To enhance the versatility of the short-tau inversion-recovery (STIR) sequences, the authors determined a range of repetition time (TR) and inversion time (TI) combinations that suppress signal intensity from fat by study of both patient and phantom images. To make fast STIR images, variations in the following pulsing conditions were studied with use of an interactive computer program: decreasing the TR, limiting the number of excitations, and limiting the number of phase-encoding steps. The authors found that (a) STIR imaging need not be time consuming, (b) fat suppression can be accomplished at shorter TR by using shorter TI, and (c) short-TR fast STIR imaging is sensitive to enhancement with gadopentetate dimeglumine.

An ischemic clamp model of exercise was used to evaluate the potential role of blood flow in mediating changes in the magnetic resonance imaging appearance of skeletal muscle. Proton relaxation times of muscle were serially estimated in 10 healthy subjects (a) before exercise, (b) after exercise in the presence of vascular occlusion (VO1), (c) during vascular reocclusion after 1 minute of reperfusion (VO2), and (d) after reinstitution of continuous flow. T1 and T2 of active muscles were increased during VO1. During VO2, there were additional increases in relaxation times of active muscles. Reinstitution of continuous flow was associated with a continuous decrease in the T2 of exercised muscle. Hence, blood flow was not required for increases in T1 and T2 with exercise. Additional relaxation time increases occurred after a brief period of reperfusion; however, continuous flow was associated with a decrease in T2.

The purpose of this study was to evaluate the clinical utility of specialized coils with magnetic resonance (MR) imaging and to determine the potential improvement in the signal-to-noise ratio (SNR) provided by the various coils. A total of 48 patients were studied-33 with surface coils and 15 with limb coils. MR imaging was performed with a superconducting magnet operating at 0.35 T. Two applications of surface coils were evaluated; one used for both transmitting and receiving and the other used only for receiving. Structures studied with the surface coils included the orbit, carotid artery, cervical and lumbar spine, parotid and thyroid glands, other neck structures, femoral artery, kidney, prostate, hip, and heart. The regions studied with the limb coil were the ankle, knee, wrist, elbow and popliteal artery. We calculated the SNR, and the results demonstrated a marked improvement with the specialized coils: a twofold increase for the 10-cm surface coil versus the head coil and a 4.6-fold increase compared with the body coil, a 2.3-fold increase for the 20-cm surface coil compared with the body coil, and 2.8- and 6.4-fold increases for the limb coil versus the head coil and the body coil, respectively. The use of specialized coils was feasible in the clinical setting and they provided a marked improvement in the image SNR, which facilitated the imaging of small and superficial structures.

Given a suitable trigger signal, cardiac synchronized magnetic resonance (MR) imaging is simple to implement; however, single section techniques are not efficacious, especially when the heart rate sets the repetition interval. We demonstrate multi-section, double, and single-echo imaging, any of which rapidly covers the cardiac volume; 3-D modes capable of achieving very thin sections; and cycled multi-section imaging capable of efficaciously providing dynamic data on heart motion. These modes form a complementary, powerful set of options for clinical work.

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