Virtual laryngotracheal endoscopy based on geometric surface modeling using spiral computed tomography data.

This prospective study describes the clinical utility of virtual endoscopy based on geometric surface modeling of the laryngotracheal lumen. Eighteen children with dyspnea related to either subglottic angioma (n = 5) or laryngotracheal stenosis (n = 13) were included. All patients underwent video-recorded operative endoscopy, spiral computed tomography, and 3-dimensional reconstruction of the laryngotracheal lumen. Modeling was achieved by contour detection on spiral computed tomographic images and reconstruction using a geometric shape-recognition algorithm. The generated surface was used for diagnosis and measurement using interactive and automatic tools. Findings of virtual endoscopy and operative endoscopy were compared. Virtual endoscopy confirmed narrowing of the airway in all cases. In 9 cases, high-grade stenosis prevented complete operative endoscopy, but virtual endoscopy allowed accurate assessment and measurement of the stenosis. The findings of operative and virtual endoscopy were concordant in 9 cases. We conclude that surface modeling provides valuable information for preoperative evaluation of laryngotracheal narrowing. The ability to assess extraluminal anatomy provides a clearer picture of overall disease involvement. In the future, virtual endoscopy will probably be used in conjunction with operative endoscopy for therapeutic decision-making. Noninvasive virtual endoscopy could become an alternative to traditional endoscopy under general anesthesia for therapeutic follow-up.     

Evaluation of airway obstruction using virtual endoscopy

OBJECTIVES: This study examines the use of virtual endoscopy (VE) in the evaluation of patients with upper airway obstruction. The utility of VE compared with actual endoscopy was investigated with respect to accuracy of diagnosis and reproduction of endoscopic images. STUDY DESIGN: A random cohort of 30 patients with various causes of airway obstruction was examined. METHODS: The computed tomography (CT) data were reconstructed using a proprietary VE software program, FreeFlight, blind to the actual endoscopic findings. The cause of obstruction was identified and compared with actual endoscopic findings. This included 21 patients with airway stenoses, 8 patients with laryngotracheomalacia, 3 tracheal tumors, 2 glottic webs, 5 patients with innominate artery compression, 2 tracheal granulomas, and 7 patients with impaired true vocal cord mobility. RESULTS: Virtual endoscopic evaluation was accurate in assessing stenosis width and length of fixed airway lesions. Correlation of stenosis shape and contour between actual endoscopy and VE was excellent. The stenosis-to-lumen ratios were compared between VE and actual endoscopy and were found to be within 10% (SD = 8). However, virtual endoscopic evaluation could not illustrate one of the glottic webs, half of the cases of tracheomalacia, or any of the cases of impaired true vocal cord mobility. CONCLUSIONS: Virtual endoscopy was not as sensitive as actual endoscopy in detecting the cause of airway obstruction that was based on dynamic movement. However, VE was excellent for the measurement and definition of fixed airway lesions.     

CT and virtual endoscopy findings in congenital laryngeal web

Laryngeal web is a rare lesion resulting from incomplete recanalization of the primitive larynx. Because the extent of airway involvement affects surgical management, patients should be studied thoroughly before treatment. Although the diagnosis is based on the endoscopy findings in most of the cases, laryngoscopy may fail to show the subglottic extension of the disease. Virtual endoscopy may provide the information needed for surgery in such cases. Here, we report the computed tomography and virtual endoscopy findings in a 5-year-old child with a laryngeal web.     

Long-term study of endonasal duraplasty and review of the literature

Many different techniques have been proposed to repair frontobasal dura mater lesions. Because of its low morbidity and high success rate, the endonasal approach has become a preferred route for treating cerebrospinal fluid fistulas of the anterior skull base. This article presents a retrospective evaluation of 136 endonasal duraplasties (126 patients) performed between July 1980 and May 1998 at a tertiary care facility. Follow-up consisted of clinical examinations including nasal endoscopy, objective measures, and telephone interviews. The following measures were used to evaluate the results of these duraplasties: postoperative nasal fluorescein endoscopy in 71 cases, computed tomographic cisternography in 2, nasal fluorescein endoscopy with computed tomographic cistemography in 19, magnetic resonance imaging in 6, and nasal fluorescein endoscopy with magnetic resonance imaging in 1. Tight closure was accomplished in 129 dural lesions (94.9%) on the first attempt. In 3 cases, recurrence of cerebrospinal fluid leakage was treated successfully by 1 endonasal revision, and in 1 case, a tight duraplasty was achieved after 2 endonasal revisions. Its high success rate, low rate of morbidity, and good long-term results recommend endonasal duraplasty as a primary treatment modality for frontobasal dural lesions. For extended frontobasal dural lesions, for which intracranial dural repair is the preferred approach, the endonasal approach should be used to close additional dural leaks of the sphenoid sinus.     

Complications of laser surgery for laryngeal papillomatosis.

Carbon dioxide laser surgery has become the treatment of choice for laryngeal papillomatosis. The purpose of this study was to determine the type, incidence, and severity of complications that occur with laser microlaryngoscopy for a disease that often requires multiple operations. Forty patients with laryngeal papillomatosis underwent a total of 222 carbon dioxide laser laryngoscopies over the 6 1/2-year period from June 1977 through December 1983. The results showed that 13 patients sustained a total of 23 separate complications. Intraoperative complications consisted of one episode of bilateral pneumothorax and one episode of cervical subcutaneous emphysema, both associated with the use of jet ventilation anesthesia, and one episode of a loosened tooth in a child with carious teeth. The delayed complications consisted of 10 patients with anterior laryngeal webbing, 2 patients with posterior webbing, 6 patients with laryngeal edema or fibrosis, and one episode each of prolonged dysphagia and tracheal foreign body. No airway fires occurred. Only 2 of 28 patients who had 5 or fewer laser laryngoscopies developed complications, but 11 or 12 patients undergoing 6 or more laser operations had complications. In summary, although the incidence of life threatening complications was low, the occurrence of minor complications such as small anterior glottic webs and persistent edema was relatively high, especially in those patients who required multiple laser laryngoscopies.     

The treatment of T3 glottic carcinoma with vertical partial laryngectomy

Total laryngectomy has traditionally been considered the optimal treatment for patients with advanced glottic carcinoma who present with a fixed true vocal cord. However, using whole-organ sectioning techniques, it has been demonstrated that vertical partial laryngectomy is a sound oncologic procedure for selected fixed vocal cord lesions. During the period 1969 to 1984, 27 patients who presented at UCLA with T3 glottic carcinoma were treated using vertical partial laryngectomy. Follow-up for these patients averaged 4.0 years. The absolute two-year disease-free survival rate for this group was 85% (23 of 27 patients), and the local cancer recurrence rate during a two-year postoperative interval was 11% (three of 27 patients). These encouraging results support the continued use of partial laryngeal surgery for a subgroup of patients with T3 glottic cancer. Successful patient selection requires a careful analysis of disease extent based on data obtained from physical examination, magnetic resonance imaging or computed tomographic scanning, and direct laryngoscopy.     

CT仿真喉镜的临床应用

目的 探讨ＣＴ新技术仿真内窥镜成像在喉科的临床应用价值。方法 对４名健康者、９例喉癌、１例喉癌术后复发气道狭窄、１例喉内外弥漫纤维瘤样增生、１例双侧声带息肉患者行螺旋ＣＴ扫描后经软件处理获得仿真喉镜影像，并与纤维喉镜、手术所见对照分析。结果 ＣＴ仿真内窥镜显示喉内正常解剖结构与纤维喉镜所见一致；显示喉内病变的位置、范围与纤维喉镜所见类型，还可从足端入路观察到喉镜所看不到的狭窄远端和声门下区情况。绪     

Virtual rendering techniques in otologic imaging

Virtual postprocessing techniques combine the advantages of condensing the large amounts of data provided by high-resolution (HR) cross-sectional imaging modalities with those of three-dimensional (3D) imaging. The techniques and indications for virtual representations in imaging of the middle ear (ME), internal ear (IE), and cerebellopontine angle (CPA) are presented together with practical examples. MATERIAL AND METHODS: HR data sets acquired by computed tomography (CT) and magnetic resonance imaging (MRI) in patients with ME, IE, and CPA pathologies were transferred to a workstation via an internal network to generate endo- or extraluminal 3D views by means of the volume rendering technique (VRT). The source data were acquired using scanners and imaging protocols with the highest resolution available at present: a multislice spiral CT (MSCT) with a slice thickness of 0.5 mm and a reconstruction increment of 0.2 mm and a 3D CISS sequence with a slice thickness of 0.5 mm for MRI. RESULTS: Virtual endoscopy was superior to cross-sectional images for assessing ME pathologies like dysplasia, postoperative changes, and destructive bone processes with extensive soft-tissue involvement; fibrous obliterations of the internal ear and labyrinthine dysplasia were depicted with a superior image quality on 3D renderings compared to conventional reconstruction techniques. Virtual endoscopy of the CPA and external acoustic meatus (EAM) was helpful in detecting and visualizing neurovascular conflicts and in assigning small intrameatal tumors to components of the acousticofacial bundle. A common feature of all applications was that the large numbers of source images could be reduced to a few 3D reconstructions for documentation and optimized communication of the findings between the radiologist and otologist. CONCLUSION: Virtual rendering makes an important contribution towards establishing, presenting, and documenting the findings when certain otologic pathologies have to be assessed. It can be used for routine imaging and allows for more efficient handling of the large amounts of imaging data generated by high-resolution cross-sectional imaging modalities.     

Virtual endoscopy of the middle and inner ear with spiral computed tomography

OBJECTIVE: To evaluate the inner anatomy of the auditory apparatus by means of virtual endoscopy of spiral computed tomography (CT) data sets. BACKGROUND: Virtual endoscopy permits simulation of the fiberoptic endoscopy perspective by processing CT or magnetic resonance images. METHODS: Seven formalin-fixed specimens of human mastoid were scanned with spiral CT with the following protocol: beam collimation 1 mm, pitch ratio 1, reconstruction spacing 0.2 to 0.5 mm, field of view 90 mm. For the generation of endoscopic views of the auditory spaces, the axial images were processed with Navigator software 2.0 running on UltraSparc I workstation. RESULTS: Virtual endoscopy allowed the demonstration of the external auditory canal, the head and handle of the malleus, the stapes and incudostapedial articulation, the corpus, the long process of the incus with its lenticular process and the short limb, the malleoincudal articulation, the rounded promontory, the round and oval windows, and Prussak's space. From inside the basal turn of the cochlea, virtual endoscopy showed the orifices of the fenestrae cochlea and vestibuli, the origin of the lateral and the anterior semicircular canals, and the basal turn of cochlea. The optimal perspectives that allowed demonstration of the anatomical details of the middle and inner ear are described. CONCLUSION: Virtual endoscopy allows the generation of inner views of the auditory spaces. This new method of image processing can be proposed as an integrative tool of spiral CT imaging.     

Comparison of virtual and conventional endoscopy of nose and paranasal sinuses

We compared computed tomographic virtual rhinosinus endoscopy (VRS) and conventional fiberoptic endoscopy (FE) for the detection of inflammatory-obstructive rhinosinusal disease. We recruited 158 patients; 100 (group A) had inflammatory-obstructive rhinosinus disease, and 58 (group B) had a history of rhinosinus surgery. All patients underwent VRS within 2 to 6 hours of FE, and VRS was able to demonstrate the anatomic details of the nasal fossa and rhinopharynx with a high correspondence to FE. A satisfying representation of anatomic detail was found in both groups A and B. The VRS was able to visualize invasiveness of the endosinusal cavities, which was not accessible to FE. The VRS is a fast, relatively easy, and noninvasive technique that could be integrated into FE or used as an alternative when FE is unfeasible. Because of the ability to explore the sinus cavity, we suggest that virtual rhinosinusoscopy should be considered as the appropriate term, instead of virtual rhinoscopy.     

Is virtual endoscopy of the middle ear useful?

Virtual endoscopy is a relatively new imaging technology in otology, and therefore data on its efficacy in clinical situations are limited. We conducted a prospective study to evaluate the clinical relevance of radiologic diagnoses based on virtual endoscopy of the middle ear. Our patient population was made up of 30 adults who were scheduled to undergo surgery to correct conductive hearing loss of unknown etiology. Virtual endoscopy was performed on three-dimensional images that were constructed from images obtained with conventional two-dimensional computed tomography (CT). Findings on virtual endoscopy were then compared with the subsequent surgical findings. Virtual endoscopy suggested a middle ear pathology in 19 patients and a normal middle ear in 11 patients. Postoperatively, we found that the virtual diagnoses correlated moderately well with the surgical findings in the group of patients with predicted pathology; 13 of these 19 patients were found to have middle ear problems such as ossicular chain anomalies, otosclerosis, and cholesteatoma (positive predictive value: 68%). However, among the 11 patients whose middle ear structures were radiologically predicted to be normal, only 2 had negative middle ear findings on surgical exploration; of the remaining 9 patients, 8 had otosclerosis and 1 had malleus fixation (negative predictive value: 18%). Thus, the sensitivity and specificity of virtual endoscopy were 59 and 25%, respectively. Virtual endoscopy provides images from a surgeon's perspective, and so it has the potential to be useful in the preoperative evaluation of the middle ear cavity. With ongoing advancements in computer systems and imaging techniques, the cost, reliability, and efficacy of virtual endoscopy may improve. However, further clinical validation and cost-benefit analysis are required before we can determine if it has any additional advantages over conventional two-dimensional CT.     

Virtual endoscopy of the nasal cavity in comparison with fiberoptic endoscopy

Purpose: To apply virtual-endoscopic mode to display the nasal cavity and to evaluate clinical application of virtual endoscopy in comparison with nasal fiberoptic endoscopy. Materials and methods: Eleven patients were examined by virtual endoscopy after axial spiral computed tomography (CT) scanning was performed. In addition, 9 out of these 11 patients underwent fiberoptic endoscopy. Spiral CT scanning was performed with 1-mm collimation, 0.5- to 1-mm increment, 25–250 mA s, and pitch 1–2. Virtual endoscopy was performed by Explorer software package. Results: Virtual endoscopy could clearly demonstrate anatomic structures in the nasal cavity, septal deviation, stenosis and obstruction of the middle meatus, turbinate hyperplasia, and pathological masses larger than 3 mm in diameter. However, “false adhesions” may appear in virtual endoscopy. The main limitation of virtual endoscopy was the inability to evaluate mucosa and its surface. Conclusion: Virtual endoscopy of the nasal cavity is a new and noninvasive method. It can demonstrate normal and pathological structures in the nasal cavity. Its ability to visualize is comparable with fiberoptic endoscopy except for evaluating mucosal surface and secretions. In the future, this method will probably be a basic instrument of computer-assisted surgery in the midfacial region. Received: 9 December 1999 / Accepted: 7 September 2000     

Real-time, cine magnetic resonance imaging for evaluation of the pediatric airway.

BACKGROUND: Standard magnetic resonance imaging (MRI) and computed tomographic (CT) modalities are limited in their ability to image dynamic organs. New real-time, dynamic, cine magnetic resonance imaging (CMRI) techniques have the potential to image moving structures. OBJECTIVE: We therefore investigated the feasibility of using CMRI techniques to dynamically image the human airway, to assess laryngeal and tracheal patency and function. METHODS: A cohort of 10 pediatric patients, 10 adult patients, and 10 normal volunteers underwent routine static MRI, as well as CMRI using a Siemens 1.5 T Vision system (Siemens, Erlangen, Germany). Patients also underwent endoscopic evaluation. Cine axial, coronal, and sagittal sequences of the larynx and trachea were obtained during quiet respiration, as well as during a variety of provocative maneuvers. RESULTS: CMRI readily demonstrated normal vocal cord mobility and tracheal stability in normal volunteers. Abnormal vocal mobility was easily appreciated using the CMRI imaging system. Similarly, dynamic effects of tracheomalacia were clearly demonstrated using CMRI. Dynamic extrinsic tracheal compression resulting from mass lesions or anomalous vasculature was also visualized using CMRI. CONCLUSIONS: Cine MRI of the airway has the potential to provide novel data regarding laryngeal and tracheal patency and function. This evolving modality may serve as a valuable adjunct to static MR and CT imaging, as well as endoscopy, in the assessment of the airway.     

Inner surface imaging of laryngeal and tracheal stenosis by spiral-CT: role of a new diagnostic procedure

BACKGROUND: Inner-surface-reconstruction calculated from helical-CT data sets offers a new diagnostic option for upper airway assessment. Using a special software, it is possible to create a continuous overview on the inner surface of hollow viscera on a monitor, similar to an endoscopic view. However, reports on the clinical value of this examination procedure with regard to laryngeal or tracheal stenosis are rare. METHOD: We compared the results of this "virtual endoscopy" with real endoscopic or intraoperative findings in 11 patients suffering from laryngeal or tracheal stenosis of various etiologies. RESULTS: Data on extension and localization of airway stenosis obtained by virtual endoscopy corresponded well with our endoscopic or intraoperative findings in all patients. The grade of airway stenosis as assessed by inner-surface-reconstruction could be confirmed by endoscopy in 8 of 11 cases investigated. Detection of 2 additional airway stenoses distal to an endoscopically non-passable tracheal stenosis was possible by virtual endoscopy in one case. CONCLUSION: As a supportive diagnostic procedure, virtual endoscopy offers a valuable overview on extension and localization of laryngeal or tracheal stenoses with regard to a possible therapeutic management.     

Computed tomography in the evaluation of acquired stenosis in the neonate

We studied the feasibility of computed tomographic evaluation of the neonatal airway. Three neonatal larynges, removed at necroscopy, were examined by computed tomography. Good resolution of soft tissue, cartilage and airway lumen was obtained in these small specimens. On the basis of these findings two neonates with acquired subglottic stenosis were examined by endoscopy, soft tissue airway radiographs, and computed tomography. Measurements of radiation dose revealed that a computed tomographic study delivered 36% of the mean tissue dose of standard image intensifier fluoroscopy. Computed tomography and fluoroscopy both demonstrated the degree and length of this stenosis accurately. An advantage of CT over conventional imaging procedures was better definition of the cross sectional area of the airway.     

Application of magnetic resonance virtual endoscopy as a presurgical procedure before sialoendoscopy

Objectives: The objectives of this study were to investigate the feasibility of clinical application of magnetic resonance (MR) virtual endoscopy as a presurgical procedure before sialoendoscopy and to evaluate its value in the diagnosis of obstructive salivary gland diseases and preoperative visualization of endoluminal views. Study Design: This study presents our initial experience to use MR virtual endoscopy for the presurgical visualization of salivary duct lumen and ductal pathologies in comparison to the sialoendoscopy findings in a feasibility study. Methods: Six consecutive patients with suspected obstructive salivary gland diseases underwent MR sialography with a three‐dimensional fast imaging using steady‐state acquisition. The three‐dimensional MR data were transferred to an independent workstation and were postprocessed with navigator software to generate three‐dimensional reconstruction and virtual endoscopic images. The fly‐through mode was used to imitate the sialoendoscopic exploratory procedure. Then the patients underwent sialoendoscopy and the endoscopic findings were compared with the preoperative virtual endoscopic images. Results: The MR data acquisition and postprocessing protocol were feasible. The virtual endoscopy created clear endoluminal views of salivary duct and the ductal pathologies. The diagnoses were all confirmed by surgical sialoendoscopy. The virtual endoscopic images showed close resemblance to the sialoendoscopic findings. Conclusions: MR virtual endoscopy is an effective and noninvasive diagnostic method for evaluating the endoluminal anatomy and pathologies of the salivary duct. The clinical application of MR virtual endoscopy as a presurgical procedure before sialoendoscopy is a valuable and promising approach, which can provide surgeons useful morphologic and pathologic information.     

纤维喉镜与模拟内镜技术对阻塞性睡眠呼吸暂停低通气综合征的诊断价值

目的:比较纤维喉镜与模拟内镜技术在阻塞性睡眠呼吸暂停低通气综合征(OSAHS)诊断中的作用和各自的优缺点;进一步探讨上呼吸道在阻塞通气过程中的变化特点.方法:我们对21例经睡眠监测确诊为OSAHS的患者行电子纤维喉镜检查,并行螺旋CT扫描后经软件处理.获得仿真上呼吸道图像.检查在清醒和睡眠2种状态下进行.测量软腭平面、悬雍垂平面、舌后平面和会厌平面的前后径和左右径.结果:纤维喉镜与仿真上呼吸道图像在上呼吸道的4个平面的测量上均差异有统计学意义;在清醒和睡眠状态下,软腭后区前后径的变化差异无统计学意义,其左右径差异有统计学意义.结论:清醒与睡眠状态下,上呼吸道的腔径有明显不同;腔径的变化以左右径变化为主;纤维喉镜在上呼吸道的动态观察中有很重要的诊断价值;仿真上呼吸道图像能够真实的显示上呼吸道狭窄的部位和程度;结合原始的二维图像可提供解剖结构和病理变化的相关信息.     

The utility of magnetic resonance imaging in the diagnosis of intranasal meningoencephaloceles.

We present three patients in whom the diagnosis of intranasal meningoencephalocele was made by magnetic resonance imaging. The initial clinical evaluation and computed tomographic examinations of these patients failed to distinguish between chronic inflammation and intranasal meningoencephalocele. Although both computed tomography and magnetic resonance imaging are used to distinguish between normal, inflammatory, and neoplastic tissue in the nasal cavity and paranasal sinuses, limitations do exist and these are the focus of our communication. A clear understanding of the efficacy of these radiographic modalities will enhance surgical planning and can preclude severe complications.     

Virtual endoscopy imaging of the middle ear cavity and ossicles

Ten cadaver temporal bone blocks were studied with high-resolution computed tomography (HRCT) in order to produce topographic images, which are more informative than ordinary CT slices. Virtual endoscopic images were produced with separate, commercially available software, paying attention to the middle ear cavity and ossicles. Four major viewing locations for virtual endoscopy (the ear canal, hypotympanum, attic and eustachian tube) developed images acceptably. The malleus and incus were visualized properly. Small structures such as the lenticular process and the stapes sometimes failed to have good imaging. The eustachian tube and attic virtual views, which are usually not receptive to ordinary endoscopy, gave proper visualization of middle ear structures. Even the smallest structure, the stapes, can produce a virtual image.Virtual endoscopic images, or topographic images, of the middle ear and ossicles contribute to the understanding of the anatomy of the middle ear, thus enhancing the chances for successful surgery. Received: 2 January 2001 / Accepted: 9 July 2001