Cancer Imaging: Can PET Track Targeted Alpha Therapy?

What did the cancer imaging study actually show?

The study, published online on September 30 in the Journal of Nuclear Medicine, tested time-of-flight cascade gamma-ray imaging, or TOF-CGI. Researchers evaluated radioactive samples, clinical-size imaging models called phantoms, and one patient receiving actinium-225 PSMA-targeted treatment. The patient scan showed activity in a known tumor in the prostate bed. [Original research](https://pubmed.ncbi.nlm.nih.gov/42816123/).

In phantom experiments, detection efficiency was approximately ten times that of SPECT, another nuclear imaging technique. This measures how efficiently the system captures radioactive signals; it does not mean ten times better cancer detection or treatment. The patient images also had a higher signal-to-noise ratio than SPECT. These findings establish technical feasibility, while the single-patient design leaves diagnostic accuracy and clinical benefit unresolved. [Study results](https://pubmed.ncbi.nlm.nih.gov/42816123/).

How can PET scanners visualize targeted alpha therapy?

Standard PET imaging uses signals produced when positrons meet electrons. Actinium-225 primarily offers a different therapeutic tool: alpha particles, which deposit substantial energy over very short distances. TOF-CGI uses gamma-ray pairs produced further along its decay chain, combining their detection times and positions to estimate where emissions originated. This creates a way to study an alpha-emitting treatment with PET hardware. Berkeley Lab describes the approach as a new image-reconstruction method. [Berkeley Lab research announcement](https://newscenter.lbl.gov/2026/10/01/targeted-cancer-therapy-gets-a-sharper-focus/).

In targeted alpha therapy, a molecule carries the radioactive material toward particular tumor targets. The aim is concentrated radiation damage with less exposure elsewhere. However, targeting does not guarantee that healthy tissue escapes harm. The National Institute of Standards and Technology emphasizes that accurate radioactivity measurements are essential: excessive exposure can cause injury, while insufficient exposure may fail to treat the cancer adequately. [NIST explanation of actinium-225 dosing](https://www.nist.gov/news-events/news/2025/06/new-nist-standard-helps-deliver-right-dosage-cancer-fighting-drugs).

Could this technique help personalize cancer treatment?

The potential clinical value is understanding where a radioactive medicine goes after administration. Better distribution measurements could inform research into individualized radiation dosing. That is a prospective application, rather than an outcome established by this pilot. Berkeley Lab says future work will investigate other radioisotopes and scanners covering more of the body. [Planned research](https://newscenter.lbl.gov/2026/10/01/targeted-cancer-therapy-gets-a-sharper-focus/).

To establish clinical usefulness, subsequent studies would need to test reproducibility, measurement accuracy and whether imaging changes management in ways that benefit patients. Detecting radioactivity in a tumor alone does not establish that the tumor is shrinking or that survival will improve. Researchers must connect the imaging information to meaningful treatment outcomes.

Actinium-225 medicines also differ in the molecules used to direct them toward cancer. For example, an NCI-listed phase I study of an actinium-labeled antibody targeting CEA is investigating safety and dose selection. Results from one drug or imaging experiment cannot establish suitability across cancers. Patients considering these treatments need an oncology assessment specific to their tumor and the proposed medicine. [NCI clinical trial description](https://www.cancer.gov/research/participate/clinical-trials-search/v?id=NCI-2021-14101).