Computer-Aided Diagnosis of Thyroid Nodule: A Review

ABSTRAC

Application of Advanced MRI to Fetal Medicine and Surgery

Robust imaging is essential for comprehensive preoperative evaluation, prognostication, and surgical planning in the field of fetal medicine and surgery. This is a challenging task given the small fetal size and increased fetal and maternal motion which affect MRI spatial resolution. This thesis explores the clinical applicability of post-acquisition processing using MRI advances such as super-resolution reconstruction (SRR) to generate optimal 3D isotropic volumes of anatomical structures by mitigating unpredictable fetal and maternal motion artefact. It paves the way for automated robust and accurate rapid segmentation of the fetal brain. This enables a hierarchical analysis of volume, followed by a local surface-based shape analysis (joint spectral matching) using mathematical markers (curvedness, shape index) that infer gyrification. This allows for more precise, quantitative measurements, and calculation of longitudinal correspondences of cortical brain development. I explore the potential of these MRI advances in three clinical settings: fetal brain development in the context of fetal surgery for spina bifida, airway assessment in fetal tracheolaryngeal obstruction, and the placental-myometrial-bladder interface in placenta accreta spectrum (PAS). For the fetal brain, MRI advances demonstrated an understanding of the impact of intervention on cortical development which may improve fetal candidate selection, neurocognitive prognostication, and parental counselling. This is of critical importance given that spina bifida fetal surgery is now a clinical reality and is routinely being performed globally. For the fetal trachea, SRR can provide improved anatomical information to better select those pregnancies where an EXIT procedure is required to enable the fetal airway to be secured in a timely manner. This would improve maternal and fetal morbidity outcomes associated with haemorrhage and hypoxic brain injury. Similarly, in PAS, SRR may assist surgical planning by providing enhanced anatomical assessment and prediction for adverse peri-operative maternal outcome such as bladder injury, catastrophic obstetric haemorrhage and maternal death

Evaluation of fetal kidney length measurement in estimation of gestational age in late trimester

OBJECTIVE: 1. To evaluate the accuracy of fetal kidney length measurement in estimating gestational age. 2. To compare its efficacy in estimating gestational age with other routinely used biometric indices and to find out the most accurate parameter in estimating gestational age. STUDY DESIGN: Two hundred pregnant women with singleton uncomplicated pregnancies with the gestational age between 24 to 40 weeks of gestation were selected for the study. They underwent ultrasound fetal biometry and fetal kidney length measurement. These measurements were used to date the pregnancies and compared with clinical gestational age derived from last menstrual period and dating scan. Linear regression analysis was done to find out the best parameter for estimating gestational age. Pearson correlation was done to determine the accuracy of these parameters in the dermination of gestational age. RESULTS: The mean fetal kidney length showed a linear correlation with gestational age. Fetal kidney length determines gestational age with the accuracy of + 9.8 days. BPD dates pregnancy with the accuracy of + 11.5 days, Head circumference by + 12.4 days, Femur length by + 11.3 days, Abdominal circumference by + 12.6 days, suggesting that Abdominal circumference is the worst predictor for estimating gestational age. CONCLUSION: From this study it was concluded that fetal kidney length measurement is the most accurate method of determining gestational age than other fetal biometric indices like biparietal diameter,head circumference, abdominal circumference, femur length between 24 to 40 weeks of gestation

The characterisation of growth hormone-related cardiac disease with magnetic resonance imaging & The effects of growth hormone dysregulation on adenosine monophosphate-activated protein kinase in cardiac tissue

PhDChronic growth hormone (GH) excess, acromegaly, causes a specific cardiomyopathy, which remains poorly understood. The pattern of hypertrophy is distinct from other forms of cardiac disease and begins to appear before hypertension or diabetes. GH deficiency (GHD) also causes cardiovascular problems, with reduced ability to mount a cardiovascular response to exercise. Acromegaly and GHD patients have increased cardiac mortality. Cardiac magnetic resonance imaging (CMR) is the gold standard for assessment of cardiac mass and provides data on cardiac function, fibrosis, valve function and ischaemia. This study used CMR to assess 23 patients with acromegaly or GHD, before and after treatment of their GH disorder, and 23 healthy controls. Patients with acromegaly demonstrated increased left ventricular mass index (LVMi), end diastolic volume index, stroke volume index and cardiac index, which persisted at one year, despite treatment of underlying disease. Patients with GHD demonstrated LVMi at the bottom (males) or beneath (females) published normal references ranges, which increased with one year of GH replacement. The mechanisms by which GH influences cardiac tissue are poorly understood. Adenosine monophosphate-activated protein kinase (AMPK) is an energy-regulator enzyme, which interacts with several metabolic hormones. Mutations in AMPK cause arrhythmias and cardiac hypertrophy. AMPK activation may be a mechanism by which GH causes some of its cardiac effects. This study used primary cardiomyocytes and mouse and rat models of GH excess and deficiency to study the effects of GH on cardiac AMPK. Acute GH treatment increased AMPK activity in both in vivo and in vitro studies; acute IGF-I treatment had the opposite effect. In 2 and 8 month old bovine GH-overexpressing (bGH) and GH receptor knock out (GHRKO) mice, functional AMPK assay did not demonstrate any difference in cardiac AMPK activity between transgenics and controls. However, Western blotting for Threonine-172 phospho (p)AMPK levels, a marker of AMPK activity, demonstrated increased cardiac pAMPK in 2 month old bGH mice and a reduction in cardiac pAMPK levels in 8 month old animals. A trend towards the same findings was seen in GHRKO mice. This indicates that both GH and IGF-I interact with myocardial AMPK, apparently via different mechanisms

A Standardized Ultrasonography Classification for Channel Catfish Ovarian Development

The goal of this dissertation was to develop application of ultrasonography as a decision-making tool in genetic improvement programs for channel catfish Ictalurus punctatus. A literature review on the use of ultrasonography in fish reproduction generated a comprehensive reference data set intended to benefit existing and potential users. It exposed the need for reporting of instrument control settings and standardization of fish handling and imaging procedures. These issues were addressed from the onset of this work by assessing more than 6,300 channel catfish ovaries by use of initial fish handling and imaging procedures developed (2004-2005) at the Louisiana State University Agricultural Center Aquaculture Research Station. The development of a standardized and systematic approach to interpretation of ultrasound images emphasized the interplay of technical and biological aspects of ultrasonography assessments. This showed the importance of the control settings and identified disruptive ultrasound artifacts to avoid for observation of the ovary and oocytes. A preliminary ultrasound imaging classification index for assessing ovarian development during the annual reproductive cycle was developed, used and evaluated. This led to the creation of seven well-defined, standardized ultrasound imaging classifications of channel catfish ovarian development based on the annual cycle. Histology of each ultrasound image in the classification index was included as a Reference Guide to provide insight into the processes observed during ultrasonography. Finally, the ultrasound imaging classification index was used for identification and selection of females for hormone-induced spawning in commercial hatchery production of F1 hybrids (channel catfish female x blue catfish male I. furcatus). In sum, this dissertation provides a systematic method of ultrasound imaging assessment of channel catfish ovarian development enabling progress towards standardization in the use of ultrasonography in fish reproduction

Genetics and genomics of aortic form and function

The thoracic aorta is a dynamic organ which adapts and remodels throughout life. Thoracic aortic size, shape and function are important contributors to both cardiovascular health and disease and risk of aortic disease. A complex interaction of environmental, genetic and haemodynamic factors is mediated by cells of the aortic wall. This thesis presents aortic phenotyping, genotyping and genome-wide associations of aortic traits in a large healthy cohort of 1218 volunteers. This is the largest study to report normal parameters for healthy thoracic aortic size, shape and function derived from cardiovascular magnetic resonance imaging. Anthropometric and cardiovascular risk factors such as age, gender, body fat mass and lipid profile are identified as significant determinants of aortic phenotype. The work suggests that cardiovascular risk factors could impair normal adaptive aortic remodelling with age. Genome-wide association studies of aortic dimensions and function identify new common variants, genes and pathways which could be important in aortic biology and cardiovascular risk. These include genes involved in cardiovascular development (eg PCDH7 and SON associated with aortic root diameter), autonomic cardiovascular responses (eg GABA receptor genes associated with aortic root diameter), fibrosis (eg ACTC1, AGTR1 associated with ascending aortic distensibility, BAMBI and MYOD associated with descending aortic distensibility) and obesity (eg ARID5B and IRX3 associated with aortic pulse wave velocity and ascending aortic area respectively). Multiple regulatory pathways including TGF-ß and IGF signalling (IGF1R, IGF2R), are identified which are associated with aortic dimensions and function. Joint trait analysis of aortic root dimensions identifies a new genome-wide significant association with TENM4, a key driver of early mesodermal development, and suggestive association with PTN, which is functionally related and plays a key role in angiogenesis. The primary analyses are complemented by exploratory assessment of rare genetic variation in bicuspid aortic valve (BAV) using panel sequencing in 177 patients. Rare variants might cause, or modify phenotype in BAV, but the clinical utility of panel sequencing remains poor. A further complementary study investigates the interaction of haemodynamics with aortic cellular phenotype, using microarray assessment of aortic endothelial cell transcriptomic response to shear stress pattern. Several genes of interest in atherosclerosis and aortic disease are differentially expressed with shear stress pattern, such as FABP4, ANGPT2, FILIP1, KIT, DCHS1, TGFBR3 and LOX. This work yields new insights into aortic phenotype, identifies key loci which might determine aortic traits and explores the complex interdependence of genetics, haemodynamics and environmental variables in aortic biology.Open Acces

Doppler ultrasonography of the human fetal pulmonary circulation

Pulmonary hypoplasia is a condition characterized by a decrease in the number of lung cells, airways and alveoli with a resulting decrease in organ size and weight. The reported incidence of pulmonary hypoplasia in the general population is about 1 per 1000 live births and it is one of the most common single abnormalities found at postmortem examination. The occurrence of pulmonary hypoplasia is mostly secondary to congenital anomalies or pregnancy complications that inhibit lung development. For instance prolonged oligohydramnios due to premature rupture of membranes (PROM) or fetal renal and urinary tract malformations may lead to abnormal fetal lung development with subsequent severe respiratory distress immediately after birth and even neonatal death

Characterization of alar ligament on 3.0T MRI: a cross-sectional study in IIUM Medical Centre, Kuantan

INTRODUCTION: The main purpose of the study is to compare the normal anatomy of alar ligament on MRI between male and female. The specific objectives are to assess the prevalence of alar ligament visualized on MRI, to describe its characteristics in term of its course, shape and signal homogeneity and to find differences in alar ligament signal intensity between male and female. This study also aims to determine the association between the heights of respondents with alar ligament signal intensity and dimensions. MATERIALS & METHODS: 50 healthy volunteers were studied on 3.0T MR scanner Siemens Magnetom Spectra using 2-mm proton density, T2 and fat-suppression sequences. Alar ligament is depicted in 3 planes and the visualization and variability of the ligament courses, shapes and signal intensity characteristics were determined. The alar ligament dimensions were also measured. RESULTS: Alar ligament was best depicted in coronal plane, followed by sagittal and axial planes. The orientations were laterally ascending in most of the subjects (60%), predominantly oval in shaped (54%) and 67% showed inhomogenous signal. No significant difference of alar ligament signal intensity between male and female respondents. No significant association was found between the heights of the respondents with alar ligament signal intensity and dimensions. CONCLUSION: Employing a 3.0T MR scanner, the alar ligament is best portrayed on coronal plane, followed by sagittal and axial planes. However, tremendous variability of alar ligament as depicted in our data shows that caution needs to be exercised when evaluating alar ligament, especially during circumstances of injury