Improved tumour control probability with MRI-based prostate brachytherapy treatment planning

Figures & data

Table I. Prostate volumes (cm³) as measured on US (during implantation), CT and MRI.

Patient	US	CT	MRI
1	27.2	52.4	30.2
2	49.4	40.1	50.2
3	N/A	48.1	52.5
4	N/A	20.7	18.9
5	52.0	44.4	57.1
6	41.1	47.3	36.7
7	36.5	41.7	37.4
8	N/A	36.4	26.5
9	34.9	35.7	28.9
10	30.5	46.0	33.1
11	39.5	44.4	38.6
12	33.4	27.4	37.9
13	38.2	41.4	45.8
Mean	38.3	40.4	38.0
SD	7.8	8.7	11.0

N/A, Not available in the pre-planning software.

Figure 1. PTV coverage (V₁₀₀) for all patients of the different plans.

Figure 2. Dose parameters for the PTV and its two subvolumes (apical and basal part) of the different plans. Bars marked with a * give a statistically significant different result from the original CT-plans (p < 0.05). Error bars show 95% confidence intervals.

Table II. Median and IQR (interquartile range) of the quality indices for the different plans.

	NDR		QI		CN
	Median	IQR	Median	IQR	Median	IQR
CT-plans	1.10	1.08–1.10	1.50	1.46–1.5	0.58	0.58–0.59
MRI-plans	1.05	1.0–1.05	1.58	1.47–1.57	0.53	0.46–0.53
CT-plans_MRI-contours	as CT		as CT		0.50	0.39–0.50

For parameters in bold, the difference to the original CT-plans is statistically significant (p < 0.05).

Figure 3. Example of TCPs as a function of V₁₀₀ for one parameter sets (α = 0.15 Gy²¹, and β = 0.1 Gy²²). For this set, mean TCP improved 10% for MRI-plans, compared to CT-plans_MRI-contours.

Table III. TCPs from CT-plans_MRI-contours and MRI-plans for different sets of radiobiological parameters.

				CT-plansMRI-contours				MRI-plans				Difference
α (Gy^-1)	β (Gy^-2)	ρ (cm^-3)	α/β (Gy)	Mean	SD	Min	Max	Mean	SD	Min	Max	Mean	SD	p-value
0.03	0.05	5.E + 02	0.6	0.89	0.09	0.68	0.98	0.95	0.02	0.91	0.99	0.06	0.09	0.019
0.10	0.05	6.E + 04	2	0.91	0.10	0.67	0.99	0.97	0.01	0.95	1.00	0.06	0.09	0.009
0.15	0.05	8.E + 06	3	0.91	0.11	0.62	0.99	0.98	0.01	0.96	1.00	0.07	0.11	0.007
0.30	0.05	6.E + 10	6	0.89	0.17	0.43	1.00	0.99	0.01	0.96	1.00	0.09	0.16	0.003
0.03	0.10	6.E + 05	0.3	0.90	0.14	0.54	1.00	0.98	0.01	0.96	1.00	0.08	0.13	0.003
0.10	0.10	7.E + 07	1	0.90	0.16	0.46	1.00	0.99	0.01	0.97	1.00	0.09	0.16	0.002
0.15	0.10	2.E + 09	1.5	0.89	0.17	0.40	1.00	0.99	0.01	0.97	1.00	0.10	0.17	0.002
0.30	0.10	4.E + 13	3	0.90	0.20	0.30	1.00	0.99	0.01	0.98	1.00	0.10	0.20	0.002

Differences were tested with a Wilcoxon signed-rank test.