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MSK > S1L2 - MSK Radiology > Flashcards

S1L2 - MSK Radiology Flashcards

1
Q

How are x-ray images generated?

A

By projecting a beam of electrons through an object onto an image detector plate

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2
Q

What objects appear white in an x-ray?

A

Objects that are dense and thick and therefore absorb a lot of the radiation passing through. Often used to image bone.

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3
Q

What is the detector plate?

A

The plate that measures the radio waves not absorbed by the object. Similar to a photographic film, turning black when x-rays hit the plate.

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4
Q

What are the advantages of x-rays?

A
  • Quick
  • readily available
  • inexpensive
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5
Q

What are the disadvantages of x-rays?

A
  • involve transmission of radiation to patient (less than CT)
  • poor soft tissue contrast resolution
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6
Q

What are x-rays commonly used for?

A
  • skeletal trauma (fractures/joint dislocation)

- evaluation of chronic bone or joint pathologies (osteomyelitis/chronic arthritis)

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7
Q

What is a bone fracture?

A

Complete or incomplete break in the continuity of a bone.

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8
Q

Name the 6 different fracture types

A 
Transverse
Linear
Greenstick
Spiral
Oblique 
Comminuted
Epiphyseal separation
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9
Q

How do epiphyseal plates present on an x-ray?

A

Less mineralised and therefore less radio opaque so can be seen on an x-ray as dark lines. These lines generated by the epiphyseal growth plate become thinner, eventually disappearing and becoming closed.

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10
Q

How do we conduct a bone age study of a child?

A

By performing an x-ray of the child’s left wrist and comparing the degree of ossification of the carpal bones to images of those in a standard atlas of bone development.

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11
Q

What clinical significance does a difference between a child’s bone age and their chronological age represent?

A
  • precocious or delayed puberty
  • growth hormone deficiency
  • hypothyroidism
  • Hyperthyroidism
  • malnutrition
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12
Q

What are the stages of fracture healing?

A
  1. Haematoma formation
  2. Tissue death
  3. Inflammation / cellular proliferation
  4. angiogenesis / formation of granulation tissue / procallus
  5. Soft (fibrocartilaginous) callus formation
  6. Consolidation / hard callus formation
  7. Lamellar bone
  8. Remodelling
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13
Q

What is radiographic union?

A

When the fracture line on an x-ray becomes completely obscured following the bone repair and remodelling

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14
Q

How does a CT scan work?

A

A CT (computed tomography) scan, also known as computerised axial tomography (CAT) scan, uses narrow x-ray beams to produce cross-sectional slices of an object which are then digitally reassembled to generate two and three dimensional images.

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15
Q

What are the advantages of CT scans?

A
  • soft tissue detail is better than plain x-rays
  • gives detailed information about the bone structure and pathology
  • whole body CT scan can be performed in a short period of time (quicker than MRI/longer than x-ray)
  • better visualisation of subtle undisplaced fractures than x-ray.
  • complex fractures can be seen in greater detail
  • ## slices can be reformatted to create multiplanar and 3D images.
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16
Q

What is the function of CT?

A
  • used to guide injections, biopsies and aspirations in real time
17
Q

What are the disadvantages of CT scans?

A
  • high radiation dose than plain x-ray
  • motion artefact if patient moves
  • poor soft tissue detail when compared to MRI
  • severely obese patients cannot always be accommodated within the scanner.
  • some patients may be allergic to the intravenous contrast used.
18
Q

How is the density of body tissues measured in a CT scan?

A

Hounds field units (HU)

19
Q

How do we interpret CT scans?

A

Similar to x-rays. Sir is black, dense materials such as bone is white.

20
Q

What is meant by the windows of a CT scan?

A

The software attached to the CT scanner can be used to manipulate the grey scale component of the image, creating different windows. This gives us the ability to focus on certain tissues of interest.

21
Q

How does an MRI work?

A

Magnetic Resonance Imaging (MRI) utilises magnetic resonance of hydrogen nuclei to produce high quality cross-sectional images of the body in any plane. The radio frequency signal pulses are applied to the tissue which deflects the protons. When the pulse is terminated, the protons realign and emit a signal as they do so.

22
Q

When is MRI used?

A
  • good for soft tissue imaging
  • detecting pathology (osteomyelitis/malignancy/muscle contusions/ prolapsed intervertebral discs/occult fractures)
  • used to image tendons and ligaments.
23
Q

Advantages of MRI imaging?

A
  • better at imaging soft tissue
  • useful for generating multiplanar images (images taken from multiple angles)
  • patient receives no radiation
  • useful for assessment of bones, joints and associated soft tissue
  • excellent for bone marrow imaging
  • detailed anatomy of joints.
24
Q

How do we interpret T1 weighted MRI images?

A

Fat appears bright, fluid appears dark

25
Q

How do we interpret T2 weighted images

A

Both fat and fluid appear bright

26
Q

How do we interpret STIR sequence MRI’s?

A

Signal from fat appears dark and fluid appears bright - useful for detecting areas of oedema

27
Q

How is gadolinium use in imaging?

A

May be injected pericutaneously into a joint or administered intravenously to ad the diagnosis of conditions such as a tear in the joint labrum.

28
Q

What are the disadvantages of MRI scans?

A
  • any magnetic metalwork must be removed (shrapnel) as it can migrate under the influence of the magnet causing injury.
  • imaging time is longer than CT, about an hour, Paine movement more problematic
  • non-metallic metal screws, foreign bodies and prostheses can produce significant artefact.
  • scanner a noisy tunnel, difficult for obese and claustrophobic patients.
  • patients with implants electronic devices cannot go into the magnetic field as these devices can malfunction.
  • poor at showing the micro-architecture of bones.
29
Q

How does ultrasound/ultrasonography work?

A

High frequency sound waves produced by a transducer and travel through the patient. Tissues and tissues planes deflect the waves back to the transducer and are then analysed to creat an image.

30
Q

what are the advantages of ultrasound scans?

A
  • non-invasive
  • do not use radiation so less harmful for patients
  • ## excellent soft tissue resolution for superficial soft tissue
31
Q

What are ultrasound scans used for?

A
  • imaging soft tissues so can show non-ossified structures
  • used to locate fluid collections/Haematomas, target injections and perform aspirations of joints
  • useful for assessment of tendons and muscles
32
Q

What are the disadvantages of an ultrasound scan?

A

Highly dependent on a skilled operator for interpretation of images.
Resolution of deep tissues is poor
Limited suitability for bone and intra-Articular imaging

33
Q

What is nuclear imaging?

A

A radioisotope-labelled, biologically active drugs are administered to the patient to serve as a marker of biological activity. Images are produced are a collection of radiation emissions from the isotopes.

34
Q

When is nuclear imaging used?

A
  • used to assess areas of metabolically active bone such as when trying to localise metastatic disease, healing fractures or identify ares of osteomyelitis
35
Q

What are the disadvantages of using nuclear imaging?

A
  • radiation produced by the radioisotopic labelling is ionising and can deposit energy in organs and tissues, leading to DNA damage.

MSK (17 decks)

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