Ultrasonographic three-dimensional scanning for determination of intraocular tumour volume

Important prognostic information may be gained from knowing the volume and the rate of growth of intraocular tumours, such as choroidal melanomas. An ultrasonographic 3-D scanning system based on rotation of a commercial sector scanning transducer applied directly onto a closed eyelid was designed to measure such volume. Control of movement, data acquisition, and image analysis are accomplished by means of a microcomputer and application-specific software. The elapsed time for scanning and digitizing 20 cross-sectional images is about 1 sec. Outlines of specific structures are traced manually. The system var tested through repeated measurements of known volumes of meat. The mean variation coefficient of these measurements was 2.8%. The traced volumes were linearly dependent on gain setting of the system requiring a fixed setting for accurate estimates. The procedures of scanning and tracing contributed about equally to the total variance. This method allows repeatable, reliable, and easily generated quantitative measurements of volume with a great potential for use in the diagnosis of malignant tumours and control of the effectiveness of radiotherapy.