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Dosimetric Impact of MRI Distortions: A Study on Head and Neck Cancers
Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.ORCID-id: 0000-0003-3217-3208
Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
Vise andre og tillknytning
2019 (engelsk)Inngår i: International Journal of Radiation Oncology, Biology, Physics, ISSN 0360-3016, E-ISSN 1879-355X, Vol. 103, nr 4, s. 994-1003Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Purpose: To evaluate the effect of magnetic resonance (MR) imaging (MRI) geometric distortions on head and neck radiation therapy treatment planning (RTP) for an MRI-only RTP. We also assessed the potential benefits of patient-specific shimming to reduce the magnitude of MR distortions for a 3-T scanner.

Methods and Materials: Using an in-house Matlab algorithm, shimming within entire imaging volumes and user-defined regions of interest were simulated. We deformed 21 patient computed tomography (CT) images with MR distortion fields (gradient nonlinearity and patient-induced susceptibility effects) to create distorted CT (dCT) images using bandwidths of 122 and 488 Hz/mm at 3 T. Field parameters from volumetric modulated arc therapy plans initially optimized on dCT data sets were transferred to CT data to compute a new plan. Both plans were compared to determine the impact of distortions on dose distributions.

Results: Shimming across entire patient volumes decreased the percentage of voxels with distortions of more than 2 mm from 15.4% to 2.0%. Using the user-defined region of interest (ROI) shimming strategy, (here the Planning target volume (PTV) was the chosen ROI volume) led to increased geometric for volumes outside the PTV, as such voxels within the spinal cord with geometric shifts above 2 mm increased from 11.5% to 32.3%. The worst phantom-measured residual system distortions after 3-dimensional gradient nonlinearity correction within a radial distance of 200 mm from the isocenter was 2.17 mm. For all patients, voxels with distortion shifts of more than 2 mm resulting from patient-induced susceptibility effects were 15.4% and 0.0% using bandwidths of 122 Hz/mm and 488 Hz/mm at 3 T. Dose differences between dCT and CT treatment plans in D-50 at the planning target volume were 0.4% +/- 0.6% and 0.3% +/- 0.5% at 122 and 488 Hz/mm, respectively.

Conclusions: The overall effect of MRI geometric distortions on data used for RTP was minimal. Shimming over entire imaging volumes decreased distortions, but user-defined subvolume shimming introduced significant errors in nearby organs and should probably be avoided.

sted, utgiver, år, opplag, sider
Elsevier, 2019. Vol. 103, nr 4, s. 994-1003
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Identifikatorer
URN: urn:nbn:se:umu:diva-157192DOI: 10.1016/j.ijrobp.2018.11.037ISI: 000459153600031PubMedID: 30496879OAI: oai:DiVA.org:umu-157192DiVA, id: diva2:1304925
Tilgjengelig fra: 2019-04-15 Laget: 2019-04-15 Sist oppdatert: 2019-04-15bibliografisk kontrollert

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Adjeiwaah, MaryBylund, MikaelLundman, Josef A.Söderström, KarinZackrisson, BjörnJonsson, Joakim H.Garpebring, AndersNyholm, Tufve

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