Optimizing Transducer array placement when treating pancreatic cancer using Tumor Treating Fields (TTFields)

Introduction

Tumor Treating Fields (TTFields) are a cancer-treatment-modality that uses alternating electric fields in the intermediate frequency (100-300 kHz). TTFields are delivered in two orthogonal directions using 2 pairs of transducer arrays placed on the skin.

Preclinical studies suggest that the effect of TTFields is intensity-dependent and that the field distribution within the body depends on the location of the arrays on the skin. Therefore, there is a need to develop principles for personalizing array placement to optimize TTFields distribution when treating pancreatic cancer. In particular, it is necessary to develop guidelines for array placement that maximize field intensities in the region of disease, whilst minimizing the size of the arrays placed on the body. Minimizing array size is important to enable periodic shifting of the arrays for potentially reducing skin irritation associated with TTFields therapy. Here we present a systematic study investigating how the location and size of the arrays on the abdomen influences the field distribution.

Methods

To simulate delivery of TTFields to the abdomen, we used 3 realistic computerized models (from ZMT_Zurich) of: a male (DUKE 3.0); b) , a female (ELLA 3.0); and an obese male (FATS 3.0). Different arrays layouts utilizing combinations of arrays with either 13 or 20 disks per-array were placed over the upper 6 standard abdominopelvic of the models, and field intensity distributions within these regions were evaluated. In order to generate TTFields, an alternating voltage at a frequency of 150 KHz was imposed on the outer surfaces of the disks of each pair of arrays. The voltage was set to deliver a current of 200 mA peak to peak per-disk (total current 2.6 A for 13-disk arrays, 4.0 A for 20-disk arrays). The simulations were performed using ZMT`s Sim4Life V3.0 electro-quasi-static solver.

Results

The large arrays generally generated higher field intensities than the small arrays. However, On ELLA and DUKE, the large arrays covered most of the skin around the abdomen, leaving little room for shifting the arrays. On DUKE and ELLA, when using small arrays, the average field intensity in the abdominopelvic region over which the arrays were placed was above the therapeutic threshold of 1 V/cm.

Conclusion

This work shows that TTFields array placement can be optimized to deliver TTFields at therapeutic intensities to specific abdominopelvic regions. Tailoring the size and position of the arrays based on disease site and patient size may help to improve overall treatment outcome