A 46 year-old female had undergone regadenosan stress myocardial perfusion imaging with 99mTc Tetrofosmin.
What is the diagnosis?
A small defect of mild to moderate severity involving the apex and apicoanterior segments is noted which worsens on rest images.
In addition, here is an incidental finding of increased tracer uptake in the superior mediastinum which is suspicious for a hypermetabolic lesion.
In this the patient with myasthenia gravis, the lesion was an invasive thymoma, and this study was done for pre-surgical evaluation. 99mTc Tetrofosmin like 99mTc MIBI, localizes to tissues with a high number of mitochondria implying hypermetabolic/dividing cells.
The uptake of this tracer like 99mTc MIBI can be noted in various infectious/inflammatory or neoplastic conditions.
The differential diagnosis includes breast attenuation artifact in a female patient as attenuation correction was not applied. Also, there is worsening of the defect noted on rest images which further suggests that this is not a true defect and is, rather, due to an attenuation artifact.
The differential diagnosis for a superior/anterior mediastinal mass broadly includes thymoma, teratoma, and lymphoma.
It is always useful to evaluate the raw MIP images of myocardial perfusion imaging to identify incidental findings/uptake which can be of significant clinical relevance.
1.Hawkins M, Scarsbrook AF, Pavlitchouk S, Moore NR, Bradley KM. Detection of an occult thymoma on 99Tcm-Tetrofosmin myocardial scintigraphy. Br J Radiol. 2007 Apr;80(952):e72-4.
2. Chamarthy M, Travin MI. Altered biodistribution and incidental findings on myocardial perfusion imaging. Semin Nucl Med. 2010 Jul;40(4):257-70.