Temperature quantitation and mapping of frozen tissue

A method was developed for quantitating the temperature within frozen tissu e with the magnetic resonance (MR) parameter R2*. The pulse sequence uses h alf-pulse excitation and a short spiral readout to achieve echo times as sh ort as 0.2 msec. Fiber-optic temperature sensors were inserted into bovine liver tissue. The tissue was frozen at one end while being held warm at the other end. Once steady state was reached, the parameter R2* was measured. A linear dependence of R2* on temperature was demonstrated. R2* is Independ ent of freeze number and of the orientation of the temperature gradient wit h respect to the main magnetic field. Feasibility in a canine prostate duri ng cryosurgery is demonstrated. (C) 2001 Wiley-Liss, Inc.