Quantitative angiographic blood-flow measurement using pulsed intra-arterial injection.

A technique for quantitative blood-flow measurement using a novel pulsed injection of radiographic contrast agent is reported. A pressurized source of contrast agent is interrupted by a rotary valve at rates ranging from 1 to 30 Hz, producing well-defined boli at the end of a catheter. The position of these boli can be recorded by a digital radiographic system and analyzed by one of several previously reported techniques, to produce quantitative measurements of blood velocity and flow rate throughout the cardiac cycle. The contrast-agent flow wave form produced by the pulsed injector has been measured with an electromagnetic flow meter, for driving pressures ranging from 600 to 1500 kPa. Excellent modulation of the contrast agent is observed for injection frequencies up to 20 Hz, through catheters up to 100 cm in length. Preliminary in vitro angiographic flow measurements have been performed using an x-ray image intensifier, coupled to a linear photodiode array as the digital detector. Both constant flow and pulsatile human blood-flow wave forms were simulated within a 6.4-mm-diam straight tube and monitored with an electromagnetic flow meter. These experiments indicate that the pulsed injector can be used to provide estimates of arterial blood flow over the entire cardiac cycle (including reverse flow), to within about +/-11%, following injection of less than 10 ml of iodinated contrast agent.     

Power injection of peripherally inserted central catheters

PURPOSETo study the tolerance of peripherally inserted central catheters (PICCs) of varying sizes and materials to power injection of radiographic contrast agents.MATERIALS AND METHODSEight different models of silicone and five different models of polyurethane single-lumen PICCs were injected with increasing rates of iothalamate 60% with use of a power injector. Tolerated and bursting rates and pressures were recorded.RESULTSThere was a wide range of tolerated rates and pressures, depending on the inner and outer diameters of the catheters and on the catheter material. Silicone PICCs tolerated rates between 0.4 and 7.0 mL/sec and polyurethane PICCs tolerated rates between 0.6 and 10.2 mL/sec, depending on the specific catheter. The 5 Fr silicone PICCs and the 4 Fr and 5Fr polyurethane PICCs tested all tolerated rates greater than 4 mL/sec. Silicone catheters tolerated pressures between 107 and 184 psi, and polyurethane catheters tolerated pressures between l60 and 314 psi.CONCLUSIONSLarger single-lumen silicone and polyurethane PICCs may be suitable for power injection of contrast agents.     

超低对比剂剂量和流率在头颈部CT血管造影中的应用

目的:探讨双层探测器光谱CT在对比剂低耐受度患者头颈部CT血管造影（CTA）检查中应用超低对比剂剂量和流率扫描的优势。方法:收集对比剂低耐受度患者40例（观察组）,对比剂用量20 mL,流率2 mL/s,所得图像行40 keV单能谱重建;选取同期普通患者40例（对照组）,对比剂用量50 mL,流率5 mL/s;两组患者体质量均在70 kg以下。比较两组患者图像的主观评分、CT值、信号噪声比（SNR）、对比噪声比（CNR）和辐射剂量。结果:两组动脉显影图像主观评分比较差异无统计学意义（P>0.05）;在主动脉弓水平,观察组图像CT值、SNR和CNR均显著高于对照组（P<0.05）;在双侧颈总动脉分叉处及双侧大脑中动脉M1段,两组图像CT值比较差异无统计学意义（P>0.05）,但观察组图像SNR和CNR值均显著高于对照组（P<0.05）;观察组和对照组间容积CT剂量指数、剂量长度乘积、有效辐射剂量比较差异均无统计学意义（P>0.05）。结论:双层探测器光谱CT在低耐受度患者头颈CTA检查中应用超低对比剂剂量和流率的扫描方案可以满足诊断需求,降低了对比剂肾病、对比剂外渗等副作用风险,且未增加辐射剂量。     

Intravenous myocardial contrast echocardiography; recent advances

Until quite recently, contrast echocardiography for myocardial perfusion imaging has required the invasive direct injection of contrast agent into the coronary artery. Recent advances in ultrasonic technology and contrast agents have enabled myocardial contrast echocardiography with intra-venous injection of contrast agent in the clinical setting. This noninvasive technique has made the following clinical applications; left ventricular opacification, determination of the endocardium, enhancement of the Doppler flow signals, and detection of myocardial perfusion. Furthermore, in the near future, local drug delivery and pathology-specific targeted adherence of contrast agent may be added to the applications for the treatment. Intravenous myocardial contrast echocardiography is expected to have wide-ranging clinical potential.     

Dual assessment of kidney perfusion and pH by exploiting a dynamic CEST‐MRI approach in an acute kidney ischemia–reperfusion injury murine model

Several factors can lead to acute kidney injury, but damage following ischemia and reperfusion injuries is the main risk factor and usually develops into chronic disease. MRI has often been proposed as a method with which to assess renal function. It does so by measuring the renal perfusion of an injected Gd‐based contrast agent. The use of pH‐responsive agents as part of the CEST (chemical exchange saturation transfer)‐MRI technique has recently shown that pH homeostasis is also an important indicator of kidney functionality. However, there is still a need for methods that can provide more than one type of information following the injection of a single contrast agent for the characterization of renal function. Herein we propose, for the first time, dynamic CEST acquisition following iopamidol injection to quantify renal function by assessing both perfusion and pH homeostasis. The aim of this study is to assess renal functionality in a murine unilateral ischemia–reperfusion injury model at two time points (3 and 7 days) after acute kidney injury. The renal‐perfusion estimates measured with iopamidol were compared with those obtained with a gadolinium‐based agent, via a dynamic contrast enhanced (DCE)‐MRI approach, to validate the proposed method. Compared with the contralateral kidneys, the clamped ones showed a significant decrease in renal perfusion, as measured using the DCE‐MRI approach, which is consistent with reduced filtration capability. Dynamic CEST‐MRI findings provided similar results, indicating that the clamped kidneys displayed significantly reduced renal filtration that persisted up to 7 days after the damage. In addition, CEST‐MRI pH imaging showed that the clamped kidneys displayed significantly increased pH values, reflecting the disturbance to pH homeostasis. Our results demonstrate that a single CEST‐MRI contrast agent can provide multiple types of information related to renal function and can discern healthy kidneys from pathological ones by combining perfusion measurements with renal pH mapping.     

The influence of contrast agent injection on physiological flow in the circle of Willis

X-ray videodensitometry allows in vivo flow measurements from gradients in contrast agent concentration. However, the injection of contrast agent alters the flow to be measured. Here, the temporal, spatial, and inter-patient variability of the response to injection are examined. To this purpose, an injection is prescribed in the internal carotid in a 1D wave propagation model of the arterial circulation. Although the resulting effect of injection is constant over a cardiac cycle, the response does vary with the location within the cerebral circulation and the geometry of the circle of Willis. At the injection site, the injection partly suppresses the incoming blood flow, such that the distal flow is increased by approximately 10%. This corresponds to approximately 20% of the injection rate added to the blood flow during injection, depending on the vascular geometry. In the communicating arteries, the flow direction is reversed during injection. Since the measured flow is not equal to the physiological blood flow, the effect of injection should be taken into account when deriving the flow from travelling contrast agent.     

The use of Thiel embalmed human cadavers for retrograde injection and visualization of the lymphatic system

In order to provide an alternative for fresh frozen specimens to map the lymphatic system, the possibility of using Thiel embalmed specimens for this purpose was explored. The thoracic duct was used to investigate if retrograde injection of contrast agent was possible in Thiel embalmed specimens and to verify up to which diameter lymphatic vessels could be reconstructed and rendered in 3D, after CT scanning. 3D renderings were used for digital diameter measurement, to determine the smallest lymphatic diameter that could still be visualized on CT. Finally, the contrast agent concentration was adapted based on the findings during image reconstruction and 3D rendering. All Thiel embalmed specimens proved suitable for retrograde injection of contrast agent into the thoracic duct and all 3D renderings perfectly overlapped with the dissection pictures. The smallest diameter of contrast filled lymphatics that could be reconstructed and rendered in 3D was 0.23 mm. Increasing the concentration of barium sulfate from 10 to 50% reduced the postprocessing time needed to render a “clean” 3D structure, following automatic segmentation based on grey values, by 95%. The authors would recommend the use of Thiel embalmed specimens for mapping the lymphatic system, as these specimens do not show the rapid putrefaction that occurs in fresh frozen specimens, thus greatly facilitating experimental planning.     

4D micro-CT for cardiac and perfusion applications with view under sampling

Micro-CT is commonly used in preclinical studies to provide anatomical information. There is growing interest in obtaining functional measurements from 4D micro-CT. We report here strategies for 4D micro-CT with a focus on two applications: (i) cardiac imaging based on retrospective gating and (ii) pulmonary perfusion using multiple contrast injections/rotations paradigm. A dual source micro-CT system is used for image acquisition with a sampling rate of 20 projections per second. The cardiac micro-CT protocol involves the use of a liposomal blood pool contrast agent. Fast scanning of free breathing mice is achieved using retrospective gating. The ECG and respiratory signals are used to sort projections into ten cardiac phases. The pulmonary perfusion protocol uses a conventional contrast agent (Isovue 370) delivered by a micro-injector in four injections separated by 2 min intervals to allow for clearance. Each injection is synchronized with the rotation of the animal, and each of the four rotations is started with an angular offset of 22.5 from the starting angle of the previous rotation. Both cardiac and perfusion protocols result in an irregular angular distribution of projections that causes significant streaking artifacts in reconstructions when using traditional filtered backprojection (FBP) algorithms. The reconstruction involves the use of the point spread function of the micro-CT system for each time point, and the analysis of the distribution of the reconstructed data in the Fourier domain. This enables us to correct for angular inconsistencies via deconvolution and identify regions where data is missing. The missing regions are filled with data from a high quality but temporally averaged prior image reconstructed with all available projections. Simulations indicate that deconvolution successfully removes the streaking artifacts while preserving temporal information. 4D cardiac micro-CT in a mouse was performed with adequate image quality at isotropic voxel size of 88 μm and 10 ms temporal resolution. 4D pulmonary perfusion images were obtained in a mouse at 176 μm and 687 ms temporal resolution. Compared with FBP reconstruction, the streak reduction ratio is 70% and the contrast to noise ratio is 2.5 times greater in the deconvolved images. The radiation dose associated with the proposed methods is in the range of a typical micro-CT dose (0.17 Gy for the cardiac study and 0.21 Gy for the perfusion study). The low dose 4D micro-CT imaging presented here can be applied in high-throughput longitudinal studies in a wide range of applications, including drug safety and cardiopulmonary phenotyping.     

Maximum Flow Rates Possible During Power Injection Through Currently Available PICCs: An In-Vitro Study

PurposeCurrently available 4 French and 5 French PICCs were investigated to evaluate their possible application for contrast injection using power injectors. The study was performed using an in-vitro model to demonstrate the feasibility of using PICCs for contrast enhanced studies.Materials and MethodsAn evaluation of 24 catheter versions consisting of 4 French single lumen and 5 French dual lumen PICCs from 13 different manufacturers was conducted. Six of the catheter types were silicone and 18 catheter types were polyurethane. Ten catheters of each type were evaluated with five at full length and five trimmed to 40 cm. Using a silicone-based simulated superior vena cava model, the catheters were infused with 50 cc of intravenous contrast at each flow rate increment. Catheters were tested at increasing flow rates from 0.5 cc/second to 5 cc/second in 0.5 cc/second increments using a Percupump CT injector. Catheters that failed to rupture were then infused at 1 cc/second increments at flow rates from 5 cc/second to 17 cc/second using a MedRad Mark V™ power injector. Tolerated and bursting pressures were recorded.ResultsPolyurethane catheters ruptured at flow rates between 4–15.4 cc/second, with one catheter not rupturing at the maximum flow rate (17 cc/second). Silicone catheters ruptured at flow rates between 0.5–3.5 cc/second. Average rupture locations by type and length were at the extension leg/hub connection area on 5 of the PICCs, on the extension legs on 21 of the PICCs, on the catheter/hub connection on 4 PICCs, and on the proximal catheter on 16 of the PICCs.ConclusionThe low burst rates at which all silicone catheters ruptured suggest those catheters are not able to withstand typical flow rates used for CTA. Conversely, although a wide range of discrepancy is found in the polyurethane catheter burst pressures, many polyurethane catheters can tolerate relatively high flow rates without rupture. This suggests that they may be safely used for CTA with appropriate precautions and protocols in place.     

CT检查中对比剂注射部位及延迟扫描时间不同对奇静脉弓瓣显示的影响

目的 探讨CT检查时对比剂注射部位、延迟扫描时间不同对奇静脉弓瓣显示的影响。方法 回顾性研究。纳入2021年11月—2022年2月山东大学齐鲁医院德州医院562例行CT检查的患者的影像学资料。其中,头颈CTA检查276例,男165例、女111例,年龄10~84（62.3±10.9）岁,左肘注射对比剂18例,右肘注射258例;胸部增强CT检查286例,男179例、女107例,年龄11~85（61.7±11.3）岁,均为右肘注射对比剂。观察项目：（1）比较不同部位（左、右肘）注射对比剂时奇静脉弓瓣显示率的差异;（2）观察胸部增强CT检查患者的动脉期（短延迟扫描时间）与静脉期（长延迟扫描时间）奇静脉弓瓣显示率的差异。（3）观察奇静脉弓瓣的形态。结果 （1）左肘注射18例患者中有1例（1/18）显示奇静脉弓瓣,右肘注射的544例患者中245例（45.04%,245/544）显示奇静脉弓瓣,右肘注射显示率明显高于左肘注射,差异有统计学意义（χ²=11.03,P=0.001）。（2）胸部增强CT检查中,短延迟扫描时间奇静脉弓瓣显示率为28.32%（81/286）,高于长延迟扫描时间的显示率（2.10%,6/286）,差异有统计学意义（χ²=75.00,P<0.001）。（3）562例患者共显示奇静脉弓瓣246例,其中二叶瓣（224例）明显多于三叶瓣（22例）。二叶瓣的患者中,两个瓣叶的排列方向呈左右垂直奇静脉弓排列188例、呈上下垂直奇静脉弓排列36例。结论 CT检查中,右肘注射对比剂、短延迟扫描时间时奇静脉弓瓣的显示率更高。奇静脉弓瓣有二叶瓣和三叶瓣,其中二叶瓣更常见,其2个瓣叶的排列方向以左右垂直奇静脉弓为多。     

Evaluation of techniques for measuring negative intramuscular pressures in humans

Negative external pressure has been used previously in experiments on the blood circulation in humans and is currently being considered as a countermeasure to the musculoskeletal deconditioning which occurs during the exposure to microgravity. Intramuscular pressure (IMP) measurement is an important tool for determining the effectiveness of the transmission of negative pressure. Therefore two IMP techniques, a fibre optic transducer-tipped catheter and a fluid-filled teflon catheter with side holes, were evaluated using laboratory and human tests for measuring negative pressures. For the laboratory tests, both catheters were placed inside a lower leg negative pressure (LLNP) chamber and pressures of 0, –20, –50, –80, –100 and back to 0?mmHg were applied. Both catheters measured pressures equally and remained stable over 1 min at all pressure levels. When the teflon catheter was infused at rates commonly used for IMP recordings at normal atmospheric pressures, the drip rate at the catheter tip increased inversely with the magnitude of negative pressure. The cables and pressure tubings of the catheters within the LLNP chamber were not affected by the negative pressures. For tests in humans, the catheters were inserted side by side in the tibialis anterior muscle in eight legs of four human volunteers. The leg was placed in the LLNP chamber and pressures of 0, –20, –50, –80 and back to 0?mmHg were applied. The teflon catheter was used without infusion. Both catheters measured IMP similarly at rest and both remained stable over 1 min at all pressure levels; also the IMP during muscle contractions and immediately following contractions was similarly recorded by both catheters. We concluded that both catheter systems are suitable for recording negative pressures over a wide range. As is the case with recordings at normal atmospheric pressures, the fibre optic tranducer-tipped catheter system may be preferred when recording IMP in a negative pressure environment when complex limb movements are involved.     

Magnetic resonance imaging of the central nervous system in children with a new nonionic gadolinium contrast agent--gadoteridol injection (ProHance).

This article reports the results of clinical testing in pediatric patients of a new contrast agent, gadoteridol injection (ProHance), developed by Squibb Diagnostic as a nonionic gadolinium agent for use in magnetic resonance imaging (MRI). Thirteen children (four girls and nine boys) ranging in age from 10 to 18 years were enrolled in the study. The children had MR studies of the brain and/or spine with T1-weighted, T2-weighted, and postgadoteridol injection T1-weighted sequences. Five children had primary brain or spine neoplasms, three children had metastatic disease to the central nervous system, one child had a recurrent brain neoplasm and spinal canal metastasis, one child had an arteriovenous malformation, and two children were normal on the MRI studies. No minor or major reactions to gadoteridol injection developed in the 13 patients. Gadoteridol injection provided excellent delineation and enhancement of the arteriovenous malformation and all of the primary and secondary neoplasms of the central nervous system except for one case of a grade 1 glioma of the midbrain. Gadoteridol injection is a safe and excellent contrast agent for use in MRI.     

The assessment of tubal functional status by tubal perfusion pressure measurements

The measurement of tubal perfusion pressures (TPP) is a recent advance in the field of gynaecoradiology. Measurement of TPP involves a standardized technique using transcervically placed tubal catheters which is reviewed in detail. TPP assesses the functional status of the Fallopian tubes, i.e. their ability to permit pregnancy. Infertile patients with normal TPP demonstrated a higher pregnancy rate (10 out of 23) than patients with elevated TPP (four out of 24, P < 0.05). Analysis of patients who had undergone a laparoscopy as well as measurement of TPP suggest that elevated TPP are highly indicative of tubal endometriosis. Tubal catheterization with wireguides was successful in reducing mildly elevated TPP. The impact of this procedure on pregnancy rates is not known. The use of the gynaecoradiological techniques discussed in this paper has reduced the need for diagnostic laparoscopy at our centre by >60%. This was achieved without compromise in pregnancy rates and has resulted in a considerable reduction in cost.     

Temporal covariance analysis of first-pass contrast-enhanced myocardial magnetic resonance images

In this paper a temporal covariance method designed to analyze a Magnetic resonance (MR) image sequence of myocardial perfusion is presented. This method is used to map the first-pass transit of a contrast agent (Gd-chelates) through the heart. A map of bolus transit delay is constructed pixel by pixel corresponding to a myocardial reference using a temporal covariance measure. The resulting covariance map is a parametric image representing regions with different temporal dynamics. The proposed method is evaluated in 14 patients with coronary artery disease and eight healthy volunteers. Under rest and stress, covariance method is able to reveal a perfusion defect in stenosed coronary-artery-related myocardium. Furthermore, the method presents the advantage of its easy implementation and real-time parametric map construction.     

MRI in ocular drug delivery

Conventional pharmacokinetic methods for studying ocular drug delivery are invasive and cannot be conveniently applied to humans. The advancement of MRI technology has provided new opportunities in ocular drug-delivery research. MRI provides a means to non-invasively and continuously monitor ocular drug-delivery systems with a contrast agent or compound labeled with a contrast agent. It is a useful technique in pharmacokinetic studies, evaluation of drug-delivery methods, and drug-delivery device testing. Although the current status of the technology presents some major challenges to pharmaceutical research using MRI, it has a lot of potential. In the past decade, MRI has been used to examine ocular drug delivery via the subconjunctival route, intravitreal injection, intrascleral injection to the suprachoroidal space, episcleral and intravitreal implants, periocular injections, and ocular iontophoresis. In this review, the advantages and limitations of MRI in the study of ocular drug delivery are discussed. Different MR contrast agents and MRI techniques for ocular drug-delivery research are compared. Ocular drug-delivery studies using MRI are reviewed.     

Numerical analysis of forced injection of enzyme during thrombolysis

Numerical analysis was performed on the enzyme transport and the flow fields in order to predict the effectiveness of forced injection in thrombolytic therapy. The species and momentum transport equations were numerically solved for the case of uniform perfusion of enzyme into the fibrin clot, and the validity of our methods were verified. In order to predict the lysis efficiency of continuous and forced intermittent injections, enzyme perfusion and clot lysis were simulated for the different injection velocities and frequencies. Intermittent injection showed faster clot lysis compared to continuous perfusion, and lysis efficiency was increased as the injection velocity and period increased.     

Understanding the limitations of ultrasonic backscatter measurements from microbubble populations

Despite over ten years of in vitro investigations of ultrasound contrast agents, the level of understanding of their behaviour in ultrasound fields is limited. Several problems associated with these investigations, particular to the nature of contrast agents, are discussed. Using a commercial scanner the RF normalized backscatter of two different contrast agents (Definity and Quantison) was measured at different suspension concentrations and acoustic pressures. Both contrast agents scattered ultrasound nonlinearly and the backscatter showed a dependence on acoustic pressure. In order to assess the average behaviour of the agents across the range of acoustic pressures and microbubble concentrations the experimental data were fitted to a theoretically acceptable model using nonlinear regression analysis. The analysis showed that both the backscatter and the attenuation of the Quantison suspensions displayed a higher order of dependence on acoustic pressure than the Definity suspensions. It was also discovered that Quantison microbubbles did not demonstrate uniform behaviour across the acoustic pressure range. At lower acoustic pressures the behaviour could not follow a model similar to that which predicted the behaviour at higher acoustic pressures, which was mainly due to the fact that free bubbles were released in a fashion dependent on acoustic pressure. The fact that two different populations of scatterers exist in the same suspensions makes the assessment of the behaviour of the particular agent impossible with the high concentrations that are commonly used. Very low concentration suspensions whereby single scattering events can be monitored should be more useful. In conclusion, the approach of using high microbubble concentrations in order to investigate the properties of ultrasonic contrast agents is limited in that the results of such studies cannot be used to understand the behaviour of single microbubbles.     

胎肝血管的三维可视化建模及意义

目的　探讨胎肝血管三维模型的分割方法及其意义。 方法　采用分色和密度差金属造影剂对1例38周新鲜引产正常胎肝进行灌注并铸型,红色环氧树脂填充剂灌注腹主动脉（造影剂为氧化铅）,蓝色环氧树脂填充剂灌注下腔静脉、静脉导管、肝左静脉及肝右静脉外侧支（造影剂为二氧化钛）,紫色环氧树脂填充剂灌注肝中静脉（造影剂为氧化锌）,绿色环氧树脂填充剂灌注肝右静脉内侧支（造影剂为氧化铅）。然后行128层螺旋CT薄层扫描和Mimics软件重建胎肝三维模型。 结果 构建胎肝血管三维模型形态逼真、立体感强。调整mimics阈值间距由大逐步变小,可以有效分割出肝中静脉、肝静脉系及肝固有动脉等血管,能清晰地显示肝内多血管走行及分布情况。 结论　不同密度金属造影剂灌注分割胎肝内多血管方法简便可行,能够为研究者对胎肝血管发生发展及其移植术的研究提供理想技术支持。     

Increased fronto-temporal perfusion in bipolar disorder

OBJECTIVES: Previous imaging reports showed over-activation of fronto-limbic structures in bipolar patients, particularly in response to emotional stimuli. In this study, for the first time, we used perfusion weighted imaging (PWI) to analyze lobar cerebral blood volume (CBV) in bipolar disorder to further explore the vascular component to its pathophysiology. METHODS: Fourteen patients with DSM-IV bipolar disorder (mean age+/-SD=49.00+/-12.30 years; 6 males, 8 females) and 29 normal controls (mean age+/-SD=45.07+/-10.30 years; 13 males, 16 females) were studied. PWI images were obtained following intravenous injection of paramagnetic contrast agent (Gadolinium-DTPA), with a 1.5 T Siemens magnet using an echo-planar sequence. The contrast of enhancement (CE), was calculated pixel by pixel as the ratio of the maximum signal intensity drop during the passage of contrast agent (Sm) by the baseline pre-bolus signal intensity (So) (CE=Sm/So*100) for frontal, temporal, parietal, and occipital lobes, bilaterally, on two axial images. Higher CE values correspond to lower CBV and viceversa. RESULTS: Bipolar patients had significantly lower CE values in left frontal and temporal lobes (p=0.01 and p=0.03, respectively) and significantly inverse laterality index for frontal lobe (p=0.017) compared to normal controls. No significant correlations between CE measure and age or clinical variables were found (p>0.05). CONCLUSION: This study found increased left frontal and temporal CBV in bipolar disorder. Fronto-temporal hyper-perfusion may sustain over-activation of these structures during emotion modulation, which have been observed in patients with bipolar illness.     

Adherence of coagulase-negative staphylococci onto polyethylene catheters in vitro and in vivo: a study on the influence of various plasma proteins

Bacterial adherence on PE catheters inserted into the carotid artery of rabbits was assessed at 5, 30, and 240 min after injection with bacteria of five coagulase-negative staphylococci (CN Staph). These studies revealed that CN Staph adhere onto PE catheters 5 min after injection with bacteria. At 240 min after injection with bacteria almost all catheters were sterile, indicating that initially adherent bacteria on PE catheters disappear with time. EM studies revealed high numbers of platelets and leukocytes and many fibrin deposits on the surface of the PE catheter. In addition, the adherence of the five test strains on PE catheters was determined in vitro. In these in vitro studies the bacteria and catheters were pretreated with either fibrinogen, fibronectin, albumin or citrated whole plasma or the liquid adherence medium was supplemented with these proteins or the adherence assay was done in citrated whole plasma. The presence of proteins in the adherence medium or pretreatment of the catheter or bacteria with either fibronectin, albumin or whole citrated plasma markedly inhibited bacterial adherence. In contrast, pretreatment of bacteria or both bacteria and catheters with fibrinogen enhanced bacterial adherence suggesting the presence of ligands for fibrinogen on the cell surface of CN Staph.