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


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).


CONCLUSIONS
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.
Mueller-Lisse
U G
UG
Department of Diagnostic Radiology, Klinikum Grosshadern, University of Munich Ludwig Maximilian, Germany.
Thoma
M
M
Faber
S
S
Heuck
A F
AF
Muschter
R
R
Schneede
P
P
Weninger
E
E
Hofstetter
A G
AG
Reiser
M F
MF
D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D007430:Intraoperative Care; D017075:Laser Coagulation; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009862:Online Systems; D011467:Prostate / Q000473:pathology*; D011470:Prostatic Hyperplasia / Q000473:pathology / Q000601:surgery*; D013997:Time Factors