Showing papers in "Journal of Computer Assisted Tomography in 1978"
TL;DR: A method that corrects for artifacts in X-ray transmission scanners created by the alteration of the energy spectrum by bone is described and the nonlinear nature of the spectral artifacts is shown to produce streaks in certain phantoms.
Abstract: A method that corrects for artifacts in X-ray transmission scanners created by the alteration of the energy spectrum by bone is described. The method involves two reconstructions of the pictures: the first establishes the approximate distribution of bone and the second enables the artifacts to be eliminated. The first reconstruction is needed to establish the total amount of bone along each ray. Assuming that the X-ray energy spectrum is known, it is shown how the line integrals can be corrected. The method was tested on several mathematical phantoms as well as on human head data. The nonlinear nature of the spectral artifacts is shown to produce streaks in certain phantoms.
300 citations
TL;DR: Hemispheral asymmetries tend to be less striking in left handed individuals, but widening of the left frontal and right occipital regions is more common in left handers than right handers.
Abstract: Numerous cerebral asymmetries are shown on cerebral computed tomography (CT). Those seen most commonly are: (a) the left occipital pole is frequently wider and protrudes further posteriorly than the right; (b) the right frontal area often measures wider than the left, and the right frontal pole usually protrudes either as far forward as the left or extends beyond the left; and (c) the calcified glomus of the left lateral ventricle commonly lies posterior to that of the right when there is posterior protrusion of the left occipital pole beyond the right. The above hemispheral asymmetries are more common in right handed individuals. Hemispheral asymmetries tend to be less striking in left handed individuals, but widening of the left frontal and right occipital regions is more common in left handers than right handers. In both right and left handers, the central portion of the right hemisphere is frequently wider than the left; the pineal therefore often lies slightly to the left of the midline in normal brains. A study of cerebral asymmetries should help in the detection of early mass lesions and may also help in the study of hemispheral specialization for behavioral function.
234 citations
TL;DR: Computed tomography scans of 15 long-term steroid users showed varying degrees of apparent cerebral atrophy, not expected at their ages, but in two of the cases, the appearance of the brain improved following decrease or cessation of steroid use.
Abstract: Computed tomography scans of 15 long-term steroid users showed varying degrees of apparent cerebral atrophy, not expected at their ages (8 to 40 years). Most were suffering from autoimmune diseases. There appeared to be some correlation between dosage and degree of apparent atrophy. There was surprisingly little clinical evidence of cerebral dysfunction associated with this apparent atrophy. In two of the cases, the appearance of the brain improved following decrease or cessation of steroid use. Speculations are made on possible causes.
232 citations
TL;DR: The need for full neuroradiological evaluation, including angiography, is thus stressed if this highly fatal yet treatable condition is not to remain undiagnosed.
Abstract: Eleven patients with angiographically and/or pathologically verified cerebral sinovenous occlusions not directly caused by trauma were studied by computed cranial tomography (CCT). Static radionuclide brain scans and dynamic radionuclide flow studies were also obtained in four patients; in two, findings diagnostic of lateral sinus thrombosis were noted. These comprised a “negative on dynamic, hot on static” image, as well as a “hot on static with nonfilling on angiography.” Computed cranial tomography findings included visualization of the thrombosed vein (“cord sign”) or sinus (“empty triangle” or “Δsign”), multiple focal bilateral parasagittal hemorrhages, intense tentorial enhancement, gyral enhancement indistinguishable from infarct, solitary intracerebral hematoma, small ventricles, and normal scan. Excluding the patients with underlying meningioma, all three of whom survived, seven of the remaining eight patients expired during the acute phase of their illness, an 88% mortality. This group includes one patient who had normal CCT findings, albeit without contrast enhancement, who was diagnosed as pseudotumor cerebri. The need for full neuroradiological evaluation, including angiography, is thus stressed if this highly fatal yet treatable condition is not to remain undiagnosed.
199 citations
114 citations
TL;DR: A multislice positron emission tomograph (PETT V) for imaging the human brain and the whole body of small experimental animals and the overall sensitivity of PETT V is 350,000 counts/sec/mCi.
Abstract: Imaging of the brain by positron emission tomography can be optimized for sensitivity by dedicating the design of the tomograph to this application. We have designed a multislice positron emission tomograph (PETT V) for imaging the human brain and the whole body of small experimental animals. The detector system of PETT V consists of a circular array of 48 NaI(Tl) scintillation detectors, each fitted with two photomultiplier tubes, with one dimensional positioning capability. Suitable sampling is achieved by rotation of the circular array of detectors and by a wobbling motion of the detector circle. The proposed system is capable of providing seven slices simultaneously, with a spatial resolution in the plane of the slice from 7 to 15 mm and with slice thicknesses of 7 and 14 mm. The minimum scanning time is 1 sec. The estimated overall sensitivity of PETT V is 350,000 counts/sec/mCi in a 20 cm diameter phantom for a resolution of approximately 1.5 x 1.5 cm. The system is under construction.
111 citations
TL;DR: The reproducibility of the method is demonstrated as well as the limitations caused by artifacts and incomplete inspiration, and this method is suggested for follow-up studies of patients with diseases affecting the entire lung.
Abstract: Computed tomography scanners can be calibrated to provide reproducible measurements for a quantitative analysis of lung density. Typical histograms for inspiration and expiration are presented. The reproducibility of the method is demonstrated as well as the limitations caused by artifacts a
103 citations
TL;DR: The present report stresses the importance of correlating the findings on computed tomography scans and zones of high radiation dose on dose reconstruction plans in order to differentiate between delayed radiation necrosis and tumors of the brain.
Abstract: Delayed necrosis of the brain following exposure to high doses of radiation is a recognized hazard. It is important to predict the nature of these postradiation changes, since surgical removal of radiation necrosis may reverse neurological deterioration of patients so affected. The present report stresses the importance of correlating the findings on computed tomography (CT) scans and zones of high radiation dose on dose reconstruction plans in order to differentiate between delayed radiation necrosis and tumors of the brain. This differentiation is not possible using the criteria of CT alone.
81 citations
79 citations
TL;DR: It is shown that predicted noise power spectra compare well with those estimated from CT reconstructions of simulated noise for both the ramp filter and the Hanning-weighted ramp filter.
Abstract: An expression is derived showing that the two-dimensional noise power spectrum of computed X-ray tomography is proportional to [G(k)]2/k where k is the radial spatial frequency and G(k) is the one-dimensional corrective filter used in the filtered back-projection reconstuction technique. It is shown that predicted noise power spectra compare well with those estimated from CT reconstructions of simulated noise for both the ramp filter and the Hanning-weighted ramp filter. A consequence of the non-uniform shape of the noise power spectrum is that statistical noise in CT reconstructions is correlated from point to point. Because of this correlation when the reconstructed CT values are averaged over some region, the uncertainty of the average depends on the shape of the region as well as its area. This dependence is confirmed by computer simulations.
77 citations
TL;DR: Computed tomography proved insensitive to leptomeningeal spread of hematologic malignancies including leukemia, lymphoma, and malignant histiocytosis and evidence of communicating hydrocephalus, previously thought to be a major factor in clinical symptomatology, occurred in only 11% of patients.
Abstract: Computed tomography proved insensitive to leptomeningeal spread of hematologic malignancies including leukemia, lymphoma, and malignant histiocytosis. In only 3% of patients did it directly demonstrate leptomeningeal tumor. In comparison, the detection rate of leptomeningeal tumor secondary to carcinoma was 44% and for melanoma, 100%. Intracranial subarachnoid seeding from primary brain gliomas was detected in each instance. The simultaneous presence of parenchymal metastases with leptomeningeal carcinomatosis occurred in 18% of patients with nonhematologic malignancies. Computed tomography evidence of communicating hydrocephalus, previously thought to be a major factor in clinical symptomatology, occurred in only 11% of patients.
TL;DR: This work focuses on X-ray scanners presently in production that use a method of image reconstruction called filtered back-projection, which has two limitations in data sampling which require that approximations be used during the back- projection operation, and hence result in error in the reconstructed image.
Abstract: Most X-ray scanners presently in production use a method of image reconstruction called filtered back-projection. There are two limitations in data sampling which require that approximations be used during the back-projection operation, and hence result in error in the reconstructed image. I
TL;DR: A series of artifacts in computed tomography (CT) images, consisting of streaks coming off edges and flares surrounding the object being scanned, is shown to be due to polychromaticity of the X-ray beam.
Abstract: A series of artifacts in computed tomography (CT) images, consisting of streaks coming off edges and flares surrounding the object being scanned, is shown to be due to polychromaticity of the X-ray beam. These artifacts are seldom seen on conventional CT brain scans. They are helpful in understandin
TL;DR: An artifact that can cause an elevation in CT numbers of as much as 20 Hounsfield units toward the apex of the head is described and its primary origin is the beam hardening distortion due to the large amount of bone present in apical cuts.
Abstract: An artifact that can cause an elevation in CT numbers of as much as 20 Hounsfield units toward the apex of the head is described. This artifact was first noted on the EMI CT1010 scanner but has been observed in other scanners as well. Phantom studies of this artifact have revealed that its primary origin is the beam hardening distortion due to the large amount of bone present in apical cuts. This has been verified by computer simulations. An intuitive explanation of the origin of the artifact is also presented.
TL;DR: Pneumoencephalography is superior to CT in detecting suprasellar pearly tumors when they are isodense with the cerebrospinal fluid and the CT findings include a low density lesion with no enhancement after contrast medium injection.
Abstract: The findings in computed tomography (CT) and other radiological examinations in nine histologically proven cases of intracranial pearly tumors are presented. The CT findings include a low density lesion with no enhancement after contrast medium injection and in some cases a lesser degree of mass effect than would be expected from the size and site of such lesions. Pneumoencephalography is superior to CT in detecting suprasellar pearly tumors when they are isodense with the cerebrospinal fluid.
TL;DR: Computer assisted tomography (CAT) data from 10 patients with histologically verified primary malignant lymphomas of the brain are reported, and blurred margin of the tumor after contrast enhancement was found in half the patients.
Abstract: Computer assisted tomography (CAT) data from 10 patients with histologically verified primary malignant lymphomas of the brain are reported. Studies both prior to and after contrast medium administration were done on nine patients. In all these patients, tumor nodules presented with slightly increased density in the precontrast scan and considerable contrast enhancement. The appearance of malignant lymphomas in the CAT scan may be similar to that of meningiomas. Pituitary adenoma, medulloblastoma, and metastasis of malignant melanoma may not be ruled out in a particular case from the CAT picture alone. Blurred margin of the tumor after contrast enhancement was found in half the patients. Diffusely growing malignant lymphomas produce low density areas in the CAT scan without contrast medium uptake.
TL;DR: In 16 patients with clinical evidence of pulmonary thromboembolism, often corroborated by diagnostic procedures other than CT, a variety of CT patterns of increased attenuation were noted, and a distinct wedge shaped appearance was observed.
Abstract: A wedge shaped pulmonary density with its broad base against a peripheral pleural surface and with its tip pointing to the parahilar area is suggestive of pulmonary infarction. This pattern can be shown more often with computed tomography (CT) scanning than in plain chest X-ray films. In 16 patients with clinical evidence of pulmonary thromboembolism, often corroborated by diagnostic procedures other than CT, a variety of CT patterns of increased attenuation were noted. In seven (44%) of these cases, a distinct wedge shaped appearance was observed.
TL;DR: A material-selective beam hardening correction procedure has been developed that allows the reconstruction of good approximations of linear attenuation coefficients with respect to a reference energy and its insensitivity with regard to energy settings and other machine parameters.
Abstract: Polychromaticity of the X-rays used in computed tomography (CT) has made it difficult to establish an absolute scale for CT values and has made quantitative comparisons between patients unreliable. The spectral shift of the X-rays depends on the material distribution within the structure measured and is significant if substantial amounts of bone, fat, or injected contrast material are present. A material-selective beam hardening correction procedure has been developed that allows the reconstruction of good approximations of linear attenuation coefficients with respect to a reference energy. With the aid of mathematical simulations and measurements on a physical phantom, the feasibility of the procedure and its insensitivity with regard to energy settings and other machine parameters are documented.
TL;DR: Intracranial lipomata can be found in both symptomatic and asymptomatic patients and can be diagnosed by computed tomography without further investigative procedures.
Abstract: Intracranial lipomata can be found in both symptomatic and asymptomatic patients. The tumors, which are rare, can be diagnosed by computed tomography without further investigative procedures.
TL;DR: The normal anatomy of the paranasal sinuses and face imaged by CT in both the transverse and coronal planes is reviewed.
Abstract: With the ability to image both bone and soft tissue structures, computed tomography (CT) is capable of visualizing many normal anatomical structures of the paranasal sinuses and face not seen with other radiological techniques. The superficial and deep fat planes, all of the muscles of mastication, and many of the facial muscles are readily identified. The extraocular muscles, optic nerves, and globes are clearly seen. The purpose of this report is to review the normal anatomy of the paranasal sinuses and face imaged by CT in both the transverse and coronal planes.
TL;DR: A total of 210 cases of head trauma were examined using noncontrast enhanced and contrast enhanced computed tomography scans and it is felt that contrast enhanced scans are valuable in the evaluation of the full extent ofHead trauma.
Abstract: A total of 210 cases of head trauma were examined using noncontrast enhanced and contrast enhanced computed tomography scans. Evidence of contrast enhancement was seen in 97 cases (46%). Subdural hematoma and focal contusion were the most frequent entities demonstrating contrast enhancement. This finding was also frequently seen in patients with intraventricular hemorrhage (IVH) (5 of 17). Every one of the five patients in this series with IVH whose scans showed enhancement died, whereas out of the 12 whose scans showed no enhancement, five survived. Illustrative cases are presented. The authors feel that contrast enhanced scans are valuable in the evaluation of the full extent of head trauma.
TL;DR: This report concerns four cases in which good correlation between the location of the brain lesion and the abnormality on computed tomography scan was demonstrated.
Abstract: Primary malignant lymphoma of the brain is a rare lesion characterized clinically by varied nonspecific neurologic deficits and usually a rapid fulminant deterioration and death. This course may be altered by radiotherapy, and early diagnosis assumes major importance. Laboratory tests, EEG, radionuclide scans, angiography, and pneumoencephalography may not show definite abnormality in the early stages. This report concerns four cases in which good correlation between the location of the brain lesion and the abnormality on computed tomography scan was demonstrated.
TL;DR: Five cases of histologically confirmed olfactory neuroblastoma (esthesioneuroblastomas) have been studied by computed tomography and it appears that the attenuation values can be useful for differentiating between invasion by contiguity (two cases) versus metastasis (one case).
Abstract: Five cases of histologically confirmed olfactory neuroblastoma (esthesioneuroblastomas) have been studied by computed tomography (CT). Both the clinical symptoms (in particular, unilateral nasal obstruction and recurring epistaxis) and radiological findings (opacity of the paranasal sinuses) are non
TL;DR: This study reviews some of the experiences in the investigation of a variety of lesions within the orbit and attempts, in particular, to illustrate the value of direct coronal studies.
Abstract: Computed tomography (CT) of the orbit is capable of demonstrating soft tissue structures not visualized yet by any other radiological modality. The possibility of obtaining direct coronal slices has added a new dimension to the study. Direct enlargement viewing on the display console reveals many anatomical details. For better evaluation of pathological findings, an accurate anatomical knowledge is required. The purpose of this study is to report on the normal anatomy of the orbital soft tissues made visible by CT. with emphasis on the coronal views.
TL;DR: Four cases of adrenal tumors with unusually low attenuation coefficients are reported, with an unusually high lipid content, which may be responsible for the lucent appearance.
Abstract: Four cases of adrenal tumors with unusually low attenuation coefficients are reported. The tumors presented with values ranging from 8 to 17 EMI units (EU: 500 scale) instead of the expected 30 to 40 EU range of the remainder of our adrenal tumors. Two of these patients had primary aldosteronism and two had Cushing's syndrome. An unusually high lipid content may be responsible for the lucent appearance.
TL;DR: The ease with which the glands were shown in detail by computer assisted tomography (CAT) contrasts with other methods of demonstration, namely, retroperitoneal pneumography, angiography, and venography.
Abstract: The anatomy of 60 right and 80 left normal suprarenal (adrenal) glands in 90 patients was studied. In the transaxial view, the glands have a triradiate shape, which varies on serial sections. The medial posterior limbs of each gland were visualized on the more cranial sections. The transaxial positions of the glands are related to the vertebrae and, on the left side, to the aorta and kidney, in accordance with known anatomical associations. The cranio-caudal positions of the glands have been defined by using the kidney as a "renal ruler". The right gland lies cranial to the anterior and medial renal margin, and it extends dorsally beyond the vertebral body in 18% of the right glands studied. The left gland lies anterior to the upper renal pole. The ease with which the glands were shown in detail by computer assisted tomography (CAT) contrasts with other methods of demonstration, namely, retroperitoneal pneumography, angiography, and venography. The difficulties of visualizing the glands with CAT are discussed and illustrated. The findings are used to suggest guidelines for conventional tomography.
TL;DR: An investigation into the feasibility of using X-ray computed tomography to measure disease induced changes in bone mineral content of the human spine is described, and an experimental measurement indicates that in practice the reproducibility of such measurements would be about 1 EU.
Abstract: An investigation into the feasibility of using X-ray computed tomography (CT) to measure disease induced changes in bone mineral content of the human spine is described. A theoretical study of this type of measurement has been made using a mathematical model of osteomalacia. The measured EMI number changes linearly with the mineral content, and the sensitivity is shown to be 1.2 EMI units (EU: 500 scale)/1% change in mineral content in vertebral bone. The physical sensitivity to an equal mineral change in cortical bone is found to be 8.6 times greater. The mineral selectivity of the CT method is such that only about half the change in the EMI number arising from progressive osteomalacia reflects change in actual mineral content, while half is due merely to changes in bone density that accompany demineralization. In addition, the perturbing effects of beam hardening on measurement accuracy are evaluated and shown to be significant. Finally, an experimental measurement indicates that in practice the reproducibility of such measurements would be about 1 EU, and it is shown that the measured parameter correlates well with the calculated total linear attenuation coefficients.
TL;DR: This work presents three cases in which a GIA was mistakenly diagnosed as a brain neoplasm on the basis of CT findings, and the correct diagnosis was made by cerebral angiography.
Abstract: Giant intracranial aneurysms (GIA) may simulate brain neoplasms on computed tomography (CT) scans. We present three cases in which a GIA was mistakenly diagnosed as a brain neoplasm on the basis of CT findings. The correct diagnosis was made in each case by cerebral angiography. The possibility of GIA must be considered when a nonenhanced CT study shows a well circumscribed mass without edema at the base of the brain and contrast infusion reveals homogeneous or inhomogeneous enhancement.
TL;DR: It is concluded that thoracic CT provided information not otherwise available in one third of the patients with complex combined pleural and parenchymal disease examined in this series.
Abstract: We report an analysis of computed tomography (CT) of the thorax in 75 patients with combinations of pleural and parenchymal disease or complex pleural shadows. These patients were among more than 300 with pulmonary disease examined by this method. Twenty-eight percent of the 75 scans within this group were classified as high value, contributing information which was not available from other clinical or roentgenographic data, and which directly altered the management, diagnosis, or prognosis of these patients. Forty percent of the scans were classified as of intermediate value, contributing to better understanding of the case but with no major influence on patient management or prognosis. Thirty-two percent of the scans added no additional information to the chest roentgenograms. Thirty-seven percent of the 46 scans done specifically to differentiate pleural from parenchymal disease were classified as of high value, but only 14% of the scans in patients with pleural fluid loculations or pleural masses were placed in this category. We conclude that thoracic CT provided information not otherwise available in one third of the patients with complex combined pleural and parenchymal disease examined in our series.