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Coagulative Interstitial Laser-induced Thermotherapy of Benign Prostatic Hyperplasia: Online Imaging with a T2-weighted Fast Spin-Echo MR Sequence—Experience in Six Patients

¹ Departments of Diagnostic Radiology (U.G.M.L., M.T., S.F., A.F.H., M.F.R.)
² Urology (U.G.M.L., R.M., P.S., A.G.H.)
³ Anaesthesiology (E.W.), Klinikum Grosshadern, University of Munich "Ludwig Maximilian," Germany.

PURPOSE: To determine if hypointense lesions clearly outline on T2-weighted fast spin-echo (SE) magnetic resonance (MR) images obtained during coagulative interstitial laser-induced thermotherapy (LITT) of a prostate with benign hyperplasia.

MATERIALS AND METHODS: In six patients with benign prostatic hyperplasia (BPH), 12 LITT treatments were followed online with repetitive axial T2-weighted fast SE imaging (repetition time, 3,700 msec; echo time, 138 msec; acquisition time, 19 seconds). Development, time course, correlation with interstitial tissue temperature, and diameters of hypointense lesions around the laser diffusor tip were investigated. Lesion diameters on T2-weighted images acquired during LITT were compared with diameters of final lesions on T2-weighted images and unperfused lesions on enhanced T1-weighted SE images obtained at the end of therapy.

RESULTS: Hypointense lesions developed within 20–40 seconds of LITT. Average correlation coefficients between interstitial temperature development and signal intensity development were 0.92 during LITT and 0.90 after LITT. Regression slopes were significantly steeper during LITT (0.67% signal intensity change per degree Celsius) than after LITT (0.47% per degree Celsius; P = .038). Lesions remained visible after LITT for all procedures. Average maximum diameters of lesions were 1–3 mm larger during LITT than after LITT (P = .0006–.019).

CONCLUSION: Repetitive T2-weighted fast SE MR imaging during interstitial coagulative LITT of BPH demonstrates the development of permanent hypointense prostate lesions. However, posttherapeutic lesion diameters tend to be overestimated during LITT.

Index terms: Lasers, interstitial therapy, 844.1269 • Magnetic resonance (MR), guidance, 844.316 • Magnetic resonance (MR), rapid imaging, 844.121416 • Prostate, hyperplasia, 844.316

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