Figure 9

Median nerve contrast study by solenoid coil high resolution, high field MRI. All images are from a single image slice of rabbit upper arm. Image (a) is collected with a STIR (short tau inversion recovery) sequence which suppresses signal from fat - it reduces the marrow signal (6), and also identifies structure (1) as the median nerve[44], structure (7) as the ulnar nerve, structure (8) as the flow void of he brachial artery and structure 9 as the flow void of the basilic vein. Images (b) & (c)are colorized spin echo studies obtained at 90 minutes and 360 minutes after injection, respectively. Note that the marrow (3) appears shifted out the humerus (partially overlapped dark circle) by chemical shift effects. The shift at 4.7 Tesla is 1.85 millimeters. Similar shifts are seen at (4), and serve at (5) to leave two bright structures in a gap between triceps and biceps. (a-m), (b-m), (c-m) are magnified views of the space between the biceps and triceps on the medial aspect of the upper arm. Structure (2) is a small amount of fatty tissue that is actually located on the inferior left surface of the brachial artery, but chemical shift has placed its fat image into the midst of the basilic vein. Structure (2) disappears in the STIR image due to fat suppression. Based on this identification, the median nerve (1/1a) is compared to the non-neural structure (2/2a) and is seen to lose intensity in the four and half hour interval between images (b) and (c) reflecting transport of the WGA-magnetite contrast agent injected in the forearm flexor muscles [24]. The image conspicuity of this structure was measured by multiplying its volume times the intensity in grayscale and this reveals a decrease of 52% in the 270 minute interval. Scale bars are 6 mm for (a), (b), and (c) and 3 mm for (am), (bm) and (cm).