Purpose: To evaluate the clinical significance of T1 high signal intensity on the globus pallidus as a predictor of severe hepatic encephalopathy in patients with acute-on-chronic liver failure (ACLF), which is a distinct syndrome characterized by multi-organ dysfunction including cerebral failure. Materials and Methods: From January 2002 to April 2014, we retrospectively reviewed the magnetic resonance imaging (MRI) findings and clinical and magnetic resonance (MR) features of 74 consecutive patients (44 men and 30 women; mean age, 59.5 years) with liver cirrhosis. The chronic liver failure-sequential organ failure assessment score was used to diagnose ACLF. The pallidal index (PI), calculated by dividing the mean signal intensity of the globus pallidus by that of the subcortical frontal white matter were compared according to ACLF. The PI was compared with the Model for End-Stage Liver Disease (MELD) score in predicting the development of ACLF. Results: Fifteen patients who were diagnosed with ACLF had higher hepatic encephalopathy grades (initial, P = 0.024; follow-up, P = 0.002), MELD scores (P < 0.001), and PI (P = 0.048). In the ACLF group, the mean PI in patients with cerebral failure was significantly higher than that in the patients without cerebral failure (1.33 vs. 1.20, P = 0.039). In patients with ACLF, the area under the curve (AUC) for PI was 0.680 (95% confidence intervals [CI], 0.52-0.85), which was significantly lower than that for the MELD score (AUC, 0.88; 95% CI, 0.77-0.99) (P = 0.04). Conclusion: The PI can be an ancillary biomarker for predicting the development of ACLF and severe hepatic encephalopathy.

Purpose: To optimize the timing of scans using cardiac magnetic resonance contrast-enhanced timing robust angiography (CMR-CENTRA) for electroanatomic mapping (EAM) of the right atrium (RA) and left atrium (LA) in patients with atrial fibrillation (AF). Materials and Methods: Fifty patients with AF (38 men; mean age, $59.6{\pm}9.3years$) underwent CMR-CENTRA in preparation for EAM. The CMR-CENTRA data were acquired at five different scan times: 0 seconds, 5 seconds, 10 seconds, 15 seconds, and 20 seconds after an intravenous injection of contrast media. To evaluate the degree of contrast enhancement, right atrial relative contrast (RA-RC) and left atrial relative contrast (LA-RC) on the CMR-CENTRA scans were assessed at each time point. The three-dimensional (3D) reconstruction of the RA and LA for the EAM system was performed using the CMR-CENTRA data. Results: A CMR-CENTRA at a scan time of 10 seconds showed significantly greater LA-RC (P < 0.05) compared with all other scan times. A CMR-CENTRA at a scan time of 15 seconds showed significantly greater RA-RC (P < 0.05) compared with all other scan times. In the 3D reconstruction of the RA, the success rates of CMR-CENTRA at scan times of 10 seconds and 15 seconds were 18% and 100%, respectively. In the 3D reconstruction of the LA, the success rates of CMR-CENTRA at 10- and 15-second scan times were 100%. Conclusion: The CMR-CENTRA data acquired at 15 seconds after the injection of contrast media is appropriate for the preparation of an EAM system that is focused on the RA and LA in patients with AF.

Purpose: To evaluate differences in staging accuracy of prostate cancer according to the extent of hemorrhage on multiparametric MRI performed after biopsy. Materials and Methods: We enrolled 71 consecutive patients with biopsy-proven prostate cancer. Patients underwent MRI followed by a prostatectomy at our institution in 2014. Two radiologists reviewed the MRI to determine the tumor stage. Correlation between biopsy-MRI interval and extent of hemorrhage was evaluated. Regression analyses were used to determine factors associated with accuracy of tumor staging. Results: The mean interval between biopsy and MRI was $17.4{\pm}10.2days$ (range, 0-73 days). The interval between prostate biopsy and MRI and the extent of hemorrhage were not significantly correlated (P = 0.880). There was no significant difference in the accuracy rate of staging between the small and large hemorrhage groups. Conclusion: Biopsy-induced hemorrhage in the prostate gland is not sufficiently absorbed over time. The extent of hemorrhage and the short interval between biopsy and MRI may not impair tumor detection or staging on multiparametric MRI.

Purpose: To identify the differences between injected cement volumes during vertebroplasty procedures according to the enhancement pattern of pre-procedure magnetic resonance imaging (MRI) findings. Materials and Methods: Thirty-two patients who underwent 52 vertebroplasty procedures as well as pre-procedure contrast-enhanced spine MRI in the authors' institution were reviewed retrospectively. The 52 procedures were divided into two groups according to different enhancement patterns shown by pre-procedure MR imaging [E(+) and E(-)]. The volumes of the enhancing/non-enhancing portions of the fractured vertebral body shown by pre-procedural MR imaging were calculated and compared to the volumes of the injected cement during the vertebroplasty procedures. Results: The 52 injections included 28 (56%) in Group E(+) and 24 (44%) in Group E(-). The actual volume ratio of the injected cement to the volume of the non-enhanced or enhanced region calculated based on the contrast-enhanced MRI was $0.22{\pm}0.11(cc/cm^3)$ in the E(+) group and $0.93{\pm}0.62(cc/cm^3)$ in the E(-) group. The average amount of injected cement was significantly different between Group E(+) and Group E(-) (P < 0.001). In addition, the ratio of the injected cement amount to the volume of the enhanced or non-enhanced portion based on the contrast-enhanced MRI in Group E(-) was significantly higher than that of Group E(+) (P < 0.001). Conclusion: Different enhancement patterns shown by pre-procedure MRI can predictors of the injected cement volume during vertebroplasty procedures for osteoporotic fractures.

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.

Purpose: To evaluate the imaging findings of desmoid tumors using various imaging modalities and to evaluate whether diffusion-weighted imaging (DWI) can help differentiate between desmoid and malignant tumors. Materials and Methods: The study included 27 patients with pathologically confirmed desmoid tumors. Two radiologists reviewed 23 computed tomography (CT), 12 magnetic resonance imaging (MRI) and 8 positron emission tomography-computed tomography (PET-CT) scans of desmoid tumors and recorded data regarding the shape, multiplicity, size, location, degree of enhancement, and presence or absence of calcification or hemorrhage. The signal intensity of masses on T1- and T2-weighted imaging and the presence or absence of whirling or band-like low signal intensity on T2-weighted imaging were recorded. The apparent diffusion coefficient (ADC) values of the desmoid tumors in nine patients with DWIs were compared with the ADC values of 32 malignant tumors. The maximum standardized uptake value ($SUV_{max}$) on PET-CT images was measured in 8 patients who underwent a PET-CT. Results: The mean size of the 27 tumors was 6.77 cm (range, 2.5-26 cm) and four tumors exhibited multiplicity. The desmoid tumors were classified by shape as either mass forming (n = 18), infiltrative (n = 4), or combined (n = 5). The location of the tumors was either intra-abdominal (n = 15), within the abdominal wall (n = 8) or extra-abdominal (n = 4). Among the 27 tumors, 21 showed moderate to marked enhancement and 22 showed homogeneous enhancement. Two tumors showed calcifications and one displayed hemorrhage. Eleven of the 12 MR T2-weighted images showed whirling or band-like low signal intensity areas in the mass. The mean ADC value of the desmoid tumors ($1493{\times}10^{-6}mm^2/s$) was significantly higher than the mean of the malignant soft tissue tumors ($873{\times}10^{-6}mm^2/s$, P < 0.001). On the PET-CT images, all tumors exhibited an intermediate $SUV_{max}$ (mean, 3.7; range, 2.3-4.5). Conclusion: Desmoids tumors showed homogenous, moderate to marked enhancement on CT and MRI scans and a characteristic whirling or band-like pattern on T2-weighted images. DWI can be useful for the differentiation of desmoid tumors from malignant soft tissue tumors.

Purpose: To compare different MR sequences for quantification of gadolinium concentration. Materials and Methods: Gadolinium contrast agents were diluted into 36 different concentrations. They were scanned using gradient echo (GRE) and ultrashort echo time (UTE) and R1, $R2^*$ and phase values were estimated from collected data. For analysis, ROI masks were made for each concentration and then ROI value was measured by mean and standard deviation from the estimated quantitative maps. Correlation analysis was performed and correlation coefficient was calculated. Results: Using GRE sequence, R1 showed a strong linear correlation at concentrations of 10 mM or less, and $R2^*$ showed a strong linear correlation between 10 to 100 mM. The phase of GRE generally exhibited a negative linear relationship for concentrations of 100 mM or less. In the case of UTE, the phase had a strong negative linear relationship at concentrations 100 mM or above. Conclusion: R1, which was calculated by conventional GRE, showed a high performance of quantification for lower concentrations, with a correlation coefficient of 0.966 (10 mM or less). $R2^*$ showed stronger potential for higher concentrations with a correlation coefficient of 0.984 (10 to 100 mM), and UTE phase showed potential for even higher concentrations with a correlation coefficient of 0.992 (100 mM or above).

Schwannomas are benign nerve sheath tumors that are typically located in soft tissue. Occasionally, schwannomas involve osseous structures. These intraosseous schwannomas are generally benign neoplasms that account for less than 0.2% of primary bone tumors. Schwannomas are very rarely observed in long bones. We present a case of a schwannoma affecting the proximal femur with a coincident subchondral fracture of the femoral head. A 38-year-old-male presented with left hip pain without deteriorating locomotor function. Plain film radiographs displayed a lobulating contoured lesion within the intertrochanteric portion of the femur. The magnetic resonance imaging (MRI) scans showed a tumor occupying the intertrochanteric region. Diffuse bone marrow edema, especially in the subchondral and head portions of the femur that was possibly due to the subchondral insufficiency fracture was also noted. The lesion was surgically excised and bone grafting was performed. Histologically, there was diffuse infiltrative growth of the elongated, wavy, and tapered cells with collagen fibers, which are findings that are characteristic of intraosseous schwannoma. Although very rare, intraosseous schwannoma should be included in the differential diagnosis of radiographically benign-appearing, non-aggressive lesions arising in the femur. The concomitant subchondral fracture of the femoral head confounded the correct diagnosis of intraosseous schwannoma in this case.

A 7-year-old boy, diagnosed with an arachnoid cyst and subdural effusion on initial MRI, was admitted with left limb weakness and no history of head trauma. A subsequent follow-up MRI showed different stages of hematoma within multilayered enhancing membranes and in the arachnoid cyst, which was separated by the cerebrospinal fluid cleft. Craniotomy and fenestration of the cyst wall and hematoma removal were performed. The patient was diagnosed as a having a hemorrhagic rupture of an arachnoid cyst into the intradural space, probably via some one-way valve-like defect, based on the MRI and surgical findings. The MRI features and possible mechanism of this rare disease are discussed within the literature review.

Bone marrow aspirates concentrate (BMAC) transplantation is a well-known technique for cartilage regeneration with good clinical outcomes for symptoms in patients with osteoarthritis (OA). Magnetic resonance imaging (MRI) has an important role in evaluating the degree of cartilage repair in cartilage regeneration therapy instead of a second assessment via an arthroscopy. We experienced a case of hypertrophic regeneration of the cartilage and a presumed simultaneous regeneration of the posterior horn of the lateral meniscus after BMAC transplantation for a cartilage defect at the lateral tibial and femoral condyle. This report provides the details of a case of an unusual treatment response after a BMAC transplant. This report is the first of its kind to demonstrate a MR image that displays the simultaneous regeneration of the cartilage and meniscus with a differentiation ability of the mesenchymal stem cell to the desired cell lineage.

Giant arachnoid granulations have been reported to be associated with headaches, which can be acute or chronic in presentation. In some cases, idiopathic intracranial hypertension, previously called pseudotumor cerebri, may occur. The pathophysiology of these enlarged structures seen as filling defects on imaging is not clearly defined, although they are presumed to cause symptoms such as headache via pressure resulting from secondary venous sinus obstruction. We present a unique presentation of secondary headache in a 39-year-old man with no prior history of headaches found to have giant arachnoid granulations, presenting as migraine with aura.

Idiopathic brain herniation is a rare condition. We believe that this is the first reported case of idiopathic herniation of the lingual gyrus. The case involves a 57-year-old woman presenting with frontal headache without overt visual symptoms. Magnetic resonance imaging (MRI) revealed an idiopathic herniation of the lingual gyrus of the occipital lobe extending into the quadrigeminal cistern. No other adjacent intracranial abnormalities were observed. Although some conditions may be considered in the differential diagnosis, accurate diagnosis of idiopathic brain herniation in medical practice can prevent unnecessary additional imaging procedures and invasive open biopsy in patients with typical imaging findings.