Liver and vertebral uptake of Tc-99m macroaggregated albumin (MAA)

Unexpected Vertebral Bodies Trapping of 99mTc-Macroaggregated Albumin During Lung Perfusion Scintigraphy in a Patient With Collateral Paravertebral Venous System

ABSTRACT

A 35-year-old woman was referred to our nuclear medicine center for a ventilation and perfusion (VQ) pulmonary scintigraphy to detect pulmonary embolism. She was treated with low-molecular-weight heparin following a proximal venous thrombosis of the right upper limb and had a previous history of an infiltrating ductal carcinoma of the right breast. Surprisingly, the VQ scintigraphy showed uptake of 99mTc-MAA in several superior vertebrae. A contrast-enhanced CT scan revealed a dilated collateral paravertebral venous system due to the deep vein thrombosis extended from superior vena cava to brachiocephalic trunk. 99mTc-MAA was trapped through the dilated vertebral venous system.

Superior Vena Cava Syndrome Induced Collateral Circulation on 99mTc-Macroaggregated Albumin Lung Perfusion Scintigraphy

Perfusion lung scintigraphy using SPECT/CT is one mainstay in diagnosing pulmonary embolism. Although typically almost all tracer will be accumulated in the lung capillaries, occasionally abnormal uptake can be detected. As superior vena cava syndrome leads to aberrant blood flow, tracer injected to an arm vein might partly circumvent the pulmonary capillary bed and accumulate in well-perfused anatomical structures. In this case, next to the commonly described liver enhancement, more prominent pseudo-uptake of various thoracic vertebrae was observable. However, a time-related FDG PET/CT demonstrated only the hepatic pseudo-uptake. Taken together, careful assessment of superior vena cava syndrome patient studies is highly recommended.

Perfusion Scintigraphy in Diagnosis and Management of Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a life-threatening complication of acute pulmonary embolism (PE). Because the treatment of CTEPH is markedly different from that of other types of pulmonary hypertension, lung ventilation-perfusion (V/Q) scintigraphy is recommended for the workup of patients with unexplained pulmonary hypertension. Lung V/Q scintigraphy is superior to CT pulmonary angiography for detecting CTEPH. Perfusion defect findings of CTEPH can be different from those of acute PE. Familiarity with the patterns of perfusion defects seen during the initial workup of CTEPH and the expected posttreatment changes seen at follow-up imaging is essential for accurate interpretation of V/Q scintigraphy findings. ^©RSNA, 2019.

Unexpected Hepatic Uptake of Tc-99m-MAA in Lung Perfusion Scintigraphy in a Patient with End-stage Renal Disease

Extra-pulmonary accumulation of Tc-99m-macroaggregated albumin (MAA) is described as uptake areas out of the lung in perfusion scintigraphy. If the particles spread throughout the body before reaching the lung via venous collaterals or due to right-to-left shunt, or if the particles are too small to occlude the pulmonary capillaries, then the agent can be seen at different locations of the body. Extra-pulmonary accumulation of Tc-99m-MAA can be detected mostly in the liver as well as in the brain, kidney, thyroid, myocardium, spleen and vertebra. Herein, we present lung scanning images with unexpected hepatic accumulation of Tc-99m-MAA. This pulmonary perfusion scintigraphy was performed in a patient with end-stage renal disease due to dyspnea in the post-operative period of kidney transplantation

Vertebral Uptake of Tc-99m Macroaggregated Albumin (MAA) with SPECT/CT Occurring in Superior Vena Cava Obstruction

A 67-year-old male presented with dyspnea for which lung scintigraphy was ordered to rule out pulmonary embolus. Planar images demonstrated abnormal midline uptake of Tc-99m macroaggregated albumin, which SPECT/CT localized to several thoracic vertebrae. Thoracic vertebral uptake on perfusion lung scintigraphy was previously described on planar imaging. Radionuclide venography and contrast-enhanced CT subsequently demonstrated superior vena cava (SVC) obstruction with collateralization through the azygous/hemiazygous system and vertebral venous plexus. SPECT/CT differentiated residual esophageal/tracheal ventilation activity, a clinically insignificant finding, from vertebral uptake indicative of SVC obstruction, a potentially life-threatening condition.

Unusual Visualization of the Ilium in Lower-Extremity Radionuclide Venography With 99mTc MAA

A 60-year-old man was admitted with dilated cardiomyopathy, right-sided heart failure, and massive ascites. Tc-labeled macroaggregated albumin radionuclide venography of the lower extremities was performed, which showed stagnated radioactivity in the heart chambers, decreased uptake in the lung, and increased uptake in the proximal main renal veins and hepatic vein. Unexpectedly, radioactive accumulation in the ilium was noted on subsequent images acquired 3 minutes later.

Focal Hepatic Activity During Ventilation-Perfusion Scintigraphy Due to Systemic-Portal Shunt Due to Superior Vena Cava Obstruction From Histoplasmosis-Induced Fibrosing Mediastinitis

A 59-year-old woman with a history of fibrosing mediastinitis secondary to histoplasmosis diagnosed on mediastinoscopy presented with dyspnea. A ventilation-perfusion scan demonstrated decreased perfusion to the entire right lung. In addition, the perfusion images demonstrated focal abnormal activity in part of the liver. On computed tomography of the chest, there was significant soft tissue opacification in the mediastinum occluding the right pulmonary artery, with passage of the injected contrast via collateral vessels to the liver. The main collateral pathway was via the right internal thoracic vein and the umbilical vein. Pulmonary angiography confirmed complete occlusion of the right pulmonary artery.

Uncommon findings in Tc-99m macroaggregated albumin venography in distal inferior vena cava obstruction

In inferior vena cava obstruction, collateral pathways allow the retrograde flow of venous blood from the lower part of the body. Unanticipated findings of Tc-99m macroaggregated albumin (MAA) venography in 3 cases with deep vein thrombosis of the legs and infrarenal inferior vena cava obstruction are presented. Apart from extensive collateral networks in the legs and the abdomen, the visualization of the liver indicates a shunt of the systemic venous blood flow through the paraumbilical vein to the portal vein. The visualization of lumbar and thoracic vertebrae is attributed to venous flow through a dilated vertebral plexus, resulting in trapping of tracer in the neighboring bone marrow.