Automated Computer Analysis of Radiographic Images
Abstract
Lee B. Lusted in his Memorial Fund Lecture (1) anticipated the device: “an electronic ‘scanner-computer’ to look at chest photofluorograms and to separate the clearly normal chest films from the abnormal chest films. The abnormal chest films would be marked for later study by the radiologist.” This automated computer analysis concept was based on some preliminary studies by Pendergrass and Tolles who showed that automatic scanning of photofluorograms could produce satisfactory density tracings.
We are now reporting a method of automated computer analysis of radiographic images utilizing algorithms (a rule of procedure for solving a recurrent mathematical or logical problem) for recognizing parts of the radiographic image.
Method and Results
Thirty-seven 70 mm. photofluorograms were digitized and put on magnetic tape, using an improved image-scanning system similar to one previously reported (2). The radiographic image of the chest on magnetic tape contains 502 digit samples per line times 320 horizontal scan lines for a total of 160,000 two-digit samples per 70 mm photofluorogram of the chest.
The computer then processes the digital image by integrating each of its vertical columns on the IBM 1410 computer and writes out one record on magnetic tape for each of the input image matrices. The radiograph is now represented on magnetic tape by a single record containing 500 samples. With another program the computer can print out a plotted curve analogous to an electrocardiogram tracing, which represents the radiograph. (Figure 1 depicts an integrated strip chart of a 70 mm photofluorogram of the chest.)
The magnetic “summed tapes” which have the integrated vertical columns of each radiograph are then used as an input for the stored program containing the algorithm.
Eight indices are determined and automatically printed as follows:
Address of left rib peak (LRP)
Address of left edge of heart (LEH)
Address of maximum value in heart band (MVH)
Address of right edge of heart (REH)
Address of right rib peak (RRP)
Maximum transverse diameter of the heart (MDH)
Maximum transverse diameter of the thorax (MDT)
Cardiothoracic ratio (MDH/MDT = CR) (4) (Fig. 5).
Figures 2 and 3 are condensed flow charts of the data through the programs.
Tables IA and IB show the cardiothoracic ratios computed and measured with per cent differences between these values.
Discussion
For the detailed analysis of the programming and electronics involved, the reader is referred to other work by our group (2).
The results of the automated comouter analysis of the cardiothoracic ratios are summarized in Tables IA and IB. Table IA shows the cardiothoracic ratios as measured by four investigators: (a) an American Board certified radiologist; (b) a resident in radiology; (c) a computer scientist; and (d) a biomedical engineer.
Article History
Accepted: May 1964Published in print: Dec 1964
