Use of kilovoltage X-ray volume imaging in patient dose calculation for head-and-neck and partial brain radiation therapy

Table 4 Dose comparisons of the first and second CBCT images.

	Mean dose (Gy)					Maximal dose (Gy)
	GTV	CTV	PTV	Left-parotid	Right-parotid	Brain-stem	Spinal-cord	Whole-body
kV CT	50.72	51.04	51.02	32.14	30.40	50.92	31.76	55.78
1^st kV CBCT	50.23	50.77	50.74	31.88	30.57	51.21	31.17	55.63
Dose difference between 1^st kV CBCT and kV CT(%)	0.98%	0.54%	0.54%	0.8%	-0.56%	0.57%	-1.87%	-0.26%
2^nd kV CBCT	50.37	50.77	50.76	32.56	28.73	51.36	32.96	55.71
Dose difference between 2^nd kV CBCT and kV CT(%)	0.7%	0.53%	0.52%	-1.3%	5.81%	0.86%	3.77%	-0.11%

Dose comparison of the first and second CBCTs to the reference planning kVCT in a patient (patient 4) with marked anatomical changes. The largest changes in dose difference between CBCT and planning CT are found in the spinal cord (from -1.87% to 3.77%) and in the right parotid (from -0.56% to 5.81%).

ISSN: 1748-717X