Virtual Endoscopy of the Paranasal Sinuses Using Perspective Volume Rendered Helical Sinus Computed Tomography

Our goal was to use three-dimensional information obtained from helical computed tomographic (CT) data to explore and evaluate the nasal cavity, nasopharynx, and paranasal sinuses by simulated virtual endoscopy (VE). This was done by utilizing a new image reconstruction method known as perspective volume rendering (PVR). Thin-section helical CT of the nasal cavity, nasopharynx, and paranasal sinuses was performed on a conventional CT scanner. The data were transferred to a workstation to create views similar to those seen with endoscopy. Additional views not normally accessible by conventional endoscopy were generated. Key perspectives were selected, and a video “flight” model was choreographed and synthesized through the nasal cavity and sinuses based on the CT data. VE allows evaluation of the nasal cavity, nasopharynx, and paranasal sinuses with appreciation of the relationships of these spatially complex structures. In addition, this technique allows structural visualization with unconventional angles, perspectives, and locations not conventionally accessible. Although biopsies, cultures, and lavages routinely done with endoscopy cannot be performed with VE, this technique holds promise for improving the diagnostic evaluation of the nasal cavity, the nasopharynx, and the paranasal sinuses. The unconventional visual perspectives and very low morbidity may complement many applications of simple diagnostic endoscopy.     

Preoperative Computed Tomography Scans for Parotid Tumor Evaluation

Objective We sought to determine whether an advantage is obtained in the routine use of computed tomography (CT) scans in preoperative assessments of parotid tumors. Methods A prospective study of 32 consecutive cases of patients who underwent evaluation for parotidectomies was performed. Twenty‐nine received preoperative CT scans. The scans were systematically reviewed to see if they correlated with the clinical findings. Specifically, we compared clinical and CT assessments of tumor size, location, density, and malignancy. Further comparisons were performed based on postoperative tissue pathology. Results In our series of patients, routine preoperative CT scans resulted in the discovery of details not revealed on clinical examination: some masses were found to be extra‐parotid rather than primary parotid tumors, some tumors deemed to be deep were superficial, tumor density was more clearly identified, and certain pathology correlates were clarified. Most importantly, there were instances of detection of additional tumors in the same lobe, and in one instance in the opposite lobe, that were not otherwise noticed. Conclusions To reduce errors of omission in the treatment of suspected parotid tumors, it would seem appropriate to consider the inclusion of CT scans for the routine preoperative evaluation of all parotid masses.     

上鼓室内陷袋的高分辨CT表现

目的 探讨上鼓室内陷袋颞骨高分辨CT的表现及其中耳、乳突通气情况.方法 对43例(54耳)上鼓室内陷袋患者(内陷袋组)行颞骨高分辨CT检查,重建其乳突气房,对蒲氏间隙、鼓峡、盾板到锤骨柄的距离、上鼓室等进行观察.正常44耳作为对照组.结果 ①内陷袋组乳突气化良好率和气化不良率分别为9.3%、90.7%,其乳突气房平均容积为0.350 cm3;正常组乳突气化良好率和不良率分别为75%、25%,乳突气房平均容积为4.854 cm3,二者间差异有统计学意义(P＜0.05);②内陷袋组盾板最低点到锤骨间距离平均值为0.20±0.05cm,对照组平均值为0.23±0.06 cm,二者间差异有统计学意义(P＜0.05);③Ⅲ、Ⅳ级内陷袋盾板破坏,外上鼓室增宽,Ⅳ级内陷袋多伴听骨链破坏;④内陷袋组蒲氏间隙堵塞占66.7%,鼓峡堵塞占63%,上鼓室、鼓窦、乳突、中鼓室及咽鼓管口软组织影出现率分别为59.2%、66.7%、30%、16.8%、13%.结论 ①乳突气房发育是内陷袋形成的原因之一,其气化程度和内陷袋的程度无关;②内陷袋的形成和蒲氏间隙的狭窄、堵塞及鼓峡堵塞导致通气不良有关,炎性病变多以听骨链区域为主.     

Anatomic Variants on Computed Tomography in Congenital Aural Atresia and Stenosis

Objectives

To quantitatively analyzing the anatomic variants on temporal computed tomography (CT) in congenital external auditory canal stenosis (EACS), congenital aural atresia (CAA), and normal ear structure.

Methods

Through a retrospective study, we analyzed 142 temporal high-resolution CT studies performed in 71 microtia patients. The following 6 parameters were compared among the three groups: Marx classification, medial canal diameter, vertical facial nerve (VFN) anterior displacement, tegmen mastoideum position, tympanic cavity volume, and malleus-incus joint or malleus-incus complex (MIC) area.

Results

The results showed that the microtia distributions in the Marx classification in these three groups were significantly different, as 86% (31 of 35) of ears with major microtia (third-degree dysplasia) had an atresia, and in 54.8% (23 of 42) of the minor microtic (first-degree or second-degree) ears, the bony or cartilaginous part of the external auditory canal was stenotic. Measurement data also showed that the potential medial canal diameter of the atresia group was obviously shorter than that of the stenosis group. The VFN anterior displacement and temporomandibular joint backward-shift together lead to medial canal diameters in ears with atresic canals that is smaller than those with stenotic canals. The tegmen mastoideum position was not significantly different between the three groups.

Conclusion

The mal-development of the external auditory canal is significantly associated with auricle and middle ear developmental anomalies. Compared with CAA ears, EACS have better development of the auricle, canal, tympanic cavity and MIC and relatively safer surgical operation except for the position of the tegmen mastoideum and the VFN.     

Anatomical Analysis of Intraorbital Structures Regarding Sinus Surgery Using Multiplanar Reconstruction of Computed Tomography Scans

Objectives

This study aimed to investigate the anatomy of the intraorbital structures regarding to endoscopic sinus surgery and external frontal sinus surgery analyzing computer tomography (CT) scans.

Methods

The CT scans of 100 patients were retrospectively evaluated. The anatomic relationships between the intraorbital structures and paranasal structures were measured using multiplanar reconstruction of the CT scan.

Results

The mean distances from the medial orbital floor (MOF) to the intraorbital structures were measured at the depth of the anterior ethmoid (AE), basal lamella (BL), and midportion of posterior ethmoid (PE) in the coronal planes respectively. The mean distances from the MOF to the medial rectus muscle and inferior rectus muscle at the depth of AE were approximately 8 mm and those distances in the BL and PE decreased rapidly. The mean distances from the MOF to the infraorbital nerve at the depth of the AE and BL were approximately more than 10 mm. The mean distances from the vertical axis, which passed through the MOF, to the superior oblique muscle and optic nerve at the depth of the PE were approximately 5 mm medially and 1 mm laterally. In addition, the mean distance from the midline to the trochlea of the superior oblique muscle was approximately 15 mm.

Conclusions

Those measurements provide spatial information on the placements of the extraocular muscles within the orbit. The measurements will contribute to the avoidance of orbital complications during sinus surgery.     

Applied Anatomic Site Study of Palatal Anchorage Implants Using Cone Beam Computed Tomography

Aim The purpose of this study was to conduct quantitative research on bone height and bone mineral density of palatal implant sites for implantation, and to provide reference sites for safe and stable palatal implants. Methodology Three-dimensional reformatting images were reconstructed by cone beam computed tomography (CBCT) in 34 patients, aged 18 to 35 years, using EZ Implant software. Bone height was measured at 20 sites of interest on the palate. Bone mineral density was measured at the 10 sites with the highest implantation rate, classified using K-mean cluster analysis based on bone height and bone mineral density.Results According to the cluster analysis, 10 sites were classified into three clusters. Significant differences in bone height and bone mineral density were detected between these three clusters (P<0.05). The greatest bone height was obtained in cluster 2, followed by cluster 1 and cluster 3. The highest bone mineral density was found in cluster 3, followed by cluster 1 and cluster 2. Conclusion CBCT plays an important role in pre-surgical treatment planning. CBCT is helpful in identifying safe and stable implantation sites for palatal anchorage.     

Test-Retest Reliability of Computed Tomography in the Assessment of Chronic Rhinosinusitis

Objective: Computed tomography (CT) of the paranasal sinuses has emerged as the standard test for the assessment of chronic rhinosinusitis, as evidenced by the emergence of several CT-based staging systems. Despite its central role in the diagnosis and treatment planning for chronic rhinosinusitis, the sinus CT represents a “snapshot in time.” This study was conducted to determine the reliability of the CT scan for chronic sinus disease: are the CT findings in chronic rhinosinusitis stable over time? Methods: A prospective series of patients scheduled for endoscopic sinus surgery was evaluated. A total of 45 patients received two CT scans: an initial scan obtained during routine diagnostic evaluation, and a second scan performed for use as part of an image-guided sinus surgery protocol. No surgical intervention occurred between scans. The patients' scans were staged according to the Lund system by a blinded observer. The correlation between scans for each patient was determined using the matched pairs t test and the Pearson correlation coefficient. Results: The mean time interval between scans was 122.6 days (range, 5–364 d). The average Lund scores for the initial and second scans were 13.56 and 13.27, respectively. The Lund score for 5 patients remained the same, increased in 22 patients, and decreased in 18 patients. Overall, 75.6% of patients' second scans were within ±2 points of the first scan Lund score. The mean change in score between scans of —0.29 was not significant (P = .606, paired samples t test). The Pearson correlation coefficient between scans was 0.796 (P > .0001). Conclusions: CT scan assessment of chronic rhinosinusitis is a reliable test. The CT findings in patients with chronic rhinosinusitis remain consistent over time.     

Classification of External Auditory Canal Cholesteatoma by Computed Tomography

Objectives

We propose here a classification system for external auditory canal cholesteatoma (EACC). We classified the EACC by the computed tomography findings and clinical findings of the patients, and we evaluated the EACC characteristics by the proposed staging system.

Methods

Stage classification was done according to the results of temporal bone computed tomography and the clinical findings of the patients. Stage I indicates that the EACC lesion is limited to the external auditory canal. Stage II indicates that the EACC lesion invades the tympanic membrane and middle ear. Stage III indicates that the EACC lesion creates a defect of the external auditory canal and it involves the air cells in the mastoid bone. Stage IV indicates that the EACC lesion is beyond the temporal bone. Between 1996 and 2006, 29 patients with EACC and who underwent surgery were prospectively collected. This study was comprised of 16 males and 13 females with a mean age of 22.8±15.0 yr. We reviewed the characteristics and results of surgery by our proposed staging system.

Results

A total of 29 patients who underwent operation due to EACC were classified by this system, and the number of stage I, II, III, and IV cases was 14, 3, 10, and 2, respectively. Symptoms such as otorrhea, hearing impairment and otalgia occurred in 12, 17, and 17 cases, respectively. The most common wall invaded by EACC was the inferior wall. The number of cases that had a spontaneous, congenital, post-traumatic, post-inflammatory or tumorous origin was 14, 9, 2, 2, and 1, respectively. Cholesteatoma recurred in 2 patients after surgery. Both cases were stage 1 and both were caused by congenital disease. There were 3 cases with meatal stenosis after surgery, and their primary disease was congenital.

Conclusion

This proposed staging is simple and easily applicable for use when deciding the treatment plan for patients with EACC.     

Two-Phase Helical Computed Tomography Study of Salivary Gland Warthin Tumors: A Radiologic Findings and Surgical Applications

Objectives

The goal of this study was to define the radiologic characteristics of two-phase computed tomography (CT) of salivary gland Warthin tumors and to compare them to pleomorphic adenomas. We also aimed to provide a foundation for selecting a surgical method on the basis of radiologic findings.

Methods

We prospectively enrolled 116 patients with parotid gland tumors, who underwent two-phase CT preoperatively. Early and delayed phase scans were obtained, with scanning delays of 30 and 120 seconds, respectively. The attenuation changes and enhancement patterns were analyzed. In cases when the attenuation changes were decreased, we presumed Warthin tumor preoperatively and performed extracapsular dissection. When the attenuation changes were increased, superficial parotidectomy was performed on the parotid gland tumors. We analyzed the operation times, incision sizes, complications, and recurrence rates.

Results

Attenuation of Warthin tumors was decreased from early to delayed scans. The ratio of CT numbers in Warthin tumors was also significantly different from other tumors. Warthin tumors were diagnosed with a sensitivity of 96.1% and specificity of 97% using two-phase CT. The mean operation time was 38 minutes and the mean incision size was 36.2 mm for Warthin tumors. However, for the other parotid tumors, the average operation time was 122 minutes and the average incision size was 91.8 mm (P<0.05).

Conclusion

Salivary Warthin tumor has a distinct pattern of contrast enhancement on two-phase CT, which can guide treatment decisions. The preoperative diagnosis of Warthin tumor made extracapsular dissection possible instead of superficial parotidectomy.     

Computed Tomography and Magnetic Resonance Diagnosis of Allergic Fungal Sinusitis

The objective of this study was to describe CT and MR findings in patients with allergic fungal sinusitis (AFS). CT and MR images were examined from 10 patients with histologically proven AFS. All patients demonstrated CT evidence of central sinus high attenuation and T2-weighted MR signal void corresponding to surgically proven areas of thick inspissated allergic mucin. AFS is a distinct clinical entity with a highly specific radiographic appearance based on CT and MRI.     

环杓关节脱位的CT影像表现

目的 总结环杓关节脱位在螺旋CT影像上的表现,探讨CT在环杓关节脱位诊断中的参考作用.方法 25例(左侧19例,右侧6倒)经电子喉镜、喉肌电图检查并结合病史诊断为环杓关节脱位患者,在平静呼吸及Valsalva呼吸状态下,分别进行喉部多层螺旋CT扫描,在CT轴位图像上设计两种测量方法,记录测量数据,并与20例健康人比较.结果 25例患者轴位CT图像均显示左右环杓关节不对称,声门裂水平形成的三角形两侧底角不相等,角度相差18.80°±9.86°(7°～45°),13例(左侧9例,右侧4例)患侧底角大于健侧底角;左右声带突水平线均不重合,距离为2.62°±0.76°(1～4)mm,17例(左侧14例,右侧3例)患侧声带突水平线高于健侧.14例前脱位患者的患侧水平线均高于健侧水平线,11例后脱位的患者中,8例患侧水平线低于健侧水平线,正常对照组中15例两侧底角完全相等,5例两侧底角差值为1°～3°;16例左右声带突水平线完全重合,4例差距为0.5～1mm.环杓关节脱位患者的声门裂两侧底角和声带突水平线的差值与正常对照组比较差异均有统计学意义(P＜0.01).结论 喉部轴位CT图像声门裂两侧底角及声带突水平线的比较可以提供诊断环杓关节脱位的有效参数.     

Three-Dimensional Endoscopic Mode for Observation of Laryngeal Structures by Helical Computed Tomography

We produced high-quality three-dimensional (3D) endoscopic images of the larynx using helical scanning computed tomography. Subjects included two normal volunteers and 10 patients: five with laryngeal cancer, four with unilateral recurrent laryngeal nerve (RLN) palsy, and one with atrophied vocal folds. Two vertically split hemilaryngeal images were displayed together with the oral and tracheal views. Although motion artifacts were seen in four patients, laryngeal structures including the vocal fold, ventricular fold, and ventricle were clearly identified in all subjects. In the patients with cancer, axial images showing the extent of the tumor in each patient provided more information than 3D endoscopic images. In the patients with RLN palsy and atrophied vocal fold, combination of 3D endoscopic and cross-sectional images offered more diagnostic information than axial images alone.