Broken bones (fractures) are a common problem in several serious health conditions, such as osteoporosis, kidney failure, and sickle cell disease. To better understand and treat these diseases, researchers need a reliable way to measure how much blood flows through our bones.
In animal studies, a special scan called PET (Positron Emission Tomography) has been used successfully to measure bone blood flow. This scan uses a safe, low dose of a radioactive substance called sodium fluoride, which helps show how blood moves through the bones. However, using this method in people has been difficult in the past because older PET scanners were not sensitive enough to give accurate results.
Recently, St Thomas' Hospital in London has received two new, state-of-the-art PET scanners. These scanners can take pictures of the whole body at once and are much more sensitive than older models. They can also take images of the heart during the scan, which is important because it allows researchers to measure how much of the radioactive tracer is being delivered to the bones through the bloodstream. This is a big improvement over older, more invasive methods that required taking many blood samples.
The main goal of this pilot study is to develop a better, more reliable way to measure bone blood flow in healthy volunteers using these new PET scanners. The researchers also want to check if measuring the tracer in the heart is as good as, or better than, the previous method of taking frequent blood samples.
To do this, the researchers will invite ten healthy volunteers-men and postmenopausal women over the age of 50-to take part in our study. Each volunteer will have a one-hour PET/CT scan, which takes images from the head down to the upper thighs after a small injection of the radioactive tracer. To compare the new method with the old one, the researchers will also take five small blood samples from the volunteer's arm at different times during the scan.
The research team hope that this study will lead to better ways of studying and treating bone diseases in the future, making the process easier and less invasive for patients.
5 male and 5 female healthy volunteers aged over 50 years
No metabolic bone disease (e.g. osteoporosis)
No metastatic bone disease
Good venous access
Over 1.85 metres (6.1 feet) in height to ensure adequate skeletal coverage
Over 95 kg (15 stone) in weight to ensure image quality
Claustrophobia
Uncontrolled high blood pressure
Ten healthy volunteers aged over 50 years old
Other
Prospective
1-hour Total Body PET/CT scan using the tracer [18F]-sodium fluoride
Diagnostic testEach volunteer will have a 1-hour dynamic TB-PET/CT scan from vertex to mid-thighs following a bolus injection of 90 MBq of \[18F\]-sodium fluoride (\[18F\]-NaF) to measure bone perfusion (K1) and regional bone plasma clearance (Ki).
To measure bone perfusion (K1) and bone plasma clearance (Ki) with [18F]-sodium fluoride TB-PET/CT at multiple sites across the whole skeleton in 10 healthy volunteers, both are measured in units of mL per min per mL.
Dynamic \[18F\]-sodium fluoride PET/CT scans can measure both effective bone plasma flow (K1), and bone plasma clearance (Ki), the latter reflecting regional bone formation. Both are measured in units of mL per min per mL (or mL min-¹ mL-¹), which signifies the volume of plasma cleared of the tracer per minute per unit volume of tissue.
To develop an improved method of measuring the arterial input function (AIF) by using a volume of interest (VOI) in the left ventricle (LV) of the heart in the same 10 healthy volunteers.
This is an important secondary outcome because both K1 and Ki require knowing the arterial input function (AIF), which is essentially how much tracer is available to the bone. Previously, the only accurate way of measuring this was by direct arterial blood sampling, which is an invasive procedure, and an alternative technique was to derive a semi-population input function. However, the new scanners include the heart in the field of view enabling the AIF to be measured more reliably, and the researchers hope that this will significantly improve the measurement of bone blood flow and bone formation in the future.
Click on the lead sponsor to view all of their trials.
King's College London
Lead sponsor
Guy's and St Thomas' NHS Foundation Trust
Collaborator
