What ' s known on the subject? and What does the study add? Focal ablation of prostate cancer by laser interstitial thermotherapy (LITT) consists of including a tissue necrosis by thermotherapy using diffusing laser fi tres located in the prostate. Because of its compatibility with magnetic resonance imaging, LITT offers the advantage in terms of lesion targeting and real-time monitoring processing over other minimally invasive techniques using transrectal ultrasound. Moreover, the feasibility of MRI thermometry allows real-time monitoring of LITT treatment.Our study proves reproducibility of laser interstitial thermotherapy at 980 nm in homogenous prostate cancer model. OBJECTIVE• To examine the feasibility and reproducibility of laser interstitial thermotherapy (LITT) as a minimally invasive method for the treatment of prostate cancer. MATERIALS AND METHODS• Heterotopic tumours of prostatic adenocarcinoma (Dunning R3327-AT2) were induced in 10 male Copenhagen rats.• After preoperative magnetic resonance imaging (MRI), a 10-mm cylindrical diffusing fi bre developed by our research department was inserted under ultrasonographic guidanceinto the tumour.• LITT was performed with a 980-nm diode laser (power 5 W) for75 s (fl uence rate of 1145 J/cm 2 ).• Non-enhanced T2-weighted and dynamic gadolinium-enhanced T1-weighted MRI examinations were performed at baseline, 1 and 48 h after the procedure and correlated with histological fi ndings. RESULTS• The necrosis lesions induced by LITT were visible on MRI.• The mean (SD) ellipsoid necrosis volumes were 0.748 (0.075) mL at 1 h and 0.982 (0.052) mL at 48 h after the LITT procedure, and signifi cantly different ( P < 0.001).• Histological analysis showed a strong correlation ( r = 0.87) with the mean necrosis volume obtained by MRI at 48 h after LITT. CONCLUSIONS• In a prostatic adenocarcinoma model, 980-nm LITT induces reproducible necrosis volumes.• Further characterization of the response to LITT in an animal model and in human tissues will be important in establishing the effi cacy of the procedure for prostate cancer focal therapy.
Endovenous laser treatment (ELT) has been proposed as an alternative in the treatment of reflux of the great saphenous vein. Before the procedure, peri-saphenous subcutaneous tumescent saline solution infiltration is usually performed. However, diffusion of this tumescent fluid is rapidly observed and can potentially reduce the efficacy as a heat sink. External skin cooling with cold air was proposed as an alternative solution. The objective of this study is to compare endovenous laser treatment without and with air cooling by realistic numerical simulations. An optical-thermal damage model was formulated and implemented using finite element modeling. The general model simulated light distribution using the diffusion approximation of the transport theory, temperature rise using the bioheat equation, and laser-induced injury using the Arrhenius damage model. Parameters, used in clinical procedures, were considered: power, 15 W; pulse duration, 1 s; fiber pull back, 3-mm increments every second; cold air applied in continuous mode during ELT; and no tumescent anesthesia. Simulations were performed for vein locations at 5, 10, and 15 mm in depth, with and without air cooling. For a vein located at 15 mm in depth, no significant difference was observed with and without cooling. For a vein located at 10 mm in depth, surface temperature increase up to 45 °C is observed without cooling. For a vein located at 5 mm, without cooling, temperature increase leads to irreversible damage of dermis and epidermis. Conversely, with air cooling, surface temperature reaches a maximum of 38 °C in accordance with recordings performed on patients. ELT of the incompetent great saphenous vein with external air cooling system is a promising therapy technique. Use of cold air on the skin continuously flowing in the area of laser shot decreased significantly the heat extent and the thermal damage in the perivenous tissues and the skin.
In this study, a good correlation was established between simulation and ex vivo experiments of LITT for fibroadenoma breast cancer.
When accounting for the shrinkage effect of excision of cutaneous tissues, a good correlation can be established between the simulation and the histological analysis results.
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