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PubMed1976

[Radiation dose to the head, and particularly to the lens of the eye, during tomography with EMI scanner].

Radiation dose to the lens of the eye was estimated using thermoluminescence and film dosimetry on patients undergoing computerised axial skull tomography with the EMI scanner, and also on various phantoms. The dose decreases from the lateral margin of the right eye to the lateral margin of the left eye. During conventional three layer tomography, maximal exposure to the eye is about 0.6 R (1.55 X 10 10-4 C.kg-1), produced entirely by scatter. Direct irradiation of the plane of orbits produces maximal exposure rate of 3 R (7.7X 10-4 C.kg-1). Maximal dose to the head depends on skull size and is about 4 R (approximately 10-3 C.kg-1). The local dose dependence of the eyes was confirmed theoretically by drawing up a computer programme, and was related to the method used by the EMI scanner.

Film Dosimetry↗
PubMedDate not supplied

Modulation transfer function of the EMI CT head scanner.

The two-dimensional modulation transfer function [MTF(vx, vy)] has been determined for the EMI CT head scanner by measuring the point spread function (PSF) in different locations in the field of view. This PSF was obtained by scanning a fine wire supported perpendicular to the tomographic slice. Based on these MTFs, the resolving power of the EMI scanner was found to be 3.1 line pairs/cm. Our results also verify the symmetry of the system response and the uniformity of the system resolution.

Tomography, X-Ray Computed↗
PubMed1975

Computerized axial tomography: the normal EMI scan.

Computerized axial tomography using the EMI scanner as a new method of using x-rays in diagnosis. The technique displays intracranial and orbital structures in the transverse plane. The appearances of normal EMI Scans are described and correlated with cerebral and orbital anatomy seen in transverse section.

Brain↗
PubMed1977

Scattered radiation doses to infants and children during EMI head scans.

Scattered radiation doses to the eyes, thyroid and gonads of infants and children undergoing EMI head scans have been measured with thermoluminescent dosimeters. An average skin dose of 1.3 rad per scan was measured. Results are reported relative to incident skin dose and indicate that it is likely that there is no somatic or genetic hazard due to scattered radiation during an EMI head scan.

Body Height↗
PubMed1976

Computer tomography in the evaluation of pulmonary asbestosis. Preliminary experiences with the EMI general purpose scanner.

Thirteen individuals with varying lengths of exposure to asbestosis were examined by computer tomography with the EMI Scanner. Various pleuroparenchymal abnormalities were found, many not being seen on standard chest films. In some cases, with normal chest radiography, definite pleural involvement could be demonstrated, particularly that in the posterior sulci on the diaphragm and at the mediastinum. Tissue attenuation measurements in regions of parenchymal involvement reached 90 EMI units above normal lung tissue. The normal gravity effect is abolished in cases of parenchymal disease caused by asbestosis. Parenchymal disease was much more obvious on the CT scans than on conventional chest films.

Asbestosis↗
PubMed1976

The ventricular-brain ratio using planimetric measurement of EMI scans.

A correlation has been shown between the cross-sectional area of the cerebral ventricular system and the cross-sectional area of the brain in 62 patients, using the EMI Scanner. The percentage ratio has been abbreviated to VBR. The patients were divided into normal, equivocal, cerebral atrophy and hydrocephalus, according to their PEG's. The measurements were obtained by the use of a plaimeter and by outlining the ventricular and cerebral perimeters from the EMI Polaroid pictures. The VBR was found to be approximately five in those patients without detectable pathology, about seven in equivocal cases, and above ten in abnormal cases (atrophy, hydrocephalus). The hydrocephalic readings were generally higher than those for cerebral atrophy.

Adult↗
PubMed1978

Bone mineral measurement using an EMI scanner and standard methods: a comparative study.

The established techniques of scanning photon densitometry and radiographic microdenstiometry for the analysis of bone mineral content are compared with results obtained using a modified EMI brain scanner. The EMI method shows significantly greater sensitivity to changes in bone density than either of the other two methods. This latter method also has the added advantage of being able to visualize and measure the density of trabecular bone, which is a very sensitive indicator of bone mineral changes.

Absorptiometry, Photon↗
PubMed1979

The radiation dose to patients from EMI brain and body scanners.

Absorbed doses throughout the head of a Rando standard man phantom have been measured during simulated neurological examination with the EMI Mk I brain scanner and the second generation CT 1010 brain scanner. Similar measurements have been made with the CT 5005 whole-body scanner which have also included scans through thoracic and abdominal sections of the phantom. Lithium borate thermoluminescent dosimeters placed at regular intervals throughout, and on either side of the scanned volume, have enabled estimates to be made of the total energy imparted to the phantom by each scanner as well as the absorbed dose at various locations including organs of interest in health physics such as the lens of the eye, thyroid and gonads. Isodose curves have been plotted for the central transverse section of each simulated examination. Results are reported for both the standard and high accuracy scan speed options on the two scanners where this choice is available. It would appear that all three machines when operated at their standard scan speeds impart no more energy to the phantom than that associated with a few conventional radiographs of the same part of the body. Maximum skin doses vary from 30 to 56 mGy (3.0 to 5.6 rad) being highest for the CT 1010 scanner. Use of the high accuracy scan option increases the energy imparted and the maximum skin doses by a factor of about five, while providing much enhanced tissue density discrimination. In the case of the body scanner this higher value of energy imparted becomes comparable to that associated with lengthy fluoroscopic examinations like barium enemas. Recent work by EMI involving further refinements to the collimation system has reduced the dose levels by typically 50%. Some preliminary results with this new system are included to indicate the likely degree of improvement, but a detailed account will be the subject of a separate paper.

Brain↗
PubMed1982

A preliminary investigation of radiation dose reduction on an EMI CT5005 whole body scanner using a copper wedge.

The effects of the existing filtration system upon a narrow, parallel beam of X rays were considered. The profile of a Cu filter to be placed on the tube-side A1 wedge was calculated on the basis that the total energy incident on the detector box would remain unchanged when the other A1 wedge was removed. A Cu wedge was machined according to this profile. The effects of this modification on surface radiation dose delivered to a 25 cm EMI water phantom were both predicted and measured for horizontal traverses, and were in broad agreement. The reduction in integral radiation dose to the 25 cm water phantom was predicted as 39%. Dose reductions measured at several points on the surface and within an Alderson Rando anthropomorphic phantom head averaged 53% and 20% respectively. The modified system was evaluated in terms of imaging ability, and although some degradation was seen, images of the EMI composite phantom remained "diagnostic" in quality, despite non-ideal responses of some photomultiplier tubes at intermediate and extreme positions of the traverse periphery.

Copper↗
PubMed1976

Cerebral tuberculoma localized by EMI scan.

A case of isolated supratentorial tuberculoma is described. The patient had a left facial palsy, left hemiplegia, and left proprioceptive and stereognostic deficits with negative studies until the lesion was delineated with computerized axial tomography (EMI scan). The characteristics EMI scan is helpful in delineating the nature and precise location of the lesion prior to surgery.

Adult↗
PubMed2005

[The helminth fauna of Emys orbicularis (european pond turtle) (Linnaeus, 1758) living in freshwater.].

Twelve European pond turtles, Emys orbicularis, collected during 1996-2003 in various areas of the Bursa region were examined for helminths. During dissection, the following organs were surveyed for parasites: alimentary tract, lungs and urinary bladder. The 4 helminth species found were Patagium lazarewi (Digenea), Serpinema microcephalus, Spironoura armenica and Spiroxys contortus (Nematoda). This study that aimed at determining the helminth fauna of vertebrates in Turkey is the first survey on the host, Emys orbicularis. Also, this is the first time that Spiroxys contortus has been found among the helminth fauna of Turkey.

English Abstract↗
PubMed1981

[Comparative study of the neuronal and synaptic organization of the tectum mesencephali in the Caspian (Clemmys caspica Gmel.) and pond (Emys orbicularis L.) tortoises].

The neuronal and synaptic organization of tectum opticum was studied in two species of tortoises (Clemmys caspica Gmel, and Emys orbicularis L.) by means of Nissl, Golgi and electron microscopical methods. The Clemmys caspica tectum differs from that of the Emys orbicularis in a greater diversity of neuronal composition; a greater variety and quantity of cells with short axons, the presence of neurons with relatively short dendrites, in a greater relative thickness of the upper and deep systems of horizontal neurons, in a small number of axo-axonal synapses in sublayer Ia, a more diverse composition of synaptic zones in sublayers IIa and IIb, the presence of axons in layers Ib and IIb with certain species specific features of degeneration, the pattern of localization of tectal ganglionic cell projections. The above mentioned specific features appear to be connected with the species differences of these tortoises.

Afferent Pathways↗
PubMed1976

A comparison of computer asisted tomography (EMI scanner) with conventional neuroradiologic methods in the investigation of patients clinically suspected of intracranial tumor.

Computerized tomography has been used as the initial radiologic investigation among 212 intracranial tumor suspects. Ninety-five of these patients were ultimately shown to have tumors as a result of all their investigations. Eighty tumors were clearly defined by EMI scanning, four further scans were suspicious but not unequivocally abnormal and six scans showed complications of the tumor rather than the lesion itself. Thus, only five scans were falsely negative in the presence of a tumor. The false positive and false negative rates for EMI scanning have been compared with conventional techniques and computerized tomography shown to compare favourably with angiography or encephalography.

Brain Neoplasms↗
PubMed1999

Reelin mRNA expression during embryonic brain development in the turtle Emys orbicularis.

The expression of reelin messenger ribonucleic acid (mRNA) was studied during embryonic brain development in the turtle Emys orbicularis, by using radioactive in situ hybridization. A high expression was consistently found in the olfactory bulb and in a few neurons in the marginal zone and, to a lesser extent, in the subplate of the dorsal and medial cortical sectors. In the diencephalon, the ventral division of lateral geniculate nuclei and the prospective reticular thalamic nuclei were strongly positive. High reelin signal was also associated with some layers of the tectum and with the external granule cell layer of the cerebellum. A more moderate signal was detected in the septal nuclei, striatum, dorsal ventricular ridge, retina, habenular nuclei, and hypothalamus, and in some reticular nuclei of the midbrain and hindbrain and in ventral spinal cord. The cortical plate, basal forebrain, amygdala, and tegmentum were weakly labeled. When they are compared to reelin expression during mammalian brain development, our data reveal an evolutionarily conserved canvas of reelin expression and significant differences, particularly in developing cortical fields. Most significantly, the developing turtle cortex does not display the heavy reelin expression in subpial Cajal-Retzius cells that is so typical of its mammalian counterpart. Given the key role of reelin in laminar cortical development, our data suggest that the increase in the number of reelin-producing cells and/or the amplification of reelin expression in the cortical marginal zone might have been a driving factor during the evolution of the laminated cerebral cortex from stem reptiles to mammals, as indicated in previous comparative analyses.

Animals↗
PubMed1998

Sexual differentiation of gonads as a function of temperature in the turtle Emys orbicularis: endocrine function, intersexuality and growth.

Emys orbicularis is a freshwater turtle with temperature-dependent sex determination. Estrogens play a major role in gonadal differentiation; when they are produced at high levels during the thermosensitive period (TSP), ovaries differentiate; when their synthesis is very low, testes differentiate. Estrogens are synthesized from androgens through the activity of aromatase. We examine here two aspects of gonadal differentiation, intersexuality and growth, in E. orbicularis. For gonadal intersexuality, we studied the relationship between gonadal aromatase activity and gonadal structure at 28.5 degrees C (pivotal temperature), from the beginning of TSP to hatching, and compared results to those obtained at 30 degrees C (producing 100% females) and 25 degrees C (producing 100% males). At 28.5 degrees C, both males and females are obtained. However, histological differentiation of gonads is delayed compared to that at 25 degrees C and 30 degrees C, and an ovarian-like cortex of various thicknesses often develops at the surface of the male gonads; thus, several individuals display ovotestes at hatching. Despite important individual variations, the aromatase activity in ovaries differentiating at 28.5 degrees C increases during development as in ovaries differentiating at 30 degrees C. In most cases, however, activity is slightly lower than at 30 degrees C, and at the end of embryonic life, it becomes similar to that at 30 degrees C. In testes or ovotestes differentiating at 28.5 degrees C, aromatase activity remains low but is generally slightly higher than in testes at 25 degrees C; however, at the end of embryonic development, it becomes similar to that at 25 degrees C. Oocytes in the cortex of ovotestes begin to degenerate around hatching and continue to degenerate after hatching. Therefore, ovotestes evolve as testes. However, some oocytes may persist at the surface of testes up to the adult age. To estimate gonadal growth, the protein content was measured at different embryonic stages at 25 degrees C and at 30 degrees C. Testis growth is fast during TSP, somewhat slower after TSP, and decreases around hatching. Ovary growth is much slower than testis growth during TSP and then accelerates up to the end of embryonic development. This differential growth is well correlated with gonadal aromatase activity--much higher at 30 degrees C than at 25 degrees C--and can be explained by the fact that during TSP, testicular cords develop at 25 degrees C whereas they are inhibited at 30 degrees C; the ovarian cortex begins to form during this period but grows chiefly after TSP. Both inhibition of testicular cord development and stimulation of cortex development are under the control of endogenous estrogens. In the case of ovotestes, slight increases in estrogen synthesis, compared to that in typical testes, are sufficient to induce the transient formation of an ovarian-like cortex although they do not inhibit the development of testicular cords.

Animals↗
PubMed1995

Endocrine sex reversal of gonads by the aromatase inhibitor Letrozole (CGS 20267) in Emys orbicularis, a turtle with temperature-dependent sex determination.

In embryos of Emys orbicularis, the sexual differentiation of gonads is influenced by the incubation temperature of eggs. Estrogens administered during the thermosensitive period result in the feminization of gonads at 25 degrees (male-producing temperature), whereas an antiestrogen or aromatase inhibitors masculinize the gonads at 30 degrees (female-producing temperature). The nonsteroidal aromatase inhibitor Letrozole induces gonads with different degrees of masculinization, from ovary-like to testis-like. The present study examines the endocrine function of such masculinized gonads, at the end of embryonic life. Aromatase activity (which is involved in estrogen synthesis in ovary) and the status of Müllerian ducts (the regression of which reflects the secretion of a putative anti-Müllerian hormone by the Sertoli cells) were examined. One month after treatment with Letrozole, the gonads of embryos presented various levels of aromatase activity. There was a strong correlation among aromatase activity, gonadal structure, and Müllerian duct status; high levels of aromatase (similar or close to those in control females) were found in ovary-like gonads; intermediate levels were found in gonads (masculinized ovaries or ovotestes?) exhibiting a cortex and a composite medulla containing a mixture of ovarian lacunae and testicular cord-like structures; low levels (similar or close to those in control males) were found in strongly masculinized gonads (testis-like or ovotestes). Müllerian ducts were regressing in the majority of embryos with gonads containing low levels of aromatase activity. In these individuals, gonads functioned as embryonic testes. These results confirm the implication of estrogens in gonadal differentiation. The origin of these hormones is controversial, so that the aromatase activity was compared in gonads, in the undissociated adrenal-mesonephric complex (AM), and in different parts of this complex during the thermosensitive period. At the female-producing temperature, the aromatase activity per unit of tissue increased in differentiating ovaries but it was low in AM and similar to that found in AM at male-producing temperature. In embryos whose gonads had been masculinized by early treatment with Letrozole, aromatase activity was unchanged in AM. These results suggest that the main source of estrogens involved in ovarian differentiation is the gonad itself.

Analysis of Variance↗
PubMed1976

Measurement of effective atomic number and electron density using an EMI scanner.

Computed tomography, employing an EMI scanner at two beam energies, can be used to obtain information about the electron density and the effective atomic number of materials. The theory which is discussed has been verified experimentally and then applied in the investigation of some brain tumours in vivo. It is anticipated that, as techniques improve, the ability to carry out chemical and physical analysis of pathological processes in vivo will be an important application of computed tomography.

Brain Chemistry↗