Magnetic Resonance in Medical Sciences

Featured article

Volume 3 (2004) Issue 1 Pages 11-17

The Optimal Trackability Threshold of Fractional Anisotropy for Diffusion Tensor Tractography of the Corticospinal Tract

Akira KUNIMATSU, Shigeki AOKI, Yoshitaka MASUTANI, Osamu ABE, Naoto HAYASHI, Harushi MORI, Tomohiko MASUMOTO, Kuni OHTOMO

Purpose: In order to ensure that three-dimensional diffusion tensor tractography (3D-DTT) of the corticospinal tract (CST), is performed accurately and efficiently, we set out to find the optimal lower threshold of fractional anisotropy (FA) below which tract elongation is terminated (trackability threshold).
Methods: Thirteen patients with acute or early subacute ischemic stroke causing motor deficits were enrolled in this study. We performed 3D-DTT of the CST with diffusion tensor MR (magnetic resonance) imaging. We segmented the CST and established a cross-section of the CST in a transaxial plane as a region of interest. Thus, we selectively measured the FA values of the right and left corticospinal tracts at the level of the cerebral peduncle, the posterior limb of the internal capsule, and the centrum semiovale. The FA values of the CST were also measured on the affected side at the level where the clinically relevant infarction was present in isotropic diffusion-weighted imaging.
Results: 3D-DTT allowed us to selectively measure the FA values of the CST. Among the 267 regions of interest we measured, the minimum FA value was 0.22. The FA values of the CST were smaller and more variable in the centrum semiovale than in the other regions. The mean minus twice the standard deviation of the FA values of the CST in the centrum semiovale was calculated at 0.22 on the normal unaffected side and 0.16 on the affected side.
Conclusion: An FA value of about 0.20 was found to be the optimal trackability threshold.

Editor’s picks

(Author's comments) Neural fiber tractography is one of the useful clinical applications of diffusion tensor imaging (DTI). We sought an optimal threshold of fractional anisotropy (FA), a standard metric derived from DTI, when depicting tractograms of the corticospinal tracts in the brain. We carried out a tract-specific analysis of normal and diseased corticospinal tracts by ischemic stroke. Our results suggested that optimal FA threshold values may be around 0.20. We had an opportunity to carry out this study at the beginning of clinical use of DTI and are now privileged to introduce our paper as one of the most cited papers.

Volume 4 (2005) Issue 1 Pages 35-42

ADC Mapping of Benign and Malignant Breast Tumors

Reiko WOODHAMS, Keiji MATSUNAGA, Shinichi KAN, Hirofumi HATA, Masanori OZAKI, Keiichi IWABUCHI, Masaru KURANAMI, Masahiko WATANABE, Kazushige HAYAKAWA

Purpose: The purpose of this study was to investigate the utility of diffusion-weighted imaging (DWI) and the apparent diffusion coefficient (ADC) value in differentiating benign and malignant breast lesions and evaluating the detection accuracy of the cancer extension.
Materials and Methods: We used DWI to obtain images of 191 benign and malignant lesions (24 benign, 167 malignant) before surgical excision. The ADC values of the benign and malignant lesions were compared, as were the values of noninvasive ductal carcinoma (NIDC) and invasive ductal carcinoma (IDC). We also evaluated the ADC map, which represents the distribution of ADC values, and compared it with the cancer extension.
Results: The mean ADC value of each type of lesion was as follows: malignant lesions, 1.22±0.31×10^-3 mm²/s; benign lesions, 1.67±0.54×10^-3 mm²/s; normal tissues, 2.09±0.27×10^-3 mm²/s. The mean ADC value of the malignant lesions was statistically lower than that of the benign lesions and normal breast tissues. The ADC value of IDC was statistically lower than that of NIDC. The sensitivity of the ADC value for malignant lesions with a threshold of less than 1.6×10^-3 mm²/s was 95% and the specificity was 46%. A full 75% of all malignant cases exhibited a near precise distribution of low ADC values on ADC maps to describe malignant lesions. The main causes of false negative and underestimation of cancer spread were susceptibility artifact because of bleeding and tumor structure. Major histologic types of false-positive lesions were intraductal papilloma and fibrocystic diseases. Fibrocystic diseases also resulted in overestimation of cancer extension.
Conclusions: DWI has the potential in clinical appreciation to detect malignant breast tumors and support the evaluation of tumor extension. However, the benign proliferative change remains to be studied as it mimics the malignant phenomenon on the ADC map.

Editor’s picks

(Author’s comments) In early 2000s, several reports showing the utility of diffusion weighted imaging (DWI) for detecting breast cancer had emerged. DWI had been focused because it can visualize the breast cancer with high contrast without contrast material. In our article, we try to evaluate how accurate the DWI can demonstrate distribution of breast cancer. DWI of the breast is more challenging than that of other organs due to the convex shape, the air surrounding the breast, and rich fat tissue. These issues has been improving due to progression of hardware including multichannel coil and higher gradient and parallel imaging. However, there are still some limitations exist. Currently, there are two directions of breast DWI in which screening and evaluation of biological characteristics. To accomplish both, better spatial resolution, higher signal to noise ratio, stable imaging quality, and repeatability has to be obtained.

Volume 16 (2017) Issue 1 Pages 61-65

Gd-based Contrast Enhancement of the Perivascular Spaces in the Basal Ganglia

Shinji Naganawa, Toshiki Nakane, Hisashi Kawai, Toshiaki Taoka

Purpose: In textbooks, the perivascular space (PVS) is described as non-enhancing after the intravenous administration of gadolinium-based contrast agent (IV-GBCA). We noticed that the PVS sometimes has high signal intensity (SI) on heavily T₂-weighted 3D-FLAIR (hT₂-FL) images obtained 4 h after IV-GBCA. The purpose of this study was to retrospectively evaluate the contrast enhancement of the PVS.

Materials and Methods: In 8 healthy subjects and 19 patients with suspected endolymphatic hydrops, magnetic resonance cisternography (MRC) and hT₂-FL images were obtained before and 4 h after a single dose of IV-GBCA. No subjects had renal insufficiency. On axial MRC at the level of the anterior commissure (AC)-posterior commissure (PC) line, 1 cm circular regions of interest (ROIs) were drawn centering on the PVS in the bilateral basal ganglia and thalami. Three-millimeter diameter ROIs were set in the cerebrospinal fluid (CSF) of the bilateral ambient cistern. The ROIs on MRC were copied onto the hT₂-FL images and the SI was measured. The SI ratio (SIR) was defined as SIR_PVS = SI of PVS/SI of the thalami, and SIR_CSF = SI of CSF/SI of the thalami. The average of the bilateral values was used for the calculation. The SIR_CSF, SIR_PVS, and SI of the thalami were compared between before and 4 h after IV-GBCA.

Results: The SIR was increased significantly from 1.02 ± 0.37 to 2.65 ± 0.82 in the CSF (P < 0.01) and from 1.20 ± 0.35 to 2.13 ± 1.23 in the PVS at 4 h after IV-GBCA (P < 0.01). The SI of the thalami showed no significant difference.

Conclusion: The enhancement of the PVS at 4 h after IV-GBCA was confirmed even in subjects without renal insufficiency. It is possible that the GBCA in the blood vessels might have permeated into the cerebrospinal fluid (CSF) space and the PVS. This might be a first step in the imaging evaluation of the glymphatic system (waste clearance system) of the brain.

Volume 16 (2017) Issue 1 Pages 3-15

High-Resolution 3T MR Imaging of the Triangular Fibrocartilage Complex

Donald von Borstel, Michael Wang, Kirstin Small, Taiki Nozaki, Hiroshi Yoshioka

This study is intended as a review of 3Tesla (T) magnetic resonance (MR) imaging of the triangular fibrocartilage complex (TFCC). The recent advances in MR imaging, which includes high field strength magnets, multi-channel coils, and isotropic 3-dimensional (3D) sequences have enabled the visualization of precise TFCC anatomy with high spatial and contrast resolution. In addition to the routine wrist protocol, there are specific techniques used to optimize 3T imaging of the wrist; including driven equilibrium sequence (DRIVE), parallel imaging, and 3D imaging. The coil choice for 3T imaging of the wrist depends on a number of variables, and the proper coil design selection is critical for high-resolution wrist imaging with high signal and contrast-to-noise ratio. The TFCC is a complex structure and is composed of the articular disc (disc proper), the triangular ligament, the dorsal and volar radioulnar ligaments, the meniscus homologue, the ulnar collateral ligament (UCL), the extensor carpi ulnaris (ECU) tendon sheath, and the ulnolunate and ulnotriquetral ligaments. The Palmer classification categorizes TFCC lesions as traumatic (type 1) or degenerative (type 2). In this review article, we present clinical high-resolution MR images of normal TFCC anatomy and TFCC injuries with this classification system.

Volume 16 (2017) Issue 1 Pages 16-22

Volume of Interest Analysis of Spatially Normalized PRESTO Imaging to Differentiate between Parkinson Disease and Atypical Parkinsonian Syndrome

Keita Sakurai, Etsuko Imabayashi, Aya M. Tokumaru, Kimiteru Ito, Keigo Shimoji, Motoo Nakagawa, Yoshiyuki Ozawa, Masashi Shimohira, Masaki Ogawa, Satoru Morimoto, Ikuko Aiba, Noriyuki Matsukawa, Yuta Shibamoto

Purpose: Various magnetic resonance imaging (MRI) techniques including T₂*-weighted imaging, susceptibility-weighted imaging, and MR relaxometry had been performed to evaluate different patterns of brain iron depositions in Parkinsonian syndrome. The aim of the present study was to evaluate the diagnostic value of a volume of interest (VOI) analysis on the principles of echo shifting with a train of observations (PRESTO) imaging using the statistical parametric mapping (SPM) 8 and the WFU PickAtlas program for the diagnosis of Parkinsonian syndrome.,
Methods: Fifty subjects, including 13 with the Parkinsonian variant of multiple system atrophy (MSA-P), 12 with progressive supranuclear palsy (PSP), 12 with Parkinson’s disease (PD) and 13 controls were evaluated in this study. After the spatial normalization of PRESTO images on SPM8, the WFU PickAtlas program was performed to create target VOIs in the putamen, red nucleus, substantia nigra, subthalamic nucleus, and dentate nucleus. The signal intensity ratio (SIR) was calculated by normalizing the signal of each VOI to that of the cerebrospinal fluid space. These SIRs were used as determinants in receiver operating characteristic (ROC) analyses.
Results: SIR of the putamen was significantly lower in MSA-P than in PSP (P = 0.0051) and controls (P = 0.0004). In contrast, SIR of the red nucleus was significantly lower in PSP than in MSA-P (P = 0.0003), PD (P = 0.0029), and controls (P = 0.0011). In ROC analyses, SIR of the putamen exhibited the highest areas under the curves (AUCs) of 0.83 (vs. PSP) and 0.91 (vs. controls) in the diagnosis of MSA-P. On the other hand, SIR of the red nucleus exhibited the highest AUCs of 0.87 (vs. MSA-P), 0.90 (vs. PD), and 0.89 (vs. controls) in the diagnosis of PSP.
Conclusions: The VOI analysis based on spatially normalized PRESTO images may be useful for depicting hypointensity, indicative of abnormal iron depositions, of the putamen and red nucleus in the diagnosis of MSA-P and PSP.

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2018 Volume 17 Issue 3

Additive Value of 3T 3D CISS Imaging to Conventional MRI for Assessing the Abnormal Vessels of Spinal Dural Arteriovenous Fistulae Hiroyuki Uetani, Toshinori Hirai, Mika Kitajima, Minako Azuma, Shigetoshi Yano, Hideo Nakamura, Keishi Makino, Yutaka Kai, Yasunori Nagayama, Yoshihito Kadota, Yasuyuki Yamashita
MR Imaging of Xanthogranulomatous Oophoritis Minako Maruyama, Takeshi Yoshizako, Rika Yoshida, Noriyoshi Ishikawa, Satoru Kyo, Hajime Kitagaki
Time-spatial Labeling Inversion Pulse (Time-SLIP) with Pencil Beam Pulse: A Selective Labeling Technique for Observing Cerebrospinal Fluid Flow Dynamics Shuhei Shibukawa, Tosiaki Miyati, Tetsu Niwa, Mitsunori Matsumae, Tetsuo Ogino, Tomohiko Horie, Yutaka Imai, Isao Muro
Indirect Proton MR Imaging and Kinetic Analysis of ¹⁷O-Labeled Water Tracer in the Brain Kohsuke Kudo, Taisuke Harada, Hiroyuki Kameda, Ikuko Uwano, Fumio Yamashita, Satomi Higuchi, Kunihiro Yoshioka, Makoto Sasaki

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