Combining two imaging agents with dual isotope SPECT/CT provides diabetic patients an excellent infection screening method that has already spared a number of patients from aggressive amputation of infected feet, according to an ongoing study presented at SNM's 58th annual meeting in San Antonio, Texas.
Foot infection and osteomyelitis suspicion account for the highest hospital admissions among diabetic patients, according to the researchers. Accurate diagnosis and precise localization of osteomyelitis is necessary to provide effective treatment and to avoid unnecessary major amputation that can be detrimental to quality of life and survival.
In this study, Sherif Heiba, MD, associate professor of radiology at Mount Sinai School of Medicine in New York City, and colleagues assessed the consequence of dual-isotope SPECT/CT use on diabetic patient foot infection management.
The researchers obtained blood flow and pool images of three-phase bone scan followed by In-111 WBC reinjection and next day dual-isotope SPECT/CT (Tc-99m HDP/In-111 WBC) planar and SPECT/CT acquisitions. On the following day, they obtained bone marrow (Tc-99m SC)/In-111 WBC SPECT/CT (step two dual-isotope) when images were suspicious for mid- or hind-foot osteomyelitis.
Heiba and colleagues enrolled 191 diabetic patients (125 men, median age 60 years), who had undergone molecular imaging with “two imaging agents known for their superior effectiveness with infected tissue and bone.” Subjects were scanned with SPECT/CT.
As of the time of the SNM presentation, the study comprised 227 scans performed with dual isotopes Tc-99m HDP and In-111 WBC on the 191 diabetic patients. Scans were performed using Tc-99m SC and In-111 WBC for patients suspected of having mid- or hind-foot infection.
Results showed 84 cases of osteomyelitis, 93 infections of the soft tissue, 25 combinations of both and 25 other pathologies. These diagnoses were accurately confirmed by tissue culture in 66 of the cases and follow-up examinations for 161 scans. There were five false negative studies and one false positive diagnosis for the entire cohort. Patient treatment planning was directed by 94 percent of imaging studies.
Of the 207 clinical decisions based on each scan, 72 percent were followed with conservative therapy including local debridement of affected tissues and antibiotics, and 24 percent of scans led to minor procedures such as partial bony resection and toe amputation in order to salvage the limb, the researchers reported.
"As a result of this study we have concluded that dual isotope SPECT/CT is an important method for detecting infection in diabetic patients who might otherwise receive unnecessarily aggressive treatment such as amputation," says Heiba. "We want to avoid amputation whenever possible, because it has been shown to be detrimental to patients in terms of both quality of life and survival."