Pulmonary hemorrhage in fiberoptic transbronchial biopsy

Transbronchial forceps biopsy via the flexible fiberoptic bronchoscope is described as a "safe," high-yielding procedure, but the potential danger of serious hemorrhage is of concern to chest physicians. In a collected series of 438 patients, the incidence of mild to "explosive" hemorrhage was 9 percent in "routine" cases, 29 percent (eight) in 31 immunosuppressed patients, and 45 percent (five) in 11 uremic patients. One death resulted from massive hemorrhage. A new "wedge" method of transbronchial forceps biopsy is now being utilized in our bronchoscopic unit. The tip of the flexible fiberoptic bronchoscope is lodged into the appropriate segmental bronchus to tamponade any bleeding and, thus, prevent blood from flooding the airway. Careful screening of patients and competence in procedural techniques are necessary. Otherwise, transbronchial forceps biopsy should be performed through a rigid open-tube bronchoscopicronchoscope or performed through a rigid open-tube bronchoscope or lung tissue should be obtained via thoracotomy.     

Correlation between the clinical and pathohistologic diagnosis in "small biopsies" of the lung

INTRODUCTION: During the last 20 years routine application of various methods of multiple "small biopsies" of the lungs such as forceps, transbronchial, trucut percutaneous and so on, has significantly increased the efficacy of diagnostics of bronchopulmonary and pleural diseases. Tissue samples, not bigger than 3-4 mm, in which diagnostic pathological changes are expected on the basis of previous clinical, radiological and bronchoscopic examinations, can be the basis for making a definite therapeutical decision only if a skillful surgeon has performed the biopsy by correct instruments and from the right place and sent it for histological analysis with other important clinical information. This study is a comment on quality, significance and possibilities of improving clinical-pathological cooperation in this field of clinical pathology. MATERIAL AND METHODS: By correlation of clinical and histological diagnoses we analyzed the diagnostic efficiency of microscopic examinations of "small biopsies" of the respiratory tract in 319 patients (175 bronchial forceps biopsies, 31 transbronchial biopsies, 22 percutaneous needle pleural biopsies and 91 combined forceps and transbronchial biopsies) in whom biopsies were performed during 1996 in the Specialized Hospital for Lung Diseases Brezovik. RESULTS: Overall concordance between the clinical and histopathological diagnosis was 82.2%. In 99 cases (73.3%) out of 135 clinically "obvious" neoplasms, the histopathological examination confirmed existence of malignant tumor: squamous cell carcinoma in 80%, small cell carcinoma in 9.6% and adenocarcinoma in 5.6% of patients. In other patients it was not possible to perform a more precise classification. Endoscopic specimens of 29 patients (9.1%) were not representative. CONCLUSION: The level of diagnostic efficiency (73.3%) of definitive histopathological verification of bronchopulmonary lesions, which have been clinically diagnosed as malignancies, is rather high, but the increase of diagnostic efficiency requires application of more sophisticated histological diagnostic methods (immunohistochemical) and more frequent utilization of bioptic procedures which are more convenient for detection of peripheral pulmonary lesions (transbronchial and percutaneous fine needle aspiration biopsies of the lungs).     

Virtual bronchoscopy for directing transbronchial needle aspiration of hilar and mediastinal lymph nodes: a pilot study

OBJECTIVE: We conducted a preliminary investigation of virtual bronchoscopy as a guide for transbronchial needle aspiration of hilar or mediastinal lymph nodes to assess the usefulness of this technique. CONCLUSION: Virtual bronchoscopic images derived from routine helical CT scans were useful for directing transbronchial needle aspiration in a clinical setting. In addition, virtual bronchoscopy may have been responsible for improving the yield of transbronchial needle aspirations done by our bronchoscopists when 22-gauge needles were used.     

Automated 3-D registration of MR and CT images of the head

This paper discusses the application of voxel similarity measures in the automated registration of clinically acquired MR and CT data of the head. We describe a novel single-start multi-resolution approach to the optimization of these measures, and the issues involved in applying this to data having a range of different fields of view and sampling resolution. We compare four proposed measures of voxel similarity using the same optimization scheme when presented with 10 pairs of images with a range of initial misregistrations. The registration estimates are compared with those provided by manual point-based registration and evaluated by visual inspection to give an assessment of the robustness and accuracy of the different measures. One full-volume CT image set is used to investigate the performance of each measure when used to align truncated images from different regions in the head. The soft tissue correlation and mutual information measures were found to provide the most robust measures of misregistration, providing results comparable to or better than those from manual point-based registration for all but the most truncated image volumes.     

Virtual bronchoscopy: the correlation between endoscopic simulation and bronchoscopic findings

PURPOSE: We carried out a preliminary clinical validation of 3D spiral CT virtual endoscopic reconstructions of the tracheobronchial tree, by comparing virtual bronchoscopic images with actual endoscopic findings. MATERIALS AND METHODS: Twenty-two patients with tracheobronchial disease suspected at preliminary clinical, cytopathological and plain chest film findings were submitted to spiral CT of the chest and bronchoscopy. CT was repeated after endobronchial therapy in 2 cases. Virtual endoscopic shaded-surface-display views of the tracheobronchial tree were reconstructed from reformatted CT data with an Advantage Navigator software. Virtual bronchoscopic images were preliminarily evaluated with a semi-quantitative quality score (excellent/good/fair/poor). The depiction of consecutive airway branches was then considered. Virtual bronchoscopies were finally submitted to double-blind comparison with actual endoscopies. RESULTS: Virtual image quality was considered excellent in 8 cases, good in 14 and fair in 2. Virtual exploration was stopped at the lobar bronchi in one case only; the origin of segmental bronchi was depicted in 23 cases and that of some subsegmental branches in 2 cases. Agreement between actual and virtual bronchoscopic findings was good in all cases but 3 where it was nevertheless considered satisfactory. The yield of clinically useful information differed in 8/24 cases: virtual reconstructions provided more information than bronchoscopy in 5 cases and vice versa in 3. Virtual reconstructions are limited in that the procedure is long and difficult and needing a strictly standardized threshold value not to alter virtual findings. Moreover, the reconstructed surface lacks transparency, there is the partial volume effect and the branches < or = 4 pixels phi and/or meandering ones are difficult to explore. CONCLUSIONS: Our preliminary data are encouraging. Segmental bronchi were depicted in nearly all cases, except for the branches involved by disease. Obstructing lesions could be bypassed in some cases, making an indication for endoscopic laser therapy. Future didactic perspectives and applications to minimally invasive or virtual reality-assisted therapy seem promising, even though actual clinical applications require further studies.     

Fluoroscopically controlled transbronchial biopsy of solitary peripheral pulmonary lesions using the fibreoptic bronchoscope

Experience of fluoroscopically controlled transbronchial biopsy using the fibreoptic bronchoscope in 30 patients with solitary lesions in the peripheral lung fields beyond bronchoscopic vision is described. At the time of submitting this paper for publication (30 January 1978) no account of the technique has been reported in the British literature. In 21 patients with a final diagnosis of bronchial carcinoma a positive biopsy diagnosis was obtained in 14 (67%). Five of seven patients (71%) with a final diagnosis of an inflammatory condition showed evidence of acute or chronic inflammation on biopsy. There were no complications. The procedure is indicated when a definitive diagnosis is required for management planning in clinically inoperable patients, or when a tissue diagnosis is particularly desired in an attempt to obviate the need for thoracotomy. The relative safety makes this the biopsy technique of choice for the evaluation of isolated peripheral pulmonary opacities.     

Visual assessment of the accuracy of retrospective registration of MR and CT images of the brain

In a previous study we demonstrated that automatic retrospective registration algorithms can frequently register magnetic resonance (MR) and computed tomography (CT) images of the brain with an accuracy of better than 2 mm, but in that same study we found that such algorithms sometimes fail, leading to errors of 6 mm or more. Before these algorithms can be used routinely in the clinic, methods must be provided for distinguishing between registration solutions that are clinically satisfactory and those that are not. One approach is to rely on a human observer to inspect the registration results and reject images that have been registered with insufficient accuracy. In this paper, we present a methodology for evaluating the efficacy of the visual assessment of registration accuracy. Since the clinical requirements for level of registration accuracy are likely to be application dependent, we have evaluated the accuracy of the observer's estimate relative to six thresholds: 1-6 mm. The performance of the observers was evaluated relative to the registration solution obtained using external fiducial markers that are screwed into the patient's skull and that are visible in both MR and CT images. This fiducial marker system provides the gold standard for our study. Its accuracy is shown to be approximately 0.5 mm. Two experienced, blinded observers viewed five pairs of clinical MR and CT brain images, each of which had each been misregistered with respect to the gold standard solution. Fourteen misregistrations were assessed for each image pair with misregistration errors distributed between 0 and 10 mm with approximate uniformity. For each misregistered image pair each observer estimated the registration error (in millimeters) at each of five locations distributed around the head using each of three assessment methods. These estimated errors were compared with the errors as measured by the gold standard to determine agreement relative to each of the six thresholds, where agreement means that the two errors lie on the same side of the threshold. The effect of error in the gold standard itself is taken into account in the analysis of the assessment methods. The results were analyzed by means of the Kappa statistic, the agreement rate, and the area of receiver-operating-characteristic (ROC) curves. No assessment performed well at 1 mm, but all methods performed well at 2 mm and higher. For these five thresholds, two methods agreed with the standard at least 80% of the time and exhibited mean ROC areas greater than 0.84. One of these same methods exhibited Kappa statistics that indicated good agreement relative to chance (Kappa > 0.6) between the pooled observers and the standard for these same five thresholds. Further analysis demonstrates that the results depend strongly on the choice of the distribution of misregistration errors presented to the observers.     

Feasibility study of magnetic resonance imaging-guided intranasal flexible microendoscopy

Interventional magnetic resonance imaging (MRI) offers potential advantages over conventional interventional modalities such as X-ray fluoroscopy, ultrasonography, and computed tomography (CT). In particular, it does not use ionizing radiation, can provide high-quality images, and allows acquisition of oblique sections. We have carried out a feasibility study on the use of interventional MRI to track a flexible microendoscope in the paranasal sinuses. In this cadaver study, high-speed MRI was used to track a passive marker attached to the end of the endoscope. Automatic image registration algorithms were used to transfer the coordinates of the endoscope tip into the preoperative MRI and CT images, enabling us to display the position of the endoscope in reformatted orthogonal views or in a rendered view of the preoperative images. The endoscope video images were digitized and could be displayed alongside an approximately aligned, rendered preoperative image. Intraoperative display was provided in the scanner room by means of an liquid crystal display (LCD) projector. We estimate the accuracy of the endoscope tracking to be approximately 2 mm.     

Primary lung cancer associated with diffuse granulomatous lesions in the pulmonary parenchyma

A 60-year-old man was admitted to our hospital for productive cough. Chest roentgenography and CT scan disclosed a left hilar tumor invading the mediastinum, with mediastinal lymphadenopathy and diffuse micronodular shadows in both lung fields. A biopsied sample of the tumor revealed squamous cell carcinoma, while noncaseating epithelioid cell granulomas were observed in the samples obtained by transbronchial lung biopsy. The granulomas in the pulmonary parenchyma were determined to be sarcoid reactions secondary to lung cancer, since there was no evidence of sarcoidosis. Combination chemotherapy was effective for the tumor, and the granulomas disappeared after completion of the chemotherapy. These findings suggest the presence of a relationship between sarcoid reactions and lung cancer in this case.     

Reactive oxygen species act at both TGF-beta-dependent and -independent steps during induction of apoptosis of transformed cells by normal cells

PURPOSE: In clinical practice, physicians are constantly comparing multiple images taken at various times during the patient's treatment course. One goal of such a comparison is to accurately define the gross tumor volume (GTV). The introduction of three-dimensional treatment planning has greatly enhanced the ability to define the GTV, but there are times when the GTV is not visible on the treatment-planning computed tomography (CT) scan. We have modified our treatment-planning software to allow for interactive display of multiple, registered images that enhance the physician's ability to accurately determine the GTV. METHODS AND MATERIALS: Images are registered using interactive tools developed at the University of North Carolina at Chapel Hill (UNC). Automated methods are also available. Images registered with the treatment-planning CT scan are digitized from film. After a physician has approved the registration, the registered images are made available to the treatment-planning software. Structures and volumes of interest are contoured on all images. In the beam's eye view, wire loop representations of these structures can be visualized from all image types simultaneously. Each registered image can be seamlessly viewed during the treatment-planning process, and all contours from all image types can be seen on any registered image. A beam may, therefore, be designed based on any contour. RESULTS: Nineteen patients have been planned and treated using multimodality imaging from November 1993 through August 1994. All registered images were digitized from film, and many were from outside institutions. Brain has been the most common site (12), but the techniques of registration and image display have also been used for the thorax (4), abdomen (2), and extremity (1). The registered image has been an magnetic resonance (MR) scan in 15 cases and a diagnostic CT scan in 5 cases. In one case, sequential MRs, one before treatment and another after 30 Gy, were used to plan patient's initial fields and boost, respectively. Case illustrations are shown. CONCLUSIONS: We have successfully integrated multimodality imaging into our treatment-planning system, and its routine use is increasing. Multimodality imaging holds out the promise of improving treatment planning accuracy and, thus, takes maximum advantage of three dimensional treatment planning systems.     

Atypical squamous cell carcinoma of the larynx and hypopharynx: radiologic features and pathologic correlation

The objective of this study was to analyze the radiologic features of atypical forms of squamous cell cancer and correlate them with clinical, endoscopic, and histopathologic findings. The CT and MRI images of 31 patients with atypical forms of squamous cell carcinoma were reviewed retrospectively and the radiologic findings were correlated with clinical, endoscopic, and histopathologic findings. Histopathologic diagnoses included undifferentiated carcinoma of nasopharyngeal type (n = 8), verrucous carcinoma (n = 18), spindle cell carcinoma (n = 3), and basaloid cell carcinoma (n = 2). Undifferentiated carcinoma of nasopharyngeal type was located in the supraglottis or piriform sinus beneath an intact mucosa and initial endoscopic biopsy was most often negative. The discrepancy between an intact mucosa at endoscopy and a solid mass with homogenous enhancement at CT or MRI was characteristic for these tumors and warranted further investigations to obtain the definitive histologic diagnosis. Verrucous carcinoma displayed characteristic clinical, radiologic, and pathologic features, namely, an exophytic tumor arising from the glottic level displaying a rugged surface with finger-like projections but with only minor submucosal infiltration. Spindle cell carcinoma appeared as a polypoid mass with a thin stalk arising from the supraglottis. Basaloid cell carcinoma displayed a distinct lobulated enhancement pattern which was observed on contrast-enhanced T1-weighted SE images. Although the MR and CT features of atypical forms of squamous cell carcinoma cannot be considered pathognomonic they should raise the differential diagnosis even if endoscopic biopsy has been negative. The radiologist's awareness of the appearance of these unusual tumors on CT and MR images may greatly facilitate the diagnostic work-up and helps to guide the endoscopist to the adequate biopsy site in order to establish the correct diagnosis.     

Posterior traumatic dislocation of a Thompson prosthesis: report of a case

Fluorine-18-fluorodeoxyglucose (F-18 FDG) PET was used to evaluate early-stage larynx cancer before and after radiotherapy. Less radical salvage surgery might be possible after timely diagnosis of recurrent or persistent tumor after radiotherapy. Eight patients with early-stage laryngeal cancer (two carcinoma in situ; six stage T1: tumor limited to vocal cords with normal mobility) underwent irradiation for potential cure. Five patients had pre- and postradiotherapy F-18 FDG PET, and three had postradiotherapy F-18 FDG PET only. All patients underwent a CT scan of the neck at the time of the F-18 FDG PET scan. One patient had a positive result of postradiotherapy F-18 FDG PET but a negative result of a CT of the neck, and biopsy revealed recurrent squamous carcinoma. Seven patients who had negative results of postradiotherapy F-18 FDG PET were free of disease at the 15-month median follow-up evaluation. (Three of them had no cancer on biopsy of the larynx, and four others were followed with periodic endoscopic examinations that revealed complete disappearance of the tumor.) F-18 FDG PET scan may be useful for earlier diagnosis of recurrent or persistent laryngeal cancer after radiotherapy and is preferable to repeated biopsies, which would traumatize radiation-damaged tissues. A prompt early diagnosis of failure of radiotherapy will lead to less radical salvage surgery.     

基于监督学习的前列腺MR/TRUS图像分割和配准方法

前列腺核磁超声图像配准融合有助于实现前列腺肿瘤的靶向穿刺。传统的配准方法主要是针对手动分割的前列腺核磁（Magnetic resonance, MR）和经直肠超声（Trans-rectal ultrasound, TRUS）图像上对应的生理特征点作为参考点,进行刚体或非刚体配准。针对超声图像因成像质量低导致手动分割配准效率低下的问题,提出一种基于监督学习的前列腺MR/TRUS图像自动分割方法,与术前核磁图像进行非刚体配准。首先,针对图像分割任务训练前列腺超声图像的活动表观模型（Active appearance model, AAM）,并基于随机森林建立边界驱动的数学模型,实现超声图像自动分割。接着,提取术前分割的核磁图像与自动分割的超声图像建立轮廓的形状特征矢量,进行特征匹配与图像配准。实验结果表明,本文方法能准确实现前列腺超声图像自动分割与配准融合,9组配准结果的戴斯相似性系数（Dice similarity coefficient, DSC）均大于0.98,同时尿道口处特征点的平均定位精度达1.64 mm,相比传统方法具有更高的配准精度。      

Tc-99m MIBI uptake in simultaneous thyroid and lung cancers

The authors present a patient with simultaneous follicular thyroid and small-cell lung cancers, both of which showed Tc-99m MIBI uptake. CT scans showed two masses: one involving the right lower neck including the right supraclavicular area and the right superior mediastinum, and the other involving the peripheral portion of the right upper lobe of the lung. I-131 imaging showed increased uptake in the right neck mass only. Tc-99m MIBI imaging, which was performed for evaluation of chest pain, showed intense uptake in the neck mass (tumor to heart ratios in planar and tomographic images were 0.92 and 0.96, respectively), and less uptake in the lung mass (tumor to heart ratios in planar and tomographic images were 0.53 and 0.40, respectively). Biopsy of the right supraclavicular mass revealed a follicular carcinoma, and a bronchoscopic biopsy of the right upper lobe mass revealed a small cell carcinoma.     

A neural network based artificial vision system for licence plate recognition

This paper presents a neural network based artificial vision system able to analyze the image of a car given by a camera, locate the registration plate and recognize the registration number of the car. The paper describes in detail various practical problems encountered in implementing this particular application and the solutions used to solve them. The main features of the system presented are: controlled stability-plasticity behavior, controlled reliability threshold, both off-line and on-line learning, self assessment of the output reliability and high reliability based on high level multiple feedback. The system has been designed using a modular approach. Sub-modules can be upgraded and/or substituted independently, thus making the system potentially suitable in a large variety of vision applications. The OCR engine was designed as an interchangeable plug-in module. This allows the user to choose an OCR engine which is suited to the particular application and to upgrade it easily in the future. At present, there are several versions of this OCR engine. One of them is based on a fully connected feedforward artificial neural network with sigmoidal activation functions. This network can be trained with various training algorithms such as error backpropagation. An alternative OCR engine is based on the constraint based decomposition (CBD) training architecture. The system has showed the following performances (on average) on real-world data: successful plate location and segmentation about 99%, successful character recognition about 98% and successful recognition of complete registration plates about 80%.     

In vivo validation of tissue segmentation based on a 3D feature map using both a hamster brain tumor model and stereotactically guided biopsy of brain tumors in man

The purpose of this study was to validate our MR tissue segmentation technique using a hamster brain tumor model and malignant brain tumors in man. We used a multispectral tissue segmentation analysis. Three sets of MRI data were included: proton density, T2-weighted fast spin echo, and T1-weighted spin echo, as inputs. Three image preprocessing steps included correcting image nonuniformity, application of an anisotropic diffusion type filter, and data point selection by a qualified observer. We used the k-Nearest Neighbor segmentation algorithm, which does not require prior knowledge of the sample distribution. This choice allowed us to optimize the different tissue clusters present in three-dimensional (3D) feature space. In vivo validation of the technique was performed in hamsters harboring tumors induced with JC virus-transformed HJC-15 cells, as compared to three control animals. Human brain tumors obtained by stereotactically guided biopsy in six patients were also included in the study. Finally, brain tumors were removed from two patients who underwent conventional craniotomy using segmentation-derived images as a guide. In the hamsters, 10 tissues were correctly identified by segmentation and were confirmed histologically (P < .02). In the patients, there was also a strong correlation between our segmentation results and the tissue obtained by stereotactic biopsy (P < .01). In one of the two patients who underwent open craniotomy, segmentation images were useful in revealing tumor spread into vital areas of the brain (motor area). In conclusion, the results of segmentation correlate well with the tissues in vivo and thus warrant further clinical utilization and evaluation.     

Leg blood flow during slow head-down tilt with and without leg venous congestion

BACKGROUND AND STUDY AIMS: Endoscopy and biopsy from a suspicious Vater's papilla may establish an early preoperative diagnosis of a periampullary tumor. However, information regarding the diagnostic accuracy of this procedure is limited and variable. The aim of the present study was to evaluate retrospectively the accuracy of this procedure compared to that of other diagnostic methods. PATIENTS AND METHODS: Among 928 patients referred to our institute for endoscopic retrograde cholangiopancreatography (ERCP), a suspicious Vater's papilla was seen in 28. In each case comparison was made between the pre-ERCP clinical diagnosis, endoscopic appearance, histologic interpretation of endoscopic biopsies, and the final diagnosis. Two patients in whom a final diagnosis was not available were excluded from the study. RESULTS: A final diagnosis of an ampullary or periampullary carcinoma was established in 17 patients (65%), a carcinoma within an adenoma of the papilla in three patients (12%), and adenoma and a metastatic gallbladder carcinoma in one patient each. The remaining four patients (15%) were finally diagnosed as having "pseudotumors" (due to choledocholithiasis). Eight (38%) of the 21 patients with ampullary or periampullary neoplasm also had gallstones. A pre-ERCP diagnosis (by clinical evaluation and non-invasive imaging) of tumor versus choledocholithiasis was accurate in only 65% of all 26 patients. In these, the diagnostic accuracy of endoscopic appearance and endoscopic biopsy was 77% and 85%, respectively. Regarding the 21 patients with carcinomas, the diagnosis by endoscopic appearance was more accurate than that by endoscopic biopsy (90% vs 81%). Unlike the positive predictive values, the negative predictive values for malignancy were weak: 33% for the endoscopic appearance and 50% for the endoscopic biopsy. CONCLUSIONS: Because of a high incidence of concurrent cholelithiasis, many patients with a periampullary tumor seen during ERCP are misdiagnosed earlier (by clinical evaluation and non-invasive imaging) as having choledocholithiasis only. However, the accuracy of endoscopy and biopsy is also limited. This limitation must be considered when evaluating the optimal management of patients with suspected periampullary tumor.     

Examination using the gastro-camera and gastroscopy--confrontation and complementation

Both the gastro-camera and gastroscopy are methods of examination dating back to the last century. Since 1955 examination with the gastro-camera has gained major importance in Japan. Not until the efficient gastroscopic instruments based on fiber optics and with extremely flexible points as well as advance view optical systems were developed large-scale, introduction esophageal gastro-bulboscopy in hospitals and in offices of specialists became possible. In our view the replacement of the gastro-camera method of diagnosis as a basic examination by gastroscopy is not justified. The gastro-camera is highly efficient and easily applied if centers for early diagnosis of gastric tumor cooperate with the examining physicans; their own experience with the gastro-camera is a premise for this arrangement. The principal task of endoscopic diagnosis is the determination as to therapy, namely whether surgery or a conservative method should be applied: this is particularly true in the case of early carcinoma stages where a 90% 5-year survival chance prevails. For various reasons gastro-camera examination should be assigned a more prominent role. Gastroscopy and histological examination represent further steps in diagnosing malignant processes. It is not possible to preclude the possiblity of a malignant tumor by means of gastroscopic biopsy.     

一种改进的非刚性图像配准算法

非刚性图像配准一直是计算机视觉领域的研究重点. 为解决上述问题, 提出一种改进的光流场模型算法, 以提高光流估计的准确度. 算法首先对原始变分光流模型进行了改进, 提出利用新的各向异性正则项来代替原来的同向扩散函数, 以避免图像模糊, 保留图像的边缘特征与细节特征; 此外, 通过引入包含邻域信息的非局部平滑项来去除光流噪点, 同时增加了一个结合图像结构与光流运动信息的权函数, 以减少过平滑所造成的细节丢失, 提高算法的鲁棒性. 最后, 利用交替最小化与金字塔分层迭代策略相结合的方法求解位移场, 实现非刚性图像的自动配准. 仿真实验结果表明, 与传统方法相比, 本文算法对不同类型的非刚性图像均具有较高的鲁棒性, 取得了理想的图像配准效果.      

Norbornane compounds in pharmaceutical research

The multi-slice CT scanner refers to a special CT system equipped with a multiple-row detector array to simultaneously collect data at different slice locations. The multi-slice CT scanner has the capability of rapidly scanning large longitudinal (z) volume with high z-axis resolution. It also presents new challenges and new characteristics. In this paper, we study the scan and reconstruction principles of the multi-slice helical CT in general and the 4-slice helical CT in particular. The multi-slice helical computed tomography consists of the following three key components: the preferred helical pitches for efficient z sampling in data collection and better artifact control; the new helical interpolation algorithms to correct for fast simultaneous patient translation; and the z-filtering reconstruction for providing multiple tradeoffs of the slice thickness, image noise and artifacts to suit for different application requirements. The concept of the preferred helical pitch is discussed with a newly proposed z sampling analysis. New helical reconstruction algorithms and z-filtering reconstruction are developed for multi-slice CT in general. Furthermore, the theoretical models of slice profile and image noise are established for multi-slice helical CT. For 4-slice helical CT in particular, preferred helical pitches are discussed. Special reconstruction algorithms are developed. Slice profiles, image noises, and artifacts of 4-slice helical CT are studied and compared with single slice helical CT. The results show that the slice profile, image artifacts, and noise exhibit performance peaks or valleys at certain helical pitches in the multi-slice CT, whereas in the single-slice CT the image noise remains unchanged and the slice profile and image artifacts steadily deteriorate with helical pitch. The study indicates that the 4-slice helical CT can provide equivalent image quality at 2 to 3 times the volume coverage speed of the single slice helical CT.