Noha Hassan

FDTD analysis of a noninvasive hyperthermia system for brain tumors

BackgroundHyperthermia is considered one of the new therapeutic modalities for cancer treatment and is based on the difference in thermal sensitivity between healthy tissues and tumors. During hyperthermia treatment, the temperature of the tumor is raised to 40–45°C for a definite period resulting in the destruction of cancer cells. This paper investigates design, modeling and simulation of a new non-invasive hyperthermia applicator system capable of effectively heating deep seated as well as superficial brain tumors using inexpensive, simple, and easy to fabricate components without harming surrounding healthy brain tissues.MethodsThe proposed hyperthermia applicator system is composed of an air filled partial half ellipsoidal chamber, a patch antenna, and a head model with an embedded tumor at an arbitrary location. The irradiating antenna is placed at one of the foci of the hyperthermia chamber while the center of the brain tumor is placed at the other focus. The finite difference time domain (FDTD) method is used to compute both the SAR patterns and the temperature distribution in three different head models due to two different patch antennas at a frequency of 915 MHz.ResultsThe obtained results suggest that by using the proposed noninvasive hyperthermia system it is feasible to achieve sufficient and focused energy deposition and temperature rise to therapeutic values in deep seated as well as superficial brain tumors without harming surrounding healthy tissue.ConclusionsThe proposed noninvasive hyperthermia system proved suitable for raising the temperature in tumors embedded in the brain to therapeutic values by carefully selecting the systems components. The operator of the system only needs to place the center of the brain tumor at a pre-specified location and excite the antenna at a single frequency of 915 MHz. Our study may provide a basis for a clinical applicator prototype capable of heating brain tumors.

A resonant handset antenna that can cover all bands of UHF mobile TV, GSM and CDMA without using matching circuits

Antennas for mobile digital TV are required to have a very wide frequency band. For example, UHF DVB-H is designed to work in the frequency band from 470 MHz to 862 MHz. This is a very wide bandwidth which is difficult to cover with a single resonant antenna. Therefore, matching circuits are usually used to tune the antenna for this band [1]-[3]. Matching circuits increase the complexity, the size and the costs of the antenna and also reduce its efficiency. On the other hand, the mobile TV band overlaps with the CDMA/GSM800 band (824–894 MHz) and it is also too close to the E-GSM900 band (880–960 MHz). This overlapping may cause severe interference between the antennas of these applications especially if they were placed close to each other inside the handset. A novel solution to overcome all these problems is to use only one wideband resonant antenna that can cover all bands of UHF mobile digital TV, 700 MHz WiMax (698–806 MHz), CDMA, GSM800 and E-GSM900.

A Three-Dimensional Finite Element Analysis of the Osseointegration Progression in the Human Mandible

In this study, three-dimensional (3D) finite element analysis was used to model the effect of the peri-implant bone geometry and thickness on the biomechanical behavior of a dental implant/supporting bone system. The 3D finite element model of the jaw bone, cancellous and cortical, was developed based on computerized tomography (CT) scan technology while the dental implant model was created based on a commercially available implant design. Two models, cylindrical and threaded, representing the peri-implant bone region were simulated. In addition, various thicknesses (0.1 mm, 0.3 mm, 0.5 mm) of the peri-implant bone region were modeled to account for the misalingnment during the drilling process. Different biomechanical properties of the peri-implant bone region were used to simulate the progression of the osseointegration process with time. Four stages of osseointegration were modeled to mimic different phases of tissue healing of the peri- implant region starting with soft connective tissue and ending with complete bone maturation. For the realistic threaded model of the peri-implant bone region, the maximum von Mises stress and displacement in the dental implant and jaw bone were higher than those computed for the simple cylindrical peri-implant bone region model. The average von Mises stress and displacement in the dental implant and the jaw bone decreased as the oseeointegration progressed with time for all thicknesses of the peri-implant bone region. On the other hand, the maximum absolute vertical displacement of the dental implant increased as the drilled thickness of the peri-implant bone region increased.

An internal EBG antenna for indoor reception of UHF terrestrial digital TV broadcasting

A novel internal antenna has been developed for indoor reception of UHF terrestrial digital TV broadcasting. The new antenna has a bandwidth of more than 60%. It is an unbalanced resonant antenna that does not need a matching circuit or a balun. The overall size of the new antenna is very small and its manufacturing costs are very low. It is made of a flexible material and it can be bent and/or folded and shaped in any form. It can be used as an internal, external or partially internal and partially external antenna. The new digital TV receiving antenna is linearly polarized. It can also be modified in order to be dual-polarized, which is a very important factor in all indoor applications. This can be easily achieved by bending the antenna 90°. Bending the antenna in more than one direction significantly increases its sensitivity to different polarizations and also reduces the effect of the surrounding environment on the antenna. The overall efficiency of the new indoor digital TV receiving antenna is more than 80% and its peak gain is about 2 dBi over the whole UHF band. The peak gain can be increased to more than 5 dBi over the whole band by adding EBG (electromagnetic band gap) structures to the new digital TV receiving antenna. The EBG structure also improves the return loss of the antenna and increases its efficiency to around 90% over most of the band.

Novel Wideband MIMO Antennas That Can Cover the Whole LTE Spectrum in Handsets and Portable Computers

A dual resonant antenna configuration is developed for multistandard multifunction mobile handsets and portable computers. Only two wideband resonant antennas can cover most of the LTE spectrums in portable communication equipment. The bandwidth that can be covered by each antenna exceeds 70% without using any matching or tuning circuits, with efficiencies that reach 80%. Thus, a dual configuration of them is capable of covering up to 39 LTE (4G) bands besides the existing 2G and 3G bands. 2 × 2 MIMO configurations have been also developed for the two wideband antennas with a maximum isolation and a minimum correlation coefficient between the primary and the diversity antennas.

A low wind load lightweight dual cylindrical reflector antenna with a novel feed for direct broadcast satellite TV reception

A low-coast, lightweight, low wind load, transparent antenna for DBS TV reception has been developed using dual parabolic cylindrical reflectors with a novel broadband small size feed. The feed is mounted on the main reflector or close to it. It is mechanically rigid and it does not cause any considerable blockage. The reflectors of the new antenna are easy to manufacture with a very high surface accuracy. They can be shipped and stored in a form of flat sheets. The new DBS TV reception antenna is easy to assemble and disassemble and has a simple lightweight mounting system that is easy to install. To reduce the weight of the new reflectors, several holes are punched in their surfaces. These holes also make the metallic sheets transparent. Punched reflectors are stable and not significantly affected by strong winds. The overall weight of the new Ku-band DBS TV reception antenna including its mounting system is less than 1 kg.

Low-Interference Dual Resonant Antenna Configurations for Multistandard Multifunction Handsets and Portable Computers

Low-interference dual resonant antenna configurations are developed for multistandard multifunction mobile handsets and portable computers. Only two wideband resonant antennas can cover most of the important wireless applications in portable communication equipment. The frequency bands of the dual antenna configuration can be adjusted according to the wireless applications that are required to be covered. The bandwidth that can be covered by each antenna is about 80% without using matching or tuning circuits. Three sample dual antenna configurations with different frequency bands are presented. The interference between the low-band and high-band antennas of these three configurations is investigated, and the ways of reducing this interference are studied. The most effective factor on the interference between the low-band and high-band antennas is their relative orientations. When the low-band and high-band antennas of each configuration are perpendicular to each other, the isolation between them significantly increases. This eliminates the need for any special tools or techniques to suppress the mutual coupling between them. The new antennas have very small cross-sectional areas, and they are made of a flexible material. They do not require any additional components or ground planes. They can be used as internal, external, or partially internal and partially external antennas.

A novel dual resonant antenna configuration for mobile laptop, notebook and palmtop computers

There is a fast development and expansion of portable computer wireless systems. Cellular network radios are integrated into some modern laptop, notebook and palmtop computers in order to give the user access to the Internet in areas not covered by WLANs. Furthermore, computer manufacturers are now offering integrated WiMax as an option on some notebooks and laptops. Introduction of other applications such as GPS and digital TV, built into portable computers, is expected in the near future. On the other hand, most of these applications have different standards with different frequency allocations worldwide. For example, DVB-H mobile TV is designed to work in different bands such as UHF and L bands. Also, WiMax has many frequency allocations worldwide such as 700 MHz, 2.5 GHz and 3.5 GHz. Even GPS has different codes at different bands such as L1 (1575.42 MHz) and L2 (1227.6 MHz). In order to cover all these bands, several antennas have to be used. The problem is that the bands of some applications are very close to each other or even overlapping as in GSM and UHF digital TV. As a result, there will be a severe interference between these antennas.

A Multi-band Antenna Configuration for MIMO WiMax in Multi-standard Multifunction Handsets

A novel multi-band internal antenna configuration has been developed for WiMax-capable cellular phones. The new antenna configuration covers all the WiMax bands with other applications in multi-standard multifunction handsets. It consists of three new wideband antennas, which together can cover the whole band from 470 MHz to 6 GHz. The three antennas may have to be used together or only one or two of them may be required depending on the allocated frequencies of WiMax and the other applications in the handset. Each of the three new antennas has a bandwidth of more than 65%. They are low-cost multi-polarized unbalanced resonant antennas that do not need matching circuits or baluns. Their overall sizes are very small and they have high efficiencies and high peak gains. The performance of the new internal antenna is superior in Multi-Input Multi-Output (MIMO) techniques. Two or more similar internal antennas having the same frequency band can be embedded inside the handset for MIMO. The locations and orientations of MOMO antennas are optimized for both space and polarization diversity with minimum coupling between them.

A Novel Internal Dual-Polarized EBG Antenna for Indoor Reception of UHF Terrestrial Digital TV Broadcasting

A novel internal antenna has been developed for indoor reception of UHF terrestrial digital TV broadcasting. The overall size of some configurations of the new antenna is less than 2 cm3, and its weight is less than 1 gm. It is made of a flexible material that can be bent or folded and shaped in any form. It is an unbalanced resonant antenna that does not need a matching circuit. The new antenna can be fully embedded inside TV sets or portable computers. It has a bandwidth of about 68%. Thus, it can also cover the bands of GSM and CDMA, which is advantageous in case of portable computers. The new antenna is linearly polarized. It can be easily modified to be dual polarized by combining two orthogonal antennas with one or two feed points. The overall efficiency of some configurations of the new indoor digital TV receiving antenna is more than 80%, and its peak gain is about 2 dBi over the whole UHF band. The peak gain can be increased to more than 5 dBi by adding EBG (electromagnetic bandgap) structures. The EBG structure also increases the efficiency to around 90%.