Chemical Exchange Saturation Transfer MR Imaging: Preliminary Results for Differentiation of Malignant and Benign Thoracic Lesions

Abstract

).q RSNA, 2015 Purpose:To prospectively evaluate the capability of amide proton transfer-weighted chemical exchange saturation transfer magnetic resonance (MR) imaging for characterization of thoracic lesions. Materials and Methods:The institutional review board approved this study, and written informed consent was obtained from 21 patients (13 men and eight women; mean age, 72 years) prior to enrollment. Each patient underwent chemical exchange saturation transfer MR imaging by using respiratorysynchronized half-Fourier fast spin-echo imaging after a series of magnetization transfer pulses. Next, a magnetization transfer ratio asymmetry at 3.5 ppm map was computationally generated. Pathology examinations resulted in a diagnosis of 13 malignant and eight benign thoracic lesions. The malignant lesions were further diagnosed as being nine lung cancers, comprising six adenocarcinomas, three squamous cell carcinomas, and four other thoracic malignancies. The Student t test was used to evaluate the capability of magnetization transfer ratio asymmetry (at 3.5 ppm), as assessed by means of region of interest measurements, for differentiating benign and malignant lesions, lung cancers and other thoracic lesions, and adenocarcinomas and squamous cell carcinomas. Results:Magnetization transfer ratio asymmetry (at 3.5 ppm) was significantly higher for malignant tumors (mean 6 standard deviation, 3.56% 6 3.01) than for benign lesions (0.33% 6 0.38, P = .008). It was also significantly higher for other thoracic malignancies (6.71% 6 3.46) than for lung cancer (2.16% 6 1.41, P = .005) and for adenocarcinoma (2.88% 6 1.13) than for squamous cell carcinoma (0.71% 6 0.17, P = .02). Conclusion:Amide proton transfer-weighted chemical exchange saturation transfer MR imaging allows characterization of thoracic lesions.q RSNA, 2015

MRI for solitary pulmonary nodule and mass assessment: Current state of the art

“…In the early 1990s, CEST was introduced as a new type of method which has drawn considerable attention as a novel mechanism to produce modified tissue contrast for MRI based on exchangeable protons (-NH, -OH, -SH, others) on endogenous or exogenous molecules. 79 Although the number of study participants in this study was small, the results were close to the in vitro study. 76 Amide proton transfer (APT) imaging is one subset of CEST imaging that applies specifically to the chemical exchange between protons of free tissue water (bulk-water) and amide (-NH) groups.…”

“…75 This method employs a technique utilizing saturation transfer (ST) mainly via dipolar exchange and has been widely used to produce modified tissue contrast for MRI in clinical settings. 79,80 In the first of these two studies, sensitivity, specificity, and accuracy for distinguishing malignant thoracic from other lesions were 100%, 75%, and 90.5%, respectively, those for differentiating lung cancer from other thoracic malignancies were 100%, 75%, and 92.3%, and those for distinguishing adenocarcinoma from squamous cell carcinoma were 100%, 100%, and 100%, respectively. Since this method is also a technique utilizing ST but via chemical exchange, it uses an RF pulse at a specific frequency so that the target molecule is selectively saturated, and the saturation is transferred to the bulk water.…”

“…Most of the agents in clinical use today are Gd contrast media that shorten the relaxation time of the free water protons. [77][78][79][80] Although the method is sensitive to motion and B 0 inhomogeneity, a few studies have applied APT imaging to the thorax. 73 In addition to the use of relaxation-based contrast agents, MRI offers a variety of contrast techniques based on the intrinsic properties of tissue, such as coupling to neighboring nuclei, CEST, or flow.…”

Amide proton transfer‐weighted imaging to differentiate malignant from benign pulmonary lesions: Comparison with diffusion‐weighted imaging and FDG‐PET/CT

“…Chemical exchange saturation transfer (CEST) has been introduced as a technique for providing additional physiological and functional information to conventional MRI and has become prominent in the field of molecular imaging . CEST imaging is achieved by applying multiple magnetization transfer pulses to the resonance frequency of a slow to intermediate rate exchanging protons (NH‐, OH‐, or metal‐bound water molecule) of endogenous or exogenous agents .…”

“…In addition, amide proton transfer (APT) imaging is a subset of CEST imaging that applies specifically to chemical exchange between protons of bulk water and amide groups (‐NH) of endogenous mobile proteins and peptides. It has been reported that such exchangeable protons are more abundant in tumors than in healthy tissues, and it has been demonstrated in in vitro and in vivo studies that there is a significant difference in the APT between malignant and benign or healthy tissues . Moreover, APT‐weighted (APTw) imaging was found to be potentially useful for characterizing subtypes of lung cancer in an in vitro study, for differentiating malignant from benign thoracic tumors, and in an in vivo study, and for distinguishing lung cancer from other thoracic malignancies and adenocarcinoma from squamous cell carcinoma .…”