Diffusion-weighted Imaging for Predicting Ablation
Title: Intraprocedural Diffusion-weighted Imaging for Predicting Ablation Zone during MRI-guided Focused Ultrasound of Prostate Cancer
Abstract:
Purpose
To compare diffusion-weighted imaging (DWI) with thermal dosimetry as a noncontrast method to predict ablation margins in individuals with prostate cancer treated with MRI-guided focused ultrasound (MRgFUS) ablation.
Materials and Methods
This secondary analysis of a prospective trial (ClinicalTrials.gov no. NCT01657942) included 17 participants (mean age, 64 years ± 6 [SD]; all male) who were treated for prostate cancer using MRgFUS in whom DWI was performed immediately after treatment. Ablation contours from computed thermal dosimetry and DWI as drawn by two blinded radiologists were compared against the reference standard of ablation assessment, posttreatment contrast-enhanced nonperfused volume (NPV) contours. The ability of each method to predict the ablation zone was analyzed quantitively using Dice similarity coefficients (DSCs) and mean Hausdorff distances (mHDs).
Results
DWI revealed a hyperintense rim at the margin of the ablation zone. While DWI accurately helped predict treatment margins, thermal dose contours underestimated the extent of the ablation zone compared with the T1-weighted NPV imaging reference standard. Quantitatively, contour assessment between methods showed that DWI-drawn contours matched postcontrast NPV contours (mean DSC = 0.84 ± 0.05 for DWI, mHD = 0.27 mm ± 0.13) better than the thermal dose contours did (mean DSC = 0.64 ± 0.12, mHD = 1.53 mm ± 1.20) (P < .001).
Conclusion
This study demonstrates that DWI, which can visualize the ablation zone directly, is a promising noncontrast method that is robust to treatment-related bulk motion compared with thermal dosimetry and correlates better than thermal dosimetry with the reference standard T1-weighted NPV.
Keywords: Interventional-Body, Ultrasound–High-Intensity Focused (HIFU), Genital/Reproductive, Prostate, Oncology, Imaging Sequences, MRI-guided Focused Ultrasound, MR Thermometry, Diffusion weighted Imaging, Prostate Cancer
ClinicalTrials.gov Identifier no. NCT01657942
Summary
Diffusion-weighted imaging visualized the ablation zone directly in participants with prostate cancer who underwent MRI-guided focused ultrasound ablation, thus correcting for prior ablation-induced motion, and correlated better than thermal dosimetry with the reference standard posttreatment postcontrast nonperfused ablation volume.
Key Points
- ■ During ablative treatment, prostate motion and edema were observed in all 17 study participants, reducing accuracy of thermal dosimetry to predict treatment boundaries.
- ■ Intraoperative diffusion-weighted images showed increased signal intensity with hyperintense rim demarcating the ablation zone.
- ■ The ablation zone delineated by diffusion-weighted imaging more accurately corresponded to the reference standard ablation zone using T1-weighted contrast-enhanced imaging compared with the thermal dose–delineated volume (mean Dice similarity coefficient 0.84 ± 0.05 [SD] vs 0.64 ± 0.12 and mean Hausdorff distance 0.27 mm ± 0.13 vs 1.53 mm ± 1.20, respectively; P < .001).
Citation:
Rachelle R. Bitton, Wei Shao, Yosef Chodakeiwitz, Ryan L. Brunsing, Geoffery Sonn, Mirabela Rusu, and Pejman Ghanouni, “Intraprocedural Diffusion-weighted Imaging for Predicting Ablation Zone during MRI-guided Focused Ultrasound of Prostate Cancer”, Radiology: Imaging Cancer, 2024, 6:5
