| 1. |
- Lendaro, Eva, 1989
(författare)
-
On the use of Phantom Motor Execution for the treatment of Phantom Limb Pain
- 2020
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Phantom limb pain (PLP) is a common complaint among amputees and despite having been studied for centuries, it remains a mysterious object of debate among researcher. To date, a vast number of ways to treat PLP has been proposed in the literature, however none of them has proven to be universally effective, thus creating uncertainty on how to operate clinically. The uncertainty is largely attributable to the scarcity of well conducted randomized controlled trials (RCTs) to prove the efficacy of PLP treatments. Phantom Motor Execution (PME) -exertion of voluntary phantom limb movements – aims at restoring the control over the phantom limb and the exercise of such control has been hypothesized to reverse neural changes implicated in PLP. Preliminary evidence supporting this hypothesis has been provided by clinical investigations on upper limb amputees. The main purpose of this Licentiate thesis was to enable a RCT on the use of PME for the treatment of PLP in order to provide robust and unbiased evidence for clinical practice. However, the implementation and kick-off of this clinical investigation required to complete few preparatory steps. For example, most amputees and PLP patients have lower limb amputation, thus PME needed to be adapted and validated for this population. Further, the RCT protocol needed to be carefully planned and made openly accessible, as per guidelines for conducting and publishing clinical RCT. Finally, a secondary aim of this thesis emerged with the need of providing long term relief from PLP to patient. Preliminary evidence seemed to indicate that in order to maintain pain relief, periodic rehearsal of the phantom motor skills acquired through PME is necessary. This raised the question of whether it is beneficial and possible to translate the technology from clinic to home use, question that was explored employing both quantitative and qualitative methods from engineering, medical anthropology, and user interface design. The work conducted within this thesis resulted in the extension of PME to lower limb patients by proposal and validation of a new and more user-friendly recording configuration to record EMG signals. The use of PME was then shown to be efficacious in relieving PLP with a case study on a patient. The protocol for the RCT was then designed and published. These two first steps permitted the establishment of the RCT, which is currently ongoing and expected to close in March 2021. With regard to the secondary aim of this thesis, the work conducted enabled PME to be used by the patients in the comfort of their home, while it also allowed investigate the benefits and challenges generally faced (not only by PME) in the transition from the clinic to home and its effects on treatment adherence. The work conducted is presented in the three appended publications. Future work includes the presentation of the results of the RCT. Further, having a way to modulate PLP is an incredibly useful tool to study the neural basis of PLP. By capitalizing on this tool, we are currently conducting brain imaging studies using fMRI and electroencephalography that are the main focus of the work that lies ahead.
|
|
| 2. |
- Deyhle Jr, Richard
(författare)
-
Cross-modal Imaging in Lung Research: From µCT dosimetry to synchrotron phase contrast microtomography biomechanical insights in preclinical lung injury models
- 2024
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lung diseases continue to present a large burden to public health, especially in industrialized countries. For abetter understanding of the underlying patho-mechanisms in lung related diseases as well as for testing theefficacy of novel therapies, preclinical studies in animal models are indispensable. The significance of preclinical X-ray based micro-computed tomography (µCT) research lies in its ability to provide high-resolution, non-invasive lung imaging of small animals as the air inside the lung acts as a natural contrast and to image the lung parenchyma longitudinally to assess functional and morphological alterations and test efficacy of therapeutic interventions. This often requires requires imaging protocols that balance between sufficient image quality and clinically relevant radiation absorbed doses. A reproducible method for evaluation of absorbed radiation absorbed doses is desirable. Absorbed radiation absorbed doses were measured in a polymethyl methacrylate (PMMA) phantom using standard TLD and a novel type of OSLD made form household salt. Four imaging protocols from MILabs “xUHR-µCT” scanner were tested. A large discrepancy was observed from results compared to vendor-provided values. The results indicate a need for thorough empirical dose measurements prior to performing longitudinal studies. Four-dimensional imaging, allows for investigation of the dynamics of regional lung functional parameters simultaneously with structural deformation of the lung as a function of time. It is of significant interest to have direct visualization and quantification of interstitial lung diseases at spatial resolutions beyond the capabilities of clinical and conventional absorption-based only CT. Thus far, the high intensity of synchrotron X-ray light sources offer a tool to investigate dynamic morphological and mechanistic features, enabling dynamic in-vivo microscopy. This investigation elucidates the direct effects of interventions targeting the pathophysiology of Acute Respiratory Distress Syndrome (ARDS) and Ventilator-Induced Lung Injury (VILI) on the terminal airways and alveolar microstructure within intact lungs. In such conditions, the relationship between microscopic strain within the mechanics of the alveolar structure and the broader mechanical characteristics and viscoelastic properties of the lungs remains poorly understood. A time-resolved synchrotron phase-contrast micro-computed tomography imaging acquisition protocol based on the synchronization between the mechanical ventilation and the cardiac activity was used to resolve the lung parenchyma motion with an effective isotropic voxel size of 6 µm. Quantitative maps of microscopic local lung tissue strain within aerated lung alveolar tissue under protective mechanical ventilation in anesthetized rats were obtained. This approach was used to assess the effect of alterations in lung tissue biomechanics induced by lung injury at 7 days after single-dose, intratracheal bleomycin instillation in combination with short-term high-tidal volume (VT) mechanical ventilation. Overall, this work address the aspects of radiation exposure to in experimental imaging of small animals and lays a foundation for a more nuanced understanding of lung injury and mechanical ventilation. In the future, it may result in a more effective and less injurious respiratory support for patients with acute lung injury or chronic lung diseases.
|
|
| 3. |
- Adjeiwaah, Mary, 1980-
(författare)
-
Quality assurance for magnetic resonance imaging (MRI) in radiotherapy
- 2017
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Magnetic resonance imaging (MRI) utilizes the magnetic properties of tissues to generate image-forming signals. MRI has exquisite soft-tissue contrast and since tumors are mainly soft-tissues, it offers improved delineation of the target volume and nearby organs at risk. The proposed Magnetic Resonance-only Radiotherapy (MR-only RT) work flow allows for the use of MRI as the sole imaging modality in the radiotherapy (RT) treatment planning of cancer. There are, however, issues with geometric distortions inherent with MR image acquisition processes. These distortions result from imperfections in the main magnetic field, nonlinear gradients, as well as field disturbances introduced by the imaged object. In this thesis, we quantified the effect of system related and patient-induced susceptibility geometric distortions on dose distributions for prostate as well as head and neck cancers. Methods to mitigate these distortions were also studied.In Study I, mean worst system related residual distortions of 3.19, 2.52 and 2.08 mm at bandwidths (BW) of 122, 244 and 488 Hz/pixel up to a radial distance of 25 cm from a 3T PET/MR scanner was measured with a large field of view (FoV) phantom. Subsequently, we estimated maximum shifts of 5.8, 2.9 and 1.5 mm due to patient-induced susceptibility distortions. VMAT-optimized treatment plans initially performed on distorted CT (dCT) images and recalculated on real CT datasets resulted in a dose difference of less than 0.5%. The magnetic susceptibility differences at tissue-metallic,-air and -bone interfaces result in local B0 magnetic field inhomogeneities. The distortion shifts caused by these field inhomogeneities can be reduced by shimming. Study II aimed to investigate the use of shimming to improve the homogeneity of local B0 magnetic field which will be beneficial for radiotherapy applications. A shimming simulation based on spherical harmonics modeling was developed. The spinal cord, an organ at risk is surrounded by bone and in close proximity to the lungs may have high susceptibility differences. In this region, mean pixel shifts caused by local B0 field inhomogeneities were reduced from 3.47±1.22 mm to 1.35±0.44 mm and 0.99±0.30 mm using first and second order shimming respectively. This was for a bandwidth of 122 Hz/pixel and an in-plane voxel size of 1×1 mm2. Also examined in Study II as in Study I was the dosimetric effect of geometric distortions on 21 Head and Neck cancer treatment plans. The dose difference in D50 at the PTV between distorted CT and real CT plans was less than 1.0%.In conclusion, the effect of MR geometric distortions on dose plans was small. Generally, we found patient-induced susceptibility distortions were larger compared with residual system distortions at all delineated structures except the external contour. This information will be relevant when setting margins for treatment volumes and organs at risk. The current practice of characterizing MR geometric distortions utilizing spatial accuracy phantoms alone may not be enough for an MR-only radiotherapy workflow. Therefore, measures to mitigate patient-induced susceptibility effects in clinical practice such as patient-specific correction algorithms are needed to complement existing distortion reduction methods such as high acquisition bandwidth and shimming.
|
|
| 4. |
- Rigato, Cristina, 1989
(författare)
-
Direct Drive Bone Conduction Stimulation: Experimental Studies on Functionality and Transmission with Focus on the Bone Conduction Implant
- 2017
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sound is conducted to the inner ear in two ways: by air and by bone. Air conduction (AC) hearing consists of sound waves entering the ear canal and reaching the cochlea, the main hearing organ, via the middle ear. In bone conduction (BC) hearing, instead, the transmission is through soft tissues and bone. These two pathways coexist and complement each other, although innormal hearing subjects the AC part is prevalent over the BC part in most of the ordinary hearing situations.BC hearing can represent an effective way to rehabilitate hearing impaired patients who would not benet from conventional AC hearing aids. This is the case when the hearing impairment is located in the outer or middle ear, or if the patients have chronic infections or malformations preventing them from wearing earmolds. The key idea in bone conduction devices (BCDs) isto generate vibrations with a transducer and transmit them via the skull bone to the inner ear.At present, the most common BCD is probably the bone anchored hearing aid (BAHA), consisting of a single-unit device attached to a skin penetrating screw in the parietal bone. To overcome the issues related to the skin penetration, the development of BCDs is recently focusing on so-called active transcutaneous devices, whose main feature is to have the bone transducer implanted under intact skin.In this thesis, the novel active transcutaneous bone conduction implant (BCI), currently in advanced clinical trial phase, was compared to BAHAs in terms of audiological tests and perceived rehabilitation effect. The outcomes showed that the BCI can be a valid alternative to BAHAs for indicated patients. Preliminary investigations were also performed on how the transmission of vibrations is affected by different ways of attaching the transducer to the skull bone. It was found that the relation varies substantially with frequency, with a general trend of improved transmission when the contact area between transducer and bone is limited.Finally, a new verication method of the implant functionality was evaluated intra- and post- operatively. The method, consisting in the measurement of the sound pressure in the nostril, seems promising and the implant to bone transmission was found stable over time.
|
|
| 5. |
- Persson, Urban, 1961-
(författare)
-
Realise the Potential! : Cost Effective and Energy Efficient District Heating in European Urban Areas
- 2011
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Member States of EU27 need to accelerate the integration of energy efficient technology solutions to reach the 20% energy efficiency target set for 2020. At current pace, projections indicate that only half of expected primary energy reductions will be reached. To meet the energy demands of growing populations and a vibrant economy, while simultaneously reducing primary energy supplies, the European continent faces a new kind of challenge never previously encountered. The identification and application of feasible, competitive, and comprehensive solutions to this problem are of highest priority if the remaining gap is to be closed in time. How is this multi-dimensional and complex dilemma to be dissolved? In this work, expanded use of district heating technology is conceived as a possible solution to substantially reduce future primary energy demands in Europe. By extended recovery and utilisation of vast volumes of currently disregarded excess heat from energy and industry sector fuel transformation processes, district heating systems and combined generation of heat and power can improve the general efficiency of the European energy balance. To investigate the possible range of this solution, this thesis introduces a set of methodologies, theoretical concepts, and model tools, by which a plausible future excess heat utilisation potential, by means of district heat deliveries to residential and service sectors, is estimated. At current conditions and compared to current levels, this potential correspond to a threefold expansion possibility for directly feasible district heating systems in European urban areas and a fourfold increase of European excess heat utilisation.
|
|
| 6. |
- Olsson, Caroline, 1970
(författare)
-
Predicting Normal Tissue Complications after External Beam Radiation Therapy
- 2010
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Although modern external beam radiation (EBRT) therapy has the ability to conform the dose tightly around the volume to be treated, unwanted irradiation to surrounding normal tissue is still a problem. The probability of a side effect arising in normal tissue after EBRT is commonly modelled by an s-shaped dose-volume response curve where dose or volume are plotted against response (i.e. the frequency with which the side effect occurs). The models are based on sigmoid mathematical functions and are fitted to input data representing the outcome (absence or presence of the studied symptom associated with the side effect) and the dose distribution for potentially injured organs using statistical methods. The purpose of this thesis is to give an overview of the current forms of outcome and dose data, how they are generated and used to model side effects today, some of their limitations, and potential future directions. The results are based on concepts from the literature as well as from the three appended papers. The first two present questionnaire-collected outcome data and 2D dose-volume histogram data of the pubic bone for 650 long-term gynecological cancer survivors treated with pelvic radiation therapy between 1991 and 2003 where one in every ten women reported pubic bone pain. The mean dose to the pubic bone proved critical for pain occurrence and the risk to experience pubic bone pain two or more years after pelvic radiation therapy is expected to be 5 % for a mean absorbed dose of 25 Gy. The third paper presents dose differences between non-corrected and fractionation-corrected combined doses in sequential two-phase treatments using 16 combined dose distributions over a model organ at risk (OAR) “irradiated” with a conventional fractionation schedule (2 Gy per fraction; 46 Gy + 22 Gy). Dose differences up to 6 Gy (50 % of a reference total dose
|
|
| 7. |
|
|
| 8. |
- Ghaderi Aram, Morteza, 1988
(författare)
-
Antenna Design, Radiobiological Modelling, and Non-invasive Monitoring for Microwave Hyperthermia
- 2022
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The death toll of cancers is on the rise worldwide and surviving patients suffer significant side effects from conventional therapies. To reduce the level of toxicity in patients treated with the conventional treatment modalities, hyperthermia (HT) has been investigated as an adjuvant modality and shown to be a potent tumor cell sensitizer for radio- and chemotherapy. During the past couple of decades, several clinical radiofrequency HT systems, aka applicators, have been developed to heat tumors. Systems based on radiative applicators are the most widely used within the hyperthermic community. They consist of a conformal antenna array and need a beamforming method in order to focus EM energy on the tumor through constructive interference while sparing the healthy tissue from excessive heating. Therefore, a hyperthermia treatment planning (HTP) stage is required before each patient's first treatment session to optimize and control the EM power deposition as well as the resultant temperature distribution. Despite the vast amount of effort invested in HTP and the progress made in this regard during recent years, the clinical exploitation of HT is still hampered by technical limitations and patients can still experience discomfort during clinical trials. This, therefore, calls for a more efficient hardware design, better control of EM power deposition to minimize unwanted hotspots, and more accurate quantification and monitoring of the treatment outcome. Given these demands, the present report tries to address some of the above-mentioned challenges by proposing - A new antenna model customized for HT applications that surpasses previously proposed models from several points of view. - A hybrid beamforming method for faster convergence and a versatile, robust thermal solver for handling sophisticated scenarios. - A radiobiological model to quantify the outcome of a combined treatment modality of the Gamma Knife radiosurgery and HT. - A differential image reconstruction method to assess the feasibility of using the same system for both heating and microwave thermometry.
|
|
