Further, power Doppler quantification is currently considered a limited tool to assess vascularization, mainly because of the high dependence of gain and other machine settings, attenuation, and reproducibility.
One alternative that could compensate for the effects of machine settings, attenuation, organ position and other confounding factors is fractional moving blood volume (FMBV), which can provide a more robust estimation of vascularity [ 50– 50].
Moreover, fractional moving blood volume (FMBV), as a quantitative methodology that compensates for common estimation errors, may need to reduce the dependency of machine settings and attenuation.
The difference in deflector/detector attenuation settings might also explain why, contrary to the CRC set, in the BC set more peaks were detected by the ProteinChip software in the PBS-IIc spectra than by Ciphergen Express™ in the PCS 4000 spectra.
These two datasets differed in their deflector/detector attenuation settings (CRC: 2000 Da, BC: 1000 Da), but in both sets, the noise was calculated between 2 and 200 kDa.
Due to the difference in detector attenuation settings, this low molecular weight range will contain a higher signal in the BC spectra than in the CRC spectra.
Although deflector/detector attenuation settings were different for the fractionation spectra on IMAC and CM10 chips, peak clustering results were highly similar for the two array types used, contrary to the results obtained in the CRC and BC sample sets.
After analysing these different reconstruction methods, we also paid attention to the effect of several correction settings (scatter correction (SC), attenuation correction (AC) and collimator correction (CC)) on the pancreas visualization and quantification.
Since there are no means of correcting scatter in the clinical program, thereby making a "fair" comparison impossible, we used the clinically employed settings (i.e. no attenuation correction).
MR-based attenuation correction, TOF and reconstruction settings have little impact on the quantitative MBF values.
Fig. 4 Settings for minimal (1) and maximal (2) attenuation thresholds, naming the ROI (3), and options (4).
