Cone beam computed tomography based image guidance and quality assessment of prostate cancer for magnetic resonance imaging-only radiotherapy in the pelvis

Edmund, Jens; Andreasen, Daniel; Leemput, Koen Van

doi:10.1016/j.phro.2021.05.001

Cited by 4 publications

(9 citation statements)

References 26 publications

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“…Our results are in line with those in the literature, whether comparing against the baseline findings from prostate studies [5][6][7][8][9][10] or the more relevant rectum study findings of Maspero [13] and Tyyger [14]. We found the systematic impact of sCT and MR on translations and rotations were <± 1 mm and <±0.5 • similarly to Maspero for sCT reference images.…”

Section: Tablesupporting

confidence: 90%

“…Therefore MR-only treatment pathways must use either the MR-simulation or sCT instead. However, there is limited assessment within the current literature of CBCT registration accuracy [4] when using sCT or MR as the reference image, with the majority of those assessing prostate [5][6][7][8][9][10] CBCT patients, with Kemppainen [6] also assessing gynaecological patients. These assessments can be used as a bench mark level of acceptability for other pelvic sites with mean 3D translational differences between MR/sCT and CT of <±2 mm.…”

Section: Introductionmentioning

confidence: 99%

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Patient position verification in magnetic-resonance imaging only radiotherapy of anal and rectal cancers

Bird

Beasley

Nix

et al. 2021

Physics and Imaging in Radiation Oncology

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Background and Purpose: Magnetic resonance (MR)-only treatment pathways require either the MR-simulation or synthetic-computed tomography (sCT) as an alternative reference image for cone beam computed tomography (CBCT) patient position verification. This study assessed whether using T2 MR or sCT as CBCT reference images introduces systematic registration errors as compared to CT for anal and rectal cancers. Materials and Methods: A total of 32 patients (18 rectum,14 anus) received pre-treatment CT-and T2 MRsimulation. Routine treatment CBCTs were acquired. sCTs were generated using a validated research model. The local clinical registration protocol, using a grey-scale registration algorithm, was performed for 216 CBCTs using CT, MR and sCT as the reference image. Linear mixed effects modelling identified systematic differences between modalities. Results: Systematic translation and rotation differences to CT for MR were − 0.3 to + 0.3 mm and − 0.1 to 0.4 • for anal cancers and − 0.4 to 0.0 mm and 0.0 to 0.1 • for rectal cancers, and for sCT were − 0.4 to + 0.8 mm, − 0.1 to 0.2 • for anal cancers and − 0.6 to + 0.2 mm, − 0.1 to + 0.1 • for rectal cancers. Conclusions: T2 MR or sCT can successfully be used as reference images for anal and rectal cancer CBCT position verification with systematic differences to CT <±1 mm and <±0.5 • . Clinical enabling of alternative modalities as reference images by vendors is required to reduce challenges associated with their use.

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Section: Tablesupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Patient position verification in magnetic-resonance imaging only radiotherapy of anal and rectal cancers

Bird

Beasley

Nix

et al. 2021

Physics and Imaging in Radiation Oncology

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“…A maximum mean difference of −0.2 mm in the P‐A direction has been shown for H&N cancer, 20 compared with our maximum mean difference of −0.3 mm in the I‐S direction. The translational and rotational differences are also similar for patient positioning using CBCT, where a maximum mean difference of 1.5 mm (P‐A) and 1.2° (around R‐L) was shown for prostate 17 . Both the 2D‐ and 3D‐evaluation had the largest translational differences in displacement in the I‐S directions.…”

Section: Discussionmentioning

confidence: 60%

“…The translational and rotational differences are also similar for patient positioning using CBCT, where a maximum mean difference of 1.5 mm (P‐A) and 1.2° (around R‐L) was shown for prostate. 17 Both the 2D‐ and 3D‐evaluation had the largest translational differences in displacement in the I‐S directions. This might be the result of a slice thickness of 2.0 mm compared to the reconstructed in‐plane resolution of 1.1 × 1.1 mm.…”

Section: Discussionmentioning

confidence: 93%

“…There are some validations of bone‐based patient positioning using sDRR and/or sCT for brain, 13 , 14 prostate, 15 , 16 , 17 rectum, 18 and pelvis. 19 However, very few investigations of sCT‐based patient positioning have been performed for the H&N region 20 and to our knowledge, there are no publications available that evaluate rotations for positioning of H&N cancer patients.…”

Section: Introductionmentioning

confidence: 99%

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Head and neck cancer patient positioning using synthetic CT data in MRI‐only radiation therapy

Palmér

Nordström

Karlsson

et al. 2022

J Applied Clin Med Phys

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Purpose The accuracy and precision of patient positioning is crucial in radiotherapy; however, there are no publications available using synthetic computed tomography (sCT) that evaluate rotations in head and neck (H&N) patients positioning or the effect of translation and rotation combined. The aim of this work was to evaluate the differences between using sCT with the CT for 2D‐ and 3D‐patient positioning in a magnetic resonance imaging (MRI)‐only workflow. Methods This study included 14 H&N cancer patients, with generated sCT data (MRI Planner v2.2) and the CT deformably registered to the MRI. Patient positioning was evaluated by comparing sCT against CT data: 3D cone beam CT (CBCT) was registered to the deformed CT (dCT) and sCT in six degrees of freedom (DoF) with a rigid auto‐registration algorithm and bone threshold, and 2D deformed digital reconstructed radiographs (dDRR) and synthetic DRRs (sDRR) were manually registered to orthogonal projections in five DoF by six blinded observers. The difference in displacement in all DoF were calculated for dCT and sCT, as well as for dDRR and sDRR. The interobserver variation was evaluated by separate application of the paired dDRR and sDRR registration matrices to the original coordinates of the planning target volume (PTV) structures and calculation of the Euclidean distance between the corresponding points. The Dice similarity coefficient (DSC) was calculated between dDRR/sDRR‐registered PTVs. Results The mean difference in patient positioning using CBCT was <0.7 mm and <0.3° and using orthogonal projections <0.4 mm and <0.2° in all directions. The maximum Euclidean distance was 5.1 mm, the corresponding mean (1SD) Euclidean distance and mean DSC were 3.5 ± 0.7 mm and 0.93, respectively. Conclusions This study shows that the sCT‐based patient positioning gives a comparable result with that based on CT images, allowing sCT to replace CT as reference for patient treatment positioning.

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Evaluation of MRI‐only based online adaptive radiotherapy of abdominal region on MR‐linac

Nousiainen

Santurio

Lundahl

et al. 2022

J Applied Clin Med Phys

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A hybrid magnetic resonance linear accelerator (MRL) can perform magnetic resonance imaging (MRI) with high soft-tissue contrast to be used for online adaptive radiotherapy (oART). To obtain electron densities needed for the oART dose calculation, a computed tomography (CT) is often deformably registered to MRI. Our aim was to evaluate an MRI-only based synthetic CT (sCT) generation as an alternative to the deformed CT (dCT)-based oART in the abdominal region. Methods: The study data consisted of 57 patients who were treated on a 0.35 T MRL system mainly for abdominal tumors. Simulation MRI-CT pairs of 43 patients were used for training and validation of a prototype convolutional neural network sCT-generation algorithm, based on HighRes3DNet, for the abdominal region. For remaining test patients, sCT images were produced from simulation MRIs and daily MRIs. The dCT-based plans were re-calculated on sCT with identical calculation parameters. The sCT and dCT were compared in terms of geometric agreement and calculated dose. Results:The mean and one standard deviation of the geometric agreement metrics over dCT-sCT-pairs were: mean error of 8 ± 10 HU, mean absolute error of 49 ± 10 HU, and Dice similarity coefficient of 55 ± 12%, 60 ± 5%, and 82 ± 15% for bone, fat, and lung tissues, respectively. The dose differences between the sCT and dCT-based dose for planning target volumes were 0.5 ± 0.9%, 0.6 ± 0.8%, and 0.5 ± 0.8% at D 2% , D 50% , and D 98% in physical dose and 0.8 ± 1.4%, 0.8 ± 1.2%, and 0.6 ± 1.1% in biologically effective dose (BED). For organs-at-risk,the dose differences of all evaluated dose-volume histogram points were within [-4.5%, 7.8%] and [-1.1 Gy, 3.5 Gy] in both physical dose and BED. Conclusions:The geometric agreement metrics were within typically reported values and most average relative dose differences were within 1%. Thus, an MRI-only sCT-based approach is a promising alternative to the current clinical practice of the abdominal oART on MRL.

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Cone beam computed tomography based image guidance and quality assessment of prostate cancer for magnetic resonance imaging-only radiotherapy in the pelvis

Cited by 4 publications

References 26 publications

Patient position verification in magnetic-resonance imaging only radiotherapy of anal and rectal cancers

Patient position verification in magnetic-resonance imaging only radiotherapy of anal and rectal cancers

Head and neck cancer patient positioning using synthetic CT data in MRI‐only radiation therapy

Evaluation of MRI‐only based online adaptive radiotherapy of abdominal region on MR‐linac

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