Basic in vitro cell experiments were conducted on the P388 mouse leukaemia cell line to determine whether a supra-additive cell killing effect from combining hyperthermia with ionising radiation exists in the case of leukaemia. Methods were established to measure the cell kill, using a Coulter counter, from hyperthermia alone, radiation alone and several combined regimes. The cell kill from hyperthermia, in the range of 38-50 degrees for 30 minutes, 1 hour, 2 hours and 3 hours, and radiation, for 1, 3, 5, 9, 11 and 15 Gy was investigated. The approach used had various limitations, such as the underestimation of cell kill. Consistent trends, however, were found for the hyperthermia and radiation data, in accordance with the literature, which killed cells in a predictable manner. Subsequently, after other preliminary combined experiments were completed, the cell kill from both 5 and 11 Gy combined with hyperthermia at 43, 45 and 47 degrees for 2 hours were investigated. 5 Gy in combination with all levels of hyperthermia resulted in a direct additive cell killing effect. This, however, was not observed for 11 Gy in which a diminished effect was found. The overall level of cell kill from 5 Gy combined with hyperthermia was found to be equal, in the case of 43 degrees, or higher, as for 45 and 47 degrees, to that of those combined with 11 Gy. A supra-additive effect was not observed.

This thesis focuses on how physical and biological factors influence the outcome of exposures to γ/X-rays. That the dose rate changes during real life exposure scenarios is well-known, but radiobiological data from exposures performed at increasing or decreasing dose rates is lacking. In paper I, it was found that an exposure where the dose rate decreases exponentially induces significantly higher levels of micronuclei in TK6 cells than exposures at an increasing or constant dose rate. Paper II describes the construction and validation of novel exposure equipment used to further study this “decreasing dose rate effect”, which is described in paper III. In paper I we also observed a radioprotective effect when cells were exposed on ice. This “temperature effect” (TE) has been known for decades but it is still not fully understood how hypothermia acts in a radioprotective manner. This was investigated in paper IV, where a multiparametric approach was used to investigate the underlying mechanisms. In paper V the aim was to investigate the role of biomarkers and clinical parameters as possible risk factors for late adverse effects to radiotherapy (RT). This was studied in a rare cohort of head-and-neck cancer patients that developed mandibular osteoradionecrosis (ORN) as a severe late adverse effect of RT. Biomarker measurements and clinical factors were then subjected to multivariate analysis in order to identify ORN risk factors. The results suggest that the patient’s oxidative stress response is an important factor in ORN pathogenesis, and support the current view that patient-related factors constitute the largest source of variation seen in the frequency of late adverse effects to RT. In summary, this thesis provides new and important insights into the roles of biological and physical factors in determining the consequences of γ/X-ray exposures. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 5: Manuscript.</p>

Usefulness of a particular clinical assay is directly correlated with its ability to extract highest possible signal from available data. This is particularly relevant for personalized radiation therapy since early plan modifications confer greater benefits to treatment outcome. Recent studies have demonstrated capability of single-cell Raman microscopy to detect cellular radiation response at clinical (below 10Gy) doses, but only in certain strongly responding cell lines and after at least two day incubation. One possible cause is rather unoptimized signal processing used. This work investigates application of several advanced multivariate methods - weighted principal component analysis (WPCA), robust PCA, probabilistic PCA, and nonlinear PCA to increase radiation response signal. Representative datasets from strongly (H460 - human lung) and weakly (LNCaP - human prostate) responding cell lines were analysed in 0-50Gy and 0-10Gy dose ranges and results quantified to determine relative and absolute algorithm performance. It was found that with careful tuning, significant improvements in sensitivity and better signal separation could be achieved as compared to conventional PCA. / Graduate

Compared to normal cells, cancer cells tend to have higher concentrations of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) due to an accelerated cellular metabolism. The high ROS content leaves cancer cells increasingly susceptible to oxidative stress-induced cell death. This susceptibility can be manipulated in selective cancer therapy by further increasing production of ROS or inhibiting peroxide removal systems or a combination of the two. Pharmacological ascorbate (high-dose intravenous ascorbate) has been shown to sensitize pancreatic cancer to ionizing radiation (IR) by increasing production of ROS such as H2O2. Glutathione reductase (GR) and thioredoxin reductase (TrxR) are both important enzymes in peroxide removal systems. GR and TrxR function to recycle key electron donors in the cellular removal of H2O2. We hypothesized that inhibiting the peroxide removal systems via inhibition of GR and TrxR would enhance ascorbate-induced cytotoxicity in pancreatic cancer cells. Inhibition of TrxR activity enhanced ascorbate-induced cytotoxicity in MIA PaCa-2 pancreatic cancer cells. Additionally, knockdown of GR protein expression in combination with pharmacological ascorbate treatment increased MIA PaCa-2 pancreatic cancer cell sensitivity to IR. In MIA PaCa-2 and 403 F1 patient-derived pancreatic cancer cells, inhibition of both TrxR and GR activity combined with pharmacological ascorbate enhanced radiosensitivity. However, this effect was not seen in 339 patient-derived pancreatic cancer cells treated with the same dose of ascorbate. In conclusion, inhibition of TrxR activity, GR activity, or both enhances radiosensitivity and ascorbate-induced cytotoxicity in some, but not all, pancreatic cancer cell lines. Treatments combining ascorbate with inhibition of H2O2 removal may be an effective strategy for treatment of pancreatic adenocarcinoma.

<p>Biological treatment optimization aim at improving radiation therapy by accounting for the radiobiological tumour and normal tissues response properties when optimizing the dose delivery. Generally traditional methods, using only dosimetrical measures, disregard the nonlinear radiation response of different tumours and normal tissues. The accumulated knowledge on tissue response to radiation, in the form of more accurate dose response relations, cell survival models and their associated biological parameters, alongside with the tools for biological treatment plan optimization, has allowed the present investigation on the potential merits of biologically based treatment optimization in radiation therapy.</p><p>With a more widespread implementation of intensity modulated radiation therapy in the clinic, there is an increasing demand for faster and safer treatment delivery techniques. In this thesis biological treatment plan optimization, using the probability to achieve complication free tumour control as the quantifier for treatment outcome, was applied to radiation therapy of early breast cancer and advanced cervix cancer. It is shown that very conformal dose distributions can generally be produced with 3 or 4 optimally orientated coplanar intensity modulated beams, without having clinically significant losses in treatment outcome from the optimal dose distribution.</p><p>By using exhaustive search methods, the optimal coplanar beam directions for intensity modulated photon beams for early breast cancer and the optimal non-coplanar directions for an advanced cervix cancer were investigated. Although time consuming, exhaustive search methods have the advantage of revealing most features involving interactions between a small number of beams and how this may influence the treatment outcome. Thus phase spaces may serve as a general database for selecting an almost optimal treatment configuration for similar patients. Previous knowledge acquired with physically optimized uniform beam radiation therapy may not apply when intensity modulated biological optimization is used. Thus unconventional treatment directions were sometimes found.</p>

<p>One of the main problems in curing cancer resides in the different microenvironment existing in tumours compared to the normal tissues. The mechanisms of failure are different for radiotherapy and chemotherapy, but they all relate to the poor blood supply known to exist in tumours. It is therefore very important to know the tumour microenvironmental conditions in order to devise techniques that will overcome the problems and will therefore improve the result of the treatment.</p><p>The aims of the thesis were the modelling of tumour oxygenation and the simulation of polarographic oxygen measurements in order to assess and possibly to improve the accuracy of the electrode in measuring tumour oxygenation. It also aimed to evaluate the implications of tumour microenvironment for the radiotherapy outcome.</p><p>The project used theoretical modelling as the main tool. The processes of oxygen diffusion and consumption were described mathematically for different conditions, the result being very accurate distributions of oxygen in tissues. A first simple model of tissue oxygenation was based on the oxygen diffusion around a single blood vessel. A more complex model built from the basic physical processes and measurable parameters allowed the simulation of realistical tissues with heterogeneous vasculature. This model also allowed the modelling of the two types of hypoxia known to appear in tumours and their influence on the tumour microenvironment. The computer simulation of tissues was also used for assessing the accuracy of the polarographic technique for measuring tumour oxygenation.</p><p>The results of this study have shown that it is possible to model theoretically the tissue oxygenation starting from the basic physical processes. The particular application of our theoretical simulation to the polarographic oxygen electrode has shown that this experimental method does not give the oxygen values in individual cells. Because the electrode measures the average oxygenation in a relatively large tissue volume, the resulting oxygen distributions are different from the real ones and the extreme high and low values are not detected. It has further been found that the polarographic electrode cannot make distinction between various types of hypoxia existing in tumours, the geometrical distribution of the hypoxic cells influencing mostly the accuracy of the measurement.</p><p>It was also shown that because of the averaging implied by the measurement process, electrode results should not be used directly to predict the response to radiation. Thus, the differences between the predictions in clinical tumour control obtained from the real or the measured oxygenations are of the order of tens of percents in absolute value. A method to improve the accuracy of the electrode, i.e. to improve the correlation between the results of the measurements and the actual tissue oxygenation, was proposed.</p><p>In conclusion, theoretical modelling has been shown to be a very powerful tool for predicting the outcome of radiotherapy and it has the advantage of describing the tumour oxygenation in the least invasive manner. Furthermore it allows the investigation of the invasiveness and the accuracy of various experimental methods.</p>

<p>The increasing demand for characterization of nuclear fuel, both from an operator and authority point of view, motivates the development of new experimental and, preferable, non-destructive methods. In this thesis, some methods based on nuclear spectroscopic techniques are presented.</p><p>Various parameters of irradiated fuel are shown to be determined with high accuracy and confidence by utilizing gamma-ray scanning, tomography and passive neutron assay.</p><p>Specifically, fuel parameters relevant for a secure storage of spent nuclear fuel in a long-term repository, such as e.g. burnup and decay heat, are shown to be determined with adequate accuracy. The techniques developed are expected to be implemented in the planned encapsulation facility in Sweden.</p><p>Also, a device for tomographic measurements of the spatial distribution of thermal power in nuclear fuel assemblies has been built, tested and evaluated. The device utilizes single photon emission computed tomography (SPECT) in order to reconstruct the gamma-ray source distribution within a fuel assembly. The device is expected to be an important tool for validating reactor core simulators regarding new fuel designs.</p><p>For safeguards purposes, two experimental methods for verifying the integrity, i.e. the possible loss of fissile material from a nuclear fuel assembly, are presented. Verification of integrity is shown to be possible on an individual fuel rod level.</p>

<p>Tumour targeted radiotherapy is an appealing approach for treatment of disseminated tumour cells. A targeting agent that specifically binds to a structure on tumour cells is then used to transport therapeutically relevant radionuclides. The epidermal growth factor receptor, EGFR, is overexpressed on tumour cells in several malignancies, e.g. highly malignant gliomas. In this thesis, three types of radiolabelled EGF-conjugates, aimed for targeting to EGFR-expressing tumour cells, were developed and studied: EGF-dextran labelled with ¹²⁵I, EGF labelled with ²¹¹At, and two EGF-chelates, DTPA-EGF and Bz-DTPA-EGF, labelled with the radioactive metals ¹¹¹In and ¹⁷⁷Lu. </p><p>The targeting properties of radioiodinated EGF-dextran were first studied in cultured glioma cells. Radioiodine coupled to the dextran part of EGF-dextran was retained in cells appreciably longer than radioiodine coupled to EGF. This can give about 100 times increased radiation dose to tumour cells.</p><p>Targeting with ²¹¹At-EGF was investigated in combination with the tyrosine kinase inhibitor gefitinib (Iressa™, ZD1839). The uptake of ²¹¹At-EGF in EGFR-expressing tumour cells increased with increasing gefitinib concentrations. This was the case for both gefitinib-resistant and gefitinib-sensitive cell lines. The effect of the combined treatment on cell survival, however, differed between the cell lines in an unexpected way. In gefitinib resistant cells, combined treatment decreased cell survival approximately 3.5 times relative to ²¹¹At-EGF treatment alone. In gefitinib sensitive cells, however, combined treatment increased the cell survival (i.e. a protective effect).</p><p>The EGF-chelates studied ([¹¹¹In]DTPA-EGF, [¹¹¹In]Bz-DTPA-EGF and [¹⁷⁷Lu]Bz-DTPA-EGF) all bound specifically with high affinity (K_d≈2 nM) to EGFR on cultured glioma cells. They were internalised after binding, and the cellular retention of radionuclides was high (60% remained after 45 h). A biodistribution study in mice showed that liver and kidneys accumulated a majority of the radioactivity. The EGF-chelates bound EGFR specifically also <i>in vivo</i>. A tumour-to-blood ratio of 25 was achieved in a preliminary study.</p>

<p>The development of digital detectors for X-ray imaging in medical diagnostics receives an increasing amount of attention. The detector under development at the Department of Radiation Sciences at Uppsala University is a hybrid pixel detector, which consists of a semiconductor sensor mounted onto a readout chip. The readout chip is capable of performing photon counting and has an externally adjustable threshold.</p><p>A simulation tool for the detector and a model applying the linear-systems transfer theory to X-ray hybrid pixel detectors have been developed. Also a characterization of the readout chip has been done. In order to estimate the potential of the detector for diagnostic radiology, we investigate the image quality using the spatial frequency dependent detective quantum efficiency (DQE). By means of the detector simulations, the influence of threshold setting, noise sources, level of exposure and charge sharing on the DQE have been studied. By means of the linear-systems theory, a single analytical expression is provided to obtain the DQE of a hybrid pixel detector.</p><p>The method developed in this thesis will make it possible to optimize a detector design according to a particular medical application. It will also permit modifications and new features to be included without having to construct a full detector system.</p>

<p>Medical X-ray imaging is an important tool in diagnostic radiology. The ionising-radiation dose to the patient is justified by the clinical benefit of the examination. Nonetheless, detectors that operate at even lower doses and provide more information to the radiologist are desired. A hybrid pixel detector has the potential to provide a leap in detector technology as it incorporates a more advanced signal-processing capability than currently used detectors.</p><p>The DIXI digital detector is a hybrid pixel detector developed for X-ray imaging. It consists of a readout chip and a semiconductor sensor. The division in two parts makes it possible to optimise each part individually. The detector is divided into square pixels with a size of 270 x 270 μm2. DIXI has the ability to count single photons and every readout pixel has two embedded counters to allow the acquisition of two images close in time. A discriminator enables the selection of photons with energies above a preset threshold level.</p><p>The readout chip Angie has been developed and its performance has been evaluated in terms of noise, threshold variation and capability to perform energy weighted counting. Silicon sensors have been fabricated, and a control system for DIXI has been designed and built. An electroless process for deposition of Ni/Au bumps on the chip and sensor has been optimised as a preparation for the assembly of a complete detector, which is being assembled by flip-chip bonding using anisotropic conductive film.</p><p>A simulation library for the DIXI detector has been set up and results on the image quality are reported for different exposures and working conditions. A theoretical model for hybrid pixel detectors based on the cascaded linear system theory has been developed. The model can be used to investigate and optimise the detector for different detector configurations and operating conditions.</p>