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Biomedical subjects

A Constantinesco

Publications and source records attributed to A Constantinesco.

At least 37 records · Page 2Linked to original sources
PubMed1996

[Interventional MRI. Value of low field strength and very fast 3D steady state imaging sequences for the guidance of a "non" ferromagnetic needle].

PURPOSE: The excellent tissue differenciation provided by MRI in the three directions and the lack of ionizing radiations make it ideal for interventional procedures. Many problems must still be solved: the access to the patient, the size of the artefact produced by interventional instruments and the acquisition time. In this study, we evaluated the influence of field strength for standard imaging sequences on the MRI artefact of a non ferro-magnetic biopsy needle. Then, we developed very fast sequences on a opened 0.1 T dedicated magnet to test in vitro and ex vivo the potential ability of this system in the guidance of the needle. MATERIAL AND METHODS: The biopsy needle was a new stainless steel needle made of 49% Nickel. The needle artefact's size measurements were made at 0.1 T, 0.5 T and 1 T on a bicompartmental phantom (one compartment with a long T1 and another with a long T2), with standard gradient echo (400/12/90 degrees) and spin echo (500/25) sequences. At 0.1 T, we optimized very fast steady state 3D FAST (T1 weighted) and 3D CE-FAST (T2 weighted) sequences to reduce the acquisition time, preserving good image contrasts for a field of view reaching 38 mm and 48 x 64 or 24 x 32 matrix. RESULTS: The larger needle artefact observed on gradient echo images varied from 3.6 mm at 0.1 T to 8.6 mm at 1 T. The shortest acquisition time for 4 contiguous slices of 2mm with a 1.2 mm/pixel resolution and a 24 x 32 matrix was 1.5 s for the 3D FAST (16/9/65 degrees) sequence and 3 s for the 3D CE-FAST (29/22/65 degrees) sequence. We realized a complete MRI guided abdominal puncture on a cat cadaver with 4 series of 15 s 3D FAST images (16/9/65 degrees, 4 slices, 5 excitations, 1.2 mm/pixel, FOV = 77 mm). Besides the cat positioning and the image reconstruction time, the whole puncture lasted 1 min (4 x 15 s). CONCLUSION: Low field MRI (0.1 T) combined with very fast 3D steady state sequences is adapted for the real time guidance of biopsy needles.

Biopsy, Needle↗
PubMed1995

An in vitro study at low field for MR guidance of a biopsy needle.

The aim of this study is to demonstrate in vitro that low field strength can be used for MR interventional procedures. At 0.1 T, we developed 3D, T1-, and T2-weighted fast steady state sequences and measured the artifact created by an MR biopsy needle (22 gauge, 0.7 mm diameter) on a bicompartmental phantom. The artifact generated by the needle placed perpendicular to B0 did not exceed 3.6 mm for 3D steady state sequences and acquisition times reaching 1.5 s. Corresponding artifacts at higher field strength were 7.6 mm for 0.5 T and 8.6 mm for 1 T. Low field MRI proved to be potentially adaptable for the guidance of MR biopsy needles.

Artifacts↗
PubMed1994

Detection of glomus tumor of the finger by dedicated MRI at 0.1 T.

Three glomus tumors of the fingers were detected using a dedicated hand and wrist low field (0.1 T) MR imager equipped with solenoidal coils allowing a FOV of 2 cm. Three-dimensional T1-, T*2-, or T2-weighted images were used (8 contiguous slices of 2 mm thickness). Glomus tumors had low or intermediate signal intensity (2 cases) or no signal (1 case) on T1-weighted images. On T*2- or T2-weighted images they had high signal intensity. MRI findings correlate well with surgery and biopsy.

Adult↗
PubMed1994

A study of cerebral perfusion using single photon emission computed tomography in neonates with brain lesions.

In this study we used a single photon emission computed tomography technique (SPECT) with radiolabelled 99mTcHMPAO to assess cerebral perfusion in newborn infants with documented cerebral lesions and to determine to what extent brain SPECT might be useful in the neonatal period. A total of 15 newborn infants with the following cerebral pathologies were enrolled: severe parietal bilateral periventricular leucomalacia (PVL, n = 6); moderate parietal bilateral PVL (n = 2); intraventricular haemorrhage grade II with unilateral parietal parenchymal extension (IHV + PE, n = 3); cerebral infarction (CI, n = 2) in the zone of middle cerebral artery; and post-haemorrhagic hydrocephalus (n = 2). Follow-up was available in all infants. Alterations in cerebral perfusion were seen in only 12 of 15 infants and at the location of severe PVL, PE and CI. We have noted that the regions of diminished perfusion extended beyond the apparent extent of cerebral pathology delineated by ultrasound or magnetic resonance imaging. Markedly diminished perfusion was seen in 1 infant with hydrocephalus, which recovered following placement of ventriculo-peritoneal shunt. Regarding outcome, SPECT data failed to provide additional information than that of neuroradiological investigations. We conclude that the use of SPECT, under these conditions, to assess alteration of cerebral perfusion in the neonatal period will not provide any additional information than that of neuroradiological investigations.

Brain↗
PubMed1994

Cerebral perfusion studies during maturation using single photon emission computed tomography in the neonatal period.

In this study, we used single photon emission computed tomography (SPECT) radiolabelled 99mTc HMPAO to assess cerebral perfusion during maturation in the neonatal period. Results of SPECT examinations in 18 newborn infants, in whom gestational age ranged form 30 to 41 weeks, and who were found to be neurologically normal in retrospect, were reviewed. The developmental changes in cerebral perfusion during the neonatal period shown by SPECT parallel findings of other methods on maturational changes of the central nervous system (neuropathological studies, positron emission tomography scan, magnetic resonance imaging). Cerebral perfusion progresses from the central part of the brain to the cerebellum, sensorimotor and then visual cortex. A close relation seems to exist between cerebral perfusion, metabolism and behavior under normal conditions in the neonatal period.

Brain↗
PubMed1994

Biopsy and quantitative hepatobiliary scintigraphy in the evaluation of liver transplantation.

METHODS: Hepatobiliary scintigraphy with technetium-99m-mebrofenin including a first-pass study of 60 two-sec images and a functional phase of 40 one-min images was performed in 26 patients (42.5 +/- 12.5 yr) in the early postoperative period (9.1 +/- 4.3 days) after liver grafting. Needle biopsy was carried out within a mean of 0.5 +/- 2.2 days of the scintigraphy study. Considering only rejection and cholestasis, biopsy results were used to classify the patients in three groups: control group I (11 patients) with minimal lesions, group II (9 patients) with moderate histologic modifications, and group III (6 patients) with severe dysfunction showing important structural changes. First-pass time-activity curves were used to calculate arterial (alpha-A) and portal (alpha-P) angles as well as a portal perfusion index. Functional time-activity curves were used to define two blood retention indices (BRI1 and BRI2) and two liver uptake indices (LUI1 and LUI2). Excretion was not quantified. RESULTS: Simple linear regression analysis showed a significant correlation between portal perfusion index and BRI1 (p < 0.05, r = -0.43) and BRI2 (p = 0.01, r = -0.53). The validity of the histologic classification was assessed by the existence of significantly different (p < 0.05) mean values for alpha-P, portal perfusion index and LUI1 in the three groups. All other indices could distinguish significantly between groups I and II. Furthermore, arterial angle alpha-A allowed differentiation of group II from group III but not group I from group II; on the contrary, LUI2 and BRI1 distinguished group I from group II but not group II from group III. CONCLUSION: This study demonstrated a close correlation between early biopsy results and perfusion indices in patients with a liver graft as well as uptake parameters determined by hepatobiliary scintigraphy.

Adult↗
PubMed1993

In vitro proton NMR study of collagen in human aortic wall.

The authors relate the findings in the 1H solid state line shape (at 60 MHz) of human aortic walls (n = 12) in native state and after histologically controlled selective lysis of collagen and elastin. An analysis of the line shape shows a composite free induction decay (FID) consisting of a low amplitude (3-7%) fast decaying component (T2 approximately 20 microseconds) and a slow decaying one (T2 > 1 ms). The fast component is identified as the protons of the collagen macromolecules. The second moment computed from the experimental fast component of the FID is in agreement with published studies examining the motional characteristics of collagen by multinuclear NMR employing spin labeling. A theoretical second moment is computed for the collagen macromolecular backbone from the atomic positions in the superhelix. Comparison with the observed experimental values allows determination of the step angle (29 degrees) of the fast rotational motion of the collagen strands along their long axis.

Aged↗
PubMed1993

Characterization of human aortic collagen's elasticity by nuclear magnetic resonance.

The elasticity of the human aortic wall in longitudinal uniaxial elongation at high strain, known to be determined mostly from tissular collagen's behaviour, is studied and compared to the second moment of the 1H nuclear magnetic resonance (NMR) solid state line-shape, a proton nuclear magnetic resonance (at 60 MHz) characteristic for the molecular motion and the rigidity of the collagen macromolecular backbone. The 1H NMR signal of collagen is identified after selective histologically controlled chemical lysis. The computed second moment of the line-shape shows statistically significant correlation with the slope of the strain-stress curve of the aorta at high strain, thus proving the relationship between a macroscopic tissular elasticity parameter and a macromolecular rigidity characteristic of collagen, a major tissular component. In vivo extension of this technique (e.g., MRI) would allow us to gain information on the biomechanical state of the aorta, a naturally highly stressed and strained tissue.

Aged↗
PubMed1993

Distal ulnar nerve entrapment due to tumors of Guyon's canal. A series of ten cases.

The authors reviewed ten cases of distal ulnar nerve entrapment neuropathy due to tumors of Guyon's canal. Clinically, there were two sensory, four purely motor, and four mixed neuropalsies. EMG findings correlated with clinical signs. At surgery, six simple ganglia, two intra-osseous tumors of the hook of the hamate (one ganglion, one chondroma), one giant cell tumor, one intraneural ganglion, and one schwannoma were found. Complete recovery was observed in nine out of a total of ten cases within six to eight months after surgery; the tenth case developed recurrent symptoms.

Adult↗
PubMed1992

High resolution MRI of the normal finger at 0.1 T: anatomic correlations.

MR images of the fingers are obtained in a 128 x 128 or 256 x 256 matrix format using a prototype of a mini imager dedicated to the hand. The vertical field of 0.1 T is provided by an electro-magnet with an air gap of 15 cm equipped with a single solenoidal coil. No Faraday cage is used. The maximum in plane pixel resolution of 100 mu is obtained for a field of view of 2.5 cm with a slice thickness of 2 mm. The identification of fine structures of the finger is demonstrated by the anatomical and histological correlations. This type of imager which is adapted to very limited field of views demonstrate that high resolution MRI of limb extremities can be achieved at 0.1 T.

Fingers↗
PubMed1992

MRI of hand and wrist with a dedicated low field mini imager: preliminary report.

In this paper we describe the development and the early results of an MRI system designed specifically for imaging of the hand and wrist. The imager takes up little space, uses a small 0.1 Tesla water-cooled electro-magnet with a vertical magnetic field and a 15 cm air gap. The system is based on a PC micro-computer and an integrated image processing board. There is no need for a Faraday cage. The image resolution is less than 1 mm using a 128 x 128 matrix format for a typical slice thickness of 3 mm. It is possible to achieve a 0.2 mm per pixel spatial resolution when imaging the fingers.

Hand↗
PubMed1992

Increase in radionuclide left ventricular ejection fraction after cardioversion of chronic atrial fibrillation in idiopathic dilated cardiomyopathy.

To assess the potential improvement in left ventricular ejection fraction after cardioversion of chronic atrial fibrillation to sinus rhythm in idiopathic dilated cardiomyopathy, we studied prospectively 17 patients, aged 58 +/- 6 years, by radionuclide angiocardiography at rest. Left ventricular ejection fraction was determined before treatment and at a mean delay of 4.7 months after cardioversion. Return to sinus rhythm was obtained in 12 patients, pharmacologically or by electrical cardioversion. Five patients remained in atrial fibrillation. No clinical, echocardiographic or haemodynamic finding could predict the success of cardioversion. In chronic atrial fibrillation, the ejection fraction did not change significantly: 30.0 +/- 9.1% (19 to 44%) at the first evaluation and 29.5 +/- 8.3% (22 to 41%) after 4.7 months. After successful cardioversion, left ventricular ejection fraction improved from 32.1 +/- 5.3% (24 to 41%) to 52.9 +/- 9.7% (37 to 71%) (P less than 0.001). The difference was 20.8 +/- 11.3% and left ventricular ejection fraction was normalized in 50% (6/12) of the patients. There was a significant reduction in the cardiothoracic ratio on chest X-rays and of the left ventricular end-diastolic diameter on echocardiography; fractional shortening increased (27.7 +/- 4.3% vs 20.3 +/- 2.7%, P less than 0.01). A third evaluation was realized after a mean delay of 11.7 months in the patients with successful cardioversion. Sinus rhythm was present in 83% (10/12) of the patients: seven patients were reevaluated by radionuclide angiography. The improvement in left ventricular function observed at the 4.7 months evaluation was still present. In two patients with recurrence of atrial fibrillation, there was a severe deterioration of left ventricular systolic function.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Proton magnetic resonance relaxation times and biomechanical properties of human vascular wall. In vitro study at 4 MHz.

OBJECTIVES AND RATIONALE: Previous studies have suggested a relationship between tissue magnetic resonance (MR) relaxation times and its biomechanical behavior. To further investigate this relationship, the authors studied 41 human vascular wall samples from different anatomic localizations, including systemic and pulmonary arterial, as well as venous tissues. METHODS: The authors measured water content, proton MR T1 and T2 relaxation times, and two viscoelastic parameters of the samples at 4 MHz. RESULTS: T2, water content, and both viscoelastic variables significantly differed among the five anatomic localizations (P less than .05). Both T1 and T2 were significantly (P less than .05) and linearly related to viscoelastic parameters. Multiple linear regression showed that both viscoelastic parameters of a sample can be predicted from the measured values of T1 and T2. CONCLUSIONS: These results provide a basis for characterizing the mechanical stress of a tissue by knowing its MR relaxation times.

Adult↗
PubMed1991

MR imaging of hand and wrist with a dedicated 0.1-T low-field imaging system.

We describe the first results of a new magnetic resonance imaging (MRI) system specially developed for hand and wrist imaging. The system uses a small resistive water-cooled magnet with a vertical magnetic field of 0.1 T in an air gap of 15 cm. The console is based on a microcomputer with a vector signal processor and an image-processing board. There is actually no Faraday cage. For the whole hand, the in-plane spatial resolution is less than 1 mm in the 128 x 128-pixels format for typical slice thicknesses of 3 to 5 mm. Solenoidal volume coils for fingers were developed, giving, in the same matrix format, an in-plane high spatial resolution of 0.22 mm for a typical slice thickness of 3 mm.

Hand↗
PubMed1991

[Congestive heart failure with intact systolic function].

A retrospective study was undertaken of the cases of patients admitted for congestive cardiac failure over a 4 year period, and investigated by radionuclide angiography to determine the prevalence of cardiac failure with normal left ventricular systolic function, to document the underlying mechanisms of this condition and to assess whether the clinical data could predict the presence or absence of left ventricular systolic dysfunction. After excluding patients with significant valvular disease, severe renal failure, or myocardial infarction in the previous 2 months, the study population comprised 152 patients divided into 2 groups: Group I (N = 112) with abnormal systolic function (radionuclide ejection fraction less than 45%) and Group II (N = 40) with normal systolic function (radionuclide ejection fraction greater than or equal to 45%). The clinical, echocardiographic and radionuclide angiographic data was analysed (global ejection fraction in both groups and peak filling rate in Group II). The patients in Group II (26% of the total study population) were older (66.5 +/- 12.4 vs 61.3 +/- 12.3 years, p less than or equal to 0.02), were more often female (35% vs 17.9%, p less than or equal to 0.02), had acute cardiac failure (75% vs 37%, p less than 0.00001), and were frequently hypertensive (65% vs 39%, p less than or equal to 0.005). Univariate analysis of clinical and radiological signs did not show any significant difference between the two groups except for increased jugular venous pressure and cardiomegaly which were more common in Group I (56% vs 25%, p less than 0.00001 and 93% vs 68%, p less than or equal to 0.00001, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Local intravenous treatment of algodystrophy of the hand: buflomedil versus guanethidine, long term follow-up].

This report compares the results obtained after treatment of reflex sympathetic dystrophies (algodystrophies) of the hand by pharmacological segmental blocks with buflomedil (51 cases) versus guanethidine (30 cases). The results were similar for all the different stages of algodystrophies treated: 65% satisfactory to excellent results with buflomedil, versus 63% with guanethidine. The sooner the algodystrophy is treated after its onset, the better the results. On TPBS, when the technique is effective, both hemovelocity and blood pool return to normal, along with the improvement in the patient's condition. Early and delayed bone fixations evolve independently of the treatment. These techniques should always be associated with active, mild physiotherapy, and in some cases with dynamic splints in order to prevent the development of functional sequelae in the form or capsulo-aponeurotic retraction.

Adult↗
PubMed1990

Alterations in left ventricular diastolic function in chronic ischemic heart failure. Assessment by radionuclide angiography.

Using radionuclide angiography at rest, we studied several parameters of left ventricular systolic and diastolic function in 60 patients divided into three groups, a control group (G1) of 15 patients and two groups of patients with chronic ischemic heart disease and previous anterior wall myocardial infarction but without aneurysm or dyskinetic wall motion, a second group (G2) of 23 patients with no history of heart failure, and a third group (G3) of 22 patients in New York Heart Association (NYHA) class II or III of heart failure. Ejection fraction, peak emptying, and peak filling rates, in addition to times to reach peak rates, were evaluated after constructing a global time-activity curve and its first time derivative. In addition, we computed the first time-derivative curves for each image pixel and obtained functional images (MIN/MAX images) representing the distribution of times to peak emptying or filling rates Using a left ventricular region of interest, time histograms were generated, and indexes of dispersion of times to peak rates, defined as the full width at half maximum of the histograms, were obtained. Significant (p less than or equal to 0.01) differences were observed among all groups for ejection fraction, peak emptying rate, and peak filling rate. The decrease of the peak filling rate still remained significant from group G1 to group G3 even after adjustment for differences in ejection fraction and heart rate. Peak filling rate was linearly correlated with ejection fraction in the population with ischemic heart disease (G2 + G3) (r = 0.68, p less than or equal to 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗