Lung Perfusion Imaging with Technetium-99m Macroaggregated Albumin should be Combined with Contrast-enhanced Echocardiography for the Diagnosis of Hepatopulmonary Syndrome

We have read with great interest the recent article by Alipour et al. (1) regarding the diagnosis of hepatopulmonary syndrome (HPS) with right-to-left (R-L) shunt in cirrhotic patients using the technetium-99m macroaggregated albumin (Tc-99m MAA) lung perfusion scintigraphy (LPS). The authors have found that LPS was more sensitive than contrast-enhanced echocardiography (CEE) for detecting intrapulmonary vascular dilatations (IPVDs) and concluded that Tc-99m MAA LPS can be used complementarily with other diagnostic methods in the assessment of HPS (1). However, we have some concerns regarding this work. The authors appraised the shunt fraction (SF) by using the formula SF=(geometric mean of brain counts)/(geometric mean of brain counts+geometric mean of lung counts), without dividing the geometric mean of brain counts ...