Tracer kinetic analysis of dynamic contrast‐enhanced MRI and CT bladder cancer data: A preliminary comparison to assess the magnitude of water exchange effects

Abstract

The purpose of this study was to determine the impact of water exchange on tracer kinetic parameter estimates derived from T 1 -weighted dynamic contrast-enhanced (DCE)-MRI data using a direct quantitative comparison with DCE-CT. Data were acquired from 12 patients with bladder cancer who underwent DCE-CT followed by DCE-MRI within a week. A two-compartment tracer kinetic model was fitted to the CT data, and two versions of the same model with modifications to account for the fast exchange and no exchange limits of water exchange were fitted to the MR data. The two-compartment tracer kinetic model provided estimates of the fractional plasma volume (v p ), the extravascular extracellular space fraction (v e ), plasma perfusion (F p ), and the microvascular permeability surface area product. Our findings suggest that DCE-CT is an appropriate reference for DCE-MRI in bladder cancers as the only significant difference found between CT and MR parameter estimates were the no exchange limit estimates of v p (P 5 0.002). These results suggest that although water exchange between the intracellular and extravascularextracellular space has a negligible effect on DCE-MRI, vascular-extravascular-extracellular space water exchange may be more important. Magn Reson Med 64:595-603,

Discrimination of Benign and Malignant Breast Lesions by Using Shutter-Speed Dynamic Contrast-enhanced MR Imaging

“…When dynamic contrast-enhanced MR imaging exchangesensitivity is absent, ⌬ K trans will be effectively zero for both malignant and benign tumors. The results here suggest that data acquisition schemes with decreased exchange-sensitivity ( 41,42 ) would diminish shutter-speed approach breast cancer diagnostic accuracy. protocols, it has been shown that diagnostic accuracies of both standard and shutter-speed approaches decrease substantially ( 45 ).…”

Practical Dynamic Contrast Enhanced MRI in Small Animal Models of Cancer: Data Acquisition, Data Analysis, and Interpretation

“…The most common transformation from CA concentration to tissue R 1 is given by Equation 1 [34]: R 1 = r 1 · [ RA ] + R 10 where R 10 is the baseline relaxation of the tissue, [ CA ] is the concentration of the CA in the tissue, and r 1 is the CA-specific relaxivity (in units of mM −1 s −1 ). (We note that Equation 1 is a “fast exchange limit” relation and assumes a linear relationship between CA concentration and R 1 ; for more information on this somewhat controversial point, the interested reader is referred to, e.g., references [35,36,37,38]. We revisit this point in Section 6.)…”

“…As one might guess, the estimated pharmacokinetic parameters may differ significantly [35,161,162,163,164,168] depending on the model that was used to extract them, and these differences may have a significant effect on establishing if, for example, a tumor is responding to treatment. However, there is some disagreement as to whether this formalism is truly justified in a standard DCE-MRI study and it is therefore an active area of investigation [37,38]. …”

Analysis of contrast-enhanced medical images.

“…The PK models are typically refined to more closely reflect physiological processes by including additional parameters, e.g., water exchange and CA diffusion. However, the refinement mostly complicates DCE-MRI analysis, and its usefulness requires additional investigation [197,290,[307][308][309].…”

“…Classifi-cation of breast tumors by Brix et al [192] was its first DCE-MRI application. Recently, the 2CXM is gradually becoming popular in various applications, such as brain [193,195,287] and lung cancer [288], myometrium [289], cervix [194] and bladder cancer [290], head and neck tumors [291], and carotid atherosclerotic plaques [191].…”