UJI LINEAR- SHIFT INVARIANT SISTEM MIKRORADIOGRAFI SINAR-X DIGITAL

NURUL HIDAYAH SAM, Dr. Gede Bayu Suparta

2014 | Tesis | S2 Ilmu Fisika

Telah dilakukan penelitian pengujian sistem pencitraan mikroradiografi sinarX digital yang dikembangkan oleh Grup Riset Fisika Citra-Universitas Gadjah Mada (GRFC-UGM). Pengujian awal dilakukan menggunakan obyek uji pinhole untuk mengetahui sifat Linear-Shift Invariant (LSI) sistem mikroradiografi sinar-X digital. Obyek uji pinhole berbentuk lingkaran berdiameter 5 cm dipenuhi lubang-lubang berdiameter 0,4 mm dengan jarak antar lubang 1,5 mm. Citra asli yang diperoleh kemudian dikoreksi dengan metode curve fitting Gaussian. Citra koreksi selanjutnya dibandingkan dengan citra asli berdasarkan profil garis dan Full Width at Half Maximum (FWHM) menggunakan perangkat lunak ImageJ dan Matlab7. Citra koreksi yang diperoleh memiliki nilai sebaran intensitas linear dibandingkan citra asli. Namun, respon sebaran resolusi spasial sedikit tak seragam untuk titik diposisi sudut. Berdasarkan hasil analisis citra koreksi diperoleh bahwa sifat pencitraan sistem mikroradiografi sinar-X digital tidak bersifat Linear-Shift Invariant (LSI). Jadi, penggunaan obyek uji pinhole dan metode koreksi Gaussian dapat diterapkan untuk menganalisa dan mengoreksi sistem pencitraan agar respon keluaran bersifat Linear-Shift Invariant (LSI).

Research testing on the digital X-ray microradiography imaging system developed by the Grup Riset Fisika Citra–Universitas Gadjah Mada (UGM GRFC) had been conducted. A pinhole testing object was used to determine the Linear Shift Invariant (LSI) characteristic of digital X-rays microradiography imaging system in the initial testing phase. It has 5 cm circular holes diameter filled with 0.4 mm diameter holes spaced 1.5 mm. Then original image obtained was corrected with the Gaussian curve fitting method. The corrected image was compared with the original image based on the line profile and Full Width at Half Maximum (FWHM) value using ImageJ software and Matlab7. The results showed that corrected image had a linear intensity distribution value compared the original image. However, the response distribution of spatial resolution was slightly uneven at the point of angel position. Based on the results obtained by analysising the corrected image, the nature of the digital X-ray microradiography imaging system was non - Linear Shift Invariant (LSI). Thus, a pinhole testing object and Gaussian correction method can be applied to analyze and correct the imaging system so that the output response becomes Linear Shift - Invariant (LSI).

Kata Kunci : Mikroradiografi Sinar-X Digital, Linear shift-Invariant, Kualitas Citra.