Alignment

The alignment statistics indicate how the phantom is aligned in the X, Y, and Z axes. Excessive misalignment may affect some of the analytical measurements.

The alignment statistics are calculated as follows:

The four 0.5mm diameter aluminum beads shown in the image are located in X, Y, and Z directions. The precise center is located using a sinc interpolation in all three axes and then taking the center of half-max measurements on a smoothed curve of the signal intensity.

Figure 9.1: Maximum Intensity Image showing the location of the Aluminum beads used for alignment.

Refer to the bead numbers in the drawing

Yaw

• xYaw = (Bead3X [pixels]- Bead2X [pixels])*X Pixel Spacing [mm/pixel]
• yYaw = (Bead3Y (pixels)- Bead2Y [pixels]*Y Pixel Spacing [mm/pixel]
• Yaw = tan^-1(xYaw /yYaw)

Pitch

• zPitch = (Bead1Z [slices]-Bead4Z [slices] * Measured Slice Thickness [mm/slice]
• xPitch = (Bead1X [pixels]- Bead4X [pixels])*X Pixel Spacing [mm/pixel]
• Pitch = tan^-1(zPitch /xPitch )

Roll

• zRoll= ((Bead3Z [slices]-Bead2Z [slices] * Measured Slice Thickness [mm/slice]
• yRoll= (Bead3Y [pixels]- Bead2Y [pixels]*Y Pixel Spacing [mm/pixel]
• Roll = tan^-1(zRoll /yRoll )