Signal intensity form of the Tofts model for quantitative analysis of prostate dynamic contrast enhanced MRI data

Abstract

The aim of this study is to develop a signal intensity (S(t)) form of the standard Tofts pharmacokinetic model that avoids the need to calculate tissue contrast agent concentration (C(t)) as function of time (t). We refer to this as ‘SI-Tofts’ model. Physiological parameters (K trans and v e) calculated using the SI-Tofts and standard Tofts models were compared by using simulations and human prostate dynamic contrast enhanced (DCE) MRI data. This approach was also applied to the Patlak model to compare K trans values calculated from C(t) and S(t). Simulations were performed on DCE-MRI data from the quantitative imaging biomarkers alliance to validate SI-Tofts model. In addition, ultrafast DCE-MRI data were acquired from 18 prostate cancer patients on a Philips Achieva 3T-TX scanner. Regions-of-interest (ROIs) for prostate cancer, normal tissue, gluteal muscle, and iliac artery were manually traced. The C(t) was calculated for each ROI using the standard model with measured pre-contrast tissue T 1 values. Both the simulation and clinical results showed strong correlation (r = 0.87–0.99, p < 0.001) for K trans and v e calculated from the SI-Tofts and standard Tofts models. The SI-Tofts model with a correction factor using the T 1 ratio of blood to tissue significantly improved the K trans estimates. The correlation of K trans obtained from the Patlak model with C(t) vs S(t) was also strong (r = 0.95–0.99, p < 0.001). These preliminary results suggest that physiological parameters from DCE-MRI can be reliably estimated from the SI-Tofts model without contrast agent concentration calculation.

Repeatability of tumor perfusion kinetics from dynamic contrast-enhanced MRI in glioblastoma

“… 34 Additionally, we also recommend converting MR signal intensity curves to contrast agent concentration curves and fitting to these, as accurate PK model fitting to DCE-MRI signal intensity data requires careful correction for internal consistency. 35 …”

Pharmacokinetic Analysis of Enhancement-Constrained Acceleration (ECA) reconstruction-based high temporal resolution breast DCE-MRI

“…For lesion voxels, we measured K trans , the volume transfer constant between blood plasma and extravascular extracellular space. We calculated K trans from a signal intensity form of the Tofts model, which was introduced in an earlier study [ 43 ]: where S b (0) and S t (0) are the baseline signal intensity in blood vessel and in lesion, respectively. PSE b ( t ) and PSE t ( t ) are the percent signal enhancement in blood vessel and in lesion, Hct is the hematocrit ( Hct = 0.42) [ 6 ], v e is the volume of EES per unit volume of tissue v e ∈[0, 1].…”