title: Imaging discordance between hepatic angiography versus Tc-99m-MAA SPECT/CT: a case series, technical discussion and clinical implications.
abstract: During pre-therapy evaluation for yttrium-90 (Y-90) radioembolization, it is uncommon to find severe imaging discordance between hepatic angiography versus technetium-99m-macroaggregated albumin (Tc-99m-MAA) single photon emission computed tomography with integrated low-dose CT (SPECT/CT). The reasons for severe imaging discordance are unclear, and literature is scarce. We describe 3 patients with severe imaging discordance, whereby tumor angiographic contrast hypervascularity was markedly mismatched to the corresponding Tc-99m-MAA SPECT/CT, and its clinical impact. The incidence of severe imaging discordance at our institution was 4% (3 of 74 cases). We postulate that imaging discordance could be due to a combination of 3 factors: (1) different injection rates between soluble contrast molecules versus Tc-99m-MAA; (2) different arterial flow hemodynamics between soluble contrast molecules versus Tc-99m-MAA; (3) eccentric release position of Tc-99m-MAA due to microcatheter tip location, inadvertently selecting non-target microparticle trajectories. Tc-99m-MAA SPECT/CT more accurately represents hepatic microparticle biodistribution than soluble contrast hepatic angiography and should be a key criterion in patient selection for Y-90 radioembolization. Tc-99m-MAA SPECT/CT provides more information than planar scintigraphy to guide radiation planning and clinical decision making. Severe imaging discordance at pre-therapy evaluation is ominous and should be followed up by changes to the final vascular approach during Y-90 radioembolization.
authors.affiliation: Department of Nuclear Medicine and PET, Singapore General Hospital, Singapore 169608, Singapore. yung.h.kao@gmail.com
authors.forename: Yung Hsiang
authors.initials: YH
authors.lastname: Kao
authors.forename: Eik Hock
authors.initials: EH
authors.lastname: Tan
authors.forename: Terence Kiat Beng
authors.initials: TK
authors.lastname: Teo
authors.forename: Chee Eng
authors.initials: CE
authors.lastname: Ng
authors.forename: Soon Whatt
authors.initials: SW
authors.lastname: Goh
mesh_terms: D000369:Aged, 80 and over; D000792:Angiography / Q000379:methods*; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging*; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D049268:Positron-Emission Tomography; D013668:Technetium Tc 99m Aggregated Albumin; D014057:Tomography, X-Ray Computed
chemical_list: D013668:Technetium Tc 99m Aggregated Albumin