Energy Modulated Photon Radiotherapy: A Monte Carlo Feasibility Study

Table 6

Comparison of dose indices of the organs-at-risk (OARs) between the IMRT and the EMXRT plans for the six cases in this study.

Tumor site	OARs	Indices	IMRT/Gy	EMXRT/Gy	Relative difference/%
Prostate	Rectum		32.5	31.5	−3.1
			49.7	50.7	+2.1
	Bladder		34.0	33.8	−0.6
			57.9	57.3	−1.0
	Femur head		10.6	13.7	+29.2
			15.4	21.9	+42.2
Head and neck	Spinal cord		14.3	13.9	−2.8
			44.7	45.2	+1.1
	Brainstem		14.0	13.5	−3.6
			44.6	43.1	−3.4
	Mandible		31.2	31.6	+1.3
			82.1	80.3	−2.2
	Left parotid		13.4	14.9	+11.2
	Right parotid		26.7	28.6	+7.1
Lung	Spinal cord		7.7	6.3	−18.2
			19.4	17.2	−11.3
	Left lung		3.5	2.6	−25.7
	Right lung		1.7	1.1	−35.3
	Trachea		13.1	12.9	−1.5
	Esophagus		8.5	7.4	−12.9
Spine	Spinal cord		4.9	4.7	−4.1
			15.9	14.6	−8.2
	Liver		1.3	1.2	−7.7
	Kidneys		0.3	0.3	0.0
Brain	Brainstem		6.3	5.9	−6.3
			20.2	20.2	0.0
	Eyes		3.1	2.7	−12.9
	Chiasm		2.6	2.4	−7.7
Thyroid	Spinal cord		17.6	16.0	−9.0
			41.6	40.6	−2.3
	Esophagus		44	43.3	−1.7
	Trachea		43.2	42.0	−2.7
	Pharynx		8	9.7	+21.1

Relative difference = 100%  ×  (  −  )/. The “+” and “−” indicate whether the dose index of the EMXRT plan is larger or smaller than that of IMRT plan. is the mean dose, and is the maximum dose.