Revision History


If appropriate, planar and/or SPECT phantom images must be obtained and submitted for review using the phantom that has been approved by the ACR Committee on Nuclear Medicine Accreditation.


Some unit manufacturers provide this phantom with the purchase of nuclear medicine units. If you currently have a phantom that meets the specifications outlined below (with or without flange), we recommend that you contact the manufacturer to make sure all joints, O-rings, and seals are still intact. If the phantom has not been drained and allowed to dry before storage it may have deteriorated.


The ACR-approved SPECT phantom is commonly used for quality control in nuclear medicine. For cameras that are used to perform planar and SPECT imaging studies, an ACR-approved phantom must be used for evaluating planar and tomographic image quality. The phantom is a cylinder with an internal diameter of 20.4 cm (flangeless phantom). The lower portion of the phantom contains 6 sets of acrylic rods arranged in a pie-shaped pattern with the following diameters: 4.8, 6.4, 7.9, 9.5, 11.1, and 12.7 mm. The upper section contains six solid spheres with the following diameters: 9.5, 12.7, 15.9, 19.1, 25.4, and 31.8 mm.


The ACR has also approved a Data Spectrum small SPECT Phantom. The phantom is a cylinder with an internal diameter of 14 cm (flangeless phantom). The lower portion of the phantom contains 6 sets of acrylic rods arranged in a pie-shaped pattern with the following diameters: 4.8, 6.4, 7.9, 9.5, 11.1, and 12.7 mm. The upper section contains six solid spheres with the following diameters: 6.4, 9.5, 12.7, 15.9, 19.1, and 25.4 mm.


Cameras that can use Small SPECT phantom: D-SPECT, GE 530c, GE 570c, CardiArc, maiCam, C!, P3000, ClearVision, Digirad 3XPO

Optional (can use either): c.cam, CardioMD, Ventri


The following are available directly from Data Spectrum of Durham, NC (order forms are available on the ACR website for both the large phantom and small phantom):

  • Jaszczak Deluxe Flangeless ECT phantom and PET faceplate (can be used for both SPECT and PET acquisitions): $2689

  • Jaszczak Deluxe Flangeless ECT phantom (for SPECT only): $1613

  • Small SPECT Phantom (for SPECT only): $1392

  • Flangeless PET phantom (for PET only): $2150

  • PET faceplate made to fit an existing flangeless or flanged Jaszczak Deluxe ECT phantom: $1079


One set of Site Scanning Data Forms, along with all pertinent worksheets, should be completed for each camera system that is undergoing accreditation.

  

Phantom Requirements by Module

All Modules (Planar Only or SPECT with Planar): All applicants are required to submit a Tc-99m or Co-57 intrinsic or system flood field image, as well as a Tl-201 and/or a Ga-67/In-111 flood field image (if applicable). If both Tl-201 and Ga67/In-111 are currently used, planar uniformity and planar spatial resolution images are required for both isotopes.


Module 1 (Planar Imaging Only): If a unit performs only planar imaging and is only applying for accreditation in Module 1, Planar Imaging, the number and complexity of the tests you are asked to perform, evaluate and submit for review are different than those required for a unit that performs SPECT. You must provide images documenting the planar uniformity and spatial resolution of your camera detector(s).


If accreditation is requested for planar imaging only, intrinsic or system spatial resolution images must be submitted. The phantom for this data is the four-quadrant bar phantom that you should already own and use on a regular basis. The smallest bars must be between 2 and 3 mm. Planar images acquired with the ACR SPECT phantom are not required for applicants that are requesting accreditation for Module 1 only but are acceptable in lieu of the four-quadrant bar phantom.


The Planar Only Protocol should be followed for camera systems seeking only accreditation for the Planar Module. For systems with more than one detector (such as whole body scanners), images must be submitted for each detector.


For each of the tests, plan the sequence so that the minimum time is required. For example, if you are acquiring a system uniformity image using a fillable source, fill it with the shortest half-life isotope first (Tc-99m) and then with the longer half-life isotope (Tl-201 or Ga-67/In-111). Please note that if the additional isotopes include both Ga-67 and In-111, you only need one submission for Ga-67 or In-111. 


Planar Only Protocol

Acquisition One: Tc-99m (Preferred) or Co-57

Field Uniformity (Each Detector)

Spatial Resolution (Four-Quadrant Bar Phantom)

Set the acquisition for Tc-99m or Co-57 and acquire an intrinsic or system uniformity image (whichever is routinely used) using a 256 x 256 matrix. For large rectangular field cameras (longest dimension > 32 cm), acquire 10 million counts. For large and small circular detectors and small rectangular field cameras (longest dimension < 32 cm), 5 million counts are satisfactory.

Set the appropriate energy and acquire an intrinsic or system (whichever type is routinely used for quality control) spatial resolution pattern image using a 512 x 512 matrix (or the finest matrix that is available). For large rectangular field cameras (longest dimension > 32 cm), acquire 5 million counts. For large and small circular detectors and small rectangular field cameras (longest dimension < 32 cm), 3 million counts are satisfactory. (Tl-201 and Ga-67/In-111 are only required if used currently on the unit).

Acquisition Two: Tl-201

Field Uniformity (Each Detector)

Spatial Resolution (Four-Quadrant Bar Phantom)

Set the camera for T1-201 and acquire an intrinsic or system uniformity image (whichever is routinely used) as described above for Tc-99m. Use the clinical analyzer window(s) settings.

Set the energy window for T1-201 and acquire an intrinsic or system spatial resolution pattern image (whichever is routinely used) as described above for Tc-99m. Use the clinical analyzer window(s) settings.

Acquisition Three – Ga-67/In-111

Field Uniformity (Each Detector)

Spatial Resolution (Four-Quadrant Bar Phantom)

Set the camera for Ga-67 or In-111 and acquire an intrinsic or system uniformity image (whichever is routinely used) as described above for Tc-99m. Use the clinical analyzer window(s) settings.

Set the energy window for Ga-67 or In-111 and acquire an intrinsic or system spatial resolution pattern image (whichever is routinely used) as described above for Tc-99m. Use the clinical analyzer window(s) settings.

Planar Images for Submission

  • Submit only gray scale images.

  • Use linear mapping of the display with the lower threshold set at 0 (or ≤ 5% of the maximum upper level) and the upper threshold set to the maximum count.

  • All images should be appropriately labeled. Make sure Site Scanning Data forms are filled out completely.


Module 2 and/or 3 (SPECT with Planar): If your facility performs SPECT imaging and is applying for accreditation in SPECT Module or Nuclear Cardiology Module, you must perform, evaluate and submit planar and SPECT information for review. Most of the planar and SPECT data are obtained with the ACR-approved phantoms available from Data Spectrum. Submission of accreditation data from any other phantom without ACR permission will disqualify the site. The ACR-approved phantom is the Data Spectrum Deluxe flanged or flangeless phantom. The ACR-approved phantom was chosen for the evaluation of tomographic systems because it is relatively easy to fill and set up for a SPECT study and can be used to measure planar resolution and tomographic uniformity, spatial resolution, and contrast. The wide variety of elements for evaluating spatial resolution and contrast are sufficient to enable the user to see relatively subtle differences in system performance.


The recommended activity for the ACR approved phantom is 10- 20 mCi Tc-99m. The recommended activity for the small SPECT phantom is 5 - 15 mCi Tc99m. Lower quantities may be used but the imaging time will be proportionately longer. These activities are recommended to provide a good compromise between count rate limits, acquisition time, and cost.


For both phantoms, the spheres must be placed in order of increasing size (clockwise as viewed from the top) and the rod and sphere diameters must be the same as listed in the worksheets. In addition, the rods and the spheres should be lined up. The reviewers will use this information to properly score the images.


Acquire and process the best possible images on your system within the guidelines provided. All settings must be documented.


The ACR requires semiannual but strongly recommends quarterly testing of each SPECT system with the ACR-approved phantom described above, in addition to other QC tests.


For systems with more than one detector, planar images must be submitted for each detector. For cameras that are unable to acquire planar images (D-SPECT, GE Discovery 530, 570, 630, 710 & CardiArc), please proceed to SPECT Images below.


Sites are no longer required to submit SPECT phantom images utilizing T1201, Ga67, or In111. Sites performing SPECT imaging will still be required to submit Tc99m SPECT phantom images. Please note that if sites are utilizing Tl201, Ga67, and/or In111 for either planar or SPECT imaging, sites will still be required to submit both planar uniformity and planar spatial resolution images with these isotopes (see the Planar Only Protocol).


Planar Images Protocol

Acquisition One: Tc-99m or Co-57

Planar Field Uniformity (Each Detector)

Planar Spatial Resolution

Set the acquisition for Tc-99m or Co-57 and acquire an intrinsic or system uniformity image (whichever is routinely used) using a 256 x 256 matrix. For large rectangular field cameras (longest dimension > 32 cm), acquire 10 million counts. For large and small circular detectors and small rectangular field cameras (longest dimension < 32 cm), 5 million counts are satisfactory.



With ACR Phantom if SPECT Phantom to be acquired: Fill the phantom with an aqueous solution of Tc-99m, taking care to ensure that it is thoroughly mixed. It is advisable to perform the Tc-99m studies first, and then fill the phantom with T1-201 or Ga-67/In-111 after the Tc-99m has decayed. Place the bottom of the phantom (the flat bottom of the cylinder on the rod side) on top and in the center of the highest resolution low energy parallel hole collimator (LEHR collimator is preferred) that is used for the indicated radionuclide. The matrix size should be 256 x 256 and the count rate should not exceed 50 kcps. Set the acquisition for Tc-99m, no zoom, and acquire a 600,000 static image.

With Four-Quadrant Bar Phantom if SPECT not acquired: Set the appropriate energy and acquire an intrinsic or system (whichever type is routinely used for quality control) resolution pattern image using a 512 x 512 matrix (or the finest matrix that is available). For large rectangular field cameras (longest dimension > 32 cm), acquire 5 million counts. For large and small circular detectors and small rectangular field cameras (longest dimension < 32 cm), 3 million counts are satisfactory.

Planar Images for Submission

  • Submit only gray scale images.

  • Use linear mapping of the display with the lower threshold set at 0 (or ≤ 5% of the maximum upper level) and the upper threshold set to the maximum count.

  • All images should be appropriately labeled. Make sure the Site Scanning Data forms are filled out completely.



SPECT Images Protocol

  • QC Information: Center-of-rotation and flood uniformity calibrations are regularly performed on SPECT systems. Fill in the appropriate data fields based on the most recent calibrations.

  • The ACR phantom used for the SPECT tests must be described on the Site Scanning Data Forms.

  •  For more information, please see the ACR’s SPECT Phantom Video.

Acquisition One: Tc-99m

Positioning of ACR Phantom for Tomography:

Place the phantom on the patient support (bed, chair, etc) so that it is positioned lengthwise, corresponding to the primary patient axis. The phantom’s long axis must be parallel to the z-axis of the detector system with the phantom level and the uniformity section should be “head first” into the camera. Phantoms with flanges may require extra support for leveling. The phantom should be positioned in the center of the field of view of the detector(s), with the spheres placed in order of increasing size, clockwise as viewed from the top when a clockwise acquisition will be performed.


Note: For a single detector camera which is only capable of rotating thru 180 degrees, rather than a complete 360 degrees, special caution must be exercised in the orientation of the spheres. The phantom must be positioned so that the largest sphere is at the center of the 180-degree sweep for frame 1. If a Dual head, fixed 90 degrees detector configuration that only has a 180-degree acquisition arc is being tested, the largest sphere must be positioned in the center of the leading detector for frame one. Failure to follow these directions will produce images with poor contrast in the cold spheres.

Collimator: 

Use the highest resolution low-energy parallel hole collimator that is routinely used for clinical studies.

Acquisition:

  • Select the appropriate isotope and acquire a SPECT study with the window setting, orbit shape, and detector motion (step-and-shoot or continuous for rotating cameras) that is used clinically.

  • Total counts - For SPECT acquisitions the total count for the sum of all images (for all heads on multiple detector systems) should be approximately 32 million counts (based on counts in the first view) and 20 million counts for the Small SPECT phantom. A sample calculation is provided below.

  • Count rate should not exceed 50 kcps.

  • Use a 128 x 128 matrix regardless of which phantom is used. Acquire 120 (or 128) views over 360 degrees for rotating SPECT cameras. Cameras that do not rotate should use the angular sampling that is used clinically.

  • Radius of rotation should be as close as possible to 20 cm, if applicable, and the center of the phantom must be close to the axis-of-rotation so that the distance from the face of the collimator(s) to the phantom does not change significantly during rotation (except in the case of non-circular orbits). The small phantom should be placed at the optimal clinical imaging position for cameras that do not rotate around the patient.

  • For an acquisition matrix of 128 x128, pixel size should be near 2.7 to 3.3 mm. Some systems will require an acquisition zoom factor (up to a maximum of 1.6) to achieve the appropriate pixel size.

Reconstruction:

  • Sites should use the clinical filter they are currently using with parameters optimized for the ACR Phantom; however, sites may substitute the Butterworth filter that is available on most commercial systems. The filter and parameters must be documented on the site scanning data form.

  • Reconstruct the entire phantom with a slice thickness 0.6-0.9 cm by summing 2 or 3 slices. For most large FOV cameras, summing 2 slices will generate the appropriate thickness. Thickness, filter and attenuation coefficient values must be entered on the parameter sheet. Most sites will reconstruct the entire phantom with filtered-back-projection and a Butterworth or substitute filter.

  • For the Butterworth filter, suggested parameters = slope of 6 and cutoff of 0.55, which is optimal for many systems (for some vendors the cutoff will be close to 0.35); however, parameter values can be adjusted to optimize contrast of spheres and sharpness of smallest visible rods in the transaxial slices.

  • Apply the attenuation correction so that a profile across the phantom is essentially flat. For most cameras, the linear attenuation coefficient for Tc-99m is 0.11 to 0.12/cm. Use the uniform part of the phantom to define the boundary for attenuation correction.

SPECT Images for Submission

  • Submit images of transaxial slices (0.6 to 0.9 cm thick) on 2 or 3 pages Image size should be adjusted with the display zoom. Additionally, submit a composite of up to 12 summed images through the rod section. For the Small SPECT phantom, sum 5 images.

  • Submit only gray scale images.

  • Use linear mapping of the display with the lower threshold set at 0 (or ≤ 5% of the maximum upper level) and the upper threshold set to the maximum count.

  • All images should be appropriately labeled. Make sure Site Scanning Data forms are filled out completely.


Sample Calculation for SPECT Acquisition Time 

Calculation of the time per view to acquire approximately 32M counts in the SPECT study: If the system you are using shows the count rate prior to starting the SPECT acquisition, use the procedure given below. If the count rate is not shown, just prior to starting the SPECT study, acquire a planar acquisition for 10 seconds (be sure the imaging table is not between the detector you are using and the phantom) and divide by 10 to get the rate in counts per second. Example:


R = count rate in counts per second for one of the detectors

N = number of views (120 or 128, whichever is available or whichever you want to use if both are available)

T = time for the first view


Assume R = 28,000 counts per second. Assume N = 120 views.

Round time up to the next whole number if the fraction of a second is greater than 0.5. Round time down to the next whole number if the fraction of a second is less than 0.5.

If the system has two detectors, the total acquisition time will be approximately one-half of the time for a single detector system. If the system has three detectors, the total acquisition time will be approximately one-third of the time for a single detector system.


Evaluation of the Images Submitted 

Uniformity and noise are evaluated qualitatively by inspection of planar images and reconstructed tomographic sections. Optimal density ranges should be comparable to those used for clinical images. Planar spatial resolution is judged by identifying the smallest bars in a resolution phantom that can be visualized on cameras used for planar imaging only. For tomographic systems, the smallest “cold” rods in the ACR approved phantom are used. Collimator type (e.g. general purpose, high resolution) is considered in scoring the spatial resolution. The reconstructed transaxial slices containing the cold spheres are used to visually evaluate image contrast based on the amount of image blur and identifying the smallest “cold” sphere. As with the evaluation of spatial resolution, collimator type is considered when the score for contrast is determined.


Some cardiac SPECT systems cannot acquire a single set of projections over 360 degrees. For these systems, the phantom should be acquired with the maximum (128 or 64) allowable rotational steps for the standard rotational arc. For multi-head cameras, separate data sets for each head should not be submitted.



Revision History for this Article

Date

Section

Description of Revision(s)

12-12-19

All

Article created; FAQs incorporated; No criteria changes




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