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    Comparison of QCT and DEXA findings for lumbar vertebra in young adults and the elderly
    (Sage Publications Ltd, 2024) Acikgoz, Gunes; Bora, Aydin; Nur, Sureyya
    Background: The use of dual-energy X-ray absorptiometry (DEXA) and quantitative computed tomography (QCT) methods are important for the diagnosis and follow-up of osteoporosis, and are used especially in cases to determine the degree of osteoporosis and the risk of fracture, monitoring the effectiveness of the treatment applied. Purpose: To compare the parameters measured using the DEXA method from the lumbar (L1-L4) vertebrae and the Hounsfield unit (HU) values measured with QCT at the same levels among young adults and the elderly. Material and Methods: The study included 155 patients (age range = 26-93 years). A total of 57 (36.8%) patients (age range = 26-64 years) were defined as the first group, and 98 (63.2%) patients (aged >= 65 years) were defined as the second group. T-test and correlation analysis were performed to compare bone mineral density (BMD), T score, and HU values measured using DEXA and QCT. Results: A statistically significant difference was found between T score, lumbar total BMD, and HU values according to age and sex (P < 0.05). When the values measured from lumbar vertebrae were compared using both DEXA and CT, a high correlation was found between them. Conclusion: In the study, it was observed that QCT attenuation measurements of the lumbar spine measured between different age groups provided reliable results in terms of BMD scanning, as in DEXA. It should be noted that QCT has a longer imaging time and higher radiation dose compared to DEXA, and unnecessary scans should be avoided.
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    Öğe
    High intensity focused ultrasound pressure field characterization
    (Institute of Electrical and Electronics Engineers Inc., 2020) Karaboce, Baki; Nur, Sureyya; Sahin, Ali
    One of the innovative methods in cancer treatment is to use high intensity focused ultrasound (HIFU) technology. HIFU transducers create a very high acoustic pressure (tens of MPa) area at the focal point of the tissue inside the body. The HIFU transducer pressure area should be characterized for effective and safe use in applications in cancer treatment. A system was established in TÜBİTAK Ultrasound Laboratory for the characterization of acoustic pressure field produced by HIFU systems. The system is controlled by a LabVIEW-based data processing program. A signal generator card was used to drive the HIFU converter and an oscilloscope card was used to process the signal received from the hydrophone. HIFU pressure area scanning measurements were performed at pressure levels of approximately 1 MPa -3 MPa. The theoretical model, based on the Khokhlov-Zabolotskaya-Kuznetsov equation, was not initially analyzed for periodic wave clusters with a homogeneous amplitude distribution. Numerical solutions have been shown to be compatible with experimental data. The choice of the PZT type to manufacture the HIFU transducer was modeled theoretically and its effect on the field structure was also emphasized. © 2020 IEEE.