Current output dose measurement in CT is based on the Computed Tomography Dose Index (CTDI) . The CTDI method utilizes a 10-cm long pencil ionization chamber placed in a 16-cm long Perspex phantom at 5 different sites. The CTDI dose estimation is performed using a single rotation for each reference site and excluding the contribution of radiation scattered beyond the 100-mm range of integration along z. The conventional methodology of CT dosimetric performance characterization is not appropriate to modern CT scanners with helical scanning modes,...

•With the small ion chamber method , the accumulated dose was directly measured by integrating the current from an ion chamber located at a fixed point in the phantom at the mid-point of the scanned length (Figure 6) , while the water phantom central axis was aligned with the CT rotation axis. The Farmer chamber was placed in the phantom in order to centre the charge collection volume. The charge collected by the ion chamber, qh (nC), was converted to accumulated dose using the equation...

Normal 0 false false false EN-IE X-NONE X-NONE Planar Average Equilibrium Dose D(eq.t) The central and peripheral axes were measured for three protocols to find the planar average equilibrium dose, as shown in Table 1. The planar average equilibrium dose was 12.3 mGy for all protocols. Protocols Center axis(mGy) Peripheral axis(mGy) D(eq.t)(mGy) Head 12.63 14.94 13.78 Chest 10.58 12.5 11.55 Abdomen 10 13.22 11.61 Average 12.3 CTDI volume measurements and comparison with

Normal 0 false false false EN-IE X-NONE X-NONE A study conducted by the Radiological Protection Institute of Ireland (now EPA) found that artificial sources such as medical ionizing radiation was by far the largest contribution to the population dose, particularly diagnostic X rays (above 90%); moreover, one of the largest contributors is CT, which contributes up to 55% of the collective dose(5). Currently, assessments of radiation dose in CT are based on the metric CTDI, introduced more than 30 years ago. CTDI underestimates the dose...

Dixon, R.L., 2003. A new look at CT dose measurement: Beyond CTDI. Med. Phys. 30, 1272–1280. doi:10.1118/1.1576952 Dixon, R.L., Ballard, A.C., 2007. Experimental validation of a versatile system of CT dosimetry using a conventional ion chamber: Beyond CTDI100: A versatile CT dosimetry system. Med. Phys. 34, 3399–3413. doi:10.1118/1.2757084 Descamps, C., Gonzalez, M., Garrigo, E., Germanier, A., Venencia, D., 2012. Measurements of the dose delivered during CT exams using AAPM Task Group Report No. 111. J. Appl. Clin. Med. Phys. 13. International Atomic Energy Agency, 2011....