Biomedical subjects

L Fog

Publications and source records attributed to L Fog.

10 recordsLinked to original sources

PubMed2006

The prediction of transmitted dose distributions using a 3D treatment planning system.

Patient dose verification is becoming increasingly important with the advent of new complex radiotherapy techniques such as conformal radiotherapy (CRT) and intensity-modulated radiotherapy (IMRT). An electronic portal imaging device (EPID) has potential application for in vivo dosimetry. In the current work, an EPID has been modelled using a treatment planning system (TPS) to predict transmitted dose maps. A thin slab of RW3 material used to initially represent the EPID. A homogeneous RW3 phantom and the thin RW3 slab placed at a clinical distance away from the phantom were scanned using a CT simulator. The resulting CT images were transferred via DICOM to the TPS and the density of the CT data corresponding to the thin RW3 slab was changed to 1 g/cm3. Transmitted dose maps (TDMs) in the modelled EPID were calculated by the TPS using the collapsed-cone (C-C) convolution superposition (C/S) algorithm. A 6 MV beam was used in the simulation to deliver 300 MU to the homogenous phantom using an isocentric and SSD (source-to-surface) technique. The phantom thickness was varied and the calculated TDMs in the modelled EPID were compared with corresponding measurements obtained from a calibrated scanning liquid-filled ionisation chamber (SLIC) EPID. The two TDMs were compared using the gamma evaluation technique of Low et al. The predicted and measured TDMs agree to within 2 % (averaged over all phantom thicknesses) on the central beam axis. More than 90 % of points in the dose maps (excluding field edges) produce a gamma index less than or equal to 1, for dose difference (averaged over all phantom thicknesses), and distance-to-agreement criteria of 4 %, 3.8 mm, respectively. In addition, the noise level on the central axis in the predicted dose maps is less than 0.1 %. We found that phantom thickness changes of approximately 1 mm, which correspond to dose changes on the central beam axis of less than 0.6 %, can be detected in the predicted transmitted dose distributions.

Algorithms↗

PubMed2003

Long QT syndrome patients may faint due to neurocardiogenic syncope.

AIMS: Syncope in long QT syndrome (LQTS) is expected to be due to Torsades de Pointes ventricular tachycardia (TdP). Often these patients faint in situations with emotional stress. The aim of the present study was to evaluate whether neurocardiogenic syncope occurs in LQTS. METHODS AND RESULTS: Ten untreated consecutive LQTS patients (age 11-72 years, median 37.5 years, five males and five females from five different families (one KvLQT1 mutation, two HERG mutations in three families and one without established genetic background)) were examined by a head-up tilt-table test (HUT). If syncope did not occur within 25 min, the patient received 0.25 mg nitroglycerine sublingually and the HUT was continued for 20 min. Nine out of 10 patients had a positive HUT. The syncope resulted from a combined vasodepressor and bradycardiac response. There were no cases of TdP. No syncope occurred in a 42-year-old asymptomatic male LQTS patient with a borderline prolonged QTc of 0.45 s and a HERG mutation. In 11 of 21 patients referred for syncope without LQTS a positive HUT was found (P < 0.10). CONCLUSION: Syncope in LQTS can be of neurocardiogenic origin and is not necessarily due to TdP. The reason for neurocardiogenic syncope in LQTS is unknown, but involvement of the autonomic nervous system outside the heart is possible.

Adult↗

PubMed2002

In-medium modifications of the pipi interaction in photon-induced reactions.

Differential cross sections of the reactions (gamma,pi(0)pi(0)) and (gamma,pi(0)pi(+/-)) have been measured for several nuclei (1H,12C, and (nat)Pb) at an incident-photon energy of E(gamma)=400-460 MeV at the tagged-photon facility at MAMI-B using the TAPS spectrometer. A significant nuclear-mass dependence of the pipi invariant-mass distribution is found in the pi(0)pi(0) channel. This dependence is not observed in the pi(0)pi(+/-) channel and is consistent with an in-medium modification of the pipi interaction in the I=J=0 channel. The data are compared to pi-induced measurements and to calculations within a chiral-unitary approach.

Journal Article↗

PubMed2001

C-reactive protein, dietary n-3 fatty acids, and the extent of coronary artery disease.

The acute-phase reactant C-reactive protein (CRP) has emerged as an independent risk factor for coronary artery disease. Experimental and clinical studies provide evidence of anti-inflammatory effects of n-3 polyunsaturated fatty acids (PUFA) derived from fish. We have studied the effect of marine n-3 PUFA on CRP levels in 269 patients referred for coronary angiography because of clinical suspicion of coronary artery disease. All patients filled out a food questionnaire regarding fish intake. The n-3 PUFA content of granulocyte membranes was determined and the concentration of CRP in serum was measured using a highly sensitive assay. The results were related to angiographic findings. CRP was significantly higher in patients with significant coronary stenoses than in those with no significant angiographic changes (p <0.001), but the CRP levels were not associated with the number of diseased vessels. Subjects with CRP levels in the lower quartile had a significantly higher content of docosahexaenoic acid (DHA) in granulocytes than subjects with CRP levels in the upper quartile (p = 0.02), and in a multivariate linear regression analysis, DHA was independently correlated to CRP (R(2) = 0.179; p = 0.003). The inverse correlation between CRP and DHA may reflect an anti-inflammatory effect of DHA in patients with stable coronary artery disease and suggest a novel mechanism by which fish consumption may decrease the risk of coronary artery disease.

Adult↗

PubMed2001

Marine n-3 fatty acids, wine intake, and heart rate variability in patients referred for coronary angiography.

BACKGROUND: Dietary n-3 polyunsaturated fatty acids (PUFAs) derived from fish may reduce the incidence of sudden cardiac death (SCD). In addition, wine drinking is suggested to have a protective effect against cardiovascular death. METHODS AND RESULTS: We included 291 patients referred for coronary angiography in whom ischemic heart disease was suspected and all of whom completed a food questionnaire regarding fish and wine intake. The n-3 PUFA composition of granulocyte membranes and of adipose tissue was measured. In addition, 24-hour heart rate variability (HRV) was analyzed. Fish intake was positively associated with the level of n-3 PUFAs in adipose tissue. Significant positive correlation coefficients were found between HRV indices and the levels of n-3 PUFAs in granulocytes. Wine intake was also significantly positively related to HRV, but the patients with the highest wine intake also had the highest intake of fish, as documented by a high n-3 PUFA content in adipose tissue. Multiple linear regression analysis revealed that traditional factors such as treatment with ss-blockers, smoking, age, and previous myocardial infarction were independently related to HRV, and furthermore that n-3 PUFAs (but not wine intake) were significantly independently associated with HRV. CONCLUSIONS: The close positive association between n-3 PUFAs and HRV in patients suspected of having ischemic heart disease may indicate a protective effect of n-3 PUFAs against SCD. This may partly explain the reduction in SCD observed in humans with a modest intake of n-3 PUFA. Wine intake was also positively correlated with HRV, but this correlation was no longer significant after controlling for the cellular level of n-3 PUFA.

Aged↗

PubMed1999

In-hospital outcome for diabetic patients with acute myocardial infarction in the thrombolytic era.

A 3-year retrospective study was carried out at the Department of Cardiology, Aalborg Hospital, Denmark. The aim of the study was to investigate the in-hospital mortality and complications resulting from acute myocardial infarction in diabetic patients compared with non-diabetic patients in the thrombolytic era and to investigate the correlation between mortality and blood glucose levels in diabetic patients. All patients admitted to the study suffered acute myocardial infarctions. One hundred and twenty-three patients with diabetes and 856 patients without diabetes were included. Mortality was 13% (110 patients) in non-diabetic patients compared with 28% (34 patients) in diabetic patients (p = 0.00002). Eighty-nine patients with diabetes (72%) experienced heart failure or a worsening of heart failure compared with 424 patients without diabetes (50%), p = 0.00001. Twenty-eight diabetic patients (23%) had high-degree atrioventricular block, compared with only 99 non-diabetic patients (12%), p = 0.001. Atrial fibrillation developed in 35 patients with diabetes (28%) and in only 141 patients without diabetes (16%), p = 0.002. No difference was seen in occurrence of ventricular tachyarrhythmias. Diabetic patients with a fatal outcome had significantly higher blood glucose values at admission compared with diabetic patients who survived (17.1 +/- 8.3 vs 13.5 +/- 6.3 mmol/l; p = 0.034), and during hospitalization (85.7 +/- 26.0% of blood glucose values exceeding 10 mmol/l vs 64.5 +/- 33.1; p = 0.00065). In the thrombolytic era diabetic patients with acute myocardial infarction had a higher mortality and experienced more complications during hospitalization compared with non-diabetic patients, and diabetic patients with a fatal outcome had higher blood glucose levels compared with surviving diabetic patients.

Aged↗

PubMed1996

Thrombolytic therapy in diabetic patients with acute myocardial infarction.

OBJECTIVE: To compare the frequency of thrombolytic therapy in diabetic and nondiabetic patients with acute myocardial infarction (MI) and to examine why some diabetic patients do not receive thrombolytic therapy. RESEARCH DESIGN AND METHODS: Retrospective study of all diabetic patients with acute MI admitted to the coronary care unit of Aalborg Hospital within a 3-year period. RESULTS: Only 35% (43 of 123) of patients with diabetes compared with 47% (404 of 856) of patients without diabetes received thrombolytic therapy (P < 0.002). There was no difference in the percentage of patients thrombolyzed among patients admitted to the hospital within 12 h after onset of symptoms. Of diabetic patients who were not thrombolyzed, 60% (48 of 80) arrived at the hospital later than 12 h after onset of symptoms. Among patients who arrived late, 63% (35 of 56) had Q wave infarction and 84% (47 of 56) had symptoms typical of acute MI. Mortality was 29% (16 of 56) in this group. Only one patient did not receive thrombolytic therapy due to diabetic retinopathy. CONCLUSIONS: Significantly fewer diabetic patients received thrombolytic therapy compared with patients without diabetes. The main reason diabetic patients did not receive thrombolytic therapy was late arrival to the hospital.

Aged↗

PubMed1995

[Hypertensive crises. 1. Pathogenesis and symptomatology].

Hypertensive crisis is a medical emergency presenting with a severely increased blood pressure. The condition is associated with a state of increased vasoconstriction, coexisting hyponatriaemia and hypovolaemia. Besides the absolute level of blood pressure evidence of organ damage is also important in initial judgement of the case. Hypertensive crises are most commonly seen in younger patients with essential hypertension and in patients with secondary hypertension. It is unknown why a patient with hypertension suddenly develops a hypertensive crisis, but the renin-angiotension system seems to play an important role. Untreated, the disease will lead to irreversible end-organ damage. Hypertensive crises may be divided into "hypertensive emergencies" with evidence of severe new and/or progressive end-organ damage, requiring careful reduction of blood pressure within an hour, and "hypertensive urgencies" with no evidence of end-organ damage or complications where reduction of blood pressure to a safe level must be achieved within a few hours.

Critical Illness↗

PubMed1995

[Hypertensive crises. 2. Treatment].

Hypertensive crisis is a rare condition with increased blood pressure and evidence of new or progressive severe end-organ damage. The patients should be admitted to hospital, and the blood pressure reduced gradually. Blood pressure should not be normalized, but a reduction in mean arterial pressure of 20-25% or to a diastolic blood pressure > 100-110 mmHg should be achieved. Patients at particular risk for further complications are elderly, patients with hypovolaemia, renal insufficiency, ischaemic heart disease and patients with neurological deficits. The ideal antihypertensive drug for any form of hypertensive crisis does not exist. If the patient can cooperate with oral treatment, nifedipine may be used, usually administered as capsules of 10 mg orally, producing a rapid and safe reduction in blood pressure of 25% within 10-15 minutes with a maximal action after 30-60 minutes. The dose may be repeated after 30 minutes in case of insufficient blood pressure response. Hypotension is rare. Nifedipine in combination with nitroglycerine is of special benefit in hypertensive pulmonary oedema. In cases of treatment failure or if the patient cannot cooperate with oral treatment, the choice of drug lies between labetalol and sodium nitroprusside. Nitroprusside is administered as continuous intravenous infusion, the drug is safe to use and is recommended in conditions where reduction of blood pressure must be performed with extreme caution such as in cases of cerebral infarction and intracranial hemorrhage. Infusion of nitroprusside for more than 48-72 hours is inexpedient because the metabolites of nitroprusside need monitoring as well. Parenteral drug therapy with labetalol is more simple than treatment with nitroprusside, but at the same time somewhat more difficult to titrate. Nitroglycerine is very suitable in moderate hypertension and ischaemic heart disease, but in severe hypertension with heart disease nitroprusside is the treatment of choice. Loop diuretics should not be used as first-line drugs, but only in conditions with evidence of volume-overload. Patients with hypertensive crisis most often show volume depletion which is aggravated by loop diuretics, therefore they should not be used routinely. When the blood pressure has been stabilized, an oral antihypertensive drug should be started concomitantly to a gradual reduction of the initial parenteral drug therapy.

Antihypertensive Agents↗

PubMed1995

Ultradian variation in serum phosphate concentration in patients on haemodialysis.

To study how much the serum phosphate concentration could vary on the day before scheduled dialysis we obtained 24-37 timed measurements during 24 h in nine patients on maintenance haemodialysis. During the observation there was an increase in serum phosphate concentration of 0.239 +/- 0.022, P < 0.01). Surprisingly six of the nine patients exhibited nine statistically and clinically significant nadirs with decrements of 0.21 +/- 0.04 mmol/l against an intra-assay standard deviation of about 0.05 mmol/l. Five of the nadirs occurred at 11.40-14.50, mean 12.59, and three at 19.00-21.30, mean 20.00. We found no coinciding changes in the serum calcium concentration. These findings indicate that serum phosphate concentrations do not always reflect phosphorus balance or intake.

Activity Cycles↗