Diagnostic Ultrasound Safety Review for Point-of-Care Ultrasound Practitioners

Potential ultrasound exposure safety issues are reviewed, with guidance for prudent use of point-of-care ultrasound (POCUS). Safety assurance begins with the training of POCUS practitioners in the generation and interpretation of diagnostically valid and clinically relevant images. Sonographers themselves should minimize patient exposure in accordance with the as-low-as-reasonably-achievable principle, particularly for the safety of the eye, lung, and fetus. This practice entails the reduction of output indices or the exposure duration, consistent with the acquisition of diagnostically definitive images. Informed adoption of POCUS worldwide promises a reduction of ionizing radiation risks, enhanced cost-effectiveness, and prompt diagnoses for optimal patient care.

Safety of ultrasonic examinations; thermal and mechanical indices

This review article combines the reports on the biophysical effects in ultrasonography and provides the rationale behind the mechanical index (MI) and thermal index (TI) complying with the Output Display Standard (ODS). Safe ultrasonic doses are determined according to specific rules, and the screen displays the associated quantities MI and TI. The introduced indices MI and TI take into account the physical mechanism of interaction between ultrasounds and biological tissue, which depends on the temporal and spatial parameters of the acoustic field generated by ultrasound transducers. The predicted temperature increase is determined using three different tissue models: homogeneous, layered and bone/tissue interface.

Diagnostic accuracy of ultrasound-guided core biopsy of peripheral nerve sheath tumors

PURPOSE

To retrospectively evaluate the diagnostic accuracy of and complications from ultrasound-guided core needle biopsy (UGCNB) of suspected peripheral nerve sheath tumors (PNSTs).

METHODS

Patients undergoing UGCNB from January 2004 to December 2016, based on the suspicion of PNST, were included in the study. Age, gender, anatomical location, dates of relevant events, and histopathological reports of the UGCNB cores and the resected tumors were retrieved from the patients' medical records.

RESULTS

A total of 154 UGCNBs were identified. One hundred and forty (90.9%) of these resulted in a conclusive histopathological report, while 14 were unsuited for histopathological analysis due to insufficient amount of tissue and/or nonrepresentative tissue. The overall diagnostic accuracy of UGCNB with respect to discriminate malignant from benign tumors was 99.3%, while correct specific UGCNB diagnoses were confirmed in 95.1% of the cases. Sensitivity and specificity were 90.9% (95% CI: 58.7-99.8%) and 100% (95% CI: 97.2-100%), respectively. The positive predictive value was 100%, and the negative predictive value was 99.2%. Except for one patient, who reported mild dysesthesia, which resolved 2 days after the UGCNB, no complications were reported.

CONCLUSION

This study suggests that UGCNB is accurate and safe in patients suspected for PNST.

Intracystic Hemorrhage and Its Management During Ultrasound-Guided Percutaneous Microwave Ablation for Cystic Thyroid Nodules

Background: Intracystic hemorrhage can present occasionally during ultrasound-guided percutaneous microwave ablation (PMWA) for cystic thyroid nodules. It can affect treatment outcome, can lead to ablation failure, and even conversion to open surgery. We aim to avoid such cases in the future by exploring their causes and management. Methods: From March 2017 to December 2019, we retrospectively studied 87 cystic thyroid nodules in 59 patients who underwent PMWA in the First Hospital of Jilin University. All patients were followed at 1, 3, 6, and 12 months after treatment. Results: All patients completed the treatment successfully. Nine cystic thyroid nodules presented with intracystic hemorrhage during the ultrasound-guided PMWA, giving an incidence of 10.3% (9/87 cysts). Larger cystic thyroid nodules were more likely to develop intracystic bleeding during ultrasound-guided PMWA. Intracystic hemorrhage resulted in significantly prolonged ablation time and had a negative effect on treatment outcome. No patients had other complications, but temporary post-operative pain and local swelling were more obvious in patients with intracystic hemorrhage. Conclusion: Intracystic hemorrhage is not rare during ultrasound-guided PMWA for cystic thyroid nodules. Doctors should pay more attention to it, learn to manage it and try to avoid it in clinical practice.

Contraindications and adverse effects in abdominal imaging

Ultrasound (US), computed-tomography (CT) and magnetic resonance imaging (MRI) are the most frequently used imaging techniques in abdominal pathology. US plays a pivotal role in evaluating abdominal disease, sometimes being sufficient for a complete diagnosis and has virtually no contraindications. The usage of US contrast agents will add useful diagnostic information in both hepatic and non-hepatic pathology. CT has, over MRI, the advantage of being readily available. The usage of ionizing radiation is the main pitfall of CT. Allergies and contrast induced nephropathy in patients with an impaired renal function are the major risks of contrast media administration in CT. Its excellent tissue resolution makes MRI a very useful technique in abdominal pathology, the major contraindications being the presence of MRI "unsafe" implants and devices and the presence of metallic foreign bodies, particularly close to vital structures like the eyes or major vessels. Contrast administration in MRI is restricted in patients with renal insufficiency due to the risk of nephrogenic systemic fibrosis. Allergies to MRI contrast media are rare and less important compared to allergies due to CT contrast media.

Adverse reactions after the use of SonoVue contrast agent: Characteristics and nursing care experience

The aim of this study was to analyze the clinical manifestations of adverse reactions after the use of SonoVue contrast agent from a large retrospective database, and to evaluate the nursing care strategies and the efficacy of standardized procedure for adverse reactions of SonoVue (SPARS).From January 1, 2012 to December 30, 2018, 34,478 cases of contrast-enhanced ultrasonography were performed in our center. The clinical manifestations of adverse reactions after the use of SonoVue contrast agent were identified and analyzed. The nursing care strategies were evaluated and the outcomes of patients with moderate and severe adverse reactions before and after the application of SPARS were compared.Of the 34,478 cases, 40 cases (0.12%) of adverse reactions after the use of SonoVue were identified. Adverse reactions included anaphylatic shock, skin allergies, nausea or vomiting, dizziness or headache, numbness, chest distress, back pain, and local reactions of the injection site. Most of the adverse reactions were mild and self-limited. Only 3 cases of anaphylatic shock and 2 cases of severe rash underwent further treatments. The 3 patients who were managed by SPARS recovered quicker and spent less comparing with the other 2 patients who were not.SonoVue was a safe contrast agent, with few and mostly mild adverse reactions. SPARS may be an efficient way in tackling moderate to severe adverse reactions, although of which the incidence was rare.

Capillary Hemorrhage Induced by Contrast-Enhanced Diagnostic Ultrasound in Rat Intestine

Contrast-enhanced diagnostic ultrasound (CEDUS) can lead to microvascular injury and petechial hemorrhage by the cavitational mechanism of ultrasonic bioeffects. Capillary hemorrhage has been noted in the heart and kidney, which are common targets of CEDUS examination. CEDUS has also become useful for monitoring intestinal inflammation. In the 1990s, the risk of intestinal microvascular hemorrhage was investigated both for incidental exposure by lithotripter shockwaves and for contrast agent microbubbles acting as cavitation nuclei with laboratory pulsed ultrasound systems. This study was initiated to update the risk assessment for intestine exposed to diagnostic imaging simulating CEDUS. The abdomens of anesthetized rats were scanned by a 1.6 MHz phased array probe during infusion of microbubble suspensions simulating Definity ultrasound contrast agent. Dual image frames were triggered intermittently, and the output power was varied to assess the exposure response. Petechiae counts in small intestine mucosa and muscle layers increased with increasing trigger interval from 2 s to 10 s, indicative of a slow refill after microbubble destruction. The counts increased with increasing output above a threshold of 1.4 MPa peak rarefactional pressure amplitude. Petechiae were also seen in Peyer's patches, and occult blood was detected in many affected segments of intestine. These results are consistent with early laboratory pulsed-ultrasound results.

Ultrasound imaging obtained by emergency department physicians to diagnose deep vein thrombosis: accuracy, safety, and efficiency

OBJECTIVES

To assess the accuracy, safety, and efficiency of ultrasound images obtained by emergency physician to diagnose deep vein thrombosis (DVT). patients with acute heart failure (AHF) attended in a hospital emergency department (ED).

MATERIAL AND METHODS

Prospective multicenter cohort study. We assigned patients suspected of having DVT to an intervention or control group. Emergency physicians took ultrasound images that were later evaluated by a radiologist in the intervention group. In the control group, images were evaluated only by the radiologist. We analyzed patient, physician, and episode variables. Test results, times until imaging, and 30-day adverse events were also analyzed. Sensitivity, specificity, positive and negative likelihood ratios, and agreement between physicians and radiologists (κ statistic) were calculated.

RESULTS

A total of 304 patients (209 in the intervention group and 95 controls) were included. The groups were comparable. The overall prevalence of DVT was 35.5% (95% CI, 30.3-41.0). The sensitivity of ultrasound images obtained by emergency physicians was superior in relation to experience: 71.4 (95% CI, 50.0-86.0) for those in a training course, 75.0 (95% CI, 80.0-95.4) for those with at least 2 months' practical experience, and 94.7 (95% CI, 82.7-98.5) for routine users. Specificity statistics for the 3 levels of physician experience were 83.3 (95% CI 55.2- 95.2), 100 (95% CI 83.0-100), and 96.6 (95% CI 88.4-99.0), respectively. The positive and negative likelihood ratios for ultrasound imaging by physicians were 27.94 and 0.054, respectively. The κ statistic was 0.80. Mean (SD) time until a physician took ultrasound images was 1.81 (1.46) hours versus 4.39 (1.81) hours until a radiologist obtained images (P = .007). Three deaths occurred within 30 days. They were not attributable to recurrence or bleeding.

CONCLUSION

Ultrasound images taken by emergency physicians to diagnose DVT are accurate and safe and may be efficient. However, routine experience with ultrasound is necessary.

Role of abdominal ultrasound for the surveillance follow-up of pancreatic cystic neoplasms: a cost-effective safe alternative to the routine use of magnetic resonance imaging

BACKGROUND

Patients with pancreatic cystic neoplasms (PCN), without surgical indication at the time of diagnosis according to current guidelines, require lifetime image-based surveillance follow-up. In these patients, the current European evidenced-based guidelines advise magnetic resonance imaging (MRI) scanning every 6 mo in the first year, then annually for the next five years, without reference to any role for trans-abdominal ultrasound (US). In this study, we report on our clinical experience of a follow-up strategy of image-based surveillance with US, and restricted use of MRI every two years and for urgent evaluation whenever suspicious changes are detected by US.

AIM

To report the results and cost-efficacy of a US-based surveillance follow-up for known PCNs, with restricted use of MRI.

METHODS

We retrospectively evaluated the records of all the patients treated in our institution with non-surgical PCN who received follow-up abdominal US and restricted MRI from the time of diagnosis, between January 2012 and January 2017. After US diagnosis and MRI confirmation, all patients underwent US surveillance every 6 mo for the first year, and then annually. A MRI scan was routinely performed every 2 years, or at any stage for all suspicious US findings. In this communication, we reported the clinical results of this alternative follow-up, and the results of a comparative cost-analysis between our surveillance protocol (abdominal US and restricted MRI) and the same patient cohort that has been followed-up in strict accordance with the European guidelines recommended for an exclusive MRI-based surveillance protocol.

RESULTS

In the 5-year period, 200 patients entered the prescribed US-restricted MRI surveillance follow-up. Mean follow-up period was 25.1 ± 18.2 mo. Surgery was required in two patients (1%) because of the appearance of suspicious features at imaging (with complete concordance between the US scan and the on-demand MRI). During the follow-up, US revealed changes in PCN appearance in 28 patients (14%). These comprised main pancreatic duct dilatation (n = 1), increased size of the main cyst (n = 14) and increased number of PNC (n = 13). In all of these patients, MRI confirmed US findings, without adding more information. The bi-annual MRI identified evolution of the lesions not identified by US in only 11 patients with intraductal papillary mucinous neoplasms (5.5%), largely consisting of an increased number of very small PCN (P = 0.14). The overall mean cost of surveillance, based on a theoretical use of the European evidenced-based exclusive MRI surveillance in the same group of patients, would have been 1158.9 ± 798.6 € per patient, in contrast with a significantly lower cost of 366.4 ± 348.7 € (P < 0.0001) incurred by the US-restricted MRI surveillance used at our institution.

CONCLUSION

In patients with non-surgical PCN at the time of diagnosis, US surveillance could be a safe complementary approach to MRI, delaying and reducing the numbers of second level examinations and therefore reducing the costs.

Ultrasound gel as a source of hospital outbreaks: Indian experience and literature review

Purpose

Hospital outbreaks are observed increasingly worldwide with various organisms from different sources such as contaminated ultrasound gel, intravenous (IV) fluids and IV medications. Among these, ultrasound gel is one of the most commonly reported sources for Burkholderia cepacia complex (Bcc) outbreaks. In this study, we describe our experience on investigation and the management of Bcc bacteraemia outbreak due to contaminated ultrasound gel from a tertiary care centre, South India.

Materials and Methods

Over a 10-day period in October 2016, seven children in our Paediatric intensive care unit (ICU) were found to have bacteraemia with Bcc isolated from their blood culture. Repeated isolation of the same organism with similar antimicrobial susceptibility pattern over a short incubation period from the same location, confirmed the outbreak. An active outbreak investigation, including environmental surveillance, was carried out to find the source and control the outbreak. Isolates were subjected to multi-locus sequence typing (MLST) and global eBURST (goeBURST) analysis.

Results

Environmental surveillance revealed contaminated ultrasound gel as the source of infection. MLST and goeBURST analysis confirmed that the outbreak was caused by a novel sequence type 1362 with the same clonal complex CC517. The outbreak was controlled by stringent infection control measures, withdrawal of contaminated ultrasound gel from regular usage and implementing the practice of using ultrasonogram (USG) probe cover for USG screening and guided procedures.

Conclusion

This report highlights the importance of early identification of an outbreak, prompt response of the ICU and infection control teams, sound environmental and epidemiological surveillance methods to identify the source and stringent infection control measures to control the outbreak. Contaminated ultrasound gel can be a potential source for healthcare-associated infection, which cannot be overlooked.

Use of intraoperative intracavitary (direct-contact) ultrasound for resection control in transsphenoidal surgery for pituitary tumors: evaluation of a microsurgical series

BACKGROUND

Perisellar infiltration may be responsible for incomplete removal of pituitary tumors. Since intraoperative visualization of parasellar structures is difficult during transsphenoidal surgery, we are describing the use of intraoperative direct contact ultrasound (IOUS).

METHODS

Within 5 years, in 113 transsphenoidal operations (58 male, 55 female, age 14-81 years, 110 pituitary adenomas (mean diameter 26.6 mm, 69 non-secreting adenomas, 41 secreting adenomas), and 1 of each Rathke's cleft cyst, craniopharyngioma, and xanthogranuloma), IOUS was applied. After wide opening of the sellar floor and removal of the intrasellar tumor portions, a commercially available side fire ultrasound probe is introduced, and in direct contact to the sellar envelope, the perisellar space is scanned perpendicular to the axis of the working channel. We compared the results of IOUS to postoperative MRI after 3-6 months.

RESULTS

Identification of the intracavernous ICA, the anterior optic pathway, and the ACA, was possible, it was safe to operate close to them. In 65 operations (58%), further resection of tumor remnants was performed after IOUS. In this selected series, complete resection of tumors (stated by postoperative MRI after 3-6 months) was achieved in 75 operations (66%) and remission was achieved in 18 operations of secreting adenomas (44%). Compared to MRI after 3 to 6 months, the sensitivity of IOUS was 0.568 and the specificity was 0.907. No complications related to IOUS were seen.

CONCLUSIONS

Visualization of the perisellar compartments by IOUS is easy and fast to perform. It allows the surgeon to identify resectable tumor remnants intraoperatively, which otherwise could be missed.

The Possibility of Transmitting Infections with Vaginal Ultrasound Probes: Why We Cannot Meet the Guidelines

The use of ultrasound endovaginal probes is common practice in the fields of gynecology and obstetrics. The vagina serves as a host environment for many microorganisms, contributing greatly to its defensive mechanisms. It is not known whether the introduction of other microorganisms into the vaginal region are detrimental or require intensive preventative measures. Several national ultrasonography societies, as well as the Israel Ministry of Health, have addressed the proper and adequate handling of sonographic endovaginal probes, including the use of high-level disinfecting agents following cleansing and prior to using probe covers between patients. However, many obstetrics and gynecology ultrasound units in Israel find it difficult to adhere to these strict disinfecting requirements. While most of the guidelines are based on the theoretical risk of contaminations when ultrasound endovaginal probes are used, the rate of nosocomial infections linked to the use of these probes has yet to be verified. Based on the information available, there is an urgent need to find a solution that enables gynecological ultrasound users to properly disinfect endovaginal probes between patients. Currently, it is almost impossible to pragmatically adhere to the Israel Ministry of Health guidelines.

Non-linear Wave Propagation and Safety Standards for Diagnostic Ultrasound Devices

Safety standards for clinical diagnostic ultrasonic devices were developed for use in relatively low-frequency systems (1-10 MHz), under the assumption that non-linear effects would be negligible. This article reviews ways in which neglecting non-linear wave propagation affects the measurements and calculations required to comply with safety standards and U.S. Food and Drug Administration guidance that recognizes these standards. An attempt is made to evaluate whether ignoring non-linear effects could result in significant error in the exposure quantities defined in these standards at either low or high frequencies, based on published literature. This article maintains that although non-linear effects have been considered in some parts of safety standards related to hydrophone requirements, the coverage is inadequate, especially for modern equipment with high working frequencies. A new approach is required to assess the magnitude of thermal heating for recently developed high-frequency systems to incorporate non-linear effects. In contrast, the current approach for evaluating the risk of cavitation can be used after appropriate modifications.

On heating of tissues by shear waves generated by ultrasound

An additional heating caused by the shear wave generated by an ultrasonic wave incident on a soft tissue boundary is considered for different tissue parameters and wave frequencies in the MHz range. The shear wave structure and the space-time dynamics of the temperature field are studied for three realistic examples of tissue parameters. It is shown that in viscous tissues the shear component can significantly contribute to the heating in a narrow layer near the boundary.

Decrease in uterine perforations with ultrasound image-guided applicator insertion in intracavitary brachytherapy for cervical cancer: A systematic review and meta-analysis

PURPOSE

To estimate uterine perforations rates during intracavitary brachytherapy for cervical cancer with and without ultrasound (US) image guidance.

MATERIALS AND METHODS

A systematic search of databases (PubMed and EMBASE) was performed. The pooled summary uterine perforation rate (detected by postinsertion CT or MRI) for the un-guided insertion group and the guided insertion group was calculated by using the random-effects model weighted by the inverse variance.

RESULTS

A total of 690 articles were initially found, resulting in 12 studies that met the inclusion criteria. A total of 1757 insertions and 766 patients were included in the meta-analysis. The overall uterine perforation rate per insertion was 4.56% (95%CI: 2.35-8.67) and per patient was 7.39% (95%CI: 3.92-13.50). The pooled perforation rate per insertion without image guidance was 10.54% (95%CI: 6.12-17.57) versus 1.06% (95%CI: 0.41-2.67) with image guidance (p < 0.01). The pooled perforation rate per patient without guidance was 16.67% (95%CI: 10.01-26.45) versus 2.54% (95%CI: 1.21-5.24) with image guidance (p < 0.01). The ratio of perforations in the un-guided/guided groups was 9.94 and 6.56, per insertion and per patient, respectively. The most common sites of perforation were the posterior wall (>47 events) and the uterine fundus (24 events). None of the studies reported significant acute clinical consequences. Prophylactic antibiotic after perforation was used in 3 of the 4 studies that described the management.

CONCLUSION

Using postinsertion CT or MRI to detect the perforation, the rate of uterine perforation per insertion in patients who received US-guided intracavitary brachytherapy insertion is 90% lower than with un-guided insertion.

Frequency bands for ultrasound, suitable for the consideration of its health effects

It is proposed that the ultrasound frequency spectrum should be divided into three bands in order to facilitate a more rational assessment of its health effects. Whilst statement of the frequencies at the borders of these bands facilitates their definition, it is recognized that these observables vary continuously with frequency and consequently these border frequencies should not be used to rule out the possibility of a given effect occurring. The lowest band, US(A), lies between 17.8 and 500 kHz. In this band acoustic cavitation and its associated forces form the dominant process resulting in biological effects in liquids and soft tissues, whereas health effects from airborne ultrasound have been reported but are far less researched. In the middle band, US(B), between 500 kHz and 100 MHz, temperature rise in tissues becomes the most important biological effect of exposure. The highest band, US(C), covers frequencies above 100 MHz, for which the radiation force becomes an increasingly important biophysical mechanism. A justification for the selection of 17.8 kHz in preference to any other threshold for the lower frequency limit for ultrasound is given.

State-of-the-art of microbubble-assisted blood-brain barrier disruption

Focused ultrasound with microbubbles promises unprecedented advantages for blood-brain barrier disruption over existing intracranial drug delivery methods, as well as a significant number of tunable parameters that affect its safety and efficacy. This review provides an engineering perspective on the state-of-the-art of the technology, considering the mechanism of action, effects of microbubble properties, ultrasound parameters and physiological variables, as well as safety and potential therapeutic applications. Emphasis is placed on the use of unified parameters, such as microbubble volume dose (MVD) and ultrasound mechanical index, to optimize the procedure and establish safety limits. It is concluded that, while efficacy has been demonstrated in several animal models with a wide range of payloads, acceptable measures of safety should be adopted to accelerate collaboration and improve understanding and clinical relevance.

Pulmonary Capillary Hemorrhage Induced by Diagnostic Ultrasound in Ventilated Rats

Pulmonary capillary hemorrhage (PCH) can be induced by diagnostic ultrasound-a potential safety issue. Anesthetized rats were intubated for intermittent positive-pressure ventilation (IPPV) with 0 end-expiratory pressure, +4 cm H₂O end-expiratory pressure (PEEP) and -4 cm H₂O end-expiratory pressure (NEEP). Rats were imaged at 7.6 MHz with a Philips HDI 5000 ultrasound machine. The output was low (mechanical index [MI] = 0.22) for aiming and then was raised for 5 min in 20 different exposure groups with n = 8. Peak rarefactional pressure amplitudes were measured in water and de-rated for chest attenuation. The PCH areas were measured on the lung surface. At 2.2 MPa, PCH was 9.3 ± 6.6 mm² for IPPV, 1.6 ± 3.2 mm² for PEEP (p <0.001) and 26.8 ± 6.4 mm² for NEEP (p <0.001). Thresholds were 1.3 MPa for IPPV, 2.1 MPa for PEEP and 1.0 MPa for NEEP. The small ventilator pressures subtracted or added to trans-capillary stress generated by diagnostic ultrasound pulses, virtually eliminating PCH for PEEP but enhancing PCH for NEEP.

Does Intravenous Infusion Influence Diagnostic Ultrasound-Induced Pulmonary Capillary Hemorrhage?

OBJECTIVES

Pulmonary diagnostic ultrasound (US) can induce pulmonary capillary hemorrhage (PCH) in mammals. This singular biological effect of diagnostic US imaging was discovered more than 25 years ago but remains poorly understood. Our objective here was to investigate rapid infusion of intravenous fluids as a possible stressor for capillaries, which might enhance pulmonary diagnostic US-induced PCH.

METHODS

Rats were anesthetized with Telazol (Zoetis, Inc, Kalamazoo, MI), which yielded relatively low pulmonary diagnostic US-induced PCH, or Telazol and xylazine, which yielded relatively high pulmonary diagnostic US-induced PCH. Groups of rats were not infused or infused either with normal saline, 10% mannitol, or 5% albumin. Rats were scanned in a warmed water bath with B-mode US for 5 minutes with a 7.6-MHz linear array set to different mechanical index values to obtain exposure response information. Pulmonary capillary hemorrhage was observed as comet tail artifacts in the image and measured on the lung surface.

RESULTS

For Telazol anesthesia, all of the PCH results were very low, with no significant differences at the maximum output with an in situ peak rarefactional pressure amplitude of 2.1 MPa (on-screen mechanical index, 0.9). The addition of xylazine to the Telazol anesthetic significantly enhanced the PCH (P < .001) without infusion and likewise for the mannitol and albumin infusion. Saline infusion eliminated this enhancement, with significantly reduced PCH for Telazol-plus-xylazine anesthesia (P < .001); however, both mannitol and albumin infusion resulted in significantly more PCH than saline infusion (P < .01).

CONCLUSIONS

These results show PCH dependence on the specific intravenous infusion fluid and illustrate the complex importance of physiologic parameters for US-induced PCH.

Do Participants Report Any Undesired Effects in Ultrasound Speech Therapy?

Purpose

Ultrasound visual feedback of the tongue is increasingly used as a component of speech therapy in clinical research and practice. The purpose is to offer a preliminary summary of the nature of participant-reported undesired effects related to ultrasound visual feedback.

Method

Sixty-two participants across 3 sites (mean age = 11.9 years) and 38 parents responded to a 2-item verbal questionnaire following 14-16 hr of treatment regarding any aspects of the treatment they did not like. Responses were thematically categorized.

Results

The 62 participants provided 65 distinct responses, which were categorized as follows: 31% no concerns, 40% gel-related (e.g., cold, sticky), 21% positioning of the probe (e.g., uncomfortable, annoying), 3% chin hurting (qualified as being minor in nature), and 5% other (i.e., unrelated to the use of the ultrasound). Responses from all parents suggested no concerns about the use of ultrasound; however, 8% expressed concerns unrelated to ultrasound use (e.g., fatigue).

Conclusion

These data inform clinicians and researchers about participant's experience and highlight the type of comments most likely to be encountered with ultrasound in speech therapy. Although the reported adverse effects can be considered minor, they should be weighed against the potential benefits of visual feedback in treatment.

Pulmonary Capillary Hemorrhage Induced by Different Imaging Modes of Diagnostic Ultrasound

The induction of pulmonary capillary hemorrhage (PCH) is a well-established non-thermal biological effect of pulsed ultrasound in animal models. Typically, research has been done using laboratory pulsed ultrasound systems with a fixed beam and, recently, by B-mode diagnostic ultrasound. In this study, a GE Vivid 7 Dimension ultrasound machine with 10 L linear array probe was used at 6.6 MHz to explore the relative PCH efficacy of B-mode imaging, M-mode (fixed beam), color angio mode Doppler imaging and pulsed Doppler mode (fixed beam). Anesthetized rats were scanned in a warmed water bath, and thresholds were determined by scanning at different power steps, 2 dB apart, in different groups of six rats. Exposures were performed for 5 min, except for a 15-s M-mode group. Peak rarefactional pressure amplitude thresholds were 1.5 MPa for B-mode and 1.1 MPa for angio Doppler mode. For the non-scanned modes, thresholds were 1.1 MPa for M-mode and 0.6 MPa for pulsed Doppler mode with its relatively high duty cycle (7.7 × 10^-3 vs. 0.27 × 10^-3 for M-mode). Reducing the duration of M-mode to 15 s (from 300 s) did not significantly reduce PCH (area, volume or depth) for some power settings, but the threshold was increased to 1.4 MPa. Pulmonary sonographers should be aware of this unique adverse bio-effect of diagnostic ultrasound and should consider reduced on-screen mechanical index settings for potentially vulnerable patients.

The Dependence of Glomerular Capillary Hemorrhage Induced by Contrast Enhanced Diagnostic Ultrasound on Microbubble Diameter

A recently proposed two-criterion model for cavitational bioeffects in tissue with microbubbles (MBs) was tested. The glomerular capillary hemorrhage bioeffect was observed in rat kidney for contrast agent MB suspensions with mean diameters of 1.6, 3.1 and 5.5 µm. A diagnostic ultrasound machine was used at 3.6 MHz and 5.5 MHz for intermittent scans at power settings 2 dB apart. Petechial hemorrhage counts scored on the surface of the kidneys, and glomeruli were scored in histology. Thresholds for the petechial hemorrhage measurements were the same for the large and medium MB suspensions but substantially higher for the small MBs. For the histology, the medium MBs gave a higher threshold than the large MBs at 5.5 MHz. The pressure amplitude thresholds are in approximate agreement with theory, and the optimum MB size counterintuitively increased for increasing ultrasound frequency, as predicted. The two-criterion model of MB-associated capillary hemorrhage is supported.

The Negative Chronotropic Effect in Rat Heart Stimulated by Ultrasonic Pulses: Role of Sex and Age

OBJECTIVES

The goal of this study is to investigate the role of sex and age of the negative chronotropic effect after exposure of 3.5-MHz pulsed ultrasound (US) to the rat heart.

METHODS

Forty F344 rats were exposed transthoracically to ultrasonic pulses at a duty factor of approximately 1.0% at 2.0-MPa peak rarefactional pressure amplitude. The transthoracic ultrasonic bursts were delivered consecutively in five 10-s intervals, that is, 10 s of 6-Hz pulse repetition frequency (PRF), 10 s of 5-Hz PRF, 10 s of 4-Hz PRF, 10 s of 5-Hz PRF, and 10 s of 6-Hz, for a 50-s total exposure duration. The rats were divided into 8 groups (n = 5 each): US young male, control young male, US young female, control young female, US old male, control old male, US old female, and control old female.

RESULTS

Two-way ANOVA for repeated measures was used to compare heart rate, cardiac output, arterial pressure, and other hemodynamic values (baseline) before and after US stimulation. Sex versus age versus US interaction was detected for heart rate. Cardiac output showed an age effect, and ejection fraction showed age and US effects. The arterial pressure showed a sex effect. A negative chronotropic effect (∼30% decrease in heart rate) was observed for young female rats. An hypothesis is that the US effect is weight (menopause) dependent, because the young (premenopausal) female rats weighed approximately 40 to 60% less than other groups of rats.

CONCLUSIONS

It is likely that the ovarian hormones are responsible for different US-induced cardiac bioeffects in different ages and sexes.

Neonatal Cranial Ultrasound: Are Current Safety Guidelines Appropriate?

Ultrasound can lead to thermal and mechanical effects in interrogated tissues. We reviewed the literature to explore the evidence on ultrasound heating on fetal and neonatal neural tissue. The results of animal studies have suggested that ultrasound exposure of the fetal or neonatal brain may lead to a significant temperature elevation at the bone-brain interface above current recommended safety thresholds. Temperature increases between 4.3 and 5.6°C have been recorded. Such temperature elevations can potentially affect neuronal structure and function and may also affect behavioral and cognitive function, such as memory and learning. However, the majority of these studies were carried out more than 25 y ago using non-diagnostic equipment with power outputs much lower than those of modern machines. New studies to address the safety issues of cranial ultrasound are imperative to provide current clinical guidelines and safety recommendations.