Forwarded from تصویربرداری پزشکی
Forwarded from Radiology_Tums
👆👆👆
گردآوری شده توسط دانشجویان رادیولوژی دانشگاه علوم پزشکی تهران تحت نظارت مستقیم اساتید دانشگاه علوم پزشکی تهران:
دکتر شهریار شهریاران,عضو هیئت علمی دانشگاه علوم پزشکی تهران
خانم پاکروان مدرس دانشگاه علوم پزشکی تهران.
قابل تهیه در نمایشگاه کتاب غرفه نور دانش.
@Radiologytums
گردآوری شده توسط دانشجویان رادیولوژی دانشگاه علوم پزشکی تهران تحت نظارت مستقیم اساتید دانشگاه علوم پزشکی تهران:
دکتر شهریار شهریاران,عضو هیئت علمی دانشگاه علوم پزشکی تهران
خانم پاکروان مدرس دانشگاه علوم پزشکی تهران.
قابل تهیه در نمایشگاه کتاب غرفه نور دانش.
@Radiologytums
Forwarded from متن یار - تبدیل عکس به متن فارسی
_
93
ത്ത -—ത്ത
acquisition, there is no crosstalk between slices, as may be seen in a 2D acquisition (which leads to a loss of SNR and changes in image contrast in 2D), 3D acquisitions inherently have higher SNR because of the additional data sampling due to phase encoding in the third dimension. Lastly, if one were to acquire the dataset using an isotropic voxel (voxel dimensions equal in all three dimensions), or simply a small voxel with near equal dimensions in all three axes, the dataset may be reformatted with high resolution in any plane. This feature is illustrated in Fig. 45.2, which compares (a) a 2D axial FLAIR scan to (b-d) axial, sagittal, and coronal high-resolution images all reformatted from a single 3D SPACE scan. In this instance, the 2D acquisition was performed with fat saturation, and thus the fat globule, although well depicted (arrow) on (b-d) the SPACE images, is not well seen in (a). Scan times were 4:32 versus 6:32 min:sec for the 2D and 3D scans, respectively, with a 4-mm slice thickness for the 2D scan and a 1 x 1 x 0.9 mm voxel dimension for the 3D scan. Due to the requirement for a small, near isotropic voxel, all contrast-enhanced MR angiographic studies are obtained using 3D technique. Potential negatives to a 3D acquisition (which apply more to 3D MR imaging and not MRA) include scan time (typically longer than for alternative clinical 2D scans) and motion artifacts, the latter often accentuated due to the long scan time and propagated along two axes (as opposed to one in a 2D scan) given that there are two phase encoding directions.
93
ത്ത -—ത്ത
acquisition, there is no crosstalk between slices, as may be seen in a 2D acquisition (which leads to a loss of SNR and changes in image contrast in 2D), 3D acquisitions inherently have higher SNR because of the additional data sampling due to phase encoding in the third dimension. Lastly, if one were to acquire the dataset using an isotropic voxel (voxel dimensions equal in all three dimensions), or simply a small voxel with near equal dimensions in all three axes, the dataset may be reformatted with high resolution in any plane. This feature is illustrated in Fig. 45.2, which compares (a) a 2D axial FLAIR scan to (b-d) axial, sagittal, and coronal high-resolution images all reformatted from a single 3D SPACE scan. In this instance, the 2D acquisition was performed with fat saturation, and thus the fat globule, although well depicted (arrow) on (b-d) the SPACE images, is not well seen in (a). Scan times were 4:32 versus 6:32 min:sec for the 2D and 3D scans, respectively, with a 4-mm slice thickness for the 2D scan and a 1 x 1 x 0.9 mm voxel dimension for the 3D scan. Due to the requirement for a small, near isotropic voxel, all contrast-enhanced MR angiographic studies are obtained using 3D technique. Potential negatives to a 3D acquisition (which apply more to 3D MR imaging and not MRA) include scan time (typically longer than for alternative clinical 2D scans) and motion artifacts, the latter often accentuated due to the long scan time and propagated along two axes (as opposed to one in a 2D scan) given that there are two phase encoding directions.
Forwarded from Sadegh
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ربات: @matnyar_bot
پشتیبانی: @dsupport
ربات: @matnyar_bot
پشتیبانی: @dsupport