Download or read book Thermal Ablation Monitoring Using Ultrasound Echo Decorrelation Imaging written by Swetha Subramanian and published by . This book was released on 2015 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hepatocellular carcinoma (HCC) and colorectal metastases (CRC) are common tumors worldwide with an increasing incidence in the United States. Thermal ablation techniques such as radiofrequency ablation (RFA), high intensity focused ultrasound (HIFU), microwave and laser ablation techniques have shown potential to treat unresectable tumors. Still lacking is a treatment monitoring technique that can accurately predict ablation. Echo decorrelation imaging is a novel pulse-echo ultrasound imaging method that quantifies and maps changes in echo signals occurring over millisecond time scales during thermal ablation. In this dissertation, the utility of echo decorrelation imaging as a treatment monitoring tool was assessed during in vivo and in vitro thermal ablation. To test the utility of echo decorrelation imaging for the prediction of ablation, RFA was performed on ex vivo bovine liver ( N = 9). Echo decorrelation was computed from the Hilbert transformed pulse-echo data acquired during RFA treatments. For comparison, integrated backscatter was also computed from the same data. Pixel-by-pixel comparison between the echo decorrelation and integrated backscatter maps and the ablated region from gross tissue histology was performed using receiver operating characteristic (ROC) curves. Echo decorrelation and integrated backscatter were then quantitatively evaluated as predictors of ablation. The area under the ROC curves (AUROC) was determined for both echo decorrelation and integrated backscatter imaging methods. Ablation was predicted more accurately with echo decorrelation (AUROC = 0.820) than with integrated backscatter (AUROC = 0.668). To test the utility of echo decorrelation imaging for the prediction of ablation during in vivo thermal ablation, RFA was performed on normal swine liver ( N = 5) and ultrasound ablation using image-ablate arrays was performed on rabbit liver implanted with VX2 tumors ( N = 2). Consistent with the in vitro studies, ablation was predicted more accurately with echo decorrelation (AUROC = 0.833 and 0.776 for RFA and ultrasound ablation, respectively) than with integrated backscatter (AUROC = 0.733 and 0.494). Mean cumulative echo decorrelation was greater in the ablated tissue regions compared to the unablated regions for both in vitro ( t = 6.808, p = 6.10-6, N = 9) and in vivo ( t = 3.498, p = 0.036, N = 5) RFA treatments, indicating the ability of echo decorrelation to delineate between the ablated and unablated regions. For in vivo RFA, motion gating reduced the mean echo decorrelation in both ablated ( t = 3.526, p = 0.036, N = 5) and unablated ( t = 5.173, p = 0.013, N = 5) regions. However, with or without motion gating, the mean cumulative echo decorrelation was significantly greater in the ablated region than in the unablated region ( t = 3.883, p = 0.008, N = 5). The effect of tissue temperature on echo decorrelation was assessed during in vitro RFA. RFA experiments ( N = 15) were performed on ex vivo bovine liver tissue. Temperature maps were simulated by a finite element method, with tissue parameters determined using an unscented Kalman filter to best match measured ablation results. Significantly higher AUROC values ( p = 0.019, p = 10-14, p = 10-14) were obtained for the prediction of tissue temperatures greater than 40, 60, and 80° C with echo decorrelation (AUROC = 0.871, 0.948, and 0.966) when compared to integrated backscatter (AUROC = 0.865, 0.877, and 0.832). Overall, the results presented in this dissertation show potential for the utility of echo decorrelation imaging as a treatment monitoring tool.

Download or read book Echo Decorrelation Imaging of In Vivo HIFU and Bulk Ultrasound Ablation written by Tyler R. Fosnight and published by . This book was released on 2015 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt: Echo decorrelation imaging, a pulse-echo method that maps heat-induced changes in ultrasound echoes, was investigated for in vivo monitoring of thermal ablation in a liver cancer model. In open surgical procedures, rabbit liver with implanted VX2 tumor were imaged by image-ablate arrays and treated with bulk ultrasound (unfocused) ablation (N=10) or high-intensity focused ultrasound (HIFU) (N=13). Echo decorrelation and integrated backscatter (IBS) images were formed from pulse-echo images recorded during rest periods following each sonication pulse. Echo decorrelation images were corrected for motion- and noise-induced artifacts using measured echo decorrelation from corresponding sham trials. Sectioned ablated tissue was vitally stained with triphenyl tetrazolium chloride (TTC) and binary images were constructed based on local TTC staining. Analysis was performed for the focused exposures, unfocused exposures and for all exposures combined. Motion correction significantly reduced echo decorrelation in non-ablated liver regions. The reduction was significant in non-ablated VX2 tumor regions for focused exposures and all exposures combined. The reduction was not significant in ablated VX2 tumor regions for unfocused exposures. Echo decorrelation reduction was marginally significant in ablated regions for focused and unfocused exposures and was significant for all exposures combined. Prediction of ablation by echo decorrelation and IBS imaging was assessed using receiver operating characteristic (ROC) curves. Areas under the ROC curve (AUC) were significantly greater than chance for ablated liver prediction by corrected echo decorrelation and IBS. Echo decorrelation did not predict ablated VX2 tumor significantly better than chance for focused exposures. IBS did not predict ablated VX2 tumor better than chance for focused exposures and unfocused exposures. Corrected echo decorrelation predicted ablated liver significantly better than IBS for the focused exposures and all exposures combined. AUC differences between corrected echo decorrelation and IBS were not significant for all exposure groups in ablated VX2 tumor, for which echo decorrelation was marginally higher. At the optimal threshold, defined as the threshold corresponding to the point nearest to the top left-hand corner of the ROC plot, echo decorrelation had a better sensitivity than specificity for the focused and unfocused exposures in normal liver and VX2 tumor. To assess tissue motion effects due to large inter-frame times, echo decorrelation and IBS was computed for inter-frame times up to 847.5 ms. Uncorrected and corrected echo decorrelation prediction performance was marginally affected by large inter-frame times; however, corrected decorrelation was less affected. IBS prediction performance was nearly constant by comparison for large inter-frame times. Over the range of inter-frame times investigated, IBS predicted overall better than echo decorrelation for the unfocused group while echo decorrelation predicted overall better than IBS for the focused group. These results indicate echo decorrelation imaging is a successful predictor of local ablation, with potential for successful clinical implementation.

Download or read book The Application of Heat in Oncology written by Devashish Shrivastava and published by John Wiley & Sons. This book was released on 2023-09-13 with total page 581 pages. Available in PDF, EPUB and Kindle. Book excerpt: THE APPLICATION OF HEAT IN ONCOLOGY Understand the use of heat to destroy tumors with this comprehensive guide Heat is an indispensable resource in the destruction of cancerous tumors to potentially treat cancers. There are also real challenges, however, involved in the total destruction of tumors without destroying healthy tissue surrounding the tumor in the process. A detailed understanding of the propagation of thermal energy, induced heating, and tissue responses to heat is required to safely and successfully apply heat-based technologies in clinical oncology. The Application of Heat in Oncology supplies this understanding, with a thorough, comprehensive overview of the principle and practice involved. Offering both a detailed introduction to the physics and thermodynamics of induced heat and an analysis of its clinical applications, this is an essential resource for clinicians, technicians, and others in oncological practice. The Application of Heat in Oncology readers will also find: Guidelines for applying heat both safely and effectively Detailed discussion of topics including energy delivery (e.g., via RF, MW, ultrasound, laser, cryoagents, hyperthermia, nanoparticles, etc.), temperature assessment, damage assessment, image guidance, and more Summary of current practice along with suggestions for future areas of technological improvement The Application of Heat in Oncology is ideal for all clinicians working in the field of cancer treatment, including medical students, residents, researchers, engineers, radiologists, surgeons, and more.

Download or read book Magnetic Resonance Imaging Monitoring of Focused Ultrasound Thermal Ablation microform written by Hai-Ling Margaret Cheng and published by National Library of Canada = Bibliothèque nationale du Canada. This book was released on 2003 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Biomechanical Assessment and Monitoring of Thermal Ablation Using Harmonic Motion Imaging for Focused Ultrasound HMIFU written by Yi Hou and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In conclusion, the outcomes from the aforementioned studies successfully showed the feasibility of both HMIFU systems in multi-parametric monitoring of HIFU treatment with slow denaturation and boiling, which prepares its stage towards clinical translation.

Download or read book Validation Platform for Ultrasound based Monitoring of Thermal Ablation written by Hamed Peikari and published by . This book was released on 2011 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: PURPOSE: Thermal ablation therapy is an emerging local cancer treatment to destroy cancer tissue using heat. However variations in blood flow and energy absorption rates make it extremely challenging to monitor thermal changes. Insufficient ablation may lead to recurrence of the cancer while excessive ablation may damage adjacent healthy tissues. Ultrasound could be a convenient and inexpensive imaging modality for real-time monitoring of the ablation. For the development and optimization of these methods, it is essential to have ground truth data and a reliable and quantitative validation technique before beginning clinical trials on humans. In this dissertation, my primary focus was to solve the image-to-physical space registration problem using stereotactic fiducials that provide accurate correlation of ultrasound and pathology (ground truth) images. METHOD: A previously developed validation test-bed prototype was evaluated using phantom experiments to identify the shortcomings and limitations. In order to develop an improved validation platform, a simulator was implemented for evaluating registration methods as well as different line fiducial structures. New fiducial line structures were proposed, and new methods were implemented to overcome the limitations of the old system. The new methods were then tested using simulation results and phantom studies. Phantom experiments were conducted to improve the visibility of fiducials, as well as the quality of acquired ultrasound and pathology image datasets. RESULTS: The new system outperforms the previous one in terms of accuracy, robustness, and simplicity. The new registration method is robust to missing fiducials. I also achieved complete fiducial visibility in all images. Enhancing the tissue fixation medium improved the ultrasound data quality. The quality of pathology images were improved by a new imaging method. Simulation results show improvement in pose recovery accuracy using my proposed fiducial structure. This was validated by phantom studies reducing spatial misalignment between the US and pathology image sets. CONCLUSION: A new generation of test-bed was developed that provides a reliable and quantitative validation technique for evaluating and optimizing ablation monitoring methods.

Download or read book Ultrasound Elastographic Imaging of Thermal Lesions and Temperature Profiles During Radiofrequency Ablation written by Udomchai Techavipoo and published by . This book was released on 2004 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Ultrasound Strain Imaging Using Sector Arrays for Monitoring Prostate Ablation Therapy written by Mehrdad Pourfathi and published by . This book was released on 2011 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal ablation treatment is a relatively new method for prostate cancer therapy, where high energy focused ultrasound is used to thermally coagulate cancerous tissue. Thermal ablation is advantageous in comparison to other invasive treatment methods such as surgery, radiation therapy, or chemotherapy due to its minimally invasive nature. Currently, magnetic resonance thermal imaging (MRTI) is used to monitor the temperature distribution during the ablation treatment. However, MRTI is not only an expensive method, but it is also difficult to set up. Ultrasound strain imaging, on the other hand, has proven to be an effective method to detect and track lesion boundaries in soft tissues such as the liver and breast. Several strain-imaging algorithms have been developed, each one tailored for certain application and tissue geometry. In this thesis, we develop a new algorithm based on the cross-correlation method to potentially detect and track lesions during a prostate ablation treatment. In order to verify the performance of the algorithm and mimic the desired clinical scenario, we used three different ultrasound phantoms to verify the performance of the developed algorithm in terms of speed, resolution and accuracy. The results show that using the ultrasound data taken by a sector scanner, the algorithm can generate strain images with millimeter-order spatial resolution and enough contrast level to allow for detection of the lesion.

Download or read book Quantitative Ultrasound Imaging During Ablation Procedures written by Kayvan Samimi and published by . This book was released on 2017 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional ultrasound imaging (i.e. B-mode sonogram) is a qualitative mode of imaging based on visualizing the relative echogenicity of different tissue types within the body. This useful mode of imaging has aided clinicians for more than 50 years. However, B-mode imaging does not capture any of the frequency-dependent information that is contained within the ultrasound echo signal. Additionally, due to its qualitative nature, there is much inter-system and inter-observer variability with regard to generation and interpretation of B-mode images. Quantitative Ultrasound (QUS) methods have been developed to extract additional information by estimating acoustic properties of tissue from the frequency-domain representation of echo signals. These estimates can be converted to color-coded maps that are visualized along with conventional B-mode images to form enhanced ultrasound images. Such images can potentially provide valuable diagnostic and prognostic information to medical professionals. Some of the more important acoustic parameters of interest in QUS and tissue characterization are the ultrasonic attenuation coefficient and the backscatter coefficient. Attenuation has been studied as a potential classifier of normal and pathological liver tissue. In addition to providing pathological information for diagnosis, monitoring these QUS parameters during therapeutic procedures such as tumor ablation can lead to targeted and optimized treatment. The goals of this dissertation are to theoretically model and analyze current methods of acoustic attenuation estimation; improve attenuation estimation algorithms to enhance the quality of subsequent QUS images; and correlate changes in QUS parameter values with progression of thermally ablative procedures for ex-vivo and in-vivo liver ablations. Although QUS imaging may be used to assist clinicians in various stages of diagnosis and treatment of diseases in a multitude of bodily organs and tissue types, this dissertation focuses on thermal ablation of primary or metastatic liver tumors in order to showcase the possible benefits of the proposed estimation methods and to compare their performance with existing estimation techniques. Additionally, simulated and physical tissue-mimicking (TM) phantoms with known acoustic properties are used to statistically test and compare the accuracy and precision of these methods. Theoretical analysis and experimental results suggest that our proposed method for estimation of the ultrasonic attenuation coefficient based on measurement of frequency shifts in a normalized power-spectral representation of the ultrasonic echo signal is best suited to in-vivo QUS imaging in clinical settings and provides estimates with standard deviations that are at least three times smaller than was previously possible with other methods.

Download or read book Physics of Thermal Therapy written by Eduardo Moros and published by CRC Press. This book was released on 2012-12-05 with total page 383 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of thermal therapy has been growing tenaciously in the last few decades. The application of heat to living tissues, from mild hyperthermia to high-temperature thermal ablation, has produced a host of well-documented genetic, cellular, and physiological responses that are being researched intensely for medical applications, particularly for treatment of solid cancerous tumors using image guidance. The controlled application of thermal energy to living tissues has proven a great challenge, requiring expertise from multiple disciplines, thereby leading to the development of many sophisticated pre-clinical and clinical devices and treatment techniques. Physics of Thermal Therapy: Fundamentals and Clinical Applications captures the breadth and depth of this highly multidisciplinary field. Focusing on applications in cancer treatment, this book covers basic principles, practical aspects, and clinical applications of thermal therapy. An overview of the fundamentals shows how use of controlled heat in medicine and biology involves electromagnetics, acoustics, thermodynamics, heat transfer, and imaging sciences. The book discusses challenges in the use of thermal energy on living tissues and explores the genetic, cellular, and physiological responses that can be employed in the fight against cancer from the physics and engineering perspectives. It also highlights recent advances, including the treatment of solid tumors using image-guided thermal therapy, microbubbles, nanoparticles, and other cutting-edge techniques.

Download or read book Real time Monitoring of Thermal Ablation with Ultrasound written by Itai Winkler and published by . This book was released on 2010 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Quantitative Ultrasound Imaging of Thermal Ablation Therapy in the Liver written by and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this dissertation is to investigate methods for delineating the extent of the thermally coagulated region following thermal ablation therapy of malignant tumors in the liver. In this dissertation, we examine quasistatic elasticity imaging for delineating the extent of the treated region. Next, we characterize scattering in normal, untreated liver and thermally coagulated liver. Finally, we examine attenuation estimation with reference phantom methods in the liver. It has been well established that the Young's modulus of thermally coagulated tissue is much larger than in untreated liver tissue, making elastographic imaging an attractive candidate for delineating the extent of thermal coagulation. In quasistatic elastographic imaging of superficial organs such as the breast, external compression may be performed with a compressor plate or the transducer itself. However, in abdominal imaging, external compression is not effective. In response, our laboratory has developed electrode displacement for strain and modulus imaging. In electrode displacement strain imaging, deformation is applied by displacing the end of the RF electrode or microwave antenna by a small amount following treatment. We present electrode displacement strain images of thermally coagulated regions in in vivo porcine animal models during open surgery. We show that cross-sectional areas of treated regions delineated on electrode displacement strain images correlate well with coagulated areas determined on optical photographs of ablated regions of the excised livers. Additionally, we present electrode displacement strain images of VX2 tumors in rabbit animal models prior to and following thermal ablation. Next, we develop mean scatterer spacing (MSS) estimation in the liver. In the liver, it has been hypothesized that periodic scattering results from a unique arrangement of microvasculature. Indeed, the liver is a unique organ because of its dual vascular supply from the hepatic artery and portal vein. We first show that utilizing a multi-taper spectral calculation results in a lower mean square error in MSS estimates using simulations of periodic tissue. Next, we show that average spectral coherence decreases in thermally coagulated liver compared with untreated liver in a small number of ex vivo RF ablations. Finally, we demonstrate that thermally coagulated regions are best modeled by aperiodic collections of scatterers, while normal liver exhibits periodicity. In the final section of the dissertation we consider attenuation estimation. This is an attractive area of research because the attenuation coefficient is approximately doubles in the liver following thermal ablation. In past works, authors have developed attenuation algorithms with the assumption that the tissue being imaged may be modeled by a collection of a large number of randomly distributed scatterers. We show that in ex vivo bovine liver the scatterer number density is small. We demonstrate that the effect this has on attenuation estimation is to significantly increase the variance in attenuation estimation relative to tissue that may be modeled with a large scatterer number density. Using computer simulation and phantom experiments we show that when the scatterer number density is sufficiently large it is possible to achieve low variance, high resolution attenuation estimates. However, as the scatterer number density decreases either spatial resolution in the attenuation estimate must be sacrificed or attenuation estimate variance will increase. We find a linear attenuation coefficient in thermally coagulated liver that is approximately double the attenuation coefficient of normal, untreated liver. However, we also find a low scatterer number density in these tissues and a correspondingly high attenuation estimation variance.

Download or read book Monitoring Microwave Ablation Treatments for Liver Tumors Using Ultrasound Elastography written by Wenjun Yang and published by . This book was released on 2017 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Liver cancer is the sixth most common and the third leading cause of cancer related deaths world-wide. New cases and mortality in the U.S. have doubled during the past two decades, increasing at a rate of 3.4% per year from 2007 to 2011. Existing treatment methods for liver cancer include partial hepatectomy, embolization with chemotherapy, liver transplant, and percutaneous ablation. Percutaneous ablation is increasingly being adopted as an effective treatment method for liver cancer by thermal necrosis of cancerous tissue, with the advantage of promising treatment outcomes, and minimally invasive procedures. Previously percutaneous ablation was performed using radiofrequency ablation (RFA), which uses a local circuit loop to generate a thermal dose. To improve the heating rate and volume treated with RFA, microwave ablation (MWA) was introduced which heated local tissue by agitating water molecules using microwave energy. The key factor to yield a promising treatment outcome with MWA is to effectively monitor the ablation margin of the treated region. The guidance imaging modality for MWA, namely ultrasound B-mode imaging is not sufficient to delineate the ablated region after the MWA procedure. Thus, computed tomography (CT) is adopted as the current gold standard to determine the ablation margin by comparing the pre- and post- treatment images. However, CT scans prolong the treatment time and expose the patients to ionizing radiation. In this dissertation, an ultrasound elastography technique, which is referred to as electrode displacement elastography (EDE), is applied for monitoring clinical MWA procedures. By comparison with B-mode imaging and commercial acoustic radiation force impulse imaging (ARFI), EDE is potentially an alternative imaging modality to provide effective real-time feedback of the ablated margin, which might improve treatment outcomes with MWA. In addition, our previously introduced three-dimensional (3D) reconstruction algorithm, Sheaf of Ultrasound Planes Reconstruction (SOUPR) was applied for a phantom study to depict the ablation inclusion as a 3D volume instead of a single 2D ultrasound plane. An image fusion technique is also developed to register EDE and CT to determine the ablation margin on EDE with comparison to the current gold standard.

Download or read book Ultrasound Cardiac Therapy Guided by Elastography and Ultrafast Imaging written by Wojciech Kwiecinski and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atrial fibrillation (AF) affects 2-3% of the European and North-American population, whereas ventricular tachyarrhythmia (VT) is related to an important risk of sudden death. AF and VT originate from dysfunctional electrical activity in cardiac tissues. Minimally-invasive approaches such as Radio-Frequency Catheter Ablation (RFCA) have revolutionized the treatment of these diseases; however the success rate of RFCA is currently limited by the lack of monitoring techniques to precisely control the extent of thermally ablated tissue.The aim of this thesis is to propose novel ultrasound-based approaches for minimally invasive cardiac ablation under guidance of ultrasound imaging. For this, first, we validated the accuracy and clinical viability of Shear-Wave Elastography (SWE) as a real-time quantitative imaging modality for thermal ablation monitoring in vivo. Second we implemented SWE on an intracardiac transducer and validated the feasibility of evaluating thermal ablation in vitro and in vivo on beating hearts of a large animal model. Third, a dual-mode intracardiac transducer was developed to perform both ultrasound therapy and imaging with the same elements, on the same device. SWE-controlled High-Intensity-Focused-Ultrasound thermal lesions were successfully performed in vivo in the atria and the ventricles of a large animal model. At last, SWE was implemented on a transesophageal ultrasound imaging and therapy device and the feasibility of transesophageal approach was demonstrated in vitro and in vivo. These novel approaches may lead to new clinical devices for a safer and controlled treatment of a wide variety of cardiac arrhythmias and diseases.

Download or read book Application of Magnetic Resonance guided Focused Ultrasound Thermal Ablation for Drug Delivery written by Andrew Wei Ping Wong and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In Magnetic Resonance-guided Focused Ultrasound (MRgFUS), highly focused ultrasound noninvasively heats tissue under the guidance of magnetic resonance imaging and thermometry. To prevent recurrence, the treatment of cancer requires complete destruction, which is a challenge for noninvasive local therapy. We hypothesize that thermal ablation can enhance the accumulation of nanoparticle chemotherapeutics, and therefore combining chemotherapy and ultrasound is attractive. A combination of ultrasound and chemotherapeutic drugs may allow ultrasound thermal ablation to more effectively treat malignancy. MRgFUS can ablate tissue by raising temperatures to cytotoxic levels. Burn injuries release histamine, VEGF, and other factors which induce local edema and inflammation. Local inflammation prompts invasion by immune cells, while necrotic tumor cells release tumor specific antigen, events which may prompt the immune system to further respond to cancer. Histamine and VEGF also enhance the accumulation of nanoparticles, and preclinical trials using radiofrequency ablation have demonstrated greater accumulation of nanoparticle chemotherapy within tumors. Similar effects can be obtained with MRgFUS, with the added advantages of deeper penetration, a conformal region of interest and improved temperature control. Moreover, use of focused ultrasound provides the opportunity to explore ultrasonic mechanical effects. In this dissertation, we synthesize several types of labeled and chemotherapeutic liposomes, demonstrate the suitability of Positron Emission Tomography (PET) for the assessment of drug delivery, enhance delivery of liposomes with MRgFUS, examine the distribution of nanoparticles in a syngeneic murine model of mammary carcinoma, and examine the effect of this combination therapy on tumor growth and survival. As described in Chapter 3, an initial assessment of 64Cu-labeled long-circulating liposomes as PET contrast agents reveals excellent image contrast and quantitative mapping of tumor drug concentration. The tumor contrast ratio of 64Cu-labeled long-circulating liposomes was compared to 18F-FDG, the dominant clinical tracer. 18F-FDG demonstrated a contrast ratio of 0.88 ± 0.01 (mean ± standard error of the mean), while contrast ratio achieved with 64Cu-labeled long-circulating liposomes ranged from 0.78 ± 0.01 at 6 hours to 0.94 ± 0.01 at 48 hours, increasing over time as liposomes cleared from circulation. PET was then applied in Chapter 4 to evaluate the accumulation of nanoparticles within tumors following MRgFUS ablation. In mouse models, free doxorubicin has demonstrated tumor accumulation of 1-3 %ID/cc; nanoparticle formulations improve this by increasing circulation time and facilitating accumulation only in regions with leaky vasculature. Three strategies for MRgFUS application were compared: grid and circular protocols that mimic conformal ablation strategies and a single point ablation that enhances delivery but incompletely ablates the tumor. All strategies resulted in enhanced accumulation of 64Cu-LCL within tumors, with more than 80% of the accumulation occurring within 3 hours after ablation. At 20 hours after insonation, the spatial maximum accumulation was 33.8 ± 1.9, 39.7 ± 8.6, 27.4 ± 2.1, 8.6 ± 0.8 (%ID/cc, mean ± standard error of the mean), in grid protocol, circle protocol, single point, and untreated tumors, respectively. Autoradiography and fluorescence imaging confirmed the greatly enhanced accumulation in the remaining tumor. Locally-enhanced accumulation of LCL was preserved even after a multi-week protocol of doxorubicin-containing LCL (6 mg/kg) and MRgFUS. Following intraperitoneal injection, gadoteridol was also preferentially retained between 0 and 3 hours after ablation but was cleared after 3 hours and subsequent intravenous injections of contrast did not enhance imaging of the treated tumor. The combination of ultrasound and both long-circulating and thermally-sensitive copper-doxorubicin liposomes results in delayed tumor growth and enhanced survival, as described in Chapter 5. Four weeks of a single point ultrasound thermal ablation and biweekly copper-doxorubicin long-circulating liposomes (6 mg/kg) enhanced median survival from 43 ± 1 days (median ℗ł median absolute deviation) in untreated tumors to 114 ± 19 days. Substantial inhibition of tumor growth was also observed following four weeks of weekly copper-doxorubicin temperature sensitive liposomes (6 mg/kg) and weekly circle-patterned ultrasound. Taken as a whole, the work described here demonstrates the impact of combining chemotherapy with MRgFUS. This dissertation represents a small subset of potential ultrasound exposures, chemotherapeutic nanoparticles, and model systems. Future directions include modification of ultrasound frequency, intensity, and duty factor or inclusion of ultrasound contrast agents to induce mechanical disruption of tumor vasculature to further enhance local drug delivery.

Download or read book Ultrasound Strain Imaging for Verification of Prostate Thermal Therapy written by Nicole B. Chubb and published by . This book was released on 2010 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal (heat) therapy, such as thermal ablation, using catheter-based devices with ultrasound for treatment of prostate cancers is becoming a minimally invasive option to surgery, especially when combined with MRI thermal imaging to ensure accurate treatment delivery. The main hurdles to implementing this technology on a regular basis are the cost, resources, and requirements associated with MRI imaging. This project proposes a new treatment-monitoring technique that uses ultrasonic strain imaging to replace MRI thermal imaging. The basis of this proposed monitoring technique is that significant changes in the physical and mechanical characteristics of tissue occur during any thermal ablation treatment. The scope of this project involves developing strain- imaging algorithms and testing on data collected from phantom and ex vivo tissue, mimicking the setup used in clinical scenarios.

Download or read book Interventional Magnetic Resonance Imaging written by Thomas Kahn and published by Springer Science & Business Media. This book was released on 2012-08-27 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: The idea of using the enormous potential of magnetic resonance imaging (MRI) not only for diagnostic but also for interventional purposes may seem obvious, but it took major efforts by engineers, physicists, and clinicians to come up with dedicated interventional techniques and scanners, and improvements are still ongoing. Since the inception of interventional MRI in the mid-1990s, the numbers of settings, techniques, and clinical applications have increased dramatically. This state of the art book covers all aspects of interventional MRI. The more technical contributions offer an overview of the fundamental ideas and concepts and present the available instrumentation. The richly illustrated clinical contributions, ranging from MRI-guided biopsies to completely MRI-controlled therapies in various body regions, provide detailed information on established and emerging applications and identify future trends and challenges.