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AJNR - American Journal of Neuroradiology

A, Nonsterile skin entry localizer is composed of two image-conspicuous lines (barium impregnated silicon) in a truncated inverted V-shaped triangular configuration. The millimeter distance measured between the two V limbs of the pattern is equal to the actual image section plane location on the printed millimeter scale. The pattern has a thicker image-conspicuous band paralleling the radiologic right V limb that is used as a right-left reference. The radiologic right V limb is the 0-mm reference. A series of offset lines at 10-mm increments are printed on the pattern. The intersection of the chosen vector with the pattern is defined as a specific point on the pattern by the two coordinates (slice select, offset). In this example, the skin entry point located at slice select 53 mm and offset 8 mm is marked with a pen.

B, Sterile skin entry-point localizer. The center of this pattern is centered over the predefined marked skin entry point.

C, View of the upper vector point components parallel to the skin. The device comes with an incorporated sterile adhesive drape and a circular opening with an attached base ring to support the upper level pattern platform.

D, View of the upper vector point localizer seen from above. The upper vector point localizer has a clear diaphragm pattern and printed scale that is used in a manner identical to that of the skin point localizer.

A, A 3-mm axial CT image with a 19° angle gantry tilt. This is the planning image for the procedure, with the goal to biopsy the L5-S1 level. An ideal vector is drawn from the target to the skin. Nonsterile skin entry-point pattern is seen as two hyperattenuating dots. The distance measured is 53 mm and defines the entry-point slice select coordinate. The second coordinate offset value is 8 mm. The skin entry-point localizer is punctured at this point and lines are drawn parallel to the slice on the patient’s skin.

B, First poststerile CT image with the multilevel device placed over the target. The sterile pattern localizer is seen as two small hyperattenuating dots on the skin. The ideal targeting vector is drawn on the monitor, and its intersection point with the upper level pattern component is measured. The slice location is 63 mm and the offset 15 mm. The diaphragm is punctured at this point, and the needle is placed at the predefined skin entry point. After one adjustment, the needle is advance the measured depth to the target.

C, CT image shows the needle entering the target along the predefined vector. The upper diaphragm was sliced, allowing the probe to pass through the diaphragm to reach the target. Despite the complex double oblique vector, the entire needle is visible, demonstrating the accuracy of the device.