Ferlic Filter: Lateral C-Spine
Computerized imaging limitations are when one part of the anatomy requires 5X or more overexposure to image an adjacent area whose thickness requires this large increase to bring the anatomy to the proper density. This is true in imaging the lateral cervical spine when imaging the thicker area of C7/T1. The filter is designed to reduce the need for the swimmers view by increasing visualization of the C7/T1 in the lateral cervical spine view.
The filter balances the exposure between the mid-cervical spine area and the C7/T1 junction. In the upright position the top of the shoulders will normally fall slightly below the level of the C7/T1 junction on most people. It is the thickness of the trapezius muscle at the level of C7/T1 that diminishes viewing density of the C7/T1 junction. The reduced thickness of the wedge on the distal portion increases the density by reducing absorption which results in an increase penetration of the C7/T1 junction.
Using the Filter
The technologist slides the filter in the collimator rails until it stops: opens the hinged filter, collimates, closes the filter and exposes. The starting technique is labeled on the filter.
Lateral Cervical Spine Features:
- The swimmers view has viewing limitations due to the patients overlapping anatomy. Positioning can be difficult. The reader would prefer Interpreting an image of C7/T1 in a true lateral position without the imposition of anatomy
- The mr measured with the phantom in place: Entrance dosage mid level cervical spine without filter 69.2 mr 20 mas 80 kVp, Mid level cervical spine with filter 40.9 mr 95 kVp 63 mas T1 area with filter 96.4 mr The swimmers view would be about 5 X the mr.