Alexander J. Gougoutas

Proteoglycan‐induced changes in T1ρ‐relaxation of articular cartilage at 4T

Proteoglycan (PG) depletion‐induced changes in T1ρ (spin‐lattice relaxation in rotating frame) relaxation and dispersion in articular cartilage were studied at 4T. Using a spin‐lock cluster pre‐encoded fast spin echo sequence, T1ρ maps of healthy bovine specimens and specimens that were subjected to PG depletion were computed at varying spin‐lock frequencies. Sequential PG depletion was induced by trypsinization of cartilage for varying amounts of time. Results demonstrated that over 50% depletion of PG from bovine articular cartilage resulted in average T1ρ increases from 110–170 ms. Regression analysis of the data showed a strong correlation (R2 = 0.987) between changes in PG and T1ρ. T1ρ values were highest at the superficial zone and decreased gradually in the middle zone and again showed an increasing trend in the region near the subchondral bone. The potentials of this method in detecting early degenerative changes of cartilage are discussed. Also, T1ρ‐dispersion changes as a function of PG depletion are described. Magn Reson Med 46:419–423, 2001.

Correlation of T1ρ with fixed charge density in cartilage

To establish the specificity of T1ρ with respect to fixed charge density (FCD) as a measure of proteoglycan (PG) content in cartilage during the onset of osteoarthritis (OA).

In vivo measurement of T1ρ dispersion in the human brain at 1.5 tesla

To measure T1ρ relaxation times and T1ρ dispersion in the human brain in vivo.

A phenotypic assessment tool for craniofacial microsomia.

Background: Craniofacial microsomia is one of the most common conditions treated by craniofacial teams. However, research regarding the cause of this condition or the surgical outcomes of treatment is scant. This is attributable to the lack of diagnostic criteria and the wide phenotypic spectrum. Standardized description of the craniofacial malformations associated with craniofacial microsomia is a necessary first step for multicenter, interdisciplinary research into this complex condition. Methods: The authors used the previously published pictorial Orbit, Mandible, Ear, Nerve, and Soft tissue–Plus classification scheme to assign a phenotypic severity score to patients with craniofacial microsomia treated at the Craniofacial Center at Seattle Childrens Hospital. The authors modified the tool based on feedback from multidisciplinary focus groups. The authors also developed a standardized photographic protocol to facilitate assessment of patients using two-dimensional images. Results: Feedback from focus groups was synthesized to create a phenotypic assessment tool for craniofacial microsomia based on the pictorial Orbit, Mandible, Ear, Nerve, and Soft tissue–Plus classification system. This tool allows for more comprehensive description of the phenotype of craniofacial microsomia and is found to be effective for clinical use within a multidisciplinary craniofacial team. In addition, the photographic protocol for patients with craniofacial microsomia allows for classification from a two-dimensional photographic database, thereby facilitating research using archived photographs. Conclusions: The phenotypic assessment tool for craniofacial microsomia protocol provides a simple and standardized method for practitioners and researchers to classify patients with craniofacial microsomia. We anticipate that this tool can be used in multicenter investigational studies to evaluate the cause of this condition, its natural history, and comparative effectiveness research.

An analysis of mandibular volume in hemifacial microsomia.

Background: The mandibular deformity in hemifacial microsomia is characterized by ramus-condyle unit deficiency. The Pruzansky score classifies the proximal mandible according to aberrant condylar-unit structure. The authors sought to volumetrically evaluate the hemifacial mandible compared with controls, and to assess for Pruzansky score correlation. Methods: This is a retrospective analysis of children with hemifacial microsomia. Demographic information was obtained, and computed tomographic data were analyzed by segmentation and volumetric calculations. Age-matched controls were compared using the t test. Results: Computed tomographic scans revealed 24 hemifacial and 13 controls: 62.5 percent right, 12.5 percent left, and 25 percent bilateral; and 34 percent type I, 28 percent type IIa, 16 percent type IIb, and 22 percent type III. Type IIb/III compared with type I/IIa were 11,100 and 17,773 mm3, respectively (p = 0.0029). Segmental evaluation of type IIb/III versus type I/IIa showed 3590 versus 6510 mm3 for the proximal segments (p = 0.0022) and 7449 versus 10,829 mm3 for the dental-bearing segments (p = 0.0221). All hemifacial microsomia hemimandibles (types I to III) were significantly less than controls: 14,837 versus 20,418 mm3 (p = 0.0005). Both dentate and proximal hemifacial microsomia segments statistically decreased in volume with increasing Pruzansky score. The dentate segment of the unaffected hemifacial microsomia side was statistically less than controls. Conclusions: This study volumetrically characterized the hemifacial microsomia mandibular deformity. As expected, with increasing Pruzansky severity, hemimandibular and proximal segment volumes declined. Unexpectedly, the hemifacial dentate segment also proved significantly diminished, corresponding to the degree of proximal volume loss.