Evaluasi Kurva Noise Power Spectrum (NPS) dari Citra CT Scan dengan Variasi Faktor Eksposi

Doharmansyah Putra, Ni Larasati Kartika Sari, Puji Hartoyo

Abstract


Penelitian ini menganalisis kualitas citra CT-Scan berupa noise yang diukur dengan menggunakan metode NPS. (Noise Power Spectrum). Citra CT-Scan didapatkan dengan menggunakan CT-Scan merk siemens somatom emoticon dengan menggunakan solid water phantom dan variasi faktor eksposi 80 kVdan 130 kV dengan variasi mAs 100 mAs, 150 mAs, 200 mAs, 250 mAs, 300 mAs. Program pengukuran NPS dilakukan dengan menerapkan transformasi fourier pada 4 Region of Interent (ROI) homogen di citra. Program pengukuran NPS dikembangkan dengan software matlab. Hasil penelitian menunjukan bahwa kurva NPS berbentuk parabola, dimana terdapat 2 kemiringan. Kemiringan tersebut merupakan hasil dari filtering yang dilakukan oleh algoritma rekonstruksi pada sistem reknstruksi citra CT-Scan. Selain itu tinggi puncak kurva NPS juga dipengaruhi oleh nilai kV dan mAs. Semakin tinggi nilai kV dan mAs yang diberikan maka puncak kurva NPS yang didapatkan semakin rendah. Luas di bawah kurva NPS merupakan nilai varians (σ2), sehingga hal ini menunjukan semakin tinggi kV dan mAs semakin rendah tingkat noise.

Keywords


standar deviasi, transformasi fourier, varians, noise power .spectrum

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References


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