Plan robustness in proton beam therapy of a childhood brain tumour

Figures & data

Figure 1. MR scanning for fusion with dose planning CT slice showing the tumour close to the organs at risk.

Figure 2. The VMAT arc set-up for the photon plan. The treatment technique consists of one coplanar arc and two non-coplanar arcs each of 45° to the axial plane. The two non-coplanar fields start at the PA direction and end at the eye level.

Figure 3. Planning CT with oedema present in right lateral region.

Figure 4. Dose distributions in colour wash with 30 Gy as lowest value for a) VMAT and b) IMPT. In c) the proton beam configuration is shown, with, one field in the axial plane while one non-coplanar field was used to reduce dose to the right eye.

Figure 5. Dose Volume histograms for the VMAT course A: the three targets and B: the three ORs and for the IMPT course C: the three targets and D: the three ORs, for the planned treatment as well as changes according to Scenarios A and B.

Table I. Comparison of planned treatment versus scenario A and B, for VMAT and IMPT treatment courses.

	Target coverage (%)			Maximal dose to OR (Gy)
	CTV (0 cm)	CTV (1 cm)	CTV (2 cm)	Chiasm	Brainstem	Optic nerve
VMAT planned	99.2	97.6	99.5	54.1	51.8	53.7
VMAT A	99.3	97.8	99.5	54.4	52.2	54.0
VMAT B	99.5	97.7	99.6	53.5	50.0	53.7
IMPT planned	98.7	98.0	99.6	54.1	51.8	54.0
IMPT A	99.9	99.0	99.5	60.2	56.8	60.4
IMPT B	91.5	93.0	99.2	52.1	48.6	51.7