Frank Traeber PhD, Abstract Co-Author: Nothing to Disclose

Mike P. Wattjes MD, Presenter: Nothing to Disclose

Okan Guer MD, Abstract Co-Author: Nothing to Disclose

Wolfgang Block PhD, Abstract Co-Author: Nothing to Disclose

Michael Harzheim MD, Abstract Co-Author: Nothing to Disclose

Hans Heinz Schild MD, Abstract Co-Author: Nothing to Disclose

Optimization of 1H-MRS acquisition protocols at 3T for absolute quantification of metabolite concentrations, especially for N-acetyl-aspartate (NAA) as a marker of neurodegeneration and for myo-inositol (MI) as an early indicator of inflammatory white matter (WM) disease.

47 patients with clinically isolated syndrome (CIS) suggestive of multiple sclerosis (MS) were investigated by single-voxel proton MRS on a clinical 3T whole-body MR system (Gyroscan Intera 3.0T, Philips Medical Systems). Water-suppressed PRESS spectra from an 8 ml VOI only including lesion-free normal appearing white matter (NAWM) of the centrum semiovale were acquired with TE 38 and 140ms and TR 2000ms. Absolute metabolite concentrations of NAA, total creatine (tCr), choline containing compounds (Cho) and MI were calculated using unsuppressed water signal as an internal reference. Metabolite ratios and concentrations in NAWM were compared to the respective values obtained from 20 healthy controls. Additionally, T2 relaxation times of NAA, tCr, and Cho at 3.0 T were determined in 27 of the CIS patients and in 15 of the controls.

Variation of echo time in phantoms and healthy controls yielded optimum TE in the range 35-40 ms at 3.0 T for quantification of the spin-coupled MI multiplets at 3.54 and 3.62 ppm. Metabolite and water T2 relaxation times in parietal WM did not differ significantly between CIS patients and controls. Absolute NAA concentration was significantly (p<0.01) decreased by almost 10% in the NAWM of the patient group, and a significant reduction by a similar amount was observed for the metabolite ratios NAA/tCr and NAA/Cho. Although mean MI concentration and MI/NAA ratio were elevated by about 10% in CIS patients, this increase did not reach significance due to larger coefficients of variation for these parameters. However, the subgroup of 12 patients classified as early stage MS revealed significantly (p<0.01) higher absolute and relative MI concentration.

Even in normal appearing cerebral WM of patients with CIS, 1H-MRS at 3T revealed alterations in metabolite concentrations. These observations might improve diagnostic procedures already in the very early stages of MS disease.

Traeber, F, Wattjes, M, Guer, O, Block, W, Harzheim, M, Schild, H, Determination of Absolute Metabolite Concentrations by 1H-MRS at 3.0 T in Healthy Controls and in the Normal- appearing White Matter of Patients with Clinically Isolated Syndrome (CIS).  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4411107.html