The Application Of Low Dose 640 Slice CT Scan And Low Concetration Of Contrast Agent In Head And Neck CTA In A Craniocaudal Direction-feasibility Study

Objectives:we aimed at assessing the feasibility of the application of a combination of low tube voltage,low concentration contrast medium and iterative reconstruction techniques in a craniocaudal scan direction in head and neck CTA in comparison with the conventional normal high voltage and high concentration contrast medium without iterative reconstruction in a caudocranial scan direction in accurately producing images of quality that is of diagnostic value while at the same time reducing radiation exposure and risk of contrast induced nephropathy to the patients and deducting perivenous artifacts of the images.Methods:Between September 2016 and November 2016 among patients seen in our hospital due to vascular diseases,30 patients were selected and then randomly grouped into three groups A,B and C.While group A received the conventional scan with 120 kv,320 Omnipaque contrast medium without iterative reconstruction(reconstruction was by the FBP),under automatic tube current and in a caudocranial scan direction,group B were scanned with a low tube voltage of 80 kv,low concentration of contrast agent Visipaque 270 with iterative reconstruction under same automatic tube current in caudocranial direction and finally group C was scanned with the same protocol as B but in an opposite scan direction(craniocaudal).Radiation dose,image quality and perivenous artifacts were then scrutinized and compared among the three groups.Results:The CT attenuation values were significantly higher in groups C and B compared to group A(p<0.001).Moreover there was a 15.5% deduction in the mean effective dose of iodine and a significant 50% reduction in radiation dose in groups B and C compared to group A(p-value<0.001).The overall image quality quantitatively in terms of CNR and qualitatively with regards to graininess and streak artifacts was significantly improved in protocols B and C compared to protocol A.The SVC attenuation was lower in protocol C and hence less perivenous artifacts compared to A and B.Conclusion:The use of a combination of low tube voltage,low concentration contrast medium with iterative reconstruction in a craniocaudal scan direction has proven to be a method of choice in head and neck CTA as it provides images that are of diagnostic quality while at the same time saving the patient from exposure to a ton of ionizing radiations and iodine content.This will help in patients as well as children(whose cells are still dividing and dividing cells have a higher potential to turn malignant than the matured ones)who require repeated CT examinations for chronic conditions.And this technique can also be extended to other parts of the body example lower limb CTA.