Medical Ultrasound Disinfection and Hygiene Practices: WFUMB Global Survey Results

As ultrasound technology rapidly evolves and is used more frequently in every area of medical diagnosis and treatment, it may be overlooked as a potential vector in the transmission of a health care-associated infection. A survey on disinfection and hygiene practice in medical ultrasound was disseminated via the World Federation for Ultrasound in Medicine and Biology (WFUMB) to its six member federations and associated ultrasound societies globally. One thousand twenty-nine responses were obtained across a broad range of ultrasound practitioners. A total of 76% of respondents used transducer covers every time to scan open wounds and 71% when blood and bodily fluids were present or for an interventional procedure. Approved high-level disinfectants are not always used, even when blood comes into contact with the transducer or after endocavity scans. Alcohol-based wipes were used by many respondents to clean both external transducers and endocavity transducers. Open-ended responses indicated that a large caseload hindered the time required for cleaning and that access to clear guidelines would be beneficial. Global survey results indicate that some users do not comply with disinfection practice, and there is a gap in knowledge on basic infection prevention and control education within the ultrasound unit. As the infectious status of a patient is not often disclosed prior to an ultrasound examination, training in suitable protocols for the cleaning and disinfection of ultrasound equipment is imperative to mitigate the risk of potential infection.     

Surface heating by transvaginal transducers.

OBJECTIVE: This safety study was designed to investigate tissue heating close to the surface of transvaginal ultrasound transducers, with the objective of assessing the validity of manufacturing safety standards set by the International Electrotechnical Commission (IEC). METHODS: The transducers investigated in this study were held in contact with a layered soft-tissue mimicking material (TMM), and the temperature increase was measured at various depths using a miniature thermocouple. The temperature rise at 200 s was recorded, and the measured profiles of temperature rise with depth were compared with profiles predicted from both analytical and numeric models. Two transvaginal transducers of different manufacturers were investigated, operating in B-mode imaging, color-flow imaging and pulsed Doppler modes, using scanner settings giving acoustic output power towards the upper end of that available. RESULTS: The greatest heating always occurred at the interface between the transducer and the TMM, and it reduced to about 0.1 times the surface temperature rise at a depth of 1 cm. A local maximum was observed in pulsed Doppler mode. A three-dimensional finite-element model which accounted for transducer dimensions gave a better prediction of temperature increase than a simple analytical model. The temperature profiles were compared with the depth of fetal tissue measured from a small survey of clinical scans. CONCLUSIONS: It is provisionally concluded that the transducer surface temperature rise of 6 degrees C allowed to manufacturers by the IEC may give rise to an associated worst-case contribution to temperature rise due to the transducer, in fetal tissue, of between 0.5 and 1 degrees C at 1-cm depth. The contribution to tissue heating at 2 cm and deeper is negligible. Published by John Wiley & Sons, Ltd.     

Private practice use of real-time B scan ultrasound in obstetrics and gynecology.

An informal survey of 25 obstetrics and gynecology practices that use real time B scan ultrasound equipment was carried out to assess the economic and patient-care impact of such equipment. From this informal survey, it can be seen that the incorporation of real time B scan ultrasound scanning into private practice has become economically feasible and useful for the daily clinical management of obstetric patients. The implications and economics of such changes for obstetric health care costs remain to be assessed.     

Ultrasound Transducer Selection in Clinical Imaging Practice

Many types of medical ultrasound transducers are used in clinical practice. They operate at different center frequencies, have different physical dimensions, footprints, and shapes, and provide different image formats. However, little information is available about which transducers are most appropriate for a given application, and the purpose of this article is to address this deficiency. Specifically, the relationship between the transducer, imaging format, and clinical applications is discussed, and systematic selection criteria that allow matching of transducers to specific clinical needs are presented. These criteria include access to and coverage of the region of interest, maximum scan depth, and coverage of essential diagnostic modes required to optimize a patient's diagnosis. Three comprehensive figures organize and summarize the imaging planes, scanning modes, and types of diagnostic transducers to facilitate their selection in clinical diagnosis.     

Transvaginal ultrasound in pregnancy: its acceptability to women and maternal psychological morbidity.

OBJECTIVES: To assess the acceptability to women of antenatal transvaginal ultrasound scans; to compare the characteristics of women who accept the offer of a transvaginal scan with those who decline; to establish the prevalence of any psychological morbidity associated with the scan. METHODS: The study was a cross-sectional questionnaire survey. Women were recruited from two hospitals in South London. The sample consisted of 755 pregnant women who had a transvaginal scan at 23 weeks' gestation to assess the risk of preterm delivery and 167 women who were offered the transvaginal scan but declined. Women completed a questionnaire at home. Those who reported finding the scan a difficult experience were sent a questionnaire 4 weeks post-scan to assess its longer term impact. The main outcomes were acceptability (assessed by individual questionnaire items); anxiety before and during the scan (Spielberger State-trait Anxiety Inventory); pain during the scan (Present Pain Intensity Scale of the McGill Pain Questionnaire); psychological trauma (Impact of Event Scale). RESULTS: Over half (55.2%) of women accepted the offer of a transvaginal scan, according to hospital records. The majority of study participants who had transvaginal ultrasound reported finding the experience acceptable. Women experienced some anxiety before and during the scan and over a third experienced some (usually mild) pain during the procedure. Twelve women (1.6%) reported clinically significant levels of psychological trauma in relation to the scan. CONCLUSIONS: Antenatal transvaginal ultrasound for assessing the risk of preterm delivery is an acceptable procedure for the majority of women. A significant minority decline the scan. The procedure has some psychological sequelae for some women.     

Live scanning at ultrasound scientific conferences and the need for prudent policy

The practice of using live models to demonstrate ultrasonographic imaging equipment at scientific meetings has gained popularity in recent years. However, different medical conferences organisers take different positions, possibly due to differences in interpretation of the safety issue and their definition of medically relevant use of diagnostic ultrasound (US). Some offer little, or no, restriction and other US societies have produced policy that is subject to various interpretations. For example, some justify the practice of scanning live models on the basis of an assumed "educational" benefit, but this is virtually impossible to measure in an objective sense. One issue that seems to have largely universal agreement is that nonmedical use of diagnostic US should be discouraged. The AIUM has published a statement that this is "contrary to responsible medical practice." However, the definition of "nonmedical" application is somewhat less certain. The scanning of live models to display equipment on exhibit areas may be considered "nonmedical." In fact, the BMUS has published guidelines with quite restrictive output limits to be applied for various "nondiagnostic" purposes. Although this safety issue remains debatable, the ASUM maintains a conservative unambiguous policy that prohibits scanning of live models in the exhibition area at scientific meetings. Issues such as biosafety, ethics and medicolegal implications require careful consideration by US organizations and professional conference organisers.     

Transvaginal ultrasound: does it help in the diagnosis of placenta previa?

The purpose of this study is to evaluate the use of transvaginal ultrasound in the diagnosis of placenta previa and to assess the risk of bleeding secondary to the placement of the vaginal transducer. Thirty-eight patients with an estimated gestational age equal to or greater than 26 weeks and the diagnosis of suspected placenta previa gave their consent and were randomized to two groups. Randomization was stratified by patient weight and anterior or posterior placental location. Group 1 (n = 20) had complete obstetric ultrasounds using linear and sector transducers. Group 2 (n = 18) had similar examinations followed by transvaginal ultrasound scans. Patients were rescanned to follow placental location and fetal growth parameters. On abdominal ultrasound, the posterior placenta (n = 17) was often shadowed by fetal parts. The ease of placental visualization was rated on a four-point scale with 1 being the clearest. The mean clarity score for posterior placentas on abdominal ultrasound in Group 2 was 1.6 and on transvaginal ultrasound was 1.0, p < 0.04. The use of transvaginal ultrasound consistently revealed greater clarity of diagnosis in these patients. No patient in either group experienced increased vaginal bleeding following the scanning sessions. Transvaginal ultrasound was most beneficial for those patients with posterior placenta previas because of increased clarity of diagnosis, decreased time of scanning, and no increased incidence of hemorrhage.     

Surveillance Practice for Sonographic Detection of Intracranial Abnormalities in Premature Neonates: A Snapshot of Current Neonatal Cranial Ultrasound Practice in Australia

There are no publications reporting on scan duration and Doppler use during neonatal cranial ultrasound scans. We investigated current practice of neonatal cranial ultrasound at four large tertiary neonatal intensive care units in Australia. Cranial scans were prospectively recorded between March 2015 and November 2016. Variables, including total number of scans, scan duration and frequency and duration of colour and spectral Doppler mode, were extracted. A total of 196 scans formed the final cohort. The median (range) number of scans for each neonate was 1 (1–12). The median (range) overall total scan duration was 309 (119–801) s. Colour mode with or without spectral Doppler mode was used in approximately half of the cohort (106/196, 54%). Our findings comport with our hypotheses. Operators performing neonatal cranial scans in Australia have low overall scan durations. Although the use of Doppler mode during neonatal cranial scans is not standard practice in all neonatal intensive care units, it is used widely irrespective of the degree of prematurity or the presence of brain pathology. Further efforts are required to incorporate recommendations on scan duration and the routine use of Doppler mode during neonatal cranial scans. This is especially imperative given that the most vulnerable neonates with the greater neural tissue sensitivity are likely to be scanned more often.     

Three-dimensional ultrasound evaluation of the fetal brain: the three horn view.

OBJECTIVE: To describe an easy technique for obtaining one of the most important views of the fetal brain and image. The entire lateral ventricle including the anterior, posterior and inferior horns is demonstrated on one image. We propose to call this view, obtained in an oblique plane 'the three horn view'. METHODS: Depending upon the scanning technique employed there are two ways to obtain the three horn view: (1) by two-dimensional (2D) transvaginal transfontanelle sonography obtained by using the left and right Oblique-1 sections, and (2) by three-dimensional (3D) imaging of the fetal brain, is obtained by acquiring a volume scan of the brain orienting the fetal head in the three main orthogonal planes and by rotating or tilting the midcoronal section to the left and right. RESULTS: To illustrate the technique of obtaining the three horn view four normal fetal brains were scanned. Two scans utilized the 2D transvaginal transfontanelle approach and two scans utilized the 3D scanning technique. The same technique was then applied to six fetuses with various brain malformations with inflicted changes in the shape of the proposed three horn view. CONCLUSION: The three horn view, depicting the anterior, posterior, and inferior horns on the same image, was easy to obtain using both the 2D and the 3D ultrasound techniques. It provided diagnostic and clinically useful information much like neonatal transfontanelle ultrasound imaging after which it was emulated.     

Transvaginal imaging: applied physical principles and terms

In this article the properties of ultrasound in tissues and the factors governing image quality are discussed. Particular emphasis is placed on the vaginal probe. The virtues of transvaginal scanning both in gynecology and obstetrics are well described in subsequent articles in this symposium. Only by understanding the properties of ultrasound can the capabilities and limitations of this technique be appreciated. A comprehensive knowledge of the basic physical principles is mandatory for the clinician as well the investigator to attain the highest quality results. The technical aspects of operating ultrasound instruments, e.g., machine controls, electronic image formation, scan converters and techniques for preprocessing and postprocessing, are not discussed.     

International recommendations and guidelines for the safe use of diagnostic ultrasound in medicine

Modern sophisticated ultrasonographic equipment is capable of delivering substantial levels of acoustic energy into the body when used at maximum outputs. The risk of producing bioeffects has been studied by international expert groups during symposia supported by the World Federation for Ultrasound in Medicine and Biology (WFUMB). These have resulted in the publication of internationally accepted conclusions and recommendations. National ultrasound safety committees have published guidelines as well. These recommendations and safety guidelines offer valuable information to help users apply diagnostic ultrasound in a safe and effective manner. Acoustic output from ultrasound medical devices is directly regulated only in the USA and this is done by the Food and Drug Administration (FDA). However, there is also a modern trend towards self-regulation which has implications for the worldwide use of diagnostic ultrasound. It has resulted in a move away from the relatively simple scheme of FDA-enforced, application-specific limits on acoustic output to a scheme whereby risk of adverse effects of ultrasound exposure is assessed from information provided by the equipment in the form of a real-time display of safety indices. Under this option, the FDA allows a relaxation of some intensity limits, specifically approving the use of medical ultrasound devices that can expose the fetus or embryo to nearly eight times the intensity that was previously allowed. The shift of responsibility for risk assessment from a regulatory authority to the user creates an urgent need for awareness of risk and the development of knowledgeable and responsible attitudes to safety issues. To encourage this approach, it is incumbent on authorities, ultrasound societies and expert groups to provide relevant information on biological effects that might result from ultrasonographic procedures. It is obvious from the continued stream of enquiries received by ultrasound societies that effective dissemination of such knowledge requires sustained strenuous effort on the part of ultrasound safety committees. There is a strong need for continuing education to ensure that appropriate risk/benefit assessments are made by users based on an appropriate knowledge of the probability of biological effects occurring with each type of ultrasound procedure. The primary purpose of this paper is to draw attention to current safety guidelines and show the similarities and areas of general agreement with those issued by the parent ultrasound organisation, the WFUMB. It is equally important to identify gaps in our knowledge, where applicable.     

Conditionally Increased Acoustic Pressures in Nonfetal Diagnostic Ultrasound Examinations Without Contrast Agents: A Preliminary Assessment

The mechanical index (MI) has been used by the US Food and Drug Administration (FDA) since 1992 for regulatory decisions regarding the acoustic output of diagnostic ultrasound equipment. Its formula is based on predictions of acoustic cavitation under specific conditions. Since its implementation over 2 decades ago, new imaging modes have been developed that employ unique beam sequences exploiting higher‐order acoustic phenomena, and, concurrently, studies of the bioeffects of ultrasound under a range of imaging scenarios have been conducted. In 2012, the American Institute of Ultrasound in Medicine Technical Standards Committee convened a working group of its Output Standards Subcommittee to examine and report on the potential risks and benefits of the use of conditionally increased acoustic pressures (CIP) under specific diagnostic imaging scenarios. The term “conditionally” is included to indicate that CIP would be considered on a per‐patient basis for the duration required to obtain the necessary diagnostic information. This document is a result of that effort. In summary, a fundamental assumption in the MI calculation is the presence of a preexisting gas body. For tissues not known to contain preexisting gas bodies, based on theoretical predications and experimentally reported cavitation thresholds, we find this assumption to be invalid. We thus conclude that exceeding the recommended maximum MI level given in the FDA guidance could be warranted without concern for increased risk of cavitation in these tissues. However, there is limited literature assessing the potential clinical benefit of exceeding the MI guidelines in these tissues. The report proposes a 3‐tiered approach for CIP that follows the model for employing elevated output in magnetic resonance imaging and concludes with summary recommendations to facilitate Institutional Review Board (IRB)‐monitored clinical studies investigating CIP in specific tissues.     

Function and Safety of SlowflowHD Ultrasound Doppler in Obstetrics

SlowflowHD is a new ultrasound Doppler imaging technology that allows visualization of flow within small blood vessels. In this mode, a proprietary algorithm differentiates between low-speed flow and signals attributed to tissue motion so that microvessel vasculature can be examined. Our objectives were to describe the low-velocity Doppler mode principles, to assess the bone thermal index (TIb) safety parameter in obstetric ultrasound scans and to evaluate adherence to professional guidelines. To achieve the latter goals, we retrospectively reviewed prospectively collected ultrasound images and video clips from pregnancy ultrasound scans at >10 wk of gestation over 4 mo. We used a custom-built optical character recognition-based software to automatically identify all images and video clips using this technology and extract the TIb. Overall, a total of 185 ultrasound scans performed by three fetal medicine physicians were included, of which 60, 54 and 71 scans were first-, second- and third-trimester scans, respectively. The mean (highest recorded) TIb values were 0.32 (0.70), 0.23 (0.70) and 0.32 (0.60) in the first, second, and third trimesters, respectively. Thermal index values were within recommended values set by the World Federation for Ultrasound in Medicine and Biology American Institute of Ultrasound in Medicine and British Medical Ultrasound Society in all scans.     

Real-time spatial compound imaging: Application to breast, vascular, and musculoskeletal ultrasound

Real-time spatial compound imaging (SonoCT) is an ultrasound technique that uses electronic beam steering of a transducer array to rapidly acquire several (three to nine) overlapping scans of an object from different view angles. These single-angle scans are averaged to form a multiangle compound image that is updated in real time with each subsequent scan. Compound imaging shows improved image quality compared with conventional ultrasound, primarily because of reduction of speckle, clutter, and other acoustic artifacts. Early clinical experience suggests that real-time spatial compound imaging can provide improved contrast resolution and tissue differentiation that is beneficial for imaging the breast, peripheral blood vessels, and musculoskeletal injuries. Future development of real-time spatial compound imaging will help address the bulk of general imaging applications by extending this technology to curved array transducers, tissue harmonics, panoramic imaging, and three-dimensional sonography.     

Temperature Elevation in an Instrumented Phantom Insonated by B-Mode Imaging,Pulse Doppler and Shear Wave Elastography

Diagnostic ultrasound is the gold standard for obstetric scanning and one of the most important imaging techniques for perinatal and neonatal monitoring and diagnosis. Ultrasound provides detailed real-time anatomic information, including blood flow measurements and tissue elasticity. The latter is provided through various techniques including shear wave elastography (SWE). SWE is increasingly used in many areas of medicine, especially in detection and diagnosis of breast, thyroid and prostate cancers and liver disease. More recently, SWE has found application in gynaecology and obstetrics. This method mimics manual palpation, revealing the elastic properties of soft biological tissues. Despite its rising potential and expanding clinical interest in its use in obstetrics and gynaecology (such as for assessment of cervical ripening or organ development and structure during pregnancy), its effects on and potential risks to the developing fetus remain unknown. Risks should be evaluated by regulatory bodies before recommendations are made on the use of SWE. Because ultrasound is known to produce thermal and mechanical effects, this study measured the temperature increase caused by B-mode, pulse Doppler (PD) and SWE, using an instrumented phantom with 11 embedded thermocouples. Experiments were performed with an Aixplorer diagnostic ultrasound system (Supersonic Imagine, Aix-en-Provence, France). As expected, the greatest heating was detected by the thermocouple closest to the surface in contact with the transducer (2.9°C for SWE, 1.2°C for PD, 0.7°C for B-mode after 380-s excitation). Both conduction from the transducer face and direct heating owing to ultrasound waves contribute to temperature increase in the phantom with SWE associated with a larger temperature increase than PD and B-mode. This article offers a methodological approach and reference data for future safety studies, as well as initial recommendations about SWE safety in obstetrics and gynaecology.     

Knowledge,attitudes and practices regarding COVID-19 among dental health care professionals: a cross-sectional study in Saudi Arabia

ObjectivesWith the increasing severity of the coronavirus disease (COVID-19) pandemic, it is essential that dental health care professionals (DHCPs) are prepared. The study aim was to assess the knowledge, attitudes and practices (KAP) regarding COVID-19 among DHCPs in Saudi Arabia.MethodsA cross-sectional study using a web-based survey was conducted. A validated and reliable questionnaire was developed that comprised 44 questions. Using Qualtrics survey software, DHCPs working in different settings were approached across five geographical regions of Saudi Arabia.ResultsA total of 318 respondents voluntarily participated in the survey. Most DHCPs showed a moderate level of knowledge (51.6%), a positive attitude (92.1%) and adequate practice standards (86.5%). We found that 94.7% of DHCPs had an adequate overall level of KAP. DHCPs with a doctorate significantly outscored DHCPs with other educational levels with respect to knowledge and practice. Older (51–60 years) DHCPs reported significantly more knowledge than younger DHCPs.ConclusionDHCPs displayed an average level of knowledge that needs to be enhanced through continuing education programmes. However, they showed a positive attitude and an acceptable level of practice, as they were abiding by guidelines issued from various international and national health agencies.     

Transvaginal sonography,color flow imaging,computed tomographic scanning,and CA 125 as a routine follow-up examination in women with pelvic tumor: detection of recurrent disease.

We were trying to determine whether transvaginal sonography combined with color flow imaging should be used routinely for detecting recurrent pelvic tumors in patients treated for pelvic cancer. Eighteen patients who had completed their treatment for pelvic tumor were examined every 6 months by gynecologic examination, a CT scan, serum CA 125 levels, and transvaginal sonography with color flow imaging. Laparotomy or fine-needle biopsy was performed when a recurrent pelvic mass was observed or suspected on CT scans or transvaginal sonography. In nine of 18 patients a recurrent pelvic tumor was observed or suspected on CT scans or on transvaginal sonography. A recurrent pelvic tumor was diagnosed on laparotomy in five patients. In four patients, only a fine-needle biopsy was performed and only two of them had positive results. The highest sensitivity and specificity for detecting recurrent pelvic tumors were achieved by transvaginal sonography (100 and 91%, respectively) and by color flow imaging (86 and 100%, respectively). Intratumoral blood vessels were detected in all cases with recurrent pelvic tumors, and in only one of these cases the PI was high. We recommend a routine follow-up with transvaginal sonography in women completing their treatment for pelvic tumors. When a recurrence of tumor is only suspected on transvaginal sonography, color flow imaging may be used as an additional diagnostic tool.     

Development of a thermal test object for the measurement of ultrasound intracavity transducer self-heating

The elevated surface temperature of diagnostic ultrasound transducers imposes an important limitation to their safe use in clinical situations. Moreover, particular care should be taken if transvaginal transducers are to be used during routine scans in the first few weeks of pregnancy as the transducer surface can be very close to embryonic/fetal tissues. Published results have shown that the heating of tissue due to transducer self-heating can equal and often exceed the acoustic heating contribution. In this article, we report the development of a portable self contained thermal test object (TTO) capable of assessing the self-heating of intracavity diagnostic ultrasound transducers. The thermal conductivity and volumetric heat capacity of the tissue mimicking material (TMM) used in the TTO were measured, yielding values of (0.56 +/- 0.01) W m(-1) K(-1) and (3.5 +/- 0.8) MJ m(-3) K(-1). The speed of sound of the TMM was measured as 1540 m s(-1) and the attenuation over a frequency range of 2 to 10 MHz was found to be (0.50 +/- 0.01) dB cm(-1) MHz(-1). These results are in excellent agreement with the International Electrotechnical Commission (IEC 60601-2-37) requirements and the previously published properties of biological soft tissue. The temperature stability and uniformity, and suitability of the TTO for the measurement of transducer self-heating were tested and found to be satisfactory. The TTO reached a stable temperature of 37 degrees C in 3 h and the spatial variation in temperature was less than +/- 0.2 degrees C. Lastly, transducer self-heating measurements from a transvaginal transducer exceeded the IEC temperature limit of 43 degrees C in less than 5 min and the temperature reached after 30 min was 47.3 degrees C.     

Obstetric audit: the Bradford way

Ultrasound is widely used as a screening tool in obstetrics with the aim of reducing maternal and foetal morbidity. However, to be effective it is recommended that scanning services follow standard protocols based on national guidelines and that scanning practice is audited to ensure consistency. Bradford has a multi-ethnic population with one of the highest rates of birth defects in the UK and it requires an effective foetal anomaly screening service. We implemented a rolling programme of audits of dating scans, foetal anomaly scans and growth scans carried out by sonographers in Bradford. All three categories of scan were audited using measurable parameters based on national guidelines. Following feedback and re-training to address issues identified, re-audits of dating and foetal anomaly scans were carried out. In both cases, sonographers being re-audited had a marked improvement in their practice. Analysis of foetal abnormality detection rates showed that as a department, we were reaching the nationally agreed detection rates for the Fetal Anomaly Screening Programme auditable conditions. Audit has been shown to be a useful and essential process in achieving consistent scanning practices and high quality images and measurements.