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Medical: Printed 2D phantoms with traceable activity for autoradiography calibrations
Summary
To support the development of radiopharmaceuticals based on alpha-emitting radionuclides, improved calibrations for high-resolution digital autoradiography systems are needed. Using advanced drop-on-demand inkjet metrology techniques, our team has prepared two-dimensional calibration phantoms with activity (SI unit Bq) directly traceable to primary standards.
This project grew out of the radioactive inkjet metrology program that was initially developed in support of TrueBq. Our team pulls expertise from the MML and PML at NIST and involves collaboration with researchers at the University of Wisconsin.
Description
Digital autoradiography image acquired with an ionizing radiation quantum imaging detector (iQID) at the University of Wisconsin. The image shows a series of lines printed at NIST with an 225Ac solution. The closest lines are approximately 250 μm apart.
Exciting advances in precision cancer therapy use chemical targeting to deliver alpha-emitting radionuclides to tumor sites. There, the high energy and short range of alpha particles means the tumor is killed while neighboring healthy tissue is spared. This is targeted alpha therapy (TAT). While the short range (typically < 1mm) is a big advantage for precision therapy, it presents a challenge when trying to use imaging to draw a map of the biodistribution of a radiopharmaceutical for dose planning or evaluation. The spatial resolution of state-of-the-art medical imaging modalities is insufficient to characterize biodistribution at the relevant length scales for TAT.
In preclinical studies and in pathology, the biodistribution of TAT radiopharmaceuticals can be imaged directly in tissue slices < 20 μm thick using digital autoradiography. In our laboratories, we are developing the first test objects (phantoms) that will allow the absolute calibration of autoradiography systems with direct traceability to primary standards for activity. We are advancing drop-on-demand inkjet techniques to create phantoms with radioactive material deposited in precise patterns with dimensions that are relevant to TAT and that push the limits of performance for autoradiography systems.