Practical approaches to the evaluation of signal‐to‐noise ratio performance with parallel imaging: Application with cardiac imaging and a 32‐channel cardiac coil

Abstract

In this work, two practical methods for the measurement of signal-to-noise-ratio (SNR) performance in parallel imaging are described. Phantoms and human studies were performed with a 32-channel cardiac coil in the context of ultrafast cardiac CINE imaging at 1.5 T using steady-state free precession (SSFP) and TSENSE. SNR and g-factor phantom measurements using a "multiple acquisition" method were compared to measurements from a "difference method". Excellent agreement was seen between the two methods, and the g-factor shows qualitative agreement with theoretical predictions from the literature. Examples of high temporal (42.6 ms) and spatial (2.1 ؋ 2.1 ؋ 8 mm 3 ) resolution cardiac CINE SSFP images acquired from human volunteers using TSENSE are shown for acceleration factors up to 7. Image quality agrees qualitatively with phantom SNR measurements, suggesting an optimum acceleration of 4. With this acceleration, a cardiac function study consisting of 6 image planes (3 short-axis views, 3 long-axis views) was obtained in an 18-heartbeat breath-hold. Magn Reson Med 54:748 -754, 2005.

Free‐breathing high‐spatial‐resolution delayed contrast‐enhanced three‐dimensional viability MR imaging of the myocardium at 3.0T: A feasibility study

“…priate for 3D viability imaging, or a phase-sensitive imaging technique may improve the image contrast of the free-breathing 3D viability imaging, while the present technique delineated MI and linear hyperenhancing myocardium (10,11,13,21,22). This freebreathing 3D viability imaging did not have isovoxels most appropriate for multiplanar reconstruction, although we believe that the present reconstructed images were sufficient for the detection of hyperenhancing myocardium (23).…”

“…The free-breathing 3D viability MRI was lengthy in some patients, which might induce the larger movement of diaphragm and deterioration of navigator gating. Parallel imaging techniques may be useful for reducing the scan time of free-breathing 3D viability imaging (22,24). There were several limitations to this study.…”

Evaluation of a Gadolinium-Based Nanoparticle (AGuIX) for Contrast-Enhanced MRI of the Liver in a Rat Model of Hepatic Colorectal Cancer Metastases at 9.4 Tesla

“…Based on regionof-interest (ROI) analyses, the signal intensities of normal liver tissue, homogeneously hyperenhancing and hypoenhancing parts of the induced liver tumors and the erector spinae muscles were measured for all unenhanced and contrast-enhanced sequences with the ROIs being placed in identical anatomic positions for each particular time point. The standard deviation of corresponding ROIs placed on subtracted datasets served as the background noise levels [11]. Signal-to-noise ratios (SNR) for normal liver parenchyma, hyperenhancing and hypoenhancing parts of the liver metastases as well as of the erector spinae muscle were calculated as:…”

Development and initial evaluation of 7-T q-ball imaging of the human brain

“…Since there is a spatially nonuniform distribution of noise in parallel imaging, as applied to our HARDI acquisitions, the effective SNR of the diffusion-weighted images at each field strength and at each b value was calculated using the difference method of Reeder et al [28] from two separate 6-direction DWI acquisitions using identical experimental parameters.…”