This article describes the basis and principle of ultrasound shear wave elastography and ultrasound attenuation evaluation, which are attracting attention as new quantitative ultrasound measurement technologies for tissue characterization. Shear wave elastography is an imaging technique that quantifies tissue stiffness by measuring the speed of shear waves in tissue. This technique uses dynamic excitation to generate shear waves in the body. Ultrasound amplitude attenuates due to scattering and absorption, etc., while ultrasound waves propagate through tissue. Ultrasound attenuation measurement is a method to quantify ultrasound attenuation using an attenuation constant evaluated based on echo signals.

B-lines, artifacts in lung ultrasound, have been widely utilized. The physical basis of B-lines and the mechanism in the human body have not yet been fully elucidated. The configuration of B-lines is affected by settings of ultrasound machines; however, the fact that the settings are not considered in some clinical situations is a serious issue. There have been concerns about the current definition of B-lines; therefore, it has been proposed that the artifacts extending toward ultrasound beams be called “vertical artifacts” regardless of the length. Our group has been engaged in clinical and basic research toward solving these issues. We reported that the configuration of B-lines is strongly affected by the spatial compound imaging and the focal point in clinical ultrasound. In basic research, we devised simple models of the chest wall and lung that generate a single vertical artifact. We conducted a series of experiments using the simple models and revealed that the size of contact and height (volume) of the sources are key factors in the generation, echo intensity, and length of vertical artifacts. And we also revealed that the larger the attenuation inside the sources of vertical artifacts is, the lower the intensity of vertical artifacts is and the more vertical artifacts attenuate. The results obtained from these experiments support the hypothesis that the physical basis of vertical artifacts is multiple reverberations. They help us reason the mechanism of the generation of vertical artifacts in the human body. Furthermore, they indicate that analyses of the properties of vertical artifacts and their relation to central frequencies of the ultrasound beam may be useful for differentiating diseases.

Purpose: A safety trial for early fetal treatment before 26 gestational weeks to improve the neurological prognosis of fetuses with myelomeningocele (MMC) was conducted in Japan. The aim of the study was to examine the prenatal diagnostic background and postnatal outcomes of fetuses with MMC at our institution and identify future challenges for fetal treatment. Methods: We retrospectively reviewed the medical records of MMC cases in our institution encountered between November 2014 and August 2022. The timing of prenatal diagnosis, ultrasound findings leading to diagnosis, and the vital/motor prognosis were evaluated. Results: The study included 26 cases, all of which were referred from other institutions. The median gestational age at referral was 25 weeks (range: 11-34 weeks), with 11 cases (42％) being referred after 26 weeks. Five cases were diagnosed before 22 weeks, of which three opted for elective termination. The referral indications were isolated MMC in 11 cases, isolated ventriculomegaly in five cases, combined spine and ventricular abnormalities in six cases, lemon and banana signs in one case, and other associated conditions in three cases. Excluding pregnancy terminations, the median gestational age at delivery was 38 weeks (range: 26-40 weeks). At a median follow-up of 23 months (range: 0-67 months), all cases survived; however, 14 cases (61％) exhibited motor function impairment. Ten of 15 children (67％) who were at least 18 months of age were diagnosed with neurogenic bladder or required self-urination. Conclusion: While the vital prognosis of fetuses with MMC is favorable, many exhibit motor function impairment postnatally. The current timing of prenatal diagnosis is not sufficiently early, highlighting the need to expedite the diagnosis.

Gallbladder torsion is an acute abdominal condition that causes obstruction of blood flow to the gallbladder and requires early surgical intervention. However, gallbladder torsion is sometimes difficult to distinguish from acute cholecystitis because the clinical symptoms and ultrasonographic findings are similar. We report a case in which contrast-enhanced ultrasonography (CEUS) was useful in the diagnosis of gallbladder torsion. The patient was a woman in her 80s who was referred to our hospital with a chief complaint of worsening pericardial pain. Contrast-enhanced computed tomography revealed acute cholecystitis, and ultrasonography showed an enlarged gallbladder and a hyperechoic lesion in the neck, suggesting gallbladder torsion. CEUS was Sonazoid performed to confirm the diagnosis, at which no contrast medium was seen flowing into the gallbladder wall or the cervical hyperechoic lesion. The operative findings also showed torsion in the neck of the gallbladder, and a final diagnosis of gallbladder torsion was made. CEUS can easily confirm the presence or absence of blood flow, and is thought to be capable of diagnosing gallbladder torsion. Furthermore, Sonazoid, an ultrasound contrast agent, can be used in patients with impaired renal function, and the examination can be performed with conventional ultrasound equipment at the bedside, such as in the emergency room. CEUS is a very useful method for quickly and easily differentiating acute cholecystitis and gallbladder torsion.