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Radiology > 1 > Flashcards

1 Flashcards

1
Q

what is attenuation concept? what are the 5 basic?

A
  1. Xray absorption depends on density

2. air, fat, soft tissue, bone, metal

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2
Q

what is the idea of differential density?

A

structures are visible on a radiograph when they are outlined at least in part by a structure of a different density.

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3
Q

what are the individual images called on fluoroscopy?

A

spot images

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4
Q

When is fluoroscopy great?

A

contrast media in vessels and GI tract, passing things through lumens.

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5
Q

what is the difference between CT and XR

A

x-rays pass through person and are captured on sensors and not a sheet

CONTRAST IS MUCH BETTER

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6
Q

Voxels are assigned density values called what?

A

hounsfield units

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7
Q

how many HUs is water? air? bone?

A

0
1000
>3000

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8
Q

In US, what does tissue appearance depend on?

A

echogenicities- amount of sound reflected

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9
Q

how many guass is 1T?

A

10,000

earth’s magnetic field is .5 gauss.

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10
Q

When does the MRI magnet turn off?

A

never- always on

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11
Q

How does MRI generally work?

A

protons act like little bar magnets…a little over half align with the field. RF pulses bounce them out of alignment, when RF pulse is off we listen for RF signals from the protons as they realign.

DIFFERENT TISSUES HAVE DIFFERENT PROTON CONCENTRATIONS

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12
Q

What are the two units or radiation doses? which one is for absolute and which one is for variable amounts based on the tissue?

A

Gray or Sieverts

Gray, Sieverts

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13
Q

how many mSv in CXR? CT? barium enema? cardiac angiography?

A

.1mSv
5-`0mSv
10 mSv
10mSv

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14
Q

What mode of imaging produces the highest radiation doses?

A

fluoroscopy- often 30 mGy/minute so fluoroscopy time is the most important determinant of dose

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15
Q 
How many gray cause the following? 
Decreased sperm count
Decreased lymphocyte count 
Skin erythema 
Sterility 
Death from bone marrow failure 
Death from GI failure 
Death from CNS failure
A 
Decreased sperm count – 0.25 mGy
Decreased lymphocyte count – 0.5 Gy
Skin erythema – 2 Gy (locally)
Sterility – 4-12 Gy (to gonads) depending on age and sex
Death from bone marrow failure – 2-5 Gy
Death from GI failure – 10 Gy
Death from CNS failure – 100 Gy
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16
Q

What principle do we use to encourage radiation protection?

A

ALARA principle

as low as reasonable available. (applies to everyone)

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17
Q

What are the ALARA principles applied to pregnancy?

A

Any radiation in pregnancy is potentially harmful, however there is no absolute contraindication to a radiology study.

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18
Q

during pregnancy, when is radiation the most detrimental?

A

1st trimester during organogenesis

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19
Q

radiation during pregnancy between 0-10 days GA causes what?

A

all or none response

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20
Q

radiation during pregnancy between 20-40 days causes what?

A

congenital anomolies

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21
Q

radiation during pregnancy between 50-70 days causes what?

A

microcephaly

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22
Q

radiation during pregnancy between 70-150 days causes what?

A

growth retardation/mental retardation

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23
Q

radiation during pregnancy between 150+ days and birth?

A

increased risk of childhood malignancy

24
Q

why is correlating an exact dose necessary to produce a given congenital defect difficult?

A

background incidence of the defects is 5%

25
Q

T-F– Radiation during pregnancy may have a small risk of fetal anomolies

A

increased risk of childhood malignancy

26
Q

Whatis the departmental policy on women needing imaging?

A

ask all females of childbearing age when last period was and if they could be pregnant

if unsure get preg. test

27
Q

What are the 4 possible scenarios if a pregant woman undergoes radiation imaging?

A
  1. examination above diaphragm or below hips- not direct

2. examination where fetus is in direct beam but does is

28
Q

if fetus is not going to receive a direct beam, what is the course of action

A

assure parents that there is no scientific evidence for damage

shield the abdomen and pelvis

29
Q

If fetus recieves

A
  • minimal risk of stochastic nature
  • risk versus benefits discussion between radiologist and physician
  • noted in the chart why study was essential
  • inform patient of the small dose and will be kept lowest
30
Q

If fetus receives 10-50 mGy- what is course of action

A
  • risk vs. benefits discussion
  • noted in chart why it is essential
  • patient involvement in decision- risk is small but real- especially 2-15 weeks
  • informed consent needed.
31
Q

IF fetus receives >50mGy- course of action?

A
  • formal calculation of fetal dose
  • . physician, radiologist, radiation physicist should each write a note
  • patient informed and sign informed consent.
32
Q

why do we use contrast? 2 major reasons?

A

abnormal tissues enhance diff due to capillary leak, breakdown of BBB, diff vascularity

opacify specific structures of interest (ie vessels)

33
Q

what does all CT contrast contain?

A

iodine - high molecular weight attenuates x-rays

34
Q

newer more expensive agents are nonionic and what?

A

isoosmolar

  • leads to fewer contrast reactions and less nephrotoxic
35
Q

idiosyncratic reaction to contrast results in what?. non-idiosyncratic?

A

allergic reaction from hives –> Cardiopulmonary collapse

nephrotoxicity

36
Q

review the risk factors for nephrotoxicity of IV contrast

A 
Renal insufficiency
DM
dehydration
CV disease and diuretic use
Age>70
Myeloma
Uncontrolled HTN
Gout
37
Q

What is the cut off for not giving IV contrast in normal patients and in patients with DM?

A

> 3

> 2.5

38
Q

if Cr 2-3 in normal or 1.5-2.5 in DM- what do we do?

A

only give if absolutely necessary
hydrate them first
possibly give NAC

39
Q

If patients develop ARF due to contrast toxic levels of what drug can quickly accumulate and result in a lethal what? what do we do?

A

metformin
-acidosis and hypoglycemia

stop administration of metformin for 48hrs.

40
Q

When do most allergic reactions to contrast start?

A

20 min

41
Q

how do we treat contrast reaction that is mild urticaria, pruritis, or erythema?

A

benadryl 50mg PO or IV

consider hydrocortisone 200 mg IV

42
Q

How do we treat sever contrast reaction?

A

epi .3mg IM 1:1000. if inadequate give .1mg 1:10000 slow IV up to 1 mg

43
Q

What do we do to treat laryngeal edema contrast reaction?

A

Secure IV
O2 by mask 10L/min
Epinephrine 0.1 mg (1:10,000) slow IV; up to 1 mg
CALL CODE
Hydrocortisone 200 mg IV, repeat if necessary

44
Q

What do we do to treat bronchospasm contrast reaction?

A

O2 by mask 10L/min
Albuterol inhaler 2 puffs
(moderate spasm) Epinephrine 0.3 mg (1:1000) IM; may repeat once
(severe spasm) Epinephrine 0.1 mg (1:10,000) slow IV; up to 1 mg. CALL CODE.

45
Q

How do we treat hypotension with tachycardia- contrast reaction?

A

O2 10L/min
Elevate legs, secure IV access
Lactated Ringer’s vs. NS 1-2L
(severe) Epinephrine 0.1 mg (1:10,000) slow IV; up to 1 mg. CALL CODE.

46
Q

How do we treat contrast reaction hypotension w/ bradycardia?

A

O2 10L/min
Elevate legs, secure IV access
Lactated Ringer’s vs. NS 1-2L

(severe) Atropine 0.6-1.0mg IV slow push, repeat up to 3.0 mg total

47
Q

For patients with serious IV contrast reactions like bronchospasm, hypotension or hives, what do we premedicate with?

A

Planned exam- prednisone 40 mg- PO 13, & and 1 prior ro the exam.

Semi Emergent- hydrocortisone 1 hr prior and 3 hours post- contrast and Benadryl 50mg and Famotidine

48
Q

how do we treat contrast extravasation?

A

Moderate- elevate observe ice packs

severe- plastics consult, observe for blistering or decreased sensation and do same for moderate

49
Q

Gadolinium is paramagnetic and produces what on on the images?

A

increased signal intensity on T1 weighted images

50
Q

T-F– gadolinium is not contraindicated in pregnancy- what are the relative contraindications?

A

False- it is

lactation and renal failure
It does not cause renal failure

51
Q

If gadolinium is given to a person with renal failure, what might it cause?

A

nephrogenic systemic fibrosis
Fibrosing dermopathy that may cause fibrosis of skin, eyes, joints and internal organs
Can result in death

52
Q

What is the current UIHC policy for preventing nephrogenic systemic fibrosis?

A

Patients over 70 yo, known diabetic or with renal failure have Cr and GFR drawn before scan. GFR

53
Q

Waht are the attributes of barium?

A
  • denser–more visible
  • coats mucosa well
  • don’t use if suspect perforation or obstruction, can cause barium peritonitis
54
Q

What are the attributes of water soluble iodinated contrast such as gastrografin or hypaque?

A

Can be used to r/o obstruction or perforation
Good to use when large volumes are needed, as it is cheap
Don’t use if h/o allergy to iodinated contrast
If giving it po, don’t use if patient is at risk for aspiration, can cause pulmonary edema

55
Q

what are the attribute of Visipaque?

A

Used if need to r/o esophageal perforation
Doesn’t cause pulmonary edema like Hypaque can
Expensive, so if large volumes are needed, use Hypaque if you can.

56
Q

What are the attributes of Air GI contrast?

A
  • usually used in conjunction w/ barium in double contrast studies of bowel
  • in pediatrics, air is often used alone–enema to reduce intussusceptions.

Radiology (8 decks)

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