. Radiography and radio-therapeutics . the rays in relation to a body in-terposed between the focus - tube and the sensitive plate. One threaded needle is placed upon any particular part of one of the photographic shadows of the foreign body, and the other needle upon a corresponding partin th,e second shadow. The pointwThere the threads cross and toucheach other will represent the positionof the part of the foreign bodychosen for location. A perpendicularis then dropped from the inter-section of the threads to the negativebelow, and a mark made where theperpendicular touches the
. Radiography and radio-therapeutics . the rays in relation to a body in-terposed between the focus - tube and the sensitive plate. One threaded needle is placed upon any particular part of one of the photographic shadows of the foreign body, and the other needle upon a corresponding partin th,e second shadow. The pointwThere the threads cross and toucheach other will represent the positionof the part of the foreign bodychosen for location. A perpendicularis then dropped from the inter-section of the threads to the negativebelow, and a mark made where theperpendicular touches the distance of the spot thusmarked out from the cross wires ismeasured by a pair of operator is now in possession ofthe required measurements. If thedistances are 3 cm. and 1 cm., and Fig. 135—Diagram to illustrate simple formula fae (Jepth from the Crossing of thefor localising. (After Walsh.) , * , . , _., ^ n threads to the plate 2J cm., then heknows that the foreign body lies at 2| cm. from the surface of the patients. Fig. 134.—Mackenzie Davidson cross-thread localiser. (Cox & Co.)
Size: 1419px × 1761px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookidradiographyr, bookyear1919
