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Imaging Clinical Decision Making > MSK imaging > Flashcards

MSK imaging Flashcards

1
Q

What are the available imaging modalities for evaluating the MSK system?

A 
Plain film
CT
MRI
Scintigraphy
Diagnostic ultrasound
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2
Q

What imaging technique is the most appropriate starting point for MSK conditions

A

Plain films

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3
Q

Why are Plain films appropriate staring points for MSK conditions (5)

A 
1 - effective dose is low
2 - bone and joint changes generally visible by the time they are clinically detectable
3 - inexpensive compared to alternatives
4 - readily available
5 - patients recognize it as commonplace
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4
Q

How much cortical bone loss is there before plain films can see it

A

10-15%

40-50% for medullary bone loss

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5
Q

How much medullary bone loss is there before plain films can see it

A

40-50%

10-15% for cortical bone loss

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6
Q

How many days does it take for inflammation to create a positive radiographic sign?

A

10-14 days

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7
Q

What kind of CT is the best version of CT?

A

Helical CT

Remember the isotopic voxel that allows reformatting of axial data in any plane with equal resolution to the axial data

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8
Q

Computed tomography distinguishes density differences at about____%

A

1%

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9
Q

With CT, resolution can be achieved at less than

A

1mm if needed

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10
Q

In CT, sensitivity ranges can be achieved up to _______ for most MSK conditions

A

80-100%

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11
Q

When does CT provide intraarticular morphology (another way of saying this: what do you have to do to be able to see intraarticular morphology when you’re using CT?)

A

when used in conjunction with intraarticular injection of iodine-based contrast

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12
Q

What is the benefit of intravenous iodine based contrast CT?

A

It provides a measure of the volume of blood flow and gross metabolic activity of tissues

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13
Q

What is the risk of IV contrast?

A

Chance of death

Chance of life threatening rxn

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14
Q

What imaging distinguishes changes in tissue alterations at .1%

A

magnetic resonance imaging (MRI)

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15
Q

MRI is particularly useful for distinguishing

A

Soft tissue changes from normal

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16
Q

MRI is not very good at demonstrating obvious changes in what (2) material

A

Cortical bone

Dense soft tissue calcification

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17
Q

How does MRI sensitivity and specificity compare to CT?

A

Variable, but generally higher

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18
Q

Paramagnetic intravenous contrast administration in MRI is the analogue of IV iodine-based contrast in CT. When used for MRI, it allows:

A

Assessment of tissue vascularity and hence gross metabolic activity of any given tissue

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19
Q

What does intra-articular injection of contrast agents do to sensitivity and specificity?

A

Improves them

Intraarticular agents include saline and gadolinium

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20
Q

Radionuclide scintigraphy (bone scan)

A

20 millicuries of technetium 99m chelated to a substance that has an affinity to bone. It’s injected and allows to localize to bone over several hours.

21
Q

How are images for radionuclide scintigraphy (bone scan) acquired?

A

Gamma camera measures radionuclide concentration in each body region studied

22
Q

Hot spot vs cold spot

A

Increased vs decreased metabolic activity on bone scan

(Gamma camera measures radionuclide concentration in each body region studied = increased or decreased metabolic activity)

23
Q

Sensitivity for a radionuclide scintigraphy (bone scan)

A

92-98% for changes in metabolic activity of a bone

24
Q

Specificity for a radionuclide scintigraphy (bone scan)

A

Low

25
Q

Predictive value for anatomic lesions using radionuclide scintigraphy (bone scan)?

A

High

26
Q

Can radionuclide scintigraphy (bone scan) distinguish 2 or more metabolically active conditions? E.g. infection vs aggressive neoplasm

A

Generally no

27
Q

Diagnostic ultrasound

A

Sound waves transmitted through tissue and echo back when they bounce off tissue interfaces. The returning sound waves are received by receivers in the ultrasound transducer head. So the transducer is both transmitter and receiver.

28
Q

What does diagnostic ultrasound give you?

A

A morphological assessment of muscle, tendon, small to medium size vascular and medium-size neurological structures

29
Q

For the purpose of identifying changes to the surface of a bone, how does diagnostic ultrasound (US) hold up to CT and MRI?

A

About the same as CT
Less than MRI

MRI is best, CT and US come in second

30
Q

How sensitive is US to differentiating cyst vs solid?

A

95+% sensitivity. Very good

31
Q

How does US compare to MRI or CT arthrography in terms of intra-articular applications such as large joints?

A

MRI and CT are better than US

32
Q

How does US compare to MRI or CT arthrography in terms of intra-articular applications such as small joints that are superficial?

A

US is acceptable.

However, when they are deep small joints… US is inferior

33
Q

Bone densitometry

A

Accurate and reliable measure of calcium concentration in medullary bone. Compare that measurement to reference population standards and/or to an individual’s previous bone densitometry examination(s).

34
Q

Bone densitometry is useful in evaulating

A

Effectiveness of prior or current therapies designed to improve bone density

35
Q

Single photon absorptiometry (1 type of bone densitometry)

A

A single energy beam is transmitted through bone and its incident vs. transmitted rate is measured as a proxy for the density of bone absorbing it

36
Q

Single photon absorptiometry is used only in one area

A

Peripheral skeleton only.

Because measures are not very accurate and do not generalize well together

37
Q

Dual Energy X-ray Absorptiometry (DEXA) a 2nd type of bone densitometry

A

2 x-ray beams (one low ~40kV and one high ~90kV) of differing energies are passed through bones. The differential absorption of 2 beams is detected similar to a digital x-ray. The more dense the bone, the more energy is absorbed and the less energy detected.

38
Q

How accurate is Dual Energy X-ray Absorptiometry (DEXA)

A

Highly accurate

Capable of generating a risk of fracture profile that is reasonably accurate

39
Q

CT densitometry (3rd type of bone densitometry)

A

A conventional CT scanner is used in conjunction with a series of known Ca++ concentration fluid tubes that are placed in an array beneath the patient and are scanned with their spine

The output is Hounsfield density numbers of selected marrow volumes compared to the known phantom concentrations and estimates of Ca++ concentrations are created, expressed as volume measures

40
Q

Is CT densitometry accurate?

A

Yes, capable of generating a risk of fracture profile that is reasonable accurate

41
Q

Indications for CT densitometry

A
  • All women >65 yo
  • Men >70 yo
  • Women <65 who have added risk for osteoporosis
  • Women <65 or Men <70 who have a history of smoking or thoracic kyphosis (loss of height)
  • Individuals of any age with osteopenia or fragility fractures on imaging studies, CT or MRI
  • Humans >50 with wrist, hip, spine, proximal humerus fracture with minimal or no trauma and no malignancy
  • Humans who develop 1+ insufficiency fracture
  • Humans receiving (present or future) glucocorticoid therapy for 3+ mo
  • Humans in long-term therapy with meds known to adversely affect BMD
  • Humans with endocrine disorder known to affect BMD
  • Hypogonadal men older than 18 yo
  • Men with surgically or chemotherapeutically induced castration
  • Humans with med conditions that could alter BMD
  • Humans being considered for pharmacologic therapy for osteoporosis
  • Ongoing monitoring to assess interval change in BMD in patients undergoing treatment for osteoporosis or to follow-up medical conditions associated with abnormal BMD
  • Individuals with extremes of obesity or low BMI
42
Q

Risk for osteoporosis in women (4)

A

Estrogen deficiency
History of maternal hip fracture that occurred after the age of 50
Low body mass (less than 127 lbs)
History of amenorrhea (more than 1 year before age 42)

43
Q

Meds known to adversely affect BMD (4)

A

Anticonvulsant drugs
Androgen deprivation therapy
Aromatase inhibitor therapy
Chronic heparin

44
Q

Endocrine disorders known to affect BMD (3)

A

Hyperparathyroidism
Hyperthyroidism
Cushing’s syndrome

45
Q

Medical conditions that could alter BMD (6)

A

Chronic renal failure
RA and other inflammatory arthritides
Eating disorders, including anorexia nervous and bulimia
Organ transplantation
Prolonged immobilization
Individuals who have had gastric bypass for obesity
Conditions associated with 2˚ osteoporosis

46
Q

Conditions associated with secondary osteoporosis (10)

A 
GI malabsorption
Spruce
Malnutrition
Osteomalacia
Vitamin D deficiency
Endometriosis
Acromegaly
Chronic alcoholism
Established cirrhosis
Multiple myeloma
47
Q

What scores are used to quantify risk of fracture profile?

A

Z-scores and T-scores

48
Q

Categories of MSK imaging can be remembered with CATBITES

A 
Congenital
Arthritis
Trauma
Blood/vascular
Infection
Tumors
Endocrine/metabolic
Soft tissue/surgical

Imaging Clinical Decision Making (4 decks)

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