Contrast enhanced ultrasound (CEUS) with parametric imaging after irreversible electroporation (IRE) of the prostate to assess the success of prostate cancer treatment.

ABSTRACT

AIM: The aim of this study was to assess the success of irreversible electroporation (IRE) in prostate cancer and to differentiate between reactive changes and tumor. MATERIAL AND METHODS: This is a retrospective pilot study of 50 patients after irreversible electroporation (IRE) in prostate cancer between 50-79 years (mean age 65 years). Each patient received a transabdominal sonography using a 1-6 MHz convex matrix probe. Contrast-enhanced ultrasound (CEUS) was performed after i.v. bolus injection of 2.0 ml sulphur hexafluoride microbubbles. DICOM loops were continuously stored up to one minute. Parametric images were calculated by integrated perfusion analysis software. A comparison was drawn to a follow-up MRI six months after ablation. RESULTS: While 13 patients showed local recurrence, 37 patients were successfully treated, meaning no local recurrence within six months after ablation. 18 patients showed signs of prostatitis after IRE. Tumorous changes were visually characterized by dynamic early nodular hypervascularization with fast and high wash-in. Correspondingly, nodular red and yellow shades were seen in parametric imaging. All patients with remaining tumor were correctly identified with CEUS and parametric imaging. After IRE there is a relevant decrease in tumor microcirculation in all patients, as seen in more purple shades of the prostate. The sensitivity for detecting residual tumor with CEUS compared to MRI was 76%, the specificity was 81%. The corresponding positive predictive value (PPV) was 73% and the negative predictive value (NPV) was 83%. CONCLUSION: CEUS and parametric imaging enable a critical analysis of post-ablation defects after IRE for prostate cancer even with a transabdominal approach. Remaining tumor can be detected with the help of pseudo-colors.