Introduction: Chronic
pelvic pain is a highly prevalent
pain condition among women, but identifying the exact cause of
pelvic pain remains a significant diagnostic challenge. In this study, we explored a new diagnostic approach with PET/MRI of the
sigma-1 receptor, a chaperone
protein modulating
ion channels for activating nociceptive processes. Methods: Our approach is implemented by a simultaneous PET/MRI scan with a novel radioligand [18F]
FTC-146, which is highly specific to the
sigma-1 receptor. We recruited 5 chronic
pelvic pain patients and 5 healthy volunteers and compared our PET/MRI findings between these two groups. Results: All five patients showed abnormally increased radioligand uptake on PET compared to healthy controls at various organs, including the uterus, vagina, pelvic bowel, gluteus maximus muscle, and liver. However, on MRI, only 2 patients showed abnormalities that could be potentially associated with the
pain symptoms. For a subset of patients, the association of
pain and the abnormally increased radioligand uptake was further validated by successful
pain relief outcomes following surgery or trigger point
injections to the identified abnormalities. Conclusion: In this preliminary study,
sigma-1 receptor PET/MRI demonstrated potential for identifying abnormalities associated with chronic
pelvic pain. Future studies will need to correlate samples with imaging findings to further validate the correlation between S1R distribution and pathologies of chronic
pelvic pain. Trial Registration: The clinical trial registration date is June 2, 2018, and the registration number of the study is NCT03195270 (https://clinicaltrials.gov/ct2/show/NCT03556137).