Stereology is a volume estimation method, typically applied to diagnostic imaging examinations in population studies where planimetry is too time-consuming (Chapman et al. Kidney Int 64:1035–1045, 2003), to obtain quantitative measurements (Nyengaard J Am Soc Nephrol 10:1100–1123, 1999, Michel and Cruz-Orive J Microsc 150:117–136, 1988) of certain structures or organs. However, true segmentation is required in order to perform advanced analysis of the tissues. This paper describes a novel method for segmentation of region(s) of interest using stereology data as prior information. The result is an efficient segmentation method for structures that cannot be easily segmented using other methods.
3D segmentation; Digital image processing; Biomedical image analysis; Fuzzy logic; Image segmentation; 3D imaging (three-dimensional imaging); Boundary extraction; Segmentation; Magnetic resonance imaging; MR imaging; Data extraction; Image analysis; Polycystic kidney disease; Python; Planimetry
Workflow is a widely used term to describe the sequence of steps to accomplish a task. The use of workflow technology in medicine and medical imaging in particular is limited. In this article, we describe the application of a workflow engine to improve workflow in a radiology department. We implemented a DICOM-enabled workflow engine system in our department. We designed it in a way to allow for scalability, reliability, and flexibility. We implemented several workflows, including one that replaced an existing manual workflow and measured the number of examinations prepared in time without and with the workflow system. The system significantly increased the number of examinations prepared in time for clinical review compared to human effort. It also met the design goals defined at its outset. Workflow engines appear to have value as ways to efficiently assure that complex workflows are completed in a timely fashion.
Workflow management; System architecture; DICOM; Business process management
Efficient workflow is essential for a successful business. However, there is relatively little literature on analytical tools and standards for defining workflow and measuring workflow efficiency. Here, we describe an effort to define a workflow lexicon for medical imaging departments, including the rationale, the process, and the resulting lexicon.
Workflow; Cost-effectiveness; Controlled vocabulary; Data mining; Radiology workflow; Workflow re-engineering
Recent information technology literature, in general, and radiology trade journals, in particular, are rife with allusions to the “cloud” suggesting that moving one’s compute and storage assets into someone else’s data center magically solves cost, performance, and elasticity problems. More likely, one is only trading one set of problems for another, including greater latency (aka slower turnaround times) since the image data must now leave the local area network and travel longer paths via encrypted tunnels. To offset this, an imaging system design is needed that reduces the number of high-latency image transmissions, yet can still leverage cloud strengths. This work explores the requirements for such a design.
DICOM; IHE; Cloud; WADO
In part one of this series, best practices were described for acquiring and handling data at study sites and importing them into an image repository or database. Here, we present a similar treatment on data management practices for imaging-based studies.
Clinical trials; Research image database
The purpose of this article is to describe a system we developed for importing images on compact discs (CDs) from external imaging departments into our clinical image viewing system, and to report on key metrics regarding veracity of information seen on the CDs. We recommend careful attention to the process of CD importation because of the error rate we have seen. We developed a system and process for importing images on CD into our EMR. The importation system scans the CD for digital imaging and communications in medicine (DICOM) images, and collects all patient information seen. That information is presented to the patient for verification. Once validated, the image data is copied into our clinical viewing system. The importation system includes facilities for collecting instances of incorrect data. About 90% of images are now exchanged between our healthcare enterprise and other entities via CD. Data for the wrong patient (e.g., the wrong CD) is seen in about 0.1% of cases, and a similar number of CDs have data for more than one patient on the CD(s) the patient bring to our facility. Most data are now exchanged via DICOM files. DICOM images burned onto CD media are now commonly used for image exchange. However, applications to import DICOM images are not enough. One must implement a process to assure high confidence that the data imported belongs to the patient you are importing.
Digital imaging and communications in medicine (DICOM); Electronic medical record (EMR); Image distribution; Integrating healthcare enterprise (IHE); Medical record linkage; Teleradiology; Workflow re-engineering
Intracranial aneurysms represent a significant cause of morbidity and mortality. While the risk factors for aneurysm formation are known, the detection of aneurysms remains challenging. Magnetic resonance angiography (MRA) has recently emerged as a useful non-invasive method for aneurysm detection. However, even for experienced neuroradiologists, the sensitivity to small (<5 mm) aneurysms in MRA images is poor, on the order of 30~60% in recent, large series. We describe a fully automated computer-aided detection (CAD) scheme for detecting aneurysms on 3D time-of-flight (TOF) MRA images. The scheme locates points of interest (POIs) on individual MRA datasets by combining two complementary techniques. The first technique segments the intracranial arteries automatically and finds POIs from the segmented vessels. The second technique identifies POIs directly from the raw, unsegmented image dataset. This latter technique is useful in cases of incomplete segmentation. Following a series of feature calculations, a small fraction of POIs are retained as candidate aneurysms from the collected POIs according to predetermined rules. The CAD scheme was evaluated on 287 datasets containing 147 aneurysms that were verified with digital subtraction angiography, the accepted standard of reference for aneurysm detection. For two different operating points, the CAD scheme achieved a sensitivity of 80% (71% for aneurysms less than 5 mm) with three mean false positives per case, and 95% (91% for aneurysms less than 5 mm) with nine mean false positives per case. In conclusion, the CAD scheme showed good accuracy and may have application in improving the sensitivity of aneurysm detection on MR images.
Computer-aided detection (CAD); magnetic resonance angiography (MRA); intracranial aneurysm; aneurysm detection
In this study, we present preliminary data on the effect of automated 3D image alignment on the time to arrive at a decision about an imaging finding, the agreement of multiple of multiple observers, the prevalence of comparison examinations, and technical success rates for the image alignment algorithm. We found that automated image alignment reduced the average time to make a decision by 25% for cases where the structures are rigid, and when the scanning protocol is similar. For cases where these are not true, there is little or no benefit. In our practice, 54% of cases had prior examinations that could be automatically aligned. The overall benefit seen in our department for highly similar exams might be 20% for neuro and 10% for body; the benefit seen in other practices is likely to vary based on scanning practices and prevalence of prior examinations.
Image registration; image alignment; practice efficiency; TRIP
Magnetic resonance angiography (MRA) has become the standard method for evaluation of carotid occlusive disease. Fast imaging methods combined with bolus intravenous injection of gadolinium contrast have improved the quality of these images. Nevertheless, the gold standard for evaluation was based on projection arterial angiography. The properties of these images are rather different. Whereas most previous evaluations of MRA have used visual assessment of images, we evaluate an algorithm in which a computer algorithm plays the primary role in defining arterial lumen margins, hence, disease. The accuracy of this semiautomated algorithm is shown to compare favorably with gold-standard arteriography in a series of 50 patients.
Computer-aided diagnosis has been under development for more than 3 decades. The rate of progress appears exponential, with either recent approval or pending approval for devices focusing on mammography, chest radiographs, and chest CT. Related technologies improve diagnosis for many other types of medical images including virtual colonography, vascular imaging, as well as automated quantitation of image-derived metrics. A variety of techniques are currently employed with success, likely reflecting the variety of imagery used, as well as the variety of tasks. Most areas of medical imaging have had efforts at computer assistance, and some have even received FDA approval and can be reimbursed. We anticipate that the rapid advance of these technologies will continue, and that application will broaden to cover much of medical imaging. Acceptance of, and integration of computer-aided diagnosis technology with the electronic radiology practice is a current challenge. These challenges will be overcome, and we expect that computer-aided diagnosis will be routinely applied to medical images.
The volume of data from medical imaging is growing at exponential rates, matching or exceeding the decline in the costs of digital data storage. While methods to reversibly compress image data do exist, current methods only achieve modest reductions in storage requirements. Irreversible compression can achieve substantially higher compression ratios without perceptible image degradation. These techniques are routinely applied in teleradiology, and often in Picture Archiving and Communications Systems. The practicing radiologist needs to understand how these compression techniques work and the nature of the degradation that occurs in order to optimize their medical practice. This paper describes the technology and artifacts commonly used in irreversible compression of medical images.
data compression; wavelets; JPEG
A prior ultrasound study indicated that images with low to moderate levels of JPEG and wavelet compression were acceptable for diagnostic purposes. The purpose of this study is to validate this prior finding using the Joint Photographic Experts Group (JPEG) baseline compression algorithm, at a compression ratio of approximately 10:1, on a sufficiently large number of grayscale and color ultrasound images to attain a statistically significant result. The practical goal of this study is to determine if it is feasible for radiologists to use irreversibly compressed images as an integral part of the day to day ultrasound practice (ie, perform primary diagnosis with, and store irreversibly compressed images in the ultrasound PACS archive). In this study, 5 Radiologists were asked to review 300 grayscale and color static ultrasound images selected from 4 major anatomic groups. Each image was compressed and decompressed using the JPEG baseline compression algorithm at a fixed quality factor resulting in an average compression ratio of approximately 9:1. The images were presented in pairs (original and compressed) in a blinded fashion on a PACS workstation in the ultrasound reading areas, and radiologists were asked to pick which image they preferred in terms of diagnostic utility and their degree of certainty (on a scale from 7 to 4). Of the 1,499 total readings, 50.17% (95% confidence intervals at 47.6%, and 52.7%) indicated a preference for the original image in the pair, and 49.83% (95% confidence intervals at 47.3%, and 52.0%) indicated a preference for the compressed image. These findings led the authors to conclude that static color and gray-scale ultrasound images compressed with JPEG at approximately 9:1 are statistically indistinguishable from the originals for primary diagnostic purposes. Based on the authors laboratory experience with compression and the results of this and other prior studies JPEG compression is now being applied to all ultrasound images in the authors radiology practice before reading. No image quality-related issues have been encountered after 12 months of operation (approximately 48,000 examinations).
Compression; Joint Photographic Experts Group; ultrasound; medical images; PACS; teleradiology; archive
The requirements for a clinical viewing station have some similarities to requirements of an interpretation workstation, but have some important differences. The user base is a heterogeneous group, and the tasks the clinicians perform vary substantially, increasing the variation in the requirements. However, it is possible to determine a list of requirements that satisfy most clinicians under most circumstances. In addition to the standard image manipulation tools, we have found that integration with the other clinical tools is essential to maintaining or increasing their efficiency. Providing for varying levels of functionality/complexity is also useful, because of the variation in the user base.
This report describes several image archival problems facing the authors' department and the results of their attempt to define the requirements for an enterprise digital image archive. The problems identified include the costs of supporting multiple distinct archives, the increased complexity of supporting multiple archive interfaces, the differences in data handling policies and resulting variations in data integrity, and variability in support for nonimage data. The authors also describe the data collected including image volumes and trends and imaging device trends. Finally, the resulting specification for an enterprise digital image archive, including storage and retrieval performance and interface requirements are presented.
A clinical viewing system was integrated with the Mayo Clinic Scottsdale picture archiving and communication system (PACS) for providing images and the report as part of the electronic medical record (EMR). Key attributes of the viewer include a single user log-on, an integrated patient centric EMR image access for all ordered examinations, prefetching of the most recent prior examination of the same modality, and the ability to provide comparison of current and past exams at the same time on the display. Other functions included preset windows, measurement tools, and multiformat display. Images for the prior 12 months are stored on the clinical server and are viewable in less than a second. Images available on the desktop include all computed radiography (CR), chest, magnetic resonance images (MRI), computed tomography (CT), ultrasound (U/S), nuclear, angiographic, gastrointestinal (GI) digital spots, and portable C-arm digital spots. Ad hoc queries of examinations from PACS are possible for those patients whose image may not be on the clinical server, but whose images reside on the PACS archive (10TB). Clinician satisfaction was reported to be high, especially for those staff heavily dependent on timely access to images, as well as those having heavy film usage. The desktop viewer is used for resident access to images. It is also useful for teaching conferences with large-screen projection without film. We report on the measurements of functionality, reliability, and speed of image display with this application.
The purpose of the study was to evaluate the effects of lossy compression on grayscale ultrasound images to determine how much compression can be applied while still maintaining images that are acceptable for diagnostic purposes. The study considered how the acquisition technique (video frame-grabber versus directly acquired in digital form) influences how much compression can be applied. For directly acquired digital images, the study considered how text (that is burned into the image) affects the compressibility of the image. The lossy compression techniques that were considered include JPEG and a Wavelet algorithm using set partitioning in hierarchical trees (SPIHT).
lossy compression; JPEG; wavelet compression; ultrasonography; Medical Images; picture archiving and communication systems; teleradiology
Although it is intuitively valuable that more expedient delivery of radiographic images and reports to clinicians would improve patient care, it is important to document these outcomes to validate further advances in these areas. We evaluated the care of 215 patients seen at a walk-in clinic to determine what benefit digital imaging is to the patient. Cohorts consisted of all patients for whom specified radiology examinations were ordered during a 7-day period. The first cohort was recruited when analog films were used. The second cohort received examinations performed with computed radiography (CR) acquisition and computer display, which had been in use for 2 years. Patients were categorized as to the type of study they received, as well as whether a staff radiologist was immediately available to read the study. Clinical behavior was characterized by outcome measures of time to final diagnosis, time to final treatment, and need for follow-up. Our analysis demonstrated a reduction in time to final diagnosis that was better appreciated during the times when a staff radiologist was not immediately available. It also suggested that greater time reductions were seen for patients who received extremity examinations than those who received chest, sinus, or rib films. These data suggest that digital imaging is a useful tool to improve clinical outcome of patients seen in the acute care setting.
We prospectively compared image and report delivery times in our Urgent Care Center (UCC) during a film-based practice (1995) and after complete implementation of an electronic imaging practice in 1997. Before switching to a totally electronic and filmless practice, multiple time periods were consistently measured during a 1-week period in May 1995 and then again in a similar week in May 1997 after implementation of electronic imaging. All practice patterns were the same except for a film-based practice in 1995 versus a filmless practice in 1997. The following times were measured: (1) waiting room time, (2) technologist’s time of examination, (3) time to quality control, (4) radiology interpretation times, (5) radiology image and report delivery time, (6) total radiology turn-around time, (7) time to room the patient back in the UCC, and (8) time until the ordering physician views the film. Waiting room time was longer in 1997 (average time, 26∶47) versus 1995 (average time, 15∶54). The technologist’s examination completion time was approximately the same (1995 average time, 06∶12; 1997 average time, 05∶41). There was also a slight increase in the time of the technologist’s electronic verification or quality control in 1997 (average time, 7∶17) versus the film-based practice in 1995 (average time, 2∶35). However, radiology interpretation times dramatically improved (average time, 49∶38 in 1995 versus average time 13∶50 in 1997). There was also a decrease in image delivery times to the clinicians in 1997 (median, 53 minutes) versus the film based practice of 1995 (1 hour and 40 minutes). Reports were available with the images immediately upon completion by the radiologist in 1997, compared with a median time of 27 minutes in 1995. Importantly, patients were roomed back into the UCC examination rooms faster after the radiologic procedure in 1997 (average time, 13∶36) than they were in 1995 (29∶38). Finally, the ordering physicians viewed the diagnostic images and reports in dramatically less time in 1997 (median, 26 minutes) versus 1995 (median, 1 hour and 5 minutes). In conclusion, a filmless electronic imaging practice within our UCC greatly improved radiology image and report delivery times, as well as improved clinical efficiency.
An efficient environment for picture archiving and communications systems (PACS) in the radiology department and throughout a medical practice requires good hardware, good software, and integration of the information sources that exist in a radiology department and institution. This tutorial will describe some of the considerations in evaluating a PACS workstation, with a view to the hardware requirements, user interface designs and integration with the information systems.
We developed a system for delivering radiologic images and reports to desktop computers used for the electronic medical record (EMR). This system was used by both primary care physicians and specialists primarily in the out-patient setting. The system records all physician interactions with the application to a database. This usage information was then studied in order to understand the value and requirements of an application that could display radiology information (reports and images) on EMR workstations. In this report we describe some of the differences and similarities in usage patterns for the two physician groups. A very high percentage of physicians indicated that having image display capabilities on the workstations was very valuable.
PACS; Computerized patient record; electronic medical record