Protective Methods in Radiology 265 



insisting upon inspection of their departments, and of the various 

 protective apphances, by the National Physical Laboratory. 



Influence of Early Protection Recommendations on 

 the Design of Sets 



The British Committee insisted that a primary precaution in 

 all X-ray work was to surround the X-ray tube as completely 

 as possible with adequate protective material. As lead had a 

 high absorptive value and was easily procurable and workable, 

 it became the common practice to place the tulles in lead-lined 

 boxes. These were, however, heavy and clumsy, and hindered 

 the radiologists in their work. Accordingly, efforts were made 

 to reduce the size and weight, without sacrificing any of the 

 protection. These efforts led to the introduction of the so-called 

 "self-protected" tube, of which the first example was produced 

 by N. V. Philips' Gloeilampenfabrieken, Eindhoven, Holland.^ 

 The main body of the tube was a chrome-iron cylinder, to which 

 glass was sealed directly. Surrounding the cylinder was a lead 

 sheath of sufficient thickness to absorb practically all the pri- 

 mary radiation from the target, with the exception of the useful 

 X-ray beam. 



Another unsatisfactory feature of early X-ray tubes and high- 

 tension generators was the risk of electrical shock associated 

 with their operation, since various parts of the equipment, work- 

 ing at several thousand volts, were often exposed. The British 

 Committee suggested various precautionary measures, such as 

 the introduction of earthed metal guards, the reduction of the 

 high-tension conduit system to a minimum, and the mounting 

 of the overhead conductors as high as possible, out of harm's 

 way. These measures, though obvious, had not previously been 

 generally adopted. A further advance was made in regard to 

 high-tension protection by enclosing the tube and transformer 

 in a single container and immersing them in oil. Generally 

 speaking, such units were somewhat limited in regard to move- 

 ment. In 1928, Bouwers "* designed shock-proof equipment which 

 overcame this disadvantage. The tube was mounted in an earthed 



