Intraarterial Hepatic SPECT/CT Imaging Using ^99mTc-Macroaggregated Albumin in Preparation for Radioembolization

Abstract

Current standard practice for radioembolization treatment planning makes use of nuclear medicine imaging (NMI) of 99m Tc-macroaggregated albumin ( 99m Tc-MAA) arterial distributions for the assessment of lung shunting and extrahepatic uptake. Our aim was to retrospectively compare NMI with mapping angiography in the detection and localization of extrahepatic 99m Tc-MAA and to evaluate the typical and atypical findings of NMI in association with catheter placement. Methods: One hundred seventy-four patients underwent diagnostic angiography in preparation for radioembolization. 99m Tc-MAA was administered to the liver via a microcatheter positioned in the desired hepatic artery. Planar scintigraphy imaging followed by SPECT/CT imaging was obtained within 2 h. All images were reviewed for hepatic and extrahepatic 99m Tc-MAA deposition and compared with the mapping angiogram. Results: Intrahepatic lobe shunting was present on NMI in only 2.9% of the cases but was present in 62.5% of the patients with portal vein thrombosis. Extrahepatic distributions included lungs (100%), the gallbladder (49%) if present, and locations involving hepaticoenteric arterial anatomy recognized on angiograms (16%). Free pertechnetate was identified on 38% of the nuclear medicine images. Three percent of nuclear medicine images showed alternative findings such as a thyroid nodule or metallic artifact. Conclusion: Patients being considered for radioembolization should undergo both angiography and scintigraphy for the assessment of hepaticoenteric arterial anatomy, hepatopulmonary shunting, and appropriate dosimetry considerations. Knowledge of the expected distribution of 99m Tc-MAA with normal variants and potential nontarget delivery to adjacent structures is critical in improving clinical outcomes. Cur rently, nuclear medicine imaging (NMI) of 99m Tc-labeled macroaggregated albumin ( 99m Tc-MAA) is performed routinely before radioembolization for the assessment of lung shunting and extrahepatic uptake. NMI is widely recognized to be important for minimizing the risk of potentially debilitating adverse events such as radiation-induced pneumonitis or radiation gastritis/duodenitis after radioembolization using 90 Y-microspheres for inoperable hepatic tumors (1,2). The seminal work in a canine liver model demonstrating the safety and feasibility of using 90 Y-microsphere therapy for hepatic malignancies was reported in the late 1980s. Human studies of 90 Y-microsphere therapy in liver applications followed from the late 1980s through the 1990s. These investigations established the safety of 90 Y for intrahepatic applications and the optimal dosimetry for tumor radiation kill, while minimizing exposure to normal liver tissue (3-8).Given the similarities in sizes of 90 Y-microspheres (20-40 mm) and 99m Tc-MAA (20-50 mm), the pattern of 99m Tc-MAA deposition as determined from a high-resolution SPECT/CT acquisition serves as a surrogate to demonstrate how 90 Y-microspheres will localize during treatment. Radioembolization has evolved for the ...

Safety and initial efficacy of radiation segmentectomy for the treatment of hepatic metastases​

“…Patients underwent pre-procedure mapping angiography utilizing cone beam CT (CBCT) with technetium macroaggregated albumin (MAA) SPECT fusion (23). Dosimetry varied based on tumor to normal liver uptake with an intended administered dose of 120 Gy or greater to the targeted angiosome.…”

Current Status and Future Direction of Hepatic Radioembolisation

“…The distribution of microspheres is mainly determined by catheter position, vascular anatomy and blood flow dynamics. Thus, prior to the actual treatment, a simulation angiography is carried out using a surrogate for 90 Y-microspheres in the form of gamma-radiation-emitting technetium-99m ( 99m Tc) macroaggregated albumin (MAA) (multiple suppliers available; AE150 MBq) [22]. For the simulation of 166 Ho radioembolisation, a small amount of actual 166 Ho-microspheres (QuiremScoutÒ; Terumo, Tokyo, Japan; AE250 MBq; AE2e3 million microspheres) can be used instead of 99m Tc-MAA.…”

The increasing potential of nuclear medicine imaging for the evaluation and reduction of normal tissue toxicity from radiation treatments

“…Before SIRT with 90 Y-labelled resin microspheres, the treatment is often planned with an intraarterial hepatic SPECT/CT using [ 99m Tc]Tc-macroaggregated albumin (MAA), aggregates of human serum albumin around 20-50 μm in size, to assess biodistribution and screen extrahepatic deposition, which often can occur in the lungs [74]. After administration of the microspheres, a 90 Y PET scan can also be made to accurately determine dose deposition in the tumour and other regions [75,76].…”