MEDICAL IMAGING
MEDICAL IMAGING METHODS OF MODERN IMAGING, BASED ON ELECTRO-MAGNETIC RADIATION (radiowaves, infrared radiation, X-rays, γ-rays ) AND ULTRASOUND
MEDICAL IMAGING RADIOLOGY NUCLEAR MEDICINE ULTRASONOGRAPHY (ECHOGRAPHY) MRI (MAGNETIC RESONANCE IMAGING) THERMOGRAPHY
RADIOLOGY BASED ON ABSORPTION OF X-RAYS BY THE TISSUES: RADIOGRAPHS, CT
NUCLEAR MEDICINE BASED ON RADIOACTIVE ISOTOPES CONCENTRATED IN TISSUE, EMITTING PHOTONS (γ-rays)
ULTRASONOGRAPHY BASED ON HIGH-FREQUENCY MECHANICAL OSCILLATIONS, EMITTED AND RECEIVED SIMULTANEOUSLY BY A TRANSMITTER-SENSOR (TRANSDUCER)
MRI (MAGNETIC RESONANCE IMAGING) BASED ON RADIO-FREQUENCY RADIATION PRODUCED BY THE EXCITATION OF ODD ATOMIC NUCLEI IN A STRONG MAGNETIC FIELD
THERMOGRAPHY BASED ON INFRARED RADIATION EMITTED BY LIVING TISSUE
RADIOLOGY
RADIOLOGY BASED ON ABSORPTION OF X-RAYS BY THE TISSUES X-radiation (composed of X-rays) is a form of electromagnetic radiation shorter in wavelength than UV rays X-rays are a form of ionizing radiation
RADIOLOGY Wilhelm Conrad Röntgen (27 March 1845 10 February 1923) was a German physicist, who, on 8 November 1895, produced and detected electromagnetic radiation in a wavelength range today known as x-rays or Röntgen rays, an achievement that earned him the first Nobel Prize in Physics in 1901 "Röntgen" in English is spelled "Roentgen"
RADIOLOGY The source of X-rays is an X-RAY TUBE
HIGH VOLTAGE ELECTRIC CURRENT PASSES ACROSS A VACUUM TUBE WITH TWO ELECTRODES THE BEAM OF ELECTRONS BOOSTED FROM THE INCANDESCENT-HEATED CATHODE STRIKES A HEAVY METAL ANODE THAT PRODUCES HEAT AND X-RAYS RADIOLOGY
RADIOLOGY
RADIOLOGY BASED ON ABSORPTION OF X-RAYS BY THE TISSUES ABSORPTION OF X-RAYS DEPENDS ON: Density of the structure Thickness of the structure
RADIOLOGY IMAGING GEOMETRY Distortions arise in an image due to imaging geometry and the characteristics of an object
RADIOLOGY Parallax is an apparent exaggeration of the relative position of two objects when viewed along two different lines of sight. Given the two-dimensional nature of radiographs, parallax is an important principle in localizing objects within the body. On the basis of a single frontal view, it is impossible to tell the anteroposterior location of an abnormality. However, a second view from a different perspective can be used to localize the object.
RADIOLOGY
RADIOLOGY
RADIOLOGY RADIOLOGICAL METHODS: Simple (plain) radiography Fluoroscopy Conventional Tomography Computed Tomography (CT)
RADIOLOGY Simple (plain) radiography X-ray beam modulated through the patient s body is imprinted on a photographic plate (X-ray film) or received by digital detector (digital radiography)
RADIOLOGY Simple (plain) radiography X-RAY FILM
RADIOLOGY X-RAY FILM CASSETE DIGITAL DETECTOR
RADIOLOGY X-RAY ROOM Radiograph negative image
RADIOLOGY FLUOROSCOPY X-ray beam modulated through the patient s body is projected on a fluorescent screen. The image is viewed on the monitor. positive image
RADIOLOGY TERMINOLOGY: High dens structures opaque (opacity) bones, calcification, metallic foreign bodies Low dens structures lucent (lucency, translucency, transparency) air
RADIOLOGY negative image positive image opacity lucency
RADIOLOGY Conventional Tomography Allows tissue section radiographs. During the exposure, the X-ray tube and the film are moved in opposite directions. The chosen pivot point remains stationary during the whole motion.
RADIOLOGY Computed Tomography The X-ray tube emits a sharply collimated fan beam of X-rays which passes the patient and reaches an array of detectors. Tube rotates around the patient.
RADIOLOGY Computed Tomography Spiral CT X-ray tube rotates continuously around the patient.
RADIOLOGY Computed Tomography TERMINOLOGY: High dens structures hyperdense (hyperdensity) bones, calcification, metallic foreign bodies Low dens structures hypodense (hypodensity) air
RADIOLOGY Computed Tomography
RADIOLOGY CT-Angiography
RADIOLOGY CT-3D
RADIOLOGY CT-3D
RADIOLOGY CONTRAST MEDIUM (contrast agent) A substance used to enhance the contrast of structures or fluids within the body
RADIOLOGY positive media negative media CONTRAST MEDIUM (contrast agent)
RADIOLOGY CONTRAST MEDIUM (contrast agent) Positive contrast media and the body's soft tissues contain a similar number of atoms per unit volume. Some atoms in the contrast medium (e.g. iodine or barium) have a much higher atomic number than those of the soft tissues (hydrogen, carbon, nitrogen, oxygen). A higher atomic number is generally associated with an increased ability to attenuate X-rays.
Positive contrast media RADIOLOGY CONTRAST MEDIUM (contrast agent) water insoluble contrast media, an aqueous suspension of in soluble crystals of Barium Sulphate water soluble, which in clinical practice today means water solutions of organic compounds with iodine covalently bound to an aromatic structure (Isopaque, Urografin, Angiografin, Gastrografin, Omnipaque, Ultravist..) oily (fat-soluble) contrast medium (Lipiodol)
RADIOLOGY CONTRAST MEDIUM (contrast agent) Negative contrast media (air, oxygen, nitric oxide (N 2 O) or carbon dioxide (CO 2 ) and other gases) attenuate X-rays less than the soft tissues of the body, because a gas (the negative contrast medium) contains per unit volume a much lower number of radiation attenuating atoms than the patient's soft tissues.
RADIOLOGY RADIOLOGICAL METHODS USING CONTRAST MEDIUM Angiography Bronhography Colecystography, colangiography Oral Barium Sulphate, Barium Enema Limfography Arthrography
NUCLEAR MEDICINE
NUCLEAR MEDICINE Types of nuclear radiation: Alpha decay Alpha particles Beta decay Beta particles Gamma decay Gamma ray
Types of radiation: NUCLEAR MEDICINE α - consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. Electric charge +2. Mass 4 atomic mass units. Low penetration. β - high-energy, high-speed electrons or positrons. Electric charge 1. Mass of electron. Penetration higher than α γ - electromagnetic radiation of high energy. No electic charge. Mass of a photon High penetration
NUCLEAR MEDICINE Radionuclide an atom with an unstable nucleus that decays spontaneously with the emission of energy (gamma rays). 99m-Tc, 201-Tl, 131-I, 123-I, 57Co, 133-Xe Positron emitting: 15-O, 13-N, 18F, 11C
Radiopharmaceuticals NUCLEAR MEDICINE Substances that contain one or more radioactive atoms (radionuclids), used as tracers in the diagnosis and treatment. The ideal radiopharmaceutical is distributed only to the organs or structures to be imaged.
NUCLEAR MEDICINE Methods of investigation - Scintigraphy - SPECT - PET
NUCLEAR MEDICINE Scintigraphy a diagnostic procedure consisting of the administration of a radionuclide with an affinity for the organ or tissue of interest, followed by recording the distribution of the radioactivity by a scintillation camera.
NUCLEAR MEDICINE Scintigraphy
NUCLEAR MEDICINE SPECT (Single Photon Emission Computed Tomography) - is able to provide true 3D information - is performed by using a gamma camera to acquire multiple 2-D images from multiple angles.
NUCLEAR MEDICINE PET (Positron Emission Tomography) - produces a three-dimensional image of functional processes in the body
ULTRASONOGRAPHY (ECHOGRAPHY)
ULTRASONOGRAPHY Ultrasound Is an oscillation of pressure transmitted through a solid, liquid, or gas. The sound waves used in ultrasound are between 2 and 10 MHz
ULTRASONOGRAPHY Principle Piezoelectric crystals in the transducer convert electricity into high-frequency sound waves, which are sent into tissues. The tissues scatter, reflect, and absorb the sound waves to various degrees. The sound waves that are reflected back (echoes) are converted into electric signals. A computer analyzes the signals and displays the information on a screen.
ULTRASONOGRAPHY
Modes A-mode: the simplest; ULTRASONOGRAPHY signals are recorded as spikes on a graph; the vertical (Y) axis of the display shows the echo amplitude, and the horizontal (X) axis shows depth or distance into the patient; is used for ophthalmologic scanning.
ULTRASONOGRAPHY Modes B-mode (gray-scale): most often used in diagnostic imaging; signals are displayed as a 2-dimensional anatomic image; commonly used to evaluate the developing fetus and to evaluate organs, including the liver, spleen, kidneys, thyroid gland, testes, breasts, and prostate gland; fast enough to show real-time motion, such as the motion of the beating heart or pulsating blood vessels; real-time imaging provides anatomic and functional information.
Modes B-mode ULTRASONOGRAPHY
ULTRASONOGRAPHY Modes M-mode: used to image moving structures; signals reflected by the moving structures are converted into waves that are displayed continuously across a vertical axis; is used primarily for assessment of fetal heartbeat and in cardiac imaging.
ULTRASONOGRAPHY Modes Doppler ultrasonography : is used to assess blood flow; uses the Doppler effect (alteration of sound frequency by reflection off a moving object); the moving objects are RBCs in blood.
Modes 3D ULTRASONOGRAPHY
MAGNETIC RESONANCE IMAGING (MRI)
MRI Uses magnetic fields and radio waves to produce images of thin slices of tissues (tomographic images).
MRI Normally, protons within tissues spin to produce tiny magnetic fields that are randomly aligned. When surrounded by the strong magnetic field of an MRI device, the magnetic axes align along that field.
MRI A radiofrequency pulse is then applied, causing the axes of all protons to momentarily align against the field in a high-energy state. After the pulse, some protons relax and resume their baseline alignment within the magnetic field of the MRI device. The magnitude and rate of energy release that occurs as the protons resume this alignment (T1 relaxation) and as they wobble (presses) during the process (T2 relaxation) are recorded as spatially localized signal intensities by a coil (antenna). Computer algorithms analyze these signals and produce anatomic images.
Advantages: MRI Does not use ionizing radiation. Produces sectional images in any projection without moving the patient. Requires little patient preparation and is noninvasive. Excellent soft tissue contrast Lack of artifacts from adjacent bones
MR-Angiography
MEDICAL THERMOGRAPHY
MEDICAL THERMOGRAPHY Measures body tissue heat energy. Generally "problem areas" show high or low temperatures due to increased or reduced blood flow and metabolic activity, respectively. infrared radiation is emitted by all objects based on their temperatures above -237 С.
PACS
PACS (Picture Archiving and Communication System)