Zhimin Huo

Computer-aided detection of malpositioned endotracheal tubes in portable chest radiographs

Portable chest radiographic images play a critical role in examining and monitoring the condition and progress of critically ill patients in intensive care units (ICUs). For example, portable chest images are acquired to ensure that tubes inserted into the patients are properly positioned for effective treatment. In this paper, we present a system that automatically detects the position of an endotracheal tube (ETT), which is inserted into the trachea to assist patients who have difficulty breathing. The computer detection includes the detections of the lung field, spine line, and aortic arch. These detections lead to the identification of regions of interest (ROIs) used for the subsequent detection of the ETT and carina. The detection of the ETT and carina is performed within the ROIs. Our ETT and carina detection methods were trained and tested on a large number of images. The locations of the ETT and carina were confirmed by an experienced radiologist for the purpose of performance evaluation. Our ETT detection achieved an average sensitivity of 85% at less than 0.1 false-positive detections per image. The carina approach correctly identified the carina location within a 10 mm distance from the truth location for 81% of the 217 testing images. We expect our system will assist ICU clinicians to detect malpositioned ETTs and reposition malpositioned ETTs more effectively and efficiently.

Bone suppression technique for chest radiographs

High-contrast bone structures are a major noise contributor in chest radiographic images. A signal of interest in a chest radiograph could be either partially or completely obscured or “overshadowed” by the highly contrasted bone structures in its surrounding. Thus, removing the bone structures, especially the posterior rib and clavicle structures, is highly desirable to increase the visibility of soft tissue density. We developed an innovative technology that offers a solution to suppress bone structures, including posterior ribs and clavicles, on conventional and portable chest X-ray images. The bone-suppression image processing technology includes five major steps: 1) lung segmentation, 2) rib and clavicle structure detection, 3) rib and clavicle edge detection, 4) rib and clavicle profile estimation, and 5) suppression based on the estimated profiles. The bone-suppression software outputs an image with both the rib and clavicle structures suppressed. The rib suppression performance was evaluated on 491 images. On average, 83.06% (±6.59%) of the rib structures on a standard chest image were suppressed based on the comparison of computer-identified rib areas against hand-drawn rib areas, which is equivalent to about an average of one rib that is still visible on a rib-suppressed image based on a visual assessment. Reader studies were performed to evaluate reader performance in detecting lung nodules and pneumothoraces with and without a bone-suppression companion view. Results from reader studies indicated that the bone-suppression technology significantly improved radiologists’ performance in the detection of CT-confirmed possible nodules and pneumothoraces on chest radiographs. The results also showed that radiologists were more confident in making diagnoses regarding the presence or absence of an abnormality after rib-suppressed companion views were presented

On image rendering methods for improved image consistency in PACS environment

The average workload per full-time equivalent (FTE) radiologist increased by 70% from1991-1992 to 2006- 2007. The increase is mainly due to the increase (34%) in the number of procedures, particularly in 3D imaging procedures. New technologies such as picture archiving and communication systems (PACS) and embodied viewing capability were accredited for an improved workflow environment leading to the increased productivity. However, the need for further workflow improvement is still in demand as the number of procedures continues growing. Advanced and streamlined viewing capability in PACS environment could potentially reduce the reading time, thus further increasing the productivity. With the increasing number of 3D image procedures, radiographic procedures (excluding mammography) have remained their critical roles in screening and diagnosis of various diseases. Although radiographic procedures decreased in shares from 70% to 49.5%, the total number has remained the same from 1991-1992 to 2006- 2007. Inconsistency in image quality for radiographic images has been identified as an area of concern. It affects the ability of clinicians to interpret images effectively and efficiently in areas where diagnosis, for example, in screening mammography and portable chest radiography, requires a comparison of current images with priors. These priors can potentially have different image quality. Variations in image acquisition techniques (x-ray exposure), patient and apparatus positioning, and image processing are the factors attributed to the inconsistency in image quality. The inconsistency in image quality, for example, in contrast may require manual image manipulation (i.e., windowing and leveling) of images to accomplish an optimal comparison to detect the subtle changes. We developed a tone-scale image rendering technique which improves the image consistency of chest images across time and modality. The rendering controls both the global and local contrast for a consistent look. We expect the improvement could reduce the window and level manipulation time required for an optimal comparison of priors and current images, thus improving both the efficiency and effectiveness of image interpretation. This paper presents a technique for improving the consistency of portable chest radiographic images. The technique is based on regions-of-interest (ROIs) to control both the local and global contrast consistency.