A simple graphical quantitative analysis of ultrasonography images to decide when to perform fine needle aspiration biopsy in diagnosing malignancy in solid thyroid nodules? A two centres prospective study.

OBJECTIVE

Since the prevalence of thyroid nodules is high and ultrasonography (USG)-guided fine-needle aspiration biopsy (FNAB) as a diagnostic means cannot be performed in all cases, we aimed to evaluate the feasibility and applicability of simple graphical analysis of USG two-dimensional images, to identify patients with suspicious thyroid nodules who would benefit from FNAB.

SUBJECTS AND METHODS

We studied prospectively 211 consecutive patients with thyroid nodules: 122 from the University Clinical Centre (UCC) of Maribor and 89 from the University Medical Centre (UMC) of Ljubljana who underwent USGguided FNAB from January 2011 to October 2013. The cytology report was categorized as benign or suspicious/malignant. Blind to cytology reports, we later performed graphical analysis of USG images using ImageJ (version 1.48r) which is a public domain Java image processing and analysis programme. We compared the average gray value and standard deviation (SD) of the gray values used to generate the mean gray within the selection, with cytology reports.

RESULTS

According to cytology reports, 24 thyroid nodules were suspicious/malignant (14/10) and 187 benign. Graphical analysis of USG images performed with ImageJ demonstrated significantly higher values of SD of the gray values used to generate the mean gray value in suspicious/malignant thyroid nodules as compared to unsuspicious nodules in both UCC Maribor and 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 positive and 114/187 as true negative.

CONCLUSION

Our results showed that our graphical quantitative analysis of USG images had a negative predictive value of more than 90% and was able to suggest which thyroid nodules were potentially malignant and needed further investigation.