CT Scanner Quality Control Test
40 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the axial plane spatial resolution achievable with modern CT scanners?

  • 2-5 mm
  • 1-2 mm
  • 0.6-0.9 mm (correct)
  • 0.3-0.5 mm

    • How does the number of detector rows affect scan volume and scan time?

  • More detector rows increase scan time
  • More detector rows do not affect scan time
  • More detector rows decrease scan time (correct)
  • More detector rows have no effect on scan volume

    • What is the advantage of iterative reconstruction over filtered backprojection?

  • Lower radiation doses
  • Faster reconstruction time
  • Improved image quality (correct)
  • All of the above

    • What is the advantage of using 64 active detector rows in a CT scanner?

    <p>Improved longitudinal spatial resolution</p> Signup and view all the answers

    What is the maximum scan volume covered by a 320 detector row CT scanner?

    <p>160 mm</p> Signup and view all the answers

    What is the purpose of algebraic reconstruction in CT imaging?

    <p>To improve image quality</p> Signup and view all the answers

    What is the effect of using multiple rotations in a helical acquisition?

    <p>Improved longitudinal spatial resolution</p> Signup and view all the answers

    What is the advantage of fast simple backprojection over iterative reconstruction?

    <p>Faster reconstruction time</p> Signup and view all the answers

    What is the primary limitation of spatial resolution in CT scanners?

    <p>All of the above</p> Signup and view all the answers

    What is the unit of measurement for temporal resolution in CT scanners?

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

    What is the primary factor that affects low-contrast resolution in CT scanners?

    <p>Image noise</p> Signup and view all the answers

    What is the purpose of the Catphan 500 phantom in CT quality control tests?

    <p>To measure all of the above</p> Signup and view all the answers

    What is the range of spatial resolution in 64-slice CT scanners, expressed as the full-width half-maximum of the point spread function?

    <p>0.6-0.9 mm</p> Signup and view all the answers

    What is the term used to describe the graphical representation of system performance in spatial resolution tests?

    <p>Modulation Transfer Function (MTF)</p> Signup and view all the answers

    What is the purpose of the sensitometry module in CT quality control tests?

    <p>To measure CT linearity</p> Signup and view all the answers

    What is the term used to describe the in-plane x-y direction and longitudinal in z-direction of spatial resolution in CT scanners?

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

    What is the purpose of scanning a patient in a specific position during radiotherapy treatment planning?

    <p>To ensure accurate radiation dosage</p> Signup and view all the answers

    What is the primary application of dual energy CT imaging?

    <p>Discriminating certain tissues and pathology</p> Signup and view all the answers

    What is the purpose of the CatPhan phantom in CT imaging?

    <p>To evaluate the numerical value of Hounsfield units</p> Signup and view all the answers

    What is the primary goal of daily quality control tests for CT?

    <p>To ensure optimal image quality</p> Signup and view all the answers

    What is the purpose of the air calibration test in CT quality control?

    <p>To calibrate the zero value of the detector</p> Signup and view all the answers

    What is the purpose of the standard test from safety code 35 in CT quality control?

    <p>To check CT number accuracy and cross-field uniformity</p> Signup and view all the answers

    What is the purpose of the noise test in CT quality control?

    <p>To measure the standard deviation in the phantom</p> Signup and view all the answers

    What is the primary application of 4D CT imaging?

    <p>Visualizing the movement of joints</p> Signup and view all the answers

    What is the purpose of ECG dose modulation in cardiac CT scanning?

    <p>To reduce the radiation dose in the phases that are not of interest</p> Signup and view all the answers

    What is the benefit of using prospective ECG-triggered reconstructions in cardiac CT?

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

    What is the term used to describe the ratio of table translation per 360° tube rotation relative to the nominal beam width in helical CT?

    <p>Pitch factor</p> Signup and view all the answers

    What is the advantage of using multislice CT scanners over single slice CT scanners?

    <p>Increased number of transmission profiles measured simultaneously</p> Signup and view all the answers

    What is the purpose of cardiac motion minimization in cardiac CT scanning?

    <p>To freeze the cardiac motion during scanning</p> Signup and view all the answers

    What is the benefit of retrospective ECG-gated reconstructions in cardiac CT?

    <p>Ability to select cardiac phase retrospectively</p> Signup and view all the answers

    What is the purpose of helical scanning in CT acquisition?

    <p>To enable the measurement of a large number of transmission profiles simultaneously</p> Signup and view all the answers

    What is the advantage of using 16 or 64 adjacent active arrays of detectors in multislice CT scanners?

    <p>Increased number of transmission profiles measured simultaneously</p> Signup and view all the answers

    What is the unit of measurement for CTDIvol?

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

    What is the formula to calculate DLP from CTDIvol?

    <p>DLP = CTDIvol * Scan Length</p> Signup and view all the answers

    What is the CT pitch factor, θp, equal to?

    <p>l / (N * T)</p> Signup and view all the answers

    What is the formula to calculate the weighted CT Kerma Index, Cw?

    <p>Cw = 1/3 (CPMMA,100,c + 2 * CPMMA,100,p)</p> Signup and view all the answers

    What is the unit of measurement for DLP?

    <p>mGy*cm</p> Signup and view all the answers

    What is the scan length of the patient in the example scenario?

    <p>16 cm</p> Signup and view all the answers

    What is the value of CTDIvol in the example scenario?

    <p>10 mGy</p> Signup and view all the answers

    What is the value of DLP in the example scenario?

    <p>160 mGy*cm</p> Signup and view all the answers

    Study Notes

    CT Acquisition Overview

    • Table translation in helical CT related to nominal beam width; referred to as pitch factor.
    • Launch of fast rotating multislice CT scanners in the late 1990s, enhancing clinical applications.
    • Single slice CT uses one linear detector array with a rotation time of 1-2 seconds and slice thickness of 5-10 mm.
    • Multislice CT utilizes multiple active arrays (4, 16, 64), significantly reducing rotation time to 0.3-0.4 seconds.

    Cardiac CT Techniques

    • Cardiac scanning aims to minimize motion for accurate imaging.
    • Preferred scanning phases are diastole or end systole when cardiac motion is least.

    ECG-Gated Acquisition Modes

    • Retrospective ECG-gated reconstructions involve overlapping pitch scanning and retrospectively selecting cardiac phases to minimize radiation in uninteresting phases.
    • Prospective ECG-triggered reconstructions are "step-and-shoot," reducing patient dose.

    Special CT Applications

    • Radiotherapy planning scans patients in the treatment position; wide bore scanners accommodate this.
    • Dual energy CT imaging enhances tissue discrimination by imaging at two photon energy levels.
    • Dynamic CT (4D CT) visualizes motion over time, useful for joints and perfusion studies.

    CT Image Quality Assessment

    • CatPhan phantom used for comprehensive image quality evaluation in CT scans.
    • Hounsfield units checked using inserts for specific materials to calibrate reconstructed images.
    • Low contrast acrylic inserts help assess detectability based on object size.

    Quality Control Tests

    • Daily tests by technologists include environmental inspection, tube warm-up, and air calibration.
    • Weekly tests assess CT number accuracy, cross-field uniformity, and noise levels.
    • Monthly tests check CT number linearity with various tissue densities.
    • Quarterly evaluations focus on spatial resolution, analyzing via line pairs phantom and Modulation Transfer Function (MTF) graphic representation.

    Detectors in CT Imaging

    • Multi-slice scanners are defined by their detector rows, enabling thinner, longer, and faster scans.
    • A typical single detector row scanner can cover 5 mm, whereas 4 active rows significantly improve longitudinal resolution from 5 mm to 1 mm.
    • CT scanners with up to 64 detector rows enable rapid acquisitions covering larger volumes, with 320-row scanners covering 160 mm in a single rotation.

    Image Reconstruction Techniques

    • Main techniques include simple backprojection, algebraic reconstruction, iterative reconstruction, and filtered back projection.
    • Filtered back projection (FBP) is rapid but noisy; iterative reconstruction improves picture quality at the cost of processing time.

    CT Dosimetry Parameters

    • CT pitch factor calculated by the distance moved by the patient couch per rotation, divided by the product of slice thickness and number of tomographic sections.
    • Dose-Length Product (DLP) calculated by multiplying Volume CT Dose Index (CTDIvol) by scan length.

    Example Calculations

    • An example illustrates calculating DLP using CTDIvol, which helps evaluate overall patient exposure and scan efficiency.
    • Key values for Weighted CT Kerma Index (Cw) and Volume CT Dose Index (CTDIvol) demonstrated through specific measurements, enabling assessment of radiation delivered to patients.

    General Image Quality Parameters

    • High-contrast spatial resolution factors include slice thickness, acquisition geometry, and reconstruction algorithms.
    • Current scanners achieve spatial resolution between 0.6-0.9 mm in all dimensions.

    Note on Contrast Resolution

    • Dependent on tube voltage, beam filtration, and the reconstruction algorithm, with image noise being the main limitation affecting low-contrast detectability.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Physics of Medical Imaging 1 - Ionizing Radiation - PDF

    Description

    This quiz tests knowledge of quality control tests for CT scanners, including linearity and spatial resolution tests using phantoms and modulation transfer function analysis.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser