Paper Title
Using Contrast Stretching Technique to Enhance Visibility of Low Contrast Liver Lesions in Computed Tomography: Phantom Study

Abstract
Contrast stretching technique plays an essential role in image processing for humans and computer vision. It is performed for medical image processing to aid medical practitioners in making more informed diagnoses. This study aimed to enhance liver lesions visibility in computed tomography (CT) applications via post processing contrast stretching technique. A phantom contains 16 cylindrical lesions with four different diameters (5, 8, 10 and 15 mm) and iodine concentrations (4.2, 4.4, 4.6 and 4.8 mg iodine /mL) were scanned via four CT scan protocols with energies of 80, 100, 120 and dual energy (140 and 80 kVp). The contrast stretching technique was modified to enhance the acquired images using ImageJ software program. The contrast, contrast noise ratio and statistical analysis measurements were performed to evaluate the quality of pre and post processed CT images. The results showed that contrast and visibility of the scanned lesions was improved with modifying contrast stretching technique. The lesions visibility was found to be at its highest quality when it is acquired at 80 kVp protocol and further post-processed by the contrast stretching technique. Statistically, paired t-test results showed there were significant increases in the contrast and contrast noise ratio values for the liver lesions enhanced with the contrast stretching technique, particularly at 80 kVp protocol (P values < 0.05). Keywords - Computed Tomography; Liver Lesions; Lesions Enhancement; Contrast stretching Technique