MSK imaging

Question 1

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

Answer 1

Plain film
CT
MRI
Scintigraphy
Diagnostic ultrasound

Question 2

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

Answer 2

Plain films

Question 3

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

Answer 3

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

Question 4

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

Answer 4

10-15%

40-50% for medullary bone loss

Question 5

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

Answer 5

40-50%

10-15% for cortical bone loss

Question 6

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

Answer 6

10-14 days

Question 7

What kind of CT is the best version of CT?

Answer 7

Helical CT

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

Question 8

Computed tomography distinguishes density differences at about____%

Answer 8

1%

Question 9

With CT, resolution can be achieved at less than

Answer 9

1mm if needed

Question 10

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

Answer 10

80-100%

Question 11

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?)

Answer 11

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

Question 12

What is the benefit of intravenous iodine based contrast CT?

Answer 12

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

Question 13

What is the risk of IV contrast?

Answer 13

Chance of death

Chance of life threatening rxn

Question 14

What imaging distinguishes changes in tissue alterations at .1%

Answer 14

magnetic resonance imaging (MRI)

Question 15

MRI is particularly useful for distinguishing

Answer 15

Soft tissue changes from normal

Question 16

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

Answer 16

Cortical bone

Dense soft tissue calcification

Question 17

How does MRI sensitivity and specificity compare to CT?

Answer 17

Variable, but generally higher

Question 18

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

Answer 18

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

Question 19

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

Answer 19

Improves them

Intraarticular agents include saline and gadolinium

Question 20

Radionuclide scintigraphy (bone scan)

Answer 20

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.

Question 21

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

Answer 21

Gamma camera measures radionuclide concentration in each body region studied

Question 22

Hot spot vs cold spot

Answer 22

Increased vs decreased metabolic activity on bone scan

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

Question 23

Sensitivity for a radionuclide scintigraphy (bone scan)

Answer 23

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

Question 24

Specificity for a radionuclide scintigraphy (bone scan)

Answer 24

Low

Question 25

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

Answer 25

High

Question 26

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

Answer 26

Generally no

Question 27

Diagnostic ultrasound

Answer 27

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.

Question 28

What does diagnostic ultrasound give you?

Answer 28

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

Question 29

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

Answer 29

About the same as CT Less than MRI MRI is best, CT and US come in second

Question 30

How sensitive is US to differentiating cyst vs solid?

Answer 30

95+% sensitivity. Very good

Question 31

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

Answer 31

MRI and CT are better than US

Question 32

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

Answer 32

US is acceptable. However, when they are deep small joints... US is inferior

Question 33

Bone densitometry

Answer 33

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).

Question 34

Bone densitometry is useful in evaulating

Answer 34

Effectiveness of prior or current therapies designed to improve bone density

Question 35

Single photon absorptiometry (1 type of bone densitometry)

Answer 35

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

Question 36

Single photon absorptiometry is used only in one area

Answer 36

Peripheral skeleton only. Because measures are not very accurate and do not generalize well together

Question 37

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

Answer 37

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.

Question 38

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

Answer 38

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

Question 39

CT densitometry (3rd type of bone densitometry)

Answer 39

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

Question 40

Is CT densitometry accurate?

Answer 40

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

Question 41

Indications for CT densitometry

Answer 41

*  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

Question 42

Risk for osteoporosis in women (4)

Answer 42

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)

Question 43

Meds known to adversely affect BMD (4)

Answer 43

Anticonvulsant drugs Androgen deprivation therapy Aromatase inhibitor therapy Chronic heparin

Question 44

Endocrine disorders known to affect BMD (3)

Answer 44

Hyperparathyroidism Hyperthyroidism Cushing’s syndrome

Question 45

Medical conditions that could alter BMD (6)

Answer 45

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

Question 46

Conditions associated with secondary osteoporosis (10)

Answer 46

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

Question 47

What scores are used to quantify risk of fracture profile?

Answer 47

Z-scores and T-scores

Question 48

Categories of MSK imaging can be remembered with CATBITES

Answer 48

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