T2*-weighted MRI as a non-contrast-enhanced method for assessment of focal laser ablation zone extent in prostate cancer thermotherapy.

To evaluate utility of T2*-weighted (T2*W) MRI as a tool for intra-operative identification of ablation zone extent during focal laser ablation (FLA) of prostate cancer (PCa), as compared to the current standard of contrast-enhanced T1-weighted (T1W) MRI.

Fourteen patients with biopsy-confirmed low- to intermediate-risk localized PCa received MRI-guided (1.5 T) FLA thermotherapy. Following FLA, axial multiple-TE T2*W images, diffusion-weighted images (DWI), and T2-weighted (T2W) images were acquired. Pre- and post-contrast T1W images were also acquired to assess ablation zone (n = 14) extent, as reference standard. Apparent diffusion coefficient (ADC) maps and subtracted contrast-enhanced T1W (sceT1W) images were calculated. Ablation zone regions of interest (ROIs) were outlined manually on all ablated slices. The contrast-to-noise ratio (CBR) of the ablation site ROI relative to the untreated contralateral prostate tissue was calculated on T2*W images and ADC maps and compared to that in sceT1W images.

CBRs in ablation ROIs on T2*W images (TE = 32, 63 ms) did not differ (p = 0.33, 0.25) from those in sceT1W images. Bland-Altman plots of ROI size and CBR in ablation sites showed good agreement between T2*W (TE = 32, 63 ms) and sceT1W images, with ROI sizes on T2*W (TE = 63 ms) strongly correlated (r = 0.64, p = 0.013) and within 15% of those in sceT1W images.

In detected ablation zone ROI size and CBR, non-contrast-enhanced T2*W MRI is comparable to contrast-enhanced T1W MRI, presenting as a potential method for intra-procedural monitoring of FLA for PCa.

• T2*-weighted MR images with long TE visualize post-procedure focal laser ablation zone comparably to the contrast-enhanced T1-weighted MRI. • T2*-weighted MRI could be used as a plausible method for repeated intra-operative monitoring of thermal ablation zone in prostate cancer, avoiding potential toxicity due to heating of contrast agent.

European radiology. 2020 Aug 12 [Epub ahead of print]

Chongpeng Sun, Shiyang Wang, Aritrick Chatterjee, Milica Medved, Scott Eggener, Gregory S Karczmar, Aytekin Oto

Department of Radiology, The First Affiliated Hospital of Guangzhou Medical University, No. 151, Yanjiang Road, Guangzhou, 510120, Guangdong, China., Department of Radiology, Sanford J. Grossman Center of Excellence in Prostate Imaging and Image Guided Therapy, University of Chicago, 5841 South Maryland Avenue, Chicago, IL, 60637, USA., Department of Urology, University of Chicago, 5841 South Maryland Avenue, Chicago, IL, 60637, USA., Department of Radiology, Sanford J. Grossman Center of Excellence in Prostate Imaging and Image Guided Therapy, University of Chicago, 5841 South Maryland Avenue, Chicago, IL, 60637, USA. .