Computer-Aided Classification of Visual Ventilation Patterns in Patients with Chronic Obstructive Pulmonary Disease at Two-Phase Xenon-Enhanced CT

OBJECTIVE: To evaluate the technical feasibility, performance, and interobserver agreement of a computer-aided classification (CAC) system for regional ventilation at two-phase xenon-enhanced CT in patients with chronic obstructive pulmonary disease (COPD). MATERIALS AND METHODS: Thirty-eight patients with COPD underwent two-phase xenon ventilation CT with resulting wash-in (WI) and wash-out (WO) xenon images. The regional ventilation in structural abnormalities was visually categorized into four patterns by consensus of two experienced radiologists who compared the xenon attenuation of structural abnormalities with that of adjacent normal parenchyma in the WI and WO images, and it served as the reference. Two series of image datasets of structural abnormalities were randomly extracted for optimization and validation. The proportion of agreement on a per-lesion basis and receiver operating characteristics on a per-pixel basis between CAC and reference were analyzed for optimization. Thereafter, six readers independently categorized the regional ventilation in structural abnormalities in the validation set without and with a CAC map. Interobserver agreement was also compared between assessments without and with CAC maps using multirater kappa statistics. RESULTS: Computer-aided classification maps were successfully generated in 31 patients (81.5%). The proportion of agreement and the average area under the curve of optimized CAC maps were 94% (75/80) and 0.994, respectively. Multirater kappa value was improved from moderate (kappa = 0.59; 95% confidence interval [CI], 0.56-0.62) at the initial assessment to excellent (kappa = 0.82; 95% CI, 0.79-0.85) with the CAC map. CONCLUSION: Our proposed CAC system demonstrated the potential for regional ventilation pattern analysis and enhanced interobserver agreement on visual classification of regional ventilation.

Development of 3D statistical mandible models for cephalometric measurements

PURPOSE: The aim of this study was to provide sex-matched three-dimensional (3D) statistical shape models of the mandible, which would provide cephalometric parameters for 3D treatment planning and cephalometric measurements in orthognathic surgery. MATERIALS AND METHODS: The subjects used to create the 3D shape models of the mandible included 23 males and 23 females. The mandibles were segmented semi-automatically from 3D facial CT images. Each individual mandible shape was reconstructed as a 3D surface model, which was parameterized to establish correspondence between different individual surfaces. The principal component analysis (PCA) applied to all mandible shapes produced a mean model and characteristic models of variation. The cephalometric parameters were measured directly from the mean models to evaluate the 3D shape models. The means of the measured parameters were compared with those from other conventional studies. The male and female 3D statistical mean models were developed from 23 individual mandibles, respectively. RESULTS: The male and female characteristic shapes of variation produced by PCA showed a large variability included in the individual mandibles. The cephalometric measurements from the developed models were very close to those from some conventional studies. CONCLUSION: We described the construction of 3D mandibular shape models and presented the application of the 3D mandibular template in cephalometric measurements. Optimal reference models determined from variations produced by PCA could be used for craniofacial patients with various types of skeletal shape.

Subtraction CT Angiography with Motion Correction for Detection of Intra- and Extra-cranial Vascular Lesions: Technical Considerations and Initial Experience / 신경중재치료의학

PURPOSE: Clinical implementation of subtraction computed tomographic angiography (CTA) is limited due to motion artifact and/or long processing time. We evaluated the utility of a motion-corrected subtraction CTA technique for visualization of intra- and extra-cranial vascular lesions. MATERIALS AND METHODS: Pre- and post-contrast CT images were obtained in the target region of 53 consecutive patients which were consisted of 36 patients with 53 lesions and 17 normal patients. The source images were transferred to a personal computer (PC) and were automatically post-processed within one minute using novel motion-corrected subtraction CTA. The image quality of subtraction and non-subtraction CTAs was compared in each lesion category and lesion location using 3-point scale and Chi square test. RESULTS: The image quality of subtraction CTA was better than those from non-subtraction CTA (p<0.05) especially in the skull base lesions, such as carotid-cavernous fistulas, aneurysms in the cavernous internal carotid artery (ICA), and steno-occlusive lesions of the distal ICA, and extracranial lesions such as facial arteriovenous fistulas. CONCLUSION: The PC-based motion-corrected subtraction CTA technique allows fast generation of postprocessed images and can provide improved visualization of vascular anatomy and pathologies adjacent to bone in the skull base and head and neck areas.