Dynamic susceptibility contrast perfusion MRI using phase-based venous output functions: comparison with pseudo-continuous arterial spin labelling and assessment of contrast agent concentration in large veins.
OBJECTIVE
Contrast agent (CA) relaxivities are generally not well established in vivo, and the relationship between frequency/phase shift and magnetic susceptibility might be a useful alternative for CA quantification.


METHODS
Twenty volunteers (25-84 years old) were investigated using test-retest pre-bolus dynamic susceptibility-contrast (DSC) magnetic resonance imaging (MRI). The pre-bolus phase-based venous output function (VOF) time integral was used for arterial input function (AIF) rescaling. Resulting cerebral blood flow (CBF) data for grey matter (GM) were compared with pseudo-continuous arterial spin labelling (ASL). During the main bolus CA passage, the apparent spatial shift (pixel shift) of the superior sagittal sinus (seen in single-shot echo-planar imaging (EPI)) was converted to CA concentration and compared with conventional ΔR2*-based data and with a predicted phase-based VOF from the pre-bolus experiment.


RESULTS
The phase-based pre-bolus VOF resulted in a reasonable inter-individual GM CBF variability (coefficient of variation 28 %). Comparison with ASL CBF values implied a tissue R2*-relaxivity of 32 mM-1s-1. Pixel-shift data at low concentrations (data not available at peak concentrations) were in reasonable agreement with the predicted phase-based VOF.


CONCLUSIONS
Susceptibility-induced phase shifts and pixel shifts are potentially useful for large-vein CA quantification. Previous predictions of a higher R2*-relaxivity in tissue than in blood were supported.
Department of Medical Radiation Physics, University Hospital, Lund University, SE-22185, Lund, Sweden. ronnie.wirestam@med.lu.se.
Ronnie
R
Wirestam
Department of Medical Radiation Physics, University Hospital, Lund University, SE-22185, Lund, Sweden.
Emelie
E
Lind
Department of Medical Radiation Physics, University Hospital, Lund University, SE-22185, Lund, Sweden.
André
A
Ahlgren
Department of Medical Radiation Physics, University Hospital, Lund University, SE-22185, Lund, Sweden.|Department of Diagnostic Radiology, University Hospital, Lund University, SE-22185, Lund, Sweden.
Freddy
F
Ståhlberg
Department of Medical Radiation Physics, University Hospital, Lund University, SE-22185, Lund, Sweden.
Linda
L
Knutsson
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002138:Calibration; D002560:Cerebrovascular Circulation; D003198:Computer Simulation; D003287:Contrast Media / Q000737:chemistry; D017352:Echo-Planar Imaging; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013113:Spin Labels; D014680:Veins / Q000000981:diagnostic imaging* / Q000473:pathology
D003287:Contrast Media; D013113:Spin Labels
Cerebral blood flow; Cerebrovascular circulation; Contrast agents; Gray matter; Magnetic resonance imaging