A comparative investigation of bone surface after cutting with mechanical tools and Er:YAG laser.

BACKGROUND AND OBJECTIVES: Despite of the long history of medical application, laser ablation of bone tissue became successful only recently. Laser bone cutting is proven to have higher accuracy and to increase bone healing compared to conventional mechanical bone cutting. But the reason of subsequent better healing is not biologically explained yet. In this study we present our experience with an integrated miniaturized laser system mounted on a surgical lightweight robotic arm. STUDY DESIGN/MATERIALS AND METHODS: An Erbium-doped Yttrium Aluminium Garnet (Er:YAG) laser and a piezoelectric (PZE) osteotome were used for comparison. In six grown up female Göttingen minipigs, comparative surgical interventions were done on the edentulous mandibular ridge. Our laser system was used to create different shapes of bone defects on the left side of the mandible. On the contralateral side, similar bone defects were created by PZE osteotome. Small bone samples were harvested to compare the immediate post-operative cut surface. RESULTS: The analysis of the cut surface of the laser osteotomy and conventional mechanical osteotomy revealed an essential difference. The scanning electron microscopy (SEM) analysis showed biologically open cut surfaces from the laser osteotomy. The samples from PZE osteotomy showed a flattened tissue structure over the cut surface, resembling the "smear layer" from tooth preparation. CONCLUSIONS: We concluded that our new finding with the mechanical osteotomy suggests a biological explanation to the expected difference in subsequent bone healing. Our hypothesis is that the difference of surface characteristic yields to different bleeding pattern and subsequently results in different bone healing. The analyses of bone healing will support our hypothesis.

Simultaneous intrinsic and extrinsic calibration of a laser deflecting tilting mirror in the projective voltage space.

PURPOSE  : During the past five decades, laser technology emerged and is nowadays part of a great number of scientific and industrial applications. In the medical field, the integration of laser technology is on the rise and has already been widely adopted in contemporary medical applications. However, it is new to use a laser to cut bone and perform general osteotomy surgical tasks with it. In this paper, we describe a method to calibrate a laser deflecting tilting mirror and integrate it into a sophisticated laser osteotome, involving next generation robots and optical tracking. METHODS  : A mathematical model was derived, which describes a controllable deflection mirror by the general projective transformation. This makes the application of well-known camera calibration methods possible. In particular, the direct linear transformation algorithm is applied to calibrate and integrate a laser deflecting tilting mirror into the affine transformation chain of a surgical system. RESULTS  : Experiments were performed on synthetic generated calibration input, and the calibration was tested with real data. The determined target registration errors in a working distance of 150 mm for both simulated input and real data agree at the declared noise level of the applied optical 3D tracking system: The evaluation of the synthetic input showed an error of 0.4 mm, and the error with the real data was 0.3 mm.

Mid-infrared spectroscopic investigation of methylamines by a continuous-wave difference-frequency-generation-based system.

A laser spectroscopic system based on a cw difference-frequency generation source with a ratiometric multipass absorption detection scheme was employed for high-resolution spectroscopic investigation of gas-phase monomethylamine (MMA), dimethylamine (DMA), and trimethylamine (TMA). Possible application of the system as a noninvasive human breath analyzer for renal and liver diseases is targeted. The system operates in the fundamental C-H stretch absorption region around 2740-2860 cm(-1). A detection sensitivity of 2 x 10(-6) cm(-1) Hz(-(1/2)) (for signal-to-noise ratio SNR=1) is achieved, corresponding to detection limits of 900 ppb (parts in 10(9)) for MMA, 450 ppb for DMA, and 120 ppb for TMA in mixtures containing H2O and CO2 with concentrations of up to those present in human breath (2% and 5%, respectively). Future developments are discussed to further improve these detection limits that are currently still about 2 orders of magnitude higher than required for direct methylamine monitoring in human breath.

Spectroscopic investigation of methylated amines by a cavity-ringdown-based spectrometer.

High-resolution absorption spectra of gas-phase monomethylamine (MMA, CH(3)NH(2)) and dimethylamine [DMA, (CH(3))(2)NH] in the region of the first overtone of the NH stretch vibration are reported. Measurements were performed with a near-infrared laser spectrometer based on the cavity-ringdown (CRD) detection technique. The minimum detectable absorption coefficient for the CRD detection setup is alpha(min)=1.55 x 10(-8) cm(-1) (for SNR = 1). This corresponds to detection limits of 350 parts in 10(9) (ppb) for MMA and 1.6 parts in 10(6) (ppm) for DMA in synthetic gas mixtures under interference-free conditions, or 10 ppm and 60 ppm for MMA and DMA, respectively, in the case of gas mixtures such as exhaled human breath containing H(2)O, CO(2), and other absorbing gases in this range.