The aim of this exploratory study was to evaluate the influence of hepatic steatosis on the detection rate of metastases in gadoxetic acid-enhanced liver magnetic resonance imaging (MRI). A total of 50 patients who underwent gadoxetic acid-enhanced MRI (unenhanced T1w in- and opposed-phase, T2w fat sat, unenhanced 3D-T1w fat sat and 3-phase dynamic contrast-enhanced (uDP), 3D-T1w fat sat hepatobiliary phase (HP)) were retrospectively included. Two blinded observers (O1/O2) independently assessed the images to determine the detection rate in uDP and HP. The hepatic signal fat fraction (HSFF) was determined as the relative signal intensity reduction in liver parenchyma from in- to opposed-phase images. A total of 451 liver metastases were detected (O1/O2, n = 447/411). O1/O2 detected 10.9%/9.3% of lesions exclusively in uDP and 20.2%/15.5% exclusively in HP. Lesions detected exclusively in uDP were significantly associated with a larger HSFF (area under curve (AUC) of receiver operating characteristic (ROC) analysis, 0.93; p < 0.001; cutoff, 41.5%). The exclusively HP-positive lesions were significantly associated with a smaller diameter (ROC-AUC, 0.82; p < 0.001; cutoff, 5 mm) and a smaller HSFF (ROC-AUC, 0.61; p < 0.001; cutoff, 13.3%). Gadoxetic acid imaging has the advantage of detecting small occult metastatic liver lesions in the HP. However, using non-optimized standard fat-saturated 3D-T1w protocols, severe steatosis (HSFF > 30%) is a potential pitfall for the detection of metastases in HP.

Localization of features and structures in images is an important task in medical image-processing. Characteristic structures and features are used in diagnostics and surgery planning for spatial adjustments of the volumetric data, including image registration or localization of bone-anchors and fiducials. Since this task is highly recurrent, a fast, reliable and automated approach without human interaction and parameter adjustment is of high interest. In this paper we propose and compare four image processing pipelines, including algorithms for automatic detection and localization of spherical features within 3D MRI data. We developed a convolution based method as well as algorithms based on connected-components labeling and analysis and the circular Hough-transform. A blob detection related approach, analyzing the Hessian determinant, was examined. Furthermore, we introduce a novel spherical MRI-marker design. In combination with the proposed algorithms and pipelines, this allows the detection and spatial localization, including the direction, of fiducials and bone-anchors.

No description available.

<p>Diffusion tensor (DT) and blood oxygen-level dependent (BOLD) imaging are two noninvasive magnetic resonance (MR) techniques that have been used to probe skeletal muscle microstructure and microvasculature, respectively. Over a series of four studies, the work in this thesis aimed at furthering our understanding of baseline DT metrics and BOLD signals in lower limb muscles (calf and foot) of healthy young subjects. Since postural changes have been shown to alter numerous quantities, including fluid volumes and muscle cross sectional area, DT indices and BOLD signal characteristics were examined in response to movement from upright to supine position.</p> <p>Reductions of 3.2-6.7% and 3.4-7.5% were measured in calf DT eigenvalues and apparent diffusion coefficient (ADC) in the various muscles, following 34 and 64 minutes of supine rest, respectively (P</p> <p>Establishment of baseline diffusion metrics in the foot region was feasible (chapter 6). Examination of foot DT indices in response to positional change showed that the metrics decreased from 2.7-4.6% following 34 minutes of supine rest (P</p> / Doctor of Philosophy (PhD)

In spinal cord injury the amount of total surviving white matter is known to be strongly related to post injury neurological functions (1). Accurate segmentation of these regions is shown to be critical in terms of developing effective treatment (1). Diffusion Tensor Imaging (DTI) has been shown to be effective in obtaining spinal cord images (2). However challenges still exist in clear separation of gray/white/cerebrospinal fluid (CSF) structures within the cord using DTI. The purpose of this study is to (1) test a semi-automatic tissue segmentation algorithm based on grow cut algorithm (GCA), to classify CSF, gray and white matter in conventional T2 weighted MRI and Diffusion Tensor Imaging (DTI) images in pediatric spinal cord injury (SCI) subjects, and (2) to compare the results of semi-automatic GCA segmentation with manually segmented spinal cord data performed on various DTI images by a board certified pediatric neuroradiologist. Results show that semi-automatic segmentation of the spinal cord using GCA was successfully implemented. Qualitatively, good separation of cord/CSF was seen in B0, CFA and FA maps (of a representative patient with SCI and a control using this GCA method. They demonstrate more homogeneous signal within the cervical spinal cord as well as greater conspicuity of the cord and surrounding CSF interface. Quantitative analysis of images segmented using GCA and manual segmentation between and within the groups showed no significant differences in CFA (p=0.1347) and FA (p=0.1442) images but B0 (p=0.0001) images showed statistically significant differences. Overall, in both the controls and subjects with SCI, quantitative and qualitative analysis showed a superior semi-automated segmentation on CFA and FA images over a B0 image the using modified GCA. Key words: Grow Cut Algorithm (GCA), Magnetic Resonance Imaging (MRI), segmentation, Diffusion Tensor Imaging (DTI), cervical spinal cord, cerebral-spinal fluid (CSF). / Bioengineering

Aim To review the recent evidence that has resulted from experiences in and out of conflict in relation to improving imaging in cases of major trauma. Method A search of electronic databases, the internet and Cochrane library was undertaken to identify relevant publications which were analysed in terms of quality. Evidence that has emerged from civilian and military practice that could influence the practice of major trauma imaging in future was discussed. Results The importance of speed in assessing patients suffering major trauma is becoming more recognised. There is growing evidence that the use of portable ultrasound at the site of major trauma as first line investigation has potential. In more stable patients, the evidence for whole body CT at the expense of radiography is also growing. The concern regarding availability and radiation dose related to CT scanning remain significant but with the outcome of the recent Major Trauma Review and improvements in CT scanning techniques, such concerns are being addressed. There is limited research in the use of MRI in relation to major trauma. Conclusion Ultrasound at the sight of major trauma has potential but further research will be needed. Factors such as operator training in particular need to be considered. CT scanning remains an important diagnostic tool for patients suffering major trauma and this is borne out by the Major Trauma Review and NICE guidelines. The availability of CT scanning in relation to accident and emergency scanning is a factor the Major Trauma Review has highlighted and the close proximity of new CT scanners to accident and emergency is a factor that will need to be taken into account in strategic planning. Given the growing evidence of CT involvement, the continued practice of cervical spine and pelvic radiography in cases of major trauma should be questioned.

Stroke is one of the leading causes of death and adult disability worldwide. The major therapeutic intervention for acute ischemic stroke is the administration of recombinant tissue plasminogen activator (rtPA) to help to restore blood flow to the brain. This has been shown to increase the survival rate and to reduce the disability of ischemic stroke patients. However, rtPA is associated with intracranial haemorrhage and thus its administration is currently limited to only about 5% of ischemic stroke patients. More advanced imaging techniques can be used to better stratify patients for rtPA treatment. One new imaging technique, chemical exchange saturation transfer (CEST) magnetic resonance imaging, can potentially image intracellular pH and since tissue acidification happens prior to cerebral infarction, CEST has the potential to predict ischemic injury and hence to improve patient selection. Despite this potential, most studies have generated pH-weighted rather than quantitative pH maps; the most widely used metric to quantify the CEST effect is only able to generate qualitative contrast measurements and suffers from many confounds. The greatest clinical benefit of CEST imaging lies in its ability to non-invasively measure quantitative pH values which may be useful to identify salvageable tissue. The quantitative techniques and work presented in this thesis thus provide the necessary analysis to determine whether a threshold for the quantified CEST effect or for pH exists to help to define tissue outcome following stroke; to investigate the potential of CEST for clinical stroke imaging; and subsequently to facilitate clinical translation of CEST for acute stroke management.

This dissertation is comprised of four studies investigating the hypothesis that adults and children who stutter differ from their same-age fluent peers in the neuroanatomy and neurophysiology underlying auditory speech processing. It has been consistently reported that adults who stutter demonstrate unique functional neural activation patterns during speech production, including reduced auditory activation, relative to nonstutterers. The extent to which these functional differences are accompanied by abnormal morphology of the brain in stutterers is unclear. The first study in this dissertation examined the neuroanatomical differences in speech-related cortex between adults who do and do not stutter using magnetic resonance imaging and voxel-based morphometry analyses. Adults who stutter were found to have localized grey matter volume increases in auditory and motor speech related cortex. The second study extended this line of research to children who stutter, who were found to have localized grey matter volume decreases in motor speech related cortex. Together, these studies suggest an abnormal trajectory of regional grey matter development in motor speech cortex of people who stutter. The last two studies investigated the mechanism underlying the repeated findings of reduced auditory activation during speech in people who stutter in more detail. Magnetoencephalography was used to investigate the hypothesis that people who stutter have increased speech induced suppression of early evoked auditory responses. Adults and children who stutter demonstrated typical levels of speech induced suppression relative to fluent peers. However, adults and children who stutter showed differences from peers in the timing of cortical auditory responses. Taken together, the studies demonstrate structural and functional abnormalities in brain regions related to auditory processing and point to the possibility that people who stutter have difficulty forming the neural representations of speech sounds necessary for fluent speech production.

Endometriosis is an oestrogen-dependent gynaecological condition defined as the presence of endometrial tissue outside the uterus cavity. The condition is predominantly found in women in their reproductive years, and associated with significant pelvic and abdominal chronic pain and infertility. The disease is believed to affect approximately 33% of women by a recent study. Currently, surgical intervention, often laparoscopic surgery, is the gold standard for diagnosing the disease and it remains an effective and common treatment method for all stages of endometriosis. Magnetic resonance imaging (MRI) of the patient is performed before surgery in order to locate any endometriosis lesions and to determine whether a multidisciplinary surgical team meeting is required. In this dissertation, our goal is to use image processing techniques to aid surgical planning. Specifically, we aim to improve quality of the existing images, and to automatically detect bladder endometriosis lesion in MR images as a form of bladder wall thickening. One of the main problems posed by abdominal MRI is the sparse anisotropic frequency sampling process. As a consequence, the resulting images consist of thick slices and have gaps between those slices. We have devised a method to fuse multi-view MRI consisting of axial/transverse, sagittal and coronal scans, in an attempt to restore an isotropic densely sampled frequency plane of the fused image. In addition, the proposed fusion method is steerable and is able to fuse component images in any orientation. To achieve this, we apply the Riesz transform for image decomposition and reconstruction in the frequency domain, and we propose an adaptive fusion rule to fuse multiple Riesz-components of images in different orientations. The adaptive fusion is parameterised and switches between combining frequency components via the mean and maximum rule, which is effectively a trade-off between smoothing the intrinsically noisy images while retaining the sharp delineation of features. We first validate the method using simulated images, and compare it with another fusion scheme using the discrete wavelet transform. The results show that the proposed method is better in both accuracy and computational time. Improvements of fused clinical images against unfused raw images are also illustrated. For the segmentation of the bladder wall, we investigate the level set approach. While the traditional gradient based feature detection is prone to intensity non-uniformity, we present a novel way to compute phase congruency as a reliable feature representation. In order to avoid the phase wrapping problem with inverse trigonometric functions, we devise a mathematically elegant and efficient way to combine multi-scale image features via geometric algebra. As opposed to the original phase congruency, the proposed method is more robust against noise and hence more suitable for clinical data. To address the practical issues in segmenting the bladder wall, we suggest two coupled level set frameworks to utilise information in two different MRI sequences of the same patients - the T2- and T1-weighted image. The results demonstrate a dramatic decrease in the number of failed segmentations done using a single kind of image. The resulting automated segmentations are finally validated by comparing to manual segmentations done in 2D.

Akute Enzephalitiden treten überwiegend sporadisch mit klinisch heterogener Manifestation auf und können durch Viren, andere Erreger oder Autoimmunprozesse verursacht sein, häufig bleibt die Ätiologie unklar. Ziel dieser Arbeit war es, Ursache und klinisches Erscheinungsbild einer konsekutiven Gruppe immunkompetenter erwachsener Enzephalitispatienten, deren funktionelles, neuropsychologisches und soziales Outcome im Langzeitverlauf sowie einen möglichen Hirnsubstanzverlust mittels Planimetrie von Magnetresonanztomogrammen zu untersuchen. Die retrospektive Analyse von 111 Patienten erbrachte eine eindeutige ätiologische Zuordnung in nur 28 % der Fälle; am häufigsten waren Varizella-zoster-Virus und Herpes-simplex-Virus-I. An nicht-viralen Erregern sind Mycoplasmen hervorzuheben. Mit der cranialen Magnetresonanztomographie waren bei ca. 50 % parenchymatöse Veränderungen nachweisbar. Die Sensitivität der Elektroenzephalographie betrug über 80 %. Ein Drittel der Patienten mußte intensivmedizinisch behandelt werden. Die Letalität war mit knapp 2 % gering. Die follow-up-Untersuchung von 73 Patienten mit durchschnittlich drei Jahre zurückliegender akuter Enzephalitis ergab bei 86 % der Patienten einen günstigen bis befriedigenden Verlauf mit erhaltener Selbständigkeit. Bei den ungünstig verlaufenden Fällen dominierten kognitive Beeinträchtigungen und pharmakoresistente Epilepsien, hochgradige körperliche Behinderungen persistierten nur bei 4 %. Neuropsychologisch meßbare Defizite persistierten nur bei einer geringen Zahl von Patienten. Im Vergleich zu einer Kontrollgruppe ergaben sich Defizite insbesondere für diejenigen Patienten, die während der akuten Enzephalitis viele epileptische Anfälle erlitten hatten. Diese Gruppe von Patienten hatte auch eine signifikant deutlichere Zunahme der planimetrisch bestimmten ventricle-brain-ratio, also einen stärkeren Verlust an Hirnparenchym, als die anderen Patienten. Auch die subjektive Lebensqualität war bei dieser Gruppe von Patienten am stärksten beeinträchtigt. Unabhängig vom Krankheitserreger erscheint somit das Auftreten von Serien oder Status epileptischer Anfälle bei akuten Enzephalitiden ein Prädiktor für einen ungünstigen Verlauf zu sein. / Acute encephalitis occurs mainly sporadically with heterogenous clinical manifestations and can be caused by viruses, other infectious agents or autoimmune disease; often the etiology remains unclear. The aim of this study was to analyze causes and clinical features in a consecutive study population of immunocompetent adults with acute encephalitis and to evaluate their functional, neuropsychological and social long-term outcome as well as a possible loss of brain parenchyma by means of magnetic resonance imaging planimetry. Retrospective analysis of 111 patients demonstrated a definite pathogen in only 28 % of cases, most common were Varicella-zoster virus and Herpes-simplex virus type I. The most important non-viral agent was Mycoplasma. Parenchymal lesions could be identified by cranial magnetic resonance imaging in about 50 %. Electroencephalography had a sensitivity of about 80 %. One third of the patients required intensive care therapy. Mortality was low with less than 2 %. Follow-up examination of 73 patients who had suffered from encephalitis on the average three years before demonstrated a good or satisfiable outcome with preserved independence in 86 %. In cases with unfavourable outcome, cognitive impairment and pharmaco-resistent epilepsy dominated; high-grade physical impairment persisted in only 4 %. Neuropsychologically measurable deficits persisted only in a small number of patients. Compared to a control group, impairment was predominantly found in those patients who had suffered from serial epileptic fits or status epilepticus. This group of patients also had a distinct increase of planimetrically measured ventricle-brain-ratio, i.e. a marked loss of brain parenchyma. Furthermore, self-estimated quality of life was most strongly impaired in those patients. Thus, the occurence of serial epileptic fits or status epilepticus during acute encephalitis seems to predict an unfavourable outcome, independently of the pathogenic agent.