Hypoxia dose painting in SBRT – the virtual clinical trial approach

Figures & data

Figure 1. Computational model of the tumour vasculature. a) Vasculature perfusing a spherical tumour. b) Correspondent oxygenation (red: vessels pO₂ = 40 mmHg).

Figure 2. Process of calculation of the prescribed doses to the HTV and TV-HTV. Starting from the oxygenation map (a), the correspondent radiosensitivity map is produced (b). accounting for an aimed probability of control p = 95% the theoretical dose distribution is computed (c₁, c₂); the doses are then processed to obtain a constant dose within the volumes if interest (d₁, d₂), obtaining ideally a TCP close to the aimed one.

Figure 3. Cross sections of the oxygenation maps for three different tumours.

Figure 4. Prescribed doses (a) and probabilities of control (b, c) for the HTV and the TV-HTV subvolumes of the ten simulated tumours; (b) refers to the case of constant oxygenation between fractions, while (c) includes the assumption of fast reoxygenation at every fraction after the first.

Table 1. Hypoxic fractions for the ten tumours (tum -), for the hypoxic target volume (HTV) and the remainder of the target volume (TV-HTV). pO₂ threshold for hypoxia = 10 mmHg.

Hypoxic fraction HTV
Tum 1	Tum 2	Tum 3	Tum 4	Tum 5	Tum 6	Tum 7	Tum 8	Tum 9	Tum 10
46.8%	40.1%	50.7%	41.4%	53.9%	32.8%	42.5%	42.4%	48.5%	44.0%
Hypoxic fraction TV – HTV
Tum 1	Tum 2	Tum 3	Tum 4	Tum 5	Tum 6	Tum 7	Tum 8	Tum 9	Tum 10
1.4%	1.0%	1.4%	0.9%	1.7%	1.1%	1.2%	1.9%	1.6%	1.2%

The values refer to the oxygenation before the treatment.