The overall goal of this procedure is to detect and quantify atherosclerotic plaque activity and vascular inflammation in medium and large human arteries. Start with a whole body, FDG, PET CT, scan and image the aorta and its major branches from the heart down to the feet. Then qualitatively analyze the images for presence of vascular inflammation using the registered CT scan.
Quantify the amount of radiotracer detected at each slice of the PET scan and localize regions of interest. Proceed to calculate the standard and novel outcomes that measure vascular inflammation. Ultimately, the results depict and quantify the burden of atherosclerosis in any given arterial region through the utilization of FDG PET CT with quantification.
FDG PET CT can help answer key questions in the vascular imaging field, such as how does therapy modulate plaque activity or how does vascular inflammation change over time in vivo? The implications also extend to diagnosis of subclinical atherosclerosis in vivo because current techniques do not allow for whole body real-time molecular imaging that can be used for response assessment purposes in a short term period. FDG PET CT can provide insight into the natural history of bacteria sclerosis because it can also be applied in the setting of diagnosis.
Therapeutics and prognosis. There are several advantages of FDG PET CT over existing methods like CT angiography or coronary artery calcium scoring by CT with minimal operator dependence. FDG PET CT affords high contrast resolution with real-time in vivo.
Whole body molecular imaging quantification of plaque volume with metabolic activity allow for multimodal atherosclerotic plaque quantification. These factors together facilitate ability to detect early changes in atherosclerosis in response to therapeutic intervention To ensure imaging quality, the team performing this work should be experience in pet scanning. Experience in vascular identification of structures is also important to image analysis.
So initially some may struggle if they don't know the vascular anatomy or if they're not familiar with the interpretation of PET CT imaging. However, overall, the method is quite straightforward. We believe that visual demonstration of this method will be very useful to those who are interested in applying this technique.
To study patients with atherosclerosis as it will help to provide a standardized yet easy to use approach for image acquisition and analysis, Secure a time slot for imaging on a PET CT scanner for improved image quality. Use a scanner with time of flight capabilities like this Gemini TF scanner plus CT to ensure that endogenous glucose does not compete with the FDG radio tracer. Confirm that the patient has fasted for eight hours prior to the FDG PET CT scan.
Now, check fasting serum glucose levels using a finger stick. If the FSG is less than 200 milligrams per deciliter, insert a 20 gauge intravenous line to administer the FDG radio tracer. After obtaining CT and PET images as explained in the accompanying manuscript, qualitatively delineate all vascular structures of interest using the low dose non-contrast CT images, and then assess for corresponding anatomical areas of visibly increased radiotracer uptake on pet images.
Also, qualitatively assess the CT images for gross vascular abnormalities such as mural calcification or aneurysmal dilation. First, identify boundaries to divide the aorta into segments. Start with the ascending aorta by identifying its origin from the heart and move superiorly for simplicity.
Define the aortic arch as that part of the thoracic aorta, which appears as a contiguous segment on the transverse images where the ascending and descending portions of the thoracic aorta connect. Also identify the superior end of the descending thoracic aorta. Next, identify the origin of the celiac artery to serve as the anatomical landmark between the descending thoracic aorta and abdominal aorta.
Then identify the renal arteries to define the senal and infrarenal segments of the abdominal aorta. Also identify the aortic bifurcation to serve as the anatomical landmark for the distal end of the abdominal aorta. Now measure the arterial FDG uptake on transverse PET CT images for the aorta.
Begin with the superior most aortic slice. Draw each region of interest to include the entire area of FDG uptake on that slice while avoiding other surrounding tissues with increased uptake. Next, with pet CT image analysis software, record the standardized uptake value for each vessel of interest per slice.
Be sure to record the maximum and mean SUV of each ROI as well as a cross-sectional area and slice thickness. Repeat this procedure for PET scan slices that pass through arteries of interest at regular frequency, for example, at every fourth slice. Note that the total number of slices will differ from subject to subject depending on body habitus, anatomical variation and frequency selected.
For purposes of tissue to background ratio calculation, locate the inferior vena cava in the abdomen where at least eight contiguous slices can be visualized. Place an ROI within or slightly around the IVC on each transverse slice to obtain at least eight venous mean SUV measurements. Generate mean SUV and maximum SUV measurements for each arterial segment of interest as one outcome measure of average burden of athero sclerosis within that region.
Next, divide the arterial segment mean SUV by the venous mean SUV obtained in earlier steps at the inferior vena cava for normalization purposes. This target to background ratio serves as another outcome for atherosclerotic plaque activity. For each arterial segment, calculate its volume by multiplying the sum of cross-sectional areas of all ROIs passing through the vessel by slice thickness and the frequency of slice measurement.
Finally, multiply arterial segment mean SUV by arterial segment volume. The result, the mean metabolic volumetric product is a third outcome for measurement of plaque activity and burden of the artery or arterial segment of interest. Some all the mean MVP over overall aortic segments to obtain the global inflammatory burden.
A fourth outcome for measurement of atherosclerotic plaque activity and atherosclerosis within the aorta. Initial pet reconstruction. Images of a patient in our study of aging and atherosclerosis demonstrates FDG uptake in the iliac and femoral arteries, popliteal arteries, abdominal aorta, and aortic arch.
This transverse fused FDG PET CT image shows a slice of data with ROI placement around the descending thoracic aorta. The software calculates mean SUV maximum SUV, and area of ROI. As part of an ongoing study of psoriasis.
Data derived from a single patient indicate the four determining outcomes for atherosclerotic plaque activity and vascular inflammation means standardized uptake value target to background ratio, metabolic volumetric product and global inflammatory burden. Once mastered, this technique can be performed properly in three hours from scan time to image analysis. For quantitative analysis, it's important to have good quality images because problems with images at acquisition will limit accurate quantification of vascular inflammation.
Other methods like CT angiography can be performed in order to answer additional questions like the anatomical severity of vascular inflammatory lesions once they're detected. After watching this video, you should have a good understanding of how FDG PET CT can be used to detect and quantify atherosclerotic plaque activity and vascular inflammation in human arteries. Don't forget that working with FDG can be hazardous and precautions such as standard radiation.
Safety procedures should always be taken while performing this procedure After its development. This technique paved the way for researchers in the field of atherosclerosis to understand how an atherosclerotic plaque with heavy amounts of inflammation changes after known therapeutic interventions such as statin therapy or lifestyle modification. Furthermore, this technique can be applied to novel disease populations such as our recent efforts with psoriasis who have a high risk of developing vascular disease to understand the effect of a novel disease on atherosclerosis.
