Diffusion weighted MRI for detecting and monitoring cancer: a review of current applications in body imaging

Abstract

Imaging is used to detect, characterize, and monitor cancer. Recently, diffusion-weighted magnetic resonance imaging (DWI) has become a useful adjunct for assessing tumors with magnetic resonance imaging (MRI). DWI involves the acquisition of a magnetic resonance signal related to random thermal motion (Brownian motion) or the "diffusion" of water protons in tissue. The signal obtained with DWI is a measure of the net displacement of water molecules, e.g., the water path length in the extracellular, intracellular and intravascular spaces. This motion is largely random and can be reduced by structural barriers, such as cell membranes and collagen. Restricted diffusion in biological tissues is inversely proportional to tissue cellularity and the integrity of cell membranes, and it can be quantified with apparent diffusion coefficient (ADC) measurements (1). Depending on the microarchitecture, either restricted or increased diffusion can occur in malignant tumors. For instance, diffusion is restricted in cellular portions of the tumor, but it may be increased in necrotic portions (2, 3). Other causes of enhanced diffusion include increased water content arising from intratumoral edema and cystic tumor components (4-6).Although initially used to evaluate neurological diseases, the applications of DWI have been extended to oncologic imaging throughout the body made possible by improvements in MRI hardware and new sequences. The use of DWI as a complement to conventional MRI methods has led to improvements in the detection and characterization of tumors, treatment response monitoring, and detection of recurrence in oncology patients. Basic concepts of DWIIn 1965, Stejskal and Tanner (7) proposed the application of a symmetric pair of additional gradients on either side of the 180˚ refocusing radiofrequency pulse. The Stejskal-Tanner sequence is still the basis of modern DWI. For static water molecules, the phasing effect caused by the first gradient will be reversed by the second gradient, leading to no signal loss; however, this phasing effect will not be completely reversed if the water molecules are not stationary, which results in the observed well-known diffusion signal decay. The amount of diffusion weighting is determined by the b value, which describes the amplitude, duration of the applied gradient, and time interval between the two diffusion gradients (4). The degree of signal attenuation from water molecules is cor- ABSTRACT Diffusion-weighted magnetic resonance imaging (MRI), which involves the acquisition of a magnetic resonance signal related to the Brownian motion of water protons in tissue, has become a useful technique for assessing tumors. In this article, we review the basic concepts, imaging strategies, and body applications of diffusion-weighted MRI in detecting and monitoring cancer.

Comparison of apparent diffusion coefficient values among different MRI platforms: a multicenter phantom study

“…Under this condition, receiver operative characteristic (ROC) curve analyses are performed to determine cutoff ADC values to differentiate between benign and malignant lesions. Recently, cutoff points for ADC values have increasingly been suggested to differentiate between benign and malignant lesions in different organs (3,4,7,8). However, reliable and reproducible cutoff values have not yet been confirmed.…”

Value of apparent diffusion coefficient for predicting malignancy of intraductal papillary mucinous neoplasms of the pancreas

“…This is regarded as the "T2 shine-through" effect. (12). Theoretically, this effect could be sometimes eliminated by choosing a larger b value for the acquisition of DWI.…”

“…Diffusion-weighted imaging (DWI) is widely performed in clinical practice and has been shown to be valuable in distinguishing between benign and malignant tumors (11,12). DWI can provide qualitative and quantitative information reflecting changes at a cellular level and yields unique insights into tumor cellularity and the integrity of cell membranes (12). Recently, studies have suggested that quantitative measurement of the apparent diffusion coefficient (ADC) may have potential value for the characterization of cystic pancreatic lesions (13)(14)(15)(16).…”

“… zengmengsu@126.com), Zhongshan Hospital, Fudan University and Shanghai Medical Imaging Institute, Shanghai, China. Diffusion-weighted imaging (DWI) is widely performed in clinical practice and has been shown to be valuable in distinguishing between benign and malignant tumors (11,12). DWI can provide qualitative and quantitative information reflecting changes at a cellular level and yields unique insights into tumor cellularity and the integrity of cell membranes (12).…”

Multiparametric Magnetic Resonance Imaging in the Detection of Prostate Cancer

“…Diffusion-weighted imaging visualizes the Brownian molecular motion of water. It has become an important part of oncological imaging since malignant tumors are typically comprised of densely arranged cells whose numerous cell membranes limit this Brownian molecular motion [14]. Prostate cancers are thus visualized on highly diffusion-weighted images (typically upper b-values of 800 -1000 s/mm 2 in prostate imaging) as areas with high signal intensity ( • " Fig.…”