Variability of standardized echographic ultrasound using 10 mHz and high-resolution 20 mHz B scan in measuring intraocular melanoma

Daniel Kook^*, Thomas C Kreutzer^*, Armin Wolf, Christos Haritoglou
Department of Ophthalmology, Ludwig-Maximilians University, Munich, Germany
^*These authors contributed equally

Background: The purpose of this study was to evaluate the applicability and variability of echographic imaging using 10 mHz and high-resolution 20 mHz B scanning for measurement of intraocular tumors.
Methods: This prospective consecutive study comprises 27 eyes in 27 patients with uveal melanoma. Each patient was examined by three experienced examiners independently on three occasions within a two-week time frame in a blinded manner. The height of the lesion was measured by all examiners using the 10 mHz B, 20 mHz B, and 8 mHz A scan probes. Additionally, basal diameter was examined using the 10 and 20 mHz B scan.
Results: Tumor height measurements for all examiners using the standardized A scan tended to be higher than for both B scan measurements. Statistical analysis revealed significant differences in tumor height between B and A scan measurements. No difference in tumor height was found between the two B scan techniques (P = 0.239). Basal tumor diameter measurements revealed significant differences between 10 mHz and 20 mHz B scans (P < 0.001 and P = 0.001, respectively). For the 10 mHz B scan, basal diameter results tended to be larger than for the 20 mHz B scan. No difference was found for interobserver variation in all A scan and B scan examinations. The mean standard deviation of the difference in tumor height measurements between the examiners was ±0.24 mm for the 8 mHz A scan, ±0.46 mm for the 10 mHz B scan, and ±0.42 mm for the 20 mHz B scan. Both the 10 mHz and more precise 20 mHz B scan evaluations underestimated tumor height.
Conclusion: The 20 mHz ultrasound probe, despite its theoretically higher resolution, is not able to replace A scan measurements of tumor height.

Keywords: standardized echography, 20 mHz, B scan, A scan, intraocular tumor