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Evaluation of a Workflow to Define Low Specific Absorption Rate MRI Protocols for Patients With Active Implantable Medical Devices
Author(s) -
Martinez Jessica A.,
Moulin Kévin,
Yoo Bryan,
Shi Yu,
Kim Hyun J.,
Villablanca Pablo J.,
Ennis Daniel B.
Publication year - 2020
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.27044
Subject(s) - specific absorption rate , imaging phantom , workflow , quality assurance , image quality , medicine , population , computer science , nuclear medicine , medical physics , radiology , image (mathematics) , artificial intelligence , pathology , external quality assessment , telecommunications , environmental health , database , antenna (radio)
Background MRI exams for patients with MR‐conditional active implantable medical devices (AIMDs) are contraindicated unless specific conditions are met. This limits the maximum specific absorption rate (SAR, W/kg). Currently, there is no general framework to guide meeting a lower SAR limit. Purpose To design and evaluate a workflow for modifying MRI protocols to whole‐body SAR (WB‐SAR ≤0.1 W/kg) and local‐head SAR (LH‐SAR ≤0.3 W/kg) limits while mitigating the impact on image quality and exam time. Study Type Prospective. Population Twenty healthy volunteers on head ( n = 5), C‐spine ( n = 5), T‐spine ( n = 5), and L‐spine ( n = 5) with IRB consent. Assessment Vendor‐provided head, C‐spine, T‐spine, and L‐spine protocols (SAR RT ) were modified to meet both low SAR targets (SAR LOW ) using the proposed workflow. in vitro SNR and CNR were evaluated with a T 1 ‐T 2 phantom. in vivo image quality and clinical acceptability were scored using a 5‐point Likert scale for two blinded readers. Field Strength/Sequences 1.5T/spin‐echoes, gradient‐echoes. Statistical Analysis In vitro SNR and CNR values were evaluated with a repeated measures general linear model. in vivo image quality and clinical acceptability were evaluated using a generalized estimating equation analysis (GEE). The two reader's level of agreement was analyzed using Cohen's kappa statistical analysis. Results Using the workflow, SAR limits were met. LH‐SAR: 0.12 ± 0.02 W/kg, median (SD) values for LH‐SAR were 0.12 (0.02) W/kg and WB‐SAR: 0.09 (0.01) W/kg. Examination time did not increase ≤2x the initial time. SAR RT SNR values were higher and significantly different than SAR LOW ( P < 0.05). However, no significant difference was observed between the CNR values (value = 0.21). Median (IQR) CNR values were 14.2 (25.0) vs. 15.1 (9.2) for head, 12.1 (16.9) vs. 25.3 (14.2) for C‐spine, 81.6 (70.1) vs. 71.0 (26.6) for T‐spine, and 51.4 (52.6) vs. 37.7 (27.3) for L‐spine. Image quality scores were not significantly different between SAR RT and SAR LOW (median [SD] scores were 4.0 [0.01] vs. 4.3 [0.2], P > 0.05). Data Conclusion The proposed workflow provides guidance for modifying routine MRI exams to achieve low SAR limits. This can benefit patients referred for an MRI exam with low SAR MR‐conditional AIMDs. Level of Evidence: 1 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2020;52:91–102.