Extending the Utility of 3D Printing in Your Practice: A Novel Technique for Complex Cases, Combining CT and MR Imaging into a Single 3D Print

Purpose:

The value of 3D printing for surgical planning has become well recognized in craniofacial surgery. Tangible 3D replication of patient-specific anatomy provides surgeons with immediate understanding of complex dysmorphology, enables accurate surgical planning and creation of customized implants, and aids in intraoperative orientation. However to date, 3D printing in craniofacial reconstructive surgery has focused on replication of bony anatomy based on CT imaging.

 

Methods:

Over the past two years, we have utilized a novel method for overlaying CT and MRI images to simultaneously 3D print both hard and soft tissue anatomy in complex craniofacial cases. To construct each 3D model, MR and CT imaging are first reviewed to identify complementary imaging sets with similar slice thickness and similar patient position. CT and MR images are imported into Materialise Mimics as separate files, and anatomy of interest is isolated into masks. The masks of isolated anatomy from the CT are copied into the MR segmentation file and a simulation engineer manually registers the CT to the MR using a 3D-positioning panel. A radiologist reviews the imaging overlay prior to printing the fused data set.

 

Results:

Over the past two years, we have utilized this 3D printing technique for six patients with the following diagnoses: arachnoid cyst (n=1), myxoma (n=1), occipital encephalocele (n=1), nasopharyngeal meningocele (n=1), and a large mandibular tumor (n=2). In each case, the 3D print of the CT/MR overlay improved visualization of aberrant anatomical relationships. The highlighted structures particularly included abnormal vasculature and the full extent of lesions that were difficult to appreciate on standard 2D imaging, and the 3D prints helped preoperatively plan and intra-operatively guide complex interventions.

 

Discussion/Conclusions:

3D printing from multiple imaging modalities clarifies anatomic relationships in a way not previously possible. It utilizes the best assets of both imaging modalities: segmenting structures such as bones from the CT and using the MR imaging for excellent soft tissue contrast, to enables better differentiation and delineation of important vasculature or soft tissue tumor margins, for example. This novel technique can enhance advanced hard and soft tissue planning in the most complex craniofacial operations.