The outcome of stapedotomy depends on several surgical steps. Using laser light, the ossicular chain can be handled and
the oval window can be punctured with a non-touch method. Various lasers are being used or considered, however, it is
not clear which settings and characteristics will contribute to optimal or adverse effects (vestibule damage and loss
hearing frequencies). Using a unique high speed thermal imaging setup based on Schlieren techniques, the mechanical
and thermal effects during laser stapedotomy were studied in an inner ear model consisting of human, fresh frozen stapes
positioned on a liquid filled cavity in a gel cast. The cw KTP (532 nm), cw CO2 (10.6 μm), cw Thulium (2.0 μm), pulsed
Er,Cr;YSGG (2.78 μm) coupled to special fiber delivery systems were applied at typical clinical settings for comparison.
The imaging techniques provided a good insight in the extent of heat conduction beneath the footplate and (explosive)
vapour formation on both sides. For the pulsed laser modes, explosive vapour expansion can to be controlled with
optimized pulse energies while for continuous wave lasers the thermal effects can be controlled with the pulse length and
repetition rate. The fluence at the tip of the delivery system and the distance to the footplate has a major impact on the
ablation effect. The pulsed IR lasers with fiber delivery show to be promising for a controlled stapedotomy.
Electrosurgical equipment used during surgery generate smoke consisting of particles, vapor, aerosols and potentially
harmful biological agents. Smoke evacuation systems are used more commonly and various types are available. A special
image enhancement technique was used to study the behavior of surgical smoke and the effectiveness of smoke
evacuation systems.
Three different smoke evacuation systems were investigated. Rapid vac (Valleylab Boulder CO) The Buffalo silent
whisper turbo (Buffalo, NY) ERBE IES 300 ( Tübingen, Germany)
A back scatter illumination technique in combination with a high speed camera was applied to image the dynamics of a
smoke plume generated by vaporizing a homogenous meat paste irradiated with the beam of a 10 W cw CO2 laser
moving at a constant speed. The three different smoke evacuation systems with their individual nozzles, were held 2 cm
above the surface of the meat paste and were switched on and off at fixed intervals to mimic a clinical situation. For
images analysis, software was developed to count 'smoke pixels' in the video frames as a quantification tool. For the
observer's eye, there were no differences between the systems. However, images quantification showed significantly less
'smoke' for the Buffalo system. It is expected that the performance in a clinical situation is also influenced by additional
conditions like nozzle design, airflow and noise level. Noise levels were measured at the tip of the nozzle, 80 cm from
the tip, 140 cm from the tip. The Buffalo system is the loudest system at every distance measured.
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.
The treatment of partial nefrectomies is usually performed under a warm ischemic period. Recently, various treatment
modalities have become available to perform a partial nefrectomy without clamping off the blood circulation. We have
studied three devices in laboratory setting, investigating the thermal and high speed imaging techniques in tissue models
and consequently, applying the instruments in the clinic during open procedures especially looking at efficacy and blood
loss. The continuous wave 2.0 micron laser of 70 W (Revolix, LISA laser) is used as a fiber delivered knife cutting
through circulated tissue with controlled hemostasis for vessels up to 3 mm diameter. The 2 μm wavelength effectively
vaporizes tissue water and coagulates the smaller vessels. The Hydro-Jet (ERBE, Germany) uses high pressure (20-80
bar) to ejects a water jet of 40 um diameter at high velocity (10-30 m/s). The parenchyma is resected while vessels are
preserved. Consequently, the exposed vessels can be coagulated in a controlled way with minimal blood loss. The water
jet showed to induce cavitation bubbles that resect the soft tissue from the matrix leaving the elastic microvessels intact.
Various systems are based on bipolar RF technology. We are using the Habib device (Rita 1500X RF generator) to create
a coagulation zone around the tumor. Subsequently, the tumor can be resected along the coagulation zone with minimal
bleeding. The treatment modalities investigated, have their own advantages and, stand-alone or in combination, can
facilitate laparoscopic partial nephrectomies without an ischemic period.
Recently, 2 &mgr;m cw laser systems have been introduced for surgery. The 2 &mgr;m wavelength is predominantly absorbed by
water and enables effective cutting and ablation of tissue similar to the cw CO2 laser. In contrast to the CO2 laser, the 2
&mgr;m wavelength is delivered through fiber optics and available for endoscopic procedures.
After many years of experience with the 1.06 &mgr;m Nd:YAG laser, we started to use the 2 &mgr;m cw laser as alternative for
various urological treatments. The treatments strategies and optimal settings were examined in the lab comparing the
two 1.06 and 2 &mgr;m wavelengths performing thermal measurements. Consequently, the laser was applied for various
urological cases.
Penile tumors were resected with haemostatic effects and good aesthetic healing comparable with the Nd:YAG laser.
Although the Nd:YAG has initially a deeper penetration, the blackening of the fiber during tissue cutting, provides a
more superficial effect like the 2 &mgr;m laser.
Bladder (pre)malignancies were ablated after biopsy. Only with higher stage tumors, coagulation depth of the Nd:YAG
might be preferable for adequate treatment.
Strictures in the urethra were incised and stents were effectively desobstructed: one patient with a stent implanted after a
pelvic trauma, and one patient with catheterizable apedico stoma stenoses. The thermal damage during incision to
deeper layers is minimal so recurrence due to scarring is not expected. Also hair grow in patients who underwent
urethroplasty was effectively treated and scrotal atheromata cysts were effectively resected without recurrence.
Laparoscopic nefrectomies are being considered using the 2 &mgr;m cw laser.
The 2 &mgr;m cw laser has shown to be a versatile instrument for effective treatment of various urological indications. More
patients and long term results are needed to prove the clinical significance compared to other treatment modalities
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.
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.
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.
In this study, the efficacy and optimal settings of the CO2, Diode and cw Thulium laser systems were compared for various clinical applications in ENT, Lung and Neurosurgery. The experiments were performed using a specially developed setup, based on color Schlieren techniques, which enable real-time imaging of dynamic temperature gradients complimented with thermocouple measurements in a transparent tissue model in air and water. The CO2 and cw Thulium laser are both efficient in superficial tissue ablation with minimal coagulation depth. The cw Thulium laser, however, is fiber delivered and can also be used in a water. The Diode laser has a relatively deep coagulation effect. The ablation efficacy was enhanced by coating the fiber tip with carbon particles. Our thermal imaging technique was useful to develop new strategies making use of the advantages and overcoming the drawbacks of laser systems. The CO2, Diode and cw Thulium laser can be applied for similar clinical procedures using the optimal strategy and settings for each laser type. The cw 2 μm Thulium laser shows to be a versatile laser system for a broad range of applications both in air and water.
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