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Int J Biomed Imaging ; 2009: 636240, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-20052391


This paper describes an algorithm for extracting pulmonary vascular trees (arteries plus veins) from three-dimensional (3D) thoracic computed tomographic (CT) images. The algorithm integrates tube enhancement filter and traversal approaches which are based on eigenvalues and eigenvectors of a Hessian matrix to extract thin peripheral segments as well as thick vessels close to the lung hilum. The resultant algorithm was applied to a simulation data set and 44 scans from 22 human subjects imaged via multidetector-row CT (MDCT) during breath holds at 85% and 20% of their vital capacity. A quantitative validation was performed with more than 1000 manually identified points selected from inside the vessel segments to assess true positives (TPs) and 1000 points randomly placed outside of the vessels to evaluate false positives (FPs) in each case. On average, for both the high and low volume lung images, 99% of the points was properly marked as vessel and 1% of the points were assessed as FPs. Our hybrid segmentation algorithm provides a highly reliable method of segmenting the combined pulmonary venous and arterial trees which in turn will serve as a critical starting point for further quantitative analysis tasks and aid in our overall goal of establishing a normative atlas of the human lung.

J Appl Physiol (1985) ; 102(4): 1535-44, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17122371


Xenon computed tomography (Xe-CT) is used to estimate regional ventilation by measuring regional attenuation changes over multiple breaths while rebreathing a constant Xe concentration ([Xe]). Xe-CT has potential human applications, although anesthetic properties limit [Xe] to

Criptônio , Pulmão/diagnóstico por imagem , Pulmão/fisiopatologia , Troca Gasosa Pulmonar/fisiologia , Ventilação Pulmonar/fisiologia , Intensificação de Imagem Radiográfica/métodos , Tomografia Computadorizada por Raios X/métodos , Xenônio , Administração por Inalação , Animais , Criptônio/administração & dosagem , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Ovinos , Xenônio/administração & dosagem
J Appl Physiol (1985) ; 101(5): 1451-65, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16825517


ECG-triggered computed tomography (CT) was used during passage of iodinated contrast to determine regional pulmonary blood flow (PBF) in anesthetized prone/supine dogs. PBF was evaluated as a function of height within the lung (supine and prone) as a function of various normalization methods: raw unit volume data (PBFraw) or PBF normalized to regional fraction air (PBFair), fractional non-air (PBFgm), or relative number of alveoli (PBFalv). The coefficient of variation of PBFraw, PBFair, PBFalv, and PBFgm ranged between 30 and 50% in both lungs and both body postures. The position of maximal flow along the height of the lung (MFP) was calculated for PBFraw, PBFair, PBFalv, and PBFgm. Only PBFgm showed a significantly different MFP height supine vs. prone (whole lung: 2.60 +/- 1.08 cm supine vs. 5.08 +/- 1.61 cm prone, P < 0.01). Mean slopes (ml/min/gm water content/cm) of PBFgm were steeper supine vs. prone in the right (RL) but not left lung (LL) (RL: -0.65 +/- 0.29 supine vs. -0.26 +/- 0.25 prone, P < 0.02; LL: -0.47 +/- 0.21 supine vs. -0.32 +/- 0.26 prone, P > 0.10). Mean slopes of PBFgm vs. vertical lung height were not different prone vs. supine above this vertical height of MFP (VMFP), but PBFgm slopes were steeper in the supine position below the VMFP in the RL. We conclude that PBFgm distribution was posture dependent in RL but not LL. Support of the heart may play a role. We demonstrate that normalization factors can lead to differing attributions of gravitational effects on PBF heterogeneity.

Imageamento Tridimensional/métodos , Pulmão/irrigação sanguínea , Pulmão/diagnóstico por imagem , Circulação Pulmonar/fisiologia , Fluxo Sanguíneo Regional/fisiologia , Tomografia Computadorizada por Raios X/métodos , Animais , Cães , Eletrocardiografia , Decúbito Ventral/fisiologia , Artéria Pulmonar/fisiologia , Veias Pulmonares/fisiologia
Respir Physiol Neurobiol ; 148(1-2): 65-83, 2005 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-16061426


UNLABELLED: Xenon-enhanced computed tomography (Xe-CT) has been used to measure regional ventilation by determining the wash-in (WI) and wash-out (WO) rates of stable Xe. We tested the common assumption that WI and WO rates are equal by measuring WO-WI in different anatomic lung regions of six anesthetized, supine sheep scanned using multi-detector-row computed tomography (MDCT). We further investigated the effect of tidal volume, image gating (end-expiratory EE versus end-inspiratory EI), local perfusion, and inspired Xe concentration on this phenomenon. RESULTS: WO time constant was greater than WI in all lung regions, with the greatest differences observed in dependent base regions. WO-WI time constant difference was greater during EE imaging, smaller tidal volumes, and with higher Xe concentrations. Regional perfusion did not correlate with WI-WO. We conclude that Xe-WI rate can be significantly different from the WO rate, and the data suggest that this effect may be due to a combination of anatomic and fluid mechanical factors such as Rayleigh-Taylor instabilities set up at interfaces between two gases of different densities.

Pulmão/fisiologia , Troca Gasosa Pulmonar/fisiologia , Ventilação Pulmonar/fisiologia , Tomografia Computadorizada por Raios X/métodos , Animais , Relação Dose-Resposta a Droga , Feminino , Medidas de Volume Pulmonar/métodos , Artéria Pulmonar/fisiologia , Mecânica Respiratória , Ovinos , Volume de Ventilação Pulmonar/fisiologia , Fatores de Tempo , Distribuição Tecidual/fisiologia , Resistência Vascular/fisiologia , Radioisótopos de Xenônio/farmacocinética
Acad Radiol ; 10(10): 1104-18, 2003 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-14587629


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.

Processamento de Imagem Assistida por Computador , Doenças Pulmonares Intersticiais/diagnóstico por imagem , Pulmão/diagnóstico por imagem , Tomografia Computadorizada por Raios X , Humanos , Pulmão/patologia , Pulmão/fisiologia , Doenças Pulmonares Intersticiais/patologia , Doenças Pulmonares Intersticiais/fisiopatologia , Ventilação Pulmonar