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(a) Photograph of the experimental setup for the tumour tissue experiment. (b) Close-up photograph of tumour tissue. (c) Schematic of the experimental setup for the tumour tissue experiment.
Source publication
It is demanded to monitor temperature in tissue during oncological hyperthermia therapy. In the present study, we non-invasively measured the temperature elevation inside the abdominal cavity and tumour tissue of a living rat induced by capacitive-coupled radiofrequency heating. In the analysis of ultrasound scattered echoes, the Nakagami shape par...
Contexts in source publication
Context 1
... was grown around the right femoral region of a Slc:SD female rat. Ultrasound scattered echoes from the tumour tissue were measured while the tumour tissue was heated from 35.5 to 42.5 °C. The experimental setup, a close-up photo around the tumour tissue, and the schematic of the experimental setup for the tumour tissue experiment are shown in Fig. 5(a-c). In the tumour tissue experiment, we used temperatures measured at Point 5 as a reference temperature. Figure 6(a) shows the variations in the temperature inside the tumour tissue and the surface of the skin of the rat during heating. The temperature increase from the non-induced state ΔT at each point is plotted as a function of the ...
Context 2
... elements of the transducer. The RF generator was paused emitting electromagnetic waves during acquisitions of ultrasonic echoes at the respective temperatures. The experimental setups for the healthy rat experiment and for the tumour tissue experiment are shown in Figs. 1(a) and 5(a). A close-up photo around the tumour tissue is shown in Fig. 5(b). Figures 1(b) and 5(c) show the schematic of the experimental setups for the healthy rat experiment and tumour tissue experiment. Points 1-7 in Figs. 1(b) and 5(c) indicate the positions of the tip of each sensor probe in the experimental setups for the healthy rat and tumour tissue experiments. In this study, we used temperatures ...
Citations
... where m T and m T R represent the Nakagami shape parameter m at current temperature and at a baseline temperature. Through heating experiments of porcine butt in vitro, 63 abdominal cavity and tumor tissue of a living rat in vivo 64 and tumors of patients in vivo, 65 it was found that changes of m-parameter due to the temperature elevation were dependent on initial m value. A multiplying factor γ varying as a function of the initial m value was required to modify the parameter α as ...
... All these methods are still in the stage of experimental research. Except for the envelope statistics and scatterer property parameters (ESD and EAC) methods, which were investigated in in vivo studies, 64,65,95,96 the other methods were conducted in in vitro studies. Before these methods can be applied to the clinic, more in vivo experiments need to be performed. ...
Percutaneous thermal therapy is an important clinical treatment method for some solid tumors. It is critical to use effective image visualization techniques to monitor the therapy process in real time because precise control of the therapeutic zone directly affects the prognosis of tumor treatment. Ultrasound is used in thermal therapy monitoring because of its real-time, non-invasive, non-ionizing radiation and low-cost characteristics. This paper presents a review of nine quantitative ultrasound-based methods for thermal therapy monitoring and their advances over the last decade since 2011. These methods were analyzed and compared with respect to two applications: ultrasonic thermometry and ablation zone identification. The advantages and limitations of these methods were compared and discussed, and future developments were suggested.
... A wide variety of targets have been evaluated in such studies, including vascular studies by Huang [81], ophthalmology and breast cancer by Tsui [82,83], and the liver by Tsui and Yamaguchi [84,85]. In the most recent research, the Nakagami distribution has been applied to evaluating the temperature of living tissues by Hasegawa [86,87], and Tamura and Yamaguchi have combined multiple distributions to evaluate fat and fiber in the liver simultaneously [88,89]. Figure 2 shows an example of the evaluation results of liver steatosis using the double-Nakagami model, a complex probability density function that enables quantification of the degree and distribution of fat mass in the liver [84]. ...
In the field of clinical ultrasound, the full digitalization of diagnostic equipment in the 2000s enabled the technological development of quantitative ultrasound (QUS), followed by multiple diagnostic technologies that have been put into practical use in recent years. In QUS, tissue characteristics are quantified and parameters are calculated by analyzing the radiofrequency (RF) echo signals returning to the transducer. However, the physical properties (and pathological level structure) of the biological tissues responsible for the imaging features and QUS parameters have not been sufficiently verified as there are various conditions for observing living tissue with ultrasound and inevitable discrepancies between theoretical and actual measurements. A major issue of QUS in clinical application is that the evaluation results depend on the acquisition conditions of the RF echo signal as the source of the image information, and also vary according to the model of the diagnostic device. In this paper, typical examples of QUS techniques for evaluating attenuation, speed of sound, amplitude envelope characteristics, and backscatter coefficient in living tissues are introduced. Exemplary basic research and clinical applications related to these technologies, and initiatives currently being undertaken to establish the QUS method as a true tissue characterization technology, are also discussed.
... In our previous study, we reported that the spatial gradient in the temperature distribution inside a locally heated soft tissue specimen could be clearly visualized on 2-D a mod maps (Takeuchi et al. 2019). Recently, we reported the results of our in vivo studies using SpragueÀDawley rats (Takeuchi et al. 2020). In these in vivo studies, the temperature elevation inside the abdominal cavity and tumor tissue of a living rat induced with RF current heating was detected on hot-scale images, indicating the absolute values of the percentage changes in m values, a mod . ...
... To avoid a substantial drop in temperature inside the tumor tissues from the pause in RF current emission, the application of RF current was resumed in approximately 5 s. In our previous study, the abdominal cavity and tumor tissue of a living SpragueÀDawley rat were heated by RF current as the temperature distribution inside the abdominal cavity and the tumor tissue was measured with invasive-type temperature sensor probes (Takeuchi et al. 2020). In the in vivo study, application of RF current was paused for approximately 5 s during acquisition of ultrasonic echo signals as in this study. ...
... To evaluate the temperature elevation inside the tissue, our research group employed the absolute values of the percentage changes in m values, a mod (Takeuchi et al. 2019(Takeuchi et al. , 2020. The specific parameter a mod is defined as ...
Non-invasive monitoring of temperature elevations inside tumor tissue is imperative for the oncological thermotherapy known as hyperthermia. In the present study, two cancer patients, one with a developing right renal cell carcinoma and the other with pseudomyxoma peritonei, underwent hyperthermia. The two patients were irradiated with radiofrequency current for 40 min during hyperthermia. We report the results of our clinical trial study in which the temperature increases inside the tumor tissues of patients with right renal cell carcinoma and pseudomyxoma peritonei induced by radiofrequency current irradiation for 40 min could be detected by statistical analysis of ultrasonic scattered echoes. The Nakagami shape parameter m varies depending on the temperature of the medium. We calculated the Nakagami shape parameter m by statistical analysis of the ultrasonic echoes scattered from the tumor tissues. The temperature elevations inside the tumor tissues were expressed as increases in brightness on 2-D hot-scale maps of the specific parameter αmod, indicating the absolute values of the percentage changes in m values. In the αmod map for each tumor tissue, the brightness clearly increased with treatment time. In quantitative analysis, the mean values of αmod were calculated. The mean value of αmod for the right renal cell carcinoma increased to 1.35 dB with increasing treatment time, and the mean value of αmod for pseudomyxoma peritonei increased to 1.74 with treatment time. The increase in both αmod brightness and the mean value of αmod implied temperature elevations inside the tumor tissues induced by the radiofrequency current; thus, the acoustic method is promising for monitoring temperature elevations inside tumor tissues during hyperthermia.
... Our previous studies have indicated that the absolute value of the ratio change in the logarithmic NA parameter visualizes the temperature change inside tissue-mimicking phantoms and ex vivo and in vivo biological soft tissues. [21][22][23] Another previous study has also demonstrated that the temperature change is related to variations in the ultrasonic envelope statistical properties. 24 Although the change in the NA parameter is considered to be attributed to the change in the scatterer structure during thermal expansion (contraction), evidence for this phenomenon has not been shown to date. ...
... The fluctuation of the speckle pattern leads to a fluctuation of the Δm distribution regardless of the different scatterer number densities, as shown in the current (Fig. 6) and previous studies. 23,24 One of the possible factors is considered to be the presence of wave interferences. As mentioned in a previous study, 24 backscatter signals might be affected by the components of constructive and destructive wave interferences. ...
Purpose
Our previous studies demonstrate that the variation in ultrasonic envelope statistics is correlated with the temperature change inside scattering media. This variation is identified as the change in the scatterer structure during thermal expansion or contraction. However, no specific evidence has been verified to date. This study numerically reproduces the change in the scatterer distribution during thermal expansion or contraction using finite element simulations and also investigates how the situation is altered by different material properties.
Methods
The material properties of a linear elastic solid depend on the thermal expansion coefficient, thermal conductivity, specific heat, and initial scatterer number density. Three‐dimensional displacements, calculated in the simulation, were sequentially used to update the positions of the randomly distributed scatterers. Ultrasound signals from the scatterer distribution were generated by simulating a 7.5‐MHz linear array transducer whose specifications were the same as those in the experimental measurements of several phantoms and excised porcine livers. To represent the change in the envelope statistical feature, the absolute value of the ratio change in the logarithmic Nakagami (NA) parameter, Δm, at each time was calculated as a value normalized with the initial NA parameter.
Results
The change in the scatterer number density relates to the volume change during temperature elevation. The magnitude of the Δm shift against the temperature change increases depending on the higher thermal expansion coefficient. In contrast, the relationship between Δm and the scatterer number density is similar with any material property. Additionally, the changes in Δm obtained by several experimental phantoms with low to high scatterer number densities are comparable with the numerical simulation results.
Conclusions
The change in Δm is indirectly related to the change in the scatterer number density owing to the volume change during thermal expansion or contraction.
Background
Ultrasound has played a vital role in the medical imaging system for real-time examination. It is considered safe and economical compared to other imaging modalities. Absorption of ultrasound energy by biological tissues can result in heating, especially if the high intensity is used for a long duration.
Aim
This study aims to evaluate temperature changes in diagnostic ultrasound scanning patients undergoing different ultrasound examinations.
Materials and Methods
An infrared thermometer was used to measure the temperature in the subjects’ regions of interest. The transducers of frequencies 3.5 and 7.5 MHz were used for the transmission and reception of ultrasound energy to and from the region of scanning. Three hundred and four patients were recruited from different ultrasound examinations. The thermometer was placed at a distance of 5–15 cm to record temperature changes before and during the ultrasound procedure on each of the subjects. The obtained data were statistically analyzed using the Statistical Package for the Social Sciences (SPSS) version 20.
Result
The average room temperature during the scanning was 22.2°C. The mean temperature before scanning procedures was 32.3°C. The mean maximum and minimum temperatures before and during the scanning of 304 patients recruited for this study were 34.4°C and 31.3°C, respectively. There was also a significant difference between the temperature measured before and during the scanning of the patients ( P = 0.01).
Conclusion
The findings in this study show that temperatures during the diagnostic ultrasound scanning are not above normal human body temperature; therefore, observable thermal effects are unlikely possible.
Objective:
The purpose of this study is to accurately monitor temperature during microwave hyperthermia. We propose a temperature estimation model BP-Nakagami based on neural network for Nakagami distribution.
Methods:
In this work, we designed the microwave hyperthermia experiment of fresh ex vivo pork tissue and phantom, collected ultrasonic backscatter data at different temperatures, modeled these data using Nakagami distribution, and calculated Nakagami distribution parameter m. A neural network model was built to train the relationship between Nakagami distribution parameter m and temperature, and a BP-Nakagami temperature model with good fitting was obtained. The temperature model is used to draw the two-dimensional temperature distribution map of biological tissues in microwave hyperthermia. Finally, the temperature estimated by the model is compared with the temperature measured by thermocouples.
Results:
The error between the temperature estimated by the temperature model and the temperature measured by the thermocouple is within 1°C in the range of 25°C-50°C for ex vivo pork tissue, and the error between the temperature estimated by the temperature model and the temperature measured by the thermocouple is within 0.5°C in the range of 25°C-50°C for phantom.
Conclusions:
The results show that the temperature estimation model proposed by us is an effective model for monitoring the internal temperature change of biological tissues.
In this paper, cancer cells in human breast of below 256 cell (2 cm) counts are detected through proposed Feature DnCNN (FDnCNN) enhancement algorithm. Cancer cell count below 256 is termed as T1b and T1c stages. FDnCNN is applied to the breast thermal images obtained after external heating of breast phantom through warm water. Induced heat due to warm water immersion of breast phantom helps for detection of the small size cancer cell through heat transfer capacity between normal and cancer cells. However, traditional method of breast cancer detection through thermal imaging never detects the cancer cell size of below 2 cm (256-cell) in the images. Thermal imaging breast cancer detects cancer cell of above 256 cells count in breast and never below cancer cell of count 256 cells. The proposed method of acquiring the thermal image after induced heating on the breast phantom, leads to higher interpretation of cancer cells below 256 cell count because of increase in thermogenesis of tissue. The increase in thermogenesis in cancer tissues improves visibility of cancer cell below 256 cell count. Moreover, induced heat based phantom thermal images need enhancement algorithm for better visualization of cancer cell count of below 256. The proposed FDnCNN enhancement algorithm performs better than traditional algorithms and provides an accuracy of cancer cell measurement of about 95%, when compared to ground truth measurement of cancer cells.
In the field of clinical ultrasound, the full digitalization of diagnostic equipment in the 2000s enabled the technological development of quantitative ultrasound (QUS), followed by multiple diagnostic technologies that have been put into practical use in recent years. In QUS, tissue characteristics are quantified and parameters are calculated by analyzing the radiofrequency (RF) echo signals returning to the transducer. However, the physical properties (and pathological level structure) of the biological tissues responsible for the imaging features and QUS parameters have not been sufficiently verified as there are various conditions for observing living tissue with ultrasound and inevitable discrepancies between theoretical and actual measurements. A major issue of QUS in clinical application is that the evaluation results depend on the acquisition conditions of the RF echo signal as the source of the image information, and also vary according to the model of the diagnostic device. In this paper, typical examples of QUS techniques for evaluating attenuation, speed of sound, amplitude envelope characteristics, and backscatter coefficient in living tissues are introduced. Exemplary basic research and clinical applications related to these technologies, and initiatives currently being undertaken to establish the QUS method as a true tissue characterization technology, are also discussed.
