Laser Doppler velocimetry in retinal arteries of infants

The present study was conducted to assess the feasibility of laser Doppler velocimetry in young infants, as a prelude to ultimately undertaking such measurements in premature infants. A portable, unidirectional laser Doppler velocimeter was developed based on a Kowa RC-2 hand-held fundus camera. Six infants between 1 and 21 weeks of age were studied. Relative red blood cell velocity (f_max) at the centre of retinal arteries was measured over approximately 10 heart cycles. A pulsatility parameter (P=1–f_max.dia/f_max.sys), a summary index of vascular status, was determined from the average diastolic and systolic values of f_max. Velocity waveforms were obtained in four of the six infants. Arterial pulsatility for the group was 0.63±0.13. Precise non-invasive measurement of arterial red blood cell velocity waveforms in young infants was achieved. The high signal-to-noise ratio and temporal resolution of this data suggest that relative measurements of retinal blood flow may permit assessment of haemodynamic changes in premature infants.     

The biological zero signal in laser doppler fluximetry – origins and practical implications

 This study seeks to identify the origin of the signal, known as biological zero, that is obtained using laser Doppler fluximetry when flow is arrested. It makes specific recommendations on how this signal should be measured and handled when undertaking flow studies. The experiments undertaken using flow models, animal and human tissue, organ preparations and human subjects showed that, although there may be contributions to the no-flow laser Doppler signal from vasomotion, Brownian motion from within the vascular compartment and the effects of cuff compression, the predominant contribution is from Brownian motion arising from the interstitial compartment. The biological zero signal is additive to the flow signal providing conditions within the interstitium remain constant with changes in blood flow. It is thus concluded that the biological zero signal arises from Brownian motion of the macro molecules within the interstitium. This signal should be obtained following 3–5 min of cuff occlusion with inflation applied rapidly with the smallest cuff that is compatible with flow arrest. Biological zero should be measured under each experimental condition and subtracted from the flow signal. Received: 13 August 1998 / Received after revision: 5 November 1998 / Accepted: 9 November 1998     

正常眼共焦扫描激光多普勒视网膜血流图

目的　探讨共焦扫描激光多普勒视网膜血流图的临床应用价值。方法　应用Ｈｅｉｄｅｌｂｅｒｇ共焦扫描激光多普勒视网膜血流图仪对４８ 例（８２ 只正常眼）视乳头及视网膜血流灌注进行检测。结果　视乳头大血管血流量为２０３１４ ±７４７７,血流速为６ ２７２４３ ±２ ２６００７ ,红细胞移动速率为１３１４ ±２５８ ;视乳头筛板处的血流量为２６３６ ±１４７４ ,血流速为４６７９９ ±２７０１５ ,红细胞移动速率为１９３ ±１０７ 。颞侧视乳头盘沿的血流量为２２９０ ±１１３２,血流速为５１４５３ ±３７０２１,红细胞移动速率为１６９±１１２ ;鼻侧视乳头盘沿的血流量为２１７７ ±９８３,血流速为４９３２１ ±２９０２９,红细胞移动速率为１６５±０９０;颞侧与鼻侧比较差异无显著性（ｔ 值分别为０６８２ ５ ,０４１０ ４,０２５０ １,Ｐ＞ ００５） 。颞侧视乳头旁视网膜的血流量为３２５５ ±１３００,血流速为５５８６３ ±２９３４５ ,红细胞移动速率为１７８ ±０８３;鼻侧视乳头旁视网膜的血流量为２０６１ ±８９２ ,血流速为３５８６４ ±２１２６６ ,红细胞移动速率为１２     

Diode laser thermokeratoplasty – first clinical experience

Purpose: Pulsed holmium lasers are currently used to correct hyperopia by means of laser thermokeratoplasty (LTK). Series of μs laser pulses are applied with a high repetition rate to induce shrinkage of corneal collagen fibers. The pulsed energy application results in intrastromal temperature peaks of up to 200 °C. A continuously emitting laser diode can – as we demonstrated recently in an invivo study on minipigs – be used for LTK and may be of advantage because the temperature rise is more steady. The aim of this study was to examine the safety, amount, and stability of hyperopic correction of diode LTK on blind human eyes. Methods: We used a laserdiode that was set to continuously emit light at λ = 1.854 μm/μ_a = 1.04 mm^–1(group I, n = 4) or 1.87 μm/μ_a = 1.92 mm^–1 (group II, n = 4). Radiation energy was 100 to 150 mW for 10 s per coagulation. Eight coagulations on a single ring (group I) and 16 coagulations on a double ring (group II) diameter were applied in the cornea concentric to the entrance pupil by means of a vacuum-fixed application mask (group I = conjunctival fixation; group II = corneal fixation) and a handpiece with a focusing optic. Preoperatively as well as 1 week, 1, 2, 3, 6 12 and 18 months postoperative ophthalmologic controls were performed and the corneal refractive power was measured. Results: In group I initial refractive changes of up to + 4.9 D were achieved (1 week postoperative). However, due to the great penetration depth of the laser irradiation, large endothelial defects resulted beneath the stromal coagulations. In group II an initial refractive change of up to + 6.8 D was achieved and as a result of the reduced penetration depth, the endothelial cell damage was much reduced. Partial regression of the refractive effect occured in all subjects, which continued in higher refractive changes during the 2^nd postoperative year. The refractive effect at 12 months was + 0.6 to + 1.5 D in group I and + 0.9 to + 5.7 D in group II. At 12 months the induced astigmatism was 0.5 to 2.2 D in group I and 0.3 to 1.6 D in group II. No serious adverse effects were noticed. Conclusion: A continously emitting laser diode working at a wavelength of 1.87 μm can be used to correct hyperopia by means of LTK safely and effectively. Regression occurs predominantly in the first 6 postoperative months. Further studies must be conducted to determine the importance of patient inherent parameters such as age in establishing a nomogram.      

Preliminary experiences with "real-time" intraoperative ultrasonography associated to the laser and the ultrasonic aspirator in neurosurgery

Twelve cerebral lesions were operated upon with various laser sources (carbon dioxide, neodymium-yttrium-argon-garnet, and argon) and with an ultrasonic aspirator utilizing the intraoperative "real-time" ultrasonography. With the last method, the tumor was imaged just as well through the intact dura mater as on the brain surface itself, allowing a precise localization of deep intracranial lesions. A sharp selectivity on the healthy tissues is, in this way, achievable to reach the tumor, which is successively removed with the laser and ultrasonic aspirator checking the surgical maneuvers on the visual control of the ultrasonograph.     

激光治疗闭角型青光眼

目的：评价激光虹膜切除治疗闭角型青光眼临床疗效。方法：应用Nd：YAG激光于上方或下方作周边虹膜切除。结果：107例122眼闭角型青光眼术后经过2—106月随访观察，成功115眼，失败7眼。结论：激光虹膜切除术治疗闭角型青光眼安全、有效。     

Neue Konzepte in der bildgestützten Chirurgie: automatische Patientenregistrierung anhand von Kiefer und Ohrmuschel

ZusammenfassungFragestellung Mit Hilfe einer automatischen und markerlosen Patientenregistrierung auf der Basis natürlicher anatomischer Grenzflächen kann im Vorfeld eines computergestützten chirurgischen Eingriffs eine deutliche Reduktion von Strahlenbelastung und logistischem Aufwand erreicht werden, weil auf das Platzieren und Einmessen röntgensichtbarer Referenzmarker verzichtet werden kann. In einer klinischen Studie sollte überprüft werden, ob neben dem Gesicht auch die Ohrmuschel sowie der Ober- und Unterkiefer als anatomische Grenzfläche zur intraoperativen Registrierung der Patientenlage verwendet werden können.Material und Methode Vor einem chirurgischen Eingriff wurde die räumliche Lage von 20 Patienten mit Hilfe eines hochauflösenden 3D-Laserscans registriert und markerlos mit dem präoperativen CT-Datensatz korreliert. Indikation für den chirurgischen Eingriff waren Tumoren, skelettale Fehlbildungen und Fremdkörper. Die Ohrmuschel sowie der Ober- und Unterkiefer wurden dabei zur Registrierung der Patientenlage genutzt. Durch eine zusätzliche konventionelle markerbasierte Patientenregistrierung wurde die Genauigkeit dieser neuen—an sich markerlosen—Methode klinisch evaluiert.Ergebnisse und Schlussfolgerungen Die markerlose Patientenregistrierung auf der Basis natürlicher anatomischer Grenzflächen war im Bereich des Oberkiefers verlässlich möglich (Abweichung: 0,8±0,3 mm), im Unterkiefer haben Zunge und beweglicher Mundboden zu geometrischer Inkongruenz und mangelhafter Laserregistrierung geführt. Mit Hilfe der Ohrmuschelregistrierung war eine hohe Präzision zu erzielen, solange die Ohrmuschel während der CT-Bildgebung oder während des Laserscannens nicht deformiert wurde (Abweichung: 1,9±0,9 mm). Die übliche CT-Bildakquisition mit Kopfschale führte jedoch bei mehr als der Hälfte der Patienten zu temporären Ohrmuscheldeformierungen, die eine exakte Laserscanregistrierung unmöglich machte.     

Endourologische Operationstechniken bei interstitieller Zystitis

Endourological surgical procedures (transurethral resection and fulguration, Nd-YAG-laser application) for the treatment of interstitial cystitis (IC) have been evaluated only in a few studies. Theoretically, they could be the next step in a therapeutic concept after conservative measures have failed and before open surgery is performed as an ultima ratio. However, our review of the literature suggests that to date there is no scientific evidence to support endourological techniques in the treatment of IC.     

激光多普勒血流成像技术对针灸效果的观察

目的　应用激光多普勒血流成像系统显示艾灸的治疗效果 ,了解这一新的医学影象技术在针灸经络研究中的应用价值。方法　使用激光多普勒血流成像仪 ,对 12例健康人体艾灸前后体表出现的血流变化予以大范围地显像 ,分析体表血流分布与艾灸作用的关系。结果　 (1)艾灸内关穴后 ,手掌部血流的增加以大小鱼际和内关穴区为主。(2 )艾灸外关穴后 ,指根部的血流增加显著。 (3)不艾灸对照组在 30 min内前臂、手掌和手背血流的自然波动较小。结论　艾灸可以引起手部微循环血流量的增加 ,激光多普勒血流成像仪能够以大范围成像方式显示该过程 ;新的血流成像技术将在针灸经络的研究中具有实用价值     

激光诱导脉络膜视网膜吻合初步实验研究

目的 探讨不同激光能量诱导脉络膜视网膜静脉在家免视网膜分支静脉阻塞眼的吻合成功率及安全性。方法 通过光动力法建立 20只兔眼视网膜静脉阻塞模型,24h后以 50 m 光斑,0.1 s的氪红离子激光的不同能量(A组 800mW.B组 1000mW)诱导脉络膜视网膜静脉间的吻合。对侧无静脉阻塞眼以作对照。在实验1、2、4、6 周时进行眼底照相和荧光眼底血管造影检查,测定吻合成功率。结果 在建立 BRVO模型的 20只眼中。A组诱导成功率 30%,激光对周围组织损伤中等;B组诱导成功率 40%;但激光对周围组织的损伤重。在对照组眼中,1只眼形成脉络膜视网膜静脉吻合。A、B实验组与对照组相比,诱导成功率差异有非常显著性意义(P < 0.001);A、B组之间比较成功率差异没有显著性意义(P > 0.1)。结论 利用激光诱导脉络膜视网膜静脉吻合,在技术上可行,较为安全;但在提高成功率方面尚有待进一步研究。