This is an open-label, single center design. In the first stage, five (5) healthy individuals will receive a microdose (10µg) of [11C]-NOP46, immediately followed by whole body positron emission tomography (PET)/computed tomography (CT) to determine dosimetry and perform an initial safety evaluation of the radiotracer. If no toxicities develop, then the investigation will move to the second stage, in which thirty (30) patients with chronic pain will receive a microdose of [11C]-NOP46 followed by PET/CT of region of interests.

Pain is a natural response to injury. Pain lets us know there may be damage to our bodies. Pain is the way our body tells us that we must take care of ourselves. Chronic pain is different. Chronic pain is pain that lasts for a long time. Chronic pain can last for weeks, months, and even years. In some cases chronic pain remains without any sign of body damage. Today, there is no way for a doctor to measure someone's chronic pain or accurately determine many details about chronic pain. The investigators at Columbia University are interested in new imaging test that could help doctors look at chronic pain and help patients with chronic pain. The new imaging test uses a new drug called [11C]-NOP46. [11C]-NOP46 is a radioactive drug and is experimental. It is not approved by the Food and Drug Administration (FDA). The investigators believe that, when given to patients, this new drug can go to the exact places of chronic pain within the body. Once the drug goes to the places of chronic pain, a special camera, called a Positron Emission Tomography (PET) camera, can be used to take pictures of the drug. In this study, the investigators will give [11C]-NOP46 to up to 35 subjects.

Inclusion Criteria:

• All subjects must be 18 years of age or older, able to read, understand, and voluntarily sign an informed consent document.

For Healthy Volunteers:

• Volunteers must have no current medical history of sustained pain from a focal injury.
• Negative pregnancy test if female of childbearing potential.
• Women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation.

Patients with Focal Pain:

• Subjects must have current pain from a focal injury for which they are under a physician's care.
• Subjects must have moderate to severe pain, defined as >4 on the Visual Analogue Scale
• Subjects must have a negative pregnancy test if female of childbearing potential.
• Women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation.

Exclusion Criteria:

• Participants with evidence of diffuse pain at the time of enrollment up to agent administration are to be excluded from this study.
• Inability to discontinue pain medication(s) for 48 hours prior to agent administration.(Enrolled participants who have taken pain medication within 48 hours of agent administration may be either withdrawn from the study or rescheduled at the PI's discretion).
• Concomitant medication use (including suspected illicit drugs use) that, in the judgment of the investigator, would make the participant inappropriate for enrollment.
• Severe concurrent disease, infection, or medical co-morbidity that, in the judgment of the investigator, would make the participant inappropriate for enrollment.
• Participants who are receiving any other investigational agents.
• Women who are pregnant or breastfeeding.
• Subjects who are unable to tolerate PET/CT imaging.

Final data analysis and conclusion will be submitted to scientific journals and made available for publication.

Open Label Study