A PET/CT approach to spinal cord metabolism in amyotrophic lateral sclerosis

Abstract

PurposeIn amyotrophic lateral sclerosis, functional alterations within the brain have been intensively assessed, while progression of lower motor neuron damage has scarcely been defined. The aim of the present study was to develop a computational method to systematically evaluate spinal cord metabolism as a tool to monitor disease mechanisms.MethodsA new computational three-dimensional method to extract the spinal cord from 18F-FDG PET/CT images was evaluated in 30 patients with spinal onset amyotrophic lateral sclerosis and 30 controls. The algorithm identified the skeleton on the CT images by using an extension of the Hough transform and then extracted the spinal canal and the spinal cord. In these regions, 18F-FDG standardized uptake values were measured to estimate the metabolic activity of the spinal canal and cord. Measurements were performed in the cervical and dorsal spine and normalized to the corresponding value in the liver.ResultsUptake of 18F-FDG in the spinal cord was significantly higher in patients than in controls (p < 0.05). By contrast, no significant differences were observed in spinal cord and spinal canal volumes between the two groups. 18F-FDG uptake was completely independent of age, gender, degree of functional impairment, disease duration and riluzole treatment. Kaplan-Meier analysis showed a higher mortality rate in patients with standardized uptake values above the fifth decile at the 3-year follow-up evaluation (log-rank test, p < 0.01). The independence of this value was confirmed by multivariate Cox analysis.ConclusionOur computational three-dimensional method enabled the evaluation of spinal cord metabolism and volume and might represent a potential new window onto the pathophysiology of amyotrophic lateral sclerosis.

Interplay between spinal cord and cerebral cortex metabolism in amyotrophic lateral sclerosis

“…Consequently, a large uncertainty still exists about the mechanisms underlying ALS-induced damage in the spinal cord and its relationship with cortical impairment. We recently reported the potential of the Hough transform in delineating spinal cord structure and metabolic activity in a population of ALS patients subjected to FDG PET/CT ( Marini et al , 2016 ). Specifically, this classical pattern recognition approach for the automatic identification of straight lines in the image has been recently extended to the recognition of more complex shapes.…”

[18F]FDG uptake of the normal spinal cord in PET/MR imaging: Comparison with PET/CT imaging

“…An issue addressed in the present study was the possible effect of normalizing the spinal cord SUV max and mean values to the liver [ 18 F]FDG uptake. This type of normalization was originally proposed by Marini et al [4] for spinal cord SUVmax in order to pool data provided by two PET/CT scanners. In our instance the normalization was justi ed by the need to overcome possible differences in [ 18 F]FDG uptake between PET/CT and PET/MRI due to the time interval between the two acquisitions and the tracer decay.…”

“…In addition, as suggested by Marini et al [4], a reference ROI of in the liver was measured in both PET/MRI and PET/CT and enabled to calculate the Normalized SUVmax (NSUVmax) and the Normalized SUVmean (NSUVmean). To test the coherence of the quantitative results of this study, we divided the subjects in two subgroups namely those without and those with increased uptake at visual examination in the cervical enlargement (Group 1 and Group 2 respectively), and then compare the spinal cord SUVmax values in PET/MRI and PET/CT between the two subgroups.…”

“…One entails measurement of the standardized uptake value (SUV) of the normal or affected spinal cord per se that is usually sampled with a Region Of Interest (ROI) encompassing the entire spinal canal due to lack of the spinal cord de nition and taking care to exclude the vertebral bone. The other implies measurement of the ratio of SUV to background using the activity of the normal spinal cord, lumbar thecal sac, vertebral marrow, or liver as a reference [2,3,4]. Moreover, due to inclusion of the surrounding CSF in the spinal cord ROI sampling in PET/CT, the spinal cord SUVmax, that is assumed to re ect the higher metabolic activity of the cord central gray matter, was usually preferred to SUVmean in PET/CT studies of spinal cord diseases.…”

Mechanisms underlying the predictive power of high skeletal muscle uptake of FDG in Amyotrophic Lateral Sclerosis

“…We previously reported a predictive power of spinal cord [18F]-uorodeoxyglucose (FDG) uptake computationally extracted from PET/CT images of ALS patients [7]. The apparent metabolic activation of this nervous district faced an opposite pattern in the brain cortex that showed a generalized reduction in tracer uptake [8].…”