Study evaluating possible causes of the normal variant 18F-FDG uptake in the thoracic spinal cord in patients without CNS malignancy.

Abstract

e21144 Background: Focal increased lower thoracic spinal cord 18F-FDG uptake is not infrequently observed and may be confused for spinal cord metastases. The cause of this physiological uptake is indeterminate though various theories have been postulated. We hypothesized that there may be a correlation between the thoracic (T11-T12) spinal uptake and lower limb movements or to bowel FDG activity. In the absence of paired FDG PET studies in same patients with and without leg movements we correlated the FDG uptake of the lower thoracic cord in ambulatory to that in bedridden patients. Methods: Sixty-three consecutive patients (12 bedridden) with 18F- FDG PET-CT with no known evidence of spinal cord or bony spine metastases were included. The SUV max/avg values of the liver, Thoracic: T11-T12 and Cervical: C3-C5 spinal cord segments and the bowel FDG activities of the ambulatory and bedridden patients were determined and compared. Statistical analysis was performed to evaluate various factors predictive of increased spinal cord FDG uptake. Results: Median age was 54 years (18- 93). Primary tumor histology was lung (21.8%), breast (9.3%), melanoma (15.6 %) and lymphomas (21.8%). The mean SUV max/avg values were liver (2.89/2.43); Thoracic cord (2.46/1.89); Cervical cord (2.25/1.82) and Bowel (4.4/2.9). Visible 18F-FDG thoracic spinal uptake was seen in 28%. Our analysis showed no significant correlation between the ambulatory status (p=0.219) or bowel FDG activity (p=0.210) and T11-T12 cord uptake. Conclusions: Although of no significance in this study, there might be a correlation between limb movements (amongst other factors) and physiological FDG uptake in the lower T-spine which warrants further dual studies in the same patient with and without leg motion. This may also help in differentiating normal variant spinal cord uptake from spinal cord metastatic lesions. [Table: see text]

Fluorine‐18 fluorodeoxyglucose positron emission tomography imaging exhibits increased SUVmax at the level of the spinal intumescence in normal dogs

“…As 18 F‐FDG PET imaging becomes more common in veterinary medicine with increasing usage not only for staging of oncology patients but also for musculoskeletal and non‐cancer related imaging, it is necessary to understand the normal variations in uptake of FDG. Increased avidity in specific regions within the spinal cord has been documented in the human literature and had been anecdotally observed at our institution. The results of the current study indicate this significant difference in SUVmax between spinal cord regions is a normal finding secondary to increased neuronal count and increased spinal cord area.…”

[18F]FDG-PET Evaluation of Spinal Pathology in Patients in Oncology: Pearls and Pitfalls for the Neuroradiologist

“…Specifically, relative increases in physiologic [ 18 F]FDG uptake have been demonstrated in the spinal cord at the T11 and T12 levels and, to a lesser degree, at the C4 level (Fig 1). [4][5][6] Additionally, slight relative physiologic uptake within the cord has also been noted at the level of the atlas. 7 While not definitively explained, it is theorized that the increased uptake in the lower thoracic cord is due to inadequate clearance of the radiotracer from the artery of Adamkiewicz, which originates from the aorta between T9 and T11, and/or due to the relative increased cross-sectional area of the spinal cord at the midcervical and lower thoracic levels with an associated increased ratio of gray matter.…”

“…7 While not definitively explained, it is theorized that the increased uptake in the lower thoracic cord is due to inadequate clearance of the radiotracer from the artery of Adamkiewicz, which originates from the aorta between T9 and T11, and/or due to the relative increased cross-sectional area of the spinal cord at the midcervical and lower thoracic levels with an associated increased ratio of gray matter. 4,5,7 Relative changes in physiologic uptake can also be noted within the vertebral bodies, with background marrow uptake typically having a maximum standard uptake value (SUV max ) of ,3. 8 Peak physiologic radiotracer uptake has been noted within the lower thoracic vertebral bodies, typically between T8 and T11, though standard uptake values (SUVs) are usually below those of the liver.…”

Intramedullary spinal cord metastases and whole body 18F-FDG PET-CT—A case report

“…A word of caution is that there is physiological relative increased elongated area of 18 F-FDG uptake consistently visualized in the cervical spinal cord peaking at C4 level, and in the lower thoracic spinal cord peaking at the T11-T12 segments, with intensities nearly as high as 30% greater than the liver FDG intensity, both with visual or semi-quantitative assessment (SUV value). Although various theories proposed, the cause of this physiologic FDG uptake is indeterminate (11); the interpreting physicians should be aware of this pitfall.…”