Femur: MR imaging-guided radio-frequency ablation in a porcine model-feasibility study.
OBJECTIVE
To determine the feasibility of magnetic resonance (MR) imaging-guided and -monitored radio-frequency (RF) ablation of bone.


METHODS
Seven femurs were treated in five pigs with use of a 0.2-T open MR imager. An 11-gauge bone marrow needle was percutaneously inserted into the distal femur metaphysis with MR fluoroscopy (fast imaging with steady-state precession, or FISP, sequences) to introduce an RF electrode into the bone with further image guidance. Thermal ablation was performed for 10 minutes (90 degrees C +/- 2 [mean +/- SD]). MR follow-up was performed immediately after ablation and again at 7 and 14 days after the procedure (with contrast material-enhanced T1-weighted, T2-weighted, and fast short inversion time inversion-recovery, or STIR, sequences). The animals were sacrificed at day 14. The femurs were sliced, decalcified, and stained. Image analysis was performed to measure lesion diameter and contrast-to-noise ratio (CNR) and to evaluate complications.


RESULTS
Technical success was obtained in all animals. The lesion diameter perpendicular to the electrode was 15.4 mm +/- 2.7. No significant complications were noted. The thermal lesions displayed low signal intensity with a sharp rim of high signal intensity. T2-weighted images demonstrated the highest CNR and the lowest error in predicting the lesion size immediately after ablation (2.7 mm +/- 1.3). Contrast-enhanced T1-weighted images demonstrated the highest accuracy at day 14 (1.0 mm +/- 1.0).


CONCLUSIONS
RF ablation of bone with MR imaging as the sole imaging modality is feasible and allows monitoring of the ablation.
Aschoff
Andrik J
AJ
Department of Radiology, University Hospitals of Cleveland/Case Western Reserve University, 11100 Euclid Ave, Cleveland, OH 44106, USA.
Merkle
Elmar M
EM
Emancipator
Steven N
SN
Petersilge
Cheryl A
CA
Duerk
Jeffrey L
JL
Lewin
Jonathan S
JS
D000818:Animals; D001853:Bone Marrow / Q000473:pathology*; D004566:Electrodes; D005240:Feasibility Studies; D005269:Femur / Q000473:pathology*; D006979:Hyperthermia, Induced / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008297:Male; D013552:Swine; D013813:Therapy, Computer-Assisted / Q000295:instrumentation*