Advances in pediatric MR imaging. Magn Reson Imaging Clin N Am. 2008;16:385-402, v. [PMID: 18585595 DOI: 10.1016/j.mric.2008.04.008]

Radiofrequency labeling strategies in chemical exchange saturation transfer MRI

Chemical exchange saturation transfer (CEST) MRI has generated great interest for molecular imaging applications because it can image low-concentration solute molecules in vivo with enhanced sensitivity. CEST effects are detected indirectly through a reduction in the bulk water signal after repeated perturbation of the solute proton magnetization using one or more radiofrequency (RF) irradiation pulses. The parameters used for these RF pulses-frequency offset, duration, shape, strength, phase, and interpulse spacing-determine molecular specificity and detection sensitivity, thus their judicious selection is critical for successful CEST MRI scans. This review article describes the effects of applying RF pulses on spin systems and compares conventional saturation-based RF labeling with more recent excitation-based approaches that provide spectral editing capabilities for selectively detecting molecules of interest and obtaining maximal contrast.

Pediatric magnetic resonance imaging: faster is better

Magnetic resonance imaging (MRI) has emerged as the preferred imaging modality for evaluating a wide range of pediatric medical conditions. Nevertheless, the long acquisition times associated with this technique can limit its widespread use in young children, resulting in motion-degraded or non-diagnostic studies. As a result, sedation or general anesthesia is often necessary to obtain diagnostic images, which has implications for the safety profile of MRI, the cost of the exam and the radiology department's clinical workflow. Over the last decade, several techniques have been developed to increase the speed of MRI, including parallel imaging, single-shot acquisition, controlled aliasing techniques, compressed sensing and artificial-intelligence-based reconstructions. These are advantageous because shorter examinations decrease the need for sedation and the severity of motion artifacts, increase scanner throughput, and improve system efficiency. In this review we discuss a framework for image acceleration in children that includes the synergistic use of state-of-the-art MRI hardware and optimized pulse sequences. The discussion is framed within the context of pediatric radiology and incorporates the authors' experience in deploying these techniques in routine clinical practice.

Role of imaging in the evaluation of inflammatory bowel disease: How much is too much?

Inflammatory bowel disease (IBD) is a lifelong condition with waxing and waning disease course that requires reassessment of disease status as well as screening for complications throughout a patient’s lifetime. Laboratory testing, endoscopic assessment, and fecal biomarkers are often used in the initial diagnosis and ongoing monitoring of a patient with IBD. Imaging plays an integral role in the diagnosis and evaluation of IBD. Different imaging modalities can be used over the course of a patient’s lifetime, from the initial screening and diagnosis of IBD, to determining the extent of intestinal involvement, monitoring for disease activity, and evaluating for complications of uncontrolled IBD. The various imaging modalities available to the provider each have a unique set of risks and benefits when considering cost, radiation exposure, need for anesthesia, and image quality. In this article we review the imaging techniques available for the evaluation of IBD including fluoroscopic small bowel follow-through, computed tomography enterography, magnetic resonance enterography, and transabdominal ultrasound with particular focus on the judicious use of imaging and the risks and benefits of each option. We also review the risks of ionizing radiation, strategies to reduce exposure to ionizing radiation, and current imaging guidelines among pediatric and adult patient with IBD.

Novel outcome measures for clinical trials in cystic fibrosis

Cystic fibrosis (CF) is a common inherited condition caused by mutations in the gene encoding the CF transmembrane regulator protein. With increased understanding of the molecular mechanisms underlying CF and the development of new therapies there comes the need to develop new outcome measures to assess the disease, its progression and response to treatment. As there are limitations to the current endpoints accepted for regulatory purposes, a workshop to discuss novel endpoints for clinical trials in CF was held in Anaheim, California in November 2011. The pros and cons of novel outcome measures with potential utility for evaluation of novel treatments in CF were critically evaluated. The highlights of the 2011 workshop and subsequent advances in technologies and techniques that could be used to inform the development of clinical trial endpoints are summarized in this review. Pediatr Pulmonol. © 2014 The Authors. Pediatric Pulmonology published by Wiley Periodicals, Inc.

Inflammatory bowel disease-the role of cross-sectional imaging techniques in the investigation of the small bowel

Abstract

Background: The diagnosis of inflammatory bowel disease (IBD) in children and adolescents is based on the integration of clinical, biological, endoscopic, histological and radiological data. Methods: The most important part of the diagnosis is the histology, which is acquired by endoscopy. Imaging of the small bowel has changed in recent years, but the imaging goals are primarily to determine the extent of small bowel involvement, assess complications and define candidates for surgery. Imaging techniques are divided into conventional and cross-sectional ones. Results: The spectrum of imaging findings of cross-sectional techniques is discussed, emphasising the advantages and limitations of each technique, acknowledging the specificities of the paediatric population. Cross-sectional techniques have advanced the ability to diagnose and monitor inflammatory disease of the small bowel. Conclusion: MR enterography is the technique of choice in children with known IBD, for the investigation of the small bowel and the whole GI tract. US should be the first choice examination in children with suspected IBD, while CT should be reserved for cases in which MRI is contraindicated or in acute emergency situations when US is inadequate.

Teaching Points

• Cross-sectional imaging of the small bowel is essential in paediatric IBD.

• Endoscopy is unable to assess extramural disease and examine the entire small bowel.

• US should be the first choice examination in children with suspected IBD.

• MR enterography is the technique of choice in children with known IBD.

• There are still controversies regarding the prediction of disease activity or fibrosis.

Imaging in the evaluation of the young patient with inflammatory bowel disease: what the gastroenterologist needs to know

Imaging plays a pivotal role in the diagnosis and management of children and young adults with inflammatory bowel disease. The clinician is presented with numerous imaging options, and it can be challenging to decide which test is the best option. In this article we review the present imaging techniques available in the evaluation of inflammatory bowel disease, with emphasis on the advantages, disadvantages, and radiation burden of each test. Finally, we highlight a few common clinical scenarios and propose an imaging algorithm to approach these diagnostic challenges.

Contrast-enhanced magnetic resonance imaging in pediatric patients: review and recommendations for current practice

Magnetic resonance imaging (MRI), frequently with contrast enhancement, is the preferred imaging modality for many indications in children. Practice varies widely between centers, reflecting the rapid pace of change and the need for further research. Guide-line changes, for example on contrast-medium choice, require continued practice reappraisal. This article reviews recent developments in pediatric contrast-enhanced MRI and offers recommendations on current best practice. Nine leading pediatric radiologists from internationally recognized radiology centers convened at a consensus meeting in Bordeaux, France, to discuss applications of contrast-enhanced MRI across a range of indications in children. Review of the literature indicated that few published data provide guidance on best practice in pediatric MRI. Discussion among the experts concluded that MRI is preferred over ionizing-radiation modalities for many indications, with advantages in safety and efficacy. Awareness of age-specific adaptations in MRI technique can optimize image quality. Gadolinium-based contrast media are recommended for enhancing imaging quality. The choice of most appropriate contrast medium should be based on criteria of safety, tolerability, and efficacy, characterized in age-specific clinical trials and personal experience.

Is magnetic resonance imaging a reliable diagnostic tool in the evaluation of active Crohn's disease in the small bowel?

GOALS

To evaluate the overall diagnostic accuracy of magnetic resonance imaging (MRI) in assessing the activity of Crohn's disease (CD) in the small bowel.

BACKGROUND

Cross-sectional imaging techniques are playing an increasing role in the evaluation of suspected CD. Advantages of MRI include a lack of ionizing radiation, the ability to provide dynamic information regarding bowel distention and motility, improved soft-tissue contrast, and a relatively safe intravenous contrast agent profile.

STUDY

Two reviewers searched MEDLINE, EMBASE, and other electronic databases to identify studies in which MRI imaging was evaluated for assessing the activity of CD in the small bowel from January 2001 to September 2011. Bivariate random-effects meta-analytic methods were used to estimate summary, sensitivity, specificity, and receiver operating characteristic curves.

RESULTS

MRI had a pooled sensitivity of 0.87 [95% confidence interval (CI): 0.77, 0.93] and a pooled specificity of 0.91 (95% CI: 0.81, 0.96). Overall, likelihood ratio (LR)+ was 9.5 (95% CI: 4.4, 20.6) and LR- was 0.14 (95% CI: 0.08, 0.26). In patients with high pretest probabilities, MRI enabled confirmation of active CD; in patients with low pretest probabilities, MRI enabled exclusion of active CD. Worst-case-scenario (pretest probability, 50%) posttest probabilities were 90% and 13% for positive and negative MRI results, respectively.

CONCLUSIONS

A limited number of small studies suggest that MRI has high sensitivity and specificity for diagnosis of active CD in the small bowel; MRI will likely also prove to be suitable as the primary modality for active CD imaging surveillance.

Whole-body MR imaging for staging of malignant tumors in pediatric patients: results of the American College of Radiology Imaging Network 6660 Trial

PURPOSE

To compare whole-body magnetic resonance (MR) imaging with conventional imaging for detection of distant metastases in pediatric patients with common malignant tumors.

MATERIALS AND METHODS

This institutional review board-approved, HIPAA-compliant, multicenter prospective cohort study included 188 patients (109 male, 79 female; mean age, 10.2 years; range, < 1 to 21 years) with newly diagnosed lymphoma, neuroblastoma, or soft-tissue sarcoma. Informed consent was obtained and all patients underwent noncontrast material-enhanced whole-body MR imaging and standard-practice conventional imaging. All images were reviewed centrally by 10 pairs of readers. An independent panel verified the presence or absence of distant metastases. Detection of metastasis with whole-body MR and conventional imaging was quantified by using the area under the receiver operating characteristic curve (AUC). The effects of tumor subtype, patient age, and distant skeletal and pulmonary disease on diagnostic accuracy were also analyzed.

RESULTS

Of the 134 eligible patients, 66 (33 positive and 33 negative for metastasis) were selected for image review and analysis. Whole-body MR imaging did not meet the noninferiority criterion for accuracy when compared with conventional imaging for detection of metastasis (difference between average AUCs was -0.03 [95% confidence interval: -0.10, 0.04]); however, the average AUC for solid tumors was significantly higher than that for lymphomas (P = .006). More skeletal metastases were detected by using whole-body MR imaging than by using conventional imaging (P = .03), but fewer lung metastases were detected (P < .001). Patient age did not affect accuracy.

CONCLUSION

The noninferior accuracy for diagnosis of distant metastasis in patients with common pediatric tumors was not established for the use of whole-body MR imaging compared with conventional methods. However, improved accuracy was seen with whole-body MR imaging in patients with nonlymphomatous tumors.

Targeted MRI contrast agents for pediatric hepatobiliary disease

New options are available for the magnetic resonance imaging (MRI) assessment of pediatric hepatobiliary disease. This article describes the potential utility for MRI with contrast agents tailored for hepatobiliary imaging. MRI contrast agents that preferentially target the liver may be helpful in characterizing liver masses and bile duct abnormalities in select children. The imaging approach is noninvasive and relatively rapid to perform. It also provides anatomic and functional information and is a radiation-free alternative to other imaging strategies. This relatively new imaging procedure is placed in the context of more established imaging modalities. The pharmacokinetics, technical considerations, and potential applications of these hepatobiliary-specific contrast agents also are discussed.

MRI in patients with inflammatory bowel disease

Inflammatory bowel disease (IBD) affects ≈1.4 million people in North America and, because of its typical early age of onset and episodic disease course, IBD patients often undergo numerous imaging studies over the course of their lifetimes. Computed tomography (CT) has become the standard imaging modality for assessment of IBD patients because of its widespread availability, rapid image acquisition, and ability to evaluate intraluminal and extraluminal disease. However, repetitive CT imaging has been associated with a significant ionizing radiation risk to patients, making MRI an appealing alternative IBD imaging modality. Pelvic MRI is currently the imaging gold standard for detecting perianal disease, while recent studies indicate that MRI bowel-directed techniques (enteroclysis, enterography, colonography) can accurately evaluate bowel inflammation in IBD. With recent technical innovations leading to faster and higher resolution body MRI, the role of MRI in IBD evaluation is likely to continue to expand. Future applications include surveillance imaging, detection of mural fibrosis, and early assessment of therapy response.

Magnetic resonance imaging for uterine and vaginal anomalies

PURPOSE OF REVIEW

Pediatric pelvic MRI has had dramatic advances in the past few years. This review documents studies demonstrating the accuracy of MRI for the evaluation of uterine and vaginal anomalies and discusses the salient changes to MRI methods that are particularly applicable to evaluating the pediatric patient with these developmental anomalies.

RECENT FINDINGS

MRI has high accuracy for evaluation of uterine and vaginal anomalies. Significant advances, such as volumetric imaging, increased resolution, decreased motion artifacts, and shorter examination time, have increased the access and utility of MRI for pediatric patients.

SUMMARY

MRI techniques have evolved markedly in the past several years, providing a robust method of evaluating uterine and vaginal anomalies in the pediatric patient.