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Monday Case of the Day
Physics
Paul E Kinahan, PhD
Imaging Research Laboratory, Department of Radiology, University of Washington
History:
49 yr old male with suspicion of
cancer. FDG-PET images show
abnormally increased FDG uptake
on lung boundaries and spine
(horizontal arrows) and abnormally
decreased FDG uptake in
diaphragm region (vertical arrows).
Challenge: What are the potential
causes of the FDG abnormalities?
Coronal section of attenuationcorrected FDG-PET image
PET image (now in hot metal
color scale) overlaid on CT
image
Monday Physics Case of the Day Answers (1 of 3)
Paul E Kinahan, PhD
Imaging Research Laboratory, Department of Radiology, University of Washington
Answers: By comparing with the FDG-PET image without attenuation (which is not
quantitatively accurate but can be a useful secondary check) the abnormal
uptake regions are not evident, with the exception of a potential bone lesion
(black arrow).
Coronal section of attenuationcorrected FDG-PET image
PET image (now in hot metal
color scale) overlaid on CT
image
Coronal section of FDG-PET
image without attenuationcorrection
Monday Physics Case of the Day Answers (2 of 3)
Paul E Kinahan, PhD
Imaging Research Laboratory, Department of Radiology, University of Washington
1.
The lung & spine areas of increased uptake (horizontal arrows) are likely due
to a lateral shift of the patient that occurred between the CT and PET scans.
All PET/CT scanners use the CT images for attenuation correction of the PET
data, and since attenuation is the dominant effect in PET image quality, any
miss-alignment has the potential to introduce artifacts.
Coronal section of attenuationcorrected FDG-PET image
PET image (now in hot metal
color scale) overlaid on CT
image
Coronal section of FDG-PET
image without attenuationcorrection
Monday Physics Case of the Day Answers (3 of 3)
Paul E Kinahan, PhD
Imaging Research Laboratory, Department of Radiology, University of Washington
2.
The abnormally decreased FDG uptake in diaphragm region (vertical arrows)
is likely due to miss-allignment of the diaphragm due to respiratory motion
differences between the PET and CT scans as indicated by the horizontal
green lines. Again, since attenuation is the dominant effect in PET image
quality, any miss-alignment has the potential to introduce artifacts.
Coronal section of attenuationcorrected FDG-PET image
PET image (now in hot metal
color scale) overlaid on CT
image
Coronal section of FDG-PET
image without attenuationcorrection