| 1. |
- Ceberg, Crister, et al.
(författare)
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A new method for quantification of image distortion due to pile-up in scintillation cameras
- 1991
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Ingår i: European Journal Of Nuclear Medicine. - 1432-105X. ; 18:12, s. 959-963
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Tidskriftsartikel (refereegranskat)abstract
- Characterization of the count-rate performance of scintillation cameras should include not only the specification of count losses. At high count rates, there is also an image distortion due to the mispositioning of pile-up events. In this paper a simple and clinically relevant procedure to quantify this distortion is presented. The images of a square uniform technetium-99m phantom at high and low count rates are used. The fraction of the total counts being correctly positioned is determined as the peripheral count density divided by the total average count density. This ratio, corrected for the camera non-uniformity at low count rates, is called the 'positioning ability'. According to the National Electrical Manufacturers' Association (NEMA), the 'system count rate performance with scatter' should be reported as the measured count rate giving 20% count losses. In this paper it is suggested that this measure be complemented by a measure of the fraction correct positioned events at this count rate. This fraction, the 'high count rate positioning ability', can be easily and accurately measured using our method. The method has been tested on two different scintillation cameras. For one of them the high count rate positioning ability was determined as 91% at a measured count rate of 30,000 s-1 with 20% count losses. For the other camera, the corresponding figures were 88% at 59,000 s-1 and close to 100% at 38,000 s-1, before and after the installation of a new pile-up rejection circuit, respectively.
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| 2. |
- Ceberg, Crister, et al.
(författare)
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Enhanced boron uptake in RG 2 rat gliomas by electropermeabilization in vivo--a new possibility in boron neutron capture therapy
- 1994
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Ingår i: Anti-Cancer Drugs. - 0959-4973. ; 5:4, s. 463-466
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Tidskriftsartikel (refereegranskat)abstract
- Accumulation of boron in tumor tissue is an indispensable requirement for boron neutron capture therapy and it is important that the uptake is as high as possible. In this work we have studied the influence of electropermeabilization in vivo on the uptake of boron in normal and RG 2 glioma bearing Fischer 344 rats. Two different boron compounds, a sulfhydryl boron hydride (BSH) and a boronated porphyrin (BOPP), have been investigated. The rats were infused intravenously during 5 min with 175 micrograms BSH/g body weight or 12 micrograms BOPP/g body weight. Two electrodes were placed 5 mm apart in the brain and electropermeabilization was performed with eight square 400 V pulses at 4 and 7 min after the end of the infusion. After 6 h the animals were killed, and the boron content in the tumors and the surrounding brain was measured with neutron-activated autoradiography. In electropermeabilized healthy animals the BOPP uptake was low and limited to the electrode lesions, whereas BSH was spread extensively throughout the hemisphere. Rats with gliomas showed doubled (BOPP) to 10-fold (BSH) uptake of boron in the tumor when electropermeabilization was performed as compared with untreated animals. We conclude that electropermeabilization in the future may provide an interesting possibility to increase the uptake of certain boron compounds before neutron capture therapy.
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| 3. |
- Ceberg, Crister, et al.
(författare)
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Neutron capture imaging of 10B in tissue specimens
- 1993
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Ingår i: Radiotherapy and Oncology. - 1879-0887. ; 26:2, s. 139-146
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Tidskriftsartikel (refereegranskat)abstract
- Boron Neutron Capture Therapy (BNCT) is an attractive concept for radiation treatment of malignant tumours. The patients receive a 10B-carrying compound with selective uptake in tumour cells, after which they are irradiated with epithermal neutrons. Theoretically, the tumour cells are killed by the high-LET particles produces in 10B(n, alpha)7Li reactions inside or close to the cell nucleus, while healthy brain cells with no boron uptake will be spared. In practice, a successful BNCT depends on the actual boron-distribution in the tissue, and consequently a new boron-compound aimed for BNCT must undergo detailed bio-distribution studies before clinical trials. In experimental work there is accordingly a great need for methods for quantitative bio-distribution measurements in tissue samples. In this paper we present an improved technique for neutron activated autoradiography providing quantitative boron images of freeze-sectioned tissue specimens from highly malignant rat brain gliomas. Particular attention has been paid to the correlation with the morphology of the specimens and to the altered self-absorption properties due to freeze-drying. A self-absorption correction factor for tumour tissue has been experimentally determined.
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| 4. |
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| 5. |
- 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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| 6. |
- Salford, Leif, et al.
(författare)
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A new brain tumour therapy combining bleomycin with in vivo electropermeabilization
- 1993
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Ingår i: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; 194:2, s. 938-943
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Tidskriftsartikel (refereegranskat)abstract
- The potentials of in vivo electropermeabilization in combination with bleomycin in brain tumor treatment have been explored. In the brain of normal Fischer 344 rats, 2 electrodes were placed 5 mm apart. Electropermeabilization was performed with 8 to 12 exponential 400 V pulses with a time constant of 325 microseconds. Some animals were given bleomycin i.v., 1mg/kg b.w., 4 minutes before electric pulses delivery. No adverse effects were recorded during the observation of the animals during the following month. The effect of bleomycin and electropermeabilization upon tumour growth was studied in rats with glioma cells (RG2) implanted in the head of the right caudate nucleus. Treatment was given at different time intervals after the implantation of tumor cells and the effect upon survival was studied. Bleomycin alone did not prolong the survival of the animals. On the contrary, bleomycin plus electropermeabilization on the 10th, 11th or 12th day after inoculation increased the survival time to almost double that of untreated animals. We conclude that this treatment may be of value in brain tumour therapy.
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| 7. |
- Wanying, Q, et al.
(författare)
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Radio-iodinated and internally labelled (35S) IgM monoclonal antibodies in a syngenic rat model
- 1991
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 1651-226X .- 0284-186X. ; 30:3, s. 379-383
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Tidskriftsartikel (refereegranskat)abstract
- To simulate the human situation concerning human monoclonal antibodies (MAbs), we have introduced a new syngenic rat model with an implanted rat colon carcinoma. Rat IgM MAbs (10B12), labelled by the chloramine-T method with 125I or internally with 35S, were injected intravenously into the rats and the biodistribution was studied for 8 days. The radioactivity uptake in the tumours of the 35S label was higher than that of the 125I label and the retention of 35S in the tumours gave tumour/blood ratios 8 times higher than those of 125I at 48 and 96 h after injection. In this model we have shown that dehalogenation of iodinated IgM MAbs is a serious problem. We therefore suggest that internally labelled MAbs should be used and that further investigations should be carried out in a syngenic rat model, since this probably reflects the clinical situation better than the nude mouse model.
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