MRI and contrast-enhanced ultrasound monitoring of prostate microwave focal thermal therapy: an in vivo canine study.
OBJECTIVE
To compare the value of diffusion-weighted MRI (DWI), dynamic contrast-enhanced (DCE) MRI, and microbubble contrast-enhanced ultrasound (CEUS) for assessment of the thermal lesion created by interstitial microwave heating of the normal canine prostate.


METHODS
A microwave antenna was inserted into each lobe of the prostate in seven dogs to induce coagulation necrosis. Immediately after therapy the lesion was assessed using CEUS, DCE-MRI, and DWI. The prostates were excised, photographed, and prepared for hematoxylin and eosin staining. Results from posttreatment MRI and ultrasound were compared to histology.


RESULTS
The apparent diffusion coefficient (ADC) was slightly lowered within the thermal lesion but was drastically reduced in a ring-like region that corresponds to a grossly appearing red thermal damage zone immediately peripheral to the central coagulum. Both DCE-MRI and CEUS delineated a smaller area of vascular damage, for which the borders lie within the red zone.


CONCLUSIONS
The red zone encompasses a range of vascular responses, including hyperemia and hemostasis, and is known to progress to necrosis and tissue nonviability. DWI clearly depicts this zone as a region of sharply reduced ADC, and may be better than contrast-enhanced imaging for accurate assessment of the eventual full extent of thermal damage.
Cheng
Hai-Ling Margaret
HL
Department of Diagnostic Imaging, Hospital for Sick Children Research Institute, 555 University Avenue, Toronto, Ontario, Canada. hai-ling.cheng@sickkids.ca
Haider
Masoom A
MA
Dill-Macky
Marcus J
MJ
Sweet
Joan M
JM
Trachtenberg
John
J
Gertner
Mark R
MR
D000818:Animals; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D004285:Dogs; D007089:Image Enhancement; D008297:Male; D008872:Microwaves / Q000627:therapeutic use; D009336:Necrosis; D011467:Prostate / Q000000981:diagnostic imaging / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000175:diagnosis; D014463:Ultrasonography / Q000379:methods