Abstract

Purpose 18F-FDG PET is used to investigate the metabolic activity of neural tissue. MRI is used to visualize morphological changes, but the relationship between intramedullary signal changes and clinical outcome remains controversial. The present study was designed to evaluate the use of 3-D MRI/18F-FDG PET fusion imaging for defining intramedullary signal changes on MRI scans and local glucose metabolic rate measured on 18F-FDG PET scans in relation to clinical outcome and prognosis.MethodsWe studied 24 patients undergoing decompressive surgery for cervical compressive myelopathy. All patients underwent 3-D MRI and 18F-FDG PET before surgery. Quantitative analysis of intramedullary signal changes on MRI scans included calculation of the signal intensity ratio (SIR) as the ratio between the increased lesional signal intensity and the signal intensity at the level of the C7/T1 disc. Using an Advantage workstation, the same slices of cervical 3-D MRI and 18F-FDG PET images were fused. On the fused images, the maximal count of the lesion was adopted as the standardized uptake value (SUVmax). In a similar manner to SIR, the SUV ratio (SUVR) was also calculated. Neurological assessment was conducted using the Japanese Orthopedic Association (JOA) scoring system for cervical myelopathy.ResultsThe SIR on T1-weighted (T1-W) images, but not SIR on T2-W images, was significantly correlated with preoperative JOA score and postoperative neurological improvement. Lesion SUVmax was significantly correlated with SIR on T1-W images, but not with SIR on T2-W images, and also with postoperative neurological outcome. The SUVR correlated better than SIR on T1-W images and lesion SUVmax with neurological improvement. Longer symptom duration was correlated negatively with SIR on T1-W images, positively with SIR on T2-W images, and negatively with SUVmax.ConclusionOur results suggest that low-intensity signal on T1-W images, but not on T2-W images, is correlated with a poor postoperative neurological outcome. SUVmax of lesions showing increased signal intensity and SUVR measured on fusion MRI/PET scans are more sensitive parameters for predicting clinical outcome than signal intensity on the MRI scan.

Highlights

  • Materials and methodsIt is important to assess spinal cord function in patients with cervical compressive myelopathy considered suitable for neurosurgical treatment

  • Lesion SUVmax was significantly correlated with signal intensity ratio (SIR) on T1-W images, but not with SIR on T2-W images, and with postoperative neurological outcome

  • Our results suggest that low-intensity signal on T1-W images, but not on T2-W images, is correlated with a poor postoperative neurological outcome

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Summary

Introduction

Materials and methodsIt is important to assess spinal cord function in patients with cervical compressive myelopathy considered suitable for neurosurgical treatment. Many authors have reported high intramedullary signal intensity on T2-weighted (T2-W) MR images in patients with compressive spondylotic lesions of the cervical spinal cord [2,3,4,5]. This abnormality in intramedullary signal intensity is considered to represent myelomalacia or cord gliosis secondary to longstanding compression of the spinal cord [4]. The presence of high intramedullary signal intensity in patients with compressive myelopathy indicates the existence of a compressive spinal cord lesion of long duration. The cause of controversy is thought to be the lack of quantitative assessment of these changes in signal intensity

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