Whole-body magnetic resonance imaging in pediatric oncology - recommendations by the Oncology Task Force of the ESPR

Staging and Restaging Pediatric Abdominal and Pelvic Tumors: A Practical Guide

The most common abdominal malignancies diagnosed in the pediatric population include neuroblastoma, Wilms tumor, hepatoblastoma, lymphoma, germ cell tumor, and rhabdomyosarcoma. There are distinctive imaging findings and patterns of spread for each of these tumors that radiologists must know for diagnosis and staging and for monitoring the patient's response to treatment. The multidisciplinary treatment group that includes oncologists, surgeons, and radiation oncologists relies heavily on imaging evaluation to identify the best treatment course and prognostication of imaging findings, such as the image-defined risk factors for neuroblastomas, the PRETreatment EXtent of Disease staging system for hepatoblastoma, and the Ann Arbor staging system for lymphomas. It is imperative for radiologists to be able to correctly indicate the best imaging methods for diagnosis, staging, and restaging of each of these most prevalent tumors to avoid inconclusive or unnecessary examinations. The authors review in a practical manner the most updated key points in diagnosing and staging disease and assessing response to treatment of the most common pediatric abdominal tumors. ©RSNA, 2024 Supplemental material is available for this article.

Applications of Diffusion-Weighted MRI to the Musculoskeletal System

Diffusion-weighted imaging (DWI) is an established MRI technique that can investigate tissue microstructure at the scale of a few micrometers. Musculoskeletal tissues typically have a highly ordered structure to fulfill their functions and therefore represent an optimal application of DWI. Even more since disruption of tissue organization affects its biomechanical properties and may indicate irreversible damage. The application of DWI to the musculoskeletal system faces application-specific challenges on data acquisition including susceptibility effects, the low T2 relaxation time of most musculoskeletal tissues (2-70 msec) and the need for sub-millimetric resolution. Thus, musculoskeletal applications have been an area of development of new DWI methods. In this review, we provide an overview of the technical aspects of DWI acquisition including diffusion-weighting, MRI pulse sequences and different diffusion regimes to study tissue microstructure. For each tissue type (growth plate, articular cartilage, muscle, bone marrow, intervertebral discs, ligaments, tendons, menisci, and synovium), the rationale for the use of DWI and clinical studies in support of its use as a biomarker are presented. The review describes studies showing that DTI of the growth plate has predictive value for child growth and that DTI of articular cartilage has potential to predict the radiographic progression of joint damage in early stages of osteoarthritis. DTI has been used extensively in skeletal muscle where it has shown potential to detect microstructural and functional changes in a wide range of muscle pathologies. DWI of bone marrow showed to be a valuable tool for the diagnosis of benign and malignant acute vertebral fractures and bone metastases. DTI and diffusion kurtosis have been investigated as markers of early intervertebral disc degeneration and lower back pain. Finally, promising new applications of DTI to anterior cruciate ligament grafts and synovium are presented. The review ends with an overview of the use of DWI in clinical routine. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 3.

Pediatric whole-body magnetic resonance imaging: comparison of STIR and T2 Dixon sequences in the detection and grading of high signal bone marrow changes

OBJECTIVES

To compare short time inversion recovery (STIR) and T2 Dixon in the detection and grading of high signal intensity areas in bone marrow on whole-body MRI in healthy children.

METHODS

Prospective study, including whole-body 1.5-T MRIs from 77 healthy children. Two experienced radiologists in consensus identified and graded areas of high bone marrow signal on STIR and T2-weighted (T2W) turbo spin echo (TSE) Dixon images (presence, extension) in two different sessions at an interval of at least 3 weeks. In a third session, a third observer joined the two readers for an additional consensus reading with all sequences available (substitute gold standard).

RESULTS

Four hundred ninety of 545 (89.9%) high signal areas were visible on both sequences, while 27 (5.0%) were visible on STIR only and 28 (5.1%) on T2W Dixon only. Twenty-four of 27 (89%) lesions seen on STIR only, and 25/28 (89%) seen on T2W Dixon only, were graded as mildly increased signal intensity. The proportion of true positive high signal lesions was higher for the T2W Dixon images as compared to STIR (74.2% vs. 68.2%) (p = 0.029), while the proportion of false negatives was lower (25.9% vs. 31.7% (p = 0.035) for T2W Dixon and STIR, respectively). There was a moderate agreement between the T2W Dixon and STIR-based extension scores on a 0-4 scale, with a kappa of 0.45 (95% CI = 0.34-0.56).

CONCLUSIONS

Most high signal bone marrow changes identified on a 1.5-T whole-body MRI were seen on both STIR and water-only T2W Dixon, underscoring the importance of using identical protocols when following bone-marrow signal changes over time.

KEY POINTS

• Whole-body MRI is increasingly being used to diagnose and monitor diseases in children, such as chronic non-bacterial osteomyelitis, malignant/metastatic disease, and histiocytosis. • Standardized and validated imaging protocols, as well as reference standards by age for the growing skeleton are lacking. • Prospective single-center study showed that 90% of high signal bone marrow areas identified on a 1.5-T whole-body MRI in healthy children is seen on both STIR and water-only T2W Dixon, while 5% is seen on STIR only and 5% on T2W Dixon only.

SPECT/CT, PET/CT and PET/MRI: oncologic and infectious applications and protocol considerations

Functional imaging is playing an increasingly important role in pediatric radiology. Hybrid imaging techniques utilizing PET/CT (positron emission tomography/computed tomography), PET/MRI (positron emission tomography/magnetic resonance imaging), or SPECT/CT (single photon emission computed tomography/computed tomography) are now available in nearly every clinical practice. There are an increasing number of indications for the use of functional imaging, including oncologic and infectious indications, and it is essential to select and design the hybrid imaging protocol in order to optimize both the functional and anatomic components of the examination. Optimizing the protocol includes strategies for dose reduction, judicious use of contrast media and diagnostic quality imaging as appropriate, and for the greatest reduction in exposure to ionizing radiation, utilizing PET/MRI, whenever available. This review will provide an overview of hybrid imaging protocol considerations with a focus on oncologic and infectious indications.

Whole-body diffusion magnetic resonance imaging with simultaneous multi-slice excitation in children and adolescents

BACKGROUND

Whole-body magnetic resonance imaging (WB-MRI) is an increasingly used guideline-based imaging modality for oncological and non-oncological pathologies during childhood and adolescence. While diffusion-weighted imaging (DWI), a part of WB-MRI, enhances image interpretation and improves sensitivity, it also requires the longest acquisition time during a typical WB-MRI scan protocol. Interleaved short tau inversion recovery (STIR) DWI with simultaneous multi-slice (SMS) acquisition is an effective way to speed up examinations.

OBJECTIVE

In this study of children and adolescents, we compared the acquisition time, image quality, signal-to-noise ratio (SNR) and apparent diffusion coefficient (ADC) values of an interleaved STIR SMS-DWI sequence with a standard non-accelerated DWI sequence for WB-MRI.

MATERIALS AND METHODS

Twenty children and adolescents (mean age: 13.9 years) who received two WB-MRI scans at a maximum interval of 18 months, consisting of either standard DWI or SMS-DWI MRI, respectively, were included. For quantitative evaluation, the signal-to-noise ratio (SNR) was determined for b800 images and ADC maps of seven anatomical regions. Image quality evaluation was independently performed by two experienced paediatric radiologists using a 5-point Likert scale. The measurement time per slice stack, pause between measurements including shim and total measurement time of DWI for standard DWI and SMS-DWI were extracted directly from the scan data.

RESULTS

When including the shim duration, the acquisition time for SMS-DWI was 43% faster than for standard DWI. Qualitatively, the scores of SMS-DWI were higher in six locations in the b800 images and four locations in the ADC maps. There was substantial agreement between both readers, with a Cohen's kappa of 0.75. Quantitatively, the SNR in the b800 images and the ADC maps did not differ significantly from one another.

CONCLUSION

Whole body-MRI with SMS-DWI provided equivalent image quality and reduced the acquisition time almost by half compared to the standard WB-DWI protocol.

Whole-body MRI for cancer surveillance in ataxia-telangiectasia: A qualitative study of the perspectives of people affected by A-T and their families

BACKGROUND/OBJECTIVES

Ataxia-telangiectasia (A-T) is a complex inherited disease associated with an increased risk of malignancy. Surveillance guidelines have demonstrated significant health benefits in other cancer predisposition syndromes. However, evidence-based guidelines for cancer screening are not currently used in the United Kingdom for people affected by A-T. This study aims to understand how people with A-T and their parents feel about cancer surveillance using whole-body magnetic resonance imaging (MRI) to inform the future development of cancer surveillance guidelines.

DESIGN/METHODS

We conducted semistructured interviews with people affected by A-T. Data were analysed inductively using thematic analysis.

RESULTS

Nine parents of children with A-T and four adults with A-T were interviewed. Five main themes emerged from the data, including (1) cancer screening was considered invaluable with the perceived value of early detection highlighted; (2) the cancer fear can increase anxiety; (3) the perceived limitations around current practice, with the responsibility for monitoring falling too strongly on parents and patients; (4) the need for effective preparation for cancer screening, including clear communication and (5) the challenges associated with MRI screening, where specific recommendations were made for improving the child's experience.

CONCLUSION

This study suggests that stakeholders are positive about the perceived advantages of a cancer screening programme. Ongoing support and preparation techniques should be adopted to maximise adherence and minimise adverse psychosocial outcomes.

PATIENT OR PUBLIC CONTRIBUTION

People with A-T and parents of people with A-T were actively involved in this study by giving their consent to be interviewed. An independent parent representative contributed to the study, supporting the research team in interpreting and commenting on the appropriateness of the language used in this report.

[Whole-body MRI in cancer predisposition syndromes]

BACKGROUND

In recent decades, whole-body magnetic resonance imaging (WB-MRI) has become established as the modality of choice for the diagnosis, staging, and follow-up of oncological diseases as well as for the screening of cancer predisposition syndromes, such as Li-Fraumeni syndrome.

METHODS

As a comprehensive imaging modality without ionizing radiation, WB-MRI can be used repetitively and because of its excellent soft tissue contrast and high resolution provides early and precise detection of pathologies. This article discusses the technical requirements, some examination strategies and the clinical significance of typical findings of WB-MRI in patients with cancer predisposition syndromes.

Whole-body MRI in children: state of the art

Whole-body magnetic resonance imaging (WBMRI) is an increasingly popular technique in paediatric imaging. It provides high-resolution anatomical information, with the potential for further exciting developments in acquisition of functional data with advanced MR sequences and hybrid imaging with radionuclide tracers. WBMRI demonstrates the extent of disease in a range of multisystem conditions and, in some cases, disease burden prior to the onset of clinical features. The current applications of WBMRI in children are hereby reviewed, along with suggested anatomical stations and sequence protocols for acquisition.

Improving protocols for whole-body magnetic resonance imaging: oncological and inflammatory applications

Whole-body MRI is increasingly used in the evaluation of a range of oncological and non-oncological diseases in infants, children and adolescents. Technical innovation in MRI scanners, coils and sequences have enabled whole-body MRI to be performed more rapidly, offering large field-of-view imaging suitable for multifocal and multisystem disease processes in a clinically useful timeframe. Together with a lack of ionizing radiation, this makes whole-body MRI especially attractive in the pediatric population. Indications include lesion detection in cancer predisposition syndrome surveillance and in the workup of children with known malignancies, and diagnosis and monitoring of a host of infectious and non-infectious inflammatory conditions. Choosing which patients are most likely to benefit from this technology is crucial, but so is adjusting protocols to the patient and disease to optimize lesion detection. The focus of this review is on protocols and the elements impacting image acquisition in pediatric whole-body MRI. We consider the practical aspects, from scanner and coil selection to patient positioning, single-center generic and indication-specific protocols with technical parameters, motion reduction strategies and post-processing. When optimized, collectively these lead to better standardization of whole-body MRI, and when married to systematic analysis and interpretation, they can improve diagnostic accuracy.

Guidelines for magnetic resonance imaging in pediatric head and neck pathologies: a multicentre international consensus paper

The use of standardized imaging protocols is paramount in order to facilitate comparable, reproducible images and, consequently, to optimize patient care. Standardized MR protocols are lacking when studying head and neck pathologies in the pediatric population. We propose an international, multicenter consensus paper focused on providing the best combination of acquisition time/technical requirements and image quality. Distinct protocols for different regions of the head and neck and, in some cases, for specific pathologies or clinical indications are recommended. This white paper is endorsed by several international scientific societies and it is the result of discussion, in consensus, among experts in pediatric head and neck imaging.

Screening of cancer predisposition syndromes

Pediatric patients with cancer predisposition syndromes are at increased risk of developing malignancies compared with their age-matched peers, necessitating regular surveillance. Screening protocols differ among syndromes and are composed of a number of elements, imaging being one. Surveillance can be initiated in infants, children and adolescents with a tumor known or suspected of being related to a cancer predisposition syndrome or where genetic testing identifies a germline pathogenic gene variant in an asymptomatic child. Pre-symptomatic detection of malignant neoplasms offers potential to improve treatment options and survival outcomes, but the benefits and risks of screening need to be weighed, particularly with variable penetrance in many cancer predisposition syndromes. In this review we discuss the benefits and risks of surveillance imaging and the importance of integrating imaging and non-imaging screening elements. We explore the principles of surveillance imaging with particular reference to whole-body MRI, considering the strategies to minimize false-negative and manage false-positive whole-body MRI results, the value of standardized nomenclature when reporting risk stratification to better guide patient management, and the need for timely communication of results to allay anxiety. Cancer predisposition syndrome screening is a multimodality, multidisciplinary and longitudinal process, so developing formalized frameworks for surveillance imaging programs should enhance diagnostic performance while improving the patient experience.

[Bone and soft tissue tumours in children : Proposal for a rational diagnostic approach]

CLINICAL/METHODOLOGICAL ISSUE

Bone and soft tissue tumours are often incidental findings in children. Because they are usually benign tumours, nonspecialised radiologists generally have little experience in the diagnosis and differentiation from malignant tumours. Various imaging techniques are used in the diagnosis of skeletal tumours.

STANDARD RADIOLOGICAL METHODS

Imaging techniques used to evaluate bone and soft tissue tumours include sonography, computed tomography (CT) and magnetic resonance imaging (MRI).

METHODOLOGICAL INNOVATIONS

An algorithm to determine malignancy of bone and soft tissue tumours in children is proposed.

PERFORMANCE

By using the presented algorithms, further diagnostic procedures such as biopsies can be avoided in the majority of children with bone and soft tissue tumours. Aggressive bone lesions and unclear soft tissue tumours are guided to biopsy to confirm diagnosis.

ACHIEVEMENTS

The algorithms presented are based on the proposals of European professional societies and have been adapted by the authors for use in children and adolescents.

PRACTICAL RECOMMENDATIONS

In the clarification of soft tissue tumours, sonography is the first diagnostic tool; depending on the sonographic findings, MRI is the technique for further clarification. Biopsy confirmation of the diagnosis in unclear cases or in cases of probable malignancy should be carried out in a paediatric oncology centre.

Skeletal staging in Langerhans cell histiocytosis: a multimodality imaging review

Evaluating the extent of skeletal disease in Langerhans cell histiocytosis (LCH) is a major predictor of patient outcome. Traditionally, whole-body skeletal staging consists of plain radiography and bone scintigraphy. However, more recently whole-body MRI has been shown to be accurate in detecting osseous and extra-osseous lesions, but no large-scale studies analysing its role within the diagnostic algorithm of LCH skeletal staging currently exist. In addition, FDG PET-CT provides useful information regarding disease activity and treatment response, but has an inherent radiation dose which is not ideal in children. Currently, radiographic skeletal survey remains the gold standard with cross-sectional imaging only performed for further characterisation. However, radiographs have shown a wide sensitivity range for skeletal staging and have clear limitations in detecting extra-skeletal disease, a crucial component of stratification in identifying 'at risk' organs. We aim to highlight the various appearances of bony LCH across all the imaging modalities for primary skeletal staging. We will also review the advantages, disadvantages, sensitivity and specificity of each, and establish their role in staging skeletal LCH. Recent studies using whole-body MRI have shown promising results, with radiographs and other modalities playing a more complementary role.

European guideline for imaging in paediatric and adolescent rhabdomyosarcoma - joint statement by the European Paediatric Soft Tissue Sarcoma Study Group, the Cooperative Weichteilsarkom Studiengruppe and the Oncology Task Force of the European Society of Paediatric Radiology

Appropriate imaging is essential in the treatment of children and adolescents with rhabdomyosarcoma. For adequate stratification and optimal individualised local treatment utilising surgery and radiotherapy, high-quality imaging is crucial. The paediatric radiologist, therefore, is an essential member of the multi-disciplinary team providing clinical care and research. This manuscript presents the European rhabdomyosarcoma imaging guideline, based on the recently developed guideline of the European Paediatric Soft Tissue Sarcoma Study Group (EpSSG) Imaging Committee. This guideline was developed in collaboration between the EpSSG Imaging Committee, the Cooperative Weichteilsarkom Studiengruppe (CWS) Imaging Group, and the Oncology Task Force of the European Society of Paediatric Radiology (ESPR). MRI is recommended, at diagnosis and follow-up, for the evaluation of the primary tumour and its relationship to surrounding tissues, including assessment of neurovascular structures and loco-regional lymphadenopathy. Chest CT along with [F-18]2-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET)/CT or PET/MRI are recommended for the detection and evaluation of loco-regional and distant metastatic disease. Guidance on the estimation of treatment response, optimal long-term follow-up, technical imaging settings and standardised reporting are described. This European imaging guideline outlines the recommendations for imaging in children and adolescents with rhabdomyosarcoma, with the aim to harmonise imaging and to advance patient care.