Apparent Diffusion Coefficient (ADC) as a quantitative parameter in diffusion weighted MR imaging in gynecologic cancer: Dependence on b-values used

Figures & data

Table I. Patient specific data.

Patient no	Site	FIGO	TNM	Cell type	VOI
1	Cervix	IIB	T2NxMx	Squamous cell	66 cm^3
2	Cervix	IIIA	T3N0M0	Adenocarcinoma	44 cm^3
3	Cervix	IIIB	T3NxM0	Squamous cell	85 cm^3
4	Cervix	IIB	T3N1M0	Squamous cell	66 cm^3
5^a	Vagina		T2N0M0	Squamous cell	74 cm^3
6	Cervix	IIB	T2N1M0	Squamous cell	92 cm^3

^aPatient 5 was a vaginal cancer and could not be staged under FIGO guidelines.

Figure 1. Volume of Interest (VOI). Transversal (top), coronal (middle) and sagital (bottom) slice showing the VOI for a patient with advanced cervical cancer. Overlaid is the diffusion map calculated using a monoexponential model to the b-values in the range 150–1 000 s/mm². The color scale has the units × 10⁻³ mm²/s.

Table II. Comparison of different combinations of diffusion gradients (b-values).

b-values [s/mm^2]	Patient 1	Patient 2	Patient 3	Patient 4	Patient 5	Patient 6	Average and SD
0 + 400	48%	20%	45%	32%	55%	37%	40 ± 13%
0 + 700	27%	16%	27%	16%	32%	22%	23 ± 7%
0 + 1000	18%	10%	14%	7%	21%	15%	14 ± 5%
0 + 400 + 700	25%	14%	29%	21%	38%	26%	26 ± 8%
0 + 700 + 1000	18%	12%	16%	11%	25%	18%	17 ± 5%
150 + 400	23%	20%	15%	10%	22%	19%	18 ± 5%
150 + 700	10%	9%	8%	1%	11%	9%	8 ± 3%
150 + 400 + 700	9%	10%	8%	3%	12%	11%	9 ± 3%
150 + 1000	6%	4%	−1%	−4%	5%	5%	3 ± 4%
150 + 700 + 1000	6%	5%	0%	−2%	7%	7%	4 ± 4%
All 150–1000	5%	5%	1%	−2%	8%	6%	4 ± 4%
Reference ADC [10^−3mm^2/s]	0.67 ± 0.05	0.74 ± 0.06	0.69 ± 0.07	0.78 ± 0.05	0.59 ± 0.09	0.89 ± 0.06	0.72 ± 0.1
Perfusion coefficient [10^−3mm^2/s]	11 ± 8	118 ± 78	7 ± 6	34 ± 20	14 ± 9	68 ± 60	42 ± 44

Deviation of ADC values from reference ADC for different combinations of b-values (monoexponential model). The reference ADC values were calculated by using a biexponential model.

Figure 2. Curvature of the biexponential fits to the diffusion data. The maximum curvature indicates the limit where the contributions from perfusion and diffusion changes dominance. This was consequently found to be at b = 43 ± 15 s/mm².

Figure 3. Variation of the apparent diffusion coefficient. The blue line is the signal decay from patient 1. The red line corresponds to an ADC of 0.99 mm²/s obtained by monoexponential fit using b-values 0 and 400 s/mm². The black line corresponds to an ADC 0.79 mm²/s (b-values 0 and 1000 s/mm²). The diffusion coefficients are overestimated by 48% and 18%, respectively.