1-2 Flashcards
(14 cards)
basic principles of sonography (3)
- very high frequency sound waves (above human hearing, 20,000Hz)
- makes use of principle of Piezoelectric effect
what happens to the Piezoelectric element when a voltage or vibration (ultrasonic wave)
voltage: vibrates to generate sound wave
vibration: generates voltage
steps to the pulse echo principle (7)
- electrical voltage supplied to crystal
- crystal generates sound waves
- sound waves penetrates tissues in the body
- some sound waves “echo” back to the crystal
- Piezoelectric crystal converts “echo” into electrical charge
- crystal converts “echo” into electric signals for computer
- computer converts electrical signals into points of brightness of the image where the brighter it is the stronger the echo
uses of ultrasound (2 +)
diagnostics/ study tissue structures:
obstetrics, gynaecology, neonatal head, musculo-skeletal, urinary/renal, vascular, cardiac, breasts, testes, thyroid
treatment/ theraphy:
increase circulation to soft tissue
basic principles of Magnetic Resonance Imaging (3)
- uses concept of Magnetism and Radio
Frequencies to create sectional images of the
body - Uses non-ionising radiation
- Makes use of water in the body, the most abundant atom in body (H2O)
body without external magnetism (MRI) (1)
Each H-atom randomly
orientated in human body,
NET magnetisation is ZERO
body with external magnetism (MRI) (2)
- nucleus spins (creates its own magnetic field), wobbles and vibrates
- forces the H protons to align and moves slowly in the directions of the magnetic field
body with external magnetism and radio frequency (MRI) (1+)
- Magnetic Resonance created by applying Radio Frequency perpendicular to the magnetic field
Effect: forces nuclei to spin out of equilibrium against the pull of the magnetic field
what happens when the radio frequency ends (MRI) (1+)
atoms relax to original state
Effect: Released energy is detected as an MRI signal
what is Fourier reconstruction (MRI)
when the MRI signal is received, Machine uses Fourier reconstruction to convert energy signals to corresponding colour levels to create an image
Positron Emission Tomography (PET) basic principles (2)
- medical specialty that uses radioactive tracers to asses bodily functions to diagnose/treat diseases
- radioactive tracer shows the activity and function of the tissues/organs eg bloodflow, oxygen
How does a Positron Emission Tomography (PET) work (6)
- Radiopharmaceutical is injected/swallowed into body.
- Radiopharmaceutical collides with an electron
- positron is emitted
- gamma rays generated
- Gamma rays are detected externally by special gamma or PET cameras
- electrical signals are then processed by the computer to generate images
What is a radiopharmaceutical (PET)
Radioactive + isotope Carrier ( sugar/protein molecule) = radiopharmaceutical
uses of Positron Emission Tomography (PET) (2+)
- diagnosis of organs
- study tissue physiology: cancer, blood flow in organs, , metabolic/enzyme activity
