Utilizing ¹⁸F-FDG PET/CT Imaging and Quantitative Histology to Measure Dynamic Changes in the Glucose Metabolism in Mouse Models of Lung Cancer

This method can help answer key questions in the fields of cancer metabolism and cancer therapeutics. Such as the identification of novel therapies that can modulate tumor growth, as well as tumor metabolism. The main advantage of this technique is that we can perform non invasive imaging of lung tumors as they develop over time.

This is important because we can better understand how tumor metabolism responds to various therapeutic interventions in real time. Demonstrating these procedures will be imaging scientist, From the Crump Institute's Preclinical Imaging Center. Caution:use protective equipment and follow all applicable regulatory procedures when handling radioactivity.

Begin by warming the cage of mice to be imaged at 37 degrees Celsius for the hour prior to the fluorine 18 labeled fluoro-deoxyglucose injection. This reduces the brown fat consumption of the tracer. Weigh the first mouse and record its weight.

After anesthetizing the mouse using an institutionally-approved method, test the depth of anesthesia by pinching the toe. If no response is seen, continue the procedure by applying ophthalmic ointment to the eyes to prevent any dryness during the anesthesia. Carefully dilute fluorine 18 labeled fluoro-deoxyglucose which has a 109 minute radioactive half life, in sterile saline at an adjusted decay corrected injection concentration of 70 to 75 microcurie per 100 microliters.

Then draw 100 microliters into an insulin syringe with a 28-gauge needle and measure the radioactivity dose using a dose calibrator. Record the measurement and time of measurement to determine the decay correction. Place the syringe in a lead syringe holder.

To inject, first warm the tail for 1 to 2 minutes with a gauze soaked in warm water. And then wipe with 70%isopropanol to dilate the tail vein just prior to the injection. Administer the entire volume in the syringe with a bolus injection via the lateral tail vein.

And record the time of injection. Then measure the remaining dose in the syringe using the dose calibrator and record the measurement and time. Finally, place the injected mouse in an anesthesia chamber with 1.5 to 2%isoflurane at 37 degrees Celsius to allow the probe to be distributed via the mouse's systemic circulation for one hour prior to the PET scan.

After 1 hour, place the first mouse in an imaging chamber set at 37 degrees Celsius under nose cone isoflurane anesthesia. And secure its limbs in place with medical tape in a supine position. Place the imaging chamber in the PET CT scanner and acquire the PET and CT scans as described in the PET CT scanner manual.

After the PET CT is completed, remove the mouse from the imaging chamber and allow it to recover in its cage. Import the reconstructed PET CT images into AMOD software by clicking File, then Import File. And selecting the appropriate DICOM file.

Right click on the PET data set. And locate the percent injected dose per gram field on the basic info tab. Enter the percent injected dose per gram reported earlier.

Draw the regions of interest on the tumor and normal tissues by clicking on Edit and then Add ROI. Select the shape for the ROI and give the ROI a name. Draw ROIs over tumors and tissues and adjust their dimensions to cover the tissue of interest in all three axes.

Fluorine 18 labeled fluoro-deoxyglucose PET imaging was performed on mice bearing tumors with KRAS and LKB1 co-mutations referred to as KL mice. The tumors in these mice were highly glycolytic. As shown by an elevated F-FDG consumption.

In line with previously published studies. A resection of whole lungs revealed to the presence of several tumors, shown here in transverse, sagittal and coronal views. The five lobes of the mouse lung were stained with H&E to visualize the morphology of the tissue.

Lobes 1-5 were stained for glucose transporter 1. The expression and localization of Glut1 to the plasma membrane of tumor cells directly correlate with the standard uptake value for fluorine 18 labeled fluoro-deoxyglucose. When performing this procedure, it is important to remember that FDG bio-distribution is dependent upon animal handling conditions.

Such as anesthesia, warming and fasting. To ensure reproducibility, these steps must be performed consistently. Following this general procedure, other PET traces can be used to measure various biological processes in vivo, such as amino acid metabolism, and receptor-ligand interactions.