Abstract
This paper overviews Yttrium-90 (90Y) as a theranostic and nuclear medicine imaging of 90Y radioactivity with bremsstrahlung imaging and positron emission tomography. In addition, detection and optical imaging of 90Y radioactivity using Cerenkov luminescence will also be reviewed. Methods and approaches for qualitative and quantitative 90Y imaging will be briefly discussed. Although challenges remain for 90Y imaging, continued clinical demand for predictive imaging response assessment and target/nontarget dosimetry will drive research and technical innovation to provide greater clinical utility of 90Y as a theranostic agent.
Highlights
Theranostics are agents that possess diagnostic and therapeutic attributes for personalized patient treatment for various diseases [1]
The rare-earth lanthanide, Yttrium-90 (90Y), is almost exclusively a high-energy beta-particle emitting radionuclide used for radiotherapy with a maximum particle energy of 2.28 MeV that allows for high dose deposition with an average and maximum soft tissue penetration of 2.5 mm and 11 mm, respectively [2, 3]. 90Y has a physical half-life of 64.1 h [4] which makes it amenable for a variety of targeted radiotherapy applications including 90Y-labeled colloid [5, 6], somatostatin-receptor targeting peptides [7, 8], tumortargeting antibodies [9, 10], and resin/glass microspheres for catheter-directed embolization of hepatic malignancy and metastases [3, 11,12,13]
Regardless of the targeted delivery agent used, the selection of 90Y and its use for radiotherapy are complex and necessitate close collaboration among various medical specialties including nuclear medicine, interventional radiology, medical oncology, and radiation medicine [14]. 90Y can be administered via direct injection into a space or cavity, intravenously for peptide receptor radionuclide therapy (PRRT) and radioimmunotherapy (RIT), and intra-arterially for radioembolization (RE) therapy
Summary
Theranostics are agents that possess diagnostic and therapeutic attributes for personalized patient treatment for various diseases [1]. Other therapeutic β− emitting radioisotopes (e.g., 131I for thyroid cancer [15] and Samarium-153 (153Sm) for osseous metastases [16]) produce discrete gamma photons which can be imaged after therapy but contribute to additional absorbed radiation dose. Because of the lack of gamma photons from 90Y, conventional scintigraphic imaging and assessment of the posttherapy distribution of its radioactivity are challenging. This lack of gamma photons led to the development and use of surrogate gamma-emitting radioisotopes (e.g., Indium-111- (111In-) labeled peptides and antibodies) with analogous chemical properties as a tracer for 90Y dosimetric assessment and pharmacokinetics [2, 17]. This review will subsequently discuss the different diagnostic imaging approaches used for therapeutic 90Y radioactivity assessment (Figure 1)
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