Study of iterative Dixon water-fat separation with echo asymmetric and least-squares estimation for evaluation of intervertebral disc degeneration / 国际生物医学工程杂志

ABSTRACT

Objective To analyze quantitatively the multiple parameters of iterative Dixon water-fat separation with echo asymmetric and least-squares estimation (IDEAL) MR imaging sequence, in order to realize safe, noninvasive and accurate observation of intervertebral disc degeneration, and to predict early degeneration in time, improve image quality, and to realize precision medical treatment by providing personalized examinations and optimized imaging protocols.Methods A total of 40 volunteers, 23 males and 17 females, with 20-84 years of age (mean (53.4±16.5) years), were participated in our study to accept lumbar spine MRI examination, including sequences of OSAG T2 FSE, OSAG T1 FSE, OAX T2 FSE, OSAG T2 FSE FS and OSAG IDEAL T2.Lumbar intervertebral disc degeneration was evaluated by Pfirrmann classification.The water signal fraction (WSF) of each disc was measured and calculated accurately with IDEAL in phase and IDEAL out phase images.The differences between Pfirrmann grade and WSF were analyzed statistically.The signal-to-noise ratio (SNR) measurements were carried out on equal size region of interest (ROI) from the same levels of vertebral body (L3) and background zone of T2 FSE FS and T2 IDEAL water image mid-sagittal planes, respectively, and the average value of vertebral body signal strength and the standard deviation of background signal were measured.SNRs of the two sequences were calculated, and the image qualities were compared statistically.Results Of all 200 lumbar discs that measured using Pfirrmann classification, 39 discs were classified as Pfirrmann grade Ⅰ, 42 as grade Ⅱ, 27 as grade Ⅲ, 53 as grade Ⅳ, and 39 as grade Ⅴ.The SNR of T2 FSE FS images was (11.42±6.17) dB, while that of the IDEAL water images was (20.63±9.44) dB, and there was a statistically significant difference between them (P＜0.05).The WSF decreased along with the increase of Pfirrmann grade.The significant differences of WSF were found in all grades (P＜0.05) except for the grade Ⅳ and Ⅴ (P＞0.05).Conclusions The SNR of the IDEAL water images is significantly higher than that of T2 FSE FS images, which bring about better image quality.The WSF calculated based on the IDEAL in phase and IDEAL out phase images will make possible the quantitative, noninvasive and accurate analysis of lumbar disc degeneration, especially on the early stage of disc degeneration.