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The purpose of this study was to evaluate 1/T1rho in relation to 1/T1 and 1/T2 in characterizing normal and diseased muscle. We measured the muscle relaxation rates 1/T1 and 1/T2 at 0.1 T and 1/T1rho at on-resonance locking fields B1 between 10 and 160 microT in myositis patients and normal volunteers. 1/T2 and 1/T1rho of muscle were lower in the patients than in the volunteers, whereas there was no difference in the 1/T1 values. The lower relaxation rates 1/T2 and 1/T1rho in the diseased muscle may be due to fat and connective tissue infiltrations and edema. 1/T1rho contrast between muscle and subcutaneous fat was higher than 1/T2 and 1/T1 contrast. This may be explained by the different B1 dispersion behavior of these two tissue types. 1/T1rho of fat is B1 field independent, whereas 1/T1rho of muscle decreases clearly with increasing B1 field. In conclusion, 1/T1rho provides a useful tool in manipulating contrast in magnetic resonance imaging of diseased muscle.

Rationale and Objectives. Tendon xanthomas are atherosclerotic plaquelike collections of lipids that develop with age in the Achilles tendons of patients having familial hypercholesterolemia (FH). We tested a fat—water discrimination technique for imaging Achilles tendon xanthomatosis. Methods. We used the spin-warp imaging technique optimized for low-field magnetic resonance (MR) imaging to obtain separate fat and water images of the Achilles tendon. Seven patients with FII, two patients with normal tendons, and three patients with other tendon pathology were studied. Results. Normal tendons showed an intensity near or equal to that of the noisy background in all images. Compared with the background, the intensity of the FH tendons was approximately fivefold greater in magnitude images, fourfold in fat images, and 10-fold in water images. Conclusion. The method sensitively detected even subtle xanthomatosis in young patients, but differentiation of xanthomas from other pathologic lesions was possible with this method only when the tendons were significantly thickened.

Preoperative and postoperative magnetic resonance imaging (MRI) of the lumbar spine was performed on 41 patients treated either microsurgically or with percutaneous nucleotomy for lumbar disc herniation. On the first postoperative day, MRI revealed an edematous mass effect at the level of surgery in 25 (61%) patients. The mass effect caused compression of the anterior dural sac mimicking preoperative disc herniation. After the follow-up of 6 months, the mass effect had disappeared in all patients, and the MRI finding in the operated disc space was that of a prolapse in six (15%) patients and that of a protrusion in 16 (39%) patients. Postoperative scarring was detected in 23 (56%) patients. The amount of the epidural scar tissue was significantly (p = 0.0002) associated with the extent of the early postoperative hemorrhagic changes detected in these patients with MRI. No association was observed between these MRI findings (mass effect, disc herniation, epidural scarring) and the clinical outcome of the patients.

We evaluated the incidence of postoperative extradural hematomas by means of magnetic resonance imaging (MRI) technique in 44 patients who underwent successful surgery for a virgin lumbar disc herniation. Of these patients, 28 were treated with microdiscectomy and 16 with percutaneous nucleotomy. Postoperative hematoma proved to be a universal MRI finding in the microsurgically treated patients: hematomas were found in all patients in the microdiscectomy group. In 12 (43%) patients the hematoma extended into the dural sack. The incidence of hematomas was significantly (p = 0.001) lower in the patients treated with percutaneous nucleotomy: hematomas were detected in only 10 (63%) of the 16 patients in the nucleotomy group. The hematomas in these patients were also smaller in size and none of them connected with the dural sac. Correlation between the hematomas and clinical findings showed that the presence of a hematoma had no obvious effect on the immediate postoperative recovery of a patient.

A method for windowing specific T1 values is presented. A 1.0 T imager with two routine pulse sequences was employed: A T1-weighted spin echo (SE) sequence and a short tau inversion recovery STIR sequence (fat-suppressed IR). A T1 window for fat was obtained by subtracting the STIR image from the SE image. Negative values were coded black. The method was tested on a normal human thigh, on a human liver with confirmed fatty infiltration, and on the livers of four live burbots. The fat-containing tissues of the two human volunteers were well depicted. The differences in fat concentration among the burbot livers were also clearly shown. The fat intensity seen in the images correlated well with the chemically measured fat concentration. This subtraction method for windowing T1 values proved feasible for fat. The method could be used for tissues with other short T1 values as well.