Correlation between central zone perfusion defects on gadolinium-enhanced MRI and intraprostatic temperatures during transurethral microwave thermotherapy

Background and Purpose: The likelihood of success of thermoablation of pros tatic hyperplasia depends on delivering an optimal thermal dose, but data o n the temperatures achieved with these methods are few. We sought to develo p a noninvasive method for monitoring intraprostatic heat distribution. Patients and Methods: Thirteen patients ranging from 50 to 76 (mean 61.3 +/ - 8.1) years were enrolled in this study, all of whom had evidence of obstr uction by uroflowmetry and pressure-flow studies. The mean total volume of the gland was 40.3 +/- 13.1 cc, while the mean adenoma volume was 20.4 +/- 10.1 cc, as estimated by preoperative transrectal ultrasonography, All the patients were treated with the Urologix Targis device for at least 45 minut es. Continuous temperature mapping was performed during the therapy using s patially dispersed thermosensors at 16 prostatic sites. The patients were e valuated 5 to 12 days postoperatively with MRI of the prostate utilizing a pelvic phased-array coil at 1.5 T. Results: Postprocedure MRI demonstrated a mean perfusion defect of 28.1 +/- 2.1% and 63.6 +/- 34% of the total gland and transition zone volumes, resp ectively. The mean anteroposterior (AP) and transverse diameters of the per fusion defects, as measured on the MRI images, were 29.2 +/- 5.2 mm and 32. 7 +/- 5.9 mm, respectively. The maximum mean peak temperatures were 66.8 +/ - 13 degreesC and were recorded at 4 mm from the urethra. No temperatures h igher than 45 degreesC were recorded beyond 15 mm on either side of the ure thra in the AP direction and beyond 16 mm on either side of the urethra in the transverse diameter. This perfusion defect was persistent for 27.7 +/- 5.2 mm in the superoinferior diameter, which is equivalent to the length of the antenna (28 mm). Conclusion: Perfusion defect diameters as measured by postprocedure MRI acc urately represent the prostatic tissues exposed to temperatures of greater than or equal to 45 degreesC for 45 minutes or more. So, MRI provides an ac curate, noninvasive method for screening the effective heat pattern generat ed in the prostate during transurethral microwave thermotherapy.