How does the anode heel effect work?
In X-ray tubes, the heel effect, or, more precisely, the anode heel effect is a variation of the intensity of X-rays emitted by the anode depending on the direction of emission along the anode-cathode axis. The effect stems from the absorption of X-ray photons before they leave the anode in which they are produced.
What does the heel effect results in?
In the digitized mammography, the percentages of the optical density of all the pixels of the analyzed image are also calculated. The Heel effect causes a Gaussian distribution around the anode–cathode axis and a logarithmic distribution parallel to this axis.
Does anode heel effect contrast?
In an anode with a smaller heel angle (α), the X-ray photons have to traverse a longer distance to exit the anode. This attenuates the X-ray photons more. By contrast, in an anode with a larger heel angle (β), the X-ray photons have to traverse a shorter distance to exit the anode. The radiation is thus stronger.
How do you increase the anode heel effect?
anode angle: by increasing the angle, the amount of target material perpendicular to the anode is decreased resulting in less resorption of x-rays produced. target-to-film distance: increase in distance reduces heel effect by allowing more divergence of the beam which produces a more uniform image.
Why is a rotating anode used?
The reason behind the introduction of rotating anodes is related to the dispersal of heat. In the case of a rotating anode tube, the heat of the incoming cathode beam is dispersed evenly across the entire surface of the anode as it rotates. This enables rotating anode users to perform longer scans and at higher doses.
How can you compensate for the heel effect?
To compensate for the heel effect, we developed a heel effect compensation (HEC) filter. The HEC filter rendered the dose distribution uniform and reduced the dose by an average of 25% for free air and by 20% for CTDI phantoms compared to doses with the conventional filter.
What is stationary anode?
A stationary anode is used in dental X-ray machines, portable X-ray units, and special purpose units, where high tube current and power are not required. Tubes with rotating anodes are used in X-ray units of larger capacity capable of producing high intensity X-ray beam in a short time.
Which is true of the anode heel effect?
Andrew Murphy ◉ and Dr Aditya Shetty ◉ et al. Anode heel effect refers to the lower field intensity towards the anode in comparison to the cathode due to lower x-ray emissions from the target material at angles perpendicular to the electron beam.
How does the heel effect affect the image?
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.
What happens when the anode angle is increased?
The end result is that the field intensity towards the cathode is more than that towards the anode. anode angle: by increasing the angle, the amount of target material perpendicular to the anode is decreased resulting in less resorption of x-rays produced.
Which is closer to the anode or the cathode?
More target material needs to be traversed at emission angles that are perpendicular to the electron beam (closer to the anode) than at those more parallel to it (closer to the cathode).