Evaluation of thermometric monitoring for intradiscal laser ablation in an open 1.0 T MR scanner.
OBJECTIVE
The purpose of this study was to evaluate different methods of magnetic resonance thermometry (MRTh) for the monitoring of intradiscal laser ablation therapy in an open 1.0 Tesla magnetic resonance (MR) scanner.


METHODS
MRTh methods based on the two endogenous MR temperature indicators of spin-lattice relaxation time T1 and water proton resonance frequency (PRF) shift were optimised and compared in vitro. For the latter, we measured the effective spin-spin relaxation times T2* in intervertebral discs of volunteers. Then we compared four gradient echo-based imaging techniques to monitor laser ablations in human disc specimens. Criteria of assessment were outline of anatomic detail, immunity against needle artefacts, signal-to-noise ratio (SNR) and accuracy of the calculated temperature.


RESULTS
T2* decreased in an inverse and almost linear manner with the patients' age (r = 0.9) from 70 to 30 ms (mean of 49 ms). The optimum image quality (anatomic details, needle artefacts, SNR) and temperature accuracy (+/-1.09 degrees C for T1-based and +/-1.11 degrees C for PRF-based MRTh) was achieved with a non-spoiled gradient-echo sequence with an echo time of TE = 10 ms.


CONCLUSIONS
Combination of anatomic and thermometric non-invasive monitoring of laser ablations in the lumbar spine is feasible. The temperature accuracy of the investigated T1- and PRF-based MRTh methods in vitro is high enough and promises to be reliable in vivo as well.
Wonneberger
Uta
U
Institut für Radiologie, Charité, Universitätsmedizin Berlin, Germany. uta.wonneberger@charite.de
Schnackenburg
Bernhard
B
Wlodarczyk
Waldemar
W
Rump
Jens
J
Walter
Thula
T
Streitparth
Florian
F
Teichgräber
Ulf Karl Mart
UK
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D001831:Body Temperature / Q000528:radiation effects*; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000601:surgery*; D053685:Laser Therapy / Q000379:methods*; D008159:Lumbar Vertebrae / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods; D019047:Phantoms, Imaging; D055815:Young Adult