Perioperative prediction by MRI of prostate volume six to twelve months after laser-induced thermotherapy of benign prostatic hyperplasia

The purpose of this study was to predict prostate volume outcome 6-12 months after interstitial, laser-induced thermotherapy (LITT) for benign prostatic hyperplasia (BPH) on the basis of prostate magnetic resonance (MR) images obtained within 48 hours before and after LITT. Twenty patients (age, 64.2 +/- 7.4 years) with symptomatic BPH had LITT of the transitional zone of the prostate. MRI was performed within 48 hours before and after LITT, and 6-12 months after LITT (late follow-up). MRI included axial and sagittal T2-weighted fast spin-echo (FSE) images and contrast-enhanced, axial T1-weighted images. Volumes of different prostatic compartments (total prostate, transitional zone, peripheral zone, LITT lesions) were measured by planimetry. Subtraction of LITT lesion volume less than 48 hours after LITT from total and transitional zone volume before LITT, respectively, predicted respective prostatic volumes at late follow-up. Pearson correlations of predicted and measured total prostate and transitional zone volumes were 0.972 and 0.975, respectively. Total prostate volume at late follow-up was accurately predicted (difference, -0.5 +/- 5.7 cc; P = 0.6981, two-tailed paired t-test). Transitional zone volume was underestimated (difference, -3.1 +/- 4.7 cc; P = 0.0075). Peripheral zone volume was overestimated (difference, 2.6 +/- 3.5 cc; P = 0.0034). Perioperative MRI allows accurate prediction of prostate volume 6-12 months after LITT for BPH. Underestimation of transitional zone volume may be due to ongoing growth of BPH. LITT appears to affect peripheral zone tissue outside the target region. J. Magn. Reson. Imaging 2001;13:64-68.