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. Author manuscript; available in PMC: 2018 Sep 1.
Published in final edited form as: J Neuroimaging. 2017 Mar 7;27(5):453–460. doi: 10.1111/jon.12432

Figure 4.

Figure 4

Balloon-Inflation algorithm

Note. A given point on the scalp (P, blue asterisk) is projected onto the cortical surface (gray dots). The 200 points on the cortical surface closest to P are selected (green dots), and their centroid is found (Pce, purple asterisk). A virtual rod (blue cylinder) is passed from P, through Pce, to the cortical surface (green and gray dots). The three closest cortical surface points within the virtual rod are chosen, and their centroid is determined as the cortical projection point (Pc, orange asterisk). Reprinted from Neuroimage, Vol 26, Okamoto M, Dan I., T Automated cortical projection of head-surface locations for transcranial functional brain mapping, pp 18–28, Copyright (2005),23 with permission from Elsevier.