DMI 65 Quiz 1 - Chapters 1 (1-60) 10 (61-79)

What does the acronym CAT now stand for if used?

Computer Assisted Tomography. This is because newer models offer options in more than just the transverse/axial plane (i.e. coronal or sagittal)

The process of using raw data to create an image is called what?

image reconstruction

What is the post-processing technique that allows a sectional image to be generated in any desired plane?

multiplanar reconstruction (MPR)

intimate, personal, social, or public distance are examples of what type of nonverbal communication?

space (variations in accepted norms owing to ethnicity, age and gender differences)

the use of touch to impart meaning is an example of what type of nonverbal communication?

tactile

x-ray photons that are absorbed = _____________

white area on image

List the 5 types of nonverbal communication:

1. visual 2. tactile (touch) 3. vocal 4. use of time, space, images 5. objects/values

Estimates suggest that ___ % to ___ % of a message's meaning is lost in transmission

40 to 60

Studies have shown that as much as ____ % of the meaning we derive from communication comes from the nonverbal cues that the other person gives.

90

The CT process can be broken down into 3 main segments:

1. Data acquisition (get data) 2. Image reconstruction (use data) 3. Image display (display data)

List some benefits of effective communication:

-improved pt. safety -improved pt. compliance -improved pt. retention -improved referral rate -improved staff morale -improved efficiency -less risk of malpractice suits -improved exam quality -less staff turnover

CT nomenclature refers to the various terms used by different manufacturers to describe the same thing. List the following terms used for a preliminary image taken before a scan by the brands listed: -Siemens: -GE: -Toshiba: -Picker:

-Siemens: topogram -GE: scout -Toshiba: scanogram -Picker: pilot

The shades of gray on the image is determined by the quantity of x-ray photons that pass through the body. What determines if these photons pass through or not?

-The energy or strength of the x-ray photons -The characteristics of the object (thickness, density and atomic number)

Habits to adopt in communication:

-be a good listener -use focused questions -use the pt.'s name -use touch to comfort and be aware of nonverbal messages -develop rapport with the pt. -explain before acting -give pt. an opportunity to ask questions -use reflective speech (statements that further clarify a patient's message to check for accurate understanding) -give consistent messages

CT components:

-computer -gantry -table

What are the main advantages of CT over conventional radiography?

-elimination of superimposed structures -differentiation between adjacent structures w/ similar densities -image quality and formation of 3D image

What types of exams are axial modes usually preferred?

-exams that do not present the chance of motion or require patient to hold breath *image quality better

What types of exams are helical modes usually preferred?

-exams where motion is of concern *Usually presents a higher dose than axial

Habits to avoid in communication:

-false pretenses -ignoring pt.'s wishes -speaking like you're talking to a child -don't assume a non-responsive pt. can't hear -don't hold a separate conversation with a coworker in pt.'s presence -don't interpret professionalism as being cold -don't blame the pt. -don't use abbreviations or medical lingo

In general, how are the following spaces defined? -intimate: -personal: -social: -public:

-intimate: 1.5' or less -personal: 1.5' to 4' -social: 4' to 12' -public: 12' or more *distances are also influenced by ethnicity, age and sex

Barriers to communication:

-language -power struggles -misreading of body language -assumptions -past experiences -cultural differences -preconceptions -receiver distortion (selective hearing)

what does "rotate" and "translate" refer to?

-translate: linear tube movement -rotate: rotation of 1 degree for 1st gen. and 10 degrees for 2nd gen.

What important components does the gantry house?

-x-ray tube -DAS (data aquis. system) -detector array

Two reasons for changing image plane:

1) Orientation of AOI (i.e. vertical AOI might be better demonstrated on a coronal or sagittal plane instead of axial) 2) Reduce artifacts from surrounding structures

Describe the step and shoot scanning mode (commonly compared to axial) :

1) x-ray tube rotates 360 degrees and stops 2) gantry is advanced for next slice location 3) steps 1 and 2 repeated until all AOI is scanned

List the responsibilities of the speaker:

1. be audible 2. be aware that your listener may not have understood you 3. be willing to ask questions of your listener to confirm accurate understanding

List the responsibilities of the listener:

1. let the speaker know if they are inaudible 2. let the speaker know that you are attentive 3. if the speaker's message is unclear, request clarification

CT process (in depth)

1. tube rotates around AOI and detectors measure the transmitted x-ray values (raw data) 2. x-ray values are converted to an electrical signal which is relayed to comp. 3. numerical values are arranged in matrix providing image [each pixel within matrix is assigned a number that is related to the linear attenuation coefficient of the tissue within each voxel (these numbers are called CT #s or HU) and correspond to the gray level assigned]

1st and 2nd generation needed to scan how many degrees?

180 degrees. A process referred to as "rotate and translate"

What is a pixel?

A 2D representation that utilizes the X and Y axis.

Describe the helical (spiral) scanning mode:

A continuous acquisition scanning mode that was made possible with the elimination of the system cables enabling continuous rotation of gantry.

Once the Z axis (thickness) is taken into account the pixel is then referred to as what?

A voxel (volume element)

Why is it important to filter out the low energy x-ray photons?

Because beam hardening artifacts can be produced, known as "cupping artifacts".

Why was the step and shoot mode necessary at the time?

Because the x-ray tube's rotation entwined the cables

How can volume averaging be reduced when the AOI is smaller or consists of varying tissue densities?

By reducing the z axis or thickness which has a significant effect. The y and x dimensions of the pixel also influence volume averaging.

Earlier developed scanners were referred to as CAT scans. Why was this?

CAT scan stands for Computerized Axial Tomography and this is because earlier machines could only produce axial cuts.

The tube used in CT is similar to the tubes used in conventional radiography, but what is a key difference?

CT tubes are designed to handle and dissipate excessive heat units

What is the purpose of a scout image?

Demonstrates AOI and detects the proper technique to use.

Reformation provides us with what?

Different planes (sagittal, coronal, axial, etc) *without reconstruction, reformation would result in a very poor image

What is a special feature of CT where raw data is acquired and stored on comp. and reconstruction is bypassed to shorten scan time?

Dynamic Scanning (Vol 3 pg. 311)

Who developed the concept of CT?

Godfrey Hounsfield

The 4th generation featured a gantry that continuously moved, giving it what name?

Helical

Quantifies the degree that a structure will attenuate an x-ray beam.

Hounsfield Units (HU) ; AKA CT numbers or density values

Once the raw data has been processed and each pixel is assigned a HU, the data is referred to as what?

Image data

The ability of a system to differentiate, on the image, objects with similar densities is known as what?

Low contrast resolution

When was the first CT scanner introduced in America?

May of 1972

Low-density contrast agents are referred to as what? Give example

Negative contrast agents (water)

Materials of a higher density than the structure are referred to as what? Give an example

Positive contrast agents (barium sulfate, iodine)

All data acquired by the system with each scan which is waiting to be processed and has not yet been assigned a HU is known as what?

Raw data (AKA scan data)

The ability of a system to separate small objects that are very close together is known as what?

Spacial resolution

The speed that the data can be acquired is known as what?

Temporal resolution - Which is important to reduce artifacts resulting from motion such as those commonly seen during heart imaging.

A grid formed from the rows and columns of pixels is known as what?

The Matrix (most common is 512 x 512)

Which part of the body plays the largest role in body language communication?

The face

How was scanning time again reduced in the 3rd generation?

The number of tubes and detectors increased

When HU are used, what are the densities being defined compared to?

The numbers are based on the material's density compared to distilled water.

What is the aperture referring to?

The opening in center of gantry

Define communication:

The process of creating meaning

All x-ray beam sources for CT produce x-rays that are polychromatic. What does this mean?

The x-ray beam is composed of photons with varying energies.

-Materials denser than water = whiter (CSF, blood, bone) -Materials less dense than water = darker (fat, air) True or False?

True

The 3rd generation scanners introduced the "rotate/rotate" concept where the tube and detector rotated around patient simultaneously. T or F?

True

You cannot really transmit meaning. T or F?

True; what you can transmit is the message, but meaning is interpreted by the person receiving the massage.

What are the HU of water, air and bone?

Water: 0 Bone: 1000 Air: -1000

y axis direction:

anterior to posterior (height)

The degree to which an x-ray beam is reduced by an object is referred to as what?

attenuation

x-ray photons that pass through unimpeded = ___________

black area on image

What determines the amount of data to be displayed on the monitor?

field of view (FOV)

z axis direction:

head to toe (determines slice thickness)

What do healthcare professionals cite as the main reason for not talking more to patients?

lack of time

Which barrier to communication is considered the main cause?

language barrier

The reconstruction that is automatically produced during scanning is often called what?

prospective reconstruction

When the same raw data is then used at a later time to generate new images, the process is called what?

retrospective reconstruction

x axis direction:

right to left (width)

2 basic types of tubes used in CT:

scintillation (solid state) and ionization (xenon gas)

What was introduced in the 2nd generation scanners that greatly reduced scanning time?

the fan beam configuration (replaced the pencil beam)

The word tomography has as its root tomo, meaning what?

to cut, slice, section, etc.

Areas of intermediate attenuations are represented by _____________

various shades of gray

eye contact, posture, etc. are examples of what type of nonverbal communication?

visual communication which is often referred to as body language

the intonation (pitch) of a person's voice is an example of what type of nonverbal communication?

vocal

The process in CT by which different tissue attenuation values are averaged to produce one less accurate pixel reading is called what?

volume averaging