EXTENDED FIELD OF VIEW IMAGING

This technique is helpful in situations in which the anatomy in question extends beyond the maximum field of view, (FOV), allowed by the MR scanner.This maximum has historically been approximately 45 cm or less. One example necessitating a larger FOV is in angiographic peripheral runoff imaging.For this situation an MR contrast agent is injected intravenously and the vasculature is imaged upon the passage of that contrast agent.

Figure 1.

Figure 1 shows a comparison of the present "multi-station" technique with the new continuously moving table technique developed at the MR Research Lab.In the case of the former, three static stations are imaged separately and the table is moved one FOV between scans.This technique can be inefficient because significant time is required to move to the next FOV and set up steady state conditions.On the right, the continuously moving table technique acquires the same total FOV in one smooth motion, nominally moving from torso to feet along with the contrast bolus.

Figure 2.

Figure 2 shows an example of a runoff study acquired with the moving table method.Arterial vasculature is readily seen from the aorta to the vessels of the calf.The runoff acquisition can also be viewed in real-time as each anatomical section is acquired.

Figure 4.

Figure 3.

Figure 3 is a movie clip of what the MR operator sees as the acquisition proceeds from chest to feet. Click on the image to activate the video (1.6 Mb.)

Figure 4 shows a whole-body spin-echo image.This image has a total superior/inferior dimension of over 175 cm or a factor of four greater than the largest typical MR image previously allowed.Whole body imaging may prove helpful in screening for cancer metastatic disease.This technique might be especially useful when used with a contrast agent which is targeted to a specific cancer.