Magphan® Quantitative Imaging Phantom (ADNI)
Precise, Comprehensive Measurement of 3d Spatial Distortion Quality Control
from inferior side
The ADNI (Alzheimer's Disease Neuroimaging Initiative) Magphan® phantom is used for detailed measurements of volume distortion in MR scanners.
The Magphan® Quantitative Imaging Phantom contains a total of 165 spheres made from polycarbonate plastic. These spheres are filled with copper sulfate and water solutions. The spheres are mounted on a series of polycarbonate plates and posts to maintain their fixed positions inside the phantom. The phantom includes one 6cm diameter sphere, four 3cm diameter spheres, two 1.5cm diameter spheres and one hundred fifty-eight 1cm spheres. Measurements of the phantom are compared with the known positions of the spheres to give an accurate measurement of the distortion of the scanner.
The 20cm ID housing is cast from a clear urethane material. The two halves of the sphere are sealed together with a threaded flange ring. The ring can be unthreaded if there is need to access the phantom’s interior.
The ADNI Magphan® was originally developed for General Electric's MR research facility. GE developed an algorithm to process phantom images to evaluate spatial characteristics of MR scanners. This method for MR spatial assessment was adopted for use in the ADNI project.
Image Owl, Inc., provides comprehensive data analysis, organization, and storage for users of the ADNI Magphan®. Image Owl software precisely measures, maps, and documents the volume stability or distortion. This service is purchased separately from the phantom. Please visit the Image Owl website at www.imageowl.com.
Scanning the PhantomThe Magphan® EMR051 phantom has a flat end enabling it to be placed on a shelf or table without rolling off. Because each coil is unique there is no standard method for positioning the phantom in a coil.
The established protocol for the ADNI study is to position the phantom's flat side on anterior and then rotate the phantom on the rounded fill port until the L, R (for left and right) and I, S (for inferior and superior) are in the correct position with regard to the patient table. Positioning pads or foam can be used to stabilize the phantom in the correct orientation.
Scans should be done following the patient protocols for which you are verifying the scanner's performance.
Initial Phantom SetupThe Magphan® EMR051 phantom is shipped with all spheres filled. Upon receipt of the phantom open the case, remove and discard the aluminum foil wrap and inspect the phantom to see that it is full of water.
After unpacking the phantom allow the phantom to reach room temperature, then remove the pressure expansion balloon screw from the top of the phantom. Top off the phantom with distilled water (the water may be approximately 1cm below the top) and insert the flat head screw with o-ring into the phantom. It is normal for the phantom's water level to be around 1cm below the top of the phantom. However, if the water level is more than 2cm below the top, the phantom has drained during shipment, in this case fill the phantom with distilled water and contact The Phantom Laboratory.
This phantom has 7 test planes (note 3 and 3b are made from multiple planes). The drawing below shows the different planes within the phantom. These are drawings with the layout of each plane.
WARNING
To avoid phantom damage
- This phantom should be stored at room temperature. Do not allow this phantom to be frozen or subjected to high heat. If this phantom is frozen the housing and spheres will be damaged beyond repair.
- Do not allow phantom to sit without water. If the phantom sits empty the contrast spheres will dry out and develop air bubbles and cracks. If for some reason the phantom is drained it should not be allowed to dry out and must be filled quickly.
- This phantom is not intended to be shipped from site to site. If you have to ship the phantom you must insert the pressure expansion balloon screw into the top of the phantom. If this is not installed the housing seal may release and the phantom will drain.