The biological effects of ultrasound exposure can be categorized into thermal and non-thermal effects. Non-thermal effects include primary effects that are directly induced by ultrasound pressure and secondary effects that are generated by ultrasonically induced cavitation phenomena. This tutorial has been written to provide a better understanding of the secondary effects of ultrasound exposure. The dynamics of cavitation bubbles under ultrasound exposure are described to show the mechanisms by which the dynamics of bubbles cause biological effects. The mechanisms are also discussed by comparing ultrasound and X-ray imaging and showing key features of cavitation phenomena in induction of biological effects. Ultrasound therapies that mainly utilize cavitation mechanisms are introduced to show the importance of ultrasound therapies in current and future medicine.

Purpose: Histological classification of breast tumors edited by the Japanese Breast Cancer Society was revised in 2018. The purpose of this study was to clarify the impact of the revision on diagnostic imaging of invasive ductal carcinomas. Subjects and Methods: We investigated ultrasound images of 91 cases diagnosed as papillotubular carcinoma of invasive ductal carcinoma according to the old classification. Results and Discussion: The histological subtypes according to the new classification were microinvasive carcinoma in 26 cases (28.6%), invasive carcinoma with a predominant intraductal component in 51 cases (56.0%), and tubule forming type of invasive ductal carcinoma in 14 cases (15.4%). Ultrasound imaging showed a mass in 41 cases (45.1%) and a non-mass lesion in 48 cases (52.7%). In the remaining two cases, ultrasonography could not detect any abnormal findings. Of the microinvasive carcinoma cases, 19 cases (73.1%) showed a non-mass lesion that mimicked ductal carcinoma in situ. Ultrasound imaging of the cases diagnosed as invasive carcinoma with a predominant intraductal component revealed a mass in 22 cases (43.1%) and a non-mass lesion in 27 cases (52.9%). Twelve (85.7%) of the 14 cases with tubule forming type showed a solid mass. Of these, seven cases (58.3%) revealed discontinuity of borderline between mammary gland and fat tissue, suggesting invasive carcinoma. Papillotubular carcinomas showing various ultrasound images were divided into three histological types by the new classification, and each type showed characteristic ultrasound images. Conclusion: The new classification enables breast tumors to be correctly diagnosed by means of imaging.

Purpose: We have encountered cases of hypoechoic lesions on breast ultrasonography that were diagnosed as normal anatomic variants based on further examinations or follow-up, despite the presence of distortion-like findings. In this study, we investigated what additional findings should be considered for such hypoechoic lesions to avoid unnecessary follow-up examinations. Subjects and Methods: In 27 patients with localized distortions suggestive of breast cancer during ultrasound screenings performed between April 2013 and March 2015, a total of 31 hypoechoic lesions were evaluated retrospectively. Seven of these 31 lesions did not show any obvious lesions on further examination, and 24 lesions did not require further examination and were followed up by repeat ultrasound. We retrospectively examined the ultrasound findings in these patients and confirmed their subsequent outcome. Results and Discussion: The common findings based on the 31 lesions were: (1) Its localization was not consistent with Cooper’s ligaments in some cases, (2) unbranched vessels were observed on color Doppler imaging, and (3) no strain reduction was observed in any cases in which strain elastography was performed. These lesions were mostly located in the lateral part of the breast. No proliferative lesions were found among the four lesions in which we performed fine-needle aspiration biopsy or core needle biopsy. During a median follow-up of 60 months, no cancer was found in any of the cases, including those under scrutiny. Conclusion: Our study suggests that some of lesions with distortion-like findings resembling breast cancer on ultrasound are normal anatomic variants. It seems extremely important to understand such lesions to avoid unnecessary scrutiny and biopsy.

Purpose: There is already a consensus on the usefulness of elastography in breast ultrasonography. However, it is known that the cut-off strain ratio (SR: FLR) differs depending on the manufacturer. There have been few reports on the optimal cut-off FLR in Strain Imaging on Canon equipment, and no data have been presented in Japan. The purpose of this study was to determine the optimal cut-off value between benign breast masses and invasive carcinoma on a Canon device. Subjects & Methods: The subjects were patients who underwent breast ultrasound and FLR measurement with an Aplio i800 between October 1, 2018 and March 31, 2019. Sixty cases showed benign masses, and 70 cases showed invasive cancer. The charts were reviewed and the FLR values were checked retrospectively, and the appropriate cut-off value was examined using the Youden index. Results & Discussion: The optimal cut-off FLR was 4.38.It has been pointed out that the cut-off SR may be different due to differences in ultrasound equipment and examination technique in the JABTS guideline. The value for the Hitachi device was reported to be 4.8, and we previously reported a value of about 3 for the GE device. It is important to be aware that the values vary depending on the device used. Conclusion: The optimal cut-off FLR in elastography is about 4.38 for Canon’s system.

Purpose: We evaluated the benign and malignant diagnosis of breast tumors by adding shear wave elastography (SWE) to BI-RADS ultrasound (US). Methods: The maximum tumor diameter and depth width ratio (D/W) were measured by B-mode and categorized according to BI-RADS US in 97 breast tumors (55 benign and 42 malignant). Shear wave speed, elastic modulus, and color pattern classification of modulus were evaluated by SWE to determine the difference between benign and malignant tumors and to evaluate the diagnostic rate of malignant tumors. Results and Discussion: Malignant tumors were significantly older and had higher values for maximum tumor diameter, D/W, shear wave speed, and elastic modulus. Color pattern classification of the modulus in malignant tumors was often pattern 3 and 4 (p＜0.0001). Corrected for confounding factors, shear wave speed ≥4.07 m/s (odds ratio 17.1), elastic modulus ≥53.7 kPa (odds ratio 17.1), and color pattern ≥3 (odds ratio 19.2) were useful. Furthermore, in the analysis of 76 patients classified as BI-RADS US categories 3 and 4, the highest negative predictive value (91.7%) was found for color pattern ≥3, and the highest positive predictive value (61.9%) was found for shear wave speed ≥4.07 m/s or elastic modulus ≥53.7 kPa, suggesting the usefulness of additional evaluation of SWE. Conclusion: Addition of SWE findings to BI-RADS US findings, especially in cases of categories 3 and 4, might improve the diagnostic rate.

Purpose: We measured R-P time using the inguinal and ankle Doppler waveforms before and after endovascular treatment (EVT) in the lower extremity arteries, and examined whether the ratio could be used as an index for hemodynamic evaluation of the lower limb arteries. Subjects and Methods: We enrolled 108 patients who did not have any stenotic lesions in the lower limb arteries between April 2019 and September 2020 as a control group, and 67 patients with 78 lesions (46 above-the-knee lesions, 32 below-the-knee lesions) who underwent EVT, duplex echo, and ankle brachial index (ABI) measurement before and after EVT. R-P time was measured at the common femoral artery (CFA), anterior tibial artery (ATA), and posterior tibial artery (PTA) at the ankle joint, and ATA/CFA R-P time ratio (R-P time ratio: RPR) and PTA/CFA RPR were calculated based on the R-P time of the CFA. Results and Discussion: The value of RPR was significantly higher in the diseased group than the control group. When the cutoff value was set to 1.41 based on the control group data, the sensitivity was 96%. Before and after EVT for above-the-knee lesions, RPR was significantly changed as well as ABI. On the other hand, ABI showed no significant difference before and after EVT for below-the-knee lesions, but RPR was significantly shortened. Conclusion: RPR was easily measured for evaluation of the hemodynamics of the lower limbs with high sensitivity. It could be suggested that RPR was able to achieve more precise evaluation of lower limb hemodynamics, especially in below-the-knee arteries, than ABI.

A woman in her seventies, who was suspected of acute hepatitis or acute cholangitis and tumor of pulmonary hilar lesion at another hospital, was referred to our hospital for detailed examination and treatment. Laboratory examination showed mild anemia, high hepatobiliary enzyme levels, and mild inflammatory findings. On B-mode US, the liver was markedly swollen at both lobes, with low to isoechoic tumors with halo in the liver parenchyma near the surface. Contrast-enhanced ultrasonography (post-vascular phase) observation with a convex probe revealed a large number of defects up to 8 mm in size in the liver. Furthermore, contrast-enhanced ultrasonography (post-vascular phase) observation of with a linear probe revealed innumerable minute defects in the liver. Tumor markers NSE and ProGRP were 562.0 ng/mL and 36,325.4 pg/mL, respectively. Mediastinal lymph nodes were punctured using bronchoscopy. Fine-needle aspiration cytology revealed lymph node metastasis from small cell lung cancer. By using contrast-enhanced ultrasonography (post-vascular phase) with a linear probe, we could detect innumerable minute defects in the liver that were unclear with a convex probe. They were diagnosed as diffuse liver metastasis from small cell lung cancer based on the assessment of tumor markers. In cases with an unknown liver disorder, if a malignant disease is suspected and we can detect hepatomegaly or liver tumor on B-mode US, it is necessary to distinguish diffuse liver metastasis. The suggestion of CEUS examination from the examiner to the physician could help early diagnosis of diffuse liver metastasis.

Testicular torsion is a urologic emergency in acute scrotum. Rapid diagnosis and subsequent therapy are required to salvage the testicle. It is often difficult to diagnose and cure intermittent testicular torsion, because the clinical and radiographic evaluations may be normal. In the present case, we evaluated the mobility of the testis and succeeded in diagnosing intermittent testicular torsion. A man in his 20s had a 5-day history of intermittent left scrotal pain. A 180-degree counterclockwise rotation of the affected left testis was detected by probe scanning. There were no complaints of increased scrotal pain during the examination.

Ectopic breast tissue is a common anomaly of the breast that generally presents along the embryonic milk line; however, fibroadenoma of ectopic breast tissue is a rare disease. In this article, we report a rare case of fibroadenoma that developed in the ectopic breast tissue of the right axilla in a 25-year-old Japanese woman. Ultrasonography, fine-needle aspiration cytology (FNAC), and core needle biopsy (CNB) were done, and the mass was diagnosed as fibroadenoma of the ectopic breast tissue. As with normal breast tissue, various breast tumors can develop in ectopic breast tissue. In addition to ectopic breast tumors, axillary tumors need to be further differentiated from metastatic lymph nodes, abscesses, lymphomas, and so forth; thus, it is difficult to diagnose such tumors quickly and accurately. Ultrasonography, cytology, and histology are invaluable for determining the diagnosis and treatment.