%0 Journal Article
%T Proton Beam Ocular Treatment in Eyes with Intraocular Silicone Oil: Effects on Physical Beam Parameters and Clinical Relevance of Silicone Oil in EYEPLAN Dose-Volume Histograms
%A Inder K. Daftari
%A Kavita K. Mishra
%A Michael Seider
%A Bertil E. Damato
%J International Journal of Medical Physics,Clinical Engineering and Radiation Oncology
%P 347-362
%@ 2168-5444
%D 2018
%I Scientific Research Publishing
%R 10.4236/ijmpcero.2018.73029
%X Proton
beam therapy (PBRT) is an essential tool in the treatment of certain ocular
tumors due to its characteristic fall-off and sharp beam parameters at critical
structures. Review of clinical cases in our ocular PBRT program identified
patients with silicone oil used as an intraocular tamponade following pars
plana vitrectomy for repair of retinal detachment. Patient¡¯s eye may be filled
with silicone oil prior to PBRT for an ocular tumor. The objective of this
study was to extend our knowledge of the physical characteristics of proton
beams in silicone oil by measuring dose within a silicone tank itself, hence
better representing the surgical eye, as well as applying the range changes to
EYEPLAN software to estimate clinical impact. The relevant proton beam physical
parameters in silicone oil were studied using a 67.5 MeV un-modulated proton
beam. The beam parameters being defined included: 1) residual range; 2)
peak/plateau ratio; 3) full width at half maximum (FWHM) of the Bragg peak; and
4) distal penumbra. Initially, the dose uniformity of the proton beam was
confirmed at 10 mm and 28 mm depth, corresponding to plateau and peak region of
the Bragg peak using Gefchromic film. Once the beam was established as expected,
three sets of measurements of the beam parameters were taken in</span><span style=\"font-family:Verdana;\">:</span><span style=\"font-family:Verdana;\"> a) water (control); b) silicone-1000 oil and water;
and c) silicone-1000 oil only. Central-axis depth-ionization measurements were
performed in a tank (¡°main tank¡±) with a 0.1cc ionization chamber (Model IC-18,
Far west) having walls made of Shonka A150 plastic. The tank was 92 mm (length) </span><span style=\"font-family:&quot;\"><span style=\"font-family:Verdana;\">¡Á</span><span style=\"font-family:Verdana;\"> 40 mm (height) </span><span style=\"font-family:Verdana;\">¡Á</span><span style=\"font-family:Verdana;\"> 40 mm (depth). The tank had a 0.13 mm thick
kapton entrance window through which the proton beam was incident. The
ionization chamber was always positioned in the center of the circular field of
diameter 30 mm with the phantom surface at isocenter. The ionization chamber
measurements were taken at defined depths in increments of 2 mm, from 0 to 35
mm. To define the effect of silicone oil on the physical characteristics of
proton beam, the above-defined three sets of measurements were made. In the
first run (a), the Bragg-peak measurements were made in the main tank filled
with water. In the second run (b), a second smaller tank filled with 10 mm
depth silicone oil was
%K Proton Beam Therapy
%K Uveal Melanoma
%K Depth Dose and Silicone Oil
%U http://www.scirp.org/journal/PaperInformation.aspx?PaperID=86743