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

RADIOLOGY

• 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 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

CT-Angiography

RADIOLOGY

CT-3D

RADIOLOGY

CT-3D

RADIOLOGY

RADIOLOGY

CONTRAST MEDIUM

(contrast agent)

• A substance used to enhance the

contrast of structures or fluids within

the body

RADIOLOGY

CONTRAST MEDIUM

(contrast agent)

• positive media

• negative media

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.

RADIOLOGY

CONTRAST MEDIUM (contrast agent)

• Positive contrast media

– 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 (N2O) or

carbon dioxide (CO2) 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

NUCLEAR MEDICINE

Types of radiation:

• 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

NUCLEAR MEDICINE

Radiopharmaceuticals

• 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

ULTRASONOGRAPHY Modes

• A-mode:

– the simplest;

– 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.

ULTRASONOGRAPHY Modes

• B-mode

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.

ULTRASONOGRAPHY Modes

• 3D

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.

MRI Advantages:

• 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)