PURPOSE: A new inhomogeneity correction method based on two-point Dixon sequence is proposed to obtain water and fat images at 0.35T, low field magnetic resonance imaging (MRI) system. MATERIALS AND METHODS: Joint phase-magnitude density function (JPMF) is obtained from the in-phase and out-of-phase images by the two-point Dixon method. The range of the water signal is adjusted from the JPMF, and 3D inhomogeneity map is obtained from the phase of corresponding water volume. The 3D inhomogeneity map is used to correct the inhomogeneity field iteratively. RESULTS: The proposed water-fat imaging method was successfully applied to various organs. The proposed 3D inhomogeneity correction algorithm provides good performances in overall multi-slice images. CONCLUSION: The proposed water-fat separation method using JPMF is robust to field inhomogeneity. Three dimensional inhomogeneity map and the iterative inhomogeneity correction algorithm improve water and fat imaging substantially.
Joints ; Magnetic Resonance Imaging ; Water

Objective: The purpose of this study was to evaluate the magnetic resonance (MR) characteristics and applicability of new, uniform, extremely small iron-based nanoparticles (ESIONs) with 3–4-nm iron cores using contrast-enhanced magnetic resonance angiography (MRA). Materials and Methods: Seven types of ESIONs were used in phantom and animal experiments with 1.5T, 3T, and 4.7T scanners. The MR characteristics of the ESIONs were evaluated via phantom experiments. With the ESIONs selected by the phantom experiments, animal experiments were performed on eight rabbits. In the animal experiments, the in vivo kinetics and enhancement effect of the ESIONs were evaluated using half-diluted and non-diluted ESIONs. The between-group differences were assessed using a linear mixed model. A commercially available gadolinium-based contrast agent (GBCA) was used as a control. Results: All ESIONs showed a good T1 shortening effect and were applicable for MRA at 1.5T and 3T. The relaxivity ratio of the ESIONs increased with increasing magnetic field strength. In the animal experiments, the ESIONs showed peak signal intensity on the first-pass images and persistent vascular enhancement until 90 minutes. On the 1-week follow-up images, the ESIONs were nearly washed out from the vascular structures and organs. The peak signal intensity on the first-pass images showed no significant difference between the non-diluted ESIONs with 3-mm iron cores and GBCA (p = 1.000). On the 10-minutes post-contrast images, the non-diluted ESIONs showed a significantly higher signal intensity than did the GBCA (p < 0.001). Conclusion In the phantom experiments, the ESIONs with 3–4-nm iron oxide cores showed a good T1 shortening effect at 1.5T and 3T. In the animal experiments, the ESIONs with 3-nm iron cores showed comparable enhancement on the first-pass images and superior enhancement effect on the delayed images compared to the commercially available GBCA at 3T.

Objective: The purpose of this study was to evaluate the magnetic resonance (MR) characteristics and applicability of new, uniform, extremely small iron-based nanoparticles (ESIONs) with 3–4-nm iron cores using contrast-enhanced magnetic resonance angiography (MRA). Materials and Methods: Seven types of ESIONs were used in phantom and animal experiments with 1.5T, 3T, and 4.7T scanners. The MR characteristics of the ESIONs were evaluated via phantom experiments. With the ESIONs selected by the phantom experiments, animal experiments were performed on eight rabbits. In the animal experiments, the in vivo kinetics and enhancement effect of the ESIONs were evaluated using half-diluted and non-diluted ESIONs. The between-group differences were assessed using a linear mixed model. A commercially available gadolinium-based contrast agent (GBCA) was used as a control. Results: All ESIONs showed a good T1 shortening effect and were applicable for MRA at 1.5T and 3T. The relaxivity ratio of the ESIONs increased with increasing magnetic field strength. In the animal experiments, the ESIONs showed peak signal intensity on the first-pass images and persistent vascular enhancement until 90 minutes. On the 1-week follow-up images, the ESIONs were nearly washed out from the vascular structures and organs. The peak signal intensity on the first-pass images showed no significant difference between the non-diluted ESIONs with 3-mm iron cores and GBCA (p = 1.000). On the 10-minutes post-contrast images, the non-diluted ESIONs showed a significantly higher signal intensity than did the GBCA (p < 0.001). Conclusion In the phantom experiments, the ESIONs with 3–4-nm iron oxide cores showed a good T1 shortening effect at 1.5T and 3T. In the animal experiments, the ESIONs with 3-nm iron cores showed comparable enhancement on the first-pass images and superior enhancement effect on the delayed images compared to the commercially available GBCA at 3T.

E.S.T. is performed not only for the treatment but also for the diagnosis of biliary tract diseases. E.S.T. serves as a diagnostic aid for some of biliary tract diseases which require such procedures as a peroral cholangioscopy or biopsy of the biliary duct for precise diagnosis and further differential diagnosis. The diseases of our patients were diagnosed by clinical findings and such diagnostic maneuvers as abdominal ultrasonography, intravenous cholangiography, percutaneous transhepatic chorangiography(P.T.C.), endoscopic retrograde chorangiopancreatography(E.R.C.P.), In all the two cases, abdominal ultrasonography revealed dilated extrahepatic duct, but biliary trees were not visualized at E.R.C.P. In one of the two cases, P.T.C. revealed a filling defect with dilated common bile ducts(CBD) but we could not make a differential diagnosis of CBD stone from CBD cancer. In another of the two cases, on which intravenous cholangiography was done, we could not see CBD. For the purpuse of precise diagnosis and further differential diagnosis, we performed EST and then ERCP thraugh widened papillae. With those procedures, CBD stones were shown.
Bile ; Biliary Tract Diseases ; Biopsy ; Cholangiography ; Cholangiopancreatography, Endoscopic Retrograde ; Diagnosis ; Diagnosis, Differential ; Humans ; Ultrasonography

We found an error in our published article.

PURPOSE: We investigate biases in the assessments of left ventricular function (LVF), by compressed sensing (CS)-cine magnetic resonance imaging (MRI). MATERIALS AND METHODS: Cardiovascular cine images with short axis view, were obtained for 8 volunteers without CS. LVFs were assessed with subsampled data, with compression factors (CF) of 2, 3, 4, and 8. A semi-automatic segmentation program was used, for the assessment. The assessments by 3 CS methods (ITSC, FOCUSS, and view sharing (VS)), were compared to those without CS. Bland-Altman analysis and paired t-test were used, for comparison. In addition, real-time CS-cine imaging was also performed, with CF of 2, 3, 4, and 8 for the same volunteers. Assessments of LVF were similarly made, for CS data. A fixed compensation technique is suggested, to reduce the bias. RESULTS: The assessment of LVF by CS-cine, includes bias and random noise. Bias appeared much larger than random noise. Median of end-diastolic volume (EDV) with CS-cine (ITSC or FOCUSS) appeared −1.4% to −7.1% smaller, compared to that of standard cine, depending on CF from (2 to 8). End-systolic volume (ESV) appeared +1.6% to +14.3% larger, stroke volume (SV), −2.4% to −16.4% smaller, and ejection fraction (EF), −1.1% to −9.2% smaller, with P < 0.05. Bias was reduced from −5.6% to −1.8% for EF, by compensation applied to real-time CS-cine (CF = 8). CONCLUSION: Loss of temporal resolution by adopting missing data from nearby cardiac frames, causes an underestimation for EDV, and an overestimation for ESV, resulting in underestimations for SV and EF. The bias is not random. Thus it should be removed or reduced for better diagnosis. A fixed compensation is suggested, to reduce bias in the assessment of LVF.
Bias (Epidemiology) ; Compensation and Redress ; Diagnosis ; Magnetic Resonance Imaging ; Magnetic Resonance Imaging, Cine ; Noise ; Stroke Volume ; Ventricular Function, Left ; Volunteers

Purpose: Myocardial T1 and T2 relaxation times are affected by technical factors such as cardiovascular magnetic resonance platform/vendor. We aimed to validate T1 and T2 mapping sequences using a phantom; establish reference T1, T2, and extracellular volume (ECV) measurements using two sequences at 3T in normal Koreans; and compare the protocols and evaluate the differences from previously reported measurements. Materials and Methods: Eleven healthy subjects underwent cardiac magnetic resonance imaging (MRI) using 3T MRI equipment (Verio, Siemens, Erlangen, Germany). We did phantom validation before volunteer scanning: T1 mapping with modified look locker inversion recovery (MOLLI) with 5(3)3 and 4(1)3(1)2 sequences, and T2 mapping with gradient echo (GRE) and TrueFISP sequences. We did T1 and T2 mappings on the volunteers with the same sequences. ECV was also calculated with both sequences after gadolinium enhancement. Results: The phantom study showed no significant differences from the gold standard T1 and T2 values in either sequence. Pre-contrast T1 relaxation times of the 4(1)3(1)2 protocol was 1142.27 ± 36.64 ms and of the 5(3)3 was 1266.03 ± 32.86 ms on the volunteer study. T2 relaxation times of GRE were 40.09 ± 2.45 ms and T2 relaxation times of TrueFISP were 38.20 ± 1.64 ms in each. ECV calculation was 24.42% ± 2.41% and 26.11% ± 2.39% in the 4(1)3(1)2 and 5(3)3 protocols, respectively, and showed no differences at any segment or slice between the sequences. We also calculated ECV from the pre-enhancement T1 relaxation time of MOLLI 5(3)3 and the postenhancement T1 relaxation time of MOLLI 4(1)3(1)2, with no significant differences between the combinations. Conclusion Using phantom-validated sequences, we reported the normal myocardial T1, T2, and ECV reference values of healthy Koreans at 3T. There were no statistically significant differences between the sequences, although it has limited statistical value due to the small number of subjects studied. ECV showed no significant differences between calculations based on various pre- and post-mapping combinations.

About 50 cases of Listeria monocytogenes endocarditis were reported in worldwide literature in 1950-1995. Though clinical and laboratory data suggest a similarity with other types of bacterial endocarditis, the prognosis is more unfavorable and the mortality rate is higher. However, there has not been a report in Korean literature. We report a case of 55 year-old male with rapidly progressive native aortic endocarditis caused by L. monocytogenes. He had neither history of underlying cardiac disease nor definitive predisposing factor. He presented mild dyspnes, chest pain and febrile sensation for a week. Echocardiography showed large vegetation in aortic valve and severe aortic regurgitation. L. monocytogenes grew on blood culture. We underwent artificial aortic valve replacement due to rapidly progessive heart failure. A thromboembolism occured at right femoral artery on postoperative 2nd day was removed successfully. He discharged without any sequellae.
Adult* ; Aortic Valve ; Aortic Valve Insufficiency ; Causality ; Chest Pain ; Echocardiography ; Endocarditis* ; Endocarditis, Bacterial ; Femoral Artery ; Heart Diseases ; Heart Failure ; Humans ; Listeria monocytogenes* ; Listeria* ; Male ; Middle Aged ; Mortality ; Prognosis ; Sensation ; Thromboembolism

PURPOSE: This study was performed to evaluate the characteristics of rat mesenchymal stem cells (RMSCs) transduced with human ferritin gene and investigate in vitro MRI detectability of ferritin-transduced RMSCs. MATERIALS AND METHODS: The RMSCs expressing both myc-tagged human ferritin heavy chain subunit (myc-FTH) and green fluorescence protein (GFP) were transduced with lentiviurs. Transduced cells were sorted by GFP expression using a fluorescence-activated cell sorter. Myc-FTH and GFP expression in transduced cells were detected by immunofluorescence staining. The cell proliferative ability and viability were assessed by MTT assay. The RMSC surface markers (CD29+/CD45-) were analyzed by flow cytometry. The intracellular iron amount was measured spectrophotometically and the presence of ferritin-iron accumulation was detected by Prussian blue staining. In vitro magnetic resonance imaging (MRI) study of cell phantoms was done on 9.4 T MR scanner to evaluate the feasibility of imaging the ferritin-transduced RMSCs. RESULTS: The myc-FTH and GFP genes were stably transduced into RMSCs. No significant differences were observed in terms of biologic properties in transduced RMSCs compared with non-transduced RMSCs. Ferritin-transduced RMSCs exhibited increased iron accumulation ability and showed significantly lower T2 relaxation time than non-transduced RMSCs. CONCLUSION: Ferritin gene as MR reporter gene could be used for non-invasive tracking and visualization of therapeutic mesenchymal stem cells by MRI.
Animals ; Apoferritins ; Ferritins ; Ferrocyanides ; Flow Cytometry ; Fluorescence ; Fluorescent Antibody Technique ; Genes, Reporter ; Humans ; Iron ; Magnetic Resonance Imaging ; Mesenchymal Stromal Cells ; Rats ; Relaxation ; Track and Field

PURPOSE: To evaluate the ability of optical coherence tomography (OCT) to provide real-time, high-resolution structural analysis of the full thickness rabbit articular repair tissue following chondrocyte transplantation. MATERIALS AND METHODS: Full thickness articular cartilage defects were created in the patellar grooves of the distal femur of 30 adult rabbit knee joints. Allogenic cultured chondrocytes embedded in collagen gels were implanted into the surgical defects. Six animals per time point were sacrificed at 2, 4, 8, 12 and 24 weeks after surgery. The repair tissues were sequentially analyzed by arthroscopic surface imaging, OCT, and histology. RESULTS: OCT was able to identify the bone and cartilage interface in normal rabbit articular cartilage and regenerated cartilage at 24 weeks post chondrocyte implantation. OCT was able to identify fine surface fibrillations at 24 weeks. More importantly, OCT was able to detect the embedded gaps between the repair tissue and surrounding cartilage. CONCLUSION: OCT provides a minimal invasive means to obtain an instant "optical biopsy" of the rabbit articular repair tissue without damaging the specimen.
Adult ; Animals ; Cartilage ; Cartilage, Articular* ; Chondrocytes* ; Collagen ; Femur ; Gels ; Humans ; Knee Joint ; Tomography, Optical Coherence*