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Biomedical subjects

G Jarry

Publications and source records attributed to G Jarry.

At least 19 recordsLinked to original sources
PubMed2003

A Monte Carlo-based method to estimate radiation dose from spiral CT: from phantom testing to patient-specific models.

The purpose of this work is to develop and test a method to estimate the relative and absolute absorbed radiation dose from axial and spiral CT scans using a Monte Carlo approach. Initial testing was done in phantoms and preliminary results were obtained from a standard mathematical anthropomorphic model (MIRD V) and voxelized patient data. To accomplish this we have modified a general purpose Monte Carlo transport code (MCNP4B) to simulate the CT x-ray source and movement, and then to calculate absorbed radiation dose in desired objects. The movement of the source in either axial or spiral modes was modelled explicitly while the CT system components were modelled using published information about x-ray spectra as well as information provided by the manufacturer. Simulations were performed for single axial scans using the head and body computed tomography dose index (CTDI) polymethylmethacrylate phantoms at both central and peripheral positions for all available beam energies and slice thicknesses. For comparison, corresponding physical measurements of CTDI in phantom were made with an ion chamber. To obtain absolute dose values, simulations and measurements were performed in air at the scanner isocentre for each beam energy. To extend the verification, the CT scanner model was applied to the MIRD V model and compared with published results using similar technical factors. After verification of the model, the generalized source was simulated and applied to voxelized models of patient anatomy. The simulated and measured absolute dose data in phantom agreed to within 2% for the head phantom and within 4% for the body phantom at 120 and 140 kVp; this extends to 8% for the head and 9% for the body phantom across all available beam energies and positions. For the head phantom, the simulated and measured absolute dose data agree to within 2% across all slice thicknesses at 120 kVp. Our results in the MIRD phantom agree within 11% of all the different organ dose values published by the UK's ImPACT group for a scan using an equivalent scanner, kVp, collimation, pitch and mAs. The CT source model was shown to calculate both a relative and absolute radiation dose distribution throughout the entire volume in a patient-specific matrix geometry. Results of initial testing are promising and application to patient models was shown to be feasible.

Adult↗
PubMed2003

Intimo-intimal intussusception: a rare clinical form of aortic dissection.

A 33-year-old hypertensive man presented with epigastric pain radiating to the back. Transoesophageal echocardiography (TOE) revealed an intimal flap on the aortic arch and descending aorta. No intimal flap of the ascending aorta was detected on TOE or CT. The diagnosis was made on opening the ascending aorta: complete circumferential dissection of the ascending aorta flush with the coronary ostia, with no residual intimal flap, and intimo-intimal glove-finger intussusception of the internal channel into the descending thoracic aorta. Aortic intussusception is a very rare form of Type I dissection, and the absence of intimal tear in the ascending aorta can be misleading and delay the diagnosis.

Adult↗
PubMed2002

Clinical application of laser evoked potentials using the Nd:YAG laser.

The clinical interest of a new type of laser evoked potentials (LEPs) using Nd:YAG laser was assessed in the diagnosis of peripheral neuropathies affecting the small-diameter nerve fibres, and of spinal cord lesions, affecting the spinothalamic tract. Twelve patients aged from 26 to 79 years with sensory neuropathies (n = 6) or spinal cord lesions (n = 6) underwent neurophysiological examination of the lower limbs comprising quantitative sensory testing, i.e., the determination of vibratory and thermal thresholds (VT and TT), somatosensory evoked potentials (SEPs) to electrical stimulation and Nd:YAG LEPs. VT and SEPs were used to assess large-diameter afferent nerve fibres and the lemniscal pathways while TT and LEPs were used to assess small-diameter afferent nerve fibres and the spinothalamic tract. In addition, patients with peripheral neuropathy underwent also standard nerve conduction studies to explore large fibres and the recording of sympathetic skin responses (SSRs) to explore small fibres, whereas motor evoked potentials were performed in patients with spinal cord lesion. LEPs were absent bilaterally in all patients with polyneuropathy, even when TT remained within the normal limits and SSRs were present. LEPs were absent after stimulation of the affected limb in all patients with a spinal cord lesion, and allowed to detect subclinical contralateral lesion in two cases. LEPs following Nd:YAG laser stimulation are sensitive in the diagnosis of peripheral and/or central nervous system disorders and they give complementary information as compared to routine electrophysiological tests.

Aged↗
PubMed2002

The role of myoglobin in retarding oxygen depletion in anoxic heart.

The present study explores the role of myoglobin (Mb) in retarding the development of anoxia in the perfused working rat heart. We examine this phenomenon by analyzing the behavior and the kinetics of Mb oxygenation and cytochrome aa3 (cytaa3) redoxation. Absorbance changes, measured at wavelength pairs specific to Mb and cytaa3, show parallelism between the Mb oxygenation status and the redox states of cytaa3. Induction of anoxia leads to early and accelerated Mb deoxygenation whereas cytaa3 reduction marks a slight delay and its rate is twice slower than that of Mb. Then, when Mb is desatured above 50%, the cytaa3 reduction becomes accelerated. With the reoxygenated perfusion following the anoxia, the rate of Mb reoxygenation is twice faster than that of the cytaa3 reoxidation. When the oxygen-binding function of Mb, in situ in the heart, is abolished by treatment with sodium nitrite (NaNO2), the redox kinetics of cytaa3 show significant perturbations. Induction of anoxia leads to a precocious and accelerated reduction of cytaa3, compared to the same anoxic heart before the treatment. At reoxygenation, the reoxidation rate of cytaa3 decreases significantly, compared to that before the treatment. Similarly, in the nitrite treated heart, the phosphocreatine (PCr) level decreases to 60% of the control, whereas the inorganic phosphate (Pi) level increases to 300%. ATP concentration, however, remains constant. We conclude from these results that Mb may support mitochondrial respiration at the critical levels of the myocardial O2 supply.

Animals↗
PubMed2001

Laser evoked potentials using the Nd:YAG laser.

Pain-related cortical potentials were evoked by skin stimulation of the face and the limbs with 5-ns-duration laser pulses delivered by a Q-switched Nd:YAG laser. Such laser pulses, in the nanosecond range, were able to induce pinprick pain sensations and to evoke reproducible laser evoked potentials (LEPs) without visible skin lesions for an energy density of less than 18 mJ/mm(2). Low energy densities, around 10 mJ/mm(2), were sufficient to reach the pain threshold and to induce LEP. The mean conduction velocity of the stimulated afferent fibers was close to 20 m/s, consistent with the stimulation of Adelta fibers. The amplitude of LEP correlated with pain perception rather than with energy density. The differences, such as wavelength and stimulus duration, between the Q-switched Nd:YAG laser we used and the lasers that are currently used in LEP studies (i.e., CO(2), argon, or Tm:YAG lasers in the millisecond range) are discussed. Our study opens novel perspectives in the LEP field of research by using a new type of laser with a very short pulse duration.

Afferent Pathways↗
PubMed2001

[Dissection of the aorta complicated by aorto-pulmonary fistula].

The authors report the case of chronic dissection of the aorta presenting with congestive cardiac failure. The diagnosis was made for the first time by transoesophageal echocardiography which showed both the dissection of the aorta and its fistulalisation into the pulmonary artery. Aortography confirmed the diagnosis. The patient underwent surgery which consisted of suture of the fistula and replacement of the ascending aorta with a prosthetic tube. The outcome was favourable after 8 months follow-up.

Aged↗
PubMed2000

Congestive heart failure and myocarditis after seroconversion for toxoplasmosis in two immunocompetent patients.

Two cases of myocarditis and congestive heart failure in immunocompetent patients with seroconversion for toxoplasmosis are reported. Serological tests showed that in the first case the cardiac manifestations occurred at the time of seroconversion (low IgG, raised IgM and IgA), whereas in the second case they occurred several months after the initial infection when IgM was decreasing, IgG levels were very high (>1000 IU/ml) and IgG had high affinity for the antigen. The pathophysiological mechanisms underlying cardiac involvement in acute or chronic toxoplasmosis are discussed.

Adult↗
PubMed2000

[Effect of the moon on the nocturnal postnuptial migration of the skylark Alauda arvensis L. in France].

Night-migrating skylarks (Alauda arvensis) were captured during four successive autumns in France. The study aimed at detecting a possible influence of the lunar cycle on the nocturnal migration of this species. Though nocturnal postnuptial migration of the skylarks can occur during every phase of the moon, main nocturnal movements occurred when the moon was in its waxing gibbous phase. This phase gives the best conditions for migration because from the very beginning of night, it provides the necessary horizon for individuals to navigate and its light allows the use of topographic cues. In addition it allows the species to benefit from optimal conditions of illumination for almost a week.

Animals↗
PubMed2000

Anisotropy and multiple scattering in thick mammalian tissues.

A dual-channel Mach-Zehnder interferometer using heterodyne detection allowed us to measure simultaneously parallel and perpendicular polarization components through various mammalian tissues at a wavelength of lambda = 633 nm. By contrast with liver tissue, squeletic muscles of a few millimeters thickness exhibit strong anisotropic properties that change the direction of the linear polarization of the light. This rotation of the initial plane of polarization is to be distinguished from the depolarization that is due to the multiple light scattering that goes along with large temporal fluctuations. Complementary photos under linearly polarized light illustrate the behavior difference between liver (isotropic medium) and muscle (anisotropic medium).

Animals↗
PubMed1998

[Drug therapy of ventricular tachycardia].

Despite the introduction of new therapeutic techniques such as radiofrequency ablation and the implantable defibrillator, the classical opposition of monomorphic ventricular tachycardia in apparently normal hearts and that arising from documented cardiac disease remains useful. In the first case, treatment is only symptomatic whereas, in the second, lethal progression to sudden death must be prevented. Generally speaking, in chronic post-infarct situations, betablockers are underused although they have been shown beyond doubt to reduce cardiovascular mortality. This is probably explained by the fear of possible haemodynamic decompensation in patients who often have left ventricular dysfunction. Nevertheless, different randomised studies of the use of betablockers in cardiac failure have reported reduced mortality with no serious side effects. The use of beta-blockers is therefore advisable, and possible inpatients with or without sustained ventricular tachycardia and underlying cardiac disease. In cases at high risk of sudden death, amiodarone may be associated. Recent randomised studies (MADIT, AVID), comparing the use of implantable defibrillators with those of antiarrhythmic therapy, have shown better results with the implantable defibrillator. However, in these studies, only about 10% of patients received betablockers in the antiarrhythmic treatment groups. This factor has introduced some doubt as to the real benefit of implantable defibrillators. Therefore, a randomised study comparing the efficacy of betablockers with amiodarone against implantable defibrillators is desirable in order to determine the respective indications of each of these two therapeutic modalities.

Anti-Arrhythmia Agents↗
PubMed1997

Familial incidence of late ventricular potentials and electrocardiographic abnormalities in arrhythmogenic right ventricular dysplasia.

Familial forms of arrhythmogenic right ventricular dysplasia (ARVD) have been described. Signal-averaged electrocardiograms (SAECGs) and standard electrocardiograms have been used to detect ARVD. The purpose of this prospective study, for a given family member, was to evaluate the risk of having ARVD or only belonging to an affected family. To address these issues, we assessed the incidence of late ventricular potentials and electrocardiographic (ECG) abnormalities in the families of our patients with ARVD. SAECGs and electrocardiograms were recorded in 101 eligible family members and compared with those recorded in ARVD patients with sustained ventricular tachycardia (13 patients in 12 families), and in 37 control subjects with a normal electrocardiogram. The incidence of late ventricular potentials was significantly higher in family members than in control subjects (16% vs 3%, p <0.05). The incidence of ECG abnormalities was 34% in family members. When the incidence of late ventricular potentials and/or ECG abnormalities were added up, results were 38% abnormal findings in family members. Late ventricular potentials and/or ECG abnormalities were found in members of all 7 families; these abnormalities were initially thought to be sporadic forms, and thereafter were classified as familial forms. Thus, SAECGs and standard ECG recordings in ARVD family members showed 38% abnormal findings, and that all cases of ARVD could be classified as familial forms. The incidence of familial forms of ARVD was greater than was previously believed, which is highly suggestive of a genetic transmission of the disease in our geographic area.

Adult↗
PubMed1997

Twin zygosity diagnosis by mailed questionnaire below age twelve months. Le Groupe Romulus.

Parents of a sample of 76 same sexed pairs of twins aged 3 to 9 months completed a mailed similarity questionnaire. It included the Bonnelykke et al.'s questionnaire and a four anthropological variable scale. To improve each of these two methods, three other combined methods were carried out and results were compared with the biological zygosity diagnosis. The Bonnelykke et al.'s classification combined with anthropological scale (method 4) gave only 1.2% misclassified in the whole sample. It is concluded that zygosity diagnosis using this type of procedure to distinguish MZ and DZ pairs would be important not only for epidemiological study but also for pediatricians and parents.

Humans↗
PubMed1996

[Pulmonary embolism and thrombus trapped in a patent foramen ovale. Cure by heparin therapy].

The authors report the case of a 84-year old patient admitted to hospital for pulmonary embolism. The diagnosis was made by ventilation and perfusion pulmonary scintigraphy. Transthoracic echocardiography was performed routinely and showed a thrombus wedged across a patient foramen ovale, confirmed at transoesophageal echocardiography. Spiral thoracic computerised tomography showed thrombus in the two main pulmonary arteries and the inferior vena cava. Thrombolysis or thrombectomy under cardiopulmonary bypass, was thought to carry an excessive risk at that age and with the left-sided position of the thrombus. The alternative was therefore anticoagulation which led to dissolution of the thrombus without recurrence of pulmonary embolism or cerebrovascular accident.

Aged↗
PubMed1996

[Echo-Doppler and stenosis of the renal arteries. Report of 86 cases].

Duplex-scan is widely used for arterial stenosis diagnosis. Its role in detection of renal artery stenosis remains controversial (2, 17, 19, 28). The aim of this study was to determine retrospectively if duplex-scan is accurate for diagnosis of renal artery stenosis. During 36 months, 764 patients had a renal artery examination with duplex-scan: 90 patients had also renal arteriography. Duplex-scan was feasible in 95% of cases (excess bowel gas or major obesity gave to duplex-scan incomplete results in four patients upon 90). Ninety-three per cent of patients had hypertension; 20% had renal failure; 61% had obstruction of coronary, carotid artery or lower limb arteries. Nineteen patients among 86 had also an intravenous renal arteriography. We compared duplex-scan with venous angiography and intra-arterial arteriography. Duplex-scan criteria for stenoses were: a maximal systolic velocity (MSV) above 180 cm/s for detection of 60% to 79% stenoses and a MSV superior to 300 cm/s for detection of 80% to 99% stenoses. Global results showed a good sensitivity 59/64 (92%) and specificity 112/117 (96%) for duplex-scan. Duplex-scan is accurate for diagnosis of renal artery stenosis in a selected population.

Aged↗
PubMed1996

[Ablation of the slow pathway in reciprocating nodal rhythms by radiofrequency].

Radiofrequency ablation is a therapeutic alternative to drug therapy in recurrent reciprocating nodal rhythms. Selective ablation of the slow pathway guided by endocavitary recordings has the advantage of being effective at the price of a very low incidence of atrioventricular block. The authors report their experience with this technique. Fifty consecutive patients with recurrent attacks which were syncopal or uncontrolled by medical therapy, underwent selective ablation of the slow pathway. Firstly, they all underwent electrophysiological investigation to confirm the nodal origin of the reciprocating rhythm before proceeding to ablation itself, guided by the search for the slow pathway potentials. After ablation, it was impossible to trigger reciprocating tachycardia. Interruption of the anterograde slow pathway was achieved in 24 patients and of the retrograde pathway in 1 patient : the other 25 patients went on having dual conduction but with a prolongation of the effective refractory period of the slow pathway (268 +/- 46 ms vs 251 +/- 41 ms : p < 0.01). There were no cases of permanent complete atrioventricular block. Interruption of the slow pathway was associated with shortening of the effective refractory period of the rapid pathway (323 +/- 71 ms vs 348 +/- 80 ms : p < 0.01), which was not observed in cases of persistent dual conduction. No recurrence of tachycardia was observed during follow-up (mean period = 19.2 months) : however, control endocavitary studies in 25 asymptomatic patients after 1 to 3 months showed recurrence in 4 cases, which led to immediate further radiofrequency ablation which was successful. The authors conclude that guided selective radiofrequency of the slow intranodal pathway is a remarkably effective and reliable method of treating poorly tolerated or resistant reciprocating nodal tachycardias. Widening of the clinical indications to patients not wishing to undergo long-term antiarrhythmic therapy is now possible.

Adolescent↗
PubMed1995

[Delayed angioplasty of residual coronary stenosis after thrombolysis of myocardial infarction: prognostic factors of left ventricular function].

The aim of this study was to analyse the prognostic factors of long term left ventricular function after successful delayed angioplasty of residual coronary stenosis after thrombolysis for myocardial infarction. The left ventricular function of fifty patients, aged 54 +/- 10 years, who underwent intravenous thrombolysis 2.9 +/- 1.3 hours after the onset of myocardial infarction (28 anterior, 22 inferior wall) was assessed by angiography at the 6.1 +/- 1.7th day and 6.1 +/- 2.5 months after successful angioplasty undertaken on the 8.3 +/- 5.2nd day. In cases without reocclusion (n = 44), the ejection fraction and the wall motion of the infarcted region improved significantly from 56.8 +/- 12.2% to 59.5 +/- 15.4% (p < 0.002) and from 8.4 +/- 14.8% to 18.3 +/- 24.3% (p = 0.0001), respectively. These parameters did not change in cases with reocclusion (n = 6). When the dilated artery remained patent, an improvement in motion of the infarcted region was observed in 69.5% of hypokinesis (n = 23), 50% of akinesis (n = 10) and 9.1% of dyskinesis (n = 11) (p < 0.005). The improvement in motion of the infarcted zone was negatively correlated with the delay of thrombolysis (r = 0.36; p < 0.02) and peak CPK levels (r = 0.31; p < 0.04). Over 60% restenosis on digitalised densitometry (n = 11) did not compromise the possibilities of improvement, the evolution of wall motion of the infarcted zone and volumes with respect to cases without restenosis (n = 33).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

[Coronary angioplasty and electric alternans of the ST segment].

Alternans of the ST segment is a rare phenomenon during coronary angioplasty. The authors report three cases. It is usually observed in left anterior descending arteries without collateral circulation. Alternans is not accompanied by haemodynamic changes and does not initiate malignant ventricular arrhythmias. It is a transient phenomenon. Electrical alternans is thought to be due to changes in the configuration of the transmembrane action potential and modifications of calcium exchanges.

Action Potentials↗