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Results for “Tomography, Emission-Computed”

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At least 19 recordsLinked to original sources
PubMed1979

Emission-computed tomography and its application to imaging of acute myocardial infarction in intact dogs using Tc-99m pyrophosphate.

The techniques of emission-computed tomography have been used to obtain in vivo quantitative estimates of the three-dimensional distribution of gamma-emitting radionuclides in dog hearts. Conjugate views, obtained for 60 equiangular projections around 360 degrees by rotating the object in front of a gamma camera, were used to reconstruct multiple-level emission transaxial images for various test objects, and for dogs with surgically induced acute myocardial infarcts. Corrections for attenuation were performed in the backprojection step of the convolution algorithm used for reconstruction. Quantitative estimates of the spatial extent and concentration of activity were obtained to within 10--15% rms error. Correlations were obtained between the radionuclide and histopathologic estimates of the extent and location of infarction.

Animals↗
PubMed1979

Tomographic measurement of local cerebral glucose metabolic rate in humans with (F-18)2-fluoro-2-deoxy-D-glucose: validation of method.

Tracer techniques and quantitative autoradiographic and tissue counting models for measurement of metabolic rates were combined with positron computed tomography (PCT) and (F-18)2-fluoro-2-deoxy-D-glucose (FDG) for the measurement of local cerebral metabolic rate for glucose (LCMRGlc) in humans. A three-compartment model, which incorporates hydrolysis of FDG-6-PO4 to FDG, was developed for the measure of kinetic constants and calculation of LCMRGlc. Our model is an extension of that developed by Sokoloff et al. Although small, hydrolysis of FDG-6-PO4 was found to be significant. A PCT system, the ECAT, was used to determine the rate constants, lumped constant, and stability of the model in human beings. The data indicate that cerebral FDG-6-PO4 in humans increases for about 90 minutes, plateaus, and then slowly decreases. After 10 minutes, cerebral blood FDG activity levels were found to be a minor fraction of tissue activity. Precursor pool turnover rate, distribution volumes, and red blood cell-plasma concentration ratios were determined. Reproducibility (precision) of LCMRGlc measurements (approximate 2 cm2 regions) was +/- 5.5% over a 5-hour period. The replacement of arterial blood sampling with venous sampling was validated.

Animals↗
PubMed1979

[Classification and course of cerebral infarcts on computer tomography (author's transl)].

The typical computer tomographic signs of ischaemic cerebral infarct are discussed on the basis of 631 cases. Infarcts have three typical stages. Stage I, one week, fresh infarct with signs of oedema (space-occupying lesion with an unsharp margin, slightly reduced density, lack of contrast uptake). Stage II, second to fourth week, reduction in the oedema. Frequently very marked contrast enhancement of the cortex and basal nuclei. Stage III, later than four weeks. Development of malacic cysts, with further reduction in density and size. Development of homolateral atrophy. The computer tomographic diagnosis of cerebral infarcts during Stage I is often very difficult. Distinction from infiltrating tumour is often possible only after further observation. The diagnosis of cerebral infarcts in stages II and III is possible in most cases. Haemorrhagic cerebral infarcts do not follow a temporal pattern as accurately as anaemic infarcts. They show circular increase in contrast of slowly diminishing size. The increased contrast persists considerably longer and is clearly distinguished from that in an anaemic cerebral infarct.

Adolescent↗
PubMed1979

[CT of the pelvis and abdomen during childhood (author's transl)].

The use of CT in the abdomen and pelvis in 25 children is described. Certain problems which reduce the value of the technique are discussed; these include the lack of intra- and retro-peritoneal fat, movement artefacts, the importance of exact indications and the problems of radiation dosage.

Adolescent↗
PubMed1979

[A comparison of computer tomography and ultrasound for the demonstration of vessels in the abdomen and retroperitoneal space (author's transl)].

The value of computer tomography and ultrasound for demonstrating vessels in the abdomen and retroperitoneal space was compared. The methods were equal in their ability to demonstrate the major vessels situated centrally, but computer tomography proved better at differentiating arteries and veins situated peripherally. On the other hand, sonography proved a simple means of differentiating intrahepatic vascular structures.

Abdomen↗
PubMed1979

[Computer tomography in the diagnosis of local recurrences after resection for carcinoma of the rectum (author's transl)].

Presacral or pelvic floor tumour recurrence after abdomino-perineal resection for rectal or anal carcinomas has not been amenable to early radiological diagnosis. Computer tomography is a procedure which can demonstrate recurrences of two to three cm. Within the pelvis with certainty. The reliability of the method has been demonstrated in 27 patients suspected of having recurrences. The effect of demonstrating or excluding a recurrence on subsequent treatment is discussed. The value of computer tomographic examination of the pelvis for demonstrating the position and extent of a recurrence, the displacement of neighbouring organs, destruction of the pelvis and involvement of iliac lymph nodes is shown.

Adult↗
PubMed1979

[Computer tomography and retroperitoneal fibrosis (Ormond's disease) (author's transl)].

Four patients with retroperitoneal fibrosis (Ormond's disease) were examined by computer tomography; the appearances are described and the differential diagnosis discussed. Computer tomography clearly defines the proliferative-inflammatory process and together with conventional radiology, angiography and lymphangiography it permits a presumptive diagnosis of retroperitoneal fibrosis. The non-invasive nature of computer tomography makes it the method of choice for follow-up of this disease.

Aged↗
PubMed1979

[Computer tomography for rare soft tissue tumours of the extremities (author's transl)].

Five patients with undiagnosed soft tissue masses in the extremities were examined and in two a pathological diagnosis could be made. One was an extensive, invasive fibroma (desmoid) 22 cm long which could be followed from the thigh almost into the pelvis. It was sharply demarkated form the surrounding muscles and of higher density. The second case was a 12 cm long cavernous haemangioma in the semi-membranosus muscle. This was originally hypo-dense, but showed marked increase in its density after the administration of contrast.

Adolescent↗
PubMed1979

[Ultrasonography of the adrenals--limits of a real time scanner (author's transl)].

Sonography is an efficient, non invasive diagnostic tool in evaluating pathological enlargement of the adrenals. In 11 out of 27 patients, who had adrenal sonography, a tumor diagnosis was established. In 7 patients the sonographic findings and diagnosis were proved by scintigraphy, surgery and histology. With conventional ultrasound technique one cannot see the normal and nodular hyperplastic adrenal. At the same time we believe, tumors smaller than 2.5 cm cannot be diagnosed accurately in general. Some problems of adrenal sonography could be eliminated with most recent ultrasound technology. (Grayscale processing, scan converter system, electronically focused transducers with higher frequencies). In future patients with pathologies in the adrenals can be evaluated non-invasive and definitely by ultrasound and computerized tomography.

Adolescent↗
PubMed1979

["Cold lesions" in bone scintigraphy (author's transl)].

Frequency and location of "cold lesions" has been analysed in 1000 consecutive bone scans. Among the 554 abnormal cases there were 18 (1,8% of the total) with localized diminished activity due to metastatic lesions and 5 (0,5%) secondary to radiation osteitis. 10 of the 18 patients with metastatic disease had pure defects while 8 showed a reactive margin. It is pointed out that the quality of the examination is crucial for the demonstration of such defects and that single scans of the different regions of the skeleton are superior to a whole body scan. The survey of the literature shows that "cold lesions" are predominant in malignant bone diseases, however no relation exists to a definite histology.

Adult↗
PubMed2026

An automated geometric modeling framework in GATE for the design and optimization of high-sensitivity converging-beam SPECT collimators.

Objective.The trade-off between detection sensitivity and spatial resolution is a fundamental challenge in designing organ-dedicated Single-photon emission computed tomography (SPECT) collimators. While converging-hole geometries offer a solution, their optimization is often hindered by the lack of flexible computational tools capable of modeling large-scale, non-parallel hole arrays. This study aims to develop an automated geometric modeling framework to facilitate the design and evaluation of complex converging- and diverging-hole collimators within standard Monte Carlo environments.Approach.We developed a specialized modeling framework by implementing custom C++ classes and a vector-based alignment algorithm within GATE. This platform enables automated, orientation-consistent construction of large-scale converging arrays not natively supported by standard implementations. A high-sensitivity pure cone-beam collimator (CBC) was designed using this framework. The evaluation used hot-rod, disc, and Jaszczak phantoms for physical characterization, while XCAT and dedicated brain models were employed for clinical tasks, including cardiac, brain perfusion, and DaTscan SPECT simulations.Main results.The CBC achieved a nearly fourfold sensitivity increase compared to a conventional low-energy high-resolution parallel-hole collimator at a 20 cm radius of rotation, while maintaining comparable spatial resolution. Despite a 52.3% field of view reduction, the CBC yielded a 2.2-fold noise reduction (CV: 11.7% vs 25.9%) and mitigated partial volume effects via geometric magnification. XCAT and brain phantom simulations confirmed enhanced anatomical definition and contrast recovery in cardiac, perfusion, and DaTscan tasks.Significance.This work provides an efficient computational tool for rapid design space exploration of advanced collimator geometries. The results demonstrate that the proposed CBC design offers a significant sensitivity advantage, making it highly suitable for high-performance, small-volume clinical applications such as brain and cardiac molecular imaging.

Tomography, Emission-Computed, Single-Photon↗