Biomedical subjects

Geoffrey McLennan

Publications and source records attributed to Geoffrey McLennan.

29 records · Page 2Linked to original sources

PubMed2004

Evaluation of the human airway with multi-detector x-ray-computed tomography and optical imaging.

Defining the healthy human airway is important in enhancing our understanding of pulmonary disease states such as inflammation and cancer. The structure of the human airway, both static and dynamic, can be assessed using multi-detector CT (MDCT) scanning. This modality also allows for the evaluation of structures outside of the airway. The airway wall can be directly visualized using CCD chip high-resolution color optical imaging through endoscopy allowing bronchial wall evaluation by traditional biopsy methods, as well as by newer optically based strategies. We suggest that these two imaging modalities, MDCT and optical imaging, provide complementary information about the normal airway, and the airway in various diseases. Methods for evaluating the human airway using MDCT images are presented facilitating automatic airway segmentation, branchpoint finding and airway dimension analysis. The airway wall color is objectively evaluated as an important surrogate for airway wall inflammation and cancer formation, and the integration of the color endoscopic information into the MDCT scan data set is currently ongoing. The amalgamation of these two digital imaging modalities appears increasingly useful for enabling biopsy techniques, and for relating structure and function of the airway. In addition, these developments may be progressively more useful in understanding the normal airway structure and function, for defining airway diseases patterns and for guiding biopsy and therapeutic procedures.

Bronchoscopy↗

PubMed2004

Lung image database consortium: developing a resource for the medical imaging research community.

To stimulate the advancement of computer-aided diagnostic (CAD) research for lung nodules in thoracic computed tomography (CT), the National Cancer Institute launched a cooperative effort known as the Lung Image Database Consortium (LIDC). The LIDC is composed of five academic institutions from across the United States that are working together to develop an image database that will serve as an international research resource for the development, training, and evaluation of CAD methods in the detection of lung nodules on CT scans. Prior to the collection of CT images and associated patient data, the LIDC has been engaged in a consensus process to identify, address, and resolve a host of challenging technical and clinical issues to provide a solid foundation for a scientifically robust database. These issues include the establishment of (a) a governing mission statement, (b) criteria to determine whether a CT scan is eligible for inclusion in the database, (c) an appropriate definition of the term qualifying nodule, (d) an appropriate definition of "truth" requirements, (e) a process model through which the database will be populated, and (f) a statistical framework to guide the application of assessment methods by users of the database. Through a consensus process in which careful planning and proper consideration of fundamental issues have been emphasized, the LIDC database is expected to provide a powerful resource for the medical imaging research community. This article is intended to share with the community the breadth and depth of these key issues.

Biomedical Research↗

PubMed2003

Characterization of the interstitial lung diseases via density-based and texture-based analysis of computed tomography images of lung structure and function.

RATIONALE AND OBJECTIVES: Efforts to establish a quantitative approach to the computed tomography (CT)-based character ization of the lung parenchyma in interstitial lung disease (including emphysema) has been sought. The accuracy of these tools must be site independent. Multi-detector row CT has remained the gold standard for imaging the lung, and it provides the ability to image both lung structure as well as lung function. MATERIAL AND METHODS: Imaging is via multi-detector row CT and protocols include careful control of lung volume during scanning. Characterization includes not only anatomic-based measures but also functional measures including regional parameters derived from measures of pulmonary blood flow and ventilation. Image processing includes the automated detection of the lungs, lobes, and airways. The airways provide the road map to the lung parenchyma. Software automatically detects the airways, the airway centerlines, and the branch points, and then automatically labels the airway tree segments with a standardized set of labels, allowing for intersubject as well intrasubject comparisons across time. By warping all lungs to a common atlas, the atlas provides the range of normality for the various parameters provided by CT imaging. RESULTS: Imaged density and textural changes mark underlying structural changes at the most peripheral regions of the lung. Additionally, texture-based alterations in the parameters of blood flow may provide early evidence of pathologic processes. Imaging of stable xenon gas provides a regional measure of ventilation which, when coupled with measures of flow, provide for a textural analysis regional of ventilation-perfusion matching. CONCLUSION: With the improved resolution and speed of CT imaging, the patchy nature of regional parenchymal pathology can be imaged as texture of structure and function. With careful control of imaging protocols and the use of objective image analysis methods it is possible to provide site-independent tools for the assessment of interstitial lung disease. There remains a need to validate these methods, which requires interdisciplinary and cross-institutional efforts to gather appropriate data bases of images along with a consensus on appropriate ground truths associated with the images. Furthermore, there is the growing need for scanner manufacturers to focus on not just visually pleasing images, but on quantitatifiably accurate images.

Humans↗

PubMed2003

Establishing a normative atlas of the human lung: intersubject warping and registration of volumetric CT images.

RATIONALE AND OBJECTIVES: To establish the range of normal values for quantitative CT-based measures of lung structure and function, the authors developed a method for matching pulmonary structures across individuals and creating a normative human lung atlas. MATERIALS AND METHODS: A computerized human lung atlas was synthesized from computed tomographic (CT) images from six subjects by means of three-dimensional image registration. The authors identified a set of reproducible feature points for each CT image and used these points to establish correspondences across subjects, used a landmark- and intensity-based consistent image registration algorithm to register a template image volume from the population to the rest of the pulmonary CT volumes in the population, averaged these transformations, and constructed an atlas by deforming the template with the average transformation. RESULTS: The effectiveness of the authors' method was evaluated and visualized by means of both gray-level and segmented CT images. The method reduced the average landmark registration error from 10.5 mm to 0.4 mm and the average relative volume overlap error from 0.7 to 0.11 for the six data sets studied. CONCLUSION: The method, and the computerized human lung atlas constructed and visualized by the authors with this method, provides a basis for establishing regional ranges of normative values for structural and functional measures of the human lung.

Algorithms↗

PubMed2003

Segmentation and analysis of the human airway tree from three-dimensional X-ray CT images.

The lungs exchange air with the external environment via the pulmonary airways. Computed tomography (CT) scanning can be used to obtain detailed images of the pulmonary anatomy, including the airways. These images have been used to measure airway geometry, study airway reactivity, and guide surgical interventions. Prior to these applications, airway segmentation can be used to identify the airway lumen in the CT images. Airway tree segmentation can be performed manually by an image analyst, but the complexity of the tree makes manual segmentation tedious and extremely time-consuming. We describe a fully automatic technique for segmenting the airway tree in three-dimensional (3-D) CT images of the thorax. We use grayscale morphological reconstruction to identify candidate airways on CT slices and then reconstruct a connected 3-D airway tree. After segmentation, we estimate airway branchpoints based on connectivity changes in the reconstructed tree. Compared to manual analysis on 3-mm-thick electron-beam CT images, the automatic approach has an overall airway branch detection sensitivity of approximately 73%.

Anatomy, Cross-Sectional↗

PubMed2003

Two year prognosis of sarcoidosis: the ACCESS experience.

A cohort of 215 sarcoidosis patients from the ACCESS study underwent a clinical evaluation at study enrollment and two years later. Approximately 80% of subjects had an improved or stable FVC, FEV1, chest radiograph determined by Scadding stage, and dyspnea scale. African-Americans had less improvement in FVC than Caucasians (p = 0.04). Patients with erythema nodosum at presentation were more likely to have improvement in the chest radiograph at two-year follow-up (p = 0.007). Patients with a lower annual family income were more likely to worsen with respect to dyspnea (p = 0.01) and more likely to have new organ involvement at two-year follow-up (p = 0.045). The development of new organ involvement over the two year follow-up period was more common in African-Americans compared to Caucasians (p = 0.002) and more likely in those with extrapulmonary involvement at study entry (p = 0.003). There was an excellent concordance between changes in FVC and FEV1 over the two-year period. However, changes in FVC alone were inadequate to describe the change in pulmonary status of the patients, as changes in chest radiographic findings or the level of dyspnea did often but not always move in the same direction as FVC. In conclusion, data from this heterogeneous United States sarcoidosis population indicate that sarcoidosis tends to improve or remain stable over two years in the majority of patients. Several factors associated with improved or worse outcome over two years were identified.

Adult↗

PubMed2002

FDG-PET imaging and the diagnosis of non-small cell lung cancer in a region of high histoplasmosis prevalence.

STUDY OBJECTIVE: Determine the sensitivity and specificity of [F-18]-fluorine-2-deoxy-D-glucose positron emission tomography (FDG-PET) in differentiating non-small cell lung cancer (NSCLC) from benign solitary pulmonary nodules (SPNs) in a region with a high endemic rate of histoplamosis. DESIGN: Prospective, clinical study. SETTING: University, tertiary referral hospital in the upper Mississippi River valley. PATIENTS: Ninety patients with SPNs. INTERVENTIONS: Independent interpretation of FDG-PET imaging, computed tomography and pathologic evaluation of the SPNs. MEASUREMENTS AND RESULTS: To detect malignant SPNs, FDG-PET imaging had a sensitivity of 93%, a specificity of 40%, a positive predictive value (PPV) of 88% and a negative predictive value (NPV) of 55%. CONCLUSIONS: In a region with a high prevalence of pulmonary fungal infection, FDG-PET is sensitive but has a low specificity and NPV for identifying NSCLC. In our study cohort, FDG-PET does not appear to reduce the need for SPN biopsies.

Adult↗

PubMed2002

Three-dimensional human airway segmentation methods for clinical virtual bronchoscopy.

RATIONALE AND OBJECTIVES: The segmentation of airways from CT images is a critical first step for numerous virtual bronchoscopic (VB) applications. Automatic or semiautomatic methods are necessary, since manual segmentation is prohibitively time consuming. The methods must be robust and operate within a reasonable time frame to be useful for clinical VB use. The authors developed an integrated airway segmentation system and demonstrated its effectiveness on a series of human images. MATERIALS AND METHODS: The authors' airway segmentation system draws on two segmentation algorithms: (a) an adaptive region-growing algorithm and (b) a new hybrid algorithm that uses both region growing and mathematical morphology. Images from an ongoing VB study were segmented by means of both the adaptive region-growing and the new hybrid methods. The segmentation volume, branch number estimate, and segmentation quality were determined for each case. RESULTS: The results demonstrate the need for an integrated segmentation system, since no single method is superior for all clinically relevant cases. The region-growing algorithm is the fastest and provides acceptable segmentations for most VB applications, but the hybrid method provides superior airway edge localization, making it better suited for quantitative applications. In addition, the authors show that prefiltering the image data before airway segmentation increases the robustness of both region-growing and hybrid methods. CONCLUSION: The combination of these two algorithms with the prefiltering options allowed the successful segmentation of all test images. The times required for all segmentations were acceptable, and the results were suitable for the authors' VB application needs.

Algorithms↗

PubMed2002

Ultrathin bronchoscopy as an adjunct to standard bronchoscopy in the diagnosis of peripheral lung lesions. A preliminary report.

BACKGROUND: The role of the standard bronchoscope as a method of diagnosis of peripheral lung lesions is limited. OBJECTIVES: To evaluate the role of the ultrathin bronchoscope as an adjunct to standard bronchoscopy in the diagnosis of peripheral lung lesions. METHODS: Seventeen consecutive patients with a peripheral lung lesion on chest radiography or chest CT. All patients underwent a bronchoscopic examination with a standard size bronchoscope, and if there was no evidence of endobronchial lesion, these patients were subsequently examined with an Olympus 3C40 ultrathin bronchoscope (external diameter of 3.6 mm). Under fluoroscopic guidance, cytological brushing samples were taken with the ultrathin bronchoscope followed by a reexamination with the standard bronchoscope which followed the same 'pathway' to the lesion established by the 3C40 ultrathin bronchoscope. Transbronchial biopsies (TBB) and cytological samples were taken with the standard bronchoscope. RESULTS: The size of the lesions ranged from 1.5 to 7.0 cm. A positive bronchoscopic diagnosis by TBB was obtained in 11 out of 17 patients (64.7%) and a diagnosis of atypical cells suspicious for malignancy noted in a further 3 patients. For lesions less than 3 cm in size, a positive diagnosis by TBB was achieved in 7 out of 10 of these cases. The lesion was directly visualized with the ultrathin bronchoscope in 4 cases. CONCLUSIONS: Ultrathin bronchoscopy appears to be a useful adjunct to standard bronchoscopy by providing an accurate pathway to the lesion in question. However, further studies with larger patient groups are warranted.

Aged↗

PubMedDate not supplied

Bronchoscopic imaging of pulmonary mucosal vasculature responses to inflammatory mediators.

In current clinical practice, the initial stage in the detection of pulmonary airway disease is the clinician's interpretation of a bronchoscopy procedure. Due to the nature of this form of detection, diseases are often well advanced upon discovery. This paper proposes a new method for examining the pulmonary airway microcirculatory system via fluorescein imaging techniques similar to those used extensively in ophthalmology. Through the use of a specialized bronchoscopy imaging system we are able to successfully show that fluorescein emission detected in the rabbit trachea exhibits a clear response to inflammatory mediators and thus to changing local vascularity. The clinical implications of this technique are extensive including most importantly the potential use as an evaluation tool for pulmonary disease evaluation and likely other endoscopically accessible organs.

Animals↗

PubMedDate not supplied

Macro-optical color assessment of the pulmonary airways with subsequent three-dimensional multidetector-x-ray-computed-tomography assisted display.

Bronchial diseases alter the color and structural characteristics of the pulmonary mucosa through changes in blood flow, epithelial thickening, and abnormal cell growth. Current analysis of these subtle changes includes visual interpretation of the airway color and topography through bronchoscopy procedures, and quantitative multidetector-x-ray-computed-tomography (MDCT)-based structural analysis, each affording valuable insights to the health of the lungs. The fusion of the bronchoscopy and MDCT image data promises to provide a synergistic data set exhibiting both mucosal color and topography crucial to fostering an understanding of airway structure and function. A real-time airway color analysis imaging system is developed and utilized to perform pulmonary mucosal color assessment in healthy volunteers with subsequent comparative studies performed in example disease states. Our results indicate that macro-optical digital bronchoscopes with appropriate image analysis may have a significant impact on understanding bronchial diseases. To ensure the correct interpretation of scene content, which is critical in the assessment of airway topography, we are developing methods of extracting 3-D structure from 2-D bronchoscope images utilizing MDCT imaging techniques. The resulting 3-D true-color images of the pulmonary mucosa facilitate the combination of mucosal color and topography analysis as well as region of interest localization within the airway tree.

Bronchoscopy↗