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Biomedical subjects

N E Herrera

Publications and source records attributed to N E Herrera.

At least 19 recordsLinked to original sources
PubMed1989

Immunoglobulin-secreting cells in close proximity to the mid-gestation mouse embryo.

A reverse haemolytic plaque assay has been used to detect cells secreting IgM and IgG from areas in close proximity to mid-gestation mouse embryos. These cells were obtained from the fetal-placental unit and from the decidual mass of mice on the 9th or 10th day of syngeneic pregnancy. Cryohistology using affinity prepared goat antibodies specific for mouse Ig isotypes, coupled to horseradish peroxidase by a second antibody, showed that free Ig and cells containing Ig, are located closely but externally to the extra-embryonic membranes and also in areas close to the developing placenta in the decidua basalis. We suggest that some of the identified Ig-forming cells may be producing antibodies specific for antigens on the extra-embryonic membranes and may thus be acting as blocking (enhancing) antibodies.

Animals↗
PubMed1988

Placental pathology at term associated with elevated midtrimester maternal serum alpha-fetoprotein concentration.

Reports have supported an association between elevated midtrimester maternal serum alpha-fetoprotein concentrations (unexplained by fetal anomalies) and intrauterine growth retardation. Our observations show an association between such elevations of maternal serum alpha-fetoprotein levels and two types of placental pathology at delivery, chronic villitis and placental vascular lesions of infarction or intervillous thrombosis. If chronic villitis was present, the frequency of intrauterine growth retardation was significantly increased, whereas no increase in intrauterine growth retardation was found in the absence of placental pathology.

Chorionic Villi↗
PubMed1988

Nuclear medicine studies of aging--III. Radial bone mineral content by single and dual photon absorptiometry.

Measurement of bone mineral content of the radius has been possible by single photon absorptiometry. Recently, dual photon devices have become widely used for measuring the quantity of lumbar vertebral bone mineral. Therefore, we studied the utility of a dual beam machine for quantifying the bone mineral content of the radius, and compared results with those obtained by single photon absorptiometry in the same patient on the same day. There was an excellent correlation between single and dual beam measurements of the radius. The present study indicates that a dual photon machine can be used for assessing not only vertebral, but radial bone mineral content as well. This may facilitate studies of the two sites by use of one machine.

Adolescent↗
PubMed1988

Nuclear medicine studies of aging--VI. Dual photon absorptiometry and bone scans in "at risk" women with back pain.

We studied 20 women who were at risk for osteoporosis (postmenopausal, or on dialysis, or on steroids), who presented with severe back pain. Patients underwent a dual photon (153Gd) densitometry study of the L2-L4 vertebrae, as well as an emission bone scan (99mTc-MDP). The dual photon method revealed abnormal results (20% or more below the mean expected value) in 13/20 patients (65%), and below the "fracture threshold" in 15/20 (75%). The emission bone scan delineated abnormal foci of uptake in 15/19 (79%). We conclude that women at risk for osteoporosis, who present with severe back pain, are likely to have a positive bone scan due to compression fracture or other derangements related to bone demineralization.

Adult↗
PubMed1988

Brain death: confirmation by radionuclide cerebral angiography.

Dynamic radionuclide cerebral angiography was performed in 14 patients with suspected brain death. In 10 of 14 patients, no intracranial arterial perfusion was demonstrable, thus confirming brain death. In four patients, faint venous activity was seen in the sagittal sinus only. All these patients also eventually died. Radionuclide cerebral angiography provides a simple and noninvasive means to confirm brain death in critically ill patients maintained on life support systems particularly when an electroencephalogram and four vessel contrast angiography may be either impractical or equivocal.

Adolescent↗
PubMed1986

Aberrant cerebrospinal fluid pathway. Detection by scintigraphy.

Radionuclide cisternography is routinely performed for assessment of normal and abnormal pathways and the hydrodynamics of cerebrospinal fluid (CSF). An unusual case of a woman in whom cisternography provided the diagnosis of an iatrosenic spinopleural fistula with a large CSF collection in the pleural cavity, following surgical resection of a vertebra for a malignant tumor is presented.

Adult↗
PubMed1985

Assessment of right ventricular ejection fraction during intravenous 133Xe pulmonary ventilation study.

Intravenous 133Xe in saline was used to estimate right-ventricular ejection fraction (RVEF). In three healthy volunteers, the first pass RVEF with 133Xe was followed by RVEF estimation by intravenous 99mTc-pertechnetate. There was agreement between the 133Xe and 99mTc determined values. Subjects rebreathed the liberated 133Xe gas, allowing an estimation of regional pulmonary ventilation. Intravenous 133Xe in saline may have potential use in measuring RVEF, as well as in evaluating pulmonary function in cor pulmonale.

Cardiac Output↗
PubMed1985

Parathyroid adenomas and hyperplasia. Dual radionuclide scintigraphy and bone densitometry studies.

Dual radionuclide imaging of the neck (Tc-99m pertechnetate and TI-201 thallous chloride) was performed in 22 patients with chemical evidence of hyperparathyroidism (elevated blood calcium and parathormone [PTH] levels). Of these, 19 of 22 had localization of a TI-201 "excess" area on radiothallium-radiotechnetium subtraction images. In 13 patients who have had operative confirmation at this writing, the dual radionuclide imaging was positive in 12 (12/13 = 92.3%). One patient had two parathyroid adenomas, both of which were seen on the images; thus, overall detection was 13 out of 14 or 92.8%. The parathyroid adenomas visualized weighed from 0.06 to 3.0 g; the one not detected weighed 0.25 g. In three patients with parathyroid hyperplasia secondary to renal disease, the subtraction imaging detected eight of 12 glands (66.7%). The forearm bone mineral content and bone density were determined in eight patients with parathyroid adenomas; results were abnormally low in five of these eight. One of the three patients with secondary hyperparathyroidism had an abnormally low radial bone mass. The combination of dual radionuclide imaging and radial bone mass determination may present a useful approach in both localizing abnormal parathyroid tissue and in examining its functional consequences.

Adenoma↗
PubMed1984

The relationship of instrument parameters to performance within a survey peer group.

Using simulators of transmission imaging, an interlaboratory survey assessed the discriminatory performance of 86 subscribers, each of whom imaged a liver phantom in anterior and right lateral projections. Analysis was by receiver operating characteristic (ROC) with Az, the area under the ROC curve, used as a measure of accuracy unconfounded by decision bias. Az values were then defined as the dependent variable in a statistical model that related performance to several instrument design and operating parameters. Six of 14 postulated parameters explained approximately half of observed subscriber variability. These were: year of camera manufacture or upgrade, number of photomultiplier tubes, collimator type, total counts collected, use of a Co-57 disk source for imaging the phantom, and computer processing of the image. The findings confirm previous inferences drawn from controlled intralaboratory experimentation, but hitherto unsubstantiated by clinical imaging data.

Humans↗
PubMed1983

Iodine-123 assay using a radionuclide calibrator.

Iodine-123 (123I), an accelerator-produced radionuclide, gained wide acceptance recently in medical applications. Radionuclide dose calibrators are commonly used to assay radioactivities of radiopharmaceuticals, and should be maintained to read within +/- 5%, both for constancy and accuracy. Radionuclidic impurities present in commercial 123I preparations may produce an assay error larger than 10%. The type and quantity of impurities depend on the mode of production of 123I. The impurities can be reduced by either increasing the energy of the proton beam (over 60 MeV) and using the 127I (p,5n) 133Xe leads to 123I indirect reaction or using lower energies and highly enriched (better than 99%) 124Te (or 122Te) target for the direct production of 123I via 124Te (p, 2n) 123I or 122Te (d, n) 123I. A survey of radionuclide calibrators was undertaken to investigate the extent of the 123I assay error due to impurities present in commercially available preparations of 123I. Results from 24 calibrators indicate that the activity of a (p, 2n) 123I capsule is overestimated on average by 22% two half-lives after calibration time, while the activity of a (p, 5n) 123I capsule remains within the accuracy of the radionuclide calibrator of +/- 5%. The 124I fraction increases significantly with time during the useful life of a (p, 2n) 123I capsule introducing large 123I assay errors.

Calibration↗
PubMed1983

College of American Pathologists "Series X" program.

Physical parameters that control detectability of low contrast lesions by current Nuclear Medicine imaging instruments are presented. The findings were derived from statistical analysis of data collected over a period of 6 yr by the Nuclear Medicine Resource Committee of the College of American Pathologists using the external Quality Control technique known as Interlaboratory Comparison.

Canada↗
PubMed1982

Radionuclide scanning for the rapid diagnosis of acute cholecystitis.

Radionuclide scanning with Technetium 99-m HIDA was performed in eighty-nine patients with suspected acute cholecystitis. In twenty-three patients (25.8%), the study demonstrated evidence of cystic duct obstruction and non-visualisation of the gallbladder. Almost all of these patients subsequently were shown to have acute cholecystitis at surgery. The sensitivity and specificity of the procedure for the diagnosis of acute cholecystitis was 95.8% and 100% respectively. The use of radionuclide cholescintigraphy in the assessment of hepatobiliary disorders is reviewed, and it is suggested that it is the test of choice at present for diagnosis of acute cholecystitis.

Acute Disease↗
PubMed1980

Pathogenesis of jaundice in histiocytic medullary reticulosis. A correlative scintigraphic, histologic and biochemical study.

Liver scanning with 131Iodine Rose bengal was performed on two patients with histiocytic medullary reticulosis. The diagnosis was confirmed in both cases on subsequent autopsies. The studies demonstrated obstructive pattern in both cases on scanning and correlated well with the biochemical and histological findings. The pathogenesis of jaundice in this condition is reviewed and it is suggested that intrahepatic obstruction plays a significant role in its causation.

Aged↗
PubMed1980

The College of American Pathologists Phantom Series--an assessment of current nuclear imaging capabilities.

Twelve sets of emission phantoms were distributed semiannually to laboratories of nuclear medicine from 1973 through 1978. This survey aimed to create a national peer group within which it might become possible to compare and standardize nuclear imaging technics, and to evaluate and define the current state of the art in a clinical setting. Results were analyzed in terms of sensitivity (percentage of true-positives), nonspecificity (percentage of false-positives), and performance indices (true-positive/false-negative ratios) for conventional gamma cameras and for rectilinear scanners. The chief determinants of target detectability proved to be target-to-surface depth, target diameter, and intrinsic target contrast. Operational variables and instrument type produced relatively minor effect upon subscriber performance. Gamma cameras tended to show slightly more sensitivity than rectilinear scanners, but were somewhat troubled by nonspecificity. Improvements in the intrinsic resolution of second- and third-generation gamma cameras increasingly employed since 1975 showed negligible impact on performance indices. A consideration of the overall survey performance indices. A consideration of the overall survey performance permits the beginning of a quantitative estimate of current detection capability in day-to-day nuclear imaging.

Evaluation Studies as Topic↗