Extra cardiac activity detected on myocardial perfusion scintigraphy after intra-arterial injection of 99mTc-MIBI

Purpose: We present an unusual case of extra cardiac activity of (99m)Tc-MIBI in the left part of thorax and left upper extremity in a patient admitted for myocardial perfusion scintigraphy. Methods: A standard 2-day protocol of (99m)Tc-MIBI perfusion scintigraphies starting day 1 with stress (dipyridamol) imaging and followed by rest imaging day 2 was performed. Results: On day 2, when rest perfusion scintigraphy was carried out, extra cardiac activity was present in the left part of thorax and in the left upper extremity resulting in reduced accumulation of (99m)Tc-MIBI in cardiac tissue, prolongation of the study and interference of the extra cardiac activity with the cardiac image reconstructions. Whole-body scintigraphy disclosed an arterial flow distribution of activity to skeletal muscles in left shoulder and upper limb. Conclusion: Accidentally injected radiotracer retrogradely into the arterial system resulted in an unusual extra cardiac activity interfering with later image processing.