Physics in Modern Medicine Examine the following listing of K absorption edges f
ID: 1089777 • Letter: P
Question
Physics in Modern Medicine
Examine the following listing of K absorption edges for various types of phosphors used in film-screen receptors for detecting x-rays. Explain why the traditional phosphor calcium tungstate is appropriate for chest x-rays, while the rare earth compounds gadolinium oxysulfide, lanthanum oxybromide, and yttrium oxysulfide are better for mammography. Which of the latter materials would you guess to be most effective, based on this information alone? Q5.6. Phosphor material Calcium tungstate Gadolinium oxysulfide Lanthanum oxybromide Yttrium oxysulfide K absorption edge (ke V) 69.5 50.2 38.9 17.1Explanation / Answer
X- rays having higher energy than K absorption edge will be absorbed for a particular Phosphor material.
Lower energy x-ray while having less penetration give better contrast which is especially important in mammographs, that is why Gadolinium, Lanthanum and Yttrium compounds would be suitable as a Phosphor material in mammography. Based upon this information alone, Yttrium oxysulfide gives better resolution.
A chest scan needs high energy x ray to penetrate thick material (Ribcage and hard tissues), that's why Calcium tungstate with high value of absorption edge is required.