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| 2. |
- Engvall, Christian, et al.
(författare)
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Human cerebral blood volume (CBV) measured by dynamic susceptibility contrast MRI and 99mTc-RBC SPECT.
- 2008
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Ingår i: Journal of Neurosurgical Anesthesiology. - 1537-1921. ; 20:1, s. 41-44
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Patients with elevated intracranial pressure risk compromising their cerebral blood flow, resulting in ischemia. Lowering of the raised intracranial pressure, is therefore, mandatory. Reduction of the cerebral blood volume (CBV) might be target. In finding ways to do so, one has to be able to measure CBV. Measurement of CBV is, however, difficult. Radio(99mTc-)labeled erythrocytes (99mTcRBC) single photon emission computer-aided tomography (SPECT) is one established method used for CBV measurement. Recently, dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI), has also been successfully used for this purpose. The aim of this study was to validate the use of DSC-MRI for the measurement of CBV by the investigation of the correlation between the regional distributions of 99mTc-RBC SPECT and DSC-MRI measurement of CBV in humans. If possible, the aim was also to find a conversion constant that will enable the DCS-MRI to be interpreted as CBV (percent of brain volume). METHODS: CBV of 8 volunteers were studied under normocapnic and hypocapnic conditions. CBV was measured with both 99mTc-RBC SPECT and DSC-MRI. RESULTS: There were significant correlations between the regional distributions of CBV measured by 99mTc-RBC SPECT and DSC-MRI (rest: F=4.53, P<0.05; hypocapnia: F=9.61, P<0.005). The derived conversion factor between DSC-MRI voxel values and 99mTc-RBC SPECT CBV (percent of brain volume) at rest was 0.0059+/-0.0013. Global CBV during normocapnia was 4.3%+/-0.6% of brain volume as measured by SPECT of brain volume and 4.5%+/-0.9% as measured by MRI. Decreasing the end-tidal pCO2 by 1.8 kPa by spontaneous hyperventilation reduced the global CBV significantly to 3.9%+/-0.5% in the SPECT group and to 3.5%+/-0.6% in the MRI group. CONCLUSIONS: The comparison of 99mTc-RBC SPECT and DSC-MRI measurements in our study indicates that DSC-MRI can be a useful method to measure CBV as a percent of brain volume.
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| 3. |
- Eriksson, Mats, et al.
(författare)
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Plutonium hot particle separation techniques using real-time digital image systems
- 2002
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 488:1-2, s. 375-380
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Tidskriftsartikel (refereegranskat)abstract
- Two real-time digital imaging systems, able to replace conventional autoradiography for radioactive hot particle separation and identification, are presented in this paper. The hot plutonium particles used for the study originate from the Thule nuclear weapon accident, Both of the real-time imaging techniques are initiated with sample splitting and measurements with a HPGe detector. in order to detect the gamma-emitting Pu-241 daughter Am-241, which is an indicator of plutonium hot particle in the sample. The time required for the whole process of separation and identification of one single particle from a bulk sediment sample (150 g dry weight) is of the order of 1-2 days, and is highly dependent on its activity. The real-time digital imaging systems presented in this paper are preferable, compared to conventional autoradiography and the CR-39 technique, when separation and identification of hot particles are needed as they are much faster and in addition give a real-time image of the particle. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 4. |
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| 5. |
- Ljunggren, Kaj
(författare)
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Beta Camera: Development and applications.
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A new detector for on-line digital detection of charged particles (beta-particles, conversion electrons and alpha-particles) from thin samples for rapid autoradiography has been developed; the Beta Camera. The device consists of a photon-sensitive detector (image photon detector, IPD); the main component of which is a microchannel plate. The sample to be measured is mounted in close contact to a thin scintillator on the IPD. Electrons are generated from the photocathode and the electron avalanche through the microchannel plate is registered by a resistive anode. The results are stored in an image memory for visual studies and further processing. The detector has a linear response making quantification easy. Results show that the Beta Camera can image radionuclide distributions with a spatial resolution of 500 µm, has good homogeneity and time resolution, and better sensitivy than film autoradiography. Biomedical samples have been imaged with the Beta Camera in several applications in real time. The open face of the detector (the scintillator) gives considerable freedom allowing a wide range of applications. In this thesis various examples of the use of the Beta Camera are given, such as imaging of tumours, normal tissues and living cells (nerves), as well as alpha-emitting environmental samples. The Beta Camera developed in this work has shown to provide a complement to ordinary filmautoradiography, but with fast, real-time and digital registration of radionuclide distributions.
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| 6. |
- Ljunggren, Kaj, et al.
(författare)
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Beta camera low activity tumor imaging
- 1993
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 1651-226X .- 0284-186X. ; 32:7-8, s. 869-872
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Tidskriftsartikel (refereegranskat)abstract
- A new technique, the beta camera, to complement film autoradiography, with fast quantitative imaging of beta particle-emitting radionuclides has been developed. It consists of a thin plastic scintillator and a light-sensitive microchannel plate detector. The thin tissue sample is mounted on the scintillator. Our first system had a high background and a moderate spatial resolution of 900 microns. We now report an improved system with a photomultiplier tube mounted on the scintillator of the microchannel plate detector. Only events registered by both detectors are accepted. A fast coincidence unit processes the signals, and if a time overlap exists, an event is generated in the beta camera. In the coincidence mode, images with low activity distribution of 201Tl (count rate 1 s-1) in 50 microns-thick slices of a human glioma tumor could be recorded with a spatial resolution of 500 microns.
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| 7. |
- Peterson, Mikael, et al.
(författare)
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Construction of a Pre-Clinical High Resolution Tomographic Scintillation Camera System
- 2009
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Ingår i: 2009 IEEE Nuclear Science Symposium Conference Record, Vols 1-5. - 1082-3654. ; , s. 3670-3671
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Konferensbidrag (refereegranskat)abstract
- We are constructing a High Resolution Tomographic Scintillation Camera System for small animal imaging. The system consists of a CsI(Tl) scintillator coupled to a military surplus image intensifier with a CCD camera focused on the output window. The system operates in photons counting mode and the spatial resolution is improved by centroid calculations for every photon interaction. The system can be mounted on an optical rail together with a pinhole collimator and a rotating table. A hot rod phantom was filled with Tl-201 or Tc-99m solute and imaged. The phantom rod diameters range from 1.1 to 1.6 mm. 64 projections were acquired (300 s/projection) with 1 mm pinhole insert. Data was reconstructed using an OSEM algorithm. Image data was corrected for decay, position non-linearities in image intensifier and the angular dependence of the pinhole. The reconstructed resolution is 13 mm (by visual inspection) for both Tc-99m and Tl-201. Higher spatial resolution is achievable with smaller pinhole diameters. Future work includes optimizing spatial resolution and sensitivity of a single system using analytical calculations, experiments and simulations. With the conclusions drawn from those calculations we plan to construct a multi-camera system.
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| 8. |
- Reinstrup, Peter, et al.
(författare)
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Regional cerebral metabolic rate (positron emission tomography) during inhalation of nitrous oxide 50% in humans
- 2008
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Ingår i: British Journal of Anaesthesia. - : Elsevier BV. - 1471-6771 .- 0007-0912. ; 100:1, s. 66-71
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Recent studies in man have shown that cerebral blood flow increases during inhalation of nitrous oxide (N2O), a finding which is believed to be a result of an increased cerebral metabolic rate (CMR). However, this has not previously been evaluated in man. METHODS: Regional CMR(glu) (rCMR(glu)) was measured three dimensionally with positron emission tomography (PET) after injection of 2-(18F)fluoro-2-deoxy-D-glucose in 10 spontaneously breathing men (mean age 31 yr) inhaling either N2O 50% in O2 30% or O2 30% in N2. RESULTS: Global CMR(glu) in young men was 27 (3) micromol 100 g(-1) min(-1) [mean (SD)]. Inhalation of N2O 50% did not change global CMR(glu) [30 (5) micromol 100 g(-1) min(-1)] significantly, but it changed the distribution of the metabolism in the brain (P<0.0001 analysis of variance). Compared with inhalation of O2 30% in N2, N2O 50% inhalation increased the metabolism in the basal ganglia [14 (17)%, P<0.05] and thalamus [22 (23) %, P<0.05]. There was a prolonged metabolic effect of N2O inhalation seen on a succeeding PET scan with oxygen-enriched air (P<0.0001) performed 1 h after the N2O administration. CONCLUSIONS: Inhalation of N2O 50% did not change global CMR(glu), but the metabolism increased in central brain structures, an effect that was still present 1 h after discontinuation of N2O.
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| 9. |
- Risberg, Jarl, et al.
(författare)
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A new tomographic technique for absolute measurements of white and gray matter blood flow
- 2004
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Ingår i: Proceedings of the 8th Nordic Meeting in Neuropsychology, Turku, Finland, August 26–29, 2004, 85.
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Konferensbidrag (refereegranskat)abstract
- Objective. Most methods for measurements of the regional cerebral blood flow are unable to provide absolute blood flow values. Until now interest has been focused on measurement of the gray matter blood flow, while the white matter blood flow has been rather neglected. The aim of the present project was to develop and evaluate an improved method for reliable tomographic measurements of absolute white and gray matter blood flow Method. The new tomographic method (modified Xe-SPECT) is based on an extension of the period of 133Xe inhalation from one to eight minutes followed by 22 instead of four minutes of breathing of ambient air. This gives a markedly enhanced signal from the white matter and better basis for correct quantification of the blood flow. The arrival and clearance of the tracer are recorded by a three head gamma camera system that provides flow maps with a spatial resolution of about one cm. Results The new method has been evaluated in 33 healthy younger and older (around 70 years) subjects as well as in a group of elderly patients with organic dementia. Our preliminary findings indicate that new and clinically valuable information is obtained by the improved Xe-SPECT method.
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| 10. |
- Risberg, Jarl, et al.
(författare)
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A new tomographic technique for absolute measurements of white and gray matter blood flow
- 2003
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Ingår i: Journal of the International Neuropsychological Society. - 1355-6177. ; 9, s. 323-323
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Konferensbidrag (refereegranskat)abstract
- The integrity of the white matter is as important as that of the gray matter and white matter pathology has commonly been reported in elderly subjects and in patients with organic dementia. The aim of the present study is to develop and evaluate an improved method for reliable tomographic measurements of absolute white and gray matter blood flow. The new tomographic method (modified Xe-SPECT) is based on an extension of the period of 133Xe inhalation from one to eight minutes followed by 22 instead of four minutes of breathing of ambient air. This gives a markedly enhanced signal from the white matter and better basis for correct quantification pf the blood flow. The arrival and clearance of the tracer are recorded by a three head gamma camera system that provides flow maps with a spatial resolution of about one cm. The new method has been evaluated in healthy younger and older (around 70 years) subjects as well as in a group of elderly patients with organic dementia. Our preliminary findings indicate that new and clinically valuable information is obtained by the improved Xe-SPECT method
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