It is not uncommon for acute abdomen to require some therapeutic intervention, such as surgery, and appropriate measures must be taken within a limited period. However, the causes of acute abdomen are diverse, and the diagnosis is not easy. Usually, a comprehensive diagnosis is made based on medical history, physical examination, blood tests, and imaging studies, and a treatment plan is determined. However, the number of radiologists in Japan is much less than in other countries, and only a few facilities, such as university hospitals, are capable of providing 24-hour, 365-day care. Under these circumstances, the physician in charge of each department has no choice but to perform everything from selection of tests to diagnosis. In order to do so, it is necessary to understand the advantages and disadvantages of each imaging study, and to consider what kind of information each study can provide that will affect the treatment plan.

Respiratory diseases in children include not only respiratory tract infections but also congenital diseases and allergic diseases. Furthermore, due to the addition of factors related to growth and development, there are age-related differences even in the same category of diseases. Infants and younger children are often difficult to diagnose because of their anatomical and respiratory physiological issues, which are prone to respiratory symptoms and the inability to perform lung function tests. Furthermore, the parents of these patients tend to be physically and mentally exhausted not only due to anxiety about the disease but also due to their own disturbed sleep, as their child’s symptoms tend to appear at night. For these reasons, diagnostic imaging seems extremely important for the diagnosis and judgment of therapeutic effect in pediatric patients. Chest X-ray photography is the most common imaging technique. Even with simple radiography, a lot of information can be obtained. Understanding the characteristics of respiratory organs and the characteristics of respiratory diseases in children can aid in extracting sufficient information to make an early diagnosis and determine the efficacy of treatment.

Chest radiography is the imaging study obtained most frequently to evaluate the respiratory system in pediatric patients. CT has become the standard imaging method for detailed imaging assessment of both pulmonary and mediastinal structures. Although MRI has the advantages of noninvasive imaging and lack of radiation exposure, its disadvantages in the chest region are the extremely short T2 of the lung, low proton density, and respiration and heartbeat motion artifacts. In addition, the application of techniques to reduce motion artifacts, such as cardiac and respiratory gating, is usually difficult because of quick movements in infants. However, these disadvantages of MRI can be overcome by a new MRI technique that uses an ultrashort echo time (UTE). Recent studies have shown good visualization of the lung parenchyma and mediastinum in adult patients using UTE-MRI. Pointwise encoding time reduction with radial acquisition (PETRA) is a UTE technique that has demonstrated submillimeter imaging of the bronchi and lung parenchyma. We are working on the possibility that PETRA may be feasible for the assessment of the airway system in neonates with congenital cystic lung disease thereby reducing the frequency of the CT exams needed in children.

This review article introduces the diagnostic process of skeletal dysplasia in pediatric radiology. The diagnostic process of skeletal dysplasia was established by identification of key findings. Also, recognition of the pathognomonic findings plays an important role in the definite diagnosis of skeletal dysplasia. This article includes four pathognomonic findings as follows: 1) asymmetric appearance of long bones in chondrodysplasia punctata (XLD): Conradi-Hunermann type, 2) Scimiter-like patella calcification in Zellweger syndrome, 3) Wormian bone in osteogenesis imperfecta, 4) Bowdler spur in congenital hypophosphatasia. Among the radiological clues described above, Scimiter-like patella calcification in Zellweger syndrome and Bowdler spur in congenital hypophosphatasia were thought to be pathognomonic findings in the narrow sense. If a pathognomonic finding is found from a skeletal survey, the definite diagnosis might be obtained despite the rarity of the disease. We pediatric radiologists need to know these important clues to make a diagnosis of the specific type of skeletal dysplasia.

Congenital skeletal diseases (CSDs) can be diagnosed early by advances in diagnostic imaging and identification of causative genes. However, many patients have a fatal course or severely impaired daily activities. Therefore, therapeutic improvements are expected. To establish curative and permanent therapy for one of CSDs, hypophosphatasia (HPP), we are trying to achieve bone regeneration using mesenchymal stem cells (MSCs), which bring about bone and cartilage regeneration. So far, we succeeded in not only recovery of bone mineralization but also improvement of muscle weakness, respiratory disturbance and mental retardation for fatal HPP patients using allogeneic MSC transplantation, resulting in improvement in both prognosis and quality of life. But, normal bone architecture has not been restored. In the near future, we plan a new cell transplantation using highly-purified MSCs (rapidly expanded cells; REC), which have excellent proliferative ability and bone differentiation. Bone regenerative therapy using MSCs can be expected to be applied to curative treatments for patients with CSDs including HPP if these methodologies are established.

Imaging diagnosis of pediatric head injuries is extremely important for identifying abusive head trauma (AHT). Although there has been much debate about the pathophysiology and diagnostic imaging of AHT, a consensus has not yet been established. In this review, to deepen our understanding of pediatric head injury including AHT, we describe the development and anatomy of the skull (particularly the calvarium and suture) and meninges (particularly the dural border cell layer). In addition, we discuss the pathogenesis and relationship between acute cerebral edema and subdural hematoma with special reference to neuronal excitotoxicity.

Neuroimaging has an important role in the diagnosis of underlying disorders and seizure focus in childhood epilepsy. In mesial temporal lobe epilepsy (MTLE), MRI shows hippocampal atrophy and hyperintense signal that are called hippocampal sclerosis. Recent high-resolution images reveal internal structural abnormality in the hippocampus. Many patients with MTLE have febrile status epilepticus (FSE) during infancy. We have revealed hippocampal enlargement and high intense signal on diffusion-weighted images during the acute period after FSE, and subsequent hippocampal atrophy. Hippocampal enlargement and DWI high intensity suggest cytotoxic edema caused by FSE.

MRI shows thick cortex, blurred cortical-subcortical junction, and subcortical high intensity at the site of focal cortical dysplasia. However, these findings are often difficult to detect during the infantile period because of incomplete myelination.

New MRI techniques such as diffusion tensor imaging or simultaneous recording of electroencephalogram and functional MRI (EEG-fMRI) are promising tools to reveal the pathophysiology and epilepsy focus in childhood epilepsy.

Voxel-based morphometry (VBM) and surface-based morphometry (SBM) done by means of MRI have provided new insights into the neuroanatomical basis for subjects with several conditions. Recently, VBM has been applied to investigate not only regional volumetric changes but also voxel-wise maps of fractional anisotropy (FA) computed from diffusion tensor imaging (DTI). Furthermore, we can acquire structural networks using recently introduced technique of source-based morphometry, which applies an independent component analysis (ICA) to a segmented image, arranges voxels into sets that contain similar information, and acquires common morphological features of the gray matter concentration among individuals at the network level. The aim of this article is to review the recent work using VBM and SBM technique in particular focusing on pediatric MRI. VBM approach detects the structural brain abnormalities that appear normal on conventional MRI. Thus, in the future, large cohort studies to monitor whole brain changes on a VBM basis will facilitate further understanding of the neuropathology of several pediatric conditions, such as autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD).

Purpose: In recent years, it has become possible to display and view the three-dimensional structure of organs in 3D by the virtual reality (VR) technology that is rapidly spreading. This time, we conducted this study to examine the effectiveness of VR in the field of pediatric surgery.

Materials and Methods: Thirty students were randomly divided into two groups, one with CT images of cystic disease cases and the other with VR images of the same cases (CT (ct→vr) group, VR (vr→ct) group). A test was conducted to measure comprehension. After that, the CT image and VR image were exchanged (CT (vr→ct) group, VR (ct→vr) group) and a crossover test was performed.

Results: Comparing the time required for each test, that of the group that viewed VR was significantly shorter. In addition, the percentage of correct answers was significantly higher in the groups that previously viewed the VR images (VR (vr→ct) group and CT (vr→ct) group).

Conclusion: In cases where it is difficult to understand the three-dimensional structure of organs, it is considered effective to first grasp the whole with a VR image and then confirm the CT image in detail.

Cardiac catheterization is used to diagnose, treat, and monitor the progress of congenital heart disease (CHD). International multicenter trials using database data have been conducted. In these trials, methods of monitoring radiation dose using kerma-area product (KAP) divided by body weight (BW) have been assessed. However, in Japan, dose monitoring methods that take KAP into consideration are not widely used. We aimed to analyze previous reports on the radiation dose received by CHD patients during diagnostic and therapeutic procedures, propose a standard method for monitoring radiation dose in Japan, and ensure that this method will be applicable to database-type data repositories. To evaluate the use of fluoroscopic dose rate (FDR) as a means of monitoring radiation doses, we calculated correlation coefficients for KAP/BW with FDR, FDR/BW, FDR/Height, and the index of FDR and BW in the diagnostic, therapeutic, and total categories. FDR/BW correlated best with KAP/BW, and the coefficients ranged between 0.4 and 0.6. Additionally, correlation coefficients according to age (in days) across all categories were calculated. FDR/BW was a reliable index to compare Japanese and international data. We therefore propose the use of FDR/BW as a standardized method for monitoring stochastic effects related to radiation dose. Calculating this statistic is easy, and future database research may facilitate inter-center comparisons.

We report a case of fallopian tube torsion with specific imaging findings. An 11-year-old female presented with a chief complaint of lower left abdominal pain. She had experienced intermittent lower left abdominal pain for 5 days prior to presentation. An egg-sized mass was palpable in the lower left abdomen, and ultrasound revealed a tubular structure in the pelvis. A paraovarian cyst and cystadenoma were considered in the differential diagnosis. Plain magnetic resonance imaging (MRI) of the abdomen performed on the same day revealed normal ovaries but dilated luminal structures with low T1 and high T2 signals to the left of the uterus, suggesting a hydrosalpinx. Because the abdominal pain did not resolve, we reviewed the MRI, as whirlpool signs were pointed out. Torsion of the fallopian tube was strongly suspected. This was confirmed on laparoscopic surgery, and a necrotic fallopian tube was resected. Tubal torsion is a rare disease in children, and pre-operative diagnosis is difficult, often resulting in delayed treatment. Although one of the pre-operative differential diagnoses for this patient was accurate and urgent surgery was performed, the fallopian tube could not be preserved.

Gastrointestinal duplication cysts are rare congenital anomalies that develop anywhere in the gastrointestinal system. The prevalence of these cysts is 1 in 4,500 births. They are usually detected prenatally due to improvements in prenatal screening ultrasonography. However, the cyst size, location, and type, mucosal pattern, and presence of complications result in varying clinical presentations and imaging findings, and therefore, it is difficult to distinguish between gastrointestinal duplication cysts and other cystic lesions before surgery. We report a case of duplication cyst diagnosed in a newborn female infant based on the surgical findings, although the cyst had been suspected to be a liver cyst before birth, and it was suspected to be an ovarian cyst or a mesenteric cyst, based on imaging tests performed after her birth.

We review the clinical presentations and imaging findings of duplication cyst by comparing our case and other past cases.

We herein report a case of cervical lymphadenitis with pharyngeal cellulitis and laryngeal edema, which was diagnosed by a contrast enhanced computed tomography (CT) examination for the purpose of deep neck infection evaluation. An 11-year-old girl was referred to our hospital with a fever, sore throat, and swelling on the right side of the neck. Ultrasonography revealed a swelling on the Bright cervical lymph nodes, but no abscess, and therefore we made a diagnosis of cervical lymphadenitis. The symptoms persisted, and the patient began experiencing pain while swallowing. We then performed a cervical contrast-enhanced computed tomography, which revealed a low absorption area in the right parapharyngeal space and swelling of the epiglottis and arytenoid. These findings improved with the administration of corticosteroids. Deep neck infection with laryngeal edema is rare in children. In this case, laryngeal edema secondary to cervical lymphadenitis may have occurred. Ultrasonography may be useful for determining the condition of the cervical lymph nodes and presence or absence of an abscess; however, it is not helpful for evaluating a deep neck infection. Contrast-enhanced CT is useful for evaluation of inflammation and airway lesions in case of a suspected deep neck infection.

We experienced a case of severe mediastinal emphysema exacerbated by pharyngeal injury caused by a toothbrush. The case was a 2-year-old 2-month-old boy. He fell down with holding a toothbrush in the mouth. There was no damage to the toothbrush. From the next day, fever and swelling of the lower jaw were observed, and he visited a local physician. He was referred to our otolaryngologist for scrutiny without pharyngeal mucosal defects and referred to our department for the purpose of examining the fever source without finding any perforation in the laryngeal fiber. Percutaneous oxygen saturation (SpO₂) decreased to 87% in room air, and computerized tomography (CT) showed extensive emphysema from the deep neck to the mediastinum. He was diagnosed with hypoxemia and the possibility of sudden exacerbation of emphysema, and was transferred to the Pediatric Intensive Care Unit (PICU). The patient was cured without any sequelae by ventilator management and antibiotic administration. Oral and pharyngeal injuries due to a toothbrush are clinically common, but there are many cases of minor injuries. Early physical examination of the neck and thoracic CT was considered to be effective in diagnosing worsening disease and deciding the treatment strategy if there were any physical findings and/or exacerbation of vital signs.

Vigabatrin is one of the first-line interventions in infantile spasms. Vigabatrin irreversibly inhibits GABA transaminase, resulting in an increase in the GABA concentration in the brain. Vigabatrin-associated brain abnormalities on magnetic resonance imaging (VABAM) show abnormalities on magnetic resonance imaging (MRI) due to the administration of vigabatrin. VABAM shows MRI signal changes in thalami, basal ganglia, brainstem tegmentum, and cerebella nuclei on T2-weighted and diffusion-weighted images. These changes improve with drug reduction or discontinuation.

We herein report two cases with typical presentation of VABAM.

Case 1. A 2-month-old infant who was diagnosed with infantile spasms underwent vigabatrin and ACTH therapy. One month later, a follow-up MRI showed abnormalities in substantia nigra and globus pallidus on T2-weighted and diffusion-weighted images.

Case 2. A 6-month-old infant with tuberous sclerosis complex was treated with vigabatrin. A follow-up MRI showed signal changes on diffusion-weighted images.

No clinical symptoms were found in either case 1 or case 2.

A 1-year-old girl convulsed and was diagnosed with simple febrile seizure at another hospital on the second day of fever. Day 3 of fever, she was diagnosed as having KD based on the presence of 6 out of 6 criteria at our hospital and was hospitalized and treated with intravenous immune globulin (IVIG) and oral aspirin. She had convulsions twice that night. On the 4th day, she exhibited a persistent disturbance of consciousness and was diagnosed as having MERS type 2 based on the presence of enhanced signals in the splenium of the corpus callosum and cerebral cortex in her diffusion-weighted brain MRI. The treatment with IVIG for KD and pulsed methylprednisolone for MERS type 2 was started because her consciousness had deteriorated. Afterwards her consciousness improved and there were no sequelae. We should be careful that even if a child is diagnosed with febrile seizure at some point, it may be encephalitis/encephalopathy in KD later.