New PET method spots early signs of inflammatory bowel disease
A new PET imaging method could provide earlier detection of inflammatory bowel disease (IBD) and potentially guide decisions on when patients should start treatment.
New research in the Journal of Nuclear Medicine discusses the use of granzyme B (GZMB) PET for identifying and measuring immune system activation associated with IBD. Experts involved in the study suggested that their findings could be used to tailor treatment to patients struggling with IBD, as PET imaging offers a noninvasive way to monitor disease progression and treatment responses.
“Currently, there is no accurate method to detect and differentiate active inflammation from chronic disease. MRI and CT look at the structural changes in the bowel, while other imaging techniques look at the increased number of immune cells in the tissue. None of the tools, however, capture the dynamic nature of immune responses in the colon,” said Pedram Heidari, MD, radiologist and service chief of nuclear medicine at Massachusetts General Hospital, Harvard Medical School, noted.
For the study, researchers first examined how the expression levels of GZMB differed between tissue from inflamed and noninflamed bowel samples of individuals with Crohn’s disease or ulcerative colitis (both active and inactive). Later, two groups of mice—one healthy control and one colitis-induced—underwent PET imaging using a GZMB-binding peptide labeled with 68Ga to identify areas of inflammation.
On the tissue samples, GZMB was significantly upregulated in the inflamed bowel group, notably so in the group in active disease. A sub analysis of treatment responses also revealed that GZMB expression was lower in the group that responded to treatment versus the group that did not.
For the imaging portion of the study, the mice underwent 68Ga-NOTA-GZP PET one, three and four weeks after colitis induction. The colitis group showed significantly higher uptake of the tracer in the bowel compared to the control group. Treatment was shown to decrease tracer uptake; however, the colitis-induced group showed substantially higher uptake than the control group throughout every exam.
Their findings indicate that targeting GZMB not only helps to identify inflammatory disease that may have previously been difficult or impossible to detect, but it also provides insight into the effects of treatment, the researchers noted.
“Granzyme B PET can help with the timely detection of the active disease, determination of the need to start treatment, and monitoring the response to treatment to ensure the resolution of the inflammation. This is particularly important for monitoring inflammation in the parts of the bowel that are not accessible for endoscopy and tissue sampling,” Heidari stated. “This is a unique tool that can significantly change the trajectory of disease by closely monitoring treatment efficacy and is the true definition of precision medicine.”
The study abstract is available here.
In addition to her background in journalism, Hannah also has patient-facing experience in clinical settings, having spent more than 12 years working as a registered rad tech. She began covering the medical imaging industry for Innovate Healthcare in 2021.