Planar scintigraphy and SPET with Tc-99(m)-HMPAO-labelled leukocytes in patients with median sternotomy: Normal patterns

The aim of this study was to determine the normal planar and SPET patterns of the thoracic distribution of Tc-99(m)-hexamethylpropylene amine oxime (T c-99(m)-HMPAO) in 20 patients who had undergone a previous median sternotom y and without infectious complications at follow-up. The study included ant erior and oblique anterior planar views at 4 and 20 h. SPET of the cl lest was also carried out at 4 and 20 h. At 4 h, the planar views showed low bac kground vascular activity in the lungs and cardiac region in addition to th e sternal uptake, which showed two patterns: homogeneous in five patients a nd heterogeneous in 15. A long and narrow defect of uptake along the sterna l midline was the most characteristic finding. At 4 h, in addition to the b ackground vascular activity in the lungs and cardiac region, the greatest u ptake on SPET was in the sternum anteriorly and the marrow spine posteriorl y without any focal uptake, allowing visualization of the mediastinum free of focal activity. At 20 h, both the planar and SPET images showed a higher organ-to-background ratio. Knowledge of these post-surgical patterns will make it easier to interpret planar and SPET images when Tc-99(m)-HMPAO-labe lled leukocytes are used in the diagnosis of mediastinitis and sternal infe ctions in patients who had previously undergone median sternotomy. Planar v iews were better for the asessment of sternal uptake, but SPET views were b etter for the direct visualization of the mediastinum by eliminating overla pping sternal uptake. ((C) 1999 Lippincott Williams & Wilkins).