Predictive value of some ultrasound characteristics of thyroid nodules by using a mathematical model for analyzing ultrasound images

Introduction Since the prevalence of thyroid nodules is high and ultrasound-guided fine-needle aspiration biopsy (FNAB) as a gold diagnostic standard cannot be performed in all cases, we aimed to evaluate the feasibility and applicability of simple graphical analysis of ultrasound two-dimensional images to identify patients with suspicious nodules who would benefit from FNAB.;Patients and methods In our prospective two-centre clinical study, we included 211 consecutive patients with thyroid nodules -- 122 from University Medical Centre (UMC) Maribor and 89 from University Medical Centre (UMC) Ljubljana who underwent ultrasound-guided FNAB from January 2011 to October 2013. The cytology report was descriptive and later categorized as benign or suspicious/malignant. Blind to cytology reports, we later performed graphical analysis of ultrasound images using Java based application for analyzing images (ImageJ), and compared them with cytology reports.;Results According to cytology reports, 24 thyroid nodules were suspicious/malignant and 187 benign. Graphical analysis of ultrasound images performed with ImageJ demonstrated significantly higher value of standard deviation (SD) of the gray values used to generate the mean gray value in suspicious/malignant thyroid nodules as compared to unsuspicious nodules in UMC Maribor as well as in UMC Ljubljana (p?0.001 and p=0.002, respectively). A higher value of the SD of gray value used to generate the mean gray value meant variation or dispersion from the average value and was correlated by the presence of micro-calcifications. By applying a cut-off level of the quotient between the SD value of an examined thyroid nodule and the SD value of normal/reference thyroid tissue of 1.20, we found that 21/24 nodules were classified as true cytologically positive and 114/187 as true cytologically negative for thyroid malignoma.;Conclusion A quantitative graphical analysis of ultrasound images enabled us with a negative predictive value of more than 90% to foresee which thyroid nodules were cytologically suspicious/malignant and needed further investigations. Graphical analysis of ultrasound images was proved to be a useful additional diagnostic tool and needs to be further evaluated.