The objective of this study is to answer the following questions:

1. Does the appearance of the reconstructed anterior cruciate ligament (ACL) vary in appearance on PET/MRI depending on graft type and time after surgery?
2. What is the appearance of the native ACL on Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI)?

This Phase I feasibility trial will evaluate knee injuries utilizing a standard of care non-contrast 3 Tesla (T) MRI. In addition, knee injuries will be assessed with a low dose (1/5 of the dose given for standard of care PET scans) fluorodeoxyglucose (FDG) PET research scan with CEST sequences. Patients enrolled in this study will include both those with and without a history of ACL repair; however, patients receiving the standard of care MRI will not be currently suspected of having an ACL injury based on physical examination and history.

Patients with and without a history of ACL reconstruction will undergo a low dose FDG PET scan in the same setting as their MRI. The PET examination will be performed such that the early phase of imaging is performed prior to the MRI and the delayed phase is completed immediately following the MRI. This dual-phase scanning will allow for both assessment of the vascularity of the graft as well as its metabolic activity.

Patients will be asked to provide study personnel with authorization to their medical records regarding the outcome of the knee graft. This authorization will be provided for 10 years from date of signed consent.

Comparisons of the finding in normal and reconstructed ligaments as well as between graft types based on time from reconstruction will demonstrate the feasibility of this imaging technique and allow for generation of an imaging based hypothesis that will provide metabolic activity of the graft in a post-operative knee.

Inclusion Criteria:

• Male and female patients between 18 and 60 years of age.
• Patients scheduled for a standard of care MRI at OSU.

Exclusion Criteria:

• Patients with a suspected ACL injury.
• Patients who are pregnant or lactating.
• Patients who are prisoners.
• Patients who are unable to provide consent.
• Patient with significant renal insufficiency, i.e. an estimated glomerular filtration rate (eGFR) less than 30 mL/min/1.73m2.
• Patients who exhibit noticeable anxiety and/or claustrophobia or who exhibit sever vertigo when they are moved into the MR.
• Subjects with any type of bioimplant activated by mechanical, electronic, or magnetic means (e.g., cochlear implants, pacemakers, neurostimulators, biostimulators, electronic infusion pumps, etc.).
• Subjects with any type of ferromagnetic bioimplant that could potentially be displaced or damaged.
• Subjects that have vascular or aneurysm clips, or metallic staples from a surgical procedure.
• Subjects with permanent tattoo eye liner (may contain metallic coloring).
• Subjects that may have shrapnel imbedded in their bodies, such as from war wounds, metal workers and machinists (metallic fragments in or near eyes), severe auto accident victims.