Unenhanced Magnetic Resonance Research Articles

Effectiveness of a Staged US and Unenhanced MR Imaging Algorithm in the Diagnosis of Pediatric Appendicitis.

Purpose To establish, in a large cohort, the diagnostic performance of a staged algorithm involving ultrasonography (US) followed by conditional unenhanced magnetic resonance (MR) imaging for the imaging work-up of pediatric appendicitis. Materials and Methods A staged imaging algorithm in which US and unenhanced MR imaging were performed in pediatric patients suspected of having appendicitis was implemented at the authors' institution on January 1, 2011, with US as the initial modality followed by unenhanced MR imaging when US findings were equivocal. A search of the radiology database revealed 2180 pediatric patients who had undergone imaging for suspected appendicitis from January 1, 2011, through December 31, 2012. Of the 2180 patients, 1982 (90.9%) were evaluated according to the algorithm. The authors reviewed the electronic medical records and imaging reports for all patients. Imaging reports were reviewed and classified as positive, negative, or equivocal for appendicitis and correlated with surgical and pathology reports. Results The frequency of appendicitis was 20.5% (407 of 1982 patients). US alone was performed in 1905 of the 1982 patients (96.1%), yielding a sensitivity of 98.7% (386 of 391 patients) and specificity of 97.1% (1470 of 1514 patients) for appendicitis. Seventy-seven patients underwent unenhanced MR imaging after equivocal US findings, yielding an overall algorithm sensitivity of 98.2% (400 of 407 patients) and specificity of 97.1% (1530 of 1575 patients). Seven of the 1982 patients (0.4%) had false-negative results with the staged algorithm. The negative predictive value of the staged algorithm was 99.5% (1530 of 1537 patients). Conclusion A staged algorithm of US and unenhanced MR imaging for pediatric appendicitis appears to be effective. The results of this study demonstrate that this staged algorithm is 98.2% sensitive and 97.1% specific for the diagnosis of appendicitis in pediatric patients. © RSNA, 2017.

Signal Enhancement of the Dentate Nucleus at Unenhanced MR Imaging after Very High Cumulative Doses of the Macrocyclic Gadolinium-based Contrast Agent Gadobutrol: An Observational Study.

Purpose To test for measurable visual enhancement of the dentate nucleus (DN) on unenhanced T1-weighted magnetic resonance (MR) images in a cohort of patients with a primary brain tumor who had not received linear gadolinium-based contrast agents (GBCAs) but had received many injections of macrocyclic GBCAs. Materials and Methods Seventeen patients with high-grade gliomas who had received 10-44 administrations of the macrocyclic GBCA gadobutrol (0.1 mmol/kg of body weight) were retrospectively included in this regional ethics committee-approved study. Two neuroradiologists inspected T1-weighted MR images with optimized window settings to visualize small differences in contrast at the baseline and at the last examination for the presence of visual DN signal enhancement. Signal intensity (SI) in the DN was normalized to the SI of the pons, and a one-sample t test was used to test for differences between baseline normalized SI (nSI) in the DN (nSIDN) and the average change in nSIDN of all postbaseline MR imaging sessions (ΔnSIDNavg) or the change in nSIDN from baseline to the last MR imaging session (ΔnSIDN). Linear and quadratic correlation analyses were used to examine the association between the number of macrocyclic GBCA administrations and ΔnSIDN or ΔnSIDNavg. Results The mean ± standard deviation number of macrocyclic GBCA administrations was 22.2 ± 10.6 administered throughout 706 days ± 454. Visually appreciable signal enhancement was observed in two patients who had received 37 and 44 macrocyclic GBCA injections. Mean ΔnSIDN was greater than zero (0.03 ± 0.05; P = .016), and there was a significant linear association between the number of macrocyclic GBCA injections and ΔnSIDN (r = 0.69, P = .002) and ΔnSIDNavg (r = 0.77, P < .001). Conclusion A small but statistically significant dose-dependent T1-weighted signal enhancement was observed in the DN after multiple macrocyclic GBCA injections. Visually appreciable enhancement in the DN was observed on contrast-optimized images in two patients who had received 37 and 44 standard doses of macrocyclic GBCAs. © RSNA, 2017 Online supplemental material is available for this article.

Unenhanced magnetic resonance imaging immediately after radiofrequency ablation of liver malignancy: preliminary results.

To assess the accuracy of unenhanced magnetic resonance imaging (MRI) immediately after the percutaneous ultrasound-guided radiofrequency ablation (RFA) of liver malignancy in predicting treatment efficacy at CT follow-up. Percutaneous ablation was prospectively performed in 23 liver malignancies (20 hepatocarcinomas and 3 metastases). After the procedure in the same day all patients were studied with unenhanced MRI. The best sequence to detect the coagulative necrosis was visually established. Pre-RFA CT and post-RFA MRI were registered with non-rigid transformation algorithm. Manual segmentation of lesions and ablated areas in pre-RFA CT, post-RFA MRI, and follow-up CT were obtained. Sensitivity, specificity, positive predictive value (PPV), negative predicitve value (NPV), and accuracy of MRI in predicting the correct centering and the complete treatment of the lesion were calculated in respect to the 1-month follow-up CT. Fat-saturated T1-weighted (fs T1-w) was the sequence in which the best conspicuity of the ablated area was depicted. Coagulative necrosis was hyperintense in fs T1-w sequence in 17/23 (74%). In respect to follow-up CT, MRI predicted the correct centering of the lesions in 19/20 lesions with sensitivity, specificity, PPV, NPV, and accuracy of 100%, 75%, 95%, 100%, and 100%, respectively. MRI predicted the complete treatment of the lesions in 17/17 lesions with sensitivity, specificity, PPV, NPV, and accuracy of 100%. MRI with the single fs T1-w sequence was highly accurate in predicting the treatment efficacy of percutaneous ablation of liver malignancies in comparison to follow-up CT control. Unnecessary CT in case of incomplete treatment can be therefore easily avoided.

Deep neural network-based computer-assisted detection of cerebral aneurysms in MR angiography.

The usefulness of computer-assisted detection (CAD) for detecting cerebral aneurysms has been reported; therefore, the improved performance of CAD will help to detect cerebral aneurysms. To develop a CAD system for intracranial aneurysms on unenhanced magnetic resonance angiography (MRA) images based on a deep convolutional neural network (CNN) and a maximum intensity projection (MIP) algorithm, and to demonstrate the usefulness of the system by training and evaluating it using a large dataset. Retrospective study. There were 450 cases with intracranial aneurysms. The diagnoses of brain aneurysms were made on the basis of MRA, which was performed as part of a brain screening program. Noncontrast-enhanced 3D time-of-flight (TOF) MRA on 3T MR scanners. In our CAD, we used a CNN classifier that predicts whether each voxel is inside or outside aneurysms by inputting MIP images generated from a volume of interest (VOI) around the voxel. The CNN was trained in advance using manually inputted labels. We evaluated our method using 450 cases with intracranial aneurysms, 300 of which were used for training, 50 for parameter tuning, and 100 for the final evaluation. Free-response receiver operating characteristic (FROC) analysis. Our CAD system detected 94.2% (98/104) of aneurysms with 2.9 false positives per case (FPs/case). At a sensitivity of 70%, the number of FPs/case was 0.26. We showed that the combination of a CNN and an MIP algorithm is useful for the detection of intracranial aneurysms. 4 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:948-953.

Value of unenhanced MRI with diffusion-weighted imaging for detection of primary small (≤20 mm) solid pancreatic tumours and prediction of pancreatic ductal adenocarcinoma

To determine the diagnostic performance of unenhanced magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI; NonMRI) for the detection of primary small (≤20mm) pancreatic solid tumours and prediction of pancreatic ductal adenocarcinoma (PDAC) in comparison with pancreatic computed tomography (CT; PanCT) and pancreatic MRI with magnetic resonance cholangiopancreatography (PanMRI). The institutional review board approved this retrospective study and waived the requirement for informed consent. A total of 126 patients who underwent PanCT and PanMRI, including 94 small (≤20mm) pancreatic tumours (51 PDACs, 34 neuroendocrine tumours [NETs], nine solid pseudopapillary tumours [SPTs]), and 32 patients with a normal pancreas, comprised the study population. Two observers assessed three sets of images: PanCT, PanMRI and NonMRI (T1- and T2-weighted images and DWI). Receiver operating characteristic curve analysis and diagnostic accuracy using the area under the receiver operating characteristic curve (Az) were used for statistical analysis. On NonMRI and PanMRI, all of tumours except one NET were detected, but eight tumours (six NETs, one PDAC, one SPT) were not detected on PanCT (p<0.01). For prediction of PDAC, the Az value of the NonMRI (0.884 for observer 1; 0.930 for observer 2) was comparable with PanCT (0.922; 0.924; p>0.05), and inferior to PanMRI (0.930; 0.977; p<0.05), but all of 51 PDACs were considered as probable or definite PDAC on NonMRI by both observers. NonMRI showed better performance than PanCT, and competitive performance to PanMRI for the detection of primary small solid pancreatic tumours, and showed reasonable sensitivity for prediction of PDACs compared with PanCT and PanMRI.

Gadolinium Brain Deposition after Macrocyclic Gadolinium Administration: A Pediatric Case-Control Study.

Purpose To determine whether signal intensity (SI) in T1 sequences as a potential indicator of gadolinium deposition increases after repeated administration of the macrocyclic gadolinium-based contrast agents (GBCAs) gadoteridol and gadoterate meglumine in a pediatric cohort. Materials and Methods This retrospective case-control study of children with brain tumors who underwent nine or more contrast material-enhanced brain magnetic resonance (MR) imaging studies from 2008 to 2015 was approved by the local ethics board. Informed consent was obtained for MR imaging. Twenty-four case patients aged 5-18 years and appropriate control patients with nonpathologic MR neuroimaging findings (and no GBCA administration), matched for age and sex, were inculded. SI was measured on unenhanced T1-weighted MR images for the following five regions of interest (ROIs): the dentate nucleus (DN), pons, substantia nigra (SN), pulvinar thalami, and globus pallidus (GP). Paired t tests were used to compare SI and SI ratios (DN to pons, GP to thalamus) between case patients and control patients. Pearson correlations between relative signal changes and the number of GBCA administrations and total GBCA dose were calculated. Results The mean number of GBCA administrations was 14.2. No significant differences in mean SI for any ROI and no group differences were found when DN-to-pons and GP-to-pulvinar ratios were compared (DN-to-pons ratio in case patients: mean, 1.0083 ± 0.0373 [standard deviation]; DN-to-pons ratio in control patients: mean, 1.0183 ± 0.01917; P = .37; GP-to-pulvinar ratio in case patients: mean, 1.1335 ± 0.04528; and GP-to-pulvinar ratio in control patients: mean, 1.1141 ± 0.07058; P = .29). No correlation was found between the number of GBCA administrations or the total amount of GBCA administered and signal change for any ROI. (Number of GBCA applications: DN: r = -0.254, P = .31; pons: r = -0.097, P = .65; SN: r = -0.194, P = .38; GP: r = -0.175, P = .41; pulvinar: r = -0.067, P = .75; total amount of administered GBCA: DN: r = 0.091, P = .72; pons: r = 0.106, P = .62; SN: r = -0.165, P = .45; GP: r = 0.111, P = .61; pulvinar: r = 0.173, P = .42.) Conclusion Multiple intravenous administrations of these macrocyclic GBCAs in children were not associated with a measurable increase in SI in T1 sequences as an indicator of brain gadolinium deposition detectable by using MR imaging. Additional imaging and pathologic studies are needed to confirm these findings. © RSNA, 2017 Online supplemental material is available for this article.

Assessment of thoracic vasculature in patients with central bronchogenic carcinoma by unenhanced magnetic resonance angiography: comparison between 2D free-breathing TrueFISP, 2D breath-hold TrueFISP and 3D respiratory-triggered SPACE.

Preoperative assessment of the integrity of major thoracic vessels in central bronchogenic carcinoma is vital for tumor staging and treatment planning. Contrast-enhanced CT is currently the first choice of modality for this purpose in clinical practice with limitations including exposure to ionizing radiation and the use of iodinated contrast material. MRI has been increasingly employed for the staging of lung cancer. More recently, unenhanced magnetic resonance angiography (MRA) which is totally non-invasive and contrast-free has been reported able to show thoracic vessels. This study was to compare image qualities of three unenhanced-MRAs and to evaluate accuracy of them in assessing thoracic vessel invasion by using contrast-enhanced CT as a reference standard. A total of 30 patients with central bronchogenic carcinoma confirmed by pathology were examined by CT and unenhanced MRA including 2D free-breathing (FB)-TrueFISP, breath-holding (BH)-TrueFISP and 3D respiratory-triggered (RT)-SPACE. Image qualities of pulmonary arteries and veins, thoracic aorta and vena cava were scored for each MRA sequence. Vessel to lung tissue signal contrast-to-noise ratio (CNR), vessel to tumor signal contrast ratio (VTR), and tumor to background signal contrast ratio (TBR) were calculated. On each method, vessel invasion was evaluated according to types of morphological relationships between the tumor and major vessels. The three MRAs showed no significant difference in CNR (P=0.518) while TrueFISP MRAs were better than SPACE in terms of VTR (P=0.000) and image quality (P=0.002). Excellent consistency with CT was found for all three MRAs in assessment of the morphological relationships between tumors and major vessels (FB-TrueFISP: kappa =0.821; BH-TrueFISP: kappa =0.862; RT-SPACE: kappa =0.811). Both TrueFISP and SPACE allow satisfactory visualization of major mediastinal and hilar vessels and are comparable to MDCT in assessment of vessel invasion in patients with central lung cancer. TrueFISP sequences are better than SPACE in regard to image quality and VTR.

Repeated administrations of macrocyclic gadolinium based contrast agents in multiple sclerosis patients do not cause increased signal intensity in dentate nucleus and globus pallidus on T1-weighted unenhanced magnetic resonance images (P4.363)

Repeated administrations of macrocyclic gadolinium based contrast agents in multiple sclerosis patients do not cause increased signal intensity in dentate nucleus and globus pallidus on T1-weighted unenhanced magnetic resonance images (P4.363)

Peptide Receptor-Targeted Fluorescent Probe: Visualization and Discrimination between Chronic and Acute Ulcerative Colitis.

The inflammatory activity of ulcerative colitis plays an important role in the medical treatment. However, accurate and real-time monitoring of the colitis activity with noninvasive bioimaging method is still challenging, especially in distinguishing between chronic and acute colitis. As a good receptor, the oligopeptide transporter (PepT1) is overexpressed in the colonic epithelial cells of chronic ulcerative colitis, which can deliver tripeptide KPV (Lys-Pro-Val, the C-terminal sequence of α-MSH) into cytosol in the intestine. Herein, we report a PepT1 peptide receptor-targeted fluorescent probe, dicyanomethylene-4H-pyran (DCM)-KPV, with the strategy of conjugating the KPV into the DCM chromophore. The diagnostic fluorescent probe bestows a specific receptor-targeted interaction with PepT1 through the KPV moiety, possessing several beneficial characteristics, such as efficient long emission, low photobleaching, negligible cytotoxicity, and high cytocompatibility in living cells. We build the overexpressed PepT1 on the cytomembrane of ulcerative colitis model Caco-2 cell as the efficient receptor to accumulate the targeted tripeptide KPV in the cytoplasm and nucleus. With the co-localization of DCM-KPV and the DNA-specific fluorophore, DAPI, the specifically long emission from chromophore DCM and efficient receptor-targeted peptide KPV, the fluorescent probe of DCM-KPV makes a breakthrough to the direct noninvasive observation of the accumulation in colon inflammation regions via intestinal mucosa, even successfully distinguishing the chronic, acute ulcerative colitis and normal groups. Compared with the traditional unenhanced magnetic resonance imaging and hematoxylin and eosin (H&E) staining, we make full use of exploiting the specific target-receptor interaction between the tripeptide unit, KPV, and the oligopeptide transporter, PepT1, for sensing selectivity. The desirable diagnostic ability of DCM-KPV can guarantee the real-time tracking and visualization of the role of intracellular KPV on ulcerative colitis, which provides an alternative to replace the time-consuming and tissue sampling-invasive H&E staining diagnosis.

Effect of Intravenous Administration of Contrast Media on Serum Creatinine Levels in Neonates.

Purpose To assess the effect of intravenous contrast media on renal function in neonates. Materials and Methods Institutional review board approval was obtained with waiver of consent. Electronic health records from January 2011 to April 2013 were reviewed retrospectively. Measures of renal function were obtained in inpatient neonates who underwent magnetic resonance (MR) imaging or computed tomography (CT) and for whom serum creatinine (Cr) levels were obtained within 72 hours before imaging and at least one time after imaging (>1 day after administration of contrast material). A total of 140 neonates who received contrast material (59 who underwent CT with iohexol or iodixanol and 81 who underwent MR imaging with gadopentetate dimeglumine) were identified. These neonates were frequency matched according to sex, gestational and postnatal age, and preimaging serum Cr levels with neonates who underwent unenhanced MR imaging or CT. Cr levels and glomerular filtration rates (GFRs) were grouped according to when they were obtained (before imaging, 1-2 days after imaging, 3-5 days after imaging, 6-9 days after imaging, 10-45 days after imaging, and more than 45 days after imaging). Serum Cr levels and GFRs for each time period were compared between groups by using hierarchic regressions or χ2 or Fisher exact tests and with repeated-measures analysis of variance to compare groups on the rate of change in serum Cr levels and GFRs from before to after imaging. Results Cr levels decreased and GFRs increased in both groups from before to after imaging (CT group, P ≤ .01; MR imaging group, P ≤ .01). The neonates who underwent contrast material-enhanced imaging and the neonates who underwent unenhanced imaging showed similar serum Cr levels at all examined time periods. Groups also did not differ in the proportion of neonates with serum Cr levels higher than the reference range (>0.4 mg/dL) at any time point (iodine- [P > .12] or gadolinium-based [P > .13] contrast material). Similar findings were observed for GFRs. None of the neonates developed nephrogenic systemic fibrosis. Conclusion In the absence of known renal failure, neonates receiving standard inpatient care do not appear to be at increased risk for developing renal toxicity due to administration of intravenous iodine- and gadolinium-based contrast material. © RSNA, 2017.

Pediatric Brain: No Increased Signal Intensity in the Dentate Nucleus on Unenhanced T1-weighted MR Images after Consecutive Exposure to a Macrocyclic Gadolinium-based Contrast Agent.

Purpose To determine the effect of at least five serial injections of the macrocyclic gadolinium-based contrast agent (GBCA) gadoterate meglumine on the signal intensity (SI) of the dentate nucleus (DN) of the pediatric brain on nonenhanced T1-weighted magnetic resonance (MR) images. Materials and Methods In this retrospective, institutional review board-approved study, 41 pediatric patients (age range, 3-17 years) who were imaged in at least five consecutive 1.5-T MR examinations with the exclusive use of gadoterate meglumine (plus a final additional nonenhanced MR imaging examination) were evaluated. SI ratio differences between the first and last MR examination were calculated for DN-to-pons and DN-to-middle cerebellar peduncle (MCP) ratios in a region-of-interest-based analysis, and one-sample t tests were used to examine if the SI ratio differences differed from 0. Bayes factors were calculated to quantify the strength of evidence for each test. Results Patients underwent a mean of 8.6 ± 3.9 GBCA administrations (mean accumulated dose, 32.07 mmol ± 17.62, with an average of 16.7 weeks ± 7.9 between every administration). Both ratio differences did not differ significantly from 0 (DN-to-pons ratio: -0.0012 ± 0.0101, P = .436; DN-to-MCP ratio: 0.0007 ± 0.0088, P = .604), and one-sided Bayes factors provided substantial evidence against an SI ratio increase (0.10 for DN-to-pons ratio; 0.27 for DN-to-MCP ratio). Conclusion No increase of the SI in the DN was found after a mean of 8.6 serial injections of the macrocyclic GBCA gadoterate meglumine in pediatric patients, confirming previous studies that did not find this effect after serial injections of macrocyclic GBCAs in adults. © RSNA, 2017.

Prediction of malignancy by a radiomic signature from contrast agent-free diffusion MRI in suspicious breast lesions found on screening mammography.

To assess radiomics as a tool to determine how well lesions found suspicious on breast cancer screening X-ray mammography can be categorized into malignant and benign with unenhanced magnetic resonance (MR) mammography with diffusion-weighted imaging and T2 -weighted sequences. From an asymptomatic screening cohort, 50 women with mammographically suspicious findings were examined with contrast-enhanced breast MRI (ceMRI) at 1.5T. Out of this protocol an unenhanced, abbreviated diffusion-weighted imaging protocol (ueMRI) including T2 -weighted, (T2 w), diffusion-weighted imaging (DWI), and DWI with background suppression (DWIBS) sequences and corresponding apparent diffusion coefficient (ADC) maps were extracted. From ueMRI-derived radiomic features, three Lasso-supervised machine-learning classifiers were constructed and compared with the clinical performance of a highly experienced radiologist: 1) univariate mean ADC model, 2) unconstrained radiomic model, 3) constrained radiomic model with mandatory inclusion of mean ADC. The unconstrained and constrained radiomic classifiers consisted of 11 parameters each and achieved differentiation of malignant from benign lesions with a .632 + bootstrap receiver operating characteristics (ROC) area under the curve (AUC) of 84.2%/85.1%, compared to 77.4% for mean ADC and 95.9%/95.9% for the experienced radiologist using ceMRI/ueMRI. In this pilot study we identified two ueMRI radiomics classifiers that performed well in the differentiation of malignant from benign lesions and achieved higher performance than the mean ADC parameter alone. Classification was lower than the almost perfect performance of a highly experienced breast radiologist. The potential of radiomics to provide a training-independent diagnostic decision tool is indicated. A performance reaching the human expert would be highly desirable and based on our results is considered possible when the concept is extended in larger cohorts with further development and validation of the technique. 1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:604-616.

Unenhanced renal magnetic resonance angiography in patients with chronic kidney disease & suspected renovascular hypertension: Can it affect patient management?

Background & objectives:Renal artery stenosis (RAS) is an important cause of severe hypertension in patients with chronic kidney disease (CKD). It is important to detect RAS early as it can reverse hypertension and stop rapid deterioration of renal function. The potential drawbacks of various imaging modalities used to detect RAS including contrast-related adverse effects associated with diagnostic angiography have led to increasing interest in unenhanced magnetic resonance (MR) renal angiography. The aim of this study was to detect and grade RAS in patients with CKD and suspected renovascular hypertension using unenhanced MR angiography (UMRA) and to identify patients with significant RAS (>70%) who would subsequently require further investigation and revascularization.Methods:Thirty five CKD patients with suspected RAS were subjected to UMRA using non-contrast MR angiography of ArTery and VEins 3D True fast imaging with steady state precession technique over a three year period. Patients with RAS >70 per cent on UMRA were subjected to digital subtraction angiography (DSA) with intervention if indicated.Results:In all, 76 renal arteries were evaluated using UMRA in 35 patients, of which 18 arteries showed stenosis and 11 were haemodynamically significant (eight patients). Seven patients (10 renal arteries) underwent DSA.Interpretation & conclusions:An association between UMRA and DSA findings was obtained in six patients (nine renal arteries), and these patients were stented. Post-procedure follow up showed good improvement in blood pressure and renal function. UMRA was found to be a useful non-invasive imaging modality to detect RAS in CKD patients. It can identify patients who require further invasive angiography and revascularization.

The value of Gd-BOPTA- enhanced MRIs and DWI in the diagnosis of intrahepatic mass-forming cholangiocarcinoma.

The aim of this study is to explore the value of unenhanced magnetic resonance imaging (MRI), gadobenate dimeglumine injection (Gd-BOPTA)-enhanced MRI and diffusion-weighted imaging (DWI) in the diagnosis of intrahepatic mass-forming cholangiocarcinoma (IMCC). Totally 59 IMCC patients who underwent Gd-BOPTA-enhanced MRIs were recruited. The time-signal intensity curves and lesion periphery enhancement rates of the IMCC and liver parenchyma was drawn using apparent diffusion coefficient (ADC) values. The Gd-BOPTA-enhanced MRI showed that the peripheries of 30 lesions in the arterial phase exhibited irregular ring enhancement. However, lesions in the portal and delayed phases (which were gradually filled with a contrast agent), presented a patchy or latticed enhancement. Twenty-two lesions in the arterial and delayed phases exhibited uneven mild/moderate patchy enhancements with a progressive and centripetal lesion. Five lesions emerged from the arterial phase without any significant enhancement and had only gradual enhancement during the delayed phase. The remaining 2 lesions had a decreased mild enhancement, presented comparatively high signals and the lesion center had visible small spotted low signals. The DWI signals displayed a slightly high or high unevenness. Some lesion peripheries had a high signal but lesion centers displayed a relatively low or slightly low signal and irregular patches. There were significant differences between the ADC values of the lesion edge, lesion center and liver parenchyma. The IMCC detection rates of the Gd-BOPTA-enhanced MRI and DWI were higher than those of the unenhanced MRI. Our study demonstrated that both the Gd-BOPTA-enhanced MRI and DWI had higher accuracies rates than an unenhanced MRI. Furthermore, the hepatobiliary phase of IMCC plays an important role in the diagnosis and identification of IMCC constituents.

No Signal Intensity Increase in the Dentate Nucleus on Unenhanced T1-weighted MR Images after More than 20 Serial Injections of Macrocyclic Gadolinium-based Contrast Agents

Purpose To determine the effect of more than 20 serial injections of macrocyclic gadolinium-based contrast agents (GBCAs) on the signal intensity (SI) of the dentate nucleus (DN) on unenhanced T1-weighted magnetic resonance (MR) images. Materials and Methods In this retrospective, institutional review board-approved study, 33 patients who underwent at least 20 consecutive MR imaging examinations (plus an additional MR imaging for reference) with the exclusive use of macrocyclic GBCAs gadoterate meglumine and gadobutrol were analyzed. SI ratio differences were calculated for DN-to-pons and DN-to-middle cerebellar peduncle (MCP) ratios by subtracting the SI ratio at the first MR imaging examination from the SI ratio at the last MR imaging examination. One-sample t tests were used to examine if the SI ratio differences differed from 0, and Bayes factors were calculated to quantify the strength of evidence for each test. Results Patients underwent a mean of 23.03 ± (standard deviation) 4.20 GBCA administrations (mean accumulated dose, 491.21 mL ± 87.04 of a 0.5 M GBCA solution) with an average of 12.09 weeks ± 2.16 between every administration. Both ratio differences did not differ significantly from 0 (DN-to-pons ratio: -0.0032 ± 0.0154, P = .248; DN-to-MCP ratio: -0.0011 ± 0.0093, P = .521), and one-sided Bayes factors provided substantial to strong evidence against an SI ratio increase (Bayes factor for DN-to-pons ratio = 0.09 and that for DN-to-MCP ratio = 0.12). Conclusion The study indicates that 20 or more serial injections of macrocyclic GBCAs administered with on average 3 months between each injection are not associated with an SI increase in the DN. © RSNA, 2016.

Injections of Intravenous Contrast for Computerized Tomography Scans Precipitate Migraines in Hereditary Hemorrhagic Telangiectasia Subjects at Risk of Paradoxical Emboli: Implications for Right-to-Left Shunt Risks.

ObjectiveTo evaluate if injection of intravenous particles may provoke migraines in subjects with right‐to‐left shunts due to pulmonary arteriovenous malformations (AVMs).BackgroundMigraine headaches commonly affect people with hereditary hemorrhagic telangiectasia (HHT), especially those with pulmonary AVMs that provide right‐to‐left shunts. In our clinical practice, patients occasionally reported acute precipitation of migraine headaches following injection of technetium‐labeled albumin macroaggregates for nuclear medicine scans.MethodsSelf‐reported migraine features and exacerbations were examined in HHT subjects with and without pulmonary AVMs, for a series of noninvasive and invasive investigations, using an unbiased online survey.ResultsOne hundred and sixty‐six subjects were classified as having both HHT and migraines. HHT subjects with migraines were more likely to have pulmonary AVMs (P < .0001). HHT subjects with pulmonary AVMs were more likely to report photophobia (P = .010), “flashes of light” (P = .011), or transient visual loss (P = .040). Pulse oximetry, x‐rays, ultrasound, and computerized tomography (CT) scans without intravenous contrast medium rarely, if ever, provoked migraines, but unenhanced magnetic resonance imaging (MRI) was reported to exacerbate migraines by 14/124 (11.2%) subjects. One hundred and fourteen subjects had both enhanced and unenhanced CT examinations: studies with contrast media were more commonly reported to start (9/114 [7.8%]), and/or worsen migraines (18/114 [15.7%]), compared to those undertaken without contrast medium (P < .01), or after simple blood tests (P < .05). Additionally, migraine exacerbation was reported by 9/90 (10%) after contrast echocardiography, 2/44 (4.5%) after nuclear medicine scans, and 10/154 (6.5%) after blood tests.ConclusionsHHT subjects frequently report migraine exacerbation following blood tests, contrast echocardiograms, MRI imaging, and CT studies performed with intravenous contrast medium. Since air emboli are recognized to complicate intravenous injections, particularly those given by a pressurized pump during contrast enhanced CT, future studies should re‐evaluate whether particulate emboli provoke migraines.

Extent of Signal Hyperintensity on Unenhanced T1-weighted Brain MR Images after More than 35 Administrations of Linear Gadolinium-based Contrast Agents.

Purpose To explore the extent of signal hyperintensity in the brain on unenhanced T1-weighted magnetic resonance (MR) images with increasing gadolinium-based contrast agent (GBCA) doses in patients who received 35 or more linear GBCA administrations. Materials and Methods In this institutional review board-approved HIPAA-compliant retrospective study, picture archiving and communication systems of two tertiary referral hospitals were searched to identify patients who received 35 or more linear GBCA administrations. Unenhanced T1-weighted images of the brain in patients after six, 12, and 24 GBCA administrations and after the final GBCA administration were independently reviewed by three radiologists to identify sites where T1 signal intensity was increasing. Areas identified by all three observers as increasing in T1 signal intensity when compared with baseline images were further analyzed with a quantitative region of interest analysis measuring the rate of signal increase per injection and the total change after 24 linear GBCA administrations relative to reference tissues that did not show T1 shortening. Results Qualitative analysis of 13 patients with 39-59 linear GBCA administrations showed visually detectable T1 shortening in the dentate nucleus (n = 13), globus pallidus (n = 13), substantia nigra (n = 13), posterior thalamus (n = 12), red nucleus (n = 10), colliculi (n = 10), superior cerebellar peduncle (n = 7), caudate nucleus (n = 4), whole thalamus (n = 3), and putamen (n = 2). Quantitative analysis enable confirmation of signal intensity increases on unenhanced T1-weighted images relative to reference tissues in the dentate nucleus (0.53% signal intensity increase per injection, P < .001), globus pallidus (0.23% increase, P = .009), posterior thalamus (0.26% increase, P < .001), substantia nigra (0.25% increase, P = .01), red nucleus (0.25% increase, P = .01), cerebellar peduncle (0.19% increase, P = .001), and colliculi (0.21% increase, P = .02). Conclusion Increased signal intensity on unenhanced T1-weighted images was seen in the posterior thalamus, substantia nigra, red nucleus, cerebellar peduncle, colliculi, dentate nucleus, and globus pallidus. © RSNA, 2016.

The Effect of Unenhanced MRI on the Surgeons’ Decision‐Making Process in Females with Suspected Appendicitis

BackgroundThis prospective study evaluated the impact of the results of unenhanced magnetic resonance imaging (MRI) on the surgeon’s diagnosis of acute appendicitis in potentially fertile females.Methods112 female patients, aged 12–55, with suspected appendicitis underwent MRI of the abdomen. At three defined intervals; admission and clinical re-evaluation before and after revealing the MRI results, the surgeon recorded the attendance of each patient in operative treatment, observation or discharge. Appendicitis was confirmed or declined by pathology or by telephone follow-up in case of non-intervention.FindingsAppendicitis was confirmed in 29 of 112 patients. At admission the surgeon’s disposition had a sensitivity of 97 % and specificity of 29 %. After knowing the MRI results, sensitivity was 97 % and specificity 64 %. The sensitivity and specificity of MRI alone were 89 and 100 %, with a negative and positive predictive value of 96 and 100 %, respectively.ConclusionWe believe that MRI should perhaps be standard in all female patients during their reproductive years with suspected appendicitis. It avoids an operation in 32 % of cases and allows earlier planning for patients with an equivocal clinical picture. Trial number: OND1292733 (Narcis.nl).

Pediatric Brain: Repeated Exposure to Linear Gadolinium-based Contrast Material Is Associated with Increased Signal Intensity at Unenhanced T1-weighted MR Imaging.

Purpose To determine whether repeated exposure of the pediatric brain to a linear gadolinium-based contrast agent (GBCA) is associated with an increase in signal intensity (SI) relative to that in GBCA-naive control subjects at unenhanced T1-weighted magnetic resonance (MR) imaging. Materials and Methods This single-center, retrospective study was approved by the institutional review board and compliant with HIPAA. The authors evaluated 46 pediatric patients who had undergone at least three GBCA-enhanced MR examinations (30 patients for two-group analysis and 16 for pre- and post-GBCA exposure comparisons) and 57 age-matched GBCA-naive control subjects. The SI in the globus pallidus, thalamus, dentate nucleus, and pons was measured at unenhanced T1-weighted MR imaging. Globus pallidus-thalamus and dentate nucleus-pons SI ratios were calculated and compared between groups and relative to total cumulative gadolinium dose, age, sex, and number of and mean time between GBCA-enhanced examinations. Analysis included the Wilcoxon signed rank test, Wilcoxon rank sum test, and Spearman correlation coefficient. Results Patients who underwent multiple GBCA-enhanced examinations had increased SI ratios within the dentate nucleus (mean SI ratio ± standard error of the mean for two-group comparison: 1.007 ± 0.0058 for GBCA-naive group and 1.046 ± 0.0060 for GBCA-exposed group [P < .001]; mean SI ratio for pre- and post-GBCA comparison: 0.995 ± 0.0062 for pre-GBCA group and 1.035 ± 0.0063 for post-GBCA group [P < .001]) but not the globus pallidus (mean SI ratio for two-group comparison: 1.131 ± 0.0070 for GBCA-naive group and 1.014 ± 0.0091 for GBCA-exposed group [P = .21]; mean SI ratio for pre- and post-GBCA comparison: 1.068 ± 0.0094 for pre-GBCA group and 1.093 ± 0.0134 for post-GBCA group [P = .12]). There was a significant correlation between dentate nucleus SI and total cumulative gadolinium dose (r = 0.4; 95% confidence interval [CI]: 0.03, 0.67; P = .03), but not between dentate nucleus SI and patient age (r = 0.23; 95% CI: -0.15, 0.56; P = .22), sex (mean SI ratio: 1.046 ± 0.0072 for boys and 1.045 ± 0.0110 for girls; P = .88), number of contrast-enhanced examinations (r = 0.13; 95% CI: -0.25, 0.48; P = .49), or time between contrast-enhanced examinations (r = -0.06; 95% CI: -0.42, 0.32; P = .75). Conclusion SI in the pediatric brain increases on unenhanced T1-weighted MR images with repeated exposure to a linear GBCA. © RSNA, 2016.

Homogeneous T1 Hyperintense Renal Lesions with Smooth Borders: Is Contrast-enhanced MR Imaging Needed?

Purpose To retrospectively determine if homogeneous high T1 signal intensity (SI) masses with smooth borders on unenhanced magnetic resonance (MR) images can be characterized as benign. Materials and Methods Institutional review board approval was obtained for this HIPAA-compliant retrospective study, with waiver of informed consent. MR images in 84 patients with hemorrhagic or proteinaceous cysts and 50 patients with renal cell carcinoma (RCC) were evaluated. Sixty-three cysts and 49 RCCs underwent unenhanced computed tomography (CT). SI ratio and CT attenuation were determined. Two radiologists evaluated lesions as follows: score 1, homogeneous with smooth borders; score 2, mildly heterogeneous with mildly lobulated borders; score 3, moderately heterogeneous and irregular borders; and score 4, markedly heterogeneous with markedly irregular borders. Statistical analysis was performed by using multivariable logistic regression, Welch t test, Z test, Fisher-exact test, Shapiro-Wilk test, and receiver operating characteristic curve analysis. A diagnostic criterion was formulated by using classification and regression tree analysis. Results SI ratio and attenuation of hemorrhagic or proteinaceous cysts were significantly higher than those of RCCs (SI ratio: cyst 2.4 ± 0.8, RCC 1.5 ± 0.3; attenuation: cyst 51.9 ± 21.5, RCC: 34.8 ± 10.0). Reader 1 scored morphology of 68 (81%) hemorrhagic or proteinaceous cysts as score 1 on MR images and as score 45 (71%) on CT scans. Reader 2 scored morphology of 59 (70%) hemorrhagic or proteinaceous cysts as score 1 on MR images and as score 43 (68%) on CT scans. Two-step classification tree suggested that homogeneous high T1 SI lesions with smooth borders and SI ratio of greater than 1.6 predict the lesion as benign cysts. Similar algorithm for CT suggested threshold of 51 HU. Increasing threshold to 2.5 for SI ratio and 66 for Hounsfield units resulted in 99.9% confidence for characterizing benign cysts. Conclusion The retrospective assessment shows that morphologic assessment and SI quantification on unenhanced T1-weighted MR images can be used to differentiate benign hemorrhagic or proteinaceous cysts from RCC, although prospective assessment will be needed to confirm these results. (©) RSNA, 2016.