Accuracy of formula versus neuroradiologists at our institution (fellow or attending, n = 19) in selecting the appropriate needle lengtha
| Actual SCD | Formula | Neuroradiologists |
|---|---|---|
| <3.5 inches | 28/31 (90%)b | 30/31 (97%)b |
| >3.5 inches | 7/7 (100%)c | 5/7 (71%)d |
| Total | 35/38 (92%) | 35/38 (92%) |
↵a In 7/45 patients, the actual SCD is 3.5 inches. Our formula predicted a 5-inch needle in 3/7 (43%) patients and a 3.5-inch needle in 4/7 (57%) patients, and the neuroradiologists selected a 3.5-inch needle in 6/7 (86%) patients and a 5-inch needle in 1/7 (14%) patients.
↵b Predicted 3.5-inch needle.
↵c Predicted 5-inch needle.
↵d A 3.5-inch needle was unsuccessfully used in 1 patient, and a 7-inch needle, in another patient by 2 different neuroradiologists.