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Biomedical subjects

M Abreu

Publications and source records attributed to M Abreu.

At least 19 recordsLinked to original sources
PubMed2004

Calcification in calcium pyrophosphate dihydrate (CPPD) crystalline deposits in the knee: anatomic, radiographic, MR imaging, and histologic study in cadavers.

OBJECTIVE: To demonstrate and determine the frequency and location of calcification within cadaveric knees with or without calcification typical of calcium pyrophosphate dihydrate (CPPD), utilizing histologic, radiographic and MR imaging techniques. DESIGN AND PATIENTS: Ten cadaveric knees of elderly individuals that demonstrated no radiographic evidence of prior surgery or trauma were studied with MR imaging and subsequently sectioned in planes corresponding to those obtained with MR imaging. The slices were imaged with high-resolution radiography. Two musculoskeletal radiologists correlated the anatomic, MR and radiographic findings. Three of the knees, which did not demonstrate calcifications, were utilized as controls. Histologic sections were obtained from four knees that contained calcifications and from the three controls, and analyzed with special histologic stains that demonstrate phosphorus and calcium. RESULTS: Radiographic imaging and histologic analysis demonstrated widespread CPPD crystal deposition in four of the 10 knee specimens (40%). MR imaging demonstrated some calcifications only within the articular cartilage of the femoral condyles in three of the four (75%) specimens that had CPPD deposits. In all four specimens radiographs and histologic analysis were more sensitive than MR imaging. Histologic analysis demonstrated no evidence of CPPD crystals in the control specimens. CONCLUSION: MR imaging is insensitive to the presence of CPPD deposits in the knee, even when such deposits are widespread. Our study suggests that the sensitivity of MR imaging was significantly better in detecting CPPD deposits in the hyaline cartilage of the femoral condyles when compared with other internal structures, even when such structures contained a higher amount of calcification.

Aged↗
PubMed2004

Comparative diagnostic performance of TACT slices and its multiple source images: an in vitro study.

OBJECTIVE: To compare the diagnostic performances provided by tuned aperture computed tomography (TACT) slices and the multiple images that they originate from in the detection of primary caries on the proximal surfaces of posterior teeth. STUDY DESIGN: Eight direct digital radiography images of each of 40 posterior teeth were acquired with a digital sensor. These source images were used to generate TACT slices of the teeth. Eight trained observers were calibrated in the use of both TACT slices and the eight source images of each tooth. They were asked to assess the presence/absence of proximal caries in the teeth using a 5-point rating scale. Observers' assessments were compared with the ground truth provided by histological examination of tooth sections. Areas under the receiver operating characteristic (ROC) curves (Az) were calculated for each combination of observer and image modality. Analysis of variance (ANOVA) was used to test the ROC values for potential statistical differences. RESULTS: Mean ROC Az values were 0.760 for TACT slices and 0.771 for its multiple source images for the detection of primary proximal caries. ANOVA showed no statistically significant differences either between modalities (P = 0.656) or between observers (P = 0.851). CONCLUSION: TACT slices and its multiple source images provide comparable diagnostic performance for proximal caries detection.

Analysis of Variance↗
PubMed2003

Effect of data compression on proximal caries detection: observer performance with DenOptix photostimulable phosphor images.

OBJECTIVES: To study the effect of lossy image compression on caries detection. Null hypothesis states no difference in caries detection efficacy among observers using original digital images versus images compressed at various rates of compression. METHODS: Digital images of 41 extracted posterior teeth were obtained with a storage phosphor DenOptix (Gendex DenOptix Imaging system) system. Images were exported in Tagged Image File Format (TIFF) and compressed with Joint Photographic Experts Group File Interchange Format (JFIF), as provided by the software of the imaging system. The compressions options JFIF100%, JFIF75% and JFIF50% resulted in reducing the image size to 1:2, 1:11 and 1:16, respectively. Eight observers evaluated the presence or absence of caries on a 5-point confidence scale. The actual caries status of each proximal surface was determined by ground section histology. Responses were evaluated by receiver operating characteristic (ROC) analysis. Areas under the curves (Az) were assessed using analysis of variance (ANOVA). RESULTS: The mean Az scores were 0.85 for original/uncompressed images, and 0.89 for JFIF100%, 0.88 for JFIF75% and 0.88 for JFIF50% images. These differences were not statistically significant (P = 0.26). Differences between observers were also not statistically significant (P = 0.12). CONCLUSIONS: JFIF compression at the level of 1:16 can be used without significant deterioration in diagnostic accuracy for proximal caries detection.

Analysis of Variance↗
PubMed2002

[Detection of the cutaneous melanomas, their metastasis and relapses by scintigraphies with 99MTC-HMPAO].

A pilot study was carried out in the Nuclear Medicine Department of the National Institute of Oncology and Radiobiology to learn the diagnostic efficacy of the 99mTc-HMPAO scintigraphy in the detection of cutaneous melanoma, distant and local metastases, in patients with a confirmed histological diagnosis. The planar and/or SPECT scintigraphy was performed in 17 patients and revealed 90% sensitivity for the detection of the disease. We calculated the tumor/background index in all the images obtained and found a value greater than 1 in every case. Thus, we can affirm that the 99mTc-HMPAO accumulation in tumors was higher than the background in all cases. We recommend that this procedure be considered in the follow up of these patients as a new diagnostic method which is very useful in the determination of the patient stage and prognostic evaluation.

Adult↗
PubMed2002

Influence of the number of basis images and projection array on caries detection using tuned aperture computed tomography (TACT).

OBJECTIVES: to determine if the number of basis images and spatial distribution of the projection array used for TACT slice generation influence observer performance in caries detection. METHODS: In the first experiment, 2, 4, 8 and 12 basis projections of each of 40 teeth were acquired using a CMOS digital radiography sensor. Projections were distributed radially in space using a 20 degree angular disparity. TACT slices were generated from the four subgroups of images, presented to eight observers, and viewed on a high-resolution monitor. Observers scored the presence/absence of caries using a 5-point confidence scale. Gold standard was histological examination of tooth sections. ROC curves measured observer diagnostic performance. ANOVA tested for significant differences between observers and experimental conditions. In the second experiment, the number of basis projections judged to be satisfactory for TACT slice generation was used. Horizontal and vertical linear arrays of projections were compared to the circular projection array. RESULTS: There was a statistically significant difference between the numbers of basis projections in the detection of both occlusal (P=0.006) and proximal caries (P=0.005). No significant difference was found between projection arrays in the detection of either occlusal (P=0.065) or proximal (P=0.515) caries. CONCLUSIONS: The number of TACT basis projections significantly influences caries detection. Eight or more images should be used. Either linear-vertical, linear-horizontal or circular arrays of basis projections may be used for TACT slice generation in caries detection tasks.

Analysis of Variance↗
PubMed2001

Performance of a new F-speed film for caries detection.

OBJECTIVE: To compare films from three speed groups for the detection of approximal caries. STUDY DESIGN: Insight, Ektaspeed Plus and Ultra-speed (Eastman-Kodak, Rochester, NY, USA) radiographs of the proximal surfaces of 40 extracted posterior teeth were evaluated by six observers. The presence or absence of caries was scored using a 5-point confidence scale. The actual status of each surface was determined from histology of ground sections. Observer responses were evaluated using ROC analysis and areas under the ROC curves (A(Z)) assessed using ANOVA. RESULTS: Ultra-speed film had a mean A(Z) of 0.88, Ektaspeed Plus 0.85, and Insight 0.84. These differences were not statistically significant (P=0.5). Differences between observers were also not statistically significant (P=0.42). CONCLUSIONS: The performance of the new F-speed film was not statistically different from E or D speed for caries detection. This film shows promise as a means of reducing patient dose while maintaining diagnostic quality.

Analysis of Variance↗
PubMed2001

The effect of the number of iterative restorations on tuned aperture computed tomography for approximal caries detection.

OBJECTIVES: To determine whether the number of iterative restorations performed on TACT images affects observers' ability to detect dental caries. METHODS: Eight TACT basis images of 40 extracted human posterior teeth were acquired using a CCD sensor. TACT slices of each tooth were generated and subsequently submitted to 1, 2 or 3 iterative restorations. Stacks of images from the three experimental conditions were presented to six observers in a balanced order, on a high-resolution 21' color monitor. Observers scored the presence or absence of approximal caries using a 5-point confidence scale. Observers' assessments were compared with the results of histological examination. Receiver operating characteristic (ROC) curves were generated and possible significant differences between observers and between modalities tested by ANOVA. The level of significance was set at alpha=0.05. Interobserver reliability was calculated as intraclass correlation. RESULTS: Mean areas under the ROC curves (A(z)) for the three experimental conditions were 0.791 (one iterative restoration), 0.81 (two iterative restorations), and 0.778 (three iterative restorations). ANOVA did not demonstrate any significant difference between modalities (P=0.25) but did so between observers (P=0.031). Interobserver reliability was similar for all experimental conditions tested. CONCLUSIONS: Varying the number of iterative restorations from one to three does not affect observers' ability to detect approximal caries with TACT slices.

Analysis of Variance↗
PubMed2001

Performance of RVGui sensor and Kodak Ektaspeed Plus film for proximal caries detection.

OBJECTIVE: A high-resolution charge-coupled device was used to compare the diagnostic performances obtained with Trophy's new RVGui sensor and Kodak Ektaspeed Plus film with respect to caries detection. STUDY DESIGN: Three acquisition modes of the Trophy RVGui sensor were compared with Kodak Ektaspeed Plus film. Images of the proximal surfaces of 40 extracted posterior teeth were evaluated by 6 observers. The presence or absence of caries was scored by means of a 5-point confidence scale. The actual caries status of each surface was determined through ground-section histology. Responses were evaluated by means of receiver operating characteristic analysis. Areas under receiver operating characteristic curves (A(Z)) were assessed through analysis of variance. RESULTS: The mean A(Z) scores were 0.85 for film, 0.84 for the high-resolution caries mode, and 0.82 for both the low resolution caries mode and the high-resolution periodontal mode. These differences were not statistically significant (P =.70). The differences among observers also were not statistically significant (P =.23). CONCLUSION: The performance of the RVGui sensor in high- and low-resolution modes for proximal caries detection is comparable to that of Ektaspeed Plus film.

Analysis of Variance↗
PubMed2001

Effect of angular disparity of basis images and projection geometry on caries detection using tuned-aperture computed tomography.

OBJECTIVE: The purpose of this study was to determine whether projection geometry and angular disparity of basis images used for tuned-aperture computed tomography (TACT) slice generation influence observer performance in caries detection. STUDY DESIGN: Four sets of 8 projections of each of 40 teeth were acquired by using a digital sensor. Each set was radially distributed and subtended angular disparities of 10 degrees, 20 degrees, 30 degrees, and 40 degrees, representing strict projection geometries. A fifth set of images was acquired by using unconstrained geometry. TACT slices were generated from all experimental conditions and presented to 8 observers who viewed the images on a high-resolution monitor. Observers scored the presence/absence of caries with a 5-point confidence scale. Ground truth was achieved by histologic examination of tooth sections. Receiver operating characteristic curves measured observers' diagnostic performance. Analysis of variance was used to test for significant differences among observers and between experimental conditions. RESULTS: No statistically significant difference between angular disparities was found for the detection of either occlusal (P =.105) or proximal (P =.052) caries. No statistically significant difference between unconstrained and stringent projection geometries was found for the detection of either occlusal (P =.879) or proximal (P =.130) caries. CONCLUSIONS: Angular disparities ranging from 10 degrees to 40 degrees provide comparable performance in caries detection with TACT. Both unconstrained and stringent projection geometries may be used when reconstructing TACT slices for caries detection tasks.

Analysis of Variance↗
PubMed2001

Generation of TACT image slices using different reconstruction algorithms: effects on natural caries detection.

OBJECTIVE: The purpose of this study was to determine whether the method of reconstruction of tuned-aperture computed tomography (TACT) slices has an influence on observer performance in caries detection. STUDY DESIGN: Eight images of each of 40 extracted posterior teeth were acquired by using a solid state intraoral detector. Stacks of tuned-aperture computed tomography slices were generated by using the minimum and average reconstruction methods. Slices of the 2 experimental conditions were presented to 8 observers in a balanced order. Images were viewed on a high-resolution 21-in color monitor. Observers scored the presence/absence of caries by using a 5-point confidence scale. Observers' assessments were compared with histologic examinations of tooth sections. Receiver operating characteristic curves measured observers' diagnostic performance. Analysis of variance was used to test for possible significant differences between observers and between experimental conditions. Sensitivity, specificity, accuracy, and interobserver reliability were also calculated. RESULTS: No statistically significant differences between the 2 methods of reconstruction were found for the detection of either occlusal (P =.07) or proximal (P =.52) caries. Interobserver reliability was similar for both experimental conditions. CONCLUSIONS: The minimum and average methods of TACT reconstruction provide comparable performances for caries detection tasks.

Algorithms↗
PubMed2000

The importance of language and culture in pediatric care: case studies from the Latino community.

BACKGROUND: Few studies have examined culture's effect on pediatric care. OBJECTIVES: To analyze 3 cases illustrating the importance of culture in pediatrics. METHODS: Case analysis with a cultural competency model. RESULTS: No interpreter was available for the parents of a 3-year-old brought to the emergency department because of abdominal pain; she was discharged twice, returned with an acute abdomen, and was hospitalized for treatment of appendiceal rupture and peritonitis. A 2-year-old fractured her clavicle in a fall but was placed in social services' custody because of a pediatrician's misinterpretation. Parents of a ventilation-dependent 2-week-old with encephalopathy, seizures, and renal failure were unaware of the infant's poor prognosis, despite use of an interpreter. CONCLUSIONS: Culture can have a significant impact on pediatric care; use of a simple model can ensure that pediatricians provide culturally competent care.

Abdominal Pain↗
PubMed1999

Detection of caries with conventional digital imaging and tuned aperture computed tomography using CRT monitor and laptop displays.

OBJECTIVE: The purpose of this study was to compare the diagnostic performance of conventional digital images and tuned aperture computed tomography (TACT) slices in caries detection through use of cathode-ray tube monitor and laptop displays. STUDY DESIGN: Forty-two extracted posterior teeth were mounted and imaged with a direct digital radiography system. Conventional digital bitewing projections and TACT slices were acquired. Images were viewed on a high-resolution cathode-ray tube monitor and on an active-matrix laptop display. Eight observers assessed caries status of occlusal and proximal surfaces of the teeth using all combinations of image and display modality. Observers' assessments were compared with the results of histologic examination of tooth sections. Possible differences in receiver operating characteristic curve areas among displays, image modalities, observers, and surfaces were analyzed by means of analysis of variance. RESULTS: There was no statistically significant difference between the diagnostic performances provided by the cathode-ray tube monitor and laptop displays in caries detection (P = .588). In addition, the performances of digital images and TACT slices were not significantly different (P = .843). CONCLUSIONS: Modern active-matrix laptop displays provide diagnostic quality for caries detection comparable to that obtainable with cathode-ray tube monitors.

Analysis of Variance↗
PubMed1999

Performance of film, desktop monitor and laptop displays in caries detection.

OBJECTIVES: To compare film, desktop monitor and laptop displays of digitized film images for accuracy of caries detection. METHODS: Sixty-four extracted teeth were mounted in eight models and radiographed with E-speed bitewing film. Films were digitized and displayed on a desktop monitor and a laptop display. Six observers scored the presence or absence of enamel and dentinal caries for each proximal surface for film, desktop and laptop displays. Results were compared with the histology of ground sections. ROC curve areas for each display mode and observer were assessed for significant differences with ANOVA. RESULTS: Diagnostic accuracy for proximal surface caries detection was not significantly different for conventional film or desktop monitor and laptop displays for detection of enamel caries (P = 0.9112) or dentin caries (P = 0.2796). CONCLUSIONS: Current laptop active matrix liquid crystal displays provide diagnostic quality for caries detection comparable with conventional film and desktop monitor displays.

Analysis of Variance↗
PubMed1998

Access barriers to health care for Latino children.

BACKGROUND: Latinos will soon be the largest minority group in the United States, but too little is known about major access barriers to health care for this group and whether these barriers result in adverse consequences. OBJECTIVE: To identify important access barriers to health care for Latino children, as cited by parents. DESIGN: Cross-sectional survey of parents of all 203 children coming to the pediatric Latino clinic at an innercity hospital. Questions focused on barriers to health care experienced prior to receiving care at the Latino clinic. RESULTS: Parental ethnicity included Dominican (36%), Puerto Rican (34%), Central American (13%), and South American (11%). Only 42% of parents were American citizens, whereas 36% had green cards, and 13% had no documentation. Eight percent of parents and 65% of the children were born in the United States. Parents rated their ability to speak English as follows: very well/well, 27%; not very well, 46%; and not at all, 26%. The median annual household income was $11,000; 40% of parents never graduated from high school, and 49% headed single-parent households. Forty-three percent of the children were uninsured. A sick child was routinely brought to hospital clinics by 56% of parents, to the emergency department by 21%, and to neighborhood health centers by 21%. When asked to name the single greatest barrier to health care for their children, parents cited language problems (26%), long waiting time at the physician's office (15%), no medical insurance (13%), and difficulty paying medical bills (7%). When parents were asked if a particular barrier had ever caused them not to bring their children in, transportation was cited by 21%; not being able to afford health care, 18%; excessive waiting time in the clinic, 17%; no health insurance, 16%; and lack of cultural understanding by staff, 11%. Some parents who spoke little or no English reported that medical staff not speaking Spanish had led to adverse health consequences for their children, including poor medical care (8%), misdiagnosis (6%), and prescription of inappropriate medications (5%). Multivariate analyses of selected health outcomes using 7 independent variables showed that low family income was significantly associated with greater odds of a child's having suboptimal health status (odds ratio, 1.5; 95% confidence interval, 1.04-2.2) and an increased number of physician visits in the past year (P<.04), but reduced odds (odds ratio, 0.6; 95% confidence interval, 0.4-0.9) of the child's being brought to the emergency department for a routine sick visit. Children whose parents had resided in the United States for fewer than 8 years were at reduced odds (odds ratio, 0.5; 95% confidence interval, 0.2-0.9) for having spent a day or more in bed for illness in the past year. CONCLUSIONS: Parents identified language problems, cultural differences, poverty, lack of health insurance, transportation difficulties, and long waiting times as the major access barriers to health care for Latino children. Language problems can result in adverse health consequences for some children, including poor medical care, misdiagnosis, and inappropriate medication and hospitalization. Low family income is an important independent risk factor among Latino children for suboptimal health and high utilization of health services.

Adult↗
PubMed1993

Displaced amacrine cells in the ganglion cell layer of the ground squirrel retina.

In some mammals a large portion of the retinal neurons of the ganglion cell layer are not ganglion cells. These neurons, lacking axons which pass to the brain via the optic nerve, are termed displaced amacrine cells. The present study assessed the number of displaced amacrine cells in the thirteen-lined ground squirrel (Spermophilus tridecemlineatus). We compared the number of labeled cells in the ganglion cell layer after HRP injection of optic tracts and target nuclei with the total number of neurons in the ganglion cell layer. We conclude that approximately one half of the neurons in the ganglion cell layer are displaced amacrine cells, the other one half are ganglion cells. The displaced amacrine cells are on the average smaller than the ganglion cells. Our results provide a rationale for renewed study of relation of ganglion cell morphology and physiological functional type in this species.

Animals↗
PubMed1991

Effects of competitive N-methyl-D-aspartate antagonists on midbrain dopamine neurons: an electrophysiological and behavioral comparison to phencyclidine.

Electrophysiological and behavioral methods were used to evaluate and compare the effects of the competitive N-methyl-D-aspartate (NMDA) receptor blocker, NPC 12626, with the non-competitive NMDA antagonist, phencyclidine (PCP), on the activity of mesolimbic dopamine neurons. NPC 12626 (50 mg/kg, i.p.) produced a degree of locomotor hyperactivity comparable to that seen with PCP (5 mg/kg). However, 6-hydroxydopamine lesions of the nucleus accumbens blocked the PCP-induced hyperactivity but not the behavioral activation evoked by NPC 12626. Single-unit extracellular recordings from ventral tegmental A10 dopamine neurons also found marked differences between the competitive and non-competitive NMDA antagonists. Intravenous injections of NPC 12626 and CGS 19755 in doses up to 60 mg/kg failed to change A10 activity. This was in contrast to the striking bimodal dose-dependent increase-decrease in firing rate elicited by PCP. The absence of an effect of NPC 12626 on A10 neurons was not evidently related to a lack of access to central sites since NPC pretreatment (40 mg/kg, i.v.) completely antagonized the neurotoxicity caused by intrastriatal injection of quinolinic acid, an NMDA agonist, but not that caused by the non-NMDA compound, kainic acid. Thus, competitive NMDA antagonists do not share PCP's properties of activating mesolimbic dopaminergic systems, and as such they may be devoid of the potent psychotomimetic effects or the abuse liability associated with non-competitive NMDA receptor blockers such as PCP.

Amino Acids↗
PubMed1990

Effect of the ingestion of an extract from Bauhinia monandra seeds on rats.

Bauhinia monandra is a leguminous plant that would be used in human nutrition, however it shows a high hemagglutinating activity against trypsin-treated erythrocytes of rabbit, 2 ml of a NaCl-solution extract of the seeds was given to a group of rats for 10 days. Intestinal disaccharidase activity was determined. Histopathological and histochemical examinations were also performed. Lectins from Bauhinia monandra seeds did not cause any visible intestinal damage even when they seem to be able to bind to the enterocyte brush border. The low disaccharidase activity in the membrane and enterocyte fractions, which represent the enzyme synthesis level, indicates that lectins could reduce the synthesis of these enzymes rather than inhibit the active sites of the enzymes. This effect could be in turn related with the binding action of lectins, because no effect of the autoclaved extract on the disaccharidase activity was observed.

Animals↗