New Imaging Technique Could Measure Absorbed Dose from Radiation Therapy

Patients with cancer that has spread to the bone are sometimes treated with alpha particle radiation therapy that is delivered into or very close to the tumor. However, it is unknown whether the radioactive particles are distributed through the surrounding region or to the body’s vital organs, where they could have toxic effects. Now, researchers plan to measure this distribution using a novel imaging method with a four-year USD2.2 million grant from the National Institutes of Health (NIH, Bethesda, MD, USA).

Using a novel low-count quantitative single photon emission computed tomography (LC-QSPECT), researchers at Washington University in St. Louis (St. Louis, MO, USA) plan to build a computational framework from which to measure the concentration of the radiopharmaceutical material. Scans with this technology will allow the team to measure the concentration of the radiopharmaceutical activity in the tumor and the various radio-sensitive organs of the body. SPECT imaging could provide a mechanism to see where the drug has gone in the body. However, the challenge is that the number of counts detected with these treatments is very small. Conventional approaches that reconstruct the distribution of the isotopes and estimate the uptake from reconstructed images are not accurate at low count levels, so there is a need for new approaches to quantify the drug in a patient.

The approach that the team proposes stems from their previous research in which the researchers had found that a low-count quantitative single-photon emission computed tomography (LC-QSPECT) method provided reliable measurements of the radionuclide uptake. To validate this method, the team also plans a human trial in patients with metastatic prostate cancer who no longer responds to hormone therapy, or castrate resistant. The team has already done a computational clinical trial in a simulated patient population. The results showed that the method was yielding highly accurate and precise values of radionuclide organ uptake.

“Our eventual goal is clinical translation of this method so that it can benefit patients being treated with these therapies,” said Abhinav Jha, an assistant professor of biomedical engineering at the McKelvey School of Engineering and of radiology at the School of Medicine’s Mallinckrodt Institute of Radiology (MIR), both at Washington University in St. Louis. “There is much excitement surrounding this use of SPECT imaging for therapy. We are delighted to have the opportunity to contribute to this space.”

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