Through-time 3D radial GRAPPA for whole heart cardiac imaging

Summary Through-Time 3D Radial GRAPPA can be used to reconstruct 3D CINE images covering the whole heart in a single breathhold. Background Through-Time Non-Cartesian GRAPPA has been previously demonstrated for real-time 2D cardiac imaging (Seiberlich, et al. Magn Reson Med. 2011 Feb;65(2):492-505.). This parallel imaging method works by acquiring several fully-sampled non-Cartesian datasets with a low temporal resolution, and using the coil sensitivity information from these datasets to reconstruct highly undersampled non-Cartesian data acquired in real-time. By modifying this through-time non-Cartesian GRAPPA method to reconstruct highly undersampled 3D data, whole heart 3D CINE images can be generated using data acquired in a single breathhold. Methods A total of 20 fully-sampled 3D stack-of-stars radial datasets were acquired during free-breathing with no EKG gating using a 1.5T Siemens Espree and the following parameters: bSSFP sequence, TE=1.52ms, TR=3.04ms, matrix size = 128x128x20, projections/partition=128, FOV=300x300x90mm3, Flip Angle=45°, 5/8 Partial Fourier, 18 receiver channels. Segmented undersampled data (using only 16 projections/partition, an acceleration factor of R=8) were acquired with EKG gating and the above parameters during a breathhold for 15 heartbeats, resulting in 15 CINE frames. In order to perform the calibration, each of the time frames and partitions were employed as separate sources of calibration information; thus, a total of 300 repetitions could be used to generate the through-time GRAPPA weight sets. After reconstruction, the undersampled data yielded fully-sampled 3D CINE images, each with a temporal footprint of 48ms, an in-plane resolution of 2.3mm2, and a through-plane resolution of 6mm. The total acquisition time was 116s for the calibration and approximately 15 s for the breathhold CINE acquisition. Results Example images from diastole and systole of one healthy volunteer are shown in Figures 1 and 2. It is important to note that these represent just two of the 15 CINE frames acquired in this dataset. Despite the high acceleration factor (R=8 in comparison to the fully-sampled calibration data), the images demonstrate only minor residual aliasing artifacts. Because a 3D dataset is acquired, the images from each partition can be shown in the same cardiac phase, which is challenging when using multiple breathholds to acquire several 2D CINE slices

Subacute Tension Hemopneumothorax with Novel Electrocardiogram Findings

This case report describes a patient with a subacute right-sided tension hemopneumothorax following an occult stab. The patient’s electrocardiogram (ECG), performed as part of a standardized triage process, demonstrated significant abnormalities that misguided initial resuscitation, but resolved following evacuation of the tension hemopneumothorax. Tension pneumothorax is typically regarded as an immediately life-threatening condition that requires emergent management with needle or tube thoracostomy. However, we believe that subacute tension pneumothorax may be a rarely observed clinical phenomenon and may lead to unique ECG findings. We believe that the ECG changes we observed provided an early clue to the eventual diagnosis of a subacute tension pneumothorax and have not been previously described in this setting.

Cardiac cine magnetic resonance fingerprinting for combined ejection fraction, T1 and T2 quantification

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156191/2/nbm4323_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156191/1/nbm4323.pd

Evaluation of left ventricular ejection fraction using through-time radial GRAPPA

BACKGROUND: The determination of left ventricular ejection fraction using cardiovascular magnetic resonance (CMR) requires a steady cardiac rhythm for electrocardiogram (ECG) gating and multiple breathholds to minimize respiratory motion artifacts, which often leads to scan times of several minutes. The need for gating and breathholding can be eliminated by employing real-time CMR methods such as through-time radial GRAPPA. The aim of this study is to compare left ventricular cardiac functional parameters obtained using current gold-standard breathhold ECG-gated functional scans with non-gated free-breathing real-time imaging using radial GRAPPA, and to determine whether scan time or the occurrence of artifacts are reduced when using this real-time approach. METHODS: 63 patients were scanned on a 1.5T CMR scanner using both the standard cardiac functional examination with gating and breathholding and the real-time method. Total scan durations were noted. Through-time radial GRAPPA was employed to reconstruct images from the highly accelerated real-time data. The blood volume in the left ventricle was assessed to determine the end systolic volume (ESV), end diastolic volume (EDV), and ejection fraction (EF) for both methods, and images were rated for the presence of artifacts and quality of specific image features by two cardiac readers. Linear regression analysis, Bland-Altman plots and two-sided t-tests were performed to compare the quantitative parameters. A two-sample t-test was performed to compare the scan durations, and a two-sample test of proportion was used to analyze the presence of artifacts. For the reviewers´ ratings the Wilcoxon test for the equality of the scores’ distributions was employed. RESULTS: The differences in EF, EDV, and ESV between the gold-standard and real-time methods were not statistically significant (p-values of 0.77, 0.82, and 0.97, respectively). Additionally, the scan time was significantly shorter for the real-time data collection (p<0.001) and fewer artifacts were reported in the real-time images (p<0.01). In the qualitative image analysis, reviewers marginally preferred the standard images although some features including cardiac motion were equivalently rated. CONCLUSION: Real-time functional CMR with through-time radial GRAPPA performed without ECG-gating under free-breathing can be considered as an alternative to gold-standard breathhold cine imaging for the evaluation of ejection fraction in patients

Assessing infant cognition in field settings using eye-tracking: A pilot cohort trial in Sierra Leone

OBJECTIVES: To investigate the feasibility of eye-tracking-based testing of the speed of visual orienting in malnourished young children at rural clinics in Sierra Leone. DESIGN: Prospective dual cohort study nested in a cluster-randomised trial. SETTING: 8 sites participating in a cluster-randomised trial of supplementary feeding for moderate acute malnutrition (MAM). PARTICIPANTS: For the MAM cohort, all infants aged 7-11 months at the eight sites were enrolled, 138 altogether. For controls, a convenience sample of all non-malnourished infants aged 7-11 months at the same sites were eligible, 60 altogether. A sample of 30 adults at the sites also underwent eye-tracking tests as a further control. INTERVENTIONS: Infants with MAM were provided with supplementary feeding. OUTCOME MEASURES: The primary outcomes were feasibility and reliability of eye-tracking-based testing of saccadic reaction time (SRT). Feasibility was assessed by the percent of successful tests in the infants. Reliability was measured with intraclass correlation coefficients (ICCs). Secondary outcomes were mean SRT based on nutritional state as well as and changes in mean SRT after supplementary feeding of MAM children. RESULTS: Infants exhibited consistent orienting to targets on a computer screen (\u3e95% of valid trials). Mean SRTs had moderate stability within visits (ICCs 0.60-0.69) and across the 4-week test-retest interval (0.53) in infants; the adult control group had greater SRT stability (within visit ICC=0.92). MAM infants had a trend toward higher adjusted SRT at baseline (difference=12.4 ms, 95% CI -2 to 26.9, p=0.09) and improvement in SRT 4 weeks thereafter (difference=-14 ms, 95% CI -26.2 to -1.7, p=0.025) compared with age-matched controls. CONCLUSIONS: The results demonstrate the feasibility of eye-tracking-based testing in a resource-poor field setting and suggest eye-tracking measures have utility in the detection of group level effects of supplementary feeding

Magnetic resonance fingerprinting review part 2: Technique and directions

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154317/1/jmri26877.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154317/2/jmri26877_am.pd