Extracellular Contrast Agent Research Articles

Magnetic Resonance Imaging for Colorectal Cancer Metastasis to the Liver: Comparative Effectiveness Research for the Choice of Contrast Agents.

PurposeThis study was conducted to compare the diagnostic performance and early recurrence rate between gadoxetic acid–enhanced magnetic resonance imaging (Gd-EOB-MRI) and magnetic resonance imaging (MRI) with extracellular contrast agent (ECA-MRI) for evaluating hepatic lesions in colorectal cancer.Materials and MethodsBetween 2005 and 2010, 418 colorectal cancer patients with both preoperative computed tomography (CT) and liver MRI were retrospectively reviewed. Image analysis was based on initial radiologic reports, and diagnostic performance was assessed based on the area under the receiver operating characteristic curve (AUROC). The early intrahepatic recurrence rate within 6 months was then evaluated.ResultsOverall, 291 and 127 patients underwent Gd-EOB-MRI and ECA-MRI, respectively. The AUROCs were not significantly different between Gd-EOB-MRI (0.990; 95% CI, 0.980 to 0.999) and ECA-MRI (0.985; 95% CI, 0.968 to 1.000; p=0.836). When compared with CT alone, ECA-MRI detected additional 21 lesions in 14 patients (14/127, 11.0%), whereas Gd-EOB-MRI detected 56 lesions in 33 patients (33/291, 11.3%) without a significant difference between two MRI groups (p=0.331). The early recurrence rate in the ECA-MRI (28.6%) was significantly higher than that in the Gd-EOB-MRI (11.6%) for patients who underwent hepatic resection (p=0.031).ConclusionGd-EOB-MRI is potentially better than ECA-MRI for decreasing the early intrahepatic recurrence rate, although the two MRI modalities showed comparable diagnostic performance in colorectal cancer patients.

Characterization of a Novel Hafnium-Based X-ray Contrast Agent.

Characterization of BAY-576, a new x-ray contrast agent which is not based on iodine, but rather on the heavy metal hafnium. Compared with iodine, hafnium provides better x-ray absorption in the energy range of computed tomography (CT) and allows images of comparable quality to be acquired at a significantly reduced radiation dose. A range of standard methods were used to explore the physicochemistry of BAY-576 as well as its tolerability in in vitro assays, its pharmacokinetics and toxicology in rats, and its performance in CT imaging in rabbits. BAY-576 is an extraordinarily stable chelate with a metal content of 42% (wt/wt) and with excellent water solubility. Formulations of 300 mg Hf/mL exhibited viscosity (3.3-3.6 mPa) and osmolality (860-985 mOsm/kg) in the range of nonionic x-ray agents. No relevant effects on erythrocytes, the coagulation, or complement system or on a panel of 87 potential biological targets were observed. The compound did not bind to plasma proteins of a number of species investigated. After intravenous injection in rats, it was excreted fast and mainly via the kidneys. Its pharmacokinetics was comparable to known extracellular contrast agents. A dose of 6000 mg Hf/kg, approximately 10 to 20 times the expected diagnostic dose, was well tolerated by rats with only moderate adverse effects. Computed tomography imaging in rabbits bearing a tumor in the liver demonstrated excellent image quality when compared with iopromide at the same contrast agent dose in angiography during the arterial phase. At 70% of the radiation dose, BAY-576 provided a contrast-to-noise ratio of the tumor, which was equivalent to iopromide at 100% radiation dose. The profile of BAY-576 indicates its potential as the first compound in a new class of noniodine x-ray contrast agents, which can contribute to the reduction of the radiation burden in contrast-enhanced CT imaging.

Пациенты с макроаденомами гипофиза: на что же они жалуются и кого посещают в первую очередь?

Aim: to evaluate the primary complaints of patients with pituitary macroadenomas and “first-referred” specialists for them. Material and Methods. 351 with pituitary macroadenomas (at least one size >10 mm) were examined: 144 non-functional adenomas (NFA), 65 macroprolactinomas, 142 somatotropinomas. A pituitary adenoma was considered as giant if at least one of the sizes was >40 mm. MRI with an impact study of the pituitary was performed on high field instrument Intera Achieva (PHILIPS company) 3.0 TL, with intravenous extracellular gadolinium contrast agents. Statistical analysis of the results was carried out using the IBM statistical program SPSS Statistics 20 for Windows 7.0 with variation statistics methods for nonparametric data. The data are expressed as Mе [25%, 75%]. Results. The patients’ age ranged from 20 to 80 years and were: NFA 60 [51; 66] y.o., prolactinomas 44 [35; 59] y.o. and somatotropinomas 57 [47; 66] y.o. (р<0.001). Pituitary tumour volumes were: NFA 5,526 [2,460; 11,774] mm3, prolactinomas 5,275 [1,408; 10,566]) mm3 and somatotropinomas 2,814 [1,226; 4,708] mm3 (р<0.001). First patients’ complaints were: NFA – headache (61.7%) and visual disorders (34.8%), prolactinomas – headache (36.8%) and menstrual disorders (27.3%), somatotropinomas – appearance change (31.1%) and headache (32.8%). There was no correlation found between headache and tumour volume however significant correlation was revealed between visual disorders and tumour volume as well as vertical and sagittal sizes of the tumour. The most often “first referred” specialists were: NFA – neurologist (43%) and ophthalmologist (20%), prolactinomas – gynecologist (36.4% of patients of reproductive age) and neurologist (31%); somatotropinomas – endocrinologist (28%) and therapist (25%). Among macroadenomas 32 giant tumors were found: 18 NFA (12.5% of all NFA group), 8 (12.3%) prolactinomas, 6 (4.2%) somatotropinomas. The median age of patients with giant macroadenomas were: NFA 54 [38; 68] y.o., prolactinomas 29 [25; 43] y.o. and somatotropinomas 34 [24; 46] y.o. Tumour volumes of giant adenomas were: NFA 28,190 [21,143; 44,896] mm3; prolactinomas 38,592 [15,994; 78,606] мм3; and somatotropinomas 51,209 [36,703; 102,207] mm3 (p<0.001). Main complaints for patient with giant pituitary tumours were visual impairment (60%, 18 patients – 11 patients with NFA, 4 prolactinomas and 3 somatotropinomas) and headache (44%, 14 patients – 8 patients with NFA, 5 prolactinomas and 1 patient with somatotropinoma). The most often “first referred” specialists were ophthalmologist (50%, 16 patients – 9 patients with NFA, 4 prolactinomas and 3 somatotropinomas) and neurologist (34.4%, 11 cases – 8 patients with NFA, 2 with prolactinomas and 1 with somatotropinoma). Conclusions. Headache and visual impairment were the most often complaints in our cohort of macroadenoma patients, however there were some discrepancies between groups of tumours with different hormonal activity. Neurologist and ophthalmologist should be aware of patients with pituitary macroadenomas, headache and visual disorders should be strong indications for pituitary MRI especially in patients younger than 50.

Patients with pituitary macroadenomas: what do they complain about and whom do they visit first?

Aim: to evaluate the primary complaints of patients with pituitary macroadenomas and “first-referred” specialists for them.Material and Methods. 351 with pituitary macroadenomas (at least one size &gt;10 mm) were examined: 144 non-functional adenomas (NFA), 65 macroprolactinomas, 142 somatotropinomas. A pituitary adenoma was considered as giant if at least one of the sizes was &gt;40 mm. MRI with an impact study of the pituitary was performed on high field instrument Intera Achieva (PHILIPS company) 3.0 TL, with intravenous extracellular gadolinium contrast agents. Statistical analysis of the results was carried out using the IBM statistical program SPSS Statistics 20 for Windows 7.0 with variation statistics methods for nonparametric data. The data are expressed as Mе [25%, 75%].Results. The patients’ age ranged from 20 to 80 years and were: NFA 60 [51; 66] y.o., prolactinomas 44 [35; 59] y.o. and somatotropinomas 57 [47; 66] y.o. (р&lt;0.001). Pituitary tumour volumes were: NFA 5,526 [2,460; 11,774] mm3, prolactinomas 5,275 [1,408; 10,566]) mm3 and somatotropinomas 2,814 [1,226; 4,708] mm3 (р&lt;0.001). First patients’ complaints were: NFA – headache (61.7%) and visual disorders (34.8%), prolactinomas – headache (36.8%) and menstrual disorders (27.3%), somatotropinomas – appearance change (31.1%) and headache (32.8%). There was no correlation found between headache and tumour volume however significant correlation was revealed between visual disorders and tumour volume as well as vertical and sagittal sizes of the tumour. The most often “first referred” specialists were: NFA – neurologist (43%) and ophthalmologist (20%), prolactinomas – gynecologist (36.4% of patients of reproductive age) and neurologist (31%); somatotropinomas – endocrinologist (28%) and therapist (25%). Among macroadenomas 32 giant tumors were found: 18 NFA (12.5% of all NFA group), 8 (12.3%) prolactinomas, 6 (4.2%) somatotropinomas. The median age of patients with giant macroadenomas were: NFA 54 [38; 68] y.o., prolactinomas 29 [25; 43] y.o. and somatotropinomas 34 [24; 46] y.o. Tumour volumes of giant adenomas were: NFA 28,190 [21,143; 44,896] mm3; prolactinomas 38,592 [15,994; 78,606] мм3; and somatotropinomas 51,209 [36,703; 102,207] mm3 (p&lt;0.001). Main complaints for patient with giant pituitary tumours were visual impairment (60%, 18 patients – 11 patients with NFA, 4 prolactinomas and 3 somatotropinomas) and headache (44%, 14 patients – 8 patients with NFA, 5 prolactinomas and 1 patient with somatotropinoma). The most often “first referred” specialists were ophthalmologist (50%, 16 patients – 9 patients with NFA, 4 prolactinomas and 3 somatotropinomas) and neurologist (34.4%, 11 cases – 8 patients with NFA, 2 with prolactinomas and 1 with somatotropinoma). Conclusions. Headache and visual impairment were the most often complaints in our cohort of macroadenoma patients, however there were some discrepancies between groups of tumours with different hormonal activity. Neurologist and ophthalmologist should be aware of patients with pituitary macroadenomas, headache and visual disorders should be strong indications for pituitary MRI especially in patients younger than 50.

Lower-limb magnetic resonance angiography: performance of extracellular contrast agents versus blood pool contrast agent for both dynamic and high spatial resolution imaging in extended phase

To prospectively compare the performance of extracellular space contrast agents (ECSCAs) versus a blood-pool contrast agent (BPCA) for a comprehensive lower-limb magnetic resonance angiography (MRA) protocol in patients with either claudication or critical ischaemia. Thirty patients with claudication underwent lower-limb magnetic resonance angiography (MRA) (dynamic crural, three-station bolus chase, and infra-inguinal high resolution) using a triphasic injection method with both a ECSCA and BPCA to allow intra-individual comparison, and 30 patients with critical ischaemia were scanned with either a ECSCA or BPCA. The dynamic, bolus chase, and high-resolution images were scored for quality on a Likert scale (from 1-5). Signal- and contrast-to-noise ratios were analysed and statistical analysis performed. Overall, there was no statistically significant difference between the ECSCAs and BPCA for arteriographic dynamic imaging, bolus chase MRA, or the high spatial resolution imaging. Venous image quality was rated higher quality for BPCA scans than for ECSCA images for calf veins (not significantly for thigh veins). Venous imaging signal intensity measures were higher for BPCA imaging. Extended-phase imaging using an ECSCA with this protocol provides arteriographic image quality equal to imaging with a BPCA. Venous depiction is good using ECSCAs with this approach, although better with BPCA.

Liver MR Imaging in Children: Current Concepts and Technique.

Magnetic resonance (MR) imaging is increasingly being used for comprehensive evaluation of liver diseases in children because of the lack of radiation and better lesion detection and characterization. Liver examination involves routine sequences such as T2-weighted, balanced steady-state free precession, and in-phase and out-of-phase sequences. Dynamic imaging is an essential component of liver examination to characterize focal lesions and involves capturing snapshots of the passage of contrast material in the arterial, portal venous, equilibrium, and sometimes hepatobiliary phases, generally by using T1-weighted three-dimensional gradient-echo sequences. Optimal arterial phase imaging is important for detection and characterization of hypervascular lesions. In the equilibrium phase, the concentration of contrast material is similar in the microvasculature and the extracellular interstitial space. Some superficial, spreading, inflammatory lesions are better seen on equilibrium phase images. Meticulous attention to intravenous access and use of an appropriate timing method are critical for successful dynamic imaging. Commonly used contrast media for liver imaging include gadolinium-based extracellular contrast agents and hepatobiliary contrast agents. A portion of hepatobiliary contrast agents such as gadoxetate and gadobenate is taken up by hepatocytes and excreted through bile. Hepatobiliary phase images acquired after hepatobiliary contrast agent administration are increasingly used to characterize liver lesions in children, such as focal nodular hyperplasia. Interpretation of liver MR images involves synthesis of information acquired from evaluation of background hepatic parenchyma, detection of lesions, and evaluation of signal intensity characteristics on images obtained with various sequences to arrive at a diagnosis or reasonable differential diagnoses. Understanding the appropriate technique, sequences, and contrast media when performing pediatric liver MR imaging is important for high diagnostic yield. (©)RSNA, 2016.

Combined blood pool and extracellular contrast agents for pediatric and young adult cardiovascular magnetic resonance imaging.

A comprehensive cardiac magnetic resonance (cardiac MR) study including both late gadolinium enhancement (LGE) and MR angiography may be indicated for patients with a history of acquired or congenital heart disease. To study the novel use of an extracellular agent for assessment of LGE combined with a blood pool contrast agent for detailed MR angiography evaluation to yield a comprehensive cardiac MR study in these patients. We reviewed clinical cardiac MR studies utilizing extracellular and blood pool contrast agents and noted demographics, clinical data and adverse events. We rated LGE image quality and MR angiography image quality for each vascular segment and calculated inter-rater variability. We also quantified contrast-to-noise ratio (CNR). Thirty-three patients (mean age 13.9 ± 3years) received an extracellular contrast agent (10 gadobenate dimeglumine, 23 gadopentetate dimeglumine) and blood pool contrast agent (33 gadofosveset trisodium). No adverse events were reported. MRI indications included Kawasaki disease (8), cardiomyopathy and coronary anatomy (15), repaired congenital heart disease (8), and other (2). Mean LGE quality was 2.6 ± 0.6 with 97% diagnostic imaging. LGE quality did not vary by type of contrast agent given (P = 0.07). Mean MR angiography quality score was 4.7 ± 0.6, with high inter-rater agreement (k = 0.6-0.8, P < 0.002). MR angiography quality did not vary by type of contrast agent used (P = 0.6). Cardiac MR studies utilizing both extracellular and blood pool contrast agents are feasible and safe and provide excellent-quality LGE and MR angiography images. The use of two contrast agents allows for a comprehensive assessment of both myocardial viability and vascular anatomy during the same exam.

Diagnostic criteria for hepatocellular carcinoma ⩽3 cm with hepatocyte-specific contrast-enhanced magnetic resonance imaging

Current diagnostic imaging criteria for hepatocellular carcinoma (HCC) are dedicated to imaging with nonspecific extracellular contrast agents. This study aimed to evaluate diagnostic criteria for HCC ⩽3 cm on magnetic resonance imaging (MRI) with a hepatocyte-specific contrast agent through an inception cohort study. Of 291 patients with chronic liver disease and new nodules of 1-3 cm in diameter at surveillance ultrasonography, 295 solid nodules (194 HCCs, 98 benign nodules, and three other malignancies) in 198 patients with a confirmed final diagnosis or ⩾24 months follow-up were evaluated on gadoxetic acid-enhanced MRI. Through univariate and multivariate logistic regression analyses, various diagnostic criteria were developed by combining significant MRI findings for diagnosing HCC. The diagnostic performance of each criterion was compared with that of the European Association for the Study of the Liver (EASL) criteria. Four MRI findings (arterial-phase hyperintensity, transitional-phase hypointensity, hepatobiliary-phase hypointensity, and rim enhancement) were independently significant for diagnosis of HCC ⩽3 cm. For whole nodules, EASL criteria showed the best performance for diagnosing HCC (sensitivity, 83.5%; specificity, 81.2%). For nodules ⩽2 cm in diameter, a new criterion (arterial-phase hyperintensity and hepatobiliary-phase hypointensity) showed a significantly higher sensitivity than that of the EASL criteria (83.0% vs. 74.5%, p=0.008), without a significantly different specificity (76.7% vs. 81.1%, p=0.125). EASL criteria exhibit the best diagnostic performance for HCC ⩽3 cm on hepatocyte-specific contrast-enhanced MRI. A newly identified criterion (arterial-phase hyperintensity and hepatobiliary-phase hypointensity) may increase the diagnostic sensitivity of small (⩽2 cm) HCC.

Is there an added value of a hepatobiliary phase with gadoxetate disodium following conventional MRI with an extracellular gadolinium agent in a single imaging session for detection of primary hepatic malignancies?

To determine added value of hepatobiliary phase (HBP) using gadoxetate disodium compared to MRI with extracellular gadolinium-based contrast agent (GBCA) for detection of primary hepatic malignancies in a single imaging session. IRB approved this HIPAA compliant retrospective study. Within 90days of resection or liver transplant, thirty patients underwent MRI with extracellular GBCA followed by separate injection of gadoxetate for HBP. Two sets of images were reviewed: Set #1-unenhanced and enhanced images with an extracellular GBCA and set #2-with addition of HBP. Data were analyzed in two groups, cases with hepatocellular carcinoma (HCC) only and cases with either HCC and/or cholangiocarcinoma. Observer diagnostic accuracy (Az), sensitivity, and specificity were calculated. 14/30 subjects had HCC (46%, CI 28-66%), 2/30 (2%, CI 1-22%) cholangiocarcinoma, and 14/30 (46%, CI 28-66%) no malignancy. There was no significant change in A z value with addition of gadoxetate in the detection of HCC (range 0.84-0.97 set #1 and 0.85-0.97 set #2, p>0.05). Sensitivity and specificity showed no significant differences (p>0.05) between the image sets for all readers. When stratified by lesion size, there was no significant difference in accuracy, sensitivity, or specificity for any reader (p>0.05). When compared to extracellular GBCA, gadoxetate HBP imaging does not result in a significant difference in accuracy or sensitivity in diagnosis of HCC or cholangiocarcinoma and may result in a decrease in specificity.

Optimal visualization of focal nodular hyperplasia: quantitative and qualitative evaluation of single and multiphasic arterial phase acquisition at 1.5T MR imaging.

To evaluate the qualitative and quantitative benefit of multiple arterial phase acquisitions for the depiction of hypervascularity in FNH explored MR imaging using an extracellular contrast agent. Between 2007 and 2014, all patients who underwent MR imaging for the exploration of FNH were included. The protocol included a single or a triple arterial phase ("single" and "triple" group, respectively). Arterial phases were visually divided into four types: (1) angiographic, (2) early, (3) late, and (4) portal. Signal intensity on arterial phase images was visually recorded as intense, moderate, or low for each lesion. Lesion-to-liver contrast (LLC) and relative lesion enhancement (RE) were calculated and compared between the two groups using the Mann-Whitney test. Thirty-five women were included (mean 45-year old, range 20-66), with 50 FNH (mean size 30mm). Single and triple groups included 20 patients (30 FNH) and 15 patients (20 FNH), respectively. Signal intensity was intense in all lesions in the triple group and in 22/30 (73%) in the single group (p=0.041). Intense signals were more frequently found in the early arterial phase (p<0.001). RE was not significantly different (1.78±0.84 vs. 1.98±1.81 p=0.430, in the single and triple groups, respectively) but LLC was significantly higher in the triple group (0.32±0.10 vs. 0.22±0.10, p=0.005). LLC was significantly higher in the first two arterial phases in the triple group (p<0.001). Acquisition of three arterial phases improves the visualization of hypervascularity of FNH, as lesions show high visual signal intensity and contrast. Optimal visualization is obtained in the early arterial phase.

The effects of extracellular contrast agent (Gadobutrol) on the precision and reproducibility of cardiovascular magnetic resonance feature tracking.

BackgroundToday feature tracking (FT) is considered to be a robust assessment tool in cardiovascular magnetic resonance (CMR) for strain assessment. The FT algorithm is dependent on a high contrast between blood pool and myocardium. Extracellular contrast agents decrease blood-myocardial contrast in SSFP images and thus might affect FT results. However, in a routine CMR scan, SSFP-cine images including short axis views are partly acquired after contrast agent injection. The aim of this study was to investigate the effect of extracellular contrast agent (Gadobutrol) (CA) on the precision and reproducibility of the feature tracking algorithm.MethodsA total of 40 patient volunteers (mean age 51.2 ± 19 years; mean LVEF 61 ± 9 %) were scanned in supine position on a clinical 1.5 T MR scanner (Philips Ingenia). SSFP-cine images in midventricular short axis view (SA) as well as horizontal long axis view (HLA) were acquired before and 10–15 min after injection of a double dose Gadobutrol. FT derived systolic circumferential and longitudinal strain parameters were then calculated for pre- and post-contrast images.ResultsFT derived midventricular peak systolic circumferential strain (PSCS) (-24.8 ± 6.4 % vs. -20.4 ± 6.3 %), apical PSCS (-28.67 ± 6.5 % vs. -24.06 ± 8.5 %), basal PSCS (-24.42 % ± 6.5 vs. -20.68 ± 7.1 %), peak systolic longitudinal strain (-19.57 ± 3.3 % vs. -17.24 ± 4.1 %), midventricular epicardial PSCS (-9.84 ± 3.4 % vs. -8.13 ± 3.4 %) , midventricular PSCS-rate (-1.52 ± 0.4 vs. -1.28 ± 0.5) and peak diastolic circumferential strain rate (1.4 ± 0.5 vs. 1.05 ± 0.5) were significantly reduced after CA application. Post CA strain assessment showed higher intra- and interobserver variability. Pre-CA: intraobserver: mean 0.21, Limits of agreement (LoA) -2.8 and 3.2; interobserver: mean 0.64, LoA -2.8 and 4.1. Post-CA: intraobserver: mean -0.11, LoA -5.1 to 4.9; interobserver: mean 4.93 LoA 2.4 to 12.2.ConclusionThe FT algorithm is dependent on a high contrast between blood and myocardium. Post CA strain results are significantly lower and less reproducible than pre-CA strain results.

An enzyme-activatable and cell-permeable MnIII-porphyrin as a highly efficient T1 MRI contrast agent for cell labeling.

Magnetic resonance imaging (MRI) is a preferred technique for noninvasively monitoring the fate of implanted cells, such as stem cells and immune cells in vivo. Cellular MRI requires contrast agents (CAs) to label the cells of interest. Despite promising progress made in this emerging field, highly sensitive, stable and biocompatible T1 CAs with high cell permeability and specificity remains an unmet challenge. To address this need, a novel MnIII-porphyrin, MnAMP was designed and synthesized based on the modification of MnIIItetra(carboxy-porphyrin) (MnTCP), a small and highly stable non-Gd extracellular CA with good biocompatibility and high T1 relaxivity (r1 = 7.9 mM-1 s-1) at clinical field of 3 Tesla (T). Cell permeability was achieved by masking the polar carboxylates of MnTCP with acetoxymethyl-ester (AM) groups, which are susceptible to hydrolysis by intracellular esterases. The enzymatic cleavage of AM groups led to disaggregation of the hydrophobic MnAMP, releasing activated MnTCP with significant increase in T1 relaxivity. Cell uptake of MnAMP is highly efficient as tested on two non-phagocytic human cell lines with no side effects observed on cell viability. MRI of labeled cells exhibited significant contrast enhancement with a short T1 of 161 ms at 3 T, even though a relatively low concentration of MnAMP and short incubation time was applied for cell labeling. Overall, MnAMP is among the most efficient T1 cell labeling agents developed for cellular MRI.

Contrast Enhanced MRI in the Diagnosis of HCC.

Hepatocellular carcinoma (HCC) is the 6th most common cancer worldwide. Imaging plays a critical role in HCC screening and diagnosis. Initial screening of patients at risk for HCC is performed with ultrasound. Confirmation of HCC can then be obtained by Computed Tomography (CT) or Magnetic Resonance Imaging (MRI), due to the relatively high specificity of both techniques. This article will focus on reviewing MRI techniques for imaging HCC, felt by many to be the exam of choice for HCC diagnosis. MRI relies heavily upon the use of gadolinium-based contrast agents and while primarily extracellular gadolinium-based contrast agents are used, there is an emerging role of hepatobiliary contrast agents in HCC imaging. The use of other non-contrast enhanced MRI techniques for assessing HCC will also be discussed and these MRI strategies will be reviewed in the context of the pathophysiology of HCC to help understand the MR imaging appearance of HCC.

Evaluation of a Gadolinium-Based Nanoparticle (AGuIX) for Contrast-Enhanced MRI of the Liver in a Rat Model of Hepatic Colorectal Cancer Metastases at 9.4 Tesla.

The aim of this study was to compare a Gd-based nanoparticle (AGuIX) with a standard extracellular Gd-based contrast agent (Gd-DOTA) for MRI at 9.4 T in rats with hepatic colorectal cancer metastases. 12 rats with hepatic metastases were subjected to MRI using a 9.4 T animal scanner. T1w self-gated FLASH sequences (TR/TE = 45/2.5 ms, alpha = 45°, TA = 1: 23 min, FOV = 5.12 × 5.12 cm(2), matrix = 256 × 256) were acquired before and at 10 time points after contrast injection. Each animal received 0.1 mmol/kg BW Gd-DOTA i.v. 2 days later AGuIX was applied at 0.01 mmol/kg BW (representing equal Gd doses). The SNR of normal liver (SNRliver), hyper- and hypoenhancing parts of tumors (SNRtumor, hyperenh/SNRtumor, hypoenhanc), erector spinae muscle (SNRmuscle), CNR and lesion enhancement (LE) were calculated based on ROI measurements. Mean SNRliver (Gd-DOTA: 14.6 +/- 0.7; AGuIX: 28.2+/- 2.6, p < 0.001), SNRtumor, hyperenhanc (Gd-DOTA: 18.6 +/- 1.2; AGuIX: 29.6 +/- 2.8, p < 0.001), SNRtumor, hypoenhanc (Gd-DOTA: 12.0 +/- 0.7; AGuIX: 15.4 +/- 0.7, p < 0.001), SNRmuscle (Gd-DOTA: 12.3 +/- 0.3; AGuIX: 14.0 +/- 0.7, p < 0.001), mean CNR (Gd-DOTA: -2.5 +/- 0.2; AGuIX: -7.5 +/- 1.0, p < 0.001) and LE (Gd-DOTA: 3.8 +/- 0.7; AGuIX: 14.9 +/- 2.8, p = 0.001) were significantly higher using AGuIX. Regardless of the larger molecular size, AGuIX demonstrates an early peak enhancement followed by a continuous washout. AGuIX provides better enhancement at 9.4 T compared to Gd-DOTA for equal doses of applied Gd. This is based on the molecule structure and the subsequent increased interaction with protons leading to a higher relaxivity. AGuIX potentially ameliorates the conspicuity of focal liver lesions and may improve the sensitivity in diagnostic imaging of malignant hepatic tumors. AGuIX provides superior enhancement as compared to the extracellular compound Gd-DOTA at 9.4 T. AGuIX may improve the detection and diagnostic sensitivity of malignant focal liver lesions. The small size of AGuIX allows for fast renal clearance and prevents undesirable accumulation in the body.

Application of Extracellular Gadolinium-based MRI Contrast Agents and the Risk of Nephrogenic Systemic Fibrosis

Application of Extracellular Gadolinium-based MRI Contrast Agents and the Risk of Nephrogenic Systemic Fibrosis

Assessment of MRI Contrast Agent Kinetics via Retro-Orbital Injection in Mice: Comparison with Tail Vein Injection

It is not known whether administration of contrast agent via retro-orbital injection or the tail vein route affects the efficiency of dynamic contrast-enhanced magnetic resonance imaging (MRI). Therefore, we compared the effects of retro-orbital and tail vein injection on the kinetics of the contrast agent used for MRI in mice. The same group of nine healthy female mice received contrast agent via either route. An extracellular contrast agent was infused via the tail vein and retro-orbital vein, in random order. Dynamic contrast-enhanced MRI was performed before and after administering the contrast agent. The contrast effects in the liver, kidney, lung, and myocardium were assessed. The average total times of venous puncture and mounting of the injection system were about 10 and 4 min for the tail vein and retro-orbital route, respectively. For all organs assessed, the maximum contrast ratio occurred 30 s after administration and the time course of the contrast ratio was similar with either routes. For each organ, the contrast ratios correlated strongly; the contrast ratios were similar. The retro-orbital and tail vein routes afforded similar results in terms of the kinetics of the contrast agent. The retro-orbital route can be used as a simple efficient alternative to tail vein injection for dynamic contrast-enhanced MRI of mice.

Magnetic resonance imaging of the chest in the evaluation of cancer patients: state of the art.

Recent studies have demonstrated that the use of paramagnetic hepatobiliary contrast agents in the acquisition of magnetic resonance images remarkably improves the detection and differentiation of focal liver lesions, as compared with extracellular contrast agents. Paramagnetic hepatobiliary contrast agents initially show the perfusion of the lesions, as do extracellular agents, but delayed contrast-enhanced images can demonstrate contrast uptake by functional hepatocytes, providing further information for a better characterization of the lesions. Additionally, this intrinsic characteristic increases the accuracy in the detection of hepatocellular carcinomas and metastases, particularly the small-sized ones. Recently, a hepatobiliary contrast agent called gadolinium ethoxybenzyl dimeglumine, that is simply known as gadoxetic acid, was approved by the National Health Surveillance Agency for use in humans. The authors present a literature review and a practical approach of magnetic resonance imaging utilizing gadoxetic acid as contrast agent, based on patients' images acquired during their initial experiment.

Troubleshooting Arterial-Phase MR Images of Gadoxetate Disodium-Enhanced Liver.

Gadoxetate disodium is a widely used magnetic resonance (MR) contrast agent for liver MR imaging, and it provides both dynamic and hepatobiliary phase images. However, acquiring optimal arterial phase images at liver MR using gadoxetate disodium is more challenging than using conventional extracellular MR contrast agent because of the small volume administered, the gadolinium content of the agent, and the common occurrence of transient severe motion. In this article, we identify the challenges in obtaining high-quality arterial-phase images of gadoxetate disodium-enhanced liver MR imaging and present strategies for optimizing arterial-phase imaging based on the thorough review of recent research in this field.

Blood Pool Contrast-enhanced Magnetic Resonance Angiography with Correlation to Digital Subtraction Angiography: A Pictorial Review.

Magnetic resonance angiography (MRA) provides noninvasive visualization of the vascular supply of soft tissue masses and vascular pathology, without harmful radiation. This is important for planning an endovascular intervention, and helps to evaluate the efficiency and effectiveness of the treatment. MRA with conventional extracellular contrast agents relies on accurate contrast bolus timing, limiting the imaging window to first-pass arterial phase. The recently introduced blood pool contrast agent (BPCA), gadofosveset trisodium, reversibly binds to human serum albumin, resulting in increased T1 relaxivity and prolonged intravascular retention time, permitting both first-pass and steady-state phase high-resolution imaging. In our practice, high-quality MRA serves as a detailed “roadmap” for the needed endovascular intervention. Cases of aortoiliac occlusive disease, inferior vena cava thrombus, pelvic congestion syndrome, and lower extremity arteriovenous malformation are discussed in this article. MRA was acquired at 1.5 T with an 8-channel phased array coil after intravenous administration of gadofosveset (0.03 mmol/kg body weight), at the first-pass phase. In the steady-state, serial T1-weighted 3D spoiled gradient echo images were obtained with high resolution. All patients underwent digital subtraction angiography (DSA) and endovascular treatment. MRA and DSA findings of vascular anatomy and pathology are discussed and correlated. BPCA-enhanced MRA provides high-quality first-pass and steady-state vascular imaging. This could increase the diagnostic accuracy and create a detailed map for pre-intervention planning. Understanding the pharmacokinetics of BPCA and being familiar with the indications and technique of MRA are important for diagnosis and endovascular intervention.

CT and MR imaging diagnosis and staging of hepatocellular carcinoma: part II. Extracellular agents, hepatobiliary agents, and ancillary imaging features.

Computed tomography (CT) and magnetic resonance (MR) imaging play critical roles in the diagnosis and staging of hepatocellular carcinoma (HCC). The second article of this two-part review discusses basic concepts of diagnosis and staging, reviews the diagnostic performance of CT and MR imaging with extracellular contrast agents and of MR imaging with hepatobiliary contrast agents, and examines in depth the major and ancillary imaging features used in the diagnosis and characterization of HCC.