Combined PET/MRI detects kidney transplant infections

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 - PET/MRI
MRI showing focal restriction of diffusion (A, red arrows). Biopsy from a kidney allograft shows inflammatory cell infiltration typical for allograft infection (granulocytes (CD15, B), and T cells (CD3, C). Corresponding upregulated CXCR4 expression (D, white arrows). Additional markers of cell infiltration (B cells (CD20, E), and macrophages (CD68, F). Scale bar indicates 200 μm. Photo courtesy of Hannover Medical School.

Transplanted kidney tissue is susceptible to infection, presenting an ongoing risk for patients. However, a group of German researchers have developed a nuclear medicine that can detect and ultimately help improve treatment for this problem.   

A study recently published in the November issue of The Journal of Nuclear Medicine (JNM) explains how a group of Hannover Medical School researchers developed a combined PET/MRI examination that can determine whether a kidney transplant patient has developed an infection, most commonly a urinary tract infection (UTI), according to Society of Nuclear Medicine and Molecular Imaging (SNMMI).

"Direct visualization of infiltrating leukocytes in renal allografts in the context of kidney infection has not been done before using PET," stated Thorsten Derlin, MD, from the department of nuclear medicine at Hannover Medical School. "Other imaging methods have not been very useful in the past for diagnosing renal infection, and biopsy may have complications, including bleeding." 

Developing a UTI after a kidney transplant may lead to transplant failure or continued infection. The researchers, to detect the source and extent of infections in transplanted kidney tissue, studied 13 kidney transplant recipients with UTIs for a combined PET scan with a CXCR4-ligand 68Ga-Pentixafor and diffusion-weighted MRI.  

Of the patients examined, the combined PET/MRI detected nine patients with an acute UTI and the four additional patients with lower URI/non-urological infections. Because of the study's success in accurately pinpointing infection, this PET/MRI approach has the potential to further shape how infectious and inflammatory diseases are characterized for present and possibly future kidney infection clinical studies, according to the press release.  

"This work establishes CXCR4-targeted PET as a novel approach for imaging of infection, and it strengthens the role of nuclear medicine for renal imaging," Derlin stated. "It demonstrates the potential of integrating state-of-the art imaging approaches—i.e., diffusion-weighted MRI and novel, highly specific PET tracers—for a comprehensive assessment of kidney disease and has the potential to be translated into other settings of difficult-to-diagnose infections, such as cholangitis in transplanted patients and bone infections."