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Biomedical subjects

S Miller

Publications and source records attributed to S Miller.

At least 19 recordsLinked to original sources
PubMed2007

Stereolithographic reproduction of complex cardiac morphology based on high spatial resolution imaging.

BACKGROUND: Precise knowledge of cardiac anatomy is mandatory for diagnosis and treatment of congenital heart disease. Modern imaging techniques allow high resolution three-dimensional (3D) imaging of the heart and great vessels. In this study stereolithography was evaluated for 3D reconstructions of multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) data. METHODS: A plastinated heart specimen was scanned with MDCT and after segmentation a stereolithographic (STL) model was produced with laser sinter technique. After scanning the STL model with MDCT these data were compared with those of the original specimen after rigid registration using the iterative closest points algorithm (ICP). The two surfaces of the original specimen and STL model were matched and the symmetric mean distance was calculated. Additionally, the heart and great vessels of patients (age range 41 days-21 years) with congenital heart anomalies were imaged with MDCT (n=2) or free breathing steady, state free-precession MRI (n=3). STL models were produced from these datasets and the cardiac segments were analyzed by two independent observers. RESULTS: All cardiac structures of the heart specimen were reconstructed as a STL model within sub-millimeter resolution (mean surface distance 0.27+/-0.76 mm). Cardiac segments of the STL patient models were correctly analyzed by two independent observers compared to the original 3D datasets, echocardiography (n=5), x-ray angiography (n=5), and surgery (n=4). CONCLUSIONS: High resolution MDCT or MRI 3D datasets can be accurately reconstructed using laser sinter technique. Teaching, research and preoperative planning may be facilitated in the future using this technique.

Adolescent↗
PubMed2006

Sixty-four-MSCT in the characterization of porcine acute and subacute myocardial infarction: determination of transmurality in comparison to magnetic resonance imaging and histopathology.

OBJECTIVE: The aim of this study was to assess the accuracy of MSCT in characterizing myocardial infarction (MI) and, thereby, determine the extent of early perfusion defect (ED), microvascular obstruction (MO) and transmural depth of late enhancement (LE) in comparison to MRI and histology. MATERIALS AND METHODS: Seven pigs were studied with MSCT (Somatom Sensation 64) and MRI (Magnetom Sonata) a median 1 and 21 days following temporary occlusion of a diagonal branch and creation of small reperfused infarction. For depiction of ED, CT images were acquired in the early arterial phase and following 35 s; LE and MO were evaluated on images obtained at 3, 5, 10 and 15 min. Thereby, a bolus/low-flow contrast injection protocol was used. Triphenyltetrazolium-chloride (TTC) stain and histology were obtained. Volumes of enhancement patterns were assessed as percentage of the ventricle and compared by Bland-Altman analysis. Segmental co-localization and graded transmurality was evaluated with weighted-kappa-test. RESULTS: Close spatial agreement was observed for MRI-MO and MSCT-MO (bias=0.55; CI=-1.49 to 2.60 at 5 min MSCT), TTC and MSCT-LE (bias=-1.28; CI=-3.76 to 1.19) or MRI-LE and MSCT-LE (bias=-0.79; CI=-4.19 to 2.60). There was good segmental co-localization for MO (weighted kappa=0.93) and high agreement for transmural extent of TTC, MRI-LE and MSCT-LE (weighted kappa=0.84 TTC versus MSCT; 0.86 MRI versus MSCT). Arterial and 35s ED significantly underestimated infarct size and showed poor segmental or transmural agreement (weighted kappa=0.33; 0.44). CONCLUSIONS: MSCT late-scans not only reliably depict size of MO and LE in acute or subacute infarct phases but, moreover, allow for accurate determination of LE transmurality.

Analysis of Variance↗
PubMed2006

The C-terminus of alpha2-antiplasmin interacts with endothelial cells.

The serpin, alpha(2)-antiplasmin (alpha(2)AP), has an extended C-terminus relative to other inhibitors. This 51-residue region contains an RGD sequence; such sequences constitute a key recognition sequence for cell adhesion, mediated through integrins. In the present study, this sequence was expressed in Escherichia coli and its binding to endothelial cells and whether binding depends on the RGD sequence was investigated. Binding to the surface of human umbilical vein endothelial cells (HUVEC-C) was observed by flow cytometry and immunohistochemistry. Binding studies on immobilised cells showed specific and RGD-dependent binding of the peptides to HUVEC-C. The binding of the wild-type peptide to the HUVEC-C was significantly higher than that of a mutant peptide, in which RGD was replaced by SAA (P < 0.05, n = 4). Similarly, ethylenediaminetetraacetic acid decreased the binding of the wild-type peptide (P < 0.05, n = 4). The binding was competed out by full-length alpha(2)AP, fibronectin and anti-alpha(5)beta(1). This is the first evidence of binding of the C-terminus of alpha(2)AP to endothelial cells via its RGD sequence, with most but not all of the binding being integrin-mediated. We speculate that this interaction with alpha(2)AP may potentially play a role in the control of cellular fibrinolysis by regulating local plasmin activity on cell surfaces.

Binding, Competitive↗
PubMed2006

Kinetic and proteomic analyses of S-nitrosoglutathione-treated hexokinase A: consequences for cancer energy metabolism.

Mammalian hexokinase (HXK) is found at the outer mitochondrial membrane, exposed to mitochondrial oxygen- and nitrogen-radicals. Given the important role of this enzyme in metabolic pathways and diseases, the effect of S-nitrosoglutathione (GSNO) on HXK A structure and activity was studied. To focus on the catalytic domain, yeast HXK A was used because it has a significant homology to the mammalian domain that contains both the regulatory and catalytic sites. Biologically relevant [GSNO]/[HXK] caused a significant decrease in V(max) with glucose (but not with fructose), along with oxidation of 5 Met and nitration of 4 Tyr. Preincubation of HXK with glucose abrogated the effect of GSNO whereas fructose was ineffective. These results are interpreted by considering the tight binding of glucose to the enzyme as opposed to that of fructose. The segment comprised from amino acids 304 to 306 contained the most modifications. Given that this sequence is highly conserved in HXK from various species, a decline in activity is expected when a high-affinity substrate is presented. Considering that changes in primary structure are envisioned at high [GSNO]/[HXK] ratios, like those present under normal conditions, it could be hypothesized that the high concentration of hexokinase present in fast growing tumors may serve not only to sustain high glycolysis rates, but also to minimize protein damage that might result in activity decline, compromising energy metabolism.

Amino Acid Sequence↗
PubMed2006

Late myocardial enhancement assessed by 64-MSCT in reperfused porcine myocardial infarction: diagnostic accuracy of low-dose CT protocols in comparison with magnetic resonance imaging.

The purpose was to assess the practicability of low-dose CT imaging of late enhancement in acute infarction. Following temporary occlusion of the second diagonal branch, seven pigs were studied by multislice computed tomography (MSCT) and magnetic resonance imaging (MRI). Thus, 64-slice CT was performed at 3, 5, 10 and 15 min following the injection of contrast medium according to a bolus/low-flow protocol. Standard parameters of 120 kV and 800 mAs were compared with 80 kV and 400 mAs in various combinations. Infarct volumes were assessed as percentage of the ventricle for both MSCT and MR images. CT density values for viable and infarcted myocardium were obtained and image quality assessed. Mean infarct volume as measured by MRI was 12.33+/-7.06%. MSCT achieved best correlation of volumes at 5 and 10 min. Whilst lowering of tube current resulted in poor correlation, tube voltage did not affect accuracy of infarct measurement (r (2)=0.92 or 0.93 at 5 min, 800 mAs and 80 or 120 kV). In terms of image quality, greater image noise with 80 kV was compensated by significantly better contrast enhancement between viable and non-viable myocardium at lower voltage. Myocardial viability can accurately be assessed by MSCT at 80 kV, which ensures higher contrast for late enhancement and yields good correlation with MRI.

Analysis of Variance↗
PubMed2006

[Cardiac MR tagging: optimization of sequence parameters and comparison at 1.5 T and 3.0 T in a volunteer study].

PURPOSE: The aim of this study was the optimization of a gradient echo (GRE) MR tagging sequence at 3.0 T in comparison to 1.5 T in order to obtain the best image contrast between the myocardium, tag lines and blood signal. Theoretically expected improvements of signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were also calculated. MATERIALS AND METHODS: 14 healthy volunteers (8 male, 6 female; mean age 43.4 +/- 10.3 years) were scanned using a 3.0 T as well as a 1.5 T whole-body system. A GRE flash-2 D tagging sequence was evaluated (midventricular short axis view) by varying the flip angle (8 - 16 degrees ), slice thickness (4 - 8 mm; fixed flip angle 1.5/3.0 T: 12 degrees /8 degrees , tag size 8 mm) and tag size (4 - 8 mm, fixed flip angle 1.5/3.0 T: 12 degrees /8 degrees , slice thickness 6 mm). The field of view, acquisition time and temporal resolution (45 ms) were kept constant. Qualitative and quantitative image analysis was performed by calculating the SNR, CNR (tag) as well as the relative contrast between the myocardium and tag lines (RCMT). RESULTS: Based on individual comparison, the best imaging protocol was found at a slice thickness of 6 mm, tag size of 8 mm, optimized flip angle of 8 degrees (3.0 T) and 12 degrees (1.5 T), respectively. Compared to 1.5 T, a significantly higher overall image score was determined (mean +/- sd; 3.2 +/- 0.2 vs. 2.7 +/- 0.4) and a strong correlation between the CNR (tag) and RCMT for flip angle alpha and the slice thickness was found. A higher field strength resulted in an 80 % increase in the CNR (tag) compared to 1.5 T (mean 10.7/6.1). Furthermore, the SNR was improved by 35 % (mean 20.6/15.3) and the RCMT by 35 % (mean 0.47/0.35). CONCLUSION: Myocardial tagging at 3.0 T has shown superior image quality in comparison to 1.5 T due to a higher baseline SNR and an improved CNR as well as RCMT. The suppressed fading of the tags enables the accessibility to the diastolic phase of the cardiac cycle.

Adult↗
PubMed2006

[Recurrent transient ischaemic attacks in a patient with pansinusitis].

A 31-year-old woman presented with neurological deficits after an operation for sinusitis. The cranial MRI revealed multiple ischaemic lesions. Laboratory results showed a hypereosinophilia as well as elevated creatine kinase and troponin levels. The ECG implied ST elevations, the left ventricular ejection fraction was highly reduced and the cardiac MRI was suspicious for endomyocarditis. The cardiac biopsy demonstrated the findings of Loeffler's endocarditis. In conclusion the diagnosis of hypereosinophilic syndrome was made and identified as the cause of the neurological deficits.

Adult↗
PubMed2006

Incidental diagnosis of a left ventricular thrombus through novel magnetic resonance imaging technique in a patient undergoing coronary artery bypass grafting.

Stroke after cardiac surgery is a devastating complication. We report a case of incidental diagnosis of a left ventricular thrombus in a patient scheduled to undergo coronary artery bypass grafting. The preoperative diagnosis of an apical left ventricular thrombus was assessed by a novel, whole body MRI-angiography technique (TIMRA), which led to alteration of the operative approach as an additional thrombectomy was performed through an apical left ventriculotomy.

Coronary Artery Bypass↗
PubMed2006

[Cardiovascular whole-body MR imaging in patients with symptomatic peripheral arterial occlusive disease].

PURPOSE: To examine patients with peripheral-arterial-occlusive-disease (PAOD) for systemic effects associated with atherosclerosis using a comprehensive state-of-the-art whole-body MR examination protocol. The protocol comprises the assessment of the complete arterial vasculature (except coronary arteries), the brain, and the heart. MATERIALS AND METHODS: Multi-station whole-body 3D MR angiography was performed in sixty consecutive patients with clinical suspicion for PAOD at 1.5 T (Magnetom Avanto, Siemens, Erlangen, Germany). Functional and delayed enhancement cardiac images were acquired, as well as FLAIR images of the brain and TOF angiography of intracranial vessels. MR and DSA images were assessed by independent observers for atherosclerotic manifestations and other pathology. Sensitivity and specificity for the detection of vascular pathology was calculated for MR data using conventional DSA of the symptomatic region as standard-of-reference. RESULTS: Sensitivity and specificity for the detection of significant vascular stenosis (> 70 % luminal narrowing) was 94 % and 96 % (PPV 87 %, NPV 98 %). Significant microangiopathic tissue alterations (n = 7) and/or cerebral infarction (n = 18) were diagnosed in 23/60 patients. Thirty-eight of 60 patients presented with systolic left ventricular wall motion abnormalities. In 24 patients subendocardial or transmural delayed enhancement was detected in corresponding regions, indicating prior myocardial infarction. CONCLUSION: For patients with PAOD and suspected systemic atherosclerotic disease a comprehensive diagnosis of accompanying cardiovascular pathology and therefore staging of systemic atherosclerotic disease is feasible within one MR examination.

Aged↗
PubMed2006

Reliability and construct validity of the compatible MRI scoring system for evaluation of haemophilic knees and ankles of haemophilic children. Expert MRI working group of the international prophylaxis study group.

We tested the reliability and construct validity of the Compatible magnetic resonance imaging (MRI) scale for the evaluation of haemophilic knees and ankles and compared the diagnostic performance of MRI and plain film radiographs. Sagittal and coronal gradient-echo 1.5-T MR images of knees (n=22) and ankles (n=23) were obtained from boys (age range 4-16 years; mean 11 years) in two centres (Toronto, n=26; Europe, n=19). The MR images were independently read by four blinded radiologists on two occasions. Number of previous joint bleedings and laboratory level of severity of haemophilia were the reference standards for imaging assessment. Both components of the MRI scale demonstrated high inter- and intrareader intraclass correlation coefficients (progressive (P) scale, 0.91 and 0.94; additive (A) scale, 0.81 and 0.92 respectively). The correlation between the osteochondral domain of the MRI scale and patient's age was moderate. Otherwise, correlations between A- and P-scales and clinical laboratory measurements were weak. The areas under the curve (AUCs) used for discrimination of disease severity were similar for the A- and P-scales (AUCs used for mild disease, A-scale, 0.72+/-0.07; P-scale, 0.69+/-0.08; P=0.23; AUCs for severe disease, A-scale, 0.93+/-0.05; P-scale, 0.87+/-0.08; P=0.05). No differences were noted between the AUCs of the MRI and radiographic scales used for discrimination of late osteoarticular changes; MRI scales performed better for discrimination of early changes. In conclusion, both MRI scales demonstrated excellent reliability, poor convergent validity, and moderate and excellent validity for discrimination of mild and severe diseases respectively. Compared with radiographic scores, the MRI scales performed better for discrimination of early osteoarticular changes.

Adolescent↗
PubMed2006

First aid for obstetric haemorrhage: the pilot study of the non-pneumatic anti-shock garment in Egypt.

OBJECTIVE: To compare the effect of non-pneumatic anti-shock garment (NASG) on blood loss from obstetric haemorrhage with standard management of obstetric haemorrhage. DESIGN: Observational study of consecutive obstetric haemorrhage cases before and after introduction of the NASG. SETTING: Four tertiary care maternity facilities in Egypt. SAMPLE: The sample consisted of women with obstetric haemorrhage and signs of shock and the entry criteria were: >750 mL of blood loss and either pulse of >100 beats per minute or systolic blood pressure of <100 mmHg. A total of 158 women were in the preintervention group and 206 in the postintervention group. METHODS: All the women with haemorrhage meeting the eligibility criteria were treated according to the standard protocol for 4 months (May-August 2004); blood loss was measured and recorded. The NASG was then introduced, and all the women meeting the eligibility criteria were treated according to the standard haemorrhage protocol plus the NASG for 4 months (September-December 2004). MAIN OUTCOME MEASURES: Measured blood loss collected in a closed-end, graduated, plastic, under buttocks collection drape. RESULTS: Median measured blood loss in the drape following study entry was 50% lower in those treated with the NASG (250 versus 500 mL, P < 0.001). There was also a non-statistically significant decrease in morbidity and mortality. CONCLUSIONS: This is the first comparative study of the NASG with a standard obstetric haemorrhage treatment protocol. The NASG shows promise for management of obstetric haemorrhage, particularly in lower resource settings. Larger studies will be needed to determine if the NASG contributes to statistically significant decreases in morbidity and mortality.

Adult↗
PubMed2006

Modern tennis rackets, balls, and surfaces.

Modern rackets have facilitated a change in playing style from one of technique to one characterised by power and spin. The combination of the increased stiffness of modern rackets and the tendency for tennis balls to have become harder has led to an increased shock transmission from the racket to the player, which is probably a major contributor to tennis elbow. The paucity of tennis specific research on shoes and surfaces makes it difficult to link their characteristics with lower limb injury, although, as their interaction directly affects the magnitude of the forces to which the player is exposed, such a link seems reasonable.

Equipment Design↗
PubMed2006

[Ambivalent bacteriophages of different species active on Escherichia coli K12 and Salmonella sps. strains].

A study was made of several bacteriophages (including phages U2 and LB related to T-even phages of Escherichia coli) that grow both on E. coli K12 and on some Salmonella strains. Such phages were termed ambivalent. T-even ambivalent phages (U2 and LB) are rare and have a limited number of hosts among Salmonella strains. U2 and LB are similar to canonical E. coli-specific T-even phages in morphological type and size of the phage particle and in reaction with specific anti-T4 serum. Phages U2 and LB have identical sets of structural proteins, some of which are similar in size to structural proteins of phages T2 and T4. DNA restriction patterns of phages U2 and LB differ from each other and from those of T2 and T4. Still, DNAs of all four phages have considerable homology. Unexpectedly, phages U2 and LB grown on Salmonella bungori were unstable during centrifugation in a CsCl gradient. Ambivalent bacteriophages were found in species other than T-even phages and were similar in morphotype to lambdoid and other E. coli phages. One of the ambivalent phages was highly similar to well-known Felix01, which is specific for Salmonella. Ambivalent phages can be used to develop a new set for phage typing in Salmonella. An obvious advantage is that ambivalent phages can be reproduced in the E. coli K12 laboratory strain, which does not produce active temperate phages. Consequently, the resulting typing phage preparation is devoid of an admixture of temperate phages, which are common in Salmonella. The presence of temperate phages in phage-typing preparations may cause false-positive results in identifying specific Salmonella strains isolated from the environment or salmonellosis patients. Ambivalent phages are potentially useful for phage therapy and prevention of salmonellosis in humans and animals.

Antibodies↗
PubMed2005

Laparoscopic colon surgery performed safely by general surgeons in a community hospital: a review of 154 consecutive cases.

BACKGROUND: The primary end point of this study was documentation of the feasibility, safety, and benefits of laparoscopic colon resection (LCR) performed by general surgeons in a community hospital. METHODS: The charts of 154 patients who underwent LCR between March 1998 and August 2003 by a group of three surgeons working in a community hospital were reviewed. Data extracted from the charts included patients' demographics, surgical indications and procedures, conversion rate, history, operative time, postoperative recovery time, and complication rates. RESULTS: Of the 154 patients, 70 were men. The mean age of the patients was 60 years. Overall, 62% of the patients had a history of prior abdominal surgery. In the majority of cases (77%), LCR was performed for benign disease. Segmental resection involving the left colon was performed for 122 patients, and right hemicolectomy was performed for 32 patients. The rates of conversion were 9.6% for open surgery and 12% for diverticulitis (n = 83). For LCR, the median operative time was 120 min, and the median hospital stay was 5 days. The complication rate was 21.6% for LCR, and the mortality rate was 2.1%. CONCLUSION: The outcomes for LCR performed by a team of general surgeons working together in a community hospital are similar to the historical results from academic health science centers.

Adult↗
PubMed2005

Visual impairment in elderly patients with hip fracture: causes and associations.

AIMS: To evaluate the current visual status and ophthalmic history of a sample of elderly patients with fractured neck of femur and to study the relationship between visual status and demographic factors. METHODS: A four-centre study of all patients admitted to hospital with fractured neck of femur. The setting was two district (Ayr, Dunfermline) and two teaching (Glasgow, Dundee) hospitals in Scotland. The study examined 537 patients aged 65 years and over admitted with acute fractured neck of femur to hospital. RESULTS: Bilateral visual impairment (binocular visual acuity worse than 6/12) was found in 239 of 518 patients (46%). Of this group, the principal causes for visual deficit were untreated cataract (49%), macular degeneration (21%), uncorrected refractive error (17%), and glaucoma (3%). The visually impaired group were more likely to have symptomatic visual complaints (58 vs 26%), however, were less likely to be under optometric care (71 vs 85%). A higher proportion of the group with visual impairment lived in areas of social deprivation (40 vs 26%). CONCLUSIONS: Patients with fractured neck of femur represent a frail elderly group that have poorer vision than that documented in any other elderly population. The visual defect was potentially remediable in the majority of cases but this group of individuals are not generally in touch with the ophthalmic services. Social deprivation appears to be associated with this groups' inability to access ophthalmic care.

Aged↗
PubMed2005

[Left ventricular functional parameters: comparison of 16-slice spiral CT with MRI].

PURPOSE: The quantitative measurement of left ventricular functional parameters using multislice computed tomography (MSCT) with retrospective ECG-gating and comparison of the results with magnetic resonance imaging (MRI). MATERIALS AND METHODS: Thirty-one patients with suspected or known coronary artery disease underwent MSCT angiography with retrospective ECG-gating (Sensation 16, Siemens). Based on the CT data set, short axis reformations of the left ventricle were performed for functional analysis. On a commercially available workstation, end-diastolic- (EDV), end-systolic- (ESV), stroke volume (SV), ejection fraction (EF) and myocardial mass (MM) were calculated from MSCT (temporal resolution 105 - 210 ms) data according to the modified Simpson's rule and compared to MRI (1.5 T scanner, temporal resolution 48 ms) using a 2D TrueFISP cine sequence with respiration hold. RESULTS: In all cases, the quality was adequate for both MSCT and MRI. MSCT and MRI had an excellent correlation for EDV (r = 0.86), ESV (r = 0.91), EF (r = 0.87) and MM (r = 0.88), and a good correlation for SV (r = 0.70). The mean difference was 13.2 +/- 21.9 ml for EDV, 8.7 +/- 15.9 ml for ESV, 4.6 +/- 12.3 ml for SV, 1.4 +/- 5.2 % for EF, and 11.9 +/- 13.8 g for MM. However, EDV (p = 0.002), ESV (p = 0.005), SV (p = 0.048), and MM (p < 0.0001) were significantly overestimated with MSCT compared to MRI. For EF, no significant difference between MSCT and MRI was found (p = 0.15). CONCLUSION: For left ventricular functional parameters, MSCT of the heart with retrospective ECG-gating showed a high correlation with MRI, which has an important implication when using MSCT for non-invasive cardiac imaging. Despite the high correlation, overestimation of EDV, EVS, SV, and MM with MSCT has to be taken into account when applying this technology in clinical practice. EF was not significantly different between both modalities.

Aged↗