Positron Emission Tomography (PET)

We offer in vivo micro-PET study design, execution and data analysis across a broad spectrum of disease models and analytic techniques. Our imaging experts and disease area experts design and execute PET studies for maximal clinical relevance, statistical power, and throughput. Our PET studies are performed using a Siemens Inveon or R4 microPET scanner.

Positron emission tomography (PET) is a nuclear-medicine, imaging technique that generates 3D images of an injected PET radiotracer in the body. The most common PET radiotracers are biologic molecules that are labeled with radioisotopes such as 18-fluorine (18F). Radiotracer distribution is detected via emitted gamma photons resulting from positron–electron annihilation. These gamma photons are emitted at 180o to each other and detected by scintillation crystals. PET images are reconstructed by calculating the spatial origin of multiple coincidence events, based on the trajectories of the gamma photons.

PET imaging in the preclinical setting (micro-PET) is increasingly being used in drug discovery to study tumor biology. As applications of micro-PET imaging in cancer models have increased, preclinical micro-PET equipment design and sensitivity have also improved, allowing higher resolution and throughput.

Micro-PET studies utilize the same radiotracers used in clinical PET, and provide the same versatility in imaging in vivo molecular and cellular function. Of the various PET isotopes available (18F, 13N, 11C, 64Cu, and 124I), the most commonly-used tracers utilize 18F. 18F-based radiotracers are particularly attractive because they have a longer half-life (~110 minutes) than other biologically-compatible PET isotopes. The most common 18F-based radiotracers can be used to image metabolism (18F-FDG), cellular proliferation (18F-FLT), and bone metabolism (18F-NaF) in both orthotopic and subcutaneous tumor models.

Capabilities and Applications

  • 18F-fluorodeoxyglucose (18F-FDG), a glucose analog, is the most common radiotracer and is used for assessment of tissue metabolism. As a measure of glucose utilization, 18F-FDG enters the cell via glucose transporters and is irreversibly trapped once it is phosphorylated. Since tumors generally have elevated metabolism, 18F-FDG can be used to characterize pre-treatment metabolic activity, serving as a benchmark to evaluate efficacy and response to therapy. Additionally, 18F-FDG has uses in other therapeutic areas including cardiology, inflammation (e.g. imaging acute inflammation in rheumatoid arthritis), and neurology.

    Our experience in using the preeminent, translatable PET tracer, 18F-FDG, across a broad panel of tumor models, enables us to optimize timing and uptake for imaging in a variety of treatment paradigms. Our work has led to clinical development decisions for a number of companies utilizing, or planning to utilize, FDG PET in clinical trials.

  • DNA synthesis can be quantified by imaging with 18F-FLT, the 18F-labelled nucleoside thymidine. After uptake, 18F-FLT is phosphorylated and trapped in proliferating cells. Though 18F-FLT is not incorporated into DNA during the timeframe of a typical PET study, it is a measure of thymidine uptake and phosphorylation. Based on increased tumor-based specificity of 18F-FLT uptake, signal-to-noise and signal-to-background ratios are improved for 18F-FLT, as compared to 18F-FDG. Therefore, 18F-FLT functions as a reliable biomarker for tumor proliferation. We have extensive experience with the use and optimization of 18F-FLT PET across a variety of tumor models.

  • Bone metabolism can be imaged using 18F-sodium fluoride (18F-NaF) through the rapid incorporation of NaF into bone. 18F-NaF is becoming increasingly, clinically relevant in bone disease indications. Increased bone metabolism is an indicator of oncologic processes in the bone, both metastatic disease and de novo cancers. With its high signal-to-noise ratio and fast uptake times, 18F-NaF is an effective agent for high resolution bone scans in cancer and osteoporosis models.

  • We continually evaluate new radiotracers to address an even broader set of molecular and physiologic questions. Current areas of interest include hypoxia (18F-MISO, 18F-FAZA), apoptosis (18F-Annexin-V), and angiogenesis (18F-RGD). Contact us to discuss specific PET tracers.