DESCRIPTION
Myocardial perfusion studies with Tc-99m sestamibi (MIBI) are routinely performed to evaluate patients with ischaemic heart disease. However, this tracer is not specific for myocardium and is known to concentrate in tumours and inflamed tissue. A 55-year-old male patient without known coronary risk factors was subjected to gated myocardial perfusion single photon emission computed tomography (G-SPECT) imaging in view of baseline ECG changes to rule out inducible ischaemia. The final output in the form of a bull’s eye display of perfusion and wall thickening of the heart (fig 1A) and reconstructed images (fig 1B) revealed a focus of intense tracer uptake in the anteroseptal region of the heart that paradoxically showed reduced wall thickening (fig 1A). Raw images analysis revealed an intense chest wall focus distant from heart activity (fig 2). Clinically, there was a firm palpable, immobile and non-tender 2×3 cm swelling at the corresponding site. As the swelling was asymptomatic, the patient had ignored it for 4 months. A chest roentgenogram showed soft tissue opacity in the chest wall in the left lateral view (fig 3A). A regional CT scan showed chest wall swelling involving the underlying rib (fig 3B). A biopsy from the lesion revealed features of metastatic carcinoma of the thyroid.
Figure 1.
Standard bull’s eye display of gated myocardial perfusion single photon emission computed tomography (G-SPECT) shows an area of intense tracer uptake in the anteroseptal region (A). The reconstructed short axis (B, top row), vertical long axis (B, middle row) and horizontal long axis (B, lower row) corroborated the findings of a hot spot in the anteroseptal region.
Figure 2.
Anterior and left lateral thoracic planar views showing a Tc-99m MIBI avid focus in the chest wall distant from cardiac activity. This focus corresponded to the anterior chest wall tumour, a metastasis from carcinoma of the thyroid.
Figure 3.
Left lateral chest radiogram shows a soft tissue opacity corresponding to the site of palpable swelling (A); CECT of the thorax confirms the location of the chest wall swelling and also shows underlying rib involvement (B).
Abnormal extracardiac Tc-99m MIBI uptake has been reported in approximately 1.7% of cases.1 Pathological extracardiac uptake of Tc-99m tetrofosmin, a compound similar to Tc-99m MIBI, has been reported previously.2 This case highlights the importance of surveying raw images that may reveal clinically significant findings which could be missed if only final processed images are reviewed.
Footnotes
Competing interests: none.
Patient consent: Patient/guardian consent was obtained for publication.
REFERENCES
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