Diagnostic reference levels for chest computed tomography in children as a function of patient size.

BACKGROUND: Radiation exposures from computed tomography (CT) in children are inadequately studied. Diagnostic reference levels (DRLs) can help optimise radiation doses. OBJECTIVE: To determine local DRLs for paediatric chest CT performed mainly on modern dual-source, multi-slice CT scanners as a function of patient size. MATERIALS AND METHODS: Five hundred thirty-eight chest CT scans in 345 children under 15 years (y) of age (median age: 8 y, interquartile range [IQR]: 4-13 y) performed on four different CT scanners (38% on third-generation and 43% on second-generation dual-source CT) between November 2013 and December 2020 were retrospectively analysed. Examinations were grouped by water-equivalent diameter as a measure of patient size. DRLs for volume CT dose index (CTDIvol) and dose-length product (DLP) were determined for six different patient sizes and compared to national and European DRLs. RESULTS: The DRLs for CTDIvol and DLP are determined for each patient size group as a function of water-equivalent diameter as follows: (I) < 13 cm (n = 22; median: age 7 months): 0.4 mGy, 7 mGy·cm; (II) 13 cm to less than 17 cm (n = 151; median: age 3 y): 1.2 mGy, 25 mGy·cm; (III) 17 cm to less than 21 cm (n = 211; median: age 8 y): 1.7 mGy, 44 mGy·cm; (IV) 21 cm to less than 25 cm (n = 97; median: age 14 y): 3.0 mGy, 88 mGy·cm; (V) 25 cm to less than 29 cm (n = 42; median: age 14 y): 4.5 mGy, 135 mGy·cm; (VI) ≥ 29 cm (n = 15; median: age 14 y): 8.0 mGy, 241 mGy·cm. Compared with corresponding age and weight groups, our size-based DRLs for DLP are 54% to 71% lower than national and 23% to 85% lower than European DRLs. CONCLUSION: We developed DRLs for paediatric chest CT as a function of patient size with substantially lower values than national and European DRLs. Precise knowledge of size-based DRLs may assist other institutions in further dose optimisation in children.

A Potential Role for Bile Acid Signaling in Celiac Disease-Associated Fatty Liver.

Celiac disease (CeD) is a chronic autoimmune disorder characterized by an intolerance to storage proteins of many grains. CeD is frequently associated with liver damage and steatosis. Bile acid (BA) signaling has been identified as an important mediator in gut-liver interaction and the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Here, we aimed to analyze BA signaling and liver injury in CeD patients. Therefore, we analyzed data of 20 CeD patients on a gluten-free diet compared to 20 healthy controls (HC). We furthermore analyzed transaminase levels, markers of cell death, BA, and fatty acid metabolism. Hepatic steatosis was determined via transient elastography, by MRI and non-invasive scores. In CeD, we observed an increase of the apoptosis marker M30 and more hepatic steatosis as compared to HC. Fibroblast growth factor 19 (FGF19) was repressed in CeD, while low levels were associated with steatosis, especially in patients with high levels of anti-tissue transglutaminase antibodies (anti-tTG). When comparing anti-tTG-positive CeD patients to individuals without detectable anti-tTG levels, hepatic steatosis was accentuated. CeD patients with significant sonographic steatosis (defined by CAP ≥ 283 db/m) were exclusively anti-tTG-positive. In summary, our results suggest that even in CeD patients in clinical remission under gluten-free diet, alterations in gut-liver axis, especially BA signaling, might contribute to steatotic liver injury and should be further addressed in future studies and clinical practice.

Primary renal sarcomas: imaging features and discrimination from non-sarcoma renal tumors.

OBJECTIVES: To assess imaging features of primary renal sarcomas in order to better discriminate them from non-sarcoma renal tumors. METHODS: Adult patients diagnosed with renal sarcomas from 1995 to 2018 were included from 11 European tertiary referral centers (Germany, Belgium, Turkey). Renal sarcomas were 1:4 compared to patients with non-sarcoma renal tumors. CT/MRI findings were assessed using 21 predefined imaging features. A random forest model was trained to predict "renal sarcoma vs. non-sarcoma renal tumors" based on demographics and imaging features. RESULTS: n = 34 renal sarcomas were included and compared to n = 136 non-sarcoma renal tumors. Renal sarcomas manifested in younger patients (median 55 vs. 67 years, p < 0.01) and were more complex (high RENAL score complexity 79.4% vs. 25.7%, p < 0.01). Renal sarcomas were larger (median diameter 108 vs. 43 mm, p < 0.01) with irregular shape and ill-defined margins, and more frequently demonstrated invasion of the renal vein or inferior vena cava, tumor necrosis, direct invasion of adjacent organs, and contact to renal artery or vein, compared to non-sarcoma renal tumors (p < 0.05, each). The random forest algorithm yielded a median AUC = 93.8% to predict renal sarcoma histology, with sensitivity, specificity, and positive predictive value of 90.4%, 76.5%, and 93.9%, respectively. Tumor diameter and RENAL score were the most relevant imaging features for renal sarcoma identification. CONCLUSION: Renal sarcomas are rare tumors commonly manifesting as large masses in young patients. A random forest model using demographics and imaging features shows good diagnostic accuracy for discrimination of renal sarcomas from non-sarcoma renal tumors, which might aid in clinical decision-making. KEY POINTS: • Renal sarcomas commonly manifest in younger patients as large, complex renal masses. • Compared to non-sarcoma renal tumors, renal sarcomas more frequently demonstrated invasion of the renal vein or inferior vena cava, tumor necrosis, direct invasion of adjacent organs, and contact to renal artery or vein. • Using demographics and standardized imaging features, a random forest showed excellent diagnostic performance for discrimination of sarcoma vs. non-sarcoma renal tumors (AUC = 93.8%, sensitivity = 90.4%, specificity = 76.5%, and PPV = 93.9%).

Anti-TNFα treatment in Crohn's disease: Impact on hepatic steatosis, gut-derived hormones and metabolic status.

BACKGROUND AND AIMS: An association between Crohn's disease (CD) and hepatic steatosis has been reported. However, the underlying mechanisms of steatosis progression in CD are not clear. Among the most effective CD treatments are agents that inhibit Tumor-Necrosis-Factor (TNF) activity, yet it is unclear why anti-TNFα agents would affect steatosis in CD. Recent studies suggest that microbiome can affect both, CD and steatosis pathogenesis. Therefore, we here analysed a potential relationship between anti-TNF treatment and hepatic steatosis in CD, focusing on the gut-liver axis. METHODS: This cross-sectional study evaluated patients with established CD, with and without anti-TNFα treatment, analysing serum markers of liver injury, measurement of transient elastography, controlled attenuation parameter (CAP) and MRI for fat detection. Changes in lipid and metabolic profiles were assessed by serum and stool lipidomics and metabolimics. Additionally, we analysed gut microbiota composition and mediators of bile acid (BA) signalling via stool and serum analysis. RESULTS: Patients on anti-TNFα treatment had less hepatic steatosis as assessed by CAP and MRI. Serum FGF19 levels were significantly higher in patients on anti-TNFα therapy and associate with reduced steatosis and increased bowel motility. Neutral lipids including triglycerides were reduced in the serum of patients on anti-TNF treatment. Bacteria involved in BA metabolism and FGF19 regulation, including Firmicutes, showed group-specific alterations with low levels in patients without anti-TNFα treatment. Low abundance of Firmicutes was associated with higher triglyceride levels. CONCLUSIONS: Anti-TNFα treatment is associated with reduced steatosis, lower triglyceride levels, alterations in FXR-signalling (eg FGF19) and microbiota composition in CD.

Impact of 18F-FDG PET/MR on therapeutic management in high risk primary breast cancer patients - A prospective evaluation of staging algorithms.

PURPOSE: To investigate whether potential differences in staging between a traditional staging imaging algorithm and 18F-FDG PET/MR lead to a change in patient management in breast carcinoma and to compare the diagnostic accuracy between the traditional staging algorithm and 18F-FDG PET/MR for the TNM classification. METHOD: In this prospective cohort study from two university hospitals 56 women with newly diagnosed, therapy-naive breast cancer and increased pre-test probability for distant metastases were included. All patients were examined by a traditional staging imaging algorithm (X-ray mammography, breast ultrasonography, chest plain radiography, bone scintigraphy, and ultrasonography of the liver and axillary fossa) and whole-body 18F-FDG PET/MR including dedicated 18F-FDG PET/MR breast examinations. Each patient was discussed two times in a separate tumor board session to determine a total of three therapy recommendations based on histopathological data of the primary tumor and (1) traditional algorithm only, (2) traditional algorithm and 18F-FDG PET/MR, and (3) 18F-FDG PET/MR only. Major changes in therapy recommendations and differences between the traditional staging algorithm and 18F-FDG PET/MR for the TNM classification were evaluated. RESULTS: Staging by 18F-FDG PET/MR led to a difference in treatment compared the traditional staging algorithm in 8/56 cases (14%). Therapy changes included therapy of the breast, locoregional nodes and systemic therapy. A trend to staging superiority was found for 18F-FDG PET/MRI without statistical significance (p = 0.3827). CONCLUSION: In conclusion, for breast cancer patients with elevated pre-test probability for distant metastases a change of the therapy regiment occurs in 14 % of patients when staged by 18F-FDG PET/MR and confirmed by histopathology compared to a traditional staging algorithm. In particular with regard to the amendment of the guideline further assessment of 18F-FDG-PET/MR in this setting is necessary to assess the true value of this modality.

Pharmacokinetics of Ferumoxytol in the Abdomen and Pelvis: A Dosing Study with 1.5- and 3.0-T MRI Relaxometry.

Background The off-label use of ferumoxytol (FE), an intravenous iron preparation for iron deficiency anemia, as a contrast agent for MRI is increasing; therefore, it is critical to understand its pharmacokinetics. Purpose To evaluate the pharmacokinetics of FE in the abdomen and pelvis, as assessed with quantitative 1.5- and 3.0-T MRI relaxometry. Materials and Methods R2*, an MRI technique used to estimate tissue iron content in the abdomen and pelvis, was performed at 1.5 and 3.0 T in 12 healthy volunteers between April 2015 and January 2016. Volunteers were randomly assigned to receive an FE dose of 2 mg per kilogram of body weight (FE2mg) or 4 mg/kg (FE4mg). MRI was repeated at 1.5 and 3.0 T for each volunteer at five time points: days 1, 2, 4, 7, and 30. A radiologist experienced in MRI relaxometry measured R2* in organs of the mononuclear phagocyte system (MPS) (ie, liver, spleen, and bone marrow), non-MPS anatomy (kidney, pancreas, and muscle), inguinal lymph nodes (LNs), and blood pool. A paired Student t test was used to compare changes in tissue R2*. Results Volunteers (six female; mean age, 44.3 years ± 12.2 [standard deviation]) received either FE2 mg (n = 5) or FE4 mg (n = 6). Overall R2* trend analysis was temporally significant (P < .001). Time to peak R2* in the MPS occurred on day 1 for FE2mg and between days 1 and 4 for FE4mg (P < .001 to P < .002). Time to peak R2* in non-MPS anatomy, LNs, and blood pool occurred on day 1 for both doses (P < .001 to P < .09). Except for the spleen (at 1.5 T) and liver, MPS R2* remained elevated through day 30 for both doses (P = .02 to P = .03). Except for the kidney and pancreas, non-MPS, LN, and blood pool R2* returned to baseline levels between days 2 and 4 at FE2mg (P = .06 to P = .49) and between days 4 and 7 at FE4mg (P = .06 to P = .63). There was no difference in R2* change between non-MPS and LN R2* at any time (range, 1-71 sec-1 vs 0-50 sec-1; P = .06 to P = .97). Conclusion The pharmacokinetics of ferumoxytol in lymph nodes are distinct from those in mononuclear phagocyte system (MPS) organs, parallel non-MPS anatomy, and the blood pool. © RSNA, 2019 Online supplemental material is available for this article.

Quantitative performance of 124I PET/MR of neck lesions in thyroid cancer patients using 124I PET/CT as reference.

BACKGROUND: In patients with differentiated thyroid cancer (DTC), serial 124I PET/CT imaging is, for instance, used to assess the absorbed (radiation) dose to lesions. Frequently, the lesions are located in the neck and they are close to or surrounded by different tissue types. In contrast to PET/CT, MR-based attenuation correction in PET/MR may be therefore challenging in the neck region. The aim of this retrospective study was to assess the quantitative performance of 124I PET/MRI of neck lesions by comparing the MR-based and CT-based 124I activity concentrations (ACs). Sixteen DTC patients underwent PET/CT scans at 24 and 120 h after administration of about 25 MBq 124I. Approximately 1 h before or after PET/CT examination, each patient additionally received a 24-h PET/MR scan and sometimes a 120-h PET/MR scan. PET images were reconstructed using the respective attenuation correction approach. Appropriate reconstruction parameters and corrections were used to harmonize the reconstructed PET images to provide, for instance, similar spatial resolution. For each lesion, two types of ACs were ascertained: the maximum AC (max-AC) and an average AC (avg-AC). The avg-AC is the average activity concentration obtained within a spherical volume of interest with a diameter of 7 mm, equaling the PET scanner resolution. For each type of AC, the percentage AC difference between MR-based and CT-based ACs was determined and Lin's concordance correlation analysis was applied. Quantitative performance was considered acceptable if the standard deviation was ± 25% (precision), and the mean value was within ± 10% (accuracy). RESULTS: The avg-ACs (max-ACs within parentheses) of 74 lesions ranged from 0.20 (0.33) to 657 (733) kBq/mL. Excluding two lesions with ACs of approximately 1 kBq/mL, the mean (median) ± standard deviation (range) was - 4% (- 5%) ± 14% (- 28 to 29%) for the avg-AC and - 9% (- 11%) ± 14% (- 33 to 33%) for the max-AC. Lin's concordance correlation coefficients were ≥ 0.97, indicating substantial AC agreement. CONCLUSIONS: Quantification of lesions in the neck region using 124I PET/MR showed acceptable quantitation performance to 124I PET/CT for AC above 1 kBq/mL. The PET/MRI-based 124I ACs in the neck region can be therefore reliably used in pre-therapy dosimetry planning.

Changes in signal intensity in the dentate nucleus at unenhanced T1-weighted magnetic resonance imaging depending on class of previously used gadolinium-based contrast agent.

BACKGROUND: Signal increase on T1-weighted magnetic resonance imaging (MRI) in the dentate nucleus has been reported in adults after multiple injections of gadolinium-based contrast agents. Linear contrast agents are more prone to cause this increase. Studies in children are still rare and focus mostly on the analysis of one single agent. OBJECTIVE: To compare signal intensity chances in children after more than four injections of either only linear or only macrocyclic contrast agents. MATERIALS AND METHODS: Seventy children (examined from October 2001 to February 2016) were included in this retrospective study. Signal intensities in the dentate nucleus and pons were measured on non-enhanced T1-weighted images from the first and last MRI scans. A two-sample t-test compared the dentate nucleus-to-pons signal intensity ratio differences for linear versus macrocyclic gadolinium-based contrast agent applications and also the number of applications (4-8, 9-12 or >12). Patients' charts were analysed to evaluate potentially associated neurological symptoms. RESULTS: Patients had contrast-enhanced MRI using either only linear (n=16) or only macrocyclic (n=54) gadolinium-based contrast agents. In patients with >12 injections, dentate nucleus-to-pons signal intensity ratio was statistically different concerning the contrast agent class (0.16±0.125 for macrocyclic vs. 0.0005±0.13 for linear agents). For linear agents, a statistically significant increase was found between 4-8 injections (-0.051±0.087) and >12 injections (0.16±0.125). No neurological symptoms were recorded in patients with signal changes. CONCLUSION: Multiple injections of linear gadolinium-based contrast agents lead to a signal increase of the dentate nucleus in children. Signal intensity increases depend on the number of injections of linear contrast agents.

Radiological imaging characteristics of intramammary hematological malignancies: results from a german multicenter study.

To assess radiological procedures and imaging characteristics in patients with intramammary hematological malignancies (IHM). Radiological imaging studies of histopathological proven IHM cases from ten German University affiliated breast imaging centers from 1997-2012 were retrospectively evaluated. Imaging modalities included ultrasound (US), mammography and magnetic resonance imaging (MRI). Two radiologists blinded to the histopathological diagnoses independently assessed all imaging studies. Imaging studies of 101 patients with 204 intramammary lesions were included. Most patients were women (95%) with a median age of 64 years. IHM were classified as Non Hodgkin lymphoma (77.2%), plasmacytoma (11.9%), leukemia (9.9%), and Hodgkin lymphoma (1%). The mean lesion size was 15.8 ± 10.1 mm. Most IHM presented in mammography as lesions with comparable density to the surrounding tissue, and a round or irregular shape with indistinct margins. On US, most lesions were of irregular shape with complex echo pattern and indistinct margins. MRI shows lesions with irregular or spiculated margins and miscellaneous enhancement patterns. Using US or MRI, IHM were more frequently classified as BI-RADS 4 or 5 than using mammography (96.2% and 89.3% versus 75.3%). IHM can present with miscellaneous radiological patterns. Sensitivity for detection of IHM lesions was higher in US and MRI than in mammography.

Diagnostic Accuracy of MRI Versus CT for the Evaluation of Acute Appendicitis in Children and Young Adults.

OBJECTIVE: Appendicitis is frequently diagnosed in the emergency department, most commonly using CT. The purpose of this study was to compare the diagnostic accuracy of contrast-enhanced MRI with that of contrast-enhanced CT for the diagnosis of appendicitis in adolescents when interpreted by abdominal radiologists and pediatric radiologists. SUBJECTS AND METHODS: Our study included a prospectively enrolled cohort of 48 patients (12-20 years old) with nontraumatic abdominal pain who underwent CT and MRI. Fellowship-trained abdominal and pediatric radiologists reviewed all CT and MRI studies in randomized order, blinded to patient outcome. Likelihood for appendicitis was rated on a 5-point scale (1, definitely not appendicitis; 5, definitely appendicitis) for CT, the unenhanced portion of the MRI, and the entire contrast-enhanced MRI study. ROC curves were generated and AUC compared for each scan type for all six readers and then stratified by radiologist type. Image test characteristics, interrater reliability, and reading times were compared. RESULTS: Sensitivity and specificity were 85.9% (95% CI, 76.2-92.7%) and 93.8% (95% CI, 89.7-96.7%) for unenhanced MRI, 93.6% (95% CI, 85.6-97.9%) and 94.3% (95% CI, 90.2-97%) for contrast-enhanced MRI, and 93.6% (95% CI, 85.6-97.9%) and 94.3% (95% CI, 90.2-97%) for CT. No difference was found in the diagnostic accuracy or interpretation time when comparing abdominal radiologists to pediatric radiologists (CT, 3.0 min vs 2.8 min; contrast-enhanced MRI, 2.4 min vs 1.8 min; unenhanced MRI, 1.5 min vs 2.3 min). Substantial agreement between abdominal and pediatric radiologists was seen for all methods (κ = 0.72-0.83). CONCLUSION: The diagnostic accuracy of MRI to diagnose appendicitis was very similar to CT. No statistically significant difference in accuracy was observed between imaging modality or radiologist subspecialty.

Added value of gadoxetic acid-enhanced T1-weighted magnetic resonance cholangiography for the diagnosis of post-transplant biliary complications.

OBJECTIVES: Biliary complications after liver transplantation (LT) are common. This study aimed to ascertain the value of gadoxetic acid-enhanced T1-weighted (T1w) magnetic resonance cholangiography (MRC) to evaluate anastomotic strictures (AS), non-anastomotic strictures (NAS) and biliary casts (BC). METHODS: Sixty liver-transplanted patients with suspicion of biliary complications and T2w-MRCP and T1w-MRC followed by endoscopic retrograde cholangiopancreatography (ERCP) or percutaneous transhepatic cholangiography (PTC) were analysed. Two readers reviewed the MRCs and rated image quality (IQ) and likelihood for AS/NAS/BC on Likert scales. Sensitivity, specificity and predictive values were calculated, ROC curve analysis performed, and inter-reader variability assessed. The subjective added value of T1w-MRC was rated. RESULTS: IQ was high for all sequences without significant differences (2.83-2.88). In 39 patients ERCP/PTC detected a complication. Sensitivity and specificity for AS were 64-96 using T2w-MRCP, increasing to 79-100 using all sequences. Use of all sequences increased the sensitivity of detecting NAS/BC from 72-92% to 88-100% and 67-89% to 72-94%, respectively. Kappa values were substantial (0.45-0.62). T1w-MRC was found to be helpful in 75-83.3%. CONCLUSIONS: Combining T1w-MRC and T2w-MRCP increased sensitivity and specificity and diagnostic confidence in patients after LT with suspected biliary complications. T1w-MRC is a valuable tool for evaluating post-transplant biliary complications. KEY POINTS: • T1w-MRC is a valuable tool for evaluating post-transplant biliary complications. • Adding T1w-MRC to T2w-MRC increases diagnostic confidence for detection of biliary complications. • A combination of T1w-MRC and T2w-MRCP leads to the best results.

Evaluation of PET and MR datasets in integrated 18F-FDG PET/MRI: A comparison of different MR sequences for whole-body restaging of breast cancer patients.

OBJECTIVES: To investigate the diagnostic value of different MR sequences and 18F-FDG PET data for whole-body restaging of breast cancer patients utilizing PET/MRI. METHODS: A total of 36 patients with suspected tumor recurrence of breast cancer based on clinical follow-up or abnormal findings in follow-up examinations (e.g. CT, MRI) were prospectively enrolled in this study. All patients underwent a PET/CT and subsequently an additional PET/MR scan. Two readers were instructed to identify the occurrence of a tumor relapse in subsequent MR and PET/MR readings, utilizing different MR sequence constellations for each session. The diagnostic confidence for the determination of a malignant or benign lesion was qualitatively rated (3-point ordinal scale) for each lesion in the different reading sessions and the lesion conspicuity (4-point ordinal scale) for the three different MR sequences was additionally evaluated. RESULTS: Tumor recurrence was present in 25/36 (69%) patients. All three PET/MRI readings showed a significantly higher accuracy as well as higher confidence levels for the detection of recurrent breast cancer lesions when compared to MRI alone (p<0.05). Furthermore, all three PET/MR sequence constellations showed comparable diagnostic accuracy for the identification of a breast cancer recurrence (p>0.05), yet the highest confidence levels were obtained, when all three MR sequences were used for image interpretation. Moreover, contrast-enhanced T1-weighted VIBE imaging showed significantly higher values for the delineation of malignant and benign lesions when compared to T2w HASTE and diffusion-weighted imaging. CONCLUSION: Integrated PET/MRI provides superior restaging of breast cancer patients over MRI alone. Facing the need for appropriate and efficient whole-body PET/MR protocols, our results show the feasibility of fast and morphologically adequate PET/MR protocols. However, considering an equivalent accuracy for the detection of breast cancer recurrences in the three PET/MR readings, the application of contrast-agent and the inclusion of DWI in the study protocol seems to be debatable.

Imaging findings of primary breast sarcoma: Results of a first multicenter study.

PURPOSE: To investigate imaging findings in patients with primary breast sarcoma (PBS). MATERIALS AND METHODS: A retrospective search in the databases of 10 radiological departments in Germany from 2000 to 2011 was performed. Only histologically proven cases of PBS were included into the study. Mammography was available in 31 patients (33 lesions), ultrasound images in 24 patients (24 lesions), and for 10 patients (14 lesions) magnetic resonance imaging (MRI) of the breast was performed. The breast findings were classified according to the American College of Radiology Breast Imaging Reporting and Data Systems (BI-RADS) 5th edition categories. Collected data were evaluated by means of descriptive statistics. RESULTS: Forty-two female patients (mean age 62.0 years, range, 30-86 years) were included in the study. Clinically, all women had painless lumps. Irregular (53.3% [16/30]) or oval (30.0% [9/30]) mass with indistinct (73.3% [22/30]) or microlobulated (10% [3/30]) margins were common findings on mammograms. Ultrasound revealed typically an irregular (79.2% [19/24]), hypoechoic (62.5% [15/24]) mass, with indistinct margins (79.2% [19/24]), and posterior acoustic shadowing (79.2% [19/24]). MRI showed irregular masses (81.8% [9/11]) with irregular or spiculated margins, and a rapid initial signal increase with a delayed washout in kinetic analysis. CONCLUSION: Overall, PBS has no pathognomonic imaging features and can mimic those of invasive mammary carcinoma. Breast sarcoma should be taken into the differential diagnosis of breast findings described above.

Thrombus-mimicking artifacts in two-point Dixon MRI: Prevalence, appearance, and severity.

PURPOSE: To evaluate the incidence and severity of potentially thrombus mimicking, flow-induced misallocation artifacts in a clinical setting. Two-point "Dixon" fat-water separation methods, with bipolar readout gradients, may suffer from flow-induced fat-water misallocation artifacts. If these artifacts occur within blood vessels, they may mimic thrombus. MATERIALS AND METHODS: Two-point Dixon coronal and axial images acquired in 102 consecutive patients were retrospectively evaluated for the presence of flow-induced artifacts in arteries and veins. Artifacts were graded on a 3-point scale (none, mild, severe) by two independent readers. Interreader agreement was evaluated with kappa statistics. RESULTS: Reader 1 reported 63 artifacts in 46 (45%) of the cases (severe in 19 cases, 18.6%). Reader 2 reported 51 artifacts in 43 (42.2%) of the cases (severe in 18 cases, 17.6%). Misallocation of fat and water was apparent in all datasets with severe artifacts, whereas variable signal intensity changes in water and fat images were observed in mild artifacts. Interreader agreement was good for artifacts appearing in coronal images (κ = 0.7) and fair for artifact appearance in axial images (κ = 0.24). CONCLUSION: Our study shows a high incidence of flow-induced mild and severe artifacts in a two-point Dixon method with bipolar readout gradients. This artifact should not be misinterpreted as intravascular thrombus. LEVEL OF EVIDENCE: 3 J. Magn. Reson. Imaging 2017;45:229-236.

MR visible localization device for radiographic-pathologic correlation of surgical specimens.

PURPOSE: The detection of small parenchymal hepatic lesions identified by preoperative imaging remains a challenge for traditional pathologic methods in large specimens. We developed a magnetic resonance imaging (MRI) compatible localization device for imaging of surgical specimens aimed to improve identification and localization of hepatic lesions ex vivo. MATERIALS AND METHODS: The device consists of two stationary and one removable MR-visible grids lined with silicone gel, creating an orthogonal 3D matrix for lesion localization. To test the device, five specimens of swine liver with a random number of lesions created by microwave ablation were imaged on a 3T MR scanner. Two readers independently evaluated lesion coordinates and size, which were then correlated with sectioning guided by MR imaging. RESULTS: All lesions (n=38) were detected at/very close to the expected localization. Inter-reader agreement of lesion localization was almost perfect (0.92). The lesion size estimated by MRI matched macroscopic lesion size in cut specimen (±2mm) in 34 and 35, respectively, out of 38 lesions. CONCLUSION: Use of this MR compatible device for ex vivo imaging proved feasible for detection and three-dimensional localization of liver lesions, and has potential to play an important role in the ex vivo examination of surgical specimens in which pathologic correlation is clinically important.

Comparison of the Detection Rate of Simulated Microcalcifications in Full-Field Digital Mammography, Digital Breast Tomosynthesis, and Synthetically Reconstructed 2-Dimensional Images Performed With 2 Different Digital X-ray Mammography Systems.

OBJECTIVE: The aim of this study was to compare the microcalcification detectability in an anthropomorphic phantom model regarding number, size, and shape in full-field digital mammography (FFDM), synthetically reconstructed 2-dimensional (Synthetic-2D) images, and digital breast tomosynthesis (DBT) performed with 2 different x-ray mammography systems. MATERIALS AND METHODS: Simulated microcalcifications of different numbers (0 to >39), sizes (diameter, 100-800 µm), and shapes (round vs heterogeneous) were scattered by random distribution on 50 film phantoms each divided in 4 quadrants. The FFDM and DBT x-rays were taken from each of these 50 films with both x-ray mammography systems (SenoClaire; GE Healthcare, Selenia Dimensions, Hologic) using an anthropomorphic scattering body and automatic exposure control. The resulting exposure factors were similar to a clinical setting. The synthetically reconstructed 2D images were generated automatically on both systems. All FFDM, Synthetic-2D, and DBT images were interpreted in randomized order and independently of each other by 6 radiologists using a structured questionnaire. RESULTS: The number categories of simulated microcalcifications were correctly evaluated in 55.3% of instances (quadrant by reader) in FFDM, 50.9% in the Synthetic-2D views, and 59.5% in DBT, summarized for 200 quadrants per reader for each Device A and B, respectively. Full-field digital mammography was superior to Synthetic-2D (mean difference, 4%; 95% confidence interval [CI], 2%-7%; P < 0.001), and DBT was superior to both FFDM (mean difference, 4%; 95% CI, 2%-7%; P = 0.002) and Synthetic-2D (mean difference, 9%; 95% CI, 6%-11%; P < 0.001). This trend was consistent in all subgroup analyses. The number of the smallest microcalcifications (100-399 µm) was correctly evaluated in 25.2% of the FFDM, in 14.2% for Synthetic-2D, and in 28.3% of the DBT images. Underestimations of the number of simulated microcalcifications were more common than overestimations. Regarding the size categories of simulated microcalcifications, the rates of correct assessments were in 45.4% of instances in FFDM, 39.9% in the Synthetic-2D views, and 43.6% in DBT, summarized for 200 quadrants per reader and both imaging devices. CONCLUSIONS: In the presented in vitro environment using an anthropomorphic phantom model, standard full-field digital x-ray mammography was superior to synthetically reconstructed 2-dimensional images in the detection of simulated microcalcifications. In view of these results, it is questionable whether Synthetic-2D images can replace FFDM in clinical examinations at the present time. Further investigations are needed to assess the clinical impact of the in vitro results.

Crossover comparison of ferumoxytol and gadobenate dimeglumine for abdominal MR-angiography at 3.0 tesla: Effects of contrast bolus length and flip angle.

PURPOSE: Ferumoxytol (FE) has gained interest as an alternative to gadolinium-based contrast agents (GBCAs). The purpose of this study was to evaluate and optimize ferumoxytol dose and T1 weighting, in comparison to a conventional GBCA. MATERIALS AND METHODS: Twelve healthy volunteers (six women / six men, mean age 44.3 years) were recruited for this study. Scanning was performed on a clinical 3 Tesla (T) MRI system. Gadobenate dimeglumine (GD)-enhanced MRA was performed followed by FE-enhanced MRA 1 month later. Volunteers were randomly assigned to a diluted (n = 6) or undiluted (n = 6) dose of GD (0.1 mmol/kg), and to FE doses of 4 mg/kg (n = 6) or 2 mg/kg (n = 6). First pass and steady-state MRA were performed for GD- and FE-enhanced MRA. Flip-angle optimization was performed after FE administration. Quantitative analysis included relative contrast-to-noise ratio (relCNR) measurements for all acquisitions. First pass GD- and FE-enhanced MRA images were evaluated qualitatively. RESULTS: RelCNR was significantly higher with undiluted GD (31.8, 95% confidence interval [CI], 27.7-35.9) compared with diluted GD (16.2; 95% CI, 12.2-20.3; P = 0.001) and both 4 mg/kg FE (12.5; 95% CI, 8.5-16.4; P < 0.001) and 2 mg/kg FE (9.1; 95% CI, 5.1-13.2; P < 0.001) during first pass. Relative CNR did not decrease with FE 5 min postinjection compared with GD. Flip-angle analysis revealed relative CNR-peaks at 30° for FE 4 mg/kg and at 20° for FE 2 mg/kg. Diluted GD (P = 0.013) and FE 4 mg/kg (P = 0.01) revealed significantly higher image quality scores compared with undiluted GD during first pass. CONCLUSION: This study shows an equivalent image quality of FE and GD for first pass MRA even though GD showed significantly higher relative CNR. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;45:1617-1626.

Integrated PET/MR breast cancer imaging: Attenuation correction and implementation of a 16-channel RF coil.

PURPOSE: This study aims to develop, implement, and evaluate a 16-channel radiofrequency (RF) coil for integrated positron emission tomography/magnetic resonance (PET/MR) imaging of breast cancer. The RF coil is designed for optimized MR imaging performance and PET transparency and attenuation correction (AC) is applied for accurate PET quantification. METHODS: A 16-channel breast array RF coil was designed for integrated PET/MR hybrid imaging of breast cancer lesions. The RF coil features a lightweight rigid design and is positioned with a spacer at a defined position on the patient table of an integrated PET/MR system. Attenuation correction is performed by generating and applying a dedicated 3D CT-based template attenuation map. Reposition accuracy of the RF coil on the system patient table while using the positioning frame was tested in repeated measurements using MR-visible markers. The MR, PET, and PET/MR imaging performances were systematically evaluated using modular breast phantoms. Attenuation correction of the RF coil was evaluated with difference measurements of the active breast phantoms filled with radiotracer in the PET detector with and without the RF coil in place, serving as a standard of reference measurement. The overall PET/MR imaging performance and PET quantification accuracy of the new 16-channel RF coil and its AC were then evaluated in first clinical examinations on ten patients with local breast cancer. RESULTS: The RF breast array coil provides excellent signal-to-noise ratio and signal homogeneity across the volume of the breast phantoms in MR imaging and visualizes small structures in the phantoms down to 0.4 mm in plane. Difference measurements with PET revealed a global loss and thus attenuation of counts by 13% (mean value across the whole phantom volume) when the RF coil is placed in the PET detector. Local attenuation ranging from 0% in the middle of the phantoms up to 24% was detected in the peripheral regions of the phantoms at positions closer to attenuating hardware structures of the RF coil. The position accuracy of the RF coil on the patient table when using the positioning frame was determined well below 1 mm for all three spatial dimensions. This ensures perfect position match between the RF coil and its three-dimensional attenuation template during the PET data reconstruction process. When applying the CT-based AC of the RF coil, the global attenuation bias was mostly compensated to ±0.5% across the entire breast imaging volume. The patient study revealed high quality MR, PET, and combined PET/MR imaging of breast cancer. Quantitative activity measurements in all 11 breast cancer lesions of the ten patients resulted in increased mean difference values of SUVmax 11.8% (minimum 3.2%; maximum 23.2%) between nonAC images and images when AC of the RF breast coil was applied. This supports the quantitative results of the phantom study as well as successful attenuation correction of the RF coil. CONCLUSIONS: A 16-channel breast RF coil was designed for optimized MR imaging performance and PET transparency and was successfully integrated with its dedicated attenuation correction template into a whole-body PET/MR system. Systematic PET/MR imaging evaluation with phantoms and an initial study on patients with breast cancer provided excellent MR and PET image quality and accurate PET quantification.

Magnetic resonance imaging findings of intramammary metastases.

The purpose of this study was to identify magnetic resonance imaging (MRI) findings of intramammary metastases (IM). We identified 8 cases with IM, which were investigated by breast MRI (1.5T). In every case, the diagnosis of IM was proven histopathologically on breast biopsy specimens. Overall, 187 IM were identified. IM had inconsistent MRI features, which cannot be clearly classify as benign or malignant. IM should be taken into consideration in the differential diagnosis of breast lesions to avoid possible misinterpretations.

Contrast-Enhanced Abdominal MRI for Suspected Appendicitis: How We Do It.

OBJECTIVE: The purpose of this article is to describe our approach to contrast-enhanced abdominal MRI in patients with nontraumatic abdominal pain and suspected appendicitis. We aim to share our experience on the advantages, pearls, and pitfalls of MRI in this clinical setting, in comparison with CT and ultrasound. CONCLUSION: We present some typical cases of appendicitis and alternative diagnoses in patients presenting with acute nontraumatic abdominal pain.