M.S. Theses

Permanent URI for this collection

https://digitalarchive.library.bogazici.edu.tr/handle/123456789/11717

Browse

Browsing M.S. Theses by Subject "Acoustic microscopes."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Acoustic impedance measurement of tissue mimicking phantoms by using scanning acoustic microscopy
    (Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2019., 2019.) Altun, Burak.; Garipcan, Bora.
    Phantoms are imaging objects used as stand-ins for human tissues to guarantee that algorithms and methods for monitoring the human body are functioning properly. Thus, characterization of them prior to clinical trials plays a vital role. By that, in this thesis, we aimed to characterize breast, liver and blood tissue mimicking phantoms through acoustic impedance measurements recorded by 80 MHz Scanning Acoustic Microscopy (SAM) and propose a novel and fast technique for measuring a variety of soft tissue phantoms. To our best knowledge, it is the first study that suggests SAM operating at acoustic impedance measurement mode for the quantification of tissue-mimicking phantoms. We achieved to produce breast (soft) tissue mimicking phantoms which have acoustic impedance values between the range of 1.373 0.031 and 1.707 0.036 MRayl. Our acoustic impedance measurements provide the result of 1.693 0.085 MRayl for the liver tissue mimicking phantom and 1.624 0.006 MRayl for the blood tissue mimicking phantom which is very close to acoustic impedance values of human tissues.|Keywords : Blood, Breast, Liver, Soft Tissue, Tissue Mimicking, Phantom, Acoustic Impedance, Scanning Acoustic Microscopy
  • Thumbnail Image
    Item
    Development of a novel fiber laser based backward-mode photoacoustic microscopy system and image characterization
    (Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2013., 2013.) Arabul, Mustafa Ümit.; Öztürk, Cengizhan.; Ünlü, Mehmet Burçin.
    Among all other imaging modalities, optical methods using non-ionizing radiation became popular due to safety concerns. However, pure optical methods have severe limitations for deep tissue imaging. On the other hand, photoacoustic imaging is a promising imaging modality for in vivo tissue monitoring due to its high optical contrast and high ultrasonic resolution. The parameters of the laser used in photoacoustics, namely pulse duration, pulse repetition frequency, beamwidth and output power has a quanti able impact on signal amplitude, imaging speed and resolution. In literature, Q-switched lasers, solid state lasers and ber lasers are used for the microscopic scale of photoacoustic imaging. Most of the lasers used in photoacoustic studies has a xed capacity and key parameters cannot be adjusted independently. In this study, we declare a novel all- ber mode-locked laser with adjustable pulse duration between 1 - 3 ns and selectable pulse repetition frequency between 50 kHz and 3.1 MHz. All ber integration makes our laser resistant to vibrational disturbances, yet increases its stability. Additionally, we utilized a photonic crystal ber at the output stage of the laser to generate a supercontinuum of a wavelength range of 600 - 1100 nm. We analytically reveal laser parameter dependencies of photoacoustic signals. We test our microscopy system with a phantom made of horse hair, and present resultant images with point spread function of width 500 m.|Keywords : Photoacoustics, photoacoustic microscopy, mode-locked, supercontiuum, fiber laser, pulse duration, beam width, pulse repetition frequency.