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5941.
  •  
5942.
  • Ödén, Jakob, et al. (författare)
  • Technical Note : On the calculation of stopping-power ratio for stoichiometric calibration in proton therapy
  • 2015
  • Ingår i: Medical physics (Lancaster). - 0094-2405. ; 42:9, s. 5252-5257
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Purpose: The quantitative effects of assumptions made in the calculation of stopping-power ratios (SPRs) are investigated, for stoichiometric CT calibration in proton therapy. The assumptions investigated include the use of the Bethe formula without correction terms, Bragg additivity, the choice of I-value for water, and the data source for elemental I-values. Methods: The predictions of the Bethe formula for SPR (no correction terms) were validated against more sophisticated calculations using the SRIM software package for 72 human tissues. A stoichiometric calibration was then performed at our hospital. SPR was calculated for the human tissues using either the assumption of simple Bragg additivity or the Seltzer-Berger rule (as used in ICRU Reports 37 and 49). In each case, the calculation was performed twice: First, by assuming the I-value of water was an experimentally based value of 78 eV (value proposed in Errata and Addenda for ICRU Report 73) and second, by recalculating the I-value theoretically. The discrepancy between predictions using ICRU elemental I-values and the commonly used tables of Janni was also investigated. Results: Errors due to neglecting the correction terms to the Bethe formula were calculated at less than 0.1% for biological tissues. Discrepancies greater than 1%, however, were estimated due to departures from simple Bragg additivity when a fixed I-value for water was imposed. When the I-value for water was calculated in a consistent manner to that for tissue, this disagreement was substantially reduced. The difference between SPR predictions when using Janni's or ICRU tables for I-values was up to 1.6%. Experimental data used for materials of relevance to proton therapy suggest that the ICRU-derived values provide somewhat more accurate results (root-mean-square-error: 0.8% versus 1.6%). Conclusions: The conclusions from this study are that (1) the Bethe formula can be safely used for SPR calculations without correction terms; (2) simple Bragg additivity can be reasonably assumed for compound materials; (3) if simple Bragg additivity is assumed, then the I-value for water should be calculated in a consistent manner to that of the tissue of interest (rather than using an experimentally derived value); (4) the ICRU Report 37 I-values may provide a better agreement with experiment than Janni's tables. (C) 2015 American Association of Physicists in Medicine.</p>
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5943.
  • Öhberg, Fredrik (författare)
  • The effect of anisotropic systematic errors in estimating helical angles
  • 2008
  • Ingår i: Computer Methods in Biomechanics and Biomedical Engineering. - Taylor & Francis. - 1025-5842 .- 1476-8259. ; 11:2, s. 205-213
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>A common question in movement studies is how the results should be interpreted with respect to systematic and random errors. In this study, simulations are made in order to see how a rigid body's orientation in space (i.e. helical angle between two orientations) is affected by (1) a systematic error added to a single marker (2) a combination of this systematic error and Gaussian white noise. The orientation was estimated after adding a systematic error to one marker within the rigid body. This procedure was repeated with Gaussian noise added to each marker.</p><p>In conclusion, results show that the systematic error's effect on estimated orientation depends on number of markers in the rigid body and also on which direction the systematic error is added. The systematic error has no effect if the error is added along the radial axis (i.e. the line connecting centre of mass and the affected marker).</p>
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5944.
  • Öhberg, Lars, 1947- (författare)
  • The chronic painful Achilles tendon sonographic findings and new methods for treatment
  • 2003
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • <p>The aim of the present thesis was to evaluate sonographic methods for investigation of the chronic painful Achilles tendon.</p> <p>In a prospective study on patients with chronic painful mid-portion Achilles tendinosis, grey-scale ultrasound (US) showed a decreased tendon thickness and a “normalized” structure in the majority of patients successfully treated with eccentric calf-muscle training. By combining US with colour Doppler examination (CDV), a neovascularisation was shown in the region with structural tendon changes in all painful tendons, but not in any of the pain-free normal tendons. In a small pilot study, the sclerosing agent Polidocanol was injected towards the neovessels under US and CDV guidance. The majority of the patients became painfree and had no remaining neovessels, while the patients with remaining pain had remaining neovessels. The combined findings from US, immuno-histochemical analyses of biopsies, and diagnostic injections, showed that the patients were temporarily pain-free after US and CDV guided injections of local anaesthesia towards the region with neovessels, and biopsies from the region with tendon changes and neovascularisation showed nerve structures in close relation to blood vessels. The presence of neovessels was shown also in patients with chronic pain in the Achilles tendon insertion, and it was found that treatment with sclerosing injections cured the pain in the majority of patients. A good result of treatment was associated with no remaining neovessels.</p> <p>In a prospective study on patients with chronic mid-portion Achilles tendinosis treated with eccentric training, CDV after treatment showed no remaining neovessels in the majority of the pain-free patients. In the patients with remaining tendon pain there were remaining neovessels. In conclusion, the findings in this thesis indicate that neovessels and accompanying nerves might be the source of chronic Achilles tendon pain. Sclerosing injections towards the neovessels, and eccentric training, seem to have a potential to cure the pain.</p>
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5945.
  • Öhman, Anders, et al. (författare)
  • NMR metabonomics of cerebrospinal fluid distinguishes between Parkinson's disease and controls
  • 2015
  • Ingår i: Neuroscience Letters. - 0304-3940 .- 1872-7972. ; 594, s. 36-39
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>This study assesses if nuclear magnetic resonance (NMR) metabonomics can discriminate between Parkinson's disease (PD) patients and control subjects, and consequently identify metabolic markers for the disease. One-dimensional H-1 NMR spectroscopy was used for quantitative analysis of metabolites in the cerebrospinal fluid (CSF) from 10 PD patients and 10 control individuals, together with uni- and multivariate statistical analysis to discriminate between the groups and to identify significantly altered metabolite concentrations. In total 60 metabolites were identified and of those 38 were quantified in all CSF samples. An overall lowering of metabolite content was observed in PD patients compared to control subjects (fold change of 0.85 +/- 0.30). Multivariate statistics reveal significant changes (vertical bar w*vertical bar&gt;0.2) among nine metabolites (alanine, creatinine, dimethylamine, glucose, lactate, mannose, phenylalanine, 3-hydroxyisobutyric acid and 3-hydroxyisovaleric acid). Three of these (alanine, creatinine and mannose) are identified as significantly changed also by univariate statistics (p &lt; 0.00132, Bonferroni corrected). Panels with all or a selected set of these metabolites were successfully used for discriminating between the two groups. In conclusion, NMR metabonomics can readily determine metabolite concentrations in CSF, identify putative biomarkers that distinguish between the PD patients and control subjects, and thus potentially become a tool for diagnostic purposes.</p>
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5946.
  • Örbom, Anders, et al. (författare)
  • Multi-radionuclide digital autoradiography of the intra-aortic atherosclerotic plaques using a monoclonal antibody targeting oxidized low-density lipoprotein.
  • 2014
  • Ingår i: American journal of nuclear medicine and molecular imaging. - e-Century Publishing Corporation. - 2160-8407. ; 4:2, s. 172-180
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this study was to use multi-radionuclide autoradiography to compare the different distributions of three radiolabelled tracers in an atherosclerotic mouse model. This method, along with immunohistochemistry, was applied to investigate the intra-aortic distribution of 2-deoxy-2-[(18)F]fluoro-D-glucose ((18)F-FDG), (131)I/(125)I labeled anti-oxidized Low Density Lipoprotein (oxLDL), and non-binding control antibodies. Aortas were isolated from a total of 12 apoB-100/LDL receptor deficient mice 73 h post injection of radioiodine-labeled anti-oxLDL and control antibody and 1 h post injection of (18)F-FDG. A solid-state real-time digital autoradiography system was used to image the slide mounted aortas. Contributions from each radionuclide were separated by half-life and emission energy and the aortas were subsequently stained with Oil Red O for plaque to aorta contrast ratios. Immunohistochemical staining was performed to detect anti-oxLDL and control antibody localization. Radiolabeled anti-oxLDL showed increased total activity uptake in the aorta over control antibody and immunohistochemical analysis of plaques indicated increased binding of the specific antibody compared to control. The intra-aortic activity distribution of the anti-oxLDL antibody was however very similar to that of the control antibody although both had higher atherosclerotic plaques to aorta wall ratios than (18)F-FDG. Given the right choice of radionuclides, multi-radionuclide digital autoradiography can be employed to compare several tracers ex vivo in the same animal. The distribution of anti-oxLDL antibodies did not significantly differ from the control antibody but it did appear to have a better plaque to aorta contrast at 73 h post injection than (18)F-FDG at 1 h post injection.
5947.
  • Örbom, Anders (författare)
  • Preclinical Molecular Imaging using Multi-Isotope Digital Autoradiography - Techniques and Applications
  • 2013
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Popular Abstract in Swedish Bildgivande system har en allt mer framträdande roll inom sjukvård och medicinsk forskning. En del av dessa system fungerar genom att en patient eller ett försöksdjur injiceras med ett läkemedel märkt med ett radioaktivt ämne, och sedan mäts den strålning som detta ämne avger för att skapa en bild av var ämnet, och därmed läkemedlet, befinner sig. Det finns både system som mäter fördelningen av radioaktivitet i tre dimensioner hos levande individer (till exempel PET- eller SPECT-kameror) och sådana som mäter fördelningen på en mer detaljerad nivå i tunna vävnadssnitt som är tagna från avlivade försöksdjur; den senare metoden kallas för autoradiografi. Den idag mest använda tekniken för autoradiografi baseras på plattor med fosfor-kristaller som fungerar ungefär som en svart-vit fotografisk film. De exponeras under en viss tid för vävnadsprovet med det radioaktiva ämnet, och sedan framkallas bilden med hjälp av en speciell utrustning. Det nya system som utvärderas och används i den här avhandlingen är istället en kiselbaserad halvledardetektor, och fungerar lite som en digital färgvideokamera jämfört med fosforplattorna. Det kan se signalerna från det radioaktiva preparatet i realtid, mäta när i tiden strålningen avges och vilken ”färg”, d.v.s. energi, den har. Detektorsystemet testades och olika egenskaper mättes. Det visade sig ha en låg bakgrundssignal, god förmåga att för många, men inte alla, radioaktiva ämnen avgöra vilka energier som mättes, samt korrekt kunna mäta relativt starkt radioaktiva prov. Detaljnivån, d.v.s. upplösningen, i bilden jämfördes med fosforplattorna genom att en mycket tunn radioaktiv tråd avbildades på båda systemen. Kiseldetektorn hade en högre upplösning än fosforsystemet även om skillnaden inte var drastisk. Systemet applicerades i en rad djurmodellstudier med antikroppar märkta med radioaktiva ämnen som känner igen vissa strukturer på celler i till exempel cancertumörer eller åderförkalkningsplack. Det observerades att i en råttmodell av koloncancer tar sig antikropparna först in i och behandlar tumören med strålning, men efter något dygn finns radioaktiviteten i områden av ärrvävnad i tumören där den kanske inte gör så stor nytta. Andra antikroppar testades i musmodeller av prostatacancer där de visade sig visserligen hitta tumören, men på grund av tumörens struktur och att antikroppar är relativt stora m.m. ofta ha väldigt svårt att nå in till tumörens inre. I en del av dessa studier användes flera antikroppar eller andra molekyler samtidigt och de märktes då med olika radioaktiva ämnen, som i bilden kunde separeras genom deras olika energi, eller hur snabbt de avger sin strålning. Ett sådant exempel var när en antikropp specifik mot åderförkalkningsplack testades samtidigt med en ospecifik antikropp och ett sockerliknande ämne som ackumuleras vid inflammation. Där kunde vi i en jämförelse se att den specifika antikroppen togs upp mer i plack än i omkringliggande kärlvägg. Detta i högre grad än det sockerliknande ämnet, men liknande den ospecifika antikroppen. Sammantaget visade studierna att autoradiografi med ett modernt instrument som kan separera signalen från olika radioaktiva ämnen har mycket att tillföra i studier där man tar fram nya läkemedel eller diagnostiska preparat, men att teknik och metod fortfarande behöver utvecklas.
5948.
  • Örbom, Anders, et al. (författare)
  • Serial digital autoradiography with a silicon strip detector as a high resolution imaging modality for TRT Dosimetry
  • 2007
  • Ingår i: IEEE Nuclear Science Symposium/Medical Imaging Conference,Honolulu, HI, United States,2007-10-26 - 2007-11-03. - IEEE - Institute of Electrical and Electronics Engineers Inc..
  • Konferensbidrag (refereegranskat)abstract
    • This study aims to investigate the possibility of implementing serial autoradiography using a silicon strip detector as an imaging modality in pre-clinical radionuclide therapy research, in order to study the effect of non-uniform uptake on absorbed dose distribution and biological response. Tumor tissues expressing CD20 (B-cell lymphoma) or carcinoembryonic antigen (CEA; colorectal cancer) were excised from animals injected with I-131-labelled anti-CD20 or anti-CEA antibodies and antibody fragments. The tumors were cryosectioned at 100 mu m and imaged using a real-time silicon- strip imager with a pixel-size of 50 mu m. Software was developed to correct for image artifacts and to realign the image sections into a volume by a two-step process with least square error and mutual information registration measures. The realigned volumes were convolved with beta dose point kernels to provide the dose rate distribution for I-131 and Y-90 at the time of sacrifice. Using these volumes, comparisons can be made between uptake and penetration of different antibodies and the dose rate uniformity of different radionuclides. Simulations performed using measured I-131 and I-125 energy spectra showed that energy separation with less than 5% error could be performed with 100 counts per pixel. Imaging and subsequent separation of a sample containing both I-131 and I-125 proved the possibility of simultaneous imaging of two targeting agents in the same tissue. Thinner tissue sections were also set aside and successfully used for H&E staining and immunohistochemistry to enable future comparison of uptake and dose rate in different cell-type populations in the tissue. This method successfully provides high-resolution activity and dose rate volumes and has potential for multi-labeling imaging and co-registration with histology. As a complimentary imaging modality it can aid in investigating the effect of non-uniform uptake. Optimization is still needed in both the sectioning protocol and realignment software.
  •  
5949.
5950.
  • Ören, Ünal, et al. (författare)
  • A phantom for determination of calibration coefficients and minimum detectable activities using a dual-head gammacamera for internal contamination monitoring following radiation emergency situations
  • 2016
  • Ingår i: Radiation Protection Dosimetry. - Nuclear Technology Publishing. - 1742-3406. ; 169:1, s. 297-302
  • Tidskriftsartikel (refereegranskat)abstract
    • The purpose of this study was to derive calibration coefficients (in terms of cps kBq-1) and minimum detectable activities, MDA, (in terms of kBq and corresponding dose rate) for the dual head gamma camera part of an SPECT/CT-instrument when used for in vivo internal contamination measurements in radiation emergency situations. A cylindrical-conical PMMA phantom with diameters in the range of 7-30 cm was developed in order to simulate different body parts and individuals of different sizes. A series of planar gamma camera investigations were conducted using an SPECT/CT modality with the collimators removed for 131I and 137Cs, radionuclides potentially associated with radiation emergencies. Energy windows of 337-391 and 490-690 keV were selected for 131I and 137Cs, respectively. The measurements show that the calibration coefficients for 137Cs range from 10 to 19 cps kBq-1 with MDAvalues in the range of 0.29-0.55 kBq for phantom diameters of 10-30 cm. The corresponding values for 131I are 12-37 cps kBq-1 with MDAvalues of 0.08-0.26 kBq. An internal dosimetry computer program was used for the estimation of minimum detectable dose rates. A thyroid uptake of 0.1 kBq 131I (representing MDA) corresponds to an effective dose rate of 0.6 μSv d-1. A 137Cs source position representing the colon with an MDA of 0.55 kBq corresponds to an effective dose rate was 1 μSv y-1. This method using a simple phantom for the determination of calibration coefficients, and MDA levels can be implemented within the emergency preparedness plans in hospitals with nuclear medicine departments. The derived data will help to quickly estimate the internal contamination of humans following radiation emergencies.
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