5. Radiology

Question 1

What does a disruption in the cortex on an X-ray indicate?

Answer 1

Fracture

Question 2

What is a fracture?

Answer 2

fracture is a complete or incomplete break in the continuity of a bone

Question 3

Describe how an x-ray is obtained?

Answer 3

• 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.

Question 4

What are the advantages and disadvantages of X rays

Answer 4

Advantages: Quick, painless, inexpensive, and noninvasive
Disadvantages: Radiation, possible allergic reaction to contrast materials. Poor soft tissue contrast

Question 5

How does cartilage appear on an x-ray?

Answer 5

It is radiolucent so appears as a ‘joint space’

Question 6

How do fractures show up on x-rays?

Answer 6

Have fracture lines/ lucent lines on radiograph

Question 7

What are the different types of fractures?

Answer 7

TRANSVERSE
LINEAR/SAGGITAL
OBLIQUE
SPRIAL
COMPRESSION

Question 8

Transverse fracture

Answer 8

the ‘break’ crosses the bone at a right angle to the long axis of the bone

Question 9

Linear (Sagittal plane) fracture

Answer 9

the fracture line passes in parallel to the long axis of the bone.

Question 10

Oblique fracture

Answer 10

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

Question 11

Spiral fracture

Answer 11

fracture line spirals round in multiple planes.

Question 12

Difference between oblique and spiral fractures?

Answer 12

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

Question 13

Compression fracture

Answer 13

occur in cancellous bone when an axial load compresses the bone beyond its limit.

Question 14

Where do compression fractures most commonly occur?

Answer 14

Lumbar vertebrae

Question 15

Green stick fracture

Answer 15

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

Question 16

Which two types of fractures can only occur in children? Why?

Answer 16

Greenstick
Epiphyseal separation fractures

because their bones are softer and more flexible than are the bones of adults.

Question 17

Epiphyseal separation fractures

Answer 17

when the fracture line extends through an unfused growth plate, thereby separating the epiphysis from the metaphysis.

Question 18

Epiphyseal separation fractures are mostly seen in?

Answer 18

overweight adolescent boys during rapid growth spurts and presents with hip pain and a limp.

Question 19

Which factors influence the proliferation and transformation of cells within the growth plate of long bones?

Answer 19

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

Question 20

What are symptoms of slipped upper femoral epiphysis?

Answer 20

Hip pain and a limp

Question 21

What are radiographic changes seen in bones during childhood?

Answer 21

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’

Question 22

How does a bone age study work?

Answer 22

• 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

Question 23

Why is bone age important?

Answer 23

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.

Question 24

What are the 3 phases of fracture healing in radiology

Answer 24

Inflammatory phase
Reparative phase
Remodelling phase

Question 25

Inflammatory phase consists of?

Answer 25

Haematoma formation Tissue death Inflammation / cellular proliferation Callus hasn't formed yet

Question 26

Reparative phase consists of? How long does it take?

Answer 26

Days to weeks  Angiogenesis / granulation / procallus formation  Soft (fibrocartilaginous) callus formation  Consolidation / hard callus formation

Question 27

Remodelling phase consists of? How long?

Answer 27

Months to years Gradual replacement of hard callus with mature bone.

Question 28

How is the process of fracture repair seen on an x-ray?

Answer 28

- 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

Question 29

How are CTs better than x-rays?

Answer 29

* 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

Question 30

What are drawbacks to CTs?

Answer 30

* 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

Question 31

Describe the colour that different substances appear on CT

Answer 31

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

Question 32

How can you tell when RADIOGRAPHIC UNION has occurred?

Answer 32

The fracture line eventually becomes completely obscured, at which stage radiographic union is said to have occurred.

Question 33

What are Hounsfeild units

Answer 33

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)

Question 34

How do MRIs work?

Answer 34

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.

Question 35

What are some advantages of MRI?

Answer 35

* Useful for generating multiplanar images * no radiation * It is better than CT and X-ray for imaging soft tissues

Question 36

What are some disadvantages of MRI?

Answer 36

• 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

Question 37

What are the types of MRI sequences?

Answer 37

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.

Question 38

What are fluid- sensitive sequences useful for?

Answer 38

Detecting oedema

Question 39

What can be injected to aid the diagnosis of conditions in MRI?

Answer 39

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

Question 40

How is ultrasound carried out?

Answer 40

- 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

Question 41

What is ultrasound used to look for?

Answer 41

- 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

Question 42

What are advantages of ultrasound?

Answer 42

- 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

Question 43

What are disadvantages of ultrasound?

Answer 43

- operator dependent - poor deep tissue resolution - limited bone and intra-articular imaging

Question 44

How does nuclear medicine work?

Answer 44

- uses radioisotope-labelled, biologically active drugs to mark biologic activity - images produced are a collection of radiation emissions from the isotopes

Question 45

What is nuclear medicine used to assess?

Answer 45

Areas of metabolically active bone such as when trying to localise metastatic disease, healing fractures or identify areas of osteomyelitis

Question 46

Why should a lot of care be taken in nuclear medicine?

Answer 46

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

Question 47

How should care be taken in nuclear medicine?

Answer 47

Lead aprons Monitored radiation exposure - film badges Use as low a dose as possible Radiation only used when absolutely necessary

Question 48

What is neoplasia?

Answer 48

new growth

Question 49

What is osteomyelitis?

Answer 49

infection of the bone