TY - JOUR
T1 - Effect of spine hardware on small spinal stereotactic radiosurgery dosimetry
AU - Wang, Xin
AU - Yang, James N.
AU - Li, Xiaoqiang
AU - Tailor, Ramesh
AU - Vassilliev, Oleg
AU - Brown, Paul
AU - Rhines, Laurence
AU - Chang, Eric
PY - 2013/10/7
Y1 - 2013/10/7
N2 - Monte Carlo (MC) modeling of a 6 MV photon beam was used to study the dose perturbation from a titanium rod 5 mm in diameter in various small fields range from 2 × 2 to 5 × 5 cm2. The results showed that the rod increased the dose to water by ∼6% at the water-rod interface because of electron backscattering and decreased the dose by ∼7% in the shadow of the rod because of photon attenuation. The Pinnacle3 treatment planning system calculations matched the MC results at the depths more than 1 cm past the rod when the correct titanium density of 4.5 g cm-3 was used, but significantly underestimated the backscattering dose at the water-rod interface. A CT-density table with a top density of 1.82 g cm-3 (cortical bone) is a practical way to reduce the dosimetric error from the artifacts by preventing high density assignment to them, but can underestimates the attenuation by the titanium rod by 6%. However, when multi-beam with intensity modulation is used in actual patient spinal stereotactic radiosurgery treatment, the dosimetric effect of assigning 4.5 instead of 1.82 g cm-3 to titanium implants is complicated. It ranged from minimal effect to 2% dose difference affecting 15% target volume in the study. When hardware is in the beam path, density override to the titanium hardware is recommended.
AB - Monte Carlo (MC) modeling of a 6 MV photon beam was used to study the dose perturbation from a titanium rod 5 mm in diameter in various small fields range from 2 × 2 to 5 × 5 cm2. The results showed that the rod increased the dose to water by ∼6% at the water-rod interface because of electron backscattering and decreased the dose by ∼7% in the shadow of the rod because of photon attenuation. The Pinnacle3 treatment planning system calculations matched the MC results at the depths more than 1 cm past the rod when the correct titanium density of 4.5 g cm-3 was used, but significantly underestimated the backscattering dose at the water-rod interface. A CT-density table with a top density of 1.82 g cm-3 (cortical bone) is a practical way to reduce the dosimetric error from the artifacts by preventing high density assignment to them, but can underestimates the attenuation by the titanium rod by 6%. However, when multi-beam with intensity modulation is used in actual patient spinal stereotactic radiosurgery treatment, the dosimetric effect of assigning 4.5 instead of 1.82 g cm-3 to titanium implants is complicated. It ranged from minimal effect to 2% dose difference affecting 15% target volume in the study. When hardware is in the beam path, density override to the titanium hardware is recommended.
UR - http://www.scopus.com/inward/record.url?scp=84884630828&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84884630828&partnerID=8YFLogxK
U2 - 10.1088/0031-9155/58/19/6733
DO - 10.1088/0031-9155/58/19/6733
M3 - Article
C2 - 24018829
AN - SCOPUS:84884630828
SN - 0031-9155
VL - 58
SP - 6733
EP - 6747
JO - Physics in medicine and biology
JF - Physics in medicine and biology
IS - 19
ER -