Week 2 Operators Console And Operations Flashcards
1
Q
What are the 5 components of the computer system in Ct?
A
- operators console
- host computer
- scan controller
- data acquisition system (DAS)
- array processor
2
Q
What is included in the operator’s console?
A
- computer
-keyboard
-monitor
-mouse/trackpad
3
Q
Which of the computer systems is considered the main point of interaction for a tech and scanner?
A
Operators console
4
Q
What can be done at the operators console
A
-scan parameters
-patient information
-instructions for post processing
-filming
-archiving
-networking
5
Q
Define user interface
A
The appearance of the screen
6
Q
What is Graphical User Interface (GUI)?
A
The use of icons displayed on the user interface to start tasks
7
Q
Which component of the computer systems is the primary link between the technologist and other components of the system?
A
Host computer
8
Q
How does the Host computer interact with the other components of the computer system?
A
The host computer directs the other components based on the commands of the technologist which is inputted at the operators console
9
Q
What are the five mechanical components of the host computer?
A
-input device (mouse +keyboard)
- output device (display)
- Central Processing unit (CPU) / Image Reconstruction Systems (IRS)
- Internal Memory
- External Memory
10
Q
For the Host computer Internal memory and external memory are what?
A
Forms of storage
11
Q
The monitor displays pictures made up of what?
A
Pixels
12
Q
A larger matrix =
A
More and smaller pixels
13
Q
More and smaller pixels = what
A
A larger matrix and better image resolution
14
Q
Brightness is determined by what unit?
A
Hounsfield unit (HU)
15
Q
Define attenuation
A
The reduction in intensity of the beam as it passes through matter
16
Q
Brightness is the result of what?
A
Attenuation
17
Q
What are the two types of monitors?
A
Cathode Ray tube (CRT) old and outdated (rare)
Liquid Crystal Display (LCD) standard
18
Q
Why do nearly all CT operations utilize LCD monitors?
A
- lower cost
- more compact in size
- low power consumption
- better color representation
- excellent image resolution
- more luminance (screen brightness)
19
Q
Is a laser camera considered an input or output device?
A
Output device
20
Q
What does a laser camera do?
A
Record or print CT images onto film
21
Q
CT prints are usually printed on what?
A
14x17 single emulsion film (light sensitive film only on none side of the film
22
Q
CT prints are usually completed in what formats?
A
12:1
15:1
20:1
23
Q
The CT print format of 12:1 means what?
A
12 images on 1 14x17 film arranged in a 3x4 layout
24
Q
What is the Central array processing Unit in the host computer?
A
-Considered the brains of the computer
- master chip for executing program instructions, arithmetic funct., and access to memory and peripherals
25
What does the word peripherals refer to in regards to the CT computer system?
- keyboard
- mouse
-monitor
26
Where is the CPU located?
In the Host Computer on the motherboard
27
What determines a CPU’s power?
-speed (cycles/sec)
-amount of data it is able to process
28
What is a CPU’s ability to operate at billions of cycles per second called
Gigahertz (GHz)
29
What is moore’s law?
The law based on prediction that the number of transistors (therefore processing speed) per silicon chip/ integrated circuit will double every two years, while cost per unit processing power is halved
30
The internal memory is normally what on a PC
The hard drive
31
Define internal memory
The internal data storage place of a device
32
What are the two types of internal memory
- Read only memory (ROM)
- Random Access Memory (RAM)
33
What is Read only Memory (ROM)
- Long term storage of data
- includes operating system and applications
34
What is Random Access Memory (RAM)
- Memory used for temporary storage of information
- includes data acquired from the scan
- data will eventually be deleted to free space for new data
35
Describe external memory
- data stored on external media
- removable from the host computer
- data can be transferred onto another workstation
36
List forms of external memory
- Magnetic optical disc (MOD) = holds several gigabytes
- Digital Versatile Disc (DVD) = 4.7 GB
- External Hard drives = 4.0 TB
- Picture Archiving and Communication System (PACS) = unlimited storage
37
What is the scan controller / scan controller module / system console
Responsible for image acquisition
38
What is controls can be done by the Scan Controller
- table movement
- gantry angle tilt
- start/stop X-ray exposure
- intercom controls
39
What is Data acquisition system (DAS)
A set of electronics responsible for the intake of data and measurements from the patient
40
What three tasks does the Data Acquisition system (DAS) do?
- 1)Amplify received analog signals from detectors
- 2) convert to a digital signal
- 3) send signals for reconstruction
41
What are the components of the DAS?
- digital to analog converter (DAC)
- High voltage generator
- amplifier
- sample/hold
- analog to digital converter (ADC)
42
Is the Signal from the scan controller digital or analog ?
Digital
43
List the components that require analog signals
- high voltage generator
- gantry
- X-ray tube
- detectors
- patient table
44
What is the purpose of the high voltage generator?
Generates the necessary voltage to produce xrays
45
What does the Amplifier do?
Amplifies analog signals without converting and sent to sample/ hold component
46
Where is the sample/hold component located?
Between the amplifier and ADC
47
What does the sample/hold component do?
- receives amplified signal and samples the image
48
What is sampling?
- differentiates structures imaged with various densities
- assigns various shades of gray to the pixels to represent structures
49
What does the analog to digital converter do?
Converts analog signal back to digital
- required for host computer to be able to analyze and understand data
- data is sent to array processor for reconstruction
50
What is the Array processor/ image reconstruction system (irs)
- a specialized high speed computer that receives the detector measurements to form the CT image
- primary location for mathematical calculations for image generating
51
What are the main functions of the Array processor/ image reconstruction system (IRS)
- reconstruction of attenuated raw data into a CT digital image
- perform required calculation to generate retrospective reconstructions
- post process image data
52
A normal patient table is generally maxed out at what weight?
400 - 485 lbs
53
Bariatric patient tables are maxed out at what weight?
660lbs
54
The patient coordinate system refers to a patient in what position?
Supine
55
What is the x-axis when referred to the human body
X-axis: extends from patient’s left to right side (provides sagittal images)
56
What is the Y axis for the human body?
Y-axis: Extends anterior to posterior (cutting along your-axis = coronal images)
57
What is the z-axis for the human body?
Z-axis: extends along the patient table or long axis of patient’s body (cutting along z axis = transverse /axial images)
58
What is the benefit of isocentering?
Best distribution of dose and image quality
59
Define isocentering
The technique of centering the region of interest to make sure it does not fall out of the scan field of view (SFOV)
60
Isocentering affects what?
Patient radiation exposure and image quality
61
Which axis does the gantry move along?
Z-axis
62
What is the opening of the gantry called?
Gantry aperture
63
What is landmarking
Where the technologist initially lines up the patient for where they want the scan to begin
64
How large is the opening of the gantry?
50-90cm
65
What are the Gantry internal components
- rotating frame assembly
-slip ring
66
What are the components of the rotating frame assembly
- x-ray tube
- collimator assembly
- detector array
- data acquisition system (das)
- various other electrical components
67
How fast does the rotating frame assembly turn?
80-200 RPM (rotations per minute)
68
What is a slip ring?
Large rotating ring surrounding the gantry aperture
-replaces high voltage cables
69
What does a brush block do?
Located on the slip ring the brush block sends electric and data to other components of the machine
70
What are the common gantry controls located on the ct machine
- table movement/feed
- localizer laser alignment lights
- landmark
- gantry angle tilt
- emergency stop button
71
What are some reasons to tilt the gantry?
- CT neck soft tissue to avoid dental work
- CT of sinus for air-fluid levels with patient prone
72
What is the common angle for obliquing the gantry?
30 degrees
73
Where is the X-ray tube in the gantry?
On the frame assembly
74
What are the two electrodes in the X-ray tube?
- cathode
- anode
75
What is the CT cathode filament made of?
Tungsten
76
What does the cathode do?
Expels electrons from the circuit and focuses them in a electron beam
77
A smaller focal spot = what type of electron beam?
Narrow electron beam
78
Where is the filament located?
On the cathode end of the tube in the focusing cup
79
What is the focusing cup usually made of?
Nickel
80
What is the focal spot?
Region of the anode struck by the electron beam
81
What is the process within the X-ray tube that produces electrons?
Thermionic emission
82
Define thermionic emission
The emission of electrons from a heated source
83
What influences the emission of thermionic emission
Controlled by mA
84
What affects the quantity of X-rays produced per second?
MAs
85
Complete the phrase:
Higher mA = ______ electrons = ________xrays = _______ X-ray tube
- more
-more
-hotter
86
What is tube voltage?
- kVp
- energy level of X-ray photons
87
The penetrability of an X-ray beam is influenced by what?
KVp
88
What affects image quality?
KVp
89
A higher kVp = what
Higher energy of beam
90
What is the 15% rule?
91
Which end of the X-ray tube is the main source of heat during X-ray production?
Anode
92
What is the anode usually made of?
Tungsten-rhenium (target material)
Molybdenum core
93
Why does the anode target rotate?
- prevent heat build up and melting
- prolongs anode life
94
Define interscan delay
Minimum amt of time between the end of one scan and the initiation of the next
95
What is warm-up procedure for CT
Procedure done before the use of an X-ray tube when the X-ray tube has not been in use for some time
96
What is tube arching
97
Simple version of X-ray production in the tube
Cathode heats filament in focusing cup > electrons are boiled off and emitted towards anode target > electrons hit anode target and the interaction produces the beam
98
What are the two target interactions not including heat production
- bremstrahlung radiation
- characteristic radiation
99
What is bemstrahlung radiation also known as?
Braking radiation
100
Where does the bremstrahlung radiation interaction occur?
In the nucleus of the target material atom
101
Brems radiation is considered useful or unuseful for image production?
Useful
102
How much of the X-ray beam is made of brems radiation?
About 90% of the heterogeneous beam
103
At what keV does characteristic interactions begin?
69.5 = tungsten k-shell energy
104
Describe characteristic radiation
- incident electron of at least 69.5 keV interacts with an inner shell electron of the atom
- the shell electron is ejected leaving vacancy
- outer shells shed their energy which forms xrays to drop down to fill vacancies
105
Which shell X-ray in characteristic radiation is considered useful in X-ray?
K shell
106
What percentage of characteristic radiation is within the X-ray beam?
10-12%
107
What is the purpose of a filter
Causes beam hardening
108
What is beam hardening?
The filtering of low energy photons that serve no diagnostic value. Therefore causing the overall beam energy to be increased
109
What is a common filter for the X-ray tube?
Aluminum
110
What are the two types of collimators in CT?
- pre patient collimation
- post patient collimation
111
Describe pre patient collimation
- thick metal plates attached to the bottom of the X-ray tube housing
- restricts the beam immediately after exiting ct tube, before entering PT, minimizes scatter radiation
112
Pre patient collimation on a single slice scanner determines what?
acquired slice thickness
113
Pre patient collimation on multi slice scanners work how?
The collimation selects the thickness of the X-ray beam but the final image slice is determined by reconstructed slice thickness
114
What is post patient collimation also known as?
Pre detector collimation
115
Post patient collimation does what?
Restricts unwanted X-rays from entering the detector from off (arbitrary) angles and reduces scatter radiation from fogging the image
116
What are the three conditions for a signal to be generated in a detector?
1) enter the chamber of the detector
2) photons collide with an atom in detector
3) collision must generate measurable signal such as electricity or light
117
What are the two types of detectors in CT
Gas and solid state
118
What is the most common gas used in gas detectors?
Xenon
119
Which type of detector is most efficient and common in ct?
Solid state detectors
120
In a xenon gas detector upon collision what is the result?
X-ray photon —-> * xenon gas atom = xenon ion(+) and electron (-)
121
The xenon gas detector has one or two electrical charges?
2: one side of the plate is positive the other negative.
(After xenon gas atom is split to ions the respective particles are drawn to the opposite polarity side of the plate)
122
What is a solid state detector also known as?
Scintillation detectors
123
Describe the process of a solid state detector
- X-ray photon interacts with detector material atoms
- the scintillator converts X-ray to light
- light is converted to electric signal through photodiode
- electric signal is sent to amplifier then array processor
124
What are the two configurations of detectors?
Single row array And multi row detector array
125
List the disadvantages of single slice CT
- prone to motion artifacts
- slow
- unable to gather a large amount of data
126
What does MSCT stand for?
Multi-slice CT
127
Pros of Multi slice CT
- more than one slice acquired during each rotation
- slice thickness determined by detector configuration
128
What is the equation to determine acquired slice thickness in a MSCT?
Acquired slice thickness = Collimation (thickness of X-ray beam) / total # of slices acquired in one rotation
129
Which trimester in a pregnancy is most contra indicative for a CT scan?
First trimester
130
What are the two main pieces of medical history that should be inquired for CT?
1) IV Contrast and/or shellfish allergy
2) History of Prior surgery that may cause PT anatomy to differ from norm
131
What are the potential risk factors if IV contrast is involved?
- prior allergic reaction to contrast
- asthma
- renal insufficiency
- cardiac arrhythmia
132
What are the 3 ways of obtaining informed consent?
-written
- oral
- implied
133
What are the 4 ways of monitoring a PT’s level of consciousness?
- PT breathing
- signs of complications
- signs of contrast reactions
- maintaining verbal communication w/ PT
134
Under what circumstance does a PT getting a CT require a pulse ox?
Any patient on sedation
135
What are the 4 basic vital signs to monitor a PT medical status?
- body temp
- pulse rate
- respiratory rate
- blood pressure
136
What is a normal body temp?
- mouth : 97-99
- Axilla: 96.5-998.5
- rectum: 97.5 - 99.5
137
What is the most common site to measure a pulse?
Radial pulse
138
What is the normal pulse rate for an average adult?
70-100 bpm
139
Normal pulse rate of athletic adult
45-60 bpm
140
Normal pulse rate of child
95-110 bpm
141
Normal pulse rate of infant
100-180 bpm
142
What does the systolic pressure measure?
Force of ventricular contraction
143
What does diastolic pressure measure?
Lowest pressure of ventricle
144
How is blood pressure read
Systolic/diastolic
145
Normal blood pressure of adult
Sys : 90-140
Dias: 60-90
146
Normal blood pressure for child
Sys: 85-130
Dias: 45-85
147
Normal respiratory rate of adult
12-20 breaths/min
148
Normal respiratory rate for child
15-30 breaths/min
149
Normal respiratory rate infant
25-50 breaths/min
150
Define tachycardia
Faster heart beat
151
Define Bradycardia
Slower heart beat
152
What is normal oxygen saturation ?
95-100%
153
What type of lab results are important to CT?
- renal function
- blood coagulation
154
What are the three renal function labs and normal ranges?
- BUN (blood urea nitrogen) : 5-25 mg/dl
- Creatinine : 0.6 -1.7 mg/dl
- GFR (glomerular filtration rate) : 95-120 ml/min
155
What are the tests and normal values related to blood coagulation?
- Prothrombin Time (PT): 10-14 sec
- Partial thromboplastin time (PTT): 20-40 sec
- International Normalized ratio (INR): 0.9 -1.3
- platelets: 150,000 - 400,000 mm^3
- D-diner
