PET scan mis-alignment

This patient was scheduled for a PETCT with Diagnostic CT of the chest. The patient was positioned on the scanner, the tomogram was acquired followed by the whole body CT scan. Contrast was injected and the diagnostic CT of the chest was acquired. Even though the patient had used the rest room prior to the scan, she indicated she had to go again.

When the patient was repositioned on the scan table, a new topogram and whole body scan were entered into the original set-up (Siemens Biography 16, we copied and pasted the newer acquisition into the original acquisition page).

A new topogram and CT whole body were re-acquired followed by the whole body PET scan. The computer preformed the attenuation corrected image, with the above results, showing lack of data in the right half of the brain.

Review of the uncorrected data reveal that the data was good (below), which did not give any indication as to why right portion of the brain should be lacking in counts.

The study was re-processed manually using the second whole body CT data with the corrected results shown below. The image demonstrates complete uptake by the brain when compared with the first image.

The automatic processing selected the data from the first whole body CT acquired and not the second scan acquired prior to the PET scan. The differences in patient position from the first CT scan to the second CT scan is evident in the first set of PET processed data..