AUTOMATED NERVE-FIBER SIZE AND MYELIN SHEATH MEASUREMENT USING MICROCOMPUTER-BASED DIGITAL IMAGE-ANALYSIS - THEORY, METHOD AND RESULTS

In either clinical or research settings, manual measurement and counti ng of myelinated fibres in peripheral nerve is tedious and error-prone , yet fully automatic computerized counting and measuring of fibres fa ils to count small fibres and eliminate extraneous profiles in the tis sue. This article describes an operator-interactive, semiautomated met hod for quantification of myelinated nerve fibre data using commercial ly available hardware and software on an inexpensive, yet full-feature d image analysis system based on a microcomputer. Software macros auto mate the acquisition of data from the microscope images and the produc tion of numerical and graphic data, with output to either paper hardco py or 35 mm colour slides. User control is retained for dynamic thresh olding, binary image creation and elimination of artifacts. In additio n to generating the classic histogram showing the size distribution of nerve fibres, the thickness and variability of myelin sheaths are als o graphically depicted. The method is based on measurement of myelin a rea and total perimeter, with calculation of equivalent circles and di ameters for bath axon and nerve fibre. Measured fibre sizes are thus S omewhat larger than those resulting from manual methods using the mino r diameter of an oval profile, or mean diameter of crenated or irregul ar profiles. The method allows the rapid measurement and counting of n umbers of fibres previously impossible to assess manually, or using di gitizing tablets. By increasing the speed and accuracy of data acquisi tion and processing using widely available microcomputers, the method may allow a better description of peripheral nerve changes in research and clinical settings.