mri thach
TRANSCRIPT
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Magnet Gradient Coil RF Coil
Source: Joe Gati, photos
RF Coil
3T magnet
gradient coil(inside)
Các thành phần máy
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x 60,000 =
Từ trường B0
Source: www.spacedaily.com
B0
Robarts Research Institute 3T
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Sự an toàn
Source: www.howstuffworks.com Source: http://www.simplyphysics.com/flying_objects.html
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Proton thẳng hàng trong B0
longitudinalaxis
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Phát sóng RF
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ELECTROMAGNETIC WAVES
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RELAXATION - T1
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T1 and TR
Source: Mark Cohen’s web slides
T1 = recovery of longitudinal magnetization (B0)
due to realignment of spinsTR (time to repetition) = time to wait after excitation before sampling T1
= time before next RF excitation
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RELAXATION - T2
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T2 and TE
Source: Mark Cohen’s web slides
T2 = decay of transverse (B1) magnetization
due to dephasing of spinsTE (time to echo) = time to wait before sampling T2
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Ghi nhận sóng cộng hưởng từ
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K-SPACE
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K-SPACE
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To take away
Tissue protons align with magnetic field(equilibrium state)
RF pulses
Protons absorbRF energy
(excited state)
Relaxation processes
Protons emit RF energy(return to equilibrium state)
Spatial encodingusing magneticfield gradients
Relaxation processes
NMR signaldetection
Repeat
RAW DATA MATRIX
Fourier transform
IMAGE
Magnetic field
Source: Jorge Jovicich
Kwong et al., 1992
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PULSE SEQUENCE DIAGRAM
Spin Echo Sequence
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T1-WEIGHTED IMAGE
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T2-WEIGHTED IMAGE
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STIR AND FLAIRSTIR (Short Time Inversion Recovery):
FLAIR (Fluid Attenuated Inversion Recovery)
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Màu sắc mô• Nước và mô bệnh lý
– Trắng trên T2– Đen trên T1. – Mô bệnh lý vẫn trắng trên FLAIR
• Mỡ: – Trắng trênT1 và T2– Đen trên STIR và ngoài phase
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Màu sắc mô• U: tăng sinh mạch máu:
– Trắng trên gadolinium• Tụ máu: thay đổi theo thời gian• Tủy xương: chủ yếu là mỡ
– Trắng trên T1 – Trắng trên T2– Thay đội khi phù hay bệnh lý
• Thường đen trên T1• Vỏ xương, sỏi, dây chằng
– Đen trên tất cả các xung– Dập bệnh lý thì trắng
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Màu sắc mô• T1 : Nước đen• T2 : Trắng: Nước, viêm• STIR- T2:
– Mỡ đen• Proton Density
– sụn: xám• Gadolinium enhanced: T1
– Máu sáng– Mỡ đen– Mô bệnh sáng