Computer-aided clinical image analysis as a predictor of sentinel lymph node positivity in cutaneous melanoma

Table 1 Explanation of geometric, sharpness, color and color texture variables studied[7]

Classification	Parameter	Explanation
Geometry variables	Area	Lesion surface area, measured in cm2
	Maximum diameter	The longest line that joins two points on the border of the lesion, measured in cm
	Perimeter	Total boundary length of the region of interest (i.e. lesion), measured in cm
	Circularity	Ratio of the perimeter of the lesion divided by the perimeter of a circle with the same midpoint and same area as the lesion
	Mean radius (Rm)	Mean value of the lesion’s radii
	Standard deviation of Rm	Standard deviation of the mean radius
	Coefficient of variation of Rm	Expresses the standard deviation as a percentage of the mean
	Eccentricity	Distance between color and geometric midpoint within the lesion
	Eccentricity ratio	Distance between midpoint and color midpoint expressed as a fraction of the maximum diameter
Sharpness variables	SD of gray intensity	Intensity of gray on the border of the lesion
	Coefficient of variation of SD of gray intensity	SD of gray intensity in grayscale image. The higher the value, the more discrete the lesion is from the surrounding normal skin (Manousaki et al[7], 2016)
Color texture variables	Grayscale lacunarity of lesion (Lac gray)	It is estimated in grayscale image and assesses image texture heterogeneity or incomplete space filling within the lesion
Color variables	Range of gray, red, green, blue	Range of values of gray, red, green, blue intensity
	Mean gray, red, green, blue	Mean value of gray, red, green, blue intensity within the lesion
	SD of gray, red, green, blue	Standard deviation of gray, red, green, blue intensity within the lesion
	Coefficient of variation of gray, red, green, blue	Expresses the standard deviation of gray, red, green, blue intensity values as mean percentage
	Skewness from Gaussian curve (gray, red, green, blue)	Deviation of each color’s histogram from the normal distribution curve

SD: Standard deviation.

Table 2 Demographic, clinical and image processing characteristics of melanoma patients with positive and negative sentinel lymph node biopsy

Variable		Study group, SLNB+; n = 20	Control group, SLNB-; n = 79	P value
Demographics
Sex
Male		12 (60%)	40 (50%)	0.62
Female		8 (40%)	39 (50%)
Age (yr)		61 (13)	68 (15)	0.05
Tumor thickness (mm)		2.6 (2.7)	2.2 (3.0)	0.64
Subtype	Superficial spread	3 (15%)	44 (56%)	0.04
	Nodular	10 (50%)	25 (32%)
	Secondary nodular	7 (35%)	10 (12%)
Geometric variables
Area (cm2)		3.4 (2.9)	2.8 (4.7)	0.49
MaxD (cm)		2.4 (1.2)	2 (1.1)	0.22
Perimeter (cm)		6.6 (3.0)	5.7 (3.3)	0.25
Circularity (ratio)		1.1 (0.1)	1.1 (0.1)	0.44
Rm (cm)		0.98 (0.5)	0.84 (0.5)	0.21
SDRm		0.14 (0.1)	0.12 (0.1)	0.48
CVRm		13 (7.1)	13 (5.5)	0.88
Delta (cm)		0.04 (0.03)	0.03 (0.03)	0.04
Delta ratio		1.8 (0.9)	1.6 (1.3)	0.42
Sharpness variables
Sharpness		31 (9)	26 (8)	0.02
CV sharpness		22 (6)	18 (7)	0.02
Color texture variables
Lac gray		2 (0.28)	1.97 (0.30)	0.65
Color variables
Mean gray		104 (21)	113 (24)	0.12
SD gray		32 (6)	30 (7)	0.12
CV gray		8 (2)	10 (1)	0.07
Range gray		201 (21)	187 (32)	0.03
Skewness gray		0.52 (0.5)	0.23 (0.6)	0.03
Mean red		144 (26)	157 (32)	0.06
SD red		37 (9)	33 (11)	0.14
CV red		27 (10)	23 (11)	0.14
Range red		205 (23)	190 (37)	0.04
Skewness red		0.03 (0.43)	-0.04 (0.83)	0.003
Mean green		89 (23)	96 (23)	0.24
SD green		33 (7)	31 (6)	0.19
CV green		39 (12)	35 (13)	0.13
Range green		209 (24)	195 (33)	0.04
Skewness green		0.64 (0.46)	0.41 (0.60)	0.08
Mean blue		87 (22)	94 (25)	0.22
SD blue		33 (7)	31 (6)	0.24
CV blue		40 (10)	35 (13)	0.14
Range blue		218 (23)	201 (34)	0.02
Skewness blue		0.67 (0.47)	0.42 (0.56)	0.05

All continuous variables were normally distributed and therefore expressed in mean-deviation form. Categorical variables were expressed in terms of absolute (n) and relative (%) frequencies. Statistical significance: P value < 0.05. SD: Standard deviation; CV: Coefficient of variation; MaxD: Maximum diameter; SLNB+: Tumor-positive sentinel lymph node biopsy; SLNB-: Tumor-negative sentinel lymph node biopsy; Rm: Mean radius; SDRm: Standard deviation of the mean radius; CVRm: Coefficient variation of the mean radius; Lac: Lacunarity.

Table 3 Multivariate analysis of univariately significant predictors of a positive sentinel lymph node result

Variable	Coefficient (β)	Standard Error	Wald χ2	P value	Odds ratio	95%CI
Age	-0.05	0.20	7.60	0.006	0.95	0.91 to 0.99
Subtype, nevus-associated	2.65	1.28	4.28	0.038	14.19	1.15 to 174.76
Subtype, nodular	2.37	1.01	5.51	0.019	10.71	1.48 to 77.48
Subtype, secondary nodular	2.90	1.08	7.22	0.007	18.21	2.19 to 151.22
Eccentricity	0.38	0.13	7.84	0.005	1.46	1.12 to 1.89

95%CI: The 95% confidence interval for the estimated odds ratios.