Apr. 17, 2008: Review of In-Vivo Canine Experiment

Apr. 17, 2008: Review of In-Vivo Canine Experiment

The DDDAS control system has successully demonstrated control over the bioheat transfer. VNC recordings of the treatment data are posted in 5 minute intervals below. The time interval 13_55 is when the optimal control portion of the treatment protocol begins. A visualization of the calibrated laser position may also be seen.

A late time treatment image of the control system applied to in-vivo laser treatment of canine prostate is shown in Figure 1; the entire duration of the treatment was 18 minutes. As shown, under Ideal Treatment, the goal was to demonstrate that the computational model could control the bioheat transfer and heat a region of 1.2cm in diameter to 60°C. As illustrated in the power history, the treatment protocol is divided into four stages. During the first stage, the biological domain is pulse heated and MRTI thermal image data is acquired for the heating as well as the cooling. The second stage of the treatment accounts for the time span of the calculations that use the imaging data for model calibration. The third stage accounts for the time delay to compute the optimal temperature/damage/HSP heating protocol. The laser is prevented from entering a standby mode through a series of keep-alive pulses during the computational phase. In the fourth and final stage, the optimal laser control parameters are applied to the biological domain. In the event of the detection of an unexpectedly high temperature within the biological domain, a fail-safe shutoffs the laser power. For this particular trial, the perfusion, thermal conductivity, absorption coefficient, and laser position were calibrated. Results of the real-time calibration computations moved the laser tip 5mm from where the initial position was thought to be. Cutlines illustrating the temperature as function of distance are taken through the thermal imaging data and finite element predictions for comparison. The location of the cutline is illustrated in the Anatomy and Thermal Images. The bottom right cutline shows good agreement between the desired treatment plan, the computation prediction, and the experimentally measured MRTI temperature field.

Figure 1: Depicted is the real-time visualization provided during the laser treatment. The anatomy, thermal images, FEM temperature prediction, and the power history are shown. The field of view in the Ideal Treatment window is 240x240mm. Other windows zoom in to focus on the prostate. The degree of noise prevalent is clearly seen in the cutlines of the thermal imaging. The power history shown was used in the treatment.

Figure 2 compares the laser power history recorded on the visualase to the expected power control by hp3d. The actual and expect show very good agreement.

Figure 2: A comparision between the expected and actual power history as a function of time is shown. The power history was extracted from the log files of the visualase for comparison with the expected power profile from the FEM code.