HISTOLOGICAL CHANGES IN MAN AND 



RABBITS AFTER PARENTERAL THORIUM 



ADMINISTRATION 



Charles Johansen 

 Finsen Institute, Copenhagen 



Thorium has a half-life of 1 -4 X 10^" years, the decay products have an 

 appreciably shorter life, and the activity of 4 g of thorium is fairly equivalent 

 to that of l[jig of radium. 90 per cent of the activity of thorium is due to 

 the alpha activity, 9 per cent to the beta and 1 per cent to the gamma 

 activity. The alpha radiation is thus completely dominant. Thorium is 

 generally used as a 20 per cent colloidal suspension of thorium dioxide, that 

 is to say 20 ml of this suspension are equivalent to about ly,g of radium. 



It is well known from the literature that thorium is practically not excreted 

 from the organism and, in the case of intravenous and intra-arterial adminis- 

 tration, is deposited in the cells of the reticulo-endothelial system, and 

 therefore especially in the spleen, the liver and the active bone marrow ; 

 furthermore, it is known that in and around the thorium deposits, degenerative 

 changes and fibrosis are found. 



When thorium is injected outside the blood-stream, the greater part 

 remains at the site of injection and may here produce more distinctive 

 changes, as will be shown here in the vascular wall at the site of injection, 

 in paravascular deposits and in the articular capsule when it has been used 

 for arthrography. 



It has been discussed in the literature whether the effects of thorium are so 

 detrimental that its use is dangerous. A few cases of aplastic anaemias have 

 thus been mentioned (Spier and co-workers^, Schmidt and co-workers-), 

 and the occurrence of a few tumours has been reported (MacMahon and 

 co-workers^, Ludin*, Horta^, Zollinger*', Abrahamson and O'Con- 

 nor'), and animal experiments on rats have shown an indubitable carcino- 

 genic effect of thorium. Other authors (for instance Lima^) consider that 

 they have seen no harmful sequelae of the use of thorium, while Thomas^ 

 and co-workers adopt a view between these two extremes ; on the basis of 

 a series of 4,300 patients they consider that they have seen no severe sequelae 

 but, owing to a tendency to fibrosis of the liver and the spleen and to cica- 

 tricial changes, they nevertheless think that thorium should only be used 

 when the indications weigh much in favour of such treatment. 



Our series comprises about 250 patients who received doses equivalent to 

 from 0-5 to 5[ig of radium. Four of the patients died of diseases of the 

 blood. 



These were : 



(1) A man, aged 40, who 1 1 years earlier had been given doses of thorium equiv- 

 alent to about 1 (xg of radium. He now had a severe, aregenerative anaemia with a 



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