The effect of earth magnetic field on the function of nuclear medicine imaging systems (SPECT)

Background: The nuclear medicine systems are very sensitive to the variation of the magnetic field. Photomultiplier tubes amplify low energy light signal and change it into electrical current. Low magnetic field can produce some variations in uniformity and special resolution of SPECT systems. In this study, we tried to evaluate the effects of magnetic field on the function of nuclear medicine imaging system, when system rotates in different angles. Materials and Methods: In this study, three SPECT systems with different orientation were examined. A point and line source was placed in the front of the system and when the gantry system rotated in earth magnetic field, variation of energy photo peak, spatial resolution and linearity were determined in different angles. These measurements repeated when an air conditioner was placed at 2-meter distance of the camera gantries. Results were compared using t-student test. Findings: The t-test results show that in all three SPECT systems, the variations of energy photo peak, spatial resolution and linearity were statistically significant (p<0.01). The surrounding magnetic field can effect on accurate function of nuclear medicine systems. Conclusion: The surrounding magnetic field can effect on accurate function of nuclear medicine systems.