Helical (spiral) CT of the upper airway with three-dimensional imaging: technique and clinical assessment

Using Diffusion Tensor Imaging to Explore the Changes in the Microstructure of Canine Vocal Fold Scar Tissue

OBJECTIVE

To apply diffusion tensor imaging (DTI) in measurement of the diffusion characteristics of water molecules in vocal fold scar tissue, combined with the analysis of textural characteristics of collagen fibers in the cover layer of the vocal folds to explore the feasibility of DTI in the qualitative and quantitative diagnosis of vocal fold scars and the evaluation of microstructural changes of vocal fold scar tissue.

METHODS

A unilateral injury was created using micro-cup forceps in the left vocal fold of six beagles. The contralateral normal vocal fold was used as a self-control. Five months postinjury, the larynges were excised and placed into a magnetic resonance imaging (MRI) system (9.4T BioSpec MRI, Bruker, German) for scanning and extraction of the diffusion parameters, fractional anisotropy (FA) and tensor trace in the anterior, middle, and posterior portions of the vocal fold cover layer. These parameters were then analyzed for statistical significance between the scarred vocal fold and the normal vocal fold. After MRI scanning, the tissue of the vocal folds was divided into anterior, middle, and posterior parts for sectioning and staining with hematoxylin and eosin, and samples were subsequently digitally scanned for texture analysis. The irregularity parameters, energy, contrast, correlation, and homogeneity, of collagen fibers of the vocal folds and the mean gray value of collagen fibers were calculated by the gray-level co-occurrence matrix (GLCM) texture analysis method. The differences in the mean value of the two sides of the vocal fold were compared. In addition, Pearson correlation analysis was performed between DTI parameters and irregularity parameters.

RESULTS

The FA of the left vocal fold cover layer was significantly lower compared to the self-control group (P = 0.0366), and the tensor trace value on the left vocal fold cover layer was significantly higher compared to the self-control group (P = 0.0353). The FA was significantly higher in the anterior part of the right vocal fold cover layer compared to the middle and posterior parts of the same side (P = 0.0352), and the tensor trace was significantly lower in the anterior part of the right vocal fold cover layer compared to the middle and posterior parts of the same side (P = 0.0298). There were no significant differences in FA and tensor trace between the middle and posterior parts of the vocal fold cover layer. The mean gray value of the left vocal folds cover layer was significantly smaller than the right vocal fold cover layer (P = 0.0219), the energy of the left vocal fold cover layer was significantly smaller than that of the right vocal fold cover layer (P < 0.0001), the contrast of the left vocal folds cover layer was significantly larger than that of the right vocal fold cover layer (P = 0.0002), the correlation of the left vocal folds cover layer was significantly smaller than the right vocal fold cover layer (P = 0.0002), and the homogeneity of the left vocal folds cover layer was significantly smaller than the right vocal fold cover layer (P = 0.0003). Pearson correlation analysis yielded values of r = 0.926, P = 0.000 between the FA and mean gray value; r = -0.918, P = 0.000 between FA and energy; r = -0.924, P = 0.000 between the FA and homogeneity, r = -0.949, P = 0.000 between tensor trace and mean gray value; r = 0.893, P = 0.000 between the tensor trace and energy; and r = 0.929, P = 0.000 between the tensor trace and homogeneity.

CONCLUSION

FA and tensor trace can be used as effective parameters to reflect microstructural changes in vocal fold scars. DTI is an objective and quantitative method of analyzing vocal fold scarring, and it noninvasively evaluates the microstructure of vocal fold collagen fibers.

Pre-surgery planning tool for estimation of resection volume to improve nasal breathing based on lattice Boltzmann fluid flow simulations

Purpose

State-of-the-art medical examination techniques (e.g., rhinomanometry and endoscopy) do not always lead to satisfactory postoperative outcome. A fully automatized optimization tool based on patient computer tomography (CT) data to calculate local pressure gradient regions to reshape pathological nasal cavity geometry is proposed.

Methods

Five anonymous pre- and postoperative CT datasets with nasal septum deviations were used to simulate the airflow through the nasal cavity with lattice Boltzmann (LB) simulations. Pressure gradient regions were detected by a streamline analysis. After shape optimization, the volumetric difference between the two shapes of the nasal cavity yields the estimated resection volume.

Results

At LB rhinomanometry boundary conditions (bilateral flow rate of 600 ml/s), the preliminary study shows a critical pressure gradient of −1.1 Pa/mm as optimization criterion. The maximum coronal airflow ΔA  := cross-section ratio \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\frac{\mathrm{virtual surgery }}{\mathrm{post}-\mathrm{surgery}}$$\end{document}virtualsurgerypost-surgery found close to the nostrils is 1.15. For the patients a pressure drop ratio ΔΠ  := (pre-surgery − virtual surgery)/(pre-surgery − post-surgery) between nostril and nasopharynx of 1.25, 1.72, −1.85, 0.79 and 1.02 is calculated.

Conclusions

LB fluid mechanics optimization of the nasal cavity can yield results similar to surgery for air-flow cross section and pressure drop between nostril and nasopharynx. The optimization is numerically stable in all five cases of the presented study. A limitation of this study is that anatomical constraints (e.g. mucosa) have not been considered.

Quantitative evaluation of the human vocal fold extracellular matrix using multiphoton microscopy and optical coherence tomography

Identifying distinct normal extracellular matrix (ECM) features from pathology is of the upmost clinical importance for laryngeal diagnostics and therapy. Despite remarkable histological contributions, our understanding of the vocal fold (VF) physiology remains murky. The emerging field of non-invasive 3D optical imaging may be well-suited to unravel the complexity of the VF microanatomy. This study focused on characterizing the entire VF ECM in length and depth with optical imaging. A quantitative morphometric evaluation of the human vocal fold lamina propria using two-photon excitation fluorescence (TPEF), second harmonic generation (SHG), and optical coherence tomography (OCT) was investigated. Fibrillar morphological features, such as fiber diameter, orientation, anisotropy, waviness and second-order statistics features were evaluated and compared according to their spatial distribution. The evidence acquired in this study suggests that the VF ECM is not a strict discrete three-layer structure as traditionally described but instead a continuous assembly of different fibrillar arrangement anchored by predominant collagen transitions zones. We demonstrated that the ECM composition is distinct and markedly thinned in the anterior one-third of itself, which may play a role in the development of some laryngeal diseases. We further examined and extracted the relationship between OCT and multiphoton imaging, promoting correspondences that could lead to accurate 3D mapping of the VF architecture in real-time during phonosurgeries. As miniaturization of optical probes is consistently improving, a clinical translation of OCT imaging and multiphoton imaging, with valuable qualitative and quantitative features, may have significant implications for treating voice disorders.

A clinical prediction rule to identify difficult intubation in children with Robin sequence requiring mandibular distraction osteogenesis based on craniofacial CT measures

BACKGROUND

Airway management is challenging in children with Robin sequence (RS) requiring mandibular distraction osteogenesis (MDO). We derived and validated a prediction rule to identify difficult intubation before MDO for children with RS based on craniofacial computed tomography (CT) images.

METHOD

This was a retrospective study of 69 children with RS requiring MDO from November 2016 to June 2018. Multiple CT imaging parameters and baseline characteristic (sex, age, gestational age, body mass index [BMI]) were compared between children with normal and difficult intubation according to Cormack-Lehane classification. A clinical prediction rule was established to identify difficult intubation using group differences in CT parameters (eleven distances, six angles, one section cross-sectional area, and three segment volumes) and clinicodemographic characteristics. Predictive accuracy was evaluated by receiver operating characteristic (ROC) curve analysis.

RESULTS

The overall incidence of difficult intubation was 56.52%, and there was no significant difference in sex ratio, age, weight, height, BMI, or gestational age between groups. The distance between the root of the tongue and posterior pharyngeal wall was significantly shorter, the bilateral mandibular angle shallower, and the cross-sectional area at the epiglottis tip smaller in the difficult intubation group. A clinical prediction rule based on airway cross-sectional area at the tip of the epiglottis was established. Area > 36.97 mm² predicted difficult intubation while area < 36.97 mm² predicted normal intubation with 100% sensitivity, 62.5% specificity, 78.6% positive predictive value, and 100% negative predictive value (area under the ROC curve = 0.8125).

CONCLUSION

Computed tomography measures can objectively evaluate upper airway morphology in patients with RS for prediction of difficult intubation. If validated in a larger series, the measures identified could be incorporated into airway assessment tools to guide treatment decisions. This was a retrospective study and was granted permission to access and use these medical records by the ethics committee of Guangzhou Women and Children's Medical Center.

TRIALS REGISTRATION

Registration No. ChiCTR1800018252, NaZhang, Sept 7 2018.

Three-dimensional imaging of vocalizing larynx by ultra-high-resolution computed tomography

PURPOSE

Ultra-high-resolution computed tomography (UHRCT) is an emerging imaging technology that is able to achieve simultaneous 160 slices with super-thin 0.25 mm thickness. The purpose of this study was to assess the feasibility of UHRCT to visualize laryngeal structure and kinetics.

METHODS

Three normal volunteers and three patients with unilateral vocal fold paralysis (UVFP) were incorporated in this case series. First, images were taken under five conditions in normal volunteers. Five tasks consisted of (1) air inspiration through the nose (IN), (2) breath holding (BH), (3) sustained vowel /i:/ phonation (IP), (4) humming phonation (HP), and (5) forced glottic closure during exhalation (FC). Three-dimensional CT images of arytenoid and cricoid cartilages, as well as virtual laryngoscopic images, were reconstructed using UHRCT data. Reconstructed images were compared among five conditions to assess the best tasks to picture laryngeal kinetics. Second, pre- and post-phonosurgical images were examined in UVFP patients to evaluate potential role of UHRCT to assess laryngeal pathology in hoarse patients.

RESULTS

Among the five conditions, IN and IP conditions were considered suitable to visualize laryngeal structure at rest and during phonation, respectively. Kinetic abnormalities including asymmetric motion of arytenoid cartilages were elucidated in UVFP patients, and virtual endoscopy visualized the clinically invisible posterior three-dimensional glottic chinks. Furthermore, UHRCT was useful to understand changes in laryngeal structure achieved by phonosurgery.

CONCLUSIONS

UHRCT is an emerging imaging technology that can be used for minimally invasive visualization and assessment of laryngeal structure and kinetics. Future studies to assess more number of patients with laryngeal dysfunction are warranted.

Sensitivity of nasal airflow variables computed via computational fluid dynamics to the computed tomography segmentation threshold

Computational fluid dynamics (CFD) allows quantitative assessment of transport phenomena in the human nasal cavity, including heat exchange, moisture transport, odorant uptake in the olfactory cleft, and regional delivery of pharmaceutical aerosols. The first step when applying CFD to investigate nasal airflow is to create a 3-dimensional reconstruction of the nasal anatomy from computed tomography (CT) scans or magnetic resonance images (MRI). However, a method to identify the exact location of the air-tissue boundary from CT scans or MRI is currently lacking. This introduces some uncertainty in the nasal cavity geometry. The radiodensity threshold for segmentation of the nasal airways has received little attention in the CFD literature. The goal of this study is to quantify how uncertainty in the segmentation threshold impacts CFD simulations of transport phenomena in the human nasal cavity. Three patients with nasal airway obstruction were included in the analysis. Pre-surgery CT scans were obtained after mucosal decongestion with oxymetazoline. For each patient, the nasal anatomy was reconstructed using three different thresholds in Hounsfield units (-800HU, -550HU, and -300HU). Our results demonstrate that some CFD variables (pressure drop, flowrate, airflow resistance) and anatomic variables (airspace cross-sectional area and volume) are strongly dependent on the segmentation threshold, while other CFD variables (intranasal flow distribution, surface area) are less sensitive to the segmentation threshold. These findings suggest that identification of an optimal threshold for segmentation of the nasal airway from CT scans will be important for good agreement between in vivo measurements and patient-specific CFD simulations of transport phenomena in the nasal cavity, particularly for processes sensitive to the transnasal pressure drop. We recommend that future CFD studies should always report the segmentation threshold used to reconstruct the nasal anatomy.

Computed tomographic assessment of the causal factors of unsuccessful medialization thyroplasty

CONCLUSION

The present results demonstrate that a small implant size, undercorrection of the vocal fold, antero-posterior implant malposition, and the use of expanded polytetrafluoroethylene (ePTFE) are the primary factors that cause a poor outcome of medialization thyroplasty (MT).

OBJECTIVES

To assess the postoperative laryngeal condition using computed tomography (CT) in patients with unilateral vocal fold paralysis who underwent MT alone, and to identify the primary causal factors in terms of the surgical procedures that affect the outcomes of MT.

METHODS

Twenty-two patients who underwent MT alone were divided into two groups based on either the maximal phonation time or the perceived vocal breathiness. Two laryngologists assessed the postoperative laryngeal CT images during sustained vowel phonation and judged whether there were abnormalities of the arytenoid cartilage position, window position, implant size, and implant position, as well as the degree of correction of the vocal fold. As implant material, a silicone block, ePTFE, and hydroxyapatite had been inserted in 2, 9, and 11 patients, respectively. Comparisons of the prevalence of abnormalities in the abovementioned factors between the different outcomes and between the types of material used for the implant were performed.

RESULTS

Twelve patients with a poor outcome and 10 with a good outcome showed 36 and 18 abnormal findings identified by either of the two laryngologists, respectively. In the poor outcome group, a smaller implant size and undercorrection of the vocal fold showed both high kappa values and a significantly higher prevalence than those in the good outcome group (p < 0.001 and p < 0.05), respectively. The comparison between material types demonstrated that the sheet-like material (ePTFE) group exhibited a significantly higher prevalence of undercorrection than the block-like material group (p < 0.05).

Proximal pulmonary vein stenosis detection in pediatric patients: value of multiplanar and 3-D VR imaging evaluation

BACKGROUND

One of the important benefits of using multidetector computed tomography (MDCT) is its capability to generate high-quality two-dimensional (2-D) multiplanar (MPR) and three-dimensional (3-D) images from volumetric and isotropic axial CT data. However, to the best of our knowledge, no results have been published on the potential diagnostic role of multiplanar and 3-D volume-rendered (VR) images in detecting pulmonary vein stenosis, a condition in which MDCT has recently assumed a role as the initial noninvasive imaging modality of choice.

OBJECTIVE

The purpose of this study was to compare diagnostic accuracy and interpretation time of axial, multiplanar and 3-D VR images for detection of proximal pulmonary vein stenosis in children, and to assess the potential added diagnostic value of multiplanar and 3-D VR images.

MATERIALS AND METHODS

We used our hospital information system to identify all consecutive children (< 18 years of age) with proximal pulmonary vein stenosis who had both a thoracic MDCT angiography study and a catheter-based conventional angiography within 2 months from June 2005 to February 2012. Two experienced pediatric radiologists independently reviewed each MDCT study for the presence of proximal pulmonary vein stenosis defined as ≥ 50% of luminal narrowing on axial, multiplanar and 3-D VR images. Final diagnosis was confirmed by angiographic findings. Diagnostic accuracy was compared using the z-test. Confidence level of diagnosis (scale 1-5, 5 = highest), perceived added diagnostic value (scale 1-5, 5 = highest), and interpretation time of multiplanar or 3-D VR images were compared using paired t-tests. Interobserver agreement was measured using the chance-corrected kappa coefficient.

RESULTS

The final study population consisted of 28 children (15 boys and 13 girls; mean age: 5.2 months). Diagnostic accuracy based on 116 individual pulmonary veins for detection of proximal pulmonary vein stenosis was 72.4% (84 of 116) for axial MDCT images, 77.5% (90 of 116 cases) for multiplanar MDCT images, and 93% (108 of 116 cases) for 3-D VR images with significantly higher accuracy with 3-D VR compared to axial (z = 4.17, P < 0.001) and multiplanar (z = 3.34, P < 0.001) images. Confidence levels for detection of proximal pulmonary vein stenosis were significantly higher with 3-D VR images (mean level: 4.6) compared to axial MDCT images (mean level: 1.7) and multiplanar MDCT images (mean level: 2.0) (paired t-tests, P < 0.001). Thus, 3-D VR images (mean added diagnostic value: 4.7) were found to provide added diagnostic value for detecting proximal pulmonary vein stenosis (paired t-test, P < 0.001); however, multiplanar MDCT images did not provide added value (paired t-test, P = 0.89). Interpretation time was significantly longer and interobserver agreement was higher when using 3-D VR images than using axial MDCT images or MPR MDCT images for diagnosing proximal pulmonary vein stenosis (paired t-tests, P < 0.001).

CONCLUSIONS

Use of 3-D VR images in the diagnosis of proximal pulmonary vein stenosis in children significantly increases accuracy, confidence level, added diagnostic value and interobserver agreement. Thus, the routine use of this technique should be encouraged despite its increased interpretation time.

A new method for determining the optimal CT threshold for extracting the upper airway

OBJECTIVES

The purpose of this study was to evaluate the optimal upper threshold levels of a number of individuals and determine the most suitable upper threshold.

METHODS

A phantom model and ten patients were used in this study. The phantom was made of acrylic resin and urethane resin and had nine pillar-shaped air spaces. The subjects were ten female patients with jaw deformities who were not affected by respiratory disease. The optimal threshold levels were determined using the "calculation of CT value disparities" (CCTD) technique, which we devised. In other words, the mean CT values along two lines (air space and soft tissue) were calculated and the optimal threshold level was determined as the level that produced the maximum difference between the CT values measured inside and outside of the air-space border.

RESULTS

The optimal upper threshold levels of the nine phantom holes calculated using the CCTD technique in the front-on standing position and side-on standing position were -434 HU and -456 HU, respectively. The optimal upper threshold level of the ten patients calculated using the CCTD technique was -472 HU. The true threshold level of each patient was defined as the optimal threshold level calculated using the CCTD technique. The mean threshold level was defined as -472 HU. The absolute differences between the volume measurements obtained with these two measures were considered. Therefore, the no error values were -460 HU and -470 HU.

CONCLUSIONS

We consider that the most suitable upper threshold level for extracting the airway is from -460 HU to -470 HU.

Role of virtual bronchoscopy in the evaluation of bronchial lesions

BACKGROUND

Virtual bronchoscopy (VB) is a type of 3-dimensional reconstruction in which the observation point is placed within the airway to produce an endoscopiclike view.

AIM

To evaluate the diagnostic role of VB in the diagnosis of tracheobronchial lesions, as compared to fiberoptic bronchoscopy (FOB).

SUBJECTS

Fifty patients with tracheobronchial lesions were enrolled (30 patients with bronchogenic carcinomas and 20 patients with tracheobronchial inflammatory lesions).

METHODS

The patients were examined using VB and FOB. Virtual bronchoscopic studies were calculated and reconstructed from cross-sectional images obtained from spiral computed tomographic examination of the chest.

RESULTS

Virtual bronchoscopy provided an excellent overview of the trachea, main stem, and lobar bronchi up to the fourth order. The data obtained by VB and FOB (signs of tumor infiltration including endobronchial mass, stenosis, obstruction, and external indentations) were comparable. However, FOB had the advantage of giving direct cues to color, vascularity, and motility. It also detected early tumor infiltration by picking up subtle mucosal changes. Alternatively, VB was superior in bypassing any obstruction and therefore provided an excellent view distal to the obstructive lesions or stenotic segments. Virtual bronchoscopy also defined the optimum pathway for passing instruments into lesions beyond the field of view.

CONCLUSIONS

Here, we compared the diagnostic capacities of both VB and FOB. The interventional and therapeutic ramifications of our findings await further investigations.

A new method of reconstructing the human laryngeal architecture using micro-MRI

OBJECTIVES/HYPOTHESIS

A realistic three-dimentional (3D) model of the larynx could be of value for the understanding of normal laryngeal motion and for studying pathological changes as well as in modeling potential therapy outcomes. The objective of this research was to present a new method of creating a computer model of the human larynx using data obtained through micro-magnetic resonance imaging (MRI) scanning.

STUDY DESIGN

Prospective study.

METHODS

A 7-T micro-MRI scanner was used to scan an excised larynx obtained postmortem from a 68-year-old woman. MRI data was manually segmented and compiled into 3D images using Mimics12.1 reconstruction software. Measurements of the reconstructed structures were also calculated using Mimics12.1.

RESULTS

The 3D laryngeal model contained the thyroid, cricoid, and arytenoid cartilages. Nearly all of the intrinsic muscles could be segmented. Although the cricoarytenoid joint could be visualized, the features of the cricothyroid joint were not clear. Muscle and cartilage volumes and surface areas were calculated from the 3D model.

CONCLUSIONS

The combination of MRI and 3D reconstruction generates promising results in the hopes of creating a highly realistic and detailed model of the human larynx.

Multimodal virtual bronchoscopy using PET/CT images

OBJECTIVE

To demonstrate the possibilities, advantages and limitations of virtual bronchoscopy using data sets from positron emission tomography (PET) and computed tomography (CT).

MATERIALS AND METHODS

Eight consecutive patients with non-small cell lung cancer (NSCLC) underwent PET/CT. PET was performed with a glucose analog, 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (18F-FDG), using a state-of-the-art full-ring Pico-3D PET scanner. CT was performed with a venous-dominant contrast-enhanced phase using a 16-slice CT scanner. The tracheobronchial system was segmented using the CT data set with an interactive threshold interval volume-growing segmentation algorithm. The primary tumors and lymph node metastases were segmented for virtual CT-bronchoscopy using the CT data set and for virtual hybrid bronchoscopy using the PET/CT data set. The structures of interest were visualized with a color-coded shaded-surface rendering method.

RESULTS

The use of CT and virtual CT-bronchoscopy primarily facilitates visualization of the anatomical details of the tracheobronchial system and detection of anatomical/morphologic structural changes caused by disease. PET/CT and virtual hybrid bronchoscopy, or virtual PET/CT-bronchoscopy, give superior results to virtual CT-bronchoscopy because the hybrid bronchoscopy uses both the CT information and the molecular/metabolic information about the disease obtained from PET.

CONCLUSIONS

PET/CT imaging has proven to be a highly valuable oncological diagnostic modality. Virtual hybrid bronchoscopy can be performed using a low-dose CT scan or diagnostic CT. However, it is expected to improve diagnostic accuracy in identification and characterization of malignancies, verification of infections, and differentiation of viable tumor tissue from atelectases and scar tissue, as well as assessment of tumor staging and therapeutic response, and detection of early stage recurrences that are not detectable or are liable to be misjudged using virtual CT-bronchoscopy. It could also be useful as a screening examination method for patients with suspected endobronchial malignancy. Virtual hybrid bronchoscopy with a transparent color-coded shaded-surface rendering model offers a useful alternative to fiberoptic bronchoscopy, and is particularly promising for patients for whom fiberoptic bronchoscopy is not feasible, contraindicated or refused.

Chest computed tomography with multiplanar reformatted images for diagnosing traumatic bronchial rupture: a case report

INTRODUCTION

Unnoticed bronchial injury during the early stage of resuscitation of multiple trauma is not rare and increases mortality and morbidity.

METHODS

Three-dimensional reconstruction of the airways using a workstation connected to a multidetector chest computed tomography (CT) scanner may change the diagnostic strategy in patients with blunt chest trauma with clinical signs evocative of bronchial rupture.

RESULTS

In this case report of a young motor biker, a complete disruption of the intermediary trunk was first misdiagnosed using standard chest helical CT and bronchoscopy. Postprocessing procedures including three-dimensional extraction of the tracheobronchial tree were determinants for establishing the diagnosis, and emergent surgical repair was successfully performed. Follow-up using CT with three-dimensional reconstructions evidenced a bronchial stenosis located at the site of the rupture.

CONCLUSION

The present study demonstrates the potential interest of performing three-dimensional reconstructions by extraction of the tracheal-bronchial tree in patients with severe blunt chest trauma suspected of bronchial rupture.

Laryngo-tracheal profile: a new method for assessing laryngo-tracheal stenoses

We present the clinical application of a new method for objective assessment of both grade and length of laryngo-tracheal stenoses (LTS) on a CT-based skeletonization algorithm, called laryngo-tracheal profile (LTP). Extraction of the laryngo-tracheal tract (LTT)-medial axis was performed after S-CT scanning. Orthogonal to the medial axis, the LTT cross-profile was computed, and the length and degree of LTS were presented as line charts. Clinical application of this newly developed method is demonstrated on three patients who had to undergo preoperative assessment before surgical treatment of tracheal stenoses. LTP provides an objective method of assessment of both the length and degree of tracheal stenoses in precise correlation to defined anatomical landmarks. This method provides important additive information for preoperative evaluation as well as for monitoring of therapeutical success. Current methods used so far are able to evaluate the severity of LTS, but do not provide exact quantitative assessment of complex LTS. Especially in CT-scans of strong curved passages, where an overestimation of the cross-sectional area results by an oblique cut of the tubular structure, LTP may overcome this problem by a simple post processing skeletonization algorithm.

Evaluation of obstructive airway lesions in complex congenital heart disease using composite volume-rendered images from multislice CT

BACKGROUND

Multislice CT (MSCT) allows high-quality volume-rendered (VR) and composite volume-rendered images.

OBJECTIVE

To investigate the clinical usefulness of composite VR images in the evaluation of the relationship between cardiovascular structures and the airway in children with complex congenital heart disease (CHD).

MATERIALS AND METHODS

Four- or 16-slice MSCT scanning was performed consecutively in 77 children (mean age 6.4 months) with CHD and respiratory symptoms, a chest radiographic abnormality, or abnormal course of the pulmonary artery on ECHO. MSCT scanning was performed during breathing or after sedation. Contrast medium (2 ml/kg) was administered through a pedal venous route or arm vein in all patients. The VR technique was used to reconstruct the cardiovascular structures and airway, and then both VR images were composed using the commercial software (VoxelPlus(2); Daejeon, Korea).

RESULTS

Stenoses were seen in the trachea in 1 patient and in the bronchi in 14 patients (19%). Other patients with complex CHD did not have significant airway stenoses.

CONCLUSIONS

Composite VR images with MSCT can provide more exact airway images in relationship to the surrounding cardiovascular structures and thus help in optimizing management strategies in treating CHD.

Low-dose MDCT and virtual bronchoscopy in pediatric patients with foreign body aspiration

OBJECTIVE

The purpose of this study was to investigate the potential use of low-tube-current MDCT virtual bronchoscopy for the evaluation of children with suspected foreign body aspiration.

SUBJECTS AND METHODS

Low-tube-current MDCT was performed in 23 patients (10 girls, 13 boys) with a mean age of 3.3 years (9 months-13 years) with suspicion of foreign body aspiration. Chest radiographs were obtained before CT was performed. MDCT was performed using 25- to 50-mA tube currents. MDCT virtual bronchoscopy images were obtained. Neither sedation nor IV contrast medium was used during CT scanning. All patients underwent endoscopic evaluation within 24 hr after MDCT was performed. MDCT virtual bronchoscopy findings were retrospectively compared with the results of rigid bronchoscopy.

RESULTS

The mean tube current was 35 mA (range, 25-50 mA). Imaging quality was excellent in nine studies (39%), good in 12 studies (52%), and poor in two studies (9%). Motion artifacts were present on several slices in five examinations. In 15 patients, all foreign bodies detected by conventional bronchoscopy were also revealed on MDCT virtual bronchoscopy. The foreign body was in the right main bronchus in six patients, in the bronchus intermedius in one patient, and in the left main bronchus in eight patients. No discordance was found between the two techniques. MDCT revealed hyperaeration of the ipsilateral lung in five patients, atelectasis in five patients, infiltration in three patients, and infiltration and bronchiectasis in two patients; it showed infiltration in four patients and atelectasis in one of eight patients without a foreign body detected. There were no abnormal findings in three patients.

CONCLUSION

Evaluation of foreign body aspiration of the airway in children can be accomplished by using a low-tube-current MDCT protocol. It may be useful both in showing the exact location of a foreign body before bronchoscopy and in ruling out a foreign body in patients with a low level of suspicion and normal or nonspecific findings on chest radiography.

Virtual bronchoscopy for evaluation of airway disease

The data presented above indicate that VB is a novel and extremely useful modality for airway evaluation in patients who have benign and malignant disease. VB is noninvasive, with no additional radiation exposure relative to standard CT scans of the chest. Commercial software allows for the interactivity of 2D and 3D images. The ability to examine 2D and 3D anatomic detail from multiple directions enables precise assessment of intraluminal and extraluminal pathology. The authors' experience indicates that VB is a superb modality for assessing the length of airway stenoses and ascertaining airway patency distal to these lesions (Fig. 6). As such, VB has proven to be extremely useful for determining the feasibility of endobronchial procedures such as dilations, stent placements, and laser ablation of endobronchial tumors. Ferretti et al [27] observed that VB is an excellent noninvasive means for long-term monitoring of tracheobronchial stents. Furthermore, the authors have found VB useful for guiding the bronchoscopic evaluation of patients who have intermittent hemoptysis secondary to lesions in peripheral airways. The 3D anatomic detail provided by VB has proven useful for assessing the feasibility of lung-sparing procedures in patients who have limited pulmonary reserve and for sequentially evaluating treatment response in patients who have inoperable disease. Currently, the main limitation of VB pertains to its inability to evaluate the mucosal surface of the respiratory tract reliably. Although form can be detected, mucosal color, irregularity, or friability cannot be assessed. As such, VB cannot be used for routine surveillance of patients at high risk of developing airway malignancies. The development of novel aerosolized contrast agents or spectroscopic techniques that can discriminate benign versus malignant mucosal tissues might enhance the sensitivity and specificity of VB for the detection of preinvasive cancers within the respiratory tract.

Aerodynamics, voice quality, and laryngeal image analysis of normal and pathologic voices

PURPOSE OF REVIEW

The purpose of this review is to describe examinations of phonatory function and their relation to image analysis of the unilaterally immobile larynx. Special emphasis was placed on image analysis using three-dimensional endoscopic images produced from CT scans.

RECENT FINDINGS

Developments in modern image processing technique have led to the quantification of various aspects of vocal fold vibration. Stroboscopic images of the vocal fold were digitized and, subsequently, the glottal gap area, amplitude, and degree of bowing were analyzed quantitatively in relation to phonatory function. Vocal fold vibration was observed with the aid of videokymography, during which images from a single transverse line can be recorded. Successive line images were shown in real time on a monitor, with the time dimension displayed in the vertical direction. This system enabled the assessment of left-right asymmetries, open quotient, propagation of mucosal waves, and forth. Three-dimensional endoscopic images derived from multislice CT scans provided a novel method for evaluating morphologic characteristics of the laryngeal lumen in relation to phonatory function. The combination of three-dimensional endoscopy and coronal reconstructed images supplemented stroboscopic findings exemplified by differences in vertical position and thickness between the vocal folds.

SUMMARY

Depth information about the vocal fold as well as the presence of paradoxic movement of the affected vocal fold and overadduction of the healthy vocal fold during phonation should be taken into account when surgical intervention to improve hoarseness resulting from unilateral vocal fold immobility is performed. Phonatory function tests, videostroboscopy, and laryngeal image analysis are prerequisites to achieving this goal.

Grading Airway Stenosis Down to the Segmental Level Using Virtual Bronchoscopy

OBJECTIVE

To assess the sensitivity of noninvasive virtual bronchoscopy based on multirow detector CT scanning in detecting and grading central and segmental airway stenosis using flexible bronchoscopic findings as the reference standard.

MATERIALS AND METHODS

In a blinded controlled trial, multirow detector CT virtual bronchoscopy and flexible bronchoscopy were used to search for and grade airway stenosis in 20 patients. CT scan data were obtained with a multirow detector CT scanner using 4 x 1 mm collimation. Flexible bronchoscopy findings were graded by a pulmonologist and served as the reference standard for 176 central airway regions (ie, trachea, main bronchi, and lobar bronchi) and 302 segmental airway regions. The extent of airway narrowing was categorized as grade 0 (no narrowing), grade 1 (< 50%), or grade 2 (> or =50%).

RESULTS

Flexible bronchoscopy revealed 30 stenoses in the central airways and 10 in the segmental airways. Virtual bronchoscopy detected 32 stenoses in the central airways (sensitivity, 90.0%; specificity, 96.6%; accuracy, 95.5%) and 22 in the segmental airways (sensitivity, 90.0%; specificity, 95.6%; accuracy, 95.5%). The number of false-positive findings was higher in the segmental airways (13 false-positive findings) than in the central airways (5 false-positive findings), which caused a lower positive predictive value for the segmental airways (40.9%) than for the central airways (84.4%). Flexible and virtual bronchoscopic gradings correlated better for central airway stenosis (r = 0.87) than for segmental airway stenosis (r = 0.61).

CONCLUSION

Although a high sensitivity was found for the detection of both central and segmental airway stenosis, the number of false-positive findings was higher for segmental airways. However, noninvasive multirow detector CT virtual bronchoscopy enables high-resolution endoluminal imaging of the airways down to the segmental bronchi.

Prospective comparison of 3-dimensional volume rendered computerized tomography and conventional renal arteriography for surgical planning in patients undergoing laparoscopic donor nephrectomy

PURPOSE

We prospectively assessed the accuracy of 3-dimensional (3-D) volume rendered computerized tomography (CT) and conventional renal arteriography to visualize renovascular anatomy in patients undergoing laparoscopic donor nephrectomy.

MATERIALS AND METHODS

A total of 60 consecutive patients undergoing laparoscopic donor nephrectomy (left side in 46 and right side in 14) prospectively underwent 3-D CT and renal angiography. A short videotape of 3-D CT was prepared using volume rendering software that demonstrated the anatomical location, number, anomalies and spatial interrelationships of the renal arteries and veins. These 3-D videotapes and arteriogram findings were directly correlated with intraoperative surgical findings at laparoscopy and during ex vivo bench preparation of the harvested kidney. The perceived intraoperative value of 3D-CT to delineate renovascular anatomical detail was scored subjectively by the laparoscopic surgeon for each case on a 10-point scale of 0--completely inaccurate to 10--completely accurate.

RESULTS

There were no complications related to the 3-D CT protocol and volume rendering was successful in all patients. Three-D CT accurately identified the number of renal arteries in 59 patients (98%). In 1 patient with 3 renal arteries 3-D CT and arteriogram each identified only 2. In the 46 patients undergoing left donor nephrectomy 3-D CT accurately identified the number of veins and venous anomalies in 45 (98%), including 2 with a circumaortic left renal vein. Another case of circumaortic vein was misdiagnosed as 2 renal veins. On the right side in 14 patients 3-D CT accurately identified the renal veins in 13 (94%) and missed 1 vein in a patient with 2 renal veins. Angiography correctly identified the number of renal veins in only 52 cases (87%). Furthermore, it misdiagnosed all 3 cases of circumaortic left renal vein. The laparoscopic surgeon believed that 3-D CT accurately identified the location and anatomical interrelationship of the renal vessels with precision. Mean subjective score +/- SEM was 8.5 +/- 1 for the arterial system, 8.6 +/- 1.1 for the venous system and 9.2 +/- 0.5 for any vascular anomalies.

CONCLUSIONS

Three-D CT accurately identifies renal vascular anatomy in a manner that may facilitate renal hilar dissection during laparoscopic donor nephrectomy, especially during the initial surgeon experience. This imaging modality integrates essential information from angiography, venography and excretory urography into a single study, and it can obviate the need for more invasive vascular imaging in most cases.

Virtual bronchoscopy: comparison of different surface rendering models

The aim of this study was to compare different representation models of surface-rendered virtual bronchoscopy. 10 consecutive patients with inoperable primary lung tumors underwent thin-section spiral computed tomography. The structures of interest, the tracheobronchial system and anatomical and pathological thoracic structures were segmented using an interactive threshold interval volume-growing segmentation algorithm and visualized with the aid of a color-coded surface rendering method. For virtual bronchoscopy, the tracheobronchial system was visualized using a triangle-surface rendering model, a shaded-surface rendering model and a transparent shaded-surface rendering model. The triangle-surface rendering model allowed optimum detailed spatial representation of the dimensions of extraluminal anatomical and pathological mediastinal structures. As the lumen of the tracheobronchial system was less well defined, the rendering model was of limited use for depiction of the airway surface. The shaded-surface rendering model facilitated an optimum assessment of the airway surface, but the mediastinal structures could not be depicted. The transparent shaded-surface rendering model provides simultaneous adequate to optimum visualization and assessment of the intraluminal airway surface and the extraluminal mediastinal structures as well as a quantitative assessment of the spatial relationship between these structures. Fast data acquisition with a multi-slice detector spiral computed tomography scanner and the use of virtual bronchoscopy with the transparent shaded-surface rendering model obviate the need for time consuming detailed analysis and presentation of axial source images by providing improved the diagnostic imaging of endotracheal and endobronchial diseases and offering a useful alternative to fiberoptic bronchoscopy.

Low-dose spiral CT: application to surface-rendered three-dimensional imaging of central airways

PURPOSE

The purpose of this work was to assess the utility of low-dose spiral CT for three-dimensional imaging of the central airways.

METHOD

Spiral CT was performed in 15 patients using two tube currents (50 and 240 mA), producing 30 CT data sets. Surface-rendered virtual bronchoscopy (VB) and shaded surface display (SSD) images were assessed by three radiologists for image quality. The radiologists were also asked to compare 15 matched pairs each of 50 and 240 mA VB and SSD images, blindly select the 240 mA image, and record differences in diagnostic quality between the matched images.

RESULTS

No significant difference in image quality was noted with 50 or 240 mA. Only 51.1% of 240 mA SSD and 51.1% of 240 mA VB images were correctly identified. Differences in diagnostic quality, noted in 84.4% of SSD and 33% of VB image pairs, were not ascribed to image noise.

CONCLUSION

Image quality of surface-rendered three-dimensional images of the central airways is preserved using a lower tube current.

Multidetector CT virtual bronchoscopy to grade tracheobronchial stenosis

OBJECTIVE

The purpose of this study was to compare the efficacy of noninvasive multidetector CT (virtual bronchoscopic images, axial CT slices, coronal reformatted images, and sagittal reformatted images) in depicting and allowing accurate grading of tracheobronchial stenosis with that of flexible bronchoscopy.

MATERIALS AND METHODS

Multidetector CT and flexible bronchoscopy were used to examine 200 bronchial sections obtained from 20 patients (15 patients with bronchial carcinoma and five without central airways disease). Multidetector CT was performed using the following parameters: collimation, 4 x 2 mm, pitch, 1.375; and reconstruction intervals, 2 mm. Postprocessing was performed using surface rendering and multiplanar reformatted images. CT images were independently interpreted by two radiologists. The tracheobronchial stenoses revealed on flexible bronchoscopy were graded by a pulmonologist.

RESULTS

Virtual bronchoscopic findings, axial CT scans, and multiplanar reformatted images were highly accurate (98% accuracy for virtual bronchoscopic images, 96% for axial slices and coronal reformatted images, and 96.5% for sagittal reformatted images) in revealing tracheobronchial stenosis. In allowing accurate grading of tracheobronchial stenosis, images from virtual bronchoscopy correlated closely (r = 0.91) with those of flexible bronchoscopy. Because use of virtual bronchoscopic images reduced the overestimation of stenosis, these images allowed better assessment of stenosis than did axial CT slices (r = 0.84) or multiplanar reformatted images (r = 0.84) alone.

CONCLUSION

Multidetector CT virtual bronchoscopy is a reliable noninvasive method that allows accurate grading of tracheobronchial stenosis. However, it should be combined with the interpretation of axial CT images and multiplanar reformatted images for evaluation of surrounding structures and optimal spatial orientation.

CT virtual bronchoscopy of the central airways in patients with Wegener's granulomatosis

OBJECTIVES

To compare CT virtual bronchoscopy (VB) to CT alone and to conventional bronchoscopy for evaluation of central airway stenoses in patients with Wegener's granulomatosis.

DESIGN

Prospective observer study, in which 18 thin-section helical CT scans of the trachea and bronchi of 11 patients with Wegener's granulomatosis were obtained. VB was performed using surface rendering and was evaluated by one bronchoscopist and one radiologist in a blinded fashion. Bronchoscopic correlation within an average of 1.8 days of CT was available.

MEASUREMENTS AND RESULTS

VB displayed 188 of 198 bronchi (95%). Thirty-two of 40 stenoses (80%) were detected by VB by at least one of two physicians (double reading), and 22 of 40 stenoses (55%) were detected by a third physician reading only the CT.

CONCLUSIONS

VB depicts bronchi to the segmental level and detects the majority of central airway stenoses in patients with Wegener's granulomatosis. A team approach is useful to attain optimal clinical benefit from VB for these patients.

Hybrid 3D visualization of the chest and virtual endoscopy of the tracheobronchial system: possibilities and limitations of clinical application

OBJECTIVE

A hybrid rendering method which combines a color-coded surface rendering method and a volume rendering method is described, which enables virtual endoscopic examinations using different representation models.

MATERIALS AND METHODS

14 patients with malignancies of the lung and mediastinum (n=11) and lung transplantation (n=3) underwent thin-section spiral computed tomography. The tracheobronchial system and anatomical and pathological features of the chest were segmented using an interactive threshold interval volume-growing segmentation algorithm and visualized with a color-coded surface rendering method. The structures of interest were then superimposed on a volume rendering of the other thoracic structures. For the virtual endoscopy of the tracheobronchial system, a shaded-surface model without color coding, a transparent color-coded shaded-surface model and a triangle-surface model were tested and compared.

RESULTS

The hybrid rendering technique exploit the advantages of both rendering methods, provides an excellent overview of the tracheobronchial system and allows a clear depiction of the complex spatial relationships of anatomical and pathological features. Virtual bronchoscopy with a transparent color-coded shaded-surface model allows both a simultaneous visualization of an airway, an airway lesion and mediastinal structures and a quantitative assessment of the spatial relationship between these structures, thus improving confidence in the diagnosis of endotracheal and endobronchial diseases.

CONCLUSIONS

Hybrid rendering and virtual endoscopy obviate the need for time consuming detailed analysis and presentation of axial source images. Virtual bronchoscopy with a transparent color-coded shaded-surface model offers a practical alternative to fiberoptic bronchoscopy and is particularly promising for patients in whom fiberoptic bronchoscopy is not feasible, contraindicated or refused. Furthermore, it can be used as a complementary procedure to fiberoptic bronchoscopy in evaluating airway stenosis and guiding bronchoscopic biopsy, surgical intervention and palliative therapy and is likely to be increasingly accepted as a screening method for people with suspected endobronchial malignancy and as control examination in the aftercare of patients with malignant diseases.

Benign abnormalities and carcinoid tumors of the central airways: diagnostic impact of CT bronchography

OBJECTIVE

The purpose of this retrospective study was to determine the added diagnostic value, if any, of CT bronchography for the detection and characterization of benign abnormalities and typical carcinoid tumors of the central airways.

MATERIALS AND METHODS

We used bronchoscopy and helical CT to examine 238 bronchial sections in 28 patients with 32 bronchial abnormalities and in five patients with normal bronchoscopy results. Postprocessing consisted of CT bronchography based on surface rendering. Images were interpreted independently by two observers (a radiologist and a pneumonologist) who were not informed of the bronchoscopy results. After initial interpretation of axial CT scans, the observers analyzed the axial CT scans with CT bronchograms. Results were evaluated for gain in diagnostic accuracy and in confidence.

RESULTS

Mean sensitivity for detection of abnormal bronchial sections was 89% (range, 87-90%) for axial CT and 92% (range, 90-94%) for axial CT with CT bronchography (not significant). Mean specificity of both approaches exceeded 99%. A correct diagnosis of the nature of the bronchial abnormalities was proposed for 68% of the cases in which axial CT was used alone and in 76% in which both axial CT and CT bronchography were used (not significant). The addition of CT bronchography significantly increased the confidence of the pneumonologist in the diagnoses.

CONCLUSION

Axial CT remains the technique of choice to detect and characterize benign abnormalities of the airways. CT bronchography provides little diagnostic gain but increases the confidence of chest physicians in the interpretation of CT scans for the assessment of benign abnormalities and typical carcinoids of the central airways.

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.

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.

Helical CT in emergency radiology

Today, a wide range of traumatic and nontraumatic emergency conditions are quickly and accurately diagnosed with helical computed tomography (CT). Many traditional emergency imaging procedures have been replaced with newer helical CT techniques that can be performed in less time and with greater accuracy, less patient discomfort, and decreased cost. The speed of helical technology permits CT examination of seriously ill patients in the emergency department, as well as patients who might not have been taken to CT previously because of the length of the examinations of the past. Also, helical technology permits multiple, sequential CT scans to be quickly obtained in the same patient, a great advance for the multiple-trauma patient. Higher quality CT examinations result from decreased respiratory misregistration, enhanced intravenous contrast material opacification of vascular structures and parenchymal organs, greater flexibility in image reconstruction, and improved multiplanar and three-dimensional reformations. This report summarizes the role and recommended protocols for the helical CT diagnosis of thoracic aortic trauma; aortic dissection; pulmonary embolism; acute conditions of the neck soft tissues; abdominal trauma; urinary tract stones; appendicitis; diverticulitis; abdominal aortic aneurysm; fractures of the face, spine, and extremities; and acute stroke.

Pitfalls in image reconstruction of helical CT angiography: an experimental study

This study was undertaken to evaluate the effects of the object related factors: background tissue and the direction of vessels on the morphological reproducibility of helical CT angiography. Cylindrical tubes filled with a diluted contrast medium were prepared to obtain vascular phantoms. The scan was performed within various background tissues. For the evaluation of the direction of the vessels, two types of vascular phantoms were prepared. The phantoms were scanned by varying beam collimations and scan pitches. Reconstructed CT images were markedly affected by the background tissue. The reconstructed images were also affected by the direction of vessels.

Advanced imaging concepts: a pictorial glossary of CT and MRI technology

This article serves as an illustrative glossary of concepts related to computed tomography (CT) and magnetic resonance imaging (MRI) technology. The principles of tomography, digital processing, image resolution, CT windowing, CT gray levels, contrast enhancement, and MRI spin echo pulse sequences are reviewed. Techniques not commonly described for use in animal patients are also introduced, and include gradient echo, short time of inversion recovery, fluid attenuated inversion recovery and fat saturation pulse sequences, fast imaging, MRI angiography, perfusion and diffusion imaging, brain activation, CT angiography/functional CT, interventional procedures, and three-dimensional CT.

Virtual bronchoscopy

Three-dimensional endoluminal tracheobronchial simulations can be derived successfully from thoracic helical CT scans, and can reproduce the appearances of major endobronchial abnormalities confirmed during FB. The prospects of ever-faster CT scanners (capable of submillimeter resolution) merged with greater computer power make it likely that current versions of virtual bronchoscopy images will seem primitive in the future. Initial descriptive reports suggest great potential, but the startling visual appeal of these 3-D portrayals of a patient's airway and mediastinal anatomy and the prospects of exploring this information in real time do not establish its clinical role. Such virtual bronchoscopy findings are generally predictable on the basis of currently available axial CT images alone. The extent to which these 3-D endobronchial renderings improve the already high predictive values of CT requires critical study. In their patients with lung cancer Cicero et al observed that neither the staging nor diagnosis was modified substantially, but virtual bronchoscopy contributed to enhanced understanding of the pathology of the neoplastic process. Whether this added perspective translates to tangible benefits for patients is an intriguing possibility that has yet to be proved. The unique 3-D endobronchial view may offer particular advantages in some individuals and contribute to the patient's noninvasive evaluation. Because of the already high yield of conventional CT, diagnostic yield alone is not likely to be the sole best measure of this evolving technology. Accordingly, future multidisciplinary research investigations will also need to prospectively address nuances of decision-making and measure appropriate patient outcomes. In these efforts the active dialogue between chest clinician and radiologist will remain essential to defining and realizing the true potential of virtual bronchoscopy.

Three-dimensional imaging of the speaking shunt in patients with near-total laryngectomy

OBJECTIVES

Near-total laryngectomy with creation of a speaking shunt is generally considered suitable treatment for most T3 and some T4 laryngopharyngeal cancers. In some patients, poor speech production by the shunt can be problematic and usually means that a shunt lumen is stenotic or too small. Conventional axial computed tomography (CT) of the neck is of little value in predicting the shunt function and the patency of the shunt lumen. Such defect, however, can be better overcome if the spiral CT is used.

STUDY DESIGN

This study was designed to evaluate the dynamic speaking shunt by spiral CT and a three-dimensional (3-D) imaging model of the upper airway in 59 near-total laryngectomies.

METHODS

During scanning, the patients were asked to make a single, 20-second phonation. A high-quality 3-D surface model was then rendered at an independent workstation. The 3-D model took on the appearance of the speaking shunt which could serve as a tracheopharyngeal fistulography.

RESULTS

3-D reconstruction of the images could clearly demonstrate the dynamic anatomy and patency of the speaking shunt. We found the 3-D model to be of diagnostic value, particularly in the near-total laryngectomy patients with stenotic shunts. The most common site of stenosis was at the top portion of the shunt.

CONCLUSION

The 3-D image findings of the shunts significantly improved the assessment and therapies of the patients undergoing revision surgeries of the shunt stenoses.

Tracheal involvement in Wegener's granulomatosis: evaluation using spiral CT

OBJECTIVE

To describe the computed tomography (CT) appearances of tracheal stenosis in Wegener's granulomatosis (WG) and to assess the additional value of reformatted images.

PATIENTS AND METHODS

Ten patients with tracheal involvement by WG were assessed with spiral CT and both coronal and three-dimensional surface shaded images were generated. Fibreoptic bronchoscopy was also performed in all patients.

RESULTS

Ninety per cent of lesions were situated in the subglottic region. In all cases there was circumferential mucosal thickening, in nine cases extending over a relatively short distance (mean 2.4 cm). The degree of narrowing of the axial luminal diameter ranged from 23% to 100%. In three patients there was contiguous involvement of the vocal cords evident on CT, two further cases with mild vocal cord inflammation were identified bronchoscopically. Other CT findings included mucosal irregularity and ulceration (50%), and involvement of the tracheal cartilages (20%).

CONCLUSION

Wegener's granulomatosis may involve the trachea with resultant stenosis. Spiral CT is an easily performed, non-invasive technique which provides accurate assessment of tracheal lesions and is complementary to bronchoscopy. The main additional advantage of coronal reformatted images was our added confidence in defining the upper and lower limits of lesions and in the evaluation of vocal cord involvement.

Helical CT applications in the thorax and abdomen

The past few years have witnessed a massive explosion in clinical applications for computed tomography (CT) as a result of exponential advances in technology. Most clinical practitioners have a limited understanding of the complexities and dynamics of modern CT, and even many radiologists are unable to keep up with the rapid evolution in refinements. In this article, Dr Rappaport summarizes some of the most recent advances in use of helical, or spiral, CT to diagnose diseases of the thorax and abdomen.

Image processing and spiral CT of the thorax

The data set of the thorax acquired by spiral CT is volumetric. Such data can be processed so that conventional axial sections are supplemented by reconstructed images, in an attempt to answer specific clinical questions. This review considers three reconstruction techniques: multiplanar reformation, three-dimensional rendering and sliding-thin slab reconstruction. Their relative benefits and limitations are considered, as are the implications of image processing in general.

A new diagnostic approach to vascular rings and pulmonary slings: the role of MRI

The conventional diagnostic work-up of a patient suspected of having a vascular cause for stridor, or dysphagia, includes esophagography and bronchoscopy to delineate the abnormal structure without imaging the structure itself. Cine-angiography is regarded as the golden standard, but is not routinely performed. Magnetic resonance imaging (MRI) is non-invasive and has the important advantage over cine-angiography of depicting all structures in the field of view. Color Doppler echocardiography depicts the great vessels, but not the esophagus and trachea. In 14 patients with obstructive symptoms and in four patients without obstructive symptoms MRI successfully imaged the abnormal structure, as was the case in two symptomatic patients using computer tomography. In this series, the findings were confirmed at surgery or by cine-angiography.

CONCLUSION

we suggest that in patients suspected of having a vascular cause for stridor or dysphagia, MRI should be performed. If there is need for a screening procedure, color Doppler echocardiography should be used and if that is equivocal or non-conclusive, esophagography and bronchoscopy should be used. If MRI is difficult to interpret, it should be augmented by magnetic resonance angiography before considering cine-angiography.

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.

3D virtual endoscopy of the upper airway: optimization of the scan parameters in a cadaver phantom and clinical assessment

Our goal was to evaluate the influence of the scan parameters on the 3D virtual endoscopy of the larynx and trachea and the clinical assessment. Helical CT (HiSpeed Advantage; GE, Milwaukee, WI, U.S.A.) of a cadaver phantom was performed with increased collimation (1-10 mm) and pitch (0.5-3). Seventy-two patients with complaints of the upper airways were investigated by virtual endoscopy and their results were compared with the findings of regular endoscopy. Best correlation between virtual endoscopy and anatomical findings, diagnostic quality of the axial slices, and useful longitudinal coverage of the examination were obtained with a collimation of 3 mm and a pitch of 1.5. Space-occupying tumors and stenosis were detected correctly, but the mucous membrane could not be visualized. 3D virtual endoscopy proved to be a valuable method for displaying anatomical structures. For an optimal protocol, a collimation of 3 mm with a pitch of 1.5 is recommended.