Determination of Object Contour from Projections for Attenuation Correction in Cranial Positron Emission Tomography

Bergström, Mats; Litton, J.; Eriksson, Lars; Bohm, C.; Blomqvist, G.

doi:10.1097/00004728-198204000-00022

Cited by 199 publications

(95 citation statements)

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“…Calculated attenuation correction was performed on all images using the CTI/ Siemens reconstruction software. The outline of the head was derived directly from the raw data by threshold fits to the sinograms according to the method of Bergstroem et al (1982).…”

Section: Pet Imagingmentioning

confidence: 99%

Local Brain Functional Activity Following Early Deprivation: A Study of Postinstitutionalized Romanian Orphans

et al. 2001

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Section: Pet Imagingmentioning

confidence: 99%

Local Brain Functional Activity Following Early Deprivation: A Study of Postinstitutionalized Romanian Orphans

et al. 2001

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“…The raw data obtained were corrected for variations in detector efficiency, dead time , random coincidences using the observed singles rate in each detector, attenuation using a projection thresholds method (Bergstrom et aI., 1983), and scattered coincidences using a deconvolution method similar to that of Bergstrom et al (1982). Raw coincidence data were reconstructed into a 128 x 128 image matrix using the filtered back projection method.…”

Section: Determination Of Physiological Functionsmentioning

confidence: 99%

The Effect of Nimodipine on the Evolution of Human Cerebral Infarction Studied by PET

Hakim

Evans

Berger

et al. 1989

J Cereb Blood Flow Metab

129

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Summary: Fourteen patients were studied by positron emission tomography (PET) within 48 h of onset of a hemispheric ischemic stroke and again 7 days later. After the first set of PET scans, the patients were randomized to receive either nimodipine (n = 7) or a carrier solution (n = 7) by intravenous infusion. The infusions were main tained until the end of the second PET studies. CBF, cerebral blood volume (CBV), oxygen extraction ratio (OER), CMR02, and CMRglc were measured each time. These metabolic and perfusion measurements were per formed by standard methods. A surface map of each met abolic and perfusion measurement in the cortical mantle was generated by interpolating between the available slices. The various surface maps representing the physi ological characteristics determined in the same or subse quent studies were aligned so that all data sets could be analyzed identically using an array of square regions of interest (ROIs). The functional status of each ROI was recorded at the two intervals following the cerebrovascu- 523 lar accident to characterize the evolution of the infarct, penumbra, and normal brain regions. We presumed the ischemic penumbra to be cortical regions in the proximity of the infarct and perfused at CBF values between 12 and 18 ml/loo g/min on the first PET scan, while densely isch emic regions had CBF of <12 nlllOO glmin and normally perfused brain> 18 ml/loo g/min. In the densely ischemic zone, CBF increased more in the nimodipine-treated group than in the carrier group. As well, in this region nimodipine reversed the decline in CMR02 noted in the carrier group, the difference in the changes being signif icant. In the penumbra zone, comparable trends were noted in OER and CMR02 but the difference in the changes between the two groups did not reach statistical significance. Changes in CMRglc and CBV were compa rable between the two groups in both cortical regions.

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“…The PET images were reconstructed by a filtered back-projection method yielding an in-plane spatial resolution of 8.5 mm (FWHM) and an axial resolution of 12 mm (FWHM). Corrections were applied to the data, as described by Bergstrom et al (1982) to account for photon attenuation, scattered radi ation, and detector nonuniformity. The tissue activity concentration in the PET images was cross-calibrated against a well counter using a cylindrical phantom filled with 18F solution.…”

Section: Subjectsmentioning

confidence: 99%

Evaluation of the ¹¹CO₂ Positron Emission Tomographic Method for Measuring Brain pH. II. Quantitative pH Mapping in Patients with Ischemic Cerebrovascular Diseases

Senda

Alpert²,

Mackay³

et al. 1989

J Cereb Blood Flow Metab

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Summar y : A practical method has been developed that, using II COZ and positron emission tomography (PET), computes and maps (a) "effective pH" (pH,), a weighted average of intra-and extracellular pH, and (b) "clearance" (K\), product of blood flow and llCOZ ex traction. This method, together with measurements of ce rebral blood flow (CBF) and oxygen extraction fraction (OEF), was applied to 12 patients with cerebral ischemia or stroke. The regional K\ was positively correlated with CBF (n = +0.78). The k\/CBF ratio, representing the extraction fraction ratio of llCOZ to H/50, was nega tively correlated with CBF (r = -0.54), suggesting that I leoz extraction decreases as flow increases. In five acute stroke patients within 2 days of onset, the injured cortex had lower CBF (20.6 mi/min/IOO g), higher OEF Brain pH is tightly regulated by physicochemical buffering, by metabolic breakdown and production of acids, and perhaps by active transport of H + or HC03 -. Such tight control is necessary at least in part because of the pH dependence of the activity of several enzymes involved in energy metabolism and Received March 13, 1989; revised June 5, 1989; accepted June 8, 1989 Address correspondence and reprint requests to Dr. N. M. Alpert at Division of Nuclear Medicine, Massachusetts General Hospital, Fruit Street, Boston , MA 02 114, U.S.A.Abbreviations used: ANOVA, analysis of variance; CBF, ce rebral blood flow; CBV, cerebral blood volume; CMR02 , cere bral metabolic rate of 02; CSF, cerebrospinal fluid; CT, com puted tomography; DMO, 5,5-dimethyl-2,4-oxazolidinedione; FWHM, full width at half-maximum; GLM , General Linear Model; OEF, oxygen extraction fraction; OM, orbitomeatal; PET, positron emission tomography; ROI, region of interest; TIA, transient ischemic attack. 859(78. 1 %), and lower pH, (6.96) than the contralateral cor tex (CBF = 41.4 mi/min/IOO g, OEF = 53.3%, pH, = 7.00), suggesting intracellular acidosis with intact cell membranes. In three stroke patients 5-8 days after onset, the injured cortex had higher CBF (60.9 mllmin/IOO g), lower OEF (32.0%), and higher pH, (7. 12) than the con tralateral cortex (CBF = 45.3 ml/min/IOO g, OEF = 58.0%, pH, = 7.06), which suggested an increase in ex tracellular volume compartment reflecting loss of cell membrane integrity. This method provides information on the regional tissue acid-base status and cell membrane integrity, which may be prognostic of tissue viability. Ke y Words: Brain pH-Positron emission tomography \\ COz-Stroke-Cerebral acid-base status-Hydrogen ion concentration .

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Determination of Object Contour from Projections for Attenuation Correction in Cranial Positron Emission Tomography

Cited by 199 publications

References 0 publications

Local Brain Functional Activity Following Early Deprivation: A Study of Postinstitutionalized Romanian Orphans

Local Brain Functional Activity Following Early Deprivation: A Study of Postinstitutionalized Romanian Orphans

The Effect of Nimodipine on the Evolution of Human Cerebral Infarction Studied by PET

Evaluation of the ¹¹CO₂ Positron Emission Tomographic Method for Measuring Brain pH. II. Quantitative pH Mapping in Patients with Ischemic Cerebrovascular Diseases

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Determination of Object Contour from Projections for Attenuation Correction in Cranial Positron Emission Tomography

Cited by 199 publications

References 0 publications

Local Brain Functional Activity Following Early Deprivation: A Study of Postinstitutionalized Romanian Orphans

Local Brain Functional Activity Following Early Deprivation: A Study of Postinstitutionalized Romanian Orphans

The Effect of Nimodipine on the Evolution of Human Cerebral Infarction Studied by PET

Evaluation of the 11CO2 Positron Emission Tomographic Method for Measuring Brain pH. II. Quantitative pH Mapping in Patients with Ischemic Cerebrovascular Diseases

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Evaluation of the ¹¹CO₂ Positron Emission Tomographic Method for Measuring Brain pH. II. Quantitative pH Mapping in Patients with Ischemic Cerebrovascular Diseases