FDG-PET/CT and diffusion-weighted MRI evaluation of the early therapeutic effect of radiofrequency ablation for VX2 sarcomas in rabbits / 介入放射学杂志

ABSTRACT

Objective To discuss the value of diffusion-weighted MRI (DWI) and 18F-FDG-PET/CT in assessing the early therapeutic effect of radiofrequency ablation (RFA) for VX2 sarcomas in experimental rabbits. Methods VX2 sarcoma was inoculated at bilateral hind limbs in 14 New Zealand white rabbits to establish the animal models. The implanted VX2 tumor on one hind leg was treated with ultrasound-guided percutaneous RFA (study group), while no RFA was given to the VX2 tumor on the contralateral hind leg (control group). DWI-MRI was performed at 2 days after RFA, and 18F-FDG-PET/CT examination was employed at 3 days after RFA. The mean apparent diffusion coefficient (ADC) values and standard uptake value (SUV) of the untreated tumor and the ablated tumor were separately calculated. Taking the pathologic result as the gold standard, the consistency of DWI-MRI, PET/CT as well as the combination of DWI-MRI and PET/CT with the clinical diagnosis was separately evaluated by Kappa test. Results Before RFA, DWI-MRI demonstrated that the VX2 tumor was characterized by hypo-intensity signal on T1 and hyper-intensity signal on T2 with ring-shaped enhancement on T1-weighted image; PET/CT showed that the tumor had nodular or ring-shaped 18F-FDG accumulation. After RFA, DWI-MRI revealed that the VX2 tumor was manifested as hyper-intensity signal on T1 and slight higher density on T1 with slight enhancement on contrast-enhanced T1-weighted image; PET/CT showed lowered accumulation of 18F-FDG. The mean ADC value of the ablated tumor was (1.52 ± 0.24) × 10-3 mm2/s, which was obviously higher than that of the un-ablated tumor, that was (1.09 ± 0.12) × 10-3 mm2/s, the difference was statistically significant(P0.05). The Kappa value of the consistency between combination of DWI-MRI with PET/CT and pathology was 0.786, which was significantly different from the result by simple DWI-MRI or simple PET/CT evaluation (P< 0.05). Conclusion Both ADC value of DWI-MRI and SUV value of PET/CT are useful indexes for evaluating the early therapeutic effect of RFA. Both DWI-MRI and PET/CT have their respective advantages, nevertheless, combination use of both can effectively improve the evaluation of curative effect for VX2 tumor after RFA in experimental rabbits.