Impact of contrast agents on dose algorıthms of planning systems

Abstract

Background: Use of contrast agents (CAs) during CT simula on for treatment planing system leads to changes in electron density. In this study we aimed to inves gate the effect on calculated dose of various concentra ons of CAs on treatment planing systems in different dose calcula on algorithms. Materials and Methods: Contrast agent (0.769 mg/ml Iopromid) -water mixtures at concentra ons of 0%, 1%, 2%, 5% and 10% in total volume of 500 ml for each were made by using five iden cal balloons. Calcula ons were performed by Cobalt-60 and 10 MV linear accelerator devices in CMS XIO treatment planning system. The prescribed dose of 100cGy was given to the center of balloon that is isocenter of SAD technique at 10cm from the surface. The doses at maximum dose depth (dmax) and at 5 cm were calculated according to the separate algorithms by either making or not making a correc on for CA, and the results were recorded. Results: In all algorithms, as contrast ra o increases, the dose values at dmax and 5 cm-depth increase accordingly. When the doses at dmax and 5 cm-depth were compared for Linac and Co-60 in all algorithms, it has been shown that the d max value of Co-60 was higher and the difference was greater in parallel with increasing contrast ra o in comparing with Linac. Conclusion:When required during the planning, the treatment plan should be calculated via providing an electron density correc on by contouring the volume retaining CAs along the beam line.

The Effect of Contrast Agents on Dose Calculations of Volumetric Modulated Arc Radiotherapy Plans for Critical Structures

“…These studies can be grouped into two main categories: the first one is based on phantoms and mathematical models, the second is based on clinical CT images. Studies in the first category lean toward simulating clinical observations based on the amount of contrast material and beam energy; results generally tend to emphasize the apparent significant effect of contrast material rather than the clinical effect [13,16,17]. While studies in the second category generally place emphasis on clinical outcome and reported dose, differences were mostly within clinically acceptable limits.…”

“…Jing et al [20] concluded that oral contrast agents caused clinically significant changes in the dose calculations for the targets and critical structures. Rankine et al [13] reported significant dose discrepancy for critical structures, and Burridge et al [34] found a considerable increase in MU settings due to contrast agents presence in CCT images. The results in this study show that HU variations due to contrast materials were statistically significant (p-value < 0.05) for the majority of critical structures and target volumes.…”

“…Phantom studies [11][12][13][14] investigated changes in dosimetry due to contrast materials for different energies and concentrations. Results show a significant change in the dose calculations between NCCT and CCT dose calculations plans up to 7% [13].…”

“…The reviewed literature, summarized in Table 1, generally reported limited effect of contrast agents on radiotherapy dose calculations except in a few publications [13,[16][17][18]20,30]. Nevertheless, there was no consensus on the magnitude of these effects or a clear recommendation to utilize contrast-enhanced CT simulation images for radiotherapy dose calculations.…”

Automatic contrast medium extraction system using electron density data with dual-energy CT

“…In the previous study, Izmirli et al investigated that the effect of calculated dose at various contrast medium concentrations in treatment planning systems for different dose calculation algorithms. 12 Izmirli et al reported that the dose difference for treatment plans with and without the contrast medium was within 2.2% at less than 2 mg ml −1 concentration. The contrast medium extraction method could be useful by using DECT images at 80 kV/135 kV for radiation treatment planning.…”