[Theory of EMI-scanner and normal EMI-scanner picture].
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Computers↗
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Potential artifacts associated with the scanning pattern of the EMI scanner.
Physical and geometrical considerations of the EMI scanner are used to predict that regions of the head can be missed by adopting a scanner procedure based on the nominal EMI slice thickness. Using a nominal slice thickness of 1.3 cm and effective focal spot length of 12 mm, one can predict that in the central portion of the head, up to 8% of the region scanned may not be imaged. Moreover, it is shown that simultaneous monitoring of a single focal spot by two adjacent detectors, as in the EMI system, would lead to significant overlap between the two adjacent EMI slices resulting in dual imaging. Experimental examples are shown to illustrate these two artifacts in the EMI scanner.
Computers↗
A quantitative study of the EMI values obtained for normal brain cerebral infarction and certain tumours.
A quantitative study has been made of the EMI numbers of normal brain, cerebral infarction and certain tumours. The scans were recorded on magnetic tape and analysed using a minicomuter linked to a graphic display unit. This system not only yielded 16 grey scales compared with the ten currently available, but was programmed to allow selected regions of the scans to be outlined. From these regions the computer calculated the area, the mean EMI number and its standard deviation. It was found that in 15 normal brain scans, the EMI values obtained for normal frontal and temporal lobes were similar, but that the values for the basal ganglia and occipital lobes were significantly different from the first two regions and from each other. Ten cases of cerebral infarction and 30 cases of cerebral tumour were analysed, and it was shown that analysing representative areas was more informative than surveying the whole lesion. Whilst only half of the scans of brain tumours had a significantly altered EMI number compared with that of normal brain, enhancement of tumour density with sodium iothalamate revealed a consistent and significant elevation of the EMI number for all tumours. In particular, the value for enhanced meningiomas was almost double and malignant tumours more than a third larger than normal brain. It was not possible to differentiate quantitatively between astrocytomas and metastases.
Brain↗
[Evaluation by EMI CT 5005 Scanner of bone mineral contents variations. A proposed skeletal index for clinical use (author's transl)].
Two groups of subjects, ranging from 20 to 40 years of age the first and from 65 to 85 years the second, have been submitted to bone density measurements by EMI CT 5005 All-Purpose Scanner (140 kV; 28 mAs) and the average values compared. The difference between the average values of the two groups has been taken as a scale of points to evaluate the mineral contents of bone. By the group of older subjects the loss in trabecular bone (lumbar spine L2/L3) proved to be 59.51 EMI units, corresponding to the 47.6% of the mineral contents (p = < 0.01); the loss in compact bone (femur) was 6.6 EMI units corresponding to 5.28% of the mineral contents (p = < 5). The trabecular bone and compact bone average values added together give a whole-skeleton mineral contents index. This index applied to the group of older subjects showed a diminution of 65.81 EMI units indicating a 52.6% loss of mineral contents. Repeated measurements taken at a distance of time proved the method to be fairly reliable with acceptable degree of accuracy (+/- 5%). A tentative approach to clinical use of the skeletal index gave satisfying results.
Absorptiometry, Photon↗
Computerized tomography (the EMI Scanner): a comparison with pneumoencephalography and ventriculography.
Computerized tomography, using the EMI Scanner, allows the diagnosis of cerebral atrophy or hydrocephalus to be made with the same degree of accuracy as conventional neuroradiological methods. Ventricular measurements made on EMI scans have been compared with those from pneumoencephalograms and ventriculograms. A range of normal ventricular measurements for the EMI scan is suggested.
Adolescent↗
The effect of the kVp level on EMI values. Selective imaging of various materials with different kVp settings.
A variety of materials and tissues as well as 3 patients were studied with the EMI scanner using the 100-, 120-, and 140-kVp settings. There was little shift in the EMI value for most tissues over this range, but significant shifts occurred with materials whose effective atomic number was moderately different from that of water. Use of the highest kVp setting may improve visualization of low-contrast images by decreasing the noise caused by statistical fluctuations. This shift in EMI values can be used to determine the approximate amount of material of high atomic number present, such as calcium or iodine.
Calcium↗
Frontal and lateral views of the brain reconstructed from EMI axial slices.
A computer program has been written to produce lateral and frontal views of the brain from transverse slices generated by the EMI scanner. The resulting images have markedly facilitated the planning of surgical exploration of intracranial lesions by graphically indicating their locations in a manner consistent with the familiar lateral and frontal radiographs. Our image is formed from a distribution of the average EMI density number along the directio, of projection. Incorporated in the program is a bone-searching algorithm which eliminated density from the cranium and extracranial air and water so that only brain is seen in the projection. Several enhancement algorithms are provided to enhance pathology. The images are displayed on the existing EMI viewer, where they are available for inspection and photography.
Brain↗
Comparative characterization of the basic forebrain cortical zones in Emys orbicularis (Linnaeus) and Testudo horsfieldi (Gray).
The neuronal and synaptic organization of forebrain basic cortical zones in Testudo horsfieldi and Emys orbicularis and their dendritic spines have been studied using Nissle, Golgi and electron microscopic methods. It has been shown by comparison of the results that the two spicies have marked differences in the structural organization of the forebrain cortical zones. The cortical formation in Testudo horsfieldi is different from that of Emys orbicularis in a greater diversity of neuronal types, smaller size of neurons, smaller cell density in each cortical zones, the presence of horizontal dendritic terminals in dorsomedial dorsal cortex, the absence of the large neurons in dorsomedial medial cortex, ect. Moreover, in both species the dorsomedial dorsal cortex in comparison with medial and lateral cortex is characterized by a marked complexity of the structural organization (diverse neuronal composition, the presence of the stellate cells, the highest cell density, the smallest neuronal size). The investigation of spines in the different dendritic levels (proximal, middle and distal) of neurons in three cortical basic zones has been shown that in both species it has been observed the tendency to increasing of the spine density from proximal to distal part of dendrite. at all dendritic levels noninvaginated forms of spines predominated. Invaginated spines were recorded at the proximal and middle levels of dendrites and contain more organelles and inclusions than noninvaginated spines. In Testudo horsfieldi and Emys orbicularis differences of spine thin structure and spine density in the cortical basic zones were revealed. Moreover, in both species the spines of dorsomedial dorsal cortex were more numerous, more variable in shape, more abundant in organelles. It was there that a bush-like distribution of spines was found which in evidently a special form of synaptic organization of cortical neurons. The above features of this cortical zone indicates a higher degree of differentiation, suggesting that the dorsomedial dorsal cortex is phylogenetic youth as compared with hippocampus and lobus pyriformis.
Animals↗
Calibration and response of an EMI scanner.
Computed tomography provides a measurement of the linear absorption coefficient of material in vivo. The precision and accuracy of the measurements of this parameter made by the EMI scanner have been investigated at all three recommended voltage settings of the machine. The relationship between the EMI number and the linear absorption coefficient was found to be linear despite the polychromatic nature of the X-ray beam. The spatial resolution of the machine and the response to materials at different depths within the section have also been investigated.
Computers↗
[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↗
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↗
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↗
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↗
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↗
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↗
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↗
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↗
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↗