1 / 13

Lecture 23: 1. MRI noise processes

Lecture 23: 1. MRI noise processes. MP574. Dipole Moments from Entire Sample. Magnetic Field (B 0 ). Magnetic Field (B 0 ). m. m. Positive Orientation. Negative Orientation. Source of Signal. Proton or Water MRI B o Magnetic Field Proton Nucleus S = ±ħ/2. rg. 2. 2. h. D E.

jeremy-brown
Download Presentation

Lecture 23: 1. MRI noise processes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture 23: 1. MRI noise processes MP574

  2. Dipole Moments from Entire Sample Magnetic Field (B0) Magnetic Field (B0) m m Positive Orientation Negative Orientation

  3. Source of Signal • Proton or Water MRI • Bo Magnetic Field • Proton Nucleus • S = ±ħ/2 rg 2 2 h DE D µ = E M B z o 4 kT

  4. z B1(t) F = w AB g cos( t ) 1 L g 2 w Ah B Ah = µ w w = w o L V ( t ) S ( t ) g sin( t ) g sin( t ) y L L L kT kT x Detected Signal

  5. Brownian Motion • Brownian Motion Conditions: • x0= 0 • x(t) is a continuous random variable • Increments x(t1) and x(t2) are statistically independent and normally distributed http://en.wikipedia.org/wiki/Wiener_process

  6. Brownian Motion

  7. Rp Rc Johnson or “Thermal” Noise Electrical Resistance of Coil Patient Resistance Thermal noise in patient dominant at high field strengths

  8. Johnson or “Thermal” Noise on both I and Q channels I = “in phase” Q = “quadrature” or 90o out of phase Imaginary Real

  9. Independent Realizations of GWN on each of the I,Q channels Imaginary Real

  10. Background noise Imaginary Real

  11. Rayleigh and Rician Probability Distribution Functions

  12. High SNR

  13. Dependence on SNR

More Related