Janice Cook-Granroth

Original ResearchAsthmaAirway Remodeling Measured by Multidetector CT Is Increased in Severe Asthma and Correlates With Pathology

BACKGROUND To prospectively apply an automated, quantitative three-dimensional approach to imaging and airway analysis to assess airway remodeling in asthma patients. METHODS Using quantitative software (Pulmonary Workstation, version 0.139; VIDA Diagnostics; Iowa City, IA) that enables quantitative airway segment measurements of low-dose, thin-section (0.625 to 1.25 mm), multidetector-row CT (MDCT) scans, we compared airway wall thickness (WT) and wall area (WA) in 123 subjects participating in a prospective multicenter cohort study, the National Institutes of Health Severe Asthma Research Program (patients with severe asthma, n = 63; patients with mild-to-moderate asthma, n = 35); and healthy subjects, n = 25). A subset of these subjects underwent fiberoptic bronchoscopy and endobronchial biopsies (n = 32). WT and WA measurements were corrected for total airway diameter and area: WT and WA, respectively. RESULTS Subjects with severe asthma had a significantly greater WT% than patients with mild-to-moderate asthma and healthy subjects (17.2 +/- 1.5 vs 16.5 +/- 1.6 [p = 0.014] and 16.3 +/- 1.2 [p = 0.031], respectively) and a greater WA percentage (WA%) compared to patients with mild-to-moderate asthma and healthy subjects (56.6 +/- 2.9 vs 54.7 +/- 3.3 [p = 0.005] and 54.6 +/- 2.4 [p = 0.003], respectively). Both WT% and WA% were inversely correlated with baseline FEV(1) percent predicted (r = -0.39, p < 0.0001 and r = -0.40, p < 0.0001, respectively) and positively correlated with response to a bronchodilator (r = 0.28, p = 0.002 and r = 0.35, p < 0.0001, respectively). The airway epithelial thickness measure on the biopsy sample correlated with WT% (r = 0.47; p = 0.007) and WA% (r = 0.52; p = 0.003). In the same individual, there is considerable regional heterogeneity in airway WT. CONCLUSION Patients with severe asthma have thicker airway walls as measured on MDCT scan than do patients with mild asthma or healthy subjects, which correlates with pathologic measures of remodeling and the degree of airflow obstruction. MDCT scanning may be a useful technique for assessing airway remodeling in asthma patients, but overlap among the groups limits the diagnostic value in individual subjects.

Investigation of hyperpolarized 3He magnetic resonance imaging utility in examining human airway diameter behavior in asthma through comparison with high-resolution computed tomography.

RATIONALE AND OBJECTIVES Application of a previously developed model-based algorithm on hyperpolarized (HP) (3)He magnetic resonance (MR) dynamic projection images of phantoms was extended to investigate the utility of HP (3)He MR imaging (MRI) in quantifying airway caliber changes associated with asthma. MATERIALS AND METHODS Airways of seven volunteers were imaged and measured using HP (3)He MRI and multidetector-row computed tomography (MDCT) before and after a methacholine (MCh) challenge. MDCT data were obtained at functional residual capacity and 1 L above functional residual capacity. RESULTS Comparison of the resultant data showed that HP (3)He MRI did not match MDCT in measuring the ratios of airway calibers before and after the MCh challenge in 37% to 43% of the airways from the first six generations at the two lung volumes tested. However, MDCT did yield the observation that 49% to 69% of these airways displayed bronchodilation following MCh challenge. CONCLUSION The current implementation of HP (3)He MRI did not match the MCh-induced postchallenge-to-prechallenge airway caliber ratios as measured with MDCT. Elevated parenchymal tethering due to bronchoconstriction-induced hyperinflation was proposed as a possible explanation for this airway dilation.

Use of 3-Dimensional Computed Tomography Reconstruction Studies in the Preoperative Assessment of Patients Undergoing Balloon Dilatation for Tracheobronchial Stenosis

Background: Balloon dilatation (BD) is a useful method of treating tracheobronchial stenosis (TBS); however, accurate preoperative identification of the lesion is difficult. Three-dimensional computed tomography (3D-CT) is an imaging method that may allow more accurate definition of the lesion(s) preoperatively. Study Objective: It is the aim of this study to present our finding using 3D-CT as a part of the preoperative evaluation of patients with TBS undergoing BD. Methods: We studied a prospective case series of 17 consecutive patients who underwent 29 BDs for TBS from a variety of benign and malignant causes at a tertiary care hospital. All patients had a preoperative spiral CT; these data were processed by a software program, VIDA, which was developed at this institution, and 3D-CT reconstruction images of the TBS were created. This enabled accurate preoperative anatomic definition of the lesion. The patients subsequently underwent BD. Results: All 17 patients had lesions identified with 3D-CT. Six patients had tracheal lesions and 12 patients had main stem lesions. One patient had combined tracheal and main stem lesions and 2 other patients had bilateral main stem lesions. Nine out of 17 patients required only one BD. One patient had a failed BD. The remaining 6 patients required more than one BD for optimal results (up to a maximum of 4). The follow-up period ranged from 1 to 34 months. Conclusions: 3D-CT offers accurate definition of TBS, including anatomic location, number of lesions present and status of airway distal to lesion. In this study, all preoperative lesions were correctly identified prior to BD.

Comparison of airway diameter measurements from an anthropomorphic airway tree phantom using hyperpolarized 3He MRI and high-resolution computed tomography

An anthropomorphic airway tree phantom was imaged with both hyperpolarized (HP) 3He MRI using a dynamic projection scan and computed tomography (CT). Airway diameter measurements from the HP 3He MR images obtained using a newly developed model‐based algorithm were compared against their corresponding CT values quantified with a well‐established method. Of the 45 airway segments that could be evaluated with CT, only 14 airway segments (31%) could be evaluated using HP 3He MRI. No airway segments smaller than ∼4 mm in diameter and distal to the fourth generation were adequate for analysis in MRI. For the 14 airway segments measured, only two airway segments yielded a non‐equivalent comparison between the two imaging modalities, while eight more had inconclusive comparison results, leaving only four airway segments (29%) that satisfied the designed equivalence criteria. Some of the potential problems in airway diameter quantification described in the formulation of the model‐based algorithm were observed in this study. These results suggest that dynamic projection HP 3He MRI may have limited utility for measuring airway segment diameters, particularly those of the central airways. Magn Reson Med 58:636–642, 2007.

The Use of MDCT-Based Computer-Aided Pathway Finding for Mediastinal and Perihilar Lymph Node Biopsy: A Randomized Controlled Prospective Trial

Background: Mediastinal and perihilar lymph node samples can be acquired safely through the transbronchial approach during a bronchoscopic examination that is usually required as part of the evaluation of suspected lung cancer. Typically, needle aspiration samples are performed and needle cores can be sampled if the operator is confident that the needle is within the lymph node target, partly because of the risk of bleeding if a large blood vessel is sampled during core biopsy, especially in the perihilar region. Many bronchoscopists have difficulty assessing the three-dimensional (3D) positioning for needle sampling during these procedures, especially when relying on multidetector-row computerized tomography (MDCT) images displayed two-dimensionally seen prior to and usually during the procedure. Objective: We have developed and evaluated a process model and associated software for providing interactive 3D displays of the MDCT data for procedure planning and real-time virtual bronchoscopic pathfinding for these procedures. Methods: We undertook a prospective randomized clinical study for evaluating the computer-aided pathfinding assistance in mediastinal lymph node biopsies in 87 consenting subjects. Results: We demonstrate that the addition of this computer-aided pathfinding improved operator performance in perihilar and paratracheal lymph node sampling (100 vs. 69%) but not in subcarinal sampling (82 vs. 85%). Overall success with lymph node sampling is 92% using the computer-aided method and 77% using standard clinical practice. Conclusions: The type of computer-aided pathway assistance described here, using 3D MDCT scanning information obtained before the procedure, but interacting with real-time bronchoscopic images during the bronchoscopic procedure, should improve the confidence of most bronchoscopists in performing these procedures, with improved clinical outcomes, and will add to the personalization of medicine through imaging.

Evaluation of intracranial aneurysms with CT angiography: current status and future direction

Purpose: To develop a valid, reliable and accurate system of measurement of intracranial aneurysm geometry using volumetric data obtained by CT angiography. Materials and methods: A simple model of lateral saccular aneurysm was created. Three models were prepared with different size of aneurysm sac and neck. Volumetric data was acquired using a Toshiba Xpress SX helical scanner. Geometry of an aneurysm model obtained by workstation linked to the scanner applying volume rendering display and dedicated UNIX based computer applying MPR based method. These results were compared with actual caliper measurements of the model. A clinical case of lateral aneurysm arising from the supraclinoid internal carotid artery was also studied. Results: Both the volume rendered image based method and MPR based method provided accurate geometric information of an aneurysm sac and its neck. Conclusions: Volume rendering technique requires editing by a well-informed operator and subjective, while the MPR based method is more objective and better suited for quantitative analysis. Using these mutually complimentary tools, critical geometric information of an aneurysm can be extracted from volumetric data provided by CTA.

Human airway tree structure query atlas

A queryable electronic atlas was developed to quantitatively characterize the normal human lung airway tree and to provide a better understanding of the lung for diagnosing diseases and evaluating treatments. The atlas consists of airway measurements taken from CT images using the Pulmonary Workstation II (PW2) software package. These measurements include airway cross-sectional area at midpoint between branch points; maximum and minimum diameter of a particular airway cross section at segment midpoint; average, maximum, and minimum wall thickness per branch; and wall thickness uniformity within a branch. The atlas provides user friendly interfaces for interrogating population statistics, comparing populations, comparing individuals to populations, and comparing individuals to other individuals. Populations can be selected based on age, gender, race, ethnicity, and normalcy/disease.