Accelerating TOF-MRA: The impact of the combined use of compressed sensitivity encoding and spiral imaging.

To evaluate the image quality of the combined technique of compressed sensitivity encoding (CS) and spiral imaging in time-of-flight magnetic resonance angiography (TOF-MRA), which is approximately 2.5 times faster than conventional methods. Twenty volunteers underwent four TOF-MRA sequences: sensitivity encoding (SENSE) with acceleration factor of 4 (acquisition time: 4:55 min), CS with acceleration factor of 10.9, and spiral and CS-spiral (both 1:55 min). A quantitative image analysis (signal-to-noise ratio [SNR], contrast, and full width at half maximum [FWHM] edge criterion measurements) was performed on four TOF sequences. For qualitative image analysis, two board-certified radiologists evaluated the overall depiction of the proximal, intermediate, and distal branches in CS, spiral, and CS-spiral images using SENSE as a reference. The SNR of BA in spiral and CS-spiral imaging was significantly lower than that in SENSE (p = 0.009). The contrasts of ACA and BA in CS-spiral were significantly higher and those in spiral were significantly lower than those in SENSE (p < 0.001). The FWHM in the CS image was significantly higher than that of SENSE; however, no significant differences were observed between the spiral or CS-spiral and SENSE. In qualitative analysis, the depiction of proximal vascular branches was significantly impaired in spiral than in others and that of distal vascular branches was significantly impaired in CS than in others (p < 0.001). In TOF-MRA, which is approximately 2.5 times faster than conventional methods, the combined use of CS and spiral imaging demonstrated an improvement in image quality compared to either CS or spiral imaging alone. The image quality of Compressed SENSE and spiral imaging is particularly poor in the proximal and distal vascular branches, respectively at an extremely high acceleration factor; however, CS-spiral provided stable image quality in all regions as compared with the SENSE technique.

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Declaration of Competing Interest Takeshi Nakaura has received research support from Nemoto Kyorindo Co., Ltd. Toshinori Hirai has received research support from Canon Medical Systems. The department of diagnostic imaging analysis, to which Dr. Kidoh belongs, is an endowed chair supported by Philips Healthcare. Masami Yoneyama is an employee of Philips Healthcare, and he installed CS-Spiral to MRI as a research sequence. The Nemoto Kyorindo Co., Ltd., Philips Healthcare and Canon Medical Systems had no control over the interpretation or publication of this work. Takeshi Nakaura controlled the study data. We used a prototype sequence for this volunteer study. Masami Yoneyama is responsible for providing technical advice on parameter settings, and for creating the schema and description of CS-Spiral technique.