Same day yttrium-90 radioembolization with single photon emission computed tomography/computed tomography: An opportunity to improve care during the COVID-19 pandemic and beyond

Figure 1 Flow-chart during a same day planning and therapy session. Green: Time spent in the angiography suite; Pink: Time spent in the nuclear medicine department including for treatment planning; Purple: Time spent in periprocedural areas. COVID-19: Coronavirus disease 2019; Tc-99m MAA: Technetium-99m macroaggregated albumin; SPECT/CT: Single photon emission computed tomography/computed tomography; Y-90: Yttrium-90; RE: Radioembolization; CBCT: Cone beam computer tomography.

Figure 2 Spectral analysis of Technetium-99m macroaggregated albumin and yttrium-90 during the same-day session. A: Technetium-99m macroaggregated albumin (Tc-99m MAA) gamma-ray spectrum showing Compton scatter typical of Tc-99m MAA imaging of the liver. The 140 keV, 20% energy window is shown bracketing the 140 keV photopeak (red); B. Yttrium-90 (Y-90) bremsstrahlung exhibits a broad spectrum with no peaks other than the lead x-ray peak that originates in the collimator. Each point on the spectrum is a combination of original bremsstrahlung photons and Compton scatter from higher energy bremsstrahlung. If the only activity present is Y-90, the 108 keV, 32% energy window (blue) is used as it has a good combination of counts and contrast; C: If imaging of Y-90 bremsstrahlung is attempted with Tc-99m already present in the liver, the spectrum is a combination of both Tc-99m gamma-rays and Y-90 bremsstrahlung. A significant portion of the 108 keV, 32% energy window will be from scattered Tc-99m gamma-rays and will not accurately represent the distribution of Y-90 microspheres. A 22% energy window centered at 180 keV (green), however, can be used to demonstrate the activity of Y-90 microspheres without significant contribution from Tc-99m MAA delivered earlier in the day. Tc: Technetium.

Figure 3 Patient with bilobar metastatic breast cancer to the liver. Technetium-99m macroaggregated albumin (Tc-99m MAA) was injected in a split dose fashion to right and left hepatic artery. A: Tc-99m MAA single photon emission computed tomography/computed tomography (SPECT/CT) planning images, using a 140 keV, 20% energy window; B: Bremsstrahlung SPECT/CT images after administration yttrium-90 (Y-90) particles, using a 108 keV, 32% energy window. This results in an image which includes activity from both the previously administered Tc-99m MAA and Y-90 particles, obscuring evaluation; C: Bremsstrahlung SPECT/CT with a 180 keV, 22% energy window which results in adequate filtration of Tc-99m MAA activity and accurate assessment of Y-90 microsphere distribution.

Figure 4 65 year old female with cirrhosis and a segment 6 hepatocellular carcinoma measuring 2. 1 cm. A: Angiography demonstrates a vascular tumor supplied by the posterior division right hepatic artery; B: Single photon emission computed tomography/computed tomography (SPECT/CT) after Technetium-99m macroaggregated albumin administration demonstrates adequate tumoral coverage; C: Post yttrium-90 (Y-90) bremsstrahlung SPECT/CT confirms adequate treatment with Y-90 particles; D: Pretreatment magnetic resonance imaging (MRI); E: Post-treatment MRI 4 wk after Y-90 RE demonstrating successful treatment.

Figure 5 Ovarian cancer treated with a posterior right lobe infusion. A: Computed tomography (CT) scan of a 65 year old female with ovarian cancer and a centrally necrotic metastatic lesion centered within segment 7; B: Procedural cone beam prior to Technetium-99m macroaggregated albumin (Tc-99m MAA) administration demonstrates tumoral supply from the posterior division of the right hepatic artery; C: single photon emission computed tomography (SPECT) /CT after Tc-99m MAA administration confirms dominant arterial supply of the tumor and a necrotic central portion; D and E: Adequate coverage with Y-90 particles confirmed by post-treatment bremsstrahlung SPECT/CT.