. Radiography and radio-therapeutics . er. For the examination of the mastoidregion a good technique has also beenFig. 172.—Dr. m. Berrys chair for frontal described by Dr. Howard Pirie. The sinuses, etc. (Watson & Sons.) p n • • n i i • i. j following is the technique he recommends: Technique.—The patient should lie prone on a firm couch. The head issupported on an inclined plane, making an angle of 25 degrees with the planeof the couch, as shown in Fig. 173. The photographic plate rests on this in-clined plane. The head is rotated 90 degrees so that the patient looks directlyto his side ; th
. Radiography and radio-therapeutics . er. For the examination of the mastoidregion a good technique has also beenFig. 172.—Dr. m. Berrys chair for frontal described by Dr. Howard Pirie. The sinuses, etc. (Watson & Sons.) p n • • n i i • i. j following is the technique he recommends: Technique.—The patient should lie prone on a firm couch. The head issupported on an inclined plane, making an angle of 25 degrees with the planeof the couch, as shown in Fig. 173. The photographic plate rests on this in-clined plane. The head is rotated 90 degrees so that the patient looks directlyto his side ; this brings the mastoid into contact with the plate. The pinna ofthe ear is turned forward, so as to obscure the mastoid as little as possible. Thesource of X-rays is placed vertically above the head, and the perpendicular rayis made to fall on a point 2 inches above the highest point of the pinna. Themastoid on each side must be skiagraphed separately. The glass of the focus tube should be 9 inches away from the hair. The. RADIOGRAPHY OF THE SKULL 203 exposure required will turn a Sabouraud pastille, placed at 2 centimetres fromthe glass, to one-third of the B tint. A medium hard focus tube (4-5 Benoist),with 30 milliamperes for fifteen seconds from a Snook apparatus, gives aplate which should be fully developed in seven minutes (Ilford plate anddeveloper). Skiagraphs of both right and left mastoids must be made of every case, asa single skiagraph of one mastoid is of little value. A different focus tube shouldbe used for each mastoid, as it is rarely possible to get one tube to remain con-stant in vacuum for both exposures. Both focus tubes must, of course, beof the same hardness. This is one ofthe most important points in thetechnique—viz. to have two similartubes of equal hardness and American-made tubes lend them-selves to this better than any othersI have used. Having secured radiographs ofboth right and left mastoids, oneshould place them side by si
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