4. Contrast is the. There must The function of contrast is to:. The types of contrast are.

Transcription

1 RADIOGRAPHIC VISIBILITY OF DETAIL STUDY QUESTIONS 1. What is visibility of detail? It is controlled by properties. What are the two factors that affect it? 2. What is sharpness of detail? It is controlled by properties. What are the two factors that affect it? 3. What is brightness.. It is also the of a. Tissues that attenuate the beam equally are because. A radiograph that is too light has brightness and a radiograph that is too dark has. The amount of ( ) will have on brightness. The computer will adjust the window through of the. There is a relationship between window level and brightness. 4. Contrast is the. There must The function of contrast is to:. The types of contrast are. 5. Tissue or subject contrast is the. It is affected by. controls subject contrast and of radiation Low KV wavelength has penetrating power, so it produces. The purpose of filtration is by removing, so that only the remain in the beam. Contrast will with an increase in filtration. Tissue absorption depends on the. can be used to change through the effect. The ability to distinguish among types of tissues is determined by the levels in the image or. Anatomic tissues that attenuate the beam similarly have subject contrast. Give examples. Anatomic tissues that attenuate the beam very differently have subject contrast. Give examples. So must be adjusted to compensate. 6. Radiographic or contrast is. It is the of different that can be by a computer and is called. Digital images can be to display a from contrast. The scale of contrast is determined by

2 7. The scale of contrast is determined by:. A short scale of contrast is also called contrast or in contrast. The definition for short scale of contrast is. The range of gray is. There is a change in brightness. What are the tonal values (color) for short scale? What are the uses of a short scale of contrast? Long scale of contrast is also called contrast or in contrast. The # of grey tones. The definition for long scale of contrast is. What are the tonal values (color) for long scale? What is the advantage of long scale of contrast? 8. In digital imaging contrast is called. The dynamic range is the range. The computer can manipulate the gray scale by using the. This changes the. This is related to contrast and related to the number of gray tones. 9. Contrast resolution is the ability of an imaging receptor to distinguish between. Sufficient in to the IR are necessary of the to exhibit. Contrast resolution is controlled by the, which is the. The larger the bit depth, the the number of levels of possible in the image. This determines the amount of in digitizing the analog and therefore the that can be displayed. When the bit depth is increased to 8 bits (2 ), a pixel can them have different values. Bit depth of 1 = (2 ). So as the bit depth is increased the displayed image will, so the signal value will and the image will be recorded. 10. What are the definitions of physical & visible contrast? Where are these terms used? 11. What is scatter?. The image will be causing a contrast than what is wanted. How does it affect visibility of detail? Scatter makes it difficult of between structures. Scatter is affected by. And increase in scater gives a scale of contrast. If scatter is decreased a scale of contrast is achieved. As tissue thickness or opacity increases scatter. As KV increases scatter. As collimation is increases scatter. When scatter is increased, it will give a scale of contrast. 12. The grid is used to. As the grid ratio is increased, there is scatter radiation absorbed by the grid, so you get a scale of contrast. A drawback to the use of grids is that the must be increased as the grid ratio is increased, so patient dose. Digital images are sensitive to scatter radiation. The contrast improvement factor is

3 . Higher grid ratios have contrast improvement factors. 13. Beam restriction is used to patient dose. It also the production of scatter. When beam restriction is increased, scatter, which gives a scale of contrast. What are the types of beam restricting devices?. Do lead blockers change the amount of scatter radiation produced?. They should be used on which projections? 14. When OID is below 6 inches, there is scatter, giving scale of contrast. When 6-10 OID is used this is called. The scatter radiation energy to reach the IR, so it gives a scale of contrast, but magnification will. To compensate for the magnification the SID can be 15. Compression makes the body part, so there is scatter, giving a scale of contrast. 16. List pathology that have increased attenuation (hard to penetrate) and those with decreased attenuation (easy to penetrate) 17. Circle the diseases that are hard to penetrate Paget s disease pneumopertioneum ascites bowel obstruction pneumonia pneulmthorax edema enlarged heart hydrocephalus pleural effusion emphysema empyema Increase KV Scatter Grid ratio Beam restriction (smaller field) Screen speed Excessive filtration Below 6 inches OID 6-10 inches OID Film speed Compression Amount of scatter Scale of contrast High or low contrast More grey or more black & white (less grey)

4 These will cause a short scale of contrast Decrease KV (longer wavelength) Decrease OID (1-5 in OID) Decrease window width Decrease patient thickness Decrease scatter Normal filtration Increase collimation (smaller field) Increase grid ratio Increase compression Use an air gap These will cause a long scale of contrast Increase KV (shorter wavelength) Increase OID (1-5 in OID) Increase window width Increase patient thickness Increase scatter Excessive filtration Decrease collimation (larger field) Decrease grid ratio Decrease compression Don t use an air gap For the following conditions, write shorter or longer scale of contrast. Change from 50 to 80 KV change from an 8:1 grid to no grid on a large body part. change form 1/2 inch OID to 3 inch OID. use compression on Abdominal images. change from 5:l grid to 12:l grid. change from 100 KV to 70KV. change from long wavelengths to short wavelengths. use lead blockers on a lateral lumbar spine. decrease scatter radiation. change collimation from 14 x 17 to 8 x 10. change patient size from 20cm to 30cm. use air gap technique put large patient prone for abdominal exam increase window width High contrast = scale of contrast, or contrast, KV, energy, penetration, wavelength, absorption, scatter, grid ratio, collimation, OID, compression.

5 RADIOGRAPIC QUALITY Properties Properties of detail of detail