1. Stacy Kopso, M.Ed., R.T.(R)(M)

2.  Xray photon loses energy and changes direction  Responsible for most of the scatter that fogs the image  Related to the energy of the photon As photon energy ↑, the probability of that photon penetrating a given tissue w/out interaction increases

3.  Factors that affect the amount of scatter radiation produced and exiting the patients Volume of tissue irradiated kVp  Volume of tissue depends on thickness of part and the xray beam field size  Increase the volume of tissue irradiated= Increased scatter production  Increase in kVp= Increase in scatter

4.  Adds unwanted exposure (fog) to image  More sensitive, Digital or Film Digital  Contrast Decreases  Tools to limit scatter radiation Beam restriction devices Grids

5.  Aka –Collimation  Purposes Limit pt exposure Prevent scatter production Decrease the size of the projected radiation field  Unrestricted primary beam Cone shaped Projects a round field on the pt and IR/would go beyond boundary of IR & pt if not restricted at all

6.  Increasing collimation & Field size Increasing collimation  decrease field size Decreasing collimation  increase field size  Increasing collimation & pt dose Increasing collimation  decrease pt dose

7.  Increasing the field size Collimation  Decrease Scatter  Increase Contrast  Decrease

8.  Increase in collimation Scatter  Decrease Contrast  Increase Number of photons that strike the pt  Decreases Exposure factor adjustment  Increase technique  mAs (kVp increases scatter)

9. Increase Collimation Increase Field Size Patient dose Scatter radiation Radiographic contrast Radiographic density(film) Quantum noise (digital)

10.  Aperture Diaphragms  Cones and Cylinders  Collimators  Automatic Collimator

18.  What happens if light goes out while your working on a pt?

19.  What could be the cause of a lack of accuracy in the light field? May be the mirror could be slightly out of position

20.  Automatically cones into field size to match the IR that is placed in the bucky  Used to be mandated on all new radiographic installations.

21.  Invented in 1913 by Gustave Bucky  Purpose Limits the amount of scatter radiation reaching the IR Absorbs the scatter radiation that is emitted from the patient  ¼ inch thick  Thin lead strips with radiolucent interspaces  Placed Between the patient and the IR

22.  Used when anatomic part is how thick and what range of kVp? 4 inches or greater in thickness or > 6okVp  Does it absorb all scattered radiation? No

23.  Thin lead strips or lines that have a precise height, thickness and space between them  Interspace material Aluminum  Grid Frequency # of lead lines per unit length in inch/centimeters 25-45 lines/cm or 60-110 lines/inch  Grid Ratio The ratio of the height of the lead strips to the distance between them Range from 4:1 to 16:1 (higher ratio clean up more scatter)

24.  What is the grid ratio when the lead strips are 3.2mm high and separated by.2mm? 16:1

25.  Types of Grid Pattern

26.  Types of Grid Focus

28.  Focused grids What determines the focal distance(grid radius) of a focused grid  Distance between the grid and the convergent point and convergent line  Focal distance determines the Focal range of a grid The recommended SID that can be used w/ grid Parallel can have a focal range extending from a minimum SID to infinity

30.  Types Stationary  Wafer -slip-on  Grid cassette –an IR that has a permanently mounted grid to its front  Grid cap- permanently mounted grid that allows the IR to slide in behind it Reciprocating  Part of the bucky  Potter-Bucky diaphragm

31.  Long dimension vs Short dimension Lead strips run parallel vs perpendicular 17 inch vs 14 inches

32.  Reduce the total amount of xrays reaching the IR Grid ratio increases= radiation exposure to the IR decreases  Technique adjustment mAs Grid conversion factor

33. Grid RatioConversion Factor No grid 5:1 6:1 8:1 12:1 16:1

34.  A radiographer produces a knee radiograph with a non grid exposure of 2mAs and next wants to use an 8:1 ratio grid. What new mAs should be used?  18mAs with a 16:1 grid, now wants to use a nongrid exposure  30mAs with a 6:1 ratio grid, now using a 12:1 ratio grid  40mAs with an 8:1 grid. Now using 5:1 grid

35.  A decrease in the number of transmitted photons that reach the IR Due to misalignment of the grid  Four types of grid errors 1. Upside-down focused 2. Off-Level 3. Off-Center 4. Off-Focus

40.  Occurs in digital imaging when you use a stationary grid  If the grid frequency is similar to the laser scanning frequency during image processing  How can you fix it? Use higher grid ratio or a moving grid

42.  Higher grid ratio results in Contrast Increase Pt dose Increase Grid cutoff Increase

43.  Alternative to using a grid  Limits the amount of scatter reaching the IR Increased distance between pt and IR (OID) Greater the gap, the less scatter reaches the IR Increase mAs & SID necessary