ﺑﺮﺭﺳﻲ ﺗﺄﺛﻴﺮ ﻓﻠﺰﺍﺕ ﮐﺎﺷﺘﻪ ﺷﺪﻩ ﺩﺭ ﻧﺎﺣﻴﻪ ﻟﮕﻦ ﻭ ﺁﺭﺗﻴﻔﮑﺖﻫﺎﻱ ﻓﻠﺰﻱ ﻧﺎﺷﻲ ﺍﺯ ﺁﻥ ﺩﺭ ﺗﻮﺯﻳﻊ ﺩﺯ ﻧﺎﺣﻴﻪ ﻟﮕﻦ ﺩﺭ ﭘﺮﺗﻮﺩﺭﻣﺎﻧﻲ

THE EFFECTS OF METAL IMPLANT an‎d METAL ARTIFACT ON THE DOSE DISTRIBUTION DURING RADIATION THERAPY OF THE PELVIC REGION

ﭘﻴﺶﺯﻣﻴﻨﻪ ﻭ ﻫﺪﻑ: ﮔﺎﻫﻲ ﺑﻴﻤﺎﺭﺍﻥ ﺳﺮﻃﺎﻧﻲ، ﺩﺍﺭﺍﻱ ﮐﺎﺷﺖ ﻫﺎﻱ ﻓﻠﺰﻱ ﺩﺭ ﻧﺎﺣﻴﻪ ﻟﮕﻦ ﻭ ﻓﻤﻮﺭﺍﻝ ﻫﺴﺘﻨﺪ. ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ ﺑﺮﻫﻤﮑﻨﺶﻫﺎﻱ ﻓﻮﺗﻮﻥ ﺑﺎ ﻣﺎﺩﻩ ﻭ ﻣﻮﻗﻌﻴﺖ ﻧﺎﺣﻴﻪ ﺩﺭﻣﺎﻥ ﻧﺴﺒﺖ ﺑﻪ ﮐﺎﺷﺖ ﻓﻠﺰﻱ، ﻭﺟﻮﺩ ﭼﻨﻴﻦ ﻋﻨﺎﺻﺮﻱ ﻣﻲﺗﻮﺍﻧﺪ ﻣﻨﺠﺮ ﺑﻪ ﺗﺄﺛﻴﺮ ﺑﺮ ﺩﻭﺯ ﺩﺭﻳﺎﻓﺘﻲ ﻧﺴﺒﺖ ﺑﻪ ﺩﻭﺯ ﺑﻴﺶ ﺑﻴﻨﻲ ﺷﺪﻩ ﺷﻮﺩ. ﻫﻤﭽﻨﻴﻦ، ﮐﺎﺷﺖ ﻫﺎﻱ ﻓﻠﺰﻱ ﺑﻪ ﺩﻟﻴﻞ ﻋﺪﺩ ﺍﺗﻤﻲ ﻣﺆﺛﺮ ﺑﺎﻻ ﻭ ﻣﺘﻔﺎﻭﺕ ﻧﺴﺒﺖ ﺑﻪ ﺑﺎﻓﺖ ﺑﺪﻥ ﺑﺎﻋﺚ ﺍﻳﺠﺎﺩ ﺁﺭﺗﻴﻔﮑﺖﻫﺎﻱ ﻓﻠﺰﻱ ﺩﺭ ﺗﺼﺎﻭﻳﺮ ﺳﻲ ﺗﻲ ﺍﺳﮑﻦ ﻣﻲﺷﻮﻧﺪ. ﻫﺪﻑ ﺍﺯ ﺍﻳﻦ ﻣﻄﺎﻟﻌﻪ، ﺑﺮﺭﺳﻲ ﻣﻴﺰﺍﻥ ﺗﺄﺛﻴﺮ ﮐﺎﺷﺖ ﻭ ﺁﺭﺗﻴﻔﮑﺖﻫﺎﻱ ﻓﻠﺰﻱ ﺑﺮ ﺗﻮﺯﻳﻊ ﺩﻭﺯ ﻧﺎﺣﻴﻪ ﺩﺭﻣﺎﻧﻲ ﺍﺳﺖ. ﻣﻮﺍﺩ ﻭ ﺭﻭﺵ ﮐﺎﺭ: ﺩﺭ ﺍﻳﻦ ﻣﻄﺎﻟﻌﻪ، ﺗﺼﺎﻭﻳﺮ CT ﻫﻔﺖ ﺑﻴﻤﺎﺭ ﻣﺮﺩ ﻣﺒﺘﻼ ﺑﻪ ﺳﺮﻃﺎﻥ ﭘﺮﻭﺳﺘﺎﺕ ﮐﻪ ﺩﺍﺭﺍﻱ ﮐﺎﺷﺖ ﻓﻠﺰﻱ ﺗﻴﺘﺎﻧﻴﻮﻡ ﺩﺭ ﻧﺎﺣﻴﻪ ﻓﻤﻮﺭ ﺑﻮﺩﻩ ﻭ ﺟﻬﺖ ﺩﺭﻣﺎﻥ ﺑﻪ ﺑﻴﻤﺎﺭﺳﺘﺎﻥ ﺍﻣﺎﻡ ﺧﻤﻴﻨﻲ ﺗﻬﺮﺍﻥ ﻣﺮﺍﺟﻌﻪ ﮐﺮﺩﻩ ﺑﻮﺩﻧﺪ، ﻣﻮﺭﺩ ﺑﺮﺭﺳﻲ ﻗﺮﺍﺭ ﮔﺮﻓﺘﻨﺪ. ﺩﺭ ﺍﻳﻦ ﺑﻴﻤﺎﺭﺍﻥ، ﺗﻮﺯﻳﻊ ﺩﻭﺯ ﺍﺑﺘﺪﺍ ﺑﺎ ﺩﺭ ﻧﻈﺮ ﮔﺮﻓﺘﻦ ﺗﺄﺛﻴﺮ ﺁﺭﺗﻴﻔﮑﺖ ﻓﻠﺰﻱ )ﻃﺮﺡ A( ﻭ ﻧﻴﺰ ﺗﺼﺤﻴﺢ ﺗﺼﻮﻳﺮ ﺳﻲ ﺗﻲ ﺍﺳﮑﻦ ﻭ ﺗﺒﺪﻳﻞ ﭼﮕﺎﻟﻲ ﺍﻟﮑﺘﺮﻭﻧﻲ ﻧﻮﺍﺣﻲ ﺩﺍﺭﺍﻱ ﺁﺭﺗﻴﻔﮑﺖ ﺑﻪ ﺑﺎﻓﺖ ﻧﺮﻡ )ﻃﺮﺡ B( ﻭ ﻫﻤﭽﻨﻴﻦ ﻭﺟﻮﺩ ﮐﺎﺷﺖ ﻓﻠﺰﻱ ﻭ ﻋﺒﻮﺭ ﭘﺮﺗﻮ ﺍﺯ ﻓﻠﺰ )ﻃﺮﺡ C( ﻭ ﺳﭙﺲ ﺗﻐﻴﻴﺮ ﭼﮕﺎﻟﻲ ﺍﻟﮑﺘﺮﻭﻧﻲ ﻓﻠﺰ ﺑﻪ ﺍﺳﺘﺨﻮﺍﻥ ﻣﻌﻤﻮﻟﻲ )ﻃﺮﺡ D( ﺗﻮﺳﻂ ﺳﻴﺴﺘﻢ ﻃﺮﺍﺣﻲ ﺩﺭﻣﺎﻥ ﻣﻮﻧﺎﮐﻮ ﻣﺤﺎﺳﺒﻪ ﺷﺪ. ﻧﺘﺎﻳﺞ ﺑﻪ ﺩﺳﺖ ﺁﻣﺪﻩ ﺍﺯ ﺳﻴﺴﺘﻢ ﻃﺮﺍﺣﻲ ﺩﺭﻣﺎﻥ ﻣﻮﻧﺎﮐﻮ ﺑﻪ ﻧﺮﻡ ﺍﻓﺰﺍﺭ VeriSoft ﺍﻧﺘﻘﺎﻝ ﻳﺎﻓﺖ. ﺍﺧﺘﻼﻑ ﺩﻭ ﻃﺮﺡ ﺩﺭﻣﺎﻧﻲ A ﻭ B ﺑﻪﻃﻮﺭ ﮐﻤﻲ ﻭ ﺑﺮ ﺍﺳﺎﺱ ﺷﺎﺧﺺ ﮔﺎﻣﺎ 3mm3 ﺑﻪﻭﺳﻴﻠﻪ ﺍﻳﻦ ﻧﺮﻡ ﺍﻓﺰﺍﺭ ﻣﻘﺎﻳﺴﻪ ﻭ ﻣﻮﺭﺩ ﺑﺮﺭﺳﻲ ﻗﺮﺍﺭ ﮔﺮﻓﺖ. ﻫﻤﭽﻨﻴﻦ ﺗﺄﺛﻴﺮ ﮐﺎﺷﺖ ﺗﻴﺘﺎﻧﻴﻮﻣﻲ ﺩﺭ ﺗﻀﻌﻴﻒ ﭘﺮﺗﻮ )ﻃﺮﺡ C ﻭ D( ﻧﻴﺰ ﺑﻪ ﺻﻮﺭﺕ ﮐﻤﻲ ﻣﻮﺭﺩ ﺑﺮﺭﺳﻲ ﻭ ﺗﺠﺰﻳﻪ ﻭ ﺗﺤﻠﻴﻞ ﻗﺮﺍﺭ ﮔﺮﻓﺖ. ﻳﺎﻓﺘﻪﻫﺎ: ﻧﺘﺎﻳﺞ ﺍﻳﻦ ﻣﻄﺎﻟﻌﻪ ﻧﺸﺎﻥ ﺩﺍﺩ ﮐﻪ ﻣﻴﺰﺍﻥ ﺍﺧﺘﻼﻑ ﻣﺎﻧﻴﺘﻮﺭﻳﻮﻧﻴﺖ ﻣﺤﺎﺳﺒﻪ ﺷﺪﻩ ﺩﺭ ﺩﻭ ﺻﻮﺭﺕ ﺗﺼﺤﻴﺢ ﻭ ﻋﺪﻡ ﺗﺼﺤﻴﺢ ﭼﮕﺎﻟﻲ ﺍﻟﮑﺘﺮﻭﻧﻲ ﻧﻮﺍﺣﻲ ﺣﺎﻭﻱ ﺁﺭﺗﻴﻔﮑﺖ ﻓﻠﺰﻱ، ﺍﺯ 0/81 ﺗﺎ 3/78 ﻣﺎﻧﻴﺘﻮﺭﻳﻮﻧﻴﺖ ﺑﻪ ﺍﺯﺍﻱ ﻫﺮ ﺟﻠﺴﻪ ﺩﺭﻣﺎﻥ ﻣﻲﺑﺎﺷﺪ. ﻫﻤﭽﻨﻴﻦ ﻭﺟﻮﺩ ﻓﻠﺰ ﺩﺭ ﻣﺴﻴﺮ ﭘﺮﺗﻮ ﻣﻲﺗﻮﺍﻧﺪ ﺗﺎ ﺣﺪﻭﺩ 3ﺩﺭﺻﺪ ﺍﺧﺘﻼﻑ ﻧﺴﺒﺖ ﺑﻪ ﻋﺒﻮﺭ ﭘﺮﺗﻮ ﺍﺯ ﺍﺳﺘﺨﻮﺍﻥ ﺍﻳﺠﺎﺩ ﮐﻨﺪ. ﻧﺘﻴﺠﻪ ﮔﻴﺮﻱ: ﺑﻨﺎﺑﺮﺍﻳﻦ، ﺟﻬﺖ ﭘﻴﺎﺩﻩ ﺳﺎﺯﻱ ﺩﻗﻴﻖ ﺩﺭﻣﺎﻥ ﺑﺎﻳﺪ ﺗﺼﺤﻴﺤﺎﺕ ﻻﺯﻡ ﻗﺒﻞ ﺍﺯ ﺍﻳﺠﺎﺩ ﻃﺮﺡ ﺩﺭﻣﺎﻧﻲ ﺑﺮ ﺭﻭﻱ ﺗﺼﺎﻭﻳﺮ CT ﺍﻧﺠﺎﻡ ﺷﻮﺩ ﺗﺎ ﻣﻴﺰﺍﻥ ﺧﻄﺎﻫﺎﻱ ﻣﺮﺑﻮﻁ ﺑﻪ ﻣﺤﺎﺳﺒﺎﺕ ﻣﺎﻧﻴﺘﻮﺭﻳﻮﻧﻴﺖ ﺑﻪ ﺣﺪﺍﻗﻞ ﺑﺮﺳﺪ.

Background & Aims: In some cancer patients, there are metal implants in pelvic and femoral regions. Due to the interactions of the photon with matter and location of treating region and metal implant, such high atomic numbered elements can influence absorbed dose compared to predicted values. Also, metal implants cause metal artifacts in CT images due to their highly effective atomic number compared to body texture. The aim of this study was to evaluate the effect of metal implants and metal artifacts on the dose distribution in the treatment volume. Materials & Methods: In this study, CT images of seven prostate cancer patients who were referred to Imam Khomeini hospital, Tehran for treatment with titanium metal implant in femur region were investigated. In these patients, initially dose distributions were calculated by Monaco treatment planning system considering the effects of metal artifacts (plan A), correcting CT images and modifying electron density of artifact regions to soft tissue (plan B), transmission of photon through metal (plan C) and modifying electron density of metal to bone (plan D). The obtained results from Monaco treatment planning system were then transferred to Verisoft software. The quantitative differences of plans A and B were analyzed using a gamma index of 3%/3mm in this software. Also, the effects of metal implant in beam attenuation (Plans C and D) were analyzed quantitatively. Results: This study showed that the difference of calculated monitor units in corrected and not-corrected electron density of metal artifact regions ranged between 0.81-3.78 monitor units per fraction. Also the presence of metal in beam path can lead to a 3% difference compared to beam passing through bone. Conclusion: Therefore, for the precise implementation of the treatment, necessary corrections on CT images should be considered before the treatment planning to minimize the errors related to the monitor unit calculations