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This chapter is intended to provide a quick review on recent advances in minimally invasive microwave ablation (MWA) antenna designs and emphasize the authors' collective works in this area. First, it summarizes the key details and main findings of the studies investigating MWA performance at multiple discrete frequencies from 1.9 to 18 GHz. The chapter highlights the investigation of using higher frequency microwaves for tissue ablation, which is motivated by the aspect of reduced antenna lengths as the operating frequency increases. Next, it discusses methods for reducing diameters of balun‐equipped coax‐fed antennas, starting with a comprehensive literature review and then shifting focus to the proposed antenna designs. The chapter then provides information on balun‐free coax‐fed antenna designs which represent a different group of solutions for minimizing invasiveness of MWA antennas. Finally, the effort in developing flexible antennas as well as directional‐heating antennas, aimed for increasing the flexibility and customization of MWA treatment, is documented.

Developing small‐scale soft continuum robots with large‐angle steering capacity and high‐precision manipulation offers broad opportunities in various biomedical settings. However, existing continuum robots reach the bottleneck in actuation on account of the contradiction among small size, compliance actuation, large tender range, high precision, and small dynamic error. Herein, a 3D‐printed millimeter‐scale soft continuum robot with an ultrathin hollow skeleton wall (300 μm) and a large inner‐to‐outer ratio (0.8) is reported. After coating a thin ferromagnetic elastomer layer (≈100–150 μm), the proposed soft continuum robot equipped with hybrid actuation (tendon‐ and magnetic‐driven mode) achieves large‐angle (up to 100°) steering and high‐precision (low to 2 μm for static positioning) micromanipulation simultaneously. Specifically, the robot implements an ultralow dynamic tracking error of ≈10 μm, which is ≈30‐fold improved than the state of art. Combined with a microneedle/knife or nasopharyngeal swab, the robot reveals the potential for versatile biomedical applications, such as drug injection on the target tissue, diseased tissue ablation, and COVID‐19 nasopharyngeal sampling. The proposed millimeter‐scale soft continuum robot presents remarkable advances in large‐range and high‐precise actuation, which provides a new method for miniature continuum robot design and finds broad applications in biomedical engineering., Developing small‐scale soft continuum robots offers broad opportunities in various biomedical settings. Herein, a 3D‐printed millimeter‐scale soft continuum robot equipped with hybrid actuation (tendon and magnetic driven) that can achieve large‐angle (≈100°) steering and high‐precision (≈2/10 μm for static/dynamic positioning, respectively) micromanipulation simultaneously is proposed, which reveals versatile potentials, such as microinjection/ablation and nasopharyngeal sampling.© 2020 WILEY‐VCH Verlag GmbH & Co. KGaA, WeinheimThis article is being made freely available through PubMed Central as part of the COVID-19 public health emergency response. It can be used for unrestricted research re-use and analysis in any form or by any means with acknowledgement of the original source, for the duration of the public health emergency.

Aims We evaluated a Selective Bladder Denervation (SBD) device, which uses radiofrequency ablation, for the treatment of overactive bladder syndrome in terms of its nerve denervation, ablation characteristics, and post-treatment healing. Methods Using the SBD device, eight fresh extirpated ovine bladder trigones were treated (90°C set point for 60 s) and nitroblue tetrazolium viability stained to characterize the ablation. In addition, 12 trigones were treated in vivo with three adjacent ablations and divided into survival cohorts: Day 7, Day 30, and Day 90 to assess the ablations and their associated healing. Results The ex vivo single trigone ablations had a 7.9 ± 0.9 mm width and 5.7 ± 1.0 mm thickness that involved the submucosa, detrusor muscle, adventitia, and vagina. Microscopic viability staining confirmed complete nerve necrosis within the targeted tissue. The in vivo Day 7 trigones supported the ex vivo ablation characteristics and showed up to minimal inflammation, granulation tissue, and collagen fibrosis. Day 30 trigones had essentially absent inflammation and granulation tissue with evolving collagen fibrosis at the ablation's periphery. Day 90 trigones had essentially absent acute inflammation, minimal chronic inflammation, essentially absent granulation tissue, and up to mild collagen fibrosis. No ureteral/urethral alterations, vesico-vaginal fistulas, or other complications were identified. Conclusions The SBD device provided a targeted trigone ablation with resultant denervation. The tissue healing timeline followed that expected for a hyperthermic ablation and was characterized by a fibroproliferative healing response with limited inflammation and granulation tissue. The ablations did not impact the overlying bladder mucosal surface.

Regeneration is a fascinating process that allows some organisms to reconstruct damaged tissues. In addition to the classical regeneration model of the Drosophila larval imaginal discs, the genetically induced tissue ablation model has promoted the understanding of molecular mechanisms underlying cell death, proliferation, and remodeling for tissue regeneration. Recent studies have also revealed that tissue injury responses occur not only locally but also systemically, even in the uninjured region. Genetic studies in Drosophila have demonstrated the dynamic role of the cell death-induced tissue response in the reconstruction of damaged tissues.

The near-infrared (NIR) window refers to a range of wavelengths (700–1300 nm) in which biological tissues are highly transparent.[1] Consequently, biological imaging and therapy modalities employ light at these wavelengths for the monitoring[1] and triggering[2] of biological events in vitro and in vivo. For instance, photothermal ablation takes advantage of NIR absorbing materials for transducing light into heat.[2] The resultant thermal energy can be used for a number of applications, such as tissue ablation and drug release. Despite the intense interest in NIR photothermal agents, their development has suffered from considerable challenges. In particular, few nanomaterials display the requisite absorption profiles required for NIR photothermal transduction.

Transurethral vaporization of the prostate in saline (TURisV) is an innovative endoscopic surgical modality for the treatment of benign prostatic hyperplasia (BPH) that vaporizes prostate tissue using a uniquely designed mushroom electrode. TURisV promises instant hemostatic tissue ablation under saline irrigation and offers clinical advantages for endoscopic BPH operations. From July 2008 to February 2009, TURisV was performed in 17 cases with clinically significant BPH. Median operation time was 127.0 min and median volume of vaporized prostate tissue was 41.1 g. Median International Prostate Symptom Score improved from 20 to 4 after 12 months. Median maximum flow rate increased from 5.3 mL/s to 13.8 mL/s after 12 months. Postoperative median residual urine improved from 48.0 mL to 7.0 mL after 12 months. No changes in hemoglobin or electrolyte levels were seen postoperatively. Our results suggest that TURisV is a safe and efficacious treatment for BPH.

Background: Bimodal electric tissue ablation (BETA) incorporates the process of electrolysis into radiofrequency ablation (RFA) to increase the size of tissue ablation. This study investigated whether BETA could increase the efficacy of the Cool-Tip RF system (Covidien, Boulder, CO, USA) to produce larger ablations. It also investigated whether applying electrolysis only during the pretreatment phase (called electrochemical treatment (ECT)/RFA group) is as effective as BETA (where electrolysis was used during both the pretreatment and RFA phases). Methods: A Cool-Tip RF system (Covidien) was used to test three types of ablations (RFA, BETA, and ECT/RFA) in a pig liver model. In BETA, 9 V of direct current was provided for 10 min, after which the RF generator was started and both electrical circuits were allowed to run concurrently. In ECT/RFA, however, the direct current circuit was switched off after 10 min of pretreatment and only RFA was performed as described above. Ablation sizes were measured in three dimensions. Results: The size of ablations (transverse diameter A and B) produced by BETA and ECT/RFA was significantly larger compared with standard RFA (P < 0/001). BETA also created larger ablations compared with ECT/RFA (P < 0.001). Conclusion: BETA could improve the efficacy of the Cool-Tip RF system (Covidien) to achieve larger ablations. The increased tissue hydration improved delivery of electrical energy to the tissues and delayed the process of desiccation, thus allowing the ablation process to continue for longer periods of time to produce larger ablations. BETA could be used to treat larger liver tumours more effectively than standard RFA.

Recent advances in high-intensity focused ultrasound, which was developed in the 1940s as a viable thermal tissue ablation approach, have increased its popularity. High-intensity focused ultrasound is currently utilized the most in Europe and Japan, but has not yet been approved by the Food and Drug Administration, USA, for this indication. The purpose of the present report is to review the scientific foundation of high-intensity focused ultrasound technology and the clinical outcomes achieved with commercially available devices. Recently published articles were reviewed to evaluate the current status of high-intensity focused ultrasound as a primary or salvage treatment option for localized prostate cancer. Improvements in the clinical outcome as a result of technical, imaging and technological advancements are described herein. A wide range of treatment options for organ-confined prostate cancer is available. However, high-intensity focused ultrasound is an attractive choice for men willing to choose less invasive options, although establishing the efficacy of high-intensity focused ultrasound requires longer follow-up periods. Technological advances, together with cultural and economic factors, have caused a dramatic shift from traditional open, radical prostatectomy to minimally invasive techniques. High-intensity focused ultrasound is likely to play a significant role in the future of oncology practice.

Anatomic, tissue ablation and coagulation, and histopathologic outcomes of the 150-W 980-nm diode laser selective light vaporization (SLV ) of the prostate in the first survival study of living canines were analyzed.

Auf der Grundlage des aktuellen Wissenstands zu den physikalischen Eigenschaften und den biologischen Wirkungen von Gewebekompatiblen Atmospharendruckplasmen (Tissue Tolerable Plasma, TTP) werden die Perspektiven der Plasmamedizin diskutiert. Fur folgende Moglichkeiten der medizinischen Anwendung von TTP werden derzeit die Grundlagen in interdisziplinarer Forschung erarbeitet: Pravention und/oder Therapie von Erkrankungen mit den Schwerpunkten chronische Wunden, infektiose Haut– und Schleimhauterkrankungen, lokalisierte Tumoren, Gewebeabtragung Hemmung und/oder Elimination von Biofilmen: Verhinderung der Biofilmentwicklung auf in den Menschen eingebrachte Materialien durch Oberflachenbehandlung und/oder plasmagesteuerte Auftragung antimikrobiell wirksamer Schichten mit der Funktion eines „Drug Delivery Systems” (Implantate, Kontaktlinse, Stents usw.) sowie Bekampfung von Biofilmen auf der Korperoberflache (chronische Wunde, Zahnoberflache, Prothese) Forderung der Penetration topisch applizierter Arzneimittel mit verbessertem Therapieergebnis Einsatz fur veterinarmedizinische Indikationen Verbesserte Reinigungsleistung im Aufbereitungsprozess von Medizinprodukten durch Oberflachenveranderung. Prospects of plasma medicine: Applications of Tissue Tolerable Plasmas (TTP) Based on the current knowledge on the physical properties and biological effects of tissue tolerable plasma (ttp) potential perspectives of plasma medicine are discussed. Currently, the foundations for the following medical applications of ttp are developed by an interdisciplinary research team: Prevention and/or treatment of diseases such as chronic wounds, skin and mucosal infectious diseases, localized tumors, promotion of angiogenesis, and tissue ablation Inhibition and/or elimination of biofilms by prevention of biofilm development due to surface treatment and/or plasma steered application of antimicrobial active layers with drug delivery function on foreign objects implanted into humans (implantable prosthesis, contact lenses, stents etc.) as well as elimination of biofilms by direct action of ttp on surfaces and tissues (chronic wounds, tooth surface, prosthesis) promotion of the incorporation of implants into viable tissue by changing the surface of materials (hydrophobicity) Promotion of penetration of topically applied drugs with therapeutic results Assessment of veterinary indications Improved cleaning performance in reprocessing of medical devices by surface modification.

Experimental evidence indicating the potential biomedical advantages of using a Mark-III Free-Electron Laser (FEL) for the ablation of soft tissue were first reported in 1994. Research progress since that time is reviewed, including: 1) successful human surgery using the Mark-III FEL; 2) advances in understanding the physical mechanism for infrared tissue ablation and how these mechanistic features correlate with the preferential ablative properties; 3) the pursuit of table-top, nanosecond-pulsed laser technology that mimics the preferential ablation properties of the Mark-III FEL with the aim of improving clinical acceptance of mid-infrared laser ablation of soft tissue; and 4) current research challenges.

Background: Bimodal electric tissue ablation is a novel variation to standard radiofrequency ablation that produces significantly larger ablations by the addition of a direct electrical current. The negative electrode is attached to the radiofrequency current and the positive electrode is placed nearby. It has been identified that an electrolytic injury can occur at the positive electrode site. It is suggested that by increasing the surface area that is in contact with the positive electrode, the risk of tissue injury is reduced. This hypothesis was tested in a pig model. Methods: Thirty-six ablations were carried out in the livers of six pigs (six ablations per pig). Two were standard radiofrequency ablation controls and two were carried out with positive electrode attached to a scalpel blade. Two were carried out with positive electrode attached to a grounding pad. After 48 h, liver was harvested and the ablation sizes were compared. Skin biopsies were taken from the scalpel site and one from the pad site and examined histopathologically. Results: The scalpel blade ablations were significantly larger than controls and the grounding pad ablations (P

Background The future of medicine is tied-up in robotics and lasers. We've heard the hype for years, but only in the last 10 years has it actually started to come to fruition that robotic systems are beginning to play a role in surgery. Methods Multiple groups have reported over the past 10 years on increasingly complex cardiac surgical procedures being performed with the aid of robotic systems. With an increasing percentage of atrial fibrillation and with insight that atrial fibrillation results in poor long-term survival, attempts have been made to create a surgical cure. Results Much work has been done in the past several years to develop a less-invasive surgical option than the standard cut-and-sew Maze to achieve pulmonary vein ablation. Laser is a unique energy source for tissue ablation because it is a form of light. Conclusion While traditional energy sources focus on applying heat-based elements to the tissue's surface allowing temperature to propagate across the thickness of the tissue laser is an innovative, tissue-specific energy for creating tissue ablation. Copyright © 2006 John Wiley & Sons, Ltd.

Objectives One of the major causes of chronic nasal airway obstruction is disease of the inferior turbinate. However, there is no agreement on how to deal with this problem. Comparison was made of the nasal functions after treatment by radiofrequency tissue ablation, laser ablation, and partial turbinectomy using subjective symptom scores and objective tests. Study Design Prospective, randomized clinical trial. Methods The study was conducted on three groups of 45 adult volunteer patients with symptoms and signs of nasal obstruction and stuffiness related to enlarged turbinates. In group A, laser ablation was applied to the inferior turbinate on one side and partial turbinectomy to the inferior turbinate on the other side. In group B, radiofrequency tissue ablation was applied to the inferior turbinate on one side and partial turbinectomy to the inferior turbinate on the other side. In group C, patients who were not treated by any surgical techniques were the control subjects. Clinical examinations, visual analogue scales, rhinomanometry, and isotopic study of nasal mucociliary transport time were used to assess treatment outcomes. Results At 12 weeks after surgery, the nasal mucociliary transport time results were compared in the same patients. The average time was 25.60 minutes on the side where laser ablation was applied and 11.40 minutes on the side where partial turbinectomy (PT) was applied. In the patients on whom radiofrequency tissue ablation and partial turbinectomy were applied, the average nasal mucociliary transport time was 10.33 minutes on the radiofrequency tissue ablation side, whereas it was 11.33 minutes on the partial turbinectomy side. Rhinomanometric measurements demonstrated a significant decrease in nasal resistances at 12 weeks in both sides in groups A and B. Conclusions In the study it was demonstrated that radiofrequency tissue ablation to the turbinate is effective in improving nasal obstruction objectively and in preserving nasal mucociliary function. Laser ablation of the turbinate is effective in improving the nasal obstruction; however, it disturbs the mucociliary function significantly. With the partial turbinectomy technique, results obtained were similar to the results with the radiofrequency tissue ablation technique.

The previous manuscript has the authors grouped by institution in the final paper, yielding an incorrect order of the authors (Luu, Niessen, vanWalsum, Klink, Moelker). The correct order is Ha Manh Luu, Camiel Klink,Wiro Niessen, Adriaan Moelker, Theo van Walsum.

Therapeutic ultrasound technology offers the ability to achieve non-invasive and non-ionizing treatments for soft-tissue disease throughout the body. The bio-effects in tissue caused by ultrasound energy can be thermal in nature (ranging from mild heating to tissue ablation) or can utilize the mechanical energy associated with acoustic waves. Ultrasound energy can be delivered from external devices and focused to a region of a few millimeters in the body. It can also be delivered from body cavities or from devices inserted directly into tissue. One challenge with designing therapeutic ultrasound systems is the need to consider wave propagation and distortion as energy passes through tissues. Consequently, therapeutic ultrasound systems are usually designed to target specific anatomic sites to optimize the delivery of ultrasound to these locations. In this session a number of advanced therapeutic ultrasound delivery systems will be described for the treatment of breast, brain, and prostate tissue. In addition the talks will describe both thermal and non-thermal applications of ultrasound energy. Specific topics addressed in this symposium include: (1) Advances in Focused Ultrasound Brain Therapies, (2) Breast MR guided Focused Ultrasound Hardware Design and Treatment Strategies, (3) The Role of Pulsed Focused Ultrasound in Cancer Therapy, and (4) Sonication and Feedback Control Strategies for MR guided Hyperthermia with the Insightec Prostate Array. Learning Objectives: 1. Understand the technical issues important in the design of therapeutic ultrasound systems 2. Learn about therapeutic ultrasound systems under development for brain, breast and prostate applications 3. Learn about different treatment approaches with therapeutic ultrasound including tissue ablation, hyperthermia, and drug delivery Lili Chen: Funding: FUS Foundation, DOD (PC073127,BC102806) Allison Payne: Funding: NIH (R01EB013433,R01CA178727) Vasant Salgaonkar: Funding: FUS Foundation, NIH (R01CA122276, R01CA111981)

Therapeutic ultrasound technology offers the ability to achieve non-invasive and non-ionizing treatments for soft-tissue disease throughout the body. The bio-effects in tissue caused by ultrasound energy can be thermal in nature (ranging from mild heating to tissue ablation) or can utilize the mechanical energy associated with acoustic waves. Ultrasound energy can be delivered from external devices and focused to a region of a few millimeters in the body. It can also be delivered from body cavities or from devices inserted directly into tissue. One challenge with designing therapeutic ultrasound systems is the need to consider wave propagation and distortion as energy passes through tissues. Consequently, therapeutic ultrasound systems are usually designed to target specific anatomic sites to optimize the delivery of ultrasound to these locations. In this session a number of advanced therapeutic ultrasound delivery systems will be described for the treatment of breast, brain, and prostate tissue. In addition the talks will describe both thermal and non-thermal applications of ultrasound energy. Specific topics addressed in this symposium include: (1) Advances in Focused Ultrasound Brain Therapies, (2) Breast MR guided Focused Ultrasound Hardware Design and Treatment Strategies, (3) The Role of Pulsed Focused Ultrasound in Cancer Therapy, and (4) Sonication and Feedback Control Strategies for MR guided Hyperthermia with the Insightec Prostate Array. Learning Objectives: 1. Understand the technical issues important in the design of therapeutic ultrasound systems 2. Learn about therapeutic ultrasound systems under development for brain, breast and prostate applications 3. Learn about different treatment approaches with therapeutic ultrasound including tissue ablation, hyperthermia, and drug delivery Lili Chen: Funding: FUS Foundation, DOD (PC073127,BC102806) Allison Payne: Funding: NIH (R01EB013433,R01CA178727) Vasant Salgaonkar: Funding: FUS Foundation, NIH (R01CA122276, R01CA111981)

Therapeutic ultrasound technology offers the ability to achieve non-invasive and non-ionizing treatments for soft-tissue disease throughout the body. The bio-effects in tissue caused by ultrasound energy can be thermal in nature (ranging from mild heating to tissue ablation) or can utilize the mechanical energy associated with acoustic waves. Ultrasound energy can be delivered from external devices and focused to a region of a few millimeters in the body. It can also be delivered from body cavities or from devices inserted directly into tissue. One challenge with designing therapeutic ultrasound systems is the need to consider wave propagation and distortion as energy passes through tissues. Consequently, therapeutic ultrasound systems are usually designed to target specific anatomic sites to optimize the delivery of ultrasound to these locations. In this session a number of advanced therapeutic ultrasound delivery systems will be described for the treatment of breast, brain, and prostate tissue. In addition the talks will describe both thermal and non-thermal applications of ultrasound energy. Specific topics addressed in this symposium include: (1) Advances in Focused Ultrasound Brain Therapies, (2) Breast MR guided Focused Ultrasound Hardware Design and Treatment Strategies, (3) The Role of Pulsed Focused Ultrasound in Cancer Therapy, and (4) Sonication and Feedback Control Strategies for MR guided Hyperthermia with the Insightec Prostate Array. Learning Objectives: 1. Understand the technical issues important in the design of therapeutic ultrasound systems 2. Learn about therapeutic ultrasound systems under development for brain, breast and prostate applications 3. Learn about different treatment approaches with therapeutic ultrasound including tissue ablation, hyperthermia, and drug delivery Lili Chen: Funding: FUS Foundation, DOD (PC073127,BC102806) Allison Payne: Funding: NIH (R01EB013433,R01CA178727) Vasant Salgaonkar: Funding: FUS Foundation, NIH (R01CA122276, R01CA111981)

Therapeutic ultrasound technology offers the ability to achieve non-invasive and non-ionizing treatments for soft-tissue disease throughout the body. The bio-effects in tissue caused by ultrasound energy can be thermal in nature (ranging from mild heating to tissue ablation) or can utilize the mechanical energy associated with acoustic waves. Ultrasound energy can be delivered from external devices and focused to a region of a few millimeters in the body. It can also be delivered from body cavities or from devices inserted directly into tissue. One challenge with designing therapeutic ultrasound systems is the need to consider wave propagation and distortion as energy passes through tissues. Consequently, therapeutic ultrasound systems are usually designed to target specific anatomic sites to optimize the delivery of ultrasound to these locations. In this session a number of advanced therapeutic ultrasound delivery systems will be described for the treatment of breast, brain, and prostate tissue. In addition the talks will describe both thermal and non-thermal applications of ultrasound energy. Specific topics addressed in this symposium include: (1) Advances in Focused Ultrasound Brain Therapies, (2) Breast MR guided Focused Ultrasound Hardware Design and Treatment Strategies, (3) The Role of Pulsed Focused Ultrasound in Cancer Therapy, and (4) Sonication and Feedback Control Strategies for MR guided Hyperthermia with the Insightec Prostate Array. Learning Objectives: 1. Understand the technical issues important in the design of therapeutic ultrasound systems 2. Learn about therapeutic ultrasound systems under development for brain, breast and prostate applications 3. Learn about different treatment approaches with therapeutic ultrasound including tissue ablation, hyperthermia, and drug delivery Lili Chen: Funding: FUS Foundation, DOD (PC073127,BC102806) Allison Payne: Funding: NIH (R01EB013433,R01CA178727) Vasant Salgaonkar: Funding: FUS Foundation, NIH (R01CA122276, R01CA111981)

Therapeutic ultrasound technology offers the ability to achieve non-invasive and non-ionizing treatments for soft-tissue disease throughout the body. The bio-effects in tissue caused by ultrasound energy can be thermal in nature (ranging from mild heating to tissue ablation) or can utilize the mechanical energy associated with acoustic waves. Ultrasound energy can be delivered from external devices and focused to a region of a few millimeters in the body. It can also be delivered from body cavities or from devices inserted directly into tissue. One challenge with designing therapeutic ultrasound systems is the need to consider wave propagation and distortion as energy passes through tissues. Consequently, therapeutic ultrasound systems are usually designed to target specific anatomic sites to optimize the delivery of ultrasound to these locations. In this session a number of advanced therapeutic ultrasound delivery systems will be described for the treatment of breast, brain, and prostate tissue. In addition the talks will describe both thermal and non-thermal applications of ultrasound energy. Specific topics addressed in this symposium include: (1) Advances in Focused Ultrasound Brain Therapies, (2) Breast MR guided Focused Ultrasound Hardware Design and Treatment Strategies, (3) The Role of Pulsed Focused Ultrasound in Cancer Therapy, and (4) Sonication and Feedback Control Strategies for MR guided Hyperthermia with the Insightec Prostate Array. Learning Objectives: 1. Understand the technical issues important in the design of therapeutic ultrasound systems 2. Learn about therapeutic ultrasound systems under development for brain, breast and prostate applications 3. Learn about different treatment approaches with therapeutic ultrasound including tissue ablation, hyperthermia, and drug delivery Lili Chen: Funding: FUS Foundation, DOD (PC073127,BC102806) Allison Payne: Funding: NIH (R01EB013433,R01CA178727) Vasant Salgaonkar: Funding: FUS Foundation, NIH (R01CA122276, R01CA111981)

Purpose: The objective of this work was to compare the basic physical characteristics of transmission, penumbra and Tongue & Groove of the Special Multi‐leaf Collimator (MLC) 160 MLC, SIMENS Manufactured and HighDefinition120 (HD120), VARIAN Manufactured. Methods: Under the conditions of 6 MV, SCD 100 cm, D‐Max (1.5 cm), transmission and penumbra were measured with 3D water phantom, RFA 300, dosimeter of ionization, CC13‐S and Silicon photodiode detector, Type SFD. Leaf transmission was measured in the direction of the in‐line and all leaves closed. End leaf transmission was measured in the direction of the cross‐line and the part of all leaves closed was moved every 5cm in right and left. Penumbra was measured in the direction of the cross‐line, and 10cm*10cm field was moved every 5cm in right and left. Tongue & Groove was measured with film, EDR2. Results: The average of Transmission of 160 MLC, SIEMENS was 0.42%, HD120, VARIAN was 1.6%. The average of End Leaf Transmission of 160 MLC, SIEMENS was 12.2%, HD 120, VARIAN was 26.0%. Penumbra at center of 160MLC, SIEMENS was 5.7mm, HD 120, SIEMENS was 5.5mm. Maximum of Penumbra of 160MLC, SIEMENS was 6.8mm, HD 120, VARIAN was 6.2mm. The effect of Tongue & Groove of 160 MLC, SIEMENS was about 18.0%, HD 120, VARIAN was about 20.0%. Conclusion: The difference was not found in Penumbra between 160MLC, SIEMENS and HD120, VARIAN. However, in Transmission and the effect of Tongue & Groove, 160MLC, SIEMENS was lower than HD120, VARIAN. These are depend on the effect of multiple‐curved tip shape, high leaf and slant placement of leaves.

Image guidance of focused ultrasound therapy is important for targeting the therapy, ensuring treatment and safety, and for assessing the therapy. This presentation will describe recent advances in these areas of the MR guidance of focused ultrasound. Accurate focusing of the ultrasound beam to the target tissue can be done with a low temperature rise “test shot.” Alternatively, imaging the acoustic radiation force allows visualization of the focal spot without a temperature rise. MR imaging of the acoustic radiation force displacement (MR‐ARFI) relies on the application of the ultrasound during a portion of a series of gradient lobes. In areas where the tissue is displaced, the water spins experience a different magnetic field and accumulate phase, which is not fully refocused at the time of signal measurement. The visualization of the focal spot can thus be achieved without a temperature rise. In addition to straightforward visualization of the focal spot, MR‐ARFI can provide a means for image feedback when correcting phase aberrations from the skull. An iterative method allows modification of transducer phases while maximizing the displacement at the focus. A non‐iterative method requires the MR‐ARFI measurements to be made, followed by a matrix inversion. For tissue ablation, MR thermometry can be used to accurately monitor tissue temperature. MR thermometry can be very sensitive to motion, including motion of the treated tissue or even motion of tissue in the vicinity of the treated tissue (such as due to respiration). Temperatureimaging methods must be robust to these types of motions and solutions include multibaseline, referenceless, and hybrid multibaseline/referenceless approaches. Another important task for MR guidance is in beam steering in moving organs, such as the liver and kidneys.This can be done based on imaging alone or on a combination of imaging and respiratory phase monitoring, such as can be done with the bellows. Lastly, there are a number of methods under investigation for the visualization of ablated tissue. MR‐ARFI is a potential candidate. The acoustic radiation force displacement depends both on the ultrasound intensity and on the displacement of the tissue, which in the latter case ARFI relies on tissue displacement by the ultrasound beam, which is related to the tissue stiffness. Evaluating the change in tissue stiffness provides the spatial extent of the thermal ablation. Other evaluative imaging methods includes contrast enhanced MRI, which visualizes disruption of perfusion, and diffusion‐weighted MRI, which demonstrates a 36% decrease in ADC in the ablated tissue. Learning Objectives 1. Understand the basis for acoustic radiation force imaging and its applications 2. Understand the current research in the image guidance of focused ultrasound

Minimally invasive thermal therapies deliver heat to tissue in a controlled manner in order to modulate a host of microscopic and macroscopic events in tissue. Irreversible tissue damage from heating is a cumulative process that depends on exposure time as well as temperature and is often an endpoint for thermal therapies, particularly thermal ablation.Models for predicting the extent of damage after exposure to heat have been implemented and investigated in cells and tissue. With respect to rapid, high temperature ablations, the most often used approaches include simple temperature threshold models, Arrhenius rate models, and cumulative equivalent minutes at 43°C (CEM 43°C). While displaying significantly different responses at lower temperatures or long exposure times, these approaches are more closely related at higher temperatures. In cases where the ability to visualize the spatiotemporal distribution of heat and resulting damage is realizable, comparisons between these models are possible and useful for comparing with results from imaging and/or pathology correlates. Here we provide a review of the different models for high‐temperature ablations and use magnetic resonance temperature imaging results of thermal ablations, compared to with post‐treatment imaging or histology to illustrate some of the differences between these models when used for predicting outcomes in thermal therapy. Implications for therapy monitoring and guidance are discussed as are future prospects for predicting iso‐effects other than tissue destruction in tissue. Educational Objectives: 1. Learn basic concepts of thermal dosimetry 2. Understand current usage and potential limitations of applying current models

The SonoKnife is a new line‐focused ultrasound device concept for non‐invasive thermal ablation. The concept was motivated by the poor outcome in the treatment of advanced HNSCC recurrences and positive lymph nodes comprising a high‐risk patient population. It is hypothesized that by incorporating thermal ablation, the need for further surgery may be reduced or circumvented while enhancing the therapeutic benefits of additional conventional therapies (i.e., radiotherapy and/or chemotherapy), when indicated. The basic SonoKnife applicator is a cylindrical section ultrasonic transducer (single element or array). Line‐focusing may have advantages over the more common point‐focusing HIFU approach. In particular, a line‐focused radiator will produce lower peak acoustic intensities in tissues when compared to an equivalent area spherically focused radiator, thereby minimizing nonlinear propagation and cavitation effects. Another advantage may be the faster ablation of large tumors by scanning a line‐focus rather than a “point”‐focus. Moreover, an array can be used to vary the length of the acoustic edge in real time. Numerical simulations were performed to characterize the acoustic edge and optimize basic design parameters: size, f‐number, frequency, depth of line‐focus, and thickness of coupling bolus. Pressure fields were computed using FOCUS (Fast Object‐oriented C++ Ultrasound Simulator), an open‐source software package for numerical modeling of ultrasonics for therapy and imaging. The angular spectrum method was also incorporated to speed up the calculations of 3D pressure fields. These acoustic propagation models are to be integrated with thermal models into an image‐basedtreatment planning system. The shape, volume (dimensions) and depth of the acoustic edge as a function of basic design parameters were obtained. The minimum radiating area to guarantee sufficient energy for thermal ablation was determined for several transducers for a clinical range of tumor sizes and depths. Spatial peak intensities were compared to spherically focused transducers of equivalent radiating area. Based on preliminary simulations the first prototype is being developed for laboratory measurements. In conclusion, the FOCUS simulation package was found to be an effective and efficient tool for the characterization of the SonoKnife. Simulations showed feasibility for thermal ablation with the SonoKnife in terms of energy requirements. Peak intensities were lower for the SonoKnife than for equivalent radiating area spherically curved radiators, as expected. For a more comprehensive characterization, tissue heterogeneities and nonlinear effects must be taken into account and thermal simulation studies need to be performed. Finally, the design of a clinical‐grade system must incorporate precise image‐guidance, which represents a formidable challenge. Learning Objectives: 1. Learn about the new SonoKnife concept and its potential advantages relative to spherically focused HIFU radiators for advanced recurrent cancer in the head and neck. 2. Understand the main design parameters and their effect on the acoustic edge from numerical simulation results. 3. Learn about the main components necessary for a clinical practicable treatment planning system. 4. Gain practical understanding from the first SonoKnife applicator prototype and initial laboratory measurement results. 5. Appreciate the need for real‐time image‐guidance necessary for clinical deployment of a SonoKnife system and its potential combination with IG‐IMRT/STRS. This R&D is funded by a grant from the NCI (RC1 CA147697). We gratefully acknowledge support by the Central Arkansas Radiation Therapy Institute (CARTI).

Purpose: To determine if there is a difference in dose‐area‐product (DAP) or fluoroscopy time between electrophysiology (EP) procedures performed using a mobile and a fixed C‐arm fluoroscopic unit. Method and Materials: DAP and fluoroscopy‐time data was logged for 800 EP procedures performed using a mobile C‐arm unit from 2003 to 2005. In early 2006, a fixed C‐arm unit was installed and the same data logged for over 200 procedures. The procedures were sorted into five categories: 1. electrophysiology studies, 2. radiofrequency ablations, 3. pacemaker and implantable‐cardiac‐defibrillator implants, 4. biventricular interventions, and 5. lead changes. For each category, the distributions of DAP and time were compared and the average, median and range of values determined. Results: The median fluoroscopy time more than doubled for all procedure categories when using the fixed unit. Median DAP increased significantly for procedures 3 and 4, but remained nearly the same for procedures 1, 2 and 5. In all cases, the procedures were successfully completed without evidence of compromising patient care for either unit. However, the cardiologists were much more conservative in their use of fluoroscopy for the mobile unit due to its heat loading limitations and, also, they worked quicker because of their impression that the older mobile C‐arm gave more radiation dose to themselves and the patient. In addition, fluoroscopy at 15 frames per second was used on the fixed unit versus 7 frames per second on the mobile unit. Conclusion: Although the DAP and fluoroscopy time generally was higher for the fixed installation, it should not be concluded that the mobile unit is to be preferred. Rather, these results point out the importance of physician training and dose monitoring, not only to track patient radiation risk, but also to provide physician feedback. (*Support: NIH Grant R01‐NS43924).

HIFU has long been known to offer the potential of very precise “Trackless lesioning” but has only recently with the current high quality methods of medical imaging, become a practical possibility for clinical treatment. Focused ultrasound uses ultrasound energy for tissue ablation. When the sound waves are focused to a small volume in the body, the intensity is high and the temperature at the focal point rises to 70–95°C, high enough to ablate the tissue. Proper treatment design will ensure that the energy density will be high at the focal point but low at other locations, and thus avoiding damages to nearby normal tissues. The volume of ablation (lesion) following a single HIFU exposure is small and will vary according to transducer characteristics, but it is typically cigar shaped with dimensions in the order of 1–3 mm (transverse) × 8–15 mm (along the beam axis). To ablate clinically relevant volumes these lesions must be placed side by side systematically to “paint out” the target tumor. Simply calculating an optimal treatment plan is not enough to ensure optimal outcome. Patient anatomic variability and tissue inhomogeneities have been shown to produce vastly different responses to thermal energy deposition, especially deep in the body. High quality imaging techniques can provide precise visualization and localization of the tissue damage. MR images enable the physician to localize the tumor and plan the treatment in the full 3 dimensions. Real‐time MR thermometry can provide an indication of tissue damage if critical temperatures are known. In several centers worldwide, HIFU is now being used clinically to treatment solid tumors (both malignant and benign), including those of the brain, breast, liver, kidney, prostate, bone matastases, pancreas and soft‐tissue sarcoma. The MRgFUS unit is currently available for clinical applications. This lecture will provide an overview of MrgFU and introduce the equipment that is commercially available for clinical applications in cancer treatment. Educational Objectives: 1. The principles of MRgFUS. 2. Advantages and limitations of MRgFUS for tissue ablation. 3. Potential clinical applications of MRgFUS for cancer treatment.

Ultrasound has long been known to cause tissue heating when applied in high intensities. More recently, interest has arisen in the area of High Intensity Focused Ultrasound (HIFU) for localized tissue heating effects, specifically thermal ablation. HIFU is being introduced into clinical settings for localized tissue ablation guided by MRI. All present techniques employ focused traveling high intensity acoustic waves to create a region of elevated temperature, which causes cell death. Such high intensity traveling waves can be damaging to normal tissue in the vicinity of the focal region, and have demonstrated surface burns and caused patient discomfort in certain clinical trials. The focal region is also difficult to determine due to divergence of the beam and elongation of the focus along the direction of propagation. Use of lower intensity ultrasound can minimize the side‐effects presented by HIFU. This paper demonstrates the use of multiple low intensity focused ultrasound beams resulting in stationary acoustic fields which are capable of heating a very small and more precisely located region of tissue. The intensity of the individual ultrasound beams is within FDA diagnostic ultrasound limits (0.720 W/cm2). Temperature elevation that would cause cell death was achieved in tissue‐mimicking phantoms after short exposures to the acoustic field in the region of beam overlap. The technique was tested with excised turkey breast samples. Temperature increases of 30 C above ambient (37 C) were observed after sonication times of 30 seconds. The size of the tissue ablation was a quasi‐sphere of diameter = 1 cm.

Purpose Radiofrequency ablation (RFA) is a popular method of treating unresectable liver tumours by the use of a high-frequency, alternating electrical current that heats and destroys tumour cells. The size of the ablation produced is limited by localised charring of adjacent tissue that prevents further conduction of the radiofrequency current. To overcome this problem, a Bi-modal Electric Tissue Ablation (BETA) circuit has been created that adds a direct electrical current to a radiofrequency current. Direct currents attract water to the cathode in biological tissues and this phenomenon is utilised in an effort to prevent tissue charring. The BETA circuit was tested in a pig model. Methods 2 studies have been performed with this new circuit, one to compare sizes of the ablation produced between standard RFA and the BETA circuit. This was followed by a long-term study to assess associated changes to liver function and pathological changes within the liver. Results Ablations with significantly larger diameters are created with the BETA circuit (49.6 mm +/− SE 3.46 vs 27.78 mm +/− SE 3.37, p

This article reviews Brachytherapy Physics, Second Edition. Proceedings of the Joint AAPM/American Brachytherapy Society Summer School. (AAPM Monograph No. 31) by Bruce R. Thomadsen, Mark J. Rivard, Wayne M. Butler , Madison, WI, 965 pp. Price $175 ($140 for AAPM members).

Image guided therapy is based on the concept that knowledge of the location and orientation of a therapeutic process will allow for more specific therapy. That is, more of the therapeutic process can be applied directly to the volume of interest with reduced exposure of normal tissue to that process. This is true whether one considers surgery, ablation, radiation, gene therapy, chemo‐ therapy or implantation as you therapeutic process. Each application requires a multi‐dimensional assessment of location, orientation, temporal and functional constraints so that the proper techniques can be developed, tested and validated. It is the latter that represents the greatest ongoing challenge.

The use of ultrasound in medicine is now quite commonplace, especially with the recent introduction of small, portable and relatively inexpensive, hand-held diagnostic imaging devices. Moreover, ultrasound has expanded beyond the imaging realm, with methods and applications extending to novel therapeutic and surgical uses. These applications broadly include: Tissue ablation, acoustocautery, lipoplasty, site-specific and ultrasound mediated drug activity, extracorporeal lithotripsy, and the enhancement of natural physiological functions such as wound healing and tissue regeneration. A particularly attractive aspect of this technology is that diagnostic and therapeutic systems can be combined to produce totally non-invasive, image-guided therapy. This general lecture will review a number of these exciting new applications of ultrasound and address some of the basic scientific questions and future challenges in developing these methods and technologies for general use in our society. We shall particularly emphasize the use of High Intensity Focused Ultrasound (HIFU) in the treatment of benign and malignant tumors as well as the introduction of acoustic hemostasis, especially in organs which are difficult to treat using conventional medical and surgical techniques. [Supported in part by the NIH and the US Army]

New techniques were proposed for reducing the damage incurred to living tissues owing to temperature rise induced by surgical lasers. Precooling of the tissue and spatial filtering were evaluated numerically and were shown to be most effective in most surgical procedures. Application of pulse trains was also evaluated numerically and optimal operating conditions were identified.