Potential and limitations of magnetic resonance imaging for real-time monitoring of interstitial laser phototherapy.
OBJECTIVE
Magnetic resonance (MR) imaging has been suggested as a method to monitor interstitial laser phototherapy (ILP) in deep tissues. Unfortunately, a reliable relation between temperature and MR parameters has not yet been demonstrated. In this study, we examined whether such a relation exists and whether MR imaging can measure absolute temperature or temperature changes.


METHODS
We evaluated, in the range of 21 degrees C to 80 degrees C, the temperature dependence of the MR imaging signal and T1 in samples of liver, water, CuSO4, and oil. Spin-echo and fast low-angle shot (FLASH) sequences were used.


RESULTS
The MR imaging signal of liver, CuSO4, and water continuously decreased when the temperature was increased from 21 degrees C to 80 degrees C. By contrast, the MR imaging signal of the oil increased with increasing temperature up to 40-50 degrees C and then decreased at higher temperatures. We observed a reliable linear relation only between T1 and temperature in a range' of 30-60 degrees C for oil and CuSO4.


CONCLUSIONS
MR imaging has the potential to measure thermal variations with an uncertainty of approximately +/- 10 degrees C. However, the use of MR imaging to monitor the real-time thermal effect induced in biologic tissues during laser irradiation requires further investigation before it can be applied clinically.
Pignoli
E
E
Division of Health Physics, Istituto Nazionale per lo Studio e la Cura del Tumori, Milano, Italy.
Marchesini
R
R
Curti
L
L
Sichirollo
A E
AE
Tomatis
S
S
Musumeci
R
R
D000818:Animals; D002417:Cattle; D019327:Copper Sulfate; D066298:In Vitro Techniques; D053685:Laser Therapy; D008099:Liver; D008279:Magnetic Resonance Imaging; D008991:Monitoring, Physiologic; D009821:Oils; D010789:Phototherapy; D013696:Temperature; D014867:Water
D009821:Oils; D014867:Water; D019327:Copper Sulfate