Description

Radioembolization using Y90 microspheres is a relatively new therapy option for patients with hepatocellular carcinoma (HCC) or other metastatic disease. This process requires the injection of radioactive beta-emitting spheres to delivery a targeted dose to the lesion resulting in cell death. With this technology comes many questions related to the safety and handling and usage of these products. This study will focus on three key aspects of dose delivery using these products.

The first aim will examine radiation exposure to staff that are involved in handling Y90 microspheres. Radiation exposure to employees has only been somewhat addressed with a recent publication in the European Journal of Nuclear Medicine. Although this work contained key information for assessing exposure, the methods used were characteristic of european clinics and do not mirror the typical workflows seen in North American facilities. In this study, we will use new dosimeter technology to examine radiation exposure to the hands and body of the following clinical personnel using both TheraSphere and SIR-Spheres technology:

• Nuclear medicine technologists: responsible for drawing up, transporting, and disposal of Y90 microspheres doses.
• Interventional radiologists: responsible for administration of Y90 microspheres doses

The second aim will examine the use of a modular and portable detector device to provide real-time monitoring of radiation fields surrounding the microsphere administration systems. With current workflows, the final confirmation of whether the full dose was delivered is not assessed until after the procedure is completed and residual vial activities measured. This work will examine if this type of device might be useful in providing a real-time determination of whether the prescribed Y90 microspheres dose was fully delivered to the patient. Detectors will be placed at points throughout the delivery system and data recorded before, during, and after the injection of Y90. Time activity curves will be generated and assessed to determine activity levels near the dose vial and through distribution lines as the dose is injected. We will use various analysis techniques to identify and characterize the injection to determine if a dose administration was successful prior to removing the patient from the procedure room.

The third aim will use a modular detector device as well as post-radioembolization PET/CT to examine leaching of free Y90 following injection of Y90 microspheres. Some degree of leaching is expected with any labeled product, however, the degree of leaching involved with Y90 microspheres in vivo has yet to be studied in any detail. This pilot study will use two techniques to assess the impact and degree of leaching during Y90 dose administration.

The first step will use the modular detector device used in aim two of this proposal to measure radioactivity before, during, and after the Y90 dose administration. Detectors will be placed near the patient skin surface in close proximity to the lesion(s) being treated, as well as location distal to the catheter location in other body areas, including the extremities. Time activity curves will be generated from the data collected which will enable analysis of on-target and off-target activity. This data may also be used to assess flow kinetics which may improve isolation of the cause or route of leached Y90 should it be found.

The second step will involve imaging the patients using PET/CT. Typical Y90 radioembolization focuses on only imaging the liver for assessment of dosimetry following the dose administration. In this study, we will acquire a longer axial PET/CT covering an anatomical range from the top of the head to the lower extremities. This is equivalent to a typical PET/CT protocol used in melanoma imaging. The CT used will be a low-dose CT used only for anatomical localization and PET attenuation correction while the PET acquisition will only use the on-board Y90 for imaging and will not add any additional patient dose.

Using these two methods, we hope to monitor and assess leaching both during and after Y90 radioembolization to determine key concerns, such as the following:

• The frequency of detectable levels of leaching
• Physical extent of leaching throughout the body
• Patient radiation dose estimates associated with the leaching phenomenon