(659): Using perfusion MRI to measure pain-induced changes in cerebral blood flow

Abstract

Arterial spin labeling (ASL) is a non-invasive magnetic resonance imaging (MRI) technique for measuring cerebral blood flow (CBF). Because ASL directly measures blood flow, it is well suited to pain conditions that are difficult to assess with current functional MRI, such as chronic pain. However, the use of ASL in neuroimaging has been hampered by its low sensitivity. Recent improvements in MRI technology, namely increased magnetic field strengths and phased array receiver coils, should enable ASL to measure the small changes in CBF associated with pain. The purpose of this study was to assess whether the functional activation caused by acute painful stimuli could be detected with an ASL technique. Fourteen healthy volunteers underwent two 11-minute ASL imaging sessions, during which a painful thermal stimulus (mean = 48.9 °C) was applied to the left hand. Functional image analysis software (SPM2) was used for both the fixed effects individual analyses and the random effects group analysis. The results demonstrated that the ASL technique measured changes in regional CBF in brain regions that have been previously identified with pain processing. These included bilateral CBF changes in the insula, secondary somatosensory, and cingulate cortices, as well as the supplementary motor area (SMA). Also observed were contralateral primary somatosensory and ipsilateral thalamic CBF changes. The average change in CBF for all regions of interest was 3.68 ml/100g/min, ranging from 2.97 ml/100g/min in ipsilateral thalamus to 4.91 ml/100g/min in contralateral insula. Although both sessions of data were used to obtain these results, the analysis revealed that data from a single 11-minute session were sufficient to map the pain-related areas of the brain. With its improved sensitivity, ASL will allow for more comprehensive studies of chronic pain conditions, and prolonged pain stimuli, such as tonic pain, particularly with regards to their associated cognitive and emotional components.