Brain SPECT artifacts in patients having metallic cranioplasty.

OBJECTIVE Over the past few years, we have performed several brain SPECT studies on patients who have had previous head trauma that required metallic cranioplasty. Transaxial images showed clearly defined photon-deficient areas extending from the brain tissue into the area of the scalp. To investigate the extent and pattern of this type of artifact, SPECT brain phantom studies were performed and compared with the patient studies. METHODS SPECT brain phantom studies were performed using various metallic sheets to simulate metallic plates that were used for cranioplasty. RESULTS Phantom studies using lead to represent tantalum plates were similar to our patient studies; that is, the photon-deficient area in normal brain tissue extended into the area where normal scalp activity would be. There was also increased tracer activity at the periphery of the photon-deficient area that extended to where normal scalp activity would be. This was similar to the patient studies and was not present on the phantom studies done without any metallic sheets present. CONCLUSION One would expect photon-deficient artifacts caused by radiopaque metallic plates in brain SPECT studies. The patient and phantom studies demonstrate that an increased tracer activity artifact is also present at the periphery of the photon-deficient area that extends into the area of the scalp. Knowing the appearance of this type of artifact caused by radiopaque metallic plates in brain SPECT studies could be beneficial, especially in cases with poor patient history and lacking radiographic correlation.