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"[ABSTRAKDosimetri CT scan dapat dilakukan dengan menggunakan konsep CTDI, MonteCarlo, atau dengan pengukuran langsung dalam fantom fisis. Pengukuranlangsung menggunakan thermoluminescent dosimeter (TLD) merupakan proseduryang rumit dan membutuhkan waktu yang lama. Saat ini sudah tersedia filmradiochromic yang dapat digunakan di radiologi. Pada penelitian ini dilakukanpengukuran distribusi dosis radiasi dalam fantom Rando menggunakan filmGafchromic XR-QA2 dan TLD. Film Gafchromic XR-QA2 dan TLD dikalibrasidi CT scanner Siemens Sensation 64. Pengukuran distribusi dosis dengan filmdilakukan pada faktor pitch 0.8, 1.0, dan 1.4. Film Gafchromic XR-QA2disisipkan diantara slab 22-23 (Film A), 23-24 (Film B), dan slab 24-25 (Film C).Pengukuran distribusi dosis dengan TLD dilakukan dalam slab nomor 23 denganfaktor pitch 1.4. Film Gafchromic XR-QA2 yang telah dieksposi dipindai denganflatbed scanner Epson Perfection V700 Photo. Dosis serap tulang belakang padaFilm A, Film B, dan Film C yang dieksposi dengan faktor pitch 1.4 secaraberturut-turut adalah 2.0 mGy, 1.9 mGy, dan 2.2 mGy. Berdasarkan profil dosis,rata-rata dosis serap pada film yang dieksposi dengan faktor pitch 1.0 dan 1.4secara berturut-turut adalah 8% dan 24% lebih tinggi dibanding rata-rata dosisserap pada film yang dieksposi dengan faktor pitch 0.8. Rentang dosis hasilpengukuran dengan TLD adalah (1.9 ± 0.1) – (2.3 ± 0.2) mGy dan rentang dosishasil pengukuran dengan film Gafchromic XR-QA2 adalah 1.8 – 2.3 mGy denganperbedaan maksimum 10.6%. Perbedaan tersebut masih berada dalam rentangkeakurasian TLD yaitu < 15%. Berdasarkan hasil tersebut, film Gafchromic XRQA2dapat digunakan untuk pengukuran dosis CT scan selanjutnya.

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ABSTRACTComputed tomography (CT) dosimetry can be approached by using CTDImethod, Monte Carlo computer technique, and direct measurement withinphysical phantom. Direct measurement using thermoluminescent dosimeters(TLDs) is a laborious procedure. Radiochromic film for radiology application wasavailable. In this study, dose distribution within adult anthropomorphic physicalphantom was measured using TLD and Gafchromic XR-QA2 film. TLD andGafchromic XR-QA2 film was calibrated on CT scanner Siemens Sensation 64.Gafchromic XR-QA2 film was sandwiched between slab Rando phantom number22-23 (Film A), 23-24 (Film B), and 24-25 (Film C). Pitch factor 0.8, 1.0, and 1.4were used. TLDs were placed at the holes in the slab number 23 ofanthropomorphic phantom. TLDs were scanned using pitch factor 1.4. Afterexposure, Gafchromic XR-QA2 film was digitized using Epson Perfection V700Photo flatbed scanner. Absorbed dose at vertebra on Film A, Film B, and Film Cwhich exposed by using pitch 1.4 respectively were 2.0 mGy, 1.9 mGy, and 2.2mGy. Based on dose profile, average dose of XR-QA2 film which exposed byusing pitch 1.0 and 1.4 respectively were 8% and 24% higher than average dose ofXR-QA2 film which exposed by pitch 0.8. TLDs dose range were (1.9 ± 0.1) –(2.3 ± 0.2) mGy and Gafchromic XR-QA2 film dose range were 1.8 – 2.3 mGywith maximum difference 10.6%. The difference is still within the range of TLDaccuracy, < 15%. Based on this result, Gafchromic XR-QA2 film can be used tomeasure CT dose, Computed tomography (CT) dosimetry can be approached by using CTDImethod, Monte Carlo computer technique, and direct measurement withinphysical phantom. Direct measurement using thermoluminescent dosimeters(TLDs) is a laborious procedure. Radiochromic film for radiology application wasavailable. In this study, dose distribution within adult anthropomorphic physicalphantom was measured using TLD and Gafchromic XR-QA2 film. TLD andGafchromic XR-QA2 film was calibrated on CT scanner Siemens Sensation 64.Gafchromic XR-QA2 film was sandwiched between slab Rando phantom number22-23 (Film A), 23-24 (Film B), and 24-25 (Film C). Pitch factor 0.8, 1.0, and 1.4were used. TLDs were placed at the holes in the slab number 23 ofanthropomorphic phantom. TLDs were scanned using pitch factor 1.4. Afterexposure, Gafchromic XR-QA2 film was digitized using Epson Perfection V700Photo flatbed scanner. Absorbed dose at vertebra on Film A, Film B, and Film Cwhich exposed by using pitch 1.4 respectively were 2.0 mGy, 1.9 mGy, and 2.2mGy. Based on dose profile, average dose of XR-QA2 film which exposed byusing pitch 1.0 and 1.4 respectively were 8% and 24% higher than average dose ofXR-QA2 film which exposed by pitch 0.8. TLDs dose range were (1.9 ± 0.1) –(2.3 ± 0.2) mGy and Gafchromic XR-QA2 film dose range were 1.8 – 2.3 mGywith maximum difference 10.6%. The difference is still within the range of TLDaccuracy, < 15%. Based on this result, Gafchromic XR-QA2 film can be used tomeasure CT dose]"

"Teknik akuisisi scan spiral memperkenalkan istilah Pitch. Pitch yang besar mempengaruhi proses rekonstruksi karena interpolasi data menjadi lebih lebar sehingga dapat menurunkan resolusi citra. Penelitian ini dilakukan dengan menggunakan fantom toraks in house yang dibuat dan didesain berdasarkan pengukuran data citra CT Toraks 100 pasien laki-laki. Parameter eksposi yang digunakan 130 kVp, rotasi tabung 0,6 detik, perubahan arus tabung 70 mAs dan 100 mAs serta variasi pitch mulai dari 0.5, 0.8, 1, 1.5, 1.8 dan 2. Fantom terbagi menjadi 4 bagian. Fantom bagian A untuk evaluasi akurasi posisi dan kualitas citra pada selang berisi media kontras, bagian B untuk evaluasi kualitas citra lubang udara hole , bagian C untuk evaluasi mikrokalsifikasi dengan variasi ukuran mesh pada serbuk tulang dan hidroxyapatite, dan bagian D untuk evaluasi MTF. Scanning fantom A untuk evaluasi akurasi posisi selang antara ukuran di fantom dengan monitor menunjukkan deviasi < 4 berjumlah 408 data 84 di sisi kanan dan 417 data 86 di sisi kiri dari total 486 data. Evalusi kualitas citra pada fantom A, terdapat perbedaan ?SNR pada tiap slice dengan hubungan yang linier terhadap perubahan pitch, semakin besar pitch yang digunakan ?SNR akan semakin lebar. ?SNR paling lebar terdapat pada slice ke-1 dan ke-2, selanjutnya pada slice ke-3 sampai ke-9 ?SNR stabil dan cenderung menurun. Evaluasi fantom B menunjukkan hole titik I dan J yang berdiameter 0.9 mm dan 0.625 mm tidak dapat tervisualisasi pada seluruh slice. SNR yang didapat paling tinggi pada hole tengah titik H dengan diameter 2 mm. Sensitivitas Pesawat CT dapat mendeteksi serbuk tulang ukuran mesh 10 dan 30 tetapi tidak dapat memperlihatkan serbuk tulang ukuran mesh 50 yang tersebar merata di permukaan fantom, ditunjukkan dengan nilai SNR tertinggi pada pitch 0.8 sebesar 2.659 SNR.......Acquisition technique in spiral scan introduce the term of Pitch. The big pitch could be influence for reconstruction process because interpolation will be wider, be affecting the spatial resolution. This study was performed by using in house thoracic phantom that made and designed based on image data measurement of CT Thorax of 100 men patient. Exposure Parameter which used was 130 kVp, tube rotation 0.6 second, tube current 70 mAs and 100 mAs, with pitch variation start from 0.5, 0.8, 1, 1.5, 1.8 and 2. Phantom was divided into 4 parts. Part A was used for evaluating the accuracy of position and image quality on a pipe that consist of contrast media, part B was used for evaluating image quality on hole, part C was used for evaluating micro calcification with various mesh size on bone material and hidroxyapatite, while part D was used for evaluating MTF. Phantom A scanning was performed for evaluating the accuracy of position between pipe in phantom and monitor showed deviation 4 with 408 number of data 84 on the right side and 417 data 86 on the left side from 486 all data. The result obtained for image evaluation, showed the different between delta SNR in every slice in phantom A with the pitch changing, used higher pitch becoming SNR wider. The widest SNR were occurred in the 1st and 2nd slice, furthermore in the 3rd until 9th slice SNR were stable and tend to decreased. Evaluation of phantom B showed that hole in point I and J which have diameter 0.9 mm and 0.625 mm could not visualized. The highest SNR was occurred in the middle hole point H with diameter 2 mm. The sensitivity of CT scanner is good enough to detect bone with the mesh size of 10 and 30 but not with the mesh size of 50 that spread in the phantom surface, this is shown with the highest SNR in the pitch 0.8 as 2.659 SNR."