Intervertebral disc herniations have been indicated as a possible injury development pathway due to occupational vibration exposures in seated postures through epidemiological investigations. Little experimental evidence exists to corroborate the strong epidemiological link between intervertebral disc herniations and vibration exposures using basic scientific approaches. The purpose of the current investigation was to provide some basic experimental evidence of the epidemiological link between intervertebral herniation and exposure to vibration. Partial intervertebral disc herniations were created in in-vitro porcine functional spinal units using a herniation protocol of repetitive flexion/extension motions under modest compressive forces. After herniation initiation, functional spinal units were exposed to 8 different vibration and postural constraint loading protocols consisting of two postural conditions (full flexion and neutral) and 4 vibration loading conditions (whole-body vibration, shock loading, static compressive loads, and whole-body vibration in addition to shock loading) to assess the effects of vibration and posture on functional spinal unit damage progression. There were three main outcome variables used to quantify damage progression; average stiffness changes, herniation distance progression (distance of tracking changes), and specimen height changes, while cumulative loading factors were considered. Additionally the concordance between two types of contrast enhanced medical imaging (Computed Tomography and discograms) was qualified to a dissection ‘gold standard’, and an attempt was made to classify disc damage progression via three categorical variables. Concordance to a dissection ‘gold standard’ was higher for the Computed Tomography medical imaging type that for the Discograms. The categorical criteria used to qualify disc damage progression were insufficiently sensitive to detect damage progressions illustrated through dissection and medical imaging techniques. The partial herniation loading protocol was quantified to be more damaging overall to the functional spinal units compared to the vibration and postural constraint loading protocols. However, the vibration and postural constraint loading protocols provided sufficient mechanical insult to the functional spinal units to progress damage to the intervertebral discs. Vibration loading exposures were found to alter specimen height changes and distance of tracking changes, however posture had no significant effects on these variables. Neither posture nor vibration loading had any meaningful significant effects on average stiffness changes.

The dromedary camel has a very high economic importance in the Arabic countries. Nevertheless, there is a very little background literature on the use of ultrasound (US) and computed tomography (CT) in dromedaries in comparison to other domestic and farm animal species. Therefore, the tarsal region of six cadaver limbs, obtained from three orthopedic disease free dromedary camels, was evaluated via radiography, US and CT. The limbs were frozen and sectioned transversely, sagittaly and dorsally. The anatomic structures were identified and correlated to the analogous structures on the corresponding CT slices and US images and published in two manuscripts. Radiography was performed in both standard (0º and 90º) oblique (45º and 135º) radiographic projections. The tarsus was investigated via US in four planes (dorsal, medial, lateral and plantar) and each plane was scrutinized in four levels (calcaneal tuber, tibial malleoli, base of calcaneus and proximal head of metatarsus) in both transverse and longitudinal views. Radiography provided a good representation of the bony structures and articulations with little information on the soft tissues of the tarsus and superimposition of the tarsal bones. Ultrasonography furnished adequate delineation of the peri-articular tissues of the tarsus and was limited to the bone surface. Computed tomography provided cross sectional imaging of the dromedary tarsus without bone and soft tissue overlap and allowed visualization and differentiation of tissues in almost every situation. This work was undertaken to document the normal appearance of the dromedary camel tarsus via radiography, ultrasonography, and computed tomography which may be used as a resource for interpretation of dromedary tarsal pathology using various diagnostic imaging modalities.

Sammanfattning Bakgrund Stråldosen vid en datortomografiundersökning (CT-undersökning) kan vara 100 gånger större än vid en konventionell röntgenundersökning [1]. På 10 år har antalet CT-undersökningar nästan fördubblats [2], vilket också innebär att stråldosen till patienterna ökar [1]. Bröstkörtlarna är ett av de mest strålkänsliga organen och är därför viktiga att skydda [3, 4]. Material som dämpar röntgenstrålning kraftigt och som lämpar sig för strålskydd är t.ex. bly och vismut [5]. Vismutskydd är ett tungt, metalliskt grundämne som absorberar röntgenstrålning och därmed reducerar stråldosen till vävnaderna under skyddet [6, 7]. Syfte Syftet med studien är att genom en litteraturstudie undersöka vismuts strålskyddande effekt för bröstvävnad och eventuell påverkan på bildkvalitén. Metod Artikelsökningarna gjordes i databasen PubMed med sökorden Radiation protection, Reduced radiation dosage, Radiography, Bismuth, Breasts, Bismuth shielding och image quality i olika kombinationer. Totalt valdes åtta artiklar ut. Resultat Samtliga studier har kommit fram till att vismutskyddet ensamt [8, 9, 10, 11] eller tillsammans med automatisk exponeringskontroll (AEC) reducerar stråldosen till brösten [7, 8, 12, 13, 14]. Fem studier hävdar också att bildkvalitén inte påverkas nämnvärt [7, 10, 12, 13, 14] medan två av studierna visar på en brusökning [8, 9]. Slutsats Vismutskyddet har en stråldosreducerande effekt men det bidrar även till sämre bildkvalité. Studien visar att skyddet ska användas med försiktighet och om inte tekniken utvecklas så att mAs-värdet (milliAmperesekund) lokalt över brösten kan reduceras, rekommenderas användandet av AEC istället. Nyckelord: Vismut, datortomografi, bröst, bildkvalité och stråldosreducering.

Intervertebral disc herniations have been indicated as a possible injury development pathway due to occupational vibration exposures in seated postures through epidemiological investigations. Little experimental evidence exists to corroborate the strong epidemiological link between intervertebral disc herniations and vibration exposures using basic scientific approaches. The purpose of the current investigation was to provide some basic experimental evidence of the epidemiological link between intervertebral herniation and exposure to vibration. Partial intervertebral disc herniations were created in in-vitro porcine functional spinal units using a herniation protocol of repetitive flexion/extension motions under modest compressive forces. After herniation initiation, functional spinal units were exposed to 8 different vibration and postural constraint loading protocols consisting of two postural conditions (full flexion and neutral) and 4 vibration loading conditions (whole-body vibration, shock loading, static compressive loads, and whole-body vibration in addition to shock loading) to assess the effects of vibration and posture on functional spinal unit damage progression. There were three main outcome variables used to quantify damage progression; average stiffness changes, herniation distance progression (distance of tracking changes), and specimen height changes, while cumulative loading factors were considered. Additionally the concordance between two types of contrast enhanced medical imaging (Computed Tomography and discograms) was qualified to a dissection ‘gold standard’, and an attempt was made to classify disc damage progression via three categorical variables. Concordance to a dissection ‘gold standard’ was higher for the Computed Tomography medical imaging type that for the Discograms. The categorical criteria used to qualify disc damage progression were insufficiently sensitive to detect damage progressions illustrated through dissection and medical imaging techniques. The partial herniation loading protocol was quantified to be more damaging overall to the functional spinal units compared to the vibration and postural constraint loading protocols. However, the vibration and postural constraint loading protocols provided sufficient mechanical insult to the functional spinal units to progress damage to the intervertebral discs. Vibration loading exposures were found to alter specimen height changes and distance of tracking changes, however posture had no significant effects on these variables. Neither posture nor vibration loading had any meaningful significant effects on average stiffness changes.

<p>This thesis research builds upon prior work that developed separate SPECT and CT (computed mammotomography, or breast CT) devices that were independently capable of imaging an uncompressed breast in 3D space. To further develop the system as a clinically viable device, it was necessary to integrate the separate imaging systems onto a single gantry, and to simultaneously design a patient-friendly bed that could routinely and effectively position the patient during dual-modality imaging of her uncompressed breast in the system's common field of view. This thesis describes this process and also investigates practical challenges associated with dedicated breast imaging of a prone patient using the integrated SPECT-CT device.</p> <p>We initially characterized the practicability of implementing the novel x-ray beam ultra-thick K-edge filtration scheme designed for routine use with the breast CT system. Extensive computer simulations and physical measurements were performed to characterize the x-ray beam produced using K-edge filtration with cerium and to compare it to beams produced using other filtration methods and materials. The advantages of using this heavily filtered x-ray beam for uncompressed breast CT imaging were then further evaluated by measuring the dose absorbed by an uncompressed cadaver breast during the course of a routine tomographic scan. It was found that the breast CT device is indeed capable of imaging uncompressed breasts at dose levels below that of the maximum utilized for dual-view screening mammography.</p> <p>To prepare the separate SPECT and CT systems for integration onto a single platform, the cross contamination of the image of one modality by primary and scattered photons of the complementary modality was quantified. It was found that contamination levels of the emission (SPECT) image by the x-ray transmission source were generally far less than 2% when using photopeak energy windows up to ±8%. In addition, while there was some quantifiable evidence of a variation in the transmission image in response to the presence of <super>99m</super>Tc photons in the patient, the effect of primary and scattered <super>99m</super>Tc photons on the visibility of 5 mm acrylic photons in a low contrast x-ray transmission environment was negligible. </p> <p>A novel, tiered, stainless steel patient bed was then designed to allow dual-modality imaging using the integrated SPECT-CT system. The performance of the hybrid SPECT-CT system was evaluated during early stage dual-modality patient imaging trials with particular emphasis placed on the performance of the patient bed. The bed was successful in its primary task of enabling dual-modality imaging of a patient's breast in the common field of view, but practical challenges to more effective patient imaging were identified as well as some novel solutions to these challenges.</p> <p>In the final section of the thesis research, the feasibility of using two of these solutions was investigated with a view to imaging more of the patient's posterior breast volume. Limited angle tomographic trajectories and trajectories that involve raising or lowering the patient bed in mid tomographic acquisition were initially investigated using various geometric phantoms. A very low contrast imaging task was then tested using an observer study to quantify the effect of these trajectories on the ability of observers to maintain visibility of small geometric objects. </p> <p>This initial integrated SPECT-CT imaging system has demonstrated its ability to successfully perform low dose, dual-modality imaging of the uncompressed breast. Challenges and solutions have been identified here that will make future SPECT-CT designs even more powerful and a clinically relevant technique for molecular imaging of the breast.</p> / Dissertation

The mechanical properties of the cancellous bone in the laboratory rat animal model are of great interest to the research community for the evaluation of treatments for osteoporosis. Cancellous bone responds rapidly and dramatically to disuse, various pathologies, nutritional deficiencies, and hormonal deficiencies and hence is often a primary focus in animal studies. Previous methods for evaluating the mechanical properties of cancellous bone in rat test specimens included both cortical and cancellous bone. This thesis introduces a new method to core cancellous specimens using a diamond wire saw in concert with specially designed fixtures. This method has been termed Isolated Cancellous Coring (ICC). The location and the geometry of the cored specimens were determined based on uCT analysis. The isolated cancellous specimens were subjected to uni-axial compression testing to evaluate the mechanical properties. Furthermore, the new method is evaluated by directly applying it to a study investigating the effects of estrogen replacement therapy in post-menopausal osteoporosis as simulated by the ovariectomized rat model. The results show that the ICC method can be applied to bone specimens with a large range in density and micro-architecture parameters. The compression testing of the isolated cancellous specimens provides a sensitive indicator of the effects of osteoporosis and treatment on the mechanical properties of the cancellous bone in the distal rat femur. Also, the results indicate a possible discordant relationship between bone mineral density and bone strength with respect to estrogen treatment. Power law regressions show that approximately 50% of the variation in ultimate strength can be accounted for with bone mineral density and the percent of bone volume per total volume.

In this dissertation I evaluate the potential of the morphology of the petrous portion of the human temporal bone as seen on axial CT scans of the head as a means to generate identifications of fragmentary human skeletal remains. The specific goals are threefold: (1) To investigate variability in the shape of the petrous portion of the human temporal bone using two-dimensional morphometric analysis; (2) to evaluate the reliability of the resultant method in forensic identification; and (3) to consider the results within the framework of Bayesian theory in light of recent rulings regarding the admissibility of forensic testimony. The data used in this research were collected from axial CT images of the cranium. Two sets of images were collected for each of the 115 individuals in the sample so that Euclidean distance comparisons could be made between images of the same individual and images from different individuals. I collected two-dimensional coordinate data from 36 landmarks on each of the CT images and calculated the distances between each of the coordinate points to generate the data used in the statistical analyses. I pared down this set of measurements using two different models (referred to as the biological and PCFA models). The measurement sets of both models were then compared to one another using nearest neighbor analysis, to test their relative efficiency in matching replicate images to one another. The results of both models were highly accurate. Three incorrect nearest neighbor matches resulted from the biological model and 5 from the PCFA model. The errors appear to have been the result of variation in the axial plane between the first and second scans. The results of the nearest neighbor comparisons were then considered within the context of Bayes' Theorem by calculating likelihood ratios and posterior probabilities. The likelihood ratios and posterior probabilities were very high for both models, indicating that: 1) there is significant individual variability in the measurements of the petrous portion used in this research, and 2) this variation represents a high level of potential accuracy in the application of this method in the identification of forensic remains.

No description available.

Detection of coronary calcification from computed tomography scans is a noninvasive examination and has great potential for heart disease diagnosis. This study proposes new features to characterize calcium lesions. Different from the traditional calcium score features, these features are generated from the texture, shape, and gray level statistics of the calcium lesions. We study the correlation between these features and acute myocardial infarction and then compare the results with traditional calcium score features. According to the location of the lesions, patients are first divided into two groups. In one group, the myocardial infarction is located in segment of culprit lesion. For the second group, myocardial infarction is located in segment of non-culprit lesion. In comparing their means, the corresponding p-value of gray level statistics feature ¡§histogram relative smoothness¡¨ could reach 4.47E-07, which has fairly high significance. Furthermore, in studying the differences among patients, experiment on Hypercholesterolemia provide a good result. By comparing the means of patients which are classified into Hypercholesterolemia and non-Hypercholesterolemia groups, the corresponding p-value of texture feature ¡§inverse difference moment¡¨ could reach 3.74E-04. Initially, acute myocardial infarction do not have statistically significant result However, after adding the location weighting factor for the lesions, the corresponding p-value of texture feature ¡§average of information measures of correlation¡¨ could be reduced to 8.8921E-03, and p-value of gray level statistics feature ¡§Histogram relative Smoothness¡¨ could be improved to 2.4019E-02.

Open and connected fractures, where present, control fluid flow and dominate solute transport. Flow through fractures has major implications for water resource management, underground waste repositories, contaminant remediation, and hydrocarbon exploitation. Complex fracture morphology makes it difficult to quantify and predict flow and transport accurately. The difficulty in usefully describing the complex morphology of a real fracture from a small 3-D volume or 2-D profile sample remains unresolved. Furthermore, even when complex fracture morphology is measured across three-dimensions, accurate prediction of discharge remains difficult. High resolution x-ray computed tomography (HXRCT) data collected for over 20 rock surfaces and fractures provide a useful dataset to study fracture morphology across scales of several orders of magnitude. Samples include fractured rock of varying lithology, including sandstone, volcanic tuffs and crystalline igneous and metamorphic rocks. Results suggest that the influence of grain size on surface roughness is not readily apparent due to other competing variables such as mechanics, skins and coatings, and weathering and erosion. Flow tests of HXRCT-scanned fractures provide real discharge data allowing the hydraulic aperture to be directly measured. Scale-invariant descriptions of surface roughness can produce constrained estimates of aperture variability and possibly yield better predictions of fluid flow through fractures. Often, a distinction is not made between the apparent and true fracture apertures for rough fractures measured on a 2-D topographic grid. I compare a variety of local aperture measurements, including the apparent aperture, two-dimensional circular tangential aperture, and three-dimensional spherical tangential aperture. The mechanical aperture, the arithmetic mean of the apparent local aperture, is always the largest aperture. The other aperture metrics vary in their ranking, but remain similar. Results suggest that it may not be necessary to differentiate between the apparent and true apertures. Rock fracture aperture is the predominant control on permeability, and surface roughness controls fracture aperture. A variety of surface roughness characterizations using statistical and fractal methods are compared. A combination of the root-mean-square roughness and the surface-to-footprint ratio are found to be the most useful descriptors of rock fracture roughness. Mated fracture surfaces are observed to have nearly identical characterizations of fracture surface roughness, suggesting that rock fractures can be sampled by using only one surface, resulting in a significantly easier sampling requirement. For mated fractures that have at least one point in contact, a maximum potential aperture can be constrained by reflecting and translating a single surface. The maximized aperture has a nearly perfect correlation with the RMS roughness of the surface. These results may allow better predictions of fracture permeability thereby providing a better understanding of subsurface fracture flow for applications to contaminant remediation and water and hydrocarbon management. Further research must address upscaling fracture morphology from hand samples to outcrops and characterizing entire fracture networks from samples of single fractures. / text