Application of high-frequency ultrasonography in closing small blood vessels

Abstract

One of the most common treatments performed in phlebological and aesthetic medicine clinics is closing small blood vessels in the lower extremities, so-called telangiectasias and reticular vessels. Currently, there are several methods that allow for closing the dilated vessels and obtaining desirable effects, both therapeutic and aesthetic. Unfortunately, despite applying various methods and instruments, the effects of treatments are frequently not satisfactory. The factor that largely contributes to decreasing the efficacy of such procedures is complicated anatomy of the venous system and the lack of a method to precisely specify the vessel's course, its diameter, location in the skin etc. High-frequency ultrasonography is a method enabling accurate determination of the vessels’ course as well as the measurement of their basic parameters, such as diameter, depth in the skin and presence or absence of perfusion. Thanks to ultrasound imaging with the use of high-frequency transducers, an adequate treatment method and procedure parameters may be selected, which entails enhancing the efficacy of the procedure itself. Ultrasonography may be also used for monitoring the performed procedures.

Vascular problems in the lower limbs occur very frequently. It is estimated that problems with the venous system of the lower extremities concern approximately 40–50% of the population⁽¹⁾. Unsightly appearance of the legs with multiple telangiectasias and dilated reticular vessels not only constitutes an aesthetic problem, but may also lead to severe health conditions. The procedures consisting in closing small vessels, commonly known as “spider veins,” belong to the most popular treatments performed in phlebological and aesthetic medicine clinics. The majority of patients, mainly women, do not accept the developing vascular changes appearing in the lower extremities and thus, the main reason for treatment is the improvement of their appearance⁽²⁾.

Vascular changes occurring in the legs are associated with anomalies in the superficial, epifascial venous system. The etiology of these disorders is complex. It is indicated that the most common causes of venous disorders encompass genetic and hormonal factors as well as obesity, lifestyle and pregnancy. These factors lead to the insufficiency of the venous valves and perforators, which makes the blood collect in the vessels as well as causes venous hypertension and results in dilatation of the vessels. We distinguish two main veins in the superficial venous system: great and small saphenous veins as well as multiple perforator veins and small blood vessels⁽³⁾. In order to systematize the vessels that make up the superficial venous system, it appears to be appropriate to use a classification which distinguishes five types of vessels⁽⁴⁾. Type I comprises red vessels with the diameter of 1 mm, i.e. telangiectasias. Type IA includes ver y small red vessels whose diameter is lower than 0.2 mm. These vessels have a “secondary” character (they appear in patients following treatments) and are referred to as matting. Type II encompasses purple vessels with the diameter of 1–2 mm which are raised above the skin surface. Type III includes reticular vessels with green and blue coloring and the diameter of 2–4 mm. Type IV comprises varicose veins with 3–8 mm in diameter, unrelated to the vena saphena magna. Finally, type V includes varicose veins of the vena saphena magna and parva with blue or blue-green color and diameter above 8 mm.

The dilated blood vessels in the legs may be eliminated by means of sclerotherapy or various laser treatments. Unfortunately, the efficacy of such procedures is not always satisfactory^{(2, 5)}, which is a consequence of a complex structure of the venous system, constraints of the methods used to close venous vessels and the lack of a method which would enable accurate imaging of the course of the vessels to be treated. In particular, we lack tools enabling imaging of the course of the small blood vessels. In such a situation, it is desirable to search for a method that would allow for accurate imaging of the venous system and thereby, contribute to the efficacy of the performed procedures. High-frequency ultrasound (HFU) has a chance to become a useful tool in imaging of small blood vessels.

For the purposes of this paper, the ultrasound images have been obtained by means of high-frequency equipment, i.e. Episcan with a mechanical transducer of 50 MHz (Longport International, Great Britain, USA), DermaView with a mechanical transducer of 48 MHz (Dramiński, Poland) and Sonix with an electronic linear array transducer with the frequency of 40 MHz (Ultrasonix, Canada).

Imaging of the superficial venous system

The procedures aiming at eliminating small blood vessels in the lower limbs are not easy and obtaining the outcomes satisfactory for patients may be difficult. In such a situation, an adequate diagnostic process, localizing the problem and selecting an appropriate treatment method are essential.

In the case of patients awaiting the elimination of small blood vessels, it is necessary to perform an exhaustive interview and obtain information concerning the incidence of vascular problems in the family, patient's lifestyle, history of diseases and possible symptoms and ailments which may indicate the presence of chronic venous insufficiency. Another step is Doppler ultrasound (US) examination with the use of broadband linear array transducers with the frequency of 5–12 MHz. Doppler examination plays a vital role in establishing a correct diagnosis and planning further treatment. According to Weiss, Doppler US is as essential as using a stethoscope in a routine physical examination⁽⁶⁾. Such an examination enables to assess the patency and sufficiency of the great and small saphenous veins as well as allows for a localization of incompetent veins and perforators. If the examination reveals insufficiency of the great and small saphenous veins, it must be first treated and only then the small vessels may be eliminated. Closing of telangiectasias and reticular veins with concomitant insufficiency of the main veins of the superficial system is useless because the procedure may occur completely ineffective.

Doppler sonography enables imaging of large vessels and perforators which are usually located in the deeper layers of the subcutaneous tissue (fig. 1). Unfortunately, conventional sonography is not capable of imaging smaller vessels. In order to visualize smaller vessels located near the surface of the epidermis and in the upper layer of the subcutaneous tissue, HFU is used (fig. 1). Thanks to the usage of transducers with frequencies higher than 20 MHz, a high resolution ultrasound image is obtained in which we may differentiate between structures that are smaller than 0.1 mm. However, the higher the resolution, the shallower the penetration of the ultrasound beam into the skin layers. Therefore, depending on the transducer and apparatus, it is possible to penetrate the skin to the depth of max. 20–30 mm. Such a penetration, together with high image resolution, enables the assessment of even very small blood vessels (fig. 2). During the examination with the use of high-frequency transducers, one may precisely assess the course and location of the small vessels in the skin. This is particularly relevant for the selection of the vessel closing method and planning the procedure since in practice, the surface of the skin very often shows solely a small number of vessels or a slight fragment of a vessel – only after US examination may we determine their actual number and course. For an effective closing of the vessel, it is necessary to do it on its entire length. It must not be limited to the fragment seen “with the naked eye” on the surface of the skin since closing of the fragment will cause its swift recanalization⁽⁷⁾. Frequently, the vessel visible on the surface of the skin changes its course, becomes more tortuous and travels to the deeper layers of the skin⁽⁸⁾. Therefore, the vein's course and the perforators should be well-known and determined prior to the procedure. HFU also enables imaging of the perforators between small vessels. Furthermore, apart from the assessment of the course and anatomy, ultrasound image, thanks to the ultrasound software, also enables to determine the basic parameters such as the vessel's diameter, thickness of its wall, depth in the skin as well as presence or absence of perfusion inside the vessel⁽⁶⁾ (fig. 3). Thanks to the multi-element electronic transducer with the frequency of 40 MHz introduced to the market by Ultrasonix, it is also possible to visualize perfusion in the vessels in the color Doppler mode (fig. 4).

Fig. 1.

Ultrasound presentation of the superficial venous system. The images present the skin layers: 1 – epidermal echo, 2 – dermis, 3 – subcutaneous tissue. A. Conventional sonography – Toshiba Aplio apparatus with a linear transducer of 18 MHz. B. Highfrequency ultrasound – DermaView with a mechanical transducer of 48 MHz

Fig. 2.

High-frequency ultrasound examination of small blood vessels: A. telangiectasias in a transverse view – Episcan apparatus with a transducer of 50 MHz; B. telangiectasias in a longitudinal view – Episcan apparatus with a transducer of 50 MHz; C. telangiectasias – Sonix apparatus with an electronic linear array transducer of 40 MHz; D. telangiectatic matting – DermaView apparatus with a transducer of 48 MHz

Fig. 3.

Measuring the depth of the vessel in the skin and its diameter in high-frequency ultrasound image: A. Sonix apparatus with an electronic linear array transducer of 40 MHz; B. DermaView apparatus with a transducer of 48 MHz

Fig. 4.

Perfusion imaging in a color Doppler mode in a reticular vessel – Sonix apparatus with an electronic linear array transducer of 40 MHz

Treatments eliminating small blood vessels

Currently, small blood vessels are closed by means of microsclerotherapy, surface laser treatments as well as micro-endovascular procedures⁽⁷⁾.

Laser therapy

Laser treatments consisting in a transcutaneous closing of the vessels are becoming more and more popular. The essence of these treatments lies in sending a light beam onto the vessel, which is absorbed by hemoglo bin contained in erythrocytes and transformed into heat energy. This leads to heating of the vessel wall and its coagulation. Whereas in slight telangiectasias, the effect is obtained immediately, in reticular veins, the closing occurs several weeks following the procedure⁽⁹⁾.

The efficacy of the therapy depends on adequate selection of the treatment parameters. Determining the location of the vessels in the skin layers and their diameters are of great significance. These two parameters may be accurately specified in HFU. Based on US findings, the type of laser is selected, which entails the selection of wave length, pulse width, diameter of the spotsize and pulse energy⁽⁷⁾. In laser therapy, HFU is also useful as a method for monitoring the correctness of the treatment and its effectiveness. During the procedure, US may help to ensure that the laser energy reaches the vessel – its diameter should decrease at once (fig. 5). When such an effect is not detected, the treatment parameters should be verified. Additionally, it should be checked whether the laser head is adequately applied to the skin. HFU is also used for assessing the effectiveness of performed procedures. The useful parameters in such an assessment are: presence or lack of perfusion in the vessel, presence or absence of a thrombus in the vessel's lumen, diameter of the vessel and thickness of its wall.

Fig. 5.

Ultrasound guidance of transcutaneous laser closing of the vessel: A. before the procedure; B. after the procedure – visibly decreased diameter of the vessels

Sclerotherapy

Sclerotherapy is a technique of closing vessels as a result of injecting them with a chemical sclerosant. At present, it is commonly applied and is characterized by, above all, low costs and the fact that it is relatively easy to perform. Sclerotherapy is primarily indicated for closing reticular veins that are greater than 3 mm but may also be applied if the vessels are smaller⁽¹⁰⁾. In the case of vessels smaller than 3 mm, it is more difficult to insert a needle to their lumina, which increases the risk of complications⁽⁷⁾. In such a situation, HFU occurs to be helpful. It allows for accurate visualization of the vessel's course and, subsequently, facilitates the performance of the procedure with US-guidance (fig. 6). Thus, thanks to ultrasonography, the risk of administering the sclerosant beyond the vessel's lumen, which entails necrosis, has been eliminated. High-frequency ultrasound imaging may also be used to monitor the efficacy of the procedure.

Fig. 6.

Ultrasound guidance in sclerotherapy: A. before sclerotherapy; B. introducing the needle to the lumen; C. administering a sclerosant; D. vessel filled with the sclerosant

Micro-endovascular procedure

Micro-endovascular procedure is an endovenous technique which was primarily used for the treatment of insufficiency of large veins in the superficial system and which has been adapted for smaller veins. It is currently used in closing reticular veins and telangiectasias. The procedure consists in inserting a sterile laser optical fiber and inducing coagulation of the vessels as a result of laser energy^{(7, 11)}. It requires high-frequency ultrasound-guidance. Owing to ultrasound imaging, it is possible to assess the vessel's course and anatomy, accurate insertion of the optical fiber to the vessels (fig. 7), coagulation of the vessel and efficacy of the procedure.

Fig. 7.

Micro-endovascular procedure. Ultrasound guidance during the introduction of a laser optical fiber into the vessel's lumen

Conclusion

This paper has presented the subject-matter related to the application of HFU in imaging and closing of small venous vessels, i.e. telangiectasias and reticular veins. The introduction of high-frequency transducers of above 20 MHz made it possible to visualize the vessels located in the dermis and subcutaneous tissue, which is not feasible with the use of conventional probes or other methods. Sonography as a method of small vessel imaging fulfills the expectations of surgeons and phlebologists who, until now, have been deprived of the possibility to evaluate small blood vessels. Diaphanoscopes (transilluminators) had limitations since they only enabled to assess the course of shallow vessels⁽¹²⁾ without the possibility to specify their exact location or diameter. However, the possibility to assess the course of vessels, measure their diameters and specify their location in the skin contributes to the selection of a therapeutic method. Thereby, these factors enhance the efficacy of the selected procedure and reduce the risk of complications. In the case of laser treatments, ultrasound images facilitate the selection the laser for a procedure and enable to determine the treatment parameters⁽⁷⁾. Sonography is also useful as a method of monitoring the procedures that aim at elimination of the vessels. Without ultrasound imaging, the performance of certain procedures would not be feasible, for instance, micro-endovascular procedures without ultrasound guidance or microsclerotherapy without ultrasound imaging of the small vessels. The latter procedure performed without ultrasound guidance is burdened with a large risk of complications in the form of necrosis caused by administering the sclerosant beyond the vessel's lumen.

As has been shown above, high-frequency ultrasonography is a useful method in imaging of small blood vessels. Due to a relative low cost of the examination or of high-frequency equipment as compared with other methods, such as computed tomography or magnetic resonance imaging, as well as because of it s non-invasive character, mobility, relatively easy scanning technique and possibility to repeat examinations safely for the patients, HFU has a chance to become a more widely used routine examination.

Conflict of interest

Authors do not report any financial or personal links with other persons or organizations, which might affect negatively the content of this publication and/or claim authorship rights to this publication.