Showing papers in "Investigative Radiology in 2015"

Measuring Computed Tomography Scanner Variability of Radiomics Features.

Abstract: ObjectivesThe purpose of this study was to determine the significance of interscanner variability in CT image radiomics studies.Materials and MethodsWe compared the radiomics features calculated for non–small cell lung cancer (NSCLC) tumors from 20 patients with those calculated for 17 scans of a sp

T1-Weighted Hypersignal in the Deep Cerebellar Nuclei After Repeated Administrations of Gadolinium-Based Contrast Agents in Healthy Rats: Difference Between Linear and Macrocyclic Agents.

Abstract: Objectives To prospectively compare in healthy rats the effect of multiple injections of macrocyclic (gadoterate meglumine) and linear (gadodiamide) gadolinium-based contrast agents (GBCAs) on T1-weighted signal intensity in the deep cerebellar nuclei (DCN), including the dentate nucleus.

T1 relaxivities of gadolinium-based magnetic resonance contrast agents in human whole blood at 1.5, 3, and 7 T.

Abstract: OBJECTIVES Calculation of accurate T1 relaxivity (r1) values for gadolinium-based magnetic resonance contrast agents (GBCAs) is a complex process. As such, often referenced r1 values for the GBCAs at 1.5 T, 3 T, and 7 T are based on measurements obtained in media that are not clinically relevant, derived from only a small number of concentrations, or available for only a limited number of GBCAs. This study derives the r1 values of the 8 commercially available GBCAs in human whole blood at 1.5 T, 3 T, and 7 T. MATERIALS AND METHODS Eight GBCAs were serially diluted in human whole blood, at 7 concentrations from 0.0625 to 4 mM. A custom-built phantom held the dilutions in air-tight cylindrical tubes maintained at 37 ± 0.5°C by a heat-circulating system. Images were acquired using inversion recovery sequences with inversion times from 30 milliseconds to 10 seconds at 1.5 T and 3 T as well as 60 milliseconds to 5 seconds at 7 T. A custom MATLAB program was used to automate signal intensity measurements from the images acquired of the phantom. SigmaPlot was used to calculate T1 relaxation times and, finally, r1. RESULTS Measured r1 values in units of s[BULLET OPERATOR]mM at 1.5 T (3 T/7 T) were 3.9 ± 0.2 (3.4 ± 0.4/2.8 ± 0.4) for Gd-DOTA, 4.6 ± 0.2 (4.5 ± 0.3/4.2 ± 0.3) for Gd-DO3A-butrol, 4.3 ± 0.4 (3.8 ± 0.2/3.1 ± 0.4) for Gd-DTPA, 6.2 ± 0.5 (5.4 ± 0.3/4.7 ± 0.1) for Gd-BOPTA, 4.5 ± 0.1 (3.9 ± 0.2/3.7 ± 0.2) for Gd-DTPA-BMA, 4.4 ± 0.2 (4.2 ± 0.2/4.3 ± 0.2) for Gd-DTPA-BMEA, 7.2 ± 0.2 (5.5 ± 0.3/4.9 ± 0.1) for Gd-EOB-DTPA, and 4.4 ± 0.6 (3.5 ± 0.6/3.4 ± 0.1) for Gd-HP-DO3A. The agents can be stratified by relaxivity, with a significant additional dependency on field strength. CONCLUSIONS This report quantifies, for the first time, T1 relaxivity for all 8 gadolinium chelates in common clinical use worldwide, at current relevant field strengths, in human whole blood at physiological temperature (37°C). The measured r1 values differ to a small degree from previously published values, where such comparisons exist, with the current r1 measurements being that most relevant to clinical practice. The macrocyclic agents, with the exception of Gd-DO3A-butrol, have slightly lower r1 values when compared with the 2 much less stable linear agents, Gd-DTPA-BMA and Gd-DTPA-BMEA. The 2 agents with hepatobiliary excretion, Gd-EOB-DTPA and Gd-BOPTA, have, at 1.5 and 3 T, substantially higher r1 values than all other agents.

High-signal intensity in the dentate nucleus and globus pallidus on unenhanced T1-weighted images: Evaluation of the macrocyclic gadolinium-based contrast agent gadobutrol

Abstract: ObjectiveThe aim of this study was to compare changes in the signal intensity (SI) ratio of the dentate nucleus (DN) to the pons, DN to cerebrospinal fluid (CSF), and globus pallidus (GP) to thalamus on unenhanced T1-weighted magnetic resonance imaging (MRI) scans after serial injections of the macr

Gadodiamide and Dentate Nucleus T1 Hyperintensity in Patients With Meningioma Evaluated by Multiple Follow-Up Contrast-Enhanced Magnetic Resonance Examinations With No Systemic Interval Therapy.

Abstract: The dentate nucleus of the cerebellum may appear as hyperintense on unenhanced T1 magnetic resonance images (MRIs) of the brain. Recently, T1 signal hyperintensity has received attention owing to data on the association of this finding with the history of multiple injections of gadolinium-based contrast agents, specifically gadodiamide, in patients with multiple sclerosis and brain metastases. We conducted a retrospective study on patients with a meningioma who had routinely undergone follow-up enhanced MRI scans with gadodiamide. Across a time interval of 18 months (from January 2013 to July 2014), we identified 102 consecutive patients eligible for this study. A significant increase in T1 hyperintensity of the dentate nuclei of the cerebellum on nonenhanced scans was observed between the first and the last MRI in the group of patients with a history of at least 6 enhanced MRI scans (P < 0.01), whereas no differences were observed in the group with 1 to 5 enhanced MRI scans (P = 0.74). Further research is necessary to shed light on the mechanism of the T1 hyperintensity as well as on the histological and microstructural appearance of the dentate nucleus after multiple intravenous injections of gadodiamide. The finding raises the question of substantial dechelation of this agent in patients with normal renal function.

Texture analysis as imaging biomarker of tumoral response to neoadjuvant chemoradiotherapy in rectal cancer patients studied with 3-T magnetic resonance.

Abstract: ObjectiveThe aim of this study was to determine whether texture features of rectal cancer on T2-weighted (T2w) magnetic resonance images can predict tumoral response in patients treated with neoadjuvant chemoradiotherapy (CRT).Materials and MethodsWe prospectively enrolled 15 consecutive patients (6

Quantitative Non-Gaussian Diffusion and Intravoxel Incoherent Motion Magnetic Resonance Imaging Differentiation of Malignant and Benign Breast Lesions

Abstract: ObjectivesThe purpose of this study was to explore the potential of non-Gaussian diffusion and perfusion magnetic resonance imaging (MRI) using intravoxel incoherent motion (IVIM) MRI for the diagnosis of breast lesions.Materials and MethodsThis study included 26 women with breast lesions. Diffusion

Increased Signal Intensity in the Dentate Nucleus on Unenhanced T1-Weighted Images After Gadobenate Dimeglumine Administration.

Abstract: ObjectivesThe aim of this study was to compare changes in signal intensity (SI) ratios of the dentate nucleus (DN) to pons and cerebrospinal fluid (CSF) on unenhanced T1-weighted magnetic resonance imaging (MRI) scans between the first and last MRI using the linear gadolinium-based contrast agent ga

Microstructural Characterization of Normal and Malignant Human Prostate Tissue With Vascular, Extracellular, and Restricted Diffusion for Cytometry in Tumours Magnetic Resonance Imaging

Abstract: OBJECTIVE: The aim of this study was to demonstrate the feasibility of the recently introduced Vascular, Extracellular, and Restricted Diffusion for Cytometry in Tumours (VERDICT) framework for imaging prostate cancer with diffusion-weighted magnetic resonance imaging (DW-MRI) within a clinical setting. MATERIALS AND METHODS: The VERDICT framework is a noninvasive microstructure imaging technique that combines an in-depth diffusion MRI acquisition with a mathematical model to estimate and map microstructural tissue parameters such as cell size and density and vascular perfusion. In total, 8 patients underwent 3-T MRI using 9 different b values (100-3000 s/mm). All patients were imaged before undergoing biopsy. Experiments with VERDICT analyzed DW-MRI data from patients with histologically confirmed prostate cancer in areas of cancerous and benign peripheral zone tissue. For comparison, we also fitted commonly used diffusion models such as the apparent diffusion coefficient (ADC), the intravoxel incoherent motion (IVIM), and the kurtosis model. We also investigated correlations of ADC and kurtosis with VERDICT parameters to gain some biophysical insight into the various parameter values. RESULTS: Eight patients had prostate cancer in the peripheral zone, with Gleason score 3 + 3 (n = 1), 3 + 4 (n = 6), and 4 + 3 (n = 1). The VERDICT model identified a significant increase in the intracellular and vascular volume fraction estimates in cancerous compared with benign peripheral zone, as well as a significant decrease in the volume of the extracellular-extravascular space (EES) (P = 0.05). This is in agreement with manual segmentation of the biopsies for prostate tissue component analysis, which found proliferation of epithelium, loss of surrounding stroma, and an increase in vasculature. The standard ADC and kurtosis parameters were also significantly different (P = 0.05) between tissue types. There was no significant difference in any of the IVIM parameters (P = 0.11 to 0.29). The VERDICT parametric maps from voxel-by-voxel fitting clearly differentiated cancer from benign regions. Kurtosis and ADC parameters correlated most strongly with VERDICT's intracellular volume fraction but also moderately with the EES and vascular fractions. CONCLUSIONS: The VERDICT model distinguished tumor from benign areas, while revealing differences in microstructure descriptors such as cellular, vascular, and EES fractions. The parameters of ADC and kurtosis models also discriminated between cancer and benign regions. However, VERDICT provides more specific information that disentangles the various microstructural features underlying the changes in ADC and kurtosis. These results highlight the clinical potential of the VERDICT framework and motivate the construction of a shorter, clinically viable imaging protocol to enable larger trials leading to widespread translation of the method.

Evolution in Computed Tomography: The Battle for Speed and Dose.

Abstract: The advent of computed tomography (CT) has revolutionized radiology. Starting as head-only scanners, modern CT systems are now capable of performing whole-body examinations within a couple of seconds in isotropic resolution. Technical advancements of scanner hardware and image reconstruction techniques are reviewed and discussed in their clinical context. These improvements have led to a steady increase of CT examinations in all age groups for a number of reasons. On the one hand, it is very easy today to obtain whole-body data for oncologic staging and follow-up or for trauma imaging. On the other hand, new examinations such as cardiac imaging, virtual colonoscopy, gout imaging, and whole-organ perfusion imaging have widened the application profile of CT. The increasing awareness of risks associated with radiation exposure triggered the development of a variety of dose reduction techniques. Effective dose values below 1 mSv, less than the annual natural background radiation (3.1 mSv/year on average in the United States), are now routinely possible for a number of dedicated examinations, even for coronary CT angiography.

The Importance of Spectral Separation: An Assessment of Dual-Energy Spectral Separation for Quantitative Ability and Dose Efficiency

Abstract: IntroductionOne method to acquire dual-energy (DE) computed tomography (CT) data is to perform CT scans at 2 different x-ray tube voltages, typically 80 and 140 kV, either as 2 separate scans, by means of rapid kV switching, or with the use of 2 x-ray sources as in dual-source CT (DSCT) systems. In

Multiparametric magnetic resonance imaging for predicting pathological response after the first cycle of neoadjuvant chemotherapy in breast cancer.

Abstract: Objectives To determine if combined measurements from dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) and diffusion weighted MRI (DW-MRI), obtained before and after the first cycle of neoadjuvant chemotherapy (NAC), are superior to single parameter measurements for predicting pathological complete response (pCR) in breast cancer patients.

Evaluation of Diffusion Kurtosis Imaging Versus Standard Diffusion Imaging for Detection and Grading of Peripheral Zone Prostate Cancer.

Abstract: OBJECTIVES The purpose of the study was to evaluate and validate diffusion kurtosis imaging (DKI) for detection grading of peripheral zone prostate cancer (PCa) compared with standard diffusion-weighted imaging (DWI) in a cohort of patients with biopsy-proven PCa. MATERIALS AND METHODS In this retrospective, single-institutional study, 55 patients (age, 67.5 ± 6.9 years; range, 52-84 years) who underwent multiparametric magnetic resonance imaging (MRI) before transperineal magnetic resonance/transrectal ultrasound-guided fusion biopsy were included. Suspicious lesions identified in multiparametric MRI underwent image-guided targeted biopsy procedure using a hybrid magnetic resonance/transrectal ultrasound-guided fusion biopsy system. Multiparametric MRI examinations were performed at 3.0 T using a 16-channel phased array coil. Diffusion kurtosis imaging has been acquired with 9 b values (0, 50, 250, 500, 750, 1000, 1250, 1500, and 2000 s/mm). In patients with histologically proven PCa, a representative tumor region was determined as region of interest (ROI) on axial T2-weighted images in consensus by 2 board-certified radiologists. For quantitative evaluation, ROIs located in malignant and contralateral tumor-free regions were transferred to diffusion-weighted images. Diffusion kurtosis imaging parameters (Dapp and Kapp) and apparent diffusion coefficient (ADC) values of the ROIs in tumor and contralateral remote areas were calculated. Estimation of the kurtosis-derived parameters was performed using a voxel-by-voxel fit followed by an ROI-based averaging and a second fit to ROI-averaged signal values. A subgroup analysis was performed to determine the influence of aggressiveness of PCa using ADC, Dapp, and Kapp. The receiver operating characteristic (ROC) curves were calculated for DKI parameters and ADC values. RESULTS In the 55 patients, the average prostate-specific antigen level was 12.4 ± 12.6 ng/mL (range, 2.7–75.0 ng/mL), and the median Gleason score was 7 (range, 6–10). Dapp (units, 10(-3) mm(2)/s) was significantly lower in tumor compared with control regions (1.48 ± 0.35 vs 2.00 ± 0.32, P < 0.05), and Kapp was significantly higher (1.01 ± 0.21 vs 0.76 ± 0.14, P < 0.05). Dapp was significantly higher than standard ADC (units, 10(-3) mm(2)/s) both in tumor regions and in controls (1.48 ± 0.35 vs 1.10 ± 0.25 and 2.00 ± 0.32 vs 1.43 ± 0.25, P < 0.05). Neither the ROI-based calculation of the kurtosis parameters nor the application of the noise correction significantly changed the DKI parameter estimation. There was no significant difference for the applied fitting method for DKI-derived parameters considering the differentiation between tumor and control tissue. Subsequent ROC analyses did not reveal a significant difference between DKI and ADC for detection of PCa. Sensitivities derived by Youden J statistics cutoff values ranged from 69% to 91% for DKI parameters; specificities ranged from 71% to 89%. Subgroup analysis for DKI (Dapp, Kapp) and ADC for assessing aggressiveness of PCa found significant difference (P < 0.05) for discrimination between high- and low-grade findings. However, no significant difference could be obtained between standard DWI- and DKI-derived parameters. CONCLUSIONS The results of this study demonstrated no significant benefit of DKI for detection and grading of PCa as compared with standard ADC in the peripheral zone determined from b values of 0 and 800 s/mm. For clinical routine application, ADC derived from monoexponential fitting of DWI data remains the standard for characterizing peripheral zone cancer of the prostate.

Quantitative apparent diffusion coefficient as a noninvasive imaging biomarker for the differentiation of invasive breast cancer and ductal carcinoma in situ.

Abstract: Objectives The objective of this study was to evaluate whether apparent diffusion coefficient (ADC) obtained through diffusion-weighted imaging magnetic resonance imaging at 3 T can be used as an imaging biomarker to differentiate invasive breast cancer from noninvasive ductal carcinoma in situ (DCIS). Materials and methods One hundred seventy-six histopathologically verified primary malignant breast tumors were retrospectively evaluated in 170 patients. All patients had undergone a standardized 3-T magnetic resonance imaging protocol, containing a diffusion-weighted sequence with 2 b values and a series of dynamic contrast-enhanced T1-weighted sequences. Apparent diffusion coefficient was measured manually by a reader blinded to the histopathological results. The ADC values were correlated with histopathological results. Mean ADC values were compared between invasive cancers and DCIS as well as between different tumor grades. Receiver operating characteristics curves were used to calculate diagnostic performance. Results There were 155 invasive cancers and 21 noninvasive DCIS. Mean (SD) values differed significantly between the invasive cancers (0.9 [0.15] ×10 mm/s) and the DCIS (1.24 [0.23] ×10 mm/s, P 0.05). Conclusions Apparent diffusion coefficient could be used as an imaging biomarker for the diagnosis of breast cancer. It seems to be a valuable noninvasive quantitative biomarker to assess breast cancer invasiveness. Thus, ADC measurements provide the potential to reduce overdiagnosis and subsequent overtreatment.

Very low-dose (0.15 mGy) chest CT protocols using the COPDGene 2 test object and a third-generation dual-source CT scanner with corresponding third-generation iterative reconstruction software.

Abstract: The new third-generation dual-source computed tomographic (CT) scanners and third-generation iterative reconstruction software enable substantial reductions in radiation dose to the patient.1 This is of great importance to the medical imaging community because the recent increase in the use of x-ray CT has greatly increased the amount of ionizing radiation received by populations in the United States and other countries around the world.2,3 The recently published National Lung Cancer Screening Trial study showed a 20% decrease in mortality from lung cancer with the use of screening CT scans of the thorax in patients at high risk for lung cancer.4–7 The use of CT for lung cancer screening will further increase the number of x-ray CT studies performed on the thorax. Reducing the CT radiation dose to the thorax would be of great benefit to patients enrolled in lung cancer screening programs. Computed tomography is also increasingly being used to establish quantitative phenotypes to subtype lung diseases such as COPD and asthma,8–15 and reducing the CT dose in these CT studies would also be beneficial. The medical imaging community has been trying to reduce the amount of ionizing radiation to the general population using a number of approaches. These include using medical imaging studies only when they are known to be beneficial to the patient, substituting nonionizing radiation studies such as ultrasound and magnetic resonance imaging for x-ray CT studies whenever possible, lowering the radiation dose of both radiographic and x-ray CT studies as much as possible while still maintaining adequate image quality and image noise levels, and, finally, encouraging CT manufacturers to pursue advanced technological solutions for reducing the radiation exposures necessary to provide diagnostic images of the thorax and other body parts. It is very important for quantitative CT scanning of the lung to maintain the accuracy of the CT attenuation values with acceptable levels of image noise. This is accomplished using carefully designed CT protocols.16 It is also important to monitor the performance of CT scanners that are used for obtaining quantitative measurements over time. This is typically achieved using CT test objects (CT phantoms) that are made up of nonbiologic materials that simulate different in vivo tissue CT densities such as soft tissue, water, lung tissue, and air. The COPDGene 1 test object in the COPDGene phase 1 multicenter National Institutes of Health study is one of the commonly used CT test objects that is used for CT quality control.17 This CT test object has been used in a number of National Institutes of Health and privately sponsored multicenter lung research studies that use quantitative CT to phenotype lung disease including COPDGene, multi-ethnic study of atherosclerosis, severe asthma research program, and subpopulations and intermediate outcome measures in COPD study. We have recently described18 the effects of reducing dose on CT attenuation values in the COPDGene 2 test object using a second-generation dual-source CT scanner, SOMATOM Definition FLASH, and second-generation iterative reconstruction software, SAFIRE.19 In that study, we showed that the COPDGene 2 test object can be used to assess the effects of decreasing dose on the mean attenuation values of the 8 materials in the COPDGene 2 test object using weighted filtered back projection (WFBP) and using the SAFIRE iterative reconstruction method. In this study, we have sought to evaluate the quantitative stability of measures derived from the COPDGene 2 test object while lowering imaging to ultralow doses, taking advantage of advances in third-generation dual-source CT technologies including third-generation iterative reconstruction methods.

Respiratory Motion-Resolved Compressed Sensing Reconstruction of Free-Breathing Radial Acquisition for Dynamic Liver Magnetic Resonance Imaging.

Abstract: OBJECTIVE This study aimed to demonstrate feasibility of free-breathing radial acquisition with respiratory motion-resolved compressed sensing reconstruction [extra-dimensional golden-angle radial sparse parallel imaging (XD-GRASP)] for multiphase dynamic gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced liver imaging, and to compare image quality to compressed sensing reconstruction with respiratory motion-averaging (GRASP) and prior conventional breath-held Cartesian-sampled data sets [BH volume interpolated breath-hold examination (VIBE)] in same patients. SUBJECTS AND METHODS In this Health Insurance Portability and Accountability Act-compliant prospective study, 16 subjects underwent free-breathing continuous radial acquisition during Gd-EOB-DTPA injection and had prior BH-VIBE available. Acquired data were reconstructed using motion-averaging GRASP approach in which consecutive 84 spokes were grouped in each contrast-enhanced phase for a temporal resolution of approximately 14 seconds. Additionally, respiratory motion-resolved reconstruction was performed from the same k-space data by sorting each contrast-enhanced phase into multiple respiratory motion states using compressed sensing algorithm named XD-GRASP, which exploits sparsity along both the contrast-enhancement and respiratory-state dimensions.Contrast-enhanced dynamic multiphase XD-GRASP, GRASP, and BH-VIBE images were anonymized, pooled together in a random order, and presented to 2 board-certified radiologists for independent evaluation of image quality, with higher score indicating more optimal examination. RESULTS The XD-GRASP reconstructions had significantly (all P < 0.05) higher overall image quality scores compared to GRASP for early arterial (reader 1: 4.3 ± 0.6 vs 3.31 ± 0.6; reader 2: 3.81 ± 0.8 vs 3.38 ± 0.9) and late arterial (reader 1: 4.5 ± 0.6 vs 3.63 ± 0.6; reader 2: 3.56 ± 0.5 vs 2.88 ± 0.7) phases of enhancement for both readers. The XD-GRASP also had higher overall image quality score in portal venous phase, which was significant for reader 1 (4.44 ± 0.5 vs 3.75 ± 0.8; P = 0.002). In addition, the XD-GRASP had higher overall image quality score compared to BH-VIBE for early (reader 1: 4.3 ± 0.6 vs 3.88 ± 0.6; reader 2: 3.81 ± 0.8 vs 3.50 ± 1.0) and late (reader 1: 4.5 ± 0.6 vs 3.44 ± 0.6; reader 2: 3.56 ± 0.5 vs 2.94 ± 0.9) arterial phases. CONCLUSION Free-breathing motion-resolved XD-GRASP reconstructions provide diagnostic high-quality multiphase images in patients undergoing Gd-EOB-DTPA-enhanced liver examination.

Commentary on T1-Weighted Hypersignal in the Deep Cerebellar Nuclei After Repeated Administrations of Gadolinium-Based Contrast Agents in Healthy Rats: Difference Between Linear and Macrocyclic Agents.

Abstract: I n this landmark article by Robert et al, an animal model is presented for the T1 signal hyperintensity in the deep cerebellar nuclei, including specifically the dentate nucleus, after intravenous administration of the linear gadolinium-based contrast agent gadodiamide (Omniscan) in normal renal function. This change was further demonstrated to correlate with higher gadolinium concentration in the brain, as determined by inductively coupled plasma mass spectrometry. No abnormality was noted after administration of a macrocyclic agent, gadoterate meglumine (Dotarem). The study provides a scientific basis for previous clinical observations, together with a platform for rigorous further investigation. In-depth study, using this model or similar models, of all of the approved gadolinium-based contrast agents (GBCAs) is warranted. Including the current research, there are 8 published articles to date examining this critical topic. The first two appeared in 2014, demonstrating in patients with normal renal function the progressive increase of T1 signal intensity of the dentate nucleus on unenhanced magnetic resonance (MR) images with increasing cumulative dose of gadodiamide. Subsequent clinical studies by the same 2 groups appeared in 2015, together with an additional publication from Germany, confirming the finding to be associated with prior gadodiamide administration, identifying that this also occurs with the linear GBCA gadopentetate dimeglumine (Magnevist) and demonstrating the lack of any abnormality in patients who had received themacrocyclic agent gadoteratemeglumine. Additional studies on tissue from deceased patients in 2015 identified gadolinium deposition in neuronal tissue (in patients with prior administration of gadodiamide or gadopentetate dimeglumine) and in the larger study in a dose-dependent relationship correlating with signal intensity changes on precontrast T1-weighted scans, without detectable levels in controls. Of critical importance is that this phenomenon is observed in the setting of relatively normal renal function. This topic and its evolution bring to mind that of nephrogenic systemic fibrosis (NSF). The initial article by Thomas Grobner in 2006 alerted the community to the correlation between NSF and administration of gadodiamide and was followed in 2007 by an article suggesting in vivo dechelation as the root cause. By 2008, it had been established that “the risk of NSF is unexpectedly and unacceptably high (18%) in patients with stage 5 chronic kidney disease (CKD5) exposed to gadodiamide”. In 2008 and 2009, research emerged using an animal model, confirming the correlation between disease development and chelate stability, with gadolinium deposition noted in tissues. These and other studies led to the current clinical guidelines, as reflected by the ninth version of the Contrast Media Guidelines from the Contrast Media Safety Committee of the European Society of Urogenital Radiology. In summary, gadodiamide (Omniscan), gadopentetate dimeglumine (Magnevist), and gadoversetamide (Optimark) are contraindicated in patients with CKD stages 4 and 5, acute renal failure, pregnant women, and neonates. Caution is suggested in patients with CKD stage 3 and in children younger than 1 year. Estimated glomerular filtration rate measurement and clinical assessment of patients before contrast administration are mandatory. These 3 agents are considered to have the highest risk of NSF (and the recommendations being specific to this group). In distinction, the 3 macrocyclic agents—gadobutrol (Gadovist, Gadavist), gadoterate meglumine (Dotarem), and gadoteridol (Prohance)—are considered to have the lowest risk of NSF. Stability in vivo of the gadolinium chelates is fundamental to the safety basis of this class of contrast media. This has been emphasized throughout the evolution of the field, indeed since the very first public presentation of results using a paramagnetic metal chelate. High thermodynamic and kinetic

Advanced virtual monoenergetic computed tomography of hyperattenuating and hypoattenuating liver lesions: ex-vivo and patient experience in various body sizes

Abstract: OBJECTIVE: To determine the value of advanced virtual monoenergetic images (mono+) from dual-energy computed tomography (CT) of hyperattenuating and hypoattenuating liver lesions in various phantom sizes and patients in comparison with standard monoenergetic images (mono). MATERIALS AND METHODS: Anthropomorphic phantoms simulating 4 patient sizes (S, 300 × 200 mm; M, 350 × 250 mm; L, 400 × 300 mm; and XL, 600 × 450 mm) with a liver insert containing both hyperattenuating and hypoattenuating iodine-containing lesions were imaged with dose-equivalent dual-energy (100/150 Sn kilovolt [peak] [kV{p}]) and single-energy (120 kV[p]) protocols on a 192-slice dual-source CT system. In addition, 4 patients with 3 hypoattenuating and 3 hyperattenuating hepatocellular carcinoma were included and underwent dual-energy CT imaging with the same scanner at similar kV(p) settings (100/150 Sn kV[p]). Images were reconstructed with standard mono and with the mono+ algorithm at 10-kiloelectron volt (keV) intervals from 40 to 190 keV. Attenuation of the liver and lesions were measured, and contrast-to-noise ratios (CNRs) were calculated. Lesion conspicuity was rated by 2 blinded independent readers in all mono and mono+ data sets from 40 to 190 keV using a 5-point Likert scale (1, lowest conspicuity; and 5, highest conspicuity). RESULTS: Attenuation in the liver and in both hyperattenuating and hypoattenuating lesions did not differ between mono and mono+ (P = 0.41-0.49). Noise on mono+ was significantly lower than on mono for all phantom sizes (P < 0.05) and was increasing with phantom size. Hyperattenuating lesion CNR was highest for mono+ images at 40 keV in the S phantom (6.73), with significantly higher CNR for mono+ than for mono and for single energy (120 kV[p]) in all phantom sizes (all P < 0.001) except for the XL phantom. Hypoattenuating lesion CNR was highest for high-keV mono+ being significantly higher than on mono and on single-energy (120 kV[p]) images (all P < 0.001), except for the XL phantom with significantly higher CNR for mono (1.3) compared with mono+ (0.47) and 120 kV(p) (1.26). In patients, CNR curves of hyperattenuating hepatocellular carcinoma were in accordance with the phantom data, whereas hypoattenuating lesions demonstrate varying curves, some being in accordance with findings in phantoms. Interreader agreement for lesion conspicuity was very good (intraclass correlation, 0.95), with higher conspicuity scores for mono+ than for mono and single energy (120 kV[p]) at all phantom sizes (all P < 0.05) and within patients. CONCLUSION: Our ex vivo and patient data demonstrate added value for imaging of both hyperattenuating and hypoattenuating liver lesions with advanced virtual monoenergetic dual-energy CT by decreased noise, increased CNR, and higher lesion conspicuity, although with limitations in XL body sizes.

In Vivo Dark-Field Radiography for Early Diagnosis and Staging of Pulmonary Emphysema

Abstract: The aim of this study was to evaluate the suitability of in vivo x-ray dark-field radiography for early-stage diagnosis of pulmonary emphysema in mice. Furthermore, we aimed to analyze how the dark-field signal correlates with morphological changes of lung architecture at distinct stages of emphysema.

Optimizing contrast media injection protocols in state-of-the art computed tomographic angiography.

Abstract: ObjectiveVery short acquisition times and the increasing use of low-kilovolt protocols in standard computed tomographic (CT) angiography (CTA) examinations demand modifications in the contrast media (CM) injection regimen. The aim of this study was to optimize the use of tube voltage–adjusted CM del

Ultrasound in Radiology: From Anatomic, Functional, Molecular Imaging to Drug Delivery and Image-Guided Therapy.

Abstract: During the past decade, ultrasound has expanded medical imaging well beyond the "traditional" radiology setting: a combination of portability, low cost, and ease of use makes ultrasound imaging an indispensable tool for radiologists as well as for other medical professionals who need to obtain imaging diagnosis or guide a therapeutic intervention quickly and efficiently. Ultrasound combines excellent ability for deep penetration into soft tissues with very good spatial resolution, with only a few exceptions (ie, those involving overlying bone or gas). Real-time imaging (up to hundreds and thousands of frames per second) enables guidance of therapeutic procedures and biopsies; characterization of the mechanical properties of the tissues greatly aids with the accuracy of the procedures. The ability of ultrasound to deposit energy locally brings about the potential for localized intervention encompassing the following: tissue ablation, enhancing penetration through the natural barriers to drug delivery in the body and triggering drug release from carrier microparticles and nanoparticles. The use of microbubble contrast agents brings the ability to monitor and quantify tissue perfusion, and microbubble targeting with ligand-decorated microbubbles brings the ability to obtain molecular biomarker information, that is, ultrasound molecular imaging. Overall, ultrasound has become the most widely used imaging modality in modern medicine; it will continue to grow and expand.

Multiparametric Magnetic Resonance Imaging in Prostate Cancer Management: Current Status and Future Perspectives.

Abstract: This article reviews recent and ongoing developments in multiparametric magnetic resonance imaging (mpMRI) of the prostate Advances in T2-weighted imaging, diffusion-weighted imaging, dynamic contrast-enhanced imaging, and spectroscopic imaging are described along with advances related to radiofrequency coils and imaging at high magnetic field As mpMRI is increasingly becoming routine in various aspects of clinical prostate cancer management, its role in detection, localization, staging, assessment of aggressiveness, and active surveillance is discussed Combined with growing clinical adoption of the techniques already at hand, continual optimization of acquisition techniques and image interpretation schemes will further strengthen the role of mpMRI as an important diagnostic test in prostate cancer management

Positron Emission Tomography/Magnetic Resonance Imaging for Local Tumor Staging in Patients With Primary Breast Cancer: A Comparison With Positron Emission Tomography/Computed Tomography and Magnetic Resonance Imaging.

Abstract: ObjectivesThis study aimed to assess the diagnostic performance of integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) of the breast for lesion detection and local tumor staging of patients with primary breast cancer in comparison to PET/computed tomography (CT) and MRI.Ma

Prognostic value of computed tomography texture features in non-small cell lung cancers treated with definitive concomitant chemoradiotherapy.

Abstract: ObjectivesThe aim of this study was to investigate whether the computed tomography (CT) texture features of primary tumors are associated with the overall survival (OS) of non–small cell lung cancer (NSCLC) patients undergoing definitive concomitant chemoradiotherapy (CCRT).Materials and MethodsIn t

Automated classification of usual interstitial pneumonia using regional volumetric texture analysis in high-resolution computed tomography.

Abstract: ObjectivesWe propose a novel computational approach for the automated classification of classic versus atypical usual interstitial pneumonia (UIP).Materials and MethodsThirty-three patients with UIP were enrolled in this study. They were classified as classic versus atypical UIP by a consensus of 2

Diffusion Tensor Imaging Adds Diagnostic Accuracy in Magnetic Resonance Neurography.

Abstract: OBJECTIVE The aim of this study was to determine whether quantitative diffusion tensor imaging (DTI) adds diagnostic accuracy in magnetic resonance neurography. MATERIALS AND METHODS This prospective study was approved by the institutional review board. We enrolled 16 patients with peripheral polyneuropathy of various etiologies involving the upper arm and 30 healthy controls. Magnetic resonance neurography was performed at 3 T using transverse T2-weighted (T2-w) turbo spin echo and spin echo planar imaging diffusion-weighted sequences. T2-weighted normalized signal (nT2), fractional anisotropy (FA), apparent diffusion coefficient (ADC), radial diffusivity (RD), and axial diffusivity (AD) of the median, ulnar, and radial nerves were quantified after manual segmentation. Diagnostic performance of each separate parameter and combinations of parameters was assessed using the area under the receiver operating characteristic curve (AUC). Bootstrap validation was used to adjust for potential overfitting. RESULTS Average nT2, ADC, RD, and AD values of the median, ulnar, and radial nerve were significantly increased in neuropathy patients compared with that in healthy controls (nT2, 1.49 ± 0.05 vs 1.05 ± 0.05; ADC, 1.4 × 10(-3) ± 2.8 × 10(-5) mm(2)/s vs 1.1 × 10(-3) ± 1.3 × 10(-5) mm(2)/s; RD, 9.5 × 10(-4) ± 2.9 × 10(-5) mm(2)/s vs 7.2 × 10(-4) ± 1.3 × 10(-5) mm(2)/s; AD, 2.3 × 10(-3) ± 3.7 × 10(-5) mm(2)/s vs 2.0 × 10(-3) ± 2.2 × 10(-5) mm(2)/s; P < 0.001 for all comparisons). Fractional anisotropy values were significantly decreased in patients (0.51 ± 0.01 vs 0.59 ± 0.01; P < 0.001). T2-weighted normalized signal and DTI parameters had comparable diagnostic accuracy (adjusted AUC: T2-w, 0.92; FA, 0.88; ADC, 0.89; AD, 0.84; RD, 0.86). Combining DTI parameters significantly improved the diagnostic accuracy over single-parameter analysis. In addition, the combination of nT2 with DTI parameters yielded excellent adjusted AUCs up to 0.97 (nT2 + FA). CONCLUSIONS Diffusion tensor imaging has high diagnostic accuracy in peripheral neuropathy. Combining DTI with T2 can outperform T2-w imaging alone and provides added value in magnetic resonance neurography.

Metal Artifact Reduction in Pelvic Computed Tomography With Hip Prostheses: Comparison of Virtual Monoenergetic Extrapolations From Dual-Energy Computed Tomography and an Iterative Metal Artifact Reduction Algorithm in a Phantom Study

Abstract: OBJECTIVE The aim of this study was to directly compare metal artifact reduction (MAR) of virtual monoenergetic extrapolations (VMEs) from dual-energy computed tomography (CT) with iterative MAR (iMAR) from single energy in pelvic CT with hip prostheses. MATERIALS AND METHODS A human pelvis phantom with unilateral or bilateral metal inserts of different material (steel and titanium) was scanned with third-generation dual-source CT using single (120 kVp) and dual-energy (100/150 kVp) at similar radiation dose (CT dose index, 7.15 mGy). Three image series for each phantom configuration were reconstructed: uncorrected, VME, and iMAR. Two independent, blinded radiologists assessed image quality quantitatively (noise and attenuation) and subjectively (5-point Likert scale). Intraclass correlation coefficients (ICCs) and Cohen κ were calculated to evaluate interreader agreements. Repeated measures analysis of variance and Friedman test were used to compare quantitative and qualitative image quality. Post hoc testing was performed using a corrected (Bonferroni) P < 0.017. RESULTS Agreements between readers were high for noise (all, ICC ≥ 0.975) and attenuation (all, ICC ≥ 0.986); agreements for qualitative assessment were good to perfect (all, κ ≥ 0.678). Compared with uncorrected images, VME showed significant noise reduction in the phantom with titanium only (P 0.017). Subjective image quality was rated significantly higher for images reconstructed with iMAR than for uncorrected images in all phantom configurations (all, P < 0.017). CONCLUSIONS Iterative MAR showed better MAR capabilities than VME in settings with bilateral hip prosthesis or unilateral steel prosthesis. In settings with unilateral hip prosthesis made of titanium, VME and iMAR performed similarly well.

Estimation of hepatic extracellular volume fraction using multiphasic liver computed tomography for hepatic fibrosis grading.

Abstract: OBJECTIVE The purpose of this study was to determine whether hepatic extracellular volume fractions (fECVs) measured using multiphasic liver computed tomography (CT) can be used to quantify the severity of hepatic fibrosis (HF). MATERIALS AND METHODS This retrospective study was approved by our institutional review board, and the requirement for informed consent was waived. A total of 141 patients (male-female ratio, 109:32; mean [SD] age, 59.4 [11.4] years) histologically diagnosed with HF (F0-F1 = 33 and F2-F4 = 108) underwent multiphasic liver CT. Absolute enhancements (in Hounsfield unit) of the liver parenchyma (Eliver) and aorta (Eaorta) 3 minutes after contrast administration were measured on subtraction images of precontrast and equilibrium phase scans using nonrigid registration software. The fECV was calculated using the following equation: fECV (%) = Eliver/Eaorta × (100 - Hematocrit [%]). Correlation between fECV and HF stage was evaluated using the Spearman correlation coefficient. The fECVs were compared between F0-F1 and ≥F2 as well as between child A and child B or C. Diagnostic performance of fECV in predicting significant HF (≥F2) was assessed using receiver operating curve analysis. RESULTS The fECVs showed a significant correlation with pathologic HF staging (r = 0.493, P < 0.001). The F2-F4 showed significantly higher fECVs than did F0 to F1 (33.6% [4.7%] vs 27.7% [4.4%]; P < 0.001). The fECVs were significantly higher in the patients with child B or C than those with child A (35.2% [7.0%] vs 31.3% [4.2%]; P < 0.001). The fECV values higher than 28.76% provided 87.5% sensitivity and 71.0% specificity in detecting significant HF (area under the curve, 0.832; P < 0.0001). CONCLUSIONS Because fECV was shown to increase along with HF progression, the estimation of fECV using routine multiphasic liver CT may have the potential to detect significant HF.

Persistent Pure Ground-Glass Nodules Larger Than 5 mm: Differentiation of Invasive Pulmonary Adenocarcinomas From Preinvasive Lesions or Minimally Invasive Adenocarcinomas Using Texture Analysis.

Abstract: ObjectiveTo evaluate the differentiating potentials of computed tomography texture analysis for invasive pulmonary adenocarcinomas (IPAs) from their preinvasive lesions or minimally invasive adenocarcinomas (MIAs) manifesting as persistent pure ground-glass nodules (PGGNs) larger than 5 mm.Materials

Correlation of Histological Vessel Characteristics and Diffusion-Weighted Imaging Intravoxel Incoherent Motion-Derived Parameters in Pancreatic Ductal Adenocarcinomas and Pancreatic Neuroendocrine Tumors.

Abstract: ObjectiveTo investigate the correlation between intravoxel incoherent motion (IVIM) model–derived parameters and histologically determined microvascularity in pancreatic ductal adenocarcinomas (PDACs) and pancreatic neuroendocrine tumors (PNETs).Materials and MethodsFrom April 2013 to May 2014, 42 p