Identification of a shine-through artifact in the trachea with (124)I PET/CT.
The presence of (124)I in tissue near the trachea can cause a phenomenon that might be called shine-through. The effect is due to high-energy positrons that cross the air-filled trachea and annihilate at the opposite tracheal wall, incorrectly suggesting uptake at that location.


METHODS
We investigated shine-through using (124)I, (68)Ga, and (18)F PET/CT scans of a neck phantom. Additionally, we evaluated (124)I studies of 29 patients with differentiated thyroid cancer who underwent imaging for postsurgical staging.


RESULTS
In the phantom studies with a 0.1-mL (124)I source, the relative intensity of shine-through decreased from 7% to nearly zero when the thickness of the positron-stopping layer was increased from 0.3 to 3.85 mm. In patients, shine-through was observed in 5 of the 29 studies, with intensities between 0.7% and 14%.


CONCLUSIONS
Shine-through appears rather common in differentiated thyroid cancer. Recognition is important for identification of real lesions, calculation of uptake, and dosimetry.
Abdul-Fatah
Sakar B
SB
Department of Nuclear Medicine, Maastricht University Medical Center, Maastricht, The Netherlands.
Zamburlini
Mariangela
M
Halders
Servé G E A
SG
Brans
Boudewijn
B
Teule
Gerrit J J
GJ
Kemerink
Gerrit J
GJ
D016477:Artifacts; D006801:Humans; D007457:Iodine Radioisotopes; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000379:methods*; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014132:Trachea / Q000000981:diagnostic imaging*
D007457:Iodine Radioisotopes