Health > Protective measures against dangers resulting from the use of radium, roentgen and ultra-violet rays

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as already mentioned, since only a very small proportion of the softest components
reach the fluorescent screen through the body. When a 2 mm. Al. filter is used, the
permissible exposure may be increased to about 5 minutes. Such specifications regarding
length of exposure can, of course, only possess a limited validity, seeing that the
efficiency of ray output may vary considerably with different tubes and, in particular,
that present practice in regard to the measurement of voltage still leaves much to be
desired. A recommendation that can be more unhesitatingly and decisively made is
that every single set of apparatus should be tested for dosage under the exact conditions
of operation.
It is very important that the roentgenologist should not begin the examination
until his eyes have thoroughly adjusted themselves to the darkness, and, further, that
he should procure exact information as to whether, for any reason, such as previous
X-ray examinations, sunburn, disease or the like, increased radio-sensitivity has to be
allowed for.
The international regulations sum up all these various points in the statement that
screening examinations should be conducted as rapidly as possible with minimum
intensities and apertures. In my opinion these general directions require to be consi¬
derably supplemented.
In diagnostic X-ray photography of the human body, the conditions are generally
more favourable than in screening examinations. The intensities used are commonly
very high, it is true, but we have only to reckon with very short exposures, so that the
total amount of radiation is small. Thus, for instance, very many lung photographs
can be taken without risk to the patient; circumstances arise, however, in which the
roentgenologist must carefully reflect whether he may take a further photograph; and
this mostly occurs in those very cases of difficult photography which do not always yield
a satisfactory result on the first attempt.
In gynaecological diagnosis, consideration must be given to the high radio-sensi¬
tivity of the ovaries; by way of upper limit of the dose delivered at the ovaries, I take
5 per cent of the skin unit dose 1.
The skin load is particularly great where use is made of Raster diaphragms
(Bucky) , which are designed to reduce the scattered radiation between the patient
and the plate; in such a case, where lateral photographs of the lumbar region of the
spine are taken, only two exposures are permissible.
To sum up, it may be said that greater care in the protection of the patient is
required in the medico-diagnostic use of roentgen rays, and that a proper understanding
of the dangers involved is indispensable for their avoidance.
7. Protective Measures in the Use of Gamma Rays, Corpuscular Radiation
and Ultra-Violet Light.
When gamma rays are used, care must be taken, in the very first place, to ensure
that only gamma rays are actually being administered — that is to say, that the filtering
of the preparation is sufficiently powerful to provide practically complete absorption of
the beta rays. This can only be effected with filters of 0.5 to 1 mm. thickness of
the metals with very high atomic numbers, the most frequently used being platinum,
gold or even silver. The thickness of the filter has much less influence on the intensity
of radiation with gamma rays than with X-rays, since the above-mentioned metals only
absorb about 1 per cent of the former per 0.1 mm. thickness of filter.
1 Fortschritte Rontgenstr., Volume 35, Congress edition, page 54, 1927.