Increase in complicated upper respiratory tract infection in children during the 2022/2023 winter season-a post coronavirus disease 2019 effect?

BACKGROUND: Upper respiratory tract infections usually peak during winter months. OBJECTIVE: The purpose of this study was to evaluate whether imaging of complicated upper airway infection in children increased during the winter season of 2022/2023. MATERIALS AND METHODS: In a retrospective study setting, pediatric magnetic resonance imaging (MRI) and computed tomography (CT) scans for evaluation of upper respiratory tract infection performed between October 2022 and April 2023 were analyzed regarding presence of the following complications: mastoiditis, abscess, phlegmon, meningitis, reactive vasculitis, and sinus vein thrombosis. Pathogen detection, surgery, and infection parameters were obtained. Data were compared with MRI and CT scans performed in the same months of the preceding five years, distinguishing between pandemic and pre-pandemic years. RESULTS: During the 2022/2023 winter season, the number of MRI and CT scans in children with upper airway infections, the complication rate, the rate of detected streptococcal infections, and the rate of surgery increased significantly compared to expectations based on the five prior winter seasons (all P<0.05). During the first complete pandemic winter season in Europe (2020/2021), the number of MRI and CT scans in children with upper airway infection, the complication rate, and the rates of streptococcal detection and surgery decreased significantly compared to expectations based on the pre-pandemic, the second pandemic, and the post-pandemic winter seasons (all P<0.05). CONCLUSION: After a decline during the first pandemic winter season, there was a marked rebound in complicated upper airway infection in children, with a significant increase in cases during the 2022/2023 winter season compared to the pre-pandemic and pandemic years.

Lung Function in Patients with Cystic Fibrosis before and during CFTR-Modulator Therapy Using 3D Ultrashort Echo Time MRI.

Background The triple combination of the cystic fibrosis transmembrane regulator (CFTR) modulators elexacaftor, tezacaftor, and ivacaftor (hereafter, elexacaftor/tezacaftor/ivacaftor) has a positive effect on lung function in patients with cystic fibrosis (CF). Purpose To compare three-dimensional (3D) ultrashort echo time (UTE) MRI functional lung data to common functional lung parameters in assessing lung function in patients with CF undergoing elexacaftor/tezacaftor/ivacaftor therapy. Materials and Methods In this prospective feasibility study, 16 participants with CF consented to undergo pulmonary MRI with a breath-hold 3D UTE sequence at baseline (April 2018-June 2019) and follow-up (April-July 2021). Eight participants received elexacaftor/tezacaftor/ivacaftor after baseline, and eight participants with unchanged treatment served as the control group. Lung function was assessed with body plethysmography and lung clearance index (LCI). Image-based functional lung parameters, such as ventilation inhomogeneity and ventilation defect percentage (VDP), were calculated from signal intensity change between MRI scans at inspiration and expiration. Metrics at baseline and follow-up were compared within groups (permutation test), correlation was tested (Spearman rank correlation), and 95% CIs were calculated (bootstrapping technique). Results MRI ventilation inhomogeneity correlated with LCI at baseline (r = 0.92, P < .001) and follow-up (r = 0.81, P = .002). Mean MRI ventilation inhomogeneity (baseline, 0.74 ± 0.15 [SD]; follow-up, 0.64 ± 0.11; P = .02) and mean VDP (baseline, 14.1% ± 7.4; follow-up, 8.5% ± 3.3; P = .02) decreased from baseline to follow-up in the treatment group. Lung function was stable over time (mean LCI: 9.3 turnovers ± 4.1 at baseline vs 11.5 turnovers ± 7.4 at follow-up; P = .34) in the control group. In all participants, correlation of forced expiratory volume in 1 second with MRI ventilation inhomogeneity was good at baseline (r = -0.61, P = .01) but poor during follow-up (r = -0.06, P = .82). Conclusion Noncontrast 3D UTE lung MRI functional parameters of ventilation inhomogeneity and VDP can be used to assess lung function over time in patients with CF and can add regional information to established global parameters, such as LCI. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Iwasawa in this issue.

Comparison of diagnostic quality of 3D ultrashort-echo-time techniques for pulmonary magnetic resonance imaging in free-breathing.

BACKGROUND: Ultrashort-echo-time (UTE) sequences have been developed to overcome technical limitations of pulmonary magnetic resonance imaging (MRI). Recently, it has been shown that UTE sequences with breath-hold allow rapid image acquisition with sufficient image quality. However, patients with impaired respiration require alternative acquisition strategies while breathing freely. PURPOSE: To compare the diagnostic performance of free-breathing three-dimensional (3D)-UTE sequences with different trajectories based on pulmonary imaging of immunocompromised patients. MATERIAL AND METHODS: In a prospective study setting, two 3D-UTE sequences performed in free-breathing and exploiting non-Cartesian trajectories-one using a stack-of-spirals and the other exploiting a radial trajectory-were acquired at 3 T in patients undergoing hematopoietic stem cell transplantation. Two radiologists assessed the images regarding presence of pleural effusions and pulmonary infiltrations. Computed tomography (CT) was used as reference. RESULTS: A total of 28 datasets, each consisting of free-breathing 3D-UTE MRI with the two sequence techniques and a reference CT scan, were acquired in 20 patients. Interrater agreement was substantial for pulmonary infiltrations using both sequence techniques (κ = 0.77 - 0.78). Regarding pleural effusions, agreement was almost perfect in the stack-of-spirals (κ = 0.81) and moderate in the radial sequence (κ = 0.59). No significant differences in detectability of the assessed pulmonary pathologies were observed between both 3D-UTE sequence techniques (P > 0.05), and their level of agreement was substantial throughout (κ = 0.62-0.81). Both techniques provided high sensitivities and specificities (79%-100%) for the detection of pulmonary infiltrations and pleural effusions compared to reference CT. CONCLUSION: The diagnostic performance of the assessed 3D-UTE MRI sequences was similar. Both sequences enable the detection of typical inflammatory lung pathologies.

Not all that looks fractured is broken-multipartite humeral epicondyles in children.

OBJECTIVE: Multipartite epicondyles may mimic fractures in the setting of pediatric elbow trauma. This study examines the prevalence of multipartite epicondyles during skeletal development and their association with pediatric elbow fractures. MATERIALS AND METHODS: In this retrospective analysis, 4282 elbow radiographs of 1265 elbows of 1210 patients aged 0-17 years were reviewed. The radiographs were analyzed by two radiologists in consensus reading, and the number of visible portions of the medial and lateral epicondyles was noted. For elbows in which epicondylar ossification was not yet visible, the epicondyles were already fused with the humerus or could not be sufficiently evaluated due to projection issues or because osteosynthesis material was excluded. In total, 187 elbows were included for the lateral and 715 for the medial epicondyle analyses. RESULTS: No multipartite medial epicondyles were found in patients without history of elbow fracture, whereas 9% of these patients had multipartite lateral epicondyles (p < 0.01). Current or previous elbow fractures increased the prevalence of multipartite epicondyles, with significant lateral predominance (medial epicondyle + 9% vs. lateral + 24%, p < 0.0001). Including all patients regardless of a history of elbow fracture, multipartite medial epicondyles were observed in 3% and multipartite lateral epicondyles in 18% (p < 0.0001). There was no gender difference in the prevalence of multipartition of either epicondyle, regardless of a trauma history. CONCLUSION: Multipartite medial epicondyles occur in patients with current or previous elbow fractures only, whereas multipartite lateral epicondyles may be constitutional. Elbow fractures increase the prevalence of multipartite epicondyles on both sides, with significant lateral predominance. KEY POINTS: • Multipartite medial epicondyles should be considered of traumatic origin. • Multipartite lateral epicondyles may be constitutional. • Elbow fractures increase the prevalence of multipartite epicondyles on both sides with lateral predominance.

Interobserver reliability of scapula fracture classifications in intra- and extra-articular injury patterns.

BACKGROUND: Morphology and glenoid involvement determine the necessity of surgical management in scapula fractures. While being present in only a small share of patients with shoulder trauma, numerous classification systems have been in use over the years for categorization of scapula fractures. The purpose of this study was to evaluate the established AO/OTA classification in comparison to the classification system of Euler and Rüedi (ER) with regard to interobserver reliability and confidence in clinical practice. METHODS: Based on CT imaging, 149 patients with scapula fractures were retrospectively categorized by two trauma surgeons and two radiologists using the classification systems of ER and AO/OTA. To measure the interrater reliability, Fleiss kappa (κ) was calculated independently for both fracture classifications. Rater confidence was stated subjectively on a five-point scale and compared with Wilcoxon signed rank tests. Additionally, we computed the intraclass correlation coefficient (ICC) based on absolute agreement in a two-way random effects model to assess the diagnostic confidence agreement between observers. RESULTS: In scapula fractures involving the glenoid fossa, interrater reliability was substantial (κ = 0.722; 95% confidence interval [CI] 0.676-0.769) for the AO/OTA classification in contrast to moderate agreement (κ = 0.579; 95% CI 0.525-0.634) for the ER classification system. Diagnostic confidence for intra-articular fracture patterns was superior using the AO/OTA classification compared to ER (p < 0.001) with higher confidence agreement (ICC: 0.882 versus 0.831). For extra-articular fractures, ER (κ = 0.817; 95% CI 0.771-0.863) provided better interrater reliability compared to AO/OTA (κ = 0.734; 95% CI 0.692-0.776) with higher diagnostic confidence (p < 0.001) and superior agreement between confidence ratings (ICC: 0.881 versus 0.912). CONCLUSIONS: The AO/OTA classification is most suitable to categorize intra-articular scapula fractures with glenoid involvement, whereas the classification system of Euler and Rüedi appears to be superior in extra-articular injury patterns with fractures involving only the scapula body, spine, acromion and coracoid process.

Deep learning-based segmentation of the lung in MR-images acquired by a stack-of-spirals trajectory at ultra-short echo-times.

BACKGROUND: Functional lung MRI techniques are usually associated with time-consuming post-processing, where manual lung segmentation represents the most cumbersome part. The aim of this study was to investigate whether deep learning-based segmentation of lung images which were scanned by a fast UTE sequence exploiting the stack-of-spirals trajectory can provide sufficiently good accuracy for the calculation of functional parameters. METHODS: In this study, lung images were acquired in 20 patients suffering from cystic fibrosis (CF) and 33 healthy volunteers, by a fast UTE sequence with a stack-of-spirals trajectory and a minimum echo-time of 0.05 ms. A convolutional neural network was then trained for semantic lung segmentation using 17,713 2D coronal slices, each paired with a label obtained from manual segmentation. Subsequently, the network was applied to 4920 independent 2D test images and results were compared to a manual segmentation using the Sørensen-Dice similarity coefficient (DSC) and the Hausdorff distance (HD). Obtained lung volumes and fractional ventilation values calculated from both segmentations were compared using Pearson's correlation coefficient and Bland Altman analysis. To investigate generalizability to patients outside the CF collective, in particular to those exhibiting larger consolidations inside the lung, the network was additionally applied to UTE images from four patients with pneumonia and one with lung cancer. RESULTS: The overall DSC for lung tissue was 0.967 ± 0.076 (mean ± standard deviation) and HD was 4.1 ± 4.4 mm. Lung volumes derived from manual and deep learning based segmentations as well as values for fractional ventilation exhibited a high overall correlation (Pearson's correlation coefficent = 0.99 and 1.00). For the additional cohort with unseen pathologies / consolidations, mean DSC was 0.930 ± 0.083, HD = 12.9 ± 16.2 mm and the mean difference in lung volume was 0.032 ± 0.048 L. CONCLUSIONS: Deep learning-based image segmentation in stack-of-spirals based lung MRI allows for accurate estimation of lung volumes and fractional ventilation values and promises to replace the time-consuming step of manual image segmentation in the future.

Three-dimensional Ultrashort Echo Time MRI for Functional Lung Imaging in Cystic Fibrosis.

Background In cystic fibrosis (CF), recurrent imaging and pulmonary function tests (PFTs) are needed for the assessment of lung function during disease management. Purpose To assess the clinical feasibility of pulmonary three-dimensional ultrashort echo time (UTE) MRI at breath holding for quantitative image analysis of ventilation inhomogeneity and hyperinflation in CF compared with PFT. Materials and Methods In this prospective study from May 2018 to June 2019, participants with CF and healthy control participants underwent PFTs and functional lung MRI by using a prototypical single breath-hold three-dimensional UTE sequence. Fractional ventilation (FV) was calculated from acquired data in normal inspiration and normal expiration. FV of each voxel was normalized to the whole lung mean (FVN), and interquartile range of normalized ventilation (IQRN; as a measure of ventilation heterogeneity) was calculated. UTE signal intensity (SI) was assessed in full expiration (SIN, normalized to aortic blood). Obtained metrics were compared between participants with CF and control participants. For participants with CF, MRI metrics were correlated with the standard lung clearance index (LCI) and PFT. Mann-Whitney U tests and Spearman correlation were used for statistical analysis. Results Twenty participants with CF (mean age, 17 years ± 9 [standard deviation]; 12 men) and 10 healthy control participants (24 years ± 8; five men) were included. IQRN was higher for participants with CF than for control participants (mean, 0.66 ± 0.16 vs 0.50 ± 0.04, respectively; P = .007). In the 20 participants with CF, IQRN correlated with obstruction markers forced expiratory volume in 1 second-to-forced vital capacity ratio (r = -0.70; 95% confidence interval [CI]: -0.92, -0.28; P < .001), mean expiratory flow 25% (r = 0.78; 95% CI: -0.95, -0.39; P < .001), and with the ventilation inhomogeneity parameter LCI (r = 0.90; 95% CI: 0.69, 0.96; P < .001). Mean SIN in full expiration was lower in participants with CF than in control participants (0.34 ± 0.08 vs 0.39 ± 0.03, respectively; P = .03). Conclusion Three-dimensional ultrashort echo time MRI in the lungs allowed for functional imaging of ventilation inhomogeneity within a few breath holds in patients with cystic fibrosis. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Wielpütz in this issue.

Non-rigid image registration of 4D-MRI data for improved delineation of moving tumors.

BACKGROUND: To increase the image quality of end-expiratory and end-inspiratory phases of retrospective respiratory self-gated 4D MRI data sets using non-rigid image registration for improved target delineation of moving tumors. METHODS: End-expiratory and end-inspiratory phases of volunteer and patient 4D MRI data sets are used as targets for non-rigid image registration of all other phases using two different registration schemes: In the first, all phases are registered directly (dir-Reg) while next neighbors are successively registered until the target is reached in the second (nn-Reg). Resulting data sets are quantitatively compared using diaphragm and tumor sharpness and the coefficient of variation of regions of interest in the lung, liver, and heart. Qualitative assessment of the patient data regarding noise level, tumor delineation, and overall image quality was performed by blinded reading based on a 4 point Likert scale. RESULTS: The median coefficient of variation was lower for both registration schemes compared to the target. Median dir-Reg coefficient of variation of all ROIs was 5.6% lower for expiration and 7.0% lower for inspiration compared with nn-Reg. Statistical significant differences between the two schemes were found in all comparisons. Median sharpness in inspiration is lower compared to expiration sharpness in all cases. Registered data sets were rated better compared to the targets in all categories. Over all categories, mean expiration scores were 2.92 ± 0.18 for the target, 3.19 ± 0.22 for nn-Reg and 3.56 ± 0.14 for dir-Reg and mean inspiration scores 2.25 ± 0.12 for the target, 2.72 ± 215 0.04 for nn-Reg and 3.78 ± 0.04 for dir-Reg. CONCLUSIONS: In this work, end-expiratory and inspiratory phases of a 4D MRI data sets are used as targets for non-rigid image registration of all other phases. It is qualitatively and quantitatively shown that image quality of the targets can be significantly enhanced leading to improved target delineation of moving tumors.

Magnetic Particle Imaging-Guided Stenting.

Purpose:To assess the feasibility of magnetic particle imaging (MPI) to guide stenting in a phantom model. Materials and Methods: MPI is a new tomographic imaging method based on the background-free magnetic field detection of a tracer agent composed of superparamagnetic iron oxide nanoparticles (SPIOs). All experiments were conducted on a custom-built MPI scanner (field of view: 29-mm diameter, 65-mm length; isotropic spatial resolution 1-1.5-mm). Stenosis phantoms (n=3) consisted of polyvinyl chloride (PVC) tubes (8-mm inner diameter) prepared with centrally aligned cable binders to form a ~50% stenosis. A dedicated image reconstruction algorithm allowed precise tracking of endovascular instruments at 8 frames/s with a latency time of ~115 ms. A custom-made MPI-visible lacquer was used to manually label conventional guidewires, balloon catheters, and stainless steel balloon-expandable stents. Vascular stenoses were visualized by injecting a diluted SPIO tracer (ferucarbotran, 10 mmol iron/L) into the vessel phantoms. Balloon angioplasty and stent placement were performed by inflating balloon catheters and stent delivery balloons with diluted ferucarbotran. Results: After deployment of the stent, the markers on its ends were clearly visible. The applied lacquer markers were thin enough to not relevantly alter gliding properties of the devices while withstanding friction during the experiments. Placing an optimized flexible lacquer formulation on the preexisting radiopaque stent markers provided enough stability to withstand stent expansion. Final MPA confirmed successful stenosis treatment, facilitated by the disappearance of the lacquer markers on the stent due to differences in SPIO concentration. Thus, the in-stent lumen could be visualized without interference by the signal from the markers. Conclusion: Near real-time visualization of MPI-guided stenting of stenoses in a phantom model is feasible. Optimized MPI-visible markers can withstand the expansion process of stents.

Self-gated Non-Contrast-enhanced Functional Lung MR Imaging for Quantitative Ventilation Assessment in Patients with Cystic Fibrosis.

Purpose To assess the clinical feasibility of self-gated non-contrast-enhanced functional lung (SENCEFUL) magnetic resonance (MR) imaging for quantitative ventilation (QV) imaging in patients with cystic fibrosis (CF). Materials and Methods Twenty patients with CF and 20 matched healthy volunteers underwent functional 1.5-T lung MR imaging with the SENCEFUL imaging approach, in which a two-dimensional fast low-angle shot sequence is used with quasi-random sampling. The lungs were manually segmented on the ventilation-weighted images to obtain QV measurements, which were compared between groups. QV values of the patients were correlated with results of pulmonary function testing. Three radiologists rated the images for presence of ventilation deficits by means of visual inspection. Mann-Whitney U tests, receiver operating characteristic analyses, Spearman correlations, and Gwet agreement coefficient analyses were used for statistical analysis. Results QV of the entire lungs was lower for patients with CF than for control subjects (mean ± standard deviation, 0.09 mL/mL ± 0.03 vs 0.11 mL/mL ± 0.03, respectively; P = .007). QV ratios of upper to lower lung halves were lower in patients with CF than in control subjects (right, 0.84 ± 0.2 vs 1.16 ± 0.2, respectively [P < .001]; left, 0.88 ± 0.3 vs 1.11 ± 0.1, respectively [P = .017]). Accordingly, ventilation differences between the groups were larger in the upper halves (Δ = 0.04 mL/mL, P ≤ .001-.002). QV values of patients with CF correlated with forced vital capacity (r = 0.7; 95% confidence interval [CI]: 0.21, 0.91), residual volume (static hyperinflation, r = -0.8; 95% CI: -0.94, 0.42), and forced expiratory volume in 1 second (airway obstruction, r = 0.7; 95% CI: 0.21, 0.91). Disseminated small ventilation deficits were the most frequent involvement pattern, present in 40% of the functional maps in CF versus 8% in the control subjects (P < .001). Conclusion SENCEFUL MR imaging is feasible for QV assessment. Less QV, especially in upper lung parts, and correlation to vital capacity and to markers for hyperinflation and airway obstruction were found in patients with CF. © RSNA, 2016.

Performance of cone-beam computed tomography and multidetector computed tomography in diagnostic imaging of the midface: A comparative study on Phantom and cadaver head scans.

PURPOSE: To compare multidetector computed tomography (MDCT) and cone-beam computed tomography (CBCT) regarding radiation, resolution, image noise, and image quality. METHODS: CBCT and 256-MDCT were compared based on three scan protocols: Standard-dose (≈24 mGy), reduced-dose (≈9 mGy), and low-dose (≈4 mGy). MDCT images were acquired in standard- and high-resolution mode (HR-MDCT) and reconstructed using filtered back projection (FBP) and iterative reconstruction (IR). Spatial resolution in linepairs (lp) and objective image noise (OIN) were assessed using dedicated phantoms. Image quality was assessed in scans of 25 cadaver heads using a Likert scale. RESULTS: OIN was markedly higher in FBP-MDCT when compared to CBCT. IR lowered the OIN to comparable values in standard-mode MDCT only. CBCT provided a resolution of 13 lp/cm at standard-dose and 11 lp/cm at reduced-dose vs. 11 lp/cm and 10 lp/cm in HR-MDCT. Resolution of 10 lp/cm was observed for both devices using low-dose settings. Quality scores of MDCT and CBCT did not differ at standard-dose (CBCT, 3.4; MDCT, 3.3-3.5; p > 0.05). Using reduced- and low-dose protocols, CBCT was superior (reduced-dose, 3.2 vs. 2.8; low dose, 3.0 vs. 2.3; p < 0.001). CONCLUSION: Using the low-dose protocol, the assessed CBCT provided better objective and subjective image quality and equality in resolution. Similar image quality, but better resolution using CBCT was observed at higher exposure settings. KEY POINTS: • The assessed CBCT device provided better image quality at lower doses. • Objective and subjective image quality were comparable using higher exposure settings. • CBCT showed superior spatial resolution in standard-dose and reduced-dose settings. • Modern noise-reducing tools are used in CBCT devices currently. • MDCT should be preferred for assessment of soft-tissue injuries and oncologic imaging.

Non-contrast MR angiography at 1.5 Tesla for aortic monitoring in Marfan patients after aortic root surgery.

BACKGROUND: Contrast-enhanced cardiovascular magnetic resonance angiography (CE-CMRA) is the established imaging modality for patients with Marfan syndrome requiring life-long annual aortic imaging before and after aortic root replacement. Contrast-free CMRA techniques avoiding side-effects of contrast media are highly desirable for serial imaging but have not been evaluated in the postoperative setup of Marfan patients. The purpose of this study was to assess the feasibility of non-contrast balanced steady-state free precession (bSSFP) magnetic resonance imaging for aortic monitoring of postoperative patients with Marfan syndrome. METHODS: Sixty-four adult Marfan patients after aortic root replacement were prospectively included. Fourteen patients (22%) had a residual aortic dissection after surgical treatment of type A dissection. bSSFP imaging and CE-CMRA were performed at 1.5 Tesla. Two radiologists evaluated the images regarding image quality (1 = poor, 4 = excellent), artifacts (1 = severe, 4 = none) and aortic pathologies. Readers measured the aortic diameters at defined levels in both techniques. Statistics included observer agreement for image scoring and diameter measurements and ROC analyses for comparison of the diagnostic performance of bSSFP and CE-CMRA. RESULTS: Both readers observed no significant differences in image quality between bSSFP and CE-CMRA and found a median image quality score of 4 for both techniques (all p > .05). No significant differences were found regarding the frequency of image artifacts in both sequences (all p > .05). Sensitivity and specificity for detection of aortic dissections was 100% for both readers and techniques. Compared to bSSFP imaging, CE-CMRA resulted in higher diameters (mean bias, 0.9 mm; p < .05). The inter-observer biases of diameter measurements were not significantly different (all p > .05), except for the distal graft anastomosis (p = .001). Using both techniques, the readers correctly identified a graft suture dehiscence with aneurysm formation requiring surgery. CONCLUSION: Unenhanced bSSFP CMR imaging allows for riskless aortic monitoring with high diagnostic accuracy in Marfan patients after aortic root surgery.

An intravoxel oriented flow model for diffusion-weighted imaging of the kidney.

By combining intravoxel incoherent motion (IVIM) and diffusion tensor imaging (DTI) we introduce a new diffusion model called intravoxel oriented flow (IVOF) that accounts for anisotropy of diffusion and the flow-related signal. An IVOF model using a simplified apparent flow fraction tensor (IVOFf ) is applied to diffusion-weighted imaging of human kidneys. The kidneys of 13 healthy volunteers were examined on a 3 T scanner. Diffusion-weighted images were acquired with six b values between 0 and 800 s/mm(2) and 30 diffusion directions. Diffusivity and flow fraction were calculated for different diffusion models. The Akaike information criterion was used to compare the model fit of the proposed IVOFf model to IVIM and DTI. In the majority of voxels the proposed IVOFf model with a simplified apparent flow fraction tensor performs better than IVIM and DTI. Mean diffusivity is significantly higher in DTI compared with models that account for the flow-related signal. The fractional anisotropy of diffusion is significantly reduced when flow fraction is considered to be anisotropic. Anisotropy of the apparent flow fraction tensor is significantly higher in the renal medulla than in the cortex region. The IVOFf model describes diffusion-weighted data in the human kidney more accurately than IVIM or DTI. The apparent flow fraction in the kidney proved to be anisotropic.

Reduced-dose abdominopelvic CT using hybrid iterative reconstruction in suspected left-sided colonic diverticulitis.

OBJECTIVES: To assess the effect of hybrid iterative reconstruction (HIR) and filtered back projection (FBP) on abdominopelvic CT with reduced-dose (RD-APCT) in the evaluation of acute left-sided colonic diverticulitis (ALCD). METHODS: Twenty-five consecutive patients with suspected ALCD who underwent RD-APCT (mean CTDIvol 11.2 ± 4.2 mGy) were enrolled in this study. Raw data were reconstructed using FBP and two increasing HIR levels, L4 & L6. Two radiologists assessed image quality, image noise and reviewer confidence in interpreting findings of ALCD, including wall thickening, pericolic fat inflammation, pericolic abscess, and contained or free extraluminal air. Objective image noise (OIN) was measured. RESULTS: OIN was reduced up to 54 % with HIR compared to FBP. Subjective image quality of HIR images was superior to FBP; subjective image noise was reduced. The detection rate of extraluminal air was higher with HIR L6. Reviewer confidence in interpreting CT findings of ALCD significantly improved with application of HIR. CONCLUSIONS: RD-APCT with HIR offers superior image quality and lower image noise compared to FBP, allowing a high level of reviewer confidence in interpreting CT findings in ALCD. HIR facilitates detection of ALCD findings that may be missed with the FBP algorithm. KEY POINTS: HIR significantly reduces objective image noise in comparison to conventional FBP. HIR offers superior subjective image quality in comparison to conventional FBP. HIR allows reduced-dose abdominopelvic CT with acceptable image quality. Reviewer confidence in interpreting CT findings in ALCD significantly improves with HIR.

Assessment of bone marrow inflammation in patients with myelofibrosis: an 18F-fluorodeoxyglucose PET/CT study.

PURPOSE: Myelofibrosis is a haematopoietic stem cell neoplasm characterized by bone marrow inflammation, reactive marrow fibrosis and extramedullary haematopoiesis. The aim of this study was to determine if (18)F-FDG PET/CT can be used to noninvasively visualize and quantify the extent and activity of bone marrow involvement. METHODS: In 30 patients, the biodistribution of (18)F-FDG was analysed by measuring the standardized uptake value in the bone marrow compartment and spleen. Imaging findings were compared with laboratory, cytogenetic and histopathological data. RESULTS: Retention of (18)F-FDG was observed in bone marrow and spleen. Bone marrow involvement varied, ranging from mildly increased uptake in the central skeleton to extensive uptake in most parts of the skeleton. The extent of bone marrow involvement decreased over time from initial diagnosis (r s = -0.43, p = 0.019). Metabolic activity of the bone marrow decreased as the histopathological grade of fibrosis increased (r s = -0.37, p = 0.04). There was a significant positive correlation between the metabolic activity of the bone marrow and that of the spleen (p = 0.04). CONCLUSION: (18)F-FDG PET/CT is as a promising technique for the quantitation of bone marrow inflammation in myelofibrosis. Our data indicate that the intensity of bone marrow (18)F-FDG uptake decreases as bone marrow fibrosis increases. Further evaluation in prospective studies is required to determine the potential clinical impact and prognostic significance of PET.

Magnetic resonance enterography for assessment of intestinal graft-versus-host disease after allogeneic stem cell transplantation.

OBJECTIVES: To determine the diagnostic performance of MR enterography (MRE) for detection and grading of gastrointestinal graft-versus-host disease (GI GvHD) after hematopoietic stem cell transplantation (SCT). METHODS: Forty-one patients with known GvHD or suspected GvHD underwent MRE and GI endoscopy with multi-level biopsies. MRE images were reviewed for presence of intestinal wall inflammation. Clinical grading of GI GvHD was performed. Histopathological evaluation (HPE) served as the reference standard. RESULTS: Overall, MRE demonstrated a per-patient sensitivity of 81.5 % for detection of GI GvHD. The most common findings were intestinal wall thickening (81.5 % of GvHD patients), luminal stenosis (81.5 %), mural contrast enhancement (70.4 %), and ascites (59.3 %). These findings were also observed in other conditions than GvHD. The most frequently involved intestinal segment was the sigmoid colon (63.0 %), followed by the ileum (59.3 %) and the jejeunum (51.9 %). The number of involved segments (r s =0.54, p =0.009) correlated significantly with clinical severity as determined by GvHD grading. CONCLUSIONS: After allogeneic stem cell transplantation, MRE may (1) contribute to detection and localization of GI GvHD, and (2) add information indicating the clinical severity of disease, but findings are unspecific. False negative results may be observed not only in low-grade GI GvHD. KEY POINTS: • Magnetic resonance enterography (MRE) allows for detection of GI GvHD • Common findings are wall thickening, stenosis, mural contrast enhancement, and ascites • The extent of GI involvement on MRE correlates with clinical severity of GvHD • Involvement of sigmoid colon and small intestine is common • Findings are unspecific and also observed in other conditions, e.g. infectious enteritis.

Exact monitoring of aortic diameters in Marfan patients without gadolinium contrast: intraindividual comparison of 2D SSFP imaging with 3D CE-MRA and echocardiography.

PURPOSE: To assess whether ECG-gated non-contrast 2D steady-state free precession (SSFP) imaging allows for exact monitoring of aortic diameters in Marfan syndrome (MFS) patients using non-ECG-gated contrast-enhanced 3D magnetic resonance angiography (CE-MRA) and echocardiography for intraindividual comparison. METHODS: Non-ECG-gated CE-MRA and ECG-gated non-contrast SSFP at 1.5 T were prospectively performed in 50 patients. Two readers measured aortic diameters on para-sagittal images identically aligned with the aortic arch at the sinuses of Valsalva, sinotubular junction, ascending/descending aorta and aortic arch. Image quality was assessed on a three-point scale. Aortic root diameters acquired by echocardiography were used as reference. RESULTS: Intra- and interobserver variances were smaller for SSFP at the sinuses of Valsalva (p = 0.002; p = 0.002) and sinotubular junction (p = 0.014; p = 0.043). Image quality was better in SSFP than in CE-MRA at the sinuses of Valsalva (p < 0.0001), sinotubular junction (p < 0.0001) and ascending aorta (p = 0.02). CE-MRA yielded higher diameters than SSFP at the sinuses of Valsalva (mean bias, 2.5 mm; p < 0.0001), and comparison with echocardiography confirmed a higher bias for CE-MRA (7.2 ± 3.4 mm vs. SSFP, 4.7 ± 2.6 mm). CONCLUSION: ECG-gated non-contrast 2D SSFP imaging provides superior image quality with higher validity compared to non-ECG-gated contrast-enhanced 3D imaging. Since CE-MRA requires contrast agents with potential adverse effects, non-contrast SSFP imaging is an appropriate alternative for exact and riskless aortic monitoring of MFS patients.

Contrast-enhanced voiding urosonography phantom study: intravenous iodinated and gadolinium-based contrast agents may cause false-negative results in assessment of vesicoureteral reflux in children.

BACKGROUND: Contrast-enhanced voiding urosonography (ce-VUS) is commonly requested simultaneously to other diagnostic imaging necessitating intravenous contrast agents. To date there is limited knowldedge about intravesical interactions between different types of contrast agents. OBJECTIVE: To assess the effect of excreted intravenous iodinated and gadolinium-based contrast agents on the intravesical distribution of ultrasound contrast within contrast-enhanced voiding urosonography. MATERIALS AND METHODS: Iodinated (iomeprol, iopamidol) and gadolinium-based (gadoterate meglumine) contrast agents were diluted to bladder concentration and injected into balloons filled with saline solution. CT scans were performed to assess the contrast distribution in these phantoms. Regions of interest were placed at the top and bottom side of each balloon and Hounsfield units (HU) were measured. Three other balloons were filled with saline solution and contrast media likewise. The ultrasound contrast agent sulphur hexafluoride was added and its distribution was assessed using sonography. RESULTS: MDCT scans showed a separation of two liquid layers in all bladder phantoms with the contrast layers located at the bottom and the saline solution at the top. Significant differences of the HU measurements at the top and bottom side were observed (P < 0.001-0.007). Following injection of ultrasound contrast agent, US showed its distribution exclusively among the saline solution. CONCLUSIONS: False-negative results of contrast-enhanced voiding urosonography may occur if it is performed shortly after imaging procedures requiring intravenous contrast.

MRI displays involvement of the temporalis muscle and the deep temporal artery in patients with giant cell arteritis.

PURPOSE: To assess deep temporal artery and temporalis muscle involvement in patients with giant cell arteritis (GCA). MATERIAL AND METHODS: Ninety-nine patients who received magnetic resonance imaging (MRI) and superficial temporal artery biopsy (TAB) were included in this study. Patients with positive TAB (n = 61) were defined as GCA patients, those with negative TAB (n = 38) as the GCA-negative reference group. Contrast-enhanced T1w-images were acquired utilizing 1.5 T and 3 T MRI. Two radiologists assessed the images. Mural contrast-hyperenhancement and wall thickening of the deep temporal artery and hyperenhancement of the muscle were defined as inflammation. MRI results were correlated with jaw claudication in 70 patients. RESULTS: The two observers found temporalis muscle involvement in 19.7 % (n = 12) and 21.3 % (n = 13) of GCA patients. It occurred bilaterally in 100 %. Specificities were 92/97 % and sensitivities were 20/21 %. Deep temporal artery involvement was found in 34.4 % (n = 21) and 49.2 % (n = 30) and occurred bilaterally in 80/90.5 %. Specificities were 84/95 % and sensitivities were 34/49 %. Both structures were affected simultaneously in 18/21.3 %. Jaw claudication correlated moderately with inflammation of the temporalis muscle (r = 0.31; p < 0.05) and the deep temporal artery (r = 0.38; p = 0.01). CONCLUSION: MRI visualizes changes in the temporalis muscle and the deep temporal artery in GCA. Moderate correlation of clinical symptoms with MRI results was observed. KEY POINTS: • Approximately 20 % of GCA patients presented with temporalis muscle inflammation. • A total of 34-49 % of GCA patients presented with vasculitis of the deep temporal artery. • In approximately 20 % of GCA patients, both structures were simultaneously involved. • Involvement of both structures correlated moderately with presence of jaw claudication. • MRI is a suitable tool for the assessment of vasculitis and muscle inflammation.