Acuros <scp>CTS</scp>: A fast, linear Boltzmann transport equation solver for computed tomography scatter – Part <scp>II</scp>: System modeling, scatter correction, and optimization

Wang, Adam; Maslowski, Alexander; Messmer, Philippe; Lehmann, Mathias; Strzelecki, Adam; Yu, Elaine W.; Paysan, Pascal; Brehm, Marcus; Munro, Peter; Star‐Lack, Josh; Seghers, Dieter

doi:10.1002/mp.12849

Cited by 82 publications

(79 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…All CBCT modes support image reconstruction with the conventional Feldkamp–Davis–Kress (FDK)‐based algorithm. A nonlinear reconstruction algorithm, iterative CBCT (iCBCT), is also provided for several protocols including Head, Pelvis and Image Gently. The Halcyon iCBCT and standard FDK reconstruction use the same underlying acquisition process, and therefore yield the same imaging dose.…”

Section: Methodsmentioning

confidence: 99%

“…The iCBCT algorithm uses statistical reconstruction to ensure the reconstructed volume is consistent with the measured projections (data fidelity) while applying an edge‐preserving noise reduction filter (regularization). Underlying details of the statistical reconstruction algorithm have been discussed in previous research articles . The iCBCT reconstruction parameters are currently preset for selected protocols for operational convenience.…”

Section: Methodsmentioning

confidence: 99%

“…Underlying details of the statistical reconstruction algorithm have been discussed in previous research articles. 10 The iCBCT reconstruction parameters are currently preset for selected protocols for operational convenience.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Characterization of a prototype rapid kilovoltage x‐ray image guidance system designed for a ring shape radiation therapy unit

et al. 2019

View full text Add to dashboard Cite

Purpose This study aims to characterize the performance of a prototype rapid kilovoltage (kV) x‐ray image guidance system onboard the newly released Halcyon 2.0 linear accelerator (Varian Medical Systems, Palo Alto, CA) by use of conventional and innovatively designed testing procedures. Methods Basic imaging system performance tests and radiation dose measurements were performed for all eleven kV‐cone beam computed tomography (CBCT) imaging protocols available on a preclinical Halcyon 2.0 LINAC. Both conventional CBCT reconstruction using the Feldkamp–Davis–Kress (FDK) algorithm and a novel, advanced iterative reconstruction (iCBCT) available on this platform were evaluated. Standard image quality metrics, including slice thickness accuracy, high‐contrast resolution, low‐contrast resolution, regional uniformity and noise, and CT Hounsfield unit (HU) number accuracy and linearity were evaluated using a manufacturer‐supplied QUART phantom (GmbH, Zorneding, Germany) and an independent image quality phantom (Catphan 500, The Phantom Laboratory, New York, NY). Due to the simplified design of the QUART phantom, we developed surrogate and clinically feasible strategies for measuring slice thickness and high‐ and low‐contrast resolution. Imaging dose delivered by these eleven protocols was measured using a computed tomography dose index phantom and pencil chamber with commonly accepted methods and procedures. A subset of measurements were repeated on a conventional C‐arm LINAC (TrueBeam and Trilogy, Varian Medical System) for comparison. Clinical patient images of pelvic and abdominal regions are also presented for qualitative assessment as part of a feasibility study for clinical implementation. Results Image acquisition time was 17–42 s on the Halcyon system compared with 60 s on the C‐arm LINAC systems. The kV imager projection offset, imaging and treatment isocenter coincidence and the couch three‐dimensional match movement all achieved less than1 mm mechanical accuracy. All major image quality metrics were within either the national guideline or vendor‐recommended tolerances. The designed surrogate approach with the QUART phantom showed a range of 0.24–0.35 cycles/mm for spatial resolution, a contrast‐to‐noise ratio (CNR) of 2–20 for FDK reconstruction and a tolerance of 0.5 mm for slice thickness. Other metrics derived from the Catphan images obtained on the Halcyon and C‐arm LINACs showed comparable values for the FDK reconstruction. The iterative reconstruction tended to reduce noise, as evidenced by a higher CNR ratio. The fast scan pelvis protocols for Halcyon resulted in 50% lower dose compared to the standard scans, and the thorax fast protocol similarly delivered 10% lower dose than the standard thoracic scan. Preliminary patient images indicated that rapid kV CBCT with breath‐hold is feasible, with improved imaging quality compared to free‐breathing scans. Conclusion Independent and comprehensive characterization of the kV imaging guidance system on the Halcyon 2.0 system demonstrated acceptable image qual...

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Characterization of a prototype rapid kilovoltage x‐ray image guidance system designed for a ring shape radiation therapy unit

et al. 2019

View full text Add to dashboard Cite

show abstract

“…In radiation oncology, a deterministic BTE solver is commercially available for MV therapy (Acuros ® XB, Varian Medical Systems, Palo Alto, CA, USA) and brachytherapy planning (Acuros BV, Varian Medical Systems, Palo Alto, CA, USA), and has been shown to produce similar accuracy to Monte Carlo with greatly reduced computation times. A recent study demonstrated a version of the deterministic algorithm for estimating scatter in kV projections (Acuros CTS, Varian Medical Systems, Palo Alto, CA, USA) . While the focus of this previous study was scatter estimation, the same underlying methods can be used to calculate maps of radiation dose deposition.…”

Section: Introductionmentioning

confidence: 99%

“…A recent study demonstrated a version of the deterministic algorithm for estimating scatter in kV projections (Acuros CTS, Varian Medical Systems, Palo Alto, CA, USA). 34,35 While the focus of this previous study was scatter estimation, the same underlying methods can be used to calculate maps of radiation dose deposition.…”

Section: Introductionmentioning

confidence: 99%

A fast, linear Boltzmann transport equation solver for computed tomography dose calculation (Acuros CTD)

et al. 2018

Self Cite

View full text Add to dashboard Cite

Purpose To improve dose reporting of CT scans, patient‐specific organ doses are highly desired. However, estimating the dose distribution in a fast and accurate manner remains challenging, despite advances in Monte Carlo methods. In this work, we present an alternative method that deterministically solves the linear Boltzmann transport equation (LBTE), which governs the behavior of x‐ray photon transport through an object. Methods Our deterministic solver for CT dose (Acuros CTD) is based on the same approach used to estimate scatter in projection images of a CT scan (Acuros CTS). A deterministic method is used to compute photon fluence within the object, which is then converted to deposited energy by multiplying by known, material‐specific conversion factors. To benchmark Acuros CTD, we used the AAPM Task Group 195 test for CT dose, which models an axial, fan beam scan (10 mm thick beam) and calculates energy deposited in each organ of an anthropomorphic phantom. We also validated our own Monte Carlo implementation of Geant4 to use as a reference to compare Acuros against for other common geometries like an axial, cone beam scan (160 mm thick beam) and a helical scan (40 mm thick beam with table motion for a pitch of 1). Results For the fan beam scan, Acuros CTD accurately estimated organ dose, with a maximum error of 2.7% and RMSE of 1.4% when excluding organs with <0.1% of the total energy deposited. The cone beam and helical scans yielded similar levels of accuracy compared to Geant4. Increasing the number of source positions beyond 18 or decreasing the voxel size below 5 × 5 × 5 mm3 provided marginal improvement to the accuracy for the cone beam scan but came at the expense of increased run time. Across the different scan geometries, run time of Acuros CTD ranged from 8 to 23 s. Conclusions In this digital phantom study, a deterministic LBTE solver was capable of fast and accurate organ dose estimates.

show abstract

How does CBCT reconstruction algorithm impact on deformably mapped targets and accumulated dose distributions?

Mao

Liu

Gardner

et al. 2021

J Applied Clin Med Phys

View full text Add to dashboard Cite

Purpose We performed quantitative analysis of differences in deformable image registration (DIR) and deformable dose accumulation (DDA) computed on CBCT datasets reconstructed using the standard (Feldkamp‐Davis‐Kress: FDK_CBCT) and a novel iterative (iterative_CBCT) CBCT reconstruction algorithms. Methods Both FDK_CBCT and iterative_CBCT images were reconstructed for 323 fractions of treatment for 10 prostate cancer patients. Planning CT images were deformably registered to each CBCT image data set. After daily dose distributions were computed, they were mapped to planning CT to obtain deformed doses. Dosimetric and image registration results based CBCT images reconstructed by two algorithms were compared at three levels: (A) voxel doses over entire dose calculation volume, (B) clinical constraint results on targets and sensitive structures, and (C) contours propagated to CBCT images using DIR results based on three algorithms (SmartAdapt, Velocity, and Elastix) were compared with manually delineated contours as ground truth. Results (A) Average daily dose differences and average normalized DDA differences between FDK_CBCT and iterative_CBCT were ≤1 cGy. Maximum daily point dose differences increased from 0.22 ± 0.06 Gy (before the deformable dose mapping operation) to 1.33 ± 0.38 Gy after the deformable dose mapping. Maximum differences of normalized DDA per fraction were up to 0.80 Gy (0.42 ± 0.19 Gy). (B) Differences in target minimum doses were up to 8.31 Gy (−0.62 ± 4.60 Gy) and differences in critical structure doses were 0.70 ± 1.49 Gy. (C) For mapped prostate contours based on iterative_CBCT (relative to standard FDK_CBCT), dice similarity coefficient increased by 0.10 ± 0.09 (p < 0.0001), mass center distances decreased by 2.5 ± 3.0 mm (p < 0.00005), and Hausdorff distances decreased by 3.3 ± 4.4 mm (p < 0.00015). Conclusions The new iterative CBCT reconstruction algorithm leads to different mapped volumes of interest, deformed and cumulative doses than results based on conventional FDK_CBCT.

show abstract

Acuros CTS: A fast, linear Boltzmann transport equation solver for computed tomography scatter – Part II: System modeling, scatter correction, and optimization

Cited by 82 publications

References 13 publications

Characterization of a prototype rapid kilovoltage x‐ray image guidance system designed for a ring shape radiation therapy unit

Characterization of a prototype rapid kilovoltage x‐ray image guidance system designed for a ring shape radiation therapy unit

A fast, linear Boltzmann transport equation solver for computed tomography dose calculation (Acuros CTD)

How does CBCT reconstruction algorithm impact on deformably mapped targets and accumulated dose distributions?

Contact Info

Product

Resources

About