In Vivo Evaluation of Innovative Gadolinium-Based Contrast Agents Designed for Bioimaging Applications

The aim of this study was the investigation of biochemical and histological changes induced in different tissues, as a result of the subcutaneous administration of Gd nanohydrogels (GdDOTA⸦CS-TPP/HA) in a CD-1 mouse strain. The nanohydrogels were obtained by encapsulating contrast agents (GdDOTA) in a biocompatible polymer matrix composed of chitosan (CS) and hyaluronic acid (HA) through the ionic gelation process. The effects of Gd nanohydrogels on the redox status were evaluated by measuring specific activities of the antioxidant enzymes catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD), as well as oxidative stress markers, such as reduced glutathione (GSH), malondialdehyde (MDA), advanced oxidation protein products (AOPP), and protein-reactive carbonyl groups (PRCG), in the liver, kidney, and heart tissues. The nitrosylated proteins expression were analyzed with Western Blot and the serum biochemical markers were measured with spectrophotometric methods. Also, a histological analysis of CD-1 mouse tissues was investigated. These results indicated that Gd nanohydrogels could potentially be an alternative to current MRI contrast agents thanks to their low toxicity in vivo.

Gadolinium-based contrast media does not improve the staging of neuroblastoma image-defined risk factors at diagnosis

BACKGROUND

Neuroblastoma risk stratification relies on prognostic risk factors and image-defined risk factors (IDRFs). Evaluating neuroblastoma typically involves magnetic resonance imaging (MRI) with gadolinium-based contrast media (GBCM, "contrast"). However, there are concerns regarding adverse effects and cost of GBCM. We aimed to assess the impact of intravenous GBCM on interobserver agreement for neuroblastoma staging on baseline MRI.

PROCEDURE

We reviewed baseline MRI scans of 50 children with abdominopelvic neuroblastomas confirmed by histopathology. Duplicate sets of images were created, with post-contrast T1-weighted sequences removed from one set. Four pediatric radiologists independently analyzed the scans in a randomized manner. They recorded primary tumor size, presence of IDRFs, and metastatic lesions. Agreement among the reviewers was measured using kappa and Fleiss kappa statistics.

RESULTS

Mean age of included children was 3.3 years (range: 0.01-14.9 years), and 20 [40%] were females. Mean tumor size was 5.7 cm in greatest axial diameter. Pre-contrast versus post-contrast MRI showed excellent agreement for tumor measurement. Overlapping confidence intervals (CIs) were seen in nearly all categories of interobserver agreement on the presence or absence of individual IDRFs, with agreement ranging from poor to substantial, regardless of the presence of contrast. The overall interobserver agreement on the presence of at least one IDRF was substantial with contrast (kappa = .63; 95% CI: .52-.75) and moderate without contrast (kappa = .5; 95% CI: .39-.61); although the overlapping CIs suggest a lack of meaningful difference. Similarly, interobserver agreement on the presence or absence of individual sites of metastatic disease ranged from poor to substantial. The interobserver agreement on the overall determination of presence of metastatic disease was fair with contrast (kappa = .49; 95% CI: .38-.61) and moderate without contrast (kappa = .71; 95% CI: .59-.826).

CONCLUSIONS

Contrast does not improve tumor size measurement or radiologist agreement on the presence or absence of IDRFs or metastatic disease in children with newly diagnosed neuroblastoma.

Arterial Spin Labeling technique and clinical applications of the intracranial compartment in stroke and stroke mimics - A case-based review

Magnetic resonance imaging perfusion (MRP) techniques can improve the selection of acute ischemic stroke patients for treatment by estimating the salvageable area of decreased perfusion, that is, penumbra. Arterial spin labeling (ASL) is a noncontrast MRP technique that is used to assess cerebral blood flow without the use of intravenous gadolinium contrast. Thus, ASL is of particular interest in stroke imaging. This article will review clinical applications of ASL in stroke such as assessment of the core infarct and penumbra, localization of the vascular occlusion, and collateral status. Given the nonspecific symptoms that patients can present with, differentiating between stroke and a stroke mimic is a diagnostic dilemma. ASL not only helps in differentiating stroke from stroke mimic but also can be used to specify the exact mimic when used in conjunction with the symptomatology and structural imaging. In addition to a case-based overview of clinical applications of the ASL in stroke and stroke mimics in this article, the more commonly used ASL labeling techniques as well as emerging ASL techniques, future developments, and limitations will be reviewed.

Diagnostic Performance of Diffusion-weighted Imaging for Evaluation of Bowel Inflammation in Paediatric Inflammatory Bowel Disease: A Systematic Review and Meta-analysis

BACKGROUND AND AIMS

The diagnostic performance of diffusion-weighted imaging magnetic resonance enterography [DWI-MRE] has not been clearly established in a paediatric population. We systematically evaluated the diagnostic performance of DWI-MRE for the detection of bowel inflammation in paediatric patients with suspected or known inflammatory bowel disease [IBD].

METHODS

MEDLINE/PubMed, EMBASE, Web of science and the Cochrane library were searched for articles investigating the diagnostic performance of DWI-MRE for the detection of bowel inflammation in paediatric patients with suspected or known IBD up to December 31, 2020. Pooled sensitivity and specificity were calculated using a bivariate random-effects model. Pooled inter-reader agreement for the interpretation of DWI-MRE was also calculated. This study was registered as PROSPERO CRD42021228754.

RESULTS

Nine studies covering 400 paediatric patients were included. The pooled sensitivity and specificity of DWI-MRE for the detection of bowel inflammation were 0.93 (95% confidence interval [CI], 0.88-0.96) and 0.96 [95% CI, 0.87-0.99], respectively. Substantial heterogeneity was noted in both sensitivity [I2 = 66%; p < 0.01] and specificity [I2 = 94%; p < 0.01]. Meta-regression analysis identified that the use of spasmolytics contributed to higher specificity [0.89-0.99] and that quantitative assessment with an apparent diffusion coefficient cut-off value contributed to lower sensitivity [0.93-0.85] and specificity [0.98-0.72]. The pooled coefficient of inter-reader agreement, including four studies using visual assessment, was 0.97 [95% CI, 0.78-1.00].

CONCLUSIONS

DWI-MRE, especially when used with spasmolytics, is accurate for the detection of bowel inflammation in paediatric patients with suspected or known IBD. Quantitative measurement of ADC is not practical for this purpose.

Strategies to perform magnetic resonance imaging in infants and young children without sedation

Given the increasing use of MRI in the pediatric population, the need for sedation in MRI performed in young children is a topic of growing importance. Although sedation is generally tolerated well by children, the financial and operational impacts of anesthesia on MRI workflow, as well as potential adverse effects of anesthetic medications, highlight the need to perform MRI in children without sedation whenever possible. This review focuses on current techniques to facilitate non-sedation MRI in children, including exam preparation with MRI simulation; asleep but not sedated techniques; awake and relaxed techniques using certified child life specialists, animal-assisted therapy, a child-friendly environment and in-scan entertainment; and non-sedated MRI protocol modifications such as shorter scan time, prioritizing sequences, reducing motion artifact, noise reduction, limiting use of gadolinium, employing an open MRI and modifying protocols.

Is IV contrast necessary for MRI follow-up in children with abdominal neuroblastoma?

PURPOSE

The safety of multiple doses of gadolinium-based MRI IV contrast has recently been called in to question. While the long-term safety is being investigated, here, we seek to determine if there is added value to the use of IV contrast for improving detection of tumoral recurrences in children with a history of abdominal neuroblastoma.

METHODS

This is a retrospective review of children who underwent abdominal MRI with gadolinium contrast. One radiologist reviewer determined presence or absence of tumor, both before and after administration of IV contrast material and documented level of confidence when a finding was encountered. Change in reader confidence after the use of contrast was measured and fraction of missed lesions on pre-contrast was calculated. Liver and spleen lesions were documented separately.

RESULTS

453 MRI scans in 110 unique patients were reviewed. 65 patients were documented to have a total of 125 lesions, excluding liver, spleen and bones. There were 23 instances of contrast altering the radiologist's confidence and one lesion was missed without the use of contrast. Among liver and spleen, several hepatic lesions were seen only after contrast, but all were benign lesions.

CONCLUSION

In selected patients who are undergoing MRI for neuroblastoma, it may be reasonable to forgo the use of IV contrast.

RAVE-T2/T1 - Feasibility of a new hybrid MR-sequence for free-breathing abdominal MRI in children and adolescents

BACKGROUND

The new radial volumetric encoding RAVE-T₂/T₁ hybrid sequence is a modern three-dimensional sequence with multiparametric approach, which includes T₂- and T₁-weighted contrasts obtained in identical slice position during one measurement. However, the RAVE-T₂/T₁ hybrid sequence is not yet being used in clinical routine.

PURPOSE

The aim of this study was to evaluate the RAVE-T₂/T₁ hybrid sequence in a pediatric population with a clinical indication for an abdominal MRI examination to demonstrate that the hybrid imaging may be less challenging to perform on children.

MATERIALS AND METHODS

Our retrospective observational study included pediatric patients of all age groups and required for an abdominal MRI examination. Non-contrast standard axial T₁ DIXON and non-contrast RAVE-T₂/T₁ hybrid sequence were obtained at 3 T. MRI studies were analyzed independently by two pediatric radiologists using a 5-point Likert-type scale in five different categories. T₁- and T₂-weighted sequences were each compared with the RAVE-T₂/T₁-sequence using a Wilcoxon signed-rank test.

RESULTS

The analysis included 15 children (mean age, 11 years and 4 months, 7 girls and 8 boys). The Cohens Kappa of interrater agreement measured 0.62. The T₂ weighted part of the RAVE-T₂/T₁ sequence was significantly better than the standard T₂ HASTE sequence in four of five image quality categories: overall image quality (2.2 ± 0.7 vs 1.8 ± 0,7, p = 0.03), respiratory motion artefacts (3.8 ± 0.4 vs 2.0 ± 0.7, p <= 0.01), portal vein clarity (3.3 ± 0.8 vs 2.2 ± 0.7, p <= 0.01), hepatic margin sharpness (2.4 ± 1,0 vs 1.8 ± 0.7, p <= 0.01). The T₁ weighted part of the RAVE-T₂/T₁ sequence was significantly better than the standard T₁ DIXON weighted sequence in three of five image quality categories: respiratory motion artefacts (4.0 ± 0.2 vs 3.6 ± 0.8, p = 0.01), portal vein clarity (2.7 ± 0.9 vs 2.1 ± 0.7, p <= 0.01), hepatic margin sharpness (3.2 ± 0.7 vs 2.6 ± 0.9, p <= 0.01).

CONCLUSIONS

The RAVE-T₂/T₁ hybrid sequence is feasible and equal compared to standard T₁- and T₂-weighted sequences in the assessment of abdominal organs in a pediatric population. Due to non-inferiority to the current standard sequences for abdominal imaging, the RAVE-T₂/T₁ hybrid sequence is a good alternative for children who cannot be examined in breath-hold technique.

Performance of simultaneous multi-slice accelerated diffusion-weighted imaging for assessing focal renal lesions in pediatric patients with tuberous sclerosis complex

BACKGROUND

Diffusion-weighted imaging (DWI) is a useful MRI technique to characterize abdominal lesions in children, but long acquisition times can lead to image degradation. Simultaneous multi-slice accelerated DWI is a promising technique to shorten DWI scan times.

OBJECTIVE

To test the feasibility of simultaneous multi-slice DWI of the kidneys in pediatric patients with tuberous sclerosis complex (TSC) and to evaluate the accelerated protocol regarding image quality and quantitative apparent diffusion coefficient (ADC) values compared to standard echoplanar DWI sequence.

MATERIALS AND METHODS

We included 33 children and adolescents (12 female, 21 male; mean age 10±5 years) with TSC and renal cyst or angiomyolipoma on 3-tesla (T) MRI from 2017 to 2019. All studies included both free-breathing standard echoplanar DWI and simultaneous multi-slice DWI sequences. Subjective and quantitative image quality was evaluated using a predefined 5-point scale. ADC values were obtained for all renal cysts and angiomyolipomas ≥5 mm. All statistical analysis was performed using Stata/SE v15.1.

RESULTS

Simultaneous multi-slice DWI ADC values were slightly lower compared to standard echoplanar DWI for both renal cysts and angiomyolipomas (mean difference 0.05×10^-3 mm²/s, 95% confidence interval [CI] 0.40-0.50 and 0.024×10^-3 mm²/s, 95% CI 0.17-0.21, respectively, with P>0.1). Our results showed that renal lesions with ADC values >1.69×10^-3 mm²/s were all cysts, whereas lesions with values <1.16×10^-3 mm²/s were all angiomyolipomas. However, ADC values could not discriminate between lipid-rich and lipid-poor angiomyolipomas (P>0.1, for both sequences).

CONCLUSION

A 55% reduction in scan time was achieved using simultaneous multi-slice DWI for abdominal imaging in children with TSC, with near identical image quality as standard DWI. These results suggest that multi-slice techniques should be considered more broadly as an MRI acceleration technique in children.