Three-dimensional models for head and neck tumor treatment planning

Mandible reconstruction using patient-specific pre-bent reconstruction plates: comparison of standard and transfer key methods

PURPOSE

Mandible reconstruction with reconstruction plates requires bending the plates during the operation and fixation using the "standard method" (ST-method). The ST-method is limited when a pathological process has perforated the mandibular outer cortex. A transfer key method (TK-method) was developed where plates are pre-bent using a patient-specific mandible model and positioned on the mandible with the help of transfer keys. The ST-method and TK-method were compared in a clinical trial.

METHODS

Mandibular reconstruction was performed on 42 patients in this study: 22 were performed using the TK-method and 20 using the ST-method. Pre- and postoperative CT scans were evaluated by measuring the distances between six corresponding landmarks on the mandibular condyles and rami. The difference between pre- and postoperative distances was used to evaluate reconstruction accuracy.

RESULTS

The median deviation of the unsigned/ absolute values of all six distances was 1.07 mm for the TK-method and 1.67 mm for the ST-method. The TK-method showed significantly better results. For the signed values, the median deviation of the six distances was -0.6 mm for the TK-method and -1.47 mm for the ST-method, indicating that the mandibles became narrower with both methods. This width difference was not statistically significant.

CONCLUSION

The TK-method was more accurate than the ST-method in a clinical trial. The TK-method was effective and accurate for mandible reconstruction using pre-bent fixation plates.

3D-CT imaging processing for qualitative and quantitative analysis of maxillofacial cysts and tumors

The objective of this study was to evaluate spiral-computed tomography (3D-CT) images of 20 patients presenting with cysts and tumors in the maxillofacial complex, in order to compare the surface and volume techniques of image rendering. The qualitative and quantitative appraisal indicated that the volume technique allowed a more precise and accurate observation than the surface method. On the average, the measurements obtained by means of the 3D volume-rendering technique were 6.28% higher than those obtained by means of the surface method. The sensitivity of the 3D surface technique was lower than that of the 3D volume technique for all conditions stipulated in the diagnosis and evaluation of lesions. We concluded that the 3D-CT volume rendering technique was more reproducible and sensitive than the 3D-CT surface method, in the diagnosis, treatment planning and evaluation of maxillofacial lesions, especially those with intra-osseous involvement.

[Analysis of epidermoid carcinomas using panoramic radiography and computerized tomography]

The purpose of this work was to compare radiographic findings, such as localization and extension of tumors toward the bone and soft tissues, in panoramic radiography and computed tomography (CT). Four radiologists assessed the radiographic findings of 48 patients with the histopathological diagnosis of squamous cell carcinoma in different sites of the maxillofacial region. Panoramic radiographs and computed tomographs were obtained at the University of Iowa Hospitals and Clinics, at FUNDECTO-USP and at the hospital of the University of São Paulo (USP). We observed a considerable limitation of the panoramic radiography in determining the localization and extension of tumors, since it revealed unclear delimitations. Regarding CT, better results were obtained: it was possible to observe the invasion of the tumor toward adjacent soft tissues, as well as the extension of bone destruction and the depth of the lesion, which were confirmed by surgical findings. We concluded that computed tomography demonstrated to be a sensitive radiographic technique for the detection of the involvement of bone and soft tissues, contributing for a more precise diagnosis, surgical planning and intervention. On the other hand, panoramic radiography was considered less sensitive and less efficient than CT, since it shows only unclear borders of the lesions and is not able to assess the involvement of soft tissues.

The validation of 3D spiral CT-based measurements of simulated maxillofacial neoplasms

OBJECTIVE

The purpose of this study was to determine the precision and accuracy of 3-dimensional spiral computed tomography-based linear measurements of neoplasms associated with the mandible.

STUDY DESIGN

Four cadaver heads, each with 2 simulated tumors made of clay, containing contrast medium, and positioned medial to the mandible, were examined by means of a subsecond spiral computed tomography unit. The computed tomography data were transferred to a computer workstation and analyzed through use of 3-dimensional reconstructed images. Linear measurements of the length, width, and depth of the simulated tumors were made by 2 observers, twice each. The soft tissues were then removed and the same measurements made by means of calipers.

RESULTS

There were no statistically significant differences between the 3-dimensional computed tomography and physical measurements (P >.05). The mean difference was found to be less than 0.4 mm.

CONCLUSIONS

Spiral computed tomography imaging allows for precise and accurate 3-dimensional computed tomography-based measurements for neoplastic lesions in the mandible.

Head and neck computed tomography virtual endoscopy: evaluation of a new imaging technique

OBJECTIVE

To evaluate a new radiographic imaging technique: computed tomography virtual endoscopy (CTVE) for head and neck tumors.

STUDY DESIGN

Twenty-one patients presenting with head and neck masses who underwent axial computed tomography (CT) scan with contrast were evaluated by CTVE. Comparisons were made with video-recorded images and operative records to evaluate the potential utility of this new imaging technique.

METHODS

Twenty-one patients with aerodigestive head and neck tumors were evaluated by CTVE. One patient had a nasal cylindrical cell papilloma; the remainder, squamous cell carcinomas distributed throughout the upper aerodigestive tract. Patients underwent complete head and neck examination, flexible laryngoscopy, axial CT with contrast, CTVE, and in most cases, operative endoscopy. Available clinical and radiographic evaluations were compared and correlated to CTVE findings.

RESULTS

CTVE accurately demonstrated abnormalities caused by intraluminal tumor, but where there was apposition of normal tissue against tumor, inaccurate depictions of surface contour occurred. Contour resolution was limited, and mucosal irregularity could not be defined. There was very good overall correlation between virtual images, flexible laryngoscopic findings, rigid endoscopy, and operative evaluation in cases where oncological resections were performed. CTVE appears to be most accurate in evaluation of subglottic and nasopharyngeal anatomy in our series of patients.

CONCLUSION

CTVE is a new radiographic technique that provides surface-contour details. The technique is undergoing rapid technical evolution, and although the image quality is limited in situations where there is apposition of tissue folds, there are a number of potential applications for this new imaging technique.

Computer-assisted three-dimensional reconstruction of head and neck tumors

OBJECTIVE

Because head and neck tumors reside in a complex area, having a three-dimensional (3-D) model of the patient's unique anatomical features may assist in the delineation of pathology. The authors describe a new computer technique of 3-D anatomical reconstruction from two-dimensional computed tomography (CT) and magnetic resonance (MR) data and discuss how it represents a step forward in the continuing evolution of 3-D imaging.

STUDY DESIGN

The authors selected three patients with solitary head and neck tumors and reconstructed their anatomy in a 3-D format for study. The tumors represented locations in the nose and central skull base (patient 1), temporal bone (patient 2), and neck (patient 3).

MATERIALS AND METHODS

MR and CT images from the individual patients were electronically transferred to workstations in the Surgical Planning Laboratory of the authors' institution. Registration (or fusion) was carried out between the MR and CT images. The desired anatomic components underwent segmentation (identification and isolation). Assembly of the segmented images was performed and the resulting structures were integrated to produce a 3-D model.

RESULTS

3-D models of the following were constructed and displayed in an interactive format on high-capacity computer workstations: 1) a skull base sarcoma with extension into the nasopharynx and nose; 2) an acoustic neuroma with internal auditory canal involvement; and 3) a metastatic recurrence of a tongue base squamous cell carcinoma in the posterior triangle of the right side of the neck with extension to the skull base.

CONCLUSION

The authors' Surgical Planning Laboratory has developed a 3-D reconstruction technique that has several new features. The models provided a very good 3-D interactive representation of the tumors and patient anatomy. The need now exists to develop this method of 3-D reconstruction of head and neck tumors for potential applications in treatment, research, and medical education.

Virtual otoscopy

Imaging techniques assist the surgeon in diagnosis of disease, surgical planning, and providing image guidance during surgery. Endoscopy has the drawback of being a minimally invasive procedure and limiting visualization to the inner surface of the lumen. Ultrasound, CT, and MR imaging show volumes of tissue beyond the lumen wall; however, their planar, two-dimensional representations require mental reconstruction of anatomic structures, which often proves difficult with the small, complex structures within the temporal bone. To improve three-dimensional visualization of the inner ear, we successfully completed a virtual model that can be displayed as a contiguous, three-dimensional luminal view, known as virtual otoscopy, which emulates traditional endoscopy. A concomitant global view and a view of the related CT slice adds a distinct advantage in the presentation and study of this complex organ. Advances in computer and software technology may overcome the time and cost factors that, at present, limit widespread use of virtual otoscopy. Overall, virtual otoscopy stands as a promising new visualization technique for elucidation of the middle ear, inner ear, and temporal bone structures.

Three-dimensional imaging of ENT diseases with helical computed tomography

We have employed helical computed tomography (CT) to evaluate ear, nose and throat diseases, and present herein seven typical cases: middle ear surgery, osteoma of the external ear canal, maxillary fracture, tripod fracture, submandibular gland calculus, epiglottic abscess and vocal fold palsy. Helical (CT) facilitates the assessment of these diseases and its high diagnostic value is described.