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CT boards > Notes from Mosby's Exam Review > Flashcards

Notes from Mosby's Exam Review Flashcards

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 }

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2
Q

The phantom measurement of the uniformity* of a CT system is performed primarily to assess the negative effects of:

A

Beam hardening

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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

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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

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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)

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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

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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)

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8
Q

What kind of scatter accounts for the primary interaction between x-ray photons and tissue during computed tomography?

A

compton effect

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9
Q

At what level of the spine does the abdominal aorta split into the right and left iliac arteries?

A

L4

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10
Q

What is happening in the heart during ventricular systole?

A

contraction of the left and right ventricles

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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

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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

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13
Q

In what phase of contrast will you see well-opacified ureters?

A

excretory

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14
Q

What is the approximate CT density (in HU) of the density of the unenhanced spleen?

A

between +40 and +60 HU

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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

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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)

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17
Q

What is the word for the spread of infection through a contaminated object?

A

fomite

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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

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19
Q

What is the unit of effective dose?

A

sieverts (Sv)

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20
Q

A voxel whose attenuation coefficient is less than that of water is assigned a pixel value with a _____ CT number

A

negative

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21
Q

What is used to treat a severe vagal reaction to iodinated contrast that includes bradycardia?

A

atropine

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22
Q

How thin do we scan high-res chests?

A

1 mm

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23
Q

In patients who are right dominant, the posterior descending artery branches from this coronary atery?

A

The right coronary artery

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24
Q

What type of reconstruction was used in the first prototype CT scanner?

A

iterative technique

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25
Q

Are both the kidneys and pancreas considered to be restroperitoneal?

A

yes

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26
Q

Does IV contrast improve the differentiation of subtle hemorrhage in the brain?

A

No. Contrast is initially contraindicated because the enhancement may actually mask subtle signs of hemorrhage

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27
Q

How does single-segment reconstruction change the temporal resolution

A

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

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28
Q

What is the optimum contrast phase for kidney lesions and when does it occur.

A

The nephrographic phase and it occurs between 70 and 90 seconds after the start of injection

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29
Q

What is the definition of pitch?

A

It is the relation of table speed to slice thickness

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30
Q

What is the formula to calculate pitch?

A

Pitch = travel distance of table per 360 degree rotation divided by the total xray beam collimation width. pitch = TD/TCW

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31
Q

The approximate inherent filtration of the tube housing, cooling oil, and so on amount to how thick of aluminum equivalent filtration?

A

3.0 mm

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32
Q

That is the excretion half-time of intravenous iodinated contrast media in a patient with normal renal function?

A

1 to 2 hours

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33
Q

What does the symbol “x” stand for in the lambert-beer law?

A

the absorber thickness

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34
Q

What is the term for CT images being reconstructed for only a portion of the raw data to reduce motion artifact?

A

subtraction images

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35
Q

What kind of tissue are ‘low spacial frequency’ algorithms best at demonstrating?

A

soft tissue detail (they filter out high spacial frequency information such as bone)

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36
Q

What scanning acquisition mode is used to scan prospectively ECG-gated cardiac CTA studies? (axial “step-and-shoot” or spiral)

A

axial “step-and-shoot”

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37
Q

What DFOV is commonly used to reconstruct images of the spine?

A

120 - 150 mm or 12 - 15 cm

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38
Q

A dermoid tumor of the ovary may also be referred to as ____

A

cystic teratoma

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39
Q

What is the single worst element working against a CT scanner’s contrast resolution?

A

noise

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40
Q

Name the two technological advances that enabled spiral/helical CT scanning?

A

slip-ring technology and high-efficiency x-ray tubes

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41
Q

Name two common areas of calcification in the brain.

A

choroid plexus and pineal gland

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42
Q

When performing both a CT abdomen and conventional GI studies, which should be done first and why?

A

The CT should be done first because the heavier barium used in GI studies causes streak artifact on CT.

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43
Q

How high an osmolality is high-osmolar contrast material?

A

1000-2400 mOsm/kg water

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44
Q

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

A

Radon

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45
Q

The condition whereby a portion of the small intestine collapses or telescopes into itself is termed:

A

intussusception

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46
Q

During a CT scan, each sample of ray sum measurements made by the data acquisition system (DAS) is called _____

A

view

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47
Q

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

A

3 cm

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48
Q

What three things are going on when there is ‘complete cardiac diastole’?

A

relaxation of the left and right ventricles, relaxation of the left and right atria, the T wave of the electrocardiogram (ECG)

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49
Q

What is the typical HU range for modern CT scanners?

A

-1024 to +3071

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50
Q

How much mL/100g cerebral blood volume (CBV) indicates a brain parenchyma infarct core?

A

2.5 mL/100g

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51
Q

How is a vasovagal reaction linked to blood pressue?

A

The term vasovagal pertains to systemic hypertension (often leading to cerebral ischemia)

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52
Q

What does the modulation transfer function (MTF) of a CT scanner measure?

A

It’s ability to faithfully reproduce the anatomy that is being imaged

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53
Q

What is the range of values for modulation transfer function (MTF) that describe how well the anatomy that is being imaged is reproduced?

A

0 to 1. 0 is said to have no useful informatioin and 1 is said to be perfect. Most scanners are somewhere in between.

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54
Q

What HU range is a solitary pulmonary nodule though to be benign?

A

165-200 HU

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55
Q

Between spondylolisthesis and retrolishesis, which is a forward slipping and which is a backwards slipping?

A

spondylotisthesis is a forward slipping and retrolisthesis is a backwards slipping

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56
Q

What percentage of it’s blood supply does the liver receive from the hepatic artery vs the portal vein?

A

25% from the hepatic artery and 75% from the portal vein

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57
Q

What HU unit is associated with calcium (such as in the coronary artery)?

A

+130

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58
Q

What is a standard section width (aka slice thickness) and interval (aka slice gap or incriment) used for an abdomen and pelvis scan

A

3.0/3.0 mm- 5.0/5.0 mm

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59
Q

How many shades of gray is the human eye capable of differentiating?

A

60-80

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60
Q

Each 1% difference in contrast between adjacent objects amounts to a difference in pixel value of how much (in HU)

A

10 HU

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61
Q

What is the term for too much nitrogenous material in the blood?

A

azotemia or uremia

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62
Q

Neoplasms in what body part is most commonly treated with CT-guided radio frequency ablation (RFA)

A

liver

63
Q

What stage of an ECG will the heart demonstrate the least motion?

A

T wave

64
Q

What is quantitative computed tomography (QCT) used to measure?

A

the mineral content of bone. You can calculate the BMD values (bone mineral density)

65
Q

What is the average volume of contrast for a CT myelogram

A

12-14 mL

66
Q

How long after contrast should a breastfeeding mother “pump-and-dump”

A

12-24 hours

67
Q

What is the purpose of doing the expiration part of a high-res chest?

A

to look for air trapping from COPD

68
Q

A patient with an elevated level of D dimer in the bloodstream may be at increased risk for which serious condition?

A

pulmonary embolism (PE)

69
Q

CT scanning of the liver for tumor evaluation should not be performed during which phase?

A

Equilibrium phase because it can hide hepatic lesions.

70
Q

The acronym PTT is used for which laboratory test?

A

Partial Thromboplastin Time - it indicates the coagulation time of a patients blood

71
Q

The portion of the male reproductive system responsible for the storage of the majority of the mature sperm is:

A

vas deferens

72
Q

What ligament suspends the duodenum from the diaphragm?

A

ligament of treitz

73
Q

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

a wide window width, such as 4000, should be used

74
Q

When trying to display images with many similar densities, (like abdomen) should you choose a wide or narrow window width.

A

a narrow window width, such as 400 will better display an image with many similar densities.

75
Q

What kind of detector array contains mid line narrow elements flanked by wider detectors?

A

a hybrid array

76
Q

The technique that allows the user to select the range of pixel values used in a 3D CT reformation is termed:

A

thresholding. It is what allows your render to just include bone, for instance, and not the unwanted soft tissues

77
Q

The normal range for the International Normalized Ratio (INR) for prothrombin time (PT) results is:

A

0.8 - 1.2

78
Q

Which phase of contrast provides the best gastric and intestinal wall enhancement? (think ABD/PEL W)

A

portal venous phase

79
Q

Is transdermal a route of paraenteral medication administration?

A

No it is not. But subcutaneous and intradermal are. Paraenteral = infusion or injection

80
Q

For MDCT, identified areas of calcium must demonstrate relative attenuation values greater than:

A

+130

81
Q

The calculation of the average cumulative dose to each section within an acquisition of multiple sections is termed the:

A

MSAD or Multiple Scan Average Dose

82
Q

Which window width and level would be good to look at CT colonography images?

A

Width = 1600, Level=-400 (a “lung-type” setting)

83
Q

What relationship is there between the slice width and gap when wanting an overlapping slice?

A

The section interval (slice gap) must be less than the section width (slice thickness)

84
Q

Axial CT sections of the lumbar spine for intervertebral disc evaluation is best done in which plane (think MR)

A

parallel to the plane of the intervertebral disc spaces

85
Q

The quantity of radiation dose received by the patient from a series of CT scans is referred to as:

A

MSAD (Multiple-Scan Average Dose)

86
Q

What are some of the signs and symptoms of hypovolemic shock?

A

pallor, hypotension, tachycardia, oliguria (decreased urine production)

87
Q

Do gallstones appear hyperdense on abdominal CT scans?

A

Yes!

88
Q

What does intrathecal mean?

A

occurring within or administered into the spinal theca

89
Q

Is reduction in patient dose an improvment of chest CTs with MDCT (multidetector CT)?

A

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
Q

Which two major conditions is D dimer used to asses?

A

PE (pulmonary embolism) and DVT (deep vein thrombosis) - basically stuff to do with blood clots.

91
Q

Are the following three contrast agents ever used in imaging of the chest? diatriozoate meglumine, barium sulphate, iopamidol

A

yes! all three are.

92
Q

What is the term used to describe a portion of a herniated intervertebral disc that has migrated from its normal position?

A

sequestered disc

93
Q

what type of isolation is used for patients at risk for infection due to immunosuppression?

A

“strict” isolation

94
Q

The normal range of cerebral blood volume (CBV) contained within 100g of brain tissue is

A

4-5 ml/100g

95
Q

In patients who are left dominant, the posterior descending artery branches from the _____.

A

left circumflex artery

96
Q

What is capable of causing an edge gradient artifact?

A

dense bone (occurs at areas of abrupt change in density)

97
Q

The perimetrum, myometrium, and endometrium are all parts of which structure?

A

uterus

98
Q

In addition to anatomic location of tumor activity, what other role does CT play in PET-CT studies?

A

attenuation correction of emitted photons

99
Q

The approximate radiation dose measured during a scan of a 100-mm pencil ionization chamber is termed the ____.

A

CTDI

100
Q

What is the maximum allowable blood glucose measurement for patients scheduled to undergo PET-CT examination?

A

150 mg/dl

101
Q

When you measure the standard deviation in a water phantom, what negative thing are you really trying to measure?

A

Noise.

102
Q

What is the only effective method of reducing streak artifact due to metal?

A

removing the object from the scan field.

103
Q

Areas of a CT image containing abrupt changes in tissue density are electronically represented by what kind of spatial frequencies?

A

high spatial frequencies

104
Q

The articulation between the distal tibia and fibula is called the _____.

A

syndesmosis

105
Q

By using prospective ECG gating for cardiac CT over retrospective ECG gating you can _____ the patient radiation dose.

A

reduce

106
Q

drainage-secretion precautions, enteric precautions, acid-fast bacillus, repiratory, contact, and strict, are all categories of _____ technique

A

isolations techniques

107
Q

Decreasing mAs, increasing pitch, and decreasing KVp all do what to pt dose?

A

they all will decrease patient dose

108
Q

What will increasing the pitch do to partial volume averaging?

A

It will increase the partial volume averaging effect

109
Q

What is the unit of absorbed dose?

A

grays (Gy)

110
Q

What is the normal respiration rate for an adult?

A

12-20 breaths per minute

111
Q

140,000 - 440,000/mL of blood is the normal _____ count for an adult.

A

platelet count

112
Q

The iliac artery bifurcates into the internal and external iliac arteries at about the level of what?

A

L5-S1

113
Q

What negative oral contrast agent offers the BEST visualization of the enhancing GI wall on post-IV contrast CT exam?

A

water

114
Q

A _____ spatial frquency algorithm will give the greatest soft tissue detail

A

Low Spacial Frequency

115
Q

Two pixels have a difference of 1 HU. What percentage of difference does this represent?

A

0.1%

116
Q

Why would you not use a small scan FOV in the hip?

A

it would cause an out-of-field artifact

117
Q

What can assist in visualizing the vagina during a CT study of the pelvis?

A

Tampon insertion

118
Q

What is a normal systolic blood pressure in adults?

A

95-140

119
Q

simultaneous reconstruction, ray-by-ray correction, point-by-point correction - are all types of what kind of CT reconstruction?

A

iterative method

120
Q

Which two generations of scanners used a translate-rotate mode of CT data acquisition?

A

1st and 2nd gen

121
Q

3 mg/kg body weight of IV contrast should not be exceeded in what patient group?

A

children

122
Q

A ___ spacial frequency algorithm is best at showing bony detail.

A

high

123
Q

What percentage of iodine do water-soluble oral contrast agents (gastrografin) contain when the patient drinks it?

A

2%-5%

124
Q

Are nausea and a warm, flush feeling examples of mild adverse reactions to IV contrast?

A

yes

125
Q

What portion of the nephron is responsible for filtration of unwanted materials from the blood plasma?

A

glomerulus

126
Q

What two terms are used to describe a CT scanner’s ability to differentiate objects with similar linear attention coefficients?

A

contrast resolution and sensitivity

127
Q

CT images of the abdomen should be acquired with the patient a. at full inspiration or b. with the patient at full expiration?

A

b. full expiration. because this is the most reproducible point of the respiratory cycle.

128
Q

What is formula to calculate the smallest object that a CT scanner can resolve give the limiting resolution in lp/cm

A

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
Q

A CT scanner with a limiting resolution of 15 lp/cm can resolve an object as small as ____.

A

0.3 mm

130
Q

What is the name of the photons that the detector of a PET system is sensitive to?

A

annihilation photons

131
Q

During CT colonography examinations, tagged fecal matter appears _____ on the image

A

white

132
Q

CBF = CBV/MTT is the formula illustrating what principle?

A

the central volume principle of cerebral perfusion

133
Q

Is it ionic or nonionic contrast that dissociate into charged particles when placed into solution?

A

ionic

134
Q

What is the normal BUN range?

A

5-20 mg/dl

135
Q

What two factors affect the longitudinal spacial resolution?

A

detector pitch and interpolation algorithm

136
Q

What vertebrae are the kidneys located between?

A

T12 and L3

137
Q

An Agatston score of 5 on an MDCT cardiac examination for coronary artery calcification is rated as:

A

minimal

138
Q

Is using tape an acceptable method of immobilization?

A

No, it could damage skin

139
Q

CT images that have been reconstructed from a portion of the data acquisition process in the hopes of reducing patient motion artifacts are called _____.

A

segmented images

140
Q

Do you need IV contrast to evaluate for a renal cyst? (think of our protocol at CCHS)

A

Yes, you need to determine if it enhances

141
Q

What is the normal percentage of barium sulfate in the suspensions used in CT?

A

only 1%-3%

142
Q

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?

A

True!

143
Q

What is the term used to describe the ability of an object to attenuate the x-ray beam?

A

linear attenuation coefficient (and only later to calculate the HU)

144
Q

Which layer of the uterine wall brightly enhances after IV contrast administration?

A

myometrium

145
Q

When scanning a smaller body part, like a shoulder, would you use a large or small SCAN field of view?

A

you would still use a large scan FOV to avoid out-of-field artifact and then reconstruct with a smaller display FOV.

146
Q

The majority of pancreatic tumors occur in what part of the pancreas?

A

The head

147
Q

Is transdermal a parenteral route of medication administration?

A

No.

148
Q

The corticomedullary phase is a _____ arterial phase (early or late).

A

late arterial phase at 30-40 seconds

149
Q

What is the best contrast phase to look at the pancreas?

A

arterial phase

150
Q

What phase of contrast hides hepatic lesions?

A

equilibrium phase

151
Q

Prothrombin time (PT) and partial throboplastin time (PTT) are both used to measure what?

A

blood coagulation ability

152
Q

20-30 breaths per minute is the normal range of respiration what what age group of patient patient?

A

a child

153
Q

What imaging plane do we not normally care about with IACs?

A

Sagittal (we usually do axial and coronal)

154
Q

What is the term for stones within the gallbladder?

A

cholelithiasis

CT boards (20 decks)

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