Pulsed Er:YAG laser removal of dentin and enamel tissue is effective. One of the dangers of this laser ablation is tooth overheating by the laser energy combined with heat related changes in pulp and side effects around the cavity margins. The purpose of present study was to determine the effect of the Er:YAG laser ablation in treating dental caries after a period of 5 years. During dry laser ablation, the temperature in the pulp chamber rose, and there is insufficient time for the tooth structures to dissipate the heat between the pulses. The addition ofwater mist during irradiation can speed up ablation of enamel and dentin. Water mist cools the surface sufficiently to prevent undesirable physical changes. From our results it follows that Er:YAG laser ablation is an excellent method for treating of frontal teeth - incisors, canines, premolars and initial occiusal caries of molars. However visual control of non-contact therapy is necessary. Compound, intricate cavity shape close to pulp cavity can not be prepared with laser radiation. Therefore the working time is much longer in comparison with the classical drilling machine. Low tooth sensitivity to laser ablation, preparation without unpleasant noise and vibration create a new technique, which is very successful for small and medium caries.

Hyperthermia is an important approach to treat tumor. Because the difference in the damage between normal and abnormal tissue disappears at high temperature, the distribution of temperature will influence the curative effect and the security of patients directly during laser treatment. Based on Monte-Carlo simulation of photon propagation, steady state temperature fields induced by continuous flat laser beam and Gaussian laser beam are calculated through solving bio-heat transfer equation with difference method, and the influences of various optical parameter on optical energy deposition and temperature elevation in biological are investigated in detail. The results show that pyrogenation area is wider than the area of light radiation, and the maximal energy deposition may not be corresponding to the maximal temperature elevation.

Developnient and introduction of the method of endogeni phototherapy into clinical practice using an autonomous stimulator has the aim to increase therapeutic efficiency of the given method. One of the directions allowing to solve this problem seems to be the use of chemical compounds having active optical properties. Natural and artificial food pigments, medicinal preparations, e.g. chiorophyllipt, aniline dyes as well as pigments of an organism excreted to the gastrointestinal tract (GIT) (e.g. bilirubin) can be such substances. The results ofmodification ofthe method ofendogenic phototherapy are studied in clinical trials with the help of such forms of substances as chiorophyllipt (mixture of eucalyptus chiorophylls), methylene blue, carotene as well as food pigments, e.g. red beet juice and some others. It is shown that these substances can both potentiate and reduce therapeutic effects of endogenic phototherapy (endogenic photostimulation). Of great importance is keeping a regimen of taking the proposed device and pigments per os. Thus, application of food and medicinal pigments in the method ofendogenic phototherapy enlarges considerably the range ofits use in medicine.

Hyperthermia therapy has been shown clinically effective for a variety of skin diseases but current heating equipment is inadequate for most patients. This effort describes the design and performance of a flexible microstrip array applicator intended for heating large regions of tissue over contoured anatomy while at the same time monitoring temperature of the underlying tissue by non-invasive radiometric sensing of blackbody radiation from the heated volume. For this dual purpose applicator, an array of broadband Archimedean spiral receive antennas is integrated into an array of Dual Concentric Conductor heating apertures. Applicator heating uniformity is assessed with electric field scans in homogenous muscle phantoms and with measured temperature distributions in clinical treatments of chestwall recurrence of breast carcinoma. The data demonstrate precisely controlled heating out to the perimeter of large (40 x 13 cm2) multiaperture conformal array applicators. Capabilities of the radiometry system are assessed by correlation of brightness temperatures measured in phantom loads of known temperature distribution as seen through an intervening 5 mm thick water bolus at constant 40°C. The radiometer demonstrates excellent sensitivity and an accuracy of +0.1-0.45°C for temperature measurements up to 5 cm deep in phantom when using a one dimensional weighting function analysis and up to 6 independent 500 MHz bandwidths within the 1-4 GHz range. The data clearly indicate that both heating and radiometric thermometry are possible using the same thin and flexible printed circuit board microstrip array applicator. Once development is complete, this dual mode conformal array applicator with multiplexed radiometric display system should provide significantly improved uniformity and ease of heating large area superficial tissue disease.

A dual-mode high-power ultrasound phased array with imaging capability to allow for self-guidance in noninvasive thermal surgery is described. Criteria governing the design of such dual-mode arrays to allow for high therapeutic effciency and adequate image contrast in the target volume are given. Experimental results for characterization of the array in both the imaging and therapy modes are given. Having established the dual-mode capabilities of this array, we have recently conducted a series of experiments in forming discrete and volumetric lesions in freshly excised tissue samples. Experimental results demonstrating the feasibility of visualizing the lesion formation process are presented. Images formed before and after discrete lesion formation have consistently shown increased level of echogenicity at the lesion location. Similar results were obtained for volumetric lesions. These results show that the spatial mapping of the lesion size and shape based ultrasound images obtained using the therapeutic array is feasible.

Radiofrequency (RF) tumor ablation has been demonstrated as a reliable method for creating thermally induced coagulation necrosis using either a percutaneous approach with image-guidance or direct surgical placement of thin electrodes into tissues to be treated. Early clinical trials with this technology have studied the treatment ofhepatic, cerebral, and bony malignancies. More recently this technology has been used to treat a host of malignant processes throughout the body. However, limitations in the technique and tumor biophysiology prevent optimal treatment of all desired lesions. Hence, investigators are studying combined methods of tumor destruction using RF ablation and adjuvant therapies that can modulate tumor biophysiology. These include using agents to alter tissue conductivity and blood flow, as well as combining RE with chemotherapy. Recent results using the combination therapy approach will be discussed.

Abnormal uterine bleeding (AUB) affects many women worldwide. To this end, many are debilitated and are at risk of compromising their health due to the amount of blood loss during their menstrual period. There are several treatments in clinical trials for AUB. One promising therapy is cryotherapy and a comparison will be made with RF and conductive heating. Unlike most devices for thermal therapy that have an upper limit due to steam formation, cryotherapy has no lower limit, except what is achievable at the source. A finite element model was set up to simulate cryotherapy and also RF or conductive heating. The bioheat equation was used to predict temperature distributions in tissue. Treatment safety issues will be explored as the simulations show the depth ofpenetration into the myometrium.

The breasts of adult female goats and pigs remain enlarged for sufficient time after weaning to allow survival studies of interstitial thermal therapy (ITT) lesions. The functional anatomy of the goat breast consists of breast lobules whose ducts empty into a labyrinth of increasingly dilated ducts that ultimately empty into one large chamber in the teat. On the other hand, similar to human breasts, the pig breasts are solid mixtures of lobules and ducts that empty into several smaller collecting ducts that terminate in the nipple. ITT lesions were produced using radio frequency energy source in goat and pig breasts and followed for up to 84 days (goats) and 28 days (pigs). The patterns and progression of wound healing were compared for the two species. The acute thermal lesions were formed of a central thermal coagulum surrounded by a red rim of thermal damage. At three days, the full extent of necrosis coincided with the outer boundary of the red thermal damage zone in both species. Wound organization, scar formation and epithelial regeneration originated from the peripheral viable breast tissues. Blood flow resumed in the open lumens of necrotic blood vessels in the central coagulum in both species but was more prominent in the pig. Slough of necrotic tissue was different in the goat compared to the pig because of the presence of large ducts in the goat breast. Epithelial regeneration was more prominent and extensive in the pig. Since the functional and stromal anatomy of the pig breast is similar to that of the human, the pig is a more reasonable model for human breast than the goat.

The purpose of this study was to evaluate the thermal and tissue changes associated with the use of electrocautery hemostasis on dependent tissues such as the penis. Circumcision was performed on twelve male sheep using a Gomco clamp and surgical removal. Electrocautery was then applied circumferentially to 6 separate sites along the circumcision incision for a duration of 2 seconds per application, with a 10-second interval between applications. Coagulation electrocautery power was set at either 25 or 50 Watts. Temperature changes were monitored by fiber-optic temperature probes placed immediately beneath the circumcision site in the penile urethra and at the base of the penis. Three animals were sacrificed acutely while the remaining 15 animals were sacrificed one month post-procedure. Penises were assessed by gross and histologic observation. Immediately post-procedure, epidermal and superficial dermal necrosis was observed at the cautery sites. By 32-days postprocedure, primary tissue change at the cautery site consisted of scarring and mild inflammation. Energy level (25 vs 50 Watts) did not significantly affect the level of tissue damage. Penile tissue subadjacent or distant to the cautery sites showed no gross or histologic change at the acute or chronic assessment period. During electrocautery, a maximum increase of 7°C (1-2 mm from the site of electrocautery) was observed regardless of the energy level. Temperature elevations commonly returned to near baseline within 5 minutes post-application. Smaller increases in temperature (range 1-2°C) occurred at the base of the penis. Our results document the long-held perception that electrocautery hemostasis can be safely employed in penile surgery, if the appropriate technique is used. Significant temperature and tissue changes are confined to very small/localized regions immediately adjacent to the cautery applicator.

A new ultrasound device has been developed to create holes in myocardium comparable to lasers. The device consists of 1 mm diameter solid titanium needle in a hand piece vibrating at a frequency of 24 kHz. The characteristics of the ultrasound needle were investigated using high speed and thermal imaging techniques. Similar imaging techniques were employed to investigate the C02, the Holmium, and the Excimer laser. The US needle created cavitation bubbles which rupture the structure of soft tissue and blend the cell matrix in a liquid environment. Shock waves were observed that traveled over 10 mm into the tissue without the evidence of direct tissue damage. During tissue penetration, the channel wall was heated due to the friction. In comparison, pulsed lasers generated explosive vapor bubbles that implode within 1 ms. These bubbles were bigger and appeared at a much lower frequency ( 40 Hz maximum). After vapor condensation the channel wall was heated significantly. The feasibility of the US needle was tested in-vivo in a porcine model. During activation, the US needle could perforate the left ventricular wall within a 2-4 seconds. Histology obtained acutely, showed 1 mm diameter channels with a small zone of thermal denaturation and small fissures along the channel wall similar to the excimer laser. Debris was found inside the channels as plugs of totally blended cell material. The US needle shows to be an effective device to create channels in the myocardium comparable with laser systems. The device is compact, easy to apply and cost effective compared to laser equipment. During surgery the surgeon can apply the US needle as an adjunct to CABG on sites which are unsuitable for bypassing without special precautions. Based on the characteristics the US needle device is expected to be as effective in the reduction of angina as laser systems.

Theoretical and experimental approaches were used to evaluate Internally-Cooled Direct-Coupled (ICDC) ultrasound applicators for treating disease in the prostate and liver. 2-D and 3-D transient biothermal models, which account for dynamic tissue changes, were used to calculate temperature distributions and zones of coagulation. Experimental evaluations and verification of these models were performed using in vitro tissue and in vivo porcine and canine models. Devices of 2.2 mm outer diameter were evaluated under varied applied power schemes and cooling levels. Both duty cycle power application and PI-controlled power application were found to improve applicator performance by increasing radial depths of lesions with lower maximum temperature. ICDC applicators were found to be able to create 3-5 cm diameter lesions in liver and muscle under 15 minute treatment times using the optimal designs and power application schemes found in this study. From these initial feasibility studies it has been demonstrated that ICDC devices have potential for treating cancerous tumors in prostate, liver and possibly breast.

The purpose of this study was to perform extensive temperature mapping throughout human cadaveric disc (n=12) specimens during Intradiscal Thermal Therapy IDTT using the SpineCathTM applicator. Temperature distributions and accumulated thermal dose or thermal damage calculated from the temperature-time history are used to define probable regions of thermal necrosis (destruction of nerves) or thermal coagulation (induced structural changes). The IDTT procedure using SpineCath (5 cm resistive heating segment) and the current standard heating protocol (~17 min) produces intra-discal temperatures which are too low to generate appreciable regions of thermal coagulation and resultant changes in biomechanical properties. This finding was supported by temperature measurements which were mostly below the critical temperature of 60-65°C, except for regions within 1-2 mm of the SpineCath applicator. Furthermore, the analysis of the thermal dose profiles indicate that sufficient thermal doses (240-640 EM43°C) capable of generating complete thermal damage to the nociceptive nerves fibers infiltrating the disc are limited to within ~6 mm of the nucleus and IDTT probe heating segment.

The cornea may be reshaped to correct for hyperopia by selective shrinkage of collagen in the stroma using radio frequency (RF) current from a needle electrode. Pulsed current is used to maximize therapeutic effect while minimizing radiating thermal damage. Finite difference numerical models of the electric fields and resulting thermal events were used to study the process parameters. The models were calibrated by comparison to histologic data using predicted and measured loss of birefringence in collagen as the standard of comparison.

Heat-Assisted Capsular Shift (HACS) procedures are currently applied to treat shoulder (glenohumeral) instability. The therapy aims at thermally denaturing the collagenous framework, thus shrinking the surrounding soft tissues of the lax glenohumeral joint. The desired outcome of the therapy is restoring the kinematic stability of the joint without degrading its mechanical stability. Reports describing the outcome of HACS procedures reveal considerable variations, most likely due to utilization of different heat deposition modalities and the diversity of the thermal treatment protocols applied. The uncertainty of the outcome is also amplified by the post-heating recovery from shrinkage and the heat-induced degradation of mechanical stability. This study introduces a novel method designed to minimize the adverse effects of current therapies. A mechanical property enhancement technique in the form of an adjuvant chemical treatment is presented. In-vitro experiments performed on rabbit patellar tendons using a new arthroscopic fluid with thermal treatment indicate therapeutic improvement compared to therapies based on heating alone. A decrease in the strain recovery as large as 50% and an increase in stiffness as much as 100% have been produced in collagenous tissues without compromising strength. In summary, this work presents the initial results of an effort aimed at increasing the safety and reliability of currently applied HACS procedures by optimal manipulation of novel thermo-chemical treatments.

The use of monopolar radiofrequency energy for thermal modification of tissue has expanded considerably since its rudimentary beginnings in the 1 9th century. It has been used in a number of medical fields and recently has been explored hi the orthopaedic arena. Monopolar radiofrequency energy mediates its effects through thermal tissue modification. It has been determined that type I collagen undergoes permanent structural modification between 60 and 80°C. Understanding of the mechanism of action of monopolar radiofrequency energy and the thermal properties of collagen has led to a number of clinical and basic research investigations into the use ofmonopolar radiofrequency energy to modifyjoint capsular tissue and thereby stabilize joints with excessive laxity. The technology has also been applied to ligamentous tissue. Recently, we have explored the effect of monopolar radiofrequency energy on the fibrocartilagenous structure of the meniscus. Thermal modification of musculoskeletal tissue has the potential to become a prominent modality for the treatment ofjoint disorders. It must be emphasized, however, that thermal treatment does have initial detrimental effects on tissue mechanical properties, and that long-term results have yet to be evaluated. Further controlled clinical and scientific studies should further clarify the advantages and disadvantages ofthis technique.

Cartilage fibrillation is commonly associated with injury and long-term degeneration. Contouring the articular surface with radiofrequency energy (RFE) may stabilize the surface, and improve clinical function, but subchondral bone injury has been reported in some patients. The purpose of this research was to document the effects of bipolar and monopolar RFE on articular cartilage. Bipolar RFE and monopolar RFE treatment of abraded bovine cartilage was investigated in an in vitro model. Bipolar RFE caused greater chondrocyte death than monopolar RFE, (bipolar RFE: 1700-?m; monopolar RFE: 800-?m) (p<0.05). Both bipolar RFE and monopolar RFE contoured the articular surface but the depth of chondrocyte death raised concerns regarding the clinical application of RFE. Further work investigated the arthroscopic application of bipolar RFE and monopolar RFE on human chondromalacic cartilage in vitro. Both devices smoothed the fibrillated surface, but bipolar RFE caused increased depth of chondrocyte death compared to monopolar RFE (bipolar RFE 2100-?m; monopolar RFE 620-?m (p<0.05). Fluoroptic thermometry has demonstrated cartilage matrix temperatures exceeding 70° C 2-mm below the articular surface during the application of bipolar RFE. The clinical use of the bipolar RFE systems available to date will likely result in unacceptable chondrocyte death and subchondral injury. While RFE demonstrates some promise for the management of cartilage injury, further work must be completed to define the parameters for its application.

It is well known that the static mechanical properties of living soft tissues reversibly or irreversibly change by the degree of the thermal energy exposure, several researchers including us applied various type ultrasonic elasticity imaging techniques to visualize variously energy-induced thermal tissues. Particularly, in this report we proposed that our previously developed ultrasonic strain measurement-based shear modulus imaging technique is used for monitoring the effectiveness of the interstitial RF electromagnetic wave thermal treatment. Since previously through in vivo experiment on human breast tissues we could confirm that the technique has high potential as the practical tool for differentiating early stage malignancies, we in novel realized the thermal applicator using only needle-type electrodes. Since we would also apply this therapy to deeply situated tissues, we also confirmed that on in vivo human liver shear modulus image could be stably obtained. Furthermore, to verify the feasibility as the monitoring technique we performed heating/imaging on the fresh in vitro calf liver. This imaging could specify the spatial and temporal change of elasticity due to tissue heating and cooling down. We believe that this monitoring technique will allow this type interstitial RF electromagnetic wave thermal therapy to be widely performed on various tissues. Moreover, low-invasively obtained insights about tissue thermal properties will significantly contribute to heightening the treatment efficiencies of various type thermal therapy systems.

In the destructive treatment of tumors or other lesions, laser therapies such as laser induced thermal therapy (LITT) or interstitial laser phototherapy (ILP) offer tremendous potential to minimize surgical complications, reduce recovery time and hospital stays, and decrease associated health care costs. While laser procedures have gained wide popularity in dermatology and ophthalmology, their potential has yet to be fully realized in treatment of deep tissues where the damage front created by the laser can not be readily visualized. In the present work, we facilitate this visualization by producing an image of spatial temperature distribution via non-invasive magnetic resonance imaging (MRI). Further, we have implemented a control strategy which allows us to utilize this information for the feedback control of laser thermal therapies. We have begun to explore the feasibility of using this system for improving the safety and efficacy oflaser thermal surgery.

In this study both transurethral and interstitial ultrasound thermal therapy were applied to thermally coagulate targeted portions of the canine prostate or brain and implanted TVT tumors while using MRI-based thermal mapping techniques to monitor the therapy. MRI was also used for target definition, positioning of the applicator, and evaluation of target viability post-therapy. The complex phase-difference mapping technique using an iGE-EPI sequence with lipid suppression was used for determining temperature elevations within the in vivo prostate or brain and surrounding structures. Calculated temperature distributions, thermal dose exposures, T2-wieghted & T1-contrast enhanced images, gross inspection, and histology of sectioned prostates and brains were in good agreement with each other in defining destroyed tissue zones. Interstitial and transurethral ultrasound applicators produce directed zones of thermal coagulation within targeted tissue and implanted tumor, which can be accurately monitored and evaluated by MRI.

In this paper, we present our experimental results on the determination of the thermal conductivity of biological tissues using a transient technique based on the principles of cylindrical hot-wire method. A novel, 1 .45mmdiameter, 50mm long hot wire probe was deployed. Initial measurements were made on sponge, gelatin and Styrofoam insulation to test the accuracy of the probe. Subsequent experiments conducted on sheep collagen in the range of 25°C