TECHNIQUE EVERYTHING YOU WANTED TO KNOW BUT WERE AFRAID TO ASK!!!! Chapter 4 Fauber-Review Density :CONTROLLING FACTORS/INFLUENCING FACTORS: pg 63 •m •A •s • • • • • • • • • • • • • kVp Body Habitus SID/OID Screen Grids Collimation Thickness of the part Anode heel Reciprocity Law Tube filtration Compensating filters Film Processing Digital Processing Chapter 4 Fauber-Review CONTRAST: controlling/influencing factors pg 63 •k •V •p • • • • • • • Grids Collimation OID Anatomic part Tube filtration Contrast medium Digital imaging Contrast and digital imaging • kVp still important but…. • Contrast can be manipulated post processing • Minimizing scatter important since DR is sensitive to scatter TECHNIQUE REVIEW: SID,OID,COLLIMATION,ANATOMIC PART, ANODE HEEL, GENERATOR OUTPUT,TUBE FILTRATION , COMPENSATING FILTERS FILM PROCESSING RECIPROCITY LAW • DENSITY ON THE FILM SHOULD BE THE SAME FOR ANY COMBINATION OF mAs as long as the product of the mAs is equal!!! • WHAAAAAT???? • 30 mAs – 300mA x .1 = 30 mAs – 200 mA x .15 =30 mAs – 500mA X .06 = 30 mAs Same product It makes a difference • DIGITAL • EXPOSURE ERRORS OF 50% CAN BE ADJUSTED DIGITALLY • THINK ABOUT THAT! LET’S MOVE ON TO BUSHONG NOW CHAPTER 15 PG 244 LET’S REVIEW • • • • • TABLE 15-1 – REMEMBER THIS? WHAT IS A FALLING LOAD GENERATOR? DIRECT SQUARE LAW? DOES FOCAL SPOT IMPACT TECHNIQUE? LET’S MOVE ON TO PATIENT FACTORS, PG 251 Exposure Technique charts What should be on a technique chart? Can the same chart be used for all tubes? Types of charts – pg 260-265 • Variable kVp, Fixed mAs– short contrast/more pt exposure • Fixed kVp, Variable mAs – Prefered, longer contrast less patient exposure • High kVp chart – For exams using 100 kVp or higher • Automatic exposure-PATIENT POSITIONING --VERY IMPORTANT – – – – kVp important OD important Collimation important Accessary selection – Anatomically programmed radiography (APR) What do we do in these cases? • Casts/splints • Body habitus • Pathology – Is it always necessary to compensate? – NOTE BOX 15-1 ON PAGE 253 • Soft tissue Understanding chest x-ray technical factors • Inherently, the composition of the chest is high subject contrast. • Black lungs. White bones Understanding chest x-ray technical factors • Therefore to offset the short scale contrast, low mAs is used and high kVp is needed to add the long scale needed to see all anatomy CHART DEVELOPMENT-pge 263 in FAUBER – Comparative anatomy – Proportional anatomy Abd. 76 kVp, 20 mAs…What do we adjust for the following? • Rose Aehle • A thin but healthy person • A Football linebacker or Santa Claus • A frail, tiny,elderly person IT MAKES A DIFFERENCE • mAs change of 30% or higher before a change is noted • Changes in kVp in increments of 4 will produce a change in overall density and contrast especially in the lower kVp ranges. • For every one inch of OID, SID needs to be adjusted 7 inches TRUE SCENARIO • 80 YR OLD WHEELCHAIR BOUND MALE • CANNOT GET OUT OF WHEELCHAIR • SHOULDER IN NEUTRAL POSITION BUT A FRACTURE IS SUSPECTED • TUBE DOES NOT EXPOSE AT 40”SID • CAN EXPOSE AT 72” SID BUT WALL BUCKY DOES NOT MOVE DOWN LOW ENOUGH TO PUT BEHIND THE PATIENT. • WHAT POSITION AND TECHNIQUE SHOULD YOU USE? REFER TO TECHNIQUE CHART FOR THE ROOM THAT WAS A HANDOUT.