Glargine blood biotransformation: in vitro appraisal with human insulin immunoassay.

AIM: Glargine, a long-acting insulin analogue, is metabolized in the bloodstream and in subcutaneous tissue. Glargine metabolism and its implications for diabetes therapy remain poorly understood. The aim of our study was to assess in vitro the glargine blood biotransformation and its inter-individual variability. METHODS: Formation of M1 glargine metabolite in vitro was studied with Elecsys Insulin immunoassay in pools of sera and sera from patients spiked with glargine. Elecsys Insulin assay is specific of human insulin, does not recognize glargine and its M2 metabolite but does recognize its M1 metabolite. RESULTS: Glargine incubation with serum resulted in M1 metabolite formation which was detected and characterized as an enzymatic process: metabolite kinetics were dependant on temperature, substrate concentration and serum proportion. Carboxypeptidase inhibitors and chelating agents partially inhibited the activity of the enzyme(s). Glargine biotransformation was decreased when blood was collected on EDTA tubes. After 30 min incubation of glargine (100 mU/l) in 69 sera at 37 degrees C, percentage of glargine converted into M1 ranged from 46% to 98% (mean 72%; S.D. 11%). CONCLUSION: Glargine blood biotransformation is an enzymatic process probably involving serum carboxypeptidase(s). Metabolite formation is rapid and non negligible. Inter-individual variability of glargine biotransformation is noteworthy and should be confronted to M1 metabolite bioactivity which has not been fully documented yet.

Chemical and molecular exchange effects on T2 relaxation of living tissues: a pulse spacing dependence study.

Contrast in magnetic resonance imaging depends principally on the longitudinal relaxation (R1) and the transverse relaxation rate (R2) of the observed nuclei, most often the protons. The spin-spin relaxation rate (R2) is the result of several mechanisms. The dependence of the interpulse delay of the Carr-Purcell-Meiboom-Gill sequence on the transverse relaxation rate of the water was studied in rat organs in vitro. It gives an insight into the exchange mechanisms involved. The increase of the interpulse delay from 0.2 ms to 5 ms gives an R2 increase of 23, 15, 3, and 2 s-1 for the heart, the liver, the spleen and the brain, respectively. These increases are compared to the R2 increases obtained in 17O-enriched water, amino acid and albumin solutions atomic exchange takes place. The concentration of these materials in organs cannot explain the R2 increase of the organs with the interpulse delay. Water exchange between intra and extracellular compartments is proposed to explain the R2 increase with interpulse delays in organs like the heart and the liver.

Nuclear medicine image registration by spatially noncoherent interferometry.

UNLABELLED: This article introduces a technique for obtaining high-resolution body contour data in the same coordinate frame as that of a rotating gamma camera, using a miniature range finder, the conoscope, mounted on the camera gantry. One potential application of the technique is accurate coregistration in longitudinal brain SPECT studies, using the face of the patient (or "mask"), instead of SPECT slices, to coregister subsequent acquisitions involving the brain. METHODS: Conoscopic holography is an interferometry technique that relies on spatially incoherent light interference in birefringent crystals. In this study, the conoscope was used to measure the absolute distance (Z) between a light source reflected from the skin and its observation plane. This light was emitted by a 0.2-mW laser diode. A scanning system was used to image the face during SPECT acquisition. The system consisted of a motor-driven mirror (Y axis) and the gamma-camera gantry (1 profile was obtained for each rotation step, X axis). The system was calibrated to place the conoscopic measurements and SPECT slices in the same coordinate frame. RESULTS: Through a simple and robust calibration of the system, the SE for measurements performed on geometric shapes was less than 2 mm, i.e., less than the actual pixel size of the SPECT data. Biometric measurements of an anthropomorphic brain phantom were within 3%-5% of actual values. The mask data were used to register images of a brain phantom and of a volunteer's brain, respectively. The rigid transformation that allowed the merging of masks by visual inspection was applied to the 2 sets of SPECT slices to perform the fusion of the data. CONCLUSION: At the cost of an additional low-cost setup integrated into the gamma-camera gantry, real-time data about the surface of the head were obtained. As in all other surface-based techniques (as opposed to volume-based techniques), this method allows the match of data independently from the dataset of interest and facilitates further registration of data from any other source. The main advantage of this technique compared with other optically based methods is the robustness of the calibration procedure and the compactness of the sensor as a result of the colinearity of the projected beam and the reflected (diffused) beams of the conoscope. Taking into account the experimental nature of this preliminary work, significant improvements in the accuracy and speed of measurements (up to 1000 points/s) are expected.

Left ventricular ejection fraction in obstructive sleep apnea. Effects of long-term treatment with nasal continuous positive airway pressure.

The effects of treatment with nasal continuous positive airway pressure (CPAP) on left ventricular ejection fraction (LVEF) were assessed in 29 patients with obstructive sleep apnea (OSA) in a prospective study using multiple gated equilibrium radionuclide angiocardiography. All patients were evaluated before CPAP treatment was initiated and were reevaluated after one year (mean +/- SE, 415 +/- 6 days), of home treatment with nasal CPAP. The mean LVEF increased from 59 +/- 1 percent to 63 +/- 1 percent (p less than 0.005). The degree of improvement in LVEF was correlated with baseline LVEF (r = 0.54; p less than 0.003), meaning that the lower the baseline value, the greater the increase with treatment. The changes were not different when subgroups of medicated and unmedicated patients were considered separately. These results show that long-term nasal CPAP treatment results in improved left ventricular function in OSA.

Evaluation of Elecsys free triiodothyronine assay: relevance of age-related reference ranges.

OBJECTIVE: This study aimed at evaluating Elecsys free triiodothyronine (FT3) assay performed on an Elecsys 2010 system, while paying special attention to age relationship in euthyroid subjects. DESIGN AND METHODS: FT3 levels were measured in 149 euthyroid control subjects aged between 2 and 92 years old, 33 hyperthyroid and particular euthyroid patients: female in the last 3 months of pregnancy (n = 30), nonthyroidal ill hospitalized in medical (NTlm, n = 31), or intensive care units (NTlc, n = 31) and amiodarone-treated (n = 27). RESULTS: FT3 was inversely related to age in controls (r = -0.67). Three reference ranges were used: below 20 years 4.5-9.0 pmol/L, between 20 and 60 years 3.9-7.2, and over 60 years 2.4-6.5. Compared to age-matched controls, FT3 decreased in pregnancy, NTlm, NTlc, and amiodarone groups. Use of age-related reference ranges improved the specificity markedly in amiodarone patients and to a lesser extent in NTlm and TClc patients. CONCLUSIONS: The reliability of the Elecsys FT3 assay was found to be satisfactory for clinical use, when the age of patients was taken into account.

7Li relaxation time measurements at very low magnetic field by 1H dynamic nuclear polarization.

Dynamic nuclear polarization (DNP) of water protons was used to measure the relaxation time of lithium at very low magnetic field as a demonstration of the use of DNP for nuclei less abundant than water protons. Lithium (Li+) was chosen because it is an efficient treatment for manic-depressive illness, with an unknown action mechanism. After having recalled the theoretical basis of a three-spin system comprising two nuclei-the water proton of the solvent, the dissolved Li+ ion and the free electron of a free radical-we have developed a transient solution in order to optimize potential biological applications of Li DNP. The three-spin model has allowed computation of all the parameters of the system-the longitudinal relaxation rate per unit of free radical concentration, the dipolar and scalar part of the coupling between the nuclei and the electron. and the maximum signal enhancement achievable for both proton and lithium spins. All these measurements have been obtained solely through the detection of the proton resonance.

Dynamic nuclear polarization at very low magnetic fields.

The recent developments in dynamic nuclear polarization (DNP) at low magnetic fields are presented. The first part of the paper is dedicated to DNP theory for 14N nitroxide systems. It is shown that the lower the magnetic field, the higher the DNP factor. In the second part the material necessary to perform DNP in a low magnetic field is described. The third part is devoted to potential biological applications such as oximetry and free radical imaging.

Oxygen imaging in perfused hearts by dynamic nuclear polarization.

The feasibility of localized oximetry by dynamic nuclear polarization (DNP) imaging is demonstrated on perfused sheep hearts. DNPI is a magnetic, double resonance technique, in which the electron paramagnetic resonance (EPR) of a free radical dissolved in a perfusion medium is saturated, while the nuclear magnetic resonance (NMR) of water protons is used to perform conventional NMR imaging. The presence of oxygen reduces the enhancement of the NMR signal induced by DNP. The oxygen content of sheep heart tissues was detected by the subtraction of the DNP image of the heart, perfused with a nitrogen-equilibrated solution, from an image obtained when the heart was perfused with an oxygen-equilibrated solution. This result was obtained with extreme oxygen partial pressure, and the discussion presents physical and chemical means for improving the DNP imaging method. Physical means include field cycling, electron paramagnetic rotary saturation, and the use of a 180 degrees NMR pulse before EPR irradiation. The chemical means discussed are deuterium substitution in nitroxides and the potential use of solid, free radical probes. It is suggested to use the perfused heart model for comparing the numerous methods available to measure the oxygen content of tissues.

Data-driven curvilinear reconstructions of 3D MR images: application to cryptogenic extratemporal epilepsy.

This paper presents a data-driven method for the reconstruction and visualisation of curvilinear slices from three-dimensional (3D) magnetic resonance (MR) scans of the head. Visualisation of curvilinear slices, rather than standard planar slices, produces symmetrical views of the cortex and allows small abnormalities to be detected by comparing the two hemispheres of the brain. In our method, the surface defined by the upper half of the brain is used as a reference shape for curvilinear reconstructions. The brain is first segmented from the 3D scan using a 3D region growing method associated to an unsupervised threshold selection technique. The upper half of the segmented brain is then extracted and fitted by a deformable surface model. This surface is finally interactively moved by the operator in the 3D scan, to visualise the desired curvilinear slice, which is projected on the screen as a two-dimensional image. We show an application of this visualisation technique to the localisation of cerebral epileptogenic lesions. The procedure has proven efficient and handy in clinical use.

Myocardial gated tomoscintigraphy with 99Tcm-methoxy-isobutyl-isonitrile (MIBI): regional and temporal activity curve analysis.

Myocardial gated tomoscintigraphy with hexakis-(2 methoxy-isobutyl-isonitrile) labelled with 99Tcm, is more suitable to resolve precisely the size of myocardial infarct than nongated 201Tl tomoscintigraphy. Gated tomography gives short axis slices at eight points in the cardiac cycle. A quantitative method to analyse heart wall activity and its motion is proposed. In two groups of patients, one with inferior infarct and the other with anterior infarct, the time-activity curves show a maximum in systole for healthy regions and a flattened curve in akinetic regions. Gated tomoscintigraphy assesses more accurately the size of the injured regions because there is no averaging between systolic and diastolic activity as in 201Tl tomoscintigraphy. This method should permit a better follow-up of patients with myocardial infarct.

The pitfalls of planar three-phase bone scintigraphy in nontraumatic hip avascular osteonecrosis.

PURPOSE: This study documented the previously reported lower sensitivity of routine planar three-phase bone scintigraphy (BS) performed using a high-resolution parallel-hole collimator compared with MRI to diagnose nontraumatic avascular necrosis of the hip (AVN). METHODS: Six observers reviewed 143 bone scintigrams obtained in patients with nontraumatic hip pain (n = 120) or a control group (n = 23). All patients had a standard radiograph and MRI within 2 months of the BS. Of 280 hips, 148 (53%) were painful on the day of the examination. The osteonecrosis group (AVN) consisted of 93 instances of AVN in 58 patients. Although it departs from the clinical situation, this method evaluated the intrinsic performance of the imaging method. The data were analyzed using a receiver operating characteristic method. RESULTS: For the six observers, the A(z) values were 0.65, 0.67, 0.66, 0.67, 0.73, and 0.79, respectively, and 0.66, 0.71, 0.75, 0.81, 0.81, 0.82, and 0.84 after removing hip diseases other than AVN through data manipulation. Bone marrow edema, as seen on MRI, was the most frequently reported misleading sign in false-positive diagnoses, especially in the early or late phases of the disease. False-negative diagnoses misclassified the scans as "asymptomatic hips" in 28 of 30 cases. Twenty-two of 30 scans appeared normal, but these AVN lesions were small (<25%) and were discovered by chance on MRIs that displayed bilateral involvement associated with radiographic evidence (stage 0 or 1). Thirteen of 20 patients were followed for 3 or more years, and only one worsened. CONCLUSIONS: BS is not indicated to diagnose possible contralateral AVN if the hip is asymptomatic. This study emphasizes the results from the literature; if indicated, a radionuclide hip investigation requires the use of a pin-hole collimator, a SPECT study with scatter correction and iterative reconstruction algorithms, or both.

Video loop MRI of ocular motility: a new technique: turbo rare sequence at 2 T for the study of horizontal gaze.

PURPOSE: To improve existing MRI (Magnetic Resonance Imaging) methods of assessing ocular motility in horizontal gaze by using a multi-static fast imaging T2W MRI sequence, preventing patient head motion and convergence of the eyes during the study for the diagnosis and management of complex paralytic strabismus. SUBJECTS AND METHODS: A turbo-RARE image of the orbits was acquired in a set plane each time the patient fixed on a virtual image of one of 15 LEDs (Light Emitting Diodes). Positioning and securing the head was by a security cushion with an 8 degree tilt of the 25 cm quadrature head coil. After completion of the study (5 minutes) the MRI images were transferred to a work station and on to a magnetic-video tape to be replayed in cine mode on a PC using standard software. The qualitative analysis was completed by the study of quantitative parameters: visual axis, minor axis of the lens, the lines and angles of the horizontal rectus muscles with the optic nerve and the visual axis. We used digital image analysis to measure the cross-sectional areas of these muscles and also to determine muscle volumes. Twenty normal volunteers and 3 cases of oculomotor palsies were so studied. RESULTS: The experimental setup allowed us to obtain: 1) rapid (14 s) and high resolution images (256 x 196 x 3 mm); 2) which were free artifacts; 3) with no detectable eye convergence; 4) in which the lateral and medial rectus muscles and anatomical details of the orbit were clearly depicted; 5) from which additional functional information was obtained from the cine loop analysis; 6) wherein the visual axes did not converge during horizontal versions; 7) which permitted horizontal rectus muscle angles to be followed during contraction and relaxation; and 8) allowed the cross-sectional area of the four rectus muscles to be compared during contraction and relaxation (difference of 0.2 cm2). CONCLUSIONS: This method will provide useful functional quantitative information in the evaluation of ocular motility disorders. The procedure is readily clinically applicable

[Macroprolactin detection: a new approach]. / Détection de la macroprolactine: une nouvelle approche.

Macroprolactin is a complex of prolactin with immunoglobulins (IgG) that has limited or no biological activity in vivo. Immunoassays for prolactin have variable reactivity with macroprolactin. Therefore the presence of macroprolactin should be considered in the differential diagnosis of hyperprolactinemia. We compared a valid screening test for macroprolactin, polyethyleneglycol (PEG) precipitation, with the determination of the ratio of the results of two prolactin assays: Elecsys with high cross-reactivity with macroprolactin and Centaur with low cross-reactivity. In 59 negative samples subjected to the PEG test (precipitation < 50%), the Elecsys/Centaur ratio ranged between 1.11 and 1.45. Among 35 positive samples (precipitation > 60%), 33 had, as expected, an increased ratio (over 1.45), 1 a normal ratio and 1 a decreased ratio (1.07). This decreased ratio could be due to a particular form of macroprolactin poorly recognised by the Elecsys assay. Among 5 samples in the grey zone (precipitation between 50 and 60%), the ratio was increased in 2, normal in 1 and decreased in 2. Apart from one false negative case (normal ratio with positive PEG test), the results of the Elecsys/Centaur ratio method were in good agreement with those of the PEG test. The ratio method could be helpful for samples with PEG test results in the grey zone, before undertaking a complete analysis of circulating molecular forms by gel filtration chromatography. Out of the 5 five samples in the grey zone, the ratio was 4 times out of the reference range: 2 increased, 2 decreased. Our results also underline the necessity of reevaluating the Centaur prolactin reference range from samples without macroprolactin.

Functional integration in schizophrenia: too little or too much? Preliminary results on fMRI data.

The disconnectivity hypothesis proposes that schizophrenia results from poor or miswired anatomical connections. Theoretically, its functional counterpart should be disintegration. Integration is thought to allow segregated neurons to interact as a coherent whole, referred to as the "core", while the non-interacting part of the brain is referred to as the "rest". In this study, it is suggested that schizophrenia is the result of rest noise interfering with core activity. Two possible causes are assessed: (i) defective core integration, making the core more vulnerable to noise from the rest, or (ii) the rest being too highly integrated, meaning that it can interfere with the core. These hypotheses were tested using fMRI data acquired from 13 stabilized medicated schizophrenic subjects compared to 11 matched controls. Subjects were required to perform a series of lexical decision and retrieval tasks in separate sessions. The brain was divided into 90 components. Integration was defined as the amount of information shared between the components of a sub-system. An iterative aggregation procedure made it possible to identify a core on the basis of the functional clustering index, which assesses the integration of the core relative to its integration with the rest. Correlation of component-pairs within the core was also compared between the two groups. This procedure was repeated for each subject and for each task. Cores did not differ between the two groups, either in terms of integration or in terms of functional clustering index. However, the core was still highly integrated with the rest and the rest was overly integrated in schizophrenic subjects. Both anomalies were correlated with the negative symptoms. These findings were consistent regardless of the task considered. Furthermore, within the core, anterior-posterior correlations were lower in patients (between the frontal and the parietal and posterior cingulate cortices), whereas frontal left-right correlations were excessive. No significant correlation was found with the medication. Thus, it appears that schizophrenia entails a deleterious combination of too much "noisy" integration (from the rest) and too little "significant" integration (anterior-posterior functional connectivity).

In vivo detection of injected free radicals by Overhauser effect imaging.

Proton dynamical polarization is a method which unites the advantages of continuous wave ESR sensitivity and pulsed NMR imaging in order to localize free radicals. Injected nitroxide has been imaged for the first time in living rats. The high sensitivity of this method to oxygen is demonstrated.

New method for contrast manipulation in DNP-enhanced MRI.

The magnetization subtraction technique (MS), which is equivalent to the inversion recovery technique in strong magnetic fields, has been implemented in dynamic nuclear polarization-enhanced magnetic resonance imaging (DNPI). The general theoretical basis of the MS method, which can be applied to DNPI or to prepolarized MRI in weak magnetic fields (such as Earth's magnetic field), is introduced. Details are provided about the signal amplitude, dynamic range of the method, and conditions required to observe signal void in samples with specific T1 relaxation times. The experimental results obtained with MS DNPI are presented and discussed. In the experiments, electron spin resonance irradiation frequencies of 199 MHz and 16.2 MHz were employed. Also, T1 contrast manipulation in the polarizing and in the detection magnetic field is discussed and demonstrated for MS DNPI.