Quantitative imaging for radiotherapy purposes

Gurney‐Champion, Oliver J.; Mahmood, Faisal; Schie, M. Van; Julian, Robert; George, Ben; Philippens, M.E.P.; Heide, Uulke A. van der; Thorwarth, Daniela; Redalen, Kathrine Røe

doi:10.1016/j.radonc.2020.01.026

Cited by 78 publications

(79 citation statements)

References 108 publications

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“…Quantitative MRI is a developing field that has primarily focused on methods for more specific tumor delineation, radiotherapy dose painting, interpretation of treatment response, and identification of normal tissue toxicity. 26,27 Unlike in CT, MR image intensity values do not correspond to physical or electron density, that is, a pixel value in MRI is relative to other pixel values and depends on several factors related to material composition and scan parameters. A comprehensive investigation of quantitative MRI is beyond the scope of this study; however, our model sensitivity was evaluated based on perturbations of AE10% hydrogen density and water content derived from ZTE and DIXON scans, respectively.…”

Section: E Spr Determination Sensitivity Analysismentioning

confidence: 99%

Technical Note: A methodology for improved accuracy in stopping power estimation using MRI and CT

et al. 2020

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Purpose Proton therapy is becoming an increasingly popular cancer treatment modality due to the proton’s physical advantage in that it deposits the majority of its energy at the distal end of its track where the tumor is located. The proton range in a material is determined from the stopping power ratio (SPR) of the material. However, SPR is typically estimated based on a computed tomography (CT) scan which can lead to range estimation errors due to the difference in x‐ray and proton interactions in matter, which can preclude the ability to utilize protons to their full potential. Applications of magnetic resonance imaging (MRI) in radiotherapy have increased over the past decade and using MRI to calculate SPR directly could provide numerous advantages. The purpose of this study was to develop a practical implementation of a novel multimodal imaging method for estimating SPR and compare the results of this method to physical measurements in which values were computed directly using tissue substitute materials fabricated to mimic skin, muscle, adipose, and spongiosa bone. Methods For both the multimodal imaging method and physical measurements, SPR was calculated using the Bethe‐Bloch equation from values of relative electron density and mean ionization potential determined for each tissue. Parameters used to estimate SPR using the multimodal imaging method were extracted from Dixon water‐only and (1H) proton density‐weighted zero echo time MRI sequences and CT, with both kVCT and MVCT used separately to evaluate the performance of each. For comparison, SPR was also computed from kVCT using the stoichiometric method, the current clinical standard. Results Results showed that our multimodal imaging approach using MRI with either kVCT or MVCT was in close agreement to SPR calculated from physical measurements for the four tissue substitutes evaluated. Using MRI and MVCT, SPR values estimated using our method were within 1% of physical measurements and were more accurate than the stoichiometric method for the tissue types studied. Conclusions We have demonstrated the methodology for improved estimation of SPR using the proposed multimodal imaging framework.

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Section: E Spr Determination Sensitivity Analysismentioning

confidence: 99%

Technical Note: A methodology for improved accuracy in stopping power estimation using MRI and CT

et al. 2020

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“…After completion of treatment a ''posttreatment" T2 scan is acquired. For research purposes additional sequences such as diffusion weighted imaging can be taken [14,15]. The time (in minutes) required for each step was assessed by radiotherapy therapists and rounded to whole minutes.…”

Section: Treatment Planning and Radiotherapy Workflowmentioning

confidence: 99%

Marker-less online MR-guided stereotactic body radiotherapy of liver metastases at a 1.5 T MR-Linac – Feasibility, workflow data and patient acceptance

Gani

Boeke

McNair

et al. 2021

Clinical and Translational Radiation Oncology

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Introduction: Stereotactic body radiotherapy (SBRT) is an established ablative treatment for liver tumors with excellent local control rates. Magnetic resonance imaging guided radiotherapy (MRgRT) provides superior soft tissue contrast and may therefore facilitate a marker-less liver SBRT workflow. The goal of the present study was to investigate feasibility, workflow parameters, toxicity and patient acceptance of MRgSBRT on a 1.5 T MR-Linac. Methods: Ten consecutive patients with liver metastases treated on a 1.5 T MR-Linac were included in this prospective trial. Tumor delineation was performed on four-dimensional computed tomography scans and both exhale triggered and free-breathing T2 MRI scans from the MR-Linac. An internal target volume based approach was applied. Organ at risk constraints were based on the UKSABR guidelines (Version 6.1). Patient acceptance regarding device specific aspects was assessed and toxicity was scored according to the common toxicity criteria of adverse events, version 5. Results: Nine of ten tumors were clearly visible on the 1.5 T MR-Linac. No patient had fiducial markers placed for treatment. All patients were treated with three or five fractions. Median dose to 98% of the gross tumor volume was 38.5 Gy. The median time from ''patient identity check" until ''beam-off" was 31 min. Median beam on time was 9.6 min. Online MRgRT was well accepted in general and no treatment had to be interrupted on patient request. No event of symptomatic radiation induced liver disease was observed after a median follow-up of ten month (range 3-17 months). Conclusion: Our early experience suggests that online 1.5 T MRgSBRT of liver metastases represents a promising new non-invasive marker-free treatment modality based on high image quality, clinically reasonable in-room times and high patient acceptance. Further studies are necessary to assess clinical outcome, to validate advanced motion management and to explore the benefit of online response adaptive liver SBRT.

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“…Such predictive models relating quantitative biomarkers derived from functional MRI to RT outcome might serve in the future as a basis for RT interventions aiming for personalized dose prescriptions. However, the direct use of functional imaging information for RT dose optimization requires quantitative imaging information [18] , [19] .…”

Section: Introductionmentioning

confidence: 99%

Quantitative magnetic resonance imaging on hybrid magnetic resonance linear accelerators: Perspective on technical and clinical validation

Thorwarth

Ege²,

Nachbar³

et al. 2020

Physics and Imaging in Radiation Oncology

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Many preclinical and clinical observations support that functional magnetic resonance imaging (MRI), such as diffusion weighted (DW) and dynamic contrast enhanced (DCE) MRI, might have a predictive value for radiotherapy. The aim of this review was to assess the current status of quantitative MRI on hybrid MR-Linacs. In a literature research, four publications were identified, investigating technical feasibility, accuracy, repeatability and reproducibility of DW and DCE-MRI in phantoms and first patients. Accuracy and short term repeatability was < 5% for DW-MRI in current MR-Linac systems. Consequently, quantitative imaging providing accurate and reproducible functional information seems possible in MR-Linacs.

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Quantitative imaging for radiotherapy purposes

Cited by 78 publications

References 108 publications

Technical Note: A methodology for improved accuracy in stopping power estimation using MRI and CT

Technical Note: A methodology for improved accuracy in stopping power estimation using MRI and CT

Marker-less online MR-guided stereotactic body radiotherapy of liver metastases at a 1.5 T MR-Linac – Feasibility, workflow data and patient acceptance

Quantitative magnetic resonance imaging on hybrid magnetic resonance linear accelerators: Perspective on technical and clinical validation

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