Navigator respiratory-triggered diffusion-weighted imaging in the follow-up after hepatic radiofrequency ablation-initial results.

Purpose: To evaluate diffusion alterations after hepatic radiofrequency (RF) ablation using a navigator respiratory-triggered diffusion-weighted imaging (NRT-DWI) sequence with regard to potential diagnostic information for detection of local tumor progression (LTP).

Materials And Methods: One hundred forty-eight consecutive follow-up magnetic resonance (MR) examinations of 54 patients after hepatic RF ablation were reviewed. Apparent diffusion coefficient (ADC) values of ablation zones and liver parenchyma were assessed using a single-shot echoplanar imaging sequence with the NRT technique. ADC values of ablation zones and adjacent signal alterations identified in NRT-DWI were analyzed with regard to LTP.

Results: Mean ADC values of ablation zones (119.9 +/- 30.5 x 10(-5) mm(2)/sec) and liver (106.3 +/- 21.2 x 10(-5) mm(2)/sec) differed significantly (P = 0.0003). No evident changes in ablations' ADC values over time could be identified. ADC values obtained from the entire ablation zone did not significantly differ regarding the presence of LTP. In 58 examinations, hyperintense areas in the periphery of the ablation zone were detected on the NRT-DWI. Corresponding ADC values were significantly lower in patients with LTP (102.1 +/- 22.4 versus 130.8 +/- 47.6 x 10(-5) mm(2)/sec; P = 0.0124).

Conclusion: NRT-DWI is useful in the follow-up imaging after RF ablation. ADC-based evaluation of signal alterations adjacent to the ablation zone may contribute to the identification of LTP and nontumoral posttreatment tissue changes.