Visualization and image based characterization of hydrodynamic cavity bubbles for kidney stone treatment

Accurate detection, tracking and classification of micro structures through high speed imaging are very important in many biomedical applications. In particular, visualization and characterization of hydrodynamic cavity bubbles in breaking kidney stones have become a real challenge for researchers. Various micro imaging techniques have been used to monitor either an entire bubble cloud or individual bubbles within the cloud. The main target of this thesis is to perform an image based characterization of hydrodynamic cavity bubbles for kidney stone treatment by designing and constructing a new imaging setup and implementing several image processing and computer vision algorithms for detecting, tracking and classifying cavity bubbles. A high speed CMOS camera with a long distance microscope illuminated by 2 pulsed 198 high performance LED arrays is designed. This system and a μ-PIV setup are used for capturing images of high speed bubbles. Several image processing algorithms including median and morphological filters, segmentation, edge detection and contour extraction algorithms are extensively used for the detection of the bubbles. Furthermore, incremental selftuning particle filtering (ISPF) method is utilized to track the motion of the high speed cavity bubbles. These bubbles are also classified by their geometric features such as size, shape and orientation. An extensive visualisation work is conducted on the new setup and cavity bubbles are successfully detected, tracked and classified from the microscopic images. Despite very low exposure times and high speed motion of the bubbles, developed system and methods work in a very robust manner. All the algorithms are implemented in Microsoft Visual C++ using OpenCV 2.4.2 library

Assessment of probe-to-specimen distance effect in kidney stone treatment with hydrodynamic cavitation

The aim of this study is to focus on the effect of probe-to-specimen distance in kidney stone treatment with hydrodynamic bubbly cavitation. Cavitating bubbles were generated by running Phosphate buffered saline (PBS) through stainless steel tubing of inner diameter of 1.56 mm at an inlet pressure of ~10,000 kPa, which was connected to a 0.75 mm long probe with an inner diameter of 147 um at the exit providing a sudden contraction and thus low local pressures. The bubbles were targeted on the surface of 9 calcium oxalate kidney stones (submerged in a water pool at room temperature and atmospheric pressure) from three different distances, namely 0.5 mm, 2.75 mm and 7.75 mm. The experiments were repeated for three different time durations (5 min, 10 min and 20 min). The experimental data show that amongst the three distances considered, the distance of 2.75 mm results in the highest erosion amount and highest erosion rate (up to 0.94 mg/min), which suggests that a closer distance does not necessarily lead to a higher erosion rate and that the probe-to-specimen distance is a factor of great importance, which needs to be optimized. In order to be able to explain the experimental results, a visualization study was also conducted with a high speed CMOS camera. A new correlation was developed to predict the erosion rates on kidney stones exposed to hydrodynamic cavitation as a function of material properties, time and distance