Haşim Özgür Tabakoğlu

The effect of irradiance level in 980-nm diode laser skin welding.

OBJECTIVE Current research aimed to investigate the role of irradiance in skin laser welding. BACKGROUND DATA Optical and thermal responses of tissue to infrared irradiation are highly dependent on both wavelength and tissue type. The desired effect on tissue is created by proper selection of laser power, application time, and spot size. METHODS Full-thickness skin incisions on Wistar rat dorsum were welded with 980-nm diode laser application. Two irradiance levels (200 and 16.6 W/cm(2)) were applied with high (6 W, 400 ms) and low (0.5 W, 5 s) powers of laser with the same spot size (0.03 cm(2)). Subjects were monitored throughout a 21-day recovery period; incisions were sampled for histology and mechanical tests on particular control days (1, 4, 7, 14, and 21). Closure index, thermally altered areas, epidermal thickness, and granulation areas of H&E (eosin) stained samples were calculated. The breaking point during a mechanical tensile test that ran at 5-mm/min crosshead speed was recorded. RESULTS In the suture group, there was no closure 24 h postoperation. For laser groups, immediate closure at the surface layers of the incisions was observed: Almost half-thickness (from surface to deep dermis) welding was achieved. Granulation tissue level and epidermal thickness level for all groups were similar on postoperative day 21. CONCLUSION The laser welding technique was found reliable in terms of immediate and mechanically strong closure compared with suture. Low irradiance of a 980-nm laser (16.6 W/cm(2)) yielded noticeably stronger bonds at the end of 21 days of recovery, as well as minimal thermal damage.

Modulated and continuous-wave operations of low-power thulium "Tm:YAP… laser in tissue welding

Our aim is to explore the welding capabilities of a thulium (Tm:YAP) laser in modulated and continuous-wave (CW) modes of operation. The Tm:YAP laser system developed for this study includes a Tm:YAP laser resonator, diode laser driver, water chiller, modulation controller unit, and acquisition/control software. Full-thickness incisions on Wistar rat skin were welded by the Tm:YAP laser system at 100 mW and 5 s in both modulated and CW modes of operation (34.66 Wcm(2)). The skin samples were examined during a 21-day healing period by histology and tensile tests. The results were compared with the samples closed by conventional suture technique. For the laser groups, immediate closure at the surface layers of the incisions was observed. Full closures were observed for both modulated and CW modes of operation at day 4. The tensile forces for both modulated and CW modes of operation were found to be significantly higher than the values found by conventional suture technique. The 1980-nm Tm:YAP laser system operating in both modulated and CW modes maximizes the therapeutic effect while minimizing undesired side effects of laser tissue welding. Hence, it is a potentially important alternative tool to the conventional suturing technique.

Assessment of circular wound healing in rats after exposure to 808-nm laser pulses during specific healing phases

Low‐level laser therapy (LLLT), is an important application modality for the advancement of wound healing processes. In this study, histological and morphometric analyses have been made to understand and compare effects of high‐power 808‐nm pulses on circular skin wounds among groups irradiated immediately after wounding and groups irradiated at specific stages of the healing period.

Optical Characterization of Pancreatic Normal and Tumor Tissues with Double Integrating Sphere System

In order to develop minimally invasive, fast and precise diagnostic and therapeutic methods in medicine by using optical methods, first step is to examine how the light propagates, scatters and transmitted through medium. So as to find out appropriate wavelengths, it is required to correctly determine the optical properties of tissues. The aim of this study is to measure the optical properties of both cancerous and normal ex-vivo pancreatic tissues. Results will be compared to detect how cancerous and normal tissues respond to different wavelengths. Double-integrating-sphere system and computational technique inverse adding doubling method (IAD) were used in the study. Absorption and reduced scattering coefficients of normal and cancerous pancreatic tissues have been measured within the range of 500-650 nm. Statistical significant differences between cancerous and normal tissues have been obtained at 550 nm and 630 nm for absorption coefficients. On the other hand; there were no statistical difference found for scattering coefficients at any wavelength.

Illicit drug detection with laser 1: investigation of optimal parameters in stomach tissue

Abstract. The main purpose of this study is to establish radiation-safe scanning of passersby at high security areas, such as airports and customs. The stomach was selected as the organ to be analyzed. In order to determine whether a substance found inside a human body as wrapped in a plastic bag is filled narcotics or not, many substances in white powder form including morphine-HCL were inspected. Inspection was carried out with on-ionizing radiation by irradiating stomach tissue with laser light. Optical transmittance of lamb stomach tissue was analyzed at different wavelengths. We showed that detection by 650-nm diode laser irradiation would be suitable for such a radiation-safe scan. Different materials were also investigated for absorptive properties, and closed system Raman studies were performed. The spectrum of a molecule found inside white powder placed behind the lamb stomach tissue was detected as a fingerprint. This allowed the detection of target substances without any physical contact or damage to the biological tissue.

Closure of skin incision by dual wavelength (980 and 1064 nm) laser application

ABSTRACT Thermal effect of dual wavelength (980 and 1064 nm) laser application in skin incision closure was assessed on 18 male and female Wister rats. 1-cm-long incisions were made on the shaved dorsal region of 220–250 g animals. The incisions were closed by laser irradiation at 1 W and exposure time, 5 seconds in continuous-wave mode (CW) and 1 W and exposure time, 10 seconds in pulsed mode to deliver total energies of 5 J and 10 J per spot onto the incisions, respectively. Animals from each group were sacrificed at 0th, 4th, and 7th days and the skin samples of the weld area were excised for histological analysis using Hematoxylin and Eosin (H & E) stain. Mean thermally altered area (TAA) of CW-mode laser-treated groups was found to increase significantly (p < 0.05) compared with pulsed mode laser treated group at 0th and 4th days post-irradiation while no significant difference (p > 0.05) was statistically found at 7th day post-irradiation. Moreover, tighter closure was observed with CW group at 7th day post-irradiation. We thus conclude that 1 W, 5 J for 5 seconds CW mode laser application of 980 and 1064 nm combined beam form in skin incision closure was found to have absolute wound healing capability with minimal thermal alteration.

1940 nm diode laser skin welding of surgical incision: Tensile test analysis

Using Laser applications in medical has become more and more popular. Especially, Laser tissue welding has the significant role for laser skin closure. Mechanical behaviour of the material can be determined by appliying tension to the material itself. In this study, surgical incisions which were made on the dorsal skin tissue of 6 wistar albino rats, were welded with 1940 nm diode laser. Tensile tests are designated the determined days (4,7) by excision of the welded skin tissue. There is no significant mechanical difference between 4 and 7 days(p=0,88, p=0,41).

Photodynamic therapy application of PAMAM-porphyrin molecule on stomach cancer cells

In this study, effect of a novel LED-based light source developed for 96-well-plates cell culture applications, was tried on AGS stomach cancer cell line, in combination with Poly(amido amine) (PAMAM) modified – porhyrin molecule. For each 4 generation of modified PpIX molecule 5 different concentrations tried. According to results PAMAM molecule doesnt have any photosensitizer property also didn’t show any toxic effect even if higher concentrations. Morphology and real time monitoring analysis results hold up each other and confirmed that, PpIX molecules with and without modificated high concentrations (>100μM) caused cell death via toxicicity this reason optimal concentration for PAMAM modified PpIX should be between 25 - 50 μm concentration .

Therapeutic Lasers and Skin Welding Applications

Laser systems used in therapeutic medical field are specialized in terms of energy production and optical delivery mechanisms. It is favorable that medical lasers should have compact design especially important for a surgeon who is working in operation room where bulky medical devices occupy wide spaces. With the developing technology, especially in diode electronics, lasers of dimensions as small as i.e. 20x20x20 cm3 can be produced. Laser physics can be overviewed elsewhere written in any physics or biomedical books. Here we will only mention about important mechanisms and general knowledge.

Elastic scattering spectroscopy of coagulated brain tissues

The goal of this study was to differentiate the parts of lamb brain according to elastic scattering spectroscopy and detect the optical alterations due to coagulation. Cells and tissues are not uniform and have complex structures and shapes. They can be referred to as scattering particles. The process of scattering depends on the light wavelength and on the scattering medium properties; especially on the size and the density of the medium. When elastic scattering spectroscopy (ESS) is employed, the morphological alterations of tissues can be detected using spectral measurements of the elastic scattered light over a wide range of wavelengths. In this study firstly, the slopes of ESS spectra were used to differentiate the parts of lamb brains (brainstem, cerebellum, gray matter, white matter) in vitro in the range of 450 - 750 nm. Secondly, tissues were coagulated at different temperatures (45, 60, and 80 °C) and ESS spectra were taken from native and coagulated tissues. It was observed that as the coagulation temperature increased, the slope of the elastic scattering spectra decreased. Thus, optical properties of tissues were changed with respect to the change in nuclear to cytoplasmic ratio due to the water loss. Results showed that the slopes of ESS spectra in the visible range revealed valuable information about the morphological changes caused by coagulation.