FLUOROSCOPE 



49 



Fluokoscope 



A fluoroscope is an instrument used for the roentgenoscopic examina- 

 tion of a patient. Certain minerals have the property of absorbing 

 x-radiation and re-emitting radiant energy of longer wavelengths which 

 may be of sufficient length to be classed as ordinary light. This property 

 we designate as photoluminescence or fluorescence. 



Stokes established the fact that the wavelength of the emitted energy 

 was always greater than that of the exciting energy. 



It was through the luminescence of a platinum salt that Rontgen in 

 1895 discovered x-rays. When light is used as the exciting source of 

 luminescence, the luminous radiations originate in the superficial molec- 

 ular layers and then only on that side of the material turned towards 

 the source of the radiation. If x-radiation, however, is the source of the 

 excitation, fluorescent radiations from all sides of the material may be 

 obtained. The effect may be represented to be a resonance phenomenon 

 between the frequency of vibration of the exciting absorbed radiant 

 energy and the frequency of the electrons revolving about the radiated 

 atoms. .That fluorescence is associated with the property of the periph- 

 eral electrons is supported by the changes in fluorescence due to tem- 

 perature variations and by the presence or absence of fluorescence in 

 chemical combinations of the same elements. BaCl 2 and BaPtCN 4 are 

 fluorescent; BaC0 3 , Ba 2 C0 3 , and Ba 2 FeCN 6 are non-fluorescent. The 

 platinocyanides in general exhibit varying degrees of fluorescence, 

 especially the above-mentioned barium and calcium salts, but the mag- 

 nesium salt is non-fluorescent. 



TABLE 1-9 



Compound 



Fluorescent Band 



Wavelength Range 



A 



Maximum of 

 Emission Band 



o 



at A 



CaWCV 

 BaPtCN 4 t 

 K 2 PtCN 4 

 CaPtCN 4 



4800-3750 

 5090-4420 

 4900-4120 

 5090-4550 



4330 

 4800 

 4500 

 4800 



Compounds 



Colors of Fluorescence 



CaW04, calcium tungstate (white salt) 

 CdWO*4, cadmium tungstate 

 Zn 2 Si04, zinc silicate (willemite) 

 Cadmium zinc sulfide (silver-activated) 



Light blue 

 Light blue 

 Green 

 Yellow-green 



* Used in radiographic intensifying screens. 

 t Used in visual intensifying screens. 



