Finite element analysis was utilized to segment MRI images from a patient with glioblastoma (GBM) and a concomitant epidural hematoma to assess the delivery of tumor treating fields as measured by specific absorption rate (SAR), current density (CD), and electric field (E-Field). 

Tumor Treating Fields (TTFields) therapy has been approved since 2015 as an effective treatment for glioblastoma by impairing tumor cell mitosis with alternating electric fields at 200 kHz.  These fields are applied to the head locally from electrical transducer arrays on the scalp that induce less adverse reactions in comparison to conventional treatments from chemotherapy, radiotherapy, and surgery. As about 60-70% of GBM patients undergo surgical resection of their gross tumor volume (GTV), it is important to understand how post-surgical anatomical changes in the resection cavity such as residual hematoma affect the delivery of TTFields.

Semi-automatic segmentation and finite element analysis workflow was performed in alignment with protocol developed by Lok et al. (PMID: 28544575) and Timmons et al. (PMID: 29023236).  Analysis of SAR, CD, and E-Field distributions in both the hematoma and GTV was performed using varying hematoma electrical conductivities.  

E-Field delivery to the GTV remained relatively constant while delivery to the hematoma exhibited an inverse sigmoidal behavior as a function of hematoma conductivity.  SAR of the GTV also remained relatively constant, whereas the hematoma exhibited a peak SAR near a conductivity value of 0.01 S/m.  Similarly, CD of the GTV also remained relatively constant while the hematoma exhibited a parabolic trend as a function of hematoma conductivity with a local minimum around 0.1 S/m. 

The conductivity of an epidural hematoma appears to alter the delivery of TTFields within itself but not significantly affect an adjacent GTV.