In this test demonstrated the effect of the part thickness with anode heel effect using a hand phantom.
In the first exposure with 35 x 43 cm cassette, we placed the lateral side of the hand under anode end. Exposure was taken at 80 cm SID. We used 1.3 mAs and 42 kV and checked our image with our instructor for proper exposure results. Collimations extend to the size of the cassette and it was consistent with the all exposures.
For each exposure we placed lead letter A in anode side, lead letter C in cathode side, and lead numbers (1,2,3) to show number of exposure.
For next exposures we used the same cassette, same kV and same mAs.
In the second exposure we placed the fingers of the hand under anode end.
In the last exposure we place the wrist under the anode end of the cassette
When the film is processed we evaluated the films. Took density readings at both cathode and anode ends of the all films. We write the density readings on the film:
- 1. Which exposure produced the most diagnostic image of the entire hand? Why?
In general the exposure number 2 was better diagnostic image, because the thicker part (distal radioulnar bine) located on cathode side. Since the x-ray beam will be more powerful on the cathode side, we must place thicker body parts under the cathode side to give a homogeneous exposure across the radiograph. Densities of all cathode side were higher than anode side. If diagnostic goal is bracken proximal second and third digit, the exposure number 3 shoes it more clearly. The density of bracken area in the exposure number 3 is 2.64 and for the exposure number 2 is 2.09. The exposure number is brighter with scatters.
- 2. Discuss 3 variables that influence the anode heel effect.
Due to the geometry of the oblique anode target, the radiation intensity is bigger on the cathode surface. The intensity of the x-ray beam is larger near the cathode end of the tube. The magnitude of influence of the heel effect on the image depends on factors such as: anode angle, size of film, focus to film distance- SID-, and focal spot size. one adverse result of the line-focus principle is that the radiation intensity on the cathode face of the x-ray tube is higher than the anode part. The variation in the intensity can differ by as much as 45%. If the center is 100% the anode surface of the beam can as low as 75% and the cathode as much as 120%. The heel effect must be considered when positioning areas of the body with different thickness or density. The cathode side should be over the area of greatest density. As the angle of the anode decreases, the anode heel effect increases. This can result in incomplete coverage of the film with the beam. The sharpness of the image can be dependent upon which area of the beam coverage you are looking at. In audition a larger IR will have more this effect, because being the further away from the central primary beam, lead to more changes.