From Anatomic Standardization Analysis of Perfusion SPECT Data to Perfusion Pattern Modelling

Rationale and Objectives. In the general context of perfusion pattern modelling from SPECT data, the purpose of this study was to characterize inter-individual functional variability and functional connectivity between anatomical structures in a set of SPECT data acquired from a homogeneous population of subjects. Materials and methods. From Volume of Interest (VOI)-perfusion measurements performed on anatomically standardized SPECT data, we proposed to use correspondence analysis (CA) and hierarchical clustering (HC) to explore the structure of statistical dependencies among these measurements. The method was applied to study the perfusion pattern in two populations of subjects, namely SPECT data from 27 healthy subjects and ictal SPECT data from 10 mesial temporal lobe epilepsy (MTLE) patients. Results. For healthy subjects, anatomical structures showing statistically dependent perfusion patterns were classified into four groups, namely temporo-mesial structures, internal structures, posterior structures and remaining cortex. For MTLE patients, they were classified as temporo-mesial structures, surrounding temporal structures, internal structures and remaining cortex. Anatomical structures of each group showed similar perfusion behavior so that they may be functionally connected and may belong to the same network. Our main result was that the temporal pole and the lenticular nucleus seemed to be highly relevant to characterize ictal perfusion in MTLE patients. This exploratory analysis suggested that a network involving temporal structures, lenticular nucleus, brainstem and cerebellum seems to be involved during MTLE seizures. Conclusion. CA followed by HC is a promising approach to explore brain perfusion pattern from SPECT VOI measurements.