Guillem Pratx

Job Description

The Physical Oncology Laboratory investigates how novel physical approaches can solve longstanding problems in oncology. For instance, they use single-cell radionuclide imaging to measure the uptake of clinical PET tracers in heterogeneous cell populations and thus derive a biological interpretation of PET scans that accounts for factors such as cell diversity, microenvironmental factors and cell metabolism. They are also working to develop methods capable of tracking cell migration in vivo at the whole body level. Finally, they are involved in research to elucidate the radiochemical underpinnings of ultra-high dose rate (FLASH) radiotherapy. Prof. Pratx was named a Damon Runyon Innovator and a Society of Nuclear Medicine Young Investigator. He has published over 90 papers and been principal investigator on grants from the NIH, DoD and CIRM.

Whole-body cell tracking using CellGPS

We are building new methods for tracking moving cells anywhere in the body of living subjects. The technique, which is called CellGPS, uses positron emission tomography (PET) to non-invasively measure the 3D position of individual cells as a function of time, and is being applied to study how cells navigate the body’s circulatory system. The general methodology can be applied to understand the efficacy of cell-based therapies, including cancer immunotherapy and regenerative medicine, or to study biological processes involving cell migration, such as developmental biology or cancer metastasis. This project blends disciplines such as imaging physics, algorithm development, radiochemistry, and biomedical applications.

Microphysiological models for nuclear medicine

Microphysiological tumor models (μPTMs) are miniature tumors derived from patient tissues that recapitulate the essential hallmarks of solid tumors. We are developing novel approaches to probe these models using clinical radiotracers at an unprecedented level of spatial resolution. This work is based on the development of radioluminescence microscopy, a method that was pioneered here at Stanford and that can image radionuclide-labeled molecules in a standard microscopy environment, down to the level of single cells.  Using this new workflow, we are able to incorporate translational imaging endpoints in pre-clinical organoid studies, which brides the gap between in vitro research and clinical trials.

FLASH radiotherapy

Radiation therapy is highly effective in many different cancers. However, the adverse effects of the treatment on healthy organs near the tumor remain a concern. In this context,  “FLASH” radiation, which delivers the treatment in the blink of an eye, is being investigated for its ability to spare normal tissues with no concomitant decrease in tumor control. The Physical Oncology Lab participates in ongoing efforts at Stanford to develop, apply and investigate FLASH radiotherapy. Specifically, we are interested in elucidating the role of oxygen as a potential sparing mechanism. In these studies, both theoretical and experimental models are used to tease out the relative contribution of different factors to radiation responses. These studies provide a greater mechanistic understanding of the FLASH effect critical for clinical translation in humans.

Microfluidics assays for oncology

Our research uses microfluidics technology precisely manipulate small volumes of reagents and cells for “lab-on-a-chip” assays. We have developed a number of different systems, including a single-cell radiotracer uptake assay (known as flow radiocytometry), a cell uptake kinetic assay, and a novel approach based on mechanoporation to label cells with a radiolabel for in vivo tracking studies.