Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Jan;90(1069):20160426.
doi: 10.1259/bjr.20160426. Epub 2016 Oct 27.

A kernel-based dose calculation algorithm for kV photon beams with explicit handling of energy and material dependencies

Anna Merle Reinhart  1 , Martin F Fast  1 , Peter Ziegenhein  1 , Simeon Nill  1 , Uwe Oelfke  1
Affiliations

A kernel-based dose calculation algorithm for kV photon beams with explicit handling of energy and material dependencies

Anna Merle Reinhart et al. Br J Radiol. 2017 Jan.

Abstract

Objective: Mimicking state-of-the-art patient radiotherapy with high-precision irradiators for small animals is expected to advance the understanding of dose-effect relationships and radiobiology in general. We work on the implementation of intensity-modulated radiotherapy-like irradiation schemes for small animals. As a first step, we present a fast analytical dose calculation algorithm for keV photon beams.

Methods: We follow a superposition-convolution approach adapted to kV X-rays, based on previous work for microbeam therapy. We assume local energy deposition at the photon interaction point due to the short electron ranges in tissue. This allows us to separate the dose calculation into locally absorbed primary dose and the scatter contribution, calculated in a point kernel approach. We validate our dose model against Geant4 Monte Carlo (MC) simulations and compare the results to Muriplan (XStrahl Ltd, Camberley, UK).

Results: For field sizes of (1 mm)2 to (1 cm)2 in water, the depth dose curves show a mean disagreement of 1.7% to MC simulations, with the largest deviations in the entrance region (4%) and at large depths (5% at 7 cm). Larger discrepancies are observed at water-to-bone boundaries, in bone and at the beam edges in slab phantoms and a mouse brain. Calculation times are in the order of 5 s for a single beam.

Conclusion: The algorithm shows good agreement with MC simulations in an initial validation. It has the potential to become an alternative to full MC dose calculation. Advances in knowledge: The presented algorithm demonstrates the potential of kernel-based dose calculation for kV photon beams. It will be valuable in intensity-modulated radiotherapy and inverse treatment planning for high precision small-animal radiotherapy.

PubMed Disclaimer

Figures

Figure 1.
Figure 1.
Workflow of the developed dose calculation algorithm.
Figure 2.
Figure 2.
Comparison of the analytical dose engine with Muriplan and Monte Carlo (MC) simulations in water. Depth dose curves (a,c,e) and lateral profiles at a depth of 6 mm (b,d,f) are shown for three different field sizes [(1 mm)2, a,b; (5 mm)2, c,d; (10 mm)2, e,f]. The depth dose curves are normalized to the value at 2cm depth. The local percentage differences were smoothed with a three-median filter to reduce the visual impact of MC noise.
Figure 3.
Figure 3.
Comparison of the depth dose curves of (5 mm)2 fields, normalized to the value at 2 cm depth, calculated with the analytical dose engine, Muriplan and Monte Carlo (MC) simulations in slab phantoms of soft tissue with bone (a) and lung (b) inserts. The local percentage differences, smoothed with a three-median filter, are shown in the bottom row.
Figure 4.
Figure 4.
Dose distributions from a five-field (3 mm)2 irradiation calculated on a mouse cone beam CT using the new dose engine (a), Monte Carlo (MC) simulations (b) and Muriplan (c). The absolute dose differences are shown in (d) and (e).
See this image and copyright information in PMC

References

    1. Butterworth KT, Prise KM, Verhaegen F. Small animal image-guided radiotherapy: status, considerations and potential for translational impact. Br J Radiol 2015; 88: 20140634. doi: https://doi.org/10.1259/bjr.20140634 - DOI - PMC - PubMed
    1. Wong J, Armour E, Kazanzides P, Iordachita I, Tryggestad E, Deng H, et al. . High-resolution, small animal radiation research platform with x-ray tomographic guidance capabilities. Int J Radiat Oncol Biol Phys 2008; 71: 1591–9. doi: https://doi.org/10.1016/j.ijrobp.2008.04.025 - DOI - PMC - PubMed
    1. Zhou H, Rodriguez M, van den Haak F, Nelson G, Jogani R, Xu J, et al. . Development of a micro-computed tomography-based image-guided conformal radiotherapy system for small animals. Int J Radiat Oncol Biol Phys 2010; 78: 297–305. doi: https://doi.org/10.1016/j.ijrobp.2009.11.008 - DOI - PMC - PubMed
    1. Clarkson R, Lindsay PE, Ansell S, Wilson G, Jelveh S, Hill RP, et al. . Characterization of image quality and image-guidance performance of a preclinical microirradiator. Med Phys 2011; 38: 845–56. doi: https://doi.org/10.1118/1.3533947 - DOI - PMC - PubMed
    1. Stojadinovic S, Low DA, Hope AJ, Vicic M, Deasy JO, Cui J, et al. . MicroRT-small animal conformal irradiator. Med Phys 2007; 34: 4706–16. doi: https://doi.org/10.1118/1.2799887 - DOI - PubMed