24. How to verify ? Switch ON grid to check the Phantom Alignment
25.
26.
27. CUATION Once the phantom is centered and aligned DO NOT touch or move the phantom by hand Only move or align it by table movements
28. Test 1: LASER Accuracy Align the phantom to lasers by moving the table Align all the dots to X, Y and Z LASERS as precisely as possible Scan axially with minimum slice thickness If the Image is same as previous one then LASERS are perfectly aligned OTHERWISE !
30. Z-axis Misalignment Measure the distance between center of the phantom and center of the slice Multiple by 0.42 to find the z-axis misalignment 4.99 x 0.42 = 2.1 mm
31. X and Y Misalignment Switch ON grid and measure distance of the center of the grid to center of the image in X and Y direction and multiply by 0.42
32. X and Y Misalignment X = 4.61 x 0.42 1.9 mm Y = 3.26 x 0.42 1.4 mm
33. Test 2: Patient Alignment System Take Scanogram or Scout Take an axial Scan at the crosswire Measure the accuracy of the scan
34.
35.
36. Test 3: Circular Symmetry Take an axial Scan of the CTP 404 Image must be circular not elliptical Measure diameter of the phantom in X & Y Measure distance between Teflon pins Additionally angle accuracy can be verified
40. Test 4: Slice Width Accuracy Axially scan CTP 404 with different slice widths Measure slice with at (FWHM) Full Width at Half Maximum Slice Thickness = FWHM * 0.42