Comparison of three-dimensional virtual endoscopy with bronchoscopy in patients with oesophageal carcinoma infiltrating the tracheobronchial tree.

Virtual endoscopy (VE) is a technique for performing simulated bronchoscopy using helical CT data of the tracheobronchial tree. In order to evaluate a virtual three-dimensional (3D) endoluminal procedure for the tracheobronchial tree, comparison was made between bronchoscopy, axial CT images and minimal intensity projections (MIP). 21 patients were referred for helical CT because of oesophageal carcinoma shown by bronchoscopy to infiltrate into the trachea or bronchi. Axial CT images obtained on a helical scanner were transferred to a Sparc20 workstation. VE was compared with the axial CT images and the MIP concerning additional information on the location and degree of stenosis gained after 3D reconstruction of the inner surface of the tracheobronchial tree. The accuracy of this VE system was compared with bronchoscopy. Follow-up was performed in two patients to evaluate the tracheobronchial system after stent implantation. All stenoses were identified by VE with no statistically significant difference in detection of location or grading of the stenosis to real time bronchoscopy. Passage of subtotal stenosis was only possible with VE. VE is suitable for following up stent implantation. Submucosal lesions of the tracheobronchial tree could not be detected by VE. There was no statistically significant difference regarding the location of the stenoses between VE, axial CT slices, MIP and bronchoscopy. The VE showed only a statistically significant difference with regard to the degree of stenosis which was underrated on axial CT slices and MIPs. Pitfalls including mucus plugs and wall defects due to the wrong threshold value were a limitation of VE. VE is presently too time-consuming to use in every patient with an infiltrating tumour into the tracheobronchial tree. In conclusion, while VE cannot replace endoscopy of the tracheobronchial tree or the oesophagus, it is an accurate and non-invasive method for identifying endoluminal tumours, grading stenoses and visualizing the tracheobronchial tree beyond stenoses in a small number of patients who are not amenable to endoscopy.     

多层面CT重建诊断中央大气道良性病变

目的 :分析多层面CT三维重建诊断中央大气道良性病变的价值。材料和方法 :用多层面CT对 3 5例中央气道良性病变 (解剖性异常 5例 ,炎症性病变 18例及其它 12例 )扫描 ,并全部完成三维表面遮盖显示、容积显示和仿真内窥镜检查。所有病例第一次读片时仅有横断面图像 ,第二次读片时增加重建图像。结果 :三维重建帮助 4例横断面漏误诊的解剖性异常获得确诊 ,16例炎症性病变进一步详细显示 ,2例气管支气管裂伤明确范围和程度 ;虚拟内窥镜帮助 5例横断面上不能确诊的痰液获得确诊。结论 :CT三维重建可用于解剖性异常和痰液的诊断 ,对其它良性疾病主要是对病变的另一种形式的进一步显示。     

Virtual endoscopy of the middle ear: experimental and clinical results of a standardised approach using multi-slice helical computed tomography

Virtual endoscopy (VE) enables non-invasive 3D endoluminal imaging of the middle ear by post-processing of CT data. To optimise the clinical application a standardised approach was evaluated in normal and pathologic cases. Data acquisition was performed using multi-slice helical CT in 20 normal patients and 15 patients with malformation or trauma. Virtual endoscopy of the tympanic cavity and 3D images of the ossicles were generated using surface and volume rendering. Qualitative assessment of the representation of anatomical structures was performed in normal patients. In 15 pathological cases the diagnostic benefit was evaluated by comparing the 3D images to the 2D images and intra-operative findings. In all 35 cases 3D imaging was possible using the standardised approach. The ossicular chain as well as the bony and soft tissue structures of the tympanic cavity were visualised in 20 normal patients. In 7 of 8 patients with malformation and 1 of 7 patients with trauma the original diagnosis was changed by 3D imaging. Standardisation and evaluation of the method in normal patients is essential as it enhances the diagnostic reliability. Virtual endoscopy facilitates understanding of the complex anatomy of the middle ear. In cases of suspected malformation and confirmed trauma it is helpful for diagnosis and surgical planning.     

Virtual endoscopy of the inner ear and the auditory canal

To assess the role of virtual endoscopy (VE) in the examination of intracisternal structures and of the inner ear, we studied the anatomy of the labyrinth and internal auditory canal using the original CT slices and VE on the unaffected side in three female and three male patients, age range 3–46 years, with contralateral retrocochlear hearing loss. We also examined seven patients with different pathological findings. VE was performed using an advanced postprocessing program with high- resolution 3D data sets of CT (1–1.5 mm thickness, pitch 1.25) and MRI-CISS-3D (constructive interference in steady state) images of the basal cisterns (1.5 T, slice thickness 0.7–1 mm). VE provides an endoscopic-like view from a given point within the basal cisterns of vessels and nerves (on MRI) or of the structures of the inner ear (on CT). The complex anatomy and pathological changes in the inner ear can be faithfully shown. The main advantage is not basic diagnostic information but demonstration of topographically complex situations, such as the canalicular system of the inner ear, for discussion, preoperative planning and teaching. Received: 12 July 1999 Accepted: 3 September 1999     

肺癌的CT气管、支气管树三维重建

目的：通过对63例肺癌患者的气管、支气管树三维重建进行回顾性分析,探讨CT气管、支气管树三维重建对肺癌诊断和治疗的意义。材料和方法：收集自1997年10月至2000年2月已证实的肺癌患者共63例,包括中央型肺癌35例,周围型肺癌28例。所有病例均接受了EBCT扫描。扫描条件为130kV/630mA,层厚／间隔分别为3mm/3mm或1.5mm/1.5mm,扫描方式为连续容积扫描（CVS）。三维重建方式为遮盖表面显示法（SSD）。重建阈值为－500Hu--300Hu。结果：EBCT气管、支气管树三维重建显示中央型肺癌引起的气管、支气管树狭窄或闭塞的形态为：42．9％表现为锥状中断,22．9％表现为不规则偏心性狭窄,17．1％表现为杵状中断,14．3表现为截断且断端不规则,2．8％表现为右主支气管的裂开和右上叶支气管的截断。EBCT气管、支气管树三维重建可用于确定病变的准确部位,测定狭窄的范围和程序,可显示周围性肺癌及其与周围结构的关系。结论：EBCT气管、支气管树三维重建对于中央型肺癌和周围型肺癌的诊断和治疗具有一定的辅助作用。     

3D visualisation of the middle ear and adjacent structures using reconstructed multi-slice CT datasets,correlating 3D images and virtual endoscopy to the 2D cross-sectional images

The 3D imaging of the middle ear facilitates better understanding of the patient's anatomy. Cross-sectional slices, however, often allow a more accurate evaluation of anatomical structures, as some detail may be lost through post-processing. In order to demonstrate the advantages of combining both approaches, we performed computed tomography (CT) imaging in two normal and 15 different pathological cases, and the 3D models were correlated to the cross-sectional CT slices. Reconstructed CT datasets were acquired by multi-slice CT. Post-processing was performed using the in-house software "3D Slicer", applying thresholding and manual segmentation. 3D models of the individual anatomical structures were generated and displayed in different colours. The display of relevant anatomical and pathological structures was evaluated in the greyscale 2D slices, 3D images, and the 2D slices showing the segmented 2D anatomy in different colours for each structure. Correlating 2D slices to the 3D models and virtual endoscopy helps to combine the advantages of each method. As generating 3D models can be extremely time-consuming, this approach can be a clinically applicable way of gaining a 3D understanding of the patient's anatomy by using models as a reference. Furthermore, it can help radiologists and otolaryngologists evaluating the 2D slices by adding the correct 3D information that would otherwise have to be mentally integrated. The method can be applied to radiological diagnosis, surgical planning, and especially, to teaching.     

Virtuelle Endoskopie der oberen Luftwege mit der Spiral-CT

PURPOSE: The technical conditions, the optimized scanning protocols and the facilities of virtual endoscopy (VE) are presented in an overview. METHODS: Phantom studies showed that, for a single-row-detector helical CT, collimation of 3.0 mm combined with pitch of 1.5 provided an optimal compromise between image quality and the scan duration per breath-hold. A multi-row-detector helical CT requires only a fraction of the scanning time. This is especially important for patients with dyspnea. RESULTS: The threshold-dependent virtual endoscopic surface rendering is a reliable and rapidly practicable reconstruction algorithm for the imaging of the upper airway. CONCLUSIONS: The VE technique is suitable for the imaging of space-occupying tumors and restricted stenoses. With VE follow-up examinations can be performed non-invasively and interventional procedures can be prepared in an optimal way. Because of the computed tomographic data acquisition the structure of the mucosa is not assessable and there is no opportunity to obtain a biopsy specimen.     

Diagnostic potential of virtual bronchoscopy: advantages in comparison with axial CT slices, MPR and mIP?

The aim of this study was to evaluate the diagnostic potential of virtual endoscopy (VE) and to compare it with axial CT slices, multiplanar reconstructions (MPR), minimal intensity projections (mIP), and bronchoscopy in patients diagnosed with bronchogenic carcinoma. Thirty patients underwent a spiral CT. Axial CT images were transferred to an Onyx workstation (Silicon Graphics, Sun Microsystems, Mountain View, Calif.) for performing virtual endoscopy. Accuracy for this procedure was tested by three radiologists on a monitor in comparison with axial CT slices, MPR, mIP, and bronchoscopy concerning the localization and degree of stenoses. Endoluminal tumors were identified by virtual bronchoscopy with no statistically significant difference of localization or grading of stenosis in comparison with bronchoscopy, axial CT slices, MPR and mIP. Axial CT slices, MPR, and mIP showed poorer results with over- or underestimation of stenoses compared with VE and bronchoscopy. Passing of stenoses was only possible with VE in 5 patients. Virtual endoscopy is a non-invasive method for identification of endoluminal tumors and is comparable to real bronchoscopy. Received: 18 March 1999; Revised: 21 May 1999; Accepted: 22 July 1999     

16层螺旋CT结肠三维成像与仿真内镜的临床应用研究

目的 探讨16层螺旋CT三维成像与仿真内镜在结肠肿瘤诊断中的应用价值。资料与方法 应用Lightspeed 16CT对26例纤维结肠镜活检证实的结肠癌(19例)和结肠息肉(7例)进行容积扫描．在AW4-2工作站进行三维成像和仿真内镜观察．并与纤维结肠镜结果相比较。结果 25例三维成像效果良好．仿真内镜与纤维结肠镜显示基本一致,1例因肠道准备不彻底,成像效果欠佳,但不影响诊断;CT仿真结肠镜(CTVC)结合2D多平面重建(MPR)和透明显示(Raysum)图像,可以提供更多信息,有助于病变的准确定位、定性。结论16层螺旋CT仿真内镜结合三维成像能达到与纤维结肠镜同样的敏感性和特异性,加上MPR、RavSun图像技术可以提供比纤维结肠镜更丰富的信息。     

Virtual endoscopy: development and evaluation using the Visible Human datasets.

Virtual endoscopy (VE) is a new method of diagnosis using computer processing of 3D image datasets (such as CT or MRI scans) to provide simulated visualizations of patient specific organs similar or equivalent to those produced by standard endoscopic procedures. Conventional endoscopy is invasive and often uncomfortable for patients. It sometimes has serious side effects such as perforation, infection and hemorrhage. VE visualization avoids these risks and can minimize difficulties and decrease morbidity when used before actual endoscopic procedures. In addition, there are many body regions not compatible with real endoscopy that can be explored with VE. Eventually, VE may replace many forms of real endoscopy.There remains a critical need to refine and validate VE visualizations for routine clinical use. We have used the Visible Human Dataset from the National Library of Medicine to develop and test these procedures and to evaluate their use in a variety of clinical applications. We have developed specific clinical protocols to compare virtual endoscopy with real endoscopy. We have developed informative and dynamic on-screen navigation guides to help the surgeon or physician interactively determine body orientation and precise anatomical localization while performing the VE procedures. Additionally, the adjunctive value of full 3D imaging (e.g. looking "outside" of the normal field of view) during the VE exam is being evaluated. Quantitative analyses of local geometric and densitometric properties obtained from the virtual procedures ("virtual biopsy") are being developed and compared with other direct measures. Preliminary results suggest that these virtual procedures can provide accurate, reproducible and clinically useful visualizations and measurements. These studies will help drive improvements in and lend credibility to VE procedures and simulations as routine clinical tools. VE holds significant promise for optimizing endoscopic diagnostic procedures, minimizing patient risk and morbidity, and reducing health care costs.     

Sectional depiction of the pelvic floor by CT, MR imaging and sheet plastination: computer-aided correlation and 3D model

The structures of the pelvic floor are clinically important but difficult to assess. To facilitate the understanding of the complicated pelvic floor anatomy on sectional images obtained by CT and MR imaging, and to make the representation more vivid, a computer-aided 3D model was created from a male and a female torso to develop a teaching tool. A male and a female cadaver torso were investigated by means of CT, MR imaging, and serial-section sheet plastination. A 3D reconstruction of the pelvic floor and adjacent structures was performed by fusion of CT and MR imaging data sets with sheet plastination sections. Corresponding sections from all three methods could be compared and visualized in their 3D context. Sheet plastination allows distinction of connective tissue, muscles, and pelvic organs down to a microscopic level. In combination with CT, MR imaging, and sheet plastination a 3D model of the pelvic floor offers a better understanding of the complex pelvic anatomy. This knowledge may be applied in the diagnostic imaging of urinary incontinence or prolapse and prior to prostate surgery. Received: 18 January 2000 Revised: 1 June 2000 Accepted: 6 June 2000     

成人中耳、内耳解剖结构螺旋CT三维重建技术

目的：探讨成人中耳，内耳解剖结构CT三维重建技术，方法：采用螺旋CT薄层扫描（层厚1mm或2mm)，小视野（FOV=5cm)，密集重建技术（间隔0.2mm或0.5mm），对75例成人中耳，内耳进行三维成像，包括多平面重组（MPR），最大密度投影（MaxIP)，表面成像（SSD）和仿真内镜成像（CTVE）。结果：中耳鼓室，听骨链，内耳及内耳道均获得满意三维图像。结论：螺旋CT三维重建技术的应用能够真实准确观察成人中耳，内耳立体结构。     

The nasopalatine canal revisited using 2D and 3D CT imaging

OBJECTIVES: To assess the location, morphology and dimensions of the nasopalatine canal on two-dimensional and three-dimensional (2D and 3D) CT images. METHODS: Material included 34 spiral CT scans for pre-operative planning of implant placement in the maxilla. Scanning was performed using a standard exposure and patient positioning protocol. 2D and 3D spiral CT images were carefully examined for the location, morphology and dimensions of the nasopalatine canal by two independent observers. A comparison was made between 2D observations and a 2D/3D combined observation strategy (paired t-tests). RESULTS: The nasopalatine canal typically appeared as a canal with a mean (standard deviation (SD)) length of 8.1 (3.4) mm. Its palatal opening is the incisive foramen with a mean (SD) inner ? of 4.6 (1.8) mm. At the level of the nasal floor often 2 (Y-canal morphology), but sometimes 3 or 4 openings could be observed. In particular cases, the canal showed up as a cylinder with only one nasal opening. The average (SD) maximum width of the nasopalatine canal structure at the level of the nasal floor was 4.9 (1.2) mm. The buccopalatal width of the jaw, anterior to the canal was 7.4 (2.6) mm. Interpretation of canal morphology was significantly different when comparing 2D image observation with a 2D/3D combined observation strategy. However, dimensional measurements of the canal were not significantly different for a 2D and a combined 2D/3D approach. CONCLUSIONS: The nasopalatine canal may show important anatomical variations, both with regard to morphology and dimensions. To avoid any potential complications during surgical procedures such as implant placement, a careful pre-operative observation is required. Cross-sectional imaging may be advocated to determine canal morphology and dimensions and to assess anterior bone width for potential implant placement buccally to the canal.     

多层面CT仿真内镜对中央气道良性病变的评价

目的：探讨多层螺旋CT仿真内镜（virtual endoscopy,VE)在中央气道良性病变评价中的价值。材料和方法：29例中央气道良性病变，包括解剖性异常5例（气管性支气管2例、气管憩室1例、先天性支气管闭锁1例、食管气管瘘1例），炎症性病变14例（支气管内膜结核9例、复发性多软骨炎3例、慢性炎症瘢痕2例）和其他10例（外伤性气管支气管撕裂2例、支气管腔内血凝块1例、支气管腔内痰栓5例、血管压迫2例）。痰液经CT复查或纤维支气管镜证实，其余病例均经纤维支气管镜（Fibrobronchoscope,FOB)及活检证实。采用多层面CT机，准直2．5mm或5mm,p=1.25或1．75，重建间隔1.6mm或2mm，容积性VE观察。结果：解剖性异常和痰液栓VE明确诊断（12／12），显示详细；其他气道良性疾病能一定程度上显示补充信息，对有辅助定位及判断良性狭窄的程度或范围有一定的诊断价值。与FOB有较好的一致性（22／24）。结论：VE能充分显示良性病变，对横断面起很好的补充说明作用。解剖性异常和多数痰液栓能明确诊断，可免除FOB或重复检查。     

Fusion of computed tomography data and optical 3D images of the dentition for streak artefact correction in the simulation of orthognathic surgery

OBJECTIVE: To determine the limits of accuracy of fusion of optical three-dimensional (3D) imaging and computed tomography (CT) with and without metal artefacts in an experimental setting and to show the application of this hybrid system in 3D orthognathic surgery simulation. METHODS: Ten plaster casts of dental arches were subjected to a CT scan and optical 3D surface imaging. Subsequently, the first molars in the plaster casts were supplied with metal restorations, bilaterally, and new CT scans and optical surface images were assessed. The registration of the surface data of the two imaging modalities of the study models without and with metal restorations was carried out. The mean distance between the two data sets was calculated. From a patient a CT scan of the skull as well as optical 3D images of plaster casts of the dental arches were acquired. Again the two imaging modalities were registered and virtual orthognathic surgery simulation was carried out. RESULTS: The mean distance between the corresponding data points of CT and optical 3D surface images was 0.1262+/-0.0301 mm and 0.2671+/-0.0580 mm, respectively, for the plaster casts without and with metal restorations. The differences between these data were statistically significant (P<0.0005). For the patient case a mean difference of 0.66+/-0.49 mm and 0.56+/-0.48 mm for mandible and maxilla, respectively, was calculated between CT and optical surface data. CONCLUSION: The accuracy of the fusion of 3D CT surface data and optical 3D imaging is significantly reduced by metal artefacts. However, it seems appropriate for virtual orthognathic surgery simulation, as post-operative orthodontics are performed frequently.     

Measurement of colonic polyps by radiologists and endoscopists: Who is most accurate?

The purpose was to determine the accuracy of polyp measurement by endoscopy and CT. A colonic phantom was constructed containing 12 simulated polyps of known diameter. Polyp diameter was estimated during endoscopy by two observers independently. The phantom was then scanned using a 64-detector-row machine and diameter estimated by a further two observers independently, using 2D and 3D visualisation methods. All measurements were obtained twice. Bland-Altman statistics were used to assess agreement between observers’ estimates and the reference diameter. The mean difference between observers’ measurements and the reference diameter was smallest for estimates made using 3D CT (−0.09 mm and −0.03 mm) and greatest for endoscopy (−1.10 mm and −1.19 mm), with 2D CT intermediate. However, 95% limits of agreement were largest for 3D CT estimates (−4.38 mm to 4.20 mm). Estimates by 2D CT consistently overestimated polyp diameter, whereas endoscopy consistently underestimated diameter. In contrast, measurements by 3D CT were a combination of over- and under-estimates, with a tendency for disagreement to increase with the size of the polyp. The effect of observer experience was small and repeatability was best for 2D CT. Measurement error was encountered with all three modalities tested. Estimates made by 2D CT were believed to offer the best compromise overall.     

Virtual endoscopy of the labyrinth, using a 3D-FastASE sequence

Virtual endoscopy (VE) of the labyrinth was performed using three-dimensional (3D)-fast asymmetric spin-echo MR imaging. The spatial resolution requirements and the usefulness of zero-fill interpolation (ZIP) were evaluated, and VE was used to examine three patients. The (0.6-mm) voxel data with ZIP satisfies the minimum requirements for VE for evaluation of the complex 3D anatomy and pathology of the labyrinth. J. Magn. Reson. Imaging 2001;13:792-796.     

Carotid artery stenosis: reproducibility of automated 3D CT angiography analysis method

The aim of this study was to assess the reproducibility and anatomical accuracy of automated 3D CT angiography analysis software in the evaluation of carotid artery stenosis with reference to rotational DSA (rDSA). Seventy-two vessels in 36 patients with symptomatic carotid stenosis were evaluated by 3D CT angiography and conventional DSA (cDSA). Thirty-one patients also underwent rotational 3D DSA (rDSA). Multislice CT was performed with bolus tracking and slice thickness of 1.5 mm (1-mm collimation, table feed 5 mm/s) and reconstruction interval of 1.0 mm. Two observers independently performed the stenosis measurements on 3D CTA and on MPR rDSA according to the NASCET criteria. The first measurements on CTA utilized an analysis program with automatic stenosis recognition and quantitation. In the subsequent measurements, manual corrections were applied when necessary. Interfering factors for stenosis quantitation, such as calcifications, ulcerations, and adjacent vessels, were registered. Intraobserver and interobserver correlation for CTA were 0.89 and 0.90, respectively. (p<0.001). The interobserver correlation between two observers for MPR rDSA was 0.90 (p<0.001). The intertechnique correlation between CTA and rDSA was 0.69 (p<0.001) using automated measurements but increased to 0.81 (p<0.001) with the manually corrected measurements. Automated stenosis recognition achieved a markedly poorer correlation with MPR rDSA in carotids with interfering factors than those in cases where there were no such factors. Automated 3D CT angiography analysis methods are highly reproducible. Manually corrected measurements facilitated avoidance of the interfering factors, such as ulcerations, calcifications, and adjacent vessels, and thus increased anatomical accuracy of arterial delineation by automated CT angiography with reference to MPR rDSA.     

多层螺旋CT及其三维重组对中央型肺癌的诊断价值

目的:评价多层螺旋CT(MSCT)及其三维重组对中央型肺癌(CLC)的诊断价值。方法:58例CLC患者,经MSCT平扫,增强动、静脉期扫描,二维多平面及曲面重组(MPR及CPR),三维容积重组(VR)、最大密度投影(MIP)及仿真内窥镜重组(CTVE),同时均经支气管镜及其病理检查,44例经术后病理证实。并将各种重组诊断结果与横断面扫描结果进行统计学对比分析。结果:58例CLC MSCT三维重组、支气管镜及手术分三型:腔内结节型5例,环状狭窄型19例,偏心狭窄截断型34例。MPR及CPR、MIP、CTVE诊断结果与横断面扫描相比,差异无显著性;VR差异则有显著性。结论:MSCT三维重组能准确分型诊断CLC,评价气管、支气管树肿瘤侵犯程度与范围,具有较好的临床应用价值。     

Contrast-enhanced 3D MR angiography of the carotid artery: comparison with conventional digital subtraction angiography

BACKGROUND AND PURPOSE: Since 1996, several preliminary studies have shown the usefulness of contrast material-enhanced MR angiography for imaging supraaortic vessels. The aim of this study was to compare the accuracy of contrast-enhanced 3D MR angiography with that of digital subtraction angiography (DSA) in the evaluation of carotid artery stenosis. METHODS: A blinded comparison of first-pass contrast-enhanced MR angiography with conventional DSA was performed in 120 patients (240 arteries). MR angiography was performed with a 1.5-T magnet with gradient overdrive equipment, by using a coronal radiofrequency-spoiled 3D fast low-angle-shot sequence after the intravenous injection of gadodiamide. The guidelines of the North American Symptomatic Carotid Endarterectomy Trial for measuring stenosis of the internal carotid artery were applied on maximum intensity projection (MIP) images and conventional catheter angiograms. RESULTS: Grading of stenoses on MR angiograms agreed with grading of stenoses on DSA images in 89% of arteries. In the severe stenosis group (70-99%), agreement was 93%. All internal carotid occlusions (n = 28) and seven of nine pseudo-occlusions were accurately detected with contrast-enhanced MR angiography. The correlation between MR angiography and DSA for determination of minimal, moderate, and severe stenoses and occlusion was statistically significant (r = 0.91, P<.001). CONCLUSIONS: This investigation with a large number of patients confirms that contrast-enhanced MR angiography could become a diagnostic alternative to DSA in the treatment of patients with carotid artery disease.