Fig. 2

Summed images acquired at 0–2, 2–4 and 4–6 hours following the start of administration with the catheter tip at the first cervical vertebra (C1) (top) and the tenth thoracic vertebra (T10) (middle) demonstrating the delayed distribution within the brain following delivery in the thoracic spine compared to the cervical spine. The color scale is identical for the top and middle panels (0-0.5% ID/g). The bottom panel is the same figure as the middle panel but with a different color scale (0-0.05% ID/g) demonstrating that activity is present in the brain, but in lower amounts. The low intensity in the middle panel demonstrates that there is much less activity in the brain with the T10 catheter placement and that the low tracer distribution was potentially offset by clearance rates. We used the same color scale for the top and middle panels in order to illustrate this marked difference. To demonstrate that there is indeed radioactivity in the middle panel, the color scale for the bottom panel has been changed to a range that demonstrates the lower activity (0-0.05% ID/g)