Iodine quantification with computed tomography for the purpose of dose assessment in contrast enhanced radiotherapy

Lipengolts AA1,2,3, Budaeva JA2,3, Blaickner M4, Cherepanov AA1, Menkov MA1, Kulakov VN2, Grigorieva EYu1
About authors

1 N. N. Blokhin Russian Cancer Research Center, Moscow, Russia

2 A. I. Burnazyan Federal Medical and Biophysical Center, Moscow, Russia

3 National Research Nuclear University MEPhI, Moscow, Russia

4 Austrian Institute of Technology, Vienna, Austria

Correspondence should be addressed: Alexey A. Lipengolts
Kashirskoe shosse, d. 24, Moscow, Russia, 115478; ur.liam@stlognepil

Received: 2016-12-01 Accepted: 2016-12-06 Published online: 2017-01-19

In vivo quantitative determination of high-Z elements such as iodine gadolinium, gold, etc. is an important issue for contrast enhanced radiotherapy (CERT) that aggravates its clinical implementation. X-ray computed tomography (CT) could be a reliable, convenient and universal method for this task. The aim of this study was to demonstrate the feasibility of iodine quantification with CT in a tissue equivalent phantom, meeting the demands for CERT. The results show a linear relationship between iodine concentration and radiopacity on tomographic images expressed in Hounsfield units (HU) over an iodine concentration range of 0.5–50 mg/ml. Furthermore, iodine quantification with CT proofed to be suitable for CERT since the deviation between CT- derived and actual iodine concentration does not exceed 5 % in the concentration range of 10–50 mg/ml. More significant deviations were observed for concentrations below 5 mg/ml with up to 80 %, which is still acceptable for CERT since the corresponding error for the absorbed dose in that range is less than 2.8 %. X-ray beam hardening within the tissue equivalent object does not significantly influence the accuracy of iodine quantification. The placement of iodine water solutions at the surface or in the centre of a visualized object during iodine quantification leads to a less than 2 % change in the determined iodine concentration.

Keywords: contrast enhanced radiotherapy, computed tomography, iodine, quantification, dosimetry