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Hepatic fibrosis is potentially reversible; however early diagnosis is necessary for treatment in order to halt progression to cirrhosis and development of complications including portal hypertension and hepatocellular carcinoma. Morphologic signs of cirrhosis on ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) alone are unreliable and are seen with more advanced disease. Newer imaging techniques to diagnose liver fibrosis are reliable and accurate, and include magnetic resonance elastography and US elastography (one-dimensional transient elastography and point shear wave elastography or acoustic radiation force impulse imaging). Research is ongoing with multiple other techniques for the noninvasive diagnosis of hepatic fibrosis, including MRI with diffusion-weighted imaging, hepatobiliary contrast enhancement, and perfusion; CT using perfusion, fractional extracellular space techniques, and dual-energy, contrast-enhanced US, texture analysis in multiple modalities, quantitative mapping, and direct molecular imaging probes. Efforts to advance the noninvasive imaging assessment of hepatic fibrosis will facilitate earlier diagnosis and improve patient monitoring with the goal of preventing the progression to cirrhosis and its complications.

For rectal cancer, MRI plays an important role in assessing extramural tumor spread and informs surgical planning. The contemporary standardized management of rectal cancer with total mesorectal excision guided by imaging-based risk stratification has dramatically improved patient outcomes. Colonoscopy and CT are utilized in surveillance after surgery to detect intraluminal and extramural recurrence, respectively; however, local recurrence of rectal cancer remains a challenge because postoperative changes such as fat necrosis and fibrosis can resemble tumor recurrence; additionally, mucinous adenocarcinoma recurrence may mimic fluid collection or abscess on CT. MRI and 18F-FDG PET are problem-resolving modalities for equivocal imaging findings on CT. Treatment options for recurrent rectal cancer include pelvic exenteration to achieve radical (R0 resection) resection and intraoperative radiation therapy. After pathologic diagnosis of recurrence, imaging plays an essential role for evaluating the feasibility and approach of salvage surgery. Patterns of recurrence can be divided into axial/central, anterior, lateral, and posterior. Some lateral and posterior recurrence patterns especially in patients with neurogenic pain are associated with perineural invasion. Cross-sectional imaging, especially MRI and 18F-FDG PET, permit direct visualization of perineural spread, and contribute to determining the extent of resection. Multidisciplinary discussion is essential for treatment planning of locally recurrent rectal cancer. This review article illustrates surveillance strategy after initial surgery, imaging patterns of rectal cancer recurrence based on anatomic classification, highlights imaging findings of perineural spread on each modality, and discusses how resectability and contemporary surgical approaches are determined based on imaging findings.

Purpose To describe the imaging appearance of hyperenhancing nodules arising in post-Fontan patients and to identify specific features best correlated with malignancy. Methods Hyperenhancing hepatic nodules visible on CT and/or MRI in post-Fontan patients were identified retrospectively and reviewed by subspecialty radiologists. Nodules with characteristic imaging findings of focal nodular hyperplasia (FNH) were defined as typical, the remainder were defined as atypical, described in detail according to LIRADS criteria, and length of stability over time was recorded. Clinical data, alpha fetoprotein levels (AFP), central venous pressures (CVP), and histopathology were recorded. Results 245 hyperenhancing nodules (215 typical, 30 atypical) were evaluated in 30 patients. Twenty-nine atypical nodules showed washout (portal phase in 6, delayed phase in 29), 0 showed pseudocapsule, 1 showed threshold growth, 1 showed tumor in vein, and 5 showed ancillary features favoring malignancy. Pathology confirmed hepatocellular carcinoma (HCC) in 3 atypical nodules and FNH-like histology in 3 atypical and 4 typical nodules. 2 atypical nodules were present in a patient with clinical diagnosis of HCC. 20 nodules (7 typical, 13 atypical due to washout) were studied with hepatobiliary contrast agent and all showed homogenous hepatobiliary phase retention. Atypical nodules were significantly more likely to be HCC than biopsy-proven FNH-like or stable ≥24 months when showing portal phase washout ( P  < 0.001), mosaic architecture ( P  = 0.020) or in the presence of cirrhosis ( P  = 0.004) or elevated AFP ( P  = 0.004). Atypical nodules that were HCC had higher median CVP than those that were FNH-like (19, range 16–27 vs. 13, range 12–16 mmHg, P  = 0.0003), there was not a significant difference based on median patient age (HCC 30, range 10–41 vs. FNH-like 40 range 10–41, P  = 0.244). Conclusions Benign hyperenhancing masses in Fontan patients may demonstrate washout and be mistaken for HCC by imaging criteria. Portal phase washout, mosaic architecture, elevated AFP and higher CVP were associated with HCC in the atypical nodules found in this population.

Magnetic resonance elastography (MRE) has been introduced for clinical evaluation of liver fibrosis for nearly a decade. MRE has proven to be a robust and accurate technique for diagnosis and staging of liver fibrosis. As clinical experience with MRE grows, the possible role in evaluation of other diffuse and focal disorders of liver is emerging. Stiffness maps provide an opportunity to evaluate mechanical properties within a large volume of liver tissue. This enables appreciation of spatial heterogeneity of stiffness. Stiffness maps may reveal characteristic and differentiating features of chronic liver diseases and focal liver lesions and therefore provide useful information for clinical management. The objective of this pictorial review is to recapture the essentials of MRE technique and illustrate with examples, the utility of stiffness maps in other chronic liver disorders and focal liver lesions.

Objective Our purpose is to determine the impact of CT enterography on small bowel gastrointestinal stromal tumor (GIST) detection and biologic aggressiveness, and to identify any imaging findings that correlate with biologic aggressiveness. Methods Records of patients with histologically confirmed small bowel GISTs who underwent CT imaging were reviewed. Biologic aggressiveness was based on initial histologic grading (very low, low, intermediate, high grade; or malignant), with upgrade to malignant category if local or distant metastases developed during clinical follow-up. Imaging indications, findings, and type of CT exam were compared with the biologic aggressiveness. Results 111 small bowel GISTs were identified, with suspected small bowel bleeding being the most common indication (45/111; 40.5%). While the number of malignant GISTs diagnosed by CT remained relatively constant (2–3 per year), the number of non-malignant GISTs increased substantially (mean 1.5/year, 1998–2005; 8.4/year, 2006–2013). In patients with suspected small bowel bleeding, CT enterography identified 33 GISTs (7/33, 21% malignant) compared to 12 GISTs by abdominopelvic CT (6/12, 50% malignant; p  < 0.03). Tumor size ( p  < 0.0001), internal necrosis ( p  = 0.005), internal air or enteric contrast ( p  ≤ 0.021), and ulceration ( p  ≤ 0.021) were significantly associated with high-grade and malignant tumors, and irregular or invasive tumor borders ( p  < 0.01) was associated with malignant tumors. Conclusion The detection of small bowel GISTs can increase due to the use of CT enterography in patients with suspected small bowel bleeding. The large majority of small bowel GISTs detected by CT enterography are not malignant.

Rocks may undergo complex pressure–temperature ( P – T ) histories during orogenesis in response to alternating episodes of synconvergent burial and exhumation. In this study, chemical zoning in garnets combined with textural and chemical evidence from the schist of Willow Creek in the Albion Mountains of south-central Idaho (USA), reveals a complex P – T path during the early stages of Sevier orogenesis. The distribution of quartz inclusions combined with internal resorption features establishes a hiatus in garnet growth. Chemical zoning was simulated using a G -minimization approach to yield a P – T path consisting of three distinct pressure changes during increasing temperature, defining an “N” shape. Lu–Hf isochron ages from multiple garnet fractions and whole-rock analyses in two samples are 132.1 ± 2.4 and 138.7 ± 3.5 Ma. The samples were collected from the hanging wall of the Basin-Elba thrust fault and yielded results similar to those previously obtained from the footwall. This leads to several conclusions: (1) Both the hanging wall and footwall experienced the same metamorphic event, (2) the paths document a previously unrecognized crustal thickening and synorogenic extension cycle that fills an important time gap in the shortening history of the Sevier retroarc, suggesting progressive eastward growth of the orogen rather than a two-stage history, and (3) episodes of extensional exhumation during protracted convergent orogenesis are increasingly well recognized and highlight the dynamic behavior of orogenic belts.

Disease monitoring in nonalcoholic steatohepatitis (NASH) is limited by absence of noninvasive biomarkers of disease regression or progression. We aimed to examine the role of multiparametric three‐dimensional magnetic resonance elastography (3D‐MRE) and magnetic resonance imaging proton density fat fraction (MRI‐PDFF) in the detection of NASH regression after interventions. This is a single‐center prospective clinical trial of 40 patients who underwent bariatric surgery. Imaging and liver biopsies were obtained at baseline and 1 year after surgery. The imaging protocol consisted of multifrequency 3D‐MRE to determine the shear stiffness at 60 Hz and damping ratio at 40 Hz, and MRI‐PDFF to measure the fat fraction. A logistic regression model including these three parameters was previously found to correlate with NASH. We assessed the model performance in the detection of NASH resolution after surgery by comparing the image‐predicted change in NAFLD activity score (delta NAS) to the histologic changes. A total of 38 patients (median age 43, 87% female, 30 of 38 with NAS ≥ 1, and 13 of 38 with NASH) had complete data at 1 year. The NAS decreased in all subjects with NAS ≥ 1 at index biopsy, and NASH resolved in all 13. There was a strong correlation between the predicted delta NAS by imaging and the delta NAS by histology (r = 0.73, P < 0.001). The strength of correlation between histology and the predicted delta NAS using single conventional parameters, such as the fat fraction by MRI‐PDFF or shear stiffness at 60 Hz by MRE, was r = 0.69 (P < 0.001) and r = 0.43 (P = 0.009), respectively. Conclusion: Multiparametric 3D‐MRE and MRI‐PDFF can detect histologic changes of NASH resolution after bariatric surgery. Studies in a nonbariatric setting are needed to confirm the performance as a composite noninvasive biomarker for longitudinal NASH monitoring. In this prospective clinical trial, multiparametric 3D‐MRE and MRI‐PDFF detected histologic changes of NASH resolution after bariatric surgery. Multiparametric 3D‐MRE and MRI‐PDFF are an accurate dynamic biomarker, which can be used for noninvasive diagnosis and longitudinal monitoring of NASH.

PurposePrior iterative reconstruction (PIR) uses spatial information from one phase of enhancement to reduce image noise in other phases. We sought to determine if PIR could reduce radiation dose while preserving observer performance and CT number at multi-phase dual energy (DE) renal CT.MethodsCT projection data from multi-phase DE renal CT examinations were collected. Images corresponding to 40% radiation dose were reconstructed using validated noise insertion and PIR. Three genitourinary radiologists examined routine and 40% dose PIR images. Probability of malignancy was assessed [from 0 to 100] with malignancy assumed at probability ≥ 75. Observer performance was compared on a per patient and per lesion level. CT number accuracy was measured.ResultsTwenty-three patients had 49 renal lesions (11 solid renal neoplasms). CT number was nearly identical between techniques (mean CT number difference: unenhanced 2 ± 2 HU; enhanced 4 ± 4 HU). AUC for malignancy was similar between multi-phase routine dose DE and lower dose PIR images [per patient: 0.950 vs. 0.916 (p = 0.356); per lesion: 0.931 vs. 0.884 (p = 0.304)]. Per patient sensitivity was also similar (78% routine dose vs. 82% lower dose [p ≥ 0.99]), as was specificity (91% routine dose vs. 93% lower dose PIR [p > 0.99]), with similar findings on a per lesion level. Subjective image quality was also similar (p = 0.34).ConclusionsPrior iterative reconstruction is a new reconstruction method for multi-phase CT examinations that promises to facilitate radiation dose reduction by over 50% for multi-phase DE renal CT exams without compromising CT number or observer performance.

Passive hepatic congestion may result from a variety of distinct cardiovascular conditions. Injury to the liver caused by congestion is often asymptomatic and may not be recognized clinically. Diagnosis of congestive hepatopathy is important as it has the potential to cause complications including hepatic fibrosis and development of benign and malignant liver masses. This review will summarize the pathophysiologic mechanisms of congestive hepatopathy and provide both description and examples of its multimodality imaging findings. Examples of alternative disease which may have a similar imaging appearance will be provided. Knowledge regarding the characteristic imaging findings of congestive hepatopathy will allow for its accurate identification. Reviewing both the benefits and limitations of imaging performed to evaluate congestive hepatopathy and its complications will help to avoid pitfalls and enable recommendation of appropriate next steps in diagnostic evaluation.

Pressure–temperature (P–T) modeling and U–Pb monazite petrochronology provide a detailed P–T-t history for the Funeral Mountains metamorphic core complex, revealing different aspects of the geologic history at different structural depths and enabling the dating of tectonic mode switching cycles in the southwestern US Cordillera. Monazite petrochronology and yttrium X-ray element maps reveal several generations of monazite that formed during the Jurassic to Late Cretaceous. In the Monarch Canyon study area, the staurolite-out isograd separates samples with predominantly Jurassic monazite from those with predominantly Cretaceous monazite. Monazite grains yielding Jurassic to Early Cretaceous dates are chemically distinct from those yielding mid- and Late Cretaceous dates. Jurassic monazite dates from the Funeral Mountains record both prograde and retrograde metamorphism, with the latter associated with garnet breakdown during decompression. Heavy rare earth elements and yttrium (HREE + Y) in a mid-Cretaceous 104 to 88 Ma monazite population link recrystallization to prograde garnet growth from staurolite breakdown, and in a Late Cretaceous 88 to 74 Ma population to retrograde garnet breakdown via a reversal of the staurolite breakdown reaction. Modeling and mineral textures indicate peak metamorphic conditions of 6–10 kbar at ca. 650–700 °C in the structurally deepest rocks in Monarch Canyon. In contrast, structurally shallower rocks experienced peak temperatures between 610 and 650 ºC during Jurassic metamorphism. Monazite petrochronology elucidates the progression of monazite dissolution-reprecipitation along this P–T path. Modeling reactions and mineral stability link specific reactions to changes to the HREE + Y concentrations in monazite, particularly related to garnet and staurolite reactions. This dataset, in conjunction with previous studies, enables the timing and duration of tectonic mode switching cycles in the Funeral Mountains to be quantified, improving our understanding of the complex geological evolution of this core complex.