Biomedical subjects

O Baffa

Publications and source records attributed to O Baffa.

At least 19 recordsLinked to original sources

PubMed2006

ESR dating of an ancient goat tooth from Nuoro, Sardinia, Italy.

The dating of fossil teeth of an ancient goat (Nesogoral melonii) using the electron spin resonance (ESR) technique is reported. This animal was found in the fossiliferous site at Orosei (Nuoro, Sardinia, Italy) and was endemic in the region. Molar teeth were cleaned and enamel was completely removed from dentine. Enamel was irradiated with a 60Co gamma source and measured with an ESR spectrometer (X-band) to obtain the signal vs. dose curve and fitted with an exponential function. The archeological dose obtained by the fitting was 211 +/- 34 Gy. Uranium and thorium concentrations were determined by neutron activation analysis. With the software ROSY the age estimates were 195 +/- 30 ky for early uptake, 247 +/- 40 ky for linear uptake and 243 +/- 40 ky for a combination of uptake processes.

Animals↗

PubMed2006

A novel biomagnetic approach to study caecocolonic motility in humans.

Motility patterns play a major role in human colonic functions; however, its physiological significance is poorly understood. Several studies have been introducing the Alternating Current Biosusceptometry (ACB) as a valuable tool in gastroenterology and pharmaceutical research. Using gold standard techniques, great effort has been made to validate ACB as a method for measuring gastrointestinal motility in humans and animals. The aim of this study was to evaluate caecocolonic motility and its response to a meal in healthy volunteers. The results showed a dominant frequency of 3.17 +/- 0.13 cycles per minute (mean +/- SD) that remained unchanged even after a standardized meal (P > 0.01). The colonic response to a meal was recorded as a considerable increase in amplitude, reflected by motility index (P < 0.01) and was observed for all the volunteers. The caecocolonic motility could be assessed by the ACB providing new insights into physiological patterns of motility. Moreover, the method is non-invasive, radiation-free, cost-effective and independent of bowel preparation.

Adult↗

PubMed2005

Magnetic images of the disintegration process of tablets in the human stomach by ac biosusceptometry.

Oral administration of solid dosage forms is usually preferred in drug therapy. Conventional imaging methods are essential tools to investigate the in vivo performance of these formulations. The non-invasive technique of ac biosusceptometry has been introduced as an alternative in studies focusing on gastrointestinal motility and, more recently, to evaluate the behaviour of magnetic tablets in vivo. The aim of this work was to employ a multisensor ac biosusceptometer system to obtain magnetic images of disintegration of tablets in vitro and in the human stomach. The results showed that the transition between the magnetic marker and the magnetic tracer characterized the onset of disintegration (t(50)) and occurred in a short time interval (1.1 +/- 0.4 min). The multisensor ac biosusceptometer was reliable to monitor and analyse the in vivo performance of magnetic tablets showing accuracy to quantify disintegration through the magnetic images and to characterize the profile of this process.

Administration, Oral↗

PubMed2005

AC biosusceptometry in the study of drug delivery.

Conventionally, pharmaceutical substances are administered orally because the gastrointestinal tract possesses the appropriate features for drug absorption. Nevertheless, the gastrointestinal tract physiology is complex and influenced by many factors. These factors must be completely understood for the optimization of oral drug delivery systems. Although in vitro tests provide information about release and drug absorption profiles, in vivo studies are essential, due to the biological variability. Several techniques have been employed in an attempt to conveniently characterize the behavior of solid dosage forms in vivo. The noninvasive biomagnetic technique of alternate current biosusceptometry (ACB) has been used in studies focusing on gastrointestinal motility and, more recently, to evaluate the performance of magnetic dosage forms. This article will discuss the main characteristics of AC biosusceptometry and its applicability for determination of the relationship between the human gastrointestinal tract and orally administered pharmaceutical dosage forms.

Drug Delivery Systems↗

PubMed2005

Spatiotemporal evaluation of human colon motility using three-axis fluxgates and magnetic markers.

An alternative method to study the mechanical activity of the human colon in fasting and postprandial states is presented. The method is based on measurements of the magnetic fields produced by a magnetic marker, a small cylindrical NdBFe magnet, when it was ingested by the subjects. A portable magnetic probe, consisting of two digital three-axis fluxgate magnetometers, arranged in a first-order electronic gradiometer, was implemented for this research. Measurements were taken in 16 healthy male subjects. Contractile activity frequency measurements were taken along the colon length, including the ascending, transverse and descending sections, as well as the rectal sigmoidal section. Values for the contractile activity frequency of 2-5 cycles min(-1) were measured. The set-up is simple, low-cost and suitable for use in an unshielded environment.

Adult↗

PubMed2005

Study of paramagnetic and luminescence centers of microcline feldspar.

Microcline feldspar crystal has been analyzed in order to determine the centers suitable for use in ESR and luminescence dating. ESR measurements at RT showed the Fe3+ line, and at 77K the Si-O(-) ..X signal with g=2.0052, 2.0098 and 2.0128. TL glow peak at 157 and 300 degrees C in UV interval were observed and in the VIS range we noted peaks at 150, 280 and 340 degrees C. TL growth curve of the 340 degrees C peak could be fitted by a saturating exponential equation and can be used in TL dating. Emission curves showed band widths 1.95+/-0.09, 2.73+/-0.08 and 4.94+/-0.50 eV. Transitions from 4T1-->6A1)of Fe3+ can be associated with the 1.95 eV band and the transition from 4A1 4E(G)-->6A1(S) with 2.73 eV band.

Journal Article↗

PubMed2005

Study of dental enamel and synthetic hydroxyapatite irradiated by EPR at K-band.

In this preliminary work the EPR spectra of a small dental enamel block and a synthetic B-type hydroxyapatite in powder form, both irradiated with gamma rays, were analyzed in K-band. The spectra of the dental enamel block allow the analysis of independent components with different angular orientations, while the study of the dosimetric properties of the synthetic hydroxyapatites showed good performance of this spectrometer. K-band spectra show better resolution when compared to X-band, while using significantly less sample material.

Body Burden↗

PubMed2004

In vivo tissue characterization using magnetic techniques.

Among the few non-invasive methods to quantify liver iron deposits, magnetic resonance imaging (MRI) and biomagnetic liver susceptometry (BLS) have been considered the best to evaluate iron overload in the body. This diagnosis is necessary for patients who regularly receive red blood cells transfusion and that have a genetic disorder known as hemochromatosis. In this work, we present the evaluation of the clinical usefulness of MRI and BLS of hepatic tissue to quantify iron deposits in non-transfused and transfused patients. Liver iron evaluation by MRI and BLS were performed in a group of 48 patients. The MRI images weighted in T2 were acquired using multi-slice single-spin-echo (SSE) and single-slice multi-spin-echo (MSE), conducted on a 1.5 T whole body scanner. BLS measurements were performed using an ac superconducting susceptometer based on SQUID. Typically MRI is able to evaluate iron overload in liver as high as 30 mg/g(dry tissue) when using MRI scanners provided with specially designed pulse sequences. For higher iron concentrations susceptibility measurement works better than MRI to evaluate higher iron overloads in the liver, because in this case there is saturation of MRI signal.

Adolescent↗

PubMed2004

Euterpe Olerácea (Açaí) as an alternative oral contrast agent in MRI of the gastrointestinal system: preliminary results.

Using contrast agents is a common practice in medical imaging protocols. Paramagnetic properties of certain compounds present in contrast agents can affect magnetic resonance imaging (MRI) signals. For abdominal applications, they are usually injected, but may also be administered orally. However, their use as a routine technique is limited, mainly due to the lack of appropriate oral contrast agents. We herein present the preliminary characterization and results for implementation of Euterpe Olerácea (popularly named Açaí) as a possible clinical oral contrast agent for MRI of the gastrointestinal tract. The pulp of Açaí, a fruit from the Amazon area, presented an increase in T(1)-weighted MRI signal, equivalent to that of gadolinium-diethyltriamine pentaacetic acid, and a decrease in T(2)-weighted images. We looked for intrinsic properties that could be responsible for the T(1) signal enhancement and T(2) opacification. Atomic absorption spectra revealed the presence of Fe, Mn and Cu ions in Açai. The presence of such ions contribute to the susceptometric value found of chi = -4.83 x 10(-6). This finding assents with the hypothesis that image contrast changes were due to the presence of paramagnetic material. The first measurements in vivo demonstrate a clear increase of contrast, in T(1)-weighted images, due to the presence of Açaí. Consistently, the opacification in a T(2)-weighted acquisition was evident, revealing a good contrast on bowel walls of gastric tissues.

Administration, Oral↗

PubMed2003

Shannon entropy applied to the analysis of event-related fMRI time series.

Event-related functional magnetic resonance imaging (ER-fMRI) refers to the blood oxygen level-dependent (BOLD) signal in response to a short stimulus followed by a long period of rest. These paradigms have become more popular in the last few years due to some advantages over standard block techniques. Most of the analysis of the time series generated in such exams is based on a model of specific hemodynamic response function. In this paper we propose a new method for the analysis of ER-fMRI based in a specific aspect of information theory: the entropy of a signal using the Shannon formulation, which makes no assumption about the shape of the response. The results show the ability to discriminate between activated and resting cerebral regions for motor and visual stimuli. Moreover, the results of simulated data show a more stable pattern of the method, if compared to typical algorithms, when the signal to noise ratio decreases.

Adult↗

PubMed2003

Measurement of gastric contraction activity in dogs by means of AC biosusceptometry.

The mechanical nature of gastric contraction activity (GCA) plays an important role in gastrointestinal motility. The aim of this study was to detect GCA in anaesthetized dogs, using simultaneously the techniques of AC biosusceptometry (ACB) and manometry, analysing the characteristics of frequency and amplitude (motility index) of GCA, modified by drugs such as prostigmine and N-butyl-scopolamine. The ACB method is based on a differential transformer of magnetic flux and the magnetic tracer works as a changeable external nucleus. This magnetic tracer causes a modification in the magnetic flux, which is detected by the coils. The results obtained from the ACB showed a performance comparable to the manometry in measuring the modifications in the frequency and amplitude of the GCA. We concluded that this ACB technique, non-invasive and free of ionizing radiation, is an option for evaluating GCA and can be employed in future clinical studies.

Anesthesia↗

PubMed2002

ESR dating of a subfossil shell from Couve Island, Ubatuba, Brazil.

The occurrence of subfossil material in bottom sediments of Couve Island, Ubatuba region, São Paulo State, is confirmed. The analyzed material consists of a bivalve shell that was dated by the electron spin resonance technique. By the additive irradiation method an archaeological absorbed dose of (25 +/- 5) Gy was obtained and calibration with other dating works in the same area allows the inference of an age of (25 +/- 5) x 10(2) years. The importance of this finding and its paleoecological implications could contribute to elucidating the nature of short-term environmental changes in the Brazilian coastline during the Holocene, as well as becoming an important tool to the understanding of the distribution and biological aspects of the bivalve fauna.

Animals↗

PubMed2002

Theoretical evaluation of the susceptometric measurement of iron in human liver by four different susceptometers.

This paper is an evaluation of liver iron quantification using a simulated magnetic susceptibility measurement in the hepatic region. Susceptometers having homogeneous and non-homogeneous magnetizing fields coupled with axial second-order and planar first-order gradiometric magnetic detectors were considered. The intensity of magnetic flux threading the detector coils was evaluated considering samples with volume and susceptibility equivalent to liver iron, tissue and lung air individually. These volumes were represented by cylindrical and spherical geometries. The main sources of error in quantifying iron overload in susceptometric measurement of hepatic tissue were evaluated for four configurations of the susceptometer.

Anemia, Iron-Deficiency↗

PubMed2001

Pharyngeal clearance and pharyngeal transit time determined by a biomagnetic method in normal humans.

Clearance and transit time are parameters of great value in studies of digestive transit. Such parameters are nowadays obtained by means of scintigraphy and videofluoroscopy, with each technique having advantages and disadvantages. In this study we present a new, noninvasive method to study swallowing pharyngeal clearance (PC) and pharyngeal transit time (PTT). This new method is based on variations of magnetic flux produced by a magnetic bolus passing through the pharynx and detected by an AC biosusceptometer (ACB). These measurements may be performed in a simple way, cause no discomfort, and do not use radiation. We measured PC in 8 volunteers (7 males and 1 female, 23-33 years old) and PTT in 8 other volunteers (7 males and 1 female, 21-29 years old). PC was 0.82 +/- 0.10 s (mean +/- SD) and PTT was 0.75 +/- 0.03 s. The results were similar for PC but longer for PTT than those determined by means of other techniques. We conclude that the biomagnetic method can be used to evaluate PC and PTT.

Adult↗

PubMed2001

ESR dosimetry of 89Sr and 153Sm in bone.

The radiation absorbed dose in the rabbit bone delivered by 153Sm-EDTMP (samarium ethylenediaminetetra methylene diphosphonic acid) and 89SRCl2 (strontium chloride) was measured by means of electron spin resonance (ESR). These radioisotopes are used in systemic radiotherapy for palliation of painful bone metastases. The knowledge of the dose is important in order to avoid side effects to the bone marrow. The ESR radiation dose signal was calibrated by the additive dose method using cobalt-60 gamma rays. For 153Sm-EDTMP, the bone doses in three rabbits were (4 +/- 2), (5 +/- 1) and (5 +/- 2) cGy kg/MBq. For 89SrCl2, a dose of (2 +/- 1) cGy kg/MBq was found in one rabbit.

Animals↗

PubMed2001

Dosimetry of blood irradiation using an alanine/ESR dosimeter.

A batch of 80 DL-alanine dosimeters was supplied to Hemocentro of the Hospital and Clinics of Faculdade de Medicina de Ribeirão Preto (HC-FM RP) SP, Brazil for the purpose of quality control of the radiation dose delivered to blood bags. The irradiation was made using two (40 x 40) cm2 parallel opposed radiation fields each with 80 cm of source to surface distance in the Radiotherapy Section of HC-FMRP with the 60Co teletherapy unit. The calculated radiation absorbed dose at the center of the box was 20 Gy. The dosimeter readings were performed using a Varian E-4 ESR Spectrometer operating in X-band. For the 80 dosimeters and over the irradiation volume throughout a blood bag, the minimum and maximum doses were 14 and 23 Gy, respectively. The mean dose was (18 +/- 2) Gy (1sigma), and the coefficient of variability was 11.1%. Alanine dosimeters demonstrated easy handling, good precision and adequate sensitivity for this application.

Alanine↗

PubMed2000

ESR dating of a toxodon tooth from a Brazilian karstic cave.

A pre-molar of a Toxodon platensis (sp), a large mammal that inhabited the forests of Southeast Brazil during quaternary times, was dated by electron spin resonance (ESR). Enamel and dentine were separated giving, the following archeological doses (AD): (4.0+/-0.8) and (11+/-2) Gy, respectively. This difference was explained by the higher content of Uranium in dentine (25.1+/-0.3) ppm as compared to enamel (0.37+/-0.03) ppm. Taking account of the internal dose contribution to the AD, the age obtained is (6.7+/-1.3) ky BP for dentine and (5.0+/-1.6) ky BP for enamel.

Animals↗

PubMed1999

Study of stomach motility using the relaxation of magnetic tracers.

Magnetic tracers can be observed in the interior of the human body to give information about their quantity, position and state of order. With the aim of detecting and studying the degree of disorder of these tracers after they have been previously magnetized inside the stomach, a system composed of magnetization coils and magnetic detectors was developed. Helmholtz coils of diameter 84 cm were used to magnetize the sample and the remanent magnetization (RM) was detected with two first-order gradiometric fluxgate arrays each with a 15 cm base line, sensitivity of 0.5 nT and common mode rejection (CMR) of at least 10. The system allows simultaneous measurement in the anterior and posterior projections of the stomach. Measurements of the time evolution of the RM were performed in vitro and in normal subjects after the ingestion of a test meal labelled with magnetic particles. The data were fitted with an exponential curve and the relaxation time tau was obtained. Initial studies were performed to ascertain the action of a drug that is known to affect the gastric motility, showing that the decay of the remanent magnetization was indeed due to stomach contractions.

Butylscopolammonium Bromide↗