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

Accuracy of multimodal image fusion for oral and maxillofacial tumors: A revised evaluation method and its application

OBJECTIVE

To develop a revised evaluation method for accuracy of multimodal image fusion for oral and maxillofacial tumors and explore its application for comparing the accuracy of three commonly used fusion algorithms, automatic fusion, manual fusion, and registration point-based fusion.

MATERIALS AND METHODS

Image sets of patients with oral and maxillofacial tumor were fused using the iPlan 3.0 navigation system. Fusion accuracy included two aspects: (1) overall fusion accuracy: represented by the mean value of the coordinate differences along the x-, y-, and z- axes (Δx, Δy, and Δz), mean deviation (MD), and root mean square (RMS) of six pairs of landmarks on the two image sets; (2) tumor volume fusion accuracy: represented by Fusion Index (FI), which was calculated based on the volume of tumor delineated on the two image sets.

RESULTS

Eighteen pairs of image sets of 17 patients were enrolled in this study. The Δx and Δy values for the three algorithms were less than 1.5 mm. The Δz values for automatic fusion, manual fusion and registration point-based fusion was 1.049 mm, 1.864 mm and 1.254 mm. The MD for automatic fusion, manual fusion and registration point-based fusion was 1.978 mm, 2.788 mm and 1.926 mm. Significant differences existed in Δz for manual fusion and that for automatic fusion (P = 0.058), in MD for manual fusion and that for automatic fusion (P = 0.087), and in MD for manual fusion and that for registration point-based fusion (P = 0.069). The FI for automatic fusion, manual fusion, and registration point-based fusion was 0.594, 0.520, and 0.549; the inter-algorithm differences were not significant (P = 0.290).

CONCLUSION

The automatic fusion and the registration point-based fusion were more accurate than manual fusion, and therefore were recommended to be used in multimodal image fusion for oral and maxillofacial tumors.

Virtual endoscopy of laryngeal carcinoma: Is it useful?

OBJECTIVE: To compare virtual endoscopy (VE) with flexible endoscopy in patients with cancer of the larynx.

STUDY DESIGN AND SETTINGS: This prospective study includes 24 patients with proven cancer of the larynx. Patients underwent spiral CT according to our standard protocol for upper airway imaging. This same set of axial scans was transferred to a dedicated workstation to obtain VE images. Results of VE were compared with the findings of flexible endoscopy.

RESULTS: Quality of the examination was good in 96% of the patients. VE identified all exophytic lesions. Two small flat lesions could be observed as slightly enhanced plaques only on the axial scans. Subglottic extension was correctly demonstrated in all cases by associating VE to the axial scans.

CONCLUSION: VE shows high sensitivity in the identification of exophytic lesions of the larynx and can establish relationships between cancer and nearby structures. It can be performed in the presence of severe stenosis and does not require sedation and additional scanning. On the other hand, VE show limits in the identification of flat lesions and does not allow biopsies and functional imaging to be performed.

SIGNIFICANCE: VE is a useful tool for staging and presurgery treatment of cancer of the larynx.

Current oncologic concepts and emerging techniques for imaging of head and neck squamous cell cancer

The incidence of head and neck squamous cell carcinoma (HNSCC) is increasing and currently they account for 5% of all malignancies worldwide. Inspite of ongoing developments in diagnostic imaging and new therapeutic options, HNSCC still represents a multidisciplinary challenge.One of the most important prognostic factors in HNSCC is the presence of lymph node metastases. Patients with confirmed nodal involvement have a considerable reduction of their 5-year overall survival rate. In the era of individually optimised surgery, chemotherapy and intensity modulated radiotherapy, the main role of pre- and posttherapeutic imaging remains cancer detection at an early stage and accurate follow-up. The combined effort of early diagnosis and close patient monitoring after surgery and/or radio-chemotherapy influences disease progression and outcome predicition in patients with HNSCC.This review article focuses on currrent oncologic concepts and emerging tools in imaging of head and neck squamous cell cancer. Besides the diagnostic spectrum of the individual imaging modalities, their limitations are also discussed. One main part of this article is dedicated to PET-CT which combines functional and morphological imaging. Furthermore latest developments in MRI are presented with regard to lymph node staging and response prediction. Last but not least, a clinical contribution in this review explains, which information the head and neck surgeon requires from the multimodality imaging and its impact on operation planning.

Endoscopic sinus surgery: evolution and technical innovations

Prior to the introduction of functional endoscopic sinus surgery, several surgeons had begun to use telescopes to perform surgical procedures in the nose and sinuses. However, the central concepts of functional endoscopic sinus surgery evolved primarily from Messerklinger's endoscopic study of mucociliary clearance and endoscopic detailing of intranasal pathology. The popularity of a combination of endoscopic ethmoidectomy plus opening of secondarily involved sinuses grew rapidly during the latter part of the twentieth century, and endoscopic intranasal techniques began to expand to deal with pathology other than inflammation. We present a review of the evolution of knowledge regarding the pathogenesis of inflammatory sinus disease since that point in time, and of the impact that this has had on the management of inflammatory sinus disease. We also detail the technological advances that have allowed endoscopic intranasal techniques to expand and successfully treat other pathology, including skull base and orbital disease. In addition, we describe evolving technologies which may further influence development within this field.

Technical innovations and the evolution of endoscopic sinus surgery

Since the introduction of endoscopic sinus surgery, a number of significant technological advances, as well as an improved understanding of disease pathogenesis and management, have enabled major evolutions in surgical techniques. Modifications to surgical instruments, imaging, the development of the microdebrider, and other newer instrumentation have all contributed to the current level of patient success associated with endoscopic intranasal techniques. At the same time, it has become evident that anatomic variations are less important in the pathogenesis of chronic rhinosinusitis than was previously thought, and that ventilation alone is insufficient to resolve well-established disease. This paper reviews the changes that have occurred in endoscopic sinus surgery over the past 20 years since the techniques were first introduced into the United States, and the technologies that have enabled these changes and the development of extended endoscopic techniques. Continuing developments of interactive computer-guided surgery, endoscopic 3-dimensional imagery, robotics, and improved adjunctive therapies will further extend the role of endoscopic transnasal approaches to an expanded number of skull base and intracranial lesions.

Objektivierung von Therapieergebnissen in der Schädelbasischirurgie durch virtuelle Modellanalyse

BACKGROUND

Virtual model analysis of patient head tracking allows for objectivity and the monitoring of therapeutic results of pathologies in the skull base region. The introduction of these models in clinical routine has been impaired by the extended time needed for the preparation of radiological data.

METHODS

Quality control analysis was carried out for seven cases with different pathological findings in the skull base region in patients who had undergone virtual model analysis.

RESULTS

Preparation time of radiological data for the process of segmentation required, under optimal conditions, a minimum of 30 min. Virtual model analysis enables spatial visualization of regions of interest and adjacent anatomical structures. This improves case-specific pathoanatomical understanding as well as preoperative planning of surgical strategies.

CONCLUSIONS

Virtual model analysis improves the physician's spatial comprehension of localized pathological findings at the dysmorphic interface of bone and soft tissue across the skull base. Therefore, it seems to be an adequate tool for quality control analysis of therapeutic results after extended skull base surgery.

Imaging in head and neck oncology

Evaluation of head and neck cancer with imaging is a topic that is far more extensive than can be covered in this article. The main reason for head and neck imaging is to evaluate the true extent of disease to best determine surgical and therapeutic options. This process includes evaluation of the size, location, and extent of tumor infiltration into surrounding vascular and visceral structures. Important anatomic variants must be pointed out so the surgeon can avoid potential intraoperative complications. These variant scan be evaluated with the appropriate multiplanar and three-dimensional images to provide as much information as possible to the surgeon preoperatively. Second, nodal staging should be assessed in an effort to increase the number of abnormal nodes detected by physical examination and, more important, to precisely define their location by a standard classification system that can be understood and consistently applied by the radiologist, surgeon, radiation oncologist, and pathologist. Although secondary to the previously described tasks, imaging frequently enables a limitation of the diagnostic and histologic possibilities based on lesion location and signal-attenuation characteristics, which may lead the clinical investigation along a different path. saving the patient unnecessary risk and shortening the time to diagnosis and ultimate treatment. This article has attempted to detail the current state of the controversy between CT, MRI, and other modalities, and has emphasized the constant evolution of this controversy because of the evolving imaging technology. Although CT and MRI are both well suited to evaluation of the deep spaces and submucosal spaces of the head and neck, each has some limitations.MRI has the advantages of higher soft tissue contrast resolution, the lack of iodine-based contrast agents, and high sensitivity for perineural and intracranial disease. The disadvantages of MRI include lower patient tolerance, contraindications in pacemakers and certain other implanted metallic devices, and artifacts related to multiple causes, not the least of which is motion. CT is fast, well tolerated, and readily available but has lower contrast resolution and requires iodinated contrast and ionizing radiation. The current authors' practice is heavily centered on CT for initial evaluation, preoperative planning, biopsy targeting, and postoperative follow-up. They reserve MRI for tumors that are suspicious for perineural,cartilaginous, or bony invasion on CT, or for tumors such as adenoid cystic carcinoma that are highly likely to spread by way of these routes. For patients who have head and neck cancer, a radiologist who is educated in the treatment options, patterns of tumor growth, and important surgical landmarks, and who has a well-established pattern of communication with the head and neck clinical services, including surgery, radiation oncology,and pathology, is key in providing accurate and useful image interpretation.

Cosmetic aspects of cranial reconstruction

Cranial reconstruction has evolved to achieve both functional coverage and esthetic appearance. Hair preservation/reconstruction and free flaps have markedly improved the soft tissue esthetic outcome. Restoration of bony contour has been facilitated by advanced craniofacial techniques and three-dimensional alloplast.

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.

Computer-aided surgical planning for implantation of hearing aids based on CT data in a VR environment

A study was undertaken to assess the feasibility of a preoperative fitting test for an implantable hearing aid in a virtual reality (VR) environment. High-resolution spiral computed tomography (CT) of the mastoid bone was performed, and the results of a mastoidectomy were simulated with manual segmentation on a standard medical workstation. CT was also performed on a temporal bone specimen obtained at real mastoidectomy, and the bone margins were segmented automatically with threshold-based techniques. A triangulated surface representation of the bone structures including the mastoid cavity was generated. These data as well as the computer-aided design (CAD) files of the medical devices were transferred into a VR environment. The CAD components of the hearing aid were manipulated to simulate the surgical implantation procedure. Merging CAD data of an implantable hearing aid with CT data of the temporal bone in a VR environment was shown to be a feasible method of providing three-dimensional information for the presurgical determination of fit and mountability. Advances in hardware and software are expected to improve the usability of this method. Although clinical studies are needed, these results may serve as an impetus for exploring the use of low-cost, widely available VR computer equipment in a potentially broad field of clinical applications.

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.

Paranasal sinuses and nasopharynx CT and MRI

Neoplastic disease of the nose, paranasal sinuses, the nasopharynx and the parapharyngeal space requires thorough assessment of location and extent in order to plan appropriate treatment. CT allows the deep soft tissue planes to be evaluated and provides a complement to the physical examination. It is especially helpful in regions involving thin bony structures (paranasal sinuses, orbita); here CT performs better than MRI. MRI possesses many advantages over other imaging modalities caused by its excellent tissue contrast. In evaluating regions involving predominantly soft tissue structures (ec nasopharynx and parapharyngeal space) MRI is superior to CT. The possibility to obtain strictly consecutive volume data sets with spiral CT or 3D MRI offer excellent perspectives to visualize the data via 2D or 3D postprocessing. Because head and neck tumors reside in a complex area, having a 3D model of the anatomical features may assist in the delineation of pathology. Data sets may be transferred directly into computer systems and thus be used in computer assisted surgery.

Endoscopic sinus surgery using intraoperative computed tomography imaging for updating a three-dimensional navigation system

OBJECTIVES

The use of three-dimensional navigation systems provides information on the structures surrounding the field of operation and thereby reduces the risk of iatrogenic damage. The computed tomography (CT) data conventionally used are provided by preoperative scanning procedures, which means that tissue changes coming about during surgery are not seen on the screen. An intraoperative CT scanning procedure being able to update the CT data could provide a solution.

STUDY DESIGN

Endoscopic sinus operations using an intraoperative CT updating the three-dimensional navigation system were performed on six persons to find out, whether the above is true.

METHODS

Different parameters, advantages, and disadvantages in the cases of these six patients were compared with a group of 22 patients who underwent conventional endoscopic sinus surgery with different three-dimensional navigation systems without updating the CT data set.

RESULTS

The intraoperative CT for updating the three-dimensional navigation system provides useful information for the surgeon.

CONCLUSION

Balancing its advantages against its disadvantages, the updating of the CT data set with intraoperative CT cannot be recommended for conventional standard endoscopic sinus surgery.