Tjeerd de Boorder

In vitro comparison of renal stone laser treatment using fragmentation and popcorn technique

To study the effectiveness of two laser techniques clinically used to fragment renal stones: fragmenting technique (FT) and popcorn technique (PT).

Comparing thulium laser and Nd:YAG laser in the treatment of genital and urethral condylomata acuminata in male patients

To date therapies for condylomata acuminata of the male genital are known for high recurrence rates and bothersome side effects, while urethral warts are not always reachable by most traditional therapies.

Capturing Thermal, Mechanical, and Acoustic Effects of the Diode (980 nm) Laser in Stapedotomy

Introduction The diode laser, with a wavelength of 980 nm, has promising characteristics for being used for the fenestration during stapedotomy. It is known that at this wavelength absorption in pigmented tissues is high, and absorption in water is relatively low compared with medical lasers in the infrared, making it theoretically an applicable laser for stapes surgery in patients with otosclerosis. Another important advantage is that, with respect to other lasers, this device is relatively inexpensive. Despite the potential advantages, the available literature only shows limited reports of this laser being used in stapes surgery. The present article evaluates the thermal, mechanical, and acoustic properties of the diode laser during stapes surgery. Methods For the mechanical effects, high-speed imaging with a frame rate up to 4000 f/s (=250 &mgr;s resolution) was performed in an inner ear model. For thermal effects, the high-speed Schlieren technique was used. Acoustics were recorded by a hydrophone, incorporated in the model. Pulse settings were 100 ms, 3 W, which are the same settings used during stapes surgery. Results The application of the diode laser resulted in limited mechanical and thermal effects. Impulse noise was low with an average of 52 (SD, 7.8) dB (A). Before carbonization of the tip of the delivery laser, fiber enhances ablation of the footplate. Conclusion The 980-nm diode laser is a useful tool for laser-assisted stapedotomy in patients with otosclerosis. Mechanical, thermal, and acoustic effects are limited and well within the safety limits.

Dynamic change of characteristics of (modified) fiber tips used with microsecond pulsed lasers in a liquid environment influencing the effectiveness and safety of treatment

Microsecond pulsed laser systems, like the Thulium, Holmium and Erbium laser are being used for a broad range of medical applications in a liquid environment. Usually, the tissue ablation mechanism of these lasers is based on the instant formation of water vapor. When used with fiber delivery systems, the refraction of the beam coming out of the fiber will change the moment the liquid boundary turns to vapor. This dynamic change can be used in a controlled way but can also have adverse effects if not appreciated. In this study, the effect of the vapor phase change was investigated for various fiber shapes regarding optical and mechanical properties using high speed imaging and ray-trace simulation. Fiber tips of various shapes (bare, angled, tapered, ball shaped) were imaged with high-resolution using 1 &mgr;s light flashes in a video sequence of delay times from 1 to 2000 &mgr;s during exposure with pulsed 2.1 &mgr;m Holmium and pulsed 2.9 &mgr;m Erbium laser pulses. The tip was position in water or near a tissue surface. The dynamics of the explosive vapor bubble changed due to angle of refraction at the silica/vapor interface depending of the shape of the fiber tip. Ball shaped fibers form focused and highly divergent beams, angled fibers become side firing and tapered tips more concentrated. The observations are supported by ray-trace simulation. Clinically this mechanism can be used e.g. to create tiny side firing fibers in root channels of teeth. However, a damaged fiber tip may become unexpectedly side-firing resulting in adverse effects e.g. during lithotripsy. Ball-shaped fibers may be more resistant for damage due to impact with tissue. Using microsecond pulsed laser systems, the change in optical action of the fiber tip in liquid can influence the effectiveness and safety of the procedure.

Influence of Laser-Assisted Cochleostomy on Acoustically Evoked Compound Action Potentials in the Guinea Pig

Hypothesis Making a cochleostomy with a laser can affect the inner ear function. Background Different types of lasers can be used to create a fenestration in the footplate of the stapes during stapedotomy. Because of variations in absorption spectra of the laser light in various tissues or fluids, each laser has its own characteristics and possible side effects. Materials and Methods The basal turns of the cochleae of 20 guinea pigs were fenestrated using 4 types of lasers (thulium, KTP, CO2, diode; all groups n = 4). A control group (n = 4) was included to correct for the effects of the surgery alone. At 3 different time points, acoustically evoked compound action potentials (CAPs) were recorded at 5 frequencies and at different sound pressure levels. N1-P2 amplitudes were measured, and subsequently, thresholds were calculated. A repeated measures analysis of variance was used to investigate differences between groups. Results There was a decrease in CAP amplitudes and an increase in CAP thresholds after cochleostomy with each laser. The increase in thresholds was significantly larger for higher frequencies. The thulium laser evoked the largest threshold shifts, the KTP laser the smallest with the CO2, and diode lasers in intermediate positions. Overall, there was an increase in latencies after treatment. Conclusion Laser treatment on or near the cochlea can cause damage to the sensitivity of the cochlea for sound. The thulium laser seems to be the worst choice in this respect.

Effect of KTP laser cochleostomy on morphology in the guinea pig inner ear.

Background: The main advantage of using the KTP (potassium-titanyl-phosphate) laser for stapedotomy instead of the conventional micropick instrument is the smaller risk for mechanical damage. However, the KTP laser could theoretically inflict damage to inner ear structures. We hypothesize that KTP laser light [wavelength (λ) = 532 nm] is hardly absorbed in perilymph but well absorbed in solid structures. The aim of this pilot study was to assess if damage occurred after KTP laser cochleostomy in an animal model and, if so, to what extent and at which settings. Materials and Methods: In six guinea pigs, a KTP laser cochleostomy at the basal turn was created. Laser settings of 1, 3 and 5 W and 100 ms pulse time (n = 2 each) were used. Histological preparations were studied for damage to neuroendothelial cells and intrascalar blood. Results: No damage to inner ear neuroendothelial cells was observed, even at the highest power. Blood clots in the scala tympani from vessels in the cochlear wall were seen. The effects were minimal in the lowest, currently clinically used settings. Conclusion: KTP laser cochleostomy gives no damage to inner ear neuroendothelial cells but may cause intrascalar hemorrhages.

The visualization of surgical smoke produced by energy delivery devices: significance and effectiveness of evacuation systems

Devices delivering energy to biological tissues (eg lasers, RF and ultrasound) can induce surgical smoke consisting of particles, vapor, gasses and aerosols. Besides interfering with the view of the surgeon, the smoke is a risk for the health of both the users and patients. In literature, it has been shown that surgical smoke can contain carcinogenic and harmful biological agents. However, the impact on health of the users and patients is widely debated. The use of smoke evacuation systems in the OR is usually governed by economical reason instead of safety issues. A special image enhancement technique is used to study the behavior of smoke and aerosols and the effectiveness of smoke evacuation systems. A back scatter illumination technique using 1 &mgr;s light flashes at video rate was applied to image the smoke production of various surgical devices without and with smoke evacuation while ablating biological tissues. The effectiveness of various smoke evacuation devices and strategies were compared. The ablative thermal devices produced smoke but also aerosols. If the thermal energy was delivered in high peak pulses, the presence of aerosols was more significant. Ultrasound based devices produce mainly aerosols. The distance to the target, the opening of the evacuation nozzle and the dimension of aerosols were leading for the effectiveness of the smoke evacuation. The smoke visualization technique has proven an effective tool for study the effectiveness of smoke and aerosols evacuation. The results can contribute to the necessity to use evacuation systems in the OR.

Evaluation of the response and healing effect after laser hair removal using a multi-spectral dermatoscope

A multi-spectral dermatoscope was used to investigate the effect of laser hair removal. Ten volunteers underwent three laser treatments, 6 weeks apart. In a subsequent trial, three volunteers received one laser treatment after which the skin region was imaged at short intervals. Practical solutions were developed to re-locate the investigated skin area. After exact matching using rigid and elastic registration software, the images showed acute and delayed effects on the hairs, pigment and vasculature after laser hair removal and subsequent healing response. The multi-spectral dermatoscope provides a perfect tool to study the efficacy and side effects of laser hair removal procedures and can be used to optimize the treatment plan.

Comparison of three thermotherapy modalities for the ablation of mamma carcinoma in situ using thermal imaging and mapping

A larger percentage of small tumors in the breast are being detected due to effective screening programs and improved radiological diagnostic methods. For treatment, less invasive methods are preferred which are still radical but also provide a better aesthetic result. Recently, several ablation techniques have become available to locally ablate tumors in situ. In this study, the effectiveness of three ablation techniques was compared by imaging the thermal distribution and temperature mapping in vitro. The first system (KLS Martin, Trumpf, Germany) uses Nd:YAG laser light delivered through a single diffusing fiber tip which is positioned direct into the tissue or in a water-cooled needle. The second system (Olympus-Celon, Germany) uses bipolar Radio Frequency currents between electrodes in a water-cooled needle. The RF system has a temperature feedback based on tissue impedance to prevent tissue charring. The third system is a focused ultrasound system developed in the Hospital. For all three the techniques, the dynamics of temperature gradients around the probe or focus point are visualized using color Schlieren techniques in a transparent tissue model and recorded using thermocouples. The effective lesion size and tissue temperatures were determined in in vitro bovine mamma tissue. All systems were capable to heat tissue volumes up to 3 cm in diameter. The lesion growth dependent on the power input, temperature gradient around the initial power source and treatment time. Although the three systems are capable to ablate small mamma carcinoma in situ, they differ in precision, MR compatibility, invasiveness, practical use and treatment time. The real clinical effectiveness has to be proven in large patient studies with long term follow up.

Ex vivo feasibility study of endoscopic intraductal laser ablation of the breast

To determine the feasibility and safety of breast endoscopic thulium laser ablation for treatment of intraductal neoplasia.