An Investigation of the Effects of a Strong External Magnetic Field on the Performance of a Gamma Camera.

摘要

Multimodality imaging systems, such as single-photon emission tomography (SPECT)/ magnetic resonance imaging (MRI), provide advantages from both powerful imaging modalities; however, SPECT/MRI and PET/MRI systems encounter many difficulties due to incompatible MR system with the nuclear detector system. This study is specifically concerned with the effects of a strong external magnetic field on the count rate (sensitivity) of a nuclear imaging device. A gamma camera was rotated around an electromagnet in both the saggital and transverse planes and the count rates produced by a calibrated Co-57 source were measured at several angles. The effect of the magnetic field strength on sensitivity was also investigated by changing the magnet current and then measuring the count rate. On the basis of the results of this work, it can be concluded that camera sensitivity is much more sensitive to changes in magnetic field intensity in the sagittal than the transverse planes of the magnet. The results of this research are presented such that they can be used as an aid to the design of future SPECT/MRI or PET/MRI system.