Use of reconstructed,non-orthogonal plane,high-resolution computed tomography of the temporal bone in the planning of temporal bone surgery

OBJECTIVES: To demonstrate the utility of high-resolution computed tomography (HRCT) reconstructed in non-orthogonal planes in the planning of temporal bone surgery. STUDY DESIGN: Qualitative and quantitative comparison of in vivo anatomic measurements between orthogonal and non-orthogonal plane reformatted HRCT of the temporal bone. METHODS: HRCT data of 10 normal temporal bones were reconstructed two-dimensionally in two non-orthogonal planes. Parallel to the plane defined by the superior semicircular canal (defined as transverse) as well as perpendicular to the plane defined by the superior semicircular canal (defined as longitudinal). This was done using commercially available software. Sixteen surgically important relationships between neural, vascular and/or bony structures were measured and analyzed. RESULTS: Quantitatively, wide variations were obtained in the measurements obtained from images of both non-orthogonal planar orientations. These variations were not age or sex dependent. Qualitatively, the images obtained highlight the anatomy of the temporal bone and skull base as it will be encountered during otologic surgery, since the surgical visual axis is along the long axis of the temporal bone. CONCLUSIONS: The reformatted images in non-orthogonal planes were superior to the axial and coronal series because they condensed critical relationships into a single perspective which promoted an intuitive understanding of the surgical approach. These reconstructed images show wide differences in quantitative measurements between surgically relevant landmarks. The protocol can be easily implemented in the clinical setting and is a potentially valuable educational tool. We recommend that non-orthogonal reconstructed images be routinely included with orthogonal temporal bone HRCT scans.     

High-resolution computerized tomography for ossicular replacement prostheses

IntroductionTo study the accuracy of high-resolution computed tomography (HRCT) for assessing the ossicular structures in cadaveric temporal bone by the distance between temporal bone elements is of great interest.ObjectivesTo record the distances between the malleal neck and both the stapedial head and footplate by HRCT. Further, after partially opening the temporal bone toward the ossicular structure, to record the actual distances between those structures during surgical dissection.Material and methodsThis study compared actual and HRCT measurements of cadaveric temporal bone. We studied, measured, and recorded distances within and between various structural elements. All data are reported as means and were analyzed to prove the accuracy of HRCT to assess ossicular structure from the temporal bone.ResultsThis study included the temporal bones of 10 male and 10 female cadavers (mean age, 70.4 years). By surgical dissection, the distances between the malleal neck and the stapedial head and footplate were 3.40 and 5.30 mm, respectively (measured from the bone); by HRCT, the corresponding values were 3.35 and 5.29 mm. The intraclass correlation coefficients for assessing ossicular structure in contrast to the actual measurements were 0.901 (malleal neck to stapedial head) and 0.923 (malleal neck to stapedial footplate) (p < 0.05). There were no differences between the actual malleal neck to stapedial head (p = 0.793) or footplate (p = 0.242) measurements.ConclusionHRCT produced statistically comparable, reliable, and accurate measurements compared with actual measurements in cadaveric temporal bone.     

Preoperative imaging protocol for cochlear implant candidates

OBJECTIVE: To formulate and test a CT imaging protocol for preoperative scanning of the temporal bone in cochlear implant candidates. MATERIAL AND METHODS: A human head was scanned in three CT planes: axial, axiopetrosal and semilongitudinal. Multiplanar reformats (MPRs), based on axial slices, were created and compared with the corresponding images obtained by direct scanning in the respective planes. All scans were analyzed on a viewing workstation. RESULTS: The axial plane image allowed for an overview of the temporal bone. The width of the facial recess and the cochlear nerve canal could be studied on combined axial and axiopetrosal images. Cochlear patency could be evaluated using combined axial and semilongitudinal images. Axiopetrosal and semilongitudinal MPRs were able to replace the images obtained by direct scanning in the respective planes. CONCLUSION: The combination of the axial CT plane image and MPRs was found to be sufficient for preoperative analysis of the temporal bone morphology.     

Scalar localization of the electrode array after cochlear implantation: a cadaveric validation study comparing 64-slice multidetector computed tomography with microcomputed tomography.

HYPOTHESIS: Improved resolution available with 64-slice multidetector computed tomography (MDCT) could potentially be used clinically to localize the cochlear implant (CI) electrode array within the basal turn. BACKGROUND: In CI surgery, the electrode array should be inserted into and remain within the scala tympani to avoid injury to Reissner's membrane and the scala media. Correlating the position of the electrode in the basal turn with surgical technique and implant design could be helpful in improving outcomes. METHODS: After a standard left mastoid exposure of the round window niche through the facial recess performed on a cadaver head, an electrode array from a Nucleus Softip Contour CI was fully inserted through a cochleostomy. The head was then scanned axially on a 64-slice MDCT with 0.4-mm slice thickness and reconstructed into the oblique axial, oblique coronal, and oblique sagittal planes of the cochlea. The temporal bone was then harvested and imaged on a microcomputed tomographic scanner using 20-microm slice thickness. Identical reconstructions were made and compared with the 64-slice images to confirm exact location of the electrode array. RESULTS: The 64-slice MDCT accurately localized the electrode array to the scala tympani. This was best demonstrated in the oblique sagittal plane, identifying the electrode array in the posterior inferior portion of the basal turn, posterior to the spiral lamina. CONCLUSION: This ex vivo validation study suggests that 64-slice MDCT has the potential to allow accurate localization of the CI electrode array within the basal turn of the cochlea.     

Preoperative Imaging Protocol for Cochlear Implant Candidates

Objective —To formulate and test a CT imaging protocol for preoperative scanning of the temporal bone in cochlear implant candidates.

Material and Methods —A human head was scanned in three CT planes: axial, axiopetrosal and semilongitudinal. Multiplanar reformats (MPRs), based on axial slices, were created and compared with the corresponding images obtained by direct scanning in the respective planes. All scans were analyzed on a viewing workstation.

Results —The axial plane image allowed for an overview of the temporal bone. The width of the facial recess and the cochlear nerve canal could be studied on combined axial and axiopetrosal images. Cochlear patency could be evaluated using combined axial and semilongitudinal images. Axiopetrosal and semilongitudinal MPRs were able to replace the images obtained by direct scanning in the respective planes.

Conclusion —The combination of the axial CT plane image and MPRs was found to be sufficient for preoperative analysis of the temporal bone morphology.     

Visualization of the middle ear with high resolution computed tomography and superfine fiberoptic videomicroendoscopy

Ten temporal bone blocks were dissected from fresh postmortem specimens from patients succumbing to diseases unrelated to the ears. A superfine fiberoptic videomicroendoscope (SFV) was introduced through the eustachian tube into the middle ear, and middle ear structures were visualized. The cadaver temporal bone blocks were also studied with high-resolution computed tomography (HRCT). When HRCT gave good results SFV did not succeed well and vice versa. However, SFV provided topographic anatomical information of the middle ear structures while HRCT gave cross-sectional images of the anatomy of the tympanic cavity. The different types of information obtained by the two imaging technologies supplement each other and were found to improve diagnosis in such cases as external ear canal atresia. Received: 22 July 1997 / Accepted: 28 October 1997     

高分辨率CT在窦口-鼻道复合体的临床应用价值

目的通过高分辨率CT(HRCT)对慢性鼻窦炎患者窦口-鼻道复合体(OMC)的影像分析,探讨其在功能性鼻内镜手术(FESS)的应用价值.方法收集12～54岁患者30例,常规冠状位HRCT扫描和横断面扫描,并采用适宜的窗技术观察.结果HRCT能直接显示慢性鼻窦炎病变的范围、程度以及OMC的阻塞部位;且能清晰显示解剖变异,骨质改变.结论HRCT对FESS有肯定的指导价值.     

Use of reconstructed sagittal computed tomography images to plan middle cranial fossa surgery.

OBJECTIVE: To facilitate planning in temporal bone surgery for the middle cranial fossa approach by using sagittal reconstructed temporal bone computed tomography images. STUDY DESIGN: Comparison of anatomic measurements on random high-resolution, reformatted computed tomography scans of the temporal bone. METHODS: High-resolution computed tomography of 10 normal temporal bones in the axial and coronal planes was obtained, and two-dimensional sagittal reconstructions were performed using a commercial software program. Eight anatomical relationships between neural and/or vascular structures were measured. Representative images were inverted to recreate the plane of the middle cranial fossa approach. RESULTS: Anatomical relationships among the vestibule, superior semicircular canal, internal auditory canal, internal carotid artery, and middle cranial fossa exhibited a high SD in the 10 subjects. The sample size and the large range for the eight anatomical relationships precluded the detection of a significant difference between right and left temporal bones or sex and age of the patient. CONCLUSION: The present report presents a novel, practical measurement protocol for rapidly evaluating important individual anatomical differences in patients before middle cranial fossa surgery. Inverted sagittal reconstructions facilitate presurgical planning for the middle cranial fossa approach by 1) assessing critical anatomical relationships before surgery and 2) providing customized measurements between vital landmarks and the first in vivo measurements. This decreases the likelihood of surgical mishaps and improves teaching by providing the first in vivo measurements of practical anatomical relationships in the sagittal plane.     

Correlation of high-resolution computed tomography and gross anatomic sections of the temporal bone: Part I. The facial nerve

Detailed anatomic analysis of the human temporal bone has been made possible by correlating high-resolution computed tomography (CT) with gross anatomic sections. Serial CT scans of isolated temporal bones were obtained in the transaxial (horizontal), coronal, and sagittal planes at 1.5-mm intervals. The temporal bone was sectioned at 2.0-mm intervals in planes parallel to the CT scans. Based on a correlation of these sections, the facial nerve canal was divided into four segments and the planes in which each is best observed are described and illustrated. The first segment in the internal auditory canal is best visualized in the sagittal plane, the labyrinthine segment and geniculate ganglion in the coronal and transaxial planes, the tympanic portion in the sagittal plane, the genu, between the tympanic and mastoid portion, in the sagittal plane, and the mastoid portion and the stylomastoid foramen in the coronal and sagittal planes.     

virtual temporal bone anatomy

Background The Visible Human Project(VHP) initiated by the U.S. National Library of Medicine has drawn much attention and interests from around the world. The Visible Chinese Human(VCH) project has started in China. The current study aims at acquiring a feasible virtual methodology for reconstructing the temporal bone of the Chinese population, which may provide an accurate 3-D model of important temporal bone structures that can be used in teaching and patient care for medical scientists and clinicians. Methods A series of sectional images of the temporal bone were generated from section slices of a female cadaver head. On each sectional image, SOIs (structures of interest) were segmented by carefully defining their contours and filling their areas with certain gray scale values. The processed volume data were then inducted into the 3D Slicer software(developed by the Surgical Planning Lab at Brigham and Women's Hospital and the MIT AI Lab) for resegmentation and generation of a set of tagged images of the SOIs. 3D surface models of SOIs were then reconstructed from these images. Results The temporal bone and structures in the temporal bone, including the tympanic cavity, mastoid cells, sigmoid sinus and internal carotid artery, were successfully reconstructed. The orientation of and spatial relationship among these structures were easily visualized in the reconstructed surface models. Conclusion The 3D Slicer software can be used for 3- dimensional visualization of anatomic structures in the temporal bone, which will greatly facilitate the advance of knowledge and techniques critical for studying and treating disorders involving the temporal bone.     

Measurements of normal inner ear on computed tomography in children with congenital sensorineural hearing loss

The objective of this study is to use standardized measurements of the inner ear to see whether there are subtle bony malformations in children with congenital sensorineural hearing loss (SNHL) whose temporal bone computed tomography (CT) are grossly normal. The study includes 45 ears with congenital SNHL and grossly normal temporal bone CT scans and 45 ears with normal inner ear structures and normal hearing. Standardized measurements of the inner ear structures were made on axial temporal bone CT scans. Student’s t test was performed to compare the measurements of the two groups. There were significant differences in the measurements of the bony island width of the superior semicircular canal, bony island width of the lateral semicircular canal and maximal height of cochlea between two groups (P < 0.05). In conclusion, standardized measurements of bony labyrinth of inner ear on temporal bone CT can identify subtle abnormalities of inner ear in patients with congenital SNHL having grossly normal radiological images.     

Acute temporal bone trauma: utility of high-resolution computed tomography

OBJECTIVE: To determine the clinical utility of high-resolution computed tomography (HRCT) for temporal bone trauma evaluation and management. STUDY DESIGN: Retrospective review. SETTING: Level I trauma center. PATIENTS: Patients (n = 105) with evidence of temporal bone trauma. MAIN OUTCOME MEASURES: Statistically significant associations between HRCT, clinical, audiometric, and head CT findings, and management decisions; role of HRCT in management decisions. RESULTS: Statistical analysis demonstrated poor association between specific clinical and HRCT findings, and between HRCT findings and management decisions. The HRCT complemented decision making in 10% of cases and revealed asymptomatic carotid canal fractures in 9% of cases. CONCLUSION: Routine HRCT yields minimal clinical utility. Selective use of HRCT may complement decision making, but patient management is predominantly influenced by other factors. Although angiography was performed in cases of asymptomatic carotid canal fractures, no clinical utility for this practice was demonstrated. An algorithm for temporal bone trauma evaluation and management is presented.     

High resolution computed tomography of the temporal bone in infants and children: a review

Pathologic conditions involving the temporal bone in infants and children are now commonly diagnosed by computed tomography (CT). The importance of utilizing high resolution computed tomography (HRCT) with magnified, thin (1.5 mm) scans in both the axial and coronal planes is stressed in order to obtain the maximal anatomic information that is critical for proper diagnosis. A retrospective analysis of 388 cases reveals a positive diagnostic yield ranging from 65% in temporal bone trauma to 20% in clinically suspected neoplasm. Selected case reports of congenital abnormalities, inflammatory processes, traumatic lesions, and tumors will be presented. We conclude that HRCT is an excellent diagnostic modality and should be used liberally to evaluate the temporal bone in children.     

Evaluation of the mastoid air cell system by high resolution computed tomography: three-dimensional multiplanar volume rendering technique

The mastoid air cell system is an important contributor to the pathophysiology of middle-ear inflammatory disease. The mastoid cavity is not only an air reservoir, but also an active space for gas exchange. Various methods of temporal bone imaging have been designed to investigate mastoid pneumatization. In this study, we examined 100 normal temporal bones for the evaluation of mastoid pneumatization. Mastoid air cell systems were measured by reconstructed axial and coronal high resolution computed tomography (HRCT) images. The reconstructions were made by a three-dimensional multiplanar volume rendering (3D MPVR) technique. The mean volume of the mastoid air cell pneumatization was 7.9 cm(3) (4.0-14.0 cm(3), SD = 2.3 cm(3)). The ears were allocated to the groups with respect to measured mastoid air cell pneumatization. Twenty-eight per cent of the ears have small pneumatization with an air cell system not exceeding 6 cm(3). Fifty-two per cent had an air cell system between six and 10 cm(3), and 20 per cent had an air cell system exceeding 10 cm(3). With its excellent imaging quality and the ability to eliminate bone and soft tissue, HRCT is the best method for evaluating the mastoid air cell system. The 3D MPVR technique must be used to measure the temporal bone/mastoid pneumatization for the best results.     

Pediatric temporal bone fractures.

Twenty-seven temporal bone fractures in 25 pediatric patients were evaluated over a 6-year period. The diagnosis was confirmed with otoscopy and high-resolution computed tomography scans (HRCT). Three-dimensional reconstruction of high-resolution computed tomography scans were used to aid in the diagnosis. The most common fracture was an oblique fracture which is oriented in an axial or horizontal plane with the temporal bone. Facial nerve paralysis was found in 6 of our patients, which is less than the expected incidence when compared to adults. Hearing loss was found in 24 patients, the most common of which was conductive hearing loss, which had a higher incidence than expected when compared with adults.     

CSF otorrhea complicating osteoradionecrosis of the temporal bone

Osteoradionecrosis of the temporal bone is a well-recognized complication of radiotherapy for head and neck malignancy. There are two mechanisms by which this condition can produce damage to nearby structures and even result in death. Osteoradionecrosis may (1) predispose the patient to an aggressive or chronic infectious process, or (2) cause destruction of tissue by direct necrosis. A review of the literature failed to disclose a cause of CSF otorrhea complicating osteoradionecrosis of the temporal bone. This paper describes a case of skull base osteoradionecrosis, including necrosis of the tympanic membrane, associated with CSF otorrhea. Successful control of this complication was achieved using a translabyrinthine approach to locate the fistula, which originated from the internal auditory canal and was discharging through the middle ear via the oval window. The leak was sealed, the resultant mastoid cavity was obliterated by rotation of a temporalis muscle flap, and the external auditory canal was closed by the Fisch technique.     

内耳畸形伴脑脊液耳漏的高分辨率CT特征

目的:探讨先天性内耳畸形伴脑脊液耳漏的高分辨率CT(HRCT) 特征.方法:回顾性分析11例先天性内耳畸形伴脑脊液耳漏患者的HRCT表现.结果:共11例患者,耳蜗未发育4例,共腔畸形2例,耳蜗未未分隔型3例,耳蜗不全分隔型2例.内耳道底骨质缺损8例.所有患者患侧乳突气化和发育程度与对侧一致,前庭窗处都有软组织影.结论:内耳畸形伴脑脊液耳漏患者常存在内耳道底骨质缺损.前庭窗是脑脊液由内耳进入中耳腔的好发部位.HRCT能为先天性内耳畸形伴脑脊液耳漏患者的诊断及治疗提供可靠依据.     

高分辨CT三维容积重建对颞骨骨质破坏的诊断价值

目的：探讨高分辨CT(HRCT)三维容积重建在颞骨骨质破坏中的诊断价值。方法：术前高分辨率轴位或冠状位CT上显示有颞骨骨质破坏或高度怀疑有骨质破坏的15例胆脂瘤型中耳炎患者，应用容积再现(VR)对病变区进行重建，术中观察病变范围并与重建图像比较。结果：与轴位或冠状位CT图像相比，所有重建图像均清晰地显示了骨质的破坏区域，并立体地显示了与周围骨质之间的关系，与手术结果相符合。结论：HRCT三维容积重建对颞骨骨质破坏诊断具有较高价值，并且有利于手术方式的制定。     

前庭水管HRCT图像标准化处理、径线测量及其临床应用

目的重组前庭水管标准化图像,探讨径线测量对诊断大前庭水管综合征（large vestibular aqueduct syndrome,LVAS）的价值。方法标准化处理100例（200耳）正常人的颞骨HRCT图像获得前庭水管标准化图像,测量前庭水管中段宽度值,建立99％医学参考值范围;对37例（74耳）LVAS患者前庭水管宽度进行测量,并与正常值进行统计学分析。结果前庭水管中段宽度值无男女组、左右侧之间的统计学差异。前庭水管中段宽度值：右侧（0．92&#177;0．21）mm,左侧（0．93&#177;0．26）mm;99％医学参考值范围：右侧O．27～1．15mm,左侧0．27-1．24mm。LVAS患者前庭水管中段宽度最大值为3．2mm,最小值为1．4mm,与正常组比较有显著统计学差异（P〈0．05）。结论在前庭水管标准化图像上,前庭水管中段宽度值大于1．3mm可诊断为前庭水管扩大。临床有相应的症状、体征．相关基因检测异常时．可诊断为大前庭水管综合征。     

人工耳蜗植入术后植入电极的影像学检查

目的 探讨建立螺旋CT扫描及三维重建技术观察人工耳蜗植入电极方法，并比较X线摄片方法与螺旋CT扫描三维重建方法的耳蜗内电极的影像学特征及其临床应用价值。方法 18例人工耳蜗植入患者全部作术后X线摄片检查。其中9例用经眼眶前后位摄片，9例采用侧斜位60。摄片。3例患者施行术后螺旋CT扫描及内耳三维重建方法。结果 2种投射头位的X线摄片均可显示电极形态及单个电极对，可间接判断电极在耳蜗内的植入深度。螺旋CT扫描三维重建图可直观地显示耳蜗形态、电极形态及其在耳蜗内植入的深度，可清晰识别单个电极对。结论 螺旋CT扫描三维重建方法可直观观察植入电极的形态及位置，可准确判断电极在耳蜗内植入的深度，有其独特的临床应用价值。