Imaging Flashcards
Types of Imaging
- Xray
- Computed Axial Tomography (CAT SCAN or CT)
- Magnetic Resonance Imaging (MRI)
- Ultrasound
X-RAYS
- Radiographers can change the current and voltage settings on the X-ray machine in order to manipulate the properties of the X-ray beam produced. Different X-ray beam spectra are applied to different body parts
- The image is produced by X-rays passing through the patient to a digital screen below.
- Bone absorbs most radiation, causing least exposure to the digital screen. Displayed as white on the image.
- Air absorbs least radiation, causing maximum exposure, so the image appears black. Between these two extremes, a large differential tissue absorption results in a grey scale image.
X-rays best tissue type and are particularly useful for:
Bones and dense structures
* Chest
* Abdomen
* Skeletal system: trauma, spine, joints, degenerative, metabolic and metastatic disease.
* Assessment of fracture healing
In most cases the body part is X-rayed from 2 angles –anteroposterior AP And later
Advantages of XRAY
Quick and non-invasive
Cost-effective
Detecting bone fractures
Assessing lung conditions
Widely available.
Disadvantages of XRAY
Radiation exposure to reproductive organs carries further potential risk to future generations.
All X-rays may cause alteration of cellular division and
other intracellular processes and are therefore potentially harmful to the human body.
2D images
X-rays may not be suitable for diagnosing or monitoring certain conditions. E.g. early-stage tumors
CT
- X-ray source rotates around patient, emitting beams from different angles.
The 3D image is then enhanced after being processed through a computer.
CT best tissue type
Bones, soft tissues, and organs.
CT advantages
- CT scan can be undertaken without any damage to metal implants
- Bony structures imaged more clearly and more detailed
- Rapid examination technique, so valuable for ill patients, less need to hold your breath.
- Lower cost than MRI scans *CT scan is very quick compared to MRI
CT disadvantages
- Uses X-radiation to produce images, ionising radiation is classed as a carcinogen, small risk as low dose.
- Less soft tissue detail than MRI scans
MRI
- Magnetic resonance scanning produces images of the body by utilizing the magnetic properties of certain nuclei in the body.
- The patient is positioned in the scanner, surrounded by a large magnet.
- The high intensity magnetic field displaces the nuclei from their position, when they return the nuclei release energy.
- Computer analysis processes the energy signals to a grey scale image.
- Pathological tissue returns different signals compared to normal
- MRI useful for brain and spinal imaging, internal derangement of joints.
- Primary soft tissue and bone tumours.
- Acute and chronic soft tissue injuries to tendons, ligaments and muscle.
- Osteomyelitis and soft tissue infection.
- Images can be in any plane- axial, sagittal or coronal
MRI tissue type
Soft tissues and organs
- Brain, spinal cord, joints, muscles, and organs like the heart, liver, and kidneys.
Advantages of MRI
- No documented side effects of MRI imaging
- Soft tissues pictured in more detail than CT
- Can be taken in any plane
DISADVANTAGES of MRI
- Time taken for MRI much longer than CT
- Higher cost than CT
- Patient may need to hold breath for short periods during imaging
- Patient may need to hold breath for short periods during imaging
- Patients with metal implants or certain medical devices are not able to undergo MRI imaging because of magnetic field pulses
ULTRASOUND
- Ultrasound (US) utilizes high frequency sound waves to produce images of soft tissue
- The US waves are transmitted from the US probe/transducer into the soft tissues
- A coupling gel is required on the skin surface to make good contact
- Visualisation of soft tissues is dependant on the differences in acoustic impedance of tissues and organisation of the connective tissues
Ultrasound tissue type and uses
Ultrasound is commonly used for imaging soft tissues, organs, and guiding medical procedures.
* Imaging of neonatal brain (through anterior fontanelle)
* Confirms pleural effusions and pleural masses
* Visualises liver, gall bladder, pancreas, kidneys etc.
* Useful in monitoring pregnancy; uterus and ovaries
* Assesses thyroid, testes and soft tissue lesions
* Identification of joint effusions and synovitis
