PURSUING OPTIMAL RADIATION DOSE IN PEDIATRIC CARDIAC CT: A REPORT FROM UNIVERSITY HOSPITAL LEUVEN.

BACKGROUND: Computed tomography (CT) balances between high resolution and low radiation dose. Given the greater radiosensitivity of children, it is appropriate to use child-friendly CT-protocols that reduce radiation dose at acceptable image quality.This article states the radiation dose in pediatric cardiac CT-examinations at university hospital Leuven (Belgium) and compares with findings published by similar medical centers. The diagnostic accuracy was simultaneously compared, as it correlates with radiation dose. MATERIAL AND METHODS: his retrospective observational study analyzed 58 CT-scans of 52 patients. The radiation dose was calculated in effective dose. The image quality was scored qualitatively with a 5-point scale. The diagnostic accuracy, a derivative representation of the image quality, was checked with findings from surgery or conventional angiography. RESULTS: The mean effective dose in our study population was 1.3 ± 0.4 mSv. The qualitative image quality was on average 'good', elaborated with a score of 4.0 ± 0.2. The diagnostic accuracy was 92%. Comparative literature study provides a mean effective dose of 1.5 mSv and the reported diagnostic accuracy from other centers reaches ≥90%. CONCLUSIONS: At our center pediatric cardiac CT-scans are obtained with good-to-excellent image quality and high diagnostic accuracy at low radiation doses. These results meet the radiation dose and diagnostic accuracy as published by comparable medical centers.

An automated framework for localization, segmentation and super-resolution reconstruction of fetal brain MRI.

High-resolution volume reconstruction from multiple motion-corrupted stacks of 2D slices plays an increasing role for fetal brain Magnetic Resonance Imaging (MRI) studies. Currently existing reconstruction methods are time-consuming and often require user interactions to localize and extract the brain from several stacks of 2D slices. We propose a fully automatic framework for fetal brain reconstruction that consists of four stages: 1) fetal brain localization based on a coarse segmentation by a Convolutional Neural Network (CNN), 2) fine segmentation by another CNN trained with a multi-scale loss function, 3) novel, single-parameter outlier-robust super-resolution reconstruction, and 4) fast and automatic high-resolution visualization in standard anatomical space suitable for pathological brains. We validated our framework with images from fetuses with normal brains and with variable degrees of ventriculomegaly associated with open spina bifida, a congenital malformation affecting also the brain. Experiments show that each step of our proposed pipeline outperforms state-of-the-art methods in both segmentation and reconstruction comparisons including expert-reader quality assessments. The reconstruction results of our proposed method compare favorably with those obtained by manual, labor-intensive brain segmentation, which unlocks the potential use of automatic fetal brain reconstruction studies in clinical practice.

Conservative treatment of non-aneurysmal infectious aortitis: a case report and review of the literature.

BACKGROUND:  Non-aneurysmal infectious aortitis is a rare clinical entity with most often lethal complications when surgical intervention is delayed. OBJECTIVES:  This report describes the case of a non-aneurysmal infectious aortitis complicated with a penetrating aortic ulcer in an elderly woman, caused by a methicillin-sensitive Staphylococcus aureus. Surgery was deemed contra-indicated and treatment was limited to the administration of intravenous vancomycin (2 grams daily), followed by flucloxacillin (6 times 2 grams daily). She remains well after one year. METHODS: The Internet databases Medline and Embase were searched. Articles were selected based on relevanceof abstract, article type and impact of the journal. RESULTS:  A literature review addresses current insights in the pathogenesis, diagnosis, and treatment of non-aneurysmal infectious aortitis.

Characterization of a rat orthotopic pancreatic head tumor model using three-dimensional and quantitative multi-parametric MRI.

The purpose of this study was to investigate the reliability of 3D isotropic MRI and quantitative multi-parametric MRI characterization on an orthotopic pancreatic head tumor model in rats. 3D isotropic T2 -weighted MRI was performed as a routine for tumor longitudinal follow-up and volume estimation. Common bile duct diameter was measured from 3D multiplanar reconstruction. Quantitative multi-parametric measurements including pixel-wise T2 , T1 relaxivity, apparent diffusion coefficient (ADC) and apparent diffusion kurtosis mapping were performed twice throughout tumor growth. Semi-quantitative and quantitative analyses based on an extended Tofts model were applied to region-of-interest-based dynamic contrast-enhanced imaging, followed by contrast ratio measurement on standard contrast-enhanced imaging. Moreover, low-level texture-based analysis was inspected for T2 , T1 , ADC and contrast ratio measurements. Results indicated that multi-parametric MRI showed good reproducibility for tumor characterization; the measurements were not affected by tumor growth. Tumor growth was further confirmed with histology examinations. To conclude, state-of-the-art clinical MRI techniques were translated to this preclinical tumor model with high reliability, and have paved the way for translational oncology studies on this tumor model.

Three-dimensional contrasted visualization of pancreas in rats using clinical MRI and CT scanners.

The purpose of this work was to visualize the pancreas in post-mortem rats with local contrast medium infusion by three-dimensional (3D) magnetic resonance imaging (MRI) and computed tomography (CT) using clinical imagers. A total of 16 Sprague Dawley rats of about 300 g were used for the pancreas visualization. Following the baseline imaging, a mixed contrast medium dye called GadoIodo-EB containing optimized concentrations of Gd-DOTA, iomeprol and Evens blue was infused into the distally obstructed common bile duct (CBD) for post-contrast imaging with 3.0 T MRI and 128-slice CT scanners. Images were post-processed with the MeVisLab software package. MRI findings were co-registered with CT scans and validated with histomorphology, with relative contrast ratios quantified. Without contrast enhancement, the pancreas was indiscernible. After infusion of GadoIodo-EB solution, only the pancreatic region became outstandingly visible, as shown by 3D rendering MRI and CT and proven by colored dissection and histological examinations. The measured volume of the pancreas averaged 1.12 ± 0.04 cm(3) after standardization. Relative contrast ratios were 93.28 ± 34.61% and 26.45 ± 5.29% for MRI and CT respectively. We have developed a multifunctional contrast medium dye to help clearly visualize and delineate rat pancreas in situ using clinical MRI and CT scanners. The topographic landmarks thus created with 3D demonstration may help to provide guidelines for the next in vivo pancreatic MRI research in rodents.

Aortic Annulus Rupture During TAVI: A Therapeutic Dilemma in the Inoperable Patient.

Aortic annulus rupture is a rare complication of transcatheter aortic valve implantation (TAVI), related to relative valve oversizing or eccentric calcification. A case is reported of periprocedural cardiac tamponade caused by aortic annulus rupture. Optimal management of periprocedural aortic annulus rupture and pseudoaneurysm formation in patients considered too frail for surgery should be discussed in a multidisciplinary setting.

Malignant pleural mesothelioma: visual assessment by using pleural pointillism at diffusion-weighted MR imaging.

PURPOSE: To evaluate the diagnostic accuracy of the visual assessment of malignant pleural mesothelioma (MPM) on magnetic resonance (MR) images by using two known visual markers (mediastinal pleural thickness and shrinking of the lung) and a newly introduced one (pleural pointillism). MATERIALS AND METHODS: With the approval of the local ethics committee, 100 consecutive patients (mean age, 61.4 years; age range, 18-87 years; 75 men, 25 women) suspected of having MPM pleural abnormalities underwent positron emission tomography/computed tomography and MR imaging, including diffusion-weighted (DW) MR imaging, followed by explorative thoracoscopy or guided biopsy with histopathologic confirmation. Because visual assessment is still the preferred method of image interpretation, the diagnostic accuracy of mediastinal pleural thickening, shrinking lung (hemithorax volume decrease due to fibrosis), and pleural pointillism were examined. Pleural pointillism was denoted by the presence of multiple, hyperintense pleural spots on high-b-value DW images. Histopathologic findings in the surgical specimen served as the reference standard. McNemar tests with Bonferroni correction were used to assess differences in accuracy among the three examined markers. RESULTS: Of 100 patients, 33 had benign pleural alterations, and 67 had malignant pleural diseases (MPDs); 57 of 67 had MPM. A total of 78 patients received a correct diagnosis (benign vs malignant) on the basis of mediastinal pleural thickening (sensitivity, 81%; specificity, 73%; accuracy, 78%); and 66 patients, on the basis of shrinking lung (sensitivity, 60%; specificity, 79%; accuracy, 66%). The correct diagnosis was indicated on the basis of pleural pointillism in 88 patients (sensitivity, 93%; specificity, 79%; accuracy, 88%). CONCLUSION: Visual assessment of pleural pointillism on high-b-value DW images is useful to differentiate MPD from benign alterations, performing substantially better than mediastinal pleural thickness and shrinking lung, and might obviate unnecessary invasive procedures for MPM.

Prediction of hemodynamic improvement after pulmonary endarterectomy in chronic thromboembolic pulmonary hypertension using non-invasive imaging.

Pulmonary endarterectomy (PEA) is the recommended treatment in chronic thromboembolic pulmonary hypertension (CTEPH). Prediction of outcome after PEA remains challenging. In search for pre-operative predictors we evaluated non-invasive parameters measured by chest CT-scan and echocardiography. Between May 2004 and January 2009, 52 consecutive patients with CTEPH who underwent PEA (59.6 % female, mean age 58.9 ± 13.4 years) were included. Prior to surgery, pulmonary artery (PA) diameter indices were calculated by chest CT scan and different echocardiographic measurements to evaluate pulmonary hypertension were obtained. Hemodynamic improvement after PEA was defined as a pulmonary vascular resistance (PVR) <500 dyn s cm(-5) and a mean pulmonary artery pressure <35 mmHg 3 days after PEA. Mortality was evaluated at day 30. Mean pulmonary artery pressure (PAP) at baseline was 40.1 ± 8.5 mmHg, with a PVR of 971 ± 420 dyn s cm(-5). Persistent pulmonary hypertension was observed in 15 patients (28.8 %). Gender, pre-operative mean PAP, PA diameter indices, and tricuspid annular plane systolic excursion were all predictors for hemodynamic improvement after PEA. The indexed PA diameter on CT was the only independent predictor for hemodynamic improvement: 19.4 ± 2.4 versus 22.9 ± 4.9 mm/m(2) in those without improvement (OR 0.76: 95 % CI 0.58-0.99, p = 0.04). All patients who died within 30 days (9.6 %) had persistent pulmonary hypertension, with a post-operative mean PAP of 51.6 ± 14.1 mmHg and PVR of 692 ± 216 dyn s cm(-5). The pre-operative PA diameter indexed for body surface area is the only independent predictor for hemodynamic improvement after PEA in CTEPH patients. In all patients who died within 30 days after PEA, persistent pulmonary hypertension was present.

Whole-body MRI with diffusion-weighted sequence for staging of patients with suspected ovarian cancer: a clinical feasibility study in comparison to CT and FDG-PET/CT.

OBJECTIVES: To evaluate whole-body MRI with diffusion-weighted sequence (WB-DWI/MRI) for staging and assessing operability compared with CT and FDG-PET/CT in patients with suspected ovarian cancer. METHODS: Thirty-two patients underwent 3-T WB-DWI/MRI, (18) F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) and CT before diagnostic open laparoscopy (DOL). Imaging findings for tumour characterisation, peritoneal and retroperitoneal staging were correlated with histopathology after DOL and/or open surgery. For distant metastases, FDG-PET/CT or image-guided biopsies were the reference standards. For tumour characterisation and peritoneal staging, WB-DWI/MRI was compared with CT and FDG-PET/CT. Interobserver agreement for WB-DWI/MRI was determined. RESULTS: WB-DWI/MRI showed 94 % accuracy for primary tumour characterisation compared with 88 % for CT and 94 % for FDG-PET/CT. WB-DWI/MRI showed higher accuracy of 91 % for peritoneal staging compared with CT (75 %) and FDG-PET/CT (71 %). WB-DWI/MRI and FDG-PET/CT showed higher accuracy of 87 % for detecting retroperitoneal lymphadenopathies compared with CT (71 %). WB-DWI/MRI showed excellent correlation with FDG-PET/CT (κ = 1.00) for detecting distant metastases compared with CT (κ = 0.34). Interobserver agreement was moderate to almost perfect (κ = 0.58-0.91). CONCLUSIONS: WB-DWI/MRI shows high accuracy for characterising primary tumours, peritoneal and distant staging compared with CT and FDG-PET/CT and may be valuable for assessing operability in ovarian cancer patients. KEY POINTS: • Whole-body MRI with diffusion weighting (WB-DWI/MRI) helps to assess the operability of suspected ovarian cancer. • Interobserver agreement is good for primary tumour characterisation, peritoneal and distant staging. • WB-DWI/MRI improves mesenteric/serosal metastatic spread assessment compared with CT and FDG-PET/CT. • Retroperitoneal/cervical-thoracic nodal staging using qualitative DWI criteria was reasonably accurate. • WB-DWI/MRI and FDG-PET/CT showed the highest diagnostic impact for detecting thoracic metastases.

Characterisation of solitary pulmonary lesions combining visual perfusion and quantitative diffusion MR imaging.

OBJECTIVE: To evaluate the diagnostic accuracy of dynamic contrast-enhanced (DCE) magnetic resonance (MR) and diffusion-weighted imaging (DWI) sequences for defining benignity or malignancy of solitary pulmonary lesions (SPL). METHODS: First, 54 consecutive patients with SPL, clinically staged (CT and PET or integrated PET-CT) as N0M0, were included in this prospective study. An additional 3-Tesla MR examination including DCE and DWI was performed 1 day before the surgical procedure. Histopathology of the surgical specimen served as the standard of reference. Subsequently, this functional method of SPL characterisation was validated with a second cohort of 54 patients. RESULTS: In the feasibility group, 11 benign and 43 malignant SPL were included. Using the combination of conventional MR sequences with visual interpretation of DCE-MR curves resulted in a sensitivity, specificity and accuracy of 100%, 55% and 91%, respectively. These results can be improved by DWI (with a cut-off value of 1.52 × 10(-3) mm(2)/s for ADChigh) leading to a sensitivity, specificity and accuracy of 98%, 82% and 94%, respectively. In the validation group these results were confirmed. CONCLUSION: Visual DCE-MR-based curve interpretation can be used for initial differentiation of benign from malignant SPL, while additional quantitative DWI-based interpretation can further improve the specificity. KEY POINTS: • Magnetic resonance imaging is increasingly being used to help differentiate lung lesions. • Solitary pulmonary lesions (SPL) are accurately characterised by combining DCE-MRI and DWI. • Visual DCE-MRI assessment facilitates the diagnostic throughput in patients with SPL. • DWI provides additional information in inconclusive DCE-MRI (type B pattern).

Malignant pleural disease: diagnosis by using diffusion-weighted and dynamic contrast-enhanced MR imaging--initial experience.

PURPOSE: To investigate the use of diffusion-weighted (DW) imaging for differentiating benign lesions from malignant pleural disease (MPD) and to retrospectively assess dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging acquisitions to find out whether combining these measurements with DW imaging could improve the diagnostic value of DW imaging. MATERIALS AND METHODS: This study was approved by the local ethics committee, and all patients provided written informed consent. Thirty-one consecutive patients with pleural abnormalities suspicious for MPD underwent whole-body positron emission tomography (PET)/computed tomography (CT) and thorax MR examinations. Diagnostic thoracoscopy with histopathologic analysis of pleural biopsies served as the reference standard. First-line evaluation of each suspicious lesion was performed by using the apparent diffusion coefficient (ADC) calculated from the DW image, and the optimal cutoff value was found by using receiver operating characteristic curve analysis. Afterward, DCE MR imaging data were used to improve the diagnosis in the range of ADCs where DW imaging results were equivocal. RESULTS: Sensitivity, specificity, and accuracy of PET/CT for diagnosis of MPD were 100%, 35.3%, and 64.5%. The optimal ADC threshold to differentiate benign lesions from MPD with DW MR imaging was 1.52 × 10(-3) mm(2)/sec, with sensitivity, specificity, and accuracy of 71.4%, 100%, and 87.1%, respectively. This result could be improved to 92.8%, 94.1%, and 93.5%, respectively, when DCE MR imaging data were included in those cases where ADC was between 1.52 and 2.00 × 10(-3) mm(2)/sec. A total of 20 patients had disease diagnosed correctly, nine had disease diagnosed incorrectly, and two cases were undetermined with PET/CT. DW imaging helped stage disease correctly in 27 patients and incorrectly in four. The undetermined cases at PET/CT were correctly diagnosed at MR imaging. CONCLUSION: DW imaging is a promising tool for differentiating MPD from benign lesions, with high accuracy, and supplementation with DCE MR imaging seems to further improve sensitivity.

Multidetector CT of right-sided congenital diaphragmatic hernia associated with hepatopulmonary fusion in a newborn.

We present a neonate with a complex congenital cardiopathy and a right-sided diaphragmatic hernia complicated with hepatopulmonary fusion. Radiography, abdominal US and multidetector CT (MDCT) demonstrated right-sided lung hypoplasia and liver herniation. In addition, MDCT angiography showed abnormal pulmonary vascular anatomy. At surgery, a right-sided diaphragmatic hernia with a partially herniated liver and hepatopulmonary fusion was confirmed. There was no aberrant systemic vascular supply towards the lower lobe, as seen in extralobar sequestration. MDCT angiography of the chest and upper abdomen with optimal enhancement and reconstruction of the pulmonary and hepatic vasculature can demonstrate associated anomalies in cases of suspected primary or secondary right lung hypoplasia.

High-dose intracoronary adenosine for myocardial salvage in patients with acute ST-segment elevation myocardial infarction.

AIMS: Previous studies have suggested that intravenous administration of adenosine improves myocardial reperfusion and reduces infarct size in ST-elevation myocardial infarction (STEMI) patients. Intracoronary administration of adenosine has shown conflicting results. METHODS AND RESULTS: In a prospective, single-centre, double-blind, placebo-controlled clinical study, we assessed whether selective intracoronary administration of adenosine distal to the occlusion site immediately before initial balloon inflation results in myocardial salvage and decreased microvascular obstruction (MVO) as assessed with cardiac magnetic resonance imaging (MRI). Using a combination of T(2)-weighted and contrast-enhanced sequences, myocardial salvage index (MSI) was defined as the percentage of the area at risk that did not become necrotic. We randomized 112 patients presenting with STEMI within 12 h from symptom onset to selective intracoronary administration of adenosine 4 mg or matching placebo. In 100/110 (91%) patients receiving study drug, MRI was performed on Days 2-3. No significant difference in MSI was found between adenosine- and placebo-treated patients: 41.3% (20.8, 66.7) vs. 47.8% (39.8, 60.9) [median (Q1, Q3)] (P = 0.52). The extent of MVO was comparable in both groups, with a trend favouring the placebo group: 2.4 g (0.0, 6.8) vs. 5.9 g (0.0, 12.8) after adenosine (P = 0.07). TIMI flow grade, TIMI frame count, myocardial blush grade, and ST-segment resolution after primary percutaneous coronary intervention were similar between groups. After 4 months, infarct size was similar in both treatment groups. CONCLUSION: We found no evidence that selective high-dose intracoronary administration of adenosine distal to the occlusion site of the culprit lesion in STEMI patients results in incremental myocardial salvage or a decrease in microvascular obstruction.

Non-invasive characterization of the area-at-risk using magnetic resonance imaging in chronic ischaemia.

AIMS: we investigated the performance of quantitative stress perfusion magnetic resonance imaging (MRI) as a basis for identifying and characterizing the area-at-risk subtending a chronic coronary artery (CA) stenosis. METHODS AND RESULTS: pigs underwent a percutaneous copper-coated stent implantation in the circumflex CA (n = 11) or a sham operation (n = 5). After 6 weeks, angiography and MRI were performed including cine (rest, low- and high-dose dobutamine stress), dual-bolus first-pass perfusion (rest and adenosine stress), and contrast-enhanced imaging to quantify myocardial infarction (MI). Myocardial blood flow (MBF) was quantified based on Fermi-model deconvolution and compared with microsphere measurements. On the basis of Evan's blue staining, MBF thresholds to define the area-at-risk were determined by receiver-operating characteristic (ROC) analysis. CA stenosis was 94 ± 7% and infarct size (IS) 7.3 ± 3.1% of left ventricular mass. Segmental thresholds of hyperaemic MBF yielded the best performance for detecting area-at-risk. There was a good correlation between MRI and microsphere perfusion (r(2) = 0.84, P < .0001). The area-at-risk presented a mixed substrate of non-infarcted (non-MI), <50% infarcted (MI+), and >50% infarcted (MI++) segments. MBF was reduced in at-risk vs. remote segments at rest (non-MI, 0.50 ± 0.21; MI+, 0.47 ± 0.14; MI++, 0.42 ± 0.14; remote, 0.84 ± 0.25 mL/min/g) and during stress (non-MI, 0.69 ± 0.09; MI+, 0.66 ± 0.14; MI++, 0.51 ± 0.11; remote, 1.70 ± 0.36 mL/min/g). Segmental wall thickening showed different responses to stress (remote, progressive increase during incremental stress; non-MI, increase at low-dose and discontinued at high-dose; MI+, initial increase and decrease at high-dose; MI++, progressive decrease). CONCLUSION: quantitative hyperaemic perfusion MRI accurately defines segments in the area-at-risk in chronic ischaemia, which present with different functional response to stress related to segmental IS.

(18)F-FDG PET/CT for early detection of embolism and metastatic infection in patients with infective endocarditis.

PURPOSE: In the acute setting of endocarditis it is very important to assess both the vegetation itself, as well as potential life-threatening complications, in order to decide whether antibiotic therapy will be sufficient or urgent surgery is indicated. A single whole-body scan investigating inflammatory changes could be very helpful to achieve a swift and efficient assessment. METHODS: In this study we assessed whether (18)F-FDG can be used to detect and localize peripheral embolism or distant infection. Twenty-four patients with 25 episodes of endocarditis, enrolled between March 2006 and February 2008, underwent (18)F-FDG PET/CT imaging on a dedicated PET/CT scanner. RESULTS: PET/CT imaging revealed a focus of peripheral embolization and/or metastatic infection in 11 episodes (44%). One episode had a positive PET/CT scan result for both embolism and metastatic infection. PET/CT detected seven positive cases (28%) in which there was no clinical suspicion. Valve involvement of endocarditis was seen only in three patients (12%). CONCLUSION: PET/CT may be an important diagnostic tool for tracing peripheral embolism and metastatic infection in the acute setting of infective endocarditis, since a PET/CT scan detected a clinically occult focus in nearly one third of episodes.

Evidence and patterns in lung response after fetal tracheal occlusion: clinical controlled study.

PURPOSE: To prospectively assess changes in lung volume in fetuses with isolated severe congenital diaphragmatic hernia (CDH) after fetoscopic endoluminal tracheal occlusion (FETO) compared with those in fetuses with CDH of variable severity who were expectantly managed. MATERIALS AND METHODS: Informed consent was obtained for this ethics committee-approved study. Forty fetuses with severe CDH (lung-to-head ratio < 1 and intrathoracic liver) who underwent FETO and 18 fetuses with CDH of variable severity who were expectantly managed were longitudinally followed up by using magnetic resonance (MR) imaging volume measurements. Fetuses born prior to 32 weeks were excluded from the study. For those undergoing FETO, lung volume responsiveness was defined as the proportionate increase in observed-to-expected (O/E) ratio of total fetal lung volume (TFLV) at 2-5 weeks after FETO compared with the pre-FETO value. Changes in lung volume were compared by using the Mann-Whitney U test. Regression analysis was used to investigate the effect of pre-FETO O/E ratio of TFLV, gestational age at FETO and at delivery, lung volume responsiveness, occlusion period, side of CDH, and balloon removal prior to delivery on survival. Correlation between post-FETO lung volume responsiveness and gestational age at FETO was performed by using linear regression analysis. RESULTS: A total of 260 MR imaging examinations were performed. For expectantly managed fetuses, O/E ratio of TFLV remained unchanged during gestation, whereas it significantly increased after FETO. Regression analysis demonstrated that pre-FETO O/E ratio of TFLV and lung volume responsiveness at 3.3 weeks after FETO provided significant independent prediction of postnatal survival. There was a significant negative association between lung volume responsiveness and gestational age at FETO. CONCLUSION: In fetuses with CDH, pre-FETO O/E ratio of TFLV and lung volume at 3.3 weeks after FETO provide independent prediction of postnatal survival. SUPPLEMENTAL MATERIAL: http://radiology.rsnajnls.org/cgi/content/full/2522081955/DC1.