Synthesizing 4D Magnetic Resonance Angiography From 3D Time-of-Flight Using Deep Learning: A Feasibility Study.

Objective and background This study aimed to develop a deep convolutional neural network (DCNN) model capable of generating synthetic 4D magnetic resonance angiography (MRA) from 3D time-of-flight (TOF) images, allowing estimation of temporal changes in arterial flow. TOF MRA provides static information about arterial structures through maximum intensity projection (MIP) processing, but it does not capture the dynamic information of contrast agent circulation, which is lost during MIP processing. Considering the principles of TOF, it is hypothesized that dynamic information about arterial blood flow is latent within TOF signals. Although arterial spin labeling (ASL) can extract dynamic arterial information, ASL MRA has drawbacks, such as longer imaging times and lower spatial resolution than TOF MRA. This study's primary aim is to extend the utility of TOF MRA by training a machine-learning model on paired TOF and ASL data to extract latent dynamic information from TOF signals. Methods A DCNN combining a modified U-Net and a long-short-term memory (LSTM) network was trained on a dataset of 13 subjects (11 men and two women, aged 42-77 years) using paired 3D TOF MRA and 4D ASL MRA images. Subjects had no history of cerebral vessel occlusion or significant stenosis. The dataset was acquired using a 3T MRI system with a 32-channel head coil. Preprocessing involved resampling and intensity normalization of TOF and ASL images, followed by data augmentation and arterial mask generation. The model learned to extract flow information from TOF images and generate 8-phase 4D MRA images. The precision of flow estimation was evaluated using the coefficient of determination (R²) and Bland-Altman analysis. A board-certified neuroradiologist validated the quality of the images and the absence of significant stenosis in the major cerebral arteries. Results The generated 4D MRA images closely resembled the ground-truth ASL MRA data, with R² values of 0.92, 0.85, and 0.84 for the internal carotid artery (ICA), proximal middle cerebral artery (MCA), and distal MCA, respectively. Bland-Altman analysis revealed a systematic error of -0.06, with 95% agreement limits ranging from -0.18 to 0.12. Additionally, the model successfully identified flow abnormalities in a subject with left MCA stenosis, displaying a delayed peak and subsequent flattening distal to the stenosis, indicative of reduced blood flow. Visualization of the predicted arterial flow overlaid on the original TOF MRA images highlighted the spatial progression and dynamics of the flow. Conclusions The DCNN model effectively generated synthetic 4D MRA images from TOF images, demonstrating its potential to estimate temporal changes in arterial flow accurately. This non-invasive technique offers a promising alternative to conventional methods for visualizing and evaluating healthy and pathological flow dynamics. It has significant potential to improve the diagnosis and treatment of cerebrovascular diseases by providing detailed temporal flow information without the need for contrast agents or invasive procedures. The practical implementation of this model could enable the extraction of dynamic cerebral blood flow information from routine brain MRI examinations, contributing to the early diagnosis and management of cerebrovascular disorders.

Adrenocortical Adenoma With Protrusion Into the Inferior Vena Cava Initially Suspected to Be Adrenocortical Carcinoma.

Adrenal tumors with invasion into the inferior vena cava (IVC) are typically malignant. Here, we present a case of adrenocortical adenoma with protrusion into the IVC. A 70-year-old man was referred to our hospital after his magnetic resonance imaging scan of the abdomen coincidently revealed a right adrenal tumor invading the IVC. We suspected an aggressive adrenal carcinoma and tumor resection was performed. However, all 3 existing pathological criteria (Weiss, modified Weiss, and Helsinki) suggested the tumor was benign. Immunohistochemistry for CD31 showed the tumor inside the central adrenal vein (CAV), right adrenal vein (RAV), and IVC was entirely covered with CD31-positive vascular endothelial cells. The CAV is known to sometimes lack smooth muscle in its walls and normal adrenocortical cells covered by endothelial cells sometimes protrude into the CAV from this gap. These findings suggest that this tumor likely protruded into the IVC by pushing against the CAV wall, rather than by invasion into the vascular wall. In the case with adrenal tumors protruding into the IVC, the fact that the tumor surface was covered by vascular endothelial cells was considered supportive of its benign nature.

MR Fingerprinting for Contrast Agent-free and Quantitative Characterization of Focal Liver Lesions.

Purpose To evaluate the feasibility of liver MR fingerprinting (MRF) for quantitative characterization and diagnosis of focal liver lesions. Materials and Methods This single-site, prospective study included 89 participants (mean age, 62 years ± 15 [SD]; 45 women, 44 men) with various focal liver lesions who underwent MRI between October 2021 and August 2022. The participants underwent routine clinical MRI, non-contrast-enhanced liver MRF, and reference quantitative MRI with a 1.5-T MRI scanner. The bias and repeatability of the MRF measurements were assessed using linear regression, Bland-Altman plots, and coefficients of variation. The diagnostic capability of MRF-derived T1, T2, T2*, proton density fat fraction (PDFF), and a combination of these metrics to distinguish benign from malignant lesions was analyzed according to the area under the receiver operating characteristic curve (AUC). Results Liver MRF measurements showed moderate to high agreement with reference measurements (intraclass correlation = 0.94, 0.77, 0.45, and 0.61 for T1, T2, T2*, and PDFF, respectively), with underestimation of T2 values (mean bias in lesion = -0.5%, -29%, 5.8%, and -8.2% for T1, T2, T2*, and PDFF, respectively). The median coefficients of variation for repeatability of T1, T2, and T2* values were 2.5% (IQR, 3.6%), 3.1% (IQR, 5.6%), and 6.6% (IQR, 13.9%), respectively. After considering multicollinearity, a combination of MRF measurements showed a high diagnostic performance in differentiating benign from malignant lesions (AUC = 0.92 [95% CI: 0.86, 0.98]). Conclusion Liver MRF enabled the quantitative characterization of various focal liver lesions in a single breath-hold acquisition. Keywords: MR Imaging, Abdomen/GI, Liver, Imaging Sequences, Technical Aspects, Tissue Characterization, Technology Assessment, Diagnosis, Liver Lesions, MR Fingerprinting, Quantitative Characterization Supplemental material is available for this article. © RSNA, 2023.

Deep Learning-Driven Transformation: A Novel Approach for Mitigating Batch Effects in Diffusion MRI Beyond Traditional Harmonization.

BACKGROUND: "Batch effect" in MR images, due to vendor-specific features, MR machine generations, and imaging parameters, challenges image quality and hinders deep learning (DL) model generalizability. PURPOSE: We aim to develop a DL model using contrast adjustment and super-resolution to reduce diffusion-weighted images (DWIs) diversity across magnetic field strengths and imaging parameters. STUDY TYPE: Retrospective. SUBJECTS: The DL model was built using an open dataset from one individual. The MR machine identification model was trained and validated on a dataset of 1134 adults (54% females, 46% males), with 1050 subjects showing no DWI abnormalities and 84 with conditions like stroke and tumors. The 21,000 images were divided into 80% for training, 20% for validation, and 3500 for testing. FIELD STRENGTH/SEQUENCE: Seven MR scanners from four manufacturers with 1.5 T and 3 T magnetic field strengths. DWIs were acquired using spin-echo sequences and high-resolution T2WIs using the T2-SPACE sequence. ASSESSMENT: An experienced, board-certified radiologist evaluated the effectiveness of restoring high-resolution T2WI and harmonizing diverse DWI with metrics such as PSNR and SSIM, and the texture and frequency attributes were further analyzed using gray-level co-occurrence matrix and 1-dimensional power spectral density. The model's impact on machine-specific characteristics was gauged through the performance metrics of a ResNet-50 model. Comprehensive statistical tests were employed for statistical robustness, including McNemar's test and the Dice index. RESULTS: Our DL protocol reduced DWI contrast and resolution variation. ResNet-50 model's accuracy decreased from 0.9443 to 0.5786, precision from 0.9442 to 0.6494, recall from 0.9443 to 0.5786, and F1 score from 0.9438 to 0.5587. The t-SNE visualization indicated more consistent image features across multiple MR devices. Autoencoder halved learning iterations; Dice coefficient >0.74 confirmed signal reproducibility in 84 lesions. CONCLUSION: This study presents a DL strategy to mitigate batch effects in diffusion MR images, improving their quality and generalizability. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 1.

Fiber-specific micro- and macroscopic white matter alterations in progressive supranuclear palsy and corticobasal syndrome.

Progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS) are characterized by progressive white matter (WM) alterations associated with the prion-like spreading of four-repeat tau, which has been pathologically confirmed. It has been challenging to monitor the WM degeneration patterns underlying the clinical deficits in vivo. Here, a fiber-specific fiber density and fiber cross-section, and their combined measure estimated using fixel-based analysis (FBA), were cross-sectionally and longitudinally assessed in PSP (n = 20), CBS (n = 17), and healthy controls (n = 20). FBA indicated disease-specific progression patterns of fiber density loss and subsequent bundle atrophy consistent with the tau propagation patterns previously suggested in a histopathological study. This consistency suggests the new insight that FBA can monitor the progressive tau-related WM changes in vivo. Furthermore, fixel-wise metrics indicated strong correlations with motor and cognitive dysfunction and the classifiability of highly overlapping diseases. Our findings might also provide a tool to monitor clinical decline and classify both diseases.

Feasibility of Quantitative MRI Using 3D-QALAS for Discriminating Immunohistochemical Status in Invasive Ductal Carcinoma of the Breast.

BACKGROUND: Two-dimensional synthetic MRI of the breast has limited spatial coverage. Three-dimensional (3D) synthetic MRI could provide volumetric quantitative parameters that may reflect the immunohistochemical (IHC) status in invasive ductal carcinoma (IDC) of the breast. PURPOSE: To evaluate the feasibility of 3D synthetic MRI using an interleaved Look-Locker acquisition sequence with a T2 preparation pulse (QALAS) for discriminating the IHC status, including hormone receptor (HR), human epidermal growth factor receptor 2 (HER 2), and Ki-67 expression in IDC. STUDY TYPE: Prospective observational study. POPULATION: A total of 33 females with IDC of the breast (mean, 52.3 years). FIELD STRENGTH/SEQUENCE: A 3-T, 3D-QALAS gradient-echo and fat-suppressed T1-weighted 3D fast spoiled gradient-echo sequences. ASSESSMENT: Two radiologists semiautomatically delineated 3D regions of interest (ROIs) of the whole tumors on the dynamic MRI that was registered to the synthetic T1-weighted images acquired from 3D-QALAS. The mean T1 and T2 were measured for each IDC. STATISTICAL TESTS: Intraclass correlation coefficient for assessing interobserver agreement. Mann-Whitney U test to determine the relationship between the mean T1 or T2 and the IHC status. Multivariate logistic regression analysis followed by receiver operating characteristics (ROC) analysis for discriminating IHC status. A P value <0.05 was considered statistically significant. RESULTS: The interobserver agreement was good to excellent. There was a significant difference in the mean T1 between HR-positive and HR-negative lesions, while the mean T2 value differed between HR-positive and HR-negative lesions, between the triple-negative and HR-positive or HER2-positive lesions, and between the Ki-67 level > 14% and ≤ 14%. Multivariate analysis showed that the mean T2 was higher in HR-negative IDC than in HR-positive IDC. ROC analysis revealed that the mean T2 was predictive for discriminating HR status, triple-negative status, and Ki-67 level. DATA CONCLUSION: 3D synthetic MRI using QALAS may be useful for discriminating IHC status in IDC of the breast. EVIDENCE LEVEL: 1. TECHNICAL EFFICACY: Stage 2.

Automation of a Rule-based Workflow to Estimate Age from Brain MR Imaging of Infants and Children Up to 2 Years Old Using Stacked Deep Learning.

PURPOSE: Myelination-related MR signal changes in white matter are helpful for assessing normal development in infants and children. A rule-based myelination evaluation workflow regarding signal changes on T1-weighted images (T1WIs) and T2-weighted images (T2WIs) has been widely used in radiology. This study aimed to simulate a rule-based workflow using a stacked deep learning model and evaluate age estimation accuracy. METHODS: The age estimation system involved two stacked neural networks: a target network-to extract five myelination-related images from the whole brain, and an age estimation network from extracted T1- and T2WIs separately. A dataset was constructed from 119 children aged below 2 years with two MRI systems. A four-fold cross-validation method was adopted. The correlation coefficient (CC), mean absolute error (MAE), and root mean squared error (RMSE) of the corrected chronological age of full-term birth, as well as the mean difference and the upper and lower limits of 95% agreement, were measured. Generalization performance was assessed using datasets acquired from different MR images. Age estimation was performed in Sturge-Weber syndrome (SWS) cases. RESULTS: There was a strong correlation between estimated age and corrected chronological age (MAE: 0.98 months; RMSE: 1.27 months; and CC: 0.99). The mean difference and standard deviation (SD) were -0.15 and 1.26, respectively, and the upper and lower limits of 95% agreement were 2.33 and -2.63 months. Regarding generalization performance, the performance values on the external dataset were MAE of 1.85 months, RMSE of 2.59 months, and CC of 0.93. Among 13 SWS cases, 7 exceeded the limits of 95% agreement, and a proportional bias of age estimation based on myelination acceleration was exhibited below 12 months of age (P = 0.03). CONCLUSION: Stacked deep learning models automated the rule-based workflow in radiology and achieved highly accurate age estimation in infants and children up to 2 years of age.

Effect of an Ultrahigh b Value of 3000 s/mm2 and the Minimal Echo-time on Image Quality and the T2 Shine-through Effect in Diffusion-weighted Imaging of the Liver at 3T: Phantom and Clinical Pilot Studies.

PURPOSE: To assess the effect of an ultrahigh b value of 3000 s/mm2 and the minimal TE of 53 ms on image quality and T2 shine-through effect in liver diffusion-weighted imaging (DWI) using a 3-Tesla MRI scanner with a peak gradient of 100 mT/m. METHODS: At b values of 1000 and 3000 s/mm2 and at the minimal (44-53 ms) and routine TEs (70 ms), DWI of our original phantom and liver DWI in 10 healthy volunteers and 26 patients with 35 hepatic hemangiomas were acquired with this scanner, and the quantified SNR of the phantom and the hepatic parenchyma in the volunteers and the contrast-to-noise ratio (CNR) of the hepatic hemangiomas were calculated; two independent readers qualitatively graded the overall image quality in the volunteers and determined the presence or absence of the T2 shine-through effect related to the hemangiomas in the patients. We compared the SNR and subjective overall image quality between the minimal and routine TEs and the CNR and incidence of the T2 shine-through effect between b values of 1000 and 3000 s/mm2. Inter-reader agreement was also evaluated. RESULTS: The SNR at both b values was significantly higher, and the subjective overall image quality at a b value of 3000 s/mm2 was significantly better at the minimal TE than at the routine TE (P < 0.05 for all). The CNR at both TEs and the incidence of the T2 shine-through effect at the minimal TE were significantly lower at a b value of 3000 s/mm2 than at a b value of 1000 s/mm2 (P < 0.05 for all). Inter-reader agreement was excellent. CONCLUSION: Liver DWI at the ultrahigh b value can reduce the T2 shine-through effect with improvement of image quality using the minimal TE.

MR Fingerprinting for Liver Tissue Characterization: A Histopathologic Correlation Study.

Background Liver MR fingerprinting (MRF) enables simultaneous quantification of T1, T2, T2*, and proton density fat fraction (PDFF) maps in single breath-hold acquisitions. Histopathologic correlation studies are desired for its clinical use. Purpose To compare liver MRF-derived metrics with separate reference quantitative MRI in participants with diffuse liver disease, evaluate scan-rescan repeatability of liver MRF, and validate MRF-derived measurements for histologic grading of liver biopsies. Materials and Methods This prospective study included participants with diffuse liver disease undergoing MRI from July 2021 to January 2022. Participants underwent two-dimensional single-section liver MRF and separate reference quantitative MRI. Linear regression, Bland-Altman plots, and coefficients of variation were used to assess the bias and repeatability of liver MRF measurements. For participants undergoing liver biopsy, the association between mapping and histologic grading was evaluated by using the Spearman correlation coefficient. Results Fifty-six participants (mean age, 59 years ± 15 [SD]; 32 women) were included to compare mapping techniques and 23 participants were evaluated with liver biopsy (mean age, 52.7 years ± 12.7; 14 women). The linearity of MRF with reference measurements in participants with diffuse liver disease (R2 value) for T1, T2, T2*, and PDFF maps was 0.86, 0.88, 0.54, and 0.99, respectively. The overall coefficients of variation for repeatability in the liver were 3.2%, 5.5%, 7.1%, and 4.6% for T1, T2, T2*, and PDFF maps, respectively. MRF-derived metrics showed high diagnostic performance in differentiating moderate or severe changes from mild or no changes (area under the receiver operating characteristic curve for fibrosis, inflammation, steatosis, and siderosis: 0.62 [95% CI: 0.52, 0.62], 0.92 [95% CI: 0.88, 0.92], 0.97 [95% CI: 0.96, 0.97], and 0.74 [95% CI: 0.57, 0.74], respectively). Conclusion Liver MR fingerprinting provided repeatable T1, T2, T2*, and proton density fat fraction maps in high agreement with reference quantitative mapping and may correlate with pathologic grades in participants with diffuse liver disease. © RSNA, 2022 Online supplemental material is available for this article.

Association of MRI Indices of Glymphatic System With Amyloid Deposition and Cognition in Mild Cognitive Impairment and Alzheimer Disease.

BACKGROUND AND OBJECTIVES: The glymphatic system is a whole-brain perivascular network, which promotes CSF/interstitial fluid exchange. Alterations to this system may play a pivotal role in amyloid ß (Aß) accumulation. However, its involvement in Alzheimer's disease (AD) pathogenesis is not fully understood. Here, we investigated the changes in noninvasive MRI measurements related to the perivascular network in patients with mild cognitive impairment (MCI) and AD. Additionally, we explored the associations of MRI measures with neuropsychological score, PET standardized uptake value ratio (SUVR), and Aß deposition. METHODS: MRI measures, including perivascular space (PVS) volume fraction (PVSVF), fractional volume of free water in white matter (FW-WM), and index of diffusivity along the perivascular space (ALPS index) of patients with MCI, those with AD, and healthy controls from the Alzheimer's Disease Neuroimaging Initiative database were compared. MRI measures were also correlated with the levels of CSF biomarkers, PET SUVR, and cognitive score in the combined subcohort of patients with MCI and AD. Statistical analyses were performed with age, sex, years of education, and APOE status as confounding factors. RESULTS: In total, 36 patients with AD, 44 patients with MCI, and 31 healthy controls were analyzed. Patients with AD had significantly higher total, WM, and basal ganglia PVSVF (Cohen's d = 1.15-1.48; p < 0.001), and FW-WM (Cohen's d = 0.73; p < 0.05) and a lower ALPS index (Cohen's d = 0.63; p < 0.05) than healthy controls. Meanwhile, the MCI group only showed significantly higher total (Cohen's d = 0.99; p < 0.05) and WM (Cohen's d = 0.91; p < 0.05) PVSVF. Low ALPS index was associated with lower CSF Aß42 (r s = 0.41, p fdr = 0.026), FDG-PET uptake (r s = 0.54, p fdr < 0.001), and worse multiple cognitive domain deficits. High FW-WM was also associated with lower CSF Aß42 (r s = -0.47, p fdr = 0.021) and worse cognitive performances. CONCLUSION: Our study indicates that changes in PVS-related MRI parameters occur in MCI and AD, possibly due to impairment of the glymphatic system. We also report the associations between MRI parameters and Aß deposition, neuronal change, and cognitive impairment in AD.

Lessons Learned in Practice with Li-Fraumeni Syndrome: LFS-Related Breast Cancer Treatment Strategy and Establishment of a Surveillance System.

We herein present the case of a 33-year-old woman with no family history of metachronous bilateral breast cancer and osteosarcoma, diagnosed with Li-Fraumeni syndrome (LFS), which is a rare autosomal dominant hereditary cancer syndrome associated with a germline TP53 variant. She was diagnosed with left distal femoral osteosarcoma at the age of 16, and metachronous bilateral breast cancer at the ages of 29 and 33. When the third cancer was diagnosed, a hereditary tumor syndrome was suspected and the patient was referred to our genetic outpatient clinic. There was no family history of the 'core' cancers for LFS, but since the patient met Chompret's criteria, germline TP53 genetic testing was performed with the patient's will. A pathogenic variant, TP53:c.216dupC (p.Val73ArgfsX76) was found in exon 4 of the gene. This case is didactic because radiotherapy was performed on the first breast cancer before the diagnosis of LFS was made; radiation should be avoided if there are other options in LFS because of the inability to repair DNA damage. As a lesson learned, oncologists reaffirmed the importance of being aware of hereditary tumors from the keywords "multiple," "young," "familial," and "rare," and consulting the genetic department. In addition, surveillance using whole-body magnetic resonance imaging is recommended in LFS. However, this system is not yet provided nationwide, but we have newly settled it in our hospital.

A Case of Untreated Myeloid Sarcoma of the Pancreas Head Region: Diagnostic Process of AML Subtyping in an Autoptic Case.

This study describes an autopsy case of pancreatic/peripancreatic myeloid sarcoma in a 70-year-old man, initially presenting with obstructive jaundice. Pathologically, diffuse infiltration of round cells containing atypical nuclei with marked cleavage was observed mainly in the pancreas head, peripancreatic lymph nodes, spleen, bilateral lung, and bone marrow. Immunohistochemically, the tumor cells were negative for CD20, CD79a, CD3, CD5, c-kit, CD34, and TdT and positive for myeloperoxidase, CD33, CD68, and CD163. Flow cytometry of the peripheral blood showed underexpression of CD11c and aberrant expression of CD56 in the monocyte subset. The peripheral blood smear showed an increase in monocytes and atypia in neutrophils and monocytes, as well as enlarged platelets and polychromatic erythroblasts. Hence, it was suggested that the myeloid sarcoma was derived from the acute transformation of chronic myelomonocytic leukemia. Myeloid sarcoma is an extramedullary-mass-forming hematologic malignancy that is difficult to diagnose, especially when the initial presentation is a pancreatic mass. However, early diagnosis is important for appropriate therapy. Although bone marrow examination could not be performed because of the patients' severe condition, the pathological specimen obtained with autopsy helped subtype the patient's leukemia. The immunohistochemical features of this case merit attention.

A case report of fibrolamellar hepatocellular carcinoma, with particular reference to preoperative diagnosis, value of molecular genetic diagnosis, and cell origin.

BACKGROUND: Fibrolamellar hepatocellular carcinoma (FL-HCC) is a liver tumor that occurs almost exclusively in young adults without underlying liver disease. In spite of its distinct clinical characteristics and specific imaging findings, preoperative diagnosis is often difficult due to the extremely low incidence of the tumor. Although FL-HCC shows particular morphological features on H&E-stained tissue sections, differential diagnosis from ordinary HCC, especially the scirrhous variant of HCC, and intrahepatic cholangiocarcinoma needs additional immunohistochemical (IHC) analyses and/or molecular genetic testing. CASE PRESENTATION: A 21-year-old male patient was referred to our hospital for further evaluation of a large liver mass. Abdominal ultrasound examination, contrast-enhanced computed tomography, and magnetic resonance imaging revealed a well-defined hypervascular lobulated liver mass, 11 × 11 cm in diameter, with a central scar and calcification, in segments 5/8. Under the diagnosis of FL-HCC, we carried out extended anterior sectorectomy, including a part of segment 4. On microscopic examination, the tumor was composed of proliferating polygonal cells with abundant eosinophilic granular cytoplasm containing nuclei with vesicular chromatin and enlarged nucleoli, in an abundant stroma. Collagen fibers arranged in a parallel lamellar pattern were seen in the tumor stroma. These findings, together with the results of subsequent IHC analyses using HAS, CK7, and CD 67, we made the diagnosis of FL-HCC, which was further confirmed by detection of the DNAJB1-PRKACA fusion gene in the tumor cells by RT-PCR. CONCLUSION: FL-HCC shows distinct imaging appearances. Although it also has characteristic morphological features, combined use of IHC and/or molecular genetic studies are necessary for the final diagnosis.

Quantitative analysis of gadoxetic acid-enhanced MRI for the differential diagnosis of focal liver lesions: Comparison between estimated intralesional gadoxetic acid retention by T1 mapping and conventional processing methods.

PURPOSE: To compare the estimated quantity of intratumor gadoxetic acid retention using T1 mapping of gadoxetic acid-enhanced magnetic resonance imaging (MRI) versus conventional processing methods for the differential diagnosis of focal liver lesions. METHODS: Seventy patients with hepatic lesions (colorectal metastasis (CRM) [n = 28], hepatocellular carcinoma (HCC) [n = 20], hemangioma [n = 12], and intrahepatic cholangiocarcinoma (ICC) [n = 10]) underwent gadoxetic acid-enhanced MRI, including pre- and post-contrast T1-weighted imaging and T1 mapping. Quantitative analyses included the lesion-to-liver signal intensity ratio (SIR) on hepatobiliary phase images, the pre- and post-contrast lesion T1 value difference (ΔT1 [ms]), and the lesion retention index (LRI [%]), which was the estimated intralesional gadoxetic acid retention calculated on pre- and post-contrast T1 maps using a two-compartment pharmacokinetic model. Results were compared between the four subcategories of focal liver lesions using the Kruskal-Wallis test, followed by the post-hoc Dunn's test and receiver operating characteristic (ROC) analysis to distinguish between pairs of the four lesion subcategories. RESULTS: This study identified significant differences in the LRI of the four lesion subcategories (p <  0.01), without significant differences in ΔT1 or SIR. Post-hoc analysis demonstrated significant differences in CRM vs. hemangioma (p <  0.01), hemangioma vs. ICC (p <  0.01), and HCC vs. ICC (p =  0.047) for the LRI. CONCLUSIONS: The quantity of intratumor gadoxetic acid retention estimated using pre- and post- contrast T1 mapping could distinguish focal liver lesions, unlike conventional processing methods, and captured unique lesion characteristics.

A 1.4-million-year-old bone handaxe from Konso, Ethiopia, shows advanced tool technology in the early Acheulean.

In the past decade, the early Acheulean before 1 Mya has been a focus of active research. Acheulean lithic assemblages have been shown to extend back to ∼1.75 Mya, and considerable advances in core reduction technologies are seen by 1.5 to 1.4 Mya. Here we report a bifacially flaked bone fragment (maximum dimension ∼13 cm) of a hippopotamus femur from the ∼1.4 Mya sediments of the Konso Formation in southern Ethiopia. The large number of flake scars and their distribution pattern, together with the high frequency of cone fractures, indicate anthropogenic flaking into handaxe-like form. Use-wear analyses show quasi-continuous alternate microflake scars, wear polish, edge rounding, and striae patches along an ∼5-cm-long edge toward the handaxe tip. The striae run predominantly oblique to the edge, with some perpendicular, on both the cortical and inner faces. The combined evidence is consistent with the use of this bone artifact in longitudinal motions, such as in cutting and/or sawing. This bone handaxe is the oldest known extensively flaked example from the Early Pleistocene. Despite scarcity of well-shaped bone tools, its presence at Konso shows that sophisticated flaking was practiced by ∼1.4 Mya, not only on a range of lithic materials, but also occasionally on bone, thus expanding the documented technological repertoire of African Early Pleistocene Homo.

Effect of Ultra High-Resolution Computed Tomography and Model-Based Iterative Reconstruction on Detectability of Simulated Submillimeter Artery.

OBJECTIVE: To evaluate the effect of ultra high-resolution computed tomography (UHRCT) and model-based iterative reconstruction (MBIR) on the detectability of simulated submillimeter artery. METHODS: A small vessel phantom ranging from 0.4 to 2.0 mm in diameter and edge phantoms of low to high attenuation values were scanned by UHRCT (super-high-resolution mode and normal-resolution-mode) and conventional CT, and data were reconstructed by MBIR and filtered back projection (FBP). Vessel detectability was assessed subjectively and the effective size at which 50% of response was achieved (ES50 [mm]) was calculated. Modulation transfer function (MTF) was calculated by an edge spread function method. RESULTS: ES50 of super high-resolution mode (0.36 mm for MBIR and 0.50 mm for FBP) was significantly smaller than those of normal-resolution mode (P < 0.01). In the MTF analysis, the MTF of MBIR improved as the edge phantom attenuation increased, whereas that of FBP was stable. CONCLUSIONS: Both UHRCT and MBIR are effective for the detectability of simulated submillimeter artery.

The inferior mesenteric artery arising from the superior mesenteric artery demonstrated with 3D-CT: A case report.

The inferior mesenteric artery arising from the superior mesenteric artery is an extremely rare anatomic variation. We report a case with this variation demonstrated with 3-dimensional contrast-enhanced computed tomography, which later was confirmed at surgery. The ordinary inferior mesenteric artery arising from the aorta was absent. Previously reported cases with this variation are reviewed. 3-dimensional contrast-enhanced computed tomography is useful for in vivo visualization of aberrant arterial anatomy.

Seeding of a Tumor in the Gastric Wall after Endoscopic Ultrasound-guided Fine-needle Aspiration of Solid Pseudopapillary Neoplasm of the Pancreas.

Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) is widely used as a first-line procedure for the definitive diagnosis of pancreatic solid tumor. Adverse events associated with the EUS-FNA procedure include acute pancreatitis, bleeding, infection, and duodenal perforation. Rarely, pancreatic tumors disseminate in the peritoneal cavity or seed in the gastric wall via the biopsy needle tract after EUS-FNA. Such seeding has been noted primarily in cases of adenocarcinomas and has not been associated with solid pseudopapillary neoplasm (SPN), a rare and potentially malignant tumor of the pancreas. This is the first report of a case of tumor seeding in the gastric wall after EUS-FNA of pancreatic SPN.