A methodology to investigate the impact of image distortions on the radiation dose when using magnetic resonance images for planning

Yan, Yue; Yang, Jinzhong; Beddar, Sam; Wen, Zhifei; Court, Laurence Edward; Hwang, Ken Pin; Kadbi, Mo; Krishnan, Sunil; Fuller, Clifton D.; Frank, Steven J.; Yang, James N; Balter, Peter A; Kudchadker, Rajat J.; Wang, Jihong

doi:10.1088/1361-6560/aab5c3

Cited by 18 publications

(32 citation statements)

References 26 publications

(33 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[118][119][120][121] Especially in preoperative (chemo)radiotherapy for gastric cancer, MRI evaluation of setup accuracy could be of great benefit. 122 Daily adaptation of treatment plans based on intra-and interfraction anatomical variation becomes possible, allowing better normal tissue sparing and/or radiation dose escalation. A recent case-report already provided insightful results on large inter fraction variation and deformations that were observed during MRI-guided radiotherapy for a gastric cancer patient.…”

Section: Treatment Guidancementioning

confidence: 99%

Imaging strategies in the management of gastric cancer: current role and future potential of MRI

Borggreve

Goense

Brenkman

et al. 2019

The British Journal of Radiology

View full text Add to dashboard Cite

Gastric cancer is the fifth most common malignancy in the world, with nearly one million new cases of gastric cancer diagnosed every year. 1 Curative treatment of gastric adenocarcinoma consists of partial or total resection of the stomach combined with lymphadenectomy. 2 Over the last years, multimodality treatment strategies such as neoadjuvant chemo(radio)therapy, perioperative chemotherapy and adjuvant chemotherapy have gained importance in the treatment of gastric cancer by improving the likelihood of a radical tumor resection, disease free survival and overall survival. 3-8 Unfortunately, the overall 5 year survival rate still remains poor (35-45%). 4,9 Accurate staging of gastric cancer allows for selection of the most appropriate therapy, minimizes unnecessary surgery and maximizes the likelihood of benefit from the selected treatment. After initial diagnosis by gastroscopy with tumor biopsy, diagnostic work-up can consist of endoscopic ultrasonography (EUS), computed tomography (CT) and 18 F-fluorodeoxyglucose positron emission tomography (18 F-FDG PET). However, these techniques all have their limitations. EUS is an invasive, highly operator-dependent technique and does not detect distant metastases. 10,11 CT exposes patients to ionizing radiation and has poor soft-tissue contrast. 18 F-FDG PET is impaired by the fact that not all gastric carcinomas are 18 F-FDG-avid (avidity ranging from 42-96%) and has a low spatial resolution. 12 Historically, the role of magnetic resonance imaging (MRI) in gastric cancer has been limited, since relatively long acquisition times and technical challenges of peristaltic motion and respiration artifacts resulted in poor imaging quality. 13,14 With the continuous technical improvements in MRI scanning, including fast imaging techniques, (respiratory) motion compensation techniques, use of anti peristaltic agents and the introduction of functional MRI

show abstract

Section: Treatment Guidancementioning

confidence: 99%

Imaging strategies in the management of gastric cancer: current role and future potential of MRI

Borggreve

Goense

Brenkman

et al. 2019

The British Journal of Radiology

View full text Add to dashboard Cite

show abstract

“…One potential concern regarding MR distortions is the effect it can have on dosimetric endpoints. Yan et al studied the impact of MRI distortions on the dose delivered to the target and organs at risk in 14 patients . Based on their simulation and using vendor‐corrected MR images, they found that MR distortions can lead to <4% of the target volume coverage loss and potential increased doses to organs at risk of 5–6 Gy.…”

Section: Discussionmentioning

confidence: 99%

“…Yan et al studied the impact of MRI distortions on the dose delivered to the target and organs at risk in 14 patients. 41 Based on their simulation and using vendor-corrected MR images, they found that MR distortions can lead to <4% of the target volume coverage loss and potential increased doses to organs at risk of 5-6 Gy. In another recent study, Adjeiwaah et al estimated <0.5% difference in the PTV dose in prostate cancer patients arising from residual system and patient induced susceptibility distortions.…”

Section: Discussionmentioning

confidence: 99%

Large field of view distortion assessment in a low‐field MR‐linac

Nejad-Davarani

Kim

et al. 2019

Medical Physics

View full text Add to dashboard Cite

Purpose MR‐guided radiation therapy (RT) offers unparalleled soft tissue contrast for localization and target tracking. However, MRI distortions may be detrimental to high precision RT. This work characterizes the gradient nonlinearity (GNL) and total distortions over the first year of clinical operation of a 0.35T MR‐linac. Methods For GNL characterization, an in‐house large field of view (FOV) phantom (60 × 42.5 × 55 cm3, >6000 spherical landmarks) was configured and scanned at four timepoints with forward/reverse read polarities (Gradient Echo sequence, FA/TR/TE = 28°/30 ms/6 ms). GNL was measured in Anterior‐Posterior (AP), Left‐Right (LR), and Superior‐Inferior (SI) frequency‐encoding directions based on deviation of the auto‐segmented landmark centroids between rigidly registered MR and CT images and assessed based on radial distance from magnet isocenter. Total distortion was assessed using a 30 × 30 cm2 grid phantom oriented along the cardinal axes over >1 year of operation. Results The scanner's spatial integrity within the first ~10 months was stable (maximum total distortion variation = 10/6/8%, maximum distortion = 1.41/0.99/1.56 mm in Axial/Coronal/Sagittal planes, respectively). GNL distortions measured during this time period <10 cm from isocenter were (−0.74, 0.45), (−0.67, 0.53), and (−0.86, 0.70) mm in AP/LR/SI directions. In the 10‐20 cm range, <1.5% of the distortions exceeded 2 mm in the AP and LR axes while <4% of the distortions exceeded 2 mm for SI. After major repairs and magnet re‐shim, detectable changes were observed in total and GNL distortions (20% reduction in AP and 36% increase in SI direction in the 20–25 cm range). Across all timepoints and axes, 38–53% of landmarks in the 20–25 cm range were displaced by >1 mm. Conclusions GNL distortions were negligible within a 10 cm radius from isocenter. However, in the periphery, non‐negligible distortions of up to ~7 mm were observed, which may necessitate GNL corrections for MR‐IGRT for treatment sites distant from magnet isocenter.

show abstract

“…In other words, the distortion correction can be applied to the 4D‐MRI before warping to a midP‐MRI, or to the midP‐MRI that results from warping the uncorrected 4D‐MRI, under the assumption that the anatomical warp field is not affected by the machine distortions. Yan et al . recently investigated the dosimetric impact of distortions on the Unity MR‐linac by applying a distortion model to the diagnostic CTs of 14 patients representing different anatomical sites.…”

Section: Discussionmentioning

confidence: 99%

Correcting geometric image distortions in slice‐based 4D‐MRI on the MR‐linac

et al. 2019

View full text Add to dashboard Cite

Purpose: The importance of four-dimensional-magnetic resonance imaging (4D-MRI) is increasing in guiding online plan adaptation in thoracic and abdominal radiotherapy. Many 4D-MRI sequences are based on multislice two-dimensional (2D) acquisitions which provide contrast flexibility. Intrinsic to MRI, however, are machine-and subject-related geometric image distortions. Full correction of slice-based 4D-MRIs acquired on the Unity MR-linac (Elekta AB, Stockholm, Sweden) is challenging, since through-plane corrections are currently not available for 2D sequences. In this study, we implement a full three-dimensional 3D correction and quantify the geometric and dosimetric effects of machine-related (residual) geometric image distortions. Methods: A commercial three-dimensional (3D) geometric QA phantom (Philips, Best, the Netherlands) was used to quantify the effect of gradient nonlinearity (GNL) and static-field inhomogeneity (B0I) on geometric accuracy. Additionally, the effectiveness of 2D (in-plane, machine-generic), 3D (machine-generic), and in-house developed 3D þ (machine-specific) corrections was investigated. Corrections were based on deformable vector fields derived from spherical harmonics coefficients. Three patients with oligometastases in the liver were scanned with axial 4D-MRIs on our MR-linac (total: 10 imaging sessions). For each patient, a step-and-shoot IMRT plan (3 9 20 Gy) was created based on the simulation mid-position (midP)-CT. The 4D-MRIs were then warped into a daily midP-MRI and geometrically corrected. Next, the treatment plan was adapted according to the position offset of the tumor between midP-CT and the 3D-corrected midP-MRIs. The midP-CT was also deformably registered to the daily midP-MRIs (different corrections applied) to quantify the dosimetric effects of (residual) geometric image distortions. Results: Using phantom data, median GNL distortions were 0.58 mm (no correction), 0.42-0.48 mm (2D), 0.34 mm (3D), and 0.34 mm (3D þ ), measured over a diameter of spherical volume (DSV) of 200 mm. Median B0I distortions were 0.09 mm for the same DSV. For DSVs up to 500 mm, through-plane corrections are necessary to keep the median residual GNL distortion below 1 mm. 3D and 3D þ corrections agreed within 0.15 mm. 2D-corrected images featured uncorrected through-plane distortions of up to 21.11 mm at a distance of 20-25 cm from the machine's isocenter. Based on the 4D-MRI patient scans, the average external body contour distortions were 3.1 mm (uncorrected) and 1.2 mm (2D-corrected), with maximum local distortions of 9.5 mm in the uncorrected images. No (residual) distortions were visible for the metastases, which were all located within 10 cm of the machine's isocenter. The interquartile range (IQR) of dose differences between planned and daily dose caused by variable patient setup, patient anatomy, and online plan adaptation was 1.37 Gy/Fx for the PTV D95%. When comparing dose on 3D-corrected with uncorrected (2D-corrected) images, the IQR was 0.61 (0.31) Gy/Fx. Conclusions: GNL is the ma...

show abstract

A methodology to investigate the impact of image distortions on the radiation dose when using magnetic resonance images for planning

Cited by 18 publications

References 26 publications

Imaging strategies in the management of gastric cancer: current role and future potential of MRI

Imaging strategies in the management of gastric cancer: current role and future potential of MRI

Large field of view distortion assessment in a low‐field MR‐linac

Correcting geometric image distortions in slice‐based 4D‐MRI on the MR‐linac

Contact Info

Product

Resources

About