Computed Tomography (CT) is a radiologic modality that provides clinical information in the detection, differentiation, and demarcation of disease. It is the primary diagnostic modality for a variety of presenting problems and is widely accepted as a supplement to other imaging techniques. CT is a form of medical imaging that involves the exposure of patients to ionizing radiation[1]. During a CT scan a rotating source passes x-rays through a patient’s body to produce several cross-sectional images of a particular area. These two-dimensional images can also be digitally combined to produce a single three-dimensional[2].

Computed tomography (CT) developed from an x ray modality that was limited to axial imaging of the brain in neuroradiology into a versatile 3-D whole body imaging modality for a wide range of applications, including oncology, vascular radiology, cardiology, traumatology and interventional radiology. CT is applied for diagnosis and follow-up studies of patients, for planning of radiotherapy, and even for screening of healthy subpopulations with specific risk factors[3].

Purpose

To estimated effective dose (E) in adult CT examination for Toshibax64 slice using CT. Exp version 2.5 software.

In this study the data of CT-scanner has been collected from three hospitals, which consist on survey for scanner parameters and equipment’s. Data were used to assess doses for 300 adult patients underwent head, chest, abdomen-pelvis and pelvis CT examinations. The local ethics committees of all participating institutions approved the study protocol. The collected information in regard to:

·           CTequipment-specific information

         Made/model/year of installation,

             Number of slices

·           Patient demographic data

          Age and gender

·           CT scan parameters

     kV, mA, rotation time and scan time (spiral mode),

       Scan length (start and end of scan region),

       Number of slices, slice thickness, pitch.

Dosimetric calculations

 CT Expo software was used to calculate common CT dose descriptors: (i) CT weighted dose index ( ) and volume dose index ( ) provides an indication of the average absorbed dose in the scanned region, (ii) CT dose –length product (DLP) the integrated absorbed dose along a line parallel to the axis of rotation for the complete CT examination, and (iii) effective dose (E): a method for comparing patient doses from different diagnostic procedures (Effective dose)

In this study was used CT-Expo Version 2.5 software tool for dose calculations and CT-Expo tools—based on Monte Carlo data published by the Research Center for Environment and Health in Germany—for dose calculation. Dose estimation is done based on mathematical phantoms for adult (ADAM and EVA).

 The software allows the calculations of the CT dose descriptors (  and DLP),

organ doses and effective dose in accordance with new recommendations of the international commission for radiological protection ICRP 103[4].

Doses are presented Brian, PNS, chest, pulmonary, abdomen-pelvis, pelvis, KUB and CTU CT examinations. Mean CTDIvol ranged: from 65.5 to 25.9 mGy in Brain and Pulmonary; respectively;
Mean DLP ranged from 2381 to 918 mGy.cm in CTU and Pulmonary CT; respectively; While mean effective dose ranged from 27.1 to 2.6 mSv in Abdomen/Pelvis and BNS; respectively. The results presented wide variations in technique and radiation dose for similar examinations indicating significant room for dose optimization.