[18F]FTC-146 PET/MRI in Healthy Volunteers and in CRPS and Sciatica

Inclusion Criteria: General: * At least 18 years of age * Either male or female Sciatica: * History of pain shooting down a leg below the knee, to the foot or toes * Visual analog scale (VAS) at enrollment of \>4 with leg pain greater in intensity than the back pain * Focal disc herniation on MRI correlating with radicular symptoms defined as pain or paresthesias into the leg. * Examination with correlating radicular signs defined as any of the following: * pain reproduction with straight-leg-raising (pain shooting down the leg with less than 60 degrees elevation) * radicular pattern sensory changes (such as numbness or paresthesias) in the same area as pain * signs of radiculopathy (weakened hallux extension and/or Achilles tendon reflex) * The above inclusion criteria can be met OR individuals who have been determined to have a very high clinical suspicion of having Sciatica as determined by the referring pain specialist can be included. This suspicion will be documented in the patient's medical record. CRPS: * Disease duration of 6 months or longer * Continuing pain, which is disproportionate to any inciting event * Must report at least one symptom in three of the four following categories: 1. Sensory: Reports of hyperesthesia and/or allodynia 2. Vasomotor: Reports of temperature asymmetry and/or skin color changes and/or skin color asymmetry 3. Sudomotor/Edema: Reports of edema and/or sweating changes and/or sweating asymmetry 4. Motor/Trophic: Reports of decreased range of motion and/or motor dysfunction (weakness, tremor, dystonia) and/or trophic changes (hair, nail, skin) * Must display at least one sign at time of evaluation In two or more of the following categories: 1. Sensory: Evidence of hyperalgesia (to pinprick) and/or allodynia (to light touch and/or temperature sensation and/or deep somatic pressure and/or joint movement) 2. Vasomotor: Evidence of temperature asymmetry ( \>1°C) and/or skin color changes and/or asymmetry 3. Sudomotor/Edema: Evidence of edema and/or sweating changes and/or sweating asymmetry 4. Motor/Trophic: Evidence of decreased range of motion and/or motor dysfunction (weakness, tremor, dystonia) and/or trophic changes (hair, nail, skin) * There is no other diagnosis that better explains the signs and symptoms * For research purposes, diagnostic decision rule will be at least one symptom in all four symptom categories and at least one sign (observed at evaluation) in two or more sign categories. * The above inclusion criteria can be met OR individuals who have been determined to have a very high clinical suspicion of having CRPS as determined by the referring pain specialist can be included. This suspicion will be documented in the patient's medical record. Exclusion Criteria: General: * Another active disorder which could explain the symptoms in the opinions of the investigator * Failure to give informed consent * Presence of MRI-incompatible materials/devices * Any medication that may affect pain or 18F-FTC-146 uptake or adverse drug interactions with steroids or amino amide local anesthetics (e.g. lidocaine, bupivacaine, ropivacaine) * Pregnant or nursing * Ongoing menstrual period * Severe comorbid conditions * Unable to read or complete questionnaires in English * Any other condition, which in the opinion of the investigator would impede compliance or hinder completion of the study Sciatica: * Any condition that may interfere with interpretation of 18F-FTC-146 uptake in the region of the pelvis, thighs or lower spine including, but not limited to, 1. Spinal, hip or pelvic surgery or prosthesis 2. Cancer 3. Radiation therapy 4. Autoimmune disorders 5. Current infections 6. Inability to void bladder completely, such as in prostatic enlargement 7. Any urinary retention, such as in outlet obstruction, hydronephrosis etc. 8. Cauda equina syndrome 9. Developmental spinal deformities 10. Scoliosis \>20 degrees 11. Spondylolysis 12. Vertebral fractures 13. Inflammatory spondylopathy 14. Prior lumbar surgery CRPS: * Presence of current or past pulmonary, hepatic, renal disease, arthritis, hematopoietic, and neurological diseases not related to CRPS.