The rationale for MR-only treatment planning for external radiotherapy

Jönsson, Johan; Nyholm, Tufve; Söderkvist, Karin

doi:10.1016/j.ctro.2019.03.005

Cited by 66 publications

(76 citation statements)

References 58 publications

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“…The registration between the planning CT and the CT component of the PET/CT is also a crucial step which requires 2-3 min, but does not require additional tools. Indeed, radiation oncologists deal now with functional and molecular imaging to increase the definition of target volumes in daily practice, and are increasingly familiar with registration between various imaging modalities, especially with the emergence of stereotactic radiotherapy [39,40]. To accommodate this, radiation oncology planning softwares now provide registration functionalities.…”

Section: Discussionmentioning

confidence: 99%

Impact of suboptimal dosimetric coverage of pretherapeutic 18F-FDG PET/CT hotspots on outcome in patients with locally advanced cervical cancer treated with chemoradiotherapy followed by brachytherapy

Lucia¹,

Bourbonne²,

Gujral³

et al. 2020

Clinical and Translational Radiation Oncology

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Introduction: Areas of high uptake on pre-treatment 18 F-fluorodeoxyglucose (18 F-FDG) positron emission tomography/computed tomography (PET/CT), denoted as ''hotspots", have been identified as preferential sites of local relapse in locally advanced cervical cancer (LACC). The purpose of this study was to analyze the dosimetric coverage of these hotspots with high dose-rate brachytherapy (BT). Methods: For each patient, a rigid registration of the CT from the pre-treatment PET/CT with the radiotherapy planning CT was performed using 3D Slicer TM , followed by a manual volume correction by translation and deformation if necessary. The fuzzy locally adaptive Bayesian (FLAB) algorithm was applied to PET images to simultaneously define an overall tumour volume and the high-uptake sub-volume V1. The inclusion of V1 in the high-risk clinical target volume (CTV HR) and its dosimetric coverage were evaluated using 3D Slicer TM. The average of the 3-4 BT sessions was reported. Results: Forty-two patients with recurrence after chemoradiotherapy (CRT) for LACC were matched to 42 patients without recurrence. Mean ± standard deviation follow-up was 26 ± 11 months. In the recurrence group, V1 was not included in the CTV HR and not covered by the 85 Gy isodose in 17/42 patients (41%) (1/20 with pelvic recurrence and 16/22 with distant recurrence) and not by the 80 Gy isodose in 7/42 patients (17%) (all with distant recurrence). In the non-recurrence group, V1 was not included in CTV HR and not covered by the 85 Gy isodose in 3 patients only (7%). The hotspots coverage by the 85 Gy isodose was significantly better in patients who did not recur, but only when compared to patients with distant relapse (p < 0.0001). Conclusion: Suboptimal dosimetric coverage of high FDG uptakes on pretherapeutic PET could be associated with an increased risk of recurrence.

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Section: Discussionmentioning

confidence: 99%

Impact of suboptimal dosimetric coverage of pretherapeutic 18F-FDG PET/CT hotspots on outcome in patients with locally advanced cervical cancer treated with chemoradiotherapy followed by brachytherapy

Lucia¹,

Bourbonne²,

Gujral³

et al. 2020

Clinical and Translational Radiation Oncology

View full text Add to dashboard Cite

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“…Although incorporating MRI decreases over-segmentation of structures as compared with CT-based segmentation, a combined CT + MRI method is challenging due to errors introduced by mis-registration of the image sets and the changes to the shape and location of the soft tissues e.g., bladder, rectum, and seminal vesicles, that are inherent when acquiring multiple image sets [3][4][5]. An MRI-only workflow can potentially eliminate the use of an additional CT scan and help in reducing systematic registration uncertainty [6]. Use of hybrid technologies such as MR-linear accelerator devices (MR-linac) and MR-Positron emission tomography (MR-PET) as well as integration of multiparametric MRI provides further argument for an MR-only workflow for prostate [7][8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Clinical experience and workflow challenges with magnetic resonance-only radiation therapy simulation and planning for prostate cancer

Tyagi

Zeléfsky

Wibmer

et al. 2020

Physics and Imaging in Radiation Oncology

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Background and purpose: Magnetic Resonance (MR)-only planning has been implemented clinically for radiotherapy of prostate cancer. However, fewer studies exist regarding the overall success rate of MR-only workflows. We report on successes and challenges of implementing MR-only workflows for prostate. Materials and methods: A total of 585 patients with prostate cancer underwent an MR-only simulation and planning between 06/2016-06/2018. MR simulation included images for contouring, synthetic-CT generation and fiducial identification. Workflow interruptions occurred that required a backup CT, a re-simulation or an update to our current quality assurance (QA) process. The challenges were prospectively evaluated and classified into synthetic-CT generation, motion/artifacts in the MRs, fiducial QA and bowel preparation guidelines. Results: MR-only simulation was successful in 544 (93.2%) patients. In seventeen patients (2.9%), reconstruction of synthetic-CT failed due to patient size, femur angulation, or failure to determine the body contour. Twentyfour patients (4.1%) underwent a repeat/backup CT scan because of artifacts on the MR such as image blur due to patient motion or biopsy/surgical artifacts that hampered identification of the implanted fiducial markers. In patients requiring large coverage due to nodal involvement, inhomogeneity artifacts were resolved by using a two-stack acquisition and adaptive inhomogeneity correction. Bowel preparation guidelines were modified to address frequent rectum/gas issues due to longer MR scan time. Conclusions: MR-only simulation has been successfully implemented for a majority of patients in the clinic. However, MR-CT or CT-only pathway may still be needed for patients where MR-only solution fails or patients with MR contraindications.

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“…In the head region, average registration errors <2 mm have been reported [10]. The use of MRI-only RTP workflow eliminates this systematic registration error and may therefore reduce the total dosimetric uncertainty induced during the RTP process [11].…”

Section: Introductionmentioning

confidence: 99%

Assessment of MRI-Based Attenuation Correction for MRI-Only Radiotherapy Treatment Planning of the Brain

et al. 2020

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Magnetic resonance imaging-only radiotherapy treatment planning (MRI-only RTP) and positron emission tomography (PET)–MRI imaging require generation of synthetic computed tomography (sCT) images from MRI images. In this study, initial dosimetric evaluation was performed for a previously developed MRI-based attenuation correction (MRAC) method for use in MRI-only RTP of the brain. MRAC-based sCT images were retrospectively generated from Dixon MR images of 20 patients who had previously received external beam radiation therapy (EBRT). Bone segmentation performance and Dice similarity coefficient of the sCT conversion method were evaluated for bone volumes on CT images. Dose calculation accuracy was assessed by recalculating the CT-based EBRT plans using the sCT images as the base attenuation data. Dose comparison was done for the sCT- and CT-based EBRT plans in planning target volume (PTV) and organs at risk (OAR). Parametric dose comparison showed mean relative differences of <0.4% for PTV and <1.0% for OARs. Mean gamma index pass rates of 95.7% with the 2%/2 mm agreement criterion and 96.5% with the 1%/1 mm agreement criterion were determined for glioma and metastasis patients, respectively. Based on the results, MRI-only RTP using sCT images generated from MRAC images can be a feasible alternative for radiotherapy of the brain.

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The rationale for MR-only treatment planning for external radiotherapy

Abstract: Highlights MR-only treatment planning could improve the spatial accuracy of radiotherapy. The benefit compared to a mixed MR-CT workflow will vary between patient groups. Further development of QA tools is needed before the procedure will save resources.

Cited by 66 publications

References 58 publications

Impact of suboptimal dosimetric coverage of pretherapeutic 18F-FDG PET/CT hotspots on outcome in patients with locally advanced cervical cancer treated with chemoradiotherapy followed by brachytherapy

Impact of suboptimal dosimetric coverage of pretherapeutic 18F-FDG PET/CT hotspots on outcome in patients with locally advanced cervical cancer treated with chemoradiotherapy followed by brachytherapy

Clinical experience and workflow challenges with magnetic resonance-only radiation therapy simulation and planning for prostate cancer

Assessment of MRI-Based Attenuation Correction for MRI-Only Radiotherapy Treatment Planning of the Brain

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