High-frequency linear probes used in the head and neck region have high resolution and can observe fine structures. Therefore, ultrasonography in the head and neck region is highly useful. However, the anatomy of the neck is complex, and it is necessary to understand the anatomy of the neck for ultrasound evaluation. The neck is composed of multiple overlapping fascia, and blood vessels and cervical lymph node flow are in the layer between the shallow and deep lobes of the deep cervical fascia. Since most cervical lymphadenopathies and masses are located in this layer, the examiner should focus on this area during cervical ultrasonography. When determining whether a lymph node is benign or malignant, the internal structures of the lymph node are assessed using B-mode and Doppler ultrasound. Some metastatic lymph nodes show characteristic ultrasound images depending on the carcinoma, which is also helpful in predicting the primary site. Among benign lymphadenopathies, tuberculous lymphadenitis requires attention because it is difficult to distinguish and diagnose. The mode of metastasis or recurrence of head and neck cancer differs depending on the primary site. Furthermore, ultrasonography for follow-up of cervical recurrence after head and neck surgery should be performed with caution because the anatomy of the neck has changed significantly after surgery. Medical information such as surgical records and preoperative ultrasound findings can be helpful. These topics are discussed in detail in this text.

Nonalcoholic fatty liver disease (NAFLD) is entering a new era in terms of diagnosis and conceptualization. The term NAFLD is considered to not reflect current knowledge. Metabolic dysfunction-associated fatty liver disease (MAFLD) has been suggested as a more appropriate overarching term by experts in this field. Regarding NAFLD progression, most patients die from non-liver-related diseases, even patients with advanced fibrosis. Liver biopsy is essential for the diagnosis of nonalcoholic steatohepatitis (NASH); it is the only procedure that reliably differentiates NAFLD from NASH. Recently, various noninvasive methods for diagnosing steatosis and fibrosis have been developed. Ultrasound attenuation measurements and proton density fat fraction with magnetic resonance imaging (MRI) have been developed as imaging tools for predicting steatosis. Fibrosis-4 index and NAFLD fibrosis score are complex scores for predicting fibrosis in patients with NAFLD. In addition, elastography based on ultrasound and MRI has been developed as an imaging tool for predicting fibrosis. There is a strong correlation between values from various real-time shear wave elastography devices and transient elastography, which is the gold standard for ultrasound-based measurements of liver stiffness. In conclusion, NAFLD is at a turning point in terms of its conceptualization, terminology, and diagnostics. It is now time to reconfirm the role of ultrasonography for the assessment of NAFLD.

The prevalence of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) has increased rapidly worldwide, making NAFLD/NASH an important global health problem from both a medical and socioeconomic standpoint. NAFLD is also regarded as a liver component of metabolic syndrome and is reported to be associated with the risk factors for metabolic syndrome. It has been suggested that NAFLD/NASH be recognized both as a liver-specific disease and as an early mediator of systemic diseases. Liver biopsy is recommended as the gold standard method for the diagnosis of NASH and for the staging of liver fibrosis in patients with NAFLD. However, because of its high cost, high risk, and high weightage as a healthcare resource, invasive liver biopsy is a poorly suited diagnostic test for such a highly prevalent condition. Therefore, the development of reliable noninvasive methods for the assessment of liver fibrosis has been sought to estimate the risk of progression of NASH to cirrhosis, estimate the risk of cardiovascular events, aid in the surveillance for HCC, and guide therapy in patients with NAFLD/NASH. In this review, we highlight the principles and recent advances in ultrasound elastography techniques (Real-time Tissue Elastography^®, vibration-controlled transient elastography, point shear wave elastography, and two-dimensional shear wave elastography) used to evaluate the liver fibrosis stage and steatosis grade in patients with NAFLD.

The prevalence of nonalcoholic fatty liver disease (NAFLD) is expected to increase because of the current epidemics of obesity and diabetes, and NAFLD has become a major cause of chronic liver disease worldwide. Liver fibrosis is associated with poor long-term outcomes in patients with NAFLD. Additionally, increased mortality and liver-related complications are primarily seen in patients with nonalcoholic steatohepatitis (NASH); however, nonalcoholic fatty liver (NAFL) is believed to be benign and non-progressive. Therefore, distinguishing between NASH and NAFL is clinically important. Liver biopsy is the gold standard method for the staging of liver fibrosis and distinguishing between NASH and NAFL. Unfortunately, liver biopsy is an invasive and expensive procedure. Therefore, noninvasive methods, to replace biopsy, are urgently needed for the staging of liver fibrosis and diagnosing NASH. In this review, we discuss the recent studies on magnetic resonance imaging (MRI), including magnetic resonance elastography, proton density fat fraction measurement, and multiparametric MRI (mpMRI) that can be used in the assessment of NASH components such as liver fibrosis, steatosis, and liver injury including inflammation and ballooning.

Nonalcoholic fatty liver disease (NAFLD) is based on the concept of pathological morphology as well as clinical findings, and is broadly categorized into nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH). The differential diagnosis between NAFL and NASH is important because NASH has the potential to progress to cirrhosis and hepatocellular carcinoma. NAFL is simple hepatic steatosis without hepatocellular injury, while NASH is characterized by macrovesicular steatosis, inflammation, and ballooning hepatocytes with a predominantly centrilobular (zone 3) distribution. Liver biopsy is a useful test for diagnosing NAFLD, but it is invasive. Therefore, various noninvasive methods including diagnostic imaging have been developed in recent years. To verify their usefulness, it is necessary to clarify in detail how the pathological findings are reflected in the image findings as imaging and histopathological findings are closely related. We describe the main histological features of NAFLD, i.e., steatosis, inflammation, ballooning hepatocytes, Mallory-Denk bodies, and fibrosis, as well as the evolutional process to liver cirrhosis.

A 32-year-old woman had undergone allogeneic hematopoietic stem cell transplantation for the treatment of acute myeloid leukemia. Liver stiffness (LS) at admission was 3.5 KPa. Weight gain, abdominal pain, and elevated serum total bilirubin level were observed approximately 67 days after transplantation. Ultrasonography (US) and LS measurement (LSM) were performed. LS was markedly high (at 42.2 KPa), and US revealed hepatomegaly, ascites, and decreased portal venous flow. The patient was diagnosed with late-onset sinusoidal obstruction syndrome/veno-occlusive disease (SOS/VOD). After administration of recombinant thrombomodulin, fresh frozen plasma, and low-molecular-weight heparin, LS decreased, portal blood flow improved, and serum bilirubin level decreased. Moreover, LS decreased to 25.4 and 4.9 KPa after 115 and 342 days, respectively. The diagnosis of SOS/VOD was based on clinical symptoms and US findings, and the hepatic hemodynamics were included in the diagnostic criteria for late-onset SOS/VOD (European Society for Blood marrow transplantation, 2016). However, Doppler blood flow measurement is skill-dependent and time-consuming. LS can be measured quickly, easily, and repeatedly, even by unskilled examiners. Therefore, LSM may be useful for the diagnosis and follow-up of late-onset SOS/VOD.

The patient was a woman in her 70s. She was referred to our hospital due to abnormal blood tests without any chief complaint. Her medical history included chronic hepatitis B, hysterectomy, post-oophorectomy, and hypertension. Her blood test revealed AFP 2.5 ng/ml, which was within the normal range, and PIVKA-II 216 mAU/ml, which was high, but it had decreased to 20 mAU/ml the day before surgery. There were no other particular findings. Ultrasonography showed a 14×12-mm hypoechoic space-occupying lesion with a relatively uniform, well-defined interior and irregular contours in segment 2 (S2). There was no obvious capsular structure. Because of its proximity to the heart, the blood flow signal on color Doppler was difficult to evaluate due to the beating heart. Plain CT showed a pale low-absorption area. As for EOB-MRI, T1-weighted images showed a 17-mm low-signal nodule in the hepatocellular phase at S2. On angiographic CT, tumor staining was seen in S2, and CTAP showed a 17-mm hypo-absorptive area. CTAP showed a 17-mm low-absorption area, part of which was stained by CTHA. Based on these results, intermediate differentiated hepatocellular carcinoma was suspected. Pathology revealed necrotic nests accompanied by a fibrous capsule and surrounded by an infiltrate of chronic inflammatory cells and droplet histiocytes. The cellular ghost was considered to be the image of a resolved hepatocellular carcinoma.

We report a case of hepatocellular carcinoma that was thought to have resolved spontaneously. Contrast-enhanced ultrasonography revealed characteristic findings.

A hypoechoic free space around the fetal heart can be differentiated with ultrasonography as pericardial effusion or a mediastinal cyst. Respiratory or circulatory failure may occur if the space becomes so enlarged as to put pressure on the heart and lungs. We report a case diagnosed with a neonatal mediastinal cyst after management as isolated pericardial effusion in pregnancy. The patient was 27 years old (para 1). A hypoechoic free space with a width of 2 mm around the left ventricle was detected on fetal ultrasonography at 30 weeks of gestation. The case was diagnosed as isolated pericardial effusion not complicated by fetal structural abnormalities or hydrops. Nevertheless, the hypoechoic area increased in size to 15 mm at 36 weeks of gestation, pressing on the left ventricle and the left lung; thus, a caesarean section was performed at 37 weeks and 2 days of gestation, while preparing for emergency pericardiocentesis. The neonate was stable with intubation, and a neonatal ultrasonographic examination showed the cystic lesion, which was recognized as fetal pericardial effusion; therefore, pericardiocentesis was not performed. A chest MRI diagnosed the mediastinal cyst 3 days after birth. The size of the cyst was unchanged, with no symptoms for 10 months. If a hypoechoic free space around the fetal heart is detected, we should carefully make the diagnosis, including mediastinal cyst in addition to pericardial effusion in the differential diagnosis.