Nuclear Magnetic Resonance-Bushberg Chapter 14 Diagnostic Radiology Imaging Physics Course Perfusion and Diffusion Contrast Magnetization Transfer Contrast ity hav for early ng namrow-band RF cular p'to free HO ,E Magnetization Transfer Contrast Raphex 2000 Diagnostic Questions contrast images designated as: ◆A.Fast gradient echo s5eeaCeron ◆B.Fast spin echo C.Inversion recovery D.Spin echo T1-weighted E.Spin echo T2-weighted 9,19and26May2005 18 Nuclear Magnetic Resonance – Bushberg Chapter 14 Diagnostic Radiology Imaging Physics Course 9, 19 and 26 May 2005 18 © UW and Brent K. Stewart, PhD, DABMP 69 Perfusion and Diffusion Contrast Perfusion and Diffusion Contrast ™ Tissues with Tissues with ↑ H2O mobility have mobility have greater signal loss ™ In vivo structural integrity of structural integrity of tissues measured tissues measured → apparent apparent diffusion coefficient maps ™ Sensitive indicator for early Sensitive indicator for early detection of detection of ™ Spine and spinal cord pathophysiology ™ Ischemic injury ™ Spin-echo and echoplanar pulse echo and echoplanar pulse sequences with diffusion gradients ™ Obstacles ™ Sensitivity to head/brain motion ™ Eddy currents c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2nd ed., p. 410. Diffusion-weighted image (DWI) with gray scale-encoded diffusion coefficients. T1 ρ T2 FLAIR © UW and Brent K. Stewart, PhD, DABMP 70 Magnetization Transfer Contrast Magnetization Transfer Contrast ™ Result of selective observation Result of selective observation of the interaction between the of the interaction between the p+ in free H2O molecules and O molecules and p+ in macromolecular proteins in macromolecular proteins due to coupling or chemical due to coupling or chemical exchange ™ Can be excited separately Can be excited separately using narrow-band RF ™ Magnetization transferred from Magnetization transferred from macromolecular p+ to free H2O p+ ™ Reduced signal from adjacent Reduced signal from adjacent free H2O p+ c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2nd ed., p. 412. © UW and Brent K. Stewart, PhD, DABMP 71 Magnetization Transfer Contrast Magnetization Transfer Contrast ™ This process affects only those This process affects only those p+ having chemical exchange having chemical exchange with the macromolecules and with the macromolecules and improves image contrast improves image contrast ™ Anatomic imaging of heart, Anatomic imaging of heart, eye, MS, knee cartilage and eye, MS, knee cartilage and general MR angiography ™ Tissue characterization Tissue characterization possible as the magnetization possible as the magnetization transfer ratio ( transfer ratio (MTCon/MTCoff) is caused in part by tissue￾specific surface chemistry c.f. Yao L, Thomasson D. Magnetization transfer contrast in rapid three-dimensional MR imaging using segmented radiofrequency prepulses. AJR 2002; 179: 863-5 . MR arthrograms of shoulder in 32-year-old man with suspected gleno￾humeral instability. Axial 3D gradient-echo MR image obtained using parametric magnetization transfer pulses no discernible magnetization transfer contrast in injected fluid or in fatty marrow spaces, whereas degree of magnetization transfer contrast varies in skeletal muscle, cartilage, and capsular supporting structures (color scale = 0-100%). © UW and Brent K. Stewart, PhD, DABMP 72 Raphex 2000 Diagnostic Questions Raphex 2000 Diagnostic Questions ™ D45. A 90° RF pulse followed within 100 ms by a 180° pulse with a repetition rate of 3000 ms would produce pulse with a repetition rate of 3000 ms would produce images designated as: images designated as: ™ A. Fast gradient echo A. Fast gradient echo ™ B. Fast spin echo B. Fast spin echo ™ C. Inversion recovery ™ D. Spin echo T1-weighted ™ E. Spin echo T2-weighted