267

X-RAY CINEMATOGRAPHY.*

By Russ~L REYNOLDS.

V ERY soon after the discovery of x-rays by Professor l~ntgen in November, 1895, attempts were made to obtain x-ray cinematographic effects both at home and abroad. The need

for a cinematograph film was recognised, but the task proved very difficult to fulfil.

X-rays, like light, travel in a straight line, but cannot be refracted in the same way; it is therefore impossible to construct anything in the nature of a lens which will focus them on to a photographic film. To make a cinematograph record of x-ray appearances it is therefore necessary to proceed in one of two ways.

The first, which is called the direct method, consists in using a band of film each exposure of which will be of sufficient size to contain a natural s'~ze image of the parts to be photographed, and to expose this in the place which is normally occupied by the fluorescent screen or the radiographic film, i.e. close to the patient's body. The chief disadvantages of this method are that the dimensions of each exposure must be at least 4 i~. • 5 in., or pre- ferably larger, to be of use. A film of this size is very costly, and an apparatus capable of exposing it at the rate of 8 or more exposures a second is cumbersome and difficult to design. More- over, when the film has been made it is not easily or conveniently projected again for examination or instruction.

The second, or indirect method, consists in photographing, with an ordinary cinematograph apparatus, the image on the fluorescent screen. This method has the advantage that ordinary photographic apparatus can be used, but the chief difficulty h~therto has been to obtain a screen image sufficiently brilliant to impress a clear picture on the film ordinarily used for cinematography at the high rate of speed necessary to obtain a useful record. The image on the screen can be i~tensified by increasing the power of the x-rays, but there are practical limits to the x-ray intensity that can be used. In the first place, the heavy currents required wear the tubes out quickly, and in the second place x-rays are destructive to body tissues and it would be dangerous to expose a patient to very intense radiation for the length of t'~ne necessary to take the film, more particularly if it were required to photograph the same patient more than once, for the effect of the rays is cumulative. The problem has, therefore, been to obtain the clearest possible film image with the least possible output of current, and the pur- pose of this paper is to describe briefly a method of obtaining true cinematograph pictures of bodily organs with an apparatus suffi- ciently practical to ~be used in hospitals and institutions.

Communication to the Section of Surgery, Royal LAcademy of. Medicine in Ireland, 24th January, 19a6.

268 IRISH JOURNAL OF MEDICAL SCIENCE

In 1897, Dr. John Macintyre of Glasgow showed at a meeting of the Glasgow Philosophical Society a film 40 feet long to illustrate the movements of a frog's hind leg. The movement he showed was life-like and informative, but the picture was, of course, admittedly a " fake "; he had taken a number of ordinary radiographs of the frog's leg in different positions and then arranged them i~ an order which would show the movements, and transferred them to a cinematograph film.

Until quite recently all succeeding attempts were made by the direct method, for the simple reason that no photographic apparatus existed which was nearly sensitive enough to take satis- factory moving pictures of the feeble screen image. As the large film required for the direct method could only be changed at a comparatively slow rate the early attempts hardly rank as cineradiography in the true sense at all, and if they appeared to show a movement, it was not a true record of the actual movement but rather a synthetic or built-up record which showed something approximating closely to the true movement. For instance, in 1898 Roux and Balthazard made a number of strips each containing 12 serial pictures 3 cm. wide by 6.25 era. long; these were exposed directly for a second each at regular intervals of 10 seconds, and represented the movements of the stomach of rats and froga About 1901, Carvallo took a number of films of small objects and parts at a rate of five to the second, using a mechanism much like that of the ordinary cinematograph camera. He used exposures at a one-second interval to record very slow movement.

Other workers followed in 1905. Levy and Dorn showed a synthetic film of the movements of the knee and elbow joint, obtained by placing, in order, a number of pictures taken at different times of different positions of the bones. Kiihler, in 1907, followed with another synthetic film. Haenisch, in 1911, devised an apparatus by which he could expose 10 plates at short inter- vals. Jarre and Cummings (1930), in America, used films five inches in width. Their pictures, at any rate in 1930, were not t ruly cinematographic because the intervals between the exposures were half to one second. Alvarez, in America, made pictures at 4 to 6 per second, with a film 4"x 5" in 30 ft. strips. Oroedel, in 1933, made some advance on these by taking 16 pictures a second, each 18 cm. by 24 cm. Also, Barclay, in 1935, and especially Van de Maele, who has recently developed the direct method and brought it to a greater degree of perfection. All the early workers chose the direct method owing to the impossibility of being able to photo- graph the screen image.

When the author began his experiments in 1921 he chase the indirect method, because he thought it would probably be in the end cheaper, more convenient, and more practical in use. The essential conditions that have to be fulfilled by this method are : - -

(1) The screen picture must be sufficiently brilliant to be able to impress itself satisfactorily on a cinematograph film exposed

X-RAY CINEMATOGRAPHY 269

for a fraction of a second. This requires (a) an x-ray generator of considerably greater output than that required for ordinary diagnostic work; (b) an x-ray tube which will stand up to much heavier currents than usual; (c) a lens which will give sharp definition at a very wide aperture; (d) a cinematograph film as sensitive as possible to light of the particular wavelength emitted by the screen.

(2) The film in the camera must be protected from the direct beam of x-rays.

(3) The patient must be adequately protected from undue exposure to radiation.

Since the author started this work he has, of course, met with innumerable difficulties, and the measure of success which he has been able to achieve has been largely due to the improvement which has taken place during the intervening years in the various com- ponent parts of the apparatus, such as the x-ray generator, the fluorescent screen, the lens and the cinematographic film. To give an idea of the minimum length of exposure required, in September, 1925, he was able to record the breathing movements in a young patient in ~ second, and movements of the joints in an adult in

second. These are long exposures compared with those required for adequate cinematographic record.

Perhaps the most important advance was in devising a method of obtaining a sufficiently brilliant screen pieture without exposing the patient to harmful doses of x-rays. The principle employed is that of only passing the rays at the exact instant when the camera shutter is open and they arc needed to yroduee a picture on the fluorescent screen. This object is effected by means o f a synchronising mechanism on which the author has been working for about 15 years. A standard-size cinematograph camera using 32 ram. film was employed at first, but was recently abandoned in favour of a 16 ram. camera for obvious reasons of cost and convenience.

I t was difficult at first to focus the picture accurately, because the wide-aperture lens was so very sensitive to minute changes in focus. An attempt was first made to focus by means of a ground celluloid screen put in the place of a cinema t~|m~ and a black- and-white chequered card put in the place of the fluorescent screen and illuminated with a hand-lamp. X-rays were then used with a metallic grid as object, and the resulting film exposures were found to be out of focus, the reason being that the light from the lamp used for focussing had a different wavelength from that of the light produced by the fluorescent screen. The correct setting of the micrometer screw on the lens holder was found by a series of exposures, each with a slightly different setting of the screw.

The camera takes seven pictures for each revolution of the driving spindle, and the shutter opens and closes seven times uniformly during each revolution. The lengths of time during which the shutter is opened and closed respectively are equal.

270 IRISH JOURNAL OF MEDICAL SCIENCE

The length of the exposure can therefore be exactly regulated by varying the speed of the driving spindle. The function of the synchronising switch is to switch the tube on during the time when the shutter is open, and switch it off when the shutter is closed and the film is being transported. This ensures that the patient shall receive only half the radiation that he would receive if the x-ray tube were switched on the whole time. This is the pro- vision which makes it possible to give a sufficiently long exposure without subjecting the patient to a harmful amount of radiation, or putting a destructive strain on the tube.

The rays from the tube are filtered through a filter of aluminium 0.5 mm. thick, to intercept the soft radiations. This is ordinary radiological practice. The current on the tube is 60 mA. at a maximum voltage of 120 kV. The distance of the anti-cathode from the screen varies, but the distance from the screen to the front of the camera is 63 in. This is constant, and was determined during the focussing tests mentioned above. The size of the screen picture is 10 in. • 18 in. and the screen has no lead glass over it. Lead glass is essential in the ordinary examination of a patient in order to prevent the direct beam of rays from reaching the radiologist, but it stops about one-quarter of the visible light from the screen, a fraction which one cannot afford to give away in moving-picture work. The camera is protected by a shield of lead 3 ram. thick in order to prevent the x-rays from fogging the film before and after exposure. Each frame at the instant of exposure is unprotected, but the combined effect of the glass of the lens and the distance makes the rays too weak to affect it. The fluorescent screen has a slight afterglow, but this is partially counteracted by shining a red light on it. I t is now possible to conduct x-ray cinematographic examination as routine practice as easily as it is to examine the patient on the screen or take single radiographs. He is not exposed to a greater aggregate radiation than he would be in the ordinary way. The author has given a total exposure of 16 seconds to one area, and repeated it within a few days, without any 'ill effects on the patient.

I t is rarely necessary to expose many feet of film at a time in order show what is wanted. I f the radiologist wants to demon- strate, for instance, the normal movement of respiration or the normal heart-beat, he can do so in about a yard of film. I t is then very convenient for the purposes of examination or instruc- tion to join the ends of the film and make an endless band; this can be run continuously through the projector, sa that the appear- ance is shown again and again as often as required. Once the negative has been obtained, any number of positives can be printed from it.

An apparatus for producing cineradiograms, designed on the lines of the author's experimental unit, but containing many minor improvements, is now on the market.

The system of indirect cinematography which has been described

X-RAY CINEMATOGRAPHY 271

enables the radiologist to obtain a rapid, inexpensive, and perma- nent record of the functioning of active organs. The use of a continuous band of film enables an investigator or student to watch the movement indefinitely, whereas the ordinary screen examina- tion can last only a very short time owing to the destructiveness of x-rays in large doses. For the study of a complicated organ like the heart, where several different parts are in a state of move- ment at the same time, the cinematograph record has still more obvious advantages.

These permanent records of movements may be used for purely diagnostic purposes, or a recent record can be compared with an earlier one to show the effects of treatment or the progress of disease. They are useful for teaching purposes; they can be easily transported from place to place for the use of other specialists who may be consulted in the case.

The author has collected a large number and variety of records of various movements of human organs and limbs, e.g., films show- ing the chest in the act of breathing, the movement of food through the stomach and intestines, and the movement of joints. A field of study in which the cinematograph is indispensable is the mechanism of swallowing, which takes place at such high speed that the eye can hardly follow it on the fluorescent screen. The author has produced several films in which every stage of this mechanism is shown.

Cinematography appears to open a large and varied field of research in radiology, of which it is impossible to foresee the limits. I t should prove of immense value in the investigation of disease or injury in the lungs and pleurae. I t will help immensely in the examination of gastro-intestinal lesions. When limbs and joints have been injured it will possible to study by cineradiography the progress of the case after operation as to the range of movement, etc.

Although x-rays have for years been recognised as an essential aid to a physician who examines the heart and circulation, their chief use has been to enable the heart specJaliat to check the examination which he has made by the ordinary clinical methods of the stethoscope and percussion; and to show him the condition of the cavities and great vessels of the heart. X-rays have not contributed much to our knowledge of the functioning of the heart. The cinematograph should add greatly to our knowledge of the various irregularities which occur in heart disease.

The author has recently found it possible to incorporate a graphic record of the heart action in the form of the electro- cardiograph tracing on the same film as the heart, so that the two can be seen simultaneously.