In modern clinical practice, gamma camera is one of the most important imaging modalities for tumour diagnosis. The standard technique uses scintillator-based gamma cameras equipped with parallel-hole collimator to detect the planar position of γ photon interaction (scintillation). However, the positioning is of insufficient resolution and linearity for breast imaging. With the aim to improve spatial resolution and positioning linearity, a new gamma camera configuration was described specifically for breast-imaging. This breast-specific gamma camera was supposed to have the following technical features: variable angle slant-hole collimator; double SiPM arrays readout at the front and back sides of the scintillator; diffusive reflectors at the edges around the scintillator. Because slant-hole collimator was used, a new 3D scintillation positioning method was introduced and tested. The setup of the gamma detector was created in a Monte Carlo simulation toolkit, and a library of a number of light distributions from known positions was acquired through optical simulation. Two library-based positioning algorithms, similarity comparison and maximum likelihood, were developed to estimate the 3D scintillation position by comparing the responses from simulated gamma interactions and the responses from library. Results indicated that the planar spatial resolution and positioning linearity estimated with this gamma detector setup and positioning algorithm was higher than the conventional gamma detectors. The depth-of-interaction estimation was also of high linearity and resolution. With the results presented, the gamma detector setup and positioning method is promising in future breast cancer diagnosis.

Stroke is the leading cause of disability in adults in westernized societies and it has an important impact on health and economy. Comorbid health conditions such as hypertension, inactive lifestyle, smoking, obesity and diabetes considerably increase the risk of stroke. Moreover, studies have shown an increased probability of stroke occurrence and recurrence in the type 2 diabetes (T2D). Stroke leads to neurological deficits like motor impairments, disabilities and poor quality of life. The need of finding a novel treatment that can assure neuroprotective effects is crucial considering that the incidence of T2D is increasing around the world. Thrombolytic treatment given within 3-4 h from the stroke can assure some protection. Unfortunately, too few patients can benefit of this treatment due to a delayed arrival at the hospital, incorrect diagnoses or other causes. Furthermore, drugs that have shown some neuroprotective effectiveness in the pre-clinical experiments, failed in the clinical trials and today, there is no treatment for stroke based on neuroprotection. Glucagon-like peptide 1 (GLP-1) is a peptide found in L-cells of the small intestine and is secreted after the meal. The activation of its receptor (GLP-1R) increases the glucose-dependent insulin secretion and decreases the glucagon secretion. Exendin-4 (Ex-4) is a GLP-1R agonist that showed efficacy against stroke in diabetes in animal models. Additionally, it has been demonstrated that Ex-4 is acting through the activation of GLP-1R. The aim of the present study was to determine if the receptor itself plays a role in stroke outcome (without Ex-4) and see if the stroke-induced inflammation is affected by the lack of GLP-1R. We compared knockout vs. wild type mice by evaluating the stroke volume and by performing stereological counting of neurons in the striatum and cortex. The results showed no significant differences between the two groups, indicating that the lack of GLP-1R plays no role in stroke outcome.

Heart rate variability (HRV) is the variations in time between consecutive heart beats, and reflects the functioning of the autonomic nervous system. Not only is HRV a good marker for many physiological disorders, but it is well known that HRV can be altered consciously by different approaches even though it is controlled by the autonomic nervous system. Respiration is an important factor in modulating HRV and this property is utilized in HRV biofeedback, which is a method that aims at increasing heart rate variability. HRV biofeedback systems typically measures heart rate variability and display the parameters on a screen, enabling the user to gain control and increase heart rate variations. In this thesis a software for biofeedback of heart rate variability is presented. The software was implemented for Android and runs on a tablet computer to make the biofeedback system portable and more accessible than most other biofeedback systems. The developed software has proven to be fully functional in real-time providing the user with reliable information. A small pilot study on healthy volunteers has also been made to evaluate the effects of the biofeedback training. These measurements give a preliminary indication that biofeedback session with the proposed solution increases HRV. However, a more comprehensive study with a larger population needs to be carried out in order to confidently confirm the positive effects of biofeedback sessions with the software. / Heart rate variability (HRV) är variationerna i tid mellan två efterföljande hjärtslag, och återspeglar autonomiska nervsystemets funktion. HRV är en tydlig markör for många sjukdomar, men det är också välkänt att HRV kan påverkas medvetet trots att det styrs av autonomiska nervsystemet. Andning är en viktig påverkande faktor av HRV och denna egenskap utnyttjas i HRV biofeedback, som är en teknik som syftar till att öka HRV. Typiska system för HRV biofeedback mäter variationerna i hjärtfrekvens och visar upp informationen på en display, vilket låter användaren ta kontroll över denna parameter och öka HRV. I denna uppsats presenteras ett program för biofeedback av HRV. Mjukvaran har implementerats för Android och körs på en surfplatta för att skapa ett biofeedbacksystem som är portabelt och där tillgängligheten är hög, till skillnad från de flesta andra biofeedback system som är beroende av en dator. Programmet som utvecklats har visat sig vara fullt funktionellt i realtid och visar upp pålitliga parametrar för användaren. En förstudie har även utförts för att utvärdera effekterna vid användning av programmet. Dessa mätningar indikerar att biofeedbackträning med den föreslagna lösningen ökar HRV efter användning. En mer omfattande studie med fler personer bör dock genomföras för att ge en tydligare bild av effekterna av träning med detta program.

Fluoroscopic procedures are commonly used in today’s healthcare and involve ionizing radiation exposure to personnel and patients. During these procedures the patient is placed on a surgical table. The board on which the patient is lying on is referred to as the table top, and how different table top materials affect the image quality and radiation exposure has been investigated in this report. Radiation exposure measurements at different sites have been recorded with both a polymethyl methacrylate (PMMA) and an anthropomorphic phantom representing a patient. Image quality assessment was made in terms of contrast, signal-to-noise ratio and modular transfer function. The result showed that a higher table top attenuation or a higher tube voltage may lead to a lower dose but also a reduction in image quality. The preferred tube voltage and current, and resulting image quality is task dependent, i.e. dependent on the type of clinical procedure, which makes it hard to generalize in the selection of a certain table. Two methods have been proposed when selecting a table, one which can be considered as quantification of the trade-off between image quality and radiation dose, the other one is a fast method for comparing a large amount of tables.

Ultrasound is a common modality used in healthcare today. The ultrasound images can be used as a diagnostic tool and the image quality is therefore important. Earlier studies have shown that transducers used clinically are often damaged; a type of damage is dead elements in the transducer. In this study, it has been evaluated how the number and the placement of the dead elements impact the beam profile and how this is reflected in the image quality. This has been performed with two types of simulations, one simulated beam profiles and the other simulated dead elements in a transducer used to create real images. The results showed that the beam profile was affected by both the number and the placement of dead elements. It has not been determined how the altered beam profile affected the image quality, but there were indications that the image quality deteriorated when there were dead elements in the transducer. As both the number of dead elements and their placement affected the beam profile, an acceptance level could not be suggested regarding the number of dead elements.

Projektets syfte var att med modern datortomografi (computed tomography, CT) skapa tidsupplösta tredimensionella sekvenser, även kallade 4D-sekvenser, med låg stråldos och tillräckligt bra upplösning samt att påbörja en implementering av denna metod på Karolinska Universitetssjukhuset i Huddinge. För att få ett så bra resultat som möjligt involverades ett antal personer med olika medicinsk yrkesbakgrund och olika kompetensområden. En fantomstudie utfördes genom att dra ett fantom med en konstant hastighet genom CT:n med hjälp av en motor. Efter detta utfördes en pilotstudie på två försökspersoners högerfötter som utförde en rörelse under olika lång tid under en CT-undersökning. Scanningen av fötterna genomfördes först efter att det visade sig att scanningen av fantomet gav adekvat resultat med avseende på bildkvalitet och stråldos. För att avgöra detta gjordes en analys av bilderna på fantomet och en dosberäkning. Scanningen av fötterna genererade tolkningsbara bilder med tillräckligt låg stråldos. Denna metod kommer därför säkerligen användas i undervisnings- och forskningssyfte. Den kan även användas kliniskt på Karolinska Universitetssjukhuset i Huddinge i framtiden, till exempel vid diagnostisering och rehabilitering av senor. / The purpose of the project was to create time-resolved three-dimensional sequences, so called 4D sequences, using computed tomography (CT) with low radiation dose and sufficient resolution and to start an implementation of this method at Karolinska University Hospital in Huddinge. To get as good result as possible a number of people with different medical professional background was involved. A phantom study was performed by moving a phantom with a constant velocity through the CT using a motor. After this, a pilot study was performed by scanning the right foot of two people who performed a movement for various lengths of time during a CT-scan. The scanning of the feet was done after the phantom gave adequate result with respect to image quality and radiation dose. To determine this, analyze of the images of the phantom and a calculation of the dose was made. The scanning of the feet generated interpretable images with sufficiently low radiation dose. This method will certainly be used in teaching and research purposes. It can also be used clinically at Karolinska University Hospital in Huddinge in the future, for example for the diagnosis and rehabilitation of tendons.

Ultrasound is regarded a convenient and safe tool to acquire diagnostic information that we need for clinical use. For a long time ultrasound has been counted as a harmless method, but after all, there is a heating and a me-chanical impact by ultrasound exposure. This influence can reveal both positive (e.g., cell plant growth) and negative (e.g. cell death) effects. Acoustic exposure pattern changed drastically in recent years due to the rapid, technological developments in ultrasound imaging. Ultrasound imaging has become more sophisticated and new techniques are becoming more common, bringing with them not only increased diagnostic capabilities, but also potential threats as far as safety considerations are concerned. The goal of the thesis project is to analyze the ultrasound field characteristics, based on which research would be achievable in the future about how cells are affected by ultrasound exposure with different basic parameters. These parameters include excitation pressure amplitude, number of cycles in a pulse (n), pulse repetition frequency (PRF), acoustic working frequency (f), phase of ultrasound, shape of ultrasound wave (window mode). Some pilot cell experiments are also done in this project. Ultrasound-induced bioeffects on cells have been studied by many scientists, and some experiments tell us that ultrasound beams may cause serious mechanical and thermal damage on e.g. cells. Two general indices, the thermal index (TI) the mechanical index (MI) reflect information on the output level of the ultrasound machine and how a change in output would affect the likelihood of inducing a biological effect. Besides these two indices, other six parameters also are valuable to help us understand the potential threat of ultrasound applications. These parameters are peak negative pressure, peak positive pressure, spatial peak temporal peak intensity (Isptp), spatial peak temporal average intensity (Ispta), spatial peak pulse average intensity (Isppa) and output power of transducer (Wo). The above mentioned eight parameters are important in analyzing the acoustic beams. During the first phase of the experiment (acquisition of ultrasound field parameters) a hydrophone was put at the focus point of the ultrasound beam to acquire the time domain waveform signal of the ultrasound waves. By setting up f, PRF, n, phase and window mode into the computer controlled pulser (SNAP system, Ritec Inc), dif-ferent beams were sent to the hydrophone. Different combinations of basic parameters lead to 186 sets of acoustic beams. We used the hydrophone and oscilloscope to record the waveform signal respectively. Then by self-designed MATLAB software (Mathematical Computing Software, MATLAB®, Natick, Massachusetts, United States), the desired eight characteristics of acoustic field were calculated. Human chronic myelogenous leukemia cell line (K562) were exposed to defined ultrasound waves in the second phase of the experiment. Both trypan blue and resazurin viability assays were used to evaluate effect on the cells immediately after the exposure and 24 hours after the exposure. Resazurin viability assay conducted immediately after the exposure showed reduction of the cell viability up to 46% when the attenuation of amplitude is 0 dB (i.e. the output is the biggest). No cell death was induced. It also showed that after 24 hours the cells viability partially recovered to about 85%. Trypan blue assay showed nearly no cell death was induced.

In an open thoracic surgery the surgeon dissociate the sternum, the breastbone, into two halves to be able to perform the operation. At the end of the surgery a standard technique is used which to close the sternum. The technique is based on steel wires that are wrapped around the halves of the sternum to close it. This technique is the most cost effective technique available on the market today but is still not optimal because it can cause infection, wound rupture and pain for the patient. The goal with this master thesis was to, with the help of finite element method, to find out which closure technique is the best one to close the sternum and to provide suggestions for improvement. This was done with respect to the aspects of how large the displacement between the sternum halves is and how much the stresses generated by the implants affect the sternum. Using literature studies and interviews three techniques were chosen to be simulated; the standard technique, Zipfix and Sternal Talon. Their implants consisted of stainless steel, PEEK and titanium respectively and the materials were simulated with every technique. In the lower part of the sternum it is a greater displacement between the two halves after simulation than in the rest of the sternum. An improvement was hence to simulate Zipfix and Sternal Talon with an extra steel wire in the lower part. Zipfix with the implants of titanium and the standard technique with the implants of stainless steel provided the best results with respect to the two aspects. The two improvements produced smaller displacement but the stresses were higher. / Vid öppen thoraxkirurgi öppnar kirurgen sternum, bröstbenet, i två halvor för att kunna utföra operationen. När operationen är genomförd används en standardteknik som bygger på att använda ståltrådar för att försluta de två sternumhalvorna. Denna teknik är den mest kostnadseffektiva som finns på marknaden idag, men är trots detta inte optimal då den kan ge upphov till infektioner, sårrupturer och smärta för patienten. Målet med detta examensarbete var att, med hjälp av finita elementmetoder, ta reda på vilken förslutningsmetod som är bäst samt att ge förbättringsförslag. Detta skedde utifrån aspekterna hur stor förskjutning som uppstår mellan sternumhalvorna samt hur stor spänning implantaten påverkar sternum med. Med hjälp av litteraturstudier och intervjuer valdes tre metoder ut för att simuleras; standardtekniken, Zipfix och Sternal Talon. Dessa implantat bestod av rostfritt stål, PEEK respektive titan och varje teknik simulerades med varje material. I sternums nedre del uppstod efter simulering större förskjutning av sternumhalvorna än i resterande av sternum. Ett förbättringsförslag var därför att simulera Zipfix och Sternal Talon med en extra ståltråd i nedre delen av sternum. Zipfix med implantat av titan och standardtekniken med implantat av rostfritt stål gav bäst resultat utifrån de två nämnda aspekterna. De två förbättringsförslagen gav mindre förskjutning men spänningen blev dock högre.

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Fear is an emotion expressed by a subject which is under a threat or danger to secure itself.  It causes the “Fight or Flight” sensation in the being which is under attack. In previous studies, it is found that amygdala is the central unit in brain for fear stimuli. Here we have done two different neuroscience studies on fear with ultra high field MRI. Case 1: With ultra high field MRI brain images we visualised that there is a faster and short pathway to amygdala. Fear stimuli activate the amygdale even when the images are shown for a very short time of 50ms with which conscious recognition is not possible. This shows brain reacts to fear even before we recognise it consciously. Case 2: We investigated the influence of low and high spatial frequency fearful images in amygdala because of the contradiction in some previous studies. We compared low, high and broad spatial frequency images of fearful averted gaze faces, snakes and objects and found both high and low spatial frequency fear images affect the amygdale in the similar manner.