Coagulative interstitial laser-induced thermotherapy of benign prostatic hyperplasia: Online imaging with a T2-weighted fast spin-echo MR sequence - Experience in six patients

PURPOSE: To determine if hypointense lesions clearly outline on T2-weighted fast spin-echo (SE) magnetic resonance (MR) Images obtained during coagula tive interstitial laser-induced,thermotherapy (LITT) of a prostate with ben ign hyperplasia. MATERIALS AND METHODS: In six patients with benign prostatic hyperplasia (B PH), 12 LITT treatments were followed online with repetitive axial T2-weigh ted fast;SE imaging (repetition time, 3,700 msec; echo time, 138 msec; acqu isition time,19 seconds), Development, time course, correlation with inters titial tissue temperature, and diameters of hypointense lesions around the laser diffuser tip were investigated. Lesion diameters on T2-weighted image s acquired during LITT were compared with diameters of final lesions on T2- weighted images and unperfused lesions on enhanced T1-weighted SE images ob tained at the end of therapy. RESULTS: Hypointense lesions developed within 20-40 seconds of LITT. Averag e correlation coefficients between interstitial temperature development and signal intensity development were 0.92 during LITT and 0.90 after LITT. Re gression slopes were significantly steeper during LITT (0.67% signal intens ity change per degree Celsius) than after LITT (0.47% per degree Celsius; P =.038). Lesions remained visible after LITT for all procedures. Average ma ximum diameters of lesions were 1-3 larger during LITT than after LITT (P = .0006-.019). CONCLUSION: Repetitive T2-weighted fast SE MR imaging during interstitial c oagulative LITT of BPH demonstrates the development of permanent hypointens e prostate lesions. However, posttherapeutic lesion diameters tend to be ov erestimated during LITT.