A comparative statistical analysis of brain scans using a digital computer

An improvement in brain lesion detection, using 99Tcm as the tracer isotope, has been achieved at this hospital by using a PDP8/S computer, complete with a peripheral discstore, for the statistical analysis of count data coming from a rectilinear scanner. An “off-line” procedure has been adopted using an interface specifically designed for the scanner. The interface is completely automatic and produces a paper tape, containing count data and positional information, for each scan view taken. Programmes for the PDP8/S have been developed that accept the paper tape and accurately reconstruct the scan picture. Several analyses are available which include: (1) a symbol printout, serving as a visual check and enabling measurements to be carried out; (2) antero-posterior or postero-anterior analysis which compares the two hemispheres and shows any positive difference between the two sides; (3) a lateral analysis achieved by comparing the unknown scan with a matching Standard Normal. Two Standard Normals are used for each test: (a) A complete Standard Normal constructed from a few selected scans containing the complete head outline. These standards are used for normalising patient scan material. (b) A Standard Normal pattern which uses the complete Standard Normal as a basis to construct a more representative normal pattern by adding proved normal material, not necessarily having a complete head outline. This standard is used in the comparative analyses. A reliable Standard Normal pattern contains approximately 12 normal scans.