Single-Slab 3D Fast Spin Echo Imaging: T1 -Contrast Perspective

Fast spin echo (FSE) in magnetic resonance imaging has long been a main workhorse in clinical routines due to its versatile image contrast and robustness in improving magnetic field inhomogeneities. Nevertheless, the conventional high flip angle strategy limits its imaging efficiency, including high energy deposition to subjects, prolonged imaging time due to a necessarily short echo train, and substantial signal modulation along the echo train. Particularly, achieving high resolution T1-weighted imaging within a reasonable imaging time is challenging due to a very short echo train. In this review, we introduce T1-optimized single-slab 3D FSE imaging with variable refocusing flip angles as a promising solution to the above problems with its clinical applications. We provide a general description of a single-slab 3D pulse sequence and introduce its T1-optimized version with the required configuration of radio frequency and gradient pulses. Subsequently, the T1-weighted single-slab 3D FSE is investigated for signal evolution along the echo train, image contrasts, and flow sensitivity. Given the characteristics of high T1-weighted contrast and flow sensitivity, we demonstrate the clinical application of the single-slab 3D FSE, including high resolution structural imaging, as an alternative to conventional magnetization prepared spoiled gradient echo, highly tumor-targeted contrast-enhanced imaging for efficient detection of small metastases, and high-resolution vessel wall imaging for stroke diagnosis.

COVID-19 Mimicking Acute Colitis / 대한내과학회지

On 11 February, 2020, the World Health Organization announced that COVID-19 was a novel coronavirus disease first detected in Wuhan, Hubei Province, China. COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The complete clinical picture is not fully known. Illness ranges from mild to fatal. The common symptoms include fever, cough, and dyspnea usually developing 2-14 days after exposure. However, diarrhea was present in a few patients with COVID-19. We report a case of COVID-19 mimicking acute colitis.

COVID-19 Mimicking Acute Colitis / 대한내과학회지

On 11 February, 2020, the World Health Organization announced that COVID-19 was a novel coronavirus disease first detected in Wuhan, Hubei Province, China. COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The complete clinical picture is not fully known. Illness ranges from mild to fatal. The common symptoms include fever, cough, and dyspnea usually developing 2-14 days after exposure. However, diarrhea was present in a few patients with COVID-19. We report a case of COVID-19 mimicking acute colitis.

Quality of Anticoagulation and Treatment Satisfaction in Patients with Non-Valvular Atrial Fibrillation Treated with Vitamin K Antagonist: Result from the KORean Atrial Fibrillation Investigation II

BACKGROUND: Vitamin K antagonist (VKA) to prevent thromboembolism in non-valvular atrial fibrillation (NVAF) patients has limitations such as drug interaction. This study investigated the clinical characteristics of Korean patients treated with VKA for stroke prevention and assessed quality of VKA therapy and treatment satisfaction. METHODS: We conducted a multicenter, prospective, non-interventional study. Patients with CHADS2 ≥ 1 and treated with VKA (started within the last 3 months) were enrolled from April 2013 to March 2014. Demographic and clinical features including risk factors of stroke and VKA treatment information was collected at baseline. Treatment patterns and international normalized ratio (INR) level were evaluated during follow-up. Time in therapeutic range (TTR) > 60% indicated well-controlled INR. Treatment satisfaction on the VKA use was measured by Treatment Satisfaction Questionnaire for Medication (TSQM) after 3 months of follow-up. RESULTS: A total of 877 patients (age, 67; male, 60%) were enrolled and followed up for one year. More than half of patients (56%) had CHADS2 ≥ 2 and 83.6% had CHA2DS2-VASc ≥ 2. A total of 852 patients had one or more INR measurement during their follow-up period. Among those patients, 25.5% discontinued VKA treatment during follow-up. Of all patients, 626 patients (73%) had poor-controlled INR (TTR < 60%) measure. Patients' treatment satisfaction measured with TSQM was 55.6 in global satisfaction domain. CONCLUSION: INR was poorly controlled in Korean NVAF patients treated with VKA. VKA users also showed low treatment satisfaction.

Image Denoising for Metal MRI Exploiting Sparsity and Low Rank Priors

PURPOSE: The management of metal-induced field inhomogeneities is one of the major concerns of distortion-free magnetic resonance images near metallic implants. The recently proposed method called “Slice Encoding for Metal Artifact Correction (SEMAC)” is an effective spin echo pulse sequence of magnetic resonance imaging (MRI) near metallic implants. However, as SEMAC uses the noisy resolved data elements, SEMAC images can have a major problem for improving the signal-to-noise ratio (SNR) without compromising the correction of metal artifacts. To address that issue, this paper presents a novel reconstruction technique for providing an improvement of the SNR in SEMAC images without sacrificing the correction of metal artifacts. MATERIALS AND METHODS: Low-rank approximation in each coil image is first performed to suppress the noise in the slice direction, because the signal is highly correlated between SEMAC-encoded slices. Secondly, SEMAC images are reconstructed by the best linear unbiased estimator (BLUE), also known as Gauss-Markov or weighted least squares. Noise levels and correlation in the receiver channels are considered for the sake of SNR optimization. To this end, since distorted excitation profiles are sparse, l1 minimization performs well in recovering the sparse distorted excitation profiles and the sparse modeling of our approach offers excellent correction of metal-induced distortions. RESULTS: Three images reconstructed using SEMAC, SEMAC with the conventional two-step noise reduction, and the proposed image denoising for metal MRI exploiting sparsity and low rank approximation algorithm were compared. The proposed algorithm outperformed two methods and produced 119% SNR better than SEMAC and 89% SNR better than SEMAC with the conventional two-step noise reduction. CONCLUSION: We successfully demonstrated that the proposed, novel algorithm for SEMAC, if compared with conventional de-noising methods, substantially improves SNR and reduces artifacts.

Effectiveness of 32-element Surface Coil Array for Accelerated Volume-Targeted Breath-Hold Coronary MRA

PURPOSE: To compare 12 and 32-element surface coil arrays for highly accelerated coronary magnetic resonance angiography (MRA) using parallel imaging. MATERIALS AND METHODS: Steady state free precession coronary MRA was performed in 5 healthy volunteers at 1.5 T whole body MR scanner using both 12 and 32-element surface coil arrays. Left anterior descending and right coronary artery data sets were acquired for each volunteer. Data sets were sub-sampled for parallel imaging using reduction factors from 1 to 6. Mean geometry factor (g-factor), maximum g-factor, and artifact level were calculated for each of the two coil arrays. RESULTS: Over all reduction factors, the mean and maximum g-factors and artifact level were significantly reduced using the 32-element array compared to the 12-element array (P << 0.1). The mean g-factor was sensitive to the imaging orientations of coronary arteries while the maximum g-factor and artifact level were independent of orientation. CONCLUSION: The 32-element surface coil array significantly improves artifact and noise suppression for highly accelerated coronary MRA using parallel imaging. The increased acceleration factors made feasible with the 32-element array offer the potential to enhance spatial resolution or increase volumetric coverage for 3D coronary MRA.