Anatomy Cross-Sectional Slices Measurement Quiz
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Questions and Answers

What is the main advantage of multidetector row systems (MDCT) over traditional CT systems?

  • Longer and faster z-axis coverage per gantry rotation (correct)
  • Higher radiation exposure to patients
  • Less accurate slice thicknesses
  • Shorter z-axis coverage per gantry rotation

    • In axial scanning, when are slices gapped and exposure interrupted?

  • When the acquisition speed is a major concern
  • When optimal resolution is required (correct)
  • When the scan is continuous
  • When high contrast images are needed

    • What are the key aspects of helical scanning?

  • Continually rotating x-ray tube and constant x-ray output (correct)
  • Single detector element
  • Intermittent table movement
  • Multiple x-ray tubes

    • How does helical scanning reduce motion artifacts from organs?

    <p>By adjusting for table motion in software</p> Signup and view all the answers

    What does increasing the pitch in SDCT result in?

    <p>Reducing radiation dose to the patient</p> Signup and view all the answers

    What technology improvement led to the development of helical scanning in CT systems?

    <p>Slip ring gantry design</p> Signup and view all the answers

    How are slices produced in helical scanning different from axial scanning?

    <p>They begin and end in different z-axis planes</p> Signup and view all the answers

    What happens when you decrease the pitch in SDCT?

    <p>Increase radiation dose to the patient</p> Signup and view all the answers

    In MDCT systems, what is pitch defined as?

    <p>Table movement per rotation divided by beam width</p> Signup and view all the answers

    What determines the beam width in MDCT?

    <p>Number of slices</p> Signup and view all the answers

    How does pitch affect radiation dose to the patient in SDCT?

    <p>Reduces radiation dose</p> Signup and view all the answers

    Which scan parameter is affected by decreasing the pitch in SDCT?

    <p>Radiation dose to the patient</p> Signup and view all the answers

    Which type of 3D reformation involves selecting voxels with the highest value to display?

    <p>Maximum-intensity projection (MIP)</p> Signup and view all the answers

    What kind of structures are well visualized using Maximum-intensity projection (MIP)?

    <p>Bone and contrast-filled structures</p> Signup and view all the answers

    What do Minimum intensity projection (MinIP) images typically display best?

    <p>Bronchial tree</p> Signup and view all the answers

    What is the main characteristic of MinIP images?

    <p>Selects voxels with the lowest value to display</p> Signup and view all the answers

    What is the main feature of a Single Slice CT scanner?

    <p>One x-ray tube</p> Signup and view all the answers

    What is the process called when creating an MIP from only a portion of the data set?

    <p>Variable sliding slab method</p> Signup and view all the answers

    How many images/slices can a Single Slice CT scanner produce per rotation?

    <p>One</p> Signup and view all the answers

    How many images/slices can a Dual Source CT scanner produce compared to a Single Source Multi-Slice scanner?

    <p>Dual Source produces double the number</p> Signup and view all the answers

    What differentiates a Multi-Slice CT scanner from a Single Slice CT scanner?

    <p>Multiple rows of detectors providing multiple channels of spatial data</p> Signup and view all the answers

    Which generation of CT scanners uses all stationary Electron Beam technology?

    <p>5th Generation</p> Signup and view all the answers

    In the context of CT scanners, what does 'Fan beam, stationary circular detector' describe?

    <p>4th Generation</p> Signup and view all the answers

    What aspect of image quality primarily affected by insufficient mAs?

    <p>Contrast resolution</p> Signup and view all the answers

    Which phantom is commonly used to evaluate spatial resolution?

    <p>Line pairs phantom</p> Signup and view all the answers

    How is contrast resolution evaluated using a phantom?

    <p>Scanning objects of varying sizes at different mAs settings</p> Signup and view all the answers

    Which parameter is measured using a ramp, spiral, or step-wedge phantom?

    <p>Slice thickness accuracy</p> Signup and view all the answers

    What does uniformity refer to in CT scanning?

    <p>Ability of the scanner to yield the same CT number regardless of ROI location</p> Signup and view all the answers

    Which aspect of image quality is most affected by noise?

    <p>Contrast resolution</p> Signup and view all the answers

    How is linearity measured in CT scanning?

    <p>Measuring CT numbers and linear attenuation values of objects</p> Signup and view all the answers

    Study Notes

    Image Quality

    • Insufficient mAs results in increased noise, which primarily affects contrast resolution.
    • Spatial resolution can be evaluated using a line pairs phantom.
    • Contrast resolution can be evaluated using a phantom that contains objects of varying sizes.
    • Slice thickness accuracy can be measured using a phantom that includes a ramp, spiral, or step-wedge.
    • Laser light accuracy is most often measured using a specific phantom designed for the purpose and provided by the scanner manufacturer.
    • Noise and uniformity can be measured using a water phantom.
    • Linearity is the relationship between CT numbers and the linear attenuation values of the scanned object at a designated kVp value.

    Quality Assurance

    • Quality Assurance (QA) methods are designed to ensure that the CT system is producing the best possible image quality using the minimal radiation dose to the patient.
    • QA programs are shared between CT technologists and medical physicists.
    • The tests that make up the QA program must be performed on a regular basis.
    • The results from all tests must be recorded using a consistent format.
    • Documentation should indicate whether the tested parameter is within specified guidelines.

    QA Phantoms

    • Many aspects of image quality can be evaluated using phantoms.
    • Most phantoms are designed with many components so that a single phantom can be used to examine a broad range of scanner parameters.

    Radiation Dose

    • Technologists must be well acquainted with the factors that affect the radiation dose to the patient.
    • Technologists must also provide safety instruction to anyone who must remain in the scan room.

    3D Reformation

    • Projection displays can be used to display 3D reformation.
    • Maximum-intensity projection (MIP) selects voxels with the highest value to display.
    • Minimum intensity projection (MinIP) selects voxels with the lowest value to display.

    Multidetector Row Systems (MDCT)

    • MDCT systems use many detector elements situated in a row.
    • MDCT provides longer and faster z-axis coverage per gantry rotation.
    • Slice thickness is determined by a combination of the x-ray beam width and the detector configuration.

    Applications for Axial Scanning

    • Axial scans are used in protocols in which the acquisition speed is not a major concern and optimal resolution is required.
    • Axial scans are used when slices are gapped, or when exposure will be interrupted.

    Helical Scanning

    • Helical scanning was introduced in the late 1980s.
    • Key aspects of helical scanning include continually rotating x-ray tube, constant x-ray output, and uninterrupted table movement.
    • Helical scanning eliminates the interscan delay and has several advantages, including the ability to optimize iodinated contrast agent administration, reduces respiratory misregistration, and reduces motion artifacts from organs.

    Pitch in SDCT and MDCT

    • Increasing the pitch in SDCT will result in a scan covering more anatomy lengthwise for a given total acquisition time and will reduce the radiation dose to the patient.
    • Decreasing the pitch in SDCT slows down the table speed and decreases the anatomy covered, and will increase the radiation dose to the patient.
    • Pitch in MDCT is defined as table movement per rotation divided by beam width.

    CT Scanners

    • There are three main types of CT scanners in use today: Single Slice, Multi-slice, and Dual Source.
    • Single Slice CT scanners have one x-ray tube and one row of detectors, providing 1 channel of spatial data.
    • Multi-slice CT scanners have one x-ray tube and multiple rows of detectors, providing multiple channels of spatial data.
    • Dual Source CT scanners have two x-ray tubes at 90° to each other, multiple rows of detectors x 2, providing multiple channels of spatial data.

    CT Generations

    • There are five generations of CT scanners today:
      • 1st generation: Parallel beam, translate rotate
      • 2nd generation: Fan beam, translate rotate
      • 3rd generation: Fan beam, rotate only
      • 4th generation: Fan beam, stationary circular detector
      • 5th generation: Electron Beam, all stationary

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    Description

    Test your knowledge on anatomy cross-sectional slices and measurement. Determine how much anatomy in the z-direction will be covered with specific cross-sectional slice measurements. Choose the correct answer between the given options and enhance your understanding of multidetector row systems (MDCT).

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