A Rapid Cassette Changer for Angiocardiography

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The following is a description of a simple, efficient cassette changer for use principally in angiocardiography. It permits the making of serial films at a speed faster than one per second. Usually, the first seven films are taken in four and a half to five seconds, and the rate is then slowed down so that the next four to six are finished in about fifteen seconds, depending on the problem under investigation. The changer consists of three basic parts: a tunnel for 11 X 14-inch cassettes, a lever mechanism to release the exposed cassette and arrest the following unexposed one, and an “approach” board. The x-ray team requires a “pitcher,” whose function is to push the cassettes through the tunnel and use the foot exposure switch (the anode rotating throughout the procedure), and a “catcher,” who aids in removing the exposed cassettes. For the protection of these two radiologists and the films, lead-rubber aprons are worn and lead shields are in place on each side of the patient. Measurements of the scattered radiation, with the Lansford instrument, show that the radiologists are well protected for the usual number of exposures required. If however, three or four angiographic studies were done each day, the limit of tolerance, i.e., 0.1 r would be approached. At the unprotected head of the table, where an anesthetist may be working, the Lansford instrument measured 0.07 r during one entire angiographic procedure. With a reasonable volume of work, the surgeon and the anesthetist need no shields or protective aprons. However, in institutions doing much of this work (e.g., four or more cases per day) mechanically operated apparatus would be preferable. The illustrations show the general type and design of the equipment, and also examples of the films obtainable therewith. It may be noted that the original trial model is still in satisfactory use. Acknowledgments: To Charles E. Grayson, M.D., for his design of the lever system, to A. Wayne Hackney, physicist, for the measurements of scattered radiation, and to Agnes Cameron for the drawings here reproduced, the author makes grateful acknowledgment.