Detectability of fibrils by dilation technique in digital mammography

The detectability of fibrils in mammographic phantom images by morphological enhancement was analysed in the present study. Materials that mimic fibrils were imaged by a digital mammography machine at 28 and 29 kVP. The images were processed by a dilation technique to produce second set of images. Receiver operating characteristic analysis was performed to compare the detection performance from the two sets of images. As compared to original images, the 28 kVP's fibrils images from dilation technique become more prominence to be detected by observers. While at 29 kVP only a few observers can found the fibrils images from dilation technique. This study suggests morphological enhancement of mammography image did not increase the detection of low frequency signals of the images

Lubrication effect of metal-on-metal in hip joint replacement

The use of hard-on-hard material is one of alternative methods to replace the soft-on-soft or soft-on-hard material which has long been used in hip joint replacement. The common type of hard-on-hard material used in hip joint replacement is metal-on-metal. However, the metal-on-metal hip implants produce the small wear particle as a result of attrition of the contact surface between femoral head and acetabulum cup. Therefore, the lubrication performance between the surface of the femoral head and acetabulum cup is essential to reduce wear particle. The objective of this study was to determine the effect of lubrication on metal-on-metal hip joint replacement. Two types of contact analysis were performed, without and with lubrication. In the contact analysis of without lubrication, the maximum contact pressure was 32.887 MPa while lubrication contact analysis, maximum contact pressure was lower. It was occurred because between the surface of femoral head and acetabulum cup has full fluid film lubrication. This causes the wear that produced by metal-on-metal hip joint implants can be reduced because an effective lubricant film is able to reduce wear significantly. In addition, this study focused on the design parameters, radial clearance and femoral head size. It was found that the maximum contact pressure increased when the radial clearance also increased and the maximum contact pressure decreased when the femoral head size increased

Influence of dimple depth on lubricant thickness in elastohydrodynamic lubrication for metallic hip implants using fluid structure interaction (FSI) approach

Introduction: The lubricant thickness in clearance between bearing surfaces for metallic hip implants are currently incapable of accommodating the motion experienced (high load and low entraining motion) in hip walking cycle. Thus, micro-dimpled surfaces were introduced onto surfaces of metallic acetabular cups to improve lubricant thickness. Micro-dimpled surface is a method of advanced surface improvement to increase the lubricant thickness in various tribological applications, such as hip implants. However, the application of micro-dimpled surfaces in hip implants has not yet been explored adequately. Therefore, this study aims to identify the influence of micro-dimpled depth on lubricant thickness elastohydrodynamically for metallic hip implants using Fluid-Structure Interaction (FSI) approach. Methods: Fluid-Structure Interaction (FSI) approach is an alternative method for analysing characteristics of lubrication in hip implant. Dimples of radius 0.25 mm and various depths of 5ìm, 45ìm and 100ìm were applied on the cup surfaces. The vertical load in z-direction and rotation velocity around y-axes representing the average load and flexion-extension (FE) velocity of hip joint in normal walking were applied on Elastohydrodynamic lubrication (EHL) model. Results: The metallic hip implants with micro-dimpled surfaces provided enhanced lubricant thickness, namely by 6%, compared to non-dimpled surfaces. Furthermore, it was suggested that the shallow depth of micro-dimpled surfaces contributed to the enhancement of lubricant thickness. Conclusion: Micro-dimpled surfaces application was effective to improve tribological performances, especially in increasing lubricant thickness for metallic hip implants