T1 relaxation time at 0.2 Tesla for monitoring regional hyperthermia: feasibility study in muscle and adipose tissue.
The purpose of this study was to characterize T(1), particularly in the hyperthermia temperature range (ca. 37-44 degrees C), in order to control regional hyperthermia with MR monitoring using 0.2 Tesla, and to improve T(1) mapping. A single-slice and a new multislice "T One by Multiple Read-Out Pulses" (TOMROP) pulse sequence were used for fast T(1) mapping in a clinical MRI hyperthermia hybrid system. Temporal stability, temperature sensitivity, and reversibility of T(1) were investigated in a polyamidacryl gel phantom and in samples of muscle and adipose tissues from turkey and pig, and verified in patients. In the gel phantom a high linear correlation between T(1) and temperature (R(2) = 0.97) was observed. In muscle and adipose tissue, T(1) and temperature had a linear relationship below a breakpoint of 43 degrees C. Above this breakpoint muscle tissue showed irreversible tissue changes; these effects were not visible in adipose tissue. The ex vivo results were confirmed in vivo under clinical conditions. T(1) mapping allows the characterization of hyperthermia-related tissue response in healthy tissue. T(1), in combination with fast mapping, is suitable for controlling regional hyperthermia at 0.2 T within the hybrid system.
Department of Clinical Radiology, Ludwig-Maximilians-University, Munich, Grosshadern, Germany. peller@ikra.med.uni-muenchen.de
Michael
M
Peller
Herbert M
HM
Reinl
Andreas
A
Weigel
Martin
M
Meininger
Rolf D
RD
Issels
Maximilian
M
Reiser
D000273:Adipose Tissue / Q000528:radiation effects; D000818:Animals; D005240:Feasibility Studies; D006801:Humans; D006979:Hyperthermia, Induced; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009132:Muscles / Q000528:radiation effects; D009369:Neoplasms / Q000175:diagnosis; D019047:Phantoms, Imaging; D013552:Swine; D013696:Temperature; D014422:Turkeys