In order to predict the real implications of RF-induced heating (SAR) in MRI, we have implemented the bioheat equation in some of our three-dimensional models of the human head. This allows us to predict the changes in temperature throughout the head during MRI with specific imaging sequences and specific RF coils. Our methods have also allowed us to make some predictions of Temperature changes dur to physiological activity.
Figure 2: Distributions of B1+ (left), SAR (center), and resulting temperature increase (right) for quadrature surface ciol (placed at back of head) at 300MHz. Linear grayscale from 0 (black) to 15 mT (white) for B1+, 0 to 20 w/kg for SAR, and 0 to 1.5 degree C for temperature increase. Contours for temperature increase at 0.5, 1, 1.5, 2.0, and 2.5 degree C.
Figure 3: Sagittal slice through occipital lobe showing calculated heating effects in occipital lobe during functional activation of the calcarine fissure. Model geometry (top) baseline temperature (Tbase) distribution (middle) and change in temperature upon activation (ΔT; bottom) of grey matter (G.M.) in calcarine fissure for normal physiological parameters. Slice shown is on sagittal section through calcarine fissure of complete three-dimensional head model (2). Tblood is 37 degree C.
- Collins CM, Smith MB, Turner R. Model of local temperature changes in brain upon functional activation. J Appl Physiol. 2004 Dec;97(6):2051-5. Epub 2004 Aug 20
- Collins CM, Liu W, Wang J, Gruetter R, Vaughan JT, Ugurbil K, Smith MB. Temperature and SAR calculations for a human head within volume and surface coils at 64 and 300 MHz. J Magn Reson Imaging. 2004 May;19(5):650-6.