Assessment of hepatic function employing hepatocyte specific contrast agent concentrations to multifactorially evaluate fibrotic remodeling.

Background: Diffuse parenchymal liver diseases are contributing substantially to global morbidity and represent major causes of deaths worldwide. The aim of our study is to assess whether established hepatic fat and iron quantitation and relaxometry-based quantification of hepatocyte-specific contrast material as surrogate for liver function estimation allows to evaluate liver fibrosis. Methods: Retrospective consecutive study. Seventy-two healthy patients (mean age: 53 years) without known liver disease, 21 patients with temporary elevated liver enzymes (mean: 65 years) and 109 patients with biopsy proven liver fibrosis or cirrhosis (mean: 61 years), who underwent liver magnetic resonance imaging (MRI) with a hepatocyte-specific contrast agent [gadoxetate disodium, gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA), 0.25 mmol/mL Primovist, Bayer AG, Leverkusen, Germany] at 1.5 T (n=133) and at 3 T (n=69), were included. Fibrosis was classified using the histopathological meta-analysis of histological data in viral hepatitis (METAVIR) and the clinical Child-Pugh scores. Gd-concentration were quantified using T1 map-based calculations. Gd-concentration mapping was performed by using a Look-Locker approach prior to and 912±159 s after intravenous administration of hepatocyte specific contrast agent. Additionally, parenchymal fat fraction, R2*, bilirubin, gender and age were defined as predicting factors. Diagnostic accuracy was calculated in a monoparametric (linear regression, predictor: Gd-concentration) and multiparametric model (predictors: age, bilirubin level, iron overload, liver fat fraction, Gd concentration in the left and right liver lobe). Results: Mean Gd-concentration in the liver parenchyma was significantly higher for healthy patients ([Gd] =0.51 µmol/L) than for those with liver fibrosis or cirrhosis ([Gd] =0.31 µmol/L; P<0.0001) and with acute liver disease ([Gd] =0.28 µmol/L), though there were no significant differences for the latter two groups. There was a significant moderate negative correlation for the mean Gd-concentration and the METAVIR score (ρ=-0.44, P<0.0001) as well as for the Child-Pugh stage (ρ=-0.35, P<0.0001). There was a significant strong correlation between the bilirubin concentration and the Gd-concentration (ρ=-0.61, P<0.0001). The diagnostic accuracy for the discrimination of healthy patients and patients with known fibrosis or cirrhosis was 0.74 (0.71/0.60 sensitivity/specificity) in a monoparametric and 0.76 (0.85/0.61 sensitivity/specificity) in a machine learning based multiparametric model. Conclusions: T1 mapping-based quantification of hepatic Gd-EOB-DTPA concentrations performed in a multiparametric model shows promising diagnostic accuracy for the detection of fibrotic changes. Liver biopsy might be replaced by imaging examinations.

Respiratory anomalies associated with gadoxetate disodium and gadoterate meglumine: compressed sensing MRI revealing physiologic phenomena during the entire injection cycle.

OBJECTIVES: The goal of this study was to investigate the precise timeline of respiratory events occurring after the administration of two gadolinium-based contrast agents, gadoxetate disodium and gadoterate meglumine. MATERIALS AND METHODS: This retrospective study examined 497 patients subject to hepatobiliary imaging using the GRASP MRI technique (TR/TE = 4/2 ms; ST = 2.5 mm; 384 × 384 mm). Imaging was performed after administration of gadoxetate (N = 338) and gadoterate (N = 159). All GRASP datasets were reconstructed using a temporal resolution of 1 s. Four regions-of-interest (ROIs) were placed in the liver dome, the right and left cardiac ventricle, and abdominal aorta detecting liver displacement and increasing vascular signal intensities over time. Changes in hepatic intensity reflected respiratory dynamics in temporal correlation to the vascular contrast bolus. RESULTS: In total, 216 (67%) and 41 (28%) patients presented with transient respiratory motion after administration of gadoxetate and gadoterate, respectively. The mean duration from start to acme of the respiratory episode was similar (p = 0.4) between gadoxetate (6.0 s) and gadoterate (5.6 s). Its mean onset in reference to contrast arrival in the right ventricle differed significantly (p < 0.001) between gadoxetate (15.3s) and gadoterate (1.8 s), analogously to peak inspiration timepoint in reference to the aortic enhancement arrival (gadoxetate: 0.9s after, gadoterate: 11.2 s before aortic enhancement, p < 0.001). CONCLUSIONS: The timepoint of occurrence of transient respiratory anomalies associated with gadoxetate disodium and gadoterate meglumine differs significantly between both contrast agents while the duration of the event remains similar. KEY POINTS: • Transient respiratory anomalies following the administration of gadoterate meglumine occurred during a time period usually not acquired in MR imaging. • Transient respiratory anomalies following the administration of gadoxetate disodium occurred around the initiation of arterial phase imaging. • The estimated duration of respiratory events was similar between both contrast agents.

Correction to: National survey on dose data analysis in computed tomography.

The original version of this article, published on 28 May 2018, unfortunately contained a mistake.

National survey on dose data analysis in computed tomography.

OBJECTIVES: A nationwide survey was performed assessing current practice of dose data analysis in computed tomography (CT). MATERIAL AND METHODS: All radiological departments in Switzerland were asked to participate in the on-line survey composed of 19 questions (16 multiple choice, 3 free text). It consisted of four sections: (1) general information on the department, (2) dose data analysis, (3) use of a dose management software (DMS) and (4) radiation protection activities. RESULTS: In total, 152 out of 241 Swiss radiological departments filled in the whole questionnaire (return rate, 63%). Seventy-nine per cent of the departments (n = 120/152) analyse dose data on a regular basis with considerable heterogeneity in the frequency (1-2 times per year, 45%, n = 54/120; every month, 35%, n = 42/120) and method of analysis. Manual analysis is carried out by 58% (n = 70/120) compared with 42% (n = 50/120) of departments using a DMS. Purchase of a DMS is planned by 43% (n = 30/70) of the departments with manual analysis. Real-time analysis of dose data is performed by 42% (n = 21/50) of the departments with a DMS; however, residents can access the DMS in clinical routine only in 20% (n = 10/50) of the departments. An interdisciplinary dose team, which among other things communicates dose data internally (63%, n = 76/120) and externally, is already implemented in 57% (n = 68/120) departments. CONCLUSION: Swiss radiological departments are committed to radiation safety. However, there is high heterogeneity among them regarding the frequency and method of dose data analysis as well as the use of DMS and radiation protection activities. KEY POINTS: • Swiss radiological departments are committed to and interest in radiation safety as proven by a 63% return rate of the survey. • Seventy-nine per cent of departments analyse dose data on a regular basis with differences in the frequency and method of analysis: 42% use a dose management software, while 58% currently perform manual dose data analysis. Of the latter, 43% plan to buy a dose management software. • Currently, only 25% of the departments add radiation exposure data to the final CT report.

Gain in signal-to-noise for first-pass contrast-enhanced abdominal MR angiography at 3 Tesla over standard 1.5 Tesla: prediction with a computer model.

RATIONALE AND OBJECTIVES: To estimate the gain in signal-to-noise ratio (SNR) in first-pass contrast-enhanced (CE) abdominal magnetic resonance angiography (MRA) at 3.0 T compared with 1.5 T. MATERIALS AND METHODS: Three protocols were simulated using six contrast agents: gadopentetate dimeglumine (Magnevist, Berlex, Wayne, NJ), gadoteridol (Prohance, Bracco, Princeton, NJ), gadobenate dimeglumine (Multihance, Bracco, Princeton, NJ), gadodiamide (Omniscan, Amersham Health, Princeton, NJ), gadoversetamide (Optimark, Mallinckrodt, St. Louis, MO), and gadofosveset trisodium (MS-325, EPIX Medical, Cambridge, MA). Contrast concentrations were calculated for five abdominal vessels. Based on these data, the gain in SNR during CE abdominal MRA at 3.0 T over 1.5 T was estimated. RESULTS: In these simulations, peak concentrations in all five target vessels were about 5 mM, 10 mM, and 0.7 mM for protocol 1, protocol 2, and protocol 3, respectively. A gain in SNR at 3 T over 1.5 T during CE abdominal MRA of at least 94% in all five target vessels could be achieved by applying protocol 1 or protocol 2, whereas protocol 3 provided a gain in SNR of 70%. CONCLUSIONS: Although five of the contrast agents studied fulfill the expectation of providing approximately twice the SNR at 3.0 T versus 1.5 T during CE abdominal MRA, MS-325 offers a gain in SNR of 70% only.