A new finite element approach for near real-time simulation of light propagation in locally advanced XXXX .

@entity1 @entity135 @entity1417 @entity5
BACKGROUND AND OBJECTIVES: Several clinical studies suggest that interstitial photodynamic therapy (I-PDT) may benefit @entity1 with locally advanced @entity135 (LAHNC). For I-PDT, the therapeutic light is delivered through optical fibers inserted into the target @entity5 . The complex anatomy of the head and neck requires careful planning of fiber insertions. Often the fibers' location and @entity5 optical properties may vary from the original plan therefore pretreatment planning needs near real-time updating to account for any changes. The purpose of this work was to develop a @entity1417 ( @entity1417 ) approach for near real-time simulation of light propagation in LAHNC. METHODS: Our previously developed @entity1417 for modeling light propagation in skin tissue was modified to simulate light propagation from interstitial optical fibers. The modified model was validated by comparing the calculations with measurements in a phantom mimicking @entity5 optical properties. We investigated the impact of mesh element size and growth rate on the computation time, and defined optimal settings for the @entity1417 . We demonstrated how the optimized @entity1417 can be used for simulating light propagation in two cases of LAHNC amenable to I-PDT, as proof-of-concept. RESULTS: The modified @entity1417 was in agreement with the measurements (P   =   0.0271). The optimal maximum mesh size and growth rate were 0.005-0.02   m and 2-2.5   m/m, respectively. Using these settings the computation time for simulating light propagation in LAHNC was reduced from 25.9 to 3.7   minutes in one case, and 10.1 to 4   minutes in another case. There were minor differences (1.62%, 1.13%) between the radiant exposures calculated with either mesh in both cases. CONCLUSIONS: Our @entity1417 approach can be used to model light propagation from diffused optical fibers in complex heterogeneous geometries representing LAHNC. There is a range of maximum element size (MES) and maximum element growth rate (MEGR) that can be used to minimize the computation time of the @entity1417 to 4   minutes. Lasers Surg. Med. 47:60-67, 2015.    2015 Wiley Periodicals, Inc.
