بررسی تأثیرات پهنای باند دریافتی تصویربرداری تشدید مغناطیسی بر پاسخ دزیمتر ژلی پلیمری PAGATUG

نویسنده

دانشگاه بین المللی امام خمینی قزوین

10.22052/6.1.29

چکیده

هدف از این پژوهش بررسی تأثیرات پهنای باند دریافتی تصویربرداری تشدید مغناطیسی (ام­ آر ­آی) بر پاسخ نهائی دزیمتر ژلی پلیمری PAGATUG می­باشد. افزایش پهنای باند منجر به کاهش زمان نمونه ­برداری می­ شود که کاهش زمان تصویربرداری را نتیجه می­دهد. بنابراین با انتخاب درست پهنای باند می­توان هزینه تمام شده تصویربرداری و به دنبال آن مجموع هزینه دزیمتری ژلی پلیمری را کاهش داد. به این منظور دزیمتر ژلی پلیمری PAGATUG ساخته شد و یک روز پس از ساخت با استفاده از سیستم کلینیکی کبالت 60 مورد پرتودهی قرار گرفت. پس از پرتودهی با استفاده از یک دستگاه ام­آر­آی 5/1 تسلا پاسخ ژل مورد بازخوانی قرار گرفت. پهنای باندهای 60، 80، 90، 100 و 120 هرتز بر پیکسل (Hz/pixel) برای بازخوانی انتخاب شد. آهنگ بازگشت مغناطیسی، حساسیت دزیمتر و قدرت تفکیک دز مورد بررسی قرار گرفت. در پهنای باندهای مورد بررسی، با تغییر پهنای باند مقدار R2 و حساسیت دزیمتر به­ طور معنی­داری تغییر نمی­کرد. با افزایش پهنای باند به Hz/pixel 90 قدرت تفکیک دز به­ طور معنی­ داری بدتر شد. بنابراین پهنای باند Hz/pixel 90 به­ عنوان پهنای باند بهینه مشخص شد. محاسبات نظری نشان داد که با انتخاب پهنای باند Hz/Pixel 90 آرتیفکت، جابه­ جایی شیمیائی mm 82/0 می­باشد که از مرتبه یک پیکسل بود. با این انتخاب زمان تصویربرداری حداقل 22% نسبت به تصویربرداری با پهنای باند Hz/pixel 60 کاهش پیدا می­ کرد.
 

کلیدواژه‌ها


عنوان مقاله [English]

An investigation in the effects of MRI receive bandwidth on PAGATUG polymer gel dosimeter response

نویسنده [English]

  • Sayed Mohammad Mahdi Abtahi
چکیده [English]

The aim of this research is to investigate the effects of the band width of magnetic resonance imaging (MRI) on the response of the PAGATUG polymer gel dosimeter. Sampling time decreases by increase in receive band width. Therefore, the scan time can decrease by increase in receive band width. Hence, the cost of gel dosimetry reduces by proper choose of MRI receive band width. To this aim the PAGATUG polymer gel dosimeter was prepared. The polymer gel cuvettes were irradiated using a clinical 60Co one day after preparation. Afterward, the gels responses were readout using a 1.5­T MRI system. Receive band widths of 60, 80, 90, 100 and 120 Hz/pixel were selected for imaging protocols. It was found that the R2 responses and the R2 sensitivities were not changed significantly by varying the receive band width. However, for receive band widths more than 90 Hz/pixel the dose resolution was decreased significantly. It is suggested to select the receive band width of 90 Hz/pixel for PAGATUG polymer gel dosimeters scanning. Theoretical calculations show that a receive band width of 90 Hz/Pixel causes a chemical shift of 0.82 mm which is of order of one pixel dimension. By using this receive band width the scanning time were reduced by 22% from receive band width of 60 Hz/pixel.

کلیدواژه‌ها [English]

  • Polymer gel dosimetry
  • Magnetic Resonance Imaging
  • Receive band width
  • Spin-spin relaxation rate
  • Sensitivity
  • Dose resolution
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