What is being tested? (kVp, mA, mAs, mR?) What is the purpose of the HVL test? If an x-ray tube does not pass the HVL test what is done to correct the deficiency? Can the results of this test be applied to all values up to 118? These 12 slides highlight the material from chapters 10, 12, and 40, of test #3. Along with the PowerPoint reviews for Tests 1 and 2 this completes the reviews by illustrations for the comprehensive final.

* What is the name of each of these interactions? * What energy level do each of these interactions occur at? * Of what significance (positive or negative) are each of these interactions? * What characteristics do each possess? - what part of the atom is involved? - is there ionization?

* What is the name of each of these interactions? * What energy level do each of these interactions occur at? * Of what significance (positive or negative) are each of these interactions? * What characteristics do each possess? - what part of the atom is involved? - is there ionization?

4. How is this graph different than the one above? #1. What effect is this? #2. What effect is this? 3. What does this graph tell us about these effects?

* Fluoro mA is 5 or less * Due to the length of exams patient dose is high * kVp is dependant on part thickness * Automatic Brightness Control (ABC) maintains the density when the fluoroscope is moved across varying thicknesses by adjusting the mA

Image Intensifier (II) Input Phosphor CsI Photocathode Cesium & Antimony Glass envelope Electrostatic focusing lens Output Phosphor Zinc Cadmium Sulfide Anode 25,000 V Concave surface so all electrons arrive at the output screen at the same time, but causes vignetting.

The transfer of energy through the fluoroscopic imaging chain Focal Point

Flux Gain Photocathode Electrostatic focusing lens Output Phosphor (zinc-cadmium sulfide) Anode 25kV + potential Electrons accelerated across the tube gain kinetic energy from the attractive force of the anode (conversion efficiency). The collision at the output screen liberates that energy in the form of more light photons

Minification Gain Input Phosphor (CsI) Output Phosphor (zinc-cadmium sulfide) The ratio of the areas of the input and output screens is expressed as the minification gain. 1” diameter 9” diameter = 81 times

Total Brightness Gain The product of the flux gain and the minification gain is the total brightness gain. If the flux gain were 70, and the brightness gain x 81 = 5670 total brightness gain ,000 is the range

Quantum Mottle Because the image intensifier makes the image on the output screen thousands of times brighter than the image on the input screen, much less radiation is needed. If too few photons are used, the image becomes grainy and unacceptable for diagnostic purposes. Generally speaking a better image is always obtained by using more photons, but the price is paid in patient dose. Conversion factor The intensity of illumination at the output phosphor (candela per meter squared) to the radiation intensity that produced it (mR/s) Typical conversion factors of 50 to 300 relate to the ,000 BG

A B H D C G E F K J I L Test Image