Study of temperature rise in RF irradiation during MR imaging: measurement of local temperature using a loop phantom

Cases have been reported of a local rise in temperature at the patient's skin and of burns occurring during MR imaging. To verify this phenomenon, we created a phantom from agarose, saline, and preservative, and measured the increase in local temperature. In addition, phantoms of limbs of the human body shaped such that a closed loop was formed were also used. The temperature of the phantom was measured for 50 minutes in each state, i.e., where a closed loop was formed and where the loop was incomplete. Moreover, the radio frequency (RF) and gradient fields were set as respectively independent states, and the temperature of the phantom was measured. Results of the experiment showed that temperature changed from approximately 6 degrees to 11.5 degrees in the closed loop part of the phantom, whereas there was no significant change when the loop was incomplete. In addition, with exposure to RF, a significant rise in temperature occurred where the loop was closed, whereas there was no significant increase in temperature in gradient fields. This experiment demonstrated that the increase in temperature as a result of RF irradiation occurred in the closed part of the loop phantom. Consequently, a loop formed in the human body may be subject to burns in the area of contact.