Radiation Dose Obtained from Abdominal Computed Radiography: Comparison Between Supine and Prone Positions

Abstract

The aims of this study were to compare the entrance surface dose (ESD) between anteroposterior (AP) supine with posteroanterior (PA) prone projection of computed radiography (CR) abdominal examination and to determine the relationship between body mass index (BMI) and ESD of a patient. AP supine and PA prone projections on the same patients for CR abdominal examination of intravenous urography (IVU) were acquired on 50 patients at Hospital Raja Permaisuri Bainun, Ipoh. All the radiographic examinations were carried out on a Siemens Multixtop general x-ray unit and the images were processed with CR Carestream Direct view Max. Entrance surface dose (ESD) in miligray (mGy) was measured using optical stimulated luminescence dosimeters (OSLD) calibrated by the Malaysian Nuclear Agency. Data were analyzed using dependent t-test comparing the AP and PA projections on the same subject and Pearson correlation was used to determine the relationship between BMI and percentage of reduction of ESD. Results showed a significant different (p < 0.01) between AP supine (mean ESD = 6.42 ± 7.13 mGy) and PA prone (mean ESD = 3.92 ± 3.56 mGy) projection at all BMI. The BMI has a positive correlation with percentage of reduction of ESD (r = 0. 61) and was statistically significant (p < 0.01). In conclusion, PA abdomen prone projection significantly reduces the radiation dose and there is a positive correlation between BMI and percentage of reduction of ESD. The use of PA prone projection for CR abdominal examination should be considered as the routine projection at all BMIs level. Awareness that as the BMI increases the ESD also increases at a moderate positive linear relationship. ABSTRAK Objektif kajian ini ialah untuk membandingkan dos masuk permukaan (ESD) antara projeksi anteroposterior (AP) supin dengan posteroanterior (PA) pron pada pemeriksaan radiografi berkomputer (CR) abdomen dan untuk menentukan hubungan indeks jisim tubuh (BMI) dan ESD pada pesakit. Projeksi AP supin dan PA pron telah dilakukan pada pesakit yang sama dalam pemeriksaan CR abdomen urografiintravena (UIV) ke atas 50 pesakit dari Hospital Raja Permaisuri Bainun, Ipoh. Pemeriksaan radiografi dijalankan dengan unit x-ray Siemens Multixtop, imej diproses dengan peralatan CR Carestream Direct view Max. Dos masuk permukaan dalam miligray (ESD) dalam miligray (mGy) diukur dengan menggunakan dosimeter pendarkilau optik (OSLD) ditentukurkan di Agensi Nuklear Malaysia. Data telah dianalisa menggunakan ujian-t bersandar antara projeksi terhadap BMI dan untuk hubungan antara BMI dan peratus penurunan ESD ujian korelasi Pearson telah digunakan. Keputusan menunjukkan perbezaan yang signifikan secara statistik (p < 0.01) antara projeksi AP supin (ESD min = 6.42 ± 7.13 mGy) dan PA pron (ESD min = 3.92 ± 3.56 mGy) terhadap BMI. Terdapat juga korelasi yang positif antara BMI dan peratus penurunan ESD (r = 0.61) signifikan secara statistik (p < 0.01). Projeksi PA pron abdomen mengurangkan dos sinaran secara signifikan serta terdapat korelasi yang positif antara BMI dan peratus penurunan ESD. Penggunaan projeksi PA pron bagi pemeriksaan CR abdomen perlu dipertimbangkan sebagai pemeriksaan rutin CR abdomen pada kesemua tahap BMI pesakit. Kesedaran bahawa jika BMI meningkat, ESD juga meningkat dengan linear sederhana secara positif.