 Make and type of x-ray machine  Incoming line voltage  Kilovoltage  Milliamperage and exposure time  Focal film distance/source-imagine distance  Grid type  Speed and type of films and intensifying screens  Thickness and nature of part being exposed  Temperature and time of developing

The exposure technique chart developed for one x- ray machine may not produce satisfactory results with another x-ray machine

 Fluctuation in line voltage will not allow consistent output and this will affect all other variables

 Thermionic emission  Electron cloud  Electrical current measured as milliamperes  Increase in milliamperes increase in electrons  No. Of x-rays produced depends on the size of electron cloud  Exposure length- seconds  Quantity of X-rays= mA x time(in seconds)  Murphys law

 Potential energy of electrons when they reach the target is proportional to the potential difference bt anode and cathode  kilovoltage peak kVp  Change in kilo voltage  Inverse relationship bt kVp and mAs  Measuring kVp – Sante`s rule kVp=(2 x thickness)+40

kVp RANGEkVp CHANGE REQUIRED WITH CHANGE IN mAs (DOUBLED OR HALVED) 41-50± ± ± ± ±12 kVp CHANGE REQUIRED WITH CHANGE IN mAs

 Distance bt focal spot in the target ofthe X- ray tube and X-ray film  inches / cm  Inverse square law  Change in FFD (new FFD) 2 /( old FFD) 2 = new mAs/old mAs

Inverse square law

 Prevents film from the scattered radation thereby improves radiographic contrast  Grid requires increase in exposure factor Extent of change req in mAs with use of grid Grid ratioIncrease exposure(mAs) by a factor of 5:12 8:13 12:14 16:14.5

 Screen film requires 5 times less exposure  A par speed film requires double the exposure than a high speed film  Slow speed film requires twice as much exposure as par speed film  high speed screens requires one half the exposure to same radiographic density as par speed screens  Rare earth intensifying screens decrease the exposure factors 12 times

Without pathological lesions  A) skull,vertebrae, pelvis - increase kVp 5-10  B)soft tissue in cervical region- dec kVp 5-10  C) thorax - half mAs  D) immature animals - half mAs  E) heavy muscled animals - double mAs  F) plaster cast - double mAs  G)contrast studies – inc kVp 5-10/double mAs

With pathological condition a) Those in which the radiographic density is less than suspected: -Soft tissue calcification,bone lesions resulting in increased density, ingesta filled gastrointestinal track and abnormal fluid quantity.

b. Those in which the radiographic density is greater than suspected - megaoesophagus, localised destructive bone diseases,generalised bone diseases,pulmonary cyst and presence of large volumes of gas.

 Should be constant  low/short- under exposed  High/long-dark film, over exposed

The Kv is too low the femoral condyle is under pentrated all the subject is penetrated and all the soft tissues are visible

 Shortest possible exposure time  Highest possible kVp  Highest possible constant mA  Constant FFD/SID

 Veterinary radiology –A.P.Singh/Jit singh  Radiography technology in veterinary – lawis  Veterinary diagnostic radiology -thralls  htm htm 