X-Ray Image Formation and Contrast
· While looking at a radiograph define image (radiographic) contrast and describe how it is expressed.
· Define "subject contrast" and describe how it is expressed.
· Name the factors that determine the amount of subject contrast coming from a patient's body.
· While looking at a radiograph distinguish between "object" and "area" contrast.
· Discuss the physical characteristics of an object within the body that determine its contrast.
· Explain why barium and iodine are particularly useful as contrast agents in radiology.
· Explain why air is an effective contrast agent even though its effective atomic number (6.65) is near that of soft tissue (7.42).
· Discuss the general relation of image contrast to KV.
· Identify clinical procedures in which low KV values are used and explain why.
· Describe the major disadvantages in using low KV values.
· Identify the anode and filter materials used for mammography and explain why.
· Sketch a typical x-ray spectrum used for mammography and explain how it is affected by anode material, filter material, and KV values.
· State the KV values which will generally give maximum contrast for iodine and barium and explain why.
· Describe the relationship of K-edge to contrast.
· Identify clinical procedures in which high KV values are used and explain why.
· State appropriate KV values for each general type of radiographic examination.
· Describe the effects of area contrast on object visibility.
· Describe the steps taken to reduce area contrast in mammography.
· Describe the steps taken to reduce area contrast in chest radiography.
1. Chapter 12. The Physical Principles of Medical Imaging, 2ndEd. Perry Sprawls. Medical Physics Publishing.
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