Masteruppsatser / Medicinsk strålningsvetenskap

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Browsing Masteruppsatser / Medicinsk strålningsvetenskap by Subject "Activity concentration"

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    Optimization of Kidney Dosimetry: Determination of Recovery Coefficient for Kidneys and SPECT/CT Imaging of [177Lu]Lu-DOTATATE/TOC
    (2025-10-06) Becker, Vanessa; University of Gothenburg/Institute of Clinical Sciences; Göteborgs universitet/Institutionen för kliniska vetenskaper
    Purpose: Peptide receptor radionuclide therapy (PRRT) with [177Lu]Lu-DOTATATE/TOC is an effective treatment for neuroendocrine tumors, but this treatment also involves an unwanted radiation dose to the kidneys. Dosimetry can be used to optimize treatment and reduce kidney toxicity, and therefore, obtaining an accurate estimate of activity concentration in the kidneys is essential. One of the main challenges in quantitative SPECT imaging for dosimetry is the partial volume effect, which leads to an underestimation of activity. This effect can be corrected for by using a recovery coefficient (RC). The study aimed to obtain an RC for kidneys using a software developed by Hermes for organ and tumor dosimetry. The study investigates how the RC is affected by different activity concentrations in the kidneys and the ratio between the activity concentration in the kidney and the background. It was also studied how the RC is affected by different reconstruction methods and two different projection sets, 30 and 60 projections. Method: Five 3D-printed kidney phantoms were filled with [177Lu]Lu-DOTATATE/TOC and placed in either a Jaszczak phantom or a NEMA phantom. Different activity concentrations were investigated as well as different ratios between the activity concentration in the kidney and the background. Images were collected with a SPECT/CT system (GE Healthcare Discovery NM/CT 670 Pro) and reconstructed in Hermes (Hermia Hybrid Recon 5.0.) using Ordered Subset Expectation Maximization (OSEM) and Relative Difference Prior (RDP). The kidneys were manually segmented, and the RC was determined for each measurement. In addition, the RC was compared between different segmentation methods i.e. the whole kidney segmented volume of interest (VOI), and the small VOI method was examined. Results: The RC was not statistically significantly affected by variations in activity concentration or kidney-to-background ratios. However, a statistically significant difference was shown between the two reconstruction methods, where reconstruction using RDP resulted in a higher RC than when reconstructing images with OSEM. A statistically significant difference was also found between 30 and 60 projections, probably due to increased noise in 30 projections. When comparing various activity concentrations, the whole kidney segmentation approach’s standard deviation was smaller than that of the small VOIs method. At Sahlgrenska University Hospital, the RC was determined to be 0.80 with whole kidney segmentation, 60 projections collected and reconstructed with RDP. Conclusion: The RC for kidneys in SPECT/CT imaging with [177Lu]Lu-DOTATATE/TOC are stable across the investigated range of activity concentrations and background ratios, supporting the use of a standardized RC for all imaging time points for whole kidney segmentation in dosimetry. At Sahlgrenska University Hospital, the RC was determined to be 0.80 and the method for determination of the RC is considered reasonable.
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    Uptake and retainment of radionuclides in edible mushrooms – from fruiting to cooking
    (2022-12-06) Mansour Ayoubi, Delshad; University of Gothenburg/Institute of Clinical Sciences; Göteborgs universitet/Institutionen för kliniska vetenskaper
    Purpose: The purpose of this study was to study the uptake, distribution and transfer of Mn-54, Zn-65, U-238, U-235, U-234, and Po-210 in mushrooms and their respective caps and stalks, the effects of chelates and ligands, and the potential release of radionuclides during a cooking procedure. Introduction: Fungi are organisms that are composed of a fruiting body (mushroom) and tubular hyphae, that branches out into complex networks called mycelium. Mushrooms gain their nutriments and elements by excreting organic acids that solubilizes matter, which can then be absorbed. This process can lead to certain elements being accumulated in the mushroom, as such they can be considered to be bioindicators. Among the extensively studied radionuclides that can be accumulated in mushrooms are Cs-137 and Sr-90. However, few studies have investigated the accumulation of naturally occurring radionuclides from the uranium and thorium decay series. Furthermore, studies of chelates and ligands on the uptake and distribution of radionuclides is also lacking. As for decontaminating mushrooms prior to consumption, previous studies that have investigated various cooking effects on the metal content in mushrooms have seen both an increase and decrease in metal concentrations following cooking. Stir-frying with butter, which is a common cooking procedure in Sweden, has to our knowledge, not been studied extensively. Method: Black Pearl, pink- and grey oyster, and lion’s mane mushroom were included in this study. The substrates of the kits were spiked with solutions of naturally occurring radionuclides containing U-238, U-235, U-234 and Po-210 (among others), and solutions of Mn-54 and Zn-65. The mushrooms with Mn-54 and Zn-65 were analysed with gamma spectrometry, and those with naturally occurring radionuclides were analysed by alpha spectrometry. The activity concentration in the substrates were determined by the substrate weight and amount of activity added. The uptake, distribution and transfer of radionuclides in mushrooms were calculated. To study the effects of chelates and ligands, the substrate of lion's mane was added with sodium carbonate, and Black Pearl was added with EDTA. As a means of studying the cooking effects on U-238, U-234 and Po-210 content, grey oyster mushrooms were purchased from a local supermarket and stir-fried in butter and a little salt. The samples were analysed by alpha spectrometry and the annual ingestion effective dose of cooked and uncooked samples were calculated. Results: The results showed that Black Pearl had a higher uptake of Mn-54 and Zn-65 in the cap than stalk, and that there was no difference in transfer coefficients between Mn-54 and Zn 65. For pink oysters, the uptake of Mn-54 was higher than Zn-65 in the first harvests, but similar in the second harvest, and the activity concentrations in fruiting bodies were higher than the substrate. For grey oysters, there was an accumulation of Po-210 in cap and uranium isotopes in stalk. For lion’s mane, the uptake of uranium isotopes were much higher than for grey oysters. Sodium carbonate could be effective in increasing the uptake of uranium in lion’s mane, however, there was likely a negative effect on mushroom growth. The results also showed that there was a considerable variability in radionuclide uptake between the mushrooms, between and within growing kits. The cooking effects on the activity concentration of uranium isotopes and Po-210 were seen to decrease and increase, respectively.