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Biomedical subjects

E M James

Publications and source records attributed to E M James.

At least 19 recordsLinked to original sources
PubMed2002

The effects of irreversible JPEG compression on an automated algorithm for measuring carotid artery intima-media thickness from ultrasound images.

Our ultrasound practice has begun to investigate automated measurements of carotid artery intima-media thickness (IMT) as an indicator of subtle atherosclerosis. Since our clinical ultrasound images are irreversibly compressed, we investigated the effects of this compression on our IMT measurements. We obtained 10 ultrasound images of normal carotid arteries. These were compressed using JPEG to ratios of 5:1, 10:1, 15:1, 20:1, and 30:1. IMT measurements made from all compressed and uncompressed images were compared. For compression ratios ?10:1, IMT deviations between compressed and uncompressed images were ?0.03 mm. Higher than 10:1, the overall IMT deviations were small (0.01 +/- 0.04 mm), although one 25% deviation was measured. Comparison of other parameters yielded similar results. This initial study indicates that compression at 10:1 using baseline JPEG should have little effect on IMT measurements made using the current algorithm, and that compression to 20:1 or 30:1 may be feasible.

Algorithms↗
PubMed2001

Requirements for an enterprise digital image archive.

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.

Hospital Costs↗
PubMed2001

Application of atomic scale STEM techniques to the study of interfaces and defects in materials.

Incoherent imaging and analysis techniques in the scanning transmission electron microscope (STEM) provide the potential to map changes in structure, composition and bonding that occur at materials interfaces and defects on the fundamental atomic scale. Such comprehensive characterization capabilities permit a detailed analysis of the structure-property relationships of interfaces and defects to be performed. In this paper, we discuss the resolution limits of such techniques in the JEOL 2010F STEM/TEM operating both under standard conditions and at elevated temperatures. Examples of the use of such techniques to quantify the atomic scale defect chemistry at interfaces and defects in perovskite oxides, the growth and structure of II-VI and III-V quantum dots and the electronic structure of threading dislocations in GaN will also be presented.

Journal Article↗
PubMed2000

Electronic imaging system implementation at Mayo Clinic Rochester: downtime procedures and communication plans.

Electronic imaging system implementation is a challenging process and requires: (1) thorough procedure documentation and communication plans; (2) systematic evaluation of processes by all involved personnel groups; and (3) anticipation of potential issues and documentation of new problems as they occur. Our department is continuously improving procedures and communications as opportunities arise. A downtime procedure manual and a basic communication plan has given us a foundation to build upon and will help us to maintain appropriate levels of patient care throughout electronic system failures.

Computer Communication Networks↗
PubMed2000

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).

Image Processing, Computer-Assisted↗
PubMed2000

Transcranial-transdural real-time ultrasonography during transsphenoidal resection of a large pituitary tumor. Case report.

Ultrasonography has been used in neurosurgical operative procedures for several decades. The authors report the case of a large pituitary tumor that was subtotally resected using endoscopy via the transnasal-transsphenoidal approach, with the aid of transcranial real-time ultrasound. To our knowledge, this is the first reported case in which intraoperative transcranial-transdural real-time ultrasound was used to facilitate the resection of a skull base tumor.

Adenoma↗
PubMed2000

Redefined duplex ultrasonographic criteria for diagnosis of carotid artery stenosis.

OBJECTIVE: To evaluate duplex ultrasonographic criteria for the determination of 50% or more and 70% or more stenosis of the diameter of the internal carotid artery based on conventional angiography in order to align ultrasonographic diagnostic categories with current clinical management schemes. PATIENTS AND METHODS: Between January 1, 1995, and June 30, 1999, 915 patients underwent both carotid duplex ultrasonography and cerebral angiography within 30 days at Mayo Clinic, Rochester, Minn. Of these patients, 294 were excluded from this study because of occlusion of one or both of the internal carotid arteries or atypical flow characteristics. In the remaining 621 patients (61 % male, 39% female; mean age, 67.7 years [range, 14-88 years]), 1218 vessels were available for correlation. Several Doppler ultrasonographic velocity variables were compared with the angiographic findings by use of receiver operating characteristic curve analysis. The primary end point was verification of optimal ultrasonographic criteria to diagnose 70% or more internal carotid artery stenosis. The secondary end point was establishment of threshold values to detect stenosis of 50% or more. RESULTS: At angiography, 382 patients had internal carotid arteries with 70% or more stenosis. Peak systolic and end diastolic velocities of the internal carotid artery and internal carotid artery:common carotid artery peak systolic velocity ratios were measured. For an internal carotid artery stenosis of 70% or more, a peak systolic velocity of 230 cm/s or more resulted in a sensitivity of 86.4%, a specificity of 90.1%, a positive predictive value of 82.7%, a negative predictive value of 92.3%, and an accuracy of 88.8%. An end diastolic velocity of 70 cm/s or more and an internal carotid artery:common carotid artery ratio of 3.2 or more yielded similar values. For an internal carotid artery stenosis of 50% or more, a peak systolic velocity of 130 cm/s or more resulted in a sensitivity of 92.1 %, a specificity of 89.5%, a positive predictive value of 90.3%, a negative predictive value of 91.3%, and an overall accuracy of 90.8%. An internal carotid artery:common carotid artery ratio of 1.6 or more yielded similar values. CONCLUSION: In our ultrasonography laboratory, a carotid artery stenosis of 70% or more (for which carotid endarterectomy is typically recommended in symptomatic patients) is diagnosed reliably with the following duplex ultrasonographic criteria: a peak systolic velocity of 230 cm/s or more, an end diastolic velocity of 70 cm/s or more, or an internal carotid artery:common carotid artery ratio of 3.2 or more.

Adolescent↗
PubMed1999

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 workflow. 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 communication standards improve, proper staffing models must be developed to facilitate electronic on-campus and off-campus consultation.

Diagnostic Imaging↗
PubMed1997

Initial experience with soft-copy display of computed radiography images on three picture archive and communication systems.

We recently installed picture archive and communication systems (PACS) from three different vendors on our campus for evaluation. A major part of this evaluation involved assessing the capabilities of these systems for displaying computed radiography (CR) images for primary interpretation. The three PACS provided different functionality for CR image display in terms of availability of the proprietary Fuji CR image processing algorithms, availability of user-specified contrast look-up tables, and application of the processing at the time of CR image capture or image display. We found that the Fuji processing algorithms were important for printing film, but were not necessary for acceptable soft-copy display. Non-linear contrast processing produced superior results compared to simple linear processing (via standard window width and level controls). Display processing was best applied immediately prior to the display operation, as opposed to at the image capture time. This allows the display to be adjusted to demonstrate the full 10-bit range of the CR image, and also allows raw CR data (i.e. not optimized for any particular display device) to be stored in the long-term archive.

Algorithms↗
PubMed1996

The role of ultrasonography and automatic-needle biopsy in outpatient percutaneous liver biopsy.

The risk of complications from percutaneous liver biopsy is low, but discomfort is common and complications require hospitalization in approximately 4% of patients. The optimal method of performing these biopsies is unknown. The goal of our study was to determine whether the use of ultrasonography in the biopsy room immediately prior to or during the procedure would lessen the risk of complications and to compare the safety and efficacy in obtaining tissue by use of a Trucut needle versus an automatic biopsy needle. Between 1992 and 1994, 836 patients were entered into a randomized study (489 in Rochester, MN; 347 in Barcelona, Spain). Patients were randomized immediately prior to liver biopsy into four groups: Trucut needle, or automatic biopsy needle, and with or without ultrasonography. Fisher's Exact Test and a logistic regression model were also used to assess the effect of needle and ultrasonography on the odds for complications. The four biopsy groups were well-matched at entry with respect to age, sex, underlying liver disease, hemoglobin, prothrombin time, and platelet count. The use of ultrasound was associated with a decreased rate of hospitalization for pain, hypotension, or bleeding (2 vs. 9, P < .05). No difference in safety was found between the two types of needles. The number of passes needed to obtain specimens was similar for all four groups. The average length of the specimen was slightly greater with ultrasonographic-guided biopsies (1.7 mm vs. 1.6 mm, P < .05) and with biopsies obtained using the automatic biopsy needle when compared with the Trucut needle (1.7 mm vs. 1.5 mm, P < .05), but this did not seem to be clinically important. The addition of ultrasonography reduces complications in patients undergoing percutaneous liver biopsy. The type of needle appears to offer little difference in safety or yield of diagnostic tissue. The use of ultrasonography for guidance of percutaneous liver biopsy will lead to a lower rate of complications. The value of this benefit must be weighed against the added cost of ultrasonographic guidance.

Adolescent↗
PubMed1995

Blood flow velocity measurements: a comparison of 25 clinical ultrasonographic units.

A blood-mimicking flow phantom was used to evaluate the precision of velocity measurements acquired using 25 pulsed Doppler ultrasonographic units from four vendors. Measurements were made at four constant flow rates (12 to 50 cm/s peak velocity). The average standard deviation values of the peak and time-averaged velocities among all units and all flow rates were found to be 7 and 9% of the mean, respectively, while the corresponding values for a subgroup of 20 identical units were 5 and 8%. Considered in conjunction with other published data, this suggests that units should be calibrated to an institutional standard at the time of acceptance testing.

Blood Flow Velocity↗
PubMed1994

Carotid artery occlusion: positive predictive value of duplex sonography compared with arteriography.

PURPOSE: Duplex ultrasonography is an accurate, noninvasive method for diagnosing, characterizing, and classifying atherosclerotic stenoses of the extracranial carotid artery system. To date, however, no large series has studied the predictive value of duplex sonography in the diagnosis of carotid artery occlusion, an important consideration, given the marked difference in clinical treatment between patients with high-grade stenosis (surgical therapy) and those with occlusive disease (nonsurgical therapy). METHODS: We retrospectively reviewed 158 patients with 174 occluded carotid artery segments (examined over a 6 1/2-year period) to determine the predicative value of duplex sonography in differentiating carotid artery occlusion from high-grade stenosis. RESULTS: All patients had arteriographic correlation. Duplex ultrasonography had a positive predictive value of 92.5% (7.5% false-positive rate; 95% confidence interval, 3.6% to 11.4%) in establishing a diagnosis of carotid artery occlusion. Further analysis revealed no significant improvement in the false-positive rate with the addition of color Doppler flow imaging to high-resolution B-mode scanning and pulsed Doppler spectral analysis. Predictive value increased to 96.7% (95% confidence interval, 90.7% to 99.3%) over the last 2 years of the study, a statistically significant improvement. CONCLUSIONS: We believe that duplex ultrasonography is an acceptably accurate method for diagnosing carotid arterial occlusion in most patients. Arteriography should be reserved for patients with symptoms who are surgical candidates to identify those who may still have a surgically correctable high-grade stenosis.

Aged↗
PubMed1994

Diagnosis of acute deep venous thrombosis of the lower extremities: prospective evaluation of color Doppler flow imaging versus venography.

PURPOSE: To determine the value of color Doppler flow imaging in identification of deep venous thrombosis (DVT) of the femoropopliteal system without use of venous compression. MATERIALS AND METHODS: Color Doppler flow imaging was compared with venography in 103 lower extremities in 101 patients. Results of each examination were recorded as positive or negative for acute DVT or consistent with chronic DVT. RESULTS: Color Doppler flow imaging in 97 of 103 cases had a sensitivity of 95%, specificity of 99%, positive and negative predictive values of 95% and 99%, respectively, and accuracy of 98% in detection of acute DVT and was also helpful in differentiation of chronic from acute DVT. Color Doppler flow imaging prospectively identified six of eight patients with chronic DVT and correctly identified acute DVT in two patients with underlying chronic DVT. No results were false-positive for acute DVT in a patient with chronic DVT. CONCLUSION: Color Doppler flow imaging is complementary to compression ultrasonography in evaluation of suspected acute DVT and may be helpful in evaluation of suspected DVT in patients with previous or chronic DVT.

Acute Disease↗
PubMed1994

Intraoperative color Doppler sonography during renal artery revascularization.

Intraoperative color Doppler sonography is emerging as a useful procedure for evaluating renal arteries during transaortic renal endarterectomy or bypass grafting. Technical difficulties encountered during surgical renal revascularization, such as intimal defects or flaps, partial or complete thrombosis, and anastomotic stenosis of the renal artery, can be difficult to defect and evaluate. Intraoperative color Doppler sonography allows evaluation at a time when the problem is often correctable. We have been performing intraoperative sonographic studies of the renal artery for several years and have studied 151 vessels. In this pictorial essay, we present some of our observations on these cases.

Blood Vessel Prosthesis↗
PubMed1993

Portal vein thrombosis associated with pregnancy. A case report.

This report illustrates a case of portal vein thrombosis that developed in the second trimester of pregnancy. The patient did not have any of the known associations or predisposing factors for portal vein thrombosis or any past medical history of thrombosis or bleeding disorders. Antepartum and postpartum laboratory studies showed no evidence of a coagulation disorder; therefore, it seems that the sole cause of this thrombotic event was the hypercoagulable state of pregnancy.

Adult↗
PubMed1993

Optimizing technical success of renal revascularization: the impact of intraoperative color-flow duplex ultrasonography.

PURPOSE: Technical problems with renal revascularization can be difficult to detect, especially with end points of transaortic renal endarterectomies or anastomosis of bypass grafts to small distal renal arteries. If missed, such technical mishaps may not be recognized until after operation, when the chance for timely renal salvage has often been lost. METHODS: To evaluate the value of newer color-flow duplex imaging, we performed intraoperative ultrasonography on 35 patients undergoing revascularization of 64 renal arteries, 29 patients undergoing transaortic endarterectomy, and 6 undergoing bypass grafting. Most patients (24/35; 69%) underwent concomitant aortic reconstruction. Ninety-four percent had hypertension, whereas 66% had associated chronic renal insufficiency. RESULTS: Technical abnormalities prompting operative revision were identified during surgery in 10.9% of reconstructed main renal arteries (7/64). These included two occlusions, three intimal defects, and one extrinsic tissue band after endarterectomy plus one graft anastomotic stenosis. Color-flow imaging revealed all of them. Technical defects were also associated with higher peak-systolic flow velocities (mean 2.62 m/sec; range 2.00 to 3.50 m/sec) than normal-appearing arteries (mean 1.34 m/sec; range 0.40 to 2.50 m/sec) (p = 0.004). Eighty-six percent of the defects (6/7) were immediately correctable. One patient required nephrectomy. Postoperative angiograms revealed two asymptomatic small branch-vessel occlusions (3%). Compared with preoperative levels (p < 0.01), both hypertension and renal insufficiency improved initially. The clinical outcome of patients requiring intraoperative revision did not differ from that of patients undergoing normal intraoperative studies. CONCLUSION: Intraoperative color-flow duplex detection and surgical correction of technical problems with renal revascularization have enhanced our technical success and been associated with long-term results comparable to those of patients undergoing normal intraoperative studies.

Aged↗
PubMed1992

Prediagnostic malakoplakia presenting as a chronic inflammatory mass in the soft tissues of the neck.

Malakoplakia presenting in the head and neck is very rare. We present a case of an inflammatory mass in the neck, clinically mimicking actinomycosis in a 67-year-old man. Repeated culture of E. coli and histological and electron microscopic examination of biopsy material showed an infiltration of granular macrophages and intracellular gram negative bacilli, but no classical Michaelis-Gutmann bodies. The clinical and pathological findings and criteria for the diagnosis of malakoplakia are discussed.

Aged↗