Our understanding of sonography began in the late 1700s, when two Italian zoologists discovered the acoustic orientation sense of bats (Kane et al, 2004). Almost a century later, in 1880, the Curie brothers presented the piezoelectric effect of sound waves on natural quartz (Levy et al, 2021). The application of mechanical pressure to quartz crystals generates an electrical charge on the material's surface. The converse effect, predicted by Gabriel Lippman in 1881, was subsequently proven by the Curie brothers. As such, application of an electric field to the quartz resulted in production of high-frequency sound waves or ultrasound.
The use of ultrasound in medicine began in 1942, when Karl Theodore Dussik presented work on transmission ultrasound investigation of the brain (Shampo, 1995). Subsequent works around the world helped to establish a place for ultrasound technology, but, in the 1950s, that of Donald et al (1958) in Glasgow did much to facilitate the development of practical technology and applications. Ultrasound was adopted into clinical dermatology in 1979, and it has been recognised as a means of assessing the presence of dermal filler for many years (Young et al, 2008). In 2013, it was reported that the diagnosis and management of filler nodules are greatly facilitated by ultrasonographic imaging, and, as such, it was recommended that it should become the standard of care (Cassuto and Sundaram, 2013).
Historically, ultrasound assessment has taken place exclusively in the radiology departments of hospitals. Bedside ultrasound took the scanner to the patient, in a portable form, but it was typically in a medical facility at the patient's bedside. Point-of-care ultrasound (POCUS) has changed the situation dramatically, providing a much more flexible solution to the benefits of ultrasound assessment. POCUS can now be performed anywhere that there is a need; this includes patients' homes, an ambulance or an aesthetic clinic. While it has technically been around for approximately 20 years, recent advances in the development and availability of smaller, more cost-effective scanning equipment have helped to overcome the challenges preventing Cassuto's recommendations from becoming a reality. These developments can largely be credited to the routine incorporation of ultrasound into musculoskeletal medical practice. This came about, in no small part, due to a study demonstrating that 30% of all diagnoses made using magnetic resonance imaging (MRI) could have been diagnosed using ultrasound (Parker et al, 2008).
Ultrasound applications in aesthetic practice
For many years, it has been considered normal practice to function without any access to imaging, except in rare circumstances. This would typically relate to the occurrence of a persistent nodule or nodules, but may also relate to acute, severe or complex clinical situations.
As the body of evidence in relation to filler complications grows, and access to ultrasound has improved, the use of routine ultrasound has grown dramatically in the past year.
As the body of evidence in relation to filler complications grows, and access to ultrasound has improved, the use of routine ultrasound has grown dramatically in the past year.
Other forms of imaging, including MRI, computerised tomography (CT), infrared spectroscopy and labelled white cell scintigraphy, may be required in certain circumstances. Availability, cost, need for tissue sampling and exposure to radiation are all factors that are expected to ensure their use remains rare. Their individual merits and limitations are discussed in the recent Complications in Medical Aesthetics Collaborative (CMAC) delayed onset nodule guideline (Convery et al, 2021).
Below, some of the common and accepted uses of ultrasound in aesthetic practice are considered.
Filler identification
As previously noted, ultrasound has been found to be effective in determining the presence of dermal filler (Young et al 2008). It consistently identifies a distinct border between normal tissue and quiescent filler biomaterials.
Scotto Di Santolo et al (2019) demonstrated the reliability of ultrasound in locating the presence of injected fillers. In 174 of 180 patients (97%), they further identified the type of material used, including injected autologous fat.
Bravo et al (2021) progressed our understanding of the potential of different injection techniques. Considering whether supraperiosteal application of hyaluronic acid with a cannula was possible, they used ultrasound to demonstrate that, with a 22 G cannula, it is possible in the malar/zygomatic and the chin regions, but not in the temporal region.
It is important that a comprehensive history and a longitudinal diagnostic process are used in concert with appropriate imaging.
A case report by Malik (2012) considered a patient with a periocular lesion. While the MRI scan suggested a diagnosis of arterio-venous (AV) malformation, the ultrasound scan suggested that the lesion was a dermoid. It was only when the history was revisited that the patient disclosed having had injections of polyalkylimide in the glabella 10 years previously. Migration of filler was subsequently confirmed during surgical exploration.
The increased availability of ultrasound has uncovered some worrying trends. A recent example was the identification of the presence and associated complications of dermal filler in camels' lips (Tharwat and Al-Hawas, 2021).
Vascular mapping
It is well recognised that the vascular system of the face is rich and highly variable (Hong, 2020). Areas of the face can be categorised in terms of injection risk, which ranges from low to very high (Goodman, 2020). Vascular complications can lead to skin necrosis, blindness, cerebrovascular event, pulmonary embolus and death.
» Interested clinicians continue to assume that they will receive ultrasound training from the manufacturers; however, their training is limited to the use of the device. This leaves a significant knowledge and experience gap in the performance of ultrasonography for most clinicians «
A series of articles (Lee et al, 2019; 2021a; 2021b) used ultrasound to demonstrate anatomical variability in specific high-risk anatomical locations.
Key findings in the study populations are critical to anyone injecting these regions:
- Some 20% of non-surgical rhinoplasty (NSR) patients had a dorsal nasal artery in the midline. In 8%, the artery was pre-periosteal and in the midline
- Some 41% of glabellar wrinkle lines directly overlie the supratrochlear artery
- Some 69% of nasolabial folds directly overlie the facial artery. Some 4% of facial arteries were found in the submuscular plane and deep to the nasolabial fold.
A study by Cotofana et al (2021) used ultrasound to study the change of plane of the supraorbital and supratrochlear arteries. They also discussed the variabilities and averages in depth, finding that the changes in depth as a result of ageing increases in males and decreases in females. Body mass index (BMI) did not have any influence.
While the above findings demonstrate variability in vascular location, it is only through the use of ultrasound in vascular mapping that clinicians can safely circumnavigate vessels and deliver safer treatment in the highest risk areas.
Management of vascular compromise
The management of vascular occlusion has simplified since the introduction of the high dose hyaluronidase pulsed protocol by DeLorenzi (2017). Depending on the clinical scenario presented, extremely high doses of hyaluronidase may be required to recover circulation.
Recently, there has been adoption of targeted delivery of much smaller doses of hyaluronidase, avoiding unnecessary trauma, bruising and pain (Habib et al, 2020).
Schelke et al (2019) highlighted the importance of identifying disrupted laminal flow on Doppler ultrasound in locating the site of complete or partial occlusion. External vascular compression, a reality that has been questioned by some experts, was diagnosed and treated in the perioral region by de Freitas Lima et al (2019).
Management of nodules
Filler-related delayed onset nodules are notoriously challenging to manage. Whether of acute origin or delayed onset (Convery et al, 2021), ultrasound is useful in determining their three-dimensional location and association with identifiable filler material. Ultrasound imaging can also assist in the diagnosis of foreign body granuloma where the mass has an inhomogeneous sonographic pattern and lack of a distinct border (Young, 2008). Scotto di Santolo et al (2019) demonstrated the predictive value of ultrasound, with 26 of their 31 ultrasound-diagnosed cases (84%) being confirmed by histopathology.
Not all nodules are due to local filler material. A case report by Decates (2020) used imaging, including ultrasound, to diagnose a nodule of dental origin, sited adjacent to innocent filler material.
Real-time rheology
Ultrasound imaging helps clinicians to understand, in conjunction with benchtop rheological and histological studies, how dermal filler behaves, integrates and changes in living tissue.
As an example, Restylane typically forms localised hypoechoic lobular spaces within tissue, with some tendency to spread in a vertical direction (Goh, 2014). It shows a granular appearance, with a cone of shadow underneath (Micheels et al, 2012). Belotero tended to spread more widely within the same tissue plane (Goh, 2014). Vycross filler becomes comparatively hyperechogenic and, unlike Belotero filler, becomes almost invisible after gentle massage (Micheels et al, 2017). Urdiales-Gálvez et al (2021) noted that there was a thickening of subcutaneous tissue and complete integration of Vycross filler at 30 days.
Measurements in relation to treatment outcomes
In aesthetic medicine publications, the norm is to assess outcomes subjectively. Often, this will include patient self-assessment and physician assessment, which may be blinded. Subjective outcome assessments are vulnerable to measurement error, often resulting in low reproducibility or inter-rater reliability of the measure. The supplementation of these assessment tools with surrogate or intermediate endpoints, such as ultrasound measurements, will increase the influence of a given study (Valentgas, 2013).
A study by Qiao et al (2019) demonstrated increased dermal thickness following injection of hyaluronic acid. Follow-up observed a reduction in dermal thickness at 48 weeks.
Furthermore, Pignatti et al (2013) used ultrasound to demonstrate a significant (p<0.0001) increase in cheek thickness in HIV patients following the administration of hyaluronic acid filler. This correlated well with subjective measures from the Global Aesthetic Improvement Scale, where 87.5% of the patients judged their outcome as ‘much improved’ or ‘improved’.
Challenges to the routine adoption of ultrasound
Now that appropriate ultrasound scanners are affordable and available, enhanced care for patients can be provided. However, a significant obstacle still remains. Interested clinicians continue to assume that they will receive ultrasound training from the manufacturers; however, their training is limited to the use of the device. This leaves a significant knowledge and experience gap in the performance of ultrasonography for most clinicians.
Thankfully, there are various projects underway in the UK and internationally to educate and support clinicians along their journey.
Conclusion
The main challenges to the routine adoption into aesthetic medical practice have been the accessibility of appropriate equipment and the skills needed to use it.
Until recently, equipment appropriate for the assessment of cutaneous layers has been cumbersome and expensive. Furthermore, training to use such equipment has been only available as a component of formal ultrasonography qualifications.
Now that the necessary equipment is available, education, training and support must fill the gap left by manufacturer device-related training.
Key points
- Ultrasound can be used in routine treatment planning, both for vascular mapping and for identification of pre-existing filler
- When used in addition to clinical diagnostic skills and other tests, ultrasound can help clinicians to understand and diagnose complications
- Ultrasound can facilitate targeted treatment of complications
- Ultrasound provides a simple, objective measure of change following treatment.
CPD reflective questions
- Please give an example where the use of ultrasound would be likely to have made an impact on your past care delivery
- What examples of safety in practice have you reflected on in the past year? Is easy access to ultrasound likely to have been beneficial?
- Please detail potential developments in your practice that would be facilitated through the use of ultrasound.