A case of atypical meningioma presenting spontaneous infarction: the findings of magnetic resonance imaging, including amide proton transfer-chemical exchange saturation transfer imaging.

We report the MRI findings of a patient with an atypical meningioma who presented with spontaneous infarction. A 67-year-old man with histories of recurrent meningioma complained of left ocular protrusion and a subsequent biopsy revealed atypical meningioma. Contrast-enhanced CT showed a uniformly enhancing tumour in the left ethmoid sinus, but MRI 2 days later showed no enhancement on Gd-T1WI and severe diffusion restriction on DWI, indicating spontaneous infarction. APT-CEST imaging showed slight hypointensity in comparison to the normal brain with a mean MTR asymmetry value of 0.48%. Tumour regrowth was confirmed on MRI after 2 months. The recurrent tumour showed moderate diffusion restriction on DWI and hyperintensity with a mean MTR asymmetry value of 2.59% on APT-CEST imaging. The decreased signal on APT-CEST at the time of spontaneous infarction may have been attributed to intratumoral acidosis and loss of viable tumour. APT-CEST imaging is useful for evaluating the intratumoral condition and tumour viability of the infarcted or ischemic tumour.

Ultra-high resolution computed tomography with deep-learning-reconstruction: diagnostic ability in the assessment of gastric cancer and the depth of invasion.

PURPOSE: To evaluate the image quality of ultra-high-resolution CT (U-HRCT) images reconstructed using an improved deep-learning-reconstruction (DLR) method. Additionally, we assessed the utility of U-HRCT in visualizing gastric wall structure, detecting gastric cancer, and determining the depth of invasion. METHODS: Forty-six patients with resected gastric cancer who underwent preoperative contrast-enhanced U-HRCT were included. The image quality of U-HRCT reconstructed using three different methods (standard DLR [AiCE], improved DLR-AiCE-Body Sharp [improved AiCE-BS], and hybrid-IR [AIDR3D]) was compared. Visualization of the gastric wall's three-layered structure in four regions and the visibility of gastric cancers were compared between U-HRCT and conventional HRCT (C-HRCT). The diagnostic ability of U-HRCT with the improved AiCE-BS for determining the depth of invasion of gastric cancers was assessed using postoperative pathology specimens. RESULTS: The mean noise level of U-HRCT with the improved AiCE-BS was significantly lower than that of the other two methods (p < 0.001). The overall image quality scores of the improved AiCE-BS images were significantly higher (p < 0.001). U-HRCT demonstrated significantly better conspicuity scores for the three-layered structure of the gastric wall than C-HRCT in all regions (p < 0.001). In addition, U-HRCT was found to have superior visibility of gastric cancer in comparison to C-HRCT (p < 0.001). The correct diagnostic rates for determining the depth of invasion of gastric cancer using C-HRCT and U-HRCT were 80%. CONCLUSIONS: U-HRCT reconstructed with the improved AiCE-BS provides clearer visualization of the three-layered gastric wall structure than other reconstruction methods. It is also valuable for detecting gastric cancer and assessing the depth of invasion.

Dual-Source Contrast-Enhanced Multiphasic CT of the Liver Using Low Voltage (70 kVp): Feasibility of a Reduced Radiation Dose and a 50% of Contrast Dose.

This study investigated the feasibility of both a reduced radiation dose and a 50% of contrast dose in multiphasic CT of the liver with a 70 kVp protocol compared with a standard-tube-voltage protocol derived from dual-energy (DE) CT (blended DE protocol) with a full-dose contrast-agents in the same patient group. This study included 46 patients who underwent multiphasic contrast-enhanced dynamic CT of the liver with both a 70 kVp and a blended DE protocols. For quantitative analysis, median CT values for the liver, aorta, and portal vein, as well as signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), were measured and calculated. In addition, as a qualitative analysis, the contrast effect and overall image quality of the abdominal organs were evaluated on a five-point scale. CNR and SNR of the hepatic parenchyma were not significantly different between the 70kV protocol and the Blended DE protocol in all phases. The 70 kVp protocol showed significantly better image quality compared with the blended DE protocol in the arterial phase (p = 0.035) and the equilibrium layer phase (p = 0.016). A 70 kVp CT protocol in combination with a reduced radiation dose and half-dose iodine load is feasible for multiphasic dynamic CT of the liver by maintaining the contrast enhancement effects and image quality in comparison with the blended DE CT protocol.

Automated whole-volume measurement of CT fat fraction of the pancreas: correlation with Dixon MR imaging.

OBJECTIVES: This study aimed to assess the feasibility of pancreatic steatosis quantification by automated whole-volume measurement of the fat fraction of the pancreas on CT in comparison to MRI using proton-density fat fraction (PDFF) techniques. METHODS: Fifty-nine patients who underwent both CT and MRI were analyzed. Automated whole-volume measurement of pancreatic fat on unenhanced CT was performed by a histogram analysis with local thresholding. Three sets of CT fat volume fraction (FVF) (%) values with thresholds of -30 Hounsfield unit (HU), -20 HU and -10 HU were compared to MR-FVF (%) values measured on a PDFF map. RESULTS: The median -30 HU CT-FVF, -20 HU CT-FVF, -10 HU CT-FVF and MR-FVF values of the pancreas were 8.6% (interquartile range (IQR), 11.3), 10.5% (IQR, 13.2), 13.4% (IQR, 16.1) and 10.9% (IQR, 9.7), respectively. The -30 HU CT-FVF (%), -20 HU CT-FVF (%) and -10 HU CT-FVF (%) of the pancreas showed a significant positive correlation with the MR-FVF (%) of the pancreas (ρ = 0.898, p < 0.001, ρ = 0.905, p < 0.001, ρ = 0.909, p < 0.001, respectively). The -20 HU CT-FVF (%) displayed reasonable agreement with the MR-FVF (%) with a low absolute fixed bias (mean difference, 0.32%; limit of agreement from -10.1 to 10.7%). CONCLUSION: The automated whole-volume measurement of the CT fat fraction of the pancreas using the threshold CT attenuation value of -20 HU may be a feasible, non-invasive, and convenient technique for quantifying pancreatic steatosis. ADVANCES IN KNOWLEDGE: CT-FVF value of the pancreas had a positive correlation with the MR-FVF value. The -20 HU CT-FVF may be a convenient technique for quantifying pancreatic steatosis.

Lobar hepatic steatosis: Association with portal flow hemodynamics evaluated by multiphasic dynamic contrast-enhanced CT.

PURPOSE: This study aimed to evaluate the association of portal flow hemodynamics with lobar hepatic steatosis by means of dynamic contrast-enhanced (DCE) CT. METHODS: The study population consisted of 235 patients, 77 with lobar hepatic steatosis (right, n = 67; left, n = 10), 158 with diffuse hepatic steatosis with (n = 76) and without (n = 82) a focal fatty spared area. CT attenuation values (Hounsfield units: HU) of the liver with and without hepatic steatosis were measured in unenhanced and arterial-phase CT. The contrast enhancement (CE) values were calculated as the difference in HU values between unenhanced and arterial-phase CT. RESULTS: In 67 patients with lobar steatosis of the right lobe, the median CE values of the areas of right lobar steatosis were significantly lower than those of the non-fatty left lobe (13 [IQR 7-19] vs 23 [13-33] HU, P < 0.01), suggesting dominant SMV flow to the right lobe with lobar hepatic steatosis. Conversely, in 10 patients with lobar steatosis of the left lobe, the median CE values of the areas of left lobar steatosis were lower than those of the non-fatty right lobe (15.5 [11.75-21.5] vs 16 [14.5-22] HU); however, this difference was not statistically significant (P = 0.20). In 76 patients with a focal fatty spared area, there were significant differences in the median CE values between hepatic steatosis areas and focal fatty spared areas in the gallbladder fossa group (P = 0.01) and in the segment IV group (P < 0.01). CONCLUSION: Lobar hepatic steatosis may be associated with regional changes of the portal flow hemodynamics (i.e., predominant perfusion from the SMV flow to the lobes with steatosis).

Pancreatic Steatosis Evaluated by Automated Volumetric CT Fat Fraction of the Pancreas: Association with Severity in COVID-19 Pneumonia.

This study investigated the relationship between the severity of pneumonia based on chest CT findings and that of pancreatic steatosis assessed using an automated volumetric measurement of the CT fat volume fraction (CT-FVF) of the pancreas, using unenhanced three-dimensional CT in polymerase chain reaction (PCR)-confirmed COVID-19 patients. The study population consisted of 128 patients with PCR-confirmed COVID-19 infection who underwent CT examinations. The CT-FVF of the pancreas was calculated using a histogram analysis for the isolation of fat-containing voxels in the pancreas. The CT-FVF (%) of the pancreas had a significantly positive correlation with the lung severity score on CT (ρ = 0.549, p < 0.01). CT-FVF (%) of the pancreas in the severe pneumonia group was significantly higher than that of the non-severe pneumonia group (21.7% vs. 7.8%, p < 0.01). The area under the curve of CT-FVF (%) of the pancreas in predicting the severity of pneumonia on CT was calculated to be 0.82, with a sensitivity of 88% and a specificity of 68% at a threshold for the severity score of 12.3. The automated volumetric measurement of the CT-FVF of the pancreas using unenhanced CT can help estimate disease severity in patients with COVID-19 pneumonia based on chest CT findings.

Three-Dimensional (3D) Breath-Hold Zoomed MR Cholangiopancreatography (MRCP): Evaluation of Additive Value to Conventional 3D Navigator Triggering MRCP in Patients With Branch Duct Intraductal Papillary Mucinous Neoplasms.

BACKGROUND: To resolve drawbacks of navigator triggering (NT) three-dimensional (3D) magnetic resonance cholangiopancreatography (MRCP), several approaches were proposed to obtain 3D MRCP within a single breath-hold (BH). However, reduced field-of-view technique in the phase-encoding direction combined with two-dimensional spatially selective radiofrequency excitation pulses has not yet been applied to 3D BH MRCP. PURPOSE: To investigate the feasibility and the complementary value of 3D BH zoomed MRCP to conventional 3D NT MRCP in patients with branch duct intraductal papillary mucinous neoplasms (BD-IPMNs) of the pancreas. STUDY TYPE: Retrospective. POPULATION: A total of 221 patients (116 male and 105 female, median age 73 years) with BD-IPMNs. FIELD STRENGTH/SEQUENCE: 3.0 T/3D turbo spin echo ASSESSMENT: MR images were analyzed by three radiologists (R.M., H.O., M.T., with 1, 13, and 17 years of experience) to compare blurring and motion artifacts, background suppression, visualization of main pancreatic duct (MPD), conspicuity of BD-IPMN, and overall image quality. STATISTICAL TESTS: Wilcoxon-signed rank, Mann-Whitney U, chi-squared or Fisher's exact tests (P < 0.05). RESULTS: Image quality was significantly higher on 3D NT MRCP images than on 3D BH zoomed MRCP (median (interquartile range); background suppression, 4 (4-4) vs. 3 (3-4); visualization of MPD, 4 (3-4) vs. 4 (3-4), conspicuity of BD-IPMN, 4 (3-4) vs. 3 (3-4); and overall image quality, 3 (3-4) vs. 3 (3-3)). However, in 32 (14%) patients, 3D NT MRCP showed a score of 1 or 2 in overall image quality. Regarding the conspicuity of BD-IPMN, a conspicuity score of 1 or 2 was rendered in 31 (14%) patients in 3D NT MRCP group. Conversely, 3D BH zoomed MRCP showed a score of 3 or 4 in 29 (94%) of these 31 patients. DATA CONCLUSION: 3D BH zoomed MRCP plays a complementary role to 3D NT MRCP, and may improve the conspicuity of BD-IPMNs in patients with irregular breathing pattern. LEVEL OF EVIDENCE: 4 TECHNICAL EFFICACY: Stage 2.

Assessment of the relationship between the hepatic contrast enhancement effect in the hepatobiliary phase and hepatic signal changes in free-breathing continuous multiphasic dynamic EOB-MRI.

PURPOSE: To investigate the relationship between the hepatic contrast enhancement effect in the hepatobiliary phase (HBP) and the contrast enhancement parameters based on the data of continuous signal changes in free-breathing multiphasic dynamic EOB-MR imaging using a compressed sensing (CS) and the self-gating technique, and to clarify which contrast enhancement parameters are useful for estimating the hepatic enhancement effect in the HPB. METHOD: This study included 96 patients. The contrast enhancement ratio (CER) of the liver parenchyma from phase x to phase y was calculated as follows: CERy-x: (SIy -SIx)/SIx. The gradient of the regression line (GRL) was also calculated. Patients can be divided into two groups with sufficient or insufficient liver enhancement in the HBP, then each parameter was compared between these two groups. RESULTS: In the analysis of the arterioportal phases, CER7-pre in the sufficient HBP enhancement group was significantly higher than that in the insufficient HBP enhancement group (0.50 vs 0.44, p < 0.001). Regarding 5 min early hepatocyte phase (phases 1-28) analysis, significant differences were observed in CER28-pre, CER28-7 and Gradient28-7 between the two groups (0.64 vs 0.47, 0.10 vs 0.03, 1.27 vs 0.27, all p < 0.001). For the strength of correlation, CER7-pre, CER28-pre, CER28-7, and GRL28-7 had higher correlation coefficients, compared with the blood sampling data. CONCLUSION: CER in the arterio-portal phase and 5 min early hepatocyte phase had significant correlation with hepatic contrast enhancement effects in the 20 min HBP, suggesting that sufficient 20 min HBP enhancement may be estimated by the CER in the portal phase and 5 min early hepatocyte phase.