The objective of this study was to use a combined
local descriptor, namely scale invariance feature
transform (SIFT), and a non linear support vector machine
(SVM) technique to automatically classify patients with
schizophrenia. The dorsolateral prefrontal cortex (DLPFC),
considered a reliable neuroanatomical marker of the disease,
was chosen as region of interest (ROI). Fifty-four
schizophrenia patients and 54 age- and gender-matched
normal controls were studied with a 1.5T MRI (slice
thickness 1.25 mm). Three steps were conducted: (1)
landmark detection and description of the DLPFC, (2)
feature vocabulary construction and Bag-of-Words (BoW)
computation for brain representation, (3) SVM classification
which adopted the local kernel to implicitly implement
the feature matching. Moreover, a new weighting approach
was proposed to take into account the discriminant relevance
of the detected groups of features. Substantial results
were obtained for the classification of the whole dataset
(left side 75%, right side 66.38%). The performances were
higher when females (left side 84.09%, right side 77.27%)
and seniors (left side 81.25%, right side 70.83%) were
considered separately. In general, the supervised weighed
functions increased the efficacy in all the analyses.
No effects of age, gender, antipsychotic treatment and
chronicity were shown on DLPFC volumes. This integrated
innovative ROI-SVM approach allows to reliably detect
subjects with schizophrenia, based on a structural
brain marker for the disease such as the DLPFC. Such
classification should be performed in first-episode patients
in future studies, by considering males and females
separately.