Spatial Precision in Magnetic Resonance Imaging–Guided Radiation Therapy: The Role of Geometric Distortion

Weygand, Joseph; Fuller, Clifton D.; Ibbott, Geoffrey S.; Mohamed, A.S.R.; Ding, Yao; Yang, Jinzhong; Hwang, Ken Pin; Wang, Jihong

doi:10.1016/j.ijrobp.2016.02.059

Cited by 128 publications

(208 citation statements)

References 113 publications

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“…As presented in the recent review article by Weygand et al, 29 the geometric distortion is a function of the magnetic field strength and gradient strength, i.e. higher magnetic field suffers larger geometric distortion and increased gradient strength results in reduced geometric distortion.…”

Section: Discussionmentioning

confidence: 98%

Anatomic and dosimetric changes in patients with head and neck cancer treated with an integrated MRI-tri-⁶⁰Co teletherapy device

Raghavan

Kishan

Cao

et al. 2016

BJR

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Objective: Prior studies have relied on CT to assess alterations in anatomy among patients undergoing radiation for head and neck cancer. We sought to determine the feasibility of using MRI-based image-guided radiotherapy to quantify these changes and to ascertain their potential dosimetric implications. Methods: 6 patients with head and neck cancer were treated with intensity-modulated radiotherapy (IMRT) on a novel tri- 60Co teletherapy system equipped with a 0.35-T MRI (VR, ViewRay Incorporated, Oakwood Village, OH) to 66-70 Gy in 33 fractions (fx). Pre-treatment MRIs on Fx 1, 5, 10, 15, 20, 25, 30 and 33 were imported into a contouring interface, where the primary gross tumour volume (GTV) and parotid glands were delineated. The centre of mass (COM) shifts for these structures were assessed relative to Day 1. Dosimetric data were co-registered with the MRIs, and doses to the GTV and parotid glands were assessed.Results: Primary GTVs decreased significantly over the course of IMRT (median % volume loss, 38.7%; range, 29.5-72.0%; p , 0.05) at a median rate of 1.2%/ fx (range, 0.92-2.2%/fx). Both the ipsilateral and contralateral parotid glands experienced significant volume loss (p , 0.05, for all) and shifted medially during IMRT. Weight loss correlated significantly with parotid gland volume loss and medial COM shift (p , 0.05). Conclusion: Integrated on-board MRI can be used to accurately contour and analyze primary GTVs and parotid glands over the course of IMRT. COM shifts and significant volume reductions were observed, confirming the results of prior CT-based exercises. Advances in knowledge: The superior resolution of onboard MRI may facilitate online adaptive replanning in the future.

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Section: Discussionmentioning

confidence: 98%

Anatomic and dosimetric changes in patients with head and neck cancer treated with an integrated MRI-tri-⁶⁰Co teletherapy device

Raghavan

Kishan

Cao

et al. 2016

BJR

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“…Geometric distortion is complex and depends on many factors including system imperfection, patient anatomy, pulse sequence type, and image parameters 19. System‐dependent distortion mainly stems from gradient nonlinearities, static field inhomogeneities, and eddy currents created by the switching of field gradients and maladjustments of both the gradient offsets and the radio frequency 20.…”

Section: Discussionmentioning

confidence: 99%

Quantitative analysis of image quality for acceptance and commissioning of an MRI simulator with a semiautomatic method

Chen

Dai

2018

J Applied Clin Med Phys

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Magnetic Resonance Imaging (MRI) simulation differs from diagnostic MRI in purpose, technical requirements, and implementation. We propose a semiautomatic method for image acceptance and commissioning for the scanner, the radiofrequency (RF) coils, and pulse sequences for an MRI simulator. The ACR MRI accreditation large phantom was used for image quality analysis with seven parameters. Standard ACR sequences with a split head coil were adopted to examine the scanner's basic performance. The performance of simulation RF coils were measured and compared using the standard sequence with different clinical diagnostic coils. We used simulation sequences with simulation coils to test the quality of image and advanced performance of the scanner. Codes and procedures were developed for semiautomatic image quality analysis. When using standard ACR sequences with a split head coil, image quality passed all ACR recommended criteria. The image intensity uniformity with a simulation RF coil decreased about 34% compared with the eight‐channel diagnostic head coil, while the other six image quality parameters were acceptable. Those two image quality parameters could be improved to more than 85% by built‐in intensity calibration methods. In the simulation sequences test, the contrast resolution was sensitive to the FOV and matrix settings. The geometric distortion of simulation sequences such as T1‐weighted and T2‐weighted images was well‐controlled in the isocenter and 10 cm off‐center within a range of ±1% (2 mm). We developed a semiautomatic image quality analysis method for quantitative evaluation of images and commissioning of an MRI simulator. The baseline performances of simulation RF coils and pulse sequences have been established for routine QA.

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“…Similarly, it has been suggested that magnetic susceptibility–induced geometric distortion may not be clinically relevant and that quality assurance benchmarks can be reasonably achieved with MRI guided radiation therapy 12, 13…”

Section: Discussionmentioning

confidence: 99%

Magnetic resonance imaging guided reirradiation of recurrent and second primary head and neck cancer

Chen

Cao

Hsu

et al. 2017

Advances in Radiation Oncology

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PurposeTo report a single-institutional experience using magnetic resonance imaging (MRI) guided radiation therapy for the reirradiation of recurrent and second cancers of the head and neck.Methods and materialsBetween October 2014 and August 2016, 13 consecutive patients with recurrent or new primary cancers of the head and neck that occurred in a previously irradiated field were prospectively enrolled in an institutional registry trial to investigate the feasibility and efficacy of MRI guided radiation therapy using a 0.35-T MRI scanner with a cobalt-60 radiation therapy source called the ViewRay system (ViewRay Inc., Cleveland, OH). Eligibility criteria included biopsy-proven evidence of recurrent or new primary squamous cell carcinoma of the head and neck, measurable disease, and previous radiation to >60 Gy. MRI guided reirradiation was delivered either using intensity modulated radiation therapy with conventional fractionation to a median dose of 66 Gy or stereotactic body radiation therapy (SBRT) using 7 to 8 Gy fractions on nonconsecutive days to a median dose of 40 Gy. Two patients (17%) received concurrent chemotherapy.ResultsThe 1- and 2-year estimates of in-field control were 72% and 72%, respectively. A total of 227 daily MRI scans were obtained to guide reirradiation. The 2-year estimates of overall survival and progression-free survival were 53% and 59%, respectively. There were no treatment-related fatalities or hospitalizations. Complications included skin desquamation, odynophagia, otitis externa, keratitis and/or conjunctivitis, and 1 case of aspiration pneumonia.ConclusionsOur preliminary findings show that reirradiation with MRI guided radiation therapy results in effective disease control with relatively low morbidity for patients with recurrent and second primary cancers of the head and neck. The superior soft tissue resolution of the MRI scans that were used for planning and delivery has the potential to improve the therapeutic ratio.

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Spatial Precision in Magnetic Resonance Imaging–Guided Radiation Therapy: The Role of Geometric Distortion

Cited by 128 publications

References 113 publications

Anatomic and dosimetric changes in patients with head and neck cancer treated with an integrated MRI-tri-⁶⁰Co teletherapy device

Anatomic and dosimetric changes in patients with head and neck cancer treated with an integrated MRI-tri-⁶⁰Co teletherapy device

Quantitative analysis of image quality for acceptance and commissioning of an MRI simulator with a semiautomatic method

Magnetic resonance imaging guided reirradiation of recurrent and second primary head and neck cancer

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Spatial Precision in Magnetic Resonance Imaging–Guided Radiation Therapy: The Role of Geometric Distortion

Cited by 128 publications

References 113 publications

Anatomic and dosimetric changes in patients with head and neck cancer treated with an integrated MRI-tri-60Co teletherapy device

Anatomic and dosimetric changes in patients with head and neck cancer treated with an integrated MRI-tri-60Co teletherapy device

Quantitative analysis of image quality for acceptance and commissioning of an MRI simulator with a semiautomatic method

Magnetic resonance imaging guided reirradiation of recurrent and second primary head and neck cancer

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Product

Resources

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Anatomic and dosimetric changes in patients with head and neck cancer treated with an integrated MRI-tri-⁶⁰Co teletherapy device

Anatomic and dosimetric changes in patients with head and neck cancer treated with an integrated MRI-tri-⁶⁰Co teletherapy device