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How effective is CT Colonography in detecting colon cancer?

Basem AL Al Zahrany

How effective is CT Colonography in detecting colon cancer?


The second cause leading to death in the United States is colorectal cancer in the same way colorectal cancer is the third common cancer in women and men. In the United States 135,260 people diagnosed with colorectal cancer in 2011. Colorectal cancer caused for 51,783 people from them the death. The number of colorectal cancer patients is predictable to rise in the future. Built on the present data, cost scenario and survival for colorectal cancer Yabroff et al expected the cost effect in 2020 for the primary $4.05 billion, making a significant cost load on the healthcare system. Colorectal cancer mortality was decreased by 18% to13 % with apply CT Colonography to detect colonic polyps before they developed to colorectal cancer (Trilisky et al, 2015). CT Colonography has been shown to have polyp discovery rates similar to the patient how use colonoscopy. CT Colonography is an exam for colorectal cancer screening which became generally effected for detecting polyps similar to those of colonoscopy. It has the prospective to improve colorectal cancer screening rates because of colorectal is come to be insignificant noninvasive ,faster patient in quantity ,no sedation requirement and potential for reduced cathartic examination . Appropriate program of a CT Colonography screening must implement and needs important announce to several aspects, counting proper patient preparation before the investigation, image acquisition, and post-processing of the developed images. A CT Colonography need workstation with special software and high quality monitors. Special software called Computer-Aided Detection CAD which is manipulate to reduce mistakes of spotting and showing polyps to the radiologist for images interpretation. These essay will discuss technique, advantages , disadvantages of CT Colonography and how CT Colonography can be affect for colorectal cancer .

Exam technique

Currently, patients go through intestine preparation procedure which has the purpose of avoid misdiagnosed of polyps by cleaning the colon. So far there is no agreement on a best program of food adjustment and releasing preparation of flexible period and amount. There is continuing studies aimed to rise patient relaxation and acceptance. To distinguish polyps from other residual the use usually fecal and fluid tagging with bowel laxative. Some time they do it with small quantity of both iodine-based contrast material and barium or one of them to improve the image and to eliminate the artifact of image which could be accrue ,which may rise the sensitivity of polyp detection, Digital subtraction is a post-acquisition processing technique use to improve the image quality(Trilisky,2015).

Advantages of CT Colonography

CT Colonography shows high sensitivity and specificity of detecting cancer lesions than colonoscopy. According to Perry Pickhardt(2015) the sensitivity of CT Colonography to detect lesion showed after a meta-analysis and systematic revision an overall 96% and it is coming higher if oral contrast is applied. This ratio give CT Colonography opportunity to use it for preventive and screening more than colonoscopy. In addition, colonoscopy y is invasive exam which might harmful the patients. However, this high percentage of detecting legion is my decay with lesions less than 6mm. Andrik, Aschoff (2007),fond after reviewing many studies don from 2000 until 2005 the specificity and sensitivity of catching of colon cancer is high with 10mm or more in size of polyps .He estimate that CT Colonography could increase sensitivity in this coming years and this is what happened now it is increase up to 6 mm for detection of polyps.

Bleeding, colonic perforation, cardiovascular events and even death are complication with low percent of colonoscopy exams while almost zero percent in CT Colonography when automated low – pressure CO2 is used. Igor Trilisky, is radiologist in University of Chicago Medical Center, recommended to establish CT Colonography screening program for colon cancer on condition of implementing a quality assurance in the center. Proper patient preparation and image acquisition help the radiologist to read the image correctly. High quality training of radiologist and technologist is potential to good image interpretation. In particular, time of CTC exam is short in procedure but it take time to processing the image and read it mort ah Colonoscopy. In addition, using updated CAD help to improve sensitivity in image interpretation CT Colonography exams and decrease the specificity.

All of the aforementioned reasons to prefer CT Colonography form most patients especially how had colonoscopy before or both and if we look to Self-appreciation we found it is one of the most reason push the patents to choose CT Colonography as first option. Based on Pickhardt(2015) multicenter surveying 1400 adult how had CTC before founded high satisfaction percentage almost higher than 90% and same percent preferred to choose CT Colonography again for second screening. Researcher found highly ratio of chosen CT Colonography than colonoscopy for patent how had CT Colonography and colonoscopy before with nearly 6:1 ratio. Pickhardt(2015) found same thing happened with Moawad et al. They found that 95% of patients how had both experience of exams preferred CT Colonography screening.

Disadvantages of CT Colonography

Radiation exposure is the most concern issue in CT exams in general because there is no threshold of ionization radiation. In the same time too high exposure have same value of very low exposure dose for radiologist it means no data can be collected from image. J. Stoker, H. W. Venema, and R. E. van Gelder fond in tow studies ,don in 2004, low dose technique 120Kv and 10mAs (in supine position only )with series patient preparation held on 137 patient sensitivity and specify 70% and 80.8% respectively for polyps more than 4 mm. The other study were done in same year for 203 patients with 140Kv and 10mAs ( tow position) result in 95% in sensitivity and 92.2% in specify for polyps more than 7mm and 100% for both for polyps more than9mm. The average effective doses in first study was 0.7ms for men and 1.2 ms for women and 1.8 ms for men and average effective dose 2.4ms for women in second study (Tack, Gevenois,2007). Nowadays, we have inflation of the technology of post processing data which will may increase the sensitivity and specificity of detecting polyps and as the technology progressed as the ability of diagnose the polyps in early stage. So radiation can cause cancer itself which incumbent us to adequate using of exam.

CTC has the ability to detected most of polyps which might be developed to colorectal cancer. On the other hand, it may missed detection happened with small polyps less than 5mm. Generally 90 % of polyps are detected by CTC. 3.36. Based on Pickhardt(2015) experience, radiologist in University of Wisconsin School of Medicine and Public Health, 50% from small polyps are stable, 30 % regress and 20% remaining developed under observation. Instead of this, CT Colonography is extra colonic exam as well, it can evaluate the entire organ (abdomen and pelvis) also it has opportunity to evaluate osteoporosis without need to extra radiation dose. In fact, CT Colonography has high chance to be the first screening exam for colorectal cancer.

Experience of CTC observers

CT Colonography is observer dependent make image reading defer from center to other. A cumulative experience of reading CT Colonography is helpful to increase sensitivity and specificity as the English Bowel Cancer Screening Program find high positive rate in centers with experience of interpretation of 1000 case or more and centers which have at least 175 study for radiologist yearly. This outcome of Dutch study held on six radiologist and three CT technologist. They had training program of CT Colonography image interpretation. It shows significant increasing of average sensitivity of detecting polyps 6mm or more for 50 case from 76% in first set to 91% in fourth set. They recommend 164 case for training for each radiologist to increase his ability of interpretation (Haan, 2014).

In conclusion, CT Colonography has prospect to be good option of colorectal cancer screening considering a proper patent preparation, high quality training for both radiologist and CT technologist, highly cooperation from patients and updated CAD soft were. CT scan device has an inflation of soft were and hard were in this recent year make the sensitivity of detecting polyps increase rabidly with almost zero percent of complication. In terms of this advantages medical practitioners have to trust the exam and generalize it to help patients to survive from colorectal disease.


· CAD : Computer-Aided Detection special software called CAD which is manipulate to reduce mistakes of spotting and showing polyps to the radiologist for images interpretation.

· CRC : colorectal colon cancer colorectal adenoma is a benign glandular tumor of the colon and the rectum.

· CT computer-processed combinations of many X-ray images taken from different angles to produce cross-sectional images.

· Contrast media: is a substance used to enhance the contrast of structures or fluids within the body in medical imaging.

· CTC : computer tomography for colon.

· Ionization radiation: is radiation that carries enough energy to free electrons from atoms or molecules.

· Kv: The strong of power penetration

· ms : The amount of electromagnetic radiation.

· Polyps : small clump of cells that forms on the lining of the colon. Most colon polyps are harmless. But over time, some colon polyps can develop into colon cancer, which is often fatal when found in its later stages.


· Aschoff, A.J., Ernst, A.S., Brambs, H. & Juchems, M.S. 2008, “CT colonography: an update”, European Radiology,vol. 18, no. 3, pp. 429-437. Available from:

· De Haan, M.C., Pickhardt, P.J. & Stoker, J. 2015, “CT colonography: accuracy, acceptance, safety and position in organised population screening”, Gut, vol. 64, no. 2, pp. 342-350. Available from:

· Pickhardt, P.J. 2015, “CT colonography for population screening: ready for prime time?”, Digestive diseases and sciences, vol. 60, no. 3, pp. 647-659. Available from:

· Tack, D., Gevenois, P.A., Abada, H.T. & Springer EBook Complete Collection. Owned. 2005-2014 2007, Radiation dose from adult and pediatric multidetector computed tomography, Springer, New York;Berlin;. Available from:

· Trilisky, I., Ward, E. & Dachman, A.H. 2015, “Errors in CT colonography”, Abdominal Imaging, vol. 40, no. 7, pp. 2099-2111. Available from:

· Venema, H.W., Laméris, J.S., Jensch, S., Stoker, J., Bossuyt, P.M.M., Reitsma, J.B. & Gelder, v., R.E 2006, “Effective radiation doses in CT colonography: results of an inventory among research institutions”, European Radiology, vol. 16, no. 5, pp. 981-987. Available from:


1- Introduction page 1

2- Exam technique page 2

3- Advantages of CT Colonography page2

4- Disadvantages of CT Colonography page4

5- Experience of CTC observers page5

6- Conclusion page5

How effective is CT Colonography in detecting colon cancer?

Name : Basem AL Zahrany

Class: Claudia team

Date : 15/02/2016

Word count : 1385 words


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