Patent ID: 8547097

Claim:
A method to determine SAR in a magnetic resonance tomography system with multiple, individually-controlled antenna transmission elements, and control electronics configured to control each antenna element to radiate an RF pulse into an examination subject in the tomography system that releases energy into the subject, said method comprising the steps of: in a first part of a computerized processor, said first part being in said control electronics, calculating a single-line cross-correlation matrix for each of multiple points in time or time periods that contains, as elements, respective products of a respective antenna element value of said multiple antenna elements with that or another respective antenna element value; in said first part of said processor, adding the single-line cross-correlation matrices into a sum cross-correlation matrix over a summation time period; in loading a hotspot sensitivity matrix into a second part of said processor at a different location in said tomography system from said control electronics, said hotspot sensitivity matrix comprising matrix elements respectively representing sensitivities in at least one respective direction at a plurality of hotspot points in the subject and, in said second part of said processor, multiplying said sum cross-correlation matrix with said hotspot sensitivity matrix; in said second part of said processor, multiplying the product of the sum cross-correlation matrix and the hotspot sensitivity matrix with a value representing the dielectricity at at least one hotspot point in order to determine a respective SAR value for each hotspot point; and when at least one SAR value exceeds a predetermined upper limit, reducing or deactivating in said first part of said processor a voltage applied to at least one of said antenna elements or a current flowing in at least one antenna of said elements by said control electronics.