GAMOS: A Geant4-based easy and flexible framework for nuclear medicine applications

Arce, P.; Rato, P.; Canadas, M.; Lagáres, J.I.

doi:10.1109/nssmic.2008.4775023

Cited by 80 publications

(61 citation statements)

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“…39 The process of radiation transport, dose deposition, generation ofČerenkov photons, and transport of optical photons have been explained in detail by previous studies. 31,40 Phase space files of 6 MV x-ray beams for the linear accelerator (LINAC) (Varian Clinic 2100CD) were generated in Ref.…”

Section: Methodsmentioning

confidence: 98%

Superficial dosimetry imaging based on Čerenkov emission for external beam radiotherapy with megavoltage x‐ray beam

et al. 2013

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Purpose:Čerenkov radiation emission occurs in all tissue, when charged particles (either primary or secondary) travel at velocity above the threshold for theČerenkov effect (about 220 KeV in tissue for electrons). This study presents the first examination of opticalČerenkov emission as a surrogate for the absorbed superficial dose for MV x-ray beams. Methods: In this study, Monte Carlo simulations of flat and curved surfaces were studied to analyze the energy spectra of charged particles produced in different regions near the surfaces when irradiated by MV x-ray beams.Čerenkov emission intensity and radiation dose were directly simulated in voxelized flat and cylindrical phantoms. The sampling region of superficial dosimetry based oň Cerenkov radiation was simulated in layered skin models. Angular distributions of optical emission from the surfaces were investigated. Tissue mimicking phantoms with flat and curved surfaces were imaged with a time domain gating system. The beam field sizes (50 × 50-200 × 200 mm 2 ), incident angles (0• -70 • ) and imaging regions were all varied. Results: The entrance or exit region of the tissue has nearly homogeneous energy spectra across the beam, such that theirČerenkov emission is proportional to dose. Directly simulated local intensity ofČerenkov and radiation dose in voxelized flat and cylindrical phantoms further validate that this signal is proportional to radiation dose with absolute average discrepancy within 2%, and the largest within 5% typically at the beam edges. The effective sampling depth could be tuned from near 0 up to 6 mm by spectral filtering. The angular profiles near the theoretical Lambertian emission distribution for a perfect diffusive medium, suggesting that angular correction of Cerenkov images may not be required even for curved surface. The acquisition speed and signal to noise ratio of the time domain gating system were investigated for different acquisition procedures, and the results show there is good potential for real-time superficial dose monitoring. Dose imaging under normal ambient room lighting was validated, using gated detection and a breast phantom. Conclusions

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Section: Methodsmentioning

confidence: 98%

Superficial dosimetry imaging based on Čerenkov emission for external beam radiotherapy with megavoltage x‐ray beam

et al. 2013

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“…23 To account for this phenomenon, in this study, the x-ray photon spectrum for a 6 MV beam from a Varian 2100C was simulated using a validated EGS/BEAMnrc geometry and recorded as a function of radial position on the phantom surface using the /4 architecture. [24][25][26] The results were generated for radial positions up to 20 cm for a fully open (no jaws) and represent a superposition of both the primary and extrafocal sources as detailed by Liu et al…”

Section: C Beam Hardening Correctionmentioning

confidence: 99%

Optical cone beam tomography of Cherenkov‐mediated signals for fast 3D dosimetry of x‐ray photon beams in water

et al. 2015

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Purpose: To test the use of a three-dimensional (3D) optical cone beam computed tomography reconstruction algorithm, for estimation of the imparted 3D dose distribution from megavoltage photon beams in a water tank for quality assurance, by imaging the induced Cherenkov-excited fluorescence (CEF). Methods: An intensified charge-coupled device coupled to a standard nontelecentric camera lens was used to tomographically acquire two-dimensional (2D) projection images of CEF from a complex multileaf collimator (MLC) shaped 6 MV linear accelerator x-ray photon beam operating at a dose rate of 600 MU/min. The resulting projections were used to reconstruct the 3D CEF light distribution, a potential surrogate of imparted dose, using a Feldkamp-Davis-Kress cone beam back reconstruction algorithm. Finally, the reconstructed light distributions were compared to the expected dose values from one-dimensional diode scans, 2D film measurements, and the 3D distribution generated from the clinical Varian ECLIPSE treatment planning system using a gamma index analysis. A Monte Carlo derived correction was applied to the Cherenkov reconstructions to account for beam hardening artifacts. Results: 3D light volumes were successfully reconstructed over a 400 × 400 × 350 mm 3 volume at a resolution of 1 mm. The Cherenkov reconstructions showed agreement with all comparative methods and were also able to recover both inter-and intra-MLC leaf leakage. Based upon a 3%/3 mm criterion, the experimental Cherenkov light measurements showed an 83%-99% pass fraction depending on the chosen threshold dose. Conclusions: The results from this study demonstrate the use of optical cone beam computed tomography using CEF for the profiling of the imparted dose distribution from large area megavoltage photon beams in water. C 2015 American Association of Physicists in Medicine.

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“…36,37 The GAMOS interface was chosen for its ease of use and flexibility in creating GEANT4 simulations, and the GEANT4 architecture was chosen for its robust physics package and ability to model both radiation and light transport (see Ref. 38 for details on the GEANT4 implementation of theČerenkov process).…”

Section: Iiic Monte Carlo Simulations Ofčerenkov Emission Angular Dmentioning

confidence: 99%

Projection imaging of photon beams by the Čerenkov effect

et al. 2012

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Purpose: A novel technique for beam profiling of megavoltage photon beams was investigated for the first time by capturing images of the inducedČerenkov emission in water, as a potential surrogate for the imparted dose in irradiated media. Methods: A high-sensitivity, intensified CCD camera (ICCD) was configured to acquire 2D projection images ofČerenkov emission from a 4 × 4 cm 2 6 MV linear accelerator (LINAC) x-ray photon beam operating at a dose rate of 400 MU/min incident on a water tank with transparent walls. The ICCD acquisition was gated to the LINAC sync pulse to reduce background light artifacts, and the measurement quality was investigated by evaluating the signal to noise ratio and measurement repeatability as a function of delivered dose. Monte Carlo simulations were used to derive a calibration factor for differences between the optical images and deposited dose arising from the anisotropic angular dependence ofČerenkov emission. Finally,Čerenkov-based beam profiles were compared to a percent depth dose (PDD) and lateral dose profile at a depth of d max from a reference dose distribution generated from the clinical Varian ECLIPSE treatment planning system (TPS). Results: The signal to noise ratio was found to be 20 at a delivered dose of 66.6 cGy, and proportional to the square root of the delivered dose as expected from Poisson photon counting statistics. A 2.1% mean standard deviation and 5.6% maximum variation in successive measurements were observed, and the Monte Carlo derived calibration factor resulted inČerenkov emission images which were directly correlated to deposited dose, with some spatial issues. The dose difference between the TPS and PDD predicted byČerenkov measurements was within 20% in the buildup region with a distance to agreement (DTA) of 1.5-2 mm and ±3% at depths beyond d max . In the lateral profile, the dose difference at the beam penumbra was within ±13% with a DTA of 0-2 mm, ±5% in the central beam region, and 2%-3% in the beam umbra. Conclusions:The results from this initial study demonstrate the first documented use ofČerenkov emission imaging to profile x-ray photon LINAC beams in water. The proposed modality has several potential advantages over alternative methods, and upon future refinement may prove to be a robust and novel dosimetry method.

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GAMOS: A Geant4-based easy and flexible framework for nuclear medicine applications

Cited by 80 publications

References 0 publications

Superficial dosimetry imaging based on Čerenkov emission for external beam radiotherapy with megavoltage x‐ray beam

Superficial dosimetry imaging based on Čerenkov emission for external beam radiotherapy with megavoltage x‐ray beam

Optical cone beam tomography of Cherenkov‐mediated signals for fast 3D dosimetry of x‐ray photon beams in water

Projection imaging of photon beams by the Čerenkov effect

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