Mosby’s Exam Review for Computed Tomography - E-Book: CT prep Flashcards


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Notes from Mosby 2nd Edition
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1

What is a normal pulse rate for adults?

60-100 BPM

2

What is a normal respiration rate for adults?

12-20 BPM

3

Blood Urea Nitrogen (BUN) range:

7-25 mg/dl Milligrams per deciliter

4

creatinine range:

0.5-1.5 mg/dl

5

GFR range for men & women

70 +/- 14 for men

60 +/- 10 for women

6

Prothrombin time?

12-15 seconds

7

Partial thromboplastin time?

25-35 seconds

8

platelet count?

140,000-440,000

9

BUN/Cr ratio:

6:1-22:1

10

Is BUN by itself an accurate detector of renal insufficiency?

no

11

Since Creatinine levels vary in different populations, __________ __________ are thought to be a more accurate indicator of renal compromise.

recent changes

12

_______________ is an approximation of creatinine clearance or the rate at which creatinine is filtered from the blood.

GFR

13

Prothrombin time is a measure of ____________ _______________.

blood coagulation

14

examples of positive contrast media

iodine and barium

positive contrast is radiopaque

15

___________ describes the contrast agent's tendency to cause fluid from outside the blood vessel to move into the blood stream.

osmolality

16

ionic contrast media

-salts consisting of sodium/meglumine

-each molecule consists of 3 iodine atoms

-when injected, each molecule dissociates into two charged particles, or ions.

-high osmolar contrast media

conray, hypaque

17

non-ionic contrast media

-non-salt chemical compounds with three atoms of iodine per molecule

-do not dissociate

-low osmolar contrast media

-omnipaque, isovue

18

non-ionic low osmolar contrast agents are ____ likely to cause adverse reactions.

less

19

routine transit time for for barium sulfate through the GI tract is ____ to ____ minutes.

30-90

20

do not use barium if:

1. patient has a suspected perforated bowel

2. patient will soon undergo surgery

21

air, gases, and water can be used a _________ contrast agents.

negative

22

CT enterography or enteroclysis use __________ contrast agents.

neutral, example is volumen

23

The serum iodine concentration is a measure of the amount of ______________ within the ___________.

iodine within the blood stream

24

The range of serum iodine concentration for adequate opacification is ___ to

___ mg/mL.

2-8

25

How much contrast would adequately opacify the rectum when given rectally?

150-300 ml

26

parenteral:

entreral:

intrathecal:

intra-articular:

IV

Oral/rectal

injected directly into space around spinal cord

injected directly into a joint space

27

4 H's of iodinated contrast administration

  1. History (allergies)
  2. hydration (before, during, & after instructions expecially for renally compromised pt's)
  3. have (equipment and expertise ready)
  4. heads up (constant assessment of pt for adverse reaction)
28

physiologic/pathologic conditions that may increase adverse reaction to contrast media (9):

  1. asthma
  2. allergies
  3. multiple myeloma
  4. diabetes mellitus
  5. pheochromocytoma
  6. sickle cell
  7. hyperthyroidism
  8. cardiac disease
  9. renal failure
29

mild reactions (7):

  1. nausea/vomiting
  2. mild uticaria (hives)
  3. warmth/ flushed sensation
  4. altered taste
  5. sweats/chills
  6. nasal stuffiness/sneezing
  7. anxiety
30

moderate reactions (4):

  1. mild bronchospasm
  2. moderate to sever uticaria
  3. vasovagal response (drop in blood pressure)
  4. tachycardia from hypotension
31

severe reactions (8):

  1. profound hypotension
  2. laryngeal edema
  3. severe bronchospasm
  4. pulmonary edema
  5. cardiac arrhythmia
  6. seizure
  7. cardiopulmonary arrest
  8. death
32

ABCD management for adverse reactions

A (4)

  1. Asessment: assess severity
  2. airway: maintain open airway, oxygen?
  3. assistance: immediately call for it
  4. access: obtain/ secure IV access
33

ABCD management for adverse reactions

B (2)

  1. Breathing: begin CPR if necessary
  2. beware: of atypical responses
34

ABCD management for adverse reactions

C (4)

  1. Common denominator: access cardiac output in relation to venous return
  2. categorize type of reaction and patient status
  3. call CPR team, perform if necessary
  4. Circulatory assistance, administer fluid
35

ABCD management for adverse reactions

D (4)

  1. Do assess and monitor patient
  2. Do use correct dose and administration route for drugs
  3. don't delay
  4. don't use incorrect drugs or dose
36

______________-______________ ___________ is a potentially serious delayed effect of contrast administration.

Contrast-induced nephrotoxicity

37

Patients receiving oral biguide (metformin) are at increased risk for __________ ____________.

lactic acidosis

38

Radiation dose can be divided into two categories, __________ & _____________.

1. system configuration

2. user settings

39

As the distance from the x-ray tube to the detector decreases, dose _________.

increases

40

filtration within the tube ranges from _____ to ________.

6-9 mm AL

41

_________ ______________ ___________ describes the ability of the detector to capture transmitted x-ray quanta and produce the appropriate response.

inherent absorption efficiency

42

________ ___________ describes the spatial arrangement of detector elements, including the amount of interspace material required between adjacent elements.

geometric efficiency

43

____________: when the beam is expanded to avoid exposing detectors to undesirable penumbra.

overbeaming.

data is only acquired from a portion of the exposed detector array which means patients get a radiation dose that does not contribute to the image.

44

______________ occurs when radiation dose is applied before and after the acquisition volume to ensure sufficient data collection for the interpolation algorithms.

overranging

45

noise reduction alogorithms, or ____________ ___________, are employed during the reconstruction process to reduce displayed noise.

adaptive filters

46

4 reasons why MSCT has a higher radiation dose than SSCT.

  1. decrease in focal spot-detector distance.
  2. use of cone beam instead of fan beam
  3. increases the number of phases of acquisition enabled by decreased scan times
  4. use of thinner section widths
47

_________ ____________ is the process of adjusting parameters such as mA, kVp, slice thickness, and pitch for the purpose of reducing patient radiation dose while maintaining adequate image quality.

protocol optimization

48

mA, scan time, and radiation dose have a ____________ proportional relationship.

directly

49

_________ _______: the section of the patient exposed to radation.

dose profile.

measured at the isocenter of the gantry

50

increasing the pitch will increase or decrease image noise?

increase

51

Automatic Tube current modulation (ATCM) can occur as _________ and _________.

Angular and longitudinal

52

What kind of ATCM (CT's AEC) is described below?

mA setting is adjusted according to the difference inthickness of the part as the tube rotates.

For example, during imaging of the oval torso, mA can be reduced as the beam passes from anterior to posterior because less attenuation occurs on the AP path vs. the lateral path through the patient.

Angular tube current modulation (x & y axis)

53

What kind of ATCM (CT's AEC) is described below?

Allows for the adjustment of the mA setting as the scan proceeds along the z-axis of the patient. differences in attenuation as the body thickness and tissue density change from the chest to the abdomen, and so on, are met with appropriate adjustments in mA, resulting in an overall reduction in radiation dose.

Longitudinal (z-axis) Tube Current Modulation

54

radiation protection should encompass three general principles:

  1. clinical indication
  2. shielding
  3. protocol optimization
55

__________ __________ ____________ may be used to describe the reconstructed CT section.

Slice sensitivity profile

The dose profile, or section of tissue exposed to ionizing radiation, is greater in width than the SSP.

56

_________ is the term used to describe the ability of x-rays to ionize a volume of air.

exposure.

measured in Roentgens

57

__________ __________ describes the amount of x-ray energy absorbed in a unit of mass.

Absorbed dose

measured in Gy

58

________ may also be used to describe absorbed dose. _________ ________ describes the amount of radiation absorbed by a quantity of air.

Kerma

Air Kerma

59

_________ ___________ accounts for the type of tissue that the radiation is deposited in.

Effective Dose

measured in Sv

Different tissues are assigned different weighting factors based on radiosensitivity.

Effective dose approximates the relative risk of exposure to ionizing radiation.

60

CT Dose Index (CTDI) is an approximate measure of the dose received in _________________________.

A single section or slice.

61

CTDI (Dose index) is measured using a __________ and ___________ dosimeter.

phantom & thermoluminescent

62

CTDIw is an internationally accepted __________ __________ for step and shoot axial CT scanning. (not helical)

Dose index

It is calculated by summing 2/3 of the exposure recorded at the periphery of the field with 1/3 of the centrally recorded dose.

63

CTDIvol is used to approximate radiation dose for each _________ during a helical scan.

section or slice

64

CTDIvol= ?

_____________

?

CTDIw

_________________

pitch

as pitch increases, the dose per section or CTDIvol decreases

65

CTDIw uses what axis?

CTDIvol uses what axis?

x & y

x, y & z

66

Locate the x, y and z axis.

card image
67

_______________ _________________ or _______________ is the synchronization of the data acquisition process with the cardiac cycle. Data are only acquired when the heart is at rest (diastole).

prospective gating or triggering

68

____________ ___________ involves scanning throughout the entire cardiac cycle. Only data from specific user-determined portions of the ECG waveform are reconstructed into images.

Retrospective gating

69

The _____________ scoring system quantifies the volume and density of calcium within the coronary arteries.

Agatston

70

CAC (coronary artery calcium) scores can be graded as follows:

a. ___-____ minimal

b. ___-____ mild

c. ___-____ moderate

d. ___-____ extensive

a. 1-10

b.11-100

c. 101-400

d. >400

71

Branches of the RCA (Right Coronary Artery) (6):

  1. conus artery
  2. sinus node artery
  3. right atrial branches
  4. right ventricular branches
  5. posterior descending artery
  6. posterior left ventricular branches
72

Branches of the LCA (Left Coronary Artery (2):

  1. Left Anterior descending (LAD) artery
  2. Left Circumflex artery (LCX)
73

________________ ____________ of an MDCT system describes its ability to freeze the motion of the heart as well as arterial motion velocity within the coronary vasculature.

Temporal resolution

74

The _______ _____________ __________ is the technical parameter controlling a CT systems temporal resolution.

Gantry rotation time

Directly proportional relationship

Ex) gantry rotation time 400 msec results in temporal resolution of 400 msec

75

__________ _______________ of a CT system describes its ability to image small objects.

Spatial resolution

76

________________ _______________ is the portion of the cardiac cycle in which coronary artery motion and cardiac motion are slowest.

ventricular diastole

77

The __-__ interval on ECG waveform corresponds to the entire cardiac cycle.

R-R

78

_____________ is the portion of the R-R interval (cardiac cycle) when the heart is at rest.

diastole

79

____________ is the portion of the R-R interval when the heart is in motion.

systole

80

The least heart motion occurs from approximately __% - __% of the R-R interval.

55%-75% (typically corresponds to mid-diastole)

81

The main benefit of prospective ECG gating is the potential for _______________________________.

up to a 70% reduction in patient radiation dose

82

_________ ___________ is when an inner layer of the aorta tears and a false lumen is created.

aortic dissection

83

IV should be placed in what location in which arm to avoid streaking artifact?

Right AC

84

CT ______________ is 3D CT visualization of the tracheobronchial tree.

bronchography

85

What organs are in the peritoneal cavity? (7)

  1. stomach
  2. small bowel (small portion of duodenum, all of jejunum and ileum)
  3. transverse colon
  4. liver
  5. gallbladder
  6. spleen
  7. ovaries
86

__________: a thickened portion of the peritoneum that attaches portions of the intestines to the abdominal wall

mesentery

87

_____________: a mesentery that is divided into lesser and greater components, each responsible for attaching portions of the stomach and intestines.

omentum

88

____________________: the space located between the peritoneum and the posterior abdominal wall.

retroperitoneum

89

Retroperitoneal organs (7)

  1. rest of duodenum
  2. pancreas
  3. adrenal glands
  4. KUB
  5. great vessels (aorta and IVC)
  6. prostate
  7. uterus
90

Oral contrast for distal intestines?

Amount and time

450 ml given 90-120 minutes before exam

91

oral contrast for proximal intestines?

amount and time

300-450 mL given 30 minutes before exam

92

oral contrast for stomach and duodenum?

Amount and time

150-250 mL given immediately before scanning

93

Normal unenhanced hepatic parenchyma is homogenous in appearance, with CT densities that range from ___ HU to ___ HU.

45-65

94

Hypodense lesions appear ____ dense.

less (darker on image like air)

95

Hyperdense lesions appear ______ dense.

more (Brighter on image like bone)

96

If a tumor is lower in density than the surrounding organ parenchyma is it ________.

hypovascular

97

If a tumor is higher in density than the surrounding organ parenchyma it is ______________.

card image

hypervascular

98

The most common malignant hepatic neoplasms are ________ and appear _____________.

card image

metastases appear hypodense

99

Tumors with densities equal to those of surrounding tissue are said to be __________.

card image

Isodense

100

Benign neoplasms of liver: (3)

  1. hemangioma
  2. focal nodular hyperplasia
  3. hepatic cysts
101

What benign neoplasm of the liver is described?

  • vascular
  • peripheral globular enhancement during initial post contrast image
  • progressive fill in of enhancement occurs over time
card image

Hemangioma

102

What benign neoplasm of the liver is described?

  • vascular lesion often on the surface of liver
  • intense homogenous enhancement with contrast administration
  • central scar that remains hypodense
card image

focal nodular hyperplasia

103

What benign neoplasm of the liver is described?

  • thin-walled
  • round or oval masses
  • no enhancement with contrast
  • 0-20 HU
card image

hepatic cysts

104

Malignant neoplasms of liver: (2)

  1. hepatocellular carcinoma
  2. metastases
105

What malignant neoplasm of the liver is described?

  • hypodense on non-contrast scans
  • hypervascular on arterial phase images
card image

Hepatocelluar carcinoma

106

What malignant neoplasm of the liver is described?

  • varies greatly
  • may appear solitary or multiple
  • may appear hypodense or hyperdense
  • may appear necrotic or calcified, etc

metastases

commonly from colon, lung, breast, pancreas, and stomach

107

The liver has a dual blood supply with 75% coming from the _________________

and 25% coming from the ________________.

card image

portal vein & hepatic artery

108

What are the 3 phases of hepatic contrast enhancement?

  1. arterial
  2. portal (or hepatic) venous phase
  3. equilibrium
109
card image

Identify this structure:

Adrenal glands

110
card image

Identify this mass:

Simple cyst

  • smooth round walls
  • homogenous near-water CT density (<20 HU)
111
card image

Identify this mass:

hyperdense cyst

  • 25-90 HU
  • hyperdense because of infection of hemorrhage
112
card image

Identify this disease:

polycystic kidney disease

113

What type of renal cyst is described?

  • arises from the renal pelvis instead of the cortex
  • often appear as hydronephrosis
card image

parapelvic cyst

114

Minimal enhancement (15-20 HU) of a renal cyst following contrast administration due to volume averaging is called __________.

pseudoenhancement

115

_____________ is a benign mass of blood vessels, muscle and fat and has a HU of -10

card image

angiomylolipoma

angio-vessels myo- muscle lipoma-fat

116

Most common malignant neoplasm in the kidney?

Renal cell carcinoma

117

What malignant kidney neoplasm is described?

  • originates in the urothelium
  • arises in the bladder and sometimes ureters and renal pelvis
  • hypodense lesion on unenhanced images
  • significantly enhances after contrast administration

Transitional cell carcinoma

118

What are the most common metastases in the kidneys? (3)

  1. lung
  2. colon
  3. breast
119

What are the three phases of renal contrast enhancement?

  1. corticomedullary phase
  2. nephrographic phase
  3. excretory phase
120

What renal contrast enhancement phase is described below?

  • late arterial phase, 30-40 seconds after administration
  • optimal enhancement of renal cortex and veins
card image

corticomedullary

Phase B in image

121

What renal contrast enhancement phase is described below?

  • between 70-90 seconds after administration
  • cortex and medulla reach contrast equilibrium so lesions are more visible
card image

nephrographic phase

image shows renal cell carcinoma in the left kidney that is easily visible in the nephrographic phase

122

What renal contrast enhancement phase is described below?

  • begins 3 minutes after contrast administration
  • contrast is in renal calyces
  • opacified renal pelvis ureters and bladder
  • demonstrates filling defects and urothelium lesions
card image

excretory phase

123

______________ or ______________ is a multiphasic evaluation of the urinary tract.

CT urogram or CT IVP

124

What is the most common abnormality of the ureters?

card image

dual collecting system

125

The gastrointestinal tract consists of the: (4)

  1. esophagus
  2. stomach
  3. small intestine
  4. large intestine
126

____________: puncture in the wall of the GI tract.

Perforation

127

If a patient suffers from a perforation and bowel contents leak into the abdominal cavity, the patient may contract an infection known as _____________.

peritonitis

128

An abnormal connection between the intestine and an adjacent structure:

fistula

129

A collection of pus caused by and infection or inflammatory process within the GI tract:

abcess

130

______ ____________ is the most important identifying sign of GI pathology.

wall thickening

131

Typical amount of oral contrast agent used for general studies of the abdomen and pelvis is between ____mL and ___ mL

750-1500 mL

132

1 ounce = ___ mL

29.5

48 oz H2O = 1416 mL

+50 mL omnipaque

1466 mL oral contrast (How much contrast we use)

133

Between _____ mL and ____ mL of positive contrast are used for enemas.

150-250

134

__________ ____________ are dilated veins of the esophagus that result from portal hypertension.

esophageal varices

135

A protrusion of the gastroesophogeal junction through the diaphragm into the thorax is termed a __________ __________.

card image

Hiatal hernia

136

What connects the pyloric sphincter of the stomach to the small intestine?

duodenal bulb

137

The duodenum is suspended from the diaphragm by the _________ __ _____________.

card image

ligament of Treitz

138

What are the three types of external hernias?

  1. inguinal
  2. umbilical
  3. incisional
139

What kind of external hernia is described?

lower anterior abdominal wall in the region of the groin

inguinal

140

What kind of external hernia is described?

near the umbilicus, most common in pregnant women and obese patients

card image

umbilical

141

What kind of external hernia is described?

a complication of surgery

card image

incisional hernia

142

___________ ___________ ____________ is a serious and potentially fatal pathology characterized by loops of dilated proximal small bowel ending abruptly at an area of collapsed bowel.

Small bowel obstruction or SBO

143

_______________ is when a portion of the small intestine collapses or telescopes within itself.

card image

intussusception

144

___________ is an area of intestine that has lost normal contractile motion and could cause obstruction.

ileus

145

list the sections of the large intestine: (6)

  1. cecum
  2. ascending
  3. transverse
  4. descending
  5. sigmoid
  6. rectum
146

structure that protrudes from the cecum?

card image

appendix

147

____________ ______________ is an abnormal communication between bladder and bowel.

card image

enterovesical fistula

148

_____________ is an abnormal accumulation of fluid around a testicle.

hydrocele

149

What structure is positioned between the pubic symphysis and the rectum with the bladder above it?

card image

prostate

150

___________ _____________ ___________ is an increase in prostate volume.

benign prostate hyperplasia

151

What structure is located between the prostate and base of bladder in males?

card image

seminal vesicles

152

What structure is located between the bladder and rectum in females?

card image

uterus

153

The uterine wall have 3 layers called:

  1. perimetrium or outer
  2. myometrium or middle
  3. endometrium or inner
154

Which uterine layer is vascular and enhances brightly after contrast administration?

myometrium

155

____________ is used to describe an appendage of an organ.

adnexa

156

What makes us the uterine adnexa?

fallopian tubes and ovaries

157

What are three common benign masses of the uterus?

  1. leiomyoma, or fibroid uterus
  2. ovarian cysts
  3. cystic teratoma
158

what are three common malignant masses of the uterus?

  1. cervical cancer
  2. uterine cancer with endometrial carcinoma as the most prevalent gynecological malignancy
  3. ovarian cancer
159

At approximately what level does the aorta branch into right and left common iliac arties?

L4

160

What does this statement describe?

"An image of an object may be reconstructed on the basis of the attenuation that occurs as x-radiation is transmitted through it"

The fundamental principle of CT

161

The general process of CT imaging can be divided into these steps: (4)

  1. data acquisition
  2. data reconstruction
  3. multidimensional image display
  4. image archival and communication
162

What CT imaging process is described?

"the measurment of the attenuation that occurs along each path through the patient from x-ray tube to detector"

data aquisition

163

What CT imaging process is described?

"the computerized processing of the transmission measurments into the CT image"

data reconstruction

164

What CT imaging process is described?

"display of the reconstructed gray scale image in 2D and/or 3D format; a representation of the attenuation that occurred across the scanned volume of tissue"

multidimensional image display

165

What CT imaging process is described?

"display as well as storage, both short and long term, of images on computer worksations"

image archival and communications

166

What is the most basic scan mode?

scout

167

The angle of the tube and detectors in relationship to the patient position during scout acquisition is referred to as the __________.

azimuth

168

What generally composes a CT system? (4)

  1. computer
  2. display system
  3. patient table
  4. gantry
169

What does the gantry house? (6)

  1. generator
  2. x-ray tube
  3. assorted collimators
  4. data acquisition system (DAS)
  5. slip rings
  6. detectors
170

____________________ eliminates the need for cables by utilizing a system of contact brushes that supply electricity to power the system and enable the passage of transmission data to the computer system.

slip ring technology

171

Section width is determined by:

collimation (slice thickness)

172

_____________ focal spots improve geometric efficiency leading to greater spatial resolution.

smaller

173

_______________ ____________ __________ ________________: involves the electromagnetic steering of the electron beam emitted from the cathode. The beam of electrodes is directed toward two separate locations on the rotating anode resulting in two sources of radiation.

Flying focal spot technology

174

ways to dissipate heat: (4)

  1. oil cooling
  2. air cooling
  3. increased anode diameter
  4. conduction by tube rotation
175

_________ __________ ___________ ____________: adjust the mA throughout an acquisition to reduce patient radiation dose to a minimum according to a predetermined noise index.

automatic tube current modulation ATCM

176

What directly controls the quantity of radiation and is referred to as the photon fluence?

mAs

177

The rate at which the photon fluence passes through a unit area over unit time is _____ ______.

photon flux

178

The mAs value for a given acquisition is _________ proportional to patient radiation dose and ________ proportional to image noise.

directly, indirectly

179

___________ ______ describes the calculated mAs value per acquired slice.

effective mAs

180

What is the main controlling factor for effective mAs?

table speed

181

effective mAs formula?

mAs

Effective mAs=____________________

pitch

182

_________ ___________ controls the quality of the x-ray beam with regard to its overall penetrating capabilities.

peak kilovoltage

183

mAs range:

30-800

184

kVp range:

80-140

185

_______ __________ _______ ___________ use two separate x-ray tubes and detector arrays positioned 90 degrees from each other

dual source CT systems

186

What kind of filtration is the tube housing and cooling oil?

inherent

187

Inherent filtration amounts to approximately ____ mm of aluminum equivalent.

3.0

188

______ ______ filters help shape the beam to reduce patient radiation dose.

bow tie

189

Bow tie filters reduce beam intensity toward_____________.

the outer margins

190

What kind of generator is used?

high frequency

191

collimation can be divided into two components:

  1. beam collimation
  2. detector (section) collimation
192

The general purpose of ___________ collimation is to restrict the radiation exposure to the area of interest, reducing patient dose and improving image quality.

beam

193

located just outside the tube housing, the mechanical aperture responsible for beam restriction is termed the ____-_________ collimator.

pre-patient

194

What axis does pre-patient beam collimation effect?

Z

195

On what axis do the detectors extend?

x-y

196

____________________: a mechanical device controls the aperture dimension at the x-ray tube, directly limiting the beam to the desired section width. SSCT only

pre-patient collimation

197

The radiation transmitted through the patient is controlled by pre-detector collimators. _____________ (pre-detector) collimators are used to improve image quality by limiting scatter radiation before it reaches the detectors.

post-patient

198

At a maximum, the MSCT cone beam may be collimated to the dimension equal to?

the entire multi-row detector array.

199

How would the cone beam be calculated in a 64-slice system with 0.625-mm detectors? (equation)

64 X 0.625mm= 40mm

200

What controls the number and thickness of the images acquired in MSCT? (2)

  1. user-defined beam width
  2. detector configuration
201

What is the relationship between beam collimation (width), detector size (collimation), and the number of detectors?

(equation)

D (mm) d= detector collimation

d (mm)= __________________ D= beam collimation

N N= number of detector rows

202

A 64 slice system with 0.625mm detectors would have what beam collimation?

40mm

0.625= -----------------------

64

203

In MSCT, wider collimation result in ____________ anatomic coverage with each tube rotation.

greater

204

The ____________ ____________ (slice thickness) describes the amount of tissue in the longitudinal or Z axis that is represented by the 2D CT image.

section width

205

Section width in SSCT is determined by:

Section width in MSCT is determined by:

beam collimation

beam collimation & detector collimation

206

____________ ____________ describes the process of determining section width in the MSCT system.

detector collimation

207

____________ ____________ describes the spacing between two adjacent images.

Section interval

208

Section interval is measured as the distance between:

the center of one section and the center of the next adjacent section

209

____________ __________ are those acquired with equal section thickness and interval.

contiguous images

Example: 5mm sections reconstructed every 5mm will completely cover a given volume of tissue with no unmeasured tissue

210

_____________ ____________ are those acquired with an interval greater than the section width.

noncontiguous images

example: 1mm sections reconstructed every 10mm would not evaluate the intermittent 9mm of tissue.

211

____________ ____________are reconstructed with a section interval that is less than the section width.

overlapping images

1.0mm thick images reconstructed every 0.5 mm are said to possess a 50% overlap.

212

___________ describes the relationship between collimation and table movement during scanning.

pitch

213

The original definition of pitch for SSCT scanning is:

This is now referred to as detector pitch

(equation)

table feed per rotation

pitch= __________________________________

section width

214

A new adaptation of the pitch principle termed beam pitch is required for MSCT. What is the equation for beam pitch?

table feed per rotation

beam pitch=_______________________________

total collimation

215

specific to MSCT, ________________ equals the combined thickness of all of the sections that are simultaneously acquired with each gantry rotation.

total collimation

216

What is the equation for total collimation?

total collimation= number of sections X section width

217

A pitch setting of less than 1 _____________ the table speed for each gantry revolution. This ___________ image quality, patient radiation dose and acquired data.

reduces; increases

218

A __________ pitch moves the patient through the gantry faster, exposing tissue to the beam for shorter periods, and reduces patient dose.

higher

219

___________ reduction of intensity of a radiation beam as it passes through a substance.

attenuation

220

The desired qualities of a CT detector include: (3)

  1. high efficiency
  2. rapid signal decay
  3. high dynamic range
221

_______________ _____________of a detector is its ability to quickly measure x-rays and then recover before the next measurement.

response time

222

___________ ____________ refers primarily to the tendency of scintillation crystal detectors to continue to glow in response to x-rays once the exposure source has been terminated.

after glow

223

__________ ___________ refers to the detector being sensitive enough to measure a broad range of x-rays.

dynamic range

224

CT detectors can be made of: (2)

  1. gas ionization chambers
  2. scintillation crystals
225

______________________ converts x-ray energy directly into an electrical signal.

gas ionization chamber

226

_____________ convert x-ray energy first into light energy, which must then be converted into electrical signal.

solid state scintillation crystals.

227

What gas do ionization chambers use?

xenon

228

What kind of detectors are used in modern CT?

scintillation

229

What generation used gas ionization chambers?

3rd

230

What crystal materials can be used as CT detectors? (5)

  1. cesium iodide
  2. cadmium tungstate
  3. bismuth germinate
  4. rare earths such as gadolinium oxysulfide
  5. scintillation gemstone materials
231

What does EBCT stand for?

Electron beam CT

232

What kind of CT is devoid of moving parts, or where the x-ray source and detectors are stationary?

EBCT

233

________ systems have no x-ray tube. A fan beam of x-radiation is produce by directing a beam of electrons toward stationary target rings of tungsten. Each curved tungsten target emits radiation when bombarded by the electron beam, and x-rays are collimated towards the patient.

EBCT

234

Owing to its high speed capabilities, the primary application of ABCT is ______________ imaging.

Cardiac

235

Most helical CT systems use ________________ detectors because of their efficiency and stability.

solid state scintillation

236

All MSCT systems utilize 3rd gen detector geometry and solid state scintillation detectors. T/F

True

3rd gen has a curvilinear array of detectors that rotates around the patient with the tube.

237

____________ _________ refers to the number, length and organization of the individual detector elements in MSCT.

detector configuration

238

What are the three general formats of MSCT detector configuration?

  1. uniform matrix array
  2. adaptive array
  3. hybrid array
239

What detector configuration is described?

  • multiple detectors in the longitudinal direction
  • each the same length

uniform matrix array

240

What detector configuration is described?

  • thinnest width at the center, surrounded by detectors of incrementally increasing widths along the z-axis.
card image

adaptive array

241

What detector configuration is described?

  • consists of two detector sizes
  • narrower detectors are positioned midline, flanked by the wider detectors

hybrid array

242

How many data channels does a 16 slice MSCT system have?

16

243

What is the maximum number of sections that may be reconstructed in a 16 slice MSCT system for one gantry rotation?

16

244

The number of detectors in an array is _________ or __________ the number of data channels.

equal to or greater than

a 16 slice system may use an adaptive array of 24 detectors

245

___________ refers to the electronic combination of signal from adjacent detectors to form a reconstructed slice that is thicker than the individual detector width.

binning

246

The _______________________ consists of electronic components responsible for measuring the transmitted x-radiation absorbed by the detectors.

Data acquisition system (DAS)

247

The _______________ is a component of the DAS responsible for converting the electronic signal into digital form.

analog-to-digital converter (ADC)

248

The CPU of the CT computer system is capable of performing multiple tasks simultaneously, a function that is called __________.

parallel processing

249

_______________ is an additional function of CT computer systems that further improves the speed and efficiency with which it can perform multiple simultaneous functions.

pipelining

250

What is the primary data processing component?

array processor

251

The is responsible for receiving scan data from the host computer, performing all of the major processing of the ct image, and returning the reconstructed image to the storage memory of the host computer?

array processor

252

What is a common choice for mass storage of CT computer system data?

hard disk drive

253

The measurement of transmitted radiation made by an individual detector is called ___________.

total transmission of materials along the way.

ray sum

254

sampling rate can be called ______________.

views per rotation or VPR

255

The ability of an object to attenuate the x-ray beam is assigned a value termed the ______________________.

linear attenuation coefficient

256

What equation illustrates the relationship between radiation intensity and object density, and allows for the calculation of an objects linear attenuation coefficient?

lambert-beer

257

The Lambert-Beer law is only valid for pencil beam radiation sources like what generation scanner?

1st gen

258

The mathematical process primarily responsible CT image reconstruction is called _____________. During this reconstruction method, the ray sum data acquired from each projection is projected back onto a matrix.

back-projection

259

An additional process called_________________ is applied to reduce image unsharpness. An algorithm, or ______________ kernel acts as a mathematical filter, modifying the ray sum data and removing the unwanted blurring effect of back-projection.

convolution

260

______________ is the mathematical process whereby data from tube rotations just above and just below a given slice position are used for image reconstruction. ___________ allows for the reconstruction of a thin, motion free image.

interpolation