Radiology Flashcards
What is a radiograph?
A radiograph is a projection all image generated by a passage of x-rays through an object.
How is an X-ray image generated?
Am Image is generated on a detector plate called x-ray detector.
This detector plate is like a put=topographic film. When x-rays hit the plate, it turns black. Amount of blackness depends on the number of x-rays hitting the plate.
X-rays are are stopped by materials with lots of electrons / dense materials like bone / metals so, they appear white.
What are the advantages of x-rays?
Quick
Readily available
Inexpensive
What are the disadvantages of x-rays?
Involve radiation
Poor soft tissue information
What are the roles of x-rays in the imaging of MSK system?
- They are are initial imaging of choice for skeletal muscle trauma / acute bone or joint injury. Eg:
Fractures
Joint dislocations - X-rays are also used for the evaluation of chronic bone or joint pathologies. Eg:
Chronic osteomyelitis
Chronic joint arthritis
Chronic septic arthritis
What is a fracture?
A complete or incomplete break in the continuity of the bone.
What different types of fractures can you get?
Most fractures have fracture lines / unenthusiastic lines on a radiograph. -These will be transverse / oblique or spiral fractures.
You can also get spinal compression fractures. I’m these, it is difficult to find a fracture line, bone is just crushed or deformed.
I’m childhood, you can get:
- Greenstick fractures / buckle fractures
- Epiphyseal separation fractures.
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What is a CT scan?
Computerise Tomography (CT) or Computerised Axial tomography (CAT) scanning is a diagnostic imaging procedure that uses radiation to build cross sectional images (slices) of the body.
What does CT do?
CT scans provide thin sections of the MSK system. These slices give detailed information about the bone structure and pathology.
The soft tissue detail is better than plain radiographs (X-ray).
Subtle, un-displaced fractures are better seen on CT scans.
Spinal fractures and other complex fractures (eg pelvic) are seen in greater detail.
Slices can be reformatted to give 3D construction.
What are the advantages of CT scans?
Cross sectional. Think slices of the body.
Excellent in assessment of complex bone trauma.
Fast.
Miltiplanar and 3D reconstruction.
What are some disadvantages of CT scan?
Involves significant radiation
There is poor soft tissue detail (better than x-rays). ]]]]]]]]]]]]]]]]
What is hounsfield units / density?
This is the colour seen on a CT.
Water has 0 HU.
Below 0 U -dark on CT image.
0-40 U -shades of grey
+100 -white on CT.
What is the role of MRI scanning in MSK imaging?
This is a non-invasive method of mapping the internal structures of the body.
How does MRI scanning work?
MRI utilises magnetic resonance of the hydrogen nuclei to produce high quality cross-sectional images of the body in any plane.
There is no use of ionising radiation. Instead, it utilise radio frequency radiation in presence of carefully controlled magnetic fields.
What are the fundamental objectives of MRI MSK imaging?
Definition of normal anatomy
Detection of pathology
What is MRI used for?
MRI is used for the assessment of bone, joints and associated soft tissue like ligaments and tendons.
MRI is better than CT and X-Ray in the assessment of the soft tissues.
MRI I used in assessment of MSK infection like osteomyelitis, soft tissue infection and septic arthritis.
MRI is poor at showing micro-structures of the bone.
What are the two main types of MRI sequencing?
Anatomy defining sequences: T1, proton density.
Fluid sensitive sequences: STIR or PD Fat Sat.
What is T1 MRI imaging?
Normal muscle is termed as Isointense (signal intensity).
On T1 these things show up bright (hyperintense):
- Fat
- Gadolinium
- Proteinaceous fluid
- Haemorrhage
On T1 these things show up low (hypointense):
- Fluid
- Tendons, ligaments
- Cortical bone
What is T2 MRI imaging?
Fluid is hyperintense
Fat is hyperintense
Tendons, ligaments, cortical bone are hypointense
Old haemorrhage gives low signal.
What are the advantages of MRI scanning?
Excellent or imaging of soft tissue structures like ligaments, tendons and muscles
Detailed anatomy of joints
Excellent for bone marrow imaging
What are the disadvantages of MRI scanning?
Scans take a long time (45-60mins). Patients have to stay in the tunnel for this long.
Noisy environment
Claustrophobic patients can’t tolerate the scan
Non-compatibility with metallic / electronic decides like pacemakers.
How can MRIs be used safely?
Magnetic fields in an MRI is stronger than those used industrially to move cars.
Therefore, most electronic devices and ferromagnetic metals (Iron, Nickel, Cobalt) are not compatible with MRIs
What is the role of ultrasound in MSK imaging?
Ultrasound is used for imaging of soft tissue.
What is ultrasound good for?
Ultrasound is good at finding fluid collection / haematomas or joint effusions.
It is also good for assessment of the tendons and muscles e.g. if there is suspected Achilles’ tendon rupture, an ultrasound of Achilles’ tendon will help to confirm this.
It is good for the assessment of bones or deeper structures.
