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Cranial Sutures Alter Computational Models of Transcranial Electrical Stimulation
Alistair Carroll1, Caroline Rae2, Donel Martin3
1Discipline of Psychiatry, University of New South Wales, Sydney Australia.
Background:
ROAST (Realistic vOlumetric-Approach-based Simulator for Transcranial electric stimulation) has been increasingly utilized to inform studies of transcranial electrical stimulation (tES). The precision of ROAST is dependent on anatomical accuracy.
Objectives:
The aims of the study were to compare using only T1 magnetic resonance images in ROAST (T1 model), with a combination of T1 and T2 magnetic resonance images (T1 and T2 model) and to model the electrical fields generated by tES with commonly used ECT montages: bitemporal, bifrontal, and right unilateral and varying the skull conductivities (based on the electrode position) and including cranial sutures.
Methods:
The "T1 model" was selected for computational modeling. The skull conductivity was varied from the "default setting in ROAST" (0.01S/m) to that of temporal bone (0.0038S/m) and frontal bone (0.0126S/m). "Disc" electrodes (5 cm in diameter) were applied with 1 mA of current. "Pad" electrodes, 0.1 mm high and 40 mm wide, were positioned over the squamous suture, coronal suture and sagittal suture and the skull conductivity changed to approximate suture conductivity (0.32S/m).
Results:
The "T1 model" differed from the "T1 and T2 model," which resulted in variable electric fields reaching individual tissue layers. Changing skull conductivity and simulating the cranial sutures resulted in changes to the electric current reaching the cortical and subcortical structures with the later having a greater impact.
Conclusions:
This study demonstrates the importance of anatomically accurate head models in ROAST computational modeling of tES. Varying the skull conductivity based on studies in vivo and including cranial sutures is imperative for more realistic predictions of electric field and reproducibility.
