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1 Acta Radiologica: Diagnosis ISSN: (Print) (Online) Journal homepage: Chapter II: Methods To cite this article: (1963) Chapter II: Methods, Acta Radiologica: Diagnosis, 1:sup220, To link to this article: Published online: 07 Jan Submit your article to this journal Article views: 6 View related articles Full Terms & Conditions of access and use can be found at Download by: [ ] Date: 10 January 2018, At: 01:25

2 CHAPTER I1 METHODS The present investigation has been carried out partly using cineradiographic recor.dings of thse different free movements of the temporomandibular joint, partly using oblique-lateral radiographs of certain static positions of the temporomandibular joint. The single oblique-lateral radiographs have been used partly as an aid for photogrammetrical studies of the methods, partly for a closer study of th,e movement of condyle when changing position from occlusion to rest position. The identical apparatus has been used in all investigations. I. APPARATUS Downloaded by [ ] at 01:25 10 January 2018 The rcxntgen cine-film was taken with a 5 Philips image intensifier, combined with a 35 mm Arriflex motion picture camera with two lenses Xenon 1:2/75 and Xenon 1:1.5/55. The camera allows a picture frequency of up to 50 frames/ second. The image intensifier is constructe,d principally as follows (Fig. I). In close contact with the primary fluoroscent screen of the image intensifier, a photo-cathode is fixed. The primary fluoroscopic image is converccd into an electronic image. The intensification is achiev,ed by accelerating th,ese electrons, by help of 25 kv high tension and directing them on to a ptimes smaller image I 0 25kV +A Fig. 1. Schematic drawing of the image-intensifier.

3 Downloaded by [ ] at 01:25 10 January 2018 field, the observation screen. Here another conversion takes place into visible light. For observation the reduced image is converted into natural size by optical means, for instance binoculars. The reduced image may also be photographed by a motion picture or ordinary camera. The primary fluoroscent screen of the image intensifier has an effective circular field 13 cm in diameter. The roentgen ray image intensifier produces an image about one thousand rimes brighter than that of the normal fluoroscopic image which facilitates observation of smaller details in direct vision. The roentgen ray producing apparatus which has been used together with the image intensifier consists of a Philips Rotalix roentgen tube with rotating anode and two foci 0.3 x 0.3 mm and 1.2 x 1.2 mm. In this investigation only the 0.3 x 0.3 mm focus was used. Total filtration is 2.5 mm Al. This tube is combined with a Philips Standard DLX four valve roentgen apparatus which allows a continuous change in high tension from 35 to 125 kv and in tube current from o to 300 ma. Between the roentgen tube and the image intensifier is placed a patient s chair (Fig. 2). The chair which it is possible to elevate and lower, runs on rails and Fig. 2. Apparatus used. From left: image-intensifier, patient s chair with nose-holder, the roentgen tube.

4 Downloaded by [ ] at 01:25 10 January 2018 can be moved in a direction across the beam direction. The chair is furnished with a head-rest movable only forward and backward, perpendicular to the beam.direction. To the head-rest is applied a metal arm with a graduated noseholder. The nose-holder is placed with its longitudinal axis vertical and halfway betw,een the cushions of the head-rest. The roentgen film has been analysed in a viewer from Arnoe Corporation, Copenhagen (Fig. 3), in which the film is projected on to a white metallic screen or a transluc,ent glass screen. In this projector the film can be run both forwards and backwards and can b'e projected frame by frame or continuously at any desired speed up to 50 framedsecond. An automatic counter makes it possible 16 Fig. 3. Viewer for analysis of 35 mm roentgen cine-film.

5 to locate any particular frame of the cine-film. The ab0v.e described apparatus belongs to th4e Department of Roentgenology, the Royal School of Dentistry, Stockholm. Certain analyses both of cine-film and single images have been carried out in the Department of Photogrammetry, the Royal Institute of Technology, Stockholm. 2. METHODS OF INVESTIGATION Downloaded by [ ] at 01:25 10 January 2018 In order to obtain a projection of the condyle without as far as possible overshadowing bony parts one has, as before mentioned, owing to the anatomical structure of the joint, to direct that part of the concentration of the roentgen beams, which passes the slit between condyle and fossa, to form a cranial angle against the connecting line b,etween the two condyles. From empirical knowledge it is obvious that, with the method which has been suggested by LYSHOLM (reprinted 1950) one obtains very clear images of the condyle with little overshadowing of bony parts. In the present investigation I have therefore used thax method with small modifications depending on the apparatus used. Owing to the construction of the image intensifier the central beam of the roentgen tube have to hit the fluoroscent screen of the image intensifier almost perpendiculary. Thus one cannot, as when using the Lysholm Precision Apparatus, incline the roentgen tube against the screen plane. BERRY & HOFMANN (1959) had the image intensifier and the tube horizontal, and the patients were filmed with the head inclined 20' laterally and 10' horizontally. One may, however, assume that such a forced position of the head will influence the normal movements of the temporomandibular joint in an unfavourable way. I have in the present investigation pr0ceede.d in the following manner. The image Fig. 4. Schematic drawing showing beam direction in projection technique.

6 Downloaded by [ ] at 01:25 10 January 2018 intensifier and the roentgen tube are inclined 22' against the horizontal plane. The distance focus-fluoroscent screen is 70 cm. The patient is placed in the chair and fixed by the aid of the head-rest and the nose-holder so that the median plane of the patient is vertical and the Camper line approximately horizontal. During observation in the image intensifier the position of the chair is adjusted in such a way that the image of the condyle is situated in the middle of the screen plane, that is, the central beam of the tube pass the condyle at an angle of 22' (Fig. 4). By placing an object nearer the focus the distane focus-screen plane being constant, one gets a magnified image of the object. Owing to this magnification a loss of definition occurs in the image, the bigger the size of the focal spot is, the bigger the loss of definition. If one uses a micro-focus, 0.3 x 0.3 mm, this loss of definition is not of very large extent in a two-times enlargement. An enlargement of the image, however, will simplify further analyses of the films. Therefore the patient's chair has been placed in such a way that the nose-holder and consequently even the median plane of the head of the patient is at a.distance of 35 cm from the focal spot. This will give an enlargement of approximatively 1.6 times, the variations depending on the breadth of the head. As an aid for orientation and for an approximate check on the enlargement, a metal ball-bearing 1/4" in diameter, easily seen in the screen field, is placed on the temple of the patient. The size of the image field at the image plane has been 7 x 7 cm, corresponding to an opening of the diaphragm of I x I cm. The same proceedings of projection have been used both for the cine-films and the single films. To obtain the singit= film a cassette-holder is placed in front of the image intensifier. The following movements have been registered cineradiographically. I. Occlusion 2 maximal opening. 2. Occlusion 2 maximal protrusion. All movements even the protrusive have been free, that is the movements have been carried out without contact between the teeth. All movements have begun in the occlusion position, that is the patient has been instructed to bite together in central occlusion before the beginning of each movement. The protrusive movements have in the maximal end phase stoppcd with the teeth in contact. With the aid of single films two different types of investigations have been carried out. I. One image of the temporomandibular joint has been obtained on two different occasions. With the aid of the graduation of the nose-holder and the orientation of the Camper line, attempts have been made to produce the best indentical images possible. 18

7 2. Two images have been obtained of the temporomandibular joint, one in physiological rest position, one in occlusion (Fig. 5). The patient has been placed in th,e chair and fixed in the usual manner by the aid of the head-rest and the nose-holder. One image has been exposed without any instructions to the patient. After changing the cassettes, the patient has be,en instructed to bite together in central occlusion and a new exposure has been made. 3. FILM MATERIAL AND EXPOSURE DATA Downloaded by [ ] at 01:25 10 January 2018 In cineradiography th.e film used has been Kodak Cineflour Sp 713. Exposure data kv, 4-5 ma and 20 frarnes/second. No secondary grid has been used. The film has been developed in a Kodak special film processing outfit in May and Baker X-ray developer 340 for 8 minutes at 20' C. The film for the single images has been Kodak Standard in 13 x 18 cm cassettles with two intensifying screens Caw0 Optima. Exposure data 90 kv, 13 mas. The films have been developed for 5 minutes at 20' C in May and Baker RADIATION DOSE According to investigations carried our by HENRIKSON (1960, personal communication) with the above described apparatus, 4 ma and 70 kv at a focus Fig. 5. Single radiographs of the temporomandibular joint. Left: occlusal position, right: rest position.

8 Downloaded by [ ] at 01:25 10 January 2018 Fig. 6. Ten consequtive frames from a roentgen cine-film 20

9 distance of 20 cm and total filtration of 2.5 mm A1 give a skin dose of 19 r/min or j r/io sec. The distance from the focal spot to the nearest part of the head of the patient has never been less than 20 cm and the time of exposure has never gone over 20 seconds. Consequently the patient may have received a local skin dose of maximally 6 r. The radiation dose received during exposure of the single films is far less. The gonads received no measurable dose. 5. INTERPRETATION OF THE IMAGES Downloaded by [ ] at 01:25 10 January 2018 The rlesulting cine-films (Fig. 6) have been analysed in the above described viewer in the following way. The projecting screen of the viewer was replaced by a translucent screen. This translucent screen has been shaded with black paint in such a way that the translucent field corresponds to the image size. On translucent sheets of paper tracings were made, frame by frame. Only those frames, where the magnitude of the movement is big enough to permit registrations, were traced. During these tracings the contours of the fossa mandibulae, the tuberculum articulare, caput and collum mandibulae were drawn. Although definition is quite good when the motion picture is running, there is an undesirable blurring of the image border of the stationary frame. This unsharpness, however, is not of such a degree that it prevents the cranial and posterior contours of the condyle and the posterior contour of the collum to be drawn easily. During the tracing even small details which are #easy to identify, for instance small but well marked anatomical structures, one on the top of the condyle and one on the posterior border of the collum, were marked out. These tracings were thereaftcr grouped together in a graphical figure (Fig. 7), where only the contours of fossa mandibulae and tuberculum articulare and the above mentioned points wex included. A connecting line between the two points which belong to the same frame makes it possible from this graphical figure to read off the degree of rotation and translation and even changes in distances between the condyle and the fossa during different stages of the movement. The pair of images used for investigation of the small movement from rest position to occlusion have been traced directly on millimetre-paper. From the first image the contours of the fossa mandibulae, the tuberculum articulare and the condyle were drawn. This drawing was then orientated on the second image with the fossal contours coinciding and the contour of the condyle in its new position was drawn. Three points, easy to idlmtify, on the top of the condyle were also marked out. Connecting lines between the corresponding points were used to determine the degree of translation or rotation. Some of the cine-films and the single images have, as before mentioned, been analysed in a stereocomparator.

10 Downloaded by [ ] at 01:25 10 January 2018 Fig. 7. Tracings from a cine-fi!m and resulting graphical figure. 22