Development of stereotactically guided laser interstitial thermotherapy ofbreast cancer: In situ measurement and analysis of the temperature field in ex vivo and in vivo adipose tissue

Background and Objective: The size (0.5-1.0 cm) of early nonpalpable breast tumors currently detected by mammography and confirmed by stereotactic cor e biopsy is of the order of the penetration depth of near infrared photons in breast tissue. In principle, stereotactically biopsied tumors, therefore , could be safely and efficiently treated with laser thermotherapy. The aim of the current study is to confirm the controlled heating produced by clin ically relevant power levels delivered with an interstitial laser fiber opt ic probe adapted for use with stereotactic mammography and biopsy procedure s. Study Design/Materials and Methods: Temperature increases and the resultant thermal field produced by the irradiation of ex vivo (porcine and human) a nd in vivo (porcine) tissue models appropriate to the treatment of human br east tissue by using cw Nd:YAG laser radiation delivered with a interstitia l fiber optic probe with a quartz diffusing tip, were recorded with an arra y of fifteen 23-gauge needle thermocouple probes connected to a laboratory computer-based data acquisition system, Results: By using a stepwise decreasing power cycle to avoid tissue charrin g, acceptably symmetric thermal fields of repeatable volumetric dimensions were obtained. Reproducible thermal gradients and predictable tissue necros is without carbonization could be induced in a 3-cm-diameter region around the fiber probe during a single treatment lasting only 3 minutes, The time- dependences of the temperature rise of the thermocouples surrounding the LI TT probe were quantitatively modeled with simple linear functions during th e applied laser heating cycles. Conclusion: Analysis of our experimental results show that reproducible, sy mmetric and predictable volumetric temperature increases in time can be rel iably produced by interstitial laser thermotherapy. (C) 2000 Wiley-Liss, In c.