Lecture - 2 MBBS (x-ray modalities)

Lecture for MBBS, Radiology subject. X-rays modalities

1. X-rays Modalities-I Dr. Bijay Kumar Yadav MD-Radiology Resident I.K. Akhunbaev KSMA Bishkek, Kyrgyzstan

2. Principles Of Radiation Protection:   Justification The imaging procedure should be judged to do more good (e.g. diagnostic efficacy of the images) than harm (e.g. detriment associated with radiation induced cancer or tissue effects) to the individual patient. Therefore, all examinations using ionizing radiation should be performed only when necessary to answer a medical question, treat a disease, or guide procedure. The clinical indication and patient medical history should be carefully considered before referring a patient for any X-ray examination.

3. Principles Of Radiation Protection: Optimization X-ray examinations should use techniques that are adjusted to administer the lowest radiation dose that yields an image quality adequate for diagnosis or intervention (i.e. radiation doses should be "As Low as Reasonably Achievable“ (ALARA)). The technique factors used should be chosen based on the clinical indication, patient size, and anatomical area scanned and the equipment should be properly maintained and tested.

4. Benefits Of X-ray Examinations Non invasively and painlessly help to diagnose the disease and monitor therapy. Support medical and surgical treatment planning . Guide medical personnel as they insert catheters, stents, or other devices inside the body, t reat tumors , or remove blood clots or other blockages .

5. Risks Of X-ray Examinations A small increase in the possibility that a person exposed to X-rays will develop cancer in later life. T issue effects such as cataracts, skin reddening, and hair loss, which occur at relatively high levels of radiation exposure and are rare for many types of imaging exams. Possible reactions associated with an intravenously injected contrast agent ( dye ), that is sometimes used to improve visualization .

6. Radiology And Children C hildren have an increased radio sensitivity to ionizing radiation (on average 2 - 3 times ), which creates high risk, both somatic and genetic effects of radiation; Physical and physiological differences between adults and children, including the closeness of the bodies, as well as irregular dynamics of their development, lead to higher levels of radiation to children than adults .

7. Methods Of Limiting And Reducing Radiation Exposure In Children !!!!! E xclude unnecessary studies or those studies which is of no need... !!!!! Not subject to preventive radiological studies in children up to 14 years of age and pregnant women . Women of child-bearing age should be questioned about possibility of pregnancy before abdominal X-ray investigation

8. The risk of developing cancer from medical imaging radiation exposure is generally very small, and it depends on: Radiation dose - The lifetime risk of cancer increases the larger the dose and the more X-ray exams a patient undergoes. Patient’s age - The lifetime risk of cancer is larger for a patient who receives X-rays at a younger age than for one who receives them at an older age (hormonal status and metabolism). Patient’s sex - Women are at a somewhat higher lifetime risk than men for developing radiation-associated cancer after receiving the same exposures at the same ages. Body region - Some organs are more radiosensitive than others.

9. X-Rays Wilhelm Conrad Roentgen - Father of Radiology Nov 8, 1895 – Discovered unknown radiations with photographic effect which he named ‘axa rays’ He got the Nobel prize in 1901.

10. X-rays Introduction : X-rays   represent a form of  ionizing electromagnetic radiation. They are produced by an x-ray tube, using a high voltage to accelerate the electrons produced by its  cathode . The produced electrons interact with the  anode , thus producing x-rays. The x-rays produced include   Bremsstrahlung .

11. Terminology: Generator : An x-ray generator gives power to the x-ray tube. It contains high voltage transformers, filament transformers and rectifier circuits.  Cathode : The cathode is the negative terminal of an x-ray tube. It is a tungsten filament and when current flows through it, the filament is heated and emits its surface electrons by a process called thermionic emission (TIE). Kilo voltage : High voltage, in the kilovolt range (1000 volts), is applied between the cathode and anode. This causes electrons to move towards the positive terminal (anode) of the tube at a velocity of half the speed of light (c). Anode : The positive terminal of the tube. M ade of a tungsten disc in ordinary diagnostic x-ray tubes . X-ray Tube : also called  Roentgen tube , that produces X rays by accelerating electrons to a high velocity with a high-voltage field and causing them to collide with a target, the anode plate .

12. What are x-rays? No mass No charge Energy X-rays are  a type of ionizing radiation called electromagnetic waves . X-ray imaging creates pictures of inside of our body. The images show the parts of our body in different shades of black and white. The most familiar use of x-rays is checking for fracture, but x-rays are also used in other ways.

13. X-ray Equipment: x-ray tube Table Film cassette Commonly the radiography equipment consists of a large, flat table with a drawer that holds an x-ray film cassette or a digital recording plate. With this arrangement, the x-ray tube is suspended above the table .

14. In digital radiography the radiography equipment looks like a box-like apparatus containing the recording material- such as a digital recording plate against which the individual places his/her chest and The apparatus containing the x-ray tube , usually positioned about six feet ( 72 inches ) away. 72 Inches

15. Radiography involves exposing a part of the body to a small dose of radiation to produce an image of the internal organs. When x-rays penetrate the body, they are absorbed in different amounts by different parts of the organ. For example: The ribs and spine absorb much of the radiation and appear white or light gray on the image. Lung tissue absorbs little radiation and appears dark on the image. How Does The Procedure Work ?

16. X-ray Production: X-rays  are produced due to sudden deceleration of fast-moving electrons when they collide and interact with the target anode . In this process of deceleration, more than 99% of the electron energy is converted into heat and less than 1% of energy is converted into x-rays. High Voltage Source

17. Image Formation A radiographic image is created by passing an x-ray beam through the patient and interacting with an image receptor ( a device that receives the radiation leaving the patient ) such as a film-screen or digital system. Both the quantity and quality of the primary x-ray beam affect its interaction within the various tissues that make up the anatomic part.

18. The absorption characteristics of the anatomic part are determined by its composition , such as thickness, atomic number, and tissue density or compactness of the cellular structures. Finally , the radiation that exits the patient is composed of varying energies and interacts with the image receptor to form the latent or invisible image. The process of image formation is a result of  differential absorption  of the x-ray beam as it interacts with the anatomic tissue. The term  differential  is used because varying anatomic parts do not  absorb  the primary beam to the same degree. Anatomic parts composed of bone absorb more x-ray photons than parts filled with air .

19. FIGURE : As the primary x-ray beam interacts with the anatomic part, photons are absorbed, scattered, and transmitted. The differences in the absorption characteristics of the anatomic part create an image that structurally represents the anatomic part .

20. Creating A Radiographic Image By Differential Absorption, These Several Processes Occur: Beam attenuation Absorption & Transmission Beam attenuation : As the primary x-ray beam passes through anatomic tissue, it loses some of its energy. Fewer x-ray photons remain in the beam after it interacts with anatomic tissue. This reduction in the energy or number of photons in the primary x-ray beam is known as attenuation. Two distinct processes occur during beam attenuation: A bsorption and S cattering .

21. Absorption: As the energy of the primary x-ray beam is deposited within the atoms comprising the tissue, some x-ray photons are completely absorbed. Complete absorption of the incoming x-ray photon occurs when it has enough energy to remove (eject) an inner-shell electron . Scattering: Some incoming photons are not absorbed but instead lose energy during interactions with the atoms comprising the tissue. This process is called scattering . Transmission: If the incoming x-ray photon passes through the anatomic part without any interaction with the atomic structures, it is called  transmission

22. Properties of X-rays: They have short wavelength of EMS and high frequency. Requires high voltage to produce x-rays. Highly penetrating and invisible to eyes . Liberates small amount of heat when passing through matter. They travel in a straight line with the velocity of light and do not carry an electric charge with them . They are capable of travelling in a vacuum. They are used to capture the human skeleton defects . Produce chemical and biological changes. Produce scatter and secondary radiation.

23. Characteristic of X-Ray Moving in a straight line. Has the power to penetrate an increasingly stronger in voltage used the higher. Can penetrate certain objects, such as wood up to several cm. Not deflected by a magnetic field and electric field. Can detach electrons from the metal are pounded (grind).

24. X-ray Modalities General M ethod s C omplementary M ethod s Contrast M edia Radiography Convential line a r tomograph y Barium meal Fluoroscopy D ecubitu s Barium enema Fluorography C holangiograph y Mammography Angiography CT-scan Bronchography

25. All X-ray Modalities Work On The Same Basic Principle: An X-ray beam is passed through the body where a portion of the X-rays are either absorbed or scattered by the internal structures, and the remaining X-ray pattern is transmitted to a detector (e.g. film or a computer screen) for recording or further processing by a computer.

26. Conventional Radiography

27. Principles Of Radiography Radiation is transmitted to va rying degrees depending upon the density of the material through which it is travelling. Thinner areas and materials of a less density show as darker areas on the radiograph. Thicker areas and materials of a greater density show as lighter areas on a radiograph. Applicable to metals, non-metals and composites.

28. Radiography: Conventional x-ray image are produced using a silver based photographic emulsion. Now a days digital recording is being used. Digital radiography is made by differential absorption of x-ray beam measured by special phosphor screen and read by laser . This can either write the image into film or display on monitor .

29. Radiography: 4 basic densities: Gas, Fat, Soft tissue and Calcified structures Gas absorbs less x-ray and appear black . Calcium absorbs the most and appear white . Solid soft tissue (except fat), e.g. solid viscera, muscle, blood, variety of fluids, bowel wall, etc. have similar absorptive capacity and appear grey . Fat absorbs fewer x-ray so appears blacker than other soft tissue .

30. Advantages of Radiography: Permanent record Internal flaws Can be used on most materials Direct image of flaws Real-time imaging

31. Disadvantages of Radiography: Health hazard Sensitive to defect orientation Access to both sides required Limited by material thickness Skilled interpretation required Relatively slow High capital outlay and running costs

32. Basic Concepts!!! One view is no view – use it all! Patterns are your clue Be sure you are looking Know what you’re looking for Know the limits of your test

33. One View Is No View Posterior sulcus nodule = Cancer (Mass)

34. One View Is No View RML collapse

35. Find the pathology What clues do you have?

36. Find The Pathology What Clues Do You Have? Can you recognize shapes and density?

37. History: 11 year old twisting injury of the foot

38. Epiphysis, Metaphysis, Diaphysis, Cortex, Medullary cavity Name the parts of a long bone Carpal Metacarpal Phalanges Diaphysis Metaphysis Epiphysis

39. Review: What Are The 5 Basic Radiographic Densities From Black To Bright White? Air Fat Soft tissue/fluid Bone / Mineral Metal

40. X-ray Film Displays the radiographic image and consists of E mulsion ( single or double ) of S ilver halide crystals (95 % silver bromide and 5% silver iodide ) and Gelatin. Which when exposed to light , produces a silver ion (Ag + ) and an electron. The electrons get attached to the sensitivity specks and attract the silver ion . Subsequently , the silver ions attach and clumps of metallic silver (black) are formed.

41. Layers: Base: Supports the fragile photographic emulsion. Substratum: an adhesive layer containing gelatin and solvents that bind emulsion and base. Emulsion: Photosensitive Layer of the film, silver halide and gelatin are key ingredients. Protective layer: gelatin super-coat The total thickness of the film is about 0.25 mm.

42. Super Coating Thin layer of Gelatin. Protects the emulsion from mechanical damage. Prevents scratches and pressure marks. Makes the film smooth and slick.

43. X-ray Film Gelatin Produced from the cattle bones. Advantages: Keeps “Silver Halide Grains” Well dispersed Prevent clumping of grains Developing solutions can penetrate Gelatin rapidly without damaging the structure and strength. Easily available in large and uniform quantity. Silver Halide Light sensitive material in emulsion. Composition: 90-99% S ilver Bromide 1-10% Silver Iodide – It increases sensitivity Silver Iodo -Bromide crystals are precipitated and emulsified in Gelatin Precipitation reaction involves addition of Silver Nitrate to soluble Halide to form soluble Silver Halide AgNO3 + KBr AgBr + KnO3

44. Types of x-ray film: Screen type films: faster when used with intensifying screen Conventional Orthochromatic (green sensitive) Direct exposure type: used for dental exposures.

45. The L atent Image Remnant radiation interacts with the silver halide crystals . Mainly by the photoelectric interaction. The energy deposited into the film is in the same pattern as the subject that was exposed to radiation. This invisible image is known as the Latent Image . A latent image on photographic (radiographic) film is an invisible image produced by the exposure of the film to light (radiation).

46. Formation of latent image: Metallic silver is black , so it is this metallic silver that produces black areas on a developed films. Exposure of silver- iodo -bromide grains to light photons emitted by screen / direct x-ray exposure initiates the formation of atomic silver to form a visible pattern. The M anifest Image: By chemically processing the latent image it is made visible . Certain chemicals permanently fixate the image onto the film.

47. Manual film Processing Developing – formation of the image Fixing – stopping of development, permanent fixing of image on film Washing – removal of residual fixer Drying – warm air blowing over film.

48. Automatic x-ray film processing system Systems of the Automatic Processor: The Film Feed Section Transport System Temperature Control System Recirculation System Replenishment System Dryer System Electrical System

49. Projections : Different views of the chest can be obtained by changing the relative orientation of the body and the direction of the x -ray beams : Described by the path of x-ray beam Examples: PA (postero-anterior) view means beam pass from back to the front. AP (antero-posterior) view means beam pass from front to the back. Lateral: right lateral, left lateral. Oblique: right oblique, left oblique, etc. Portable films/x-ray: Used to take radiographs in bed or operation theatre. The exposure is long and quality is compromised.

50. Projections : (PA View) PA view: Diaphragm, Breast shadow, N ipple, Soft tissue

51. Projections: (AP View )

52. Projections : (Lateral View)

53. Projections: (Oblique View)

54. Fluoroscopy

55. Fluoroscopy:   Is a type of medical imaging that shows a real time x-ray image on a monitor, much like an x-ray movie. During a fluoroscopy procedure, an x-ray beam is passed through the body. Fluoroscopic apparatus uses low current (0.5-5 mA) for continuous x-ray exposures . In recent years  flat panel detectors  (which are similar to the  digital radiography   used in  projection radiography ) have been replacing the image intensifiers . Resultant images have relatively low  signal to noise ratio (SNR)  but are of sufficient quality for patient positioning and certain diagnostic/therapeutic procedures.

56. Fluoroscopy

57. Image Intensifiers The image intensifier tube is a complex electronic device that receives the image forming x-ray beam and converts it into a visible light image of high intensity. Within an image intensifier , the input phosphor converts the x-ray photons to light photons . Which are than converted to photoelectrons within the photocathode.

58. Image Intensifiers Through this process, several thousand light photons are produced for each x-ray photon reaching the input phosphor. Most modern image intensifiers use cesium iodide for the input phosphor because it has a high absorption efficiency and thus decreases patient dose. IMAGE INTENSIFICATION = photons are amplified + multiplied

59. Applications of Fluoroscopy : Fluoroscopy is used in many types of examinations and procedures such as:- Cardiac catheterization. Arthrography (visualization of joint or joints). Lumbar puncture. Placement of intravenous (IV) catheters (hallow tubes inserted into veins or arteries). GIT investigations.

60. Fluorography Is   photography of X-ray images from a fluorescent screen . It is commonly used in some countries for chest X-ray screening , e.g . to diagnose  tuberculosis or lung cancer. The  photographic recording of fluoroscopic images on  small film using  a fast lens; used in  mass radiography  of the chest. Fluorography machines are compact and can be mounted in a car , this makes it possible to carry out mass research in those areas where there is no X-ray equipment.

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