Visibility of Detail

Transcription

1 Visibility of Detail

2 Radiographic Quality Quality radiographic images represents the, and information is for diagnosis. The of the anatomic structures and the accuracy of their ( ) determine the overall quality of the radiographic image.

3 The visibility of recorded detail refers to the of the image. The accuracy of the structural lines is achieved by maximizing the amount of.

4 Brightness Brightness range of image brightness levels visible after processing the IR is a result of the variation in as the x-ray beam passes through the tissues.

5 Brightness is the amount of.

6 Tissues that attenuate the x-ray beam equally are to visualize because the.

7 A radiograph that is too light has brightness and a radiograph that is too dark has brightness.

8 The amount of exposure (mas) will have a effect on brightness. The computer processing will adjust the through of the. There is a relationship between window level and brightness.

9 Contrast Contrast:. Function : To make. Types of contrast:

10 Subject Contrast occurring in an anatomical part and the of the beam. Affected by:

11 KV controls and of radiation. Long wavelengths ( KV) has penetrating power, so it produces because of. Short wavelengths ( KV)produces densities because of its. low KV high KV

12 Filtration Purpose by removing energy ( wavelengths) x-rays so only energy ( ) remain in beam. Contrast will with an increase in filtration

13 Tissue absorption depends on ( ) and of tissue.

14 Contrast media can be used through the.

15 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. Anatomic tissues that attenuate the beam have high subject contrast

16 Radiographic Contrast Radiographic or image contrast. The number of different that can be by a computer system is called.

17 Digital images can be to display a range of gray levels from contrast. Scale of contrast determined by the in the image.

18 SCALES OF CONTRAST Scale of contrast is determined by:

19 High contrast ( scale or in contrast) Range of image densities is and each density exhibits a difference from its neighbor density.

20 Low Contrast ( scale in contrast) Range of image densities is and each density exhibits in from its neighbor density.

21 Short Scale Vs Long Scale

22 In digital imaging it is called the. Dynamic range - the range of of the display monitor emission. It is changed by changing the relationship to contrast. The computer can as needed.

23 The computer can manipulate the gray scales as needed by using ( ). This changes the relationship to contrast, and a relationship to the of gray tones.

24 Contrast Resolution Ability of an imaging receptor to distinguish between objects having. Sufficient differences in exposure to the receptor are necessary for the.

25 Contrast resolution is controlled by the, the pixel. The larger the bit depth, the the number of levels of gray possible in the image.

26 When the pixel depth is increased to eight bits (2 8 ), a pixel can then have different gray values. Bit depth of 1 = 2 8 = = = = 4096

27 Other terms used in digital imaging related to scale of contrast: Physical contrast the total range of density values. Visible contrast the total range of density values.

28 Scatter radiation will add a layer of superimposed on the. The image will be causing a contrast that what is wanted.

29 Scatter Influenced by: Increase scatter gives scale of contrast. BUT if you clean up scatter - gives scale of contrast image.

30 Grid Most effective device for. Higher grid ratio - more scatter radiation - get a contrast No grid 12:1 grid

31 Contrast is not correctly displayed because. Digital imaging is. No grid Grid

32 The contrast improvement factor K is measured by: K = Higher ratio grids have improvement factors.

33 Beam restriction ( ) Used to. Also production of. Beam should be restricted to. Increase beam restriction - scatter contrast No collimation cone to orbit

34 Beam restriction

35 Devices to restrict beam:

36 OID (object film distance) Below 6 inches - increased scatter contrast.

37 Air gap technique (OID ) Scatter radiation reach IR. scatter contrast. Disadvantage. 2 inch OID 8 inch OID

38 Compression Makes body part - scatter produced contrast. AP pelvis PA pelvis

39 Pathology Increased attenuation Decreased attenuation