ARRS 2022 Abstracts

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E2045. Utilization of SPECT-CT in Yttrium-90 Radioembolization: Case-Based Multimodality Pictorial Review and Its Impact on Patient Management
Authors
  1. Pokhraj Suthar; Rush University Medical Center
  2. Sumeet Virmani; Rush University Medical Center
Background
Transarterial radio embolization (TARE), also called selective internal radiation therapy, using yttrium-90 (Y90)-labeled microspheres is one of several locoregional treatment options for treating nonresectable primary or metastatic liver tumors. Pretherapy SPECT-CT using 99mTc-MAA is now routinely performed to evaluate extrahepatic particle deposition and to quantify shunting of tracer to the lungs. Portal hypertension, tumor-induced angiogenesis, and occasionally accessory arteries are a few main causes for extrahepatic shunting. The lung is the most common organ for extrahepatic shunting, which necessitates calculation of lung shunt fraction. Nontarget embolization of extrahepatic tissue can lead to complications, increasing morbidity and mortality. This case-based pictorial review focuses on the spectrum of characteristic findings on both pretherapy and follow-up post-therapy Y90 bremsstrahlung SPECT-CT imaging and its impact on patient management.

Educational Goals / Teaching Points
The goals of this exhibit are to learn normal biodistribution of 99mTc-MAA mapping study for Y90 radioembolization therapy planning; know the spectrum of extrahepatic uptake of 99mTc -MAA performed for Y90 radioembolization therapy planning; calculate lung shunt fraction; and know the normal biodistribution of post-therapy Y90 bremsstrahlung SPECT-CT imaging. This exhibit also reviews the utility of SPECT-CT in diagnosing extrahepatic shunting as compared to planar imaging and diagnosing interim incidental CT findings.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
This case-based pictorial review (15 interesting cases) highlights the normal biodistribution and abnormal extra hepatic uptake of 99mTc-MAA on pretherapy SPECT CT and follow-up post-therapy Y90 bremsstrahlung SPECT CT imaging. This includes abnormal extra hepatic uptake in the lungs, gallbladder, distal common bile duct, distal esophagus, stomach, duodenum, small and large bowel, spleen, myocardium, recanalized umbilical vein, perigastric varices, splenic vein, and portal lymph nodes. Incidental visualization of tracer uptake in the salivary glands, thyroid glands, and kidneys caused by detagged 99mTc, often as a result of delayed imaging, is also discussed. Apart from demonstrating extra hepatic uptake, SPECT-CT also helps to diagnose incidental interim CT findings like pneumonia, pneumobilia, pneumoperitoneum, aortic aneurysm/dissections, and vertebral compression fractures.

Conclusion
SPECT-CT images in addition to the planar imaging should be acquired on all pre-therapy mapping studies and post-therapy bremsstrahlung imaging when available. This pictorial review highlights the clinical importance and utility of SPECT-CT and its direct impact on patient management, benefiting both the patient and interventional radiologist.