Medical imaging Flashcards
Describe the fundamental principles of how X- Rays work:
X- rays work by the passing of x rays towards a target with a detector behind, materials with high atomic numbers absorb X-rays efficiently ( bone and metal) . they reduce the amount of X-rays that reach the detector thus images can be produced.
what impacts the amount of attentuation of X rays by the patient.
( attenuation is aborption, scattering, or loss of energy as the rays pass through)
- density and atomic number of the tissue/ material
energy of the X- ray beam.
Explain the advantages and disadvantages of X-rays
+ quick
+ portable
+ cheap and simple
-radiation(relatively low)
-one plane, two dimensional
-cannot see all the pathology.
give a clinical example of where X-rays can be used efficiently
Chest:
indications : chest pain, line/tube positioning, follow up post pneumonia
diagnosis: infection, pulmonary oedema, pleural effusion, pneumothorax.
Abdomen/pelvis:
indications: neonatal, passing or urinary tract calculi, checking for the presence of foreign objects,
diagnosis: obstruction, volvulus, perforation etc.
MSK:
Indications: trauma, pain, deformity , swelling, post relocation of joint.
diagnosis: fracture, dislocation, effusion, soft tissue injury
Describe the fundamental principles of how Computed Tomography works:
Uses X rays on one side of a rotating gantry, with detectors on the other side. the patients table moves through the ring(gantry) allows for cross sectional images of the patient to be produced.
what direct do CT scans look from
feet up
the advantages and disadvantages of CT
+ Quick
+Good spatial resolution
+ Can scan most parts of the body well (but not all)
- Radiation
-does not delineate soft tissues well.
-affected by artefact
-requires breath holding
-overuse - incidental findings
-contrast reactions.
Give a clinical example of where CT scans can be used efficiently
Diagnosis: trauma, bleeding. clots, ischaemia , cancer.
Monitoring:
Cancer and ILD
Interventional:
Radiotherapy, CT guided biopsies/ drains
Describe the fundamental principles of how PET scans work:
Radionuclides send signals from the tissue of interests, they emit positrons during decay so emitted positrons collide with nearby electrons in the patient which can be detected by a gamma camera .
Flourine-8 (radionuclide) and Fluorodeoxyglucose( a glucose analogue which goes to areas of high glucose metabolism) are commonly used
they can be used in conjunction with CT to reveal abnormalities as well as show exact location of high cell activity.,
Give a clinical example of where PET scans can be used efficiently
Oncology: detection, staging, response to treatment.
Neurological: Early diagnosis of Alzheimers , localisation of seizure focus
Cardiac: Identification of poorly fused myocardium
Infection/Inflammation
Pyrexia of unknown origin
Vasculitus
Explain the advantages and disadvantages of PET scans
+ Good contrast and spatial resolution
+ Can allays anatomy and function
- Physiological uptake of radiopharmaceutical material
- Radiation dose to patient
- Risk of radiation to others
- Radioactive waste is produced
- Expensive and time consuming
- Radionuclide shortages
Describe the fundamental principles of how Fluoroscopy works:
pulsed X-rays shot at a target specimen with a detector behind it, materials with high density or large molecular weights will absorb rays more efficiently so less x rays will hit the detector, creating moving images that are enhanced using contrast (barium/iodine)
Explain the advantages and disadvantages of Fluoroscopy scans
+ dynamic studies, can assess function and carry out study in real time
+ quick
- higher radiation dose than single X-ray
Radiation exposure to interventional clinician
- one plane two dimensional
- poor soft tissue imaging
- cannot see all the pathology
Give a clinical example of where fluoroscopy can be used efficiently
It is diagnostic and interventional,
it can be used for vascular(angiography) - to check for emblem. stunting, angioplasty
GO: barium swallow, barium meal , barrel enema
GU: urogram, hysterosalpingogram ,nephrostomy insertion.
MSK: arthogram, therapeutic joint injections, orthopaedic surgery)
Describe the fundamental principles of how Medical Resonance Imaging works:
It works by creating a strong magnetic field aligning the hydrogen atoms within a patient, radio frequency pulse tips the aligned hydrogen atoms with create a detectable magnetic field. this field induces an electric current in nearby could in the MRI machine. different tissues produce different signals which are processed create images.
Explain the advantages and disadvantages of Medical Resonance Imaging scans
+ no radiation
+ good contrast resolution, especially of soft tissues
- expensive
- time consuming
- fewer machines, fewer radiographers
-contraindications with pacemakers, cochlear implants, some metal, claustrophobia, lack of mental capacity. - contrast reactions
- some other risks e.g overheating, image quality relies on magnetic field strength , risk of magnetic objects becoming missiles in the room.
list four types of imaging sequences for MRI and some brief details
High signal = Bright= Hyperintense
Low signal = Low = Hypointense
T1 weighting- fat is bright, water is dark
T2 weighting- water is very bright, fat is quite bright.
Give a clinical example of where Medical Resonance Imaging can be used efficiently
Head and Neck imaging, MSK , GI, Cardiac MRI,
Mr angiography
Describe the fundamental principles of how Ultrasound works
utilises high frequency sound waves that travel through tissue and are reflected back from boundaries between tissues of different density( acoustic impedance mismatch)
the probe detects reflected sound waves ( echoes ) and converts them into electrical signals. the time taken for the echo return is used to calculate where it was reflected from
list and explain the types of echo
hyper echoic = more refection = white on image
hypoechoic= less reflection = dark eimage.
explain what is meant by the term Doppler ultrasound
doppler ultrasound is
Give a clinical example of where Ultrasound Imaging can be used efficiently
Solid organs ( liver kidneys, spleen, thyroid, fetal brain) to show the appearance of tissues
hollow structures like the heart, vessels, urinary tract, uterus.
breasts, to assess lumps
obstretics,- pregnancy dating, fatal anomaly, placental locations, fatal growth.
musculoskeletal - assessing muscles, tendons, ligaments, joint, nerves, soft tissue masses.
interventional - US-guided injections/biopsies/drains/ aspirations.
there are transvaginal, transrectal, transoesophageal ultrasound.
Explain the advantages and disadvantages of Medical Resonance Imaging scans
+ Lack of radiation
+ Low cost
+ Portable
+Dynamic ( can see movement, assess blood flow)
- operator dependant
- no bone or gas penetration
- difficult with obese/frail/unwell patients
- theoretical risk of overheating if misused.
