The purpose of this study is to see if the spine shows areas of inflammation using a specific type of imaging (pictures).

The purpose of this study is to determine if inflammation around the spinal nerves can be identified using a radioactive tracer [11C] PBR28 and integrated PET/MRI scan for the purpose of better treating patients who have radicular lumbar pain with epidural steroid injections.

Inclusion criteria for pain subjects:

1. Subject is 18-75 years old.
2. Subject is able to give written informed consent.
3. Subject is currently diagnosed with lower extremity radicular pain regardless of specific or suspected etiologies.
4. Subject has a clear dermatomal distribution of the painful area extending to the distal lower extremities.
5. Subject reports ongoing pain intensity of 4 or greater using the visual analogue scale (VAS) during the week prior to enrollment.

Inclusion criteria for healthy subjects:

1. Subject is 18-75 years old.
2. Subject is able to give written informed consent.
3. Subject has no history of chronic back/spine pain.

Exclusion criteria for all groups:

1. Subject recently received a lumbar ESI (within 8 weeks).
2. Subject starts new NSAID medication for pain during the study.
3. Subject has predominantly axial low back pain.
4. Subject has known pain condition secondary to hip joint arthritis.
5. Subject is pregnant or breastfeeding.
6. Subject has allergy to lidocaine.
7. Subject is treated with chronic corticosteroid therapy.
8. Subject is on anticoagulation therapy (i.e. Coumadin, Plavix, or Lovenox).
9. Subject has a known bleeding disorder (i.e. hemophilia).
10. Subject has uncontrolled high blood pressure [>170/100].
11. Subject has a known heart condition.
12. Subject has known inflammatory disease (i.e. inflammatory bowel disease; ankylosing spondylitis; etc.).
13. Subject has known liver dysfunction or renal insufficiency or impaired elimination (Renal dysfunction is defined as eGFR < 60. Hepatic dysfunction is defined as LFTs ≥ 3x ULN).
14. Subject has been hospitalized recently (within one month) for a major psychiatric disorder (i.e. major depression, bipolar disorder, schizophrenia, anxiety disorder, or psychosis).
15. Subject has contraindications to MRI and PET scanning (i.e. presence of a cardiac pacemaker or pacemaker wires, metallic particles in the body, vascular clips in the head or previous neurosurgery, prosthetic heart valves, or claustrophobia).
16. Subject had research-related radiation exposure in the last 12 months.
17. Subject tests positive for use of illicit drugs, marijuana, or non-prescribed drugs.

1. Subject is currently diagnosed with lower extremity radicular/sciatica pain.
2. Healthy subjects with no pain from the local community.