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. 2006 May 25;7(2):58-63.
doi: 10.1120/jacmp.v7i2.2236.

The dosimetric effect of inhomogeneity correction in dynamic conformal arc stereotactic body radiation therapy for lung tumors

Affiliations

The dosimetric effect of inhomogeneity correction in dynamic conformal arc stereotactic body radiation therapy for lung tumors

Brian D Kavanagh et al. J Appl Clin Med Phys. .

Abstract

For patients treated with lung stereotactic body radiation therapy (SBRT) using dynamic conformal arcs, the influence of inhomogeneity correction (IC) on normal tissue and tumor dosimetry was studied. For the same numbers of monitor units, the planning target volume equivalent uniform doses calculated without path-length IC were lower than those calculated with IC (mean difference 18%, range 1-34%; p < 0.0001). Normal lung dose differences were of the same magnitude in opposite direction. In reports of SBRT, it will be helpful to maintain clear communication about the type of IC used to avoid future uncertainties about true normal tissue tolerance and tumor dose-response relationships.

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Figures

Figure 1
Figure 1
The lung phantom used for evaluating the inhomogeneity correction algorithm. The phantom allowed dose measurement via one of several measurement access points: at the isocenter, at the tumor—lung interface, within the lung‐equivalent material, and at the lung—tissue interface. Top panel: cross‐sectional sketch. The depth was 40 cm. Tissue‐like acrylic layers (density 1.0g/cm3) of 4 cm thickness surround lung‐equivalent polyurethane foam (0.32g/cm3), in the center of which is a tumor‐like acrylic section (1.0g/cm3). Center panel: photograph of the phantom with the ion chamber placed in the isocenter. Lower panel: schematic representation of the dynamic conformal arcs used to simulate an SBRT treatment.
Figure 2
Figure 2
Coronal (left) and axial (right) composite locations of planning target volumes treated. Those marked with an X are lesions for which recalculation of the equivalent uniform dose without inhomogeneous correction (IC) differed by more than 15% from the value obtained with IC; for those marked with an O, the difference was less than 15%. See Results section for additional explanation.

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