ENDOSCOPIC LASER-ABLATION OF THE PROSTATE - MR APPEARANCES DURING ANDAFTER TREATMENT AND THEIR RELATION TO CLINICAL OUTCOME

OBJECTIVE. Endoscopic laser ablation is a new treatment for benign pro static hypertrophy. The objectives of this study were to determine the appearances of the prostate on MR images obtained during, 1 week afte r, and 3 months after this procedure and to determine if a correlation exists between the MR findings and the clinical outcome. Such appeara nces could then be used to guide the application of laser energy durin g the procedure in order to optimize the clinical result. SUBJECTS AND METHODS. Eight consecutive men 58-74 years old with symptoms of bladd er outflow obstruction caused by benign prostatic hypertrophy underwen t endoscopic laser ablation of the prostate under spinal or epidural a naesthesia. Imaging was done on a 0.5-T Picker Asset system with an en dorectal receiver coil and conventional T1-weighted spin-echo, T2-weig hted spin-echo, and gradient-recalled-echo sequences. T1-weighted magn etization transfer images were obtained in three patients. Images were obtained preoperatively, after ablation of the left-sided quadrants, immediately after completion of the procedure, and 1 week and 3 months later. Preoperative and 3-month postoperative symptom scores, peak ur ine flow rates, and bladder residual volumes were studied. Images were visually assessed for signal-intensity changes and the presence of ca vitation by three radiologists in conference. The results were quantit atively analyzed by measuring prostatic volumes on the gradient-recall ed-echo images and by measuring the width and area of regions of signa l-intensity change on the T2-weighted images. RESULTS. MR images made immediately after treatment showed an increase in the volume of the pr ostate (mean, 34%) and a poorly defined, low-signal-intensity region a round the urethra on the TP-weighted images in six patients. This prob ably represented coagulative necrosis. The prostate was smaller on MR images made 1 week after treatment, and after 3 months the prostate re turned to its preoperative size. After 1 week, the low-signal-intensit y periurethral region on the T2-weighted images was less obvious, and at 3 months it was replaced in four patients by a well-demarcated low- signal-intensity ring on the T2-weighted and gradient-recalled-echo im ages. No evidence of cavity formation in the prostate was seen on MR i mages in any patient. Symptom scores and peak urinary flow rates impro ved after 3 months, with a significant difference between the mean inc rease in symptom scores in the patients with and without the periureth ral changes seen immediately after treatment. However, we found no sig nificant difference between the mean increase in peak urinary flow rat es in the patients with and without periurethral changes seen either i mmediately or at 3 months after treatment. No statistically significan t correlation was found between the amount of prostatic swelling and t he improvement in symptom scores or peak urine flow rates. CONCLUSION. In patients who have had laser prostatectomy, MR imaging shows signif icant immediate glandular swelling, which may account for the delayed improvement in symptoms reported with this technique. The presence of the periurethral changes immediately after treatment was correlated wi th a subsequent improvement in symptom scores. After 3 months, no cavi ty could be seen in the prostate. This may account for the poorer long -term clinical outcome reported with endoscopic laser ablation of the prostate compared with transurethral prostatectomy.