Prog Med Phys.  2017 Mar;28(1):27-32. 10.14316/pmp.2017.28.1.27.

Dosimetric Effects of Low Dose 4D CT Using a Commercial Iterative Reconstruction on Dose Calculation in Radiation Treatment Planning: A Phantom Study

• Kim HJ
• Park SY
• Park YH
• Chang AR

• KMID: 2382802
• DOI: http://doi.org/10.14316/pmp.2017.28.1.27

Abstract

We investigated the effect of a commercial iterative reconstruction technique (iDose, Philips) on the image quality and the dose calculation for the treatment plan. Using the electron density phantom, the 3D CT images with five different protocols (50, 100, 200, 350 and 400 mAs) were obtained. Additionally, the acquired data was reconstructed using the iDose with level 5. A lung phantom was used to acquire the 4D CT with the default protocol as a reference and the low dose (one third of the default protocol) 4D CT using the iDose for the spine and lung plans. When applying the iDose at the same mAs, the mean HU value was changed up to 85 HU. Although the 1 SD was increased with reducing the CT dose, it was decreased up to 4 HU due to the use of iDose. When using the low dose 4D CT with iDose, the dose change relative to the reference was less than 0.5% for the target and OARs in the spine plan. It was also less than 1.1% in the lung plan. Therefore, our results suggests that this dose reduction technique is applicable to the 4D CT image acquisition for the radiation treatment planning.

Keyword

Low dose 4D CT; Iterative reconstruction; Treatment planning; CT dose reduction

MeSH Terms

Four-Dimensional Computed Tomography*
Lung
Spine

Figure

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  Fig. 1. Mean change in HU depending on the CT scan parameter for different density materials relative to the default scan parameter.

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  Fig. 2. 1 Standard deviation change in HU depending on the CT scan parameter for different density materials relative to the default scan parameter.

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  Fig. 3. 4D CT images of the lung phantom acquired using the default scan parameter (600 mAs) without iDose (left) and the low dose scan parameter (200 mAs) with iDose (right).

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  Fig. 4. DVH comparison between the dose calculations on the CT images reconstructed with and without using iDose for the Spine 2D parallel-opposite (AP-PA) and VMAT plan.

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  Fig. 5. DVH comparison between the dose calculations on the CT images reconstructed with and without using iDose for the Lung 3D conformal and VMAT plan.

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  Fig. 6. Mean and 1 standard deviation changes in HU when using the x-ray energy of 90 kVp.

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