7 research outputs found
3D Normal Coordinate Systems for Cortical Areas
A surface-based diffeomorphic algorithm to generate 3D coordinate grids in
the cortical ribbon is described. In the grid, normal coordinate lines are
generated by the diffeomorphic evolution from the grey/white (inner) surface to
the grey/csf (outer) surface. Specifically, the cortical ribbon is described by
two triangulated surfaces with open boundaries. Conceptually, the inner surface
sits on top of the white matter structure and the outer on top of the gray
matter. It is assumed that the cortical ribbon consists of cortical columns
which are orthogonal to the white matter surface. This might be viewed as a
consequence of the development of the columns in the embryo. It is also assumed
that the columns are orthogonal to the outer surface so that the resultant
vector field is orthogonal to the evolving surface. Then the distance of the
normal lines from the vector field such that the inner surface evolves
diffeomorphically towards the outer one can be construed as a measure of
thickness. Applications are described for the auditory cortices in human adults
and cats with normal hearing or hearing loss. The approach offers great
potential for cortical morphometry
A new MRI rating scale for progressive supranuclear palsy and multiple system atrophy: validity and reliability
AIM
To evaluate a standardised MRI acquisition protocol and a new image rating scale for disease severity in patients with progressive supranuclear palsy (PSP) and multiple systems atrophy (MSA) in a large multicentre study.
METHODS
The MRI protocol consisted of two-dimensional sagittal and axial T1, axial PD, and axial and coronal T2 weighted acquisitions. The 32 item ordinal scale evaluated abnormalities within the basal ganglia and posterior fossa, blind to diagnosis. Among 760 patients in the study population (PSP = 362, MSA = 398), 627 had per protocol images (PSP = 297, MSA = 330). Intra-rater (n = 60) and inter-rater (n = 555) reliability were assessed through Cohen's statistic, and scale structure through principal component analysis (PCA) (n = 441). Internal consistency and reliability were checked. Discriminant and predictive validity of extracted factors and total scores were tested for disease severity as per clinical diagnosis.
RESULTS
Intra-rater and inter-rater reliability were acceptable for 25 (78%) of the items scored (≥ 0.41). PCA revealed four meaningful clusters of covarying parameters (factor (F) F1: brainstem and cerebellum; F2: midbrain; F3: putamen; F4: other basal ganglia) with good to excellent internal consistency (Cronbach α 0.75-0.93) and moderate to excellent reliability (intraclass coefficient: F1: 0.92; F2: 0.79; F3: 0.71; F4: 0.49). The total score significantly discriminated for disease severity or diagnosis; factorial scores differentially discriminated for disease severity according to diagnosis (PSP: F1-F2; MSA: F2-F3). The total score was significantly related to survival in PSP (p<0.0007) or MSA (p<0.0005), indicating good predictive validity.
CONCLUSIONS
The scale is suitable for use in the context of multicentre studies and can reliably and consistently measure MRI abnormalities in PSP and MSA. Clinical Trial Registration Number The study protocol was filed in the open clinical trial registry (http://www.clinicaltrials.gov) with ID No NCT00211224
Sub-Riemannian Methods in Shape Analysis
International audienc