Ultrasonic Relaxation and Spectroscopy Studies on Gallstones

Abstract

Bile salts are naturally occurring biological surfactants. They form micellar aggregates in aqueous solutions at a particular bile salt concentration called Critical Micelle Concentration (CMC). These micellar aggregates help to solubilise and disperse dietary lipids in small intestine. It is believed that the micelles formed by bile salts play a vital role in the early crystallization which in turn leads to gall stone formation in human beings. The present ultrasonic relaxation studies have been carried out on some gallstones at a fixed temperature of 303.15K and in the frequency range 2-15 MHz in order to ascertain the relaxation frequency and relaxation amplitudes respectively. The ultrasonic velocity is determined at 2 MHz using a Digital Ultrasonic velocity meter. The ultrasonic absorption is measured in the frequency range of 2-15 MHz using Fallen Instruments and Pulsed Power Oscillator systems. The relaxation frequency (f r ) and relaxation parameters (A&B) are determined and reported. Fourier transform infrared spectroscopy study is used to determine the constituents and their compositions of gallstones. The study reveals that cholesterol stones and mixed stones type of gallstones were predominant whereas pigment stones were less frequent in the selected region. Keywords: Ultrasonic velocity, ultrasonic absorption, micellar aggregates, Gallstones I. INTRODUCTIONGallstones are solid particles that form from bile in the gallbladder, which is a small saclike organ in the upper right part of the abdomen. It is located under the liver, just below the front rib case on the right side. The gallbladder is a part of the biliary system, which includes the liver and the pancreas. The biliary system, among other functions, produces bile and digestive enzymes. Bile is a fluid secreted by the liver to help in the digestion of fats [1]. It contains several different substances, including cholesterol and bilirubin a waste product of normal breakdown of blood cells in the liver. Bile is stored in the gallbladder until needed. When we eat a high -fat, high -cholesterol meal, the gallbladder contracts and injects bile into the small intestine via a small tube called the common bile duct for digestion [2]. Gallstones form in the gallbladder because the liver begins secreting bile that is unusually saturated with cholesterol. The cholesterol then crystallizes to form stones while in storage in the gallbladder or cystic duct. The specific mechanisms in the body which cause the bile to reach these high cholesterol levels are not entirely known. However, the liver appears to play a large part in this process since it is the source for making bile from which gallstones can form because the amount of bile acids and bile lecithin are low. Bile acids and lecithin act as an emulsifier in the bile within the gallbladder. Therefore, any inefficiency in this emulsifying process would accelerate the formation of stones. From a survey of literature, it can be seen that most of the ultrasonic relaxation studies in surfactants ar...