Biomedical subjects

Christopher W Tjoa

Publications and source records attributed to Christopher W Tjoa.

5 recordsLinked to original sources

PubMed2005

Reproducibility and accuracy of quantitative magnetic resonance imaging techniques of whole-brain atrophy measurement in multiple sclerosis.

BACKGROUND AND PURPOSE: Whole-brain atrophy is of growing interest as an outcome measure in multiple sclerosis (MS) clinical trials. The authors compared the reproducibility and accuracy of 3 quantitative techniques of measurement in patients with MS. METHODS: Thirty-four patients with relapsing-remitting MS (median Expanded Disability Status Scale disability score = 1.5) were studied. Brain parenchymal fraction (BPF) was quantified on spin-echo 2-dimensional T1-weighted axial 5-mm slice thickness sequences by semiautomated (Buffalo, Trieste) or automated (SIENAX) algorithms. RESULTS: Mean +/- SD BPFs were 0.830 +/- 0.04 with Buffalo, 0.824 +/- 0.04 with Trieste, and 0.826 +/- 0.04 with SIENAX methods (P = nonsignificant [NS]). Mean BPF scan-rescan coefficient of variation (COV) was 0.41% for Buffalo, 0.44% for Trieste, and 0.32% for SIENAX (P =NS).The semiautomated methods showed higher accuracy than the automated method in brain extraction (masking; P = .001). The errors of skull stripping included scalp, skull bone marrow, inferior parts of temporal lobes anterior to the brain stem, face structures, sagittal sinuses, eyes, and optic nerves. Buffalo (r = -0.37, P = .034) and Trieste (r = -.36, P = .039) BPFs showed stronger cor relation with disability than SIENAX (r = -0.16, P = .219). These differences were statistically significant (P = .0031 for Buffalo and P = .0037 for Trieste BPF). CONCLUSIONS: This study showed a high reproducibility of both semiautomated and automated methods for brain atrophy measurement. The semiautomated methods showed higher accuracy than the automated SIENAX method did in the evaluation of brain extraction, especially in infratentorial and cortical regions, where operator interaction during the masking processes was essential.

Adult↗

PubMed2004

Prediction of neuropsychological impairment in multiple sclerosis: comparison of conventional magnetic resonance imaging measures of atrophy and lesion burden.

BACKGROUND: Cognition and magnetic resonance imaging correlations are well established in patients with multiple sclerosis (MS), but it is unclear whether lesion burden or atrophy accounts for most of the predictive variance. These indices have been directly compared in only a few studies. No such study included measurement of the third ventricle, which was strongly predictive of neuropsychological competence in the early literature. Furthermore, few studies accounted for the influence of age, premorbid intelligence, or depression. OBJECTIVE: To determine if conventional measures of lesion burden or atrophy predict cognitive dysfunction in MS while accounting for age, premorbid intelligence, and depression. METHODS: We studied 37 patients with MS and 27 controls matched according to demographic variables. Correlations between neuropsychological tests and the following magnetic resonance imaging indices were considered: T1 hypointense lesion volume, fluid-attenuated inversion recovery hyperintense lesion volume, third ventricle width, bicaudate ratio, and brain parenchymal fraction. Regression models predicting neuropsychological performance controlled for the effects of age, premorbid intelligence, and depression. We included only those tests discriminating patients with MS from controls. RESULTS: In each regression model, third ventricle width was the sole magnetic resonance imaging measure retained. When this variable was removed from consideration, brain parenchymal fraction was retained in all analyses. CONCLUSIONS: Brain atrophy accounts for more variance than lesion burden in predicting cognitive impairment in MS, and central atrophy in particular is strongly associated with neuropsychological morbidity. This finding may be explained in part by atrophy of the thalamus, a deep gray matter structure that mediates cognitive function via cortical and subcortical pathways. Enthusiasm for the clinical utility of third ventricle width is tempered by modest intraobserver and interobserver reliability.

Adult↗

PubMed2003

A semiautomated measure of whole-brain atrophy in multiple sclerosis.

Brain atrophy is a proposed MRI marker of irreversible pathologic damage in multiple sclerosis (MS). The brain parenchymal fraction (BPF) is the ratio of brain parenchymal volume to the total volume within the surface contour. We developed a semiautomated measure of BPF using commercially available edge-finding and thresholding software (30-min analysis time per patient). We measured BPF in 78 patients with MS and 17 healthy controls. BPF was lower in a cohort of patients with MS (n=50) (0.843+/-0.042, range 0.743-0.906) age-matched to controls (0.877+/-0.020, range 0.835-0.901) (p<0.001). BPF correlated inversely with third ventricular width (r=-0.785, p<0.001), and total T1 hypointense lesion volume (r=-0.347, p=0.011), but not with total T2 hyperintense lesion volume (r=-0.213, p=0.13). BPF correlated negatively with expanded disability status scale (EDSS) score (r=-0.391, p=0.0006) and disease duration (r=-0.281, p=0.01). Stepwise regression compared the relative abilities of MRI variables to predict clinical data. By regression of age, BPF, third ventricular width, T2 lesions, and T1 lesions, BPF was the best predictor of disability score (R(2)=0.204, p<0.001). Third ventricular width was the best predictor of disease duration (R(2)=0.316, p<0.001). None of the MRI variables differed between relapsing-remitting (RR) (n=60) and secondary progressive (SP) (n=18) disease course (p>0.05). The intrarater, interrater, and scan-rescan BPF variability (COV) was 0.31%, 0.34%, and 0.41% and the accuracy against a phantom was 99.1%. We conclude that whole-brain atrophy in MS can be reliably and readily quantified by a semiautomated approach. Longitudinal studies are warranted to determine if this method provides a sensitive biologic marker of the MS disease process.

Adult↗

PubMed2003

Selective caudate atrophy in multiple sclerosis: a 3D MRI parcellation study.

Deep gray matter damage may be an important component of the multiple sclerosis (MS) disease process. We tested whether caudate atrophy occurs in MS, and whether it correlates with conventional MRI or clinical markers of disease progression. Caudate nuclei of 24 MS patients and 10 age-matched healthy controls were traced, normalized, reconstructed and visualized from MRI scans. Normalized bicaudate volume was 19% lower in MS controls ( p< 0.001), an effect that persisted after adjusting for whole-brain atrophy ( p< 0.008). Caudate volume did not correlate with disease duration, physical disability score, whole-brain atrophy, or total T2 hyperintense or T1 hypointense lesion load (all p > 0.05). We conclude that selective caudate atrophy is associated with MS and may occur through direct mechanisms.

Adult↗

PubMed2002

T2 hypointensity in the deep gray matter of patients with multiple sclerosis: a quantitative magnetic resonance imaging study.

CONTEXT: While gray matter T2 hypointensity in multiple sclerosis (MS) has been associated with physical disability and clinical course, previous studies have relied on visual magnetic resonance imaging (MRI) assessments. OBJECTIVE: To quantitatively determine if T2 hypointensity is associated with conventional MRI and clinical findings in MS. DESIGN: Case-control study. SETTING: University-affiliated community-based hospital. SUBJECTS: Sixty patients with MS and 50 controls. MAIN OUTCOME MEASURES: T2 intensities of the substantia nigra, red nucleus, thalamus, putamen, globus pallidus, and caudate; third ventricular width; total brain T1 (hypointense) and T2 (hyperintense) lesion volumes; Expanded Disability Status Scale (physical disability) score; and disease course. RESULTS: Deep gray matter T2 hypointensity was present in patients with MS in all structures (P<.005) except for the substantia nigra. T2 hypointensity was associated with third ventricle enlargement and higher T2 but not T1 plaque load. The regression model predicting third ventricle width included caudate T2 hypointensity (P =.006). The model predicting T2 lesion load included globus pallidus T2 hypointensity (P =.001). Caudate T2 hypointensity was the only variable associated with disability score in regression modeling (P =.03). All T2 hypointensities differentiated the secondary progressive from the relapsing-remitting clinical courses. The final model (P<.001) predicting clinical course retained T2 hypointensity of the thalamus, caudate, and putamen but not MRI plaques or atrophy. CONCLUSIONS: Gray matter T2 hypointensity in MS is associated with brain atrophy and is a stronger predictor of disability and clinical course than are conventional MRI findings. While longitudinal studies are warranted, these results suggest that pathologic iron deposition is a surrogate marker of the destructive disease process.

Adult↗