Table 2.

Observed dose difference causes and established course of action.

Type of Problem	Problem	Solution
Patient deform ation & set up	Anatomical variation (weight, oedema, gas, etc..…)	Verify SSD, thicknesses and replan plan with new CT data if necessary
	Unexpected object in the beam Patient setup	Review patient setup and replan acquisition
Treatment plan & choice of points of interest	Point in low‐dose area
	Find new point of interest and recalculate transit dose
		Point in high‐dose gradient
		Point in high‐dose gradient
		Point close to tongue‐and‐groove area
Point close to an heterogeneity interface
Machine & EPID	Acquisition interrupted before end of beam irradiation	Replan acquisition
	EPID in wrong position	Calibrate EPID positioning and replan acquisition
	Drift of EPID calibration in dose or machine output	Proceed to a new calibration