LIGHT EQUALIZATION RADIOGRAPHIC SCREEN/FILM CASSETTE

THE DEVELOPMENT OF A NOVEL ELECTRONIC SCREEN/FILM CASSETTE FOR USE IN MEDICAL X-RAY IMAGING (RADIOGRAPHY) IS PROPOSED. DURING PHASE I, A STANDARD CASSETTE WILL BE MODIFIED BY ADDING A TWO DIMENSIONAL ARRAY OF PHOTODETECTORS INTERDIGITATED WITH A SECOND ARRAY OF LIGHT EMITTING DIODES (LED'S), PLACED BEHIND THE BACK INTENSIFYING SCREEN. THE PHOTODETECTORS, ACTIVATED DURING A RADIOGRAPHIC EXPOSURE, WILL BE USED TO ESTIMATE THE REGIONAL X-RAY EXPOSURE RECEIVED OVER CONTIGUOUS 2-10 CM(2) REGIONS OF THE FILM. FOLLOWING THE TERMINATION OF THE X-RAY EXPOSURE, THE INTERDIGITATED ARRAY OF LEDS WOULD BE ACTIVATED MOMENTARILY,EACH DIODE DELIVERING AN ADDITIONAL AMOUNT OF LIGHT EXPOSURE, DETERMINED BY THE SIGNAL RECORDED BY NEARBY PHOTODETECTORS, SUCH THAT THE RESULTANT OPTICAL DENSITIES RECORDED ON A RADIOGRAPH, ONCE DEVELOPED, WOULD LIE ABOVE SOME PREDETERMINED THRESHOLD VALUE. USE OF THE PROPOSED CASSETTE WILL IMPROVE UPON CURRENT RADIOGRAPHIC FILM QUALITY IN THREE WAYS: 1. BY INCREASING IMAGE CONTRAST IN ORDINARILY UNDEREXPOSED REGIONS ("TOE") OF A NORMAL RADIOGRAPHIC FILM; 2. BY COMPRESSING THE RANGE OF OPTICAL DENSITIES RECORDED ON A NORMAL RADIOGRAPHIC FILM, AND; 3. BY REDUCING THE "RETAKE" RATE FOR SEVERELY UNDEREXPOSED RADIOGRAPHS. DURING PHASE II, SEVERAL PREPRODUCTION PROTOTYPE CASSETTES WILL BE CONSTRUCTED USING SEVERAL COMMONSCREEN/FILM TYPES AND EVALUATED IN A SERIES OF CLINICAL TESTS IN A VARIETY OF RADIOGRAPHIC PROCEDURES - CHEST, MAMMOGRAPHIC AND BONE RADIOGRAPHY.