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MRI of the foetal brain using a rapid 3D steady-state sequence.

ABSTRACT: OBJECTIVE: To evaluate the capacity of a rapid T2 weighted three-dimensional (3D) sequence to diagnose foetal brain abnormalities by comparing the results with current two-dimensional (2D) methods. We have also made assessments of the estimates of energy deposition using those methods. METHODS: 50 pregnant females were included in this study under the guidance of the institutional review board. All their foetuses had suspected brain abnormalities on antenatal ultrasonography or were at increased risk of a brain malformation based on the results of an earlier pregnancy. All the foetuses had a routine MR protocol that includes three orthogonal plane single-shot fast-spin echoes and 2D steady-state sequences. In addition, a 3D rapid steady-state sequence of the foetal brain was performed (acquisition time approximately 40 s), and the standard and 3D sequences were reported independently and the results were compared. The specific absorption rate (SAR) predicted by the scanner was recorded in 12 cases in order to estimate the energy deposited by the three sequences. RESULTS: The 3D rapid steady-state sequences produced diagnostic-quality images in 41/50 (82%) cases. All the failures were in second trimester foetuses (9/26-35% failure rate). There was a discrepancy between the standard report and findings using the 3D sequence in 2/41 of the foetuses with good-quality 3D imaging. The predicted SAR deposition of the 3D steady-state sequences was comparable with the single-shot fast-spin echo sequence. CONCLUSION: Our initial assessments of a 3D rapid steady-state sequence to image the foetus are encouraging in terms of diagnostic information and acceptable energy deposition values. The high failure rate in second trimester foetuses probably relates to the greater mobility of the smaller foetuses, and improvements in the 3D sequence are required in terms of reduced acquisition time and higher resolution. ADVANCES IN KNOWLEDGE: We have shown that 3D T2 weighted images of the foetal brain can be acquired in a clinical setting and produce diagnostic-quality imaging in a high proportion of cases. The success rate in acquiring diagnostic-quality images is related to gestational age. Good-quality images were obtained in all third trimester foetuses but only in approximately two-thirds of second trimester foetuses. This probably reflects the problem of the greater mobility of second trimester foetuses. 3D T2 weighted acquisitions have great potential for improving the antenatal diagnosis of foetal brain abnormalities and may reduce the time that a pregnant female needs to spend on the MR scanner.

SUBMITTER: Griffiths PD

PROVIDER: S-EPMC3798328 | biostudies-other | 2013 Oct

REPOSITORIES: biostudies-other

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Project description:BackgroundCardiovascular magnetic resonance (CMR) cine imaging is still limited by long acquisition times. This study evaluated the clinical utility of an accelerated two-dimensional (2D) cine sequence with deep learning reconstruction (Sonic DL) to decrease acquisition time without compromising quantitative volumetry or image quality.MethodsA sub-study using 16 participants was performed using Sonic DL at two different acceleration factors (8× and 12×). Quantitative left-ventricular volumetry, function, and mass measurements were compared between the two acceleration factors against a standard cine method. Following this sub-study, 108 participants were prospectively recruited and imaged using a standard cine method and the Sonic DL method with the acceleration factor that more closely matched the reference method. Two experienced clinical readers rated images based on their diagnostic utility and performed all image contouring. Quantitative contrast difference and endocardial border sharpness were also assessed. Left- and right-ventricular volumetry, left-ventricular mass, and myocardial strain measurements were compared between cine methods using Bland-Altman plots, Pearson's correlation, and paired t-tests. Comparative analysis of image quality was measured using Wilcoxon-signed-rank tests and visualized using bar graphs.ResultsSonic DL at an acceleration factor of 8 more closely matched the reference cine method. There were no significant differences found across left ventricular volumetry, function, or mass measurements. In contrast, an acceleration factor of 12 resulted in a 6% (5.51/90.16) reduction of measured ejection fraction when compared to the standard cine method and a 4% (4.32/88.98) reduction of measured ejection fraction when compared to Sonic DL at an acceleration factor of 8. Thus, Sonic DL at an acceleration factor of 8 was chosen for downstream analysis. In the larger cohort, this accelerated cine sequence was successfully performed in all participants and significantly reduced the acquisition time of cine images compared to the standard 2D method (reduction of 37% (5.98/16) p < 0.0001). Diagnostic image quality ratings and quantitative image quality evaluations were statistically not different between the two methods (p > 0.05). Left- and right-ventricular volumetry and circumferential and radial strain were also similar between methods (p > 0.05) but left-ventricular mass and longitudinal strain were over-estimated using the proposed accelerated cine method (mass over-estimated by 3.36 g/m2, p < 0.0001; longitudinal strain over-estimated by 1.97%, p = 0.001).ConclusionThis study found that an accelerated 2D cine method with DL reconstruction at an acceleration factor of 8 can reduce CMR cine acquisition time by 37% (5.98/16) without significantly affecting volumetry or image quality. Given the increase of scan time efficiency, this undersampled acquisition method using deep learning reconstruction should be considered for routine clinical CMR.

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MRI of the foetal brain using a rapid 3D steady-state sequence.

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