ABSTRACT
This study investigated the image quality using controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) to shorten the imaging time in dynamic abdominal examinations. Comparisons with the conventional generalized autocalibrating partially parallel acquisitions (GRAPPA) method were made by changing the sampling shift in CAIPIRINHA using a 3.0 T MRI. The measurements included the visual evaluation of five stages, the signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in phantom experiments. The visual evaluation (five stages) and SNR were determined using a nickel sulfate bottle phantom attached to the MRI device. Each evaluation was performed on the middle slice of the 3D image. The SNR was compared with the mean region of interest value calculated from five locations within the phantom. The CNR was determined using custommade phantoms that mimic the T1 and T2 values of the liver and spleen. In the results, at reduction factor (Rf) = 6 and 8, the SNR per unit imaging time was reduced with GRAPPA, while there was no decrease in SNR and CNR with CAIPIRINHA. By performing imaging using an appropriate sampling shift, it is possible to acquire an equivalent GRAPPA in a short period of time using CAIPIRINHA.
Subject(s)
Abdomen/diagnostic imaging , Imaging, Three-Dimensional , Magnetic Resonance Imaging , Artifacts , Humans , Phantoms, ImagingABSTRACT
The purpose of this study was to optimize scan parameters for evaluation of carotid plaque characteristics by k-space trajectory (radial scan method), using a custom-made carotid plaque phantom. The phantom was composed of simulated sternocleidomastoid muscle and four types of carotid plaque. The effect of chemical shift artifact was compared using T1 weighted images (T1WI) of the phantom obtained with and without fat suppression, and using two types of k-space trajectory (the radial scan method and the Cartesian method). The ratio of signal intensity of simulated sternocleidomastoid muscle to the signal intensity of hematoma, blood (including heparin), lard, and mayonnaise was compared among various repetition times (TR) using T1WI and T2 weighted imaging (T2WI). In terms of chemical shift artifacts, image quality was improved using fat suppression for both the radial scan and Cartesian methods. In terms of signal ratio, the highest values were obtained for the radial scan method with TR of 500 ms for T1WI, and TR of 3000 ms for T2WI. For evaluation of carotid plaque characteristics using the radial scan method, chemical shift artifacts were reduced with fat suppression. Signal ratio was improved by optimizing the TR settings for T1WI and T2WI. These results suggest the potential for using magnetic resonance imaging for detailed evaluation of carotid plaque.
