MEASUREMENT OF INTRACRANIAL TISSUE VOLUME USING COMPUTED TOMOGRAPHIC-IMAGES AND A PERSONAL-COMPUTER

A software package called MacMeasure was developed previously to measure the size of intracellular structures by means of photomicrographs. We have expanded the application of this program to computed tomographic (CT) images. Using three objects of irregular shape and unequal size (phantoms), we compared volumetric determinations made with a CT mainframe computer and a widely available personal computer. The phantom objects were scanned in a GE CT/T 9800 scanner with serial, non overlapping slices 3.0 mm in thickness. The image data were first measured directly from the magnetic archive tape with the CT control terminal. Hard copies of the CT scans were then measured with a Macintosh SE computer and a digitizing tablet with a crosshair cursor driven by the MacMeasure software package. A third method of measuring volume was by tracing individual CT images onto paper (hard copies). The tracings were then cut out, weighed, and converted to surface area by dividing the weights by a weight/surface area standard (26.37 mg = 25 cm2) calibrated to the CT image scale (5.0 cm). The total surface area value was then converted to volume by multiplying a single CT slice thickness (0.3 cm). Finally, the phantom objects were placed in water-filled graduated cylinders to determine their volume by fluid displacement. The technique using MacMeasure and the personal computer provides an accurate means of determining surface area and volumes using hard copies of CT images. It avoids occupying costly CT computer time and is the most rapid method of volume measurement of the three techniques tested (CT mainframe = 6.0 hours, trace/weigh = 3.5 hours, and PC = 1.25 hours). This capability will facilitate the study of a wide variety of neurological conditions including cerebral neoplasia, infarction, hemorrhage, hydrocephalus, atrophy, and edema. It can also be used to measure tissue volumes in other organs and is readily applicable to CT and magnetic resonance imaging scans.