Implementation of a Novel Algorithm For Generating Synthetic CT Images From Magnetic Resonance Imaging Data Sets for Prostate Cancer Radiation Therapy

Kim, Joshua; Glide-Hurst, Carri K; Doemer, Anthony; Wen, Ning; Movsas, Benjamin; Chetty, Indrin J.

doi:10.1016/j.ijrobp.2014.09.015

Cited by 96 publications

(108 citation statements)

References 38 publications

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“…The MAE obtained within the external contour for the prostate patients was on average 49.8 ± 4.6 HU, which is lower than the error obtained by Kim et al [20] (74.3 ± 10.9 HU) and is of the same order as the MAE obtained by Siversson et al [25], Dowling et al [19] and Andreasen et al [24] (36.5 ± 4.1 HU, 40.5 ± 8.2 HU and 54 ± 8 HU, respectively), when taking into account the fact that the images used in the present study had a lower resolution. The synthesis error was higher for the H&N patients as the neck is a more challenging area for registration algorithms because of the mixture of bone and air, and due to the presence of large-scale postural changes between patients, such as flexion or extension of the neck and the position of the jawbone.…”

Section: Discussioncontrasting

confidence: 60%

“…Jonsson et al [15] applied the method developed by Johansson et al [16] where a sCT was obtained from a Gaussian mixture regression model linking the MRI intensity values to the CT HUs. Another family of methods, the atlas-based methods, rely on a single template [17] or a database of MR and CT image pairs [18], [19], [20], [21], [22], [23]. First, a non-rigid registration between the atlas and test subject MR images is performed.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of a multi-atlas CT synthesis approach for MRI-only radiotherapy treatment planning

et al. 2017

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HighlightsEstablishing MRI-only RTP workflows requires synthetic CTs for dose calculation.This study evaluates the feasibility of using a multi-atlas CT synthesis approach.The proposed method was validated on head and neck and prostate cancer patients.Results showed an accurate bone estimation for future patient positioning.Results showed that synthetic CTs are suitable to perform clinical dose calculations.

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Section: Discussioncontrasting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Evaluation of a multi-atlas CT synthesis approach for MRI-only radiotherapy treatment planning

et al. 2017

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“…In previous work, several authors concluded that comparable, or even higher observed dose differences would enable accurate MR-only dose calculations (Dowling et al 2012, Korhonen et al 2014, Kim et al 2015, Siversson et al 2015. We concluded that MRCAT enables accurate MR-based dose calculation to the target.…”

Section: Discussionmentioning

confidence: 57%

Quantification of confounding factors in MRI-based dose calculations as applied to prostate IMRT

et al. 2017

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Magnetic resonance (MR)-only radiotherapy treatment planning requires pseudo-CT (pCT) images to enable MR-based dose calculations. To verify the accuracy of MR-based dose calculations, institutions interested in introducing MR-only planning will have to compare pCT-based and computer tomography (CT)-based dose calculations. However, interpreting such comparison studies may be challenging, since potential differences arise from a range of confounding factors which are not necessarily specific to MR-only planning. Therefore, the aim of this study is to identify and quantify the contribution of factors confounding dosimetric accuracy estimation in comparison studies between CT and pCT. The following factors were distinguished: set-up and positioning differences between imaging sessions, MR-related geometric inaccuracy, pCT generation, use of specific calibration curves to convert pCT into electron density information, and registration errors.The study comprised fourteen prostate cancer patients who underwent CT/ MRI-based treatment planning. To enable pCT generation, a commercial solution (MRCAT, Philips Healthcare, Vantaa, Finland) was adopted. IMRT plans were calculated on CT (gold standard) and pCTs. Dose difference maps in a high dose region (CTV) and in the body volume were evaluated, and the contribution to dose errors of possible confounding factors was individually quantified.We found that the largest confounding factor leading to dose difference was the use of different calibration curves to convert pCT and CT into electron density (0.7%). The second largest factor was the pCT generation Inter-scan differences due to patient repositioning, MR-related geometric inaccuracy, and registration errors did not significantly contribute to dose differences (0.01%). The proposed approach successfully identified and quantified the factors confounding accurate MRI-based dose calculation in the prostate. This study will be valuable for institutions interested in introducing MR-only dose planning in their clinical practice.

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“…A manual assignment process classifies each tissue type as air, bone, fat, brain matter, or CSF. Then, synCTs are generated using a bulk density representation for air, whereas all other tissue types are patient specific with intensities obtained by a voxel-based, weighted summation method from the bone-enhanced, FLAIR, and UTE images described in detail elsewhere (5, 6). Due to the reduced complexity of the phantom, the inverse UTE image and 3-kernel GMM were used for segmentation with slightly different material weightings.…”

Section: Methodsmentioning

confidence: 99%

“…We (5, 6) and others (7–12) have developed methods for generating synthetic or pseudo CTs to support MR-only treatment planning, including approaches such as Gaussian mixture modeling (GMM) (8), atlas-based solutions (10), and patch based using nearest-neighbor intensity values (9). The dosimetric differences resulting from the use of synthetic computed tomography images (synCTs) have been shown to be clinically negligible (<2% for planning target volume [PTV] metrics) (6, 9, 11, 13–15).…”

Section: Introductionmentioning

confidence: 99%

Image Guided Radiation Therapy Using Synthetic Computed Tomography Images in Brain Cancer

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Zheng

et al. 2016

International Journal of Radiation Oncology*Biology*Physics

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Purpose The development of synthetic computed tomography (CT) (synCT) derived from magnetic resonance (MR) images supports MR-only treatment planning. We evaluated the accuracy of synCT and synCT-generated digitally reconstructed radiographs (DRRs) relative to CT and determined their performance for image guided radiation therapy (IGRT). Methods and Materials Magnetic resonance simulation (MR-SIM) and CT simulation (CT-SIM) images were acquired of an anthropomorphic skull phantom and 12 patient brain cancer cases. SynCTs were generated using fluid attenuation inversion recovery, ultrashort echo time, and Dixon data sets through a voxel-based weighted summation of 5 tissue classifications. The DRRs were generated from the phantom synCT, and geometric fidelity was assessed relative to CT-generated DRRs through bounding box and landmark analysis. An offline retrospective analysis was conducted to register cone beam CTs (n=34) to synCTs and CTs using automated rigid registration in the treatment planning system. Planar MV and KV images (n=37) were rigidly registered to synCT and CT DRRs using an in-house script. Planar and volumetric registration reproducibility was assessed and margin differences were characterized by the van Herk formalism. Results Bounding box and landmark analysis of phantom synCT DRRs were within 1 mm of CT DRRs. Absolute planar registration shift differences ranged from 0.0 to 0.7 mm for phantom DRRs on all treatment platforms and from 0.0 to 0.4 mm for volumetric registrations. For patient planar registrations, the mean shift differences were 0.4 ± 0.5 mm (range, −0.6 to 1.6 mm), 0.0 ± 0.5 mm (range, −0.9 to 1.2 mm), and 0.1 ± 0.3 mm (range, −0.7 to 0.6 mm) for the superior-inferior (S-I), left-right (L-R), and anterior-posterior (A-P) axes, respectively. The mean shift differences in volumetric registrations were 0.6 ± 0.4 mm (range, −0.2 to 1.6 mm), 0.2 ± 0.4 mm (range, −0.3 to 1.2 mm), and 0.2 ± 0.3 mm (range, −0.2 to 1.2 mm) for the S-I, L-R, and A-P axes, respectively. The CT-SIM and synCT derived margins were <0.3 mm different. Conclusion DRRs generated by synCT were in close agreement with CT-SIM. Planar and volumetric image registrations to synCT-derived targets were comparable with CT for phantom and patients. This validation is the next step toward MR-only planning for the brain.

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Implementation of a Novel Algorithm For Generating Synthetic CT Images From Magnetic Resonance Imaging Data Sets for Prostate Cancer Radiation Therapy

Cited by 96 publications

References 38 publications

Evaluation of a multi-atlas CT synthesis approach for MRI-only radiotherapy treatment planning

Evaluation of a multi-atlas CT synthesis approach for MRI-only radiotherapy treatment planning

Quantification of confounding factors in MRI-based dose calculations as applied to prostate IMRT

Image Guided Radiation Therapy Using Synthetic Computed Tomography Images in Brain Cancer

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