Ongoing Projects

1. Electromagnetic Tomography using Microwave Signals and Numerically Realistic Human Head Model (PhD Project) COMPLETED on 11th November 2019

The expensive imaging modalities widely used in the world include CT, MRI and PET. The underlying physical properties being imaged, the design of radiation/ detection system and the imaging performance of each modality are quite similar; both in absolute terms as well as relative to an ideal observer. However, each technique has some associated drawbacks e.g. CT possesses ionizing effects, MRI is not appropriate for patients with metallic medical implants and PET involves a radioactive material injection. Moreover, they all are time-consuming, costly and immovable imaging modalities. Therefore, to overcome these deficiencies, there is a need of an alternate imaging technique that can provide a safe, low-cost, fast and portable imaging solution for brain anomalies diagnostics.

This forms the basis of research question considered in this study. Our study looks closely into brain stroke incidences which are not only life-threatening but also bring with them a very poor prognosis. There is an urgency to investigate the onset of stroke symptoms in a matter of few hours by the doctor. The dawn of the 21st century has brought exciting vision for innovative Microwave Imaging (MWI) systems to address the diagnostic needs in medicine and industry. The ultimate objective of MWI technique is to exploit a dielectric properties contrast which is sensitive to any physiological or pathological feature of clinical interest.

Through this study, we highlight our four major scientific contributions. Primarily, this work investigates the feasibility of EMT for brain stroke diagnostics. We achieved this by evaluating the interaction between MW signals and the stroke-affected head models. The maximum electric field differences are observed at an approximate location of stroke that vary with type and location of stroke inside the head model. It is inferred that MW scattering phenomenon of a head model changes considerably, once its complexity is increased by making it anatomically more realistic. We also evaluated the MW scattering behavior of a complete human head for two types of stroke at various locations inside the brain. A preliminary FEM-based analysis is presented using a hemorrhagic-affected 3D ellipsoid head model. The simulation results are validated through an analytical solution involving a 2D multilayer head model. Later on, an anatomically more realistic and structurally detailed 3D head model is generated by implementing a novel tissue-mapping scheme along a mixed-model approach.

We also developed an improved 2D image reconstruction algorithm for EMT of a human head using the Contrast Source Inversion (CSI) method and a customized adaptive-regularized total-variation minimization additive constraint function. The processing of MW scattering data, generated through FE simulations of 2D/ 3D realistic head model EMT setup, was done during its validation. The algorithm successfully estimated the dielectric properties of head tissues and produced better-quality images to highlight the precise location of clinical importance and perform an accurate diagnosis. The algorithm also took into account real-life noise conditions. Later on, we modified our 2D imaging algorithm for EMT of a 3D realistic head model, following a scalar approximation approach. We were able to obtain meaningful head images with an acceptable stroke diagnostics results. A simulation-driven antenna array design, an appropriate matching medium and the optimal frequency range were utilized. In addition, a safety analysis was also conducted to ensure the safe exposure of MW signals to a human head, while achieving the maximum signal penetration.

It is concluded that EMT using MW signals may potentially substitute the existing brain imaging modalities; especially at rural areas and in emergency situations like brain stroke and traumatic injuries.

2. Vibration analysis of spine with the help of finite element modeling to mitigate causes of injuries in Pilots due to seat ejection in fighter jets. (MS Project) [COMPLETED]

In high-speed fighter aircraft, seat ejection is designed mainly for the safety of the pilot in case of an emergency. Strong wind-blast due to the high velocity of flight is one main difficulty in clearance and excessive G-forces generated, immobilizes the pilot from escape. In most of the cases, seats are ejected out of the aircraft by explosives or by rocket motors attached to the bottom of the seat. Ejection forces are primarily in the vertical direction with an objective of attaining the maximum possible velocity in a specified period of time. Use of such seats, whilst generally life saving, exposes aircrew to forces that may be at the limits of human tolerance. Each phase of the ejection sequence is associated with characteristic injury patterns and of particular concern is the occurrence of spinal compression fractures, which are caused by the upward acceleration of the ejection seat. Many bio-mechanically accurate experimental model have been developed and analyzed but computerized based modeling is not that common in this area. This study is aimed at vibration analysis of human spine with the help of three-dimensional (3D) finite element (FE) model to investigate the critical excitation frequencies and providing a guide so as to reduce the spinal injury threat for ejectors.

2. Dynamic Analysis and classification of Deformation mechanism in Head Impact Injury using Image based Finite Element Method (FEM).” (MS Project) [COMPLETED 2020]

Brain injury is the leading cause of morbidity and mortality in road accidents and brings a lot of social and economic problems. Due to the large amount of traffic injuries with head trauma, it is crucial to investigate damage mechanisms for better treatment. Generally, there are three approaches for injury studies, physical tests, analytical modeling, and numerical simulations. Due to the low cost and high accuracy, numerical simulations have been widely accepted as the best way and partial alternative to the physical tests. With the help of numerical models, typically finite element (FE) model, biomechanical responses, such as intracranial pressure, stress, and strain of brain tissues, can be calculated, and the mechanism of the head traumatic brain injury can be further studied. Throughout the decades, finite element head models (FEHMs) have been used to assess the biomechanics of head injury mechanism. Given the fact that some of the internal biomechanical responses of the brain can neither be measured easily nor in-vivo by experimental techniques, FEHM offers a cost-effective alternative to experimental method in estimating the internal biomechanical responses of human head. By performing Dynamic analysis. This will enable author to evaluate the impact of transient loads or to design out potential noise and vibration problems.

3. FEM Analysis of Intracranial Pressure under the influence of Tumor. (MS Project) [COMPLETED-2020]

Brain tumor is a state in which cells of the brain grow abnormally. Since most (aggressive) tumors are diagnosed at a later stage treatment/surgery gets difficult due to aggressive nature of the tumor. In this backdrop, investigation of the biomechanical relationship between Intracranial pressure (ICP) and tumor becomes critical given the fact that one of causes of elevated ICP is due to the presence of mass lesion (Tumor). To model this, Image-based Modeling Finite element modeling is used. The results will help in three ways: First, it will help clinicians to make informed decisions before they undertake any clinically sensitive procedures on existing diagnosed patients. Second, the ICP based head model will allow help in prognosis of a future (likely) tumor presence based upon the ICP values so found out. Third, the results will add on to the existing research literature in the field of computational biomechanics vis-à-vis brain mechanics.

4. Computational Modeling of Human Head Model for Correlation Study of Cerebrospinal fluid and Tumor. (MS Project) [COMPLETED -2020]

Intracranial pressure (ICP) is the pressure inside the skull. ICP is measured in millimeters of mercury (mm Hg) and, at rest, is normally 7–15 mm Hg. However, the increased level of ICP is an alarming condition which can be due to trauma, head injury, tumor etc. The consequence of increased ICP results in major disorders such as stroke, seizures, neurological damage and eventually death. There are various methods for the measurement, continuous monitoring and treatment of raised ICP caused due to the traumatic conditions. However, no study deals with the measurement the ICP due to the presence of brain tumor non-invasively. The proposed research aims to investigate the ICP due to the presence of tumor using computer methods and numerical modeling.

5. Calculation of Fractional Flow Reserve (FFR) using CT images. (MS Project) [COMPLETED - 2020]

Fractional flow reserve (FFR) is a technique used in coronary catheterization to measure pressure differences across a coronary artery stenosis. It is measured by a pressure sensor attached on a guide wire during the process of invasive coronary angiography. No other method which can calculate FFR non-invasively is known. The application of patient-specific mathematical modeling has proven to be valuable both for diagnostics and in virtual assessment of individual treatments. Recent developments in imaging and computer technology are contributing to the feasibility of highly sophisticated computations in clinical procedures. Morris et al. from the University of Sheffield has developed methods and models achieving 97% accuracy in signifying severe lesions in 35 patients. However, their models are based on input from invasive measurements, and computations require 12-24 hours of run time, which is impractical in clinical applications. Researchers have also worked on steady and transient blood flows but pulsatile blood flow haven’t been understood and worked on. Moreover, so far the focus is more towards the reliability of coronary data available, and we believe that improving methodology might bring computationally inexpensive and efficient solutions to calculating FFR effectively. There are parameters which may serve as a spark to optimize existing methodologies for better calculations of FFR.

6. Computational and Constitutive modeling of Bone’s Mechano-sensitivity in: Virtually Repaired Bone vs. Healthy models. [COMPLETED]

Bone’s Mechano-sensitivity is a wide area of research in computational mechanics. Bone cells are capable of sensing and responding to mechanical forces. However modeling these forces requires a lot of working & assumptions. There is a string mechanical connection between mechanical signals and bone behavior. Bone behaves strongest in compression and weakest in shear. The forces that are modeled either by using traditional physical testing methods or by using numerical techniques like Finite Elements vary acc ording to the type of geometry and the loading condition. Intricate geometries end up having complicated force patterns and poor prediction of actual forces if not assumed properly. This is an important area to investigate and the subject of this thesis addresses the same.Studying the mechanics of bone is to improve the understanding of how and why bones fracture. From an engineering viewpoint, fractures represent a structural failure of the bone whereby the forces and moments applied to the bone exceed its load-bearing capacity. In this study a positive correlation is carried out using both physical testing method and Finite Elements to investigate mechanics of bones in terms of its strength, stiffness, behavior and the amount of damage as a result of external loading.The project under study employs a physical testing method (Uniaxial Compression Loading) and Finite Element Modeling approach on bird bone (Femur) in both healthy and injured condition to investigate parameters like stress, deformation, fractures and stress fractures. The typical stress fracture occurs during load application, this load may produce a shear tension, resulting in eventual random rupture of bone which is the case in the bone under study in this study as well. It is found out that these compound stress fractures not only weakens the bone resorption process but also reduces the bone deposit mechanisms to heal the bone quickly in order to strengthen the fractured area.