Prescribing and evaluating target dose in dose-painting treatment plans

Figures & data

Figure 1. Dose profile over the target volumes in a DPBC plan, showing the steep gradients of the prescribed dose (52.8 Gy to PTV3, 60 Gy to PTV2, 69.7 Gy to PTV1, 73.1 Gy to PTV-solid and 79.7 Gy to PTV-PET) and the smoother gradients of the achieved plan dose.

Table I. Prescription doses, mean doses and doses covering 95% of the target volume.

	Prescription dose [Gy]	Mean dose (range) [Gy]		D95% [Mean(range)] [Gy]
		Mean prescription	95% prescription	Mean prescription	95% prescription
PTV3	52.8	53.0 (51.4, 53.5)	55.2 (54.5, 56.7)	48.1 (45.7, 49.8)	50.9 (50.2, 51.6)
PTV2	60.0	60.2 (59.3, 60.8)	62.6 (61.9, 63.6)	54.4 (52.5, 55.8)	57.7 (57.2, 58.7)
PTV1	69.7	69.9 (69.1, 70.7)	71.4 (69.9, 72.5)	64.9 (63.3, 66.3)	67.0 (66.0, 68.2)
PTV-solid	73.1	73.5 (71.7, 74.1)	74.8 (72.0, 76.6)	69.9 (67.5, 71.0)	71.7 (69.8, 73.3)
PTV-PET	79.7	79.7 (78.8, 79.7)	79.7 (78.8, 79.7)	76.4 (75.4, 77.4)	76.6 (75.7, 77.8)
PTV-tot	–	63.6 (60.7, 69.4)	65.4 (62.2, 70.9)	–	–
Body-PTV	–	7.7 (2.6, 11.9)	8.1 (2.7, 12.2)	–	–

Table II. Comparison of the dose-painting plans of different prescription approaches by means of four different scalar measures.

	Q0.95-1.05 [mean (range)]	Q0.95-1.07 [mean (range)]	QF [mean (range)]	QRMS [mean (range)]
Mean prescription	0.683 (0.584, 0.766)	0.753 (0.665, 0.848)	0.042 (0.034, 0.051)	0.055 (0.045, 0.067)
95% prescription	0.648 (0.544, 0.729)	0.767 (0.679, 0.841)	0.047 (0.039, 0.056)	0.061 (0.053, 0.071)
p-value	0.001	0.052	0.003	0.003

Figure 2. The QVH of a suboptimal plan (solid line), shown in relation to the ‘normal zone’ of the QVH tool. The plan was re-optimized and could be improved (dotted line).

Figure 3. A suboptimal dose-painting plan shown in quality color wash. Values of Q > 107% (overdosage) appear in red and Q < 95% (underdosage) appear in blue. The high degree of overdosage occurs, inter alia, in the position of the right submandibularis (dark blue contour).

Figure 4. Comparison by means of the QVH tool between 2010 and 2012 hypopharyngeal treatment plans. The dose is reported for specific PTVs without (a) and with (b) optimization margins between them.