Evaluation of Focal Laser Ablation of Prostate Cancer Using High Spectral and Spatial Resolution Imaging: A Pilot...

Focal laser ablation (FLA) is a minimally invasive thermal ablation, guided by MRI through an optical fiber, to induce coagulative necrosis in cancer.

To evaluate the feasibility of high spectral and spatial resolution imaging using multiecho gradient echo (MEGE) MRI for identification of ablation zones, after FLA of prostate cancers.

Prospective.

Fourteen patients with biopsy-confirmed localized prostate cancers.

FLA was performed under monitored conscious sedation with a 1.5T MRI scanner. Axial MEGE images were acquired before and after the last FLA. Pre- and postcontrast enhanced T₁ -weighted (pT₁ W) images were acquired to assess the FLA zone as a reference standard.

The $$ maps and water resonance peak height (WPH) images were calculated from the MEGE data. Ablation area was outlined using an active contour method. The maximum ablation area and total ablation volume were calculated from $$ and WPH images, and compared with the sizes measured from pT₁ W images.

Nonparametric Kruskal-Wallis tests were performed to determine whether there was significant difference in calculated ablation areas and volumes between $$ , WPH, and pT₁ W images.

Average $$ (38.9 ± 14.1 msec) in the ablation area was significantly shorter (P = 0.03) than the preablation area $$ (57.8 ± 25.3 msec). The normalized WPH value over the ablation area (1.3 ± 0.6) was significantly decreased (P = 0.02) more than the preablation area (2.0 ± 0.9). The maximum ablation areas measured by $$ (295.7 ± 96.4 mm² ), WPH (312.2 ± 63.0 mm² ), and pT₁ W (320.3 ± 82.9 mm² ) images were all similar. Furthermore, there was no significant difference (P = 0.31) for measured ablation volumes 3310.5 ± 649.5, 3406.4 ± 684.9, and 3672.5 ± 832.4 mm³ between $$ , WPH, and pT₁ W images, respectively. DATA CONCLUSION: $$ and WPH images provide acceptable measurements of ablation zones during FLA treatment of prostate cancers without the need for contrast agent injection. This might allow repeated assessment following each heating period so that subsequent ablations can be optimized.

2 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2019;49:1374-1380.