DIAGNOSTIC RADIOLOGY Image quality

1. DIAGNOSTIC RADIOLOGY Image quality

2. Aim: To become familiar with the factors that determine the image clarity and the way the image quality can be improved

3. Add module code number and lesson title 3 Contents Image contrast Blur or lack of sharpness Distortion and Artifacts Image noise Explanation or/and additional information Instructions for the lecturer/trainer Explanation or/and additional information Instructions for the lecturer/trainer

4. Add module code number and lesson title 4 ??????? ????? ?? ????????? 1- ??????? ????? ?????? ???. ??? ??? ?? ??? ???? ????. 2- ?????????? ????? (Background) ????? ??? ?? ?? ?? ??????? ? noise ?? ????. -3????? ??? ????(Unsharpness) ????? focal spot size ? Screen ?? ????. -4????? ??????? ?????? ? ???? ?????? Random ???? noise ?? ????.

5. Add module code number and lesson title 5 Factors affecting image quality

6. Topic 1 : Image contrast Part …: (Add part number and title) Module…: (Add module number and title) Lesson …: (Add session number and title) Learning objectives: Upon completion of this lesson, the students will be able to: … . (Add a list of what the students are expected to learn or be able to do upon completion of the session) Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.) Duration: (Add presentation time or duration of the session – hrs) Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate) References: (List the references for the session) Part …: (Add part number and title) Module…: (Add module number and title) Lesson …: (Add session number and title) Learning objectives: Upon completion of this lesson, the students will be able to: … . (Add a list of what the students are expected to learn or be able to do upon completion of the session) Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.) Duration: (Add presentation time or duration of the session – hrs) Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate) References: (List the references for the session)

7. Add module code number and lesson title 7 Image contrast Difference in optical density between adjacent points on an image represents contrast Contrast depends on: ? Density (air, bone) ? Thickness (micro calcifications) ? Atomic number ? kVp ? Film, intensifying screen, contrast agents

8. Add module code number and lesson title 8 Receptor contrast The film as receptor has a major role to play in altering the image contrast There are high contrast and high sensitivity films The characteristic curve of the film describes the intrinsic properties of the receptor (base + fog, sensitivity, mean gradient, maximum optical density) N.B.: Film processing strongly has a pronounced effect on fog and contrast

9. Add module code number and lesson title 9 The video monitor is commonly used in fluoroscopy and digital imaging The display on the monitor adds flexibility in the choice of image contrast The dynamic range of the monitor is limited (limitation in displaying wide range of exposures) Increased flexibility in displaying image contrast is achieved by adjustment of the window level or gray levels of a digital image Video monitor

10. Topic 2 : Blur or lack of sharpness Part …: (Add part number and title) Module…: (Add module number and title) Lesson …: (Add session number and title) Learning objectives: Upon completion of this lesson, the students will be able to: … . (Add a list of what the students are expected to learn or be able to do upon completion of the session) Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.) Duration: (Add presentation time or duration of the session – hrs) Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate) References: (List the references for the session) Part …: (Add part number and title) Module…: (Add module number and title) Lesson …: (Add session number and title) Learning objectives: Upon completion of this lesson, the students will be able to: … . (Add a list of what the students are expected to learn or be able to do upon completion of the session) Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.) Duration: (Add presentation time or duration of the session – hrs) Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate) References: (List the references for the session)

11. Add module code number and lesson title 11 Blur or lack of sharpness The boundaries of an organ or lesion may be very sharp but the image shows a lack of sharpness Different factors may be responsible for such a degree of “fuzziness” or blurring The radiologist viewing the image might express an opinion that the image lacks “detail”

12. Add module code number and lesson title 12 Factors affecting image sharpness

13. Geometric blur If the focal spot is effectively small, the blur is minimized because of minimal geometric unsharpness As the focal spot increases, the blur in the image increases

14. Add module code number and lesson title 14 Geometric Unsharpness -?????? ?????? ?? ?????? ???? ?????? ?? ???? ??????? ?? ??? ??????? ??? ???????? ???????? ??????? ?????????? ???? ??? ???????? ???? ???????.

15. Lack of sharpness in the subject Not all structures in the body have well-defined boundaries (superimposition essentially present in most situations) The organs do not have square or rectangular boundaries The amount of required details in the object, is an essential requirement of any imaging system The absence of sharpness, in the subject/object is reflected in the image

16. Add module code number and lesson title 16 ?Absorption unsharpness

17. Lack of sharpness due to motion (1) Common and understandable blur in medical imaging Patient movement : uncooperative child organ contraction or relaxation heart beating, breathing etc. Voluntary motion can be controlled by keeping examination time short and asking the patient to remain still during the examination

18. Lack of sharpness due to motion (2) Shorter exposure times are achieved by the use of fast intensifying screens N.B.: Faster screens result in loss of details (receptor sharpness) Further, the use of shorter exposure time has to be compensated with increased mA to achieve a good image This often implies use of large focal spot (geometric sharpness)

19. Add module code number and lesson title 19 Movement Unsharpness -?????? ???????? ???? ??????? ???????? ???? ???????? ?????? ???????????????? ? ??? ????????? ?? ?????????????? ??????? ???? Cine- Fluorography ???? ??????? ???????? ???? -?? ?????? ???????? ??? ?????????? ????????? ?? ????? ?????? ?? ??????????????? ???????????? ????????

20. Lack of receptor sharpness The intensifying screen in radiography has a crystal size which is larger than that of the emulsion on the film An image obtained without the screen will be sharper than that obtained with the screen, but will require much more dose The thickness of the screen further results in degradation of sharpness

21. Add module code number and lesson title 21 Total Unsharpness 2/1 (Ua2 + Us2 + Um 2 + Ug 2 ) = Ut   ?? ???????????????????? ?? ??????? ??????? ???????? ??? ( edge) ?? ??? ????? ???????? ?????????? ???????? ??? ???. ?? ????????????????????? ?? ?????? ??????? (?????? ?????????????????????????? ? ???? ???? - ??? ????)? ????? ??? ???? ?? ???? ???? ?? ??? ???? ??????? ??? ?? ?? ??? ?? ??? ? ??????? ????? ??????? ?? ????.

22. Topic 3 : Distortion and artifacts Part …: (Add part number and title) Module…: (Add module number and title) Lesson …: (Add session number and title) Learning objectives: Upon completion of this lesson, the students will be able to: … . (Add a list of what the students are expected to learn or be able to do upon completion of the session) Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.) Duration: (Add presentation time or duration of the session – hrs) Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate) References: (List the references for the session) Part …: (Add part number and title) Module…: (Add module number and title) Lesson …: (Add session number and title) Learning objectives: Upon completion of this lesson, the students will be able to: … . (Add a list of what the students are expected to learn or be able to do upon completion of the session) Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.) Duration: (Add presentation time or duration of the session – hrs) Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate) References: (List the references for the session)

23. Distortion and artifacts Unequal magnification of various anatomical structures Inability to give an accurate impression of the real size, shape and relative positions Grid artifact (grid visualized on the film) Light spot simulating micro-calcifications (dust on the screen) Bad film screen contact, bad patient positioning

24. Add module code number and lesson title 24 Magnification ?? ????????? ????? ????? (Divergent) ???? ???????????? ?????? ?????? ??? ??? ??????? ??? ????. ??? ???? ??? ??????????? ????? ??? ?? ???? ?? ?? ???? ? ??? ?? ?????? ??? ????????? ?? ????? ????? ???? ?? ???? ???? ?? ???. ?????? ????? ????????? ????? (????AP ?? PA) ?????????? ?? ???? ????? ??? ??????????????? ????? ????? ?? ???.

25. Add module code number and lesson title 25 Distortion ????? ??? ( Distortion) ???? ???? ?? ????? ?????? ???? ? ????????????? ???? ?? ???. ??? ???? ??? ????? ???? ????? ??? ?? ???? ?? ?? ???? ? ???? ???? ??????????? ?? ?? ???? ?? ???? ????? ???? ???? ?? ???.

26. Artifacts

27. Topic 4 : Image noise Part …: (Add part number and title) Module…: (Add module number and title) Lesson …: (Add session number and title) Learning objectives: Upon completion of this lesson, the students will be able to: … . (Add a list of what the students are expected to learn or be able to do upon completion of the session) Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.) Duration: (Add presentation time or duration of the session – hrs) Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate) References: (List the references for the session) Part …: (Add part number and title) Module…: (Add module number and title) Lesson …: (Add session number and title) Learning objectives: Upon completion of this lesson, the students will be able to: … . (Add a list of what the students are expected to learn or be able to do upon completion of the session) Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.) Duration: (Add presentation time or duration of the session – hrs) Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate) References: (List the references for the session)

28. Image noise Information that is not useful is noise The snowing in a TV image, the speckles in an ultrasound image are examples of noise Noise interferes with visualization of image features useful for diagnosis

29. Add module code number and lesson title 29 Main Sources of Noise Radiation noise (eg; heel effect) (1 2 - Random or Stochastic noise: ??? Random ???????? x ?? ????? ????? ????? (Quantum noise). Photon Statistical Noise by low photon flux) (e.g; Screen or Coarse Grain Noise) ??? Random ???????? ???? ???? ???? ???? ?? ???????? ???? Receptor or Fine Grain Noise

30. Add module code number and lesson title 30 Main Sources of Noise 2- Structured or nonstochastic: - ?????? ?? ????? ???? ???? ????? ????? Screen ???? ??????? ?????????? ???? ????? Receptor noise, Non-uniformed film, screen defects,…  4- Electronic noise : ????? ?? ????? ???? ?????? ????? ?? ??? ???? ????? Random noise ?? ?? ??? 5- Random neural Process : ?? ??? ?? ???? ???? ????? ?????? ????? ???? ?? ???. 6) Scattered Radiation in Both Subject and Imaging Receptors

35. Add module code number and lesson title 35 Noise and Detective Quantum Efficiency

37. Add module code number and lesson title 37 Signal-to -noise Ratio: 

38. Add module code number and lesson title 38 Signal to Noise Ratio

39. Add module code number and lesson title 39 Noise Power Spectrum of film-screen system

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41. Add module code number and lesson title 41 Where to Get More Information Hendee WR, Riternour ER, eds. Medical Imaging physics, 3rd ed. St. Louis: Mosby Year Book, 1992 Sprawls Perry Jr. Ed. Pysical principles of medical imaging. Maddison: Medical Physics Publishing, 1993 Moores BM, Wall BF, Eriskat H and Schibilla H, eds. Optimization of image quality and patient exposures in diagnostic radiology. London: British Institute of Radiology 1989.