To the Editor
I read the article titled “Macroaggregated albumin (MAA) injected in hepatic artery visualized in a recanalized paraumbilical vein” by Gupta et al1 with great interest. Localization mechanism of 99mTc-MAA is related to the particle size of MAA (usually 30–50 μm), which is larger than the size of the capillary. When the particles infused into the hepatic artery, they distribute according to blood flow and are trapped on first pass in the arteriolar-capillary bed of the liver. Therefore, the 99mTc-MAA hepatic arterial scintigraphy can help to determine the possibility and amount of extrahepatic perfusion by intrahepatic infusion of 90Y microspheres, which gives rise to systemic toxicity.
The report by Hsieh et al,2 introduced on the interesting image, had demonstrated visualization of the portosystemic collateral circulation with 99mTc RBC scintigraphy and it is natural because of the localization mechanism of 99mTc RBC in blood vessels. The case report by Chernyak et al3 visualized focal tracer uptake at the abdominal wall with 99mTc-MAA scintigraphy. It might be possible by 99mTc-MAA accumulation in a small area of the abdominal wall by its possible blood supply from the patent hepatic falciform artery.
Owing to the localization mechanism of the 99mTc-MAA particle, the particles which arrived at paraumbilical vein should flow away to next arteriolar-capillary beds. Therefore, an uptake mechanism of the 99mTc-MAA at the recanalized large paraumbilical vein on the SPECT imaging of the interesting image is not obvious and hard to be conjectured. Readers of the interesting image might be more curious about the reason of MAA retention in the paraumbilical vein, and hopefully, it will be answered or suggested by the authors.
Byeong-Cheol Ahn, MD, PhD
Department of Nuclear Medicine
Kyungpook National University
School of Medicine and Hospital
Daegu, South Korea
1. Gupta A, Levitin A, Shrikanthan S. Macroaggregated albumin injected in hepatic artery visualized in a recanalized paraumbilical vein. Clin Nucl Med
. 2012; 37: 80–81.
2. Hsieh HJ, Lue KH, Kao CH, et al.. Portosystemic collateral circulation: demonstrated by Tc-99m-RBC SPECT/CT. Clin Nucl Med
. 2009; 34: 958–959.
3. Chernyak I, Bester L, Freund J, et al.. Anterior abdominal wall uptake in intrahepatic arterial brachytherapy with yttrium-90 sir spheres for hepatic malignancy. Clin Nucl Med
. 2008; 33: 677–680.