X-Rays, Apparatus and Methods Page 20

But in all troubles affecting the trunk, upper leg, etc., the indications are too blurred and vague to be relied upon. A good part of this indefiniteness is doubtless due to the phosphorescent quality of the screen, which causes images to be retained for an appreciable time after they are formed, so that unsteady holding produces superposed images, while we also have a molecular disturbance extending in every direction in the plane of the screen, producing visibility where no direct X-ray disturbance has been produced. Part of the difficulty is also probably due to the natural inefficiency of the screen, which, as employed in this country, is merely of tungstate of calcium. The platinum salts, especially the platinum barium cyanide, is much superior to the tungstate of calcium, but considerably more expensive; it is generally used abroad. The results obtained with it are much more brilliant than those gotten with the tungstate. It is probable that there are other salts or combinations of salts still more powerful than the platinum.

In using the fluoroscope the room should be made as dark as possible, as the eye thus becomes many times as sensitive. Good tubes are often condemned on account of lack of appreciation of this fact and because they do not reveal much detail when used in a lighted room. We have often seen tubes which would not reveal even the bones of the hand in a lighted room, which, after keeping the eyes in the dark for five or ten minutes, would give very clear fluoroscopic images of the ribs, spinal vertebrae, heart, etc.

It does not follow at all that tubes giving poor fluoroscopic results will also give poor photographic results, or vice versa, although usually there is a certain correspondence between the two ideas.

General Considerations. — Speaking mainly from the surgeon's point of view, only experience can insure good results with X-ray apparatus. No matter how simple the apparatus may be, how many safeguards be embodied in it, how explicit and full the directions, there are still a vast number of little points which no book can teach, no tongue tell, and which must be learned. To do the best work, one must be something of a physicist, a photographer, surgeon and doctor,