ارزیابی کمی اصلاح تضعیف و پراکندگی پرتوها در اسکن پرفیوژن قلب به روش با استفاده از شبیه سازی مونت کارلو ecg-gated spect

زمینه و هدف: در ﭘﺰﺷﻜﻰ ﻫﺴﺘﻪ ای ﻣﻰ ﺗﻮان ﺑﺠﺎی ﺗﺤﻘﻴﻖ و ﺑﺮرﺳﻰ ﺑﺮ روی ﺑﻴﻤﺎر و ﻳﺎ ﭘﺮدازش ﺗﺼﻮﻳﺮ ﺑﻴﻤﺎر، ﺗﺼﺎوﻳﺮ ﺷﺒﻴﻪ ﺳﺎزی ﺷﺪه را ﻣﻮرد ﺑﺮرﺳﻰ ﻗﺮار داد. لذا هدف این مطالعه ارزیابی کمی اصلاح تضعیف و پراکندگی پرتوها در اسکن پرفیوژن قلب به روش با استفاده از شبیه‌سازی مونت کارلو ecg-gated spect بود.روش کار: در این مطالعه تاثیر اعمال تصحیح تضعیف و پراکندگی به روش های دو پنجره انرژیی (dew) و سه پنجره انرژی (tew) در تصویربرداری اسپکت قلب مورد بررسی و ارزیابی قرار گرفت و برای شبیه‌سازی تصویربرداری اسپکت قلب، از کد اختصاصی شبیه سار مونت کارلو gate به عنوان سیستم تصویربرداری اسپکت و از فانتوم دیجیتال xcat با توزیع اکتیویته و نقشه تضعیف مطابق با واقعیت برای مدل‌سازی تنه انسان استفاده شد. یافته‌ها: مقایسه بهبود کنتراست تصاویر در حالت های مختلف اعمال تصحیح تضعیف و پراکندگی نشان می دهد که بیشترین کنتراست تصویر از روش (tew1+ac) با میانگین 25% افزایش حاصل می شود و mse در حالت های مختلف اعمال تصحیح تضعیف و پراکندگی در مقایسه با تصویر مرجع از 51.5 % تا 54.5 % کاهش یافته بود. mse در مقایسه با تصویر مرجع از 1.4 در un_cor تا 1.15، 1.13، 1.12 و 1.14 به ترتیب در ac+tew1، ac+dew، ac وac+tew2 کاهش یافت و نسبت سیگنال به نویز (snr) در تمام روش های اعمال اصلاح پراکندگی همراه با اصلاح تضعیف در مقایسه با اعمال اصلاح تضعیف (ac) تا 71% افزایش نشان داد. نتیجه‌گیری: بر طبق نتایج کمی سازی تصاویر بازسازی شده با بکارگیری اعمال تصحیح پراکندگی همراه با اعمال تصحیح تضعیف امکان‌پذیر است.

quantitative evaluation of attenuation and scattering correction in myocardial perfusion ecg-gated spect using monte carlo simulation

background & aims: nowadays, imaging of the blood supply of the heart muscle by single photon emission computed tomography (spect: single photon emission computed tomography) due to its non-invasive nature and providing information with physiological value and low cost compared to the valuable angiography method. it is highly diagnostic. but these images undergo changes and artifacts under the influence of factors, the result of which is the reduction of the diagnostic accuracy of the images and false positive cases. during the detection process, several physical effects such as attenuation, scattering, and collimator response function affect the frequency of emitted photons; this leads to the destruction of the contrast and as a result of reducing the quantitative and qualitative accuracy of the images. attenuation, as the most destructive factor of spect images, reduces the quality of spect images of heart blood supply and reduces the sensitivity of tests related to the diagnosis of coronary artery diseases, and for non-uniform environments, especially in nuclear imaging of chest areas. and the heart is necessary to produce a map of patient attenuation coefficients. the existence of scattered photons is also one of the main factors of error in quantization; the detection of scattered events affects the contrast of the lesions and causes the lack of image resolution and signal-to-noise ratio. therefore, to correct the attenuation and scattering of the rays in the heart images quantitatively and qualitatively, patterns are needed in spect systems. due to the importance of the topic, various research groups around the world have presented their research and results on correcting the effect of scattering of rays and also correcting the effect of weakening the rays. if there was no limitation of energy resolution, it was easily possible to identify the scattered rays and prevent them from being recorded in the image. because we know that scattered rays lose energy. because gamma rays are single energy and their energy amount is completely known. therefore, each photon with less energy will represent scattered rays, but due to the limited energy resolution of the gamma camera, a range is usually considered on the sides of the main energy, which is called the energy window. it is assumed that the photons recorded in this energy range are primary photons, but in fact, many photons scattered in the body are also recorded in this window. these scattered rays do not carry correct spatial information and lead to a decrease in image resolution and contrast and quantization errors in the image. in nuclear medicine, instead of researching and examining the patient or processing the image of the patient, simulated images can be examined. simulators can provide information about each of the image destruction factors. the purpose of this research is to propose a new method for scattering correction, in this research, a combination of monte carlo and modeling is used for the rapid production of scattered views, and in the proposed method, the two-matrix method is used, this method at the stage of generating mathematical views, dispersion is added and this problem leads to the removal of scattered rays.