Apparent diffusion coefficients in GEC ESTRO target volumes for image guided adaptive brachytherapy of locally advanced cervical cancer

Figures & data

Figure 1. ADC map fused with GEC-ESTRO contours (GTV_BT, HR-CTV and IR-CTV). The contour ADC_low was generated using an ADC threshold value 1.2 × 10⁻³ mm²/s and encompasses the volume with low diffusion.

Figure 2. Definition of the calculated volumes ΔHR-CTV and ΔIR-CTV based on the GEC-ESTRO volumes HR-CTV and IR-CTV.

Figure 3. Plot of mean ADC for all DW-MRI acquisitions for the three volumes analysed: GTV_BT, ΔHR-CTV and ΔIR-CTV. Filled circles represent values from BT1 and hollow circles values from BT2. The vertical line indicates the mean ADC value.

Table I. GEC-ESTRO and ADC_low volumes (mean and sd) for BT1 and BT2 and the amount of ADC_low volumes in the target volumes.

	BT1	BT2
GTV [cm^3] (Mean ± sd)	1.17 ± 0.77	0.94 ± 0.77
HRCTV [cm^3] (Mean ± sd)	42.41 ± 16.93	41.27 ± 17.76
IRCTV [cm^3] (Mean ± sd)	100.65 ± 29.06	102.36 ± 28.95
ADClow [cm^3] (Mean ± sd)	16.38 ± 16.08	11.90 ± 9.19
10%-percentile	5.62	3.66
90%-percentile	28.94	29.90
%ADClow in GTV (Mean ± sd)	36.87 ± 17.76	37.57 ± 21.36
%ADClow in ΔHRCTV (Mean ± sd)	21.83 ± 14.11	18.68 ± 13.71
%ADClow in ΔIRCTV (Mean ± sd)	12.10 ± 8.89	9.50 ± 6.78

Table II. Change of ADC level in the three GEC-ESTRO volumes as a function of therapy.

	ADC, BT1 Mean ± sd [×10^−3 mm^2/s]	ADC, BT2 Mean ± sd [×10^−3 mm^2/s]
GTV	1.33 ± 0.20	1.36 ± 0.19
ΔHR-CTV	1.56 ± 0.18	1.60 ± 0.18
ΔIR-CTV	1.83 ± 0.17	1.86 ± 0.16