Following intravenous injection of [F-18]MHF as a bolus, dynamic PET imaging of the lower limbs will be acquired for approximately 90 minutes. The acquired images will be processed and viewed on a MIMVista or similar workstation. The uptake pattern of [F-18]MHF around infected orthopedic knee implant will be determined and compared with its uptake pattern around non-infected knee implants.

This study will look at how [18F]MHF goes into normal knee replacements and those with suspected infection.

This is a study that will test a compound (chemical substance) that has a small amount of radioactivity attached to it. This substance has a natural tendency to go to bacterial infections. The substance is called [18F]MHF and it is given in the form of an injection into a vein. After the substance reaches the infected body region, scans called PET or Positron Emission Tomography, are done. This is similar to having CAT scans or x-rays. Usually a compound called [18]FDG is used for PET scans to detect bacterial infections but this substance can't distinguish between bacterial infections and inflammation. This substance called [18F]MHF does not go to inflamed tissue and may allow bacterial infections to be seen better.

This study will look at how [18F]MHF goes into normal knee replacements and those with suspected infection. This will hopefully lead to the development of better imaging techniques to look at bacterial infections. [18F]MHF is approved by the FDA (Food and Drug Administration) for research.

Inclusion Criteria for symptomatic patient cohort

• Patients must be 18 years of age or older, able to provide written informed consent, and ability to lie still for PET scanning.
• Suspected knee prosthetic infection at least 2 months after original prosthesis placement and who are scheduled to undergo surgery debridement/removal based on the clinical assessment of the referring surgeon.
• OR Inpatients or outpatients with standard clinical evidence of infected left-ventricular assist devices (LVADs), cardiac implantable electronic devices (CIEDs) such as but not restricted to pacemakers and defibrillators, and vascular grafts. Patients may be culture positive or negative, have visual evidence of infection such as frank pus, or classic radiographic evidence of infection on cross sectional imaging and/or FDG PET.
• Willingness to abstain from sexual activity involving the exchange of body fluid for 24 hours after the administration of [F-18]MHF
• Elevated CRP and ESR for orthopedic devices.

Exclusion Criteria for symptomatic patient cohort:

• Significant comorbidity such as grade ≥3 renal toxicity, septic shock, other condition in which the opinion of the PI, PET scanning would constitute significant risk

Inclusion Criteria for asymptomatic cohort:

• Patients must be 18 years of age or older, able to provide written informed consent and ability to lie still for PET scanning
• Knee prosthesis in situ without complications for 6 months or longer

Exclusion Criteria for asymptomatic cohort:

• Clinical or laboratory suspicion of knee prosthesis infection
• Recent (within 3 months) or current treatment for infected knee prosthesis
• Significant comorbidity such as grade ≥3 renal toxicity, septic shock, or other condition in which the opinion of the PI, PET scanning would constitute significant risk.

To accomplish the objectives of this proposed study, 20 patients symptomatic for infection of knee or hip prosthesis or cardiac implantable electronic devices, assist devices, or vascular grafts, and 10 patients asymptomatic for infection of knee or hip of their prosthesis will be accrued, each receiving one injection of [F-18]MHF followed by 90 minutes dynamic PET/CT imaging for outpatients and 40 minutes for inpatients. To account for screen failures, dropouts, and withdrawals, 30 and 15 patients will be enrolled in the symptomatic and asymptomatic cohorts, respectively.