Comparison of numerical calculations with phantom experiments and clinical measurements

Three-dimensional models, while fundamentally desirable in hyperthermia treatment simulation, are only beginning to emerge and may take a number of years to perfect for routine clinical use. Two dimensional calculations, on the other hand, can be efficiently performed on today's inexpensive computer workstations; however, the accuracy of two-dimensional models in the pretreatment planning context is questionable. This paper investigates the ability of a general two-dimensional finite element model to predict power deposition patterns in phantoms and temperature distributions during actual clinical treatments. The experiments and simulations have been performed for an annular phased array (APA) operating at 70 MHz. Comparisons between model predictions and measurements show that quantitative agreement occurs in phantoms containing moderate complexities in heterogeneity, but that only qualitative agreement appears possible in clinical treatments. However, the results suggest that the lack of blood flow information may contribute as much, if not more, to the uncertainties in the clinical predictions than the two-dimensional nature of the model itself.