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

Abstract

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.

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

“…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.…”

“…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.…”

“…Agreement has previously been demonstrated between Fastcat and a Varian Truebeam linac (Varian Medical Systems, Palo Alto, CA) for both a 100 kVp CBCT acquired on the OBI as well as a 6 MV CBCT acquired using the EPID. 13 Specifically, CNR in inserts of a Catphan CTP404 (The Phantom Laboratories, Salem, NY) module had an average RMSE of 2.6% and 1.4% between Fastcat and experimental measurements for the 100 kVp and 6 MV CBCTs, respectively. Likewise, Fastcat detector MTFs were assessed to be within 4.2% and 2.5% of experimental values for the kV and MV detectors, respectively.…”

Metal artifact correction in photon‐counting detector computed tomography: metal trace replacement using high‐energy data

“…CT simulations were performed using the Fastcat hybrid Monte Carlo (MC) code 53,54 . Fastcat combines MC scatter and detector response functions with GPU ray tracing to produce fast and accurate cone beam CT (CBCT) images.…”

“…CT simulations were performed using the Fastcat hybrid Monte Carlo (MC) code. 53,54 Fastcat combines MC scatter and detector response functions with GPU ray tracing to produce fast and accurate cone beam CT (CBCT) images. To mimic the experimental setup, a 330-µm pixel pitch 2-mm thick CZT detector and a 100-mm diameter, 30-mm high polyethylene phantom were simulated with 6-mm inserts of Teflon, Delrin, and acrylic to mimic the inserts found in the phantom.…”