of Pisa, Pisa, Italy.,Present contact: Paulsson, Inc., Van Nuys, CA.,NYU Medical Center, New York, NY
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11
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Quast U, Kaulich TW, Zakaria GA, Ahnesjö A, Alvarez-Romero JT, Medich D, Mourtada F, Pradhan A, Rivard M. SU-E-T-313: Probe-Type Experimental Dosimetry in Terms of Absorbed Dose to Water in Photon-Brachytherapy a Proposal for a Radiation-Quality Index. Med Phys 2012; 39:3775-3776. [PMID: 28517292 DOI: 10.1118/1.4735399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE In photon-brachytherapy (BT), all data for clinical dosimetry (e.g., the dose-rate constant) are not measured in water, but calculated, based on MC-simulation. To enable the measurement of absorbed dose to water, DW, in the vicinity of a source, the complex energy-dependence and other influence quantities must be considered. METHODS The detectors response, R=M/D, is understood as product of a detector-material dependent 'absorbed dose response', Ren, and Rin, the 'intrinsic response'. Ren is described by the Burlin-theory and because of dissimilarities between the detector-material and water, will have energy dependent correction factors which convert Ren into the clinically relevant DW,Qo=MQo × ND,W,Qo. To characterize BT- source-types, we propose a new 'radiation-quality index' QBT=Dprim(2cm)/Dprim(1cm), the ratio of the primary-dose to water at r=2cm to that at the reference distance r=1cm, similar to external beam dosimetry. Although QBT cannot be measured directly, it can be derived from primary and scatter separated dose-data, published as consensus data e.g., in the Carlton AAPM-TG-43-database. RESULTS Mean QBT-values are: for nine HDR and four PDR 192Ir-sources: 0.2258±0.5%; one 169Yb- source: 0.2142; and one 125I-source: 0.1544. CONCLUSIONS The main benefit of this new QBT-concept is that a type of BT-dosimetry-detector needs to be calibrated only for one reference radiation-quality, e.g., for Q0=192Ir. To measure the dose for different source-types, DW can be determined using calculated radiation-quality conversion factors kQ,QoBT, to be included in the AAPM-database and to be provided by the manufacturer for each detector-type. Typical BT-dosimetry-detectors are plastic scintillation detectors, radiochromic film, thermoluminescence detectors, optically stimulated detectors, and small volume ionization chambers. Recently, different DW(1cm)-primary standards have been developed in several European NMIs, enabling to calibrate BT-radiation- sources and BT-dosimetry-detectors and allowing to verify MC-calculated dose-rate constant values. The proposed definition of QBT has to be discussed internationally to find broad consensus.
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Affiliation(s)
- U Quast
- ex- Essen University Hospital, Essen, Germany.,Tuebingen University Hospital, Tuebingen, Germany.,Cologne University Teaching Hospital, Gummersbach, Germany.,Nucletron Scandinavia AB, Uppsala, Sweden.,ININ, SSDL, Salazar.,University of Massachusetts Lowell, Lowell, MA.,Christiana Care Hospital, NEWARK, DE.,Ex- Bhabhba Atomic Research Centre, Mumbai, India.,Tufts Medical Center, Boston, MA
| | - T W Kaulich
- ex- Essen University Hospital, Essen, Germany.,Tuebingen University Hospital, Tuebingen, Germany.,Cologne University Teaching Hospital, Gummersbach, Germany.,Nucletron Scandinavia AB, Uppsala, Sweden.,ININ, SSDL, Salazar.,University of Massachusetts Lowell, Lowell, MA.,Christiana Care Hospital, NEWARK, DE.,Ex- Bhabhba Atomic Research Centre, Mumbai, India.,Tufts Medical Center, Boston, MA
| | - G A Zakaria
- ex- Essen University Hospital, Essen, Germany.,Tuebingen University Hospital, Tuebingen, Germany.,Cologne University Teaching Hospital, Gummersbach, Germany.,Nucletron Scandinavia AB, Uppsala, Sweden.,ININ, SSDL, Salazar.,University of Massachusetts Lowell, Lowell, MA.,Christiana Care Hospital, NEWARK, DE.,Ex- Bhabhba Atomic Research Centre, Mumbai, India.,Tufts Medical Center, Boston, MA
| | - A Ahnesjö
- ex- Essen University Hospital, Essen, Germany.,Tuebingen University Hospital, Tuebingen, Germany.,Cologne University Teaching Hospital, Gummersbach, Germany.,Nucletron Scandinavia AB, Uppsala, Sweden.,ININ, SSDL, Salazar.,University of Massachusetts Lowell, Lowell, MA.,Christiana Care Hospital, NEWARK, DE.,Ex- Bhabhba Atomic Research Centre, Mumbai, India.,Tufts Medical Center, Boston, MA
| | - J T Alvarez-Romero
- ex- Essen University Hospital, Essen, Germany.,Tuebingen University Hospital, Tuebingen, Germany.,Cologne University Teaching Hospital, Gummersbach, Germany.,Nucletron Scandinavia AB, Uppsala, Sweden.,ININ, SSDL, Salazar.,University of Massachusetts Lowell, Lowell, MA.,Christiana Care Hospital, NEWARK, DE.,Ex- Bhabhba Atomic Research Centre, Mumbai, India.,Tufts Medical Center, Boston, MA
| | - D Medich
- ex- Essen University Hospital, Essen, Germany.,Tuebingen University Hospital, Tuebingen, Germany.,Cologne University Teaching Hospital, Gummersbach, Germany.,Nucletron Scandinavia AB, Uppsala, Sweden.,ININ, SSDL, Salazar.,University of Massachusetts Lowell, Lowell, MA.,Christiana Care Hospital, NEWARK, DE.,Ex- Bhabhba Atomic Research Centre, Mumbai, India.,Tufts Medical Center, Boston, MA
| | - F Mourtada
- ex- Essen University Hospital, Essen, Germany.,Tuebingen University Hospital, Tuebingen, Germany.,Cologne University Teaching Hospital, Gummersbach, Germany.,Nucletron Scandinavia AB, Uppsala, Sweden.,ININ, SSDL, Salazar.,University of Massachusetts Lowell, Lowell, MA.,Christiana Care Hospital, NEWARK, DE.,Ex- Bhabhba Atomic Research Centre, Mumbai, India.,Tufts Medical Center, Boston, MA
| | - A Pradhan
- ex- Essen University Hospital, Essen, Germany.,Tuebingen University Hospital, Tuebingen, Germany.,Cologne University Teaching Hospital, Gummersbach, Germany.,Nucletron Scandinavia AB, Uppsala, Sweden.,ININ, SSDL, Salazar.,University of Massachusetts Lowell, Lowell, MA.,Christiana Care Hospital, NEWARK, DE.,Ex- Bhabhba Atomic Research Centre, Mumbai, India.,Tufts Medical Center, Boston, MA
| | - M Rivard
- ex- Essen University Hospital, Essen, Germany.,Tuebingen University Hospital, Tuebingen, Germany.,Cologne University Teaching Hospital, Gummersbach, Germany.,Nucletron Scandinavia AB, Uppsala, Sweden.,ININ, SSDL, Salazar.,University of Massachusetts Lowell, Lowell, MA.,Christiana Care Hospital, NEWARK, DE.,Ex- Bhabhba Atomic Research Centre, Mumbai, India.,Tufts Medical Center, Boston, MA
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Kim S, McClish M, Alhassen F, Seo Y, Shah KS, Gould RG. Temperature dependent operation of PSAPD-based compact gamma camera for SPECT imaging. IEEE Trans Nucl Sci 2011; 58:2169-2174. [PMID: 24465051 PMCID: PMC3898791 DOI: 10.1109/tns.2011.2165324] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We investigated the dependence of image quality on the temperature of a position sensitive avalanche photodiode (PSAPD)-based small animal single photon emission computed tomography (SPECT) gamma camera with a CsI:Tl scintillator. Currently, nitrogen gas cooling is preferred to operate PSAPDs in order to minimize the dark current shot noise. Being able to operate a PSAPD at a relatively high temperature (e.g., 5 °C) would allow a more compact and simple cooling system for the PSAPD. In our investigation, the temperature of the PSAPD was controlled by varying the flow of cold nitrogen gas through the PSAPD module and varied from -40 °C to 20 °C. Three experiments were performed to demonstrate the performance variation over this temperature range. The point spread function (PSF) of the gamma camera was measured at various temperatures, showing variation of full-width-half-maximum (FWHM) of the PSF. In addition, a 99mTc-pertechnetate (140 keV) flood source was imaged and the visibility of the scintillator segmentation (16×16 array, 8 mm × 8 mm area, 400 μm pixel size) at different temperatures was evaluated. Comparison of image quality was made at -25 °C and 5 °C using a mouse heart phantom filled with an aqueous solution of 99mTc-pertechnetate and imaged using a 0.5 mm pinhole collimator made of tungsten. The reconstructed image quality of the mouse heart phantom at 5 °C degraded in comparision to the reconstructed image quality at -25 °C. However, the defect and structure of the mouse heart phantom were clearly observed, showing the feasibility of operating PSAPDs for SPECT imaging at 5 °C, a temperature that would not need the nitrogen cooling. All PSAPD evaluations were conducted with an applied bias voltage that allowed the highest gain at a given temperature.
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Affiliation(s)
- Sangtaek Kim
- Physics Research Laboratory, University of California, San Francisco, San Francisco, CA 94107 USA ( )
| | - Mickel McClish
- Radiation Monitoring Devices Inc., Watertown, MA 02472 USA
| | - Fares Alhassen
- Physics Research Laboratory, University of California, San Francisco, San Francisco, CA 94107 USA ( )
| | - Youngho Seo
- Physics Research Laboratory, University of California, San Francisco, San Francisco, CA 94107 USA ( )
| | - Kanai S Shah
- Radiation Monitoring Devices Inc., Watertown, MA 02472 USA
| | - Robert G Gould
- Physics Research Laboratory, University of California, San Francisco, San Francisco, CA 94107 USA ( )
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