In an effort to develop highly selective and potent agonists and/or antagonists for the hMC3 and hMC4 receptors, a new approach involving the use of linker arms and a backbone to side chain cyclization strategy was employed. Three key analogues were identified to have the required selectivity and potency at the hMC3 or hMC4 receptors, implicated to play pivotal roles in energy homeostasis and other biological effects. The novel cyclic peptide (O)C-CH2-CH2-C(O)-c-[His6-D-Phe7-Arg8-Trp9-Lys10]-NH2 (1) was found to be a highly selective and potent agonist of the hMC4 receptor. Structure−activity studies have shown that replacing the succinyl linker arm of 1 by an o-phthalic acid group and substituting a D-Nal(2‘)7 residue in place of D-Phe7 results in a potent antagonist 7 at the hMC4 receptor. Furthermore, increasing the 23-membered lactam ring of 1 by one carbon atom (succinyl → glutaric acid linker) gives a highly selective and potent antagonist 9 for the hMC3 receptor. Analogues 1, 7, and 9 therefore represent the first examples of a class of cyclic melanotropin ligands with high selectivity and defined biological activities at the physiologically important hMC3 and hMC4 receptors.

Ultrasonography (US) is commonly used to assess the peripheral nerves of the lower extremity because of its many advantages over magnetic resonance (MR) imaging. The most obvious advantages over MR imaging are superior soft-tissue resolution, low cost, portability, lack of magnetic susceptibility artifact, and the ability to image patients who cannot undergo MR imaging. US has been shown to have equal specificity and greater sensitivity than MR imaging in the evaluation of peripheral nerves. Additional benefits are the capability of real-time and dynamic imaging, and the ability to scan an entire extremity quickly without the need for a patient to lie motionless for long periods of time, as with MR imaging. Any abnormal findings can be easily compared against the contralateral side. Published literature has shown that US has clinical utility in patients suspected of having peripheral nerve disease: US can be used to guide diagnostic and therapeutic decisions, as well as help confirm electrodiagnostic findings. Common indications for lower extremity peripheral nerve US are the evaluation for injury due to penetrating trauma, entrapment by scar tissue, or tumor. To confidently perform US of the peripheral nerves of the lower extremity, it is important to gain a thorough knowledge of anatomic landmarks and the course of each nerve. Readers who may not be familiar with US will be introduced to the basics of scanning the peripheral nerves of the lower extremity. Important anatomic landmarks and common sites of injury and entrapment will be reviewed.

Younger children tend to have more rostral (occiput-C2) injuries compared with older children. The National Emergency X-Radiography Utilization Study protocol may have lower sensitivity in young children than in adults. Limited computed tomography from occiput-C3 may increase diagnostic yield appreciably in young children compared with flexion-extension views. Further prospective studies, especially of young children, are needed to develop reliable pediatric protocols.

Non-accidental trauma is a significant source of morbidity and mortality in the pediatric population. Given the vulnerable state of the child, the radiologist can often provide valuable diagnostic information in the setting of suspected abuse. This review focuses on common findings of abusive trauma and serves as a guide to aid in clinical decision-making for providers of emergency medicine and pediatrics. Amid this discussion is an assessment of modern controversies regarding reported mimicking pathologies, recapitulation of the current state of evidence with respect to radiologic findings of abuse, and examination of the contribution that spine imaging may add to the diagnosis of possible abusive head trauma in the acutely injured child. Recommendations for avoiding pitfalls regarding the dating of intracranial injuries are discussed, and illustrated depictions of perpetrator-induced pathology are provided to aid in the understanding of these injuries. Through the use of the appropriate approach to imaging and evidence-based guidelines regarding radiologic findings, the role of radiology is to provide fundamental clues to diagnose and prevent recurrence of abusive injury in patients who cannot speak for themselves.