Quality Control for Artifacts Seen on Pinhole Thyroid Images and Caused by a Collimator Shielding Defect

Abstract

Objective: The purpose of this study was to investigate artifacts seen on several pinhole thyroid imaging studies at one of our institutions and to determine their cause.

Methods: The pinhole collimator was tested using radioactive point sources and a thyroid phantom to determine the presence and location of a suspected shielding defect and to confirm its subsequent repair. A 14-mo retrospective review of ^99mTc and ¹²³I pinhole thyroid imaging studies was performed.

Results: The point source and thyroid phantom studies confirmed the defect, its location and repair. The patient review revealed extra thyroidal activity in 38% of the studies. The artifacts evoked several misinterpretations, but none were of clinical significance.

Conclusion: Artifacts seen during patient studies were caused by a collimator shielding defect. Due to the lack of standardized quality control for pinhole collimators, point source testing is recommended for all new and existing pinhole collimators and after any suspected damage.