NeedlePath

Calculate needle angles for difficult CT-guided needle placements

In some CT-guided procedures, there is no axial slice with a safe path from the skin surface to the target, but there may be an oblique (“out-of-plane”) approach. Estimating the proper needle angles for such procedures may be difficult without visualization tools.

NeedlePath accepts a series of DICOM images from either the Synapse 5/7 PACS or a folder of DICOM files, and allows the user to mark the needle entry and target positions on the images. NeedlePath displays the projected needle path as well as the desired in-plane and out-of-plane needle angles (in-plane angles are measured from the horizontal axis). NeedlePath will also calculate deviations from optimal angles in the position of a placed needle.

Since this is an unsigned executable, a Windows Defender SmartScreen warning may appear on first execution. Click on the “More info” link, then the “Run anyway” button to execute the script.

Basic usage:

• Left-click and drag image series from a Synapse 5/7 pane into the image box.
  • Scroll through the images using the mouse wheel or up/down arrow keys. Slice location (SL) is shown above the image.
  • Window/level images by right-clicking and dragging, or by using number key presets (0 = bone, 1 = soft tissue, 2 = lung, 9 = reset).
  • During a procedure, each new scan should be sent from the scanner to Synapse. Refresh the Synapse window with F5, then drag the new series into the NeedlePath image box.
• Use the top radiobuttons (“Left-click selects”) to change what left-clicking on the image does.
  • After selecting start (entry) and target points, NeedlePath shows in-plane and out-of-plane angles of the planned trajectory, and depicts the trajectory on the images as an orange line.
  • After selecting the tip of the needle, NeedlePath shows in-plane and out-of-plane angles of the needle, and extrapolates the needle path forward (yellow line). The green line is the straight line from the tip to the target.
  • During a procedure, it may be more useful to move the start point to a location where the needle tip can be retracted and re-directed.

This project was presented at the RSNA 2024 Annual Meeting:

Cheng PM. Needlepath: Facilitating Out-of-Plane CT-Guided Needle Placement. 110th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA), Dec. 2024.