Four-dimensional dose evaluation of inhomogeneous dose distributions planned for non-small cell lung cancer patients with lymph node involvement

Figures & data

Figure 1. Example of DVHs for a selected patient. 3D calculations (solid line), 4D inclusion of respiration (dashed line), 4D inclusion of all random and systematic uncertainties (grey region), and 3D calculation of related PTV (dotted line). The grey region is for each dose bin given as the 10th to 90th percentile of the 4D calculated DVHs.

Table I. Overview of dose and TCP values.

a) CTV
	Units	3D CTV	3D PTVCTV	4D CTV	p-value
Homogeneous plan
D98%	[Gy]	64.6 ± 0.9	63.4 ± 0.5	64.5 ± 0.8	< 0.001
Dmean	[Gy]	67.0 ± 0.7	66.5 ± 0.5	66.9 ± 0.7	< 0.001
D1cm^3	[Gy]	70.0 ± 1.3	70.5 ± 0.9	69.8 ± 1.3	< 0.001
TCPM	[%]	19.9 ± 1.1	19.2 ± 0.8	19.8 ± 1.0	< 0.001
TCPLQ	[%]	21.2 ± 8.1	20.1 ± 7.8	21.1 ± 8.1	< 0.001
Inhomogeneous plan
D98%	[Gy]	66.3 ± 2.1	64.3 ± 1.0	66.1 ± 1.9	< 0.001
Dmean	[Gy]	73.4 ± 2.0	71.0 ± 1.2	73.2 ± 1.9	< 0.001
D1cm^3	[Gy]	82.1 ± 6.3	82.1 ± 6.3	81.9 ± 6.3	0.005
TCPM	[%]	29.4 ± 2.9	25.6 ± 1.7	29.1 ± 2.7	< 0.001
TCPLQ	[%]	30.0 ± 9.7	25.8 ± 9.4	29.7 ± 9.6	< 0.001
b) GTV
	Units	3D GTV	3D PTVGTV	4D GTV	p-value
Homogeneous plan
D98%	[Gy]	64.8 ± 0.9	64.4 ± 0.9	64.8 ± 0.9	< 0.001
Dmean	[Gy]	67.0 ± 0.8	66.9 ± 0.7	67.0 ± 0.8	0.145
D1cm^3	[Gy]	69.2 ± 1.4	70.1 ± 1.3	69.2 ± 1.4	< 0.001
TCPM	[%]	19.9 ± 1.1	19.8 ± 1.0	19.9 ± 1.1	0.117
TCPLQ	[%]	21.4 ± 8.3	21.1 ± 8.1	21.3 ± 8.2	0.012
Inhomogeneous plan
D98%	[Gy]	68.3 ± 2.9	66.2 ± 2.2	68.2 ± 2.9	< 0.001
Dmean	[Gy]	75.7 ± 3.9	73.0 ± 2.0	75.4 ± 3.4	< 0.001
D1cm^3	[Gy]	81.8 ± 6.4	82.1 ± 6.3	81.6 ± 6.3	< 0.001
TCPM	[%]	33.3 ± 6.0	28.9 ± 3.2	32.9 ± 5.5	< 0.001
TCPLQ	[%]	34.1 ± 11.0	29.6 ± 10.3	33.6 ± 10.8	< 0.001

Values are mean and standard deviation over the patient population (4D patient values are averaged 4D values). Columns show the 3D calculation of CTV or GTV, the related PTV, and a 4D dose calculation of moving CTV or GTV. P-values are paired Wilcoxon sign ranked test between 3D PTV and 4D CTV or 4D GTV.

Table II. Organs at risk.

			Homogeneous plan		Inhomogeneous plan
Organ	Constraint		Aver. dev.	4D dev.	Aver. dev.	4D dev.
Lung	Dmean	[Gy]	0.0 ± 0.2	0.6	0.0 ± 0.2	0.6
Oesophagus	Dmax	[Gy]	0.2 ± 0.6	2.4	0.4 ± 0.8	2.7
Spinal canal	Dmax	[Gy]	1.1 ± 1.1	4.0	0.9 ± 1.2	4.0
Aorta	D1cm^3	[Gy]	−0.2 ± 0.2	1.4	−0.1 ± 0.4	2.2
Connective tissue	D1cm^3	[Gy]	−0.1 ± 0.1	0.3	0.1 ± 0.2	0.9
Trachea+ bronchi	D1cm^3	[Gy]	0.0 ± 0.1	1.5	0.0 ± 0.3	2.1
Heart	D1cm^3	[Gy]	−0.5 ± 2.5	6.1	−0.3 ± 2.7	7.1

Patient averaged differences between 4D and 3D calculations for organs at risk (mean and standard deviation) as well as patient averaged standard deviation of 4D calculated values.

Figure 2. Increases of TCP value by use of inhomogeneous versus homogeneous dose distributions based on 3D PTV calculation (PTV_CTV/PTV_GTV) and 4D calculation for moving CTV or GTV.