5. Radiology Flashcards
What does a disruption in the cortex on an X-ray indicate?
Fracture
What is a fracture?
fracture is a complete or incomplete break in the continuity of a bone
Describe how an x-ray is obtained?
- X-ray images are obtained by projecting a beam of electrons through an object onto an image detector.
- The image produced is a projected map of the amount of radiation absorbed by the object along the course of the X-ray beam.
- The amount of whiteness of the image is a function of the radiodensity and thickness of the object – the denser the object, the more radiation is absorbed, so the object appears lighter or whiter.
What are the advantages and disadvantages of X rays
Advantages: Quick, painless, inexpensive, and noninvasive
Disadvantages: Radiation, possible allergic reaction to contrast materials. Poor soft tissue contrast
How does cartilage appear on an x-ray?
It is radiolucent so appears as a ‘joint space’
How do fractures show up on x-rays?
Have fracture lines/ lucent lines on radiograph
What are the different types of fractures?
TRANSVERSE LINEAR/SAGGITAL OBLIQUE SPRIAL COMPRESSION
Transverse fracture
the ‘break’ crosses the bone at a right angle to the long axis of the bone
Linear (Sagittal plane) fracture
the fracture line passes in parallel to the long axis of the bone.
Oblique fracture
fracture line is at an oblique angle to the long axis of the bone. However, the fracture is still confined to one plane.
Two types:
•Oblique displaced
•Oblique non-displaced
Spiral fracture
fracture line spirals round in multiple planes.
Difference between oblique and spiral fractures?
If you take a stick and saw it at an angle so that it is divided in two, you will generate an oblique fracture. But if instead you twist the two ends of a stick in opposite directions until the stick breaks, it will result in a break pattern that will start from one point, move obliquely in one direction, reach the opposite side and then continue spiraling round the outside of the stick until it reaches the original point
Compression fracture
occur in cancellous bone when an axial load compresses the bone beyond its limit.
Where do compression fractures most commonly occur?
Lumbar vertebrae
Green stick fracture
incomplete fractures in which the bone bends and cracks instead of breaking into separate pieces. The cortex on just one side of the bone fractures
Which two types of fractures can only occur in children? Why?
Greenstick
Epiphyseal separation fractures
because their bones are softer and more flexible than are the bones of adults.
Epiphyseal separation fractures
when the fracture line extends through an unfused growth plate, thereby separating the epiphysis from the metaphysis.
Epiphyseal separation fractures are mostly seen in?
overweight adolescent boys during rapid growth spurts and presents with hip pain and a limp.
Which factors influence the proliferation and transformation of cells within the growth plate of long bones?
growth hormone promotes cellular proliferation, whereasa deficiency of thyroid hormone or excess corticosteroids both result in a reduction in cell division in the proliferation zone, leading to growth retardation
What are symptoms of slipped upper femoral epiphysis?
Hip pain and a limp
What are radiographic changes seen in bones during childhood?
Growth plates are less mineralised than surrounding bone so are less radio opaque and show up as dark line
As the child grows the plates become thinner, eventually disappearing and becoming ‘closed’
How does a bone age study work?
- estimates the maturity of a child’s MSK by looking at the degree of ossification of the carpal bones and maturation of the growth plates along long bones
- x-ray of left wrist, hand and fingers and comparing these to a standard atlas derived from pooled data from large numbers of children in the same age
- measured in years
Why is bone age important?
helps estimate the maturity of the child’s musculoskeletal system. A significant difference between a child’s bone age and their chronological age may indicate pathology such as precocious (early) or delayed (late) puberty, growth hormone deficiency, hypo- or hyperthyroidism etc. Malnutrition can also lead to delayed bone age.
What are the 3 phases of fracture healing in radiology
Inflammatory phase
Reparative phase
Remodelling phase
Inflammatory phase consists of?
Haematoma formation
Tissue death
Inflammation / cellular proliferation
Callus hasn’t formed yet
Reparative phase consists of? How long does it take?
Days to weeks
Angiogenesis / granulation / procallus formation
Soft (fibrocartilaginous) callus formation
Consolidation / hard callus formation
Remodelling phase consists of? How long?
Months to years
Gradual replacement of hard callus with mature bone.
How is the process of fracture repair seen on an x-ray?
- the mineralisation of bridging callus beneath the periosteum can be seen during the reparative phase
- soft callus has a fluffy appearance
- intramedullary callus also develops at the same time but cannot be seen
- radiographic appearance changes as soft callus becomes hard callus then to lamellar/ mature bone - radiographic appearance changes with the resorption of the woven soft callus and development of trabeculae
How are CTs better than x-rays?
- the ability to manipulate the image with computer software allows for the visualisation of many different soft tissue densities within one slice.
- Because of excellent resolution of images and thin slices, it can be used in guiding injections, biopsies and aspirations in real time.
- Whole body CT scanning can be performed in just a few minutes to look for bone or soft tissue injuries (e.g. in major trauma).
- Subtle undisplaced fractures are also better seen on CT scan than plain X-rays.
- CT slices can be reformatted to create multiplanar and 3D images
What are drawbacks to CTs?
- If a patient moves whilst in the CT scan, ‘motion artefact’ can distort the image and make interpretation difficult
- exposure to a higher radiation dose than with plain X-rays
- severely obese patients cannot always be accommodated within the scanner.
- Most CT scans are performed with injection of intravenous contrast; some patients can be allergic to this contrast and very rarely, it can cause anaphylaxis
Describe the colour that different substances appear on CT
Water has a density of 0HU. Anything less dense than, or of equal density to, water will be black; anything denser than water will be grey or white. Air, fat and water therefore appear black, soft tissue is in shades of grey, and bone is white
How can you tell when RADIOGRAPHIC UNION has occurred?
The fracture line eventually becomes completely obscured, at which stage radiographic union is said to have occurred.
What are Hounsfeild units
Ct scanning uses this to measure eh density of the body tissue. 0-40 Hu appear in shades of grey, +100 appear white and 0 is black (water)
How do MRIs work?
Magnetic Resonance Imaging (MRI) does not use radiation but instead uses a strong magnet to generate a magnetic field in which the protons in hydrogen atoms line up. Radiofrequency signal pulses are then applied to the tissue which deflects the protons. When the pulse is terminated, the protons realign and emit a signal as they do so. This signal is detected and the data from this is used to create the three dimensional image.
What are some advantages of MRI?
- Useful for generating multiplanar images
- no radiation
- It is better than CT and X-ray for imaging soft tissues
What are some disadvantages of MRI?
• Really expensive, limited availability and patient size, long exam times ,metal pacemakers, poor at showing the micro-architecture of the bone, noisy environment, can take 40-60 mins, claustrophobia, non magnetic metal screws or foreign bodies and prostheses can produce significant artefact, patient movement, pacemakers can malfunction - dangerous
What are the types of MRI sequences?
The MRI images can be manipulated by altering the way in which the pulses are delivered. T1 and T2 weighted images can be created based upon the time between repetition of the pulses and the strength of the pulse. On a T1 weighted image, fat appears bright and fluid appears dark.
On a T2 weighted image, both fat and fluid appear bright.
In a STIR sequence (a fluid-sensitive sequence), the signal from fat is supressed and it appears dark, whilst fluid appears bright.
What are fluid- sensitive sequences useful for?
Detecting oedema
What can be injected to aid the diagnosis of conditions in MRI?
Gadolinium - injected percutaneously into a joint or administer intravenously
E.g. can be injected into shoulder or hip joint to diagnose a tear of the joint labrum
How is ultrasound carried out?
- uses high frequency sound waves to produce images
- sound waves are produced by a transducer and travel through the patient
- tissue planes deflect the waves back to the transducer and are then analysed to create an image
What is ultrasound used to look for?
- to image soft tissues so can show non-ossified structures such as a paediatric femoral head in the diagnosis of hip dysplasia and dislocation
- to locate fluid collections/ haematomas
- to target infections and perform aspirations of joints
- assessment of tendons and muscles e.g. detecting rupture of the Achilles’ tendon
What are advantages of ultrasound?
- no radiation
- excellent soft tissue resolution for superficial soft tissue
- excellent imaging modality for tendons and peripheral nerves
- fluid collections
- superficial foreign bodies
- dynamic imaging
- non invasive
What are disadvantages of ultrasound?
- operator dependent
- poor deep tissue resolution
- limited bone and intra-articular imaging
How does nuclear medicine work?
- uses radioisotope-labelled, biologically active drugs to mark biologic activity
- images produced are a collection of radiation emissions from the isotopes
What is nuclear medicine used to assess?
Areas of metabolically active bone such as when trying to localise metastatic disease, healing fractures or identify areas of osteomyelitis
Why should a lot of care be taken in nuclear medicine?
Radiation is ionising and can deposit energy in organs and tissues that can lead to DNA damage
Rapidly dividing cells are most susceptible to radiation induced neoplasia so children and foetuses are very vulnerable
How should care be taken in nuclear medicine?
Lead aprons
Monitored radiation exposure - film badges
Use as low a dose as possible
Radiation only used when absolutely necessary
What is neoplasia?
new growth
What is osteomyelitis?
infection of the bone
