title: FDG-MicroPET and diffusion-weighted MR image evaluation of early changes after radiofrequency ablation in implanted VX2 tumors in rabbits.
abstract: The objective of this study was to evaluate the early changes after radiofrequency ablation (RFA) in VX2 rabbit tumors implanted into the back muscles by diffusion-weighted magnetic resonance (MR) imaging and (18)F-2-fluoro-2-deoxy-D-glucose positron emission tomography ((18)F-FDG PET). Percutaneous CT-guided RFA was conducted in seven rabbits with implanted VX2 tumors. VX2 tumors on the other side were untreated and served as the control. MR imaging was performed with a clinical 1.5-T instrument 2 days after RFA, and FDG-PET, using a high-resolution PET scanner for small animals, was obtained 3 days after the procedure. The mean apparent diffusion coefficient (ADC) values and radioactivity count of untreated and ablated tumors were calculated. Untreated VX2 tumors showed hyperintensity on T1-, T2-, and diffusion-weighted MR images, ring-enhanced on contrast-enhanced T1-weighted imaging, and ring-shaped FDG accumulation on FDG-PET. Ablated VX2 tumors showed slight hyperintensity on T1-, T2-, and diffusion-weighed images, slight enhancement on contrast-enhanced T1-weighted images, and low accumulation on FDG-PET. The ADC value of ablated VX2 tumors (1.52 +/- 0.24 x 10(-3) mm(2)/s) was significantly higher than that of untreated tumors (1.09 +/- 0.12 x 10(-3); p < 0.05). The tumor/muscle ratio of ablated tumors (0.5 +/- 0.3) was significantly lower than that of untreated tumors (11.6 +/- 3.2; p < 0.05). Histopathological examination confirmed the lack of viable tumor cells in the ablated lesions. The results indicate that both ADC value and FDG-PET are potentially useful markers for monitoring the early effects of RFA.
authors.affiliation: Department of Radiology, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Ohira
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Okuma
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Matsuoka
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Wada
authors.forename: Kenji
authors.initials: K
authors.lastname: Nakamura
authors.forename: Yasuyoshi
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Inoue
mesh_terms: D000818:Animals; D017115:Catheter Ablation; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D004195:Disease Models, Animal; D019788:Fluorodeoxyglucose F18; D019042:Muscle Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D009368:Neoplasm Transplantation; D049268:Positron-Emission Tomography / Q000379:methods*; D011817:Rabbits; D015641:Radiography, Interventional; D019275:Radiopharmaceuticals; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18