Purpose: To evaluate the short- and mid-term evolutions of the apparent diffusion
coefficient of lesions treated with RF, in order to determine if the ADC can be used
as a marker of tumour response.
Methods and Materials: Twenty patients were treated for a liver malignancy with
RF and were examined on a 1.5 T/3.0 T machine with T2, gadolinium-enhanced
T1 and diffusion sequences: before treatment (< 1 month), just after treatment (< 1
month) and midterm (3-6 months). The ADC was measured in the whole lesion
and in the area with the most restricted diffusion (MRDA). The ROI size was also
measured on the diffusion map. The Pearson/ANOVA tests were used.
Results: All patients were successfully treated with complete disappearance of
CE. The lesional size on T2 showed a negative evolution in time (p < 0.002). The
ADC in the whole lesion showed a bell-shaped evolution (increasing just after RF,
then decreasing, p = 0.02). The ROI size on the diffusion map followed a similar
course (p = 0.01). For the MRDA, such evolutions were also found, but they were
not significant. There was a negative correlation between CE and the ADC (p < 0.02)
and between the lesional size on T2 and ADC (p = 0.03) in the whole lesion. There
were also positive correlations between the ROI size and ADC (p = 0.0008) and
between CE and the size on T2 (p = 0.0002). The ADC in MRDA showed some
non-significant correlations with other variables.
Conclusion: The lesions successfully treated with RF have a clear and predictable
evolution in terms of T2 size, CE and ADC.