# Assessment of Imaging Protocol and Patients Radiation Exposure in Computed Tomography Colonography
Box 1825, Hail 6626, Saudi Arabia;  
[PERSON]RESS] (Centre for Nuclear and Radiation Physics, Department of Physics, University of Surrey,  
Gulford GU2 7 RH, UK; [EMAIL_ADDRESS]  
[PERSON]  
4 Radiology Department, King Khalid Hospital, Ministry of Health, P.O. Box 1825, Hail 6626, Saudi Arabia;  
[PERSON]RESS] (Centre for Nuclear and Radiation Physics, Department of Physics, University of Surrey,  
Gulford GU2 7 RH, UK; [EMAIL_ADDRESS]  
[PERSON]  
4 Radiology Department, King Khalid Hospital, Ministry of Health, P.O. Box 1825, Hail 6626, Saudi Arabia;  
[PERSON]RESS] (Centre for Nuclear and Radiation Physics, Department of Physics, University of Surrey,  
Gulford GU2 7 RH, UK; d.a.bradley@surrey. from CRC has decreased by 3% annually [6; 7]. In Saudi Arabia, [PERSON] et al. [8] have reported the prevailing percentages for the different CRC stages: localized disease 22.2%, regional disease 47.4%, distant disease 25.9%, and unknown 4.6%, the five-year survival rate being 63.3% for localized disease, 50.2% for the regional stage, and 14.7% for the distant stage. Thus, in Saudi Arabia as found elsewhere, it is both evident and unsurprising that early CRC detection increases the opportunity for improved outcome from treatment [8]. The Saudi Arabian Ministry of Health (MOH) actively encourages those of over 50 years of age to participate in CRC screening tests, to be repeated every 5 to 10 years. One of the options available for average-risk cancer individuals is the low radiation dose computed tomography colonography (CTC) technique [9]. CRC screening methods consist of invasive techniques such as colonoscopy and flexible sigmoidoscopy (FS). In contrast, the non-invasive procedures consist mainly of imaging procedures such as barium enema, CTC, and capsule endoscopy. CTC, also called CT enema, virtual colonoscopy, or CT pneumocolon, can identify colon and rectum malignancy (colorectal polyps) and other diagnostic findings in symptomatic and asymptomatic individuals [9; 10]. [PERSON] et al. [11] have provided estimated sensitivity and specificity values for CTC versus colonoscopy procedures, specifically for the detection of polyps or adenomas: (\(\geq\)6 mm lesion) sensitivity of 75.9% versus 82.9%, specificity 94.6% versus 91.4%; (\(\geq\)10 mm lesion) sensitivity of 83.3% versus 87.9%, specificity 98.7% versus 97.6%. An extensive study of 1233 individuals shows CTC and colonoscopy sensitivities for detecting polyps of 10 mm or more of 94% and 88% respectively [12], while another study, using an ultra-low dose protocol (10 mAs) for CTC, shows sensitivity and specificity for detection of \(\geq\)5 mm polyps of 94% and 84% respectively [13]. Radiation dose to patients during radiographic procedures is one of the public concerns. Therefore, there is a need for providing accurate information regarding patient dose and associated risk. Moreover, cancer risk is overwhelmingly estimated based on study of population survival in the aftermath of the August 1945 atomic bombings of Hiroshima and Nagasaki [14]. The Saudi Arabia government is seeking to provide diagnostic reference levels (DRL) for radiation doses arising from medical imaging [15]. CTC radiation dose can be one-half of that from the conventional abdomen-pelvis CT, with high natural contrast reference between the colonic soft tissue, gas, tagged feces, and fluids. The American College of Radiology (ACR) has recommended that the adult relative radiation level (RRL) for CTC should not exceed 10 mSv per procedure while for an average weight patient of 70 to 90 kg. The American Association of Physicists in Medicine (AAPM) note that the volume computed tomography dose index (CTDIvol) range should be 3 to 6 mGy [12; 16]. The CTC procedure is considered a frequent screening program, for asymptomatic diagnostic purpose, follow-up, or surveillance tool after surgical resection of CRC [17]. Therefore, as a low radiation dose protocol (screening protocol) the exposure factors needs to be optimized and justified according to the patient situation [18; 19].