The ‘Computed Tomography Dose Index (CTDI)’ is the fundamental CT dose descriptor. By The CTDI (unit: Milli Gray (mGy) is derived from the dose distribution along a line which is parallel to the axis of rotation for the scanner (z-axis) and which is recorded for a single rotation of the x-ray source The computed tomography dose index (CTDI). This abstract provides an overview of CT dose indices (CTDIs) currently used to quantify the amount of radiation used to perform clinical CT examinations. the standardized 100 mm length pencil ion chamber, The CTDIWis measured in dedicated plastic phantoms – 16 cm diameter for head and 32 cm diameter for body. The CTDIVol definition and measurement are based on single axial scan modes. The dose, expressed as the CTDIW. Result is to be Z test statistically analyzed for the relevant CTDIw /CTDIvol and DLP. FOR HEAD:- The mean value of CTDIvol Head (NCCT),is 51.94 mGyCTDIw is 51.94.Gy-cm. And the mean value of CTDIvol for head CECT is 104.18 mGyCTDIw is 104.18mGy-cm. The mean value of total DLP for head (NCCT), and head (CECT) is 808.4mGy-cm 1354.8 mGy-cm respectively. FOR ABDOMEN:- The mean value of CTDIvol abdomen dual phase is 28.2 mGy, CTDIw is 47mGy . And the value of CDTIvol for abdomen triple phase 29.4 mGy and CTDIw is 49.0 mGy. The mean value of total DLP for Abdomen dual phase and triple phase study) is 1085.4mGy-cm and 1088.07 mGy-cm respectively. Conclusion: - CTDIvol provides a very useful way to compare the doses delivered by various scan protocols or to achieve a specific level of image quality for a specific size of patient with use of technique charts and diagnostic reference levels. CTDIvol can be used to prescribed the right dose for specific patient size and diagnostic task. And also for quality assurance level propose.

The ‘Computed Tomography Dose Index (CTDI)’ is the fundamental CT dose descriptor.