Establishing an international reference image database for research and development in medical image processing

INTRODUCTION

The lack of comparability of evaluation results is one of the major obstacles of research and development in Medical Image Processing (MIP). The main reason for that is the usage of different image datasets with different quality, size and Gold standard.

OBJECTIVES

Therefore, one of the goals of the Working Group on Medical Image Processing of the European Federation for Medical Informatics (EFMI WG MIP) is to develop first parts of a Reference Image Database.

METHODS

Kernel of the concept is to identify highly relevant medical problems with significant potential for improvement by MIP, and then to provide respective reference datasets. The EFMI WG MIP has primarily the role of a specifying group and an information broker, while the provider user relationships are defined by bilateral co-operation or license agreements.

RESULTS

An explorative database prototype has been implemented using the MySQL database software on the Web. Templates for provider user agreements have been worked out and already applied for own 'pre-RID-MIP' co-operations of the authors.

DISCUSSION AND CONCLUSION

First steps towards a comprehensive reference image database have been done. Issues like funding, motivation, management, provision of Gold standards and evaluation guidelines are to be solved. Due to the interest from research groups and industry the efforts will be continued.

Intensive treatment of coronary artery disease in diabetic patients in clinical practice: results of the MITRA study

Patients with diabetes are at high risk for the development of coronary artery disease and have a significantly impaired prognosis after ST-elevation myocardial infarction (STEMI) as compared with non-diabetic patients. The beneficial effect of pharmaceutical treatment for secondary prevention after STEMI is proven also for diabetics, but little is known about its use in clinical practice. Between June 1994 and December 2000, consecutive patients with STEMI, admitted to hospital within 24 h of symptoms onset, were enrolled into the multicenter MITRA registry in 61 hospitals in Germany. We examined whether there were differences in the frequencies of pharmaceutical secondary prevention after STEMI and in long-term outcomes between diabetics and nondiabetics in 8206 patients who had been discharged alive and followed for a mean period of 17 months. The prevalence of diabetes in 8206 patients discharged alive after acute STEMI was 18%. Diabetics were older and more often female, and more often already had prior myocardial infarction (MI) and stroke than non-diabetics. As chronic discharge medication, diabetics received aspirin and betablockers less often, but more often ACE inhibitors than non-diabetics. The mortality rate 17 months after STEMI was nearly twice as high in diabetics than in non-diabetics (19.1% vs. 10.4%, p<0.01 at univariate analysis; OR=1.50 and 95% CI 1.27-1.77 at multivariate analysis). The combined endpoint of death, MI and stroke occurred in 25.8% of diabetics, but only in 15.8% of non-diabetics ( p<0.01). Long-term treatment with aspirin, betablockers and ACE inhibitors in diabetics was associated with a significant reduction of mortality. Diabetics received intensive pharmaceutical therapy for secondary prevention significantly less often than non-diabetics, although the beneficial effects of this treatment were similar or even more pronounced as compared with non-diabetics. Diabetes was an independent predictor of increased mortality in follow-up after acute STEMI. Intensifying secondary prevention by a more frequent use of established pharmaceutical regimes might improve the prognosis of diabetics after STEMI and prevent cardiovascular and cerebrovascular events.

Comparison of different cardiac markers in monitoring percutaneous coronary interventions with frequent use of stents and gpIIbIIIa-antagonists

Studies from the early 1990s found elevations of creatine kinase (CK) and its isoform CK-MB in 5-30% of patients after PCI, indicating minor myocardial damage. Less is known about the influence of modern improved PCI-techniques on the frequency of elevated cardiac markers and the correlation between different commonly used markers, especially cardiac troponins. From 1997 to 2001, 1486 patients undergoing PCI during the regular working hours were included in the prospective "Ludwigshafen Infarctlet Registry". Myocardial infarction in the past 48 hours was an exclusion criterion. Clinical and procedural data were documented. Follow-up data were obtained from discharge up to one year. PCI-related elevations of troponin T were found in 18%, of total-CK in 11%, of CK-MB in 33% and of myoglobin in 23% of cases. The correlation between the different markers was poor. Compared with troponin T, other markers showed low sensitivity (total-CK 58%, CK-MB 27%, myoglobin 22%) and, especially total-CK, low specificity. Stenting, side branch occlusion or major dissection, complex lesion morphology, gpIIbIIIa-antagonist application, proximal stenosis and unstable angina were independent predictors of an elevated troponin T in multivariate analysis. Due to this weak correlation between more specific and sensitive troponins and the other markers, troponins are preferred in monitoring after PCI. In addition to lesion characteristics, particularly stenting is associated with an increased rate of elevated troponin.

Direkte MR-Arthrographie des Handgelenkes - Wertigkeit im Nachweis von Komplett- und Partialdefekten der intrinsischen Ligamente und des TFCC im Vergleich zur Arthroskopie

PURPOSE

To assess the value of two-compartment magnetic resonance (MR) wrist arthrography in comparison with diagnostic arthroscopy for the evaluation of defects of the triangular fibrocartilage complex (TFCC) and intrinsic ligaments in patients with refractory wrist pain. The direct MR arthrographies were evaluated following arthroscopic classification with consideration of complete and partial defects. The distinction between these types of lesions has clinical implications for treatment procedures such as cast immobilization, arthroscopic debridement, surgical repair or partial intercarpal arthrodesis.

MATERIALS AND METHODS

Seventy-five patients (25 female, 50 males, mean age 38.3 years) who suffered from refractory wrist pain without radiography evidence of carpal instability underwent two-compartment wrist MR arthrography. Under aseptic conditions a solution of gadopentate dimeglumine and iodinated contrast agent (concentration 2.5 mmol/l) was injected into the radiocarpal and midcarpal joints under fluoroscopy guidance. Using a scanner of 1.5 T field strength and a wrist-coil following sequences were acquired: coronary and sagittal T (1)-weighted spin-echo (SE) sequences (TR 500 ms, TE 25 ms, matrix 512 x 512.3 mm) and coronary fast low angle shot (FLASH) 3D sequences (TR 24 ms, TE 11 ms, matrix 256 x 256, 1.5 mm, flip angle 50 degrees). All patients underwent subsequent arthroscopy of the wrist. The direct MR arthrographies were evaluated retrospectively by two observers experienced in the diagnosis of wrist pathology. They were not aware of the clinicial, arthrographic and arthroscopic findings. Pathology of the scapholunate ligament was classified according to the guidelines of the German Society of Hand Surgery (DGH), lesions of the lunotriquetral ligament according to Hempfling and lesions of the TFCC according to Palmer.

RESULTS

Twenty-five complete and 47 partial defects were detected arthroscopically (TFCC: 21/20, scapholunate ligament: 3/18, lunotriquetral ligament: 1/9). The TFCC showed a higher prevalence for degenerative lesions (11 type 2C-lesions and 20 type 2A/B lesions) than for traumatic lesions (5 type 1A lesions, 5 type 1D lesions). For direct MR arthrography, the obtained sensitivities and specificities in assessing complete defects were 96 % and 99.6 % (T (1)-weighted SE) and 92 % and 100 % (FLASH 3D), respectively. For all partial defects, sensitivities and specificities were 68.1 % and 93.3 % (T (1)-weighted SE) and 63 % and 96.1 % (FLASH 3D), respectively. For depicting partial defects of the scapholunate ligament the T (1)-weighted SE sequence (83.3/95.5 %) was superior to the FLASH 3D sequence (64.7/96.6 %), p < 0.05. For the evaluation of the TFCC (T (1)-weighted SE: 65/94.4 %, FLASH 3D: 70/94.6 %) and the lunotriquetral ligament (T (1)-weighted SE: 44/89.4 %, FLASH 3D: 44 /96.7 %), direct MR arthrography showed an insufficient correlation with arthroscopy.

CONCLUSION

Direct MR arthrography proved to be of equal value compared with diagnostic arthroscopy in detecting complete defects of the intrinsic ligaments and the TFCC. The method has the potential of replacing diagnostic arthroscopy for the evaluation of the intrinsic ligaments and the TFCC. The T (1)-weighted SE sequence appeared to be superior to the FLASH 3D sequence in evaluating partial defects of the scapholunate ligament. Direct MR arthrography did not reliably detect partial defects of the TFCC and the lunotriquetral ligament.

[Too many heart catheter procedures in Germany ?]

BACKGROUND AND OBJECTIVE

Absolute numbers of cardiovascular procedures are higher in Germany as compared to other European countries. This fact is used as an argument for overuse. Therefore other indicators of an inappropriate use of these resources should be of interest.

PATIENTS AND METHODS

The relationship between diagnostic cardiac catheterisations and consequent revascularisation procedures were compared in 8 European countries. In addition the indication criteria for cardiac catheterisations were reviewed in a German registry of 205.581 consecutive inpatients.

RESULTS

Revascularisation procedures after diagnostic catheterisations in 8 countries range from 39,1 % to 57,9 %. Germany reaches 43,2 %. A relation between absolute numbers of diagnostic and percent subsequent revascularisation procedures does not exist. In a German registry the following indications for cardiac catheterisation could be identified: Acute Coronary Syndrome 22,9 %. Angina pectoris according to the Canadian Cardiac Society classification was present: CCS II/III in 80,3 %, CCS IV in 17,2 %. An exercise test was performed in 43 %. Final diagnoses were: significant coronary disease 69,5 %, exclusion of disease 9,4 %, lesions < 50 % 9 %, other cardiac disease 12,1 %.

CONCLUSION

Absolute numbers cannot be used as an indicator of overuse of cardiovascular procedures. Instead standards for data acquisition should be established on European, national and regional levels. In addition a validation procedure for criteria has to be developed in order to judge the appropriateness of indications for invasive cardiac procedures in different health care systems.

Small differences in non-fatal in-hospital reinfarctions complicating acute myocardial infarction as observed in current randomised controlled trials will not essentially influence long-term mortality

BACKGROUND

Recent randomized controlled trials (RCT) comparing different nonmechanical reperfusion strategies in patients with acute ST elevation myocardial infarction (AMI) (The GUSTO V, the ASSENT 3 and the HERO 2 trials) reported no differences in mortality, but lower nonfatal reinfarction rates in each best treatment arm during the hospital stay.

METHODS

We analyzed the prospective observational Maximal Individual The rapy in Acute Myocardial Infarction (MITRA) data base selecting AMI patients similar to the RCT patients, to determine whether the observed differences in reinfarction rates will have an influence on longterm mortality.

RESULTS

Out of 6737 patients included in MITRA between 1994 and 2000, 2109 (31%) fulfilled the selection criteria simulating the RCTs and were followed up for a median of 18 (quartiles: 16/22) months. Mortality at 1-year after discharge was 6.8% (95%CI: 2.3-11.3%) in patients with versus 4.4% (95%CI: 3.5-5.3%) in patients without a non-fatal reinfarction (absolute difference 2.4%, p = 0.04 by log rank test). Transferred to the results of the RCTs, this difference would require more than 1 million patients in each treatment arm of the RCTs to show significant differences in long-term mortality.

CONCLUSION

Non-fatal in-hospital reinfarctions were associated with a higher mortality during the 18 month follow-up in MITRA. However, because the observed differences in the rates of non-fatal in hospital reinfarctions between the treatment arms in the GUSTO V, the ASSENT 3 and the HERO 2 trials were very small, our data make it very improbable that they will result in lower 1-year mortality rates.

Two year follow-up in 643 patients with non-invasively unexplained syncope and therapy guided by electrophysiologic study

AIM

Although it has become standard practice to perform electrophysiologic studies in patients with unexplained syncope, limited information exists on prognosis after therapy guided by electrophysiologic studies.

METHODS AND RESULTS

Electrophysiologic studies were performed in 643 patients with unexplained syncope. Electrophysiologic studies revealed conduction abnormalities and tachyarrhythmias accounting for syncope in 35% of patients. An ejection fraction </= 40%, a PR-interval > 2 s and injury are helpful parameters in predicting a positive electrophysiologic study. There was no difference regarding cumulative 2-year survival rate after therapy guided by positive electrophysiologic study compared to patients with negative electrophysiologic study. The cumulative 2-year survival free-of-syncope rate was significantly higher after therapy guided by electrophysiologic study compared to patients with negative electrophysiologic findings-for patients with organic heart disease (71.3% vs 48.5%, p < 0.001) and patients without disease (91.3% vs. 65.2%, p < 0.001). Using a logistic regression model, a positive electrophysiologic study was associated with a favorable outcome; multiple syncopal events or organic heart disease were associated with an unfavorable outcome.

CONCLUSION

The cumulative overall 2-year surival free-of-syncope rate is significantly higher in patients after therapy guided by electrophysiologic study compared to patients with negative electrophysiologic findings.

Diagnosis, prescription, and prognosis of a bell-state filter by quantum process tomography

We apply the techniques of quantum process tomography to characterize errors and decoherence in a prototypical two-photon operation, a singlet-state filter. The quantum process tomography results indicate a large asymmetry in the process and also the required operation to correct for this asymmetry. We quantify residual errors and decoherence of the filtering operation after this modification.

Beneficial effects of human serum albumin on stability and functionality of alginate microcapsules fabricated in different ways

A key engineering challenge in designing microcapsules made from biocompatible alginate is maintaining adequate exchange of nutrients and oxygen between the entrapped cells and the environment, while simultaneously avoiding swelling and subsequent failure of the microcapsule. Approval for the use of alginate in pharmaceutical and/or biomedical applications also strictly requires that the components of the microcapsule material must meet the safety criteria of the ASTM and FDA. Incorporation of foetal calf serum (FCS) into the microcapsules for stabilization is not in accordance with the guidelines affirmed by these organizations. FCS should be substituted by microcapsule-stabilizing additives that are medically approved. In this communication, it is shown that 10% FCS can be replaced by 1% human serum albumin (i.e. by an agent for which medical approval is granted) without compromising effects on long-term in vitro stability. Furthermore, it is demonstrated that human serum albumin (HSA) significantly enhances cell survival and, particularly, insulin secretion of encapsulated rat islets over a time period of 3 weeks when incubated in culture medium. Thus, HSA-stabilized microcapsules made from UHV(Lam) alginate are apparently a promising system for immunoisolation of cells, particularly when alginate is cross-linked by injection of BaCl(2) crystals into the alginate droplets. Slight adjustments of the alginate concentration can tailor the microcapsule permeability to the released therapeutic factor.

Size of pancreatic islets of Langerhans: a key parameter for viability after cryopreservation

Large amounts and excellent viabilities of pancreatic islets are prerequisites for recent advances in islet transplantation. Cryopreservation has been shown to enlarge transplanted cell mass, but has been accompanied by reduced viability. In this study rat pancreatic islets were differentiated into small (<200 micro m), medium (200-400 micrometers) and large (>400 micrometers) categories and their susceptibilities to different freezing conditions were evaluated: concentration of cryoprotectant (0.7-3.1 M), equilibration (15 vs. 45 min, 22 degrees C vs. on ice) and post-thaw removal of cryoprotectant (15 vs. 30 min, stepwise vs. one-step). The most prominent finding was a negative correlation between islet size and viability observed in non-frozen islets to a minor degree (r=-0.44) and significantly enhanced after cryopreservation (r<-0.8). The concentration of cryoprotectant showed the most significant influence on viability affecting small, medium and large islets. Different techniques of equilibration with the cryoprotectant resulted in significant changes of islet viability of medium islets, whereas small and large islets were unaffected. For different techniques of removal of the cryoprotectant, no significant influence on viabilities was found. We conclude that large islets represented a highly susceptible population concerning damage due to cryopreservation.

Effectiveness of the glycoprotein IIb/IIIa antagonist abciximab during percutaneous coronary interventions (PCI) in clinical practice at a single high-volume center

OBJECTIVE

Randomized controlled trials (RCTs) showed that the glycoprotein (GP) IIb/IIIa antagonist abciximab is able to reduce ischemic complications during percutaneous transluminal coronary interventions (PCIs). Its effectiveness in daily clinical practice in unselected patients remains to be determined.

DESIGN, SETTING AND PATIENTS

From 7/1997 until 12/2000, 3310 PCIs were performed at the Heart Center Ludwigshafen. Out of them, 1076 (32.5%) patients were nonrandomly treated with a GP IIb/ IIa antagonist. Patients who were treated with abciximab were matched with patients not treated with abciximab. The matching procedure resulted in 590 pairs of patients.

RESULTS

Patients treated with abciximab were more likely to have a history of former PCI (13.7% versus 8.8%, p=0.008) or coronary artery bypass surgery (19.2% versus 12.8%, p=0.003). There were no differences in concomitant diseases, left ventricular function, number of vessels diseased or target vessel. However, patients treated with abciximab had a higher rate of more complex stenosis (> or =B2; 94.4% versus 80.7%, p<0.001) and a longer x-ray exposition (median 486 s versus 422 s, p<0.001). Treatment with abciximab was associated with a significantly lower incidence of the combined endpoint of death, reinfarction or stroke during the hospital stay (2.4% versus 4.4%, p=0.039). This was confirmed after adjustment for confounding parameters (p=0.034). There was no increase in the rate of severe bleeding in the abciximab group (p=0.347). After one year the rates for the combined endpoint were 8.5% in the control group and 6.2% in the abciximab group (univariate analysis, p=0.134; multivariate analysis, p=0.143).

CONCLUSION

Treatment with abciximab during PCI in daily clinical practice at a high volume center in patients with a high rate of acute coronary syndromes seems to be as effective as shown in RCTs.

Fabrication of homogeneously cross-linked, functional alginate microcapsules validated by NMR-, CLSM- and AFM-imaging

Cross-linked alginate microcapsules of sufficient mechanical strength can immunoisolate cells for the long-term treatment of hormone and other deficiency diseases in human beings. However, gelation of alginate by external Ba(2+) (or other divalent cations) produces non-homogeneous cross-linking of the polymeric mannuronic (M) and guluronic (G) acid chains. The stability of such microcapsules is rather limited. Here, we show that homogeneous cross-linking can be achieved by injecting BaCl(2) crystals into alginate droplets before they come into contact with external BaCl(2). The high effectiveness of this crystal gun method is demonstrated by confocal laser scanning microscopy and by advanced nuclear magnetic resonance imaging. Both techniques gave clear-cut evidence that homogeneous cross-linkage throughout the microcapsule is only obtained with simultaneous internal and external gelation. Atomic force microscopy showed a very smooth surface topography for microcapsules made by the crystal gun method, provided that excess Ba(2+) ions were removed immediately after gelation. In vitro experiments showed greatly suppressed swelling for crystal gun microcapsules. Even alginate extracted from Lessonia nigrescens (highly biocompatible) yielded microcapsules with long-term mechanical stability not hitherto possible. Encapsulation of rat islets, human monoclonal antibodies secreting hybridoma cells and murine mesenchymal stem cells transfected with cDNA encoding for bone morphogenetic protein (BMP-4) revealed that injection of BaCl(2) crystals has no adverse side effects on cell viability and function. However, the release of low-molecular weight factors (such as insulin) may be delayed when using alginate concentrations in the usual range.

[Reliability and general practice value of 2 rapid Streptococcus A tests]

Rapid streptococcal-A-antigen detection assays have good specificity (over 90 percent) but moderate sensitivity (between 80 and 90 percent), when the tests are compared with a standard throat culture. Contradictory results have been found for one of the more recent tests, the optical immune assay Strep A OIA MAX, while for 6 years, we have been using the immune assay Strep A Plus. Results of the optical immunoassay and the conventional immune assay Strep A Plus were compared in 65 patients with acute pharyngitis. A standard culture was used as reference and confirmed by enhanced broth culturing and nucleic acid hybridization assay (Gen-Probe) when the two detection assays produced contradictory results. While both assays were equally sensitive (78.3%), Strep A OIA MAX and Strep A Plus had a similar specificity of 95.2% and 100%, respectively. Four and nine steps were required for Strep A Plus and for Strep A OIA MAX test procedures, respectively with results being available in 4-5 min and in 9-10 min, respectively. We conclude that both rapid immunoassays have a similar reliability while the handling of the Strep A Plus is much simpler than the handling of the Strep A OIA MAX. Neither rapid immunoassays are sensitive enough to eliminate the need for backup cultures.

Influence of inhaled iloprost on transpulmonary gradient of big endothelin in patients with pulmonary hypertension

BACKGROUND

The pulmonary circulation is an important site for the production and clearance of endothelin (ET)-1, a potent vasoactive and mitogenic peptide. In healthy individuals, 40% to 50% of circulating ET-1 is removed on each passage through the lungs resulting in an arteriovenous ratio of <1, whereas many patients with pulmonary arterial hypertension (PAH) have ratios >1, indicating reduced clearance or increased release of endothelin. The influence of inhaled prostanoids on endothelin clearance is unknown.

METHODS AND RESULTS

In a prospective investigation, plasma concentrations of big endothelin-1 (big ET-1, Elisa) were measured in 15 patients with pulmonary hypertension undergoing right heart catheterization with iloprost inhalation (4 m, 11 f, aged 35 to 75 years, mean pulmonary arterial pressure (PAPm) 54+/-2.3 mm Hg, pulmonary vascular resistance (PVR) 1061+/-141 dyn x sec x cm(-5)). There was a significant transpulmonary gradient for big ET-1 with 31% +/-11% higher concentrations in the radial artery than in the pulmonary artery (P<0.001). After inhalation of iloprost a significant decrease in the AV-ratio from 1.31+/-0.11 to 0.92+/-0.06 (P<0.007) was observed. The pulmonary net release of 3.10+/-0.65 pmol/min big ET-1 at baseline decreased to -1.24+/-1.32 pmol/min (P=0.013) within 15 minutes indicating a restored balance. Patients under long-term treatment with iloprost (n=7) tended to have a lower net release and AV-ratio for big ET-1 than patients without pretreatment.

CONCLUSION

An increase in pulmonary clearance of big-ET could be a mechanism contributing to the beneficial effects of inhaled prostanoids in the treatment of PAH.