Radiology Flashcards
Why is the use of radiology to visualise body parts, tissues and organs useful for?
Clinical diagnosis
Treatment planning
Disease monitoring
Image guided intervention
What is a Plain Radiograph?
The image produced by the passage of x-rays through an object
How is a Plain Radiograph produced?
X-rays generated and projected towards the detector with the patient positioned in between
When X-rays hit the detector plate it turns black
X-rays are absorbed/attenuated most by the dense materials in a patient like bone and any metals
What are the 4 main densities?
From most dense to least dense:
Bone
Soft tissue
Fat
Air
What are the advantages of Radiographs/X-rays?
Are quick
Readily available
Cheap
What are the disadvantages of Radiographs/X-rays?
Ionising radiation
Poor soft tissue contrast
What are Radiographs useful for?
Imaging of skeletal trauma (Fractures or Joint dislocations)
Evaluating chronic bone or joint pathologies (osteoarthritis, rheumatoid arthritis, chronic osteomyelitis)
What is articular cartilage?
The hyaline cartilage found at the ends of bones where joints are found
On an x-ray, why does articular cartilage of joints appear black/dark?
Its less dense then bone so its more radiolucent
The darkness makes it look like there’s a joint space
What is a fracture?
A complete or incomplete break in the continuity of the bone
How do fractures appear on radiographs/X-rays?
Fracture ones/lucent dark lines on the radiograph
What are the 6 types of fracture?
-Transverse
-Linear
-Oblique
-Spiral
-Greenstick
-Comminuted
What is a transverse fracture?
Fracture which is horizontal/perpendicular to the bone
What is a linear fracture?
Fracture which runs straight down the length of the bone/parallel to the bone
What is an Oblique fracture?
Fracture that happens at an angle/diagonal
What is a spiral fracture?
Fracture where the fracture line wraps around the bone in a spiral motion
What is a Greenstick fracture?
Fracture where one side of the bone will snap but the other side of the bone is fin
Medullary cavity broken but cortical bone is in tact
What is a comminuted fracture?
Fracture where there is multiple breaks in the bone
How do the bones develop in childhood?
Start as cartilaginous model/template
Calcification begins as Chondrocytes begin to oldie
Perichondrium develops into periosteum
Osteoclasts begin to resorb the bone in the medullary region forming the medullary cavity where the bone marrow can form
This leaves cartilage remaining only at the ends of the bone
Describe the structure of a long bone:
The epiphysis is the ends of the bone past the epiphyseal plate
Articular cartilage is found at the ends of long bones
The epiphyseal plate is a region of cartilage where bone growth occurs
Diaphysis is the shaft of the long bone
Metaphysics is the region between where the bone starts to widen and the epiphyseal plate
How do bones visibly change on a radiograph during childhood?
Begin to become whiter from the middle of the cartilaginous model as it calcifies to bone
Ends of bone remain dark with cartilage
What is a displaced fracture?
When the fractured bone is no linger aligned
What is an undisplaced fracture?
Fracture where the bone is still aligned
What are the 3 general stages to fracture healing?
1.) Inflammatory phase
2.) Reparative phase
3.) Remodelling phase
What happens in the inflammatory phase of the fracture healing process? (hours to days)
Haemotoma forms (blood clot)
Tissue dies
Inflammation/cell proliferation begins
What happens in the reparative phase of fracture healing? (days to weeks)
Angiogenesis (formation of new blood vessels)
procallus forms
Soft callous forms and is visible
Hard callus forms
What happens in the remodelling phase of fracture repair? (months to years)
The bone is remodelled by osteoblasts so that the fracture lie becomes completely obscured
What is CT, what radiation does it use and how does it form an image?
Computerised tomography
X-rays
X-rays emitted from a detector that spins round in a circle very quickly, these are picked up by detectors producing many transverse images that are complied together to make a 3D image
What are the advantages of CT scans?
Soft tissue detail better than plain radiographs/x-rays
Quick to do
Fractures seen much better in CT than plain radiographs
Can produce 3D images
What are the disadvantages of CT scanning?
Ionising radiation (higher than plain radiograph)
Motion artefacts if patient moves
Poor soft tissue detail compared to MRI but better than x-rays
What is the units used to state the density of body tissues?
Hounsfield Units (HU)
What colour does a structure with a very low HU appear and what about a structure with a high HU?
Very low is Black/dark
Very high is white
What is CT windowing?
When the CT image is manipulated so certain structures are highlighted
What is MRI and how does it worK?
Magnetic Resonance Imaging
Magnetic field causes H+ to align
Radio pulse unaligned the H+
Radio pulse is then turned off and the time that it’s takes for the H+ to realign is measured and is used to form a cross sectional image
What is MRI useful for imaging?
Bones, joins, ligaments and tendons is MSK
MRI is better than CT and x-rays in assessment of soft tissue
What are the advantages of MRI scranning?
Good for soft tissue structures
Detailed anatomy of joints
Excellent for bone marrow imaging
What are the disadvantages of MRI scanning?
Scan takes a long time and patients have to be still
Noisy
Claustrophobic patients can’t tolerate
Cant have patients with metallic or electronic devices like pacemakers
What are the advantages of Ultrasound imaging?
No ionising radiation
Excellent soft tissue resolution
Can see fluid collections and superficial foreign bodies
Dynamic imaging
Good for image guided MSK intervention
What are the disadvantages for Ultrasound imaging?
Operator dependant
Poor deep tissue
Limited bone and Intra articular imaging
What is nuclear medicine?
When parts of the body are radioisotope labelled
Biologically active drugs are given to the patient to serve as a marker of biological activity
What areas are usually viewed with nuclear medicine?
Bone forming metastatic lesions
Healing fractures
Areas of osteomyelitis
How do T1 weighted images differ to T2 weighted images?
T1 fat appears bright and fluid dark
T2 fat bright and fluid bright
