RED-GREEN-BLUE (RGB) IMAGE ANALYSIS OF PANCREATIC MASS-ELASTOGRAPHIES IN ENDOSCOPIC ULTRASOUND (EUS) CAN PREDICT MALIGNANCY- A PILOT STUDY

Aims To investigate the accuracy of quantitative image analysis of EUS-elastographies (tissue elasticity) to predict malignancy of solid pancreatic lesions.

Methods Elastographies of solid pancreatic masses obtained with EUS between 01/2014-06/2019 were extracted from Hitachi V70 device and analyzed retrospectively. Quantitative RGB based analysis was performed using a Java image processing program (ImageJ,NIH). Red indicates soft, blue hard, and green intermediate tissue-elasticity. The exact amount of color was measured and expressed in pixels and percentages. After calibration of each image, the color intensity was measured on a scale of 0–255 for 8-bit image. Intensity ratio for each color was defined as relation between absolute value for this color and the intensity of the sum of all three colors (R + G + B). Tissue surrounding the tumor outside well-defined margins of the lesion on ultrasound was not include in the analysis. Final diagnosis was made either by histopathology or radiological findings in combination with tumor markers and clinical follow-up.

Results 59 solid pancreas tumors evaluated by strain elastography were analyzed: 45(75%) malignant (60% adenocarcinoma,8.3% metastasis and 6.6% neuroendocrine tumors) and 14(23.3%) benign masses. Cut-offs values to differentiate between malignant and benign pancreatic tumors were calculated for parameters with good correlation for the presence of malignancy (criteria,table). Risk of malignancy according to these criteria was: 4/4(15 cases)-100%, 3/4(24 cases)- 87.5%, combined 3 or 4/4(39 cases)-92.3%; 2/4(11 cases)-54.5%, 1/4(4 cases)-75% and 0/4(5 images)-0%.

Conclusions Quantitative image analysis of solid pancreatic lesion elastographies obtained in EUS may predict (3 or 4/4 criteria) or exclude (0/4 criteria) malignancy with high accuracy.

Tab. 1 Parameters with good correlation for the presence of malignancy.

Parameter (criteria)	Cut-offs (%)	Sensitivity (%)	Specificity (%)	AUC
Blue color (%) (Spearman r = 0.192,p = 0.10)	> 55	93.3	35.7	0.62
Green color (%) (r = −0.218,p = 0.09)	< 42.5	97.8	42.5	0.64
Green color Intensity Ratio (r = −0.391,p = 0.002)	< 56	71.1	78.6	0.76
Red color Intensity Ratio (r = −0.194,p = 0.10)	< 18.5	42.2	92.9	0.63