Image quality assurance in the prostate, lung, colorectal, and ovarian cancer screening trial network of the National Lung Screening Trial.

The National Lung Screening Trial is evaluating the effectiveness of low-dose spiral CT and conventional chest X-ray as screening tests for persons who are at high risk for developing lung cancer. This multicenter trial requires quality assurance (QA) for the image quality and technical parameters of the scans. The electronic system described here helps manage the QA process. The system includes a workstation at each screening center that de-identifies the data, a DICOM storage service at the QA Coordinating Center, and Web-based systems for presenting images and QA evaluation forms to the QA radiologists. Quality assurance data are collated and analyzed by an independent statistical organization. We describe the design and implementation of this electronic QA system, emphasizing issues relating to data security and privacy, the various obstacles encountered in the installation of a common system at different participating screening centers, and the functional success of the system deployed.

Tools for managing image flow in the modality to clinical-image-review chain.

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.

Prospects for quantitative computed tomography imaging in the presence of foreign metal bodies using statistical image reconstruction.

X-ray computed tomography (CT) images of patients bearing metal intracavitary applicators or other metal foreign objects exhibit severe artifacts including streaks and aliasing. We have systematically evaluated via computer simulations the impact of scattered radiation, the polyenergetic spectrum, and measurement noise on the performance of three reconstruction algorithms: conventional filtered backprojection (FBP), deterministic iterative deblurring, and a new iterative algorithm, alternating minimization (AM), based on a CT detector model that includes noise, scatter, and polyenergetic spectra. Contrary to the dominant view of the literature, FBP streaking artifacts are due mostly to mismatches between FBP's simplified model of CT detector response and the physical process of signal acquisition. Artifacts on AM images are significantly mitigated as this algorithm substantially reduces detector-model mismatches. However, metal artifacts are reduced to acceptable levels only when prior knowledge of the metal object in the patient, including its pose, shape, and attenuation map, are used to constrain AM's iterations. AM image reconstruction, in combination with object-constrained CT to estimate the pose of metal objects in the patient, is a promising approach for effectively mitigating metal artifacts and making quantitative estimation of tissue attenuation coefficients a clinical possibility.

Observer study involving laser-digitized versus CCD-digitized images.

We compared laser- and CCD-digitized images for perceived image quality differences in a radiologist-observer study. Films of 50 two- and three-view studies (ankles, chests, c-spines, shoulders) were digitized on calibrated laser (Kodak Lumisys 75) and CCD (VIDAR SIERRA Plus) digitizers. Six radiologists independently compared digitized images on twin high-resolution monochrome monitors. Matching images were randomly presented on left/right monitors to support blinded comparisons. Observers scored image quality (for several diagnostic criteria) as "no different," left or right image "slightly" or "significantly" different. Of 7324 responses, 77.8% scored "no different" and 21.9% "slightly different" (5.9% favoring CCD, 16.0% favoring laser). In only 0.3% did observers score "significantly different." The Lumisys laser images were assessed as only slightly better than VIDAR SIERRA CCD images. Digitizer equipment-selection decisions can, therefore, be considered on the basis of price, reliability, support, ease-of-use, etc., rather than solely on the basis of image quality.

Planning and implementing image delivery to outpatient specialty clinical practices in a large medical center.

Softcopy image viewing using web-based technologies has been deployed to 3 specialty outpatient practices - Lung Center, Neurosurgery, Orthopedic Surgery - where films remain available. Physicians and staff use Philips Easyweb (a web-based image browser) and BJC HealthCare ClinDesk (a Java-based electronic patient record) clients in patient examination rooms and physician workrooms to retrieve images from a Mitra image server. Practice-specific planning and training preceded deployment; on-site training and support came with deployment; on-site and telephone support are available as needed. Softcopy viewing generally is accepted although a few physicians continue to use films. The unavailability of studies performed before the introduction of the image server remains an issue until the server builds a suitable archive. Softcopy-based clinical-image viewing can be supported with web-based technologies, but effective practice-specific planning, training, and technical support are crucial to successful deployment to those accepting softcopy image viewing.

Enhanced interfaces for web-based enterprise-wide image distribution.

Modern Web browsers support image distribution with two shortcomings: (1) image grayscale presentation at client workstations is often sub-optimal and generally inconsistent with the presentation state on diagnostic workstations and (2) an Electronic Patient Record (EPR) application usually cannot directly access images with an integrated viewer. We have modified our EPR and our Web-based image-distribution system to allow access to images from within the EPR. In addition, at the client workstation, a grayscale transformation is performed that consists of two components: a client-display-specific component based on the characteristic display function of the class of display system, and a modality-specific transformation that is downloaded with every image. The described techniques have been implemented in our institution and currently support enterprise-wide clinical image distribution. The effectiveness of the techniques is reviewed.