Validation of MR thermometry technology: a small animal model for hyperthermic treatment of tumours.
BACKGROUND
Local hyperthermia has been shown to be an effective adjuvant therapy for cancer. However, progress in this treatment modality requires the non-invasive assessment of temperature distribution in the entire tumour to enable administration of an efficient thermal dose to all tumour areas. Magnetic resonance (MR) imaging offers a promising tool to quantify, non-invasively and three-dimensionally, temperature distribution within tumours. An animal model taking into account the complex interrelationship between pathophysiological changes within a tumour during hyperthermia and temperature-sensitive MR parameters is warranted for the development and validation of new MR thermometry technology.


METHODS
An experimental set-up was implemented to allow simultaneous measurements of temperature, tumour blood flow and temperature-sensitive MR parameters under standardised conditions in vivo. Local hyperthermia was induced at 44 degrees C for 20 min under inhalation anaesthesia on seven Syrian Golden hamsters bearing an amelanotic melanoma. Fibreoptic probes were used for reference temperature measurements. Laser Doppler flowmetry served for on-line tumour blood flow determination, and MR thermometry was performed using longitudinal T1 relaxation time measurements.


RESULTS
The experimental design enables multifunctional MR thermometry. T1 relaxation times of tumours were 1.44 s (1.36, 1.46) and 1.53 s (1. 48, 1.75) at 37 degrees C and during hyperthermia at 44 degrees C, respectively (median, 25% and 75% quartiles, respectively; P<0.05). At the end of 20 min of hyperthermic treatment at 44 degrees C, relative tumour blood flow was reduced to 40.5% (20.7, 43.3) compared to values before treatment (median, 25% and 75% quartiles, respectively; P<0.05). Imaging of T1 relaxation times revealed a heterogeneous distribution in temperature during hyperthermic treatment.


CONCLUSIONS
This novel in vivo model allows standardised investigations for the development and validation of MR thermography methods.
Pahernik
S A
SA
Institute for Surgical Research, Klinikum Grosshadern, University of Munich, Germany.
Peller
M
M
Dellian
M
M
Loeffler
R
R
Issels
R
R
Reiser
M
M
Messmer
K
K
Goetz
A E
AE
D000818:Animals; D006224:Cricetinae; D004195:Disease Models, Animal; D006979:Hyperthermia, Induced / Q000592:standards*; D008279:Magnetic Resonance Imaging / Q000592:standards*; D008297:Male; D018328:Melanoma, Amelanotic / Q000628:therapy*; D008647:Mesocricetus