Quantification of amide proton transfer effect pre- and post-gadolinium contrast agent administration.
OBJECTIVE
To compare quantification of the amide proton transfer (APT) effect pre- and post-gadolinium contrast agent (Gd) administration in order to establish to what extent Gd alters quantification of the APT effect.


METHODS
Four patients with internal carotid stenosis were recruited. APT imaging was acquired pre- and post-contrast in two sessions (before and after surgery) to assess the extent of relaxation time, T1 , change on APT effect calculated using magnetization transfer ratio asymmetry analysis at offsets of ±3.5 ppm relative to water resonance. Statistical and modeling evaluations were performed on the pre- and post-contrast APT effect to study the sensitivity to contrast administration.


RESULTS
Before surgery, the post-contrast T1 was estimated to drop <10% of the pre-value for the majority of the patients. After surgery, higher post-contrast T1 reductions were observed in all the patients (maximum decrease was about 20% of the pre-value). Consistent differences between pre- and post-contrast were seen in the APT effect quantified using the asymmetry measure in most regions of the brain, with significant differences found in the white matter at the group level and in 25% of the individual patient results.


CONCLUSIONS
APT imaging should be performed prior to Gd administration to avoid potential misinterpretation of the APT effect.
Institute of Biomedical Engineering Department of Engineering Science, University of Oxford, UK; Centre for Doctoral Training in Healthcare Innovation, University of Oxford, UK.
Yee Kai
YK
Tee
Manus J
MJ
Donahue
George W J
GW
Harston
Stephen J
SJ
Payne
Michael A
MA
Chappell
D000465:Algorithms; D000577:Amides; D016893:Carotid Stenosis / Q000473:pathology*; D003287:Contrast Media / Q000008:administration & dosage; D005682:Gadolinium / Q000008:administration & dosage*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D011522:Protons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D000577:Amides; D003287:Contrast Media; D011522:Protons; D005682:Gadolinium
amide proton transfer (APT) imaging; chemical exchange saturation transfer (CEST) imaging; gadolinium contrast agents; magnetization transfer (MT) imaging