Advanced Imaging Techniques

Transcription

1 Advanced Imaging Techniques Perfusion Imaging Prof. Dr. Frank G. Zöllner Compuer Assised Clinical Medicine Medical Faculy Mannheim Heidelberg Universiy Theodor-Kuzer-Ufer 1-3 D Mannheim, Germany Learning Goals inroducion o perfusion imaging basic MRI principles -> Physics of Imaging Techniques Goals: 1. How does he echnique work? 2. Wha kind of images do we receive? 3. Where is his applied o? Slides of he lecures a hps:// Prof. Dr. Zöllner I Slide 2I 10/30/2018 1

2 Reading Alsop, D. e al. (2015). Recommended implemenaion of arerial spinlabeled Perfusion mri for clinical applicaions: A consensus of he ISMRM Perfusion Sudy group and he European consorium for ASL in demenia. Magneic Resonance in Medicine, 73(1), hp://s online.de/aslindemeniacms/basic-principles-of-asl- 2 Nery, F. e al. (2018). Non-Invasive Renal Perfusion Imaging Using Arerial Spin Labeling MRI: Challenges and Opporuniies. Diagnosics, 8(1), 2. Sourbron, S. P., & Buckley, D. L. (2013). Classic models for dynamic conras-enhanced MRI. NMR in Biomedicine, 26(8), Cao e al. Gadolinium-based nanoscale MRI conras agens for umor imaging J. Maer. Chem. B, 2017, 5, Perella e al., MR Perfusion Imaging of he Brain Techniques and Applicaions, American Journal of Roengenology. 2000;175: Prof. Dr. Zöllner I Slide 3I 10/30/2018 Wha is Perfusion? blood sream suppors issue wih oxygen and nuriens issue haemodynamics a capilary level perfusion (Fp) measures for blood flow (unis: ml/100ml/min) permeabiliy (PS) of he capilarry membranes (unis: ml/100ml/min) inerplay gives informaion on issue funcion can be measured non-invasive by MRI Perfusion Schmid RF, Thews G, Lang F: Physiologie des Menschen. Springer, 2000 Prof. Dr. Zöllner I Slide 4I 10/30/2018 2

3 Perfusion Imaging - Applicaions brain lung hear liver kidney Prof. Dr. Zöllner I Slide 5I 10/30/2018 How do we measure perfusion by MRI? Wha do we need o see a flow in issue? How is issue and blood composed of? Wha are he MRI properies of his? We need o differenciae blood and issue! Prof. Dr. Zöllner I Slide 6I 10/30/2018 3

4 How do we measure perfusion by MRI? wo basic echniques Arerial Spin Labeling (ASL) endogenous racer Dynamic Conras Enhanced MRI (DCE-MRI) exogenous racer Idea: change he conras beween flowing blood and saionary issue Prof. Dr. Zöllner I Slide 7I 10/30/2018 Arerial Spin Labeling (ASL) arerial blood used as endogenous, freely diffusible racer needs o be labeled (agged) o be idenified use of radio frequency inversion pulse basic scheme: read ou volume labeling slice longiudinal magneizaion Prof. Dr. Zöllner I Slide 8I 10/30/2018 4

5 Properies of ASL signal change due o he delivered, labeled magneizaion is ypically abou 0.5% - 1.5% of he oal signal need o average several pairs of ag/conrol o increase SNR M is a perfusion-weighed (PW) image ha direcly reflecs local perfusion however, perfusion signal does no only depend on vascular flow bu Longiudinal relaxaion imes of blood and issue, proon densiy, he ransi ime from labeling o imaging region he inflow ime TI only quanificaion of PWI akes his ino accoun Prof. Dr. Zöllner I Slide 9I 10/30/2018 ASL - Imaging building blocks of ASl sequence inversion pulse bolus arrival ime background suppression Inversion ss/ns background inversion Q2TIPS Prof. Dr. Zöllner I Slide 10I 10/30/2018 5

6 ASL Imaging, Inversion scheme Pulsed ASL (PASL): use 1 RF pulse (180 ) o inver spins wai =TI ms signal repea wihou labeling slab Inversion ss/ns Inversion ime TI Prof. Dr. Zöllner I Slide 11I 10/30/2018 ASL Imaging, Inversion scheme (pseudo) coninuous ASL ((P)CASL): coninuously use RF pulse o inver spins in hin slab for labeling ime wai pos label delay (PLD ~ TI) signal pseudo con or more shaped RF pulses a a rae of ~ 1/ms (P)CASL labeling pos inversion delay (PLD) Prof. Dr. Zöllner I Slide 12I 10/30/2018 6

7 ASL Labeling Schemes CASL Alsaedi e al. Conras Media Mol Imaging Prof. Dr. Zöllner I Slide 13I 10/30/2018 ASL- Labeling Scheme EPISTAR (PASL) Alsaedi e al. Conras Media Mol Imaging Prof. Dr. Zöllner I Slide 14I 10/30/2018 7

8 ASL Labeling Schemes FAIR (PASL) Alsaedi e al. Conras Media Mol Imaging Prof. Dr. Zöllner I Slide 15I 10/30/2018 ASL - Readou block Independen of labeling scheme EPI, bffsp, TSE, 3D GRASE selecion of scheme: SNR, CNR, ime consrains couresey of M.Günher Prof. Dr. Zöllner I Slide 16I 10/30/2018 8

9 ASL - Readou block Independen of labeling scheme EPI, SSFP, TSE, 3D - GRASE couresey of M.Günher Prof. Dr. Zöllner I Slide 17I 10/30/2018 ASL - Readou block Independen of labeling scheme EPI, SSFP, TSE, 3D - GRASE couresey of F. Zimmer Prof. Dr. Zöllner I Slide 18I 10/30/2018 9

10 ASL - Readou block Independen of labeling scheme EPI, SSFP, TSE, 3D - GRASE couresey of M.Günher Prof. Dr. Zöllner I Slide 19I 10/30/2018 ASL - Readou Alsop e al., Magn Reson Med 2015 Prof. Dr. Zöllner I Slide 20I 10/30/

11 ASL - Readou comparison of schemes Nery e al. Diagnosics, 2018 Prof. Dr. Zöllner I Slide 21I 10/30/2018 ASL Q2TIPS perfusion signal depends on inflow ime TI bu also: ransi delay /bolus arrival ime (BAT) ime of he labeled blood o arrive a he issue of ineres use sauraion pulses o shape he bolus, using e.g. quaniaive imaging of perfusion using a single subracion wih hinslice TI 1 periodic sauraion (Q2TIPS) Q2TIPS Prof. Dr. Zöllner I Slide 22I 10/30/

12 ASL Q2TIPS TI 1 o TI 1S consis of a rain of 90 exciaion pulses for sauraion TI 2 : inflow ime Luh e al, Magn Reson Med 1999 Prof. Dr. Zöllner I Slide 23I 10/30/2018 ASL Background Suppression when calculaing PWI by subracing conrol from ag image signal of saic issue is o be eliminaed low SNR of he perfusion signal small flucuaions in he issue signal can corrup he ASL signal background suppression o avoid signal from saionary issue inser inversion pulses maching T1 of saic issues o be suppressed Inversion ss/ns background inversion Q2TIPS Prof. Dr. Zöllner I Slide 24I 10/30/

13 ASL Background Suppression wo issue species wih a T1 of 1.5 s (blue) and 1.2 s (green) Prof. Dr. Zöllner I Slide 25I 10/30/2018 ASL-Background Suppression Alsop e al., Magn Reson Med 2015 Prof. Dr. Zöllner I Slide 26I 10/30/

14 ASL Summary Imaging Technology Prof. Dr. Zöllner I Slide 27I 10/30/