A non-invasive method developed by scientists at the University of Michigan allows patients to be scanned for an adrenal adenoma in a safer way, producing better quality images.
Hypertension, or excessively high blood pressure, is a widespread problem and can lead to significant cardiovascular problems and events if left untreated. Many different causes contribute to hypertension including genes, aging and diet. Around 10-15% of hypertension cases are thought to be due to high levels of the hormone aldosterone.
One common cause of high aldosterone levels is presence of an adrenal adenoma, a benign tumor on the adrenal glands. If this is detected as a cause of hypertension, the adenoma can be removed and the patient’s hypertension cured.
However, current methods of detecting adrenal adenomas are not ideal. The patient either needs to undergo an invasive procedure to sample the blood leaving the adrenal glands, or a less invasive one that uses radioactive iodine and requires a week of steroid use before screening.
In the current study, published in The Journal of Nuclear Medicine, senior author Benjamin Viglianti, associate professor of radiology at University of Michigan Medical School, and colleagues developed a new test using fluorine-18, a radioisotope commonly used in PET scans, instead of iodine. The agent is injected, taken up by the organs of interest and then imaged using positron emission tomography.
“This agent gives us a noninvasive way to find out if aldosterone is being produced abnormally, one that significantly limits the potential harm to our patients through decreased exposure to radiation and limiting of steroid use,” said Viglianti in a press statement.
Following testing of the new fluorine-18 imaging agent (18F-FNP-59) in rodents, a small trial in humans was approved. The study was carried out in four people and the agent showed no adverse effects. It reached the target tissues (those that use cholesterol) and produced better quality images than the older iodine-based agent, while exposing patients to less radiation.
The research team now plans to conduct a larger clinical trial to validate the new imaging agent in patients with hypertension caused by excessive aldosterone production. They also think it could have other clinical applications in diseases linked to cholesterol.
“Overall, this work demonstrates the initial feasibility of 18F-FNP-59 to image cholesterol trafficking and specifically uptake in human cortical adrenal tissue. Future studies will explore if [it] can serve as a non-invasive method to imaging lateral versus bilateral cause of primary aldosteronism,” conclude the authors.