Comparing cone-beam CT intensity correction methods for dose recalculation in adaptive intensity-modulated photon and proton therapy for head and neck cancer

Figures & data

Figure 1. 2D IMRT (top part) and IMPT (bottom part) dose distributions (color-wash) on the investigated CT datasets for PatCA6 in an upper (top row of each part) and lower (bottom row) axial slice. The low and high dose PTVs (green and blue structures), as well as the spinal cord planning organ at risk volume (PRV, red structure) are also shown.

Figure 2. Comparison of IMRT (A, top) and IMPT (B, bottom) dose/volume parameters for vCT (red, diamonds) and CBCT_LUT (blue, circles) dose recalculations. The dosimetric parameters correspond to the left, V₉₅ to the right axis. For each parameter, the difference to the rpCT reference is given for every patient considering the total dose of the SIB treatment phase. For the optical system (only three patients) no boxplots were generated. For display purposes, data points below -5Gy difference are indicated by the arrow but not shown.

Table I. Gamma-index and proton range pass-rates for vCT and CBCT_LUT dose recalculations.

	Gamma-index pass-rates				BEV range pass-rates
	IMRT		IMPT		IMPT
	vCT (%)	CBCTLUT (%)	vCT (%)	CBCTLUT (%)	vCT (%)	CBCTLUT (%)
PatCA1–6	95 (91,97)	89 (85,93)	90 (76,95)	80 (74,88)	93 (88,95)	87 (80,94)
PatCR1–3	96 (89,99)	97 (92,99)	95 (93,98)	95 (90,97)	95 (89,99)	85 (80,88)

The vCT- and CBCT_LUT-based dose recalculation is compared to the rpCT-based recalculation for the patients with caudal (PatCA1–6) and cranial (PatCR1-3) lesions. Pass rates of the (3%, 3 mm) gamma evaluation are shown for IMRT and IMPT, together with the amount of 1D BEV proton dose profiles exhibiting a range within 3 mm of the rpCT SFUD distribution. The mean value over the considered patients and the minimum/maximum pass-rates (in brackets) are reported. Individual patient values can be found in Supplementary Tables III and IV in the appendix.