This review covers the fundamentals of ultrasound engineering for ultrasound specialists and sonographers. To understand the brightness distribution in B-mode ultrasound images of clinically visualized target areas, it is essential to grasp how ultrasound propagates through biological tissues and the acoustic properties involved, such as sound velocity, reflection, refraction, and attenuation, at the sound pressure levels and frequency ranges used in diagnostic ultrasound systems. This knowledge also helps in understanding the mechanisms behind artifact generation. A solid comprehension of ultrasonic beam formation in both the azimuth and slice directions, as well as spatial resolution, is crucial for selecting the appropriate probe and image quality settings for the target areas. Tissue harmonic imaging is now standard in B-mode imaging, and understanding its generation mechanisms, imaging techniques, and effects is key to effective practice. Various Doppler modes used to visualize blood flow are also discussed. Understanding the aliasing phenomenon is important for setting the optimal velocity range. Additionally, moving target indicator (MTI) filters designed for removing clutter signals from surrounding tissues are explained. There is also a description of microvascular flow imaging (MVFI), which enhances the performance of clutter signal removal. Furthermore, the principles of contrast-enhanced harmonic imaging using the ultrasound contrast agent Sonozoid^® are presented. A grasp of phase modulation and amplitude modulation principles enables their appropriate selection based on the specific observation objectives.

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Purpose: To determine the optimal cutoff value of thyroid blood flow measured using the vascularity index (VI) on a Canon Aplio i800 to differentiate Graves’ disease from painless thyroiditis in patients with thyrotoxicosis. Subjects and Methods: Between June 2023 and February 2025, a total of 348 untreated patients with thyrotoxicosis who first visited our institution and underwent both radioisotope (RI) scintigraphy and ultrasonographic VI assessment were included (Graves’ disease: n=319, painless thyroiditis: n=29). Differential diagnoses were made in accordance with the Diagnostic Guidelines for Thyroid Diseases 2024 (revised in 2024) established by the Japan Thyroid Association. Thyroid blood flow was quantified as the VI (%). Receiver operating characteristic (ROC) analysis was performed to determine the optimal cutoff value. Results: The median blood flow values were 13% for Graves’ disease and 3.1% for painless thyroiditis, with significantly higher values observed in Graves’ disease (p<0.001). ROC analysis identified an optimal cutoff value for VI of 8.3% (AUC=0.927, specificity 100%). A practical threshold was considered to be approximately 10%. However, 35% of patients with Graves’ disease showed VI <10%. Conclusion: Quantitative evaluation using the VI is useful for differentiating Graves’ disease from painless thyroiditis, with a cutoff value of approximately 10% being clinically applicable. However, a comprehensive assessment incorporating laboratory data and other imaging findings is necessary.

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Paget-Schroetter syndrome (PSS) is a relatively rare form of upper extremity deep vein thrombosis (UEDVT), often associated with thoracic outlet syndrome (TOS). We report a case in which ultrasonography was useful not only for detecting thrombosis but also for dynamically evaluating venous compression during symptom-provoking maneuvers. The patient was a 37-year-old female sonographer who developed left shoulder discomfort in May, followed by mild swelling, numbness, and discoloration of the left forearm. Ultrasonography performed by the patient herself revealed thrombosis in the left subclavian vein, leading to hospital referral. Laboratory testing demonstrated no thrombophilic predisposition (D-dimer 0.53 μg/mL). Anticoagulation with a direct oral anticoagulant (DOAC) was initiated, and thrombus resolution was confirmed after 2 months. However, recurrent thrombosis was documented in the same location in December and again the following May, prompting resumption of anticoagulant therapy. At reevaluation in September of the following year, there was no muscle weakness or resting circulatory disturbance, but the Roos test was positive. Ultrasonography during arm elevation demonstrated venous compression and flow stasis at the costoclavicular space, corresponding to the site of prior thrombosis. Contrast-enhanced CT confirmed compression of the left subclavian vessels in the same posture. The patient was diagnosed with Paget-Schroetter syndrome. Notably, her occupational activity as a sonographer, which required repetitive use of the left upper limb to operate the ultrasound device, was considered a potential contributing factor to chronic venous compression. The case highlights the utility of ultrasonography performed under symptom-inducing conditions, allowing real-time assessment of venous hemodynamics, which may be overlooked in supine imaging. This case demonstrates that ultrasonography is not only effective in detecting thrombosis but also valuable in assessing dynamic positional venous compression. Ultrasonographic evaluation under symptom-provoking conditions may therefore play a critical role in the diagnosis of Paget-Schroetter syndrome.

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Reports of transvalvular leakage (TVL) following implantation of the self-expanding transcatheter aortic valve Navitor are limited, and transesophageal echocardiographic (TEE) case reports clearly demonstrating intraprosthetic regurgitation are exceedingly rare. An 89-year-old woman with symptomatic severe aortic stenosis underwent transfemoral transcatheter aortic valve implantation (TAVI) under general anesthesia using a 25-mm Navitor valve. Immediately after deployment, severe aortic regurgitation with hemodynamic deterioration occurred. Intraoperative TEE revealed minimal paravalvular leakage; a broad regurgitant jet originating from the center of the transcatheter valve was clearly visualized, consistent with predominant transvalvular leakage. Balloon post-dilatation resulted in only marginal improvement. Consequently, a valve-in-valve transcatheter procedure using a SAPIEN 3 valve was performed, completely abolishing the regurgitation and rapidly stabilizing hemodynamics. This case demonstrates that intraoperative TEE can be used to reliably identify intraprosthetic regurgitation of transcatheter valves and elucidate the mechanism of acute severe aortic regurgitation following TAVI. In cases of acute TVL after TAVI, TEE is a valuable modality for determining the origin and severity of regurgitation.

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Renal biopsy is essential for diagnosing renal diseases but can lead to hemorrhagic complications such as renal arteriovenous fistula (RAVF). A woman in her 80s developed gross hematuria after a renal biopsy performed for acute kidney injury. Color Doppler ultrasonography revealed a mosaic flow pattern with marked aliasing and a loop-like vascular structure within the kidney. Pulsed Doppler demonstrated a high-velocity, low-resistance arterial flow (peak systolic velocity: 2.2 m/s, resistive index: 0.26) and pulsatile changes in the draining vein. Based on these hemodynamic abnormalities, RAVF was strongly suspected and subsequently confirmed via contrast-enhanced CT. Transcatheter arterial embolization using coils was performed, after which follow-up ultrasonography showed disappearance of the shunt flow and normalization of hemodynamic parameters and venous waveforms. Doppler ultrasonography, integrating color and pulsed Doppler, is effective for both hemodynamic assessment and post-treatment monitoring of post-biopsy RAVF.

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Takotsubo cardiomyopathy (TCM) is characterized by transient left ventricular systolic dysfunction typically triggered by emotional or physical stress. While the prognosis is generally favorable, severe mechanical complications such as ventricular septal perforation (VSP) can occur, albeit rarely. We report a fatal case of TCM complicated by VSP in an a man in his 80s. The patient developed acute chest pain several hours after the sudden death of his wife. On admission, he presented with cardiogenic shock. Electrocardiogram showed T-wave inversion in leads Ⅱ, Ⅲ, and aVF; ST-segment elevation in V2; and giant inverted T waves in V3-6. Laboratory tests revealed elevated troponin Ⅰ and CK/CK-MB levels. Emergency coronary angiography demonstrated no significant stenosis, but left ventriculography revealed apical akinesis with basal hypercontraction and a left-to-right shunt. Transthoracic echocardiography confirmed a 10-mm apical ventricular septal perforation with a pulmonary-to-systemic blood flow ratio (Qp/Qs) of 2.9. Intra-aortic balloon pumping was deferred due to severe psychomotor agitation and difficulty maintaining the required immobilization. Hemodynamic support was attempted with fluid resuscitation and norepinephrine; however, this may have inadvertently exacerbated the intraventricular pressure gradient and mechanical stress on the fragile septum. During the clinical course, persistent hypotension necessitated sedation and endotracheal intubation. Although mechanical circulatory support devices, veno-arterial extracorporeal membrane oxygenation, and surgical intervention were considered, after explaining to the patients family the risks associated with his age, overall condition, and invasive treatments in favor of comfort-focused care. His circulatory failure progressively worsened, and he died on hospital day 5. This case highlights that VSP is a critical, though rare, complication of TCM. Early detection via color Doppler echocardiography and careful consideration of circulatory support devices are essential in managing such high-risk cases.

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