Introduction to Imaging Flashcards
What are the different types of way to image in radiology?
Radiography
Fluoroscopy
CT (computed tomography)
Ultrasound
MRI (magnetic resonance imaging)
Nuclear Medicine
PET CT/MRI (positron emission tomography)
What is cross-sectional imaging?
Cross-sectional imaging refers to techniques like CT and MRI that produce detailed slices of the body, allowing for a comprehensive view of internal structures in different planes (axial, coronal, and sagittal).
- Axial (transverse)
- Coronal (frontal)
- Sagittal (lateral)
What are the risks associated with contrast agents?
- Allergic reactions – question patient history
- Avoid if possible in pregnancy – crosses to foetus
- Alternative contrast may be suitable (radiology decision)
- Contrast induced nephrotoxicity – patient’s renal function must be established pre examination
Poor renal function – exam undertaken based on risk/benefit assessment
Nephrogenic Systemic fibrosis (NSF),
Related to Gd contrast, affects skin mainly but can also affect lungs, heart, muscles
Skin develops firm patches with oedema, develops over weeks, patients most at risk are those with severe renal disease
What is the significance of contrast use in imaging?
Contrast agents enhance the visibility of structures or fluids within the body in imaging techniques like X-rays, CT, and
MRI, helping to differentiate tissues or identify abnormalities such as tumors, blood vessels, or gastrointestinal issues.
May be injected, swallowed or administered rectally
Eliminated from the body via urine, rectally or are absorbed
What is hybrid imaging?
Fusion of 2 or more imaging modalities
Gives information on anatomy and function
Includes PET-CT & PET-MRI
CT or MRI undertaken first
What are the strengths and weaknesses of radiography?
Strengths
Great spatial resolution - especially bone
Cheap & readily available
Weaknesses
2D only (what is behind the heart?)
Ionising radiation
Very limited soft tissue visualisation
How does fluoroscopy work?
Real time examination using continuous production of X rays
Includes:
Ba examinations
Angiography
Cardiac procedures eg. stents
Use of a C arm in theatre
Urology procedures
What are the strengths and weaknesses of CT?
Strengths
Cross-sectional
Spatial resolution
Widely available
Weaknesses
Ionising radiation
Limited soft tissue contrast
What are the strengths and weaknesses of ultrasound?
Strengths
Non-ionising radiation
Multiplanar
Dynamic
Doppler
Weaknesses
Operator-dependent
Can’t see through bone or gas
Describe MRI basics
Patient lies in scanner
Hydrogen protons align to longitudinal axis of magnet
RF pulse applied which causes protons to flip
Recovery rate of these protons depends on the tissue they are in
Resultant image has range of contrast
How does nuclear medicine work in radiography and what are the strengths and weaknesses of nuclear medicine?
Uses small amounts of radioactive substances to assess organ function, diagnose and treat disease
Radioactive tracers are usually administered via intravenous injection
Radiation emitted is detected by a gamma camera
Strengths
Functional information
Weaknesses
Very limited anatomical information
Radiation- patient/staff/population
How does PET work?
Cancer cells need glucose to grow
Patient is injected with a radioactive radiopharmaceutical similar to glucose (fluorodeoxyglucose (FDG))
The PET scan detects patterns of distribution around the body
What is the difference between CT and MRI?
CT (Computerised Tomography): Uses X-rays to create detailed cross-sectional images; excellent for bone and acute injuries.
MRI (Magnetic Resonance Imaging): Uses magnetic fields and radio waves; provides superior soft tissue contrast, ideal for brain, spinal cord, and muscle imaging.
What are the 4 tissue densities?
Air, fat, soft tissue/fluid, bone
What is the central role of imaging in modern medical practice?
Imaging is vital for diagnosing diseases, guiding treatments, and monitoring patient progress, making it a cornerstone of medical decision-making and precision healthcare.
