Automatic identification of frontal (posteroanterior/anteroposterior) vs. lateral chest radiographs is an important preprocessing step in computer-assisted diagnosis, content-based image retrieval, as well as picture archiving and communication systems. Here, a new approach is presented. After the radiographs are reduced substantially in size, several distance measures are applied for nearest-neighbor classification. Leaving-one-out experiments were performed based on 1,867 radiographs from clinical routine. For comparison to existing approaches, subsets of 430 and 5 training images are also considered. The overall best correctness of 99.7% is obtained for feature images of 32 × 32 pixels, the tangent distance, and a 5-nearest-neighbor classification scheme. Applying the normalized cross correlation function, correctness yields still 99.6% and 99.3% for feature images of 32 × 32 and 8 × 8 pixel, respectively. Remaining errors are caused by image altering pathologies, metal artifacts, or other interferences with routine conditions. The proposed algorithm outperforms existing but sophisticated approaches and is easily implemented at the same time.
Content-based image retrieval (CBIR); picture archiving and communication systems (PACS); computer-aided diagnosis (CAD); image analysis; software evaluation; chest radiographs
The purpose of this study was to measure the impact of electronic signature on report turnaround time. The Radiology Information System (RIS) database was interrogated to obtain a file containing all examinations recorded within a one-month period. Two sectors were specifically studied: abdominal ultrasound and chest radiography. Each of these sectors had one reader per day. The periods studied were October 2001 (before implementation of electronic signature) and February 2002 (3 months after electronic signature implementation). For the abdominal ultrasound examinations, the median time from transcription to final signature decreased from 11 days to 3 days with the introduction of electronic signature (P < 0.001). For the chest radiographs, the median time from transcription to final signature decreased from 10 days to 5 days with the introduction of electronic signature (P < 0.001). Electronic signature significantly shortens the time interval between transcription and finalization of radiology reports.
Electronic signature; diagnostic reporting; report turnaround
Academic radiologists are experiencing increased clinical workloads. New technology such as picture archiving and communication systems (PACS) are often justified on the premise of increased efficiency. The authors believe that efficiency can be influenced by the image interpretation environment, and thus they set out to establish baseline satisfaction levels with this environment. The authors surveyed 90 Indiana University (IU) faculty radiologists, fellows, and residents. Their survey was implemented with a questionnaire sent via e-mail. Questions focused on satisfaction with the current soft-copy reading environments and preferences regarding improvements. Of the 90 radiologists surveyed, 55 (61%) responded. Several key findings emerged: (1) Overall satisfaction with the soft-copy environment is low, with nearly half (46%) of respondents rating themselves as “very dissatisfied” or “dissatisfied.” (2) Faculty are least satisfied regarding work space ergonomics, room layout, and amount of work space. Appropriate lighting also emerged as an area with low satisfaction and high importance. (3) Ninety-eight percent of respondents indicated that an “ideal” soft-copy environment would have a positive effect on their efficiency. The dissatisfaction with the current soft-copy interpretation environments used by the IU radiologists indicates that this is an area that requires attention. Furthermore, there may be a direct relationship between radiologist efficiency and satisfaction with the image interpretation environment. Attention should be focused on this environment during a soft-copy technology implementation to ensure that planned efficiency gains are realized.
Reading room; soft copy; ergonomics
The continued revolution in multidetector-row CT (MDCT) scanning increases the quality of lung imaging but at the cost of a greater burden of data for review and interpretation. This article discusses our preliminary experience with prototype software for lung nodule detection and characterization using MDCT data sets. We discuss the potential role of computer-assisted detection (CAD) as applied to the automatic detection of lung nodules. We also review the process of CAD, outline its potential results, and explore how it may fit into existing radiology practice. Finally, we discuss MDCT data-acquisition parameters and how they may affect the performance of CAD.
Computer-assisted detection; pulmonary nodules; multidetector-row CT
This article documents the results of the first in a series of experiments designed to evaluate the suitability of a novel, high resolution, color, digital, liquid crystal display (LCD) panel for diagnostic quality, gray scale image display. The goal of this experiment was to measure the performance of the display, especially with respect to luminance. The panel evaluated was the IBM T221 22.2” backlit active matrix liquid crystal display (AMLCD) with native resolution of 3840 × 2400 pixels. Taking advantage of the color capabilities of the workstation, we were able to create a 256-entry grayscale calibration look-up table derived from a palette of 1786 nearly gray luminance values. We also constructed a 256-entry grayscale calibration look-up table derived from a palette of 256 true gray values for which the red, green, and blue values were equal. These calibrations will now be used in our evaluation of human contrast-detail perception on this LCD panel.
PACS; image display; AMLCD evaluation; DICOM Part 14 calibration
One of the advantages of digital mammography is to display mammograms on softcopy (electronic displays). Softcopy display of mammography is challenging because of the spatial and contrast resolution demands present in mammograms. We have designed and developed a softcopy mammography display application, Mammoview, which is capable of allowing radiologists to read mammograms as quickly and as accurately as they can on film alternators. We review the studies using Mammoview to elucidate the requirements of a successful softcopy display station. The design and development of the Mammoview softcopy display station are described in this article, and results of several studies using Mammoview are reported, including subjective feedback from Radiological Society of North America (RSNA) conference demonstrations, and clinical studies measuring performance in terms of speed and accuracy. Additional analysis of user interactions and user feedback is used to study the successes and shortcomings of mammography display stations like Mammoview. Overall, radiologist readings using Mammoview have been shown to be as fast and as accurate as readings using mammography film alternators. However, certain parts of the softcopy interface were more successful than their film counterparts, whereas others were less successful. Data analysis of the recorded human–computer interactions for the softcopy component of the clinical trial indicate statistically significant correlations between the difference in review time of softcopy versus alternator readings and three factors: the number of interactions, the reader, and the size of the image being reviewed. The first factor (number of interactions) suggests that simpler interfaces require less time to use; the second factor, the reader, supports previous findings that radiologists vary in how fast they read screening mammography studies; the third, size of image, suggests that the speed of softcopy review is increased relative to film readings when images are significantly larger than the display size. Feedback from radiologists using the system in clinical trials and at demonstration exhibits at RSNA indicated good acceptance of the interface and easy adaptation. Radiologists indicated that they felt comfortable using the interface, and that they would use such a softcopy interface in clinical practice. Finally, preliminary work suggests that the addition of a simple interaction to incorporate computer-aided detection (CAD) results would improve reading accuracy without significantly increasing reader times.
Softcopy image display; human–computer interaction; digital mammography; image processing; pan; zoom
Web-based clinical-image viewing is commonplace in large medical centers. As demands for product and performance escalate, physicians, sold on the concept of “any image, anytime, anywhere,” fret when image studies cannot be viewed in a time frame to which they are accustomed. Image delivery pathways in large medical centers are oftentimes complicated by multiple networks, multiple picture archiving and communication systems (PACS), and multiple groups responsible for image acquisition and delivery to multiple destinations. When studies are delayed, it may be difficult to rapidly pinpoint bottlenecks. Described here are the tools used to monitor likely failure points in our modality to clinical-image-viewing chain and tools for reporting volume and throughput trends. Though perhaps unique to our environment, we believe that tools of this type are essential for understanding and monitoring image-study flow, re-configuring resources to achieve better throughput, and planning for anticipated growth. Without such tools, quality clinical-image delivery may not be what it should.
Clinical-image viewing; imaging throughput; Clinical Desktop; Imageweb
Over the past decade, the technology that permits images to be digitized and the reduction in the cost of digital equipment allows quick digital transfer of any conventional radiological film. Images then can be transferred to a personal computer, and several software programs are available that can manipulate their digital appearance. In this article, the fundamentals of digital imaging are discussed, as well as the wide variety of optional adjustments that the Adobe Photoshop 6.0 (Adobe Systems, San Jose, CA) program can offer to present radiological images with satisfactory digital imaging quality.
Images; digital imaging; digital camera; computers; processing; software application
This paper describes the authors’ experience with integrating an existing database-driven teaching file with the RSNA (Radiological Society of North America) Medical Imaging Resource Center (MIRC). MIRC is the product of an RSNA-sponsored initiative to enable medical institutions to share their electronic medical content (images, text, and multimedia) by creating a distributed repository accessible from the Internet. An existing database-driven teaching file, developed by the authors and used extensively by the University of California San Francisco (UCSF) Department of Radiology since 1998, was retrofitted to include an interface for handling broadcast queries initiated by a MIRC query service. These queries take place through the exchange of XML documents via HTTP. After all the storage services have responded, the results are collated by the query service and presented to the user. The teaching file and MIRC interface were developed using the 4th Dimension Relational Database Management System (RDBMS). The integration process primarily involved mapping the “MIRCdocument” schema to the teaching file’s schema, translating the actual MIRC query into the internal query language of the database and extending the access control mechanisms of the teaching file to allow public access. A working implementation of the interface required only 3 days of development time, with refinements taking place over several months. Interface development was greatly aided by MIRC’s use of well-established Internet standards. This project has demonstrated the feasibility of implementing a MIRC interface on an existing teaching file server.
MIRC; teaching files; XML; distributed query; 4th dimension RDBMS; Web-based
Major healthcare systems are comprised of hospitals and clinics of different sizes and locations. Many such enterprises are already using picture archiving and communication systems (PACS) and computed radiography (CR) in their main hospitals. The integration of other hospitals and clinics into PACS is a more complex problem. The introduction of CR in remote facilities presents problems, as patient populations, department sizes, and work flow patterns may differ among facilities, and inadequate implementation programs may lead to disruption of patient care services. Although the University of Florida has had an operating PACS for years, facilities affiliated with the Shands Healthcare System (SHS) had not been incorporated into PACS until recently. This article presents the 5-year process to convert all film-screen radiological services to CR in the main hospital, five affiliated community hospitals, and four clinics. The article shows the importance of leadership by the medical physicist from inception of the project through installation and clinical implementation.
CR; PACS; community hospitals; academic departments; technologist training
The objective of this study was to develop a method for measuring quality degradation in lossy wavelet image compression. Quality degradation is due to denoising and edge blurring effects that cause smoothness in the compressed image. The peak Moran z histogram ratio between the reconstructed and original images is used as an index for degradation after image compression. The Moran test is applied to images randomly selected from each medical modality, computerized tomography, magnetic resonance imaging, and computed radiography and compressed using the wavelet compression at various levels. The relationship between the quality degradation and compression ratio for each image modality agrees with previous reports that showed a preference for mildly compressed images. Preliminary results show that the peak Moran z histogram ratio can be used to quantify the quality degradation in lossy image compression. The potential for this method is applications for determining the optimal compression ratio (the maximized compression without seriously degrading image quality) of an image for teleradiology.
Wavelet compression; quality evaluation; Moran test
In 1998 we surveyed our radiologists on teleradiology satisfaction. Results were generally positive. In 2002 we experienced a sevenfold case increase in teleradiology volume. The present study surveyed the radiologists again. The hypothesis was that, with increased case volume and radiologist experience with the system, ratings would increase. Image quality was excellent/good, although plain film and ultra sound (US) had more fair/poor ratings. Monitors, navigation, image processing, and Web-based reporting were rated as excellent/good. The voice-recognition system was rated poorly. Diagnostic confidence was about the same as for film. Exceptions were magnetic resonance imaging (MRI) US, and plain film. Up to 10% of cases are unreadable because of poor image quality, not enough images, or inadequate patient history. Overall, the radiologists are satisfied, although some improvements can be made.
Teleradiology; user satisfaction; evaluation
In addition to the inherent qualities of a digital image, the qualities of the monitor and graphics control card as well as the viewing conditions will affect the perceived quality of an image that is displayed on a soft copy display (SD) system. With the implementation of picture archiving and communication systems (PACS), many diagnoses are being made based on images displayed on SD devices, and consequently SD quality may affect the accuracy of diagnosis. Unlike the traditional film-on-lightbox display, optimal SD system parameters are not well defined, and many issues remain unsettled. In this article, the human observer performance, as measured by contrast sensitivity, for several SD devices including an active matrix liquid crystal flat panel monitor is reported. Contrast sensitivities were measured with various display system configurations. Experimental results showed that contrast sensitivity depends on many factors such as the type of monitor, the monitor brightness, and the gamma settings of the graphics card in a complex manner. However, there is a clear correlation between the measured contrast thresholds and the gradient of the display device’s luminance response curve. Based on this correlation, it is proposed to use the gradient of luminance response curve as a quality-index or metric for SD devices.
Soft copy display; contrast sensitivity; gradient of luminance response curve; display quality index; human observer performance
Unsharp masking is a widely used image-enhancement method in medical imaging. Hardware-based solutions can be developed to support high computational demand for unsharp masking, but they suffer from limited flexibility. Software solutions can easily incorporate new features and modify key parameters, such as filtering kernel size, but they have not been able to meet the fast computing requirement. Modern programmable mediaprocessors can meet both fast computing and flexibility requirements, which will benefit medical image computing. In this article, we present fast adaptive unsharp masking on two leading mediaprocessors or high-end digital signal processors, Hitachi/Equator Technologies MAP-CA and Texas Instruments TMS320C64x. For a 2k × 2k 16-bit image, our adaptive unsharp masking with a 201 × 201 boxcar kernel takes 225 ms on a 300-MHz MAP-CA and 74 ms on a 600-MHz TMS320C64x. This fast unsharp masking enables technologists and/or physicians to adjust parameters interactively for optimal quality assurance and image viewing.
Adaptive unsharp masking algorithm; programmable mediaprocessors; digital signal processors; fast computing-interactive unsharp masking; medical imaging
Systems for the processing and representation of cranial computed tomograms have become a significant addition to the use of computers in medicine, particularly radiology. This paper tries to outline a global view on some of the important technical capabilities such systems can provide using techniques from Picture Processing, Image Analysis and Computer Graphics. Experimental results of the COMPACT Project are presented wherever appropriate. Further thought is also given to the framework in which CT processing may take place. To ensure clinical efficacy a concept of a Medical Work Station as part of a distributed computing network is discussed. Some consideration is then given to the physicians possible working modes within such a system.
A 10 Mbits/second fiber-optic network for the transmission of chest x-ray images has been designed and implemented at our Hospital. Images are acquired with a high-resolution laser scanner. The viewing consoles display images at spatial resolutions of either 512 square or 1024 square. User interfaces have been designed to simplify the digitization and display processes. The applications level networking software and all the image processing software has been developed in-house. The system is now serving a 11-bed critical care facility on a day-to-day basis. This paper will focus on the software design issues. The software will be presented from a systems perspective. The importance of the user in the design process will be stressed and exemplified. The role of intelligent, rule-based software will be demonstrated. Selected clinical results will be discussed.