Room: Exhibit Hall | Forum 8
Purpose: Magnetic moment or susceptibility of an object may reveal the pathophysilogical information in diseases. By integrating MR signals surrounding the object, the magnetic moment of an isolated sphere such as cerebral microbleeds can be solved in CISSCO method. However, this method may lead to the discrepancy of the magnetic moment in the heterogeneous region. In this work, we updated the conventional CISSCO by the concept of spherical symmetry in either polar or azimuthal angle to solve magnetic moment.
Methods: By utilizing this concept, the analytical formula of MR signal in a spherical object is still valid when the volume fraction remains the same. Applying this concept may avoid integrating the signal from the heterogeneous region and reduce the discrepancy of the true answer. Here, we demonstrated the feasibility of this concept in simulated and phantom images. We simulated two spheres. The distances of two spheres were 14.2 and 4.2 pixels, respectively. Following were simulated parameters: the diameter of each sphere 3.0 pixels, the main magnetic field 3.0T, the susceptibility of each sphere 1.0ppm, TE 10ms, spin density inside/outside of each sphere 5.0/10.0, and SNR 10:1. Lastly, we quantified the magnetic moment of a glass bead, diameter 3 mm, in phantom images by using the conventional and the updated CISSCO. The following were imaging parameters: Bo2.89T, TE8.07ms, the isotropic resolution 1mm, and 3D gradient-echo sequence.
Results: In simulated images, the difference between the ideal answer and the quantified values was less than 10%. In the phantom study, the results of this glass bead using the updated method agreed with that using the conventional method less than 5% difference.
Conclusion: This updated method is an effective way to quantify the magnetic moment of a sphere in the heterogeneous region. The longitudinal study of cerebral microbleeds may be beneficial using this method.