Shape accuracy of fiber optic sensing for medical devices characterized in bench experiments.

PURPOSE: Fiber Optic RealShape (FORS) is a new technology that visualizes the full three-dimensional shape of medical devices, such as catheters and guidewires, using an optical fiber embedded in the device. This three-dimensional shape provides guidance to clinicians during minimally invasive procedures, and enables intuitive navigation. The objective of this paper is to assess the accuracy of the FORS technology, as implemented in the current state-of-the-art Philips FORS system. The FORS system provides the shape of the entire device, including tip location and orientation. We consider all three aspects. METHODS: In bench experiments, we determined the accuracy of the location and orientation of the tip by displacing and rotating the fiber end, while allowing the rest of the fiber to change shape freely. To test the accuracy of the full shape, we have placed the fiber in a groove, which was accurately machined in a thick, stiff metal "path plate." We then compared the reconstructed shape with the known shape of the groove. RESULTS: The tip location is found with submillimeter accuracy, and the orientation is sensed with milliradian accuracy. The shape of a fiber in the path plate faithfully follows the known shape of the groove, with typical deviation less than 0.5 mm in the plane of the plate. Out of plane accuracy, perhaps slightly less relevant clinically, is more challenging, due to the influence of twist; yet even out of the plane, the deviation is only submillimeter. CONCLUSION: The technology achieves submillimeter precision and provides full three-dimensional shape, surpassing the reported precision of other navigation and tracking technologies, and therefore may potentially alleviate the need for fluoroscopy.

Non-invasive imaging through opaque scattering layers.

Non-invasive optical imaging techniques, such as optical coherence tomography, are essential diagnostic tools in many disciplines, from the life sciences to nanotechnology. However, present methods are not able to image through opaque layers that scatter all the incident light. Even a very thin layer of a scattering material can appear opaque and hide any objects behind it. Although great progress has been made recently with methods such as ghost imaging and wavefront shaping, present procedures are still invasive because they require either a detector or a nonlinear material to be placed behind the scattering layer. Here we report an optical method that allows non-invasive imaging of a fluorescent object that is completely hidden behind an opaque scattering layer. We illuminate the object with laser light that has passed through the scattering layer. We scan the angle of incidence of the laser beam and detect the total fluorescence of the object from the front. From the detected signal, we obtain the image of the hidden object using an iterative algorithm. As a proof of concept, we retrieve a detailed image of a fluorescent object, comparable in size (50 micrometres) to a typical human cell, hidden 6 millimetres behind an opaque optical diffuser, and an image of a complex biological sample enclosed between two opaque screens. This approach to non-invasive imaging through strongly scattering media can be generalized to other contrast mechanisms and geometries.

Frequency bandwidth of light focused through turbid media.

We study the effect of frequency detuning on light focused through turbid media. By shaping the wavefront of the incident beam light is focused through an opaque scattering layer. When detuning the laser we observe a gradual decrease of the focus intensity, while the position, size,and shape of the focus remain the same within experimental accuracy. The frequency dependence of the focus intensity follows a measured speckle correlation function. We support our experimental findings with calculations based on transport theory. Our results imply wavefront shaping methods can be generalized to allow focusing of optical pulses in turbid media.

[HIV retrospective study of the German Red Cross blood donation service in Germany]. / HIV-Lookback-Studie der DRK-Blutspendedienste in der BRD.

OBJECTIVE: It was tried to retrospectively identify HIV infections in recipients of transfusions from donors who were tested HIV positive at a subsequent donation. These lookback data were traced back to answer the following questions: 1. How many transfusion recipients were infected before the start of the routine HIV testing in 1985? 2. How great is the risk of HIV infections from infected but not yet HIV antibody-positive donors? 3. Furthermore, the transfusion of HIV-infected transfusion recipients was traced back to the involved donor to establish causality. DESIGN: Retrospective ('lookback') study. SETTING: HIV Study Group of the Red Cross Blood Banks of the Federal Republic of Germany. PARTICIPANTS: Preceding donations of HIV antibody-positive repeat donors were traced back to the transfusion recipients in order to establish their HIV antibody status. In a second lookback study, HIV-infected transfusion recipients and their corresponding donors were investigated after they had been reported to the blood bank as infected by transfusion-associated HIV. INTERVENTIONS: None. RESULTS: Recipients of 156 respectively 133 transfusions from repeat donors found to be Western blot-positive were investigated from 1985 to 1987 and from 1987 to 1992, respectively. About 50% of the recipients had died. About 40% of the recipients could not be examined, because they either were not available for testing or refused to be tested or because it was impossible to clarify the fate of the blood products. 25 HIV recipients were identified from 1981 to 1985, when routine HIV testing began. Nine transfusion-associated HIV infections were identified from 1985 to 1992. 25 million units of blood were prepared during this period. CONCLUSIONS: The risk of HIV transmission by tested transfusions is extremely rare (in the order of 1:1 million). The second lookback study suggests that in more than 50% of the blood recipients in whom HIV infection was attributed to transfusion, a causal relationship to an infected donor could not be established.

[HIV study of German Red Cross blood banks in Germany and Berlin]. / HIV-Studie der DRK-Blutspendedienste in der BRD und in Berlin.

In the HIV study of the German Red Cross blood banks the overall rate has remained constantly low, with less than two Western blot positive donors in 100,000 donors since 1987. However, the rate of HIV positivity tends to increase in male first time and in male repeat blood donors. Despite this fact, the overall rate stays constant since the number of young first time donors has decreased with increasing donations by women. Therefore the blood banks once again have to take newly intensified but also sophisticated measures to guarantee further as well a sufficient number of blood products as their HIV safety.

[Current data on the prevalence and epidemiology of HIV from the HIV study by the German Red Cross of West Germany]. / Aktuelle Daten zur Prävalenz und Epidemiologie des HIV aus der HIV-Studie der DRK-Blutspendedienste der BRD.

From the multicenter study of the Red Cross Blood Banks in the FRG HIV-antibody prevalences and incidences are documented since July 1985. Constantly low prevalences and incidences since 1987 of less than 2 Western blot (Wb)-positive donors and less than 1 Wb-positive donor per 100,000 donors respectively confirm our estimate of the rest risk of an HIV-infection by blood products of 1:500,000 to 1:3 million donations. In the epidemiologic details there seems to be a trend to an increase of the incidence in male repeat blood donors. The modes of HIV-infection in blood donors have changed to an increasing number of infections acquired in heterosexual contacts to persons at risk.

Risk of HIV infection from former blood donations of donors found to be HIV antibody-positive in blood bank routine testing. "Look-back" study in German Red Cross Blood Banks in the FRG.

Recipients of blood given by 52 repeat blood donors found to be positive by Western blot analysis for anti-HIV from April 1985 to December 1987, among a total of 1.6 million blood donors in the German Red Cross Blood Banks in the FRG, were investigated. Of 149 recipients identified, 76 (51%) had died. Ten recipients refused to be tested. Of those recipients who were tested at least 5 months after transfusion, 46 were HIV antibody negative and 17 were Western blot-positive. In 14 of the HIV antibody-positive recipients, transfusion was given during the period from 1982 to the begin of routine testing in 1985. Three recipients of HIV antibody-negative donations were subsequently identified as HIV positive. The blood had been donated a median of 3 months before HIV antibodies were detected in the donors. From a total of 3 million donations since testing has been introduced, the risk of HIV transmission in tested blood is 1:1 million in our donor population where the HIV antibody prevalence (in Western blot) is about 1 per 100,000 donations/donors.

[HIV study of the German Red Cross of West Germany 1985-1989: prevalence/incidence and mode of infection, retrospective studies]. / HIV-Studie der DRK-Blutspendedienste der BRD 1985-1989: Verlauf von Prävalenzen/Inzidenzen und Infektmodi, Look-back-Untersuchungen.

All German Red Cross Blood Banks in the FRG cooperate in a study on prevalence and epidemiology of HIV-antibodies in blood donors. The prevalences of 1 to 2 Western blot positive donors per 100,000 donors/donations quarterly since 1987 are constantly low. The measures undertaken to defer persons at risk seem to be effective. The "look back" data confirm the "rest risk" of HIV-infections by blood products in the FRG which is estimated to be about 1:1 million on the basis of the epidemiologic data. More than 90% of the donors infected are members of risk groups of heterosexual partners to persons at risk. Until today, in blood donors there is no indication of an increasing number of unaware heterosexually acquired HIV-infections.

Unsatisfactory specificities and sensitivities of six enzyme immunoassays for antibodies to hepatitis B core antigen.

To examine the consistency and comparability of anti-hepatitis B core antigen (anti-HBcAg) assays, four blood donation centers of the Red Cross in the Federal Republic of Germany tested 4,080 unselected blood donors with six different tests in parallel. Confirmation testing of reactive samples was done in the National Reference Center for Viral Hepatitis. Depending on the test kit used, 4.1 to 9.9% of serum samples were initially positive and 2.9 to 7.5% were repeatedly positive. Sixteen percent of serum samples were positive in at least one test but only three percent were positive in all six tests. Statistical analysis of frequency distribution of optical densities for each test suggested that there should be a correction of the cutoff values. This reduced the number of false-positive results by half, but a significant proportion of discrepant results could not be resolved. The lack of specificity and consistency requires cautious interpretation of isolated anti-HBcAg results in clinical specimens. Screening of predominantly anti-HBcAg-negative populations (e.g., blood donors) by the current anti-HBcAg test kits will almost necessarily give unsatisfactory results.

[Epidemiology of HIV in blood donors in West Germany]. / Epidemiologie des HIV bei Blutspendern in der Bundesrepublik Deutschland.

Of a total of 5.6 million blood donations by 1.6 million German Red Cross donors between July, 1985 and December, 1987 tested for HIV antibodies 210 were found to be positive in at least one Western blot. Calculated per quarter, the prevalence (for first-time donors) of 10 per 100,000 in 1985 decreased to 4 per 100,000 in 1986, while the incidence (for multiple donors) was a constant 2 per 100,000 for each quarter in 1987. This indicates that new HIV infections were rare in blood donors and there was no exponential increase. Further analysis revealed that over 90% of those with confirmed Western blot positive results were members of risk groups or their direct contacts. The age and sex distribution conformed to the known pattern for AIDS cases in the Federal Republic of Germany. The data demonstrate that there is at present no indication of a rapid spread of HIV infections transmitted heterosexually among blood donors.

[Prevalence of HIV antibodies in blood donors in the West Germany and West Berlin]. / Prävalenz von HIV-Antikörpern bei Blutspendern in der Bundesrepublik Deutschland und in West-Berlin.

Since 1985 all donor blood in the Federal Republic of Germany (FRG) and West Berlin (WB) have been routinely tested for HIV antibodies. The blood donor services of the German and Bavarian Red Cross have pooled their anti-HIV test data for the first year of operation (July 1985-June 1986) to obtain information on the prevalence of HIV antibodies in blood donors and in donated blood. Of 2.27 million units of blood, donated by 1.33 million donors, 218 were anti-HIV positive in the Western Blot Test, i.e. a prevalence rate of 10 per 100,000 donors. The prevalence was, as expected, higher in males than females. During the test period the anti-HIV prevalence fell, both as a total and in all subpopulations. In the second quarter of 1986 it had decreased to 6 per 100,000 donated units.

Pathogenesis of Rh immunization in primigravidas. Fetomaternal versus maternofetal bleeding.

Rh immunization occurring during a first pregnancy with no history of preceding abortion or transfusion may result when Rh incompatible fetal to maternal bleeding ensues early enough in the gestation to initiate a maternal immune response before parturition. Alternatively, the initial antigenic stimulus could be the consequence of maternal to fetal transfer of Rh-incompatible erythrocytes while the patient herself was in utero or at the time of her own delivery. These hypotheses were tested by 1) analysis of the blood group and Rh of 22 Rh-immunized primigravidas, their infants, and their own mothers; 2) comparison of the number of fetal cells in the maternal circulation during the antepartum period in 20 women at high risk for fetal to maternal bleeding with their matched controls; and 3) Rho (D) antibody determinations in 70 Rh-negative infants born to Rh-positive mothers. The results indicate that antepartum fetal to maternal bleeding is the usual cause of Rh immunization in primigravidas, and the Rh-negative woman with blood group A, B, or AB who gestates an ABO-compatible Rh-positive male is at highest risk. The antepartum use of anti-Rho (D) immune globulin has potential prophylactic value in this situation.

Hemalog-D and manual differential leukocyte counts. A laboratory comparison of results obtained with blood of hospitalized patients.

A clinical comparison of a new automated cytochemical leukocyte differential analyzer with standard 200-cell manual differential counts showed good agreement. The new apparatus (Hemalog-D) introduces a rapid, precise technic for the differentiation of peripheral-blood leukocytes.

Normal laboratory values for differential white cell counts established by manual and automated cytochemical methods (Hemalog D-TM).

The central 95 percentile estimates of the normal white cell types (as determined by a standard differential count) were calculated from 777 normal individuals. The results were divided into groups by age and sex and expressed both as percentages and as absolute numbers of cells.A similar survey was made using the prototype of a new automated differential counting method (Hemalog-D(TM)). The two sets of laboratory values showed no statistically significant differences regarding age or sex and were strikingly similar in most cell types with the exception of band and juvenile forms of granulocytes. As expected, the normal range using the manual technique was somewhat broader than that found with the automated method. In addition to being the first comparison of machine counts with visual differentials this study provides additional insight into the age distributions of normal cells.