Resonant Cavity Applicator Research Articles

Effective transmittance of Fabry–Perot cavity under non-parallel beam incidence

The Fabry–Pérot (FP) resonant cavity is widely used in laser and spectroscopic measurements due to its unique interference transfer function (ITF). In the ideal case of parallel incident light, the ITF of the FP resonant cavity can be expressed by the Airy function. However, in reality, it is difficult to achieve perfect parallelism with collimated beams. In this article, a theoretical model is established for non-parallel light incidence, which assumes that the non-parallel incident light is a cone-shaped beam, and the cone angle is used to quantify the non-parallelism of the beam. The transmittance function of the FP resonant cavity under non-parallel light incidence is derived. The accuracy of the model is experimentally verified. Based on this model, the effects of divergence angle, tilt angle and FP cavity parameters (reflectivity, cavity length) on the ITF are studied. The reasons for the decrease in peak value, broadening and asymmetry of the interference peak under non-parallel light incidence are explained. It is suggested that a fine balance between the interference peak and the collimation effect of the incident light should be considered in the design and application of FP resonant cavities, especially for tilted applications such as angle-scanned spectroscopy. The research results of this article have certain significance for the design and application of FP resonant cavities.

Heating Characteristics of Small Rectangular Resonant Cavity Applicator with Non-invasive Temperature Measurement Function

Heating Characteristics of Small Rectangular Resonant Cavity Applicator with Non-invasive Temperature Measurement Function

Heating Characteristics of Prototype Knee Rehabilitation System Using Rectangular Resonant Cavity Applicator

Heating Characteristics of Prototype Knee Rehabilitation System Using Rectangular Resonant Cavity Applicator

Temperature Distribution of Resonant Cavity Applicator for Thermal Rehabilitation Using 3D Printing

Osteoarthritis (OA) is one of the most common joint diseases. Thermotherapy, such as that using a microwave diathermy applicator, is widely used for OA. The deep tissue of a knee joint should be heated to 36 ℃-38 ℃ for an effective thermotherapy. However, heating this deep region using a microwave diathermy applicator is challenging. Previously, we proposed a resonant cavity applicator to overcome these problems and confirmed its ability (heating experiments on bovine knees) to heat the deep region of a knee joint without physical contact. Furthermore, we proposed a method of temperature measurement using ultrasound images. In this method, the temperature distribution was measured using noninvasive image analysis. In a previous study, we found temperature measurement accuracy of ≤ 1.0 ℃. In the present paper, we describe a temperature distribution using a 3D-printed knee model for treating OA. First, we created a 3D finite element model (FEM) of the knee and a 3D-printed knee model from 2D medical images. Second, we calculated temperature distributions in the FEM model and performed a heating experiment with a prototype of the heating system. Third, we performed positioning accuracy experiments to investigate the accuracy of our temperature measurement system comprising a robotic arm, 3D-printed knee model, and ultrasound diagnostics. Finally, we measured the temperature distribution inside the 3D-printed knee model from ultrasound images. The heating experiments confirmed that our proposed method could heat deep regions of a knee joint without any undesirable hotspot. Therefore, our results suggest that this method is useful for effective thermotherapy of OA.

Application of nonlinear resonant cavities in realizing a fast optical comparator

Application of nonlinear resonant cavities in realizing a fast optical comparator

Efficacy of a Deep Thermal Therapy System for Osteoarthritis of the Knee

This study sought to assess the efficacy of a deep-tissue thermal therapy system with a resonant cavity applicator (DTT-RCA), which safely heats deep joint tissue for treating osteoarthritis (OA) of the knee. Two groups of participants were recruited. The DTT-RCA group comprised 20 knees. Kellgren-Lawrence (K-L) grade was I and II in 8 knees (DTT-RCA I/II group) [mean age 73.3 years (standard deviation 11.4) ], III and VI in 12 knees (DTT-RCA III/IV group) [75.4 (8.6) years]. The control group comprised 13 knees [68.2 (10.8) years]. K-L grade was I in 7 knees and II in 6 knees. This group received exercise therapy. The DTT-RCA I/II group and the control group were imaged by MRI T2 mapping at baseline and 6 months to determine the area of cartilage degeneration. Visual Analogue Scale improved only in the DTT-RCA I/II post-intervention (p < 0.01). Japanese Orthopedic Association knee rating scores (DTT-RCA I/II: p < 0.01, control group: p < 0.01), the Japanese Knee Osteoarthritis Measure (DTT-RCA I/II: p < 0.05, control: p < 0.01), and the Knee injury and Osteoarthritis Outcome Score (DTT-RCA I/II: p < 0.01, DTT-RCA III/IV: p < 0.05, control: p < 0.01) post-intervention. The magnitude of change did not differ significantly between the three groups. The area of cartilage degeneration did not change significantly post-intervention in the DTT-RCA I/II group, not even relative to the control group. This was the first study to test a DTT-RCA system in patients with knee OA. The system reduced the clinical symptoms of knee OA and could potentially be effective for conservative therapy.

Deep heat therapy system with resonant cavity applicator for articular cartilage in knee osteoarthritis

[Purpose] Heat can prevent cartilage degeneration when applied to articular cartilage, but the size of the human knee joint makes it difficult to target cartilage during heat treatment. In this study, we aimed to establish a heat therapy method capable of safely applying heat to deep intra-articular tissues utilizing a resonant cavity applicator and to confirm the extent of cartilage heating in the human knee when using this system. [Participants and Methods] Heating experiments were carried out on the knees of healthy three volunteers using a resonant cavity applicator and a microwave diathermy system. After heat application, temperature distributions inside the knee were measured noninvasively using our measurement method based on ultrasound imaging techniques. [Results] We observed an increase in the temperature around the cartilage tissue in the knees of the volunteers using an ultrasonic thermometer; there was no increase in temperature in the overlying layers. During heating with up to 20 W of power, none of the volunteers experienced adverse reactions. [Conclusion] This study indicates the potential safety and effectiveness of the resonant cavity heat therapy system for knee osteoarthritis in a clinical setting.

Quarter mode rectangular cavity-based perfect metamaterial absorber in the terahertz region

In this work, we present the analysis and design of a perfect metamaterial absorber (MA) based on quarter mode rectangular cavity in the terahertz region. This structure is consisted of a metal plate where three different size quarter mode rectangular cavities are vertically placed on. Based on rectangular-cavity-theory, a formula is proposed to calculate the resonant frequency, which provides a guidance for designing MAs of such type. In terms of normal incidence, the simulated results show that the MA has three resonance points on 4.1301 THz, 4.6051 THz and 5.1088 THz, respectively, which is in good agreement with the calculated results. Furthermore, we present the distribution of E-field in the cavity and use the standing wave theory to explain the physical mechanism of the perfect absorption. These results verify the application of resonant cavities in the field of MA.

Permittivity Spectrum of Low-Loss Liquid and Powder Geomaterials Using Multipoint Reentrant Cavities

Permittivity is a useful tool to characterize the composition and quality of many geomaterials. In general, the non-resonant permittivity measurement methods exhibit a higher degree of uncertainty than their resonant counterparts. In resonant measurements, the reduction in uncertainty comes typically with a loss in broadband. This article describes the theory, design, and application of multipoint coaxial reentrant resonant cavities applied to low-loss geomaterials at different temperatures. Specifically, a full-wave method based on circuit analysis is developed and applied for a circular corrugated waveguide. Moreover, the mode-matching method is applied to calculate the generalized admittance matrix (GAM). Two multipoint cavities and software were built and validated. The first cavity has five resonant frequencies, between 170 MHz and 2.3 GHz, and the second has four resonant frequencies, between 1.3 and 8.6 GHz. Thus, this method allows for “broadband-resonant” measurements. The permittivity values of liquid hydrocarbons, powdered kerogen, and pyrite are shown.

Perfect metamaterial absorber based on the circular or elliptical cavity with one side open in the terahertz region

ABSTRACT In this work, we present the analysis and design of a perfect metamaterial absorber (MA) based on the circular cavity with one side open in the terahertz region. This structure consists of a metal plate where one circular cavity with one side open is vertically placed on. Based on the circular-cavity-theory, a formula can be used to calculate the resonant frequency. In terms of normal incidence, the simulated results show that the MA has one resonance point on 6.674 THz, which is consistent with the calculated results. What’s more, we present the distribution of E-field, surface current distribution and power loss density distribution in the cavity, and use the standing wave theory and electric dipole to prove the physical mechanism of the perfect absorption. Finally, an MA based on elliptical cavity with one side open is also studied. These results verify the application of resonant cavities in the field of MA.

Validation of Noninvasive Ultrasound Temperature Measurement System Through Experiments Using Resonant Cavity Applicator.

We developed a resonant cavity applicator for noninvasive deep hyperthermia treatment of osteoarthritis. In previous studies, we confirmed its viability by heating agar phantoms and conducting computer simulations. To evaluate the heating performance of this system on human subjects, it is necessary to develop a new noninvasive temperature measurement system. In this study, we developed a new temperature measurement system utilizing ultrasound imaging techniques. After heating an agar phantom with our resonant cavity applicator, temperature measurements from both our custom-made noninvasive ultrasonic thermometer and an optical fiber thermometer were collected and compared. Both temperature distributions showed a reliable trend, with heat energy concentrated at the center of the agar phantom. Average error rates were less than 13% for temperatures. The results of this study describe the viability of the temperature measurement system and the resonant cavity applicator for clinical applications.

Heating Characteristics of Developed Rectangular Resonant Cavity Applicator for Non-contact Hyperthermia Treatments

Heating Characteristics of Developed Rectangular Resonant Cavity Applicator for Non-contact Hyperthermia Treatments

Application of nonlinear PhC-based resonant cavities for realizing all optical Galois Filed adder

Galois Filed adders can play crucial roles in cryptography and coding. A typical 4th order Galois Filed adder can be realized by parallel combination of 4 XOR gates. In this paper we proposed a novel structure for realizing 4th order all optical Galois Field adder using nonlinear resonant cavities. The nonlinear resonant cavities were created by adding some nonlinear defects inside a 2D photonic crystal structure. The final structure can add two 4-bit symbols according to Galois Field rules. Maximum delay time and total footprint of the proposed structure are 12 ps and 625 μ m2 respectively.

Evaluation of Deep Thermal Rehabilitation System Using Resonant Cavity Applicator During Knee Experiments.

This paper evaluates experiments on the knee using a new heating rehabilitation system. For effective thermal rehabilitation of osteoarthritis, it is necessary to heat the deep tissue inside the knee joint. Our new rehabilitation system is based on the re-entrant type resonant cavity applicator which was developed for deep hyperthermia treatment in our previous studies. Our experimental results using agar phantoms showed our heating system is able to heat the deep tissue inside the knee without physically contacting the surface skin. In this study, we developed a prototype applicator and experimented on a healthy human subject's knee under clinical conditions. To evaluate heating performance, we conducted heating experiments with our resonant cavity applicator and a conventional microwave diathermy system and compared the results. The experimental results of temperature increase distributions inside the human body were estimated by ultrasound imaging techniques. The estimated results from our knee experiments show that our heating system is able to heat knee tissue more deeply than microwave diathermy systems can and thus would be effective for deep thermal rehabilitation applications in clinics.

Generation of Microwave Capillary Argon Plasmas at Atmospheric Pressure

A technique has been developed to generate stable Ar plasmas at atmospheric pressure inside of a quartz capillary tube. The microwave plasma in the capillary tube is produced by utilizing a single mode resonant circular cavity applicator with 2.45 GHz frequency excitation. The plasma can be confined or fully exposed outside the cavity as plasma jets depending on the operating conditions. The profile of the plasma front has been characterized as a conical tip or split branching jet plume. The measured discharge length and the power density of the plasma range from 6 to 10 cm and 35 to 75 W $\cdot $ cm $^{-3}$ , respectively. Addition of CH4 into the Ar plasma results in an increase in the abundances of excited CN and C2 carbon radicals and a concomitant decrease in the intensity of the Ar emission.

超音波ガイド機能を有する空胴共振器加温システムの開発

本論文は, 超音波ガイドによる非侵襲温度計測機能を有する非接触型空胴共振器加温システムついて述べている. 著者等はこれまで, 非接触型ハイパーサーミア加温装置である空胴共振器加温装置を提案してきた. この加温装置は, 非接触状態において深部局所加温を行える可能性を有しており, また, ホットスポットの発生位置の制御が可能な加温装置である. 臨床応用を考えた場合, 効果的かつ安全なハイパーサーミア治療には, ターゲットの位置および大きさ, さらには生体内の温度分布をリアルタイム的に把握することが不可欠である. このような背景から, 本論文では, 超音波画像診断装置をガイドに応用した, 非侵襲温度計測機能の可能性を有する空胴共振器加温システムを提案している. ここでは, まず, 温度管理された水槽中に寒天ファントムを沈め, 寒天ファントムの超音波画像を撮像することによって, 温度上昇と超音波画像の変化との関係を検討した. 次に, 試作加温システムによる加温実験を行い, 加温実験直後の寒天ファントム内部の温度分布を超音波画像から計測し, 超音波画像診断装置によってホットスポットの大きさ, および加温位置を把握できる可能性のあることを示した. 以上の結果から, 超音波画像診断装置による非侵襲温度分布計測の有用性について明らかにした.

20713 腹部腫瘍の有効加温を目的とした改良型空洞共振器アプリケータの温度分布解析

20713 腹部腫瘍の有効加温を目的とした改良型空洞共振器アプリケータの温度分布解析

効果的な脳腫瘍ハイパーサーミアを目的とした空胴共振器加温方式の分割型誘電体ボーラによる新加温位置制御方法

効果的な脳腫瘍ハイパーサーミアを目的とした空胴共振器加温方式の分割型誘電体ボーラによる新加温位置制御方法

変形性膝関節症の温熱治療を目的とした空胴共振器加温システムの加温特性

要 旨 : 本論文は, 変形性膝関節症の深部温熱リハビリテーションを目的として開発した, 空胴共振器加温方式の実験的検討について述べている. 我々は, 先行研究において, 変形性関節症の温熱治療を目的として, 空胴共振器を用いた全く新しい加温システムを提案し, その加温特性について, 三次元有限要素法解析を用いて数値的検討を行った. また, その解析結果により, 提案した加温システムの有用性について数値的に示した. 本論文では, 試作した空胴共振器加温システムを用いて, 種々の寒天ファントムの加温実験を行い, 本加温システムの加温特性について, 実験的に検討を行っている. また, 現在, 臨床で用いられている極超短波治療装置を用いた加温実験結果と本加温システムの実験結果との比較検討を行った. はじめに, 円筒型寒天ファントムを用いた基礎加温特性の比較検討を行った. 次に, 被加温体の形状による加温特性検討を行うため, 人体脚部形状の寒天ファントムを用いた比較検討を行った. 最後に, 切断加工した牛の膝を用いた空胴共振器加温システムの加温実験を行った. これらの, 加温実験結果の比較検討により, 本研究で提案している空胴共振器加温システムは, 変形性膝関節症の温熱治療に有用であることを実験的に明らかにした.

A114 超音波モニタリング機能を有する空胴共振器加温方式の加温特性

A114 超音波モニタリング機能を有する空胴共振器加温方式の加温特性