Orbital Fat Volumetry and Water Fraction Measurements Using T2-Weighted FSE-IDEAL Imaging in Patients with Thyroid-Associated Orbitopathy.

BACKGROUND AND PURPOSE: The quantitative evaluation of orbital fat proliferation and edema and the assessment of extraocular muscles are useful for diagnosing and monitoring thyroid-associated orbitopathy. To evaluate therapy-induced quantitative changes in the orbital fat of patients with thyroid-associated orbitopathy, we performed volumetric and water fraction measurements by using T2-weighted FSE iterative decomposition of water and fat with echo asymmetry and least-squares estimation (FSE-IDEAL) imaging. MATERIALS AND METHODS: Orbital FSE-IDEAL images of 30 volunteers were acquired twice within 1 week. Nine patients with thyroid-associated orbitopathy underwent FSE-IDEAL imaging before and after methylprednisolone pulse therapy, and the treatment results were assessed by using their pre- and post-methylprednisolone pulse therapy clinical activity scores. We performed volumetric and water fraction measurements of orbital fat by using FSE-IDEAL imaging and evaluated interscan differences in the volunteers. In patients with thyroid-associated orbitopathy, we compared pre- and posttherapy orbital fat measurements and assessed the correlation between the pretherapy values and clinical activity score improvement. RESULTS: The reproducibility of results obtained by the quantitative evaluation of orbital fat in volunteers was acceptable. After methylprednisolone pulse therapy, the water fraction in the orbital fat of patients with thyroid-associated orbitopathy was significantly decreased (P < .001). There was a significant positive correlation between the pretherapy water fraction and clinical activity score improvement (right, r = 0.82; left, r = 0.79) and a significant negative correlation between the pretherapy volume and clinical activity score improvement (bilateral, r = -0.84). CONCLUSIONS: Volumetric and water fraction measurements of orbital fat by using FSE-IDEAL imaging are feasible and useful for monitoring the effects of therapy and for predicting the response of patients with thyroid-associated orbitopathy to methylprednisolone pulse therapy.

Ocular volumetry using fast high-resolution MRI during visual fixation.

BACKGROUND AND PURPOSE: Volumetry may be useful for evaluating treatment response and prognosis of intraocular lesions. Phantom, volunteer, and patient studies were performed to determine whether ocular MR volumetry is reproducible. MATERIALS AND METHODS: Half-Fourier single-shot RARE and FSPGR sequences at 1.5T with a 76-mm-diameter surface coil were optimized to obtain still ocular images. Volumetry accuracies of each sequence were compared with simulated subretinal phantom volumes. Ocular volumetry was performed in 15 volunteers twice in 1 week by using contiguous axial images of the globes while the subjects stared at a target, and images were acquired in 2 seconds before the subjects were instructed to blink, with this process repeated as necessary. Imaging, intraobserver, and interobserver reproducibility for volumes of the whole eyeball and anterior chamber were assessed. Ocular volumetry was also performed in 6 patients with intraocular tumors before and after treatment. RESULTS: The phantom study demonstrated that measurement error rates with RARE were significantly lower than with FSPGR (P<.01). The volunteer study demonstrated excellent imaging and intraobserver reproducibility of RARE volumetry for whole eyeballs and anterior chambers (P<.01). Although no interobserver differences were observed in anterior chamber volume measurement (P=.33), there was a significant difference between the 2 observers in eyeball volume measurement (P<.01). Follow-up volumetric data were useful for treatment decisions in all patients. CONCLUSIONS: Ocular volumetry from contiguous ultrafast RARE images obtained during visual fixation is feasible in volunteer and patient studies and is superior to FSPGR images.

Molecular cloning and functional characterization of rat plasma protein S.

Plasma protein S is a cofactor of activated protein C (APC) in the regulation of the blood coagulation system. Rat protein S homogeneously purified from plasma showed cofactor activity for rat APC, but not for human APC when the APC cofactor activity was assayed using protein S- and C4b-binding protein (C4BP)-depleted human plasma. Rat plasma protein S was separated by gel chromatography into two forms, a free form and a form complexed with C4BP. Rat protein S forms complexes with rat and human C4BP in a solid-phase model with apparent dissociation constants (Kds) of 6.7 x 10(-8) and 1.2 x 10(-8) M, respectively, in the presence of 5 mM Ca2+. Human protein S also forms a complex with solid-phase human and rat C4BP with Kds of 6.3 x 10(-9) and 2.7 x 10(-8) M, respectively. Human C4BP strongly inhibited the APC cofactor activity of both human and rat protein S, whereas rat C4BP was only weakly inhibitory. The degree of the inhibitory activity of C4BP appears to depend on the affinity between protein S and C4BP. In order to evaluate the structure-function relationship of the rat protein S, the complete cDNA sequence of rat protein S was determined. This cDNA of 3,315 bp was composed of a 103-bp 5'-noncoding region, a 2,028-bp coding region that encodes a preprosequence of 41 amino acids, a mature protein S of 634 amino acids and a stop codon, and a 1,184-bp 3'-noncoding region. The rat mature protein S consisted of domains with distinct functions similar to those of human protein S, and with two potential Asn-linked glycosylation sites. The amino acid sequence of the mature form of rat protein S showed 80.4, 78.7, and 79.7% identity with those of human, bovine, and rabbit mature protein S, respectively. These findings suggest that despite the species-specificity of the APC cofactor activity of rat protein S, it is structurally very similar to human protein S. Expression of rat protein S mRNA (approximately 3.5 kb) was demonstrated by RNA blot analysis not only in the liver, but also in the lung, spleen, testis, and uterus of rats.