The normal variant (18)F FDG uptake in the lower thoracic spinal cord segments in cancer patients without CNS malignancy

Focal increased lower thoracic spinal cord (18)F FDG uptake is not infrequently observed as a normal physiological finding and may be confused for spinal cord metastases. This study was conducted to evaluate a possible correlation between the lower thoracic (T11-T12) spinal uptake and lower limb movements/ambulatory status of the patients as a surrogate. The primary endpoint was to identify the possible cause(s) of the normal variant focal increased thoracic spinal cord (T11-T12) (18)F FDG activity and correlate it with the lower limb movements/ambulatory status of the patients. This was a retrospective analysis of PET-CT scans of 200 patients with solid and hematological malignancies. The focal relatively increased (18)F FDG activity in the lower thoracic spinal cord correlated strongly with the (18)F FDG intensity of the liver, bowel, C3-C5 cervical cord activity, weight of the patient and injected dose of (18)F FDG. With regard to the primary endpoint, no significant correlation was found between the ambulatory status of patients in any of the groups and thoracic spine SUVmax. This could be further assessed by performing dual studies in the same patient with and without moderate to excessive leg motion. Identifying this variant focal increased (18)F FDG activity can minimize errors of misdiagnosis and unnecessary further investigation.