Use of Inert Gases for the Preservation of Nuclear Blood Cells

Abstract The subject of the study was the stability of human white blood cell membranes subject to noble gases (xenon ad krypton, 0.6 mPa) clathrate cryoanabiosis (‒80°C). A unique portable stainless steel low pressure container with a compartment for flexible plastic container was designed to ensure that the cells are saturated with gases. The samples were warmed after 1 and 30 days in a water bath (+38°C) for 35-50 sec, while the container was being tilted (2-3 times per second), until the temperature of the biological object reached +3±1°C. It was demonstrated that after 30 days of clathrate anabiosis (-80°C) over 95% (of the original number) of leukocytes remain viable, and cell membranes of 54.5±3.4% of them is resistant to trypan blue; granulocyte survival rate is 73.5±2.7%, original lipid peroxidation rate and antioxidant activity are retained. Biological object cryopreservation in noble gases environment is a promising trend in biology and medicine.

Dual-Energy CT: New Horizon in Medical Imaging

Dual-energy CT has remained underutilized over the past decade probably due to a cumbersome workflow issue and current technical limitations. Clinical radiologists should be made aware of the potential clinical benefits of dual-energy CT over single-energy CT. To accomplish this aim, the basic principle, current acquisition methods with advantages and disadvantages, and various material-specific imaging methods as clinical applications of dual-energy CT should be addressed in detail. Current dual-energy CT acquisition methods include dual tubes with or without beam filtration, rapid voltage switching, dual-layer detector, split filter technique, and sequential scanning. Dual-energy material-specific imaging methods include virtual monoenergetic or monochromatic imaging, effective atomic number map, virtual non-contrast or unenhanced imaging, virtual non-calcium imaging, iodine map, inhaled xenon map, uric acid imaging, automatic bone removal, and lung vessels analysis. In this review, we focus on dual-energy CT imaging including related issues of radiation exposure to patients, scanning and post-processing options, and potential clinical benefits mainly to improve the understanding of clinical radiologists and thus, expand the clinical use of dual-energy CT; in addition, we briefly describe the current technical limitations of dual-energy CT and the current developments of photon-counting detector.

Hazards Caused by UV Rays of Xenon Light Based High Performance Solar Simulators

BACKGROUND: Solar furnaces are used worldwide to conduct experiments to demonstrate the feasibility of solar–chemical processes with the aid of concentrated sunlight, or to qualify high temperature-resistant components. In recent years, high-flux solar simulators (HFSSs) based on short-arc xenon lamps are more frequently used. The emitted spectrum is very similar to natural sunlight but with dangerous portions of ultraviolet light as well. Due to special benefits of solar simulators the increase of construction activity for HFSS can be observed worldwide. Hence, it is quite important to protect employees against serious injuries caused by ultraviolet radiation (UVR) in a range of 100 nm to 400 nm. METHODS: The UV measurements were made at the German Aerospace Center (DLR), Cologne and Paul-Scherrer-Institute (PSI), Switzerland, during normal operations of the HFSS, with a high-precision UV-A/B radiometer using different experiment setups at different power levels. Thus, the measurement results represent UV emissions which are typical when operating a HFSS. Therefore, the biological effects on people exposed to UVR was investigated systematically to identify the existing hazard potential. RESULTS: It should be noted that the permissible workplace exposure limits for UV emissions significantly exceeded after a few seconds. One critical value was strongly exceeded by a factor of 770. CONCLUSION: The prevention of emissions must first and foremost be carried out by structural measures. Furthermore, unambiguous protocols have to be defined and compliance must be monitored. For short-term activities in the hazard area, measures for the protection of eyes and skin must be taken.

Collateral Ventilation Quantification Using Xenon-Enhanced Dynamic Dual-Energy CT: Differences between Canine and Swine Models of Bronchial Occlusion

OBJECTIVE: The aim of this study was to evaluate whether the difference in the degree of collateral ventilation between canine and swine models of bronchial obstruction could be detected by using xenon-enhanced dynamic dual-energy CT. MATERIALS AND METHODS: Eight mongrel dogs and six pigs underwent dynamic dual-energy scanning of 64-slice dual-source CT at 12-second interval for 2-minute wash-in period (60% xenon) and at 24-second interval for 3-minute wash-out period with segmental bronchus occluded. Ventilation parameters of magnitude (A value), maximal slope, velocity (K value), and time-to-peak (TTP) enhancement were calculated from dynamic xenon maps using exponential function of Kety model. RESULTS: A larger difference in A value between parenchyma was observed in pigs than in dogs (absolute difference, -33.0 +/- 5.0 Hounsfield units [HU] vs. -2.8 +/- 7.1 HU, p = 0.001; normalized percentage difference, -79.8 +/- 1.8% vs. -5.4 +/- 16.4%, p = 0.0007). Mean maximal slopes in both periods in the occluded parenchyma only decreased in pigs (all p < 0.05). K values of both periods were not different (p = 0.892) in dogs. However, a significant (p = 0.027) difference was found in pigs in the wash-in period. TTP was delayed in the occluded parenchyma in pigs (p = 0.013) but not in dogs (p = 0.892). CONCLUSION: Xenon-ventilation CT allows the quantification of collateral ventilation and detection of differences between canine and swine models of bronchial obstruction.

Computer-Aided Classification of Visual Ventilation Patterns in Patients with Chronic Obstructive Pulmonary Disease at Two-Phase Xenon-Enhanced CT

OBJECTIVE: To evaluate the technical feasibility, performance, and interobserver agreement of a computer-aided classification (CAC) system for regional ventilation at two-phase xenon-enhanced CT in patients with chronic obstructive pulmonary disease (COPD). MATERIALS AND METHODS: Thirty-eight patients with COPD underwent two-phase xenon ventilation CT with resulting wash-in (WI) and wash-out (WO) xenon images. The regional ventilation in structural abnormalities was visually categorized into four patterns by consensus of two experienced radiologists who compared the xenon attenuation of structural abnormalities with that of adjacent normal parenchyma in the WI and WO images, and it served as the reference. Two series of image datasets of structural abnormalities were randomly extracted for optimization and validation. The proportion of agreement on a per-lesion basis and receiver operating characteristics on a per-pixel basis between CAC and reference were analyzed for optimization. Thereafter, six readers independently categorized the regional ventilation in structural abnormalities in the validation set without and with a CAC map. Interobserver agreement was also compared between assessments without and with CAC maps using multirater kappa statistics. RESULTS: Computer-aided classification maps were successfully generated in 31 patients (81.5%). The proportion of agreement and the average area under the curve of optimized CAC maps were 94% (75/80) and 0.994, respectively. Multirater kappa value was improved from moderate (kappa = 0.59; 95% confidence interval [CI], 0.56-0.62) at the initial assessment to excellent (kappa = 0.82; 95% CI, 0.79-0.85) with the CAC map. CONCLUSION: Our proposed CAC system demonstrated the potential for regional ventilation pattern analysis and enhanced interobserver agreement on visual classification of regional ventilation.

Evaluation of hemodynamic effects of xenon in dogs undergoing hemorrhagic shock

OBJECTIVES: The anesthetic gas xenon is reported to preserve hemodynamic stability during general anesthesia. However, the effects of the gas during shock are unclear. The objective of this study was to evaluate the effect of Xe on hemodynamic stability and tissue perfusion in a canine model of hemorrhagic shock. METHOD: Twenty-six dogs, mechanically ventilated with a fraction of inspired oxygen of 21% and anesthetized with etomidate and vecuronium, were randomized into Xenon (Xe; n = 13) or Control (C; n = 13) groups. Following hemodynamic monitoring, a pressure-driven shock was induced to reach an arterial pressure of 40 mmHg. Hemodynamic data and blood samples were collected prior to bleeding, immediately after bleeding and 5, 20 and 40 minutes following shock. The Xe group was treated with 79% Xe diluted in ambient air, inhaled for 20 minutes after shock. RESULT: The mean bleeding volume was 44 mL.kg-1 in the C group and 40 mL.kg-1 in the Xe group. Hemorrhage promoted a decrease in both the cardiac index (p<0.001) and mean arterial pressure (p<0.001). These changes were associated with an increase in lactate levels and worsening of oxygen transport variables in both groups (p<0.05). Inhalation of xenon did not cause further worsening of hemodynamics or tissue perfusion markers. CONCLUSIONS: Xenon did not alter hemodynamic stability or tissue perfusion in an experimentally controlled hemorrhagic shock model. However, further studies are necessary to validate this drug in other contexts.

Advances in research on neuroprotective effects of inert gas / 浙江大学学报·医学版

Inert gas is a group of rare gases with very low activity, their application in medical field has increasingly drawn attentions. It is known that inert gases helium, xenon and argon have protective effects on nervous system and the mechanisms are related to eradicating free radicals, anti-inflammation, suppressing apoptosis, influencing ion channels and so on. Further study on the neuroprotective effect of inert gas will shed light on a new approach to treat neurological diseases.

Influence of plasma arc and quartz-tungsten-halogen curing lights on the polymerization of orthodontic composite resin / Influência das fontes fotoativadoras xenon e halógena na polimerização de resina composta para colagem ortodôntica

PURPOSE: To analyze, in vitro, the influence of a quartz-tungsten-halogen (QTH) and a plasma arc (PAC) on the degree of conversion and hardness of a composite resin, as well as the heat generated by the units. METHODS: Transbond XT disks were prepared and light-cured for 10, 20 and 30 seconds with a QTH (Curing Light XL 3000) or with a PAC (Apollo 95E) for 1, 2 and 3 seconds. The composite resin polymerization was evaluated by infrared spectrophotometry (FTIR) and Knoop hardness number (KHN). The temperature at the curing tip was evaluated. The results were analyzed using ANOVA and Tukey test (α=0.05). RESULTS: According to FTIR and KHN, the polymerization of the composite resin was statistically higher with the QTH. The temperature obtained with the QTH 20 s (45.44ºC) and 30 s (45.84ºC) was statistically higher than the QTH 10 s (39.90ºC). The PAC 1 s (27.12ºC), 2 s (28.48ºC) and 3 s (29.96ºC) presented the lowest temperature and did not differ statistically among them. CONCLUSION: Transbond XT light-activated for 10, 20 and 30 seconds with the QTH presented higher degree of conversion and hardness in comparison with those obtained with the PAC for 1, 2 and 3 seconds, and the QTH generated more heat than the PAC.

OBJETIVO: Analisar, in vitro, as fontes luminosas Halógena (QTH) e Xenon (PAC) no grau de conversão e dureza de uma resina composta e também o calor gerado por estas unidades. METODOLOGIA: discos com resina Transbond XT foram fotoativados por 10, 20 e 30 segundos com QTH (Curing light XL 3000) ou com PAC (Apollo 95E) por 1, 2 e 3 segundos. A resina composta foi analisada por meio de espectrofotometria infravermelha (FTIR) e pelo teste de dureza Knoop (KHN). A temperatura na ponta dos aparelhos foi também avaliada. Os resultados foram analisados usando ANOVA e Tuckey test (α=0.05). RESULTADOS: Conforme FTIR e KHN a polimerização do compósito foi estatisticamente maior com QTH. A temperatura obtida do QTH com 20 segundos (45,44ºC) foi estatisticamente maior do que com 10 segundos (39,90ºC). O PAC com 1, 2 e 3 segundos apresentou as temperaturas mais baixas e não diferem estatisticamente entre si. CONCLUSÃO: A resina Transbond XT fotoativada por 10, 20 e 30 segundos com QTH apresentou maior grau de conversão e dureza em comparação com PAC por 1, 2 e 3 segundos. O QTH produziu mais calor que o PAC.

Redistributed Regional Ventilation after the Administration of a Bronchodilator Demonstrated on Xenon-Inhaled Dual-Energy CT in a Patient with Asthma

We report here on the redistributed regional ventilation abnormalities after the administration of a bronchodilator and as seen on xenon-inhaled dual-energy CT in a patient with asthma. The improved ventilation seen in the right lower lobe and the decreased ventilation seen in the right middle lobe after the administration of a bronchodilator on xenon-inhaled dual-energy CT could explain a positive bronchodilator response on a pulmonary function test. These changes may reflect the heterogeneity of the airway responsiveness to a bronchodilator in patients with asthma.

Collateral Ventilation to Congenital Hyperlucent Lung Lesions Assessed on Xenon-Enhanced Dynamic Dual-Energy CT: an Initial Experience

OBJECTIVE: We wanted to evaluate the resistance to collateral ventilation in congenital hyperlucent lung lesions and to correlate that with the anatomic findings on xenon-enhanced dynamic dual-energy CT. MATERIALS AND METHODS: Xenon-enhanced dynamic dual-energy CT was successfully and safely performed in eight children (median age: 5.5 years, 4 boys and 4 girls) with congenital hyperlucent lung lesions. Functional assessment of the lung lesions on the xenon map was done, including performing a time-xenon value curve analysis and assessing the amplitude of xenon enhancement (A) value, the rate of xenon enhancement (K) value and the time of arrival value. Based on the A value, the lung lesions were categorized into high or low (A value > 10 Hounsfield unit [HU]) resistance to collateral ventilation. In addition, the morphologic CT findings of the lung lesions, including cyst, mucocele and an accessory or incomplete fissure, were assessed on the weighted-average CT images. The xenon-enhanced CT radiation dose was estimated. RESULTS: Five of the eight lung lesions were categorized into the high resistance group and three lesions were categorized into the low resistance group. The A and K values in the normal lung were higher than those in the low resistance group. The time of arrival values were delayed in the low resistance group. Cysts were identified in five lesions, mucocele in four, accessory fissure in three and incomplete fissure in two. Either cyst or an accessory fissure was seen in four of the five lesions showing high resistance to collateral ventilation. The xenon-enhanced CT radiation dose was 2.3 +/- 0.6 mSv. CONCLUSION: Xenon-enhanced dynamic dual-energy CT can help visualize and quantitate various degrees of collateral ventilation to congenital hyperlucent lung lesions in addition to assessing the anatomic details of the lung.

A Comparative Study of the Efficacy and Safety of 530~750 nm and 555~950 nm Wavelength Bands of 2nd Generation IPL in Korean Photo-Rejuvenation / 대한피부과학회지

BACKGROUND: Recently, the 2nd generation IPL with a filtered xenon flash lamp has been widely used in the dermatologic field. In disagreement with the manufacturer's intent, for Asian skin, there were some reports that the best results for vascular lesions were obtained with the PR applicator, while the best results for pigmented lesions were obtained with the VL applicator. OBJECTIVE: The purpose of this study is to compare the efficacy and safety of two different (530~750 nm PR applicator and the 555~950 nm VL applicator) wavelength bands of 2nd generation IPL in Korean photo-rejuvenation. In addition, we compared the improvement of telangiectasia, irregular pigmentation, and overall patient' satisfaction for both settings. METHODS: Twenty-two patients with signs of photoaging skin including irregular pigmentation and telangiectasia were treated with 2nd generation IPL (Ellipse-Flex(R), DDD, Denmark) using a split-face comparative method, comparing both sides with respect to improvement of telangiectasia, irregular pigmentation, and overall patient satisfaction. RESULTS: Comparison of the efficacy and safety between the VL and PR applicators revealed that the VL applicator was not specific for vascular lesions and that the PR applicator was not specific for pigmented lesions. Additionally, VL is not better than PR for vascular lesions (p=0.80, McNemar test) and PR is not better than VL for pigmented lesions (p=0.80, McNemar test). Finally, improvements in skin texture were not significantly different between VL and PR (p=0.80, McNemar test). CONCLUSION: The two IPL wavelength bands were found to be effective in the treatment of photo-damaged facial skin. The difference between the two treatment procedures with regard to clinical efficacy and safety was not significant.

Influence of the curing method on the post-polymerization shrinkage stress of a composite resin

The aim of this study was to evaluate the effect of different curing methods on the stress generated by the polymerization shrinkage of a restorative composite in two moments: immediately after light exposure and after 5 min. Photoactivation was performed using two different light sources: (1) xenon plasma arc (PAC) light (1,500 mW/cm2 - 3s) and (2) a quartz-tungsten-halogen (QTH) light with three light-curing regimens: continuous exposure (40 s at 800 mW/cm2 - CL); soft-start (10 s at 150 mW/cm2 and 30 s at 800 mW/cm2 - SS) and intermittent light [cycles of 4 s (2 s with light on at 600 mW/cm2 and 2 s of light off), for 80s - IL]. The composite resin was applied between two 5-mm diameter metallic rods, mounted in a servohydraulic machine. The maximum stress was recorded immediately after light exposure (FF) and after 5 min (5F). The results were submitted to ANOVA and Tukey's test (5 percent). For each method, the results obtained in FF and 5F were, respectively: CL (3.58 and 4.46 MPa); SS (2.99 and 4.36 MPa); IL (3.11 and 4.32 MPa) and PAC (0.72 and 3.27 MPa). The stress generated by the polymerization shrinkage during light exposure can be associated with the photoactivation method used. A significant increase in the stress level was observed during the post-curing period up to 5 min, for all evaluated methods.

The color stability of aesthetic restorative materials resulting from accelerated aging / 대한치과보철학회지

STATEMENT OF PROBLEM: The discoloration of anterior teeth restoration is one of the material problems demanding retreatment. OBJECTIVES: To evaluate the color stability and affecting factors on esthetic restorative materials when subjected to accelerated aging. MATERIAL AND METHODS: This study was conducted using porcelain disks (IPS Empress 2-glazed, IPS Empress 2-polished), direct restorative resin disks (SYNERGY Duo) and indirect restorative resin disks (Sinfony, TESCERA ATL). Accelerated aging was done by precipitating the specimens in 38 degrees C distilled water and irradiating with xenon light, and the total irradiation was 397.98 KJ/mm. Color and microhardness change of the specimens were measured before accelerated aging and after 100 hours, 200 hours and 300 hours of accelerated aging, and Surface of the specimens were examined with SEM before and after 300 hours of accelerated aging. RESULTS: 1. After 300 hours' accelerated aging, a delta E value was 3.3 or lower in IPS Empress 2-glazed, IPS Empress 2-polished and Sinfony. 2. After 300 hours' accelerated aging, gloss was lost and surface changes including microcracks were observed in TESCERA ATL and SYNERGY Duo, and color changes of them ranged between 3.58 and 6.40 delta E units. 3. During 300 hours' accelerated aging, the microhardness of surface was increased by 3.21 - 19.64 percent in all kinds of composites resin. CONCLUSION: After 300 hours' accelerated aging, SEM images IPS Empress 2-glazed, IPS Empress 2-polished and Sinfony showed little morphological change and their color changes were considered to be clinically acceptable. And there was significant correlation between microhardness changes and color changes of composites (P < .05).

Comparison of the shear bond strength of brackets in regards to the light curing source / 대한치과교정학회지

With the introduction of the xenon plasma arc curing light and the LED curing light as orthodontic curing lights, the polymerizing time of orthodontic composites has clearly decreased. In contrast to various research cases regarding the polymerization time and bond strength of the xenon plasma arc curing light, not enough research exists on the LED curing light, including the appropriate polymerization time. The objective of this research was to compare the bond strength of the plasma curing light and the LED curing light in regards to the polymerization time. The polymerization time needed to achieve an appropriate adhesion strength of the bracket has also been studied. After applying orthodontic brackets using composite resin onto 120 human premolars, the plasma arc curing light and the LED curing light were used for polymerization for 4, 6, and 8 seconds accordingly. This research proved that the LED curing light provided appropriate bond strength for mounting orthodontic brackets even with short seconds of polymerization. The expensive cost and large size of the device limits the use of the plasma arc curing light, whereas the low cost and easy handling of the LED curing light may lead to greater use in orthodontics.

Liver Function and Inhaled Anesthetics

The liver is the major site of endogenous and exogenous drug metabolism. The primary result of drug metabolism is the production of more water-soluble and therefore more easily excreted drug metabolites. Drugs are sometimes biotransformed into more reactive metabolites, which may lead to toxicity. Volatile anesthetics, like most drugs, undergo metabolism in the body and are sometimes associated with toxic reactions. Here, author will discuss the metabolism and hepatic toxicity of inhaled anesthetics. Toxicity and liver injury have been reported after repeated exposure on subsequent occasions to different fluorinated anesthetics. This phenomenon of cross-sensitization has also been reported with the chlorofluorocarbon(CFC) replacement agents, the hydrochlorofluorocarbons(HCFCs). Halothane, enflurane, sevoflurane, isoflurane, desflurane are all metabolized to trifluoroacetic acid, which have been reported to induce liver injury in susceptible patients. The propensity to produce liver injury appears to parrel metabolism of the parent drug: halothane(20%) >>>> enflurane(2.5%) >> sevoflurane(1%) > isoflurane(0.2%) > desflurane(0.02%). The use of any anesthetic must be based on its benefits and risks, how it may produce toxicity, and in which patients it may be most safely administered. Nonhalogenated inhaled anesthetics (nitrous oxide, xenon) chemically inert and not metabolized in human tissue. The perfect anesthetic agents dose not exist. But ongoing research attempts to uncover emerging toxicities. Xenon is not currently approved for clinical use. Other than the expense associated with its use, it may be the most ideal anesthetic agent. In general, surgical manipulation or disturbance of the surgical site appears to be more important in decreasing hepatic blood flow than current anesthetic agents such as isoflurane, sevoflurane, and desflurane or technique. However, the clinician is challenged to balance new information with current clinical practices and choice the safest, most effective agents for each patient.

Photodynamic Therapy of Actinic Keratoses Using 585nm Dye Laser and Variable Lights / 대한피부과학회지

BACKGROUND: Incohorenet lamps or pulsed/continuous wave lasers have effectively been used for photodynamic therapy (PDT). OBJECTIVE: To assess the safety and efficacy of the various light sources, such as halogen, xenon arc, and the 585nm pulsed dye laser, in photodynamic therapy for treatment of actinic keratosis. METHODS: PDT, using 5-aminolaevulinic acid (5-ALA), was used on 18 patients who had been diagnosed with actinic keratoses. A single treatment consisting of a topical application of 20% 5-aminolaevulinic acid for 4 hours, followed by halogen, xenon arch lamp and the 585nm pulsed dye laser was administered. RESULTS: Of the 227 lesions, 95/106 (89.6%), 68/77 (88.3%), and 39/44 (88.6%) lesions showed complete response to the halogen lamp, xenon arc lamp, and 595nm dye laser respectively, and 10/106 (9.4%), 9/77 (11.7%), and 5/44 (11.4%) lesions showed partial response to the above, respectively. Only one lesion (1.0%) showed no response to the halogen lamp. In all cases, cosmetic outcome was excellent, and anatomical function was preserved. Topical 5-ALA based PDT is an effective and useful treatment modality for various premalignant diseases, to the halogen lamp, xenon arc lamp, or 585nm pulsed dye laser were used. CONCLUSIONS: Treatment of actinic keratosis with various light sources, following topical application of 5-ALA is effective. However, advantages of the laser treatment may include recovery times, excellent postreatment cosmesis, and high efficacy rate.

Perfusion Computed Tomography and Trancranial Doppler in Aneurysmal Subarachnoid Hemorrhage / 대한뇌혈관외과학회지

OBJECT: This study is designed to estimate the clinical usefulness of perfusion computed tomography (perfusion CT) as an easily accessible tool to evaluate cerebral blood flow (CBF) in patients with aneurysmal subarachnoid hemorrhage. METHOD: Twenty patients with aneurysmal spontaneous subarachnoid hemorrhage who underwent either aneurysmal neck clipping or interventional coil embolization and who also had taken transcranial doppler study and perfusion CT were included as study group. And as a control group, fifteen patients without neurologic deficit were studied with the same devices. We compared the cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) from obtained perfusion CT with the results of transcranial doppler and clinical course. RESULTS: CBF parameters of perfusion CT in control group showed close accordance with those values of reported xenon CT and positron emission tomography data. In doppler study, the blood flow velocity was higher in cases with vasospasm than without it (p=0.027). There showed significant relationship between vasospasm and perfusion CT parameters, as decrease in CBF (p=0.061) and increase in MTT (p=0.013). Perfusion CT parameters were closely correlated with TCD parameters in clinical vasospasm as reverse correlation in CBF (R2=0.45) and positive in MTT (R2=0.58). CONCLUSION: The cerebral blood flow parameters of Perfusion CT showed reliable and accurate values in control group. The perfusion CT and TCD can be used as easily accessible non-invasive tools to evaluate cerebral blood flow parameters in clinical settings of patients with aneurysmal subarachnoid hemorrhage.

Short-term Effects of 308-nm Xenon-chloride Excimer Laser and Narrow-band Ultraviolet B in the Treatment of Vitiligo: A Comparative Study

We compared the clinical efficacy of a short-term intervention of 308-nm excimer laser with that of narrow-band UVB (NBUVB) phototherapy for vitiligo patients to see the early response. Twenty-three symmetrically patterned patches of vitiligo on 8 patients were selected. Vitiligo patches on one side of the body were treated 2 times per week for a maximum of 20 treatments with the excimer laser, and NBUVB phototherapy was used on patches on the other side. Improvement (repigmentation) was assessed on a visual scale via serial photographs taken every five treatments and scored as follows: 0, or=75% improvement. At five treatments, the excimer laser-treated patches had an average score of 0.26, compared with 0.04 for patches treated with NBUVB phototherapy. A slightly higher repigmentation (p>0.05) in the excimer treated area was thus observed. At 10, 15, or 20 treatments, the differences between the average scores were significant: 0.83, 1.17, and 1.39 for the excimer-treated patches, and 0.17, 0.30, and 0.74 for the NBUVB pho-totherapy-treated areas (p<0.05). In conclusion, the 308-nm excimer laser appears to be more effective than NBUVB phototherapy, as it produces more rapid and profound repigmentation.