Removing infected vascular grafts in patients involves a complex surgical procedure with high risks. Molecular imaging with positron emission tomography (PET)/computed tomography (CT) effectively diagnoses and differentiates infection, noted Israeli researchers at the 54th Annual Meeting of SNM, the world's largest society for molecular imaging and nuclear medicine professionals.
"Our pioneering results show that PET/CT imaging has the potential to become a single-step, noninvasive technique for diagnosis of infection with a complex group of patients," explained Ora Israel, director of nuclear medicine and research operations at Rambam Health Care Campus in Haifa, Israel. "Infected blood vessel grafts--while uncommon--are removed in a complex surgical procedure, " said Israel. "Sparing unnecessary high-risk operations in patients--who are often severely debilitated--is of major significance," she added. "PET/CT imaging-- fluorodeoxyglucose or FDG--can effectively diagnose graft involvement and differentiate it from infection that affects only soft tissue infection in its vicinity," she added. These two processes are treated differently. Infection of a graft requires surgery to remove the involved implant, while infection of the soft tissues in the vicinity of the graft requires mainly intravenous administration of high doses of antibiotics, she noted.
Israel explained that diagnosing a prosthetic (biological or synthetic) vascular graft infection can be a clinical challenge, and--making the situation even more difficult--early treatment is important due to the relatively high rates of limb damage that that can lead to amputation and death. "Ours is the first study to use the hybrid imaging technology of PET/CT in order to provide a solution for this difficult diagnostic problem. PET/CT demonstrates that it provides accurate detection and precise localization of vascular graft-related infections," she said.
"Blood vessels can be occluded (obstructed) due to disease processes--often as a complication of diabetes--decreasing blood flow to various regions of the body and occurring more commonly in the lower limbs," said Israel. She said that prosthetic grafts are inserted to artificially restore and ensure blood circulation through the obstructed blood vessels to areas that would otherwise suffer from the lack of sufficient blood supply. "Graft infection is an uncommon but potentially severe complication following prosthetic vascular reconstruction," noted Israel.
The overall frequency of this complication ranges between 0.5 to 5 percent and occurs, as a rule, a few months after surgery. Delay in treatment of an infected vascular graft can lead to life-threatening complications such as sepsis or hemorrhage, with limb amputation and death occurring in more than 50 percent of patients, she indicated. The clinical presentation is often subtle and non-specific.
PET is a highly specialized, noninvasive imaging technique that utilizes short-lived radioactive substances (such as FDG) that are taken up by normal organs and disease processes characterized by increased function and metabolism, such as cancer or infection. CT offers a detailed map of internal anatomy. "Combined PET/CT, therefore, enables both diagnosis of infection and determination of its precise localization, facilitating the diagnosis and guiding the appropriate treatment strategy," said Israel. With PET/CT, it can be determined if there is an infectious process and if it involves the vascular graft itself (requiring major surgery) or if it is limited only to the soft tissue in its vicinity, she noted.
"These initial findings encourage additional investigations on the role of PET/CT in larger patient populations with suspected vascular graft infection," said Israel. "It also opens new options for additional, previously unsought clinical applications for the use of FDG-PET/CT in other infection and inflammation processes," she noted.
Scientific Paper 209: Z. Keidar, R. Bar-Shalom, O. Israel, Nuclear Medicine; S. Nitecki, A. Hoffman, Vascular Surgery; and A. Engel, Diagnostic Imaging, all at Rambam Health Care Campus in Haifa, Israel, "Prosthetic Vascular Graft Infection: The Role of FDG-PET/CT," SNM's 54th Annual Meeting, June 2--6, 2007.
Materials provided by Society of Nuclear Medicine. Note: Content may be edited for style and length.
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