University of British Columbia

Author Of 1 Presentation

Imaging Poster Presentation

P0616 - PiB-PET and MRI myelin water fraction provide complementary information about myelin (ID 1474)

Speakers
Presentation Number
P0616
Presentation Topic
Imaging

Abstract

Background

Myelin water imaging can isolate the magnetic resonance imaging (MRI) signal from myelin water, providing a quantitative measure associated with myelin, termed the myelin water fraction (MWF), which has been validated in histopathologic studies. The amyloid tracer 11C Pittsburg compound B (PiB) also has an affinity for myelin and its binding can be reduced in MS lesions compared to normal-appearing white matter (NAWM). We sought to determine whether these myelin-sensitive techniques provide overlapping or complementary information in MS.

Objectives

To determine (1) whether MWF and PiB binding are decreased in lesions compared to NAWM and (2) if there is a correlation between MWF andPiB binding.

Methods

Eleven participants (5 relapsing-remitting MS, 3 secondary progressive MS, 3 primary progressive MS) were scanned on a 3T Philips MRI scanner, and on a Siemens HRRT PET scanner with an injection of 18 mCi 11C PiB. Two RRMS participants were treated with glatiramer acetate 40 mg subcutaneously three times per week. MRI scans included structural scans for tissue segmentation and a myelin water sequence for MWF calculation. PIB binding was quantified with the Logan method-derived non-displaceable binding potential (BPND) using healthy grey matter from cerebellum as reference region. Lesion masks included all lesions within the imaging volume. Regional mean values of MWF and BPND were determined for NAWM and lesions.

Results

Lesions showed a 38% decreased MWF and a 23% decreased BPND compared to NAWM (MWF: lesions=0.08±0.01 vs NAWM=0.13±0.02, p<0.0001; BPND: lesions=0.91±0.08 vs NAWM=1.18±0.07, p<0.0001). A correlation was found between MWF and BPND when including both NAWM and lesions (r=0.73, p=0.0001). However, there was no correlation when fitting for NAWM or lesions alone (NAWM: r=-0.51, p=0.06; lesions: r=0.39, p=0.23).

Conclusions

In this pilot study, lesions showed a decrease in both myelin water and PiB binding as expected in demyelinated tissue. The partial correlation between MWF and PIB BPND suggests that each technique might have different sensitivity for detecting the severity of demyelination in heterogeneously affected tissue. PIB BPND values in NAWM were relatively homogenous. PIB BPND was good at discriminating between NAWM and lesions. MWF showed more subtle differences in myelination in NAWM and lesions. PET-PiB imaging and MWF appear to provide reliable measures of myelin abnormality in MS lesions. MWF may be able to provide additional information on the heterogeneity of demyelination in lesions and NAWM.

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