Accuracy and precision of patient positioning for pelvic MR-only radiation therapy using digitally reconstructed radiographs

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Accuracy and precision of patient positioning for pelvic MR-only radiation therapy using digitally reconstructed radiographs. / Kemppainen, R.; Vaara, T.; Joensuu, T.; Kiljunen, T.

In: Physics in Medicine and Biology, Vol. 63, No. 5, 055009, 02.03.2018, p. 1-10.

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@article{b23903b189d941d499fb9e3acdbbd81c,
title = "Accuracy and precision of patient positioning for pelvic MR-only radiation therapy using digitally reconstructed radiographs",
abstract = "Background and Purpose. Magnetic resonance imaging (MRI) has in recent years emerged as an imaging modality to drive precise contouring of targets and organs at risk in external beam radiation therapy. Moreover, recent advances in MRI enable treatment of cancer without computed tomography (CT) simulation. A commercially available MR-only solution, MRCAT, offers a single-modality approach that provides density information for dose calculation and generation of positioning reference images. We evaluated the accuracy of patient positioning based on MRCAT digitally reconstructed radiographs (DRRs) by comparing to standard CT based workflow. Materials and Methods. Twenty consecutive prostate cancer patients being treated with external beam radiation therapy were included in the study. DRRs were generated for each patient based on the planning CT and MRCAT. The accuracy assessment was performed by manually registering the DRR images to planar kV setup images using bony landmarks. A Bayesian linear mixed effects model was used to separate systematic and random components (inter- and intra-observer variation) in the assessment. In addition, method agreement was assessed using a Bland-Altman analysis. Results. The systematic difference between MRCAT and CT based patient positioning, averaged over the study population, were found to be (mean [95{\%} CI]) -0.49 [-0.85 to -0.13] mm, 0.11 [-0.33 to +0.57] mm and -0.05 [-0.23 to +0.36] mm in vertical, longitudinal and lateral directions, respectively. The increases in total random uncertainty were estimated to be below 0.5 mm for all directions, when using MR-only workflow instead of CT. Conclusions. The MRCAT pseudo-CT method provides clinically acceptable accuracy and precision for patient positioning for pelvic radiation therapy based on planar DRR images. Furthermore, due to the reduction of geometric uncertainty, compared to dual-modality workflow, the approach is likely to improve the total geometric accuracy of pelvic radiation therapy.",
keywords = "digitally reconstructed radioraphs, image-guided radiotherapy, MRI-based radiotherapy, radiotherapy",
author = "R. Kemppainen and T. Vaara and T. Joensuu and T. Kiljunen",
year = "2018",
month = "3",
day = "2",
doi = "10.1088/1361-6560/aaad21",
language = "English",
volume = "63",
pages = "1--10",
journal = "Physics in Medicine and Biology",
issn = "0031-9155",
publisher = "IOP Publishing Ltd.",
number = "5",

}

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TY - JOUR

T1 - Accuracy and precision of patient positioning for pelvic MR-only radiation therapy using digitally reconstructed radiographs

AU - Kemppainen, R.

AU - Vaara, T.

AU - Joensuu, T.

AU - Kiljunen, T.

PY - 2018/3/2

Y1 - 2018/3/2

N2 - Background and Purpose. Magnetic resonance imaging (MRI) has in recent years emerged as an imaging modality to drive precise contouring of targets and organs at risk in external beam radiation therapy. Moreover, recent advances in MRI enable treatment of cancer without computed tomography (CT) simulation. A commercially available MR-only solution, MRCAT, offers a single-modality approach that provides density information for dose calculation and generation of positioning reference images. We evaluated the accuracy of patient positioning based on MRCAT digitally reconstructed radiographs (DRRs) by comparing to standard CT based workflow. Materials and Methods. Twenty consecutive prostate cancer patients being treated with external beam radiation therapy were included in the study. DRRs were generated for each patient based on the planning CT and MRCAT. The accuracy assessment was performed by manually registering the DRR images to planar kV setup images using bony landmarks. A Bayesian linear mixed effects model was used to separate systematic and random components (inter- and intra-observer variation) in the assessment. In addition, method agreement was assessed using a Bland-Altman analysis. Results. The systematic difference between MRCAT and CT based patient positioning, averaged over the study population, were found to be (mean [95% CI]) -0.49 [-0.85 to -0.13] mm, 0.11 [-0.33 to +0.57] mm and -0.05 [-0.23 to +0.36] mm in vertical, longitudinal and lateral directions, respectively. The increases in total random uncertainty were estimated to be below 0.5 mm for all directions, when using MR-only workflow instead of CT. Conclusions. The MRCAT pseudo-CT method provides clinically acceptable accuracy and precision for patient positioning for pelvic radiation therapy based on planar DRR images. Furthermore, due to the reduction of geometric uncertainty, compared to dual-modality workflow, the approach is likely to improve the total geometric accuracy of pelvic radiation therapy.

AB - Background and Purpose. Magnetic resonance imaging (MRI) has in recent years emerged as an imaging modality to drive precise contouring of targets and organs at risk in external beam radiation therapy. Moreover, recent advances in MRI enable treatment of cancer without computed tomography (CT) simulation. A commercially available MR-only solution, MRCAT, offers a single-modality approach that provides density information for dose calculation and generation of positioning reference images. We evaluated the accuracy of patient positioning based on MRCAT digitally reconstructed radiographs (DRRs) by comparing to standard CT based workflow. Materials and Methods. Twenty consecutive prostate cancer patients being treated with external beam radiation therapy were included in the study. DRRs were generated for each patient based on the planning CT and MRCAT. The accuracy assessment was performed by manually registering the DRR images to planar kV setup images using bony landmarks. A Bayesian linear mixed effects model was used to separate systematic and random components (inter- and intra-observer variation) in the assessment. In addition, method agreement was assessed using a Bland-Altman analysis. Results. The systematic difference between MRCAT and CT based patient positioning, averaged over the study population, were found to be (mean [95% CI]) -0.49 [-0.85 to -0.13] mm, 0.11 [-0.33 to +0.57] mm and -0.05 [-0.23 to +0.36] mm in vertical, longitudinal and lateral directions, respectively. The increases in total random uncertainty were estimated to be below 0.5 mm for all directions, when using MR-only workflow instead of CT. Conclusions. The MRCAT pseudo-CT method provides clinically acceptable accuracy and precision for patient positioning for pelvic radiation therapy based on planar DRR images. Furthermore, due to the reduction of geometric uncertainty, compared to dual-modality workflow, the approach is likely to improve the total geometric accuracy of pelvic radiation therapy.

KW - digitally reconstructed radioraphs

KW - image-guided radiotherapy

KW - MRI-based radiotherapy

KW - radiotherapy

UR - http://www.scopus.com/inward/record.url?scp=85043484811&partnerID=8YFLogxK

U2 - 10.1088/1361-6560/aaad21

DO - 10.1088/1361-6560/aaad21

M3 - Article

VL - 63

SP - 1

EP - 10

JO - Physics in Medicine and Biology

JF - Physics in Medicine and Biology

SN - 0031-9155

IS - 5

M1 - 055009

ER -

ID: 29744165