Whole-body magnetic resonance angiography.

Vascular disease, whether it be atherosclerosis, inflammatory, or hereditary vasculitide, is a systemic disorder with disease in one territory predictive of disease in another. Despite this, current approaches focus on single-territory assessment ignoring the global burden of disease. Advances in MRI have enabled us to surmount previous limitations and expand our approach to such conditions with the ability to simultaneously assess the entirety of the arterial tree in a single examination, allowing a staging examination as it were, of the vascular health in its totality. This review will cover the acquisition technique, reporting, clinical utility, and current evidence base for such an approach.

A Review on the Hemodialysis Reliable Outflow (HeRO) Graft for Haemodialysis Vascular Access.

OBJECTIVES: With improved dialysis survival there are increasing numbers of patients who have exhausted definitive access options due to central venous stenosis and are maintaining dialysis on a central venous catheter. The Hemodialysis Reliable Outflow (HeRO) allows an alternative by providing a definitive access solution. The aim of this study is to systematically review the published outcomes of the HeRO graft and discuss the role in complex haemodialysis patients. METHODS: Electronic databases were searched for studies assessing the use of the HeRO graft for dialysis in accordance with PRISMA published up to December 31 2014. The primary outcomes for this study were 1-year primary and secondary patency rates. Secondary outcomes were rates of dialysis access associated steal syndrome, HeRO-related bacteraemia rates and rates of interventions. RESULTS: Following strict inclusion/exclusion criteria, eight studies including 409 patients were included in our review. Primary and secondary pooled patency rates in this complex cohort of dialysis patients were found to be 21.9% (9.6-37.2%) and 59.4% (39.4-78%). The rate of dialysis access associated steal syndrome was low at 6.3% (1-14.7%) as was the range of HeRO-related bacteraemia (0.13-0.7 events per 1000 days). CONCLUSIONS: This literature review shows that the HeRO graft is an acceptable option for complex dialysis patients who are catheter dependent. Owing to device availability, published data are predominantly North American and further longer-term studies in other populations may be necessary. In this challenging patient group, randomized controlled trials are required to allow comparisons with alternative access options.

Technical assessment of whole body angiography and cardiac function within a single MRI examination.

AIM: To evaluate a combined protocol for simultaneous cardiac MRI (CMR) and contrast-enhanced (CE) whole-body MR angiography (WB-MRA) techniques within a single examination. MATERIALS AND METHODS: Asymptomatic volunteers (n = 48) with low-moderate risk of cardiovascular disease (CVD) were recruited. The protocol was divided into four sections: (1) CMR of left ventricle (LV) structure and function; (2) CE-MRA of the head, neck, and thorax followed by the distal lower limbs; (3) CMR LV "late gadolinium enhancement" assessment; and (4) CE-MRA of the abdomen and pelvis followed by the proximal lower limbs. Multiple observers undertook the image analysis. RESULTS: For CMR, the mean ejection fraction (EF) was 67.3 ± 4.8% and mean left ventricular mass (LVM) was 100.3 ± 22.8 g. The intra-observer repeatability for EF ranged from 2.1-4.7% and from 9-12 g for LVM. Interobserver repeatability was 8.1% for EF and 19.1 g for LVM. No LV delayed myocardial enhancement was observed. For WB-MRA, some degree of luminal narrowing or stenosis was seen at 3.6% of the vessel segments (involving n = 29 of 48 volunteers) and interobserver radiological opinion was consistent in 96.7% of 1488 vessel segments assessed. CONCLUSION: Combined assessment of WB-MRA and CMR can be undertaken within a single examination on a clinical MRI system. The associated analysis techniques are repeatable and may be suitable for larger-scale cardiovascular MRI studies.

Experimental Assessment of Two Non-Contrast MRI Sequences Used for Computational Fluid Dynamics: Investigation of Consistency Between Techniques.

PURPOSE: Recent studies have noted a degree of variance between the geometries segmented by different groups from 3D medical images that are used in computational fluid dynamics (CFD) simulations of patient-specific cardiovascular systems. The aim of this study was to determine if the applied sequence of magnetic resonance imaging (MRI) also introduced observable variance in CFD results. METHODS: Using a series of phantoms MR images of vessels of known diameter were assessed for the time-of-flight and multi-echo data image combination sequences. Following this, patient images of arterio-venous fistulas were acquired using the same sequences. Comparisons of geometry were made using the phantom and patient images, and of wall shear stress quantities using the CFD results from the patient images. RESULTS: Phantom images showed deviations in diameter between 0 and 15% between the sequences, depending on vessel diameter. Patient images showed different geometrical features such as narrowings that were not present on both sequences. Distributions of wall shear stress (WSS) quantities differed from simulations between the geometries obtained from the sequences. CONCLUSION: In conclusion, choosing different MRI sequences resulted in slightly different geometries of the same anatomy, which led to compounded errors in WSS quantities from CFD simulation.

Suspected malignant cord compression - improving time to diagnosis via a 'hotline': a prospective audit.

The aim of the study was to achieve earlier diagnosis of malignant cord compression (MCC) using urgent magnetic resonance imaging (MRI) for selected patients. A comparison was carried out of the current prospective audit of 100 patients referred by a general practitioner or a consultant over 32 months with both a previous national Clinical Research and Audit Group (CRAG) prospective audit (324 cases of MCC) and an earlier retrospective audit of 104 patients referred with suspected MCC. A telephone hotline rapid-referral process for patients with known malignancy and new symptoms (severe nerve root pain +/- severe back pain) was designed. Patients were considered for urgent MRI after discussion with a senior clinician responsible for the hotline. Appropriate referrals were discussed with radiology and oncology ensuring timely MRI reporting and intervention. The main outcome measures are as follows: time from referral to diagnosis; time from the onset of symptoms to diagnosis; and mobility at diagnosis. A total of 50 patients (52%) of those scanned had either MCC (44) or malignant nerve root compression (6) compared with the earlier rate of 23 out of 104 patients (22%). Ten out of 44 MCC patients (23%) were paralysed at diagnosis, compared with 149 out of 324 (46%) in the CRAG audit. Time from reporting pain to diagnosis was 32 days compared with 89 days in the CRAG audit. Median time from referral to diagnosis was 1 day, again considerably shorter than the CRAG audit time of 15 days (interquartile (IQ) range: 3-66). In patients at risk of MCC, fast-track referral with rapid access to MRI reduces time between symptom onset and diagnosis, improves mobility at diagnosis and reduces the number of negative MRI scans.

Isolation and study of an acquired inhibitor of human coagulation factor V.

A coagulation Factor V inhibitor developed in a man 75 yr of age in association with an anaplastic malignancy and drug treatment (including the aminoglycoside antibiotic, gentamicin). The patient did not bleed abnormally, despite both surgical challenge and plasma Factor V activity of less than 1%. The inhibited plasma had grossly prolonged prothrombin and activated partial thromboplastin times, but a normal thrombin time. Mixing studies indicated progressive coagulation inhibition with normal plasma, but not with Factor V-deficient plasma, and reversal of coagulation inhibition by the addition of bovine Factor V to the patient's plasma. 1 ml of patient plasma inhibited the Factor V activity of 90 ml of normal human plasma. The inhibitor was isolated by sequential affinity chromatography on protein A-Sepharose and Factor V-Sepharose. The IgG isolate markedly inhibits the activity of prothrombinase assembled from purified Factors Xa and Va, calcium ion, and phospholipid vesicles, and partially inhibits prothrombinase assembled from purified Factor Xa, calcium ion, and normal platelets. The Factor V of platelets, however, appears relatively inaccessible to the antibody, inasmuch as platelets isolated from whole blood supplemented for 8 h with the antibody functioned normally with respect to platelet Factor V-mediated prothrombinase function. The absence of obvious hemorrhagic difficulties in the patient, the total inhibition of plasma Factor V by the inhibitor, and the apparent inaccessibility of platelet Factor V to the inhibitor specifically implicate platelet Factor V in the maintenance of hemostasis.

Review of Experimental Modelling in Vascular Access for Hemodialysis.

This paper reviews applications of experimental modelling in vascular access for hemodialysis. Different techniques that are used in in-vitro experiments are bulk pressure and flow rate measurements, Laser Doppler Velocimetry and Vector Doppler Ultrasound point velocity measurements, and whole-field measurements such as Particle Image Velocimetry, Ultrasound Imaging Velocimetry, Colour Doppler Ultrasound, and Planar Laser Induced Fluorescence. Of these methods, the ultrasound techniques can also be used in-vivo, to provide realistic boundary conditions to in-vitro experiments or numerical simulations. In the reviewed work, experimental modelling is mainly used to support computational models, but also in some cases as a tool on its own. It is concluded that, to further advance the utility of computational modelling in vascular access research, a rigorous verification and validation procedure should be adopted. Experimental modelling can play an important role in both in-vitro validation, and the quantification of the accuracy, uncertainty, and reproducibility of in-vivo measurement methods.

Whole-body cardiovascular MRI for the comparison of atherosclerotic burden and cardiac remodelling in healthy South Asian and European adults.

OBJECTIVE: To determine the feasibility of using whole-body cardiovascular MRI (WB-CVMR) to compare South Asians (SAs)-a population known to have a higher risk of cardiovascular disease (CVD) but paradoxically lower prevalence of peripheral arterial disease-and Western Europeans (WEs). METHODS: 19 SAs and 38 age-, gender- and body mass index-matched WEs were recruited. All were aged 40 years and over, free from CVD and with a 10-year risk of CVD <20% as assessed by the adult treatment panel (ATP) III risk score. WB-CVMR was performed, comprising a whole-body angiogram (WBA) and cardiac MR (CMR), on a 3-T MRI scanner (Magnetom(®) Trio; Siemens, Erlangen, Germany) following dual-phase injection of gadolinium-based contrast agent. A standardized atheroma score (SAS) was calculated from the WBA while indexed left ventricular mass and volumes were calculated from the CMR. RESULTS: SAs exhibited a significantly lower iliofemoral atheroma burden (regional SAS 0.0 ± 0.0 vs 1.9 ± 6.9, p = 0.048) and a trend towards lower overall atheroma burden (whole-body SAS 0.7 ± 0.8 vs 1.8 ± 2.3, p = 0.1). They had significantly lower indexed left ventricular mass (46.9 ± 11.8 vs 56.9 ± 13.4 ml m(-2), p = 0.008), end diastolic volume (63.9 ± 10.4 vs 75.2 ± 11.4 ml m(-2), p=0.001), end systolic volume (20.5 ± 6.1 vs 24.6 ± 6.8 ml m(-2), p = 0.03) and stroke volume (43.4 ± 6.6 vs 50.6 ± 7.9 ml m(-2), p = 0.001), but with no significant difference in ejection fraction, mass-volume ratio or global functioning index. These differences persisted after accounting for CVD risk factors. CONCLUSION: WB-CVMR can quantify cardiac and atheroma burden and can detect differences in these metrics between ethnic groups that, if validated, may suggest that the paradoxical high risk of CVD compared with PVD risk may be due to an adverse cardiac haemodynamic status incurred by the smaller heart rather than atherosclerosis. ADVANCES IN KNOWLEDGE: WB-CVMR can be used to stratify and compare disease between ethnicities.

The chemical-biological interface: developments in automated and miniaturised screening technology.

The rapidly changing developments in genomics and combinatorial chemistry, generating new drug targets and large numbers of compounds, have caused a revolution in high-throughput screening technologies. Key to this revolution has been the introduction of robotics and automation, together with new biological assay technologies (e.g., homogeneous time resolved fluorescence). With ever increasing workloads, together with economic and logistical constraints, miniaturisation is rapidly becoming essential for the future of high-throughput screening and combinatorial chemistry. This is evident from the introduction of high-density microtitre plates, small volume liquid handling robots and associated detection technology.

The squalestatins: novel inhibitors of squalene synthase. Enzyme inhibitory activities and in vivo evaluation of C1-modified analogues.

Squalestatin analogues modified in the C1 side chain were prepared and evaluated for their ability to inhibit rat liver microsomal and Candida squalene synthase (SQS) in vitro. While maintaining the 4,6-dimethyloctenoate or 4,6-dimethyloctanoate ester groups at C6, a number of modifications to the C1 side chain were well tolerated. However, in the absence of the C6 ester group, similar modifications to the C1 side chain caused substantial loss of activity. Compounds were also evaluated for their ability to inhibit cholesterol biosynthesis in vivo in rats and to reduce serum cholesterol levels in marmosets. These studies revealed that compounds with similar SQS inhibitory activities can possess different in vivo durations of action and lipid-lowering abilities.

High-throughput RT-PCR analysis of multiple transcripts using a microplate RNA isolation procedure.

We have developed a high-throughput, multiplex reverse transcription PCR (RTPCR) assay that is suitable for the analysis of medium-to low-copy cellular RNA transcripts from small numbers of cells (10(4)). High throughput was attained by utilizing microplate-based RNA extraction and RTPCR protocols, followed by PCR product visualization of a multiwelled agarose gel, stained with SYBR Green I dye. The transcriptional assay was unaffected by solvents (dimethyl sulfoxide and methanol) routinely used in high-throughput drug screens at concentrations required for compound solubilization. Furthermore, it has been used successfully for the investigation of differential mRNA expression levels of tumor necrosis factor alpha (TNF-alpha) and Interleukin-1 beta (IL-1 beta) in lipopolysaccharide (LPS)-stimulated THP-1 cells (a human monocytic cell line) and the identification of specific IL-1 beta transcriptional inhibitors.

Ultrasonic assessment of hemidiaphragmatic movement: an indirect method of evaluating mediastinal invasion in non-small cell lung cancer.

This preliminary study aimed to assess the potential value of diaphragmatic ultrasound (DUS) in evaluating phrenic nerve involvement indirectly, in the non-invasive pre-operative staging of mediastinal invasion in non-small cell lung cancer (NSCLC). A prospective study of 30 patients with NSCLC comparing the findings of diaphragmatic ultrasound, chest radiograph, computed tomography (CT) thorax and mediastinoscopy was performed. In all cases adequate quantitiative assessment of hemidiaphragmatic excursion was obtained. There was discordance in four of 30 patients between DUS and chest radiograph. Three of nine patients with extensive mediastinal disease on CT had abnormal DUS, and two of eight patients with indeterminate mediastinal disease on CT had abnormal DUS and were later found to be non-resectable. No abnormal cases of DUS were found in those cases with normal mediastinal CT. There was no clear relationship between the site, size and side of the primary tumour on CT, or its pleural or diaphragmatic contiguity, and hemidiaphragmatic excursion. There was concordance between DUS and mediastinoscopy in 17 of 21 patients. Two patients had normal mediastinoscopy and abnormal DUS but were not resectable at thoracotomy. No patient with abnormal DUS was resectable. DUS may be of potential value in the pre-operative staging of NSCLC and is therefore worthy of further evaluation.

Non spiral and spiral (helical) flow patterns in stenoses. In vitro observations using spin and gradient echo magnetic resonance imaging (MRI) and computational fluid dynamic modeling.

AIM: Physiological blood flow patterns are themselves poorly understood despite their impact on arterial disease. Stable spiral (helical) laminar flow (SLF) has been observed in normal subjects. The purpose of the present study is to develop a method of magnetic resonance (MR) flow pattern visualization and to analyze spiral and non-spiral flow patterns with and without luminal narrowing in vitro. The flow conditions were then modeled using computational fluid dynamics (Star-CD). METHODS: Laminar integrity was examined in a flow-rig using spin and gradient echo magnetic resonance imaging (MRI) in non-stenosed and stenosed conduits in the presence of non-spiral and spiral flow. RESULTS: No difference was observed in a non-stenosed conduit between non-spiral and spiral flow. In the presence of a stenosis spiral flow preserves flow velocity coherence whereas non-spiral flow increasingly lost coherence beginning proximal to the stenosis. Computational fluid dynamic modeling of the in vitro experiment showed marked differences between the 2 flow patterns. Non-spiral flow produced greater inwardly directed forces just beyond the stenosis and greater outward pressures at more distal sites. The near wall turbulent energy was up to 700% less with spiral flow over non-spiral flow beyond the stenosis. CONCLUSIONS: Spiral flow appears to offer clear flow profile stabilizing advantages over non-spiral flow, by significantly reducing the turbulence caused by a stenosis. Spiral flow also produces lower forces acting on the vessel wall.

Retinal imaging as a source of biomarkers for diagnosis, characterization and prognosis of chronic illness or long-term conditions.

The black void behind the pupil was optically impenetrable before the invention of the ophthalmoscope by von Helmholtz over 150 years ago. Advances in retinal imaging and image processing, especially over the past decade, have opened a route to another unexplored landscape, the retinal neurovascular architecture and the retinal ganglion pathways linking to the central nervous system beyond. Exploiting these research opportunities requires multidisciplinary teams to explore the interface sitting at the border between ophthalmology, neurology and computing science. It is from the detail and depth of retinal phenotyping that novel metrics and candidate biomarkers are likely to emerge. Confirmation that in vivo retinal neurovascular measures are predictive of microvascular change in the brain and other organs is likely to be a major area of research activity over the next decade. Unlocking this hidden potential within the retina requires integration of structural and functional data sets, that is, multimodal mapping and longitudinal studies spanning the natural history of the disease process. And with further advances in imaging, it is likely that this area of retinal research will remain active and clinically relevant for many years to come. Accordingly, this review looks at state-of-the-art retinal imaging and its application to diagnosis, characterization and prognosis of chronic illness or long-term conditions.

Quantitative analysis of cardiac left ventricular variables obtained by MRI at 3 T: a pre- and post-contrast comparison.

Short-axis cine images are acquired during cardiac MRI in order to determine variables of cardiac left ventricular (LV) function such as ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and LV mass. In cardiac perfusion assessments this imaging can be performed in the temporal window between first pass perfusion and the acquisition of delayed enhancement images in order to minimise overall scanning time. The objective of this study was to compare pre- and post-contrast short-axis LV variables of 15 healthy volunteers using a two-dimensional cardiac-gated segmented cine true fast imaging with steady state precession sequence and a 3.0 T MRI unit in order to determine the possible effects of contrast agent on the calculated cardiac function variables. Image analysis was carried out using semi-automated software. The calculated mean LV mass was lower when derived from the post-contrast images, relative to those derived pre-contrast (102 vs 108.1 g, p<0.0001). Small but systematic significant differences were also found between the mean pre- and post-contrast values of EF (69.4% vs 68.7%, p<0.05), EDV (142.4 vs 143.7 ml, p<0.05) and ESV (44.2 vs 45.5 ml, p<0.005), but no significant differences in SV were identified. This study has highlighted that contrast agent delivery can influence the numerical outcome of cardiac variables calculated from MRI and this was particularly noticeable for LV mass. This may have important implications for the correct interpretation of patient data in clinical studies where post-contrast images are used to calculate LV variables, since LV normal ranges have been traditionally derived from pre-contrast data sets.

Left ventricular hypertrophy: reduction of blood pressure already in the normal range further regresses left ventricular mass.

OBJECTIVE: Left ventricular hypertrophy (LVH) confers high cardiovascular risk. Regression of LVH reduces risk. Patients with blood pressure in the normal range and LVH are common. We investigated whether further reduction in blood pressure would further regress LVH. METHODS: 51 subjects with blood pressure in the normal range and echocardiographic left ventricular hypertrophy were randomly assigned to active treatment (antihypertensive medication) or placebo in a ratio of 2:1. The aim was to maintain office systolic blood pressure at 10 mm Hg less than baseline in the active arm and at baseline level in the placebo arm. Cardiac magnetic resonance imaging was used to measure change in left ventricular mass index over 12 months. RESULTS: 35 subjects completed the study (active 23: placebo 12). Average mean baseline office systolic blood pressure was 122 (SD 9) mm Hg in the active group and 124 (9) mm Hg in the placebo group (p = 0.646). The mean baseline left ventricular mass index was 65.88 (11.87) g/m(2) in the active group and 59.16 (11.13) g/m(2) in the placebo group (p = 0.114). The mean difference between baseline and end of study office systolic blood pressure was -9.33 (8.56) mm Hg in the active group and -0.08 (9.27) mm Hg in the placebo group (p = 0.007). The mean change in left ventricular mass index was -4.68 (7.31) g/m(2) in the active group and +1.97 (6.68) g/m(2) in the placebo group (p = 0.014). CONCLUSIONS: Reduction in office systolic blood pressure, already in the normal range, of approximately 9 mm Hg, leads to a reduction in left ventricular mass. Further work is required to see if this also leads to a reduction in cardiovascular events. TRIAL REGISTRATION NUMBER: ISRCTN48331653.

A clinical MRI investigation of the relationship between kidney volume measurements and renal function in patients with renovascular disease.

Recent improvements in MR image acquisition and post-processing techniques have allowed quantitative kidney volume measurements to be derived from patient studies. These morphological indices can provide "snapshot" assessments that may be related to kidney function. The study objective was to measure cortical and total kidney volumes in patients with renovascular disease (RVD) using contrast-enhanced MR angiography (CE-MRA) in order to assess the reproducibility of the technique and to investigate associations between volumes and renal function as measured by glomerular filtration rate (GFR) calculations. 50 patients with RVD were scanned using CE-MRA. Kidney lengths, volumes and renal artery stenoses (RAS) were evaluated, and GFR was calculated using clinical formulae and nuclear medicine isotope renography. Mean MRI kidney lengths were 10.3+/-0.2 cm, and mean MRI volumes were 74.9+/-3.6 cm3 (cortical) and 128.5+/-5.3 cm3 (total). Kidneys supplied by moderately stenosed arteries had enlarged lengths and volumes, whilst those supplied by severely stenosed arteries had significantly smaller lengths (p<0.001) and volumes (p<0.001). There was a clear association between MRI cortical volume and GFR (r = 0.74, p<0.001, n = 48), but less so between kidney length and GFR (r = 0.54, p<0.001, n = 48). For individual patients, left/right cortical volume differences were small provided that severe RAS was not present, but large left/right volume differences and a GFR reduction were noted when severe RAS was present. The cortical volume distribution provides a useful single-timepoint indication of kidney function as defined by GFR, with no additional data acquisition required other than that of standard CE-MRA examination.

Interaction of Candida albicans with neutrophils: effect of phenotypic changes in yeast cell-surface composition.

The susceptibility of four strains of Candida albicans to phagocytosis and intracellular killing by rabbit peritoneal neutrophils was investigated. Two of the strains, isolated from active infections, were known to synthesize a surface layer of mannoprotein fibrils in response to growth on 500 mm-galactose; the other strains, from asymptomatic carriers, lacked this capability. The presence of serum opsonins greatly enhanced phagocytosis of all four strains and, following opsonization, phagocytosis of an infective strain was equally rapid after growth on either 500 mm-galactose or 50 mm-glucose. In the absence of opsonins, galactose-grown infective strains were phagocytosed faster than either glucose-grown infective strains or galactose-grown carrier strains. These differences in phagocytic uptake were paralleled by differences in neutrophil chemiluminescence response. Intracellular killing of galactose-grown infective strains was only half that of glucose-grown infective strains or galactose-grown carrier strains after incubation for 60 min. Pretreatment of neutrophils with extracellular polymeric material, which contains the surface fibrils, completely inhibited intracellular killing. These results indicate that production of the fibrillar layer promotes yeast virulence by increasing resistance to intracellular killing, although it may enhance phagocytosis in locations where opsonic activity is poor.

Salpingitis isthmica nodosa: technical success and outcome of fluoroscopic transcervical fallopian tube recanalization.

PURPOSE: To evaluate the technical success and outcome of fallopian tube recanalization (FTR) in salpingitis isthmica nodosa (SIN). METHODS: SIN is a well-recognized pathological condition affecting the proximal fallopian tube and is associated with infertility and ectopic pregnancy. We reviewed the presentations, films, and case records of all patients attending for FTR for infertility from 1990 to 1994. Technical success and total, intrauterine, and ectopic pregnancy rates at follow-up were determined. RESULTS: SIN was observed in 22 of 349 (6%) patients. FTR was attempted in 34 tubes in these 22 patients. Technical success was achieved in 23 of 34 (68%) tubes affected by SIN. In 5 of the 11 failed recanalizations, failure was due to distal obstruction. At least one tube was patent on selective postprocedural salpingography in 17 of 22 (77%) patients. There were no recorded perforations or complications. At follow-up (mean 14 months), total, intrauterine, and ectopic pregnancy rates were 23%, 18%, and 4.5%, respectively. CONCLUSION: FTR in SIN is technically successful and, compared with previously reported results in unselected infertility patients, is associated with only a slightly less favorable intrauterine pregnancy rate and a comparable ectopic pregnancy rate. The findings of SIN at FTR should not discourage attempted fluoroscopic transcervical recanalization.