Radiation dose evaluation in 64-slice CT examinations with adult and paediatric anthropomorphic phantoms

Abstract

The objective of this study was to evaluate the organ dose and effective dose to patients undergoing routine adult and paediatric CT examinations with 64-slice CT scanners and to compare the doses with those from 4-, 8- and 16-multislice CT scanners. Patient doses were measured with small (<7 mm wide) silicon photodiode dosemeters (34 in total), which were implanted at various tissue and organ positions within adult and 6-year-old child anthropomorphic phantoms. Output signals from photodiode dosemeters were read on a personal computer, from which organ and effective doses were computed. For the adult phantom, organ doses (for organs within the scan range) and effective doses were 8-35 mGy and 7-18 mSv, respectively, for chest CT, and 12-33 mGy and 10-21 mSv, respectively, for abdominopelvic CT. For the paediatric phantom, organ and effective doses were 4-17 mGy and 3-7 mSv, respectively, for chest CT, and 5-14 mGy and 3-9 mSv, respectively, for abdominopelvic CT. Doses to organs at the boundaries of the scan length were higher for 64-slice CT scanners using large beam widths and/or a large pitch because of the larger extent of over-ranging. The CT dose index (CTDI(vol)), dose-length product (DLP) and the effective dose values using 64-slice CT for the adult and paediatric phantoms were the same as those obtained using 4-, 8- and 16-slice CT. Conversion factors of DLP to the effective dose by International Commission on Radiological Protection 103 were 0.024 mSvmGy(-1)cm(-1) and 0.019 mSvmGy(-1)cm(-1) for adult chest and abdominopelvic CT scans, respectively.

Dose distribution for dental cone beam CT and its implication for defining a dose index

“…Moreover, CTDI allows for the estimation of the effective dose to the patient using conversion factors. 9 The use of the CTDI 100 has been under investigation lately for both CBCT and MDCT. [9][10][11][12][13][14][15][16] It has been shown by different authors that the increasing beam width used by modern MDCT scanners leads to a significant underestimation of the axial (z-axis) dose when measuring the CTDI 100 , as the scatter tails are not fully measured by the 100 mm pencil ion chamber.…”

“…9 The use of the CTDI 100 has been under investigation lately for both CBCT and MDCT. [9][10][11][12][13][14][15][16] It has been shown by different authors that the increasing beam width used by modern MDCT scanners leads to a significant underestimation of the axial (z-axis) dose when measuring the CTDI 100 , as the scatter tails are not fully measured by the 100 mm pencil ion chamber. [10][11][12][13] In addition, there are commercially available dental CBCT units that offer FOVs that exceed the length of the 100 mm pencil ionization chamber.…”

Using Radiation Risk Models in Cancer Screening Simulations: Important Assumptions and Effects on Outcome Projections

“…The absorbed dose to the lung with follow-up CT is 15.0 mGy for men and 15.4 mGy for women. The absorbed doses to the breast are 4.0 mGy and 15.7 mGy for screening and follow-up, respectively (28,29). FU = follow-up, FU , 4 mm = FU procedures include nodules less than 4 mm in size, no FU , 4 mm = no FU procedures included nodules less than 4 mm in size.…”

Onkológiai betegek szoros képalkotó követése – előny vagy hátrány?

“…A sugárexpozíciók összehasonlítása Ha 64 szeletes készülékkel történik a vizsgálat, a vizsgá-landó tájékok felső és alsó határainál (gyermekek esetén végzett mellkasi CT során a nyálmirigyek, gyomor; felnőttek és gyermekek esetén egyaránt hasi és kismedencei CT során az emlők és a herék) nagyobb a sugárterhelés, mivel szélesebb sugárkúp (nagyobb szórt sugárzás) és/ vagy nagy a csúcs-faktor (az asztal mozgási sebessége egy fordulatra és a teljes kollimációra vonatkoztatva) [26]. Egy PET/CT, a gép beállításától függően, 13,5-32 mSv sugárterhelést jelent, így a vizsgálat becsült rákrizikót fokozó hatása 0,163-0,514%-ra tehető [24].…”