In this review article, three important issues regarding X-ray diagnosis of skeletal dysplasia are discussed: basic knowledge of skeletal dysplasia, the concept of bone dysplasia family, and the key pathognomonic findings of whole body bone. First, young pediatric radiology residents should know that there are so many disease entities (436 diseases) and group categories (42 groups) in “Nosology and classification of genetic skeletal disorders” 2015 editions. The second topic is that pediatric radiology residents should understand the basic knowledge of formation of bone tissue; one is membranous ossification, and the other is endochondral ossification. The third topic is how to find the pathognomonic findings of skeletal changes. This article introduces typical radiological abnormalities of the metaphysis, epiphysis, and diaphysis. Also, thoracic, vertebral, and pelvic abnormalities are discussed briefly. In daily practice, the X-ray diagnosis of skeletal dysplasia is difficult for radiology residents to understand. Otherwise, radiological pattern recognition is one of our best subjects. So young radiologists should never give up learning the basic process of skeletal dysplasia.

In 2010, the Medical Safety Committee of the Japan Pediatric Society conducted a survey on the sedation management of pediatric patients undergoing MRI examination. As adverse events during the examination, 147 (35%) of 416 facilities experienced severe complications such as respiratory depression, respiratory arrest, bradycardia and cardiac arrest. Following this result, the Medical Safety Committee of the Japan Pediatric Society published “Recommendations on Pediatric Sedation for MRI Examination” on May 26, 2013. These recommendations do not describe the specific method of sedation to be used on the site, for example, the medicine to be used, its dosage, etc., but show “a way of thinking and attitude toward sedation.” Last year, we conducted a Web questionnaire survey again to know the change over three years after release of the recommendations. As for the result, rather than a specific change, it seemed to show a time when a change of consciousness regarding sedation began to appear.

In the future, research on pediatric sedation will be conducted at many facilities, and by accumulation of research results from Japan, it is my hope that guidelines on pediatric sedation for MRI examinations will be prepared here.

Diagnosis of pediatric fractures is difficult, because pediatric bone is different structurally and pathologically from that of adults. For example, the growing child’s skeleton shows more plasticity than adult skeleton, and its growth plate is the weakest region of bone.

We will illustrate some characteristic cases of pediatric fractures in terms of incomplete fracture, physeal fracture, phases of fracture healing, alignment of bone and appropriate examination.

Greenstick fracture, torus fracture and plastic bowing are incomplete fracture, and common in children. In such cases, the bony fragment cannot be seen. Physeal fractures are common between ages 10 and 16 years, because open physis is weaker than ligaments and tendons. And when the fracture line is ambiguous, it is important to check the alignment of joints, especially fracture about the elbow. Moreover, appropriate modality and optimum radiation dose are needed to obtain the precise diagnosis.

骨系統疾患に対する放射線学的診断アプローチについてbone dysplasia familyの概念にもとづいて解説する．この概念はJuergen Sprangerが提唱した疾患分類である．彼は形態的類似性に注目して，病態関連が予想される疾患群をbone dysplasia family（group）とした．代表的なものは軟骨無形成症ファミリー，先天性脊椎骨端異形成症ファミリーなどである．現在では，前者はFGFR3の対立遺伝子異常群，後者はCOL2A1の対立遺伝子異常群であることが証明されている．彼が提唱した古典的骨異形成症ファミリーに加えて，最近全貌が明らかにされた新しい骨異形成症ファミリーについても述べたい．

Synthetic MRI, a multi-slice, multi-echo, and multi-delay acquisition, enables simultaneous quantification of R1 and R2 relaxation rates (the inverses of T1 and T2 relaxation times, respectively), proton density (PD), and B1 field in only about 6 minutes for full head coverage. Based on the quantitative values, individualized contrast-weighted imaging, automated brain tissue segmentation and volumetry, and myelin measurement can be achieved by using post-processing software, called SyMRI (SyntheticMR, Linköping, Sweden). The use of synthetic MRI may overcome the limitations of conventional MRI in pediatric brain imaging. We can scan pediatric patients by synthetic MRI without adjusting MR parameters to tissue properties specific to pediatric populations. Furthermore, the scan time can be shorter than that of conventional MRI, which is critical in the pediatric population. Here we summarize and review the use of SyMRI in imaging of the pediatric brain, including the basic principles of MR quantification along with its features, clinical applications, and limitations.

The pediatric brain is not a “small adult brain”; different types of diseases and their mechanisms in the pediatric brain are remarkably different from those of the adult brain. Meninges, blood-brain/CSF barrier, and myelin sheaths are immature. Postnatal period of brain development is vulnerable to excitotoxic injury. The distribution and types of various receptors in the pediatric brain are different from those of adults. Diffusion-weighted imaging (DWI) has high tissue characteristics and can differentiate viscous fluid, abscess, hematoma, cellular edema, necrosis, and hypercellular neoplasm. It is indispensable for a correct diagnosis and differential diagnosis to consider the background pathology and pathophysiology when interpreting DWI of pediatric brain.

Gadolinium (Gd)-based contrast agents (GBCA) are commonly used in magnetic resonance imaging (MRI), and are safe for the majority of patients. Adverse reactions to GBCA are classified into: 1) acute adverse reaction, which occurs within one hour of contrast medium injection, 2) late adverse reaction, which is defined as a reaction which occurs one hour to one week after contrast medium injection, and 3) very late adverse reaction, which is nephrogenic systemic fibrosis (NSF). The risk factors of acute adverse reaction include a history of acute reaction to GBCA, asthma, and atopy requiring medical treatment. The risk factors of NSF include dialysis, eGFR < 30 ml/min/1.73 m², acute renal failure, and use of unstable linear-chelate GBCA. In recent studies, tissue retention of Gd after GBCA administration has been reported even in patients without renal dysfunction. Brain retention of Gd is able to be detected as an increased signal intensity of the brain tissue on T1-weighted images. Moreover, Gd retention has been detected in the skin, liver, kidney, lung, heart, and bones more often with linear-chelate GBCA than macrocyclic GBCA. In a study using pregnant mice, Gd was confirmed to be transferred to pups and was retained in their brain, leading to impaired brain development.

You, physicians, have always said, “All officials are idiots in the field of child abuse protection”.

You sometimes said, “I did NOT know that!, but We DID our best!”

By the way, do you know the ABC of criminal procedure law to determine the facts in criminal cases?

Diffusion-weighted imaging (DWI) is a special application of MRI that derives its contrast from differences in water molecule mobility in different tissues and structures. Water molecule mobility is restricted in tissues with higher cellular density, intact cell membranes and more complex fluid. DWI, a well-established technique in neuroimaging, is also useful in body imaging in children for tumor detection, characterization, and assessment of response to chemotherapy, and liver fibrosis.

On the other hand, gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) is a hepatobiliary MRI contrast agent. Gd-EOB-DTPA is taken up by hepatocytes and excreted via the biliary system. The advantages of Gd-EOB-DTPA include improved characterization of liver lesions and improved detection of metastases. Moreover, imaging with Gd-EOB-DTPA has been useful in the evaluation of various biliary pathologies including anatomical variants and liver function.

In this article, we introduce pediatric DWI in terms of principles, techniques, the normal appearance of abdominal anatomic structures, and current and emerging applications. And, we will describe the utility of Gd-EOB-DTPA.

A 4-year-old boy presenting with a painless scalp tumor was initially planned to undergo invasive biopsy. The MR findings of the scalp tumor itself were nonspecific; however, those of the bone marrow showed low intensities on T1 and T2 weighted images, and mild high intensity on fat saturated T2 weighted image. Diffusion-weighted image also showed high intensity with a low ADC value. Based on these MR findings, we performed bone marrow aspiration prior to biopsy which confirmed a diagnosis of acute lymphoblastic leukemia. In children with a soft tissue tumor or a tumor-like condition without any clinical symptoms or abnormalities on blood tests, we should consistently be aware of the possibility of acute lymphoblastic leukemia in the differential diagnosis. MR may provide useful information not only of a local lesion but also of the bone marrow providing clues to the diagnosis.

Objective: Deep neck abscess often has a rapid onset and can progress to life-threatening complications. The treatment of deep neck abscess in children is antibiotics and drainage through an incision. However, the timing and need for surgical intervention remain controversial. The purpose of this study was to investigate which factors were associated with failure of nonsurgical treatment.

Methods: We retrospectively examined 16 children with deep neck abscess between March 2007 and October 2010 at BellLand Hospital in Japan. We determined age, sex, symptoms, location of abscess, lesion size, clinical course, white blood cell count, CRP and result of culture from infection site on admission.

Results: 5 of 16 cases had surgical drainage, and 11 cases received conservative treatment such as intravenous antibiotics. There was a statistically significant difference in the size of the abscess between the groups of surgical drainage and conservative treatment. There were no significant differences in age, sex, white blood cell count or CRP.

Conclusion: We suggest that the abscess size may be useful in selecting patients with deep neck abscess who might be treated with intravenous antibiotics alone.

Tuberculous meningitis is a rare and potentially fatal infectious disease. Delayed diagnosis and treatment will result in a poor neurologic outcome; however, early diagnosis is not always easy because of nonspecific signs and symptoms. We report a 10-month-old boy presenting vomiting and “not doing well”, finally diagnosed as having tuberculous meningitis. Brain CT on admission showed significant basilar meningeal enhancement as well as obstructive hydrocephalus and multiple ring-enhanced parenchymal lesions. Even though the clinical manifestations or laboratory test results were not specific, the neuroimaging findings led us to raise a high index of suspicion of tuberculous meningitis. Specific laboratory tests for Mycobacterium tuberculosis were promptly initiated, which aided in the immediate confirmation of the diagnosis. The characteristics of the neuroimaging findings of tuberculous meningitis have been well documented; however, not every pediatrician is familiar with interpretation of the imaging findings. The present case will help pediatricians to be aware of clues to the early diagnosis of tuberculous meningitis.

Crowned dens syndrome (CDS) is defined as the presence of severe neck pain and calcifications around and above the odontoid process of the axis, and occurs frequently in elderly women. We report the first case of CDS in children. A 4-year-old girl presented to our hospital with neck pain and fever. She was diagnosed as having CDS after cervical computed tomography (CT) showed calcifications around the dens. Her symptoms improved spontaneously with use of nonsteroidal anti-inflammatories and bed rest. Cervical CT revealed disappearance of circumferential calcification of the dens without treatment, 14 months after onset. We conclude that CDS should be considered in the differential diagnosis, even in children presenting with severe neck pain and fever, and a cervical CT scan should be obtained.