Fixed tube current: the CT image not like conventional radiographicimaging, the CT image never looks over exposed in the sense of show too lightor too dark. The CT data ensures that the image always appears properlyexposed. The CT radiographers are not technically forced to decrease the tubecurrent time product (mAs) for small patients who may result in excessradiation dose for these patients. The radiographer should be provided withproper guidelines for (mAs) selection as a function of patient size, thicknessand weight. However, radiographers are usually standardized the tube potential(kV) and gantry rotation time (s) for a given clinical application. The fastestrotation time should be used to minimize head motion artifact and blurring.
Thelowest kV regular with the patient head size should be selected to provide amaximize image contrast with low radiation dose.One of the technical Pitfalls of CT is the use of ionizingradiation. However, the normal radiation dos age for a routine brain CT scan isbetween 2 and 5 mSv, it is important to note that radiation dose is increasewith increase scan phases. Care must be taken to reduce exposure factor KVP,MAS and scan time when imaging patients and ALARA (As low as reasonablyachievable) principle should be applied in all situations to patients andpersonnel. With the advent of MDCT, CTP and CTA, the benefit must be workagainst the increased radiation doses connected with these techniques.Useiterative reconstruction to provide an efficient image quality with lessradiation dose. Use eye protection shield to protect eye lenses.
To reduce oravoid eye exposure by radiation, the scan angle should be parallel tosupraorbital ridge and the inner table of the posterior margin of the magnumforamen. This may be done by two ways first by tilting the patient is chintoward chest or second way by tilting the CT gantry. (AdultRoutine Head Ct Protocols Version 2.0 3/1/2016, 2017) This willreduce radiation dose value affecting the eye and reduce image noise due to thesoft tissues of lower part brain Appear without superimpose with orbit bone. The mosteffective way to reduce radiation dose is to avoid performing the examinationor reduce number of brain scan phases as possible and with repeated imagingthere is increase in radiation dose. Reducing Radiation Exposure during theScan as possible, that to find the sweet spot between the lowest exposuresappropriate for the brain while still providing a strong diagnostic quality imagesfor examination.