Principles of Radiology Flashcards
(20 cards)
List 5 different imaging techniques used in Radiology.
- X-Ray - CT - PET - MRI - Ultrasound
List the 5 tissues seen on XR.
Air
Fat
Soft tissue
Bone
Metal
What is the rough process of how an X-Ray functions?
Electromagnetic wave of high energy and very short wavelength able to pass through materials with partial absorption which shows an image based on density of material and subsequent passage of radiation to form the image. Absorption ≈ density of structure.
List 5 common uses of an X-Ray.
- Trauma
- Acute abdominal emergencies
- Chest
- CV problems
- Joint problems
- Observe if lines are in the correct place
Give 3 advantages of using XR imaging modality.
+ Cheap
+ Available
+ Portable
+ Decisions r/e pt management made quickly
Give 3 disadvantages of using XR imaging modality.
- Limited differentiation of tissue densities
- 2D projection of 3D structure
- Radiation exposure
How does a CT imaging modality scan work?
Computerised (axial) tomography is a radiological imaging technique which takes a series of measurements of X-Ray absorption around the patient then the computer solves complex simultaneous equations and works out densities for voxels (volume equivalent of a pixel) with axial planes. CT scanners are used to produce a 2D projection of a 3D patient, taking axial cross sections at different levels.
Give 5 common uses of the CT imaging modality.
- Head injury
- Strokes
- Tumour staging
- Acute abdominal pain
- Circulation problems
- Coronary Artery Vessels
What is the unit of measurement in CT called?
Hounsfield Units
Give 3 advantages of using CT scans.
\+ Improved contrast resolution \+ Reduce need for exploratory surgery \+ Improved cancer diagnosis and treatment \+ Guide treatment of common conditions \+ 3D images can be generated
Give 3 disadvantages of using CT scans.
- Ionising radiation
- More expensive than XR
- Higher dose radiation cf XR
- Less portable than XR
What is PET Scanning?
Positron Emission Tomography (PET) is a type of nuclear medicine procedure which measures the metabolic activity of the cells of the body tissues. It involves the injection of a dye containing radioactive tracers (e.g. FDG) whereby an unstable compound decays by emitting positron (antimatter equivalent of electron) which is annihilated by electron with emission of two high energy photons in opposite directions and scanner detects the co-incident but opposite photons. It is now routinely combined with CT to give anatomical detail and adjust for absorption by tissue (CT-PET). PET-MRI also starting to become available too
Outline 2 advantages of CT-PET.
+ Help prevent under-staging/over-staging
+ Prevent some patient having futile surgery
Outline 2 disadvantages of CT-PET.
- Allergic reactions
- Radiotracer may cause pain and redness
- Pregnancy
What is MRI?
Magnetic Resonance Imaging is a radiographic imaging modality using a powerful magnet to produce a strong magnetic field forcing protons in the body to align with that field. A radio frequency current is pulsed through the patient, stimulating protons, and spin out of equilibrium which strains against the pull of the magnetic field. When the radio frequency field is turned off, MRI sensors can detect the energy released as protons realign with the magnetic field. The time taken for protons to realign with magnetic field and amount of energy released changes depending on the environment and chemical nature of the molecules.
Give 3 advantages to MRI.
\+ High tissue resolution \+ View in any plane \+ No radiation (non-ionising radiation) \+ Functional MRI \+ Soft tissue contrast is high
Give 3 disadvantages to MRI.
- Contraindicated if bodily metal
- Claustrophobia
- MRI £££
- Takes longer to perform
- Artifacts
- Have to be still and compliant
What is ultrasound?
Ultrasound (ultrasonography) is a diagnostic radiology imaging technique/exam using a transducer to send out ultrasound at a frequency of 1-10MHz (cf audible frequency is 20Hz-20kHz) which are reflected back by the object (soft and hard tissues) which is detected by the receiver and used to generate a picture on the screen
Give 3 advantages of Ultrasound.
\+ Safe \+ Portable \+ Readily available \+ Good soft tissue detail \+ Cheaper \+ Good spatial resolution \+ Doppler evaluation of organs (physiologic data) \+ Not as adversely affected by metallic objects
Give 3 disadvantages of Ultrasound.
- Cannot see through tissues with high acoustic impedance
- Only saves images you choose/operator skill
- Thermal heating or mechanical injury to tissues
- Artifacts
