Magn Reson Med. 2003 Jun;49(6):985-90.  

Cluster analysis of BOLD fMRI time series in tumors to study the heterogeneity
of hemodynamic response to treatment.

Baudelet C, Gallez B.

Medicinal Chemistry and Radiopharmacy Unit, Biomedical Magnetic Resonance Unit,
Universite Catholique de Louvain, Brussels, Belgium.

BOLD-contrast functional MRI (fMRI) has been used to assess the evolution of
tumor oxygenation and blood flow after treatment. The aim of this study was to
evaluate K-means-based cluster analysis as a exploratory, data-driven method.
The advantage of this approach is that it can be used to extract information
without the need for prior knowledge concerning the hemodynamic response
function. Two data sets were acquired to illustrate different types of BOLD fMRI
response inside tumors: the first set following a respiratory challenge with
carbogen, and the second after pharmacological modulation of tumor blood flow
using flunarizine. To improve the efficiency of the clustering, a power density
spectrum analysis was first used to isolate voxels for which signal changes did
not originate from noise or linear drift. The technique presented here can be
used to assess hemodynamic response to treatment, and especially to display
areas of the tumor with heterogeneous responses. Magn Reson Med 49:985-990,
2003. Copyright 2003 Wiley-Liss, Inc.

PMID: 12768574 [PubMed - in process]