Effects of Nd:YAG laser energy on the arterial wall: evaluation of a new contact delivery system

Although there has been much recent interest in the application of lasers to arterial occlusive disease, a detailed understanding of the effects of laser energy on vessel walls is lacking. This study compared the effect of a conventional, non-contact delivery system of Nd:YAG laser energy to a contact system using a 600 microns, artificial sapphire tip in eight mongrel dogs. A small section of the luminal surface of the carotid and femoral arteries was exposed to 10 or 15 joules of Nd:YAG laser power and flow was restored in the vessel. The animals were sacrificed at 0, 1, 2, 4, 7, 14, 21, and 30 days and the vessels were removed. The surface area of the laser injury for each artery was quantitated by computerized planimetry and all histologic sections were examined under light microscopy by an independent observer. Transmural necrosis occurred in 64% (20/31) of the non-contact lesions versus only 29% (9/31) of the contact lesions (P less than 0.01). Both types of laser injuries followed a predictable course with initial medial necrosis followed by formation of a fibrin erythrocyte coagulum overlying the lesions at 24 hr. The usual zones of vaporization, coagulation necrosis, and thermal damage were noted with both types of delivery systems, but the contact system resulted in more intimal vaporization. Healing of all lesions was rapid with complete endothelial coverage at two weeks. Thrombosis occurred in only 1 of 32 (3%) arteries, and there were no false aneurysms. Contact delivery of Nd:YAG laser energy produces significantly less transmural injury than does non-contact.(ABSTRACT TRUNCATED AT 250 WORDS)     

The pulsed dye laser and atherosclerotic vascular disease

The use of a pulsed dye laser to ablate atheromatous tissue obtained from post-mortem human aortic specimens is reported. Laser energy was delivered with a 600 micron quartz fibre, at a wavelength of 504 nm and a pulse length of 1 microseconds. Pulse energy was varied from 30-140 mJ, producing peak pulse powers of the order of 100 kW. With these parameters the laser ablated fatty, fibrous and calcified plaques. At this wavelength atheroma is vaporized but there is minimal damage to normal vessel wall, due to preferential absorption of the laser light. Light microscopy shows that by microsecond pulsing, thermal damage to surrounding tissues associated with continuous wave lasers is avoided. Transmission electron micrographs reveal a sharp demarcation between a laser crater and the adjacent vessel wall with little ultrastructural disruption. Scanning electron micrographs show the crater walls to be smooth. The pulsed dye laser may therefore be effective in the treatment of occlusive peripheral vascular disease without undue risk of vessel perforation.     

Hydrogen peroxide-induced stroke: elucidation of the mechanism in vivo

OBJECT: Hydrogen peroxide (H2O2) is used as a hemostatic agent in many neurosurgery centers. The authors used a 3% H2O2 solution for final hemostasis after removal of a left insular tumor. Immediately afterward, air bubbles were observed within the lumen of the polar temporal artery. Postoperative MR imaging revealed punctate areas of infarction in the lenticulostriate artery territory. The authors designed an experimental study to elucidate the mechanism of remote O2 emboli and reactive O2 species-related vasoactive responses and thrombus formation. METHODS: In this study, H2O2 irrigation was used in mice with either an intact pial layer or after the pia mater was removed through a corticotomy. Normal saline irrigation was used in the corresponding control groups. Vessels were examined for intravascular O2 emboli under the microscope. Tissue sections were then obtained and stained with H & E and the 3-nitrotyrosine (3-NT) antibody to evaluate intravascular thrombus formation and peroxynitrite reaction, respectively. RESULTS: Multiple bubbles were observed within the lumen of the vessels after exposure to H2O2 regardless of whether the pial layer was destroyed or intact. Immunofluorescent staining for 3-NT showed an abundant positive reaction in the vessel walls of all animals exposed to H2O2 as well as vascular occlusion with acute thrombus formation. Samples taken from the animals that received saline showed no positive staining for 3-NT and no vascular occlusion. CONCLUSIONS: Exposure to H2O2 may cause serious ischemic complications. The formation of peroxynitrite may cause vasoactive responses to H2O2 and platelet aggregation/thrombus formation, and the free diffusion of H2O2 through the vessel walls and its conversion to water and O2 leads to O2 bubbles within the closed vessel lumen. If used intradurally, H2O2 may have deleterious ischemic effects, and it can only be used carefully in open extradural spaces.     

Real-Time Monitoring of Blood–Brain Barrier Disruption Induced by Ultraviolet Laser Irradiation

Ultraviolet laser light of sufficient power can induce focal œdema in the brain. The formation of ultraviolet-induced vasogenic \kdema was monitored by observing real-time changes in the integrity of the blood–brain barrier. The brain surface of guinea-pigs injected with Evans blue was exposed to light from a continuous wave argon laser at 351 nm, delivered via an optical fibre. The integrity of the blood–brain barrier was evaluated by measuring surface reflectance using a separate probing light. The brain was then sectioned and examined using light and electron microscopy. Extravasation of Evans blue following vasodilatation was observed when the irradiation intensity was greater than 0.64 W/cm². The extent of glial and vascular damage could be correlated with the laser power. Irradiated vascular endothelium exhibited lipping at the tight junction, vacuolation and mitichondrial swelling. These results suggest that disruption of the blood–brain barrier induced by ultraviolet light is preceded by vasodilatation. Received for publication May 1997; accepted following revision September 1997.     

Secretory meningioma. A distinct subtype of meningioma

Six meningiomas with abundant hyaline inclusions (pseudopsammoma bodies) were studied. As seen by light and electron microscopy, hyaline inclusions are composed of material of varying structures located in intracellular lumina lined by microvilli. A remarkable pericytic proliferation within the vessel walls was found in five cases. In all six cases, immunohistochemical examination for multiple antigens showed positive staining for carcinoembryonic antigen and epithelial membrane antigen in inclusions and surrounding cells. Weak positivity was found for keratin and secretory component in five cases and for alpha-1-antitrypsin and IgM in four cases. It is concluded that secretory meningioma is a distinct type of meningioma, usually meningothelial in type. It shows characteristic light-microscopic, ultrastructural, and immunohistochemical features of epithelial and secretory differentiation with accumulation of secretory material in the form of hyaline inclusions; marked vascular pericytic proliferation is also frequently present.     

A study of the ultrastructural features of the cut margin of skin and mucous membrane specimens excised by carbon dioxide laser.

Electron microscopic examination was performed on the cut edge of three surgical specimens of skin and mucous membrane lesions to measure more precisely the depth of damage of the laser beams, appearing on light microscopy as “burn” rim.Serial sections of this material revealed that the “burn” rim extended to a depth of 200–250 μm, but damage was not equal for all tissue. Most sensitive to the laser beams are the epithelial cells and their organelles, which showed signs of necrosis to a distance of 250 μm from the cut edge. Desmosomes, cell nuclei collagen fibers, and erythrocytes are less sensitive to the laser beams and started showing some preservation of their structure on the ultrasections cut at a depth of 30–50 μm from the periphery. Capillaries revealed swollen endothelial cells with a marked narrowing of their lumen. The importance of these findings and the significance of the application of the laser in clinical surgery were discussed.     

Safety assessment of trans-tympanic photobiomodulation

We evaluated functional and morphological changes after trans-tympanic laser application using several different powers of photobiomodulation (PBM). The left (L) ears of 17 rats were irradiated for 30 min daily over 14 days using a power density of 909.1 (group A, 5040 J), 1136.4 (group B, 6300 J), and 1363.6 (group C, 7560 J) mW/cm². The right (N) ears served as controls. The safety of PBM was determined by endoscopic findings, auditory brainstem response (ABR) thresholds, and histological images of hair cells using confocal microscopy, and light microscopic images of the external auditory canal (EAC) and tympanic membrane (TM). Endoscopic findings revealed severe inflammation in the TM of C group; no other group showed damage in the TM. No significant difference in ABR threshold was found in the PBM-treated groups (excluding the group with TM damage). Confocal microscopy showed no histological difference between the AL and AN, or BL and BN groups. However, light microscopy showed more prominent edema, inflammation, and vascular congestion in the TM of BL ears. This study found a dose-response relationship between laser power parameters and TM changes. These results will be useful for defining future allowance criteria for trans-tympanic laser therapies.     

Defining parameters for peripheral laser angioplasty

In vitro studies are reported using a Pulsed Dye laser at wavelengths of 440, 480, 504, 560 and 590 nm, to vaporise multiple samples of yellow, fibrous and calcified plaque. The threshold for crater production at 440 nm was 5 mJ/pulse and at 590 nm 65 mJ/pulse. Crater depth was significantly deeper at the short wavelengths (440, 480 and 504 nm) than at the longer (560 and 590 nm). Light microscopy confirmed the absence of thermal damage associated with continuous wave lasers. Electron microscopy revealed smooth-contoured craters and no disruption of subcellular elements at the crater margin. Samples of thrombus- and atheroma-occluded human femoral artery were successfully recanalised at the 480 nm wavelength with atraumatic spherical-tipped and modified spherical tipped optical fibres. The advantages of pulsed laser energy in peripheral vessel recanalisation are discussed.     

Effect of Er:YAG, CO(2) and diode laser irradiation on surface properties of zirconia endosseous dental implants

BACKGROUND AND OBJECTIVES: Zirconia implants (ZI) are becoming more popular in implant dentistry, as a result of their favorable esthetic outcome. However, little is known about the impact laser application has on this material in the course of peri-implantitis treatment. The objective of this investigation was to analyze the influence of Er:YAG, CO(2) and diode laser irradiation on polished ZI. MATERIAL AND METHODS: Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic disks were irradiated at different power settings with either an Er:YAG, CO(2) or diode laser. The surface of the disks was analyzed by scanning electron microscopy (SEM) and confocal 3D white light microscopy (CWLM). In addition energy-dispersive X-ray (EDX) analysis was performed on all disks. Six specimens were used for each parameter set of each laser. RESULTS: SEM analysis demonstrated that, regardless of the power settings, neither the diode laser nor the Er:YAG laser caused any visible surface alterations to ZI. The results of the CWLM were in agreement with the SEM pictures. However, Er:YAG irradiation did penetrate through the disks. At various power settings, the CO(2) treatment was characterized by material cracking and melting. The increased roughness values (from CWLM) of the ZI underlined the SEM observations. CONCLUSION: In contrast to diode and Er:YAG laser irradiation, the CO(2) laser revealed distinct surface alterations to zirconia at various laser parameters. However, the Er:YAG laser cannot be recommended for the treatment of ailing implants, as the laser beam penetrates the material. In this respect, currently, diode lasers seem to be the only laser systems offering surface preservation and safety in the treatment of peri-implantits with ZI.     

Ultrastructural changes in the nuclei of human carcinoma cells after photodynamic treatment with haematoporphyrin derivative and tetrasodium-meso-tetra-(4-sulphonatophenyl)porphine

Human NHIK 3025 cells derived from a carcinoma in situ were incubated with tetrasodium-meso-tetra-(4-sulphonatophenyl)porphine (TPPS₄) or HPD and exposed to light. Two different incubation conditions were applied: 0.5h in pure phosphate-buffered saline and 22h in a medium containing 10% newborn calf serum. The cell survival curves revealed different inactivation kinetics for TPPS₄ as compared with HPD. Electron microscopy revealed qualitatively the same types of photoinduced damage to the cell nuclei for both sensitizers when the cells were examined at the same survival level. The damage was manifested as nuclear swelling and segmentation, swelling of the perinuclear cistern, simultaneous chromatin dilution and condensation, and nucleolar segregation with cap formation. For HPD, mitotic arrest with disappearance of microtubules was also observed.     

Effect of high laser output on the central bronchi and pulmonary artery

A diode-pump Nd:YAG high-power laser (wavelength 1320 nm, power 100 W) is routinely used to surgically remove lung metastases. Even pulmonary lesions in central locations are resectable via this method, yet it also carries a potential risk of damaging the larger bronchi and vessels in the vicinity. Studies investigating the safety of using high-power lasers are lacking. We therefore aimed to examine the direct effects of a 100-watt laser on the bronchi and pulmonary artery at a standard working velocity. From freshly slaughtered pigs, we isolated cylindrical specimens of the trachea, the main and lobar bronchi, and the central pulmonary artery from the both lungs. These specimens were fixed consecutively in rows behind each other on a Styrofoam surface in the laboratory. The laser’s handle was clamped into a hydraulic feed unit so that the laser was focused at constant distance perpendicular to the tissue and would move at 10 mm/s over the specimens. The Nd:YAG Laser LIMAX® 120 functioned at a consistent power of 100 W during all the experiments. The lasered specimens were examined macroscopically and histologically for tissue damage. None of the trachea or bronchial walls were perforated. Compared to the pulmonary parenchyma, we observed no vaporization effects—only minor superficial coagulation (with a mean depth of 2.1?±?0.8 mm). This finding was histologically confirmed in each specimen, which revealed mild superficial coagulation and no damage to the cartilage. In the presence of a residual peribronchial fatty tissue, the laser effect was even attenuated. The pulmonary arteries presented no lumen openings whatsoever, merely a discrete trace of coagulation. The vessel wall revealed increased vacuolization without alteration of the remaining vessel wall. In conclusion, laser resection at 100 W of the central lung areas is safe with respect to airways and blood vessels and the laser output does not need to be reduced when treating these areas.     

Evaluation of micromorphological changes in tooth enamel after mechanical and ultrafast laser preparation of surface cavities

The aim of this in vitro study was to evaluate the morphological changes that occur in tooth enamel after mechanical instrumentation and after femtosecond laser irradiation with different parameters via light and scanning electron microscopy (SEM). Twelve totally impacted third molars were collected and sectioned to provide several cut surfaces. These surfaces were exposed to infrared (λ?=?795 nm, 120 fs, 1-kHz repetition rate, maximum mean power 1 W) laser pulses and machined by means of a conventional mechanical technique. Two very different geometrical patterns were performed with femtosecond laser pulses: shallow rectangular cavities and deep cylindrical ones. The results of both machining procedures were examined using light and scanning electron microscopy. The SEM images show the femtosecond laser ability to produce high-precision cavities in tooth enamel. No signs of collateral damage, burning, melting, or cracks were observed despite the far different laser pulse energies used (ranging from 7 to 400 μJ), unlike what is seen with conventional mechanical techniques. The femtosecond laser has the potential to become an optimal tool for the treatment of dental decay and as an alternative to the conventional drill to reduce mechanical damage during removal of the hard dental tissue.     

Laser solder welding of articular cartilage: tensile strength and chondrocyte viability.

BACKGROUND AND OBJECTIVE: The surgical treatment of full-thickness cartilage defects in the knee joint remains a therapeutic challenge. Recently, new techniques for articular cartilage transplantation, such as mosaicplasty, have become available for cartilage repair. The long-term success of these techniques, however, depends not only on the chondrocyte viability but also on a lateral integration of the implant. The goal of this study was to evaluate the feasibility of cartilage welding by using albumin solder that was dye-enhanced to allow coagulation with 808-nm laser diode irradiation. STUDY DESIGN/MATERIALS AND METHODS: Conventional histology of light microscopy was compared with a viability staining to precisely determine the extent of thermal damage after laser welding. Indocyanine green (ICG) enhanced albumin solder (25% albumin, 0.5% HA, 0.1% ICG) was used for articular cartilage welding. For coagulation, the solder was irradiated through the cartilage implant by 808-nm laser light and the tensile strength of the weld was measured. RESULTS: Viability staining revealed a thermal damage of typically 500 m in depth at an irradiance of approximately 10 W/cm(2) for 8 seconds, whereas conventional histologies showed only half of the extent found by the viability test. Heat-bath investigations revealed a threshold temperature of minimum 54 degrees C for thermal damage of chondrocytes. Efficient cartilage bonding was obtained by using bovine albumin solder as adhesive. Maximum tensile strength of more than 10 N/cm(2) was achieved. CONCLUSIONS: Viability tests revealed that the thermal damage is much greater (up to twice) than expected after light microscopic characterization. This study shows the feasibility to strongly laser weld cartilage on cartilage by use of a dye-enhanced albumin solder. Possibilities to reduce the range of damage are suggested.     

Mechanisms of shock wave induced endothelial cell injury

BACKGROUND AND OBJECTIVES: Medical procedures, for example, laser angioplasty and extracorporeal lithotripsy as well as high-energy trauma expose human tissues to shock waves (SWs) that may cause tissue injury. The mechanisms for this injury, often affecting blood vessel walls, are poorly understood. Here we sought to assess the role of two suggested factors, viz., cavitation or reactive oxygen species (ROS). STUDY DESIGN/MATERIALS AND METHODS: A laser driven flyer-plate model was used to expose human umbilical cord vein endothelial cell (HUVEC) monolayers to SWs or to SWs plus cavitation (SWC). Cell injury was quantified with morphometry, trypan blue staining, and release of (51)Cr from labeled HUVECs. RESULTS: HUVECs, exposed to SWs only, could not be distinguished from controls in morphological appearance or ability to exclude trypan blue. Yet, release of (51)Cr, indicated a significant cell injury (P < 0.05). HUVEC cultures exposed to SWC, exhibited cell detachment and cell membrane damage detectable with trypan blue. Release of (51)Cr was fourfold compared to SW samples (P < 0.01). Signs of cell injury were evident at 15 minutes and did not change over the next 4 hours. No protective effects of ROS scavengers were demonstrated. CONCLUSIONS: Independent of ROS, SWC generated an immediate cell injury, which can explain, for example, vessel wall perturbation described in relation to SW treatments and trauma.     

Epidermal and vascular damage analysis of in vivo human skin in response to 595 nm pulsed laser irradiation

BACKGROUND AND OBJECTIVES: Laser irradiation is the current modality for treatment of cutaneous hypervascular malformations such as port wine stains and telangiectasia. Although cryogen spray cooling (CSC) is used to protect the epidermis from non-specific laser-induced thermal damage in moderately-pigmented skin types, individuals with high melanin content are still at risk for epidermal damage using the current laser irradiation and CSC parameters. The objective of this study was to investigate the influence of the spray Weber number (1,100 or 5,100) on epidermal protection and examine vascular coagulation in response to pulsed dye laser irradiation. STUDY DESIGN/MATERIALS AND METHODS: Normal, in vivo human skin from eight subjects of Fitzpatrick skin types I-V were precooled with either low or high Weber number cryogen sprays and subsequently irradiated with a pulsed dye laser at 595 nm. Analysis of gross purpura, morphological vascular damage, and apoptosis of the vascular walls were performed. RESULTS: Results demonstrated a high Weber number spray of 5,100 decreased the level of epidermal damage in darker and moderate pigmented individuals compared to a Weber number spray of 1,100. This study also established a positive correlation between gross purpura and the level of vessel wall apoptosis. CONCLUSIONS: This study has demonstrated that CSC with a high Weber number spray can decrease nonspecific thermal damage to the epidermis in response to laser irradiation in vivo. We have also established a positive correlation between gross purpura and the level of vessel wall apoptosis. Lasers Surg. Med. (c) 2005 Wiley-Liss, Inc.     

Intraluminal laser light source and external solder: in vivo evaluation of a new technique for microvascular anastomosis

BACKGROUND AND OBJECTIVES: Current laser-assisted end-to-end anastomoses are performed by irradiating the vessel wall from outside after additional fixation with three to six sutures. These sutures are needed to provide adequate approximation of the vessel stumps. We present a new laser soldering technique that is based on an intraluminal laser light source centered in a balloon catheter, and external application of a solder. This technique was applied in vivo in order to test its feasibility under clinical conditions. STUDY DESIGN/MATERIALS AND METHODS: Seven white pigs were treated with a total of fourteen end-to-end laser-anastomoses of their saphenous arteries having outer diameters of 2 mm. The vessels were stented over an intraluminal balloon catheter, which was maximally dilated and which allowed for a precise approximation of the vascular stumps. An 808 nm diode laser was coupled into a specially designed optical fiber producing a 360 degrees radiation ring inside the balloon catheter. An indocyanine green (ICG) doped liquid albumin solder was applied on the external surface of the vascular stumps. Laser soldering was achieved by irradiating with a 808 nm laser diode for 75 seconds. Tightness of the anastomoses was evaluated by clamping the artery distal to the anastomosis for 1 hour, and patency was tested over an observation period of 3 hours, during which the animals were heparinized. Thereafter, the anastomoses were harvested for histomorphological examination. RESULTS: All anastomoses remained patent over the entire observation period. Some leakage was observed in three anastomoses, which was explained by a deviation of the illumination fiber from the center of the balloon leading to an inhomogeneous irradiation of the vessel wall. Histology revealed perfect adaptation of the vascular stumps. A segment of denaturated vascular collagen was observed, that corresponded to the irradiated, solder-covered zone. CONCLUSION: Patent, maximally dilated and well adapted microvascular anastomoses could be obtained without the need of stay sutures. A well centered laser light source is indispensable for avoiding inhomogenous welding, thus causing leakage.     

Laser vascular welding—How does it work?

This study evaluated the histology and electron microscopy of four samples of 2 cm long venotomles and artery-vein anastomoses formed in canine femoral arteries and veins using the argon laser (0.5 W power, 1 800 J/cm², 4 min exposure/1 cm length of anastomosis). Welds were continuously irrigated with saline during the procedure to limit maximal temperatures to 44.2±1.6°C (mean±SD), and the specimens were removed immediately following fusion and preserved for examination. Histologic and electron microscopic examination of different areas of the welds revealed various mechanisms of fusion including a) apposition of denatured collagen and elastin in the media and adventitia; b) bonding of veln medial collagen and elastin to the internal elastic membrane of the artery; and c) fusion consisting of a coagulum of platelets and fibrin depending on the allgnment and apposition of the vessel edges. This study demonstrates that vascular tissue fusion by the argon laser occurs by various mechanisms. Future experiments should delineate which types of seal produce the optimal strength at the time of fusion, and enhance longterm healing. Presented at the 1986 Southern California Vascular Surgical Society meeting, September 26–28, 1986, Long Beach, California. Supported by Grants HL-32622, GM-288833, AM-28450 and AM-35297 from USPHS, National Institutes of Health.     

Laser surgery of port wine stains using local vacuum [corrected] pressure: changes in calculated energy deposition (Part II)

BACKGROUND AND OBJECTIVES: Application of local vacuum pressure to human skin during laser irradiation results in less absorption in the epidermis and more light delivered to targeted vessels with an increased blood volume. The objective of the present numerical study is to assess the effect of applying local vacuum pressure on the temperatures of the epidermis and small vessels during port wine stain (PWS) laser treatment. STUDY DESIGN/ MATERIALS AND METHODS: Mathematical models of light deposition and heat diffusion are used to compute absorbed energy and temperature distributions of skin and blood vessels with different diameters (10-60 microm) at various depths (200-800 microm) exposed to laser irradiation under atmospheric and vacuum pressures. RESULTS: Under 50 kPa (15 in Hg) vacuum pressure, peak temperatures at the inner walls of small diameter vessels (10-30 microm) located 200-300 microm below the skin surface are approximately 10 degrees C higher than those under atmospheric pressure, and peak temperatures in the epidermis of patients with skin phototype II are approximately 5 degrees C lower. In patients with darker skin phototype (IV), the peak temperature at the inner wall of a 10 microm diameter vessel located 200 microm below the skin surface is approximately 5 degrees C higher than that under atmospheric pressure, and the peak temperature in the epidermis is approximately 10 degrees C lower. CONCLUSIONS: Additional energy deposition in a larger blood volume permits higher temperatures to be achieved at vessel walls in response to laser irradiation. While more energy is deposited in every vessel, temperature gains in small diameter vessels (10-30 microm) are greater, increasing the likelihood of irreversible thermal damage to such vessels. In addition, temperatures in the epidermis decrease because less energy is absorbed therein due to reduced epidermal thickness and concentration of melanin per unit area.     

In vitro effects of CO2 laser irradiation on platelets: Influence of aspirin

Laser angioplasty involves intravascular laser irradiation which may affect platelets and aggregation. In this study we examined the in vitro effects of different energy doses and modes of CO₂ laser irradiation on the platelet number, function and ultrastructure. Since aspirin is used in many patients suffering from coronary artery disease, the consequences of laser irradiation on aspirin-treated platelets were studied as well.We found that CO₂ laser irradiation causes a dose-response reduction of the platelet number that is most pronounced with high energy-short duration irradiation, and a dose-response reduction in platelet aggregation which is independent of the mode of irradiation. Pretreatment with aspirin does not change the effects of laser irradiation on platelet number, while aggregation is reduced only at relatively high energy doses. Electron microscopy revealed significant intracellular injury following low energy irradiation, while progressive damage to membranes occurred in a dose-response mode, both in untreated and aspirin-treated platelets. The clinical application of our findings should be done cautiously since important in vivo factors, such as the effect of laser irradiation on the vessel wall and coagulation system, were not studied.     

Determination of the energy-dependent extent of vascular damage caused by high-energy shock waves in an umbilical cord model

Summary To determine the spatial extent of shock-waveinduced vascular damage human umbilical cords were exposed to electromagnetically generated, focused ultrasound waves of different energy densities. During treatment macroscopically visible hematoma and superficial holes appeared. Following exposure specimens were fixed and examined histologically. In addition to vessel wall necrosis and rupture, complete detachment of endothelial cells in defined regions was observed. A correlation of the extent of the damage with the energy density distribution revealed that a local energy density of 0.3 mJ/mm² is the lower threshold for the occurrence of severe vascular damage.