The Facts and Myths for the Use of Lasers in Orthopedic Surgery.

For the past three decades, laser use has been investigated, mainly on implant applications, as well as hard and soft tissue processing on orthopedics. However, despite significant technological advances and achievements in Biophotonics, lasers have yet to emerge as a successful tool for hard-tissue manipulation (e.g., osseous tissue). Indeed, a careful search in relevant literature reveals a limited number of laser-based clinical applications in orthopedics, except for the low-level laser therapy applications. In this review article, we give a brief overview of the biophysical mechanisms of bone tissue and biocompatible implants laser surgery and, in parallel, we summarize some specific pre-clinical and clinical laser applications in orthopedics. Taking into consideration the complexity of laser-based applications in inhomogeneous musculoskeletal biostructures and/or implants, it is justified to state that applying laser radiation is still an open field of multidisciplinary research before performing interventions in clinical praxis. The evidence from this study indicates the need for more experimental and theoretical studies regarding light transport on soft and hard tissues, in order to further enhance safe and efficient laser applications in orthopedics. This undoubtedly implies the need for developing modern light delivery devices for laser surgery, by means of implementing robotic guidance, specialized for medical procedures on various anatomic structures. The aforementioned studies could eventually revolutionize the clinical applications of laser technology in orthopedics.

Combined radiation strategies for novel and enhanced cancer treatment.

Numerous studies focus on cancer therapy worldwide, and although many advances have been recorded, the complexity of the disease dictates thinking out of the box to confront it. This study reviews some of the currently available ionizing (IR) and non-ionizing radiation (NIR)-based treatment methods and explores their possible combinations that lead to synergistic, multimodal approaches with promising therapeutic outcomes. Traditional techniques, like radiotherapy (RT) show decent results, although they cannot spare 100% the healthy tissues neighboring with the cancer ones. Targeted therapies, such as proton and photodynamic therapy (PT and PDT, respectively) present adequate outcomes, even though each one has its own drawbacks. To overcome these limitations, the combination of therapeutic modalities has been proposed and has already been showing promising results. At the same time, the recent advances in nanotechnology in the form of nanoparticles enhance cancer therapy, making multimodal treatments worthy of exploring and studying. The combination of RT and PDT has reached the level of clinical trials and is showing promising results. Moreover, in vitro and in vivo studies of nanoparticles with PDT have also provided beneficial results concerning enhanced radiation treatments. In any case, novel and multimodal approaches have to be adopted to achieve personalized, enhanced and effective cancer treatment.

Computational study of necrotic areas in rat liver tissue treated with photodynamic therapy.

BACKGROUND: Photodynamic therapy (PDT) is an alternative treatment method for liver metastatic cancer worth exploring. METHODS: This study implements a computational model of metastatic rat liver tissue subjected to superficial irradiation, after administration of 5,10,15,20-Tetrakis(3-hydroxyphenyl)chlorine (mTHPC). Spatial and temporal distributions of fundamental PDT dosimetric parameters are presented, along with calculation of necrotic distance and necrotic area percentage. Moreover, an algorithm able to calculate the minimum irradiation time needed in order to achieve various values of necrotic depth is coded. RESULTS: The intratissue distributions show that light penetration depth is approximately 1.5 mm for all fluence rate (φ) values in direction of z axis. Moreover, necrosis at r axis (horizontal axis) extends outside beam's geometrical edges at distance equal up to 55.3% of its radius. It is also noticed that both φ and concentration of ground-state photosensitizer ([S0]) can increase the necrotic distance, in a steeper manner at lower [S0] values. The irradiation time needed in order to achieve various values of necrotic depth is independent of φ for the upper tumor layers but is greater in orders of magnitude for deeper lying layers and low φ values. CONCLUSIONS: Increasing light fluence rate appears to be a more productive method than increasing photosensitizer concentration for inducing necrosis, especially in larger tumors. Finally, our results show that high φ values are necessary in order to maintain clinically applicable irradiation times.

Assessment of singlet oxygen dosimetry concepts in photodynamic therapy through computational modeling.

BACKGROUND: In photodynamic therapy (PDT) oxygen plays a vital role in killing tumor cells. Therefore oxygen dosimetry is being thoroughly studied. METHODS: Light distribution into tissue is modelled for radiation-induced fibrosarcoma (RIF) and nodular basal cell carcinoma (nBCC), in order to study the influence of blood flow on singlet oxygen concentration effectively leading to cell death ([1O2]rx) from PDT, within this light distribution. This is achieved through initial oxygen supply rate (g0) and initial molecular oxygen concentration ([3O2]0) calculations. Monte Carlo simulations and mathematical models are used for spatial and temporal distributions of [1O2]rx. Hypoxia conditions are simulated by minimizing [3O2]0 and g0. Furthermore, an optimization algorithm is developed to calculate minimum initial molecular oxygen concentration needed ([3O2]0,min) for constant [1O2]rx, when blood flow changes. RESULTS: Our results validate that in initially well-oxygenated scenarios with normal blood flow maximum [1O2]rx values are significantly higher than corresponding values of hypoxic scenarios both for RIF and nBCC models, with maximum oxygen supply rate percentage variations being independent from g0. Moreover, [1O2]rx appears to be more affected by an increase of g0 than of [3O2]0 values. For low blood flow there is a linear relationship between [3O2]0,min and g0, while for better oxygenated areas high blood flow reduces [3O2]0,min needed in exponential manner. CONCLUSIONS: Blood flow appears to be able to compensate for oxygen consumption. The developed optimization protocol on oxygen dosimetry offers a suitable combination of [3O2]0,min and g0 to achieve constant [1O2]rx, despite possible blood flow variations.