Variability of intraocular tumor height measurements by changing the probe position using a 20 MHz B scan ultrasonography

Abstract

Purpose The aim of this study was to evaluate the accuracy of tumor height measurements with variable probe positions in relation to the center of the spherical shaped globe. Patients and methods This is a retrospective study that included 27 eyes of 27 patients with different types of intraocular tumors recruited from the Ocular Oncology Service at Kasr Alainy Hospitals, Cairo, Egypt. All patients were evaluated by ocular ultrasound using a 20 MHz B scan transducer. Frames of each tumor measurements were evaluated and reassessed to get three heights (in the same visit) at three different positions: H-1: perpendicular with the tumor at central of the scan, H-2: perpendicular with the tumor oblique to the scan, and H-3: oblique with the tumor oblique to the scan. Results Different types of intraocular tumors were evaluated, with choroidal melanomas being the most common (44.4%). The median measurement in H-1 was 4.76±1.89 mm (range=1.82–8.73 mm), while the median measurement in H-2 was 4.94±1.93 mm (range=1.96–8.40 mm), and that in H-3 was 4.93±2.00 mm (range=1.99–8.73 mm). There were no statistically significant differences either between H-1 and H-2 (P=0.92) or between H-1 and H-3 measurements (P=0.97). To evaluate if the tumor height measurements were affected by the tumor size, the lesions were categorized into three groups: small-sized (tumors up to 4.0 mm), medium-sized (tumors from 4.1 to 7.0 mm), and large-sized (tumors >7.0 mm) in height. The large tumors (4/27=15%) showed differences in height measurements according to the positions of the calibers. Conclusion There was no statistically significant evidence on the effect of angulation on tumor height measurement using the 20 MHz B scan combined with vector A scan. However, large tumors should be more accurately calculated by the conventional perpendicular height (H-1) to avoid any error.