• Korean Journal of Radiology
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• v.22 no.1
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• pp.9-22
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• 2021

Diffusion-weighted (DW) magnetic resonance imaging (MRI) is a rapid, unenhanced imaging technique that measures the motion of water molecules within tissues and provides information regarding the cell density and tissue microstructure. DW MRI has demonstrated the potential to improve the specificity of breast MRI, facilitate the evaluation of tumor response to neoadjuvant chemotherapy and can be employed in unenhanced MRI screening. However, standardization of the acquisition and interpretation of DW MRI is challenging. Recently, the European Society of Breast Radiology issued a consensus statement, which described the acquisition parameters and interpretation of DW MRI. The current article describes the basic principles, standardized acquisition protocols and interpretation guidelines, and the clinical applications of DW MRI in breast imaging.

• Investigative Magnetic Resonance Imaging
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• v.20 no.2
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• pp.88-94
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• 2016

Purpose: Fluid-attenuated inversion recovery (FLAIR) imaging can be obtained faster with shorter repletion time (TR), but it gets noisier. We hypothesized that shorter-TR FLAIR obtained at 3 tesla (3T) with a 32-channel coil may be comparable to conventional FLAIR. The aim of this study was to compare the diagnostic value between conventional FLAIR (TR = 9000 ms, FLAIR9000) and shorter-TR FLAIR (TR = 6000 ms, FLAIR6000) at 3T in terms of diffusion-weighted imaging-FLAIR mismatch. Materials and Methods: We recruited 184 patients with acute ischemic stroke (28 patients < 4.5 hours) who had undergone 5-mm diffusion-weighted imaging (DWI) and two successive 5-mm FLAIR images (no gap; in-plane resolution, $0.9{\times}0.9mm$) at 3T with a 32-channel coil. The acquisition times for FLAIR9000 and FLAIR6000 were 108 seconds (generalized autocalibrating partially parallel acquisitions [GRAPPA] = 2) and 60 seconds (GRAPPA = 3), respectively. Two radiologists independently assessed the paired imaging sets (DWI-FLAIR9000 and DWI-FLAIR6000) for the presence of matched hyperintense lesions on each FLAIR imaging. The signal intensity ratios (area of DWI lesion to contralateral normal-appearing region) on both FLAIR imaging sets were compared. Results: DWI-FLAIR9000 mismatch was present in 39 of 184 (21.2%) patients, which was perfectly the same on FLAIR6000. Three of 145 patients (2%) with DWI-matched lesions on FLAIR9000 had discrepancy on FLAIR6000, showing no significant difference (P > 0.05). Interobserver agreement was excellent for both DWI-FLAIR9000 and DWI-FLAIR6000 (k = 0.904 and 0.883, respectively). Between the two FLAIR imaging sets, there was no significant difference of signal intensity ratio (mean, standard deviation; $1.25{\pm}0.20$; $1.24{\pm}0.20$, respectively) (P > 0.05). Conclusion: For the determination of mismatch or match between DWI and FLAIR imaging, there is no significant difference between FLAIR9000 and FLAIR6000 at 3T with a 32-channel coil.

• Investigative Magnetic Resonance Imaging
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• v.20 no.4
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• pp.250-253
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• 2016

Acute Japanese encephalitis (JE) is an endemic viral infectious disease in various parts of Far East and Southeast Asian countries including Korea. Bilateral thalami are the most common involving sites in JE. Other areas including the basal ganglia, substantia nigra, red nucleus, pons, cerebral cortex and cerebellum may be also involved. We report an extremely unusual brain diffusion-weighted MR imaging (DWI) findings in a 53-year-old man with serologically proven JE involving unilateral deep gray matter and temporal lobe, which shows multifocal high signal intensities in left thalamus, left substantia nigra, left caudate nucleus and left medial temporal cortex on T2-weighted image and DWI with iso-intensity on apparent diffusion coefficient (ADC) map.

• Journal of Korean Neurosurgical Society
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• v.41 no.6
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• pp.371-376
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• 2007

Objective : The aim of this study was to investigate the usefulness of diffusion-weighted imaging [DWI] and apparent diffusion coefficiency [ADC] in distinguishing brain abscesses from cystic or necrotic brain tumors, which are difficult to be differentiated by conventional magnetic resonance imaging techniques. Methods : Seven patients with brain abscesses and ten patients with cystic brain tumors were studied from September 2003 to October 2005. Abscess, subdural empyema and ventriculitis were categorized to the abscess group and cystic or necrotic brain gliomas or metastatic brain tumors into the tumor group. Preoperative magnetic resonance images were performed in all patients and diffusion-weighted images and apparent diffusion coefficiency values of lesions were calculated directly from software of 1.5 tesla MRI [General Electrics, USA]. The ratio of the ADC of the lesion to contralateral regional ADC was also measured [relative ADC, rADC]. Results : The average ADC value of pyogenic abscesses group was $0.82+/-0.14{\times}10^{-3}\;[mean+/-S.D.]\;mm^2/s$ and mean rADC was 0.75. Cystic or necrotic areas had high ADC values [$2.49+/-0.79{\times}10^{-3}\;mm^2/s$, mean rADC=2.14]. ADC and rADC values of abscesses group showed about three times lower values than those of cystic or necrotic tumor group. Conclusion : This study results based on numerical comparison of signal intensities and quantitative analysis to distinguish between brain abscess and cystic or necrotic tumor, DWI and ADC mapping are thought to be very useful diagnostic tools.

• Investigative Magnetic Resonance Imaging
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• v.26 no.2
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• pp.83-95
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• 2022

The purpose of this study was to establish and provide guidelines for the standardized acquisition and interpretation of diffusion-weighted magnetic resonance imaging (DW-MRI) to improve the image quality and reduce the variability of the results interpretation. The standardized protocol includes the use of high-resolution DW-MRI with advanced techniques and post-processing. The aim of the protocol is to increase the effectiveness of the medical image information exchange involved in the construction, activation, and exchange of clinical information for healthcare use. An organized interpretation form could make DW-MRIs' interpretation easier and more familiar. Herein, the authors briefly review the basic principles, optimized image acquisition, standardized interpretation guidelines, false negative and false positive cases of DW-MRI, and provide a standard interpretation form and examples of various cases to help users become more familiar with the DW-MRI.

• Investigative Magnetic Resonance Imaging
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• v.21 no.3
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• pp.154-161
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• 2017

Purpose: To evaluate the diagnostic performance of diffusion-weighted steady-state free precession (DW-SSFP) in comparison to diffusion-weighted echo-planar imaging (DW-EPI) for differentiating the neoplastic and benign osteoporotic vertebral compression fractures. Materials and Methods: The subjects were 40 patients with recent vertebral compression fractures but no history of vertebroplasty, spine operation, or chemotherapy. They had received 3-Tesla (T) spine magnetic resonance imaging (MRI), including both DW-SSFP and DW-EPI sequences. The 40 patients included 20 with neoplastic vertebral fracture and 20 with benign osteoporotic vertebral fracture. In each fracture lesion, we obtained the signal intensity normalized by the signal intensity of normal bone marrow (SI norm) on DW-SSFP and the apparent diffusion coefficient (ADC) on DW-EPI. The correlation between the SI norm and the ADC in each lesion was analyzed using linear regression. The optimal cut-off values for the diagnosis of neoplastic fracture were determined in each sequence using Youden's J statistics and receiver operating characteristic curve analyses. Results: In the neoplastic fracture, the median SI norm on DW-SSFP was higher and the median ADC on DW-EPI was lower than the benign osteoporotic fracture (5.24 vs. 1.30, P = 0.032, and 0.86 vs. 1.48, P = 0.041, respectively). Inverse linear correlations were evident between SI norm and ADC in both neoplastic and benign osteoporotic fractures (r = -0.45 and -0.61, respectively). The optimal cut-off values for diagnosis of neoplastic fracture were SI norm of 3.0 in DW-SSFP with the sensitivity and specificity of 90.4% (95% confidence interval [CI]: 81.0-99.0) and 95.3% (95% CI: 90.0-100.0), respectively, and ADC of 1.3 in DW-EPI with the sensitivity and specificity of 90.5% (95% CI: 80.0-100.0) and 70.4% (95% CI: 60.0-80.0), respectively. Conclusion: In 3-T MRI, DW-SSFP has comparable sensitivity and specificity to DW-EPI in differentiating the neoplastic vertebral fracture from the benign osteoporotic vertebral fracture.

• Investigative Magnetic Resonance Imaging
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• v.21 no.4
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• pp.264-268
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• 2017

South Korea has the highest reported suicide rate among all countries belonging to the Organization for Economic Cooperation and Development. Nitrogen is a colorless, odorless and nontoxic gas. Nitrogen gas has, however, been recently used as a method of attempted suicide, its nontoxity notwithstanding. We herein report on an unusual case involving a 30-year-old male who presented with symptoms after a suicide attempt by nitrogen inhalation. Diffusion-weighted imaging of his brain was showed curvilinear high signal intensity in the bilateral frontal and right occipital cortices, with subtle low apparent diffusion coefficient value. In addition, T2-weighted images and fluid attenuated inversion recovery images revealed subtle high signal intensity in the bilateral frontal cortices, basal ganglia and occipital cortices with contrast enhancement.

• Journal of Radiation Industry
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• v.10 no.4
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• pp.227-230
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• 2016

DWI of biological effects are independent of magnetic field strength in various regions. High field strength, however, does affect the signal to noise ratio (SNR) and artifacts of diffusion weighted imaging (DWI) images, which ultimately will influence the quantitative of diffusion imaging. In this study, the effects of field strength on DWI are reviewed. The effects of the diseases also are discussed. Comparing DWI in cerebellum, WM, GM, Hyperacute region measurements both as a function of field strength (1.5T and 3.0T). Overall, the SNR of the DWI roughly doubled going from 1.5 T to 3.0 T. In summary, DWI studies at 3.0 T is provided significantly improved DWI measurements relative to studies at 1.5T.

• Investigative Magnetic Resonance Imaging
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• v.18 no.2
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• pp.176-181
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• 2014

Primary non-Hodgkin lymphoma (NHL) of the breast is a very rare disease, and the mammographic and ultrasonographic findings of breast lymphoma are variable. There are several reports of magnetic resonance (MR) imaging findings in patients with breast lymphomas; however, few reports have described the findings observed on MR spectroscopy or the features of diffusion weighted (DW) imaging. The authors report the findings of classical MR imaging, MR spectroscopy and DW imaging of a 48-year-old woman and a 40-year-old woman with primary non-Hodgkin's lymphoma of breasts. Mammography and breast ultrasonography revealed a mass with circumscribed margin. The mass showed strong enhancement after contrast injection on MR imaging. DW imaging showed reduced diffusion and high-amplitude choline (Cho) peak at 3.22 ppm was detected by single voxel MR spectroscopy which was consistent with malignancy.

• Journal of Korean Neurosurgical Society
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• v.38 no.1
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• pp.23-27
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• 2005

Objective : The aim of this study is to assess the significance of an apparent diffusion coefficient[ADC] study for diagnosis of ventriculitis. Methods : Seven patients with ventriculitis were enrolled in this study. Diffusion-weighted[DW] magnetic resonance images[MRI] and ADC maps in the dependent intraventricular collection, periventricular white matter and non-dependent cerebrospinal fluid[CSF] were obtained. The images and ADC data from the different lesions were compared. Results : The DW MRI showed marked hyperintensity in the purulent pus lesion, and the corresponding ADC maps revealed prominent hypointensity and restricted ADC values compared with the non-dependent CSF and normal white matter. Conclusion : The decreased ADC value and increased signal intensity of the dependent intraventricular fluid on the DW MRI show restricted water diffusion in the purulent fluid, which is indicative of a pyogenic ventriculitis diagnosis.