Major areas of research in the Xia Lab include craniomaxillofacial surgery, surgical planning, computer modeling, rapid prototyping and surgical navigation. Specific projects are listed and described in more detail below.

Current Research Projects Include:
  • Computer-aided surgical simulation (CASS) system for craniomaxillofacial (CMF) surgery
  • Open-source CASS software framework: AnatomicAligner
  • Digital dental articulation
  • Facial soft-tissue-change simulation following orthognathic osteotomies: eFace
  • 3-D cephalometry
  • Enhanced atlas-based CBCT/CT segmentation
  • Statistical shape modeling

The ultimate goal of this project is to develop an open source novel imaging informatics platform, the AnatomicAligner, to improve the surgical planning method for craniomaxillofacial (CMF) surgery and, subsequently, to improve the treatment outcome of patients with CMF deformities.

CMF surgery involves the correction of congenital and acquired deformities of the skull and face. Due to the complex nature of the CMF skeleton, it requires extensive presurgical planning. Unfortunately, the traditional planning methods, e.g., prediction tracings and simulating surgery on stone models have remained unchanged over the last 50 years. Many unwanted surgical outcomes are the result of these deficient methods. To solve these problems, we have developed a computer-aided surgical simulation (CASS) system. Although it still needs significant improvements, the use of CASS has eliminated most of the limitations of the traditional methods. Unfortunately, it also creates a new problem that the digital establishment of dental occlusion becomes significantly more difficult. The dental articulation is an important step during the planning process to correct pre-existing malocclusions or to surgically reestablish a new occlusion. The current gold standard is to utilize stone dental models and hand-articulate them on an articulator. Unfortunately, the same is not true in a virtual world. These dental arches are 3-D images. When the digital teeth are moved toward each other, they are not stopped by collision and continue to move through each other, which does not occur in the real world.

In order to completely solve these problems, it is critical to develop a new system that will integrate fully automated process of dental articulation and significantly improve our CASS technologies. Our hypotheses is that the occlusion can be digitally and automatically established in a computer planning system and the computer-generated occlusion is as precise as the occlusion established by hand-articulating a set of stone models (the current gold standard). In order to prove our hypotheses, we are developing an open source novel imaging informatics platform, the AnatomicAligner, to improve the surgical planning method for CMF surgery and, subsequently, to improve the treatment outcome of the patients with CMF deformities.

The number of patients suffering from craniomaxillofacial (CMF) deformities and requiring surgical correction is escalating. CMF deformities may involve skeleton, overlying soft-tissues or both. Patients with CMF deformities often have psychological problems. The goal of CMF surgery is to reconstruct a normal facial appearance and function, and the outcome of the surgery is judged as such. The current problem is that we do not have a reliable way of simulating the soft-tissue-change following skeletal reconstruction. In treating patients with isolated skeletal defects, the current practice is to normalize the skeleton, hoping for optimal facial appearance. However, because the thickness and contour of the soft-tissue envelope varies from patient to patient, this approach is not reliable. The problem is even bigger in patients with composite defects. For example, in the scenario of a patient with a skeletal deformity and a mild soft-tissue defect, a surgeon would have to know, before surgery, how to overcorrect the skeleton to camouflage the soft-tissue defect. But, this information can only be attained by having an accurate planning system to simulate soft-tissue changes. In addition, from the patient’s perspective, the final facial appearance is the most apparent to them. Therefore, it is extremely important for both doctors and patients to accurately simulate soft-tissue deformation.

Simulation methods must be accurate and fast. Attaining both is difficult because these attributes are inversely related; the more accurate the model, the longer it takes to prepare and run. Among the most effective are the empirical-based model, mass spring model, finite element model and mass tensor model. Unfortunately, they are either too inaccurate or too slow, making them clinically unacceptable.

Our hypothesis is that facial soft-tissue changes following virtual osteotomy can be accurately simulated by our innovative approach using an anatomically detailed modeling and mapping routine, along with a statistical modeling technique. To test our hypothesis, we propose developing an open source novel imaging informatics platform, the eFace system, to accurately simulate soft-tissue-change following virtual osteotomies and, thus, to significantly improve the outcomes of patients undergoing facial reconstruction. This approach can not only maintain the integrity of complex facial anatomy to accurately simulate the facial soft-tissue deformation, but also significantly improve the computational efficiency in order to fit the requirement for clinical use. 

Overview of Surgical Planning Laboratory

The Surgical Planning Laboratory (SPL) is a clinical-oriented computer science laboratory in the Department of Oral and Maxillofacial Surgery at the Houston Methodist Research Institute. The SPL does research and development in image processing algorithms, software systems and medical applications. The ultimate goal of SPL is to significantly improve the care of patients with craniomaxillofacial (CMF) deformities. To this end, our team members are devoted to improving a doctor’s ability to accurately plan a CMF surgery using the computer and to precisely transfer the computerized surgical plan to the patient at the time of surgery.

Overview of Computer-Aided Surgical Simulation for Craniomaxillofacial Surgery
Over the past 15 years, our Surgical Planning Laboratory (SPL) has developed a computer-aided surgical simulation (CASS) system for CMF surgery. Using this CASS technology, surgeons can perform virtual surgery to create a 3-D prediction of the patient’s surgical outcomes in the computer and apply the computerized surgical plan to the patient at the time of surgery.

Using our CASS protocol to treat a patient who suffers from CMF deformity, an anatomically detailed 3-D model of the patient’s face is created using computed tomography (CT) and other computer modeling equipment. Once this  3-D model is then precisely oriented in 3-D space, the surgical team can then create a detailed plan for surgical intervention; design, test and custom-fit any surgical guides, templates, and grafts or prosthetic appliances that will be needed to complete the repair. If necessary, a virtual road map for the navigational surgery will also be created.

During the actual procedure, the surgical guides and templates, or the 3-D surgical road map shows surgeons precisely where to cut and move the bony segments in order to avoid collateral injury, and where to place plates or other prosthetic items. Several studies have led to successful complex reconstructive repairs, with greater accuracy and safety and reduced time in surgery. In fact, through CASS technology, cases that would traditionally take at least two surgeries may be accomplished in just one—with correspondingly diminished risks for the patient.