Bidang Ilmu: FISIKA MEDIS LAPORAN PENELITIAN HIBAH BERSAING TAHUN ANGGARAN 2011
Penentuan Dose Reference Level (DRL) pada Prosedur Diagnosis Kepala Menggunakan CT-scan sebagai Upaya Proteksi Radiasi kepada Pasien secara Nasional
Drs. Johan Andoyo Effendi Noor, M.Sc., Ph.D. dr. Indrastuti Normahayu, Sp.R.
Dibiayai oleh Direktorat Jenderal Pendidian Tinggi, Kementerian Pendidikan Nasional, melalui DIPA Universitas Brawijaya REV.1 Nomor: 0636/023-04.2.16/15/2011 R, tanggal 30 Maret 2011 dan berdasarkan surat dari DP2M Dikti Nomor: 121/D3/PL/2011 tanggal 7 Februari 2011
UNIVERSITAS BRAWIJAYA NOPEMBER 2011
RINGKASAN Salah satu aspek penting yang sangat diperlukan oleh seorang dokter, khususnya dokter spesialis penyakit dalam, dalam melakukan diagnosis suatu penyakit adalah keberadaan dari citra organ-organ dalam tubuh yang sedang didiagnosis. Dengan bantuan citra bagian dalam tubuh tersebut seorang dokter dapat melakukan diagnosis dengan lebih cermat, sehingga terhindar dari kemungkinan salah diagnosis. Sejarah pencitraan medis berawal dari ditemukannya sinar-x oleh Wilhelm Conrad Röntgen pada tahun 1895. Citra sinar-x pertama atas organ tubuh manusia adalah foto sinar-x tangan istrinya. Oleh sebab itu sampai saat ini foto-foto yang dibuat dengan menggunakan modalitas sinar-x sering juga disebut dengan foto Röntgen. Kemudian seiring dengan kemajuan di bidang komputasi, baik dalam bidang perangkat keras maupun perankat lunaknya, teknik pencitraan dengan sinar-x telah mengalami kemajuan dengan munculnya teknik Computerised Tomography, yang dikenal dengan CT-scan, yang pertama kali diperkenalkan oleh Sir Godfrey Hounsfield (Hounsfield, 1973) pada tahun 70-an. Sinar-x merupakan sepenggal spektrum gelombang elektromagnetik yang terletak di ujung energi tinggi spektrum gelombang elektromagnetik di bawah dan bersingungan dengan sinar gamma. Sinar-x mempunyai kemampuan yang sama dengan sinar gamma dalam mengionkan benda-benda yang dilaluinya, sehingga keduanya juga dikenal sebagai sinar pengion. Jika proses ionisasi ini terjadi pada jaringan lunak organ maupun cairan di dalam tubuh manusia, maka bisa mengakibatkan terjadinya kerusakan sel, mutasi gen, terbentuknya radikal bebas, dan sel-sel kanker. Proteksi radiasi di dalam praktik pencitraan diagnostik dimaksudkan untuk menjamin bahwa keuntungan penggunaan sumber radiasi lebih besar dari risikonya terhadap individu yang terlibat. Optimasi proteksi dan keselamatan dilakukan dengan prinsip “As Low As Reasonably Achievable.” Penggunaan berkas pengion sinar-x di dalam praktek pencitraan diagnostik telah mengalami kemajuan yang sangat pesat, baik dari sisi teknik pengambilan data, kualitas citra yang dihasilkan maupun jumlah tindakan. Dalam aplikasi radiasi, dosis efektif merupakan parameter yang digunakan untuk menyatakan dan membandingkan dosis radiasi yang diberikan kepada pasien. The International Commission on Radiological Protection (ICRP) telah mengeluarkan rekomendasi dosis efektif yang aman bagi manusia yang bisa digunakan sebagai standar acuan. Sehingga Pemerintah Republik Indonesia sangat perlu mempunyai standar nasionalnya yang mengacu kepada standar internasional ini. Penelitian pada tahun pertama ini dilakukan dengan mengukur, menghitung dan menganalisis dosis efektif pencitraan sinar-x pada mesin CT-scan di Instalasi Radiologi di tiga rumah sakit besar di kota Malang, yaitu Rumah Sakit Saiful Anwar (RSSA), Rumah Sakit Tentara Soepraoen (RST), dan Rumah Sakit Panti Nirmala (RSPN), yang diambil sebagai rumah sakit peserta. Pengukuran dosis dilakukan pada pasien yang menjalani eksaminasi kepala di rumah sakit peserta. Parameter-parameter CT yang diambil antara lain: tegangan tabung (dalam kVp), arus tabung (dalam mA), waktu pemindaian (dalam detik), panjang pindai (scan length dalam cm), lebar kolimator (dalam mm), CTDIvol (dalam mGy), dan Dose Length Product (DLP dalam mGy.cm). Dari data-data tersebut kemudian dihitung besar dosis efektif yang diterima oleh pasien dengan menggunakan program komputer perhitungan CTDosimetry versi 1.0.4 (dengan program Microsoft Excel) yang dibuat oleh ImpACTscan Inggris.
Hasil-hasil yang telah diperoleh memperlihatkan bahwa mesin CT scan di RSSA (buatan General Electric Healthcare Inc. dengan tipe HiSpeed DX/i) memberikan dosis efektif rata-rata sebesar 1,31 mSv untuk pasien laki-laki dan 1,19 mSv untuk pasien prempuan, mesin di RST (buatan Siemens Healthcare System dengan tipe Somatom Spirit) memberikan dosis efektif ratarata sebesar 1,38 mSv untuk pasien laki-laki dan 1,32 mSv untuk pasien prempuan, dan mesin di RSPN (buatan Siemens Healthcare System dengan tipe Emotion6) memberikan dosis efektif rata-rata sebesar 2,06 mSv untuk pasien laki-laki dan 1,93 mSv untuk pasien prempuan. Tampak dari hasil-hasil tersebut mesin Siemens Emotion6 memberikan dosis paling tinggi dan mesin CT GE HiSpeed DX/i memberikan dosis efektif paling kecil. Secara umum, mesin yang menerapkan pencatuan arus adaptif (GE) memberikan dosis yang lebih kecil dibandingkan dengan mesin yang arusnya dicatu secara tetap/konstan (Siemens).
SUMMARY One important tool required by a medical doctor, especially an internist, in conducting a clinical diagnose is internal images of the body under investigation. The images will help the doctor in diagnosing his/her patients more accurately to avoid any misdiagnose. The history of medical imaging started after the discovery of x-ray by Wilhelm Conrad Röntgen in 1895. The first x-ray image of human body ever made was the image of the hand of Mrs. Röntgen. The photography that utilizes x-ray beam to produce images is called a Röntgen photography. In the wake of and advances in computing technology, both in hardware and software aspects, the x-ray imaging technology follows by the invention of the Computerized Tomography, also known as CT-scan, by Sir Godfrey Hounsfield (Hounsfield, 1973) in early 70‘s. X-rays lie in the high energy end of the electromagnetic spectrum just below and overlap with the gamma-rays. Therefore, x-ray has the similar capability to gamma-ray in ionizing matters they are passing through. This capability makes them be called ionizingrays. If the ionization occurs in soft tissues of the organs or to the electrolites in the body, cell damage, gen mutation, free radical formation, dan cancer cells production may result in. Radiation protection in diagnostic imaging practices is aimed to ensure that the benefits of the use of ionizing radiation exceed the risk resulted in to the individuals involved. Protection and safety optimization is conducted using a principle of ALARA (As Low As Reasonably Achievable). The employment of ionizing x-ray beam in the diagnostic imaging practices has been advancing very rapidly in the aspects of image acquisition technique, image quality, and the number of procedures carried out. In the application of radiation, the effective dose is a parameter used to express and compare the radiation doses received by patients. The International Commission on Radiological Protection (ICRP) has published its recommendation on the effective dose safe to humans that can be used as the reference standard. In the sake of public protection, the Government of the Republic of Indonesia must establish a national standard by adopting the ICRP standards. The research in the first year was carried out by measuring, calculating, and analyzing the effective doses from examinations using CT-scanners at the Department of Radiology of three main hospitals in Malang: Rumah Sakit Saiful Anwar (RSSA), Rumah Sakit Tentara Soepraoen (RST), and Rumah Sakit Panti Nirmala (RSPN), that were taken as the participant hospitals. The dose estimations was conducted from patients sent to the departments for head examinations. The CT parameters taken were: tube voltage (in kVp), tube current (in mA), scan time (in second), scan length (in cm), collimator width (in mm), CTDIvol (in mGy), and the Dose Length Product (in mGy.cm). The effective dose of each patient was estimated and calculated from the acquired data using a computer programming CTDosimetry version 1.0.4 (in Microsoft Excel) written and distributed by the ImpACTscan team of the UK. The results reveal that the CT-scanner in RSSA (General Electric Healthcare Inc. type HiSpeed DX/i) gave an average effective dose of 1.31 mSv for male patients and 1.19 mSv for female patients, the CT-scanner in RST (Siemens Healthcare System type Somatom Spirit) exposed the patients an average of 1.38 mSv for male patients and 1.32 mSv for female patients, and the CT-scanner in RSPN (Siemens Healthcare System type Somatom Emotion6) delivered an average dose of 2.06 mSv for male patients and 1.93 mSv for female patients. The calculations show that the Siemens Emotion6 delivered the
highest dose and the CT GE HiSpeed DX/i delivered the lowest. This reveals that the system that employs an adaptive current supply (the GE) produces a lower radiation dose compared to the machines that use a fixed current technique (the Siemens).
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