Assessment of therapeutic response in oncology is fundamental for evaluating treatment efficacy, guiding clinical decision-making, and determining prognosis. Historically, response evaluation relied primarily on anatomical imaging criteria derived from tumor size changes on computed tomography (CT), most notably the Response Evaluation Criteria in Solid Tumors (RECIST) and its adaptations. However, advances in molecular imaging, particularly positron emission tomography (PET) using [18F]-2-fluoro-2-deoxyglucose ([18F]FDG) and other radiopharmaceuticals, have introduced new biomarkers capable of detecting tumor response earlier than structural changes. Molecular imaging-based criteria, including EORTC, PERCIST, immune-adapted PET frameworks, and disease-specific systems such as Lugano, RANO, ENETS SSTR-PeRForm and RECIP, provide quantitative assessment of tumor burden and may better reflect biologic response to therapy. This review discusses the rationale behind molecular imaging response criteria, outlines the principles of CT-based and PET-based evaluation systems, and highlights the clinical relevance of integrating metabolic imaging into tumor response.

Utilization of ultra-high-field (UHF) MRI in humans has rapidly increased over the past decade, following regulatory approval of the first clinical 7 Tesla (7T) platforms in 2017 for brain and knee imaging. Currently, there are approximately 140 MRI scanners worldwide operating at or above 7T [1]. While the majority of 7T scanners are dedicated to research and development, select hospitals have successfully implemented 7T MRI for clinical care. Key advantages of 7T over lower-field systems include higher spatial and contrast resolution for anatomic and microstructural detail, susceptibility effects for functional and vascular imaging, and spectral resolution for metabolic evaluation. However, safety considerations-particularly specific absorption rate thresholds-have historically constrained utility to patients with weights of 30 kg and above. Additional considerations, including operating costs, longer imaging times, increased artifacts, and greater bioeffects, have limited widespread adoption, especially in pediatric patients. In this article, we discuss emerging technology advances and clinical applications for 7T MRI imaging of children. Major technical considerations are scanner hardware, coils, safety, sedation, and monitoring. Important clinical applications include neurodevelopmental, epilepsy, demyelinating, vascular, genetic, neoplastic, and traumatic disorders. Major research areas involve artificial intelligence, extracranial imaging, and field strengths exceeding 10T. Real-life imaging examples are provided for children and young adults to highlight the advantages and pitfalls of 7T in this population.

A recurring argument in radiological protection holds that the radiation risk of an imaging examination must be weighed against the clinical risk of not performing it. The argument is applied inconsistently, and evidence on that clinical risk remains sparse compared with the extensive literature on radiation risk. This asymmetry masks an important distinction: the clinical risk of not imaging is not uniformly high. We propose a three-scenario framework for medical imaging, illustrated using computed tomography. In Scenario 1, the harm of withholding or delaying imaging is well documented and substantially exceeds the radiation risk, as in appendicitis, stroke, pulmonary embolism, aortic dissection, and polytrauma. In Scenario 2, imaging is repeated at low incremental yield, exposure accumulates, and guidance on intervals is limited, so radiation risk may outweigh marginal diagnostic gain. In Scenario 3, evidence on both sides is insufficient, and decisions are best supported by clinical decision rules and shared decision making. The framework addresses procedure-level and individual justification, and is confined to the balance between clinical and radiation risk. We suggest that clinical specialty organizations develop guidance on imaging frequency that incorporates review of cumulative exposure, and that ICRP address the place of such exposure within the justification framework.