MR arthrography of the shoulder: comparison of low-field (0.2 T) vs high-field (1.5 T) imaging

The objective of this study was to compare the image quality sensitivity, s pecificity, and diagnostic accuracy of an open low-field MR system (0.2 T) with a standard high-field MR system (1.5 T) after arthrography of the shou lder. Thirty-eight patients either with suspected chronic instability (n = 12) or rotator cuff abnormalities (n = 26) were examined. Intra-articular i njection of diluted Gd-DTPA was followed in randomized order either first b y imaging on an open 0.2-T system or on a 1.5-T system. The image material was evaluated independently by two radiologists in a blinded fashion with r espect to overall image quality and the detection of rotator cuff as well a s capsular and labral abnormalities. Surgical correlation was available in 27 (71%) of 38 patients. For both systems, sensitivity and specificity for rotator cuff tears were 100 % each, and for labrum pathologies, these value s were 100 and 93 %, respectively. The agreement for detection of labral pa thologies between low-field and high-field examinations was good (x = 0.69, x = 0.61). For the detection of full-thickness tears of the rotator cuff, the agreement between the low-field and high-field MR examinations was very good and significant (x = 0.93, x = 1, p < 0.001). Overall image quality w as rated good in 17 (45 %) and fair in 21 (55 %) of 38 cases on the 0.2-T M R system, and good in 32 (84 %) and fair in 6 (16 %) of 38 cases on the 1.5 -T system. Motion artifacts were considered low in 24 (63 %) and moderate i n 14 (37 %) of 38 cases for the 0.2-T system and low in 34 (89 %) and moder ate in 4 (11 %) for 1.5-T system. Based on our results, low-field MR compar es favorably to high-field MR in the detection of major abnormalities of th e glenohumeral joint, at least when MR arthrography is used. Disadvantages are the duration of the examination and thus the risk of reduced image qual ity caused by motion artifacts.