fastCAT: Fast cone beam CT (CBCT) simulation

O’Connell, Joe; Bazalova‐Carter, Magdalena

doi:10.1002/mp.15007

Cited by 14 publications

(23 citation statements)

References 40 publications

(59 reference statements)

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“…One should note that some of the MTF curves in this publication have been previously validated against experimental beams in previous studies of Fastcat 12,13 . Specifically, the 6 MV MTF curves for the CWO and GOS detectors were compared to experimental results from Star‐lack et al .…”

Section: Discussionmentioning

confidence: 91%

“…One should note that some of the MTF curves in this publication have been previously validated against experimental beams in previous studies of Fastcat. 12,13 Specifically, the 6 MV MTF curves for the CWO and GOS detectors were compared to experimental results from Star-lack et al and Shi et al, respectively. 10,22 With MTF values found to have an average root mean squared error (RMSE) of 3.5% and 1.2% compared to experimental values for the CWO and GOS detector, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…Detectors with scintillators of CWO, CsI, and GOS were modeled. The detector optical simulation method is described in detail in O'Connell and Bazalova‐Carter 12 as well as detailed descriptions of the detector materials and properties. A brief description of the detectors can be found in Table 2.…”

Section: Methodsmentioning

confidence: 99%

“…MTF for different beam detector combinations were modeled in the manner described in O'Connell and Bazalova‐Carter 12 : The monoenergetic detector OSFs were weighted by the beam energy‐spectrum to create a point spread function (PSF). This PSF was then convolved with an idealized 0.1‐mm‐wide slit angled at 1.5 degrees to generate a line spread function (LSF) as described in the work of Fujita et al 21 .…”

Section: Methodsmentioning

confidence: 99%

“…The Fastcat simulation tool 12,13 is a hybrid Monte Carlo application that was used to simulate the CBCT images presented in this work. Fastcat was demonstrated to be an ideal tool for the rapid and accurate assessment of the modulation transfer function (MTF) and CNR of MV and kV imaging setups.…”

Section: Fastcatmentioning

confidence: 99%

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Investigation of image quality of MV and kV CBCT with low‐Z beams and high DQE detector

O’Connell

Bazalova‐Carter

2022

Medical Physics

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Purpose To investigate cone beam computed tomography (CBCT) image quality using novel combinations of kilovoltage (kV) and megavoltage (MV) beams and detector materials. Methods MV and kV CBCT imaging was simulated using the Fastcat hybrid Monte Carlo application. CBCT imaging with various beam energies was investigated: 2.5 and 6 MV photon beams generated with carbon, aluminum, and tungsten targets and a 120 kVp x‐ray tube beam based off of a Varian Truebeam on‐board imager (OBI). Cadmium tungstate (CWO), gadolinium oxysulfide (GOS), and cesium iodide (CsI) detectors with identical pixel pitch of 0.784 mm were evaluated. Modulation transfer functions (MTF) for all detector/beam combinations were calculated. MV and kV CBCT images for each detector/beam combination of a contrast phantom containing inserts with rib and spongiosa bone, lung, and adipose tissues were simulated with an imaging dose of 7 mGy. Contrast to noise ratio (CNR) of all inserts were compared for all detector/beam combinations. CBCT images of an anthropomorphic head phantom with silver amalgam fillings were also generated. Results The CWO/120 kVp beam combination resulted in the highest MTF at low frequencies and the CsI detector showed the highest MTF for all other beams and at high frequencies. The CWO/120 kVp beam combination showed the highest CNR for all tissues. The unoptimized CWO/2.5 MV carbon target beam showed the highest CNR of the MV beam/detector combinations with CNR 4% and 17% worse than the optimized Truebeam CsI 120 kVp setup with a bowtie filter and antiscatter grid. Additionally, the CWO 2.5 MV setup showed qualitative reduction of metal artifacts surrounding silver amalgam fillings in an anthropomorphic head phantom. Conclusion This finding makes a compelling case that further optimization of this CWO carbon target setup could produce CBCT images with similar CNR to current OBI CBCT for equivalent dose with added resilience to metal artifacts.

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Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Fastcatmentioning

confidence: 99%

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Investigation of image quality of MV and kV CBCT with low‐Z beams and high DQE detector

O’Connell

Bazalova‐Carter

2022

Medical Physics

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Halide Perovskites for Direct Conversion Megavoltage X‐Ray Detectors

Kundu

O’Connell

Hart

et al. 2022

Adv Elect Materials

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MV X-ray sensors, which require orders of magnitude thicker materials, is prohibitively costly. Therefore, commercial MV detectors are based on scintillators, mainly gadolinium oxysulfide (GOS). Unfortunately, GOS absorbs its own scintillation photons: this property limits the thickness of GOS detectors to <0.3 mm, which in turn deteriorates the detector's resolution and sensitivity. [1] As a result, MV X-ray machines are usually equipped with a complementary kV X-ray imaging system for patient alignment. This increases the complexity and the cost of conventional X-ray treatment machines. Partly due to the high cost of such treatment machines, in 2020 alone, more than 70% of 10.35 million new registered cases of cancer in low and middle-income countries had no access to proper treatment for their disease. [2] The development of low-cost radiotherapy treatment machines, which combine real-time dosimetry and direct-conversion imaging during treatment, is imperative for improving cancer outcomes. In addition, developing direct MV sensors would lead to high atomic number artifact reduction, MV imaging for patient setup, and real-time dosimetry during treatments.Here we report a direct conversion MV X-ray detector based on solution-processed methylammonium lead bromide (MAPbBr 3 ) perovskite crystals. Due to its high density (3.8 g cm −3 ) and high atomic number (Z eff = 67.2), MAPbBr 3 offers excellent photon absorption in the MV range. Our prototype device shows a high photon-to-carrier conversion efficiency of ≈42 500%, a high signal-to-noise ratio of ≈1750 and the contrast of over −1.5% per cm of solid water to 6 MV X-ray being comparable to state-of-art commercial GOS detectors. Experimental Section MaterialsMethylamine solution (40 wt% in H 2 O), HBr (48% in H 2 O), and PbBr 2 (≥98%) were purchased from Sigma-Aldrich. Gold (99.999%) was purchased from Angstrom Engineering. Gallium (99.99%) was purchased from Amazon. DMF was purchased from Fisher Scientific. All chemicals were used without further purification.MABr was synthesized by following standard procedure. 86.4 mL of methylamine solution (40 wt% in H 2 O) was added Megavoltage (MV) X-ray detectors used in cancer treatment either suffer from low sensitivity (scintillators) or prohibitively high cost (direct conversion). Here solution-processed direct-conversion MV X-ray detectors are demonstrated based on halide perovskites. The authors' prototype devices show a sensitivity of ≈0.7 µC Gy air −1 cm -2 , high photon-to-carrier conversion efficiency of 42 500%, and a signal-to-noise ratio of ≈1750 to 6 MV X-ray beam of a medical linear accelerator. The detector shows a contrast of over −1.5% per cm of solid water, comparable to state-of-art commercial gadolinium oxysulfide (GOS) MV X-ray scintillators. This work demonstrates the first prototype of low-cost and efficient direct-conversion MV X-ray detectors.

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Experimental validation of Fastcat kV and MV cone beam CT (CBCT) simulator

2021

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Purpose:To experimentally validate the Fastcat cone beam computed tomography (CBCT) simulator against kV and MV CBCT images acquired with a Varian Truebeam linac. Methods: kV and MV CBCT images of a Catphan 504 phantom were acquired using a 100 kVp beam with the on-board imager (OBI) and a 6 MV treatment beam with the electronic portal imaging device (EPID),respectively.The kV Fastcat simulation was performed using detailed models of the x-ray source, bowtie filter, a high resolution voxelized virtual Catphan phantom, anti-scatter grid, and the CsI scintillating detector. Likewise, an MV Fastcat CBCT was simulated with detailed models for the beam energy spectrum, flattening filter, a high-resolution voxelized virtual Catphan phantom, and the gadolinium oxysulfide (GOS) scintillating detector. Experimental and simulated CBCT images of the phantom were compared with respect to HU values, contrast to noise ratio (CNR), and dose linearity. Detector modulation transfer function (MTF) for the two detectors were also experimentally validated. Fastcat's dose calculations were compared to Monte Carlo (MC) dose calculations performed with Topas. Results: For the kV and MV simulations, respectively: Contrast agreed within 14 and 9 HUs and detector MTF agreed within 4.2% and 2.5%. Likewise, CNR had a root mean squared error (RMSE) of 2.6% and 1.4%. Dose agreed within 2.4% and 1.6% of MC values. The kV and MV CBCT images took 71 and 72 s to simulate in Fastcat with 887 and 493 projections, respectively. Conclusions: We present a multienergy experimental validation of a fast and accurate CBCT simulator against a commercial linac. The simulator is open source and all models found in this work can be downloaded from https://github. com/jerichooconnell/fastcat.git.

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fastCAT: Fast cone beam CT (CBCT) simulation

Cited by 14 publications

References 40 publications

Investigation of image quality of MV and kV CBCT with low‐Z beams and high DQE detector

Investigation of image quality of MV and kV CBCT with low‐Z beams and high DQE detector

Halide Perovskites for Direct Conversion Megavoltage X‐Ray Detectors

Experimental validation of Fastcat kV and MV cone beam CT (CBCT) simulator

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