Precision radiotherapy using monochromatic inverse Compton x‐ray sources

Abstract

Purpose The dosimetric properties of inverse Compton (IC) x‐ray sources were investigated to determine their utility for stereotactic radiation therapy. Methods Monte Carlo simulations were performed using the egs brachy user code of EGSnrc. Nominal IC source x‐ray energies of 80 and 150 keV were considered in this work. Depth‐dose and lateral dose profiles in water were calculated, as was dose enhancement in the bone. Further simulations were performed for brain and spine treatment sites. The impact of gold nanoparticle doping was also investigated for the brain treatment site. Analogous dose calculations were performed in a clinical treatment planning system using a clinical 6 MV photon beam model and were compared to the Monte Carlo simulations. Results Both 80 and 150 keV IC beams were observed to have sharp 80–20 penumbra (i.e., < 0.1 mm) with broad low‐dose tails in water. For reference, the calculated penumbra for the 6 MV clinical beam was 3 mm. Maximum dose enhancement factors in bone of 3.1, 1.4, and 1.1 were observed for the 80, 150 keV, and clinical 6 MV beams, respectively. The plan quality for the single brain metastasis case was similar between the IC beams and the 6 MV beam without gold nanoparticles. As the concentration of gold within the target increased, the V12 Gy to the normal brain tissue and Dmax within the target volume significantly decreased and the conformity significantly improved, which resulted in superior plan quality over the clinical 6 MV beam plan. In the spine cases, the sharp penumbra and enhanced dose to bone of the IC beams produced superior plan quality (i.e., better conformity, normal tissue sparing, and spinal cord sparing) as compared to the clinical 6 MV beam plans. Conclusions The findings from this work indicate that inverse Compton x‐ray sources are well suited for stereotactic radiotherapy treatments due to their sharp penumbra and dose enhancement around high atomic number materials. Future work includes investigating the properties of intensity‐modulated inverse Compton x‐ray sources to improve the homogeneity within the target tissue.

Compact all-optical precision-tunable narrowband hard Compton X-ray source

“…The ongoing development of high power kilohertz repetition rate laser systems 44 – 46 can lead to photon fluxes photons/s in percent-level bandwidths in a few-mrad pencil beam. In addition to various imaging applications, a light source with the demonstrated tuning range could open the possibility for a single compact device to be used for both diagnostics 37 and subsequent precision radiation therapy 9 . The source demonstrated here will dramatically expand access to high brightness, narrow-band, tunable photon sources for a wide range of scientific and medical applications while the femtosecond duration and inherent optical synchronisation will enable many more advanced pump-probe experiments.…”

“…Since the demonstration of X-ray imaging by Röntgen in 1895 1 , development of bright X-ray sources has allowed harnessing the power of X-rays in ever-evolving and broadening fields of research and applications, leading to enormous advances in topics as varied as advanced imaging 2 – 5 and radiotherapy 6 – 9 modalities as well as in crystallography applications 10 – 13 . Examples of medical breakthroughs relying on brilliant X-ray sources include K-edge subtraction (KES) imaging 14 , a potential alternative to digital subtraction angiography, as well as X-ray fluorescence imaging (XFI) 15 , enabling in-vivo pharmacokinetic studies.…”

Hard X-ray inverse Compton scattering at photon energy of 87.5 keV

“…Free electrons should be able to propagate for micron meter ranges and thus uniform activation is anticipated. Details of Monte Carlo simulations of gold nanoparticle dose enhancement of Inverse-Compton based monoenergetic photon beams has been investigated [17,18], and these studies illuminate our discussion further. The experimental capability of creating a monochromatic hard X-ray source enables the precise physical study of complicated microscopic activation processes including fast pulse effects.…”

“…The use of AuNP for photon activation [14,17,18,26] relies on the higher optical thickness of high-Z metal nanoparticles and the relative transparency of surrounding water and organic materials. For material research or trace element analysis by hard X-ray radiography, although surrounding materials will show larger variety, as long as atomic number of elements are relatively low, a similar description would be valid.…”

“…This provides a gateway to much higher energy photons, where one may extend the reach of the source to over 100 keV, and on up to MeV or even GeV levels at modest electron beam energy. Compelling examples of potential application of monochromatic ICS X-ray sources in the service of medicine are X-ray computed tomographys [16] and photon activation therapy [17,18].…”