Lecture - 1 MBBS (Radiology introduction)

Lecture for MBBS, Radiology subject. basic concept of radiology.

1. Introduction To Clinical Radiology Dr. Bijay Kumar Yadav MD-Radiology Resident I.K. Akhunbaev KSMA

2. Contents Of Study Types and properties of electromagnetic waves. Physical and biological basis of radiation. Medical imaging. Prevention of radiation and Dosimetry.

3. Clinical Radiology It is a field of medicine which works by theory and practical application of radiation for medical purposes. Include two main disciplines: Diagnostic radiology and Therapeutic radiology (radiation therapy). Without radiology today can not do any medical discipline .

4. Radiology Importance: Radiologists need communication with clinicians to understand clinical problem. Clinician need communication with radiologists to understand the strengths and limitations of the investigations suggested. Suitable and sensible selection of imaging investigations and interventions. Approaches: Aimed in the direction of patient’s symptoms hoping that something will turn up Trial and error: try one or two likely diagnoses and carry out the appropriate test to support or refute these possibilities. Keep in mind: Less expensive Less distress to the patient Critical clinical evaluation to choose appropriate tests.

5. Types Of Radiation Electromagnetic waves Elastic waves

6. Electromagnetic W aves Theory Electromagnetic waves are waves that are created as a result of vibrations between an electric field and a magnetic field. In other words, EM waves are composed of oscillating magnetic and electric fields . Electromagnetic waves are formed when an electric field comes in contact with a magnetic field. They are hence known as ‘electromagnetic’ waves. The electric field and magnetic field of an electromagnetic wave are perpendicular to each other. They are also perpendicular to the direction of the EM wave.

7. Radiation : It is the energy that comes from the source & travel through the space & may be able to penetrate various materials. Radiation can also be produced by high-voltage devices (e.g. X-rays machine) Types of radiation: Ionizing radiation Non-Ionizing radiation

8. Why We Concerned About Radiation?? Ionizing Radiation Human cells Atoms in cells form Ions No changes in cells Change in cells Cell dies Reproduces Replaced Not replaced Benign growth Malignant growth

9. Radiation Causes Ionization Of: Cells Which May Affect Molecules Tissues Organ The whole body Which may affect Which may affect Which may affect

10. DNA Mutation

11. Ionizing Radiation: Ionizing radiation is a form of energy that acts by removing electrons from atoms & molecules that include air, water & living tissues & it can travel unseen & pass through these materials . Ionizing radiation is produced by unstable atoms. Unstable atoms differ from stable atoms because unstable atoms have an excess of energy or mass or both. Energy is “packaged” in small units known as photons or quanta.

12. EM radiation has no mass, is unaffected by either electrical or magnetic fields, and has a constant speed in a given medium . These include X- ray and gamma radiation . Examples of ionizing radiation: Natural: low level radiation which come from natural sources. - radiation from space (cosmic & solar radiation) - radiation from earth (terrestrial radiation) - radiation from building materials Man made: - X-rays, CT, PET, Fluoroscopy, Nuclear medicine procedure

13. Particulate Radiation The other type of radiation consist of small particles of matter moving through space at a very high velocity Particle radiation differs from EMR in that the particles consist of matter and have mass. Particle radiation is generally not used as an imaging radiation because of its low tissue penetration. E.g. α and β - particles, protons, neutrons, electrons, positrons, Heavy metal and other parts of the nucleus.

14. Non-Ionizing radiation A type of low-energy radiation that does not have enough energy to remove an electron (negative particle) from an atom or molecule. Non-ionizing radiation includes: Radio waves Microwaves Infrared Visible light Ultraviolet Most types of non-ionizing radiation have not been found to cause cancer.

15. Examples of Non-Ionizing radiation : Radiofrequency (RF) radiation used in many broadcast & communications applications. Microwaves used in the home kitchen. Infrared radiation used in the heat lamp. Ultraviolet radiation from the sun.

16. Ionizing v/s Non-Ionizing Radiation Ionizing Radiation Non-Ionizing Radiation Ionizes tissue Don’t ionizes tissue Causes genetic damage No known genetic damage Modalities: Modalities: CT scans Fluoroscopy Conventional radiographs (plain films) Nuclear imaging modalities ( Photons and corpuscular radiation) MRI Ultrasound Thermography X-Ray

17. Ionization: Ionization  is the principal means by which ionizing radiations dissipate their energy in matter. In this process the orbital electrons absorb energy from the incident photon, resulting in ejection of that  electron , leaving the atom positively charged ( positively ionized ). This process in tissue can damage important molecules such as DNA, that varies from minutes to weeks to years.

18. Understanding Ionization:

19. Electromagnetic Spectrum: Is the transport of energy through space as a combination of electric and magnetic fields. Is produced by a charge (charged particle) being accelerated. Electrons are consider as standing waves around the nucleus and therefore do not represent accelerating charges . Any accelerating charge not bound to atom will emit EM radiation.

20. Electromagnetic Spectrum: Ultraviolet Band: Non-Ionizing & Ionizing The electromagnetic (EM ) spectrum is the range of all types of EM  radiation .

21. Electromagnetic Spectrum: Ionizing Radiation: Short wavelength, High frequency & Higher Energy Non-Ionizing Radiation: Longer wavelength, Lower frequency & Lower energy We can say wavelength & frequency is inversely proportion where as frequency & energy is directly proportion.

22. Photoelectric Effect: The  photoelectric effect  is the emission of electrons when  electromagnetic radiation , such as  x-rays, hits a material. Electrons emitted in this manner are called photoelectrons.

23. FIGURE: Photoelectric Effect- The photoelectric effect is responsible for total absorption of the incoming x-ray photon.

24. The Penetrating Power Of Radiation In Matter

25. The Use Of Radiation In Medicine Is Based On Four Properties Of Interaction With Matter

26. Radio Sensitivity RS : Probability of a cell, tissues or organ of suffering an effect per unit of dose. Bergonie and Tribondeau (1906) : “RS LAWS” : RS will be greater if the cell: Is highly mitotic. Is undifferentiated. Has high cariocinetic future.

27. Radio Sensitivity (RS) High RS Medium RS Low RS Bone marrow Skin Muscle Gonads Mesoderm organ (Liver, Lungs, Heart etc Cartilage Thymus Bones Spleen Nervous system Lymphatic nodes Eye lens Lymphocytes

28. Elastic Waves

29. Radiation Measurements: Radiation can measured in the same manner as other physical concepts such as Time, Distance and Weight. International commission on radiation units and measurement (ICRU) has established special units for the measurement of radiation. Such units are used to define four quantities of radiation: Exposure Dose Dose equivalent Radioactivity At present, two systems are used to define radiation measurements: The older system is referred to as the traditional system, or standard system The newer system is the metric equivalent known as the SI system.

30. Exposure The term exposure refers to the measurement of ionization in air produced by X-rays. Standard unit – Roentgen (R) SI unit – Coulombs per kilogram (C/kg) Dose Dose can be defined as the amount of energy absorbed by a tissue. Standard unit – Radiation absorbed dose (rad) SI unit – Gray ( Gy )

31. Dose Equivalent Different types of radiation have different effects on tissues, the dose equivalent measurement is used to compare the biologic effects of different types of radiation. Standard unit – Roentgen equivalent (in) man (rem) Si unit – Sievert ( Sv ) 1 rem = 0.01 Sv 1 Sv = 100 rems

32. Radioactivity: It is the process by which a nucleus of an unstable atom loses energy by emitting ionizing radiation. Standard unit- Curie ( Ci ) SI unit- Becquerel ( Bq ) One Curie is equal to 3.7×10^10 (37 billion Bq ) disintegration per second. One Becquerel is equal to one disintegration per second.

33. Radioactivity : S pontaneous emission of radiation from the nucleus of an unstable atom. Isotope : A toms with the same number of protons, but different number of neutrons. Radioisotope : U nstable isotope of an element that decays or disintegrates spontaneously, emitting radiation. Approximately 5,000 natural and artificial radioisotopes have been identified .

34. Two Categories Of Radioactivity Natural radioactivity : T his is the spontaneous disintegration of naturally occurring radio-nuclides to form a more stable nuclide with the emission of radiations of alpha, beta and gamma. Artificial radioactivity : T his is the spontaneous disintegration of radio-nuclides when bombarded with a fast moving thermal neutron to produce a new nuclide with the emission of radiations of alpha, beta and gamma and a large amount heat.

35. Radioactive sources

36. Radioactive Carbon (C-14)

37. Prevention Of Radiation Sickness: Avoid unnecessary exposure to radiation. Persons working in radiation hazard areas should wear badges to measure their exposure levels.  Protective shields should always be placed over the parts of the body not being treated or studied during x-ray imaging tests or radiation therapy .

38. What Are The Basic Measures In Radiation Protection? Shortening the time of exposure, increasing distance from a radiation source and shielding are the basic protective measures to reduce doses from external exposure. Time: The less time that people are exposed to a radiation source, the less the absorbed dose. Distance : The farther away that people are from a radiation source, the less the absorbed dose .

39. Shielding: Barriers of lead, concrete or water can stop radiation or reduce radiation intensity .

40. To Reduce Doses From Intake Of Radioactive Substances, The Following Basic Countermeasures Can Be Considered: Shortening time of exposure to contaminants. P reventing surface contamination. P reventing inhalation of radioactive materials in air. P reventing ingestion of contaminated foodstuffs and drinking water .

41. Ways To Reduce Staff Radiation Exposure Reduce exposure time Increase distance from radiation Use proper shielding Wear radiation film badge is exposed to multiple x-rays.

42. Ways To Reduce Patient Exposure To Ionizing Rays Eliminate unnecessary radiographs and projections. Shield the most radiation sensitive areas (gonads, eye lens, thyroid ). Reduce area irradiated. Avoid x-rays in pregnancy.

43. Imaging Modalities X-Rays USG CT-Scan MRI PET-Scan

44. Methods/Modalities Of Investigations: Conventional radiography (x-rays) Plain x-rays Contrast radiography Conventional angiography Mammography Digital radiography Computed Tomography (CT scan) Conventional CT Spiral (helical) CT Multi-slice (multi-detector) CT: faster, thin slide, 3D reconstruction, angiography CT angiography 3D reconstruction CT Contrast CT .

45. Ultrasound Conventional USG 3D and 4D USG Doppler imaging MRI (magnetic resonance imaging) T1-weighted scan T2-weighted scan MR angiography Contrast MRI

46. Radionuclide imaging: radioactive isotope Conventional study (gamma camera) SPECT (Single photon emission computed tomography) using moving gamma camera PET (positron emission tomography): to study physiological procedure (perfusion, metabolism, etc.) using short-lived positron-emitting isotopes produced by cyclotron PACS (picture archiving and communicating systems): electronic transmission of images..

47. 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.

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