Additional imaging dose from kV-cone beam computed tomography

Abstract

Objectives: The objective of the following study is to provide the quantitative imaging dose dependency on treatment region and scanning settings concerning the additional imaging doses from kV-cone beam computed tomography (CBCT) scans. Materials and Methods: Patient imaging dose measurements were performed using head and body cylindrical poly methyl metha acrylate (PMMA) phantoms, 0.125 cm 3 ionization chamber and electrometer and metal oxide semiconductor field effect transistor dosimeter. Results: The dose values for the pelvis phantom was found vary from 8.6 mGy to 22.2 mGy for 120 kVp, 1040 mAs. For the head phantom, the dose values vary from 0.71 mGy to 1.37 mGy for 100 kVp, 36.1 mAs. For head scanning mode, the peripheral doses are greater than the central axis doses by a magnitude of 1.3-2 with the largest found consistently at 3 o'clock position of the PMMA head phantom. For the pelvis scan, the peripheral doses are greater than the central doses by a magnitude of 2.1-2.6 with the largest found consistently at 9 o'clock position of the PMMA pelvis phantom. Conclusion: One should be aware of the additional imaging dose with daily kV-CBCT when setting up CBCT scanning protocol and should try to reduce the high voltage usage since reduction of the tube voltage can reduce radiation dose to the patient, especially for pediatric patients.