"Many instruments have also been designed for the purpose of judging the penetration or quality of the ray. Most notable are the Benoist radiochrometer, the Benoist-Walter, the Wehnelt, and the Walter scales. We have found the Benoist radiochromometer sufficiently satisfactory for this purpose".
In their work, MacKee and Remer have found it better to use a "hard" tube; in the superficial type of cancers they employ a B 8 tube, and in the deeper type they may use a B 10 tube-that is, a tube ih&t will measure 8 or 10 units by the Benoist scale when tested for penetration.
The technic for measuring quantity merits a somewhat fuller description, for it is not generally employed in this country. The Holzknecht radiometer consists of a suitably tinted celluloid band, the colors of which grade from zero to 8 H units. The measurement pieces consist of pastils of platinocyanide of barium, and the estimation is made by placing a half pastil under the colored band. Another half pastil is exposed to the emanations of the tube, while the patient is under treatment, covered with celluloid, and placed in contact with the "index" half pastil, but outside of the colored band. The whole pastil is now moved down the scale until the two halves match exactly in color, and a reading is then made, somewhat as on a hemoglobinometer.
As regards dosage, the Holzknecht units are now pretty generally known and used. As already stated, 1 unit equals a dose that is one-third large enough to produce erythema of the face in an adult. The H units are accurate only when a "medium" tube is employed -a B 6 tube, for instance. It is necessary to remember that 5 H with a hard tube may produce only a temporary alopecia, while the same dose with a soft tube may cause permanent baldness, and hence it can be seen that the biological effects of the H units vary according to the quality of the ray. As a general rule, from 5 to 7 H units are employed at the first sitting, and, if necessary, four weeks later another dose of about the same size given.
Regarding the "skin distance" and the "pastil distance," the authors say: " It is customary to place the pastil exactly half way between the anode and the skin. The reason for this is that the pastil, being closer to the anode, will assume a deeper color when in this position than when placed upon the skin, and, therefore, supposedly greater latitude is obtained in estimating the change in tint. Paradoxical as it may seem, the deep orange shades are harder to match than the paler colors. Not only are the green, yellow, and lighter orange tints easier to match, but they do not fade so rapidly when they are exposed to light and moisture. Contrary to what has been published, the color acquired by an exposed pastil will fade almost as rapidly under the influence of strong artificial light as by the action of daylight, and the deeper orange tints will attenuate far more rapidly than will the paler colors. These are some of the reasons why we prefer the full 'skin distance' for the pastil. There are, also, other very important reasons. The numerals on the scale of units of the Holzknecht instrument are not equally spaced.
One has more latitude in comparing the lighter than in estimating the darker tints. . . . The pastil must be placed at least one inch from the wall of the tube to avoid the deleterious effect of heat, and hence the tube can be placed nearer the patient and the exposure shortened. . . . With the pastil on the skin, regardless of the distance of the anode, the H units must be multiplied by four to conform with the law of inverse proportions to the square of the distance-that is to say, if 1 H unit is administered in this manner, it will equal 4 H units by the 'half distance' method".
The fresh pastil is of a glazed brilliant green color, and all pastils should have this color, approximately at least. They should be kept in a well-ventilated humidor that is kept in a cool room. A used pastil can be returned to almost normal color by the action of daylight and moisture. Either the English, French, or German pastils may be used, for all seem about equally reliable. It is better to use fresh pastils each time.
Now a word as to the choice of method. Undoubtedly it is better in every particular to use as little x-ray as possible in the treatment of cutaneous affections, and this can best be done by a technic which approaches that just described. At any rate, we should make some attempt to measure our doses-this is just as important as to standardize the drugs that we administer by mouth. To the author it seems certain that in the next decade practically everyone will use instruments of precision in determining not only the quality, but the quantity of the rays that he uses. At the same time it must be remembered that very bad results are occasionally obtained when one attempts to use the massive dose. Most of these reports have come out of the dry states in the west, where there is a comparatively low-humidity, and it seems possible that the lack of moisture may affect the sensitiveness of the pastils; at any rate, there have been a. number of very bad burns reported. Also, it is more than possible that all skins do not act equally, and that what one skin will tolerate will prove very irritating to the next.
The results of x-ray therapy in cancer of the skin have usually been good in the hands of experienced men. Pusey* reports 72.5 percent of successful results in 111 unselected cases, comprising both the basal- and prickle-celled variety of cancer. Still later Pusey*, admitted only two failures in thirty-five selected cases of cancer of the lower lip, mainly, however, of the rodent ulcer variety. MacKee's results have been almost uniformly good, and there can be no doubt that the x-ray can accomplish cures in very many cases of cutaneous cancer, provided that no metastasis has taken place to the neighboring glands. The results are not, however, as sure as they are with the knife, for we find a certain percentage of cases that are absolutely intractable to the rays, the treatment is usually more prolonged, and, if a dermatitis be produced, the treatment is usually more painful. And, finally, in the hands of an expert surgeon there is not a great difference in the scarring produced by the removal of a small tumor. The x-ray has, however, a great field of usefulness. It is the ideal treatment for basal-celled cancers of the eyelids, of the naso-facial folds, and of the ears. In addition, it is useful in the very old, who cannot well submit to an operation, and in certain very extensive cases of cutaneous cancer. In some of these cases it will render the patient comfortable and prolong life, even if it will not cure. The general tendency is for the x-ray expert to belittle surgery and for the surgeon to make light of the rays, whereas in reality each field of therapy has a great field of usefulness.