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

Brain Irradiation and Gadobutrol Administration in Pediatric Patients with Brain Tumors: Effect on MRI Brain Signal Intensity

Purpose To determine whether treatment affects MRI signal intensity in pediatric patients with primary brain tumors independent of the administration of macrocyclic gadolinium-based contrast agents (GBCAs). Materials and Methods This retrospective, single-center study included 78 patients (mean age, 7.7 years ± 5.4) with primary brain tumors who underwent macrocyclic GBCA-enhanced MRI from 2015 to 2018. Three groups were compared: (a) patients who had undergone radiation therapy (37 patients, 26 of whom had undergone concurrent chemotherapy), (b) patients who had undergone chemotherapy only (17 patients), and (c) patients who had received no treatment ("no-treatment group," 24 patients). The signal intensity in the globus pallidus (GP), thalamus, dentate nucleus (DN), and pons was measured on unenhanced T1-weighted images. GP-to-thalamus and DN-to-pons signal intensity ratios were compared among groups with analysis of variance by using the Kruskal-Wallis test, followed by post hoc pairwise tests with Tukey adjustment, and were analyzed relative to group, total cumulative doses of GBCA, age, and sex with multivariable linear models. Results The mean number of GBCA-enhanced MRI examinations in the radiation therapy, chemotherapy-only, and no-treatment groups was 7.11, 7.29, and 4.96, respectively (P < .01 for the radiation therapy and chemotherapy groups compared with the no-treatment group). The DN-to-pons ratio in the radiation therapy group was higher than that in both the no-treatment group and the chemotherapy-only group (P < .01 for both). There was no significant difference in the DN-to-pons ratios between the chemotherapy-only group and the no-treatment group (P = .99). The GP-to-thalamus ratios did not differ among all three groups (P = .09). There was no dose-dependent effect of GBCA on the DN-to-pons and GP-to-thalamus ratios when adjusting for the effects of treatment (P = .21 and P = .38, respectively). Conclusion Brain irradiation contributes to a higher dentate nucleus signal intensity in pediatric patients with brain tumor independent of the administration of macrocyclic gadolinium-based contrast agents. © RSNA, 2018.

Vascular CT and MRI: a practical guide to imaging protocols

Non-invasive cross-sectional imaging techniques play a crucial role in the assessment of the varied manifestations of vascular disease. Vascular imaging encompasses a wide variety of pathology. Designing vascular imaging protocols can be challenging owing to the non-uniform velocity of blood in the aorta, differences in cardiac output between patients, and the effect of different disease states on blood flow. In this review, we provide the rationale behind—and a practical guide to—designing and implementing straightforward vascular computed tomography (CT) and magnetic resonance imaging (MRI) protocols.

Teaching Points

• There is a wide range of vascular pathologies requiring bespoke imaging protocols.

• Variations in cardiac output and non-uniform blood velocity complicate vascular imaging.

• Contrast media dose, injection rate and duration affect arterial enhancement in CTA.

• Iterative CT reconstruction can improve image quality and reduce radiation dose.

• MRA is of particular value when imaging small arteries and venous studies.

Gadolinium-Based Contrast Agent-Related Toxicities

In recent years, gadolinium-based contrast agents have been associated with different types of toxicity. In particular, nephrogenic systemic fibrosis, a progressive sclerotic-myxedematous systemic disease of unknown etiology, is related to gadolinium-based contrast agent administration in patients with kidney dysfunction. More recently, evidence of magnetic resonance signal intensity changes on pre-contrast T1-weighted images after multiple gadolinium-based contrast agent administrations resulted in the hypothesis of gadolinium brain accumulation in patients with normal renal function, subsequently confirmed in pathological samples. However, there is limited current data and further investigations are necessary before drawing definite conclusions on the clinical consequences of gadolinium-based contrast agent accumulation in human tissues and particularly in the brain. Gadolinium-based contrast agent-related toxicity appears connected to molecular stability, which varies together with the pharmacokinetic properties of the compound and depends on the individual characteristics of the subject. During a lifetime, the physiological changes occurring in the human body may influence its interaction with gadolinium-based contrast agents: the integrity and developmental stage of the organs has an effect on the dynamics of gadolinium-based contrast agent distribution and excretion, thus leading to different possible mechanisms of deposition and toxicity. Therefore, the aim of this work is to discuss the pharmacokinetics and pharmacodynamics of gadolinium-based contrast agents, with a special focus on the brain, and to explore potential predominant gadolinium-based contrast agent-related toxicity in two cornerstone periods of the human life cycle: fetal/neonatal and adulthood/aged.

Deep learning enables reduced gadolinium dose for contrast-enhanced brain MRI

BACKGROUND

There are concerns over gadolinium deposition from gadolinium-based contrast agents (GBCA) administration.

PURPOSE

To reduce gadolinium dose in contrast-enhanced brain MRI using a deep learning method.

STUDY TYPE

Retrospective, crossover.

POPULATION

Sixty patients receiving clinically indicated contrast-enhanced brain MRI.

SEQUENCE

3D T₁ -weighted inversion-recovery prepped fast-spoiled-gradient-echo (IR-FSPGR) imaging was acquired at both 1.5T and 3T. In 60 brain MRI exams, the IR-FSPGR sequence was obtained under three conditions: precontrast, postcontrast images with 10% low-dose (0.01mmol/kg) and 100% full-dose (0.1 mmol/kg) of gadobenate dimeglumine. We trained a deep learning model using the first 10 cases (with mixed indications) to approximate full-dose images from the precontrast and low-dose images. Synthesized full-dose images were created using the trained model in two test sets: 20 patients with mixed indications and 30 patients with glioma.

ASSESSMENT

For both test sets, low-dose, true full-dose, and the synthesized full-dose postcontrast image sets were compared quantitatively using peak-signal-to-noise-ratios (PSNR) and structural-similarity-index (SSIM). For the test set comprised of 20 patients with mixed indications, two neuroradiologists scored blindly and independently for the three postcontrast image sets, evaluating image quality, motion-artifact suppression, and contrast enhancement compared with precontrast images.

STATISTICAL ANALYSIS

Results were assessed using paired t-tests and noninferiority tests.

RESULTS

The proposed deep learning method yielded significant (n = 50, P < 0.001) improvements over the low-dose images (>5 dB PSNR gains and >11.0% SSIM). Ratings on image quality (n = 20, P = 0.003) and contrast enhancement (n = 20, P < 0.001) were significantly increased. Compared to true full-dose images, the synthesized full-dose images have a slight but not significant reduction in image quality (n = 20, P = 0.083) and contrast enhancement (n = 20, P = 0.068). Slightly better (n = 20, P = 0.039) motion-artifact suppression was noted in the synthesized images. The noninferiority test rejects the inferiority of the synthesized to true full-dose images for image quality (95% CI: -14-9%), artifacts suppression (95% CI: -5-20%), and contrast enhancement (95% CI: -13-6%).

DATA CONCLUSION

With the proposed deep learning method, gadolinium dose can be reduced 10-fold while preserving contrast information and avoiding significant image quality degradation.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 5 J. MAGN. RESON. IMAGING 2018;48:330-340.

Development of High Signal Intensity within the Globus Pallidus and Dentate Nucleus following Multiple Administrations of Gadobenate Dimeglumine

BACKGROUND AND PURPOSE

Previous studies have evaluated various gadolinium based contrast agents and their association with gadolinium retention, however, there is a discrepancy in the literature concerning the linear agent gadobenate dimeglumine. Our aim was to determine whether an association exists between the administration of gadobenate dimeglumine and the development of intrinsic T1-weighted signal in the dentate nucleus and globus pallidus.

MATERIALS AND METHODS

In this single-center, retrospective study, the signal intensity of the globus pallidus, dentate nucleus, thalamus, and middle cerebellar peduncle was measured on unenhanced T1-weighted images in 29 adult patients who had undergone multiple contrast MRIs using exclusively gadobenate dimeglumine (mean, 10.1 ± 3.23 doses; range, 6-18 doses). Two neuroradiologists, blinded to the number of prior gadolinium-based contrast agent administrations, separately placed ROIs within the globi pallidi, thalami, dentate nuclei, and middle cerebellar peduncles on the last MR imaging examinations. The correlations between the globus pallidus:thalamus and the dentate nucleus:middle cerebellar peduncle signal intensity ratios with the number of gadolinium-based contrast agent administrations and cumulative dose were tested with either 1-tailed Pearson or Spearman correlations. A priori, P < .05 was considered statistically significant.

RESULTS

Both the globus pallidus:thalamus and dentate nucleus:middle cerebellar peduncle ratios showed significant correlation with the number of gadolinium-based contrast agent administrations (r = 0.39, P = .017, and r = 0.58, P = .001, respectively). Additionally, the globus pallidus:thalamus and dentate nucleus:middle cerebellar peduncle ratios showed significant correlation with the cumulative dose of gadobenate dimeglumine (r = 0.48, P = .004, and r = 0.43, P = .009, respectively). Dentate nucleus hyperintensity was qualitatively present on the last MR imaging in 79.3%-86.2% of patients and in all patients who had received >10 doses.

CONCLUSIONS

At high cumulative doses (commonly experienced by patients, for example, with neoplastic disease), gadobenate dimeglumine is associated with an increase in the globus pallidus:thalamus and dentate nucleus:middle cerebellar peduncles signal intensity ratios.