A Study on MR Signal Intensity of Calcifications According to Calcium Concentration and Compound

ABSTRACT

PURPOSE: The signal of intracranial calcification on magnetic resonance (MR) imaging has been known to bevariable. The purpose of this study was to evaluate the MR signal of calcifications according to calciumconcentration and compound. MATERIALS AND METHODS: T1-weighted, proton density and T2-weighted images were obtained in phantoms with various conposition of calcium carbonate and calcium phosphate. The signal intensities and T1/T2 relaxation times were measured and analyzed according to calcium concentration and compound. The configurations of calcium particles were evaluated by scanning electron microscopy. RESULTS: The signal intensity of calcium carbonate on T1-weighted images gradually decreased as the concentration increased, while that ofcalcium phosphate showed a biphasic curve with a peak intensity at 0.2 g/ml. The signal intensity of both calcium compounds on T2-weighted images decreased as the concentration increased. The T1 relaxation time of calcium carbonate remained constant with increasing calcium concentration, however, that of calcium phosphate decreased upto 0.2g/ml and then remained constant. The T2 relaxation time of both calcium compounds decreased in a similar fashion with increasing concentration. Calcium phosphate showed larger surface area on scanning electron microscope. CONCLUSION: Calcifications show variable MR signal due to difference of T1 and T2 relaxation times according to calcium concentration and compound. Large surface area of calcium particle might cause shortening of T1 relaxation time leading to high signal on T1-weighted image. Understanding of these findings will help interpretation of MR images more precisely.