Comprehensive MRI simulation methodology using a dedicated MRI scanner in radiation oncology for external beam radiation treatment planning

Paulson, E.S.; Erickson, Beth; Schultz, Chris; Li, X. Allen

doi:10.1118/1.4896096

Cited by 129 publications

(154 citation statements)

References 41 publications

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“…In each of these applications, the soft tissue contrast of MRI is desired in order to obtain the necessary information, but the spatial distortion of the MR image presents a barrier to adoption[6,7]. …”

Section: Introductionmentioning

confidence: 99%

“…There is also interest in using MR imaging alone, without a corresponding pre-treatment computed tomography (CT) exam, for both photon and proton radiation therapy planning[6,9,10]. A major technical challenge in utilizing MRI lies in determining the geometric accuracy of the tissues that are to be targeted or avoided during radiation therapy.…”

Section: Introductionmentioning

confidence: 99%

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Image-based gradient non-linearity characterization to determine higher-order spherical harmonic coefficients for improved spatial position accuracy in magnetic resonance imaging

Weavers

Tao

Trzasko

et al. 2017

Magnetic Resonance Imaging

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Purpose Spatial position accuracy in magnetic resonance imaging (MRI) is an important concern for a variety of applications, including radiation therapy planning, surgical planning, and longitudinal studies of morphologic changes to study neurodegenerative diseases. Spatial accuracy is strongly influenced by gradient linearity. This work presents a method for characterizing the gradient non-linearity fields on a per-system basis, and using this information to provide improved and higher-order (9th vs 5th) spherical harmonic coefficients for better spatial accuracy in MRI. Methods A large fiducial phantom containing 5229 water-filled spheres in a grid pattern is scanned with the MR system, and the positions all the fiducials are measured and compared to the corresponding ground truth fiducial positions as reported from a computed tomography (CT) scan of the object. Systematic errors from off-resonance (i.e., B0) effects are minimized with the use of increased receiver bandwidth (±125 kHz) and two acquisitions with reversed readout gradient polarity. The spherical harmonic coefficients are estimated using an iterative process, and can be subsequently used to correct for gradient non-linearity. Test-retest stability was assessed with five repeated measurements on a single scanner, and cross-scanner variation on four different, identically-configured 3T wide-bore systems. Results A decrease in the root-mean-square error (RMSE) over a 50 cm diameter spherical volume from 1.80 mm to 0.77 mm is reported here in the case of replacing the vendor’s standard 5th order spherical harmonic coefficients with custom fitted 9th order coefficients, and from 1.5mm to 1mm by extending custom fitted 5th order correction to the 9th order. Minimum RMSE varied between scanners, but was stable with repeated measurements in the same scanner. Conclusions The results suggest that the proposed methods may be used on a per-system basis to more accurately calibrate MR gradient non-linearity coefficients when compared to vendor standard corrections.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Image-based gradient non-linearity characterization to determine higher-order spherical harmonic coefficients for improved spatial position accuracy in magnetic resonance imaging

Weavers

Tao

Trzasko

et al. 2017

Magnetic Resonance Imaging

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show abstract

“…Patient-induced distortions arising from susceptibility and chemical shift have shown a dependence on field strength and can be considered negligible for low field systems (18, 19). In addition, appropriate sequence selection—that is, using turbo spin echo (TSE) sequences and high readout bandwidths (20)—minimized chemical shift and susceptibility-induced distortions. It should be noted that this effect is expected to be small as 99.9% of voxels distorted less than 2.23 ppm for a brain scan acquired at 3T (21), which is equivalent to <1 pixel shift for our acquisition parameters and field strength.…”

Section: Methodsmentioning

confidence: 99%

Image Guided Radiation Therapy Using Synthetic Computed Tomography Images in Brain Cancer

Price

Kim

Zheng

et al. 2016

International Journal of Radiation Oncology*Biology*Physics

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Purpose The development of synthetic computed tomography (CT) (synCT) derived from magnetic resonance (MR) images supports MR-only treatment planning. We evaluated the accuracy of synCT and synCT-generated digitally reconstructed radiographs (DRRs) relative to CT and determined their performance for image guided radiation therapy (IGRT). Methods and Materials Magnetic resonance simulation (MR-SIM) and CT simulation (CT-SIM) images were acquired of an anthropomorphic skull phantom and 12 patient brain cancer cases. SynCTs were generated using fluid attenuation inversion recovery, ultrashort echo time, and Dixon data sets through a voxel-based weighted summation of 5 tissue classifications. The DRRs were generated from the phantom synCT, and geometric fidelity was assessed relative to CT-generated DRRs through bounding box and landmark analysis. An offline retrospective analysis was conducted to register cone beam CTs (n=34) to synCTs and CTs using automated rigid registration in the treatment planning system. Planar MV and KV images (n=37) were rigidly registered to synCT and CT DRRs using an in-house script. Planar and volumetric registration reproducibility was assessed and margin differences were characterized by the van Herk formalism. Results Bounding box and landmark analysis of phantom synCT DRRs were within 1 mm of CT DRRs. Absolute planar registration shift differences ranged from 0.0 to 0.7 mm for phantom DRRs on all treatment platforms and from 0.0 to 0.4 mm for volumetric registrations. For patient planar registrations, the mean shift differences were 0.4 ± 0.5 mm (range, −0.6 to 1.6 mm), 0.0 ± 0.5 mm (range, −0.9 to 1.2 mm), and 0.1 ± 0.3 mm (range, −0.7 to 0.6 mm) for the superior-inferior (S-I), left-right (L-R), and anterior-posterior (A-P) axes, respectively. The mean shift differences in volumetric registrations were 0.6 ± 0.4 mm (range, −0.2 to 1.6 mm), 0.2 ± 0.4 mm (range, −0.3 to 1.2 mm), and 0.2 ± 0.3 mm (range, −0.2 to 1.2 mm) for the S-I, L-R, and A-P axes, respectively. The CT-SIM and synCT derived margins were <0.3 mm different. Conclusion DRRs generated by synCT were in close agreement with CT-SIM. Planar and volumetric image registrations to synCT-derived targets were comparable with CT for phantom and patients. This validation is the next step toward MR-only planning for the brain.

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“…53,54 Newer treatment models are being developed that are trying to incorporate MRI into LINACs, allowing improved tumor visualization at the time of radiation delivery compared to CT. As imaging and molecular diagnostics become more integrated, the use of biomarkers may yield improved diagnostic tests for patients. Researchers improving tumor delineation for intracranial disease are working to understand the true extension of tumors based on functional and metabolic imaging studies.…”

Section: Future Directionsmentioning

confidence: 99%

Use of Neuroimaging for Radiation Therapy Planning

Majithia

Walston

Guiou

et al. 2016

Handbook of Neuro-Oncology Neuroimaging

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Comprehensive MRI simulation methodology using a dedicated MRI scanner in radiation oncology for external beam radiation treatment planning

Abstract: The methodology described herein contains practical strategies the authors have implemented through lessons learned performing clinical MRI simulation exams. In their experience, these strategies provide robust, high fidelity, high contrast MR images suitable for external beam RTP.

Cited by 129 publications

References 41 publications

Image-based gradient non-linearity characterization to determine higher-order spherical harmonic coefficients for improved spatial position accuracy in magnetic resonance imaging

Image-based gradient non-linearity characterization to determine higher-order spherical harmonic coefficients for improved spatial position accuracy in magnetic resonance imaging

Image Guided Radiation Therapy Using Synthetic Computed Tomography Images in Brain Cancer

Use of Neuroimaging for Radiation Therapy Planning

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