الفهرس 
Anatomy of the Colon and RectumOnly 14 pages are availabe for public view
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Abstract
An Egyptian study at national cancer institute, Cairo university showed that, rectal carcinoma constituted approximately only 2.2% of newly diagnosed cancer patient in 2005, that is representing 12.4% of the tumors of the digestive tract (Annual Cancer Conference of the Egyptian Cancer Society, Danish Cancer Society & Aarhus University Hospital February, 2005).
American cancer society, considered that the survival of the patients with colorectal cancer depends to a large extent on the stage of the disease at diagnosis.
Microvessels density has been established as a prognostic indicator for many cancers, and the most direct strategy to monitor anti-angiogenic therapy would be periodic biopsy which is invasive approach, hence the need for non-invasive method to assess the tumour vascularity and give accurate results for post therapeutic assessment.
CT perfusion is useful and non invasive technique for evaluating colorectal malignancies. Malignant and normal tissue can be accurately differentiated using perfusion maps.
Perfusion CT is found to be helpful in oncology with a wide array of application in tumour diagnosis, staging, prognostic evaluation and monitoring therapeutic response.
Perfusion CT involves dynamic scanning after the administration of iodinated contrast material followed by mathematic modeling to study contrast material kinetics in the tissue.
Estimation of tumour perfusion parameters such as blood flow , blood volume, mean transient time , and permeability surface area.
Due to optimization of surgical techniques, introduction of neoadjuvant therapies and recent developments in diagnostic imaging modalities, the mortality rate has decreased significantly by 20 % in the last years.
Value in diagnosis of CRC
A significant difference in blood flow and mean transit time between rectal tumor and normal rectum. Blood flow, blood volume, permeability surface area are significantly higher in rectal cancer than in the normal rectal wall.
CRC has high blood flow, blood volume, permeability surface area index and low mean transit time values as compared with diverticular disease, which helps differentiate cancer from colonic thickness due to diverticulitis .
Value in metastases and treatment monitoring in CRC
Perfusion CT has played an increasing role in monitoring therapeutic response to antiangiogenic drugs and chemoradiation as it may reflect tumor
Angiogenesis and provide insight of the functional tumor microvasculature.
Vascular parameter such as mean transit time was significantly high whereas tumor blood flow and permeability surface area product were low in patients who developed metastases.
Baseline perfusion values could predict the response to the chemo-radio therapy. Baseline blood flow in non-responder is found to be significantly higher and mean transit time significantly lower than in responders.
It is highly beneficial to predict the response to chemo-radio therapy so that non-responders could avoid the side effects associated with intensive therapeutic regimens, and therefore, predictive value of CTP in the response to chemo-radio therapy should be evaluated in a prospective study with a larger sample size.
To conclude, Perfusion CT plays important role in quantifying tumour angiogenesis and evaluating the disease progression and monitoring therapy effectiveness and choosing appropriate therapy.