Heel effect - Wikipedia Heel effect This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. Please help to improve this article by introducing more precise citations. ( May 2014 ) An illustration of the heel effect in an x-ray tube In X-ray tubes, the heel effect or more accurately, the anode heel effect is a variation of the intensity of X-rays emitted by the anode depending on the direction of emission. Due to the geometry of the anode, X-rays emitted towards the cathode are in general more intense than those emitted perpendicular to the cathode -- anode axis. The effect stems from the absorption of X-ray photons before they leave the anode in which they are produced. The probability of absorption depends on the distance the photons travel within the anode material, which in turn depends on the direction of emission. Contents 1 Factors 1.1 Source to Image Distance ( SID ) 1.2 Beam and receptor size 1.3 Anode angle 2 Solutions 3 References Factors Source to image distance ( SID ) The distance from the anode ( source of X-rays ) to the image receptor greatly influences the apparent magnitude of the anode heel effect. The shorter the distance, the less space the beam has to diverge. The effect is less noticeable at larger source - image distances ( SID ). Beam and receptor size Diagnostic X-ray beams can be collimated to large or small beams. A large beam will emit more intensities of the beam along the cathode - anode axis than a small beam. A large image receptor will also capture more of this beam than a small receptor. Both of these factors will greatly influence the visibility of the anode heel effect. A smaller field size results in a less pronounced heel effect. Anode angle When the angle of the anode is great, the usable X-ray photons will not have to travel through as much of the anode material to exit the tube. This results in a much less apparent anode heel effect, though the effective focal spot size is increased. Solutions Almost all modern diagnostic x-ray machines exhibit the heel effect to some degree. Its effect on images is mostly avoided through consideration of patient positioning. For example, when imaging a foot which is thicker at the ankle end than the toes, the toes should be positioned towards the anode and the ankle towards the cathode. There have also been some efforts to eliminate the heel effect through automatic software adjustment of pixel values. References Jump up ^ `` Figure 3 - 12. Anode heel effect. - Fundamentals of X-Ray Physics ''. Integrated Publishing. Retrieved 9 December 2016. Jump up ^ Curry, Thomas S. ; Dowdey, James E. ; Murry, Robert C. ( 1990 ). Christensen 's physics of diagnostic radiology ( 4th ed. ). Philadelphia : Lea & Febiger. p. 18. ISBN 9780812113105. Jump up ^ Ghom, A.G. ( 2009 ). Textbook of Oral Radiology. Elsevier India. p. 52. ISBN 9788131211489. ^ Jump up to : Huda, Walter ( 2010 ). Review of radiologic physics ( 3rd ed. ). Baltimore, MD : Lippincott Williams & Wilkins. p. 26. ISBN 9780781785693. Jump up ^ Thayalan, K. Basic Radiological Physics. New Delhi : Jaypee Brothers Publishers. p. 66. ISBN 9788171798544. ^ Jump up to : Bontrager, Kenneth L. ; Lampignano, John ( 2013 ). Textbook of Radiographic Positioning and Related Anatomy. Elsevier Health Sciences. p. 38. ISBN 9780323277556. Jump up ^ Mesbahi, Asghar ; Zakariaee, Seyed - Salman ( May 2013 ). `` Effect of anode angle on photon beam spectra and depth dose characteristics for X-RAD320 orthovoltage unit ''. Reports of Practical Oncology & Radiotherapy. 18 ( 3 ) : 148 -- 152. doi : 10.1016 / j. rpor. 2012.12. 001. Jump up ^ Andolina, Valerie F. ; Lille, Shelly ( 2010 ). Mammographic imaging : a practical guide ( 3rd ed. ). Philadelphia, Pa. : Lippincott Williams & Wilkins. p. 238. ISBN 9781605470313. Jump up ^ do Nascimento, Marcelo Zanchetta ; Frère, Annie France ; Germano, Fernao ( 11 September 2007 ). `` An Automatic Correction Method for the Heel Effect in Digitized Mammography Images ''. Journal of Digital Imaging. 21 ( 2 ) : 177 -- 187. doi : 10.1007 / s10278 - 007 - 9072 - 1. PMC 3043860. This physics - related article is a stub. You can help Wikipedia by expanding it. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Heel_effect&oldid=770659330 '' Categories : X-rays Medical physics Physics stubs Hidden categories : Articles lacking in - text citations from May 2014 All articles lacking in - text citations All stub articles Talk Contents About Wikipedia فارسی Italiano Edit links This page was last edited on 16 March 2017, at 20 : 12. About Wikipedia

Question: the prominent heel effect in mammography is due to a
Answer: absorption of X-ray photons before they leave the anode in which they are produced