A 1‐minute full brain MR exam using a multicontrast EPI sequence

Skare, Stefan; Sprenger, Tim; Norbeck, Ola; Rydén, Henric; Blomberg, Lars G.; Avventi, Enrico; Engström, Mats

doi:10.1002/mrm.26974

Cited by 60 publications

(104 citation statements)

References 15 publications

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“…Dividing the data acquisition into multiple shots and/or employing parallel imaging to shorten the readout duration was shown to improve the image quality. This enabled very rapid clinical brain exams with multicontrast information to be available in just a few minutes of scan time …”

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confidence: 99%

“…This enabled very rapid clinical brain exams with multicontrast information to be available in just a few minutes of scan time. 16,17 The work in this contribution focuses on the Wave-CAIPIRINHA (Wave-CAIPI) 18 acquisition technique that synergistically combines and extends two controlled aliasing approaches, 2D-CAIPI and bunch phase encoding (BPE) 19 to achieve controlled aliasing in all three spatial directions (x, y, z). This allows Wave-CAIPI to take advantage of the full 3D coil sensitivity information of multichannel arrays, which was shown to enable an order of magnitude acceleration for both SMS and 3D imaging sequences 18,20,21 with negligible g-factor noise amplification using commercial 32-channel receiver coils at 3 T. As Wave-CAIPI traverses k-space in a line-by-line manner with constant velocity along the readout (k x ), it also does not exhibit undesirable image distortion/blurring artifacts from magnetic field strengths variations.…”

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confidence: 99%

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Highly‐accelerated volumetric brain examination using optimized wave‐CAIPI encoding

Polak

Cauley

Huang

et al. 2019

Magnetic Resonance Imaging

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Background Rapid volumetric imaging protocols could better utilize limited scanner resources. Purpose To develop and validate an optimized 6‐minute high‐resolution volumetric brain MRI examination using Wave‐CAIPI encoding. Study Type Prospective. Population/Subjects Ten healthy subjects and 20 patients with a variety of intracranial pathologies. Field Strength/Sequence At 3 T, MPRAGE, T2‐weighted SPACE, SPACE FLAIR, and SWI were acquired at 9‐fold acceleration using Wave‐CAIPI and for comparison at 2–4‐fold acceleration using conventional GRAPPA. Assessment Extensive simulations were performed to optimize the Wave‐CAIPI protocol and minimize both g‐factor noise amplification and potential T1/T2 blurring artifacts. Moreover, refinements in the autocalibrated reconstruction of Wave‐CAIPI were developed to ensure high‐quality reconstructions in the presence of gradient imperfections. In a randomized and blinded fashion, three neuroradiologists assessed the diagnostic quality of the optimized 6‐minute Wave‐CAIPI exam and compared it to the roughly 3× slower GRAPPA accelerated protocol using both an individual and head‐to‐head analysis. Statistical Test A noninferiority test was used to test whether the diagnostic quality of Wave‐CAIPI was noninferior to the GRAPPA acquisition, with a 15% noninferiority margin. Results Among all sequences, Wave‐CAIPI achieved negligible g‐factor noise amplification (gavg ≤ 1.04) and burring artifacts from T1/T2 relaxation. Improvements of our autocalibration approach for gradient imperfections enabled increased robustness to gradient mixing imperfections in tilted‐field of view (FOV) prescriptions as well as variations in gradient and analog‐to‐digital converter (ADC) sampling rates. In the clinical evaluation, Wave‐CAIPI achieved similar mean scores when compared with GRAPPA (MPRAGE: ØW = 4.03, ØG = 3.97; T2w SPACE: ØW = 4.00, ØG = 4.00; SPACE FLAIR: ØW = 3.97, ØG = 3.97; SWI: ØW = 3.93, ØG = 3.83) and was statistically noninferior (N = 30, P < 0.05 for all sequences). Data Conclusion The proposed volumetric brain exam retained comparable image quality when compared with the much longer conventional protocol. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:961–974.

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confidence: 99%

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confidence: 99%

Highly‐accelerated volumetric brain examination using optimized wave‐CAIPI encoding

Polak

Cauley

Huang

et al. 2019

Magnetic Resonance Imaging

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“…Enabling R inplane = 8‐ or 9‐fold acceleration in other pulse sequences could help create a multicontrast msEPI clinical protocol with high geometrical fidelity. This would minimize the distortion and blurring artifacts that hamper image quality and achievable resolution in the recently developed ssEPI protocols . Utilizing msEPI readout in multi‐inversion T 1 mapping and fluid‐attenuated inversion recovery acquisitions with SMS‐NEATR reconstruction could enable a rapid MR exam with similar table time as a computed tomography (CT) scan.…”

Section: Discussionmentioning

confidence: 99%

Highly accelerated multishot echo planar imaging through synergistic machine learning and joint reconstruction

Bilgic̦

Chatnuntawech

Manhard

et al. 2019

Magnetic Resonance in Med

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Purpose To introduce a combined machine learning (ML)‐ and physics‐based image reconstruction framework that enables navigator‐free, highly accelerated multishot echo planar imaging (msEPI) and demonstrate its application in high‐resolution structural and diffusion imaging. Methods Single‐shot EPI is an efficient encoding technique, but does not lend itself well to high‐resolution imaging because of severe distortion artifacts and blurring. Although msEPI can mitigate these artifacts, high‐quality msEPI has been elusive because of phase mismatch arising from shot‐to‐shot variations which preclude the combination of the multiple‐shot data into a single image. We utilize deep learning to obtain an interim image with minimal artifacts, which permits estimation of image phase variations attributed to shot‐to‐shot changes. These variations are then included in a joint virtual coil sensitivity encoding (JVC‐SENSE) reconstruction to utilize data from all shots and improve upon the ML solution. Results Our combined ML + physics approach enabled Rinplane × multiband (MB) = 8‐ × 2‐fold acceleration using 2 EPI shots for multiecho imaging, so that whole‐brain T2 and T2* parameter maps could be derived from an 8.3‐second acquisition at 1 × 1 × 3‐mm3 resolution. This has also allowed high‐resolution diffusion imaging with high geometrical fidelity using 5 shots at Rinplane × MB = 9‐ × 2‐fold acceleration. To make these possible, we extended the state‐of‐the‐art MUSSELS reconstruction technique to simultaneous multislice encoding and used it as an input to our ML network. Conclusion Combination of ML and JVC‐SENSE enabled navigator‐free msEPI at higher accelerations than previously possible while using fewer shots, with reduced vulnerability to poor generalizability and poor acceptance of end‐to‐end ML approaches.

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“…Moreover, while the effect of head motion was outside the scope of this study, it should be noted that EPIMix is motion‐insensitive because of the fast single‐shot technique. In addition, in‐plane retrospective motion correction is an integral part of the image reconstruction for EPIMix . Fast scans may allow for an increased use of MRI in preinterventional ischemic stroke imaging, since DWI, an important tool in stroke imaging, is an integrated component of the EPIMix sequence …”

Section: Discussionmentioning

confidence: 99%

“…One previous report has shown the feasibility in healthy individuals. 12 The aim of the present study was to evaluate if EPIMix can categorize a clinical scan as either abnormal (relevant symptom-causing lesion) or normal with comparable diagnostic performance as routine clinical MRI. Secondary aims were evaluation of disease categorization, assessment of image quality, artifacts, imaging time, and diagnostic confidence.…”

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confidence: 99%

Diagnostic performance of a new multicontrast one‐minute full brain exam (EPIMix) in neuroradiology: A prospective study

Delgado

Kits

Bystam

et al. 2019

Magnetic Resonance Imaging

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Background Clinical MRI protocols are time‐consuming; hence, new faster techniques are needed. One new fast multicontrast MRI technique, called echo planar image mix (EPIMix) (including contrasts T1‐FLAIR, T2‐weighted, diffusion‐weighted images [DWI], apparent diffusion coefficient [ADC], T2*‐weighted, and T2‐FLAIR images) needs to be tested. Purpose To assess if EPIMix has comparable diagnostic performance as routine clinical brain MRI. Study Type Prospective. Population A consecutive series of 103 patients' brain MRI (January 2018 to May 2018). Field Strength/Sequence 1.5 T or 3T. EPIMix and routine clinical protocol (clinical MRI included all or some of the contrasts T1‐FLAIR, T2‐weighted, DWI, T2*‐weighted, T2‐FLAIR, 3D‐FSE). Assessment Two neuroradiologists assessed EPIMix and clinical scans and categorized the images as abnormal or normal and described diagnosis, artifacts, diagnostic confidence image quality, and comparison of imaging time. Statistical Tests Pivot tables with diagnostic performance calculated by receiver operating characteristics (ROC) and the area under curve (AUC). Disease categorization and image quality measures were evaluated. The study protocol is published at http://clinicaltrials.gov NCT03338270. Results After exclusion of 21 patients, 82 patients had a routine clinical MRI with comparable contrasts to EPIMix and were evaluated. The diagnostic performance to categorize a full brain MRI investigation as abnormal or normal was comparable between EPIMix (AUC 0.99 (95% confidence interval [CI] 0.97–1.00) and 0.99 (95% CI 0.97–1.00)) and routine clinical MRI (n = 82). Sensitivity was 95% (95% CI 88–95) and 93% (95% CI 86–98), and specificity 100% (95% CI 97–100) and 100% (95% CI 90–100). Disease categorization was congruent between EPIMix and clinical routine MRI in 90% (reader 2) and 93% (reader 1). Image quality was generally rated lower for EPIMix (P < 0.001). Imaging time was 78 seconds for EPIMix and for the same contrasts 12 minutes 29 seconds for conventional 3T MRI. Data Conclusion EPIMix has comparable diagnostic performance (disease identification and categorization) for most patients investigated in clinical routine. Level of Evidence 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1824–1833.

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A 1‐minute full brain MR exam using a multicontrast EPI sequence

Cited by 60 publications

References 15 publications

Highly‐accelerated volumetric brain examination using optimized wave‐CAIPI encoding

Highly‐accelerated volumetric brain examination using optimized wave‐CAIPI encoding

Highly accelerated multishot echo planar imaging through synergistic machine learning and joint reconstruction

Diagnostic performance of a new multicontrast one‐minute full brain exam (EPIMix) in neuroradiology: A prospective study

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