Pacific Northwest X-Ray Inc.

       Catphan 500/600 CT Phantoms.       

The Phantom Laboratory! Comprehensive CT Performance Measurements

Catphan® Phantoms are internationally recognized for measuring the MAXIMUM obtainable performance of axial, spiral and multislice CT scanners.

The Phantom Laboratory and physicist, David Goodenough, Ph.D., have worked together to develop the Catphan® Phantoms. The new Catphan® designs are based on three decades of scientific research and direct field experience in the evaluation of medical imaging equipment. These phantoms are used to complete comprehensive performance evaluations of axial, spiral and multislice CT scanners and to implement quality assurance programs.

The Catphan® Phantoms are constructed from modules that fit snugly into a durable 20cm housing. With the exception of the water tank module used in the Catphan® 424, all Catphan® modules are made from solid-cast materials. Solid-cast construction eliminates material absorption of water, freezing and leaks associated with water bath phantoms, as well as, problems related to varied water sources.

Tests - Summary

  • scan slice geometry (slice width and slice sensitivity profile)
  • high resolution (up to 20 or 21 line pairs per cm)
  • phantom position verification
  • patient alignment system check
  • low contrast sensitivity
  • comparative subslice and supra-slice low contrast sensitivity
  • spatial uniformity
  • scan incrementation
  • noise (precision) of CT systems
  • circular symmetry
  • sensitometry (linearity)
  • pixel (matrix) size
  • point spread function and modulation transfer function (MTF) for the x, y, and z axes

  • Catphan® 700 (Stock CTP700) - Complete Catphan® including housing and case, equipped with the following test modules:
    CTP682 - Geometry sensitometry and point source module
    CTP714 - 30 line pair high resolution module
    CTP515 - Subslice and supra-slice low contrast
    CTP721 - Wave insert
    CTP723 - Bead blocks
    CTP712 - Uniformity section

    Catphan® 600 (Stock CTP600) - Complete Catphan® including housing and case, equipped with the following test modules:

    CTP404 - Slice width, sensitometry and pixel size
    CTP591 - Bead Geometry module
    CTP528 - 21 line pair high reslution and point source
    CTP515 - Subslice and supra-slice low contrast
    CTP486 - Solid image uniformity module

    Catphan® 500 (Stock CTP500) - Complete Catphan including housing and case, equipped with the following test modules:

    CTP401 - Slice width, sensitometry and pixel size
    CTP528 - 21 line pair high resolution and point source
    CTP515 - Subslice and supra-slice low contrast
    CTP486 - Solid image uniformity module

    Stock #
    Your Price
    Complete Catphan® 700 including housing, case, and test modules
    Includes the following: CTP682-Geometry sensitomety and point source module, CTP714-30 line pair high resolution module, CTP515- Subslice and supra-slice low contrast, CTP721 Wave insert, CTP723-Bead blocks, CTP712 Uniformity section
    Complete Catphan® 600 including housing, case, and test modules
    Includes the following: CTP404-Slice width, sensitometry and pixel size, CTP591-Bead geometry module, CTP528-21 line pair high resolution and point source, CTP515-Subslice and supra-slice low contrast, CTP486-Solid image uniformity module
    Complete Catphan® 500 including housing, case, and test modules. Includes the following:CTP401 Slice width, sensitometry and pixel size, CTP528-21 line pair high resolution and point source, CTP515-Subslice and supra-slice low contrast, CTP486-Solid image uniformity module

           AutoQALite Software for use with the CatPhan CT Phantoms.       
    Iris QA! An updated Windows program to the original PC/AutoQA for CT. This update provides expanded image processing capacity for up to 96 images in a data set with a comprehensive trend analysis feature.


    CT AutoQA Lite can be configured with various vendor phantoms including ACR and all Catphan® models.
    CT AutoQA Lite is DICOM3.0 compatible, a DICOM Storage Provider (SCP) Application license is provided.
    CT AutoQA Lite provides the same analysis function as the original PC/AutoQA (DOS) version.

  • Pixel Size - test verifies the expected pixel size based on the display field of view and the reconstruction matrix size from the measured set of four calibration pins positioned at a known physical location as specified in the

  • Verification
    Phantom ID: 600 Series (Phantom Lab) Orientation 1
    Phantom Center:257,254 CT#Base:106 +/- 5.1
    Pixel Size
    Expected(mm) X-Axis(mm) Y-Axis(mm)
    0.49 0.49
    0.49 0.49
    Phantom Rotation: -0.5 degrees
    Phantom Center is:0.49mm Right of center
    0.98mm Above of center
    CT# Linearity
    Contrast Scale: 0.000189
    Slice Thickness
    Expected(mm) X-Axis(mm) Y-Axis(mm)
    4.89 4.91
    4.88 4.95
    Avg Slice Width: 4.91 mm
    Table Position Offset: -1.39
    Vertical Angle: 0.2 degrees
    Horizontal Angle: 0.1 degrees

    Catphan® section CTP401 and CTP404.
  • CT Linearity (Sensitometry) - Mean CT values are calculated for each reference material in the phantom test section. The measured CT numbers for test materials are fit to the linear attenuation coefficients using a linear least squares for energies from 40 to 100 keV. The variance representing the lowest variance was designated as the scanner's effective energy. The linear attenuation coefficients for this effective energy are used to determine the contrast scale from the calculated linearity slope.
  • Slice Thickness - is determined from the average full-width at half-maximum (FWHM) of the CT number profile for each wire ramp. The expected slice width is compared with all four measured ramps values. A trigonometric conversion is calculated based on the known ramp angle to yield the slice width. This test provides information on the position of the phantom and the vertical and horizontal tilt values. A rotation of the phantom about an axis perpendicular to the ramps is also computed. Since there are two pairs of ramps orientated along the orthogonal directions, phantom rotations about both the vertical and horizontal axes can be estimated.

  • Spatial Resolution
    Critical Frequencies (cy/cm)
    50% 4.64
    10% 7.54
    2% 9.12

  • Localizer and Table Incrementation Accuracy - can be evaluated from the slice width section when the ramps are paired at opposing angles. The slice width test outputs a parameter called Table Position Offset, which is an offset in the z-axis relative to the center of the opposing wire (or test section). Verification of the scanner table incrementation accuracy can be checked by incrementing the table by 30 mm and then returning the table to the starting position and scanning the slice width module. The reported table position offset values should be the same.
  • Spatial Resolution (MTF) - The modulation transfer function (MTF) is calculated from the discrete Fourier transform of the average vertical and horizontal LSF's of the point spread function from the bead or wire test section. The program reports the 50%, 10% and 2% MTF cutoff values.
  • Noise and Mean CT Number - is calculated from several regions of interest (ROI) positioned over a water/uniformity phantom section. The number, size and location of these ROI's are variable, but typically five are defined: one at the phantom center and the other four along the axes at the same radius covering a 15 x 15 pixel area.
  • Uniformity - Vertical and horizontal profiles 10 pixels wide are generated and averaged through the phantom's center. The fractional uniformity of the profile is calculated as the percentage of the pixels within an acceptable

  • Noise
    Uniformity Index:
    Standard Deviation (H):

    range determined by + 2 times the central noise or + 10H, whichever is smaller.
  • Contrast Detail (Low Contrast Resolution) - Theoretical Contrast-Detail data is calculated based on the measured noise of the water/uniformity test section. Note: low contrast modules (CTP263 and CTP515) are not used in this measurement. This represents a conservative estimate of the minimum contrast level required such that a cylindrical object of a given diameter should be detected.


    The Catphan 600 bead module consists of 2 different sets of angled ramps containing small tungsten beads in a 40mm thick section. The first set consists of 2 pairs in opposing directions, one pair oriented horizontally and the other pair oriented vertically. This uses 0.34mm diameter beads with an "effective" separation of 1.0mm. The second set contains only a single pair of smaller beads (0.17mm diameter) oriented vertically with an "effective" separation of only 0.25mm. This type of test object allows the user to make a visual estimate of the actual slice thickness by counting the

    Phantom ID: 600 Series (Phantom lab) Orientation 1
    Phantom Center: 257,254 CT# Base: 106 +/- 5.1
    (Bead Ramp)
    Expected (mm)
    Measured (mm)
    0.75 1.17
    Average Slice Width: 0.96mm
    Table Position Offset: 1.94mm
    Vertical Angle: 1.6 degrees

    individual beads in the image and multiplying by the known separation. The beads at both ends of the set that are visualized in the image may be a much less intensity than the more centrally located beads in which case they might be only counted as ½. The AutoQA Lite program basically performs this visual assessment. However, since the data is processed quantitatively, it is possible to use some weighting scheme for the terminal beads to provide a more objective weighting factor. In addition, since the ramps are always used as opposing sets, it is also possible to perform additional calculations that would affect the quality of this test and the reliability and accuracy of the results. This includes: the axial offset of the center of this module with respect to the slice location and angular tilt of the phantom vertically and horizontally. Lastly, this module contains an off-centered wire as an impulse response source through the entire 40mm module thickness allowing for MTF measurements for each slice.


    CT AutoQA Lite provides two database options for storage of test results. "Monitor Database", is the first

    database option designated for constancy/monitoring and is linked to the Trend Analysis function. The 'Service Database' is the second data base option and is designed for more extensive service and/or acceptance testing data sets. If neither of these two options is appropriate, the user can select the option to not store results but only view results. The basic display of results is provided as a scrolling window, with a print "Test Results" function button. The Trend Analysis feature is available for Noise/Mean CT number, slice width, spatial resolution (MTF), and CT linearity measurements. The Trend Analysis function is linked to the monitor database files and follows guidelines for CT constancy testing established by the International Electrotechnical Commission (IEC) 1223-2-6 (Constancy tests - X-ray equipment for computed tomography, First Edition 1994-04).


    Minimum Requirements for Windows XP, CD drive

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