Vaporization of Prostatic Tissue to Treat Benign Prostatic Hyperplasia

The prostate is a key component of the male reproductive system. Often, due to age, the prostate becomes enlarged resulting in a condition known as Benign Prostatic Hyperplasia (BPH). While pharmacological options are generally the first choice, surgery is sometimes necessary to treat this condition. Laser procedures are ideal because of the decreased risks to the patient, but complications arise when the layer of coagulated tissue created by the laser becomes too thick. An ideal laser wattage and application time must be determined in order to minimize the coagulation layer while achieving an effective level of vaporization. The goal of this simulation was to create a model from which an ideal set of laser parameters for the laser treatment of BPH can be determined. This was achieved using finite-element analysis of the laser heating of a 2-dimensional axisymmetric prostate model using COMSOL Multiphysics software. Using this simulation, the vaporization and coagulation thicknesses in prostatic tissue treated for 5 seconds with a 40W, 80W, or 120W laser, or treated for 1 second with a 60W, 80W or 120W laser were determined. The results indicated that increasing laser wattage and/or application time increases the thickness of vaporized tissue and decreases the thickness of coagulation. Furthermore, the results suggested that the thickness of the coagulation zone converges to a minimum value as wattage and/or application time is increased. This simulation was preliminary; however, this model can ideally be used to determine an ideal laser wattage-application time combination that produces the desired level of vaporization while minimizing tissue coagulation

Medical Laser-Induced Thermotherapy - Models and Applications

Heat has long been utilised as a therapeutic tool in medicine. Laser-induced thermotherapy aims at achieving the local destruction of lesions, relying on the conversion of the light absorbed by the tissue into heat. In interstitial laser-induced thermotherapy, light is focused into thin optical fibres, which are placed deep into the tumour mass. The objective of this work was to increase the understanding of the physical and biological phenomena governing the response to laser-induced thermotherapy, with special reference to treatment of liver tumours and benign prostatic hyperplasia. Mathematical models were used to calculate the distribution of light absorption and the subsequent temperature distribution in laser-irradiated tissues. The models were used to investigate the influence on the temperature distribution of a number of different factors, such as the design of the laser probe, the number of fibres, the optical properties of the tissue, the duration of irradiation, blood perfusion and boundary conditions. New results concerning transurethral microwave thermotherapy were obtained by incorporating the distribution of absorbed microwaves into the model. Prototypes of new laser applicators for anatomically correct treatment of benign prostatic hyperplasia were developed and tested ex vivo. Experimental work on liver tumours pointed to the importance of eliminating the blood flow in the liver during treatment to reduce convective heat loss. In addition, it was shown that hepatic inflow occlusion during treatment increased the thermal sensitivity of tumour tissue. The dynamic influence of interstitial laser thermotherapy on liver perfusion was investigated using interstitial laser Doppler flowmetry. Vessel damage after the combined treatment of laser-induced heat treatment and photodynamic therapy was studied

Advanced application of phosphate glass optical fibres in photonics and biophotonics

The work of this thesis is focused on two research lines: the first on the development of high power fibre lasers, the second on the development of bioresorbable, inorganic optical devices. The common aspect of these two lines is the use of phosphate glasses as a base material for the fabrication of specialty optical fibres. Phosphate glasses are extremely interesting materials in virtue of the unique combination of their properties. They have been widely exploited in laser science as active gain media, due to the high solubility of rare earths in the glass matrix, and to the high absorption/emission cross section. Calcium phosphate glasses, on the other hand, have been studied as promising biomaterials due to their solubility in aqueous media, and to the ability of being safely reabsorbed by the human body. The thesis starts with a literature review on the use of phosphate glasses in the fabrication of optical fibres and lasers. The properties of rare earth doped glasses are reviewed and a detailed description of the quenching phenomena in doped glasses reported and compared to the major results obtained in the literature. The study of the literature reveals how the issues of heat dissipation, thermal expansion and mechanical stability are still relevant problems in the field of high power lasers. These issues were studied in the course of the thesis. Results obtained on the development of a Nd3+- doped phosphate cane laser are reported in Chapter 5. Cane lasers have the same core/cladding structure that is typical of an optical fibre, but present a much larger diameter. This allows an increased mechanical stability of the device, combined with the easy cooling and good beam quality that are typical for a fibre laser. The development of a first prototype of a phosphate cane laser required the fabrication of a suitable glass (namely CL) that is featured by an exceptional matching of thermo-mechanical properties between core and cladding. A core glass composition (CL1:Nd) and a cladding glass composition (CL1) that present a difference in the glass transition temperature of only 8°C and identical coefficient of thermal expansion were fabricated ad-hoc for this scope. The materials were fully characterized and used for the fabrication of a cane with a diameter of 800μm. Power scaling experiments, performed on a 60mm-long section of the cane, show laser emission at 1054mm, with a maximum output power of 2.5W and a slope efficiency of 44% with respect to the absorbed power. Another issue that emerged from the literature and from the studies of fibre/cane lasers is the interest in developing new fibres with complex geometry. Chapter 4 of this thesis describes work carried on this topic, focusing on the critical step of fabricating and assembling a fibre preform. With the aim to develop rapidly and effectively optical fibre preforms with a wide range of geometries, a project for the in-house development of an extrusion facility in Politecnico di Torino was kick-started. A first prototype of the facility is available, and preliminary results on the extrusion of phosphate glasses are presented. The second part of the thesis is dedicated to the development of resorbable optical materials. An overview on the use of calcium phosphate glasses in the biomedical field is given, with particular interest in the use of glass fibres in biomedical applications. Subsequently, the results obtained on the use of resorbable glasses in biophotonics are reported. The idea at the basis of this research is to combine in a single device the two main field of application of phosphate glasses: the biomedical field and the optical one. This becomes particularly interesting as it enables fabricating multifunctional optical devices, which are of interest in optical sensing and photo-therapy. In particular, the bioresorbability minimizes the impact of the therapies, eliminating the need of removal surgery. Chapter 4 reports a detailed description of the design, fabrication and characterization of transparent calcium phosphate glasses. The materials show a window of transparency ranging from 240 to 2600nm, therefore are able to guide light in the near UV region, and the refractive index can be tailored according to the composition. The glasses proved to be stable against devitrification and suitable for fibre drawing. Single material fibres were fabricated and proved to be soluble in aqueous media, in simulated physiological conditions. Once the fabrication of the material is complete, resorbable glasses were used for the fabrication of single and multi-mode optical fibres. Step index fibres were fabricated using the rod in tube technique and the attenuation loss was measured by cut-back method. The fibres showed values of attenuation loss between 5 and 15dB/m in the visible region and from 2 to 5dB/m in the near infra-red. These values are from one to two orders of magnitude lower than those reported in literature for other resorbable optical devices. These results paved the way towards the application of such fibres for the inscription of fibre Bragg-gratings and for the use in time-domain diffuse optics experiments. Preliminary results on these topics are presented in Chapter 6. Finally, resorbable hollow fibres were fabricated by drawing a tube-shaped preform. These fibres were used for obtaining a controlled release of a photosensitive drug, that could be activated by the light guided trough the same fibre. Experiments on the controlled release of drugs are still ongoing, and involved the development of a silanization method for phosphate glasses, in order to increase the release time of drugs

Theoretical analysis of transurethral laser-induced thermo-therapy for treatment of benign prostatic hyperplasia. Evaluation of a water-cooled applicator

A mathematical model for predicting the temperature rise in transurethral laser-induced thermo-therapy for benign prostatic hyperplasia was developed. In the model an optical line source emitting light from an Nd:YAG laser isotropically was placed in the urethra. Water cooling of the urethral epithelium was modelled using a two-tube system. The relationship between the difference in outlet and inlet water temperatures and the highest tissue temperature level reached was theoretically investigated. It was found that the water temperature difference was linearly dependent on the steady-state maximum tissue temperature. The theoretical calculations suggest that the water-cooled applicator can be used to measure the maximum tissue temperature. With temperature control, the prostatic tissue temperature can be prevented from exceeding the boiling point of water, excluding tissue carbonization. The model was also used to evaluate the influence of a number of different parameters on the damaged tissue volume. Increasing the urethral lumen radius by a factor of two by means of inserting different sized tubes was found to augment the tissue volume raised to therapeutic temperatures by up to 50%. The calculations showed that cooling of the urethral epithelium can result in an increase in the damaged volume by 80% as compared to not applying any cooling. The temperature of the cooling water was found to influence the tissue temperature only to a small extent

Photoacoustic Image Analysis for Cancer Detection and Building a Novel Ultrasound Imaging System

Photoacoustic (PA) imaging is a rapidly emerging non-invasive soft tissue imaging modality which has the potential to detect tissue abnormality at early stage. Photoacoustic images map the spatially varying optical absorption property of tissue. In multiwavelength photoacoustic imaging, the soft tissue is imaged with different wavelengths, tuned to the absorption peaks of the specific light absorbing tissue constituents or chromophores to obtain images with different contrasts of the same tissue sample. From those images, spatially varying concentration of the chromophores can be recovered. As multiwavelength PA images can provide important physiological information related to function and molecular composition of the tissue, so they can be used for diagnosis of cancer lesions and differentiation of malignant tumors from benign tumors. In this research, a number of parameters have been extracted from multiwavelength 3D PA images of freshly excised human prostate and thyroid specimens, imaged at five different wavelengths. Using marked histology slides as ground truths, region of interests (ROI) corresponding to cancer, benign and normal regions have been identified in the PA images. The extracted parameters belong to different categories namely chromophore concentration, frequency parameters and PA image pixels and they represent different physiological and optical properties of the tissue specimens. Statistical analysis has been performed to test whether the extracted parameters are significantly different between cancer, benign and normal regions. A multidimensional [29 dimensional] feature set, built with the extracted parameters from the 3D PA images, has been divided randomly into training and testing sets. The training set has been used to train support vector machine (SVM) and neural network (NN) classifiers while the performance of the classifiers in differentiating different tissue pathologies have been determined by the testing dataset. Using the NN classifier, performance of parameters belonging to different categories in differentiating malignant tissue from nonmalignant tissue has been determined. It has been found that, among different categories, the frequency parameters performed best in differentiating malignant from nonmalignant tissue [sensitivity and specificity with testing dataset are 85% and 84%] while performance of all the categories combined was better than that [sensitivity and specificity with testing dataset are 93% and 91%]. However, PA imaging cannot be used to provide the anatomical cues required to determine the position of the detected or suspected malignant tumor region relative to familiar organ landmarks. On the other hand, although accuracy of Ultrasound (US) imaging in detecting cancer lesions is low, major anatomical cues like organ boundaries or presence of nearby major organs are visible in US images. A dual mode PA and US imaging system can potentially detect as well as localize cancer lesions with high accuracy. In this study, we have developed a novel pulse echo US imaging system which can be easily integrated with our existing ex-vivo PA imaging system to produce the dual mode imaging system. Here a Polyvinylidene fluoride (PVDF) film has been used as US transmitter. To improve the anticipated low signal to noise ratio (SNR) of the received US signal due to the low electromechanical coupling coefficient of the PVDF film, we implemented pulse compression technique using chirp signals. Comparisons among the different SNR values obtained with short pulse and after pulse compression with chirp signal show a clear improvement of the SNR for the compressed pulse. The axial resolution of the imaging system improved with increasing sweep bandwidth of input chirp signals, whereas the lateral resolution remained almost constant. This work demonstrates the feasibility of using a PVDF film transducer as an US transmitter and implementing pulse compression technique in an acoustic lens focusing based imaging system

The laser of the future: reality and expectations about the new thulium fiber laser-a systematic review

The Holmium:yttrium-aluminum-garnet (Ho:YAG) laser has been the gold-standard for laser lithotripsy over the last 20 years. However, recent reports about a new prototype thulium fiber laser (TFL) lithotripter have revealed impressive levels of performance. We therefore decided to systematically review the reality and expectations for this new TFL technology. This review was registered in the PROSPERO registry (CRD42019128695). A PubMed search was performed for papers including specific terms relevant to this systematic review published between the years 2015 and 2019, including already accepted but not yet published papers. Additionally, the medical sections of ScienceDirect, Wiley, SpringerLink, Mary Ann Liebert publishers, and Google Scholar were also searched for peer-reviewed abstract presentations. All relevant studies and data identified in the bibliographic search were selected, categorized, and summarized. The authors adhered to PRISMA guidelines for this review. The TFL emits laser radiation at a wavelength of 1,940 nm, and has an optical penetration depth in water about four-times shorter than the Ho:YAG laser. This results in four-times lower stone ablation thresholds, as well as lower tissue ablation thresholds. As the TFL uses electronically-modulated laser diodes, it offers the most comprehensive and flexible range of laser parameters among laser lithotripters, with pulse frequencies up to 2,200 Hz, very low to very high pulse energies (0.005-6 J), short to very long-pulse durations (200 µs up to 12 ms), and a total power level up to 55 W. The stone ablation efficiency is up to four-times that of the Ho:YAG laser for similar laser parameters, with associated implications for speed and operating time. When using dusting settings, the TFL outperforms the Ho:YAG laser in dust quantity and quality, producing much finer particles. Retropulsion is also significantly reduced and sometimes even absent with the TFL. The TFL can use small laser fibers (as small as 50 µm core), with resulting advantages in irrigation, scope deflection, retropulsion reduction, and (in)direct effects on accessibility, visibility, efficiency, and surgical time, as well as offering future miniaturization possibilities. Similar to the Ho:YAG laser, the TFL can also be used for soft tissue applications such as prostate enucleation (ThuFLEP). The TFL machine itself is seven times smaller and eight times lighter than a high-power Ho:YAG laser system, and consumes nine times less energy. Maintenance is expected to be very low due to the durability of its components. The safety profile is also better in many aspects, i.e., for patients, instruments, and surgeons. The advantages of the TFL over the Ho:YAG laser are simply too extensive to be ignored. The TFL appears to be a real alternative to the Ho:YAG laser and become a true game-changer in laser lithotripsy. Due to its novelty, further studies are needed to broaden our understanding of the TFL, and comprehend the full implications and benefits of this new technology, as well its limitations.info:eu-repo/semantics/publishedVersio

Low Temperature Plasma : A Novel Focal Therapy for Localized Prostate Cancer?

Despite considerable advances in recent years for the focal treatment of localized prostate cancer, high recurrence rates and detrimental side effects are still a cause for concern. In this review, we compare current focal therapies to a potentially novel approach for the treatment of early onset prostate cancer: low temperature plasma. The rapidly evolving plasma technology has the potential to deliver a wide range of promising medical applications via the delivery of plasma-induced reactive oxygen and nitrogen species. Studies assessing the effect of low temperature plasma on cell lines and xenografts have demonstrated DNA damage leading to apoptosis and reduction in cell viability. However, there have been no studies on prostate cancer, which is an obvious candidate for this novel therapy. We present here the potential of low temperature plasma as a focal therapy for prostate cancer

Radioactive seed immobilization techniques for interstitial brachytherapy

Purpose In prostate brachytherapy, seeds can detach from their deposited sites and move locally in the pelvis or migrate to distant sites including the pulmonary and cardiac regions. Undesirable consequences of seed migration include inadequate dose coverage of the prostate and tissue irradiation effects at the site of migration. Thus, it is clinically important to develop seed immobilization techniques. Methods We first analyze the possible causes for seed movement, and propose three potential techniques for seed immobilization: (1) surgical glue, (2) laser coagulation and (3) diathermy coagulation. The feasibility of each method is explored. Experiments were carried out using fresh bovine livers to investigate the efficacy of seed immobilization using surgical glue. Results Results have shown that the surgical glue can effectively immobilize the seeds. Evaluation of the radiation dose distribution revealed that the non-immobilized seed movement would change the planned isodose distribution considerably; while by using surgical glue method to immobilize the seeds, the changes were negligible. Conclusions Prostate brachytherapy seed immobilization is necessary and three alternative mechanisms are promising for addressing this issue. Experiments for exploring the efficacy of the other two proposed methods are ongoing. Devices compatible with the brachytherapy procedure will be designed in futur

Laser Ablation and Immune Stimulating Interstitial Laser Thermotherapy

Based on nineteenth-century findings that showed that heat (fever) could be used to treat cancer, local hyperthermia has been developed as a tool to eradicate local tumors when surgical excision is deemed impossible. Nonetheless many cancer patients with advanced disease still lack effective treatment. During the last decades, data has emerged indicating that in situ destruction of tumors in some cases may induce tumor antigen release which can stimulate antigen-specific cellular immunity. Immune stimulating interstitial laser thermotherapy (imILT) is a method for local hyperthermia using laser light to increase tissue temperature with a specific protocol which can result in in situ vaccination. In vivo studies have shown that the method can induce an immune response that is effective against re-challenging, therefore indicating abscopal effect. Data was collected during clinical studies to assess the safety and feasibility of the method

Effect of Green Light from Doubled Frequency Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) Laser in the Nanosecond Range on Rabbit’s Lens –In Vitro Study

 INTRODUCTION: The unprotected eye is extremely sensitive to laser radiation and can be permanently damaged from direct or reflected beams. The area of the eye damaged by laser energy is dependent upon the wavelength of the incident laser beam, duration of exposure and tissue characteristics. This study aims to investigate the effect of intense green light from doubled frequency Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) (532nm) in the nanosecond range on the protein of rabbits lenses after short and prolonged (6, 18 seconds) exposures.METHODS: The fundamental wavelength (1064 nm) was frequency doubled in β- Barium Borate (BBO) crystal for second harmonic generation (SHG). Rabbits’ lenses were irradiated in vitro, and the effect of the laser was evaluated by comparing the protein concentration, structure and conformation by sodium dodecyle sulphate polyacrylamide electrophoresis (SDS-PAGE) and Fourier transform infrared spectroscopy (FTIR).RESULTS: The results indicated a significant change in the soluble protein content, the molecular weights and the backbone structure of different lens crystallin fractions. These effects were more distinct when using laser with prolonged irradiation for 18 seconds than for 6 seconds.CONCLUSION: Irradiation with frequency doubled Nd-YAG green laser seem to be cataractous if the lens is exposed to laser that is intense enough to warrant thermal protein aggregation, folding and denaturatio