Pile-up correction techniques for real-time dosimetry in photon radiotherapy

Miklavec, Mojca; Löher, B.; Savran, D.; Novak, Roman; Širca, S.; Vencelj, M.

doi:10.1109/nssmic.2012.6551889

Cited by 5 publications

(4 citation statements)

References 5 publications

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“…Currently, optimizations on scintillation crystal size and readout techniques are being performed, in order not to oversaturate the crystal and read piled-up pulses, but still have a crystal large enough, for γ-rays to deposit all of their energy inside the scintillation crystal. Techniques on resolving pile-up pulses [34] somewhat relax these constraints. A joint JSI and French Atomic Energy and Alternative Energies Commission (CEA) γ measurement campaign has already been performed at the JSI TRIGA reactor, where all of the above mentioned detectors (or development versions for detectors under development ) were utilized for γ-ray measurements.…”

Section: Gamma Field Measurementsmentioning

confidence: 99%

Characterization of gamma field in the JSI TRIGA reactor

et al. 2018

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Abstract-Research reactors such as the "Jožef Stefan" Institute TRIGA reactor have primarily been designed for experimentation and sample irradiation with neutrons. However recent developments in incorporating additional instrumentation for nuclear power plant support and with novel high flux material testing reactor designs, γ field characterization has become of great interest for the characterization of the changes in operational parameters of electronic devices and for the evaluation of γ heating of MTR's structural materials in a representative reactor γ spectrum. In this paper, we present ongoing work on γ field characterization both experimentally, by performing γ field measurements, and by simulations, using Monte Carlo particle transport codes in conjunction with R2S methodology for delayed γ field characterization.

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Section: Gamma Field Measurementsmentioning

confidence: 99%

Characterization of gamma field in the JSI TRIGA reactor

et al. 2018

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“…The number, amplitude, and time delay of the input radiation events along with the system response of the detector are estimated by characterizing the output signal from the detector. The number of events and triggers is determined by a finite impulse response filter, and the quality of reconstruction is determined based on maximum likelihood estimation [7] or estimated RMS error, which is used for photon radiotherapy at a high count rate [8]. A new model for the NaI(Tl) detector system, whose fitting result is superior to others, has been [9] used for model-based pulse deconvolution calculations [10], with a minimum resolvable pulse interval of 200 ns and higher energy resolution.…”

Section: Introductionmentioning

confidence: 99%

An Ultra-Throughput Boost Method for Gamma-Ray Spectrometers

Li,

Zhou,

Zhang

et al. 2024

Energies

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(1) Background: Generally, in nuclear medicine and nuclear power plants, energy spectrum measurements and radioactive nuclide identification are required for evaluation of strong radiation fields to ensure nuclear safety and security; thereby, damage is prevented to nuclear facilities caused by natural disasters or the criminal smuggling of nuclear materials. High count rates can lead to signal accumulation, negatively affecting the performance of gamma spectrometers, and in severe cases, even damaging the detectors. Higher pulse throughput with better energy resolution is the ultimate goal of a gamma-ray spectrometer. Traditionally, pileup pulses, which cause dead time and affect throughput, are rejected to maintain good energy resolution. (2) Method: In this paper, an ultra-throughput boost (UTB) off-line processing method was used to improve the throughput and reduce the pileup effect of the spectrometer. Firstly, by fitting the impulse signal of the detector, the response matrix was built by the functional model of a dual exponential tail convolved with the Gaussian kernel; then, a quadratic programming method based on a non-negative least squares (NNLS) algorithm was adopted to solve the constrained optimization problem for the inversion. (3) Results: Both the simulated and experimental results of the UTB method show that most of the impulses in the pulse sequence from the scintillator detector were restored to δ-like pulses, and the throughput of the UTB method for the NaI(Tl) spectrometer reached 207 kcps with a resolution of 7.71% @661.7 keV. A reduction was also seen in the high energy pileup phenomenon. (4) Conclusions: We conclude that the UTB method can restore individual and piled-up pulses to δ-like sequences, effectively boosting pulse throughput and suppressing high-energy tailing and sum peaks caused by the pileup effect at the cost of a slight loss in energy resolution.

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“…However, as a result of pile-up rejection, information on the energy distribution using these methods would be lost. [17][18][19] In the case of the LINAC pulse structure, all the energy is deposited in the detector; therefore, if the number of events is known, it is potentially possible to correct for the effect of the pile-up.…”

Section: Introductionmentioning

confidence: 99%

“…These include using a hardware amplifier system, fast asynchronous digitization, the application of real‐time or live‐time counting digital pile‐up correction, free‐loss counting, genetic algorithms, and artificial neural‐network techniques. However, as a result of pile‐up rejection, information on the energy distribution using these methods would be lost 17–19 . In the case of the LINAC pulse structure, all the energy is deposited in the detector; therefore, if the number of events is known, it is potentially possible to correct for the effect of the pile‐up.…”

Section: Introductionmentioning

confidence: 99%

Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up

2020

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The determination of x-ray spectra near the maze entrance of linear accelerator (LINAC) rooms is challenging due to the pulsed nature of the LINAC source. Mathematical methods to account for pulse pileup have been examined. These methods utilize the highly periodic pulsing structure of the LINAC, differing from the effects of high-intensity radioactive sources. Methods: Sodium iodide (NaI) and plastic scintillation detectors were used to determine the energy spectra at different points near the maze entrance of a medical LINAC. Monte Carlo calculations of the energy distribution of scattered photons were used to simulate the energy spectrum at the maze entrance. The proposed algorithm uses the Monte Carlo code, FLUKA, to calculate a response function for both detectors. To determine the effects of the pileup in the spectra, the Poisson distribution was used, employing the average number of photons per pulse (l) interacting with the detector. The quantity, l, was obtained from the ratio of the number of events detected to the number of pulses delivered. The energy spectra at various distances from the maze entrance were measured using NaI and plastic scintillation detectors. From these measurements, the values of µ were calculated, and the pileup probability was determined. The FLUKA Monte Carlo code was used to calculate the spectrum at the maze entrance and the response matrices of the NaI and plastic scintillation detectors. The algorithm based on the Poisson distribution was applied to calculate the spectrum. Results: The agreement between the calculated and measured spectra was within the first standard deviation of the variance expected in µ. This agreement confirms that photons at the maze entrance have energies between 30 and 240 keV for a maze with three turns, with an average energy of around 85 keV. After pileup correction, the range of the pulse height distribution with the plastic scintillation detector, which has a low atomic number, was decreased (0 to 140 keV). In contrast, the range of the pulse height distribution with the NaI scintillation detector was closer to the photon spectrum (0 to 240 keV). Conclusions: The corrected spectrum demonstrates that using a FLUKA Monte Carlo code and an algorithm based on the Poisson distribution are effective methods in removing the distortion due to the pileup in LINAC spectra when measuring with NaI and plastic scintillation detectors. The agreement between the corrected and measured spectra indicates that Monte Carlo modeling can accurately determine the spectrum of a LINAC machine at the maze entrance.

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Pile-up correction techniques for real-time dosimetry in photon radiotherapy

Cited by 5 publications

References 5 publications

Characterization of gamma field in the JSI TRIGA reactor

Characterization of gamma field in the JSI TRIGA reactor

An Ultra-Throughput Boost Method for Gamma-Ray Spectrometers

Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up

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