The term venous translucence (or translumination) has been used in phlebology since 1996 by surgeon Pedro Fernandes Neto during ambulatory clinical exams in Brazil. His results were published in the annals of the national and international congresses of angiology. Venous translucence is the process of reflective visualization of veins by light, which reaches up to the superficial venous system. It is a non-invasive method. Since it is a simple, low-cost technique it can be repeated as needed, which is useful in disease-process monitoring. It is a new diagnostic procedure, still undergoing investigation; more analysis is necessary to hone its technical aspects. Venous translucence is based on optical physics. It is caused by the refraction, absorption and reflection of light (whose principle is the dispersion and absorption of light). The color which is not absorbed is reflected, and is the one that is seen. Therefore, venous translumination is based on the incidence of luminosity on the vein, where part of the light is absorbed and another reflected (supplying a silhouette of the vein in question).
Technical aspects Steps must be taken to avoid artifacts or luminous pollution during the venous translumination. Reflection and refraction of light are important to avoid distorted images which can appear during a scanning. Many are due to inappropriate sources which would provoke light loss similar to luminous pollution.
During the venous translumination, the amount of reflected light depends on the index of refraction which can be altered by the venous thrombosis. Certain types of lamps process more dispersion than reflection, and therefore favor the formation of artifacts.
Another aspect is the inability to be obtain useful images with a fiber-optic source due to the high irradiation frequency. It is also known that the reflection in an optic fiber source is initially processed internally. Certain instruments are not specific to obtain reflected images. The illumination of the skin by distant infrared light, without the impression of the source on the skin, does not reveal a diagnostic image. The translumination transductor must be in direct contact with the skin. The process should be similar to that used in Doppler ultrasonography.
Other considerations Tissue Tissue transluminated by white light has a refraction index in agreement with its texture. By the impression of the camera on the skin, red and yellow colors are observed. The red color is soon dispersed in the skin and the yellow surrounding it begins to alter its tonality with the change in source direction. A shade with the change of source direction arises. It is known that the refraction index changes in agreement with the spectrum of transmitted light; when the white light is projected and finds an obstacle, it becomes separated into the three elementary colors (red, blue and green). Light during translumination may have greater dispersion or reflection, depending on how the source is placed on the examined area. This handling may improve or degrade the image, depending on the examiner's experience.
Light interaction with skin color Skin is opaque to light. In physics light reception, heat or other type of radiant energy on the part of molecules is called absorption. When tissues are illuminated during translumination, some light is absorbed and some reflected. It is known that an object which absorbs all radiation is seen as black; the pigments that give color to the skin and the other tissues, absorb certain wavelengths of white light and transmit radiant energy. This is an aspect of color as captured by our vision. The mechanism by which certain substances absorb more light than others apparently depends on their molecular structure. Light, when reaching more pigmented areas, disperses and reflects more easily; the refraction index is smaller, and it is difficult for white light to penetrate below the skin. Studies of the distribution of elastin and collagen fibers in patients with dermal lesions need to be analyzed for changes. A study of tissue consistency using translumination and dermatoscopy could supply important data complementing the diagnosis of some collagen diseases and study tissue aging. Skin color affects the effectiveness of translumination; individuals with light skin have better venous visualization during the translumination than those with darker skin.
Blood viscosity and flow The erythrocytes absorb more light because they are oxygenated. Considering that aspect, we can deduce that venous blood has a light absorption different from arterial blood (in which sanguine viscosity is greater, due to the higher concentration of CO2. In that sense, venous blood has a greater ability to reflect light. When an arterial-venous fistulae is transluminated, there are few reflected images because flow velocity is higher and sanguine viscosity lower than in the venous segment. It is impossible to visualize arteries by translumination, because they do not provide a reflection due to their accelerated flow. Another aspect is that iron, which composes hemosiderin, emits light of several wavelengths when stimulated.
Histogram In translumination, the spectrum of white light is divided into different wavelengths (colors). A histogram represents the graphic visualization of these colors and the luminescence of the obtained images. In a histogram, the intensity of the luminescence is accompanied by a gray baseline that decreases as the source approaches, where the red scale is more intense and is represented by a line in ascension. The scales of blue and green colors represent the refraction indexes of the light emitted by the transluminator in contact with the studied area. In the histogram when the selection of a scale (for example, the green scale) is disabled, the luminescence intensity of captured images may be mapped. Bollinger et al. reported their experience: denominated fluorescence video miscroscopy, based on the video capture of images and study of their luminescence through light emission stimulated by 20% sodium-fluorocein (0.3 mL/L of blood).Bollinger, A; Haselbach, P; Schnewlin, G; Jiinger M (1985) "Microangiopathy due to Chronic Venous Incompetence Evaluated by Fluorescence Videomicroscopy". Phlebology, 255: 751- 3. The principles of spectrographic analysis of this test are similar to those used to evaluate the luminescence of captured images by venous translumination, and the histogram also evaluates the scales of red, blue and green (RGB). All organic components are composed of chemical elements that emit light according to their wavelength. This is why the histogram analysis of transluminated images could define an organic element according to the quality and amount of their components.
References
Bibliography Aburahama, AF; Sadler, D; Robinson, PA. Axillary-subclavian vein thrombosis: changing patterns of etiology, diagnostic and thera- peutic modalities. Am Surg 1991;57:101. Albrechtsson, U; Olsson, C-G. Thrombotic side-effects of lower limb phlebography. Lancet 1976; I: 723. Ackroyd, JS; Thomas, ML; Browse, NL. Deep vein reflux: an assessment by descending phlebography. Br J Surg 1986; 73:31. Adams, JT; DeWeese JA et al. Intermittent subclavian vein obstruction without THROMBOSIS. SURGERY 1968;63:147. Bettmann, MA; Salzman, EW et al. Reduction of venous thrombosis complicating phlebography. AJR 1980; 134:1169. Bettmann, MA; Robbins, A et al. Contrast venography of the leg: diagnostic efficacy, tolerance, and complication rates with ionic and nonionic contrast media. Radiology 1987;165: 113. Bettmann, MA; Paulin, S. Leg phlebography: the incidence, nature and modification of undesirable side effects. Radiology 1977; 122:101. Baxter, GM; Duffy, P et al. Colour flow imaging of calf vein thrombosis. Clin Radiol 1992;46: 198. Barnes, RW; Nix, ML et al. Perioperative asymptomatic venous thrombosis: role of duplex scanning versus venography. J Vasc Surg 1989;9:251. Bollinger, A; Haselbach P, Schnewlin G, Jiinger M (1985) Microangiopathy due to Chronic Venous Incompetence Evaluated by Fluorescence Videomicroscopy. Phlebology. 255: 751- 3. Baldridge, ED; Martin, MA et al. Clinical significance of free-floating venous thrombi. J Vasc Surg 1990;11:62. Baum, RA; Holland, GH et al. Hypogastric venous thrombosis at MR angiography. Presented at the 79th Scientific Assembly and Annual Meeting of the Radiological Society of North America, Chicago, Nov 28-Dec 3, 1993. Bräuer, K; Hahn, M (1999) Nonlinear Analysis of Blood Flux in Human Vessels. Phys. Med. Biol. 44: 1719–33. Burnand, KG; Browse, NL (1982) The Cause of Venous Ulceration. Lancet. 31: 243. Burnand, KG; Whimester, J; Nacidoo, A; Browse NL (1982) Pericapillary Fibrin in the Ulcer Bearing Skin of the Leg: The Cause of Lipodermatosderosis and Venous Ulceration. Br. Med. J. 285: 1071–2. Bernstein, EF. Recent advances in noninvasive diagnostic techniques in vascular disease. St. Louis: Mosby; 1990. Belov, S. Classification of congenital vascular defects. Int Angiol 1990; 9: 141–146. Vascular Malformations. Edit. St. Belov DA, Loose J, Weber. Einhorn Presse Verlag. Periodica Angiologica 1989: 16; 25–27. Belcaro, G; Nicolaides, AN; Veller, M. in: Assessment of the venous and lymphatic systems. Authors XX, editors. Venous disorders: a manual of diagnosis and treatment. Cidade: Saundres; 1995:41. Cranley, JJ. Diagnostic tests for venous thrombosis. In: Cranley JJ, ed. Vascular surgery. New York: Harper and Row, 1975. Christopoulos, D; Nicolaides, AN. Air plethysmography. in: Raju S, Villavicencio JL., Surgical management of venous disease. Cidade: Willians & Wilkins; 1997:93. Chiller, KG; Passaro, D; Frieden, IJ. Hemangiomas of infancy. Clinical characteristics, morphologic subtypes, and their relationship to race, ethnicity, and sex. Arch Dermatol 2002; 138: 1567–1576. Cranley, JJ; Canos, AJ et al. The diagnosis of deep venous thrombosis. Arch Surg 1976; III :34. Coei, MN; Dodge, W. Complication rate with supine phlebography. AJR 1978; 131:821. Christopoulos, D; Nicolaides, AN; Szendro, G; Irvine, AT; Bull, ML; Eastcott, HHG. Air plethysmography and the effect of elastic compression on the venous haemodynamics of the leg. J Vasc Surg 1987;5:148-159. Cherian, SM; Bobryshev, YV; Inder, SJ; Lord, RS; Ashwell, KW (1999) Dendritic Cells in Venous Pathologies. 50: 393-402 Cronan, JJ; Dorfman, GS et al. Deep vein thrombosis: US assessment using vein compression. Radiology 1987;162:191. Cohan, RH; Leder, RA et al. Extravascular extravasation of radiographic contrast media: effects of conventional and low-osmolar agents in the rat thigh. Invest RadioI 1990; 25:504. Christopoulos, D; Nicolaides, AN; Szendro, G. Venous reflux: quantification and correlation with the clinical severity of chronic venous disease. Br J Surg 1988;75:352-356. Campbell, CB; Chandler, JG et al. Axillary, subclavian and brachiocephalic vein obstruction. Surgery 1977; 82:816. Comerota, AJ; Katz, ML et al. Venous duplex imaging: should it replace hemodynamic tests for deep vein thrombosis? J Vasc Surg 1990; 11:53. Cronan, JJ. Ultrasound evaluation of deep vein thrombosis. Semin Roentgenol 1992;27:39. Cronan, JJ. Venous thromboembolic disease: the role of US. Radi- ology 1993;186:619. Darke, SG. The morphology of recurrent varicose veins. Eur J Vasc Surg 1992;6:512-517. Dorfman, GS; Froehlich, JA et al. Lower-extremity venous thrombosis in patients with acute hip fractures: determination of anatomic location and time of onset with compression sonography. AJR 1990; 154:851. Dorfman, GS; Cronan, JJ. Venous ultrasonography. Radiol Clin North Am 1992;30:879. Dimmeler, S; Assmus, B; Hermann, C; Haendeler, J; Zeiher. AM (1998) Fluid Shear Stress Stimulates Phosphorylation of Akt in Human Endothelial Cells: Involvement in Suppression of Apoptosis. Circ. Res. 83: 334–41.