The application of three-dimensional contrast-enhanced ultrasound to measure volume of affected tissue after HIFU treatment for localized prostate cancer

Introduction: Adequate monitoring of volume and location of affected tissue might provide helpful information when performing localized ablative thera py for prostate cancer. We hypothesize that the change in blood flow patter ns after therapy in comparison to the blood flow pattern prior to therapy c an be used to locate and quantify the amount of affected tissue due to the therapy. We describe the use of three-dimensional contrast-enhanced power D oppler ultrasound (3D-CE-PDU) to determine its additive value to visualize the extent of tissue defects created by high-intensity focused ultrasound ( HIFU) in correlation with the histopathology of the prostatectomy specimen. Materials and Methods: Nine patients with biopsy-proven localized prostate cancer, who gave informed consent, were included in the protocol. HIFU trea tment was performed 1 week in advance of radical retropubic prostatectomy ( RRP) as part of a protocol to study the value of HIFU treatment as local ab lative therapy for clinical T1-2N0M0 prostate carcinoma. 3D-CE-PDU was perf ormed 1 day prior to unilateral HIFU treatment of the affected lobe on biop sy indication and 1 day before RRP using 2.5 g Levovist(R) (Schering AG, Ge rmany) microbubble ultrasound contrast agent and a Kretz(R) Voluson 530D ul trasound scanner (Kretztechnik AG, Austria). Ultrasound data and pathology whole-mount sections were stored digitally to allow off-line processing. Hu man interpretations of HIFU measurements in three-dimensional ultrasound da ta were based on gray-scale information (local increase in gray level) in c ombination with power Doppler mode (absence of blood flow). Histopathologic al analysis of the whole-mount section revealed a broad band of hemorrhagic necrosis in the HIFU-treated area. Using both the ultrasound data and the pathology sections, the total volume of the prostate and of the HIFU-treate d area was measured, and relative volumes were obtained. Results: Visual inspection of the three-dimensional reconstruction of contr ast-enhanced Doppler measurements revealed the HIFU-affected prostate tissu e by the absence of a blood flow pattern. Paired t tests of the relative HI FU volume indicated that Doppler results (mean 21.7%, SD +/- 10.8%) differe d from the pathology results (mean 32.6%, SD +/- 16.0%), but a good correla tion was found between the relative pathology HIFU volume (Pearson correlat ion r = 0.94, p<0.0015) and mean 3D-CE-PDU HIFU, Closer inspection of the p athology specimen revealed that the outer ring of the macroscopic hemorrhag ic necrosis overestimated the actually dead tissue. On microscopy, the bord er of dead tissue appeared to be 1-2 mm inside the macroscopically identifi ed red hemorrhagic band. 3D-CE-PDU HIFU volumes indicated by the single obs ervers were not statistically different and correlated very well (Pearson c orrelation r = 0.98, p<0.001). Conclusion: The results illustrate that 3D-CE-PDU is a promising method to determine the size of the defect of HIFU ablative therapy for prostate carc inoma. The absence of blood flow indicated by three-dimensional power Doppl er ultrasound images reflects affected tissue after HIFU treatment, and vol ume measurements of these areas can quantify the amount of affected tissue. Copyright (C) 2000 S. Karger AG. Basel.