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PubMed2002

Diffraction effects in few-cycle optical pulses.

Basic concepts of three-dimensional wave packets are applied to the description of transverse effects on the propagation of ultrashort (femtosecond) pulses. The frequency-dependent nature of diffraction acts as a kind of dispersion that modifies the pulse front surface, its group velocity, the envelope form, and the carrier frequency. If the diffracted field in the monochromatic case is known, these changes can be straightforwardly quantified. Finding the propagated pulsed beam field reduces to a well-known and simpler problem of one-dimensional pulse propagation with group velocity dispersion. The method is applied to pulsed Gaussian beams and pulsed Bessel beams. Anomalous pulse front behavior, including superluminality in pulsed Gaussian beams is found. The carrier phase at any point of space is calculated.

Journal Article↗
PubMed2002

Multichannel pulse dynamics in a stabilized Ginzburg-Landau system.

We study the stability and interactions of chirped solitary pulses in a system of nonlinearly coupled cubic Ginzburg-Landau (CGL) equations with a group-velocity mismatch between them, where each CGL equation is stabilized by linearly coupling it to an additional linear dissipative equation. In the context of nonlinear fiber optics, the model describes transmission and collisions of pulses at different wavelengths in a dual-core fiber, in which the active core is furnished with bandwidth-limited gain, while the other, passive (lossy) one is necessary for stabilization of the solitary pulses. Complete and incomplete collisions of pulses in two channels in the cases of anomalous and normal dispersion in the active core are analyzed by means of perturbation theory and direct numerical simulations. It is demonstrated that the model may readily support fully stable pulses whose collisions are quasielastic, provided that the group-velocity difference between the two channels exceeds a critical value. In the case of quasielastic collisions, the temporal shift of pulses, predicted by the analytical approach, is in semiquantitative agreement with direct numerical results in the case of anomalous dispersion (in the opposite case, the perturbation theory does not apply). We also consider a simultaneous collision between pulses in three channels, concluding that this collision remains quasielastic, and the pulses remain completely stable. Thus, the model may be a starting point for the design of a stabilized wavelength-division-multiplexed transmission system.

Journal Article↗
PubMed2004

Electron acceleration by a self-diverging intense laser pulse.

Electron acceleration by a laser pulse having a Gaussian radial and temporal profile of intensity has been studied. The interaction region is vacuum followed by a gas. The starting point of the gas region has been chosen around the point at which the peak of the pulse interacts with the electron. The tunnel ionization of the gas causes a defocusing of the laser pulse and the electron experiences the action of a ponderomotive deceleration at the trailing part of the pulse with a lower intensity rather than an acceleration at the rising part of the laser pulse with a high intensity, and thus gains net energy. The initial density of the neutral gas atoms should be high enough to properly defocus the pulse; otherwise the electron experiences some deceleration during the trailing part of the pulse and the net energy gain is reduced. The rate of tunnel ionization increases with the increase in the laser intensity and the initial density of neutral gas atoms, and with the decreases in the laser spot size, which causes more defocusing of the laser pulse. The required initial density of neutral gas atoms decreases with the increase in the laser intensity and also with the decrease in the laser spot size.

Journal Article↗
PubMed1995

Thermal relaxation of port-wine stain vessels probed in vivo: the need for 1-10-millisecond laser pulse treatment.

Although thermal relaxation times of cutaneous port-wine stain microvessels have been calculated and used to formulate laser selective photothermolysis, they have never been measured. A scheme to do so was devised by measuring the skin response to pairs of 585-nm dye laser pulses (250-360 microseconds each) as a function of the time interval between the two pulses, in five volunteers with port-wine stains. After a pump pulse delivering 80% of the fluence necessary for causing purpura, the fluence of a second probe pulse necessary to cause purpura was determined and was found to increase with the interval between the two pulses, in a manner consistent with thermal diffusion theory. Biopsy specimens were obtained from four of the five subjects to examine the nature and extent of vessel damage and to measure the port-wine stain vessel diameters. Using diffusion theory, the thermal relaxation time was calculated based on the measured vessel diameters. These calculated values are consistent with the increase in radiant exposure (fluence) of the probe pulse necessary to induce purpura for longer time delays. Two simple models for thermal relaxation of port-wine stain vessels are presented and compared with the data. The data and histologic assessment of the vessel injury strongly suggest that pulse durations for ideal laser treatment are in the 1-10-millisecond region and depend on vessel diameter. No dermatologic lasers presently used for port-wine stain treatment operate in this pulse width domain.

Adult↗
PubMed2006

Variable-pulse Nd:YAG laser in the treatment of facial telangiectasias.

BACKGROUND: Variable-pulse 1,064 nm wavelength lasers have been used with good effectiveness on leg telangiectasias and reticular veins and have shown promising results on facial telangiectasias as well. OBJECTIVE: To investigate the effectiveness of a variable-pulse neodymium:yttrium-aluminum-garnet (Nd:YAG) laser using a small spot size in the treatment of facial telangiectasias. METHODS: Eight male patients (mean age 75 years) underwent a single treatment session using a variable-pulse 1.5 mm spot size Nd:YAG laser with epidermal cooling. Telangiectasia diameters were 0.3 to 2.0 mm. Test sites were performed using three pulse widths (3, 20, and 60 ms), with fluences varying depending on vessel size and response. Full treatments were performed using test parameters giving the best response. Thirteen weeks later, the patients returned for final evaluation and satisfaction rating. RESULTS: Fluences ranged from 226 to 425 J/cm2, with smaller vessels requiring larger energies. Pulse duration was equally divided between the 20 and 60 ms settings. The shortest pulse width (3 ms) was inferior in all patients. Longer pulse durations achieved superior vessel elimination with minimal immediate purpura and no postinflammatory hyperpigmentation. The average mean vessel clearance was 26 to 50% in half of the patients and 51 to 75% in the other half as evaluated by three unbiased dermatologists with extensive laser experience. CONCLUSION: A small-spot size Nd:YAG laser using a pulse width of 20 ms or higher appears to be effective in clearing a significant percentage of facial telangectasias with a single pass. The side effects were minimal.

Aged↗
PubMed2005

Cardiac output measurement by pulse dye densitometry in cardiac surgery.

Summary The aim of this study was to compare the accuracy of pulse dye densitometry with that of bolus thermodilution cardiac output measurement in patients before and after elective coronary artery bypass grafting. Twenty-eight patients were studied. Agreement between mean thermodilution and pulse dye densitometry cardiac output values was assessed by Bland-Altman analysis. Preoperative median [range] cardiac output was 3.87 [2.37-6.0] l.min(-1) by thermodilution, and 3.11 [1.7-5.45] l.min(-1) by pulse dye densitometry using indocyanine green 5 mg. Pulse dye densitometry underestimated cardiac output (mean bias - 0.42 l.min(-1)); the limits of agreement were +/- 1.91 l.min(-1), and mean error was 50.3%, indicating low precision. Preoperative median [range] cardiac output was 3.85 [2.2-6.0] l.min(-1) for bolus thermodilution cardiac output and 4.2 [2.0-7.2] l.min(-1) for pulse dye densitometry using indocyanine green 20 mg. Mean bias was + 0.566 l.min(-1), the limits of agreement were +/- 2.51 l.min(-1) and mean error was 60.9%. Postoperative cardiac output data were not analysed because pulse dye densitometry signals were low or absent in > 50% of the patients. We conclude that pulse dye densitometry using indocyanine green 5 mg or 20 mg is inaccurate in anaesthetised patients before coronary artery bypass surgery and cannot be used after surgery because of a high incidence of low pulse dye densitometry signal amplitudes.

Aged↗
PubMed1995

The effect of pentobarbital on the electrical activity of LHRH pulse generator in the ovariectomized rat with or without estrogen priming.

Effects of pentobarbital sodium (PB) on the electrical activity of LHRH pulse generator were investigated in the ovariectomized (OVX) rat fitted with chronically implanted electrode arrays in the arcuate-median eminence region of the hypothalamus. PB was injected intraperitoneally (i.p.) at a dose of 32 mg/kg bw, which has blocked the surge of LH secretion when injected at 13.45 on the day of proestrus, presumably by blocking the activity of the LHRH surge generator. After i.p. injection of PB, the first characteristic increase (volley) in the hypothalamic multiunit activity (MUA), each of which was associated with the initiation of an LH pulse, appeared at the mean interval of 42 min, which was significantly greater than the value, 30 min, in the rat given i.p. injection of saline. The second and third MUA volleys appeared, however, at similar intervals to those in rats given saline. There were no significant changes in the amplitude of LH pulses which followed. In the OVX rat implanted with a silastic tube packed with estradiol-benzoate (E2) for 1 day, MUA volleys were unclear, mingled with high background activities, but clear volleys appeared after PB injection. The mean interval of LH pulses in the rat given i.p. injection of saline was 51 min, by 24 min longer than the value in the E2-unimplanted OVX rat. But, after PB injection, the 1st LH pulse appeared at the interval of 37 min, which was by 25 min smaller than that after saline and the overall mean of 3 intervals was 34 min, showing a significant shortage. No PB effect was seen in the LH pulse amplitude in the E2-implanted OVX rat. The presults show that the LHRH pulse generator is much more resistant to PB than the surge generator in the OVX rat either with or without estrogen priming, and in the rat with estrogen priming, the pulse generator is rather activated by PB.

Animals↗
PubMed1995

LHRH pulse generator is stimulated by naloxone in the pentobarbital-blocked proestrous rat.

Previous studies by us and others led us to hypothesize that there are separate LHRH pulse and surge generators in the rat brain. The present study was designed to detect the activity of LHRH pulse generator by checking changes in LH secretion and the multiunit activity (MUA) of the arcuate-median eminence region of the hypothalamus during infusions of naloxone (NAL, 2 mg/h) in the proestrous rat in which the LHRH surge generator activity was blocked by pentobarbital sodium (PB, 32 mg/kg bw, ip). The animals were subjected to blood sampling in the morning (1000-1300 h) or afternoon (1400-1700), and injected with PB at 09.45 or 13.45, respectively. During saline infusions in the rat given PB injection at either 09.45 or 13.45, serum LH levels were low but fluctuated significantly, suggesting a pulsatile secretion in either the morning or the afternoon period. The pulse intervals were an average 28.2 min in the morning and 42.2 min in the afternoon. NAL infusions decreased the pulse interval significantly, to 22.0 min in the morning and to 27.0 min in the afternoon. In the electrophysiological experiment, characteristic increases in the MUA (volleys), which occur in association with the initiation of an LH pulse and therefore are considered to represent an increased activity of the LHRH pulse generator, appeared during NAL (5 mg/h) infusions in either the morning or the afternoon. These results strongly suggest that separate LHRH pulse and surge generators exist in the brain, and that, even during the critical period of proestrus, the activity of LHRH pulse generator is disclosed by PB, which, on the other hand, arrests the surge generator.

Animals↗
PubMed1996

Pulsed administration of corticosteroids in the treatment of alopecia areata.

BACKGROUND: Widespread alopecia areata (AA) is difficult to treat and modalities such as topical and systemic steroids, topical sensitizers (e.g., squaric acid dibutylester and diphencyprone), psoralen-ultraviolet A (PUVA) therapy, minoxidil, and immunomodulators have been tried. METHODS: Patients with widespread alopecia (> 40% scalp involvement), including alopecia totalis (AT) and universalis (AU), were treated with 300 mg oral prednisolone pulses at 4-week intervals, for a minimum of 4 doses or until cosmetically acceptable hair growth was obtained. Response to therapy was monitored by serial photographs and patients were examined monthly for side effects of steroids. A 1000 mg oral prednisolone pulse was administered to five patients with alopecia totalis/universalis and to three failures of the 300 mg-pulse treatment. RESULTS: Thirty-two patients (24 men, 8 women) with a mean age of 29 years were recruited. They had alopecia for a mean period of 2.8 years. Twenty-seven patients (21 alopecia areata, 5 alopecia universalis, 1 alopecia totalis) received 300 mg pulse therapy and eight patients received 1000 mg prednisolone pulses. Fourteen (58.3%) patients (13 AA, 1 AT) out of 24 evaluated treated with 300 mg pulse therapy showed complete or cosmetically acceptable hair growth. Response was evident on average after 2.4 months and was cosmetically acceptable at 4 months. Three (AA, AT, AU-one each) out of seven patients assessed for the 1000-mg pulse had cosmetically acceptable hair growth at 6-9 month. CONCLUSIONS: An oral monthly pulse of prednisolone 300 mg is effective, safe, and can be administered on an outpatient basis. It is recommended as one of the modalities for the treatment of widespread alopecia areata.

Administration, Oral↗
PubMed2005

Dark pulse suppression of P-ERK and c-Fos in the hamster suprachiasmatic nuclei.

It is well-established that light pulses regulate components of the extracellular signal-regulated kinases I/II (ERK) cascade in the suprachiasmatic nuclei (SCN) circadian clock. These events are important for photic-resetting of the circadian clock. The SCN circadian clock is also reset by pulses of dark, but it is unknown if this stimulus alters the activity of ERK, the transcription factor Elk-1 or expression of the immediate early gene c-fos in the SCN. Using Syrian hamsters free-running in constant light, we determined the effects of dark pulses on these factors in the SCN. In constant light, levels of phosphorylated ERK (P-ERK) showed significant circadian variation in the Syrian hamster SCN, while levels of c-Fos or phosphorylated Elk-1 (P-Elk-1) did not. A 6-h dark pulse beginning at circadian time (CT) 8 down-regulated expression of P-ERK and c-Fos, but not P-Elk-1, in the SCN. Following termination of the pulse, levels of c-Fos increased above time-matched control values, while P-ERK expression did not. When given at the beginning of the subjective night (CT13), a 6-h dark pulse did not phase-shift behavioural rhythms and failed to alter the expression of c-Fos, P-ERK, or P-Elk-1 in the SCN. At the level of the visual thalamus, expression of c-Fos in the intergeniculate leaflet was higher during the subjective night as compared to the subjective day, although dark pulses had no robust effects on expression of c-Fos or P-ELK-1 in this structure. We conclude that dark-pulse resetting of the circadian clock is complex and involves both non-photic and photic components.

Adaptation, Physiological↗
PubMed2006

Antecedent moisture and seasonal precipitation influence the response of canopy-scale carbon and water exchange to rainfall pulses in a semi-arid grassland.

The influences of prior monsoon-season drought (PMSD) and the seasonal timing of episodic rainfall ('pulses') on carbon and water exchange in water-limited ecosystems are poorly quantified. *In the present study, we estimated net ecosystem exchange of CO(2) (NEE) and evapotranspiration (ET) before, and for 15 d following, experimental irrigation in a semi-arid grassland during June and August 2003. Rainout shelters near Tucson, Arizona, USA, were positioned on contrasting soils (clay and sand) and planted with native (Heteropogon contortus) or non-native invasive (Eragrostis lehmanniana) C4 bunchgrasses. Plots received increased ('wet') or decreased ('dry') monsoon-season (July-September) rainfall during 2002 and 2003. Following a June 2003 39-mm pulse, species treatments had similar NEE and ET dynamics including 15-d integrated NEE (NEE(pulse)). Contrary to predictions, PMSD increased net C uptake during June in plots of both species. Greater flux rates after an August 2003 39-mm pulse reflected biotic activity associated with the North American Monsoon. Furthermore, August NEE(pulse) and ecosystem pulse-use efficiency (PUE(e) = NEE(pulse)/ET(pulse)) was greatest in Heteropogon plots. PMSD and rainfall seasonal timing may interact with bunchgrass invasions to alter NEE and ET dynamics with consequences for PUE(e) in water-limited ecosystems.

Arizona↗
PubMed1992

Do fetal pulse oximetry readings at delivery correlate with cord blood oxygenation and acidaemia?

OBJECTIVE: To assess the accuracy of a pulse oximeter in the fetus. DESIGN: A prospective descriptive study, comparing oxygenation and acidaemia of cord blood with oxygen saturation in the arteries of the fetal scalp measured by a pulse oximeter just before delivery. The data were collected using an experimental pulse oximeter and a sensor specifically adapted to cope with the problems of fetal pulse oximetry. SETTING: The labour ward in a teaching hospital. SUBJECTS: Thirty seven Caucasian fetuses presenting by the vertex in normal uncomplicated labour. MAIN OUTCOME MEASURE: Fetal pulse oximetry reading shortly before birth, umbilical cord oxygenation and pH, and Apgar scores. RESULTS: Data of sufficient quality were obtained from 28 fetuses. There was a highly significant correlation between pulse oximetry reading and umbilical vein oxygen saturation r = 0.59, P = < 0.001). There was also a significant correlation between the pulse oximeter reading and cord blood pH (vein: r = 0.57, P = 0.002, artery: r = 0.63, P = 0.001). Apgar scores were not related to the oximetry results. CONCLUSION: Pulse oximetry readings reflect fetal oxygenation at birth.

Apgar Score↗
PubMed2003

A pilot study on the treatment of facial rhytids using nonablative 585-nm pulsed dye and 532-nm Nd:YAG lasers.

BACKGROUND: There have been reports of successfully using the pulsed dye laser and long-pulse Nd:YAG laser to improve skin wrinkles. OBJECTIVE: To evaluate the efficacy of these lasers in the treatment of moderate to severe wrinkles. METHODS: Seven subjects had one side of their periorbital wrinkles treated with pulsed dye laser (585 nm, 0.45 ms, 2.5 J/cm2, single-pass 10% overlap, three treatments at 6 weeks apart). The second part of the study involved using the long-pulse Nd:YAG laser (532 nm, 2 ms, 7.0 J/cm2 with cooling, three laser passes, three treatments at 6 weeks apart) to treat the contralateral wrinkles in five subjects. Pretreatment and posttreatment photographs were taken, and blinded assessors were asked to choose the better of the two unlabeled photographs. RESULTS: Assessors found that two of the seven subjects had a better posttreatment photograph in the pulsed dye laser-treated group. Three of five subjects had a better posttreatment photograph in the long-pulse Nd:YAG laser-treated group. None of the subjects reported any subjective improvements. CONCLUSION: Neither the pulsed dye laser nor the long-pulse Nd:YAG laser at the previously mentioned parameters produced any improvement in moderate to severe facial wrinkles.

Female↗
PubMed1997

Effect of adaptive pulse train duration on latissimus dorsi blood flow.

Blood flow, intramuscular pressure, and stroke work of the trained latissimus dorsi muscle (LD) were measured during electrical stimulation at contraction rates between 20 and 160/min using pulse trains of 2 to 6 pulses in length. Epimysial electrodes and intramuscular pressure sensors were implanted in the LD of 5 dogs. The muscle remained in situ. After 12 weeks of a progressive training protocol, LD blood flow (BF) was measured using an ultrasonic flow probe and work (SW) was determined from the measured force and shortening. For pulse trains of 2 or 3 pulses, BF increased with rate, and SW was maintained at all rates. For 4 pulses, BF and SW decreased when the contraction rate exceeded 120/min. SW decreased above 100/min and 80/min for 5 and 6 pulses, respectively. An upper rate limit dependent upon the pulse train duration exists above which BF and SW decline. Exceeding these upper rate limits should be avoided in cardiomyoplasty. Excessive stimulation rates could be detrimental to the muscle by creating a metabolic insufficiency or ischemia. The cardiac assistance benefit is compromised as SW declines during high contraction rates of long pulse train duration.

Analysis of Variance↗
PubMed1996

The impact of pulse generator longevity on the long-term costs of cardiac pacing.

The long-term costs of cardiac pacing include the device costs, the procedural costs, the follow-up costs, and the replacement costs. At present, there is significant variability in the efficiencies of the integrated circuits and the total battery capacity among different pulse generators that will influence replacement rates over time. Accordingly, we compared the influence of pulse generator longevity on the long-term costs of pacing. The longevity of pulse generators was calculated based on the electrical characteristics of the device and the percentage of time the patient is paced. Replacement rates of pulse generators were estimated for our patient population over a 20-year period, based on patient survival and pulse generator longevity. The costs of pacing over this 20-year follow-up period were then calculated. The longevity of DDDR devices presently implanted in the United States ranges from 8-14 years, assuming that patients are paced 50% of the time. Replacement rates in this population over a 20-year follow-up period were calculated to range from 0.34-0.66, and the total costs of pacing would range from $11,898-14,900 per patient. The longevity of SSIR devices ranges from 7-20 years, assuming that patients are paced 50% of the time. Replacement rates were calculated over the 20-year follow-up period to range from 0.20-0.84, and the total costs of VVIR pacing would range from $8,331-13,286. Based on the proportion of pulse generator models implanted in patients in the United States, the maximum cost differential to the health care system is approximately $424 million/year comparing the devices with the shortest and greatest longevities. Thus, pulse generator longevity may significantly influence the long-term costs of pacing. Patient survival and pulse generator system longevity should be considered when selecting the appropriate pacing system for the individual patient.

Actuarial Analysis↗
PubMed1994

Impact of light pulses on 6-sulphatoxymelatonin rhythms in rats.

The acute and residual entraining effects of a 15 min pulse of light on rat pineal function in individual animals were investigated using the excretion rate of the melatonin metabolite, 6-sulphatoxymelatonin, as an index of melatonin production. In animals maintained in a 12-hr L:12-hr D photoperiod (lights off 1800), 15 min light exposure at 2000 had no significant effect on the metabolite rhythm. Light pulses at 2200 (i.e., after the onset of excretion) decreased the melatonin metabolite excretion rate for 3 hr, after which the excretion rate increased to normal. In contrast, pulses at 2400 and 0200 suppressed 6-sulphatoxymelatonin for the rest of the night such that total excretion was 58 +/- 8% and 66 +/- 6% of the amount excreted on the night before the pulse. A light pulse at 0400 had no significant effect on the 6-sulphatoxymelatonin excretion when compared with the first night collection. When the 6-sulphatoxymelatonin rhythm was assessed on the night following light pulses at 2000 and 0400, the onset of metabolite excretion was unaffected (0.2 +/- 0.75-hr advance and 0.75 +/- 0.15-hr delay, respectively). In contrast, pulses at 2200, 2400, and 0200 resulted in significant delays in the onset of 2.4 +/- 0.2-hr, 1.5 +/- 0.1-hr, and 2.1 +/- 0.3-hr, respectively (P < 0.05). The offset of metabolite excretion was not significantly affected by a prior light pulse, except in animals receiving light treatment at 0400 when the offset was advanced by 1.5 +/- 0.3 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

Auditory nerve fiber responses to electric stimulation: modulated and unmodulated pulse trains.

Many modern cochlear implants use sound processing strategies that stimulate the cochlea with modulated pulse trains. Rubinstein et al. [Hear. Res. 127, 108 (1999)] suggested that representation of the modulator in auditory nerve responses might be improved by the addition of a sustained, high-rate, desynchronizing pulse train (DPT). In addition, activity in response to the DPT may mimic the spontaneous activity (SA) in a healthy ear. The goals of this study were to compare responses of auditory nerve fibers in acutely deafened, anesthetized cats elicited by high-rate electric pulse trains delivered through an intracochlear electrode with SA, and to measure responses of these fibers to amplitude-modulated pulse trains superimposed upon a DPT. Responses to pulse trains showed variability from presentation to presentation, but differed from SA in the shape of the envelope of the interval histogram (IH) for pulse rates above 4.8 kpps (kilo pulses per second). These IHs had a prominent mode near 5 ms that was followed by a long tail. Responses to modulated biphasic pulse trains resembled responses to tones in intact ears for small (<10%) modulation depths, suggesting that acousticlike responses to sinusoidal stimuli might be obtained with a DPT. However, realistic responses were only observed over a narrow range of levels and modulation depths. Improved coding of complex stimulus waveforms may be achieved by signal processing strategies for cochlear implants that properly incorporate a DPT.

Acoustic Stimulation↗
PubMed2003

Effect of pulse polarity and energy on ultrasound-induced lung hemorrhage in adult rats.

The objective of this study was to further assess the role of inertial cavitation in ultrasound-induced lung hemorrhage by examining the effect of pulse polarity at a common in situ (at the lung surface) peak rarefactional pressure [pr(in situ)] and at a common in situ pulse intensity integral (PII(in situ)). A total of 60 rats was divided into three experimental groups of 20 animals per group and randomly exposed to pulsed ultrasound. The groups were exposed as follows: Group 1 to 0 degree polarity pulses (compression followed by rarefraction) at a pr(in situ) of 3.48 MPa and a PII(in situ) of 4.78 Ws/m2, group 2 to 180 degree polarity pulses (rarefraction followed by compression) at a pr(in situ) of 3.72 MPa and a PII(in situ) of 2.55 Ws/m2, and group 3 to 180 degree polarity pulses at a pr(in situ) of 4.97 MPa and a PII(in situ) of 4.79 Ws/m2. For all experimental groups, the frequency was 2.46 MHz, the exposure duration was 240 s, the pulse repetition frequency was 2.5 kHz, and the pulse duration was 0.42 micros. Six sham animals were also randomly distributed among the experimental animals. The lesion surface area and depth were determined for each rat as well as lesion occurrence (percentage of rats with lesions) per group. It was found that lesion occurrence and size correlated better with PII(in situ) than with pr(in situ), suggesting that a mechanism other than inertial cavitation was responsible for the damage.

Animals↗