Bradley J. Erickson

Irreversible compression of 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.

An analytical look at the effects of compression on medical images

This article will take an analytical look at how lossy Joint Photographic Experts Group (JPEG) and wavelet image compression techniques affect medical image content. It begins with a brief explanation of how the JPEG and wavelet algorithms work, and describes in general terms what effect they can have on image quality (removal of noise, blurring, and artifacts). It then focuses more specifically on medical image diagnostic content and explains why subtle pathologies, that may be difficult for the human eye to discern because of low contrast, are generally very well preserved by these compression algorithms. By applying a wavelet decomposition to the whole image and to specific regions of interest (ROI), and by understanding how the lossy quantization step attenuates signals in those decomposition energy subbands, much can be learned about how tolerant various anatomical structures are to compression. High-frequency anatomical structures that have their energy represented by a few large coefficients (in the wavelet domain) will be well preserved, while, those structures with high frequency energy distributed over numerous smaller coefficients are the most vulnerable to compression. Digitized films showing subtle chest nodules, a subtle stress fracture, and CT and MR images are used to show these results.

Electronic Imaging Impact on Image and Report Turnaround Times

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.

Pituitary Dysfunction in Granulomatosis With Polyangiitis: The Mayo Clinic Experience

CONTEXTnPituitary involvement in granulomatosis with polyangiitis (GPA) has been described in case reports. The aim of this study was to describe the clinical presentation and outcomes of pituitary disease in patients with GPA evaluated at a tertiary referral center.nnnSETTINGnA retrospective review of patients with GPA-related pituitary disease seen at the Mayo Clinic in Rochester, Minnesota.nnnPATIENTSnA total of 637 patients with antineutrophil cytoplasmic antibodies-associated vasculitis were followed at our institution from 1996 through 2011. Eight patients (1.3%) with clinically confirmed pituitary involvement formed the basis of this study.nnnINTERVENTIONSnNone.nnnMEASUREMENTSnPituitary function was assessed with hormonal testing, including TSH, free T4, cortisol, ACTH, prolactin, FSH, LH, estradiol, T, IGF-1, and simultaneous serum and urine osmolalities.nnnRESULTSnSecondary hypogonadism and diabetes insipidus were the predominant manifestations of pituitary disease (87.5 and 75% of patients, respectively). All patients had abnormal pituitary imaging. A sellar mass with central cystic change and peripheral enhancement was the commonest imaging finding. Pituitary disease was managed with glucocorticoids in combination with cyclophosphamide or rituximab, achieving disease remission in all but one patient. However, permanent anterior pituitary dysfunction was noted in 63% of the patients. Diabetes insipidus was more often reversible, with resolution in 66.7% of the patients.nnnCONCLUSIONSnPituitary involvement in GPA is rare, but it needs to be recognized to avoid unnecessary biopsies of sellar lesions encountered in the context of GPA, and to minimize the risk of irreversible pituitary function loss by prompt implementation of definitive medical therapy for the vasculitis.

Triple-dose contrast/magnetization transfer suppressed imaging of 'non-enhancing' brain gliomas

PURPOSE: Triple-dose (TD) gadolinium contrast administration and magnetization transfer suppression (MTS) in brain magnetic resonance imaging (MRI) have proven to be useful for demonstrating additional enhancing lesions in some diseases. The purpose of this study was to determine if there is a subset of brain tumors that demonstrate contrast enhancement with TD and MTS that do not enhance with standard imaging and standard contrast dose.MATERIALS AND METHODS: Fifteen patients with either newly diagnosed primary brain tumor or brain tumor that had been followed for more than 2 years were enrolled. T1-weighted MTS images without IV contrast, with 0.1u2009mmol/kg without MTS (single-dose (SD) images), and with additional 0.2u2009mmol/kg gadolinium and MTS (‘TD/MTS’) were obtained.RESULTS: None of the patients had enhancement on SD images. Six patients had areas of enhancement on TD/MTS images (‘exact’ chi-squared p=0.017).CONCLUSION: A statistically significant increased rate of contrast enhancement was found on TD/MTS images in patients whose tumors did not enhance at single dose without MTS. It is possible that small areas of enhancement seen only with TD/MTS might represent areas of higher-grade tumor.

Ultrasound grayscale image compression with JPEG and wavelet techniques

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).

Clinician usage patterns of a desktop radiology information display application.

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.

An algorithm for automatic segmentation and classification of magnetic resonance brain images.

In this article, we describe the development and validation of an automatic algorithm to segment brain from extracranial tissues, and to classify intracranial tissues as cerebrospinal fluid (CSF), gray matter (GM), white matter (WM) or pathology. T1 weighted spin echo, dual echo fast spin echo (T2 weighted and proton density (PD) weighted images) and fast Fluid Attenuated Inversion Recovery (FLAIR) magentic resonance (MR) images were acquired ino 100 normal patients and 9 multiple sclerosis (MS) patients. One of the normal studies had synthesized MS-like lesions superimposed. This allowed precise measurement of the accuracy of the classification. The 9 MS patients were imaged twice in one week. The algorithm was applied to these data sets to measure reproducibility. The accuracy was measured based on the synthetic lesion images, where the true voxel class was known. Ninety-six percent of normal intradural tissue voxels (GM, WM, and CSF) were labeled correctly, and 94% of pathological tissues were labeled correctly. A low coefficient of variation (COV) was found (mean, 4.1%) for measurement of brain tissues and pathology when comparing MRI scans on the 9 patients. A totally automatic segmentation algorithm has been described which accurately and reproducibly segments and classifies intradural tissues based on both synthetic and actual images.

READS: a radiology-oriented electronic analysis and display station.

READS is a picture archiving and communications system (PACS) display program that is tailored to allow a radiologist to efficiently perform image review tasks. In this study, the image review process was observed and functional patterns were identified. These were used to define a design that was considered to represent the optimal balance of compromises for a low-cost review station that also allowed easy addition of new functionality. As a result, a program was designed and implemented that has been found to be acceptable for image review and for special image processing function development.

Electronic imaging and clinical implementation: work group approach at Mayo Clinic, Rochester.

Electronic imaging clinical implementation strategies and principles need to be developed as we move toward replacement of film-based radiology practices. During an 8-month period (1998 to 1999), an Electronic Imaging Clinical Implementation Work Group (EICIWG) was formed from sections of our department: Informatics Lab, Finance Committee, Management Section, Regional Practice Group, as well as several organ and image modality sections of the Department of Diagnostic Radiology. This group was formed to study and implement policies and strategies regarding implementation of electronic imaging into our practice. The following clinical practice issues were identified as key focus areas: (1) optimal electronic worklist organization; (2) how and when to link images with reports; (3) how to redistribute technical and professional relative value units (RVU); (4) how to facilitate future practice changes within our department regarding physical location and work redistribution; and (5) how to integrate off-campus imaging into on-campus work-flow. The EICIWG divided their efforts into two phases. Phase I consisted of Fact finding and review of current practice patterns and current economic models, as well as radiology consulting needs. Phase II involved the development of recommendations, policies, and strategies for reengineering the radiology department to maintain current practice goals and use electronic imaging to improve practice patterns. The EICIWG concluded that electronic images should only be released with a formal report, except in emergent situations. Electronic worklists should support and maintain the physical presence of radiologists in critical areas and direct imaging to targeted subspecialists when possible. Case tools should be developed and used in radiology and hospital information systems (RIS/HIS) to monitor a number of parameters, including professional and technical RVU data. As communications standards improve, proper staffing models must be developed to facilitate electronic on-campus and off-campus consultation.