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Now showing items 1 - 16 of 71575

  • 3D printing of severe hypertrophic cardiomyopathy in a child with Rasopathy

    Johnston, N. F.   Prendiville, T.   McMahon, C. J.  

    We describe the use of 3D printing in conjunction with echocardiography in assessing hypertrophic cardiomyopathy in a boy with Rasopathy. 3D printing may supplement conventional imaging including echocardiography and MRI in the evaluation of hypertrophic cardiomyopathy.
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  • Elevated tumour marker: an indication for imaging?

    McMahon, C. J.   Crowley, V.   McCarroll, N.   Dunne, R.   Keogan, M. T.  

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  • Echocardiographic assessment of conjoined twins

    Andrews, R. E.   McMahon, C. J.   Yates, R. W. M.   Cullen, S.   de Leval, M. R.   Kiely, E. M.   Spitz, L.  

    Objective: To determine the accuracy of prenatal and postnatal echocardiography in delineating the degree of cardiac fusion, intracardiac anatomy (ICA), and ventricular function of 23 sets of conjoined twins with thoracic level fusion presenting to a single centre over a 20 year period.Methods: 13 thoracopagus, 5 thoraco-omphalopagus, and 5 parapagus pairs presenting to the authors' institution between 1985 and 2004 inclusive were assessed. Echocardiographic data were analysed together with operative intervention and outcome. Twins were classified according to the degree of cardiac fusion: separate hearts and pericardium ( group A, n = 5), separate hearts and common pericardium ( group B, n = 7), fused atria and separate ventricles ( group C, n = 2), and fused atria and ventricles ( group D, n = 9).Results: The degree of cardiac fusion was correctly diagnosed in all but one set. ICA was correctly diagnosed in all cases, although the antenatal diagnosis was revised postnatally in three cases. Abnormal ICA was found in one twin only in two group A pairs, one group B pair, and both group C pairs. All group D twins had abnormal anatomy. Ventricular function was good in all twins scanned prenatally, and postnatally function correlated well with clinical condition. Thirteen sets of twins in groups A - C were surgically separated; 16 of 26 survived. None from groups C or D survived.Conclusions: Prenatal and postnatal echocardiography accurately delineates cardiac fusion, ICA, and ventricular function in the majority of twins with thoracic level fusion. It is integral in assessing feasibility of separation. The outcome in twins with fused hearts remains dismal.
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  • Oxygen-Induced Dynamic Embrittlement in Nickel-Base Superalloys

    McMahon, C. J.   Kane, W. M.  

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  • Is diffusion-weighted MRI sufficient for follow-up of neuroendocrine tumour liver metastases?

    Lavelle, L. P.   O'Neill, A. C.   McMahon, C. J.   Cantwell, C. P.   Heffernan, E. J.   Malone, D. E.   Daly, L.   Skehan, S. J.  

    AIM: To assess if diffusion-weighted imaging (DWI) alone could be used for follow-up of neuroendocrine hepatic metastases. MATERIAL AND METHODS: This was a retrospective study, approved by the institutional review board. Twenty-two patients with neuroendocrine liver metastases who had undergone more than one liver magnetic resonance imaging (MRI) examination, (including DWI and using hepatocyte-specific contrast medium) were evaluated. Up to five metastases were measured at baseline and at each subsequent examination. The reference standard measurement was performed on the hepatocyte phase by one reader. Three independent readers separately measured the same lesions on DWI sequences alone, blinded to other sequences, and recorded the presence of any new lesions. RESULTS: The longest diameters of 317 liver metastases (91 on 22 baseline examinations and a further 226 measurements on follow-up) were measured on the reference standard by one reader and on three b-values by three other readers. The mean difference between DWI measurements and the reference standard measurement was between 0.01-0.08 cm over the nine reader/b-value combinations. Based on the width of the Bland and Altman interval containing approximately 95% of the differences between the reader observation and the mean of reference standard and DWI measurement, the narrowest interval over the nine reader/b-value combinations was -0.6 to +0.7 cm and the widest was -0.9 to 1 cm. In the evaluation of overall response using Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria, the weighted kappa statistic was between 0.49 and 0.86, indicating moderate-to-good agreement between the reference standard and DWI. CONCLUSION: The visualisation and measurement of hepatic metastases using DWI alone are within acceptable limits for clinical use, allowing the use of this rapid technique to restage hepatic disease in patients with neuroendocrine metastases. (C) 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
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  • Instantaneous frequency measurement applied to semiconductor laser relaxation oscillations

    Kane, D. M.   McMahon, C. J.  

    The frequency of relaxation oscillations in the output power of lasers, particularly semiconductor lasers, is an important parameter which can be used to inform other fundamental laser variables, for comparison with expected theory, and to show the effect of external influences, such as optical feedback, by a change in value. Thus, precision measurement of the relaxation frequency is important. Instantaneous frequency measurement algorithms are applied to experimental semiconductor laser relaxation-oscillation signals to determine whether reliable values can be extracted, for an extended range of injection current, as compared to direct measurement and fast Fourier transform techniques. Improvement is achieved but, more importantly, the technique clearly shows when other oscillations, such as those due to packaging, connectorization and power supply, dominate the oscillatory component of the output power, at low injection currents. The work further supports the finding that only mid-range injection currents can be used for reliable precision relaxation oscillation frequency measurement.
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  • Hemoptysis From Bronchial Varices Associated With Pulmonary Vein Stenosis: Role of Surgical Repair

    Walsh, A.   Canny, G.   McMahon, C. J.   Redmond, J. M.   McNally, P.  

    We present the case of a 6-year-old child who presented with an episode of life threatening hemoptysis. Investigations revealed multiple areas of endobronchial varices and abnormal pleural vessels as well as severe left pulmonary vein stenosis and an atrial septal defect (ASD). After extensive work up and consultation he underwent repair of the left pulmonary vein using a sutureless technique and ASD closure. This resulted in a marked improvement in the appearances of the left lung. The bronchial varices in the right lung remain unchanged. No further hemoptysis has occurred and the child continues to be monitored. (C) 2012 Wiley Periodicals, Inc.
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  • Dynamic Embrittlement: Quasi-Static Interfacial Decohesion

    Mcmahon, C. J.   Bassani, J. L.   Mishin, Y.  

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  • Inflammation as a predictor for delayed cerebral ischemia after aneurysmal subarachnoid haemorrhage

    McMahon, C. J.   Hopkins, S.   Vail, A.   King, A. T.   Smith, D.   Illingworth, K. J.   Clark, S.   Rothwell, N. J.   Tyrrell, P. J.  

    Background The mechanism of development of delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (SAH) is poorly understood. Inflammatory processes are implicated in the development of ischemic stroke and may also predispose to the development of DCI following SAH. The objective of this study was to test whether concentrations of circulating inflammatory markers (C-reactive protein (CRP), interleukin-6 (IL-6) and interleukin 1 receptor antagonist (IL-1Ra)) were predictive for DCI following SAH. Secondary analyses considered white cell count (WCC) and erythrocyte sedimentation rate (ESR). Methods This was a single-center case-control study nested within a prospective cohort. Plasma inflammatory markers were measured in patients up to 15days after SAH (initial, peak, average, final and rate of change to final). Cases were defined as those developing DCI. Inflammatory markers were compared between cases and randomly selected matched controls. Results Among the 179 participants there were 46 cases of DCI (26%). In primary analyses the rate of change of IL-6 was associated with DCI (OR 2.3 (95% CI 1.1 to 5.0); p=0.03). The final value and rate of change of WCC were associated with DCI (OR 1.2 (95% CI 1.0 to 1.3) and OR 1.3 (95% CI 1.0 to 1.6), respectively). High values of ESR were associated with DCI (OR 2.4 (95% CI 1.3 to 4.6) initial; OR 2.3 (95% CI 1.3 to 4.2) average; OR 2.1 (95% CI 1.1 to 3.9) peak; and OR 2.0 (95% CI 1.2 to 3.3) final value). Conclusions Leucocytosis and change in IL-6 prior to DCI reflect impending cerebral ischemia. The time-independent association of ESR with DCI after SAH may identify this as a risk factor. These data suggest that systemic inflammatory mechanisms may increase the susceptibility to the development of DCI after SAH.
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  • Predictive value of PI-RADS classification in MRI-directed transrectal ultrasound guided prostate biopsy

    NiMhurchu, E.   O'Kelly, F.   Murphy, I. G.   Lavelle, L. P.   Collins, C. D.   Lennon, G.   Galvin, D.   Mulvin, D.   Quinlan, D.   McMahon, C. J.  

    AIM: To correlate the results of transrectal ultrasound (TRUS)-guided targeted prostate biopsies (performed in the setting of at least one previous negative biopsy) with the Prostate Imaging Reporting and Data System (PI-RADS). MATERIAL AND METHODS: Fifty-two patients (mean age 64 years, range 52-76 years), with previous negative prostate biopsy underwent magnetic resonance imaging (MRI)-directed TRUS-guided targeted and sectoral biopsy. A retrospective review of MRI examinations was carried out, blinded to biopsy results. PI-RADS scores (T2, diffusion-weighted imaging [DWI] and overall) were assigned on a per lesion basis, and localised to sextants. The scores were correlated with biopsy results, and the positive predictive values (PPV) of PIRADS scores for positive biopsies were calculated. RESULTS: Overall, biopsies were positive in 23/52 (44.2%) patients. Eighty-one areas were targeted in 52 patients. On a per lesion basis, there was significant correlation between positive targeted biopsy and both T2 and overall PI-RADS score (p<0.001). The correlation between biopsy and DWI score was significant for peripheral zone tumours only, not for transitional zone tumours. The PPV of overall PI-RADS scores of 3, 4, and 5 were 10.6%, 44%, and 100%, respectively. The PPV of T2 PI-RADS scores of 3, 4, and 5 were 19.6%, 60%, and 100%, respectively. The PPV of DWI PI-RADS scores of 3, 4, and 5 were 50%, 27.3%, and 33%, respectively. When transitional tumours were excluded, the PPV of DWI PI-RADS 3, 4, and 5 were 40%, 43%, and 78%. CONCLUSION: The PIRADS score provides an effective framework for determining the likelihood of prostate cancer on MRI. The DWI PI-RADS score correlates well with the presence of peripheral zone tumour on targeted biopsy, but not with transitional zone tumours. (C) 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
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  • Further Compositional Effects on the Temper Embrittlement of 2 1/4 Cr-1 Mo Steels

    McMahon, C. J.   Murza, J. C.   Gentner, D. H.  

    As an extension of a previous study (reference [1]), the effects of a 0.3 pct nickel content, of tin in combination with several other elements, and of a 0.1 pct vs a 0.2 pct carbon content, were examined in 2 1/4 Cr-1 Mo steel having a bainitic microstructure, a hardness of Rc 15, and a grain size in the range ASTM no. 5 to 7. The main effect of the nickel was reduction in the FATT of steels in the unembrittled condition. The only deleterious effect was a small contribution to temper embrittlement in the steel containing high manganese and silicon concentrations. Tin was found not to be an embrittling element in this class of steel in the sense that it segregates and lowers intergranular cohesion. However, it strongly promotes phosphorus-induced temper embrittlement, apparently in a manner similar to silicon. A modified type of plot relating composition to temper embrittlement susceptibility is proposed. It was found that the 0.1 pct and 0.2 pct carbon steels had equivalent temper embrittlement behavior when the hardness and grain size were held constant.
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  • The reproducibility of transcranial Doppler middle cerebral artery velocity measurements: Implications for clinical practice

    McMahon, C. J.   Mcdermott, P.   Horsfall, D.   Selvarajah, J. R.   King, A. T.   Vail, A.  

    Use of transcranial Doppler (TCD) to diagnose vasospasm has been criticised. We examined reproducibility of TCD middle cerebral artery (MCA) velocity measurements. Thirty-six healthy adult volunteers were recruited. Four operators, two experienced and two inexperienced, participated. MCA velocity was measured twice by one operator and once by a second operator. Mean (95% limits of agreement) interoperator agreement was 2.4( +/- 36.7) cm/s. Experienced vs. inexperienced, inexperienced vs. inexperienced, and experienced vs. experienced operators were - 2.8(+/- 39.3), - 5.6(+/- 40.1), 1.8(+/- 22.1) cm/s, respectively. Intraoperator agreement across all operators, experienced and inexperienced were -0.5(+/- 16.9), - 1.6(+/- 19.3), 0.7(+/- 13.7) cm/s, respectively. Interoperator limits of agreement for experienced operators were almost half that of inexperienced operators. Intraoperator reproducibility was much better, regardless of level of experience, but aberrant results did occur even with experienced operators. If TCD measurements are used to guide management it is essential that operators are adequately trained, and readings repeated before potentially harmful treatments are instituted.
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  • Compositional Factors that Enhance or Retard Temper Embrittlement of Alloy Steels

    McMahon, C. J.   Yu, J.  

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  • An Investigation of the Effects of Grain Size and Hardness in Temper-Embrittled 2 1/4 Cr-1 Mo Steel

    McMahon, C. J.   Gentner, D. H.   Ucisik, A. H.  

    Measurements of FATT as a function of hardness, grain size, and fracture surface impurity concentration were made on a 2 1/4 Cr-1 Mo steel doped with Mn + Si + P in an effort to devise an embrittlement equation relating FATT to these variables, as done previously in NiCr and NiCrMoV steels. Observations of the hardness and grain size effects on an undoped steel were also made. The effects of variations of hardness and grain size were quite irregular, especially in the doped steel, and it was therefore not possible to develop the equation. The probable reasons for the inapplicability of this approach in the 2 1/4 Cr-1 Mo type of steel are discussed.
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  • ROBERT J. MCMAHON, editor. The Cold War in the Third World.

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  • ROBERT J. MCMAHON, editor. The Cold War in the Third World.

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