Zusammenfassung
Which method provides most insight into tumors ! 3T (fluid suppr.) APTw, 3T CEST-MRF or 7T multi-pool CEST?
Maria Sedykh1, Moritz Fabian1, Kai Herz2,3, Or Perlman4, Chris Farrar4, Angelika Mennecke1, Manuel Schmidt1, Arnd
Dörfler1, and Moritz Zaiss1,2
1Institute of Neuroradiology, Universitätsklinikum Erlangen, Friedrich-Alexander Universität Erlangen Nürnberg, Germany,
2Magnetic Resonance Center, Max-Planck-Institute for Biological Cybernetics, Tübingen, Germany, 3
Department of Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany, 4 Athinoula A. Martinos
Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School,
Charlestown, MA, USA
! Oral or Poster | Contact Email: moritz.zaiss@fau.de KEYWORD: ! Tumor ! Novel Acquistion
INTRODUCTION: Many CEST techniques were shown to provide insight into tumors, e.g. 3T APTw imaging, 3T CEST
fingerprinting, and 7T multi-pool CEST. Herein we report one case of a patient diagnosed with glioblastoma, WHO grade
IV, who could be measured with all above mentioned techniques to reveal their relative performance and correlations.
METHODS: The patient was measured at a Siemens PRISMA scanner (3T, 64-Rx, 1Tx) and Siemens TERRA scanner (7T,
32-Rx, 8 pTx coil) after written informed consent. The 3T APTw following the standard APTw_001(3) (pulsed rf irradiation of
2 s duration at DC = 90% and a 2 μT B1 level) was applied followed by a 3D snapshot GRE readout. The 3T CEST MRF
pulseq-files(1, 2) were played out followed by a 3D-EPI readout. The post-processing of the data included the usage of neural
networks and was performed according to (2), generating maps for MT pool fraction fmt and exchange rate kmt, and solute
amide fraction fs and exchange rate ks. The 7T multi-pool CEST protocol was measured with the MIMOSA approach (4) at
0.72 !T and 1.00 !T followed by a 3D snapshot GRE. Figure 1 shows data of the techniques in tumor and WM ROIs. !
RESULTS: The tumor area can be
outlined in all presented maps Figure
2, but with different apparent
features. The 3T-APTw highlights
the overall tumor area, including
necrotic and the liquefied tissue in
the cyst, identified on the MPRAGE
in Figure 2a. The fluid suppressed
APTw FS-APTw (see separate
abstract) the liquid areas are
suppressed. In most 3T MRF and all
7T multi-pool contrasts, the cyst and
the necrotic area are hypo-intense, in
3T MRF kmt necrosis is hyper-intense.
While the selective 7T-amide-CEST
shows similar areas highlighted as
3T-APTw (except for cyst and
necrosis) and as 3T FS-APTw, the
quantitative MRF amide exchange
rate ks and concentration fs do not
show elevated signals. Most contrast
in 3T MRF is seen in the MT pool
fraction fmt and exchange rate kmt, the
latter correlated to the MT line-width. The most plausible correlation is observed between fmt, 7T MT and 7T NOE and T1
and T2, as lowered MT pool size fmt is (anti-)correlated with all values: fmt, 7T MT and 7T NOE all are hypo-intense in the
tumor region, and WM brighter than GM, T1 and T2 the other way around. The 3T MRF MT exchange rate map shows
increased values in the tumor area, but kmt was found to be decreased in animal tumors(2).
DISCUSSION: Most prominent findings are (i) that 3T APTw has a strong relaxation and MT contribution and shows a liquid
artifact. Interestingly, 3T FS-APTw and isolated Lorentzian 7T amide CEST partly correlate in the tumor area, but 7T shows
finer structures. (ii) 7T and most MRF maps identify the necrosis and the cyst properly hypointense, while APTw shows the
cyst even brighter than the contrast enhancing tumor area. (iii) The MRF fmt contrast is in line with MT and relaxation findings,
however, the outcome of MRF kmt, fs and ks is unexpected compared to previous animal data, as well as compared to the
7T insights. As MRF has the most complicated pipeline, further investigations are needed for a better interpretation of the
method. CONCLUSION: We showed an unseen variety of CEST imaging methods applied in the same brain tumor patient.
Coarse features can be observed in all methods, with MRF and 7T CEST being more versatile in some tumor parts. Isolation,
separation and smarter combination of different contrast is still needed to improve the diagnostic performance of CEST.
