A. Sewonu

ABSTRACT In this work, we report multi-scanner quality control monitoring using a standard and automated protocol. This magnetic resonance imaging quality control protocol, based on the American College of Radiology procedures, includes weekly scans of a dedicated phantom followed by specific measurements. The processing step commonly involves manually-performed operations which can be tedious and time-consuming hence motivating their automation. QC data were collected in four sites; data from one of them served for the validation of the automatic analysis tool. Designed as a package of MATLAB® functions, this tool was successfully validated using Student's t-test and the correlation between automatic measurements and the manual ones. Besides, the multisite QC study enabled to compare the performances of these four MR facilities. In order to avoid misinterpretation or errors in multicenter clinical studies, such approach can be recommended as a preliminary step for including a site in the studies.

To study the effects of calcium on the choline peak measurements with 1H MR spectroscopy. The thigh muscles of two cadaveric specimens were prospectively evaluated on a 3 T MR unit before and after the injection of calcium carbonate (up to 0.4322 g). The choline peaks of 147 spectra from 10 different anatomic locations were quantitatively evaluated. The influence of the calcium concentration and its disposition with respect to the main magnetic field were considered. B0 phase maps were used to evaluate field inhomogeneities. The presence of calcium led to a 43 % underestimation of the choline peak and the choline concentration (p = 0.0002 and 0.0036). The mean choline concentrations before and after CaCO3 injection were 3.53 ± 1.72 mmol/l and 1.58 ± 0.63 mmol/l. The influence of calcium carbonate on the choline peak estimations was proportional to the calcium concentration. There was a significant position-dependent difference in the estimation of the choline peak amplitude (p < 0.0154). Calcium injection led to a measurable increase in field inhomogeneities. There was a significant underestimation of the choline peak amplitude and concentration in the presence of calcium, which might cause misinterpretations of MR spectra. The presence of calcium led to significant underestimation of choline measurements. The influence of calcium is dependent on its concentration and distribution. Quantitative MR spectroscopy of calcified tumours should be interpreted with caution.