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The Brantas River that crosses several districts and cities in East Java province receives pollutant loads from various human activities along its watershed. On the other hand, the Brantas river is also used as a source of water from various human activities along the watershed. Naturally, the river has the ability to recover through physical, chemical and biological processes. The ability of river to recover from pollution can be seen from the rate of carbon deoxygenation. Therefore, conducted research to see the performance of Brantas river self-purification starting from upstream in the Pendem Batu Bridge to the downstream at Padangan Mojokerto Bridge with 11 (eleven) locations of water sampling. Carbon deoxygenation determination method using Thomas method. The results showed varying deoxygenation rates with a range of values 0.001 / day to 0.028 / day. The highest rate of Carbon deoxygenation lies in the sampling location at Kesamben Bridge Blitar and the lowest is at the location at Dinoyo Bridge Malang. Brantas river deoxygenation rates is lower than Metro river in Malang regency, Brantas river in Malang city, Citarum upstream river, Cikapundung river and Citepus river. So it is concluded that the Brantas river self-purification performance from Carbon deoxygenation rate is lower. Brantas river management efforts should consider this factor in the handling of organic pollutant sources. The wastewater quality standard that have the same value.

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AbstrakCT Scan merupakan alat pencitraan sinar-X yang dipadukan dengan komputer pengolah data sehingga mampu menghasilkan gambar potongan melintang tubuh dan memiliki dosis relatif lebih tinggi, karena berasal dari radiasi primer dan radiasi hambur dari setiap slice. Dosis yang dihasilkan dipengaruhi oleh parameter scan yaitu faktor eksposi (tegangan tabung, aruswaktu rotasi) dan ketebalan irisan. Kuantitas dosis pada pemeriksaan CT Scan digunakan metode Computed Tomography Dose Index (CTDI). Penelitian ini dilakukan untuk mengatahui efek variasi parameter scan terhadap CTDI dan kualitas citra dengan menggunakan phantom. Hasil data yang diperoleh menunjukkan bahwa pada variasi 200 mAs, 120 kV dan 5 mm menghasilkan CTDIvol dan CNR optimum dengan nilai masing-masing 25.8 mGy dan 3.51. Hal ini disebabkan adanya keseimbangan nilai antara faktor eksposi yang tidak memiliki rentang yang terlalu jauh sehingga menghasilkan energi dan kuantitas sinar X yang seimbang dan ketebalan irisan tidak menghasilkan noise tinggi sehingga objek dalam phantom tetap dapat terlihat lebih baik.Kata Kunci: CT Scan, CTDI, CTDIvol, LCR, CNR. AbstractCT Scan is an X-ray imaging device integrated with a data processing computer so as to produce a cross-sectional image of the body and has a relatively higher dose, as it comes from primary radiation and scattering radiation from each slice . The resulting dose is affected by the scan parameters of the exposure factor ( tubular incision, rotational current-time) and the thickness of the incision. The quantity of dosage on CT scan is used Computed Tomography Dose Index ( CTDI ) method . This study was conducted to investigate the effect of scanning parameter variation on CTDI and image quality using phantom. The results of the obtained data show that on variations of 200 mAs, 120 kV and 5 mm yields CTDIvol and CNR optimum value of 25.8 mGy and 3.51 respectively. This is due to the balance of values between the exposure actors that do not have a range that is too far so as to produce energy and the quantity of X-ray is balanced and the thickness of the slice does not produce high noise so that the objects in the ph antom can still look better.