| 1. |
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| 2. |
- Flivik, Gunnar, et al.
(författare)
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Technetium-99m-nanocolloid scintigraphy in orthopedic infections: a comparison with indium-111-labeled leukocytes
- 1993
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Ingår i: Journal of Nuclear Medicine. - 0161-5505. ; 34:10, s. 1646-1650
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Tidskriftsartikel (refereegranskat)abstract
- Twenty-three patients with clinically suspected acute or chronic osteomyelitis and 21 patients with suspected joint prosthetic infection underwent scintigraphy using both 99mTc-nanocolloid and 111In-labeled leukocytes. The scintigrams of the two tracers were blindly interpreted by three independent observers. Their evaluations showed high correspondence. Patients were classified as having no infection, probable infection or proven infection according to specific criteria which included results of bacteriological cultures and histopathological examinations. For proven and probable infection taken together, the sensitivity with 99mTc-nanocolloid was 94%, the specificity 84% and the accuracy 87%, compared with 75%, 90% and 85% with 111In-labeled leukocytes. We conclude that 99mTc-nanocolloid scintigraphy is at least equivalent with 111In-leucocyte scintigraphy, and its additional advantages are shorter examination time, less complexity and better radiation dosimetry.
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| 3. |
- Jönsson, Bo-Anders, et al.
(författare)
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A quantitative autoradiographic study of the heterogeneous activity distribution of different indium-111-labeled radiopharmaceuticals in rat tissues
- 1992
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Ingår i: Journal of Nuclear Medicine. - 0161-5505. ; 33:10, s. 1825-1833
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Tidskriftsartikel (refereegranskat)abstract
- In light of the increased interest in small scale dosimetry, this paper presents a quantitative autoradiographic method for evaluation of heterogeneous activity distribution in tissues. This was studied in rat tissues after administration of 111In-chloride, -oxine, -tropolone, 111In-labeled homologous blood cells and 111In-anti-CEA-F(ab')2, using quantitative whole-body autoradiography. Quantification was performed utilizing an image analyzing system designed for whole-body autoradiographs. Very heterogeneous activity distribution was found in several tissues including the liver, spleen, kidneys, bone marrow, lymph nodes and testes. Notable was the high 111In uptake in organs characterized as rapidly proliferating, and known to have numerous transferrin receptors. In the gastrointestinal tract, all activity was associated with the intestinal walls. The heterogeneous tissue distribution shown in this investigation accentuates the necessity for performing detailed studies of the tissue distribution of radiopharmaceuticals. This is especially important for the radiation dosimetry of radionuclides emitting beta-particles or low energy electrons. We suggest whole-body autoradiography as an excellent implement to determine local activity concentrations in organs and tissues necessary for accurate absorbed dose calculations
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| 4. |
- Jönsson, Bo-Anders, et al.
(författare)
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Radiation dosimetry for indium-111-labeled anti-CEA-F(ab')2 fragments evaluated from tissue distribution in rats
- 1992
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Ingår i: Journal of Nuclear Medicine. - 0161-5505. ; 33:9, s. 1654-1660
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Tidskriftsartikel (refereegranskat)abstract
- Accurate dosimetric investigations are important to be able to fulfill the ambition of radiation protection in nuclear medicine and to minimize the radiation burden to the patient. This paper presents human radiation absorbed dose estimates following an administration of an 111In-labeled anti-CEA-F(ab')2 (BW431/31) based on detailed biodistribution and elimination data in a rat model. Animals were followed from the time of injection up to 28 days after injection. A significant initial uptake of 111In in the bone marrow, 25% of injected activity, was evident after 6 hr. The kidneys showed a maximal uptake of 20% at 24 hr. At the end of the study, 27% of the activity was still retained in the whole body. The estimated humans absorbed dose to the kidneys, testes, spleen and bone marrow was 2.27, 0.80, 0.51 and 0.37 mGy MBq-1, respectively. The effective dose was estimated to 0.27 mSv MBq-1. The tissue distribution in rats was comparable to that in humans, which was confirmed by whole-body scintigrams and human biopsies
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| 5. |
- Ljungberg, Michael, et al.
(författare)
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Attenuation and scatter correction in SPECT for sources in a nonhomogeneous object: a monte Carlo study
- 1991
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Ingår i: Journal of Nuclear Medicine. - 0161-5505. ; 32:6, s. 1278-1284
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Tidskriftsartikel (refereegranskat)abstract
- Single-photon emission computed tomography (SPECT) is important for imaging radioactivity distributions in vivo. Quantitative SPECT is limited due to attenuation and scatter contribution. Approximations such as constant attenuation and mono-exponential scatter functions will not be valid for non-homogeneous regions. A correction method is described where non-uniform density-maps are used in the attenuation correction. Correction for non-uniform scatter is made by a convolution technique based on scatter line-spread functions (SLSF) calculated for different locations inside a clinically realistic, nonhomogeneous, computer phantom. Calculations have been made for a myocardiac source, a uniform source in the lungs and a tumor located in the lungs. Projections were simulated for photon energies corresponding to 201Tl, 99mTc, and 111In. The results show that quantitative images can be obtained in nonhomogeneous regions. An increased contrast has also been demonstrated in the SLSF-corrected images. Comparison with measurements have been made to validate the Monte Carlo code and the scatter and attenuation method.
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| 6. |
- Ljungberg, Michael, et al.
(författare)
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Attenuation correction in SPECT based on transmission studies and Monte Carlo simulations of build-up functions
- 1990
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Ingår i: Journal of Nuclear Medicine. - 0161-5505. ; 31:4, s. 493-500
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Tidskriftsartikel (refereegranskat)abstract
- The quantitative information in SPECT images is distorted by photon attenuation and contribution of photons scattered in the object. It is, therefore, important to know the distribution of different attenuating tissues in order to be able to perform a proper attenuation correction. A correction method, based on correcting one pixel at a time by using density maps and build-up functions, has been developed. The density map has been produced by transmission measurements of the object using an external, solid 57Co flood source mounted on the scintillation camera head. The outline of the object is accurately defined by the map since the density values outside the object are very close to zero. The build-up of photons scattered in the object has been simulated by a Monte-Carlo code. SPECT-studies with 99mTc, 201T1 and 111In line sources in different parts of a non homogeneous Alderson phantom have been performed. The emission images have been corrected for photon attenuation using the measured density maps and the simulated build-up functions. The results show that quantitative measurements of the radioactivity in nonhomogeneous area can be accomplished to within +/- 10% for different radionuclides by using the attenuation correction described.
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| 7. |
- Ljungberg, Michael, et al.
(författare)
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Comparison of four scatter correction methods using Monte Carlo simulated source distributions
- 1994
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Ingår i: Journal of Nuclear Medicine. - 0161-5505. ; 35:1, s. 143-151
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Tidskriftsartikel (refereegranskat)abstract
- Scatter correction in SPECT is important for improving image quality, boundary detection and the quantification of activity in different regions. This paper presents a comparison of four scatter correction methods, three using more than one energy window and one convolution-subtraction correction method using spatial variant scatter line-spread functions. METHODS: The comparison is based on Monte Carlo simulated data for point sources on- and off-axis, hot and cold spheres of different diameters, and a clinically realistic source distribution simulating brain imaging. All studies were made for a uniform cylindrical water phantom. Since the nature of the detected photon is known with Monte Carlo simulation, separate images of primary and scattered photons can be recorded. These can then be compared with estimated scatter and primary images obtained from the different scatter correction methods. The criteria for comparison were the normalized mean square error, scatter fraction, % recovery and image contrast. RESULTS: All correction methods significantly improved image quality and quantification compared to those obtained with no correction. Quantitatively, no single method was observed to be the best by all criteria for all the source distributions. Three of the methods were observed to perform the best by at least one of the criteria for one of the source distributions. For brain imaging, the differences between all the methods were much less than the difference between them and no correction at all. CONCLUSION: It is concluded that performing scatter correction is essential for accurate quantification, and that all four methods yield a good, but not perfect, scatter correction. Since it is hard to distinguish the methods consistently in terms of their performance, it may be that the choice should be made on the basis of ease of implementation.
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| 8. |
- Ljungberg, Michael, et al.
(författare)
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Scatter and attenuation correction in SPECT using density maps and Monte Carlo simulated scatter functions
- 1990
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Ingår i: Journal of Nuclear Medicine. - 0161-5505. ; 31:9, s. 1560-1567
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Tidskriftsartikel (refereegranskat)abstract
- A new scatter and attenuation correction method is presented in which Monte Carlo simulated scatter line-spread functions for different depth and lateral positions are used. A reconstructed emission image is used as an estimate of the source distribution in order to calculate the scatter contribution in the projection data. The scatter contribution is then subtracted from the original projection prior to attenuation correction. The attenuation correction method uses density maps for the attenuation correction of projection data. Simulation studies have been done with a clinically realistic source distribution in cylindrical, homogeneous water phantoms of different sizes and with photon energies corresponding to 201T1, 99mTc, and 111In. The results show excellent quantitative results with an accuracy within +/- 10% for most of the source positions and phantom sizes. It has also been shown that the variation in the event distribution within the source region in the images has been significantly decreased and that an enhancement in the contrast has been achieved.
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| 9. |
- Norrgren, Kristina, et al.
(författare)
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A general, extracorporeal immunoadsorption method to increase the tumor-to-normal tissue ratio in radioimmunoimaging and radioimmunotherapy
- 1993
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Ingår i: Journal of Nuclear Medicine. - 0161-5505. ; 34:3, s. 448-454
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate a new extracorporeal immunoadsorption method to improve tumor-to-normal tissue ratios in radioimmunoimaging (RII) and radioimmunotherapy (RIT). We have developed and investigated a general method using biotinylated antibodies and an agarose-avidin column for extracorporeal immunoadsorption. The studies were made in an animal model and extracorporeal immunoadsorption (ECIA) was performed 24 or 48 hr after the injection of 125I-labeled biotinylated antibodies. In athymic rats, heterotransplanted with human malignant melanoma, 90%-95% of the circulating activity was removed with ECIA. The tumor-to-normal tissue ratios at 24 hr was increased 4 times (from 1.2 to 5.1) in the liver, 2.5 times (0.7 to 1.8) in the lung, 4 times (1 to 4) in the kidneys and 4 times (1.4 to 5) in the bone marrow. Whole body activity was reduced by 40%-50%. Tumor-to-organ ratios at 48 hr were increased 3.5 times (from 1.5 to 5.2) in the liver, 2 times (0.9 to 1.7) in the lung, 3 times (1.3 to 3.8) in the kidneys and 4 times (1.4 to 5.5) in the bone marrow. Whole body activity was reduced by 35% when ECIA was performed 48 hr after injection. This study proves that an important reduction in background activity, and thereby an improvement in the tumor-to-background ratio, can be achieved by using this generally applicable, biotin-avidin ECIA method. For RII, the improved ratio increases the possibilities of detecting tumors and metastases in blood-rich organs. For RIT, the procedure may lead to a decreased absorbed dose to bone marrow and other critical organs.
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| 10. |
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