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1.
AJR Am J Roentgenol ; 195(2): 486-93, 2010 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-20651209

RESUMO

OBJECTIVE: The purpose of this study was to investigate replacing unenhanced and arterial single-energy CT acquisitions after endovascular aneurysm repair with one dual-energy CT arterial acquisition. SUBJECTS AND METHODS: Thirty patients underwent arterial dual-energy CT (80 and 140 kVp) and venous single-energy CT (120 kVp) after endovascular aneurysm repair, and the radiation doses were compared with those of a standard triple-phase protocol. Both virtual unenhanced and arterial images were generated with dual-energy CT. Images were reviewed clinically for detection of endoleaks and evaluation of stent and calcium appearance. The aortic luminal attenuation on virtual unenhanced CT images was compared with that on previously acquired true unenhanced images. Virtual unenhanced, arterial, and venous images were compared for thrombus attenuation. Single-energy CT and dual-energy CT images were compared for noise. RESULTS: Replacement of two (unenhanced, arterial) of three single-energy CT acquisitions with one dual-energy CT acquisition resulted in 31% radiation dose savings. All images were clinically interpretable. Thoracic (32 +/- 2 vs 35 +/- 4 HU) and abdominal (30 +/- 3 vs 35 +/- 5 HU) aortic attenuation was similar on virtual unenhanced and true unenhanced images. Thrombus attenuation was similar on virtual unenhanced (32 +/- 6 HU), arterial phase (33 +/- 7 HU), and venous phase (34 +/- 6 HU) images. Decreased stent and calcium attenuation was observed at some locations on virtual unenhanced images. Noise in the thoracic (10 +/- 1 HU) and abdominal (12 +/- 2 HU) aorta was lower on virtual unenhanced images than on true unenhanced images (13 +/- 4 HU, 19 +/- 5 HU). Noise was comparable for dual-energy and single-energy CT (thorax, 16 +/- 2 vs 13 +/- 2 HU; abdomen, 21 +/- 3 vs 23 +/- 5 HU). CONCLUSION: Virtual unenhanced and arterial phase images derived from dual-energy CT can replace true unenhanced and arterial phase single-energy CT images in follow-up after endovascular aneurysm repair (except immediately after the procedure), providing comparable diagnostic information with substantial dose savings.


Assuntos
Angiografia/métodos , Aneurisma Aórtico/diagnóstico por imagem , Aneurisma Aórtico/cirurgia , Aortografia/métodos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tomografia Computadorizada por Raios X/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Viabilidade , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Resultado do Tratamento
2.
J Comput Assist Tomogr ; 34(1): 64-9, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20118724

RESUMO

OBJECTIVE: To compare coronary image quality at temporal resolutions associated with dual-source computed tomography (DSCT; 83 milliseconds) and 64-detector row scanning (165 milliseconds). METHODS: In 30 patients with a heart rate of less than 70 beats per minute, DSCT coronary angiograms were reconstructed at 83- and 165-millisecond temporal resolutions over different cardiac phases. A blinded observer graded coronary quality. RESULTS: The typical DSCT temporal resolution (83 milliseconds) showed a significantly greater quality at end-systole for all coronary vessels and at end-diastole for the right coronary and left anterior descending coronary arteries. For all vessels, the end-diastole produced the highest quality for both temporal resolutions. CONCLUSIONS: Imaging at 83 milliseconds creates superior quality at end-systole for all coronary vessels and at end-diastole for the right coronary and left anterior descending coronary arteries. At low heart rates, end-diastole produces the highest quality at both temporal resolutions.


Assuntos
Frequência Cardíaca , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Adulto , Idoso , Meios de Contraste/administração & dosagem , Eletrocardiografia , Feminino , Humanos , Processamento de Imagem Assistida por Computador/métodos , Masculino , Pessoa de Meia-Idade , Intensificação de Imagem Radiográfica/métodos , Estudos Retrospectivos , Ácidos Tri-Iodobenzoicos/administração & dosagem
3.
Int J Cardiovasc Imaging ; 25(8): 837-45, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19669664

RESUMO

The purpose of this study was to determine the cardiac phase having the highest coronary sharpness for low and high heart rate patients scanned with dual source CT (DSCT) and to compare coronary image sharpness over different cardiac phases. DSCT coronary CT scans for 30 low heart rate (< or =70 beats per minute- bpm) and 30 high heart rate (>70 bpm) patients were reconstructed into different cardiac phases, starting at 30% and increasing at 5% increments until 70%. A blinded observer graded image sharpness per coronary segment, from which sharpness scores were produced for the right (RCA), left main (LM), left anterior descending (LAD), and circumflex (Cx) coronary arteries. For each coronary artery, the phase with maximal image sharpness was identified with repeated measures analysis of variance. Comparison of coronary sharpness between low and high heart rate patients was made using generalized estimating equations. For low heart rates the highest sharpness scores for all four vessels (RCA, LM, LAD, and Cx) were at the 65 or 70% phase, which are end-diastolic cardiac phases. For high heart rates the highest sharpness scores were between the 35 and 45% phases, which are end-systolic phases. Low heart rate patients had higher coronary sharpness at most cardiac phases; however, patients with high heart rates had higher coronary sharpness in the 45% phase for all four vessels (P < 0.0001). Using DSCT scanning, optimal image sharpness is obtained in end-diastole at low heart rates and in end-systole in high heart rates.


Assuntos
Angiografia Coronária/métodos , Doença da Artéria Coronariana/diagnóstico por imagem , Frequência Cardíaca , Contração Miocárdica , Interpretação de Imagem Radiográfica Assistida por Computador , Tomografia Computadorizada por Raios X , Idoso , Artefatos , Doença da Artéria Coronariana/fisiopatologia , Diástole , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Estudos Retrospectivos , Sístole
4.
J Appl Physiol (1985) ; 104(4): 1177-84, 2008 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-18258804

RESUMO

Computer tomography (CT) imaging techniques permit the noninvasive measurement of regional lung function. Regional specific volume change (sVol), determined from the change in lung density over a tidal breath, should correlate with regional ventilation and regional lung expansion measured with other techniques. sVol was validated against xenon (Xe)-CT-specific ventilation (sV) in four anesthetized, intubated, mechanically ventilated sheep. Xe-CT used expiratory gated axial scanning during the washin and washout of 55% Xe. sVol was measured from the tidal changes in tissue density (H, houndsfield units) of lung regions using the relationship sVol = [1,000(Hi - He)]/[He(1,000 + Hi)], where He and Hi are expiratory and inspiratory regional density. Distinct anatomical markings were used to define corresponding lung regions of interest between inspiratory, expiratory, and Xe-CT images, with an average region of interest size of 1.6 +/- 0.7 ml. In addition, sVol was compared with regional volume changes measured directly from the positions of implanted metal markers in an additional animal. A linear relationship between sVol and sV was demonstrated over a wide range of regional sV found in the normal supine lung, with an overall correlation coefficient (R(2)) of 0.66. There was a tight correlation (R(2) = 0.97) between marker-measured volume changes and sVol. Regional sVol, which involves significantly reduced exposure to radiation and Xe gas compared with the Xe-CT method, represents a safe and efficient surrogate for measuring regional ventilation in experimental studies and patients.


Assuntos
Medidas de Volume Pulmonar/métodos , Pulmão/anatomia & histologia , Pulmão/fisiologia , Mecânica Respiratória/fisiologia , Decúbito Dorsal/fisiologia , Algoritmos , Animais , Processamento de Imagem Assistida por Computador , Pulmão/diagnóstico por imagem , Modelos Estatísticos , Ovinos , Tomografia Computadorizada por Raios X , Xenônio
5.
Clin Ophthalmol ; 2(2): 275-81, 2008 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-19668716

RESUMO

BACKGROUND: The initial use of a 64-slice computed tomography (CT) scanner for obtaining quantitative perfusion data from a large ciliochoroidal melanoma, and correlation with 3T magnetic resonance imaging (MRI) dynamic enhancement and tumor histology. METHODS: The CT perfusion scan was performed using 80 kVp, 250 mA and 1-sec rotation time for 40 sec. The analysis was performed using commercial perfusion analysis software with a prototype 3-dimensional motion correction tool. Dynamic contrast-enhanced 3-Tesla MRI measured the kinetics of enhancement to estimate the vascular permeability. The time-dependent enhancement patterns were obtained using the average signal intensity using Functool analysis software. The involved globe was enucleated and microscopic evaluation of the tumor was performed. RESULTS: The perfusion parameters blood flow, blood volume and permeability surface area product in the affected eye determined by CT perfusion analysis were 118 ml/100 ml/min, 11.3 ml/100 ml and 48 ml/100 ml/min. Dynamic MRI enhancement showed maximal intensity increase of 111%. The neoplasm was a ciliochoroidal spindle cell melanoma which was mitotically active (13 mitoses/40 hpf). Vascular loops and arcades were present throughout the tumor. The patient developed metastases within 9 months of presentation. CONCLUSION: Quantitative CT perfusion analysis of ocular tumors is feasible with motion correction software.

6.
Biomed Signal Process Control ; 3(4): 319-326, 2008 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19802329

RESUMO

In this paper, a new adaptive bolus-chasing control scheme is proposed to synchronize the bolus peak in a patient's vascular system and the imaging aperture of a computed tomography (CT) scanner. The proposed control scheme is theoretically evaluated and experimentally tested on a modified Siemens SOMATOM Volume Zoom CT scanner. The first set of experimental results are reported on bolus-chasing CT angiography using realistic bolus dynamics, real-time CT imaging and adaptive table control with physical vasculature phantoms. The data demonstrate that the proposed control approach tracks the bolus propagation well, and clearly outperforms the constant-speed scheme that is the current clinical standard.

7.
Radiology ; 243(3): 775-84, 2007 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-17446525

RESUMO

PURPOSE: To prospectively compare the dose performance of a 64-channel multi-detector row computed tomographic (CT) scanner and a 64-channel dual-source CT scanner from the same manufacturer. MATERIALS AND METHODS: To minimize dose in the cardiac (dual-source) mode, the evaluated dual-source CT system uses a cardiac beam-shaping filter, three-dimensional adaptive noise reduction, heart rate-dependent pitch, and electrocardiographically based modulation of the tube current. Weighted CT dose index per 100 mAs was measured for the head, body, and cardiac beam-shaping filters. Kerma-length product was measured in the spiral cardiac mode at four pitch values and three electrocardiographic modulation temporal windows. Noise was measured in an anthropomorphic phantom. Data were compared with data from a 64-channel multi-detector row CT scanner. RESULTS: For the multi-detector row and dual-source CT systems, respectively, weighted CT dose index per 100 mAs was 14.2 and 12.2 mGy (head CT), 6.8 and 6.4 mGy (body CT), and 6.8 and 5.3 mGy (cardiac CT). In the spiral cardiac mode (no electrocardiographically based tube current modulation, 0.2 pitch), equivalent noise occurred at volume CT dose index values of 23.7 and 35.0 mGy (coronary artery calcium CT) and 58.9 and 61.2 mGy (coronary CT angiography) for multi-detector row CT and dual-source CT, respectively. The use of heart rate-dependent pitch values reduced volume CT dose index to 46.2 mGy (0.265 pitch), 34.0 mGy (0.36 pitch), and 26.6 mGy (0.46 pitch) compared with 61.2 mGy for 0.2 pitch. The use of electrocardiographically based tube current-modulation and temporal windows of 110, 210, and 310 msec further reduced volume CT dose index to 9.1-25.1 mGy, dependent on the heart rate. CONCLUSION: For electrocardiographically gated coronary CT angiography, image noise equivalent to that of multi-detector row CT can be achieved with dual-source CT at doses comparable to or up to a factor of two lower than the doses at multi-detector row CT, depending on heart rate of the patient.


Assuntos
Análise de Falha de Equipamento , Tomografia Computadorizada por Raios X/instrumentação , Contagem Corporal Total/métodos , Carga Corporal (Radioterapia) , Desenho de Equipamento , Humanos , Doses de Radiação , Eficiência Biológica Relativa , Medição de Risco , Fatores de Risco
8.
Acad Radiol ; 14(4): 495-504, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17368220

RESUMO

RATIONALE AND OBJECTIVES: We propose a novel segmentation-based interpolation method to reduce the metal artifacts caused by surgical aneurysm clips. MATERIALS AND METHODS: Our method consists of five steps: coarse image reconstruction, metallic object segmentation, forward-projection, projection interpolation, and final image reconstruction. The major innovations are 2-fold. First, a state-of-the-art mean-shift technique in the computer vision field is used to improve the accuracy of the metallic object segmentation. Second, a feedback strategy is developed in the interpolation step to adjust the interpolated value based on the prior knowledge that the interpolated values should not be larger than the original ones. Physical phantom and real patient datasets are studied to evaluate the efficacy of our method. RESULTS: Compared to the state-of-the-art segmentation-based method designed previously, our method reduces the metal artifacts by 20-40% in terms of the standard deviation and provides more information for the assessment of soft tissues and osseous structures surrounding the surgical clips. CONCLUSION: Mean shift technique and feedback strategy can help to improve the image quality in terms of reducing metal artifacts.


Assuntos
Artefatos , Metais , Intensificação de Imagem Radiográfica/métodos , Tomografia Computadorizada por Raios X , Algoritmos , Humanos , Imagens de Fantasmas
9.
J Appl Physiol (1985) ; 102(4): 1535-44, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17122371

RESUMO

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

Assuntos
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
10.
J Comput Assist Tomogr ; 30(5): 846-9, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-16954941

RESUMO

Computed tomographic (CT) angiography is important for imaging studies on cardiovascular structures, peripheral vessels, and solid organs. In practice, a CT angiography scan is triggered by the bolus arrival at a prespecified anatomical location, which is determined using CT fluoroscopy. In this article, we propose a projection-based method adapted from the Grangeat formula to detect the bolus arrival. Then, we evaluate our new method in numerical and animal studies. Our results indicate that this method allows significantly better temporal resolution and is computationally more efficient, as compared with the image-based methods.


Assuntos
Meios de Contraste , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Algoritmos , Angiografia/métodos , Animais , Fluoroscopia/métodos , Pulmão/diagnóstico por imagem , Modelos Teóricos , Intensificação de Imagem Radiográfica/métodos , Ovinos , Fatores de Tempo
11.
Acad Radiol ; 12(11): 1371-84, 2005 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16253849

RESUMO

RATIONALE AND OBJECTIVES: The study's aim is to establish lung-imaging methods that provide for the ability to image the lung under dynamic non-breath hold conditions while providing "virtual breath hold" quantifiable volumetric image data sets. Static breath hold images are used as the gold standard for evaluating these virtual breath hold images in both a phantom and sheep. MATERIALS AND METHODS: Axial methods for gating image acquisition to multiple points in the respiratory cycle interleaved with incremental table stepping during multidetector-row computed tomographic (MDCT) scanning were developed. Data sets are generated over multiple breaths, providing volume images representative of multiple points within a respiratory cycle. To determine the reproducibility and accuracy of the methods, six anesthetized sheep were studied by means of MDCT in nongated and airway-pressure (P(awy))-gated modes in which P(awy) was 0, 7, and 15 cm H2O. RESULTS: No significant differences were found between coefficients of variation in air volume measured from repeated static scans (1.74% +/- 1.78%), gated scans: inspiratory (1.2% +/- 0.44%) or expiratory gated (1.39% +/- 0.98%), or between static (1.74% +/- 1.78%) and gated (1.39% +/- 0.98%) scanning at similar P(awy) (P > .1). Measured air volumes were larger from static versus gated scans by 5.85% +/- 3.77% at 7 cm H2O and 4.45% +/- 3.6% at 15 cm H2O of P(awy) (P < .05), consistent with hysteresis. Differences between air volumes at 7 and 15 cm H2O measured from either static or gated scans or that delivered by a super syringe were insignificant (P < .05). Visual accuracy of three-dimensional anatomic geometry was achieved, and landmark certainty was within 1 mm across respiratory cycles. CONCLUSIONS: A method has been shown that provides for accurate gating to respiratory signals during axial scanning. High-resolution volumetric image data sets are achievable while the scanned subject is breathing. Images are quantitatively similar to breath hold images, with differences likely explained by known pressure-volume hysteresis effects.


Assuntos
Medidas de Volume Pulmonar/métodos , Pulmão/diagnóstico por imagem , Tomografia Computadorizada por Raios X , Animais , Masculino , Imagens de Fantasmas , Respiração , Ovinos
12.
Respir Physiol Neurobiol ; 148(1-2): 65-83, 2005 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-16061426

RESUMO

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.


Assuntos
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
13.
Am J Respir Crit Care Med ; 172(9): 1133-8, 2005 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-16051903

RESUMO

RATIONALE: The development of early lung disease in patients with cystic fibrosis (CF) remains poorly defined. OBJECTIVE: Determine whether asymptomatic infants with CF have evidence for changes in airway structure when assessed by high-resolution computed tomography, and whether airway structure correlates with airway function in this age group. METHODS: Thirteen infants with CF (8-33 mo) and 13 control infants (7-25 mo) were evaluated. Airway wall and lumen areas were measured from three 1-mm-thick cross-sectional images obtained from upper, middle, and lower lobes during a respiratory pause with the lungs inflated to an airway pressure of 20 cm H2O. Lung tissue density was measured from images obtained during a respiratory pause at FRC. Forced expiratory flows were measured by the rapid thoracic compression technique in 11 infants with CF. RESULTS: Airway wall area increased more per unit increase in airway size, whereas airway lumen area increased less per unit increase in airway size in the CF than in the control group. Among infants with CF, a greater ratio of wall to lumen area correlated with lower airway function. In addition, lung density at relaxed (passive) FRC was lower for infants with CF than for control infants (0.38 vs. 0.43 g/ml; p < 0.02). CONCLUSIONS: Our results indicate that infants with CF have thickened airway walls, narrowed airway lumens, and air trapping, when assessed by high-resolution computed tomography, and measurements of airway structure correlated with airway function.


Assuntos
Fibrose Cística/diagnóstico por imagem , Fibrose Cística/fisiopatologia , Pulmão/diagnóstico por imagem , Pulmão/fisiopatologia , Tomografia Computadorizada por Raios X , Estudos de Casos e Controles , Pré-Escolar , Feminino , Fluxo Expiratório Forçado , Volume Expiratório Forçado , Capacidade Residual Funcional , Humanos , Lactente , Masculino
14.
Acad Radiol ; 10(10): 1104-18, 2003 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-14587629

RESUMO

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.


Assuntos
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
15.
J Appl Physiol (1985) ; 95(3): 1063-75, 2003 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-12754180

RESUMO

To objectively quantify airway geometry from three-dimensional computed tomographic (CT) images, an idealized (circular cross section) airway model is parameterized by airway luminal caliber, wall thickness, and tilt angle. Using a two-dimensional CT slice, an initial guess for the airway center, and the full-width-half-maximum principle, we form an estimate of inner and outer airway wall locations. We then fit ellipses to the inner and outer airway walls via a direct least squares fit and use the major and minor axes of the ellipses to estimate the tilt and in-plane rotation angles. Convolving the airway model, initialized with these estimates, with the three-dimensional scanner point-spread function forms the predicted image. The difference between predicted and actual images is minimized by refining the model parameter estimates via a multidimensional, unconstrained, nonlinear minimization routine. When optimization converges, airway model parameters estimate the airway inner and outer radii and tilt angle. Results using a Plexiglas phantom show that tilt angle is estimated to within +/-4 degrees and both inner and outer radii to within one-half pixel when a "standard" CT reconstruction kernel is used. By opening up the ability to measure airways that are not oriented perpendicular to the scanning plane, this method allows evaluation of a greater sampling of airways in a two-dimensional CT slice than previously possible. In addition, by combining the tilt-angle compensation with the deconvolution method, we provide significant improvement over the previous full-width-half-maximum method for assessing location of the luminal edge but not the outer edge of the airway wall.


Assuntos
Pulmão/diagnóstico por imagem , Algoritmos , Gráficos por Computador , Humanos , Pulmão/anatomia & histologia , Pulmão/fisiologia , Modelos Anatômicos , Modelos Estatísticos , Dinâmica não Linear , Tomografia Computadorizada por Raios X
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