Fig. 2
From: Implementation and experimental evaluation of Mega-voltage fan-beam CT using a linear accelerator
a The 3-degree polynomial fitting between the measured linear attenuation coefficient (LAC) and the corresponding penetration depth. The arrow indicates the estimated un-hardened LAC (i.e. 0.1380 1/cm) at 0 cm penetration depth. b The 3-degree polynomial fitting between the measured solid water attenuation and the corrected attenuation. The formula of the polynomial model is shown in Eq. (2)