Biomedical Engineering

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Browsing Biomedical Engineering by Author "Bethel, Haile"

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    Design and Evaluation of Simulated PEM Scanner for EarlyStage Breast Lesion Detection
    (Addis Ababa University, 2022-06) Bethel, Haile; Dawit, Assefa; Samuel, Taddesse (Mr.) Co-Advisor
    Breast cancer is the most commonly diagnosed cancer in females worldwide, contributing around 11.7 % (~2.3 million people) of new cancer cases in 2020 only, with a death rate of 6.9%. Early diagnosis and check-up are essential for effective treatment and reduction of incidences and mortality rates. Different modalities exist to diagnose breast cancers. Positron emission tomography (PET) is the one imaging tool in nuclear medicine providing physiological information about the breast by quantifying the metabolic activities of the cells in the breast tissues. Both whole-body (WB) PET scanners and organ-specific PET scanners are available in the market. But current trends show that there is a complete shift towards dedicated, organ specific PETs. One of those is Positron Emission Mammography (PEM), believed to be better than mammography and other imaging modalities to detect small breast lesions. Semiconductor-based PEM detectors are simulated with good spatial resolution but are expensive. Scintillator-based PET and PEM detectors can provide quit good sensitivity and are cost effective. On the contrary, these detectors cannot detect small breast lesions due to their poor spatial resolution. This requires development of detectors that give rise to better spatial resolution. In the current thesis work, a high-performance PEM scanner is simulated using TOC (Transparent Optical Ceramic) scintillators of 1 x 1 x 10mm 3 crystals with the aim to improve the spatial resolution, sensitivity as well as scattering fraction. Those TOC scintillators are LHO: cerium doped lutetium hafnate (Lu 2 Hf 2 O 7 : Ce), BHO: cerium doped barium hafnate (BaHfO 3 : Ce) and SHO: cerium doped strontium hafnate (SrHfo 3 : Ce). The design was based on the GATE (Geant4 Application for Emission Tomography) simulation software. Its performance was tested and evaluated by following the NEMA (National Electrical Manufacturers Association) NU 4-2008 standards. The complete scanner has 39 heads and 10 x 30 x 59 modules in the detector. Based on the type of scintillator used, the designed scanner provided a spatial resolution between 1.0 and 1.1 mm FWHM (Full Width at Half Maximum) in the axial direction, 7.24% to 9.11% system sensitivity and 11.01% to 11.19% scatter fraction. The design offered good uniformity as well as image quality. The computed spatial resolution, sensitivity and scatter fraction values are superior to those already reported in the literature.