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Abstract
Introduction During neurosurgical image-guided procedures, a head clamp, with attached titanium pins, is used to immobilize the head. Titanium is chosen for several reasons including cost effectiveness, biocompatibility and fracture resistance. However, titanium’s density is quite high, creating large and dense artifacts on 3D CBCT (Cone Beam CT) images. These artifacts hinder visualization of critical anatomy, and the potential for missed information is greatly increased. We present an approach to redirect artifacts caused by titanium pins.
Material and methods The objective of this study is to determine the relationship between the physical rotation angle of a neurosurgical skull clamp with respect to the patient table axis, and the angle of artifacts in a CBCT image due to titanium pins. A melon was positioned in a skull clamp attached to a flat panel detector system (Artis zeego, Siemens Healthineers, Forchheim, Germany) and titanium pins (PMI, Breisgau, Germany) were applied. CBCT images (syngo DynaCT, Siemens Healthineers, Forchheim, Germany) were acquired at 9 degree increments in the angle of the skull clamp relative to its grove attachment joint. We measured the change in angle of the generated artifacts between consecutive pairs of CBCT images.
Analysis Through rotation of the skull clamp mounting system, artifacts were rotated out of the region of interest (Figure 1). The average artifact angle change on images was 9.4°±1.0°.
Discussion With the aid of CBCT, we are able to not only rotate an artifact out of a region of interest (ROI) but also to correlate the artifact angle on CBCT to the physical rotation angle of the clamp (figure 1). One potential application is to use CBCT imaging to plan the clamp rotation angle necessary to deflect the artifacts away from an ROI. In addition, clamp rotation can reduce the path length of x-rays through the pin, thereby creating less artifacts. By rotating to accommodate for one pin artifact, the path length through another pin in the same plane may increase/decrease and cause an equal or lesser artifact. Careful consideration must be taken when attaching the skull clamp and using different angles to create a clear treatment point, free of artifacts from the titanium pins.
(A) Artifact at original angulation position. (B) Artifact rotated out of plane.
Disclosures J. DiNitto: 5; C; Siemens Medical Solutions USA, Inc.