Notes from Mosby's Exam Review Flashcards
(154 cards)
1
Q
what is the formula to calculate HU (CT number) of a tissue given the linear attenuation coefficient of water and the tissue for a particular scanner
A
(LAC of tissue - LAC of water) / LAC of water * 1000 {in other words: LAC of tissue minus LAC of water divided by LAC of water * 1000 }
2
Q
The phantom measurement of the uniformity* of a CT system is performed primarily to assess the negative effects of:
A
Beam hardening
3
Q
Which of the following components of the CT image quality may be controlled by the technologist? 1. spacial resolution 2. contrast resolution 3. noise
A
all of the above
4
Q
What is the major controlling factor of exam quality for coronary CTA?
A
patient heart rate. Stable, steady heart rates below 65-70 beats per minute (bpm) yield the best results
5
Q
What is the purpose of automatic tube current modulation (ATCM) software in the CT system?
A
decrease patient dose. It is a form of AEC (automatic exposure control)
6
Q
Which two technical factors play a role in the production of an isotropic dataset?
A
section width and display field of view (DFOV) NOT the SFOV
7
Q
What is the term that refers to the measured time in seconds required for blood to pass through an area of the brain tissue:
A
mean transit time (MTT)
8
Q
What kind of scatter accounts for the primary interaction between x-ray photons and tissue during computed tomography?
A
compton effect
9
Q
At what level of the spine does the abdominal aorta split into the right and left iliac arteries?
A
L4
10
Q
What is happening in the heart during ventricular systole?
A
contraction of the left and right ventricles
11
Q
What degree of azimuth setting is used to make a localizer or scout image?
A
0 degree - a 0 degree azimuth describes the situation in which the x-ray tube and detectors do not rotate but remain above and below the patient, providing a frontal projection
12
Q
In multislice CT (MSCT), the beam pitch is equal to the table feed per rotation divided by the _______.
A
total collimation (total collimation is equal to the combined thickness of all of the sections that are simultaneously acquired with each gantry rotation
13
Q
In what phase of contrast will you see well-opacified ureters?
A
excretory
14
Q
What is the approximate CT density (in HU) of the density of the unenhanced spleen?
A
between +40 and +60 HU
15
Q
What is a hallmark finding for focal nodular hyerplasia (FNH) of the liver in CT? (hint: it has to do with how it enhances with contrast)
A
central scar that remains hypodense after initial contrast agent administration
16
Q
As a solid-state CT detector measures transmitted radiation, it emits a proportional response in the form of _____. (analog or digital signal)
A
analog signal - (it passes this signal to the ADC)
17
Q
What is the word for the spread of infection through a contaminated object?
A
fomite
18
Q
What should a PET-CT patient avoid prior to their test so that abnormal uptake is not registered in muscle?
A
strenuous activity (because this will make the FDG uptake in the muscle
19
Q
What is the unit of effective dose?
A
sieverts (Sv)
20
Q
A voxel whose attenuation coefficient is less than that of water is assigned a pixel value with a _____ CT number
A
negative
21
Q
What is used to treat a severe vagal reaction to iodinated contrast that includes bradycardia?
A
atropine
22
Q
How thin do we scan high-res chests?
A
1 mm
23
Q
In patients who are right dominant, the posterior descending artery branches from this coronary atery?
A
The right coronary artery
24
Q
What type of reconstruction was used in the first prototype CT scanner?
A
iterative technique
25
Are both the kidneys and pancreas considered to be restroperitoneal?
yes
26
Does IV contrast improve the differentiation of subtle hemorrhage in the brain?
No. Contrast is initially contraindicated because the enhancement may actually mask subtle signs of hemorrhage
27
How does single-segment reconstruction change the temporal resolution
using single-segment aka. half-scan will half the temporal resolution. Ie. a 400-msec rotation scan will be 200-msec when reconstructed with single segment
28
What is the optimum contrast phase for kidney lesions and when does it occur.
The nephrographic phase and it occurs between 70 and 90 seconds after the start of injection
29
What is the definition of pitch?
It is the relation of table speed to slice thickness
30
What is the formula to calculate pitch?
Pitch = travel distance of table per 360 degree rotation divided by the total xray beam collimation width. pitch = TD/TCW
31
The approximate inherent filtration of the tube housing, cooling oil, and so on amount to how thick of aluminum equivalent filtration?
3.0 mm
32
That is the excretion half-time of intravenous iodinated contrast media in a patient with normal renal function?
1 to 2 hours
33
What does the symbol "x" stand for in the lambert-beer law?
the absorber thickness
34
What is the term for CT images being reconstructed for only a portion of the raw data to reduce motion artifact?
subtraction images
35
What kind of tissue are 'low spacial frequency' algorithms best at demonstrating?
soft tissue detail (they filter out high spacial frequency information such as bone)
36
What scanning acquisition mode is used to scan prospectively ECG-gated cardiac CTA studies? (axial "step-and-shoot" or spiral)
axial "step-and-shoot"
37
What DFOV is commonly used to reconstruct images of the spine?
120 - 150 mm or 12 - 15 cm
38
A dermoid tumor of the ovary may also be referred to as ____
cystic teratoma
39
What is the single worst element working against a CT scanner's contrast resolution?
noise
40
Name the two technological advances that enabled spiral/helical CT scanning?
slip-ring technology and high-efficiency x-ray tubes
41
Name two common areas of calcification in the brain.
choroid plexus and pineal gland
42
When performing both a CT abdomen and conventional GI studies, which should be done first and why?
The CT should be done first because the heavier barium used in GI studies causes streak artifact on CT.
43
How high an osmolality is high-osmolar contrast material?
1000-2400 mOsm/kg water
44
Who was the 1917 austrian mathematician who proved that it was possible to reconstruct a three-dimensional object from the infinite set of all of its projections
Radon
45
The condition whereby a portion of the small intestine collapses or telescopes into itself is termed:
intussusception
46
During a CT scan, each sample of ray sum measurements made by the data acquisition system (DAS) is called _____
view
47
By CT criteria, a solitary pulmonary nodule may be defined as a focal area of increased density in the lung that is smaller than ____cm
3 cm
48
What three things are going on when there is 'complete cardiac diastole'?
relaxation of the left and right ventricles, relaxation of the left and right atria, the T wave of the electrocardiogram (ECG)
49
What is the typical HU range for modern CT scanners?
-1024 to +3071
50
How much mL/100g cerebral blood volume (CBV) indicates a brain parenchyma infarct core?
2.5 mL/100g
51
How is a vasovagal reaction linked to blood pressue?
The term vasovagal pertains to systemic hypertension (often leading to cerebral ischemia)
52
What does the modulation transfer function (MTF) of a CT scanner measure?
It's ability to faithfully reproduce the anatomy that is being imaged
53
What is the range of values for modulation transfer function (MTF) that describe how well the anatomy that is being imaged is reproduced?
0 to 1. 0 is said to have no useful informatioin and 1 is said to be perfect. Most scanners are somewhere in between.
54
What HU range is a solitary pulmonary nodule though to be benign?
165-200 HU
55
Between spondylolisthesis and retrolishesis, which is a forward slipping and which is a backwards slipping?
spondylotisthesis is a forward slipping and retrolisthesis is a backwards slipping
56
What percentage of it's blood supply does the liver receive from the hepatic artery vs the portal vein?
25% from the hepatic artery and 75% from the portal vein
57
What HU unit is associated with calcium (such as in the coronary artery)?
+130
58
What is a standard section width (aka slice thickness) and interval (aka slice gap or incriment) used for an abdomen and pelvis scan
3.0/3.0 mm- 5.0/5.0 mm
59
How many shades of gray is the human eye capable of differentiating?
60-80
60
Each 1% difference in contrast between adjacent objects amounts to a difference in pixel value of how much (in HU)
10 HU
61
What is the term for too much nitrogenous material in the blood?
azotemia or uremia
62
Neoplasms in what body part is most commonly treated with CT-guided radio frequency ablation (RFA)
liver
63
What stage of an ECG will the heart demonstrate the least motion?
T wave
64
What is quantitative computed tomography (QCT) used to measure?
the mineral content of bone. You can calculate the BMD values (bone mineral density)
65
What is the average volume of contrast for a CT myelogram
12-14 mL
66
How long after contrast should a breastfeeding mother "pump-and-dump"
12-24 hours
67
What is the purpose of doing the expiration part of a high-res chest?
to look for air trapping from COPD
68
A patient with an elevated level of D dimer in the bloodstream may be at increased risk for which serious condition?
pulmonary embolism (PE)
69
CT scanning of the liver for tumor evaluation should not be performed during which phase?
Equilibrium phase because it can hide hepatic lesions.
70
The acronym PTT is used for which laboratory test?
Partial Thromboplastin Time - it indicates the coagulation time of a patients blood
71
The portion of the male reproductive system responsible for the storage of the majority of the mature sperm is:
vas deferens
72
What ligament suspends the duodenum from the diaphragm?
ligament of treitz
73
When trying to display images with varying density ranges (ie. mastoid tip and IACs in same image) should you use a wide or narrow window width?
a wide window width, such as 4000, should be used
74
When trying to display images with many similar densities, (like abdomen) should you choose a wide or narrow window width.
a narrow window width, such as 400 will better display an image with many similar densities.
75
What kind of detector array contains mid line narrow elements flanked by wider detectors?
a hybrid array
76
The technique that allows the user to select the range of pixel values used in a 3D CT reformation is termed:
thresholding. It is what allows your render to just include bone, for instance, and not the unwanted soft tissues
77
The normal range for the International Normalized Ratio (INR) for prothrombin time (PT) results is:
0.8 - 1.2
78
Which phase of contrast provides the best gastric and intestinal wall enhancement? (think ABD/PEL W)
portal venous phase
79
Is transdermal a route of paraenteral medication administration?
No it is not. But subcutaneous and intradermal are. Paraenteral = infusion or injection
80
For MDCT, identified areas of calcium must demonstrate relative attenuation values greater than:
+130
81
The calculation of the average cumulative dose to each section within an acquisition of multiple sections is termed the:
MSAD or Multiple Scan Average Dose
82
Which window width and level would be good to look at CT colonography images?
Width = 1600, Level=-400 (a "lung-type" setting)
83
What relationship is there between the slice width and gap when wanting an overlapping slice?
The section interval (slice gap) must be less than the section width (slice thickness)
84
Axial CT sections of the lumbar spine for intervertebral disc evaluation is best done in which plane (think MR)
parallel to the plane of the intervertebral disc spaces
85
The quantity of radiation dose received by the patient from a series of CT scans is referred to as:
MSAD (Multiple-Scan Average Dose)
86
What are some of the signs and symptoms of hypovolemic shock?
pallor, hypotension, tachycardia, oliguria (decreased urine production)
87
Do gallstones appear hyperdense on abdominal CT scans?
Yes!
88
What does intrathecal mean?
occurring within or administered into the spinal theca
89
Is reduction in patient dose an improvment of chest CTs with MDCT (multidetector CT)?
No. While you get increased speed and a reduction in the misregistration artifacts, the dose from MDCT on chests is actually higher than single-slice CT.
90
Which two major conditions is D dimer used to asses?
PE (pulmonary embolism) and DVT (deep vein thrombosis) - basically stuff to do with blood clots.
91
Are the following three contrast agents ever used in imaging of the chest? diatriozoate meglumine, barium sulphate, iopamidol
yes! all three are.
92
What is the term used to describe a portion of a herniated intervertebral disc that has migrated from its normal position?
sequestered disc
93
what type of isolation is used for patients at risk for infection due to immunosuppression?
"strict" isolation
94
The normal range of cerebral blood volume (CBV) contained within 100g of brain tissue is
4-5 ml/100g
95
In patients who are left dominant, the posterior descending artery branches from the _____.
left circumflex artery
96
What is capable of causing an edge gradient artifact?
dense bone (occurs at areas of abrupt change in density)
97
The perimetrum, myometrium, and endometrium are all parts of which structure?
uterus
98
In addition to anatomic location of tumor activity, what other role does CT play in PET-CT studies?
attenuation correction of emitted photons
99
The approximate radiation dose measured during a scan of a 100-mm pencil ionization chamber is termed the ____.
CTDI
100
What is the maximum allowable blood glucose measurement for patients scheduled to undergo PET-CT examination?
150 mg/dl
101
When you measure the standard deviation in a water phantom, what negative thing are you really trying to measure?
Noise.
102
What is the only effective method of reducing streak artifact due to metal?
removing the object from the scan field.
103
Areas of a CT image containing abrupt changes in tissue density are electronically represented by what kind of spatial frequencies?
high spatial frequencies
104
The articulation between the distal tibia and fibula is called the _____.
syndesmosis
105
By using prospective ECG gating for cardiac CT over retrospective ECG gating you can _____ the patient radiation dose.
reduce
106
drainage-secretion precautions, enteric precautions, acid-fast bacillus, repiratory, contact, and strict, are all categories of _____ technique
isolations techniques
107
Decreasing mAs, increasing pitch, and decreasing KVp all do what to pt dose?
they all will decrease patient dose
108
What will increasing the pitch do to partial volume averaging?
It will increase the partial volume averaging effect
109
What is the unit of absorbed dose?
grays (Gy)
110
What is the normal respiration rate for an adult?
12-20 breaths per minute
111
140,000 - 440,000/mL of blood is the normal _____ count for an adult.
platelet count
112
The iliac artery bifurcates into the internal and external iliac arteries at about the level of what?
L5-S1
113
What negative oral contrast agent offers the BEST visualization of the enhancing GI wall on post-IV contrast CT exam?
water
114
A _____ spatial frquency algorithm will give the greatest soft tissue detail
Low Spacial Frequency
115
Two pixels have a difference of 1 HU. What percentage of difference does this represent?
0.1%
116
Why would you not use a small scan FOV in the hip?
it would cause an out-of-field artifact
117
What can assist in visualizing the vagina during a CT study of the pelvis?
Tampon insertion
118
What is a normal systolic blood pressure in adults?
95-140
119
simultaneous reconstruction, ray-by-ray correction, point-by-point correction - are all types of what kind of CT reconstruction?
iterative method
120
Which two generations of scanners used a translate-rotate mode of CT data acquisition?
1st and 2nd gen
121
3 mg/kg body weight of IV contrast should not be exceeded in what patient group?
children
122
A ___ spacial frequency algorithm is best at showing bony detail.
high
123
What percentage of iodine do water-soluble oral contrast agents (gastrografin) contain when the patient drinks it?
2%-5%
124
Are nausea and a warm, flush feeling examples of mild adverse reactions to IV contrast?
yes
125
What portion of the nephron is responsible for filtration of unwanted materials from the blood plasma?
glomerulus
126
What two terms are used to describe a CT scanner's ability to differentiate objects with similar linear attention coefficients?
contrast resolution and sensitivity
127
CT images of the abdomen should be acquired with the patient a. at full inspiration or b. with the patient at full expiration?
b. full expiration. because this is the most reproducible point of the respiratory cycle.
128
What is formula to calculate the smallest object that a CT scanner can resolve give the limiting resolution in lp/cm
reciprical value of lp/cm x 10 to first number. divide out and split in half. eg. 15 lp/cm = 1/15 Lp/cm = 10/15 Lp/mm = .6 split in half =.3
129
A CT scanner with a limiting resolution of 15 lp/cm can resolve an object as small as ____.
0.3 mm
130
What is the name of the photons that the detector of a PET system is sensitive to?
annihilation photons
131
During CT colonography examinations, tagged fecal matter appears _____ on the image
white
132
CBF = CBV/MTT is the formula illustrating what principle?
the central volume principle of cerebral perfusion
133
Is it ionic or nonionic contrast that dissociate into charged particles when placed into solution?
ionic
134
What is the normal BUN range?
5-20 mg/dl
135
What two factors affect the longitudinal spacial resolution?
detector pitch and interpolation algorithm
136
What vertebrae are the kidneys located between?
T12 and L3
137
An Agatston score of 5 on an MDCT cardiac examination for coronary artery calcification is rated as:
minimal
138
Is using tape an acceptable method of immobilization?
No, it could damage skin
139
CT images that have been reconstructed from a portion of the data acquisition process in the hopes of reducing patient motion artifacts are called _____.
segmented images
140
Do you need IV contrast to evaluate for a renal cyst? (think of our protocol at CCHS)
Yes, you need to determine if it enhances
141
What is the normal percentage of barium sulfate in the suspensions used in CT?
only 1%-3%
142
The multiple-scan average dose (MSAD) is used to quantify the radiation dose received by the patient from a sereis of CT scans. True or false?
True!
143
What is the term used to describe the ability of an object to attenuate the x-ray beam?
linear attenuation coefficient (and only later to calculate the HU)
144
Which layer of the uterine wall brightly enhances after IV contrast administration?
myometrium
145
When scanning a smaller body part, like a shoulder, would you use a large or small SCAN field of view?
you would still use a large scan FOV to avoid out-of-field artifact and then reconstruct with a smaller display FOV.
146
The majority of pancreatic tumors occur in what part of the pancreas?
The head
147
Is transdermal a parenteral route of medication administration?
No.
148
The corticomedullary phase is a _____ arterial phase (early or late).
late arterial phase at 30-40 seconds
149
What is the best contrast phase to look at the pancreas?
arterial phase
150
What phase of contrast hides hepatic lesions?
equilibrium phase
151
Prothrombin time (PT) and partial throboplastin time (PTT) are both used to measure what?
blood coagulation ability
152
20-30 breaths per minute is the normal range of respiration what what age group of patient patient?
a child
153
What imaging plane do we not normally care about with IACs?
Sagittal (we usually do axial and coronal)
154
What is the term for stones within the gallbladder?
cholelithiasis
