| Abstract |
Coronary heart disease (CHD) is the major cardiovascular disease and remains among the leading causes of mortality and morbidity, accounting 20% of all annual deaths in Europe. Obesity along with other deleterious consequences of modern lifestyle such as smoking, unrelieved stress and reduced physical activity are CHD risk factors that may be controlled. In many countries the implementation of preventive policies on CHD has led to reduction of mortality rates. Obesity, however, appears to be an exception to this trend presenting a constant global rise over the last three decades. Hence, the identification and the appropriate management of those individuals who are at higher risk, in terms of obesity, are of great importance.
Obesity may be assessed by anthropometric measurements. Body mass index (BMI) and waist circumference (WC) are the most commonly used parameters for this type of measurements. Anthropometric techniques are fast and convenient and correlate well with abdominal fat. Therefore, they are used in clinical practice as markers for abdominal adiposity. However, anthropometry provides only an indirect assessment of adiposity without the ability to differentiate between visceral and subcutaneous fat. Moreover, despite BMI and WC may reliably discriminate obese individuals, they fail to efficiently identify the individuals who are at greater risk for CHD.
Adiposity may also be assessed by advanced imaging techniques such as Computed Tomography (CT) and Dual Energy X Ray Absorptiometry (DXA). The crossisectional CT images have been extensively employed for organ/tissue volume measurements in clinical practice. The technique of manual planimetry, based on the manual delineation of the boundaries of the region of interest on each CT section, is currently considered as the standard of reference. Stereology based on Cavalieri's principle, is an unbiased method that may estimate the volume of an object divided in a sequence of parallel crossisectional planes.
The objective of the first part of the present study was to combine the stereological point counting technique with CT data for the efficient estimation of abdominal fat volume and compare the stereological estimations with those derived by the technique of manual planimetry. Abdominal adipose tissue measurements were performed by planimetry in abdominal CT scans of 14 con¬secutive patients. The planimetric technique was considered as the reference method. In the same scans were performed stereological volume estimations using 5 different sampling intensities in combination with 100 and 200 test points for the optimization of the method.
The optimization analysis showed that the selection of 200 points along with the sampling intensity 1/8, provide efficient volume estimations in less than four minutes for visceral and subcutaneous abdominal fat together. Moreover, the results revealed that stereology in combination with point counting may be successfully applied on CT images for the direct estimation of abdominal fat volume. The optimized stereological technique reduces efficiently the time of fat volume estimations providing accurate measurements in comparison with those derived by the standard technique of manual planimetry.
Dual Energy X-ray Absorptiometry is a technique, which is extensively utilized for the screening of osteoporosis especially in post-menopausal women, by measuring bone mineral density. DXA scans, apart from bone mineral density, may also automatically quantify with high precision lean and adipose tissue mass content in the whole body and in predefined anatomic regions providing information for regional fat distribution. The aim of the second part of the study, was to determine total and regional adiposity indices in a sample of postmenopausal females subjected to DXA and compare their predictive ability regarding CHD to common anthropometrical measures of WC and BMI. Total body scans were performed in 71 consecutive postmenopausal females. Cases were considered 24 subjects with definite CHD diagnosed by myocardial perfusion imaging (MPI) whereas controls were enrolled 47 subjects with normal MPI results.
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Εκτίμηση ποσότητας και κατανομής λιπώδους ιστού με απορροφησιομετρία ακτίνων Χ (DXA) και υπολογιστική τομογραφία (CT) : μετρήσεις σε ασθενείς με στεφανιαία νόσο και βελτιστοποίηση της δόσης ακτινοβολίας
