Fast T2*‐weighted MRI of the prostate at 3 tesla

Abstract

Purpose To describe a rapid T2*-weighted (T2*W), three-dimensional (3D) echo planar imaging (EPI) sequence and its application in mapping local magnetic susceptibility variations in 3 Tesla (T) prostate MRI. To compare the sensitivity of T2*W EPI with routinely used T1-weighted turbo-spin echo sequence (T1W TSE) in detecting hemorrhage and the implications on sequences sensitive to field inhomogeneities such as MR spectroscopy (MRS). Materials and Methods B0 susceptibility weighted mapping was performed using a 3D EPI sequence featuring a 2D spatial excitation pulse with gradients of spiral k-space trajectory. A series of 11 subjects were imaged using 3T MRI and combination endorectal (ER) and six-channel phased array cardiac coils. T1W TSE and T2*W EPI sequences were analyzed quantitatively for hemorrhage contrast. Point resolved spectroscopy (PRESS MRS) was performed and data quality was analyzed. Results Two types of susceptibility variation were identified: hemorrhagic and nonhemorrhagic T2*W-positive areas. Post-biopsy hemorrhage lesions showed on average five times greater contrast on the T2*W images than T1W TSE images. Six nonhemorrhage regions of severe susceptibility artifact were apparent on the T2*W images that were not seen on standard T1W or T2W images. All nonhemorrhagic susceptibility artifact regions demonstrated compromised spectral quality on 3D MRS. Conclusion The fast T2*W EPI sequence identifies hemorrhagic and nonhemorrhagic areas of susceptibility variation that may be helpful in prostate MRI planning at 3.0T.

T2* mapping combined with conventional T2-weighted image for prostate cancer detection at 3.0T MRI: a multi-observer study

“…T2* relaxation time is becoming a novel quantitative biomarker to predict tumor cell density, and pulse sequence optimizations suited for prostate MRI have received increased attention. Hardman et al (11) established a rapid T2*W, three-dimensional (3D) EPI sequence and its application in the mapping of local magnetic susceptibility variations in 3.0T prostate MRI. However, these researchers only compared the sensitivity of T2* with routinely used T1W TSE in the detection of hemorrhage and the implications on sequences that are sensitive to field inhomogeneities, such as MR spectroscopy.…”

“…New treatment strategies, especially PCa focal therapy, have emerged recently, such as external radiation therapy, image-guided brachytherapy, cryotherapy, and highintensity focused ultrasound (US), which require more accurate diagnostics beyond tumor staging, and it is essential to provide more precise information on PCa detection and localization (4)(5)(6)(7)(8). T2*-weighted (T2*W) imaging was used recently in different body regions (myocardium, articular cartilage) (9)(10)(11). Korteweg et al (12) reported significant difference in the mean T2* value constants between malignant and benign nodes.…”

Comparison ofT2*mapping with diffusion-weighted imaging in the characterization of low-gradevsintermediate-grade and high-grade prostate cancer

“…In different body regions, T 2 * weighted imaging is applied to many organs. 15,16 In addition, sensitivity differences between nonhaemorrhagic and haemorrhagic regions can be recognized by T 2 * weighted imaging, as reported by Hardman et al 17 Moreover, increasing attention has been focused on pulse sequence optimization suitable for prostate MRI. Hardman et al used a rapid three-dimensional T 2 * weighted echoplanar imaging (EPI) sequence to map the local magnetic sensitivity differences on 3.0-T prostate MRIs.…”