1
Q
Role of contrast media
A
- improve sensitivity & specificity
- differentiation
- evaluate vascular structures
- assess abdominopelvic region
2
Q
high contrast CT exams usually require ____ to differentiate structures of different densities
A
no contrast media
3
Q
low contrast CT exams usually require ____
A
contrast media to improve tissue contrast
4
Q
what type of contrast are CO2 and Air
A
negative contrast
5
Q
what type of contrast are water & volumen
A
neutral contrast
6
Q
how does the diff contrast appear as
A
positive contrast - white
neutral “ - grey
negative “ - black
7
Q
what type of contrast are barium & iodinated
A
positive contrast
8
Q
example of barium contrast
A
barium sulphate
9
Q
example of iodinated contrast
A
iodine based IV contrast gastrografin
10
Q
limits of using plain water
A
- transits rapidly & absorbed distally
- suboptimal distension which mimics / masks lesions
11
Q
pros of using plain water
A
AVA
- administered orally
- assess luminal pathology & bowel wall
- very good for upper GIT if scanned at appropriate timing
12
Q
what does VoLumen contain
A
- diluted barium sulfate suspension
- sorbitol
13
Q
what effect does sorbitol have
A
laxative effect
14
Q
how many bottles does a patient drink
A
2-3 bottles of VoLumen
15
Q
how can barium contrast be administered
A
oral & rectal
16
Q
what is barium contrast commonly used in
A
esophagus, intestine, very intense intestinal contrast
17
Q
contra-indications of barium
A
- intestinal perforation
- intestinal obstruction
- swallowing difficulties
18
Q
K-edge of iodine
A
33.2 keV
19
Q
what is a function indicator of x-ray energy
A
probability of photoelectric absorption since it corresponds to binding energy of iodine
20
Q
higher kVp leads to ___ compton effect & ___ photoelectric effect
A
higher; lower
21
Q
properties of iodinated contrast
A
- oligomerization
- iodine concentration
- osmolarity
- viscosity
22
Q
what are the 2 main groups and subgroups of water soluble iodinated contrast
A
ionic
- monomer + dimer
non-ionic
- monomer + dimer
23
Q
currently available contrast media are either __
A
monomer (1 benzene ring) + dimer (2 benzene ring)
24
Q
examples of ionic iodinated contrast media
A
- hypaque
- isopaque coronar
- hexabrix
25
what is gastrografin
diatrizoate
26
what is hypaque AKA
diatrizoate
27
what is isopaque coronar AKA
metrizoate
28
what is hexabrix AKA
ioxaglate
29
examples of non-ionic iodinated contrast
1. ultravist
2. visipaque
30
what is ultravist AKA
iopromide
31
what is visipaque AKA
iodixanol
32
although overdose is unlikely but possible, ___ needs to be defined
upper limits
33
what factors influence iodine concentration/dose
protocol, injection rate, delay imaging
34
how is iodine concentration standardized for pediatric patients
weight
35
drink ___ of water to minimize iodine side effects
1L
36
what is osmolarity
measurement assessing number of particles dissolved in 1kg of water
37
Osmolality of iodinated contrast media is compared to the osmolality of ___
human plasma (300mOsm/kg H2O)
38
iodinated contrast is either ___ or __ tonic
hyper-; iso-
39
what does osmolarity contribute to
- non-allergic adverse reactions
- injection pain
- endothelial damage
- RBC deformation
40
what is the osmolarity of ionic CM
very high
41
what is the osmolarity of non-ionic CM
moderate to high
42
cP
centipoise
43
what is viscosity of IV CM
measure of liquid resistance / friction to flow
44
what does viscosity of IV CM influence
- IV injectability
- cannula gauge
- contrast induced kidney injury risk
45
high viscosity leads to ___ infusion times
longer
46
how much iodine containing CM is removed 24hr after IV administration
90% mostly eliminated by kidneys
47
in the event of renal failure / insufficiency, how can CM be extracted
dialysis
48
iodine containing CM can/cannot cross cell membranes or Blood brain barrier
cannot
49
CM firstly transits through the vessel system (“Vascular compartment”) and secondly enters the space between vessels and cells (“interstitial compartment”) by ____
free diffusion
50
what are the 3 main groups of IV contrast enhancement
1. patient
2. CT scanning parameters
3. contrast media
51
what are the scan delays possible
fixed, test-bolus, bolus-tracking
52
what are the injection patterns available
uniphase, biphase, exponentially decay
53
iodine dose formula
(concentration x vol of contrast) / 1000
54
why should the CM administered be greater in larger patients compared to smaller patients?
larger patients = larger blood volume = more diluted CM
55
what are the diff cannula available
18G, 20G, 22G, 24G
56
what is the flow rate of 18G
4 - 6 ml/s
57
what is the flow rate of 20G
3 - 4 ml/s
58
what is the flow rate of 22G
2 - 3 ml/s
59
what is the flow rate of 24G
1 - 1.5 ml/s
60
which cannula for pediatrics
24G
61
which cannula for difficult veins esp post chemotherapy
24G
62
which cannula for arterial & venous phase of CT scan
22G
63
which cannula for most phases
20G
64
which cannula for fast CT contrast flowing studies
18G
65
saline chaser allows for the reduction of ___
contrast volume & increases peak attenuation
66
saline chaser reduces ___ artifacts from vein & right heart
streak
67
adverse reactions of IV iodinated contrast
1. CI-AKI
2. adverse reaction post administration
3. extravasation
4. air embolism
68
CI-AKI means?
contrast induced - acute kidney injury
69
which patients are prone to CI-AKI
patients with compromised kidney function such as diabetes and chronic kidney disease
70
what indicators suggest patient is at higher risk of AKI
- eGFR (mL/min): 30 - 0
- elevated serum creatinine (mg/dL): 2 - 4.5
- Moderate reduced kidney function
71
how to reduce chance of CI-AKI
1. screen for patient risk
2. administer periprocedural hydration
3. lower osmolar iodinated contrast media
4. stop metformin
72
NSAIDs
Non-Steroidal Anti-Inflammatory Drugs
73
how to minimize reactions
- hydration
- stop NSAIDs
- use other modalities / non-contrast
74
eGFR is calculated using ___
diet modification in renal disease formula
75
what do you need for diet modification in renal disease formula
- serum creatinine
- age
- gender
76
serum creatinine is ___ indicator of kidney function
insensitive
77
what is the best overall indicator of kidney function
GFR
78
eGFR
estimated glomerular filtration rate
79
if eGFR > 90, should you continue with IV iodinated CM
yes since excretion half time is 1-2 hrs
80
if eGFR > 60, should you continue with IV iodinated CM
- weight benefits & risks with radiologist
- consider other modalities / non-contrast
- recheck serum creatinine and eGFR 48 hrs after scan
81
if eGFR < 30, should you continue with IV iodinated CM
if on dialysis, use non-contrast/other modalities
if not on dialysis, recheck serum creatinine and eGFR 48 hrs after scan
82
____ are well established methods to prevent CI-AKI
volume expansion & hydration treatment
83
IV saline hydration reduces risk of CI-AKI by ___
almost 50%
84
lactic acidosis
when lactate production exceeds its metabolism in your body
85
what is the main factor for metformin related lactic acidosis
diabetes
86
how to minimize reactions involving metformin
- discontinue 48 hrs after contrast
- check creatine before resuming
87
what causes 50% mortality for adverse reactions
metformin + chronic renal insufficiency + IV contrast = lactic acidosis
88
when to resume metformin
eGFR > 30mL/min/1.73m^2
89
protocol for eGFR < 30mL/min/1.,73m^2
stop metformin 48hrs before and after CM injection
90
which pathway involves IgE allergic reaction
anaphylactic true allergy
91
what are the IV contrast reaction pathways
- anaphylactic true allergy
- anaphylactoid "allergy-like"
92
what do IV contrast reactions activate
mast cells
93
strategies to avoid adverse reactions
1. evaluate risk and benefit
2. use other modalities / non-contrast
3. diff CMs
4. guidelines if contrast must be used
94
what causes extravasation
failed IV injection leading to compartment syndrome
95
what is compartment syndrome
increased pressure within confined space
96
management strategies for extravasation
MISE
1. elevate limbs
2. ice pack
3. monitoring
4. surgery if severe
97
clinical feature of air embolism
1. dyspnoea
2. cough
3. chest pain
98
treatment for air embolism
- 100% oxygen
- hyperbaric oxygen tank
- patient in left lateral decubitus
CT & MRI
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