Effect of Hip Prosthesis on Photon Beam Characteristics in Radiological Physics

Abstract

Introduction: Aim of study is to investigate the effect of hip prosthesis on 6 and 15 MV photon beam energies. Materials and Methods: Prosthesis was kept at the level of tray position. The measurements were done on Varian Clinac-iX linac. Customized prosthesis, termed as Prosthetic Metal Implant (PMI) was made up of wrought austenitic stainless steel rod and covered with paraffin-wax. ‘Standard prosthesis’ was made up of wrought titanium alloy. The dose profiles were measured for three field sizes i.e. 5, 10 and 20 cm at 100 cm SSD for 6 and 15 MV energies. The perturbation index (PI) was also calculated. Results: Perturbation caused by standard prosthesis was approximately 50% higher than that of PMI. This result may be due to difference in dimension and not because of material composition. Variation of central axis dose might be due to the dimensions of PMI used for experiment which gave intermediate response (e.g. 102.1%, 141.0% and 117.7% for Open, Standard and PMI respectively for 10x10 cm 2 field size, 10 cm depth and 15MV photon beam setup )as compared to the ‘open’ and ‘standard’ prosthesis. Percentage dose at 10 cm for 6MV photon increased rapidly with field-size for PMI. But, for 15MV photon, difference was not significant. Surface dose (Ds) for PMI remains significantly higher for smaller field. Conclusion: The perturbation index varied from 0.05 to 0.22 for the measured energies and gave an idea to the planner to assess the behavior of the prosthesis. This range is applicable for both type of implants and for all clinical field-sizes. The attenuation caused by the prosthesis was significant and this effect should be considered in the treatment planning calculations.

To study the impact of different optimization methods on intensity-modulated radiotherapy and volumetric-modulated arc therapy plans for hip prosthesis patients

“…There were many publications on the planning of hip implant patients. [ 4 16 32 33 ] For the hip prosthesis patients, the optimization strategies used in our study were less explored. We used seven fields for IMRT plans and two arcs for the VMAT plans.…”

“…The radiotherapy (RT) starts with the simulation of a patient and computed tomography (CT) images are standard 3-dimensional (3D) imaging procedure for RT patients. The presence of metal in the treatment region changes the attenuation profiles of photon beams passing through it[ 4 ] because of these profiles and scattered photons different artifacts are produced in the CT images. [ 5 6 7 ] A few artifacts seen during CT procedures are streaking, shading, rings, and distortions.…”

The impact of metal implants on the dose and clinical outcome of radiotherapy (Review)

“…Stainless steel is widely used in bone fixation, cardiovascular systems, catheters, surgical instruments and dental crowns ( 30 ). Furthermore, Bhushan et al ( 27 ) studied the effect of stainless-steel hip prosthesis on radiation using a customized prosthesis containing wrought austenitic stainless steel. It was observed that for 6 MV of photon irradiation, at a depth of 10 cm below the prosthesis, with field sizes of 5x5, 10x10 and 20x20, the dose attenuation was 8.3, 7.4 and 7.5% when the prosthesis was present compared with in its absence.…”

Feasibility of Monte-Carlo algorithm in comparison with collapse-cone dose calculation algorithm of a commercial treatment planning system in the presence of high-density metallic implant: a dosimetric study

“…All these information are required for executing the dose computations with precision. Bhushan et al [5] reported that dose perturbation changes with a factor for different energies also. Patients had already completed the total course of treatment.…”