Critical role of spatial resolution in dynamic contrast‐enhanced breast MRI

Abstract

The spatial resolution of three-dimensional (3D) gradientecho T1-weighted images, from 40 women with 25 malignant and 23 benign lesions, was purposely degraded to determine the role of spatial resolution in recording, analysis, and diagnosis of dynamic contrast-enhanced breast MRI. Images were recorded and analyzed at pixel resolution according to the 3TP method (Degani et al., Nat Med 1997;3:780 -782). Reduction in spatial resolution degraded the appearance of foci with fast wash-in and fast washout dynamics. This resulted in an increase in falsenegative diagnoses. The sensitivity for differentiating between malignant and benign lesions, using threshold criteria defined by the 3TP analysis, of 76% decreased to 60% and 24% for a 2-and 4-fold reduction in spatial resolution, respectively, without affecting significantly the high specificity ( Index terms: breast diagnosis; MRI; dynamic; contrast agent; spatial resolution BREAST LESIONS can be distinctly characterized by gadolinium (Gd)-based contrast-enhanced MRI (1-3). The sensitivity of breast MRI for cancer detection was found to be high (4 -13, and references cited therein); however, conflicting results were reported for the accuracy of diagnosis in terms of differentiating benign and malignant lesions (4 -13, and references cited therein). Both architectural features of the enhanced regions and dynamics of contrast enhancement served to improve the sensitivity and specificity of breast MRI diagnosis (13,14). Various methods, both empiric and model-based, have been used to extract diagnostic information from dynamic contrastenhanced signal intensity time curves (15-26). Clearly, the architectural features of lesions are better resolved in images recorded and displayed at high spatial resolution, while in dynamic contrast-enhanced images, high temporal and spatial resolution may be critical for extracting the relevant information. High temporal resolution provides detailed curves of enhancement vs. time that can be mathematically analyzed, empirically or with a modelbased equation. The spatial resolution of kinetic behavior is also significant, as tumors and particularly cancers are highly heterogeneous. Unfortunately, current standard MRI technology cannot record images with both high spatial resolution and high temporal resolution at a sufficient signal-to-noise ratio. To overcome this dilemma, we recently proposed a method that records high-resolution contrast-enhanced images at three specific time points (hence the term 3TP) (20), chosen using a model-based algorithm (27) so as to maximize the dynamic information that is guiding the diagnosis. The 3TP method was initially studied and verified in animal models of breast cancer (20, 28). The method relates changes in enhancement to the physiologic parameters that characterize malignant tumors, and differentiates them from benign ones, namely, the product of microvascular surface area and permeability of the contrast agent per unit volume (PS/V) and extracellular volume fraction (EVF) accessible to the contra...

Shutter‐speed analysis of contrast reagent bolus‐tracking data: Preliminary observations in benign and malignant breast disease

“…An area that has seen considerable such activity is breast disease (2)(3)(4)(5). The many pharmacokinetic models applied to CR B-T data can be divided into two families; one in which the CR and H 2 O are assumed uniformly distributed within each compartment entered ["well-mixed," e.g., (1)] and one in which they are not ["heterogeneous," surveyed in (6)].…”

Estudo da permeabilidade vascular e volume extra-celular na diferenciação das lesões nodulares benignas e malignas da mama

“…Degani e colaboradores [20] desde 1997 testaram um modelo, usando a RM com contraste, o Three-time-point (3TP), de alta resolução espacial e temporal, usando 3 pontos de interesse em diferentes tempos, sendo eles o primeiro no pré-contraste, e dois no pós-contraste, que permite calcular permeabilidade vascular e VEC.…”

“…Através de modelo baseado no mapa de Degani [20] , Desta maneira, um pixel vermelho escuro descreve uma região de alta permeabilidade e baixo VEC, que geralmente está associado a lesão maligna.…”

“…Degani e colaboradores [12,20] desenvolveram um modelo usando RM com contraste, com alta resolução temporal e espacial, onde com modelos matemáticos de compartimentos como os padronizados por Tofts [21] , calcula a permeabilidade vascular e VEC das lesões. [20][21][22] Existem hoje muitos aplicativos com uso de RM com contraste dinâmico para medir estes parâmetros biológicos, sendo um deles o método Full Time Point (FTP) (Cadsciences; White Plains, NY, USA), que é um sistema de detecção assistida por computador (CAD), que baseado na metodologia de Degani [20] , calcula a permeabilidade e VEC para cada pixel da lesão, traduzido em um gráfico de cores.…”

“…[20][21][22] Existem hoje muitos aplicativos com uso de RM com contraste dinâmico para medir estes parâmetros biológicos, sendo um deles o método Full Time Point (FTP) (Cadsciences; White Plains, NY, USA), que é um sistema de detecção assistida por computador (CAD), que baseado na metodologia de Degani [20] , calcula a permeabilidade e VEC para cada pixel da lesão, traduzido em um gráfico de cores.…”