Advances in CT Colonography for Colorectal Cancer Screening and Diagnosis

Abstract

CT colonography (CTC) is a validated colorectal cancer test that provides an additional minimally-invasive screening option which is likely to be preferred by some patients. Important examination prerequisites include adequate colonic cleansing and distention. Tagging of residual material aids in the differentiation of true polyps from stool. Low radiation dose technique should be employed routinely for screening studies. Readers must be skilled in the use of both 2D and 3D interpretation methods.

An approach for performing a successful computed tomography colonography examination

“…The latest CRC statistics for new cases in the USA is expected to decrease to 136 830 from the previous estimate of more than 143 000 cases in 2012. 1,2,3 The number of deaths in 2014 is expected to decrease to 50 310 from the previous figure of more than 52 000 deaths per year. 1,2,3 Most colon cancers, apart from inherited genetic disorders, such as hereditary non-polyposis colorectal cancer, arise from a pre-existing polyp which develops over a period of 10-15 years into a cancer.…”

“…1,2,3 The number of deaths in 2014 is expected to decrease to 50 310 from the previous figure of more than 52 000 deaths per year. 1,2,3 Most colon cancers, apart from inherited genetic disorders, such as hereditary non-polyposis colorectal cancer, arise from a pre-existing polyp which develops over a period of 10-15 years into a cancer. 4 Colon cancer screening is recommended every five years from the age of 50, 2 but colorectal examinations are a contested terrain of diagnostic imaging versus optical colonoscopy (OC).…”

Model-basedvshybrid iterative reconstruction technique in ultralow-dose submillisievert CT colonography

“…17 Given the great intrinsic contrast among air, tagged stool, polyps or colonic wall and the surrounding fat tissue, and the generally accepted minimal size of a clinically relevant polyp to be reported of 6 mm, decreased spatial resolution of the image is not a major concern. 3,14,15 Further techniques included tube current modulation and carefully adjusted scan length to scan only the colon with a safety margin of approximately 3 cm.…”

“…1,2 Compared with OC, its major disadvantages are the radiation dose and the inability to biopsy or remove polyps. 3,4 Although the true risk of stochastic effects from a CTC examination in adults is very low, its routine large-scale use must be responsibly weighted against its benefits.…”

Unsuspected colorectal carcinoma on routine abdominopelvic computed tomography

“…(4,6) However, with the increase in non-CTC abdominopelvic CT studies being performed for other indications, CRC may also be incidentally detected in these images. It is therefore important for radiologists to be familiar with the imaging findings of CRCs and aware of the pitfalls of detecting CRC in non-CTC abdominopelvic CT studies, in order to avoid missing an unsuspected tumour.…”