Low-amplitude ultrasound enhances hydrodynamic-based gene delivery to rat kidney.

The synergistic combination of hydrodynamic-based gene delivery and ultrasound was investigated to achieve improved gene transfer to the kidney. Plasmids encoding firefly luciferase and Erythropoietin (EPO) gene were delivered into the left kidney of rats by single or combinative application of renal vein hydrodynamic injection and ultrasound treatment with or without the addition of ultrasound contrast agents (UCA). Ultrasound exposure was found to enhance the efficiency of hydrodynamic-based gene delivery for both luciferase and EPO expression. An ultrasound exposure intensity of 2 W/cm2 at 10% duty cycle for 15 min, produced a maximal gene expression 4.5 times higher than hydrodynamic delivery alone. Duration, location, and tissue-specificity of gene expression were not changed by ultrasound exposure. Application of UCA reduced the intensity and exposure duration of ultrasound treatment needed for optimal expression. Appropriate application of ultrasound and UCA did not alter histological structure or impair physiological function of the treated kidney.

The effect of high intensity focused ultrasound treatment on metastases in a murine melanoma model.

This study aims to assess the risk of high intensity focused ultrasound (HIFU) therapy on the incidence of distant metastases and to investigate its association with HIFU-elicited anti-tumor immunity in a murine melanoma (B16-F10) model. Tumor-bearing legs were amputated immediately after or 2 days following HIFU treatment to differentiate the contribution of the elicited anti-tumor immunity. In mice undergoing amputation immediately after mechanical, thermal, or no HIFU treatment, metastasis rates were comparable (18.8%, 13.3%, and 12.5%). In contrast, with a 2-day delay in amputation, the corresponding metastasis rates were 6.7%, 11.8%, and 40%, respectively. Animal survival rate was higher and CTL activity was enhanced in the HIFU treatment groups. Altogether, our results suggest that HIFU treatment does not increase the risk of distant metastasis. Instead, HIFU treatment can elicit an anti-tumor immune response that may be harnessed to improve the overall effectiveness and quality of cancer therapy.

Investigation of HIFU-induced anti-tumor immunity in a murine tumor model.

BACKGROUND: High intensity focused ultrasound (HIFU) is an emerging non-invasive treatment modality for localized treatment of cancers. While current clinical strategies employ HIFU exclusively for thermal ablation of the target sites, biological responses associated with both thermal and mechanical damage from focused ultrasound have not been thoroughly investigated. In particular, endogenous danger signals from HIFU-damaged tumor cells may trigger the activation of dendritic cells. This response may play a critical role in a HIFU-elicited anti-tumor immune response which can be harnessed for more effective treatment. METHODS: Mice bearing MC-38 colon adenocarcinoma tumors were treated with thermal and mechanical HIFU exposure settings in order to independently observe HIFU-induced effects on the host's immunological response. In vivo dendritic cell activity was assessed along with the host's response to challenge tumor growth. RESULTS: Thermal and mechanical HIFU were found to increase CD11c+ cells 3.1-fold and 4-fold, respectively, as compared to 1.5-fold observed for DC injection alone. In addition, thermal and mechanical HIFU increased CFSE+ DC accumulation in draining lymph nodes 5-fold and 10-fold, respectively. Moreover, focused ultrasound treatments not only caused a reduction in the growth of primary tumors, with tumor volume decreasing by 85% for thermal HIFU and 43% for mechanical HIFU, but they also provided protection against subcutaneous tumor re-challenge. Further immunological assays confirmed an enhanced CTL activity and increased tumor-specific IFN-gamma-secreting cells in the mice treated by focused ultrasound, with cytotoxicity induced by mechanical HIFU reaching as high as 27% at a 10:1 effector:target ratio. CONCLUSION: These studies present initial encouraging results confirming that focused ultrasound treatment can elicit a systemic anti-tumor immune response, and they suggest that this immunity is closely related to dendritic cell activation. Because DC activation was more pronounced when tumor cells were mechanically lysed by focused ultrasound treatment, mechanical HIFU in particular may be employed as a potential strategy in combination with subsequent thermal ablations for increasing the efficacy of HIFU cancer treatment by enhancing the host's anti-tumor immunity.

3-D ultrasound guidance of surgical robotics: a feasibility study.

Laparoscopic ultrasound has seen increased use as a surgical aide in general, gynecological, and urological procedures. The application of real-time, three-dimensional (RT3D) ultrasound to these laparoscopic procedures may increase information available to the surgeon and serve as an additional intraoperative guidance tool. The integration of RT3D with recent advances in robotic surgery also can increase automation and ease of use. In this study, a 1-cm diameter probe for RT3D has been used laparoscopically for in vivo imaging of a canine. The probe, which operates at 5 MHz, was used to image the spleen, liver, and gall bladder as well as to guide surgical instruments. Furthermore, the three-dimensional (3-D) measurement system of the volumetric scanner used with this probe was tested as a guidance mechanism for a robotic linear motion system in order to simulate the feasibility of RT3D/robotic surgery integration. Using images acquired with the 3-D laparoscopic ultrasound device, coordinates were acquired by the scanner and used to direct a robotically controlled needle toward desired in vitro targets as well as targets in a post-mortem canine. The rms error for these measurements was 1.34 mm using optical alignment and 0.76 mm using ultrasound alignment.

Integrated endoscope for real-time 3D ultrasound imaging and hyperthermia: feasibility study.

The goal of this research is to determine the feasibility of using a single endoscopic probe for the combined purpose of real-time 3D (RT3D) ultrasound imaging of a target organ and the delivery of ultrasound therapy to facilitate the absorption of compounds for cancer treatment. Recent research in ultrasound therapy has shown that ultrasound-mediated drug delivery improves absorption of treatments for prostate, cervical and esophageal cancer. The ability to combine ultrasound hyperthermia and 3D imaging could improve visualization and targeting of cancerous tissues. In this study, numerical modeling and experimental measurements were developed to determine the feasibility of combined therapy and imaging with a 1 cm diameter endoscopic RT3D probe with 504 transmitters and 252 receive channels. This device operates at 5 MHz and has a 6.3 mm x 6.3 mm aperture to produce real time 3D pyramidal scans of 60-120 degrees incorporating 64 x 64 = 4096 image lines at 30 volumes/sec interleaved with a 3D steerable therapy beam. A finite-element mesh was constructed with over 128,000 elements in LS-DYNA to simulate the induced temperature rise from our transducer with a 3 cm deep focus in tissue. Quarter-symmetry of the transducer was used to reduce mesh size and computation time. Based on intensity values calculated in Field II using the transducer's array geometry, a minimum I(SPTA) of 3.6 W/cm2 is required from our endoscope probe in order to induce a temperature rise of 4 degrees C within five minutes. Experimental measurements of the array's power output capabilities were conducted using a PVDF hydrophone placed 3 cm away from the face of the transducer in a watertank. Using a PDA14 Signatec data acquisition board to capture full volumes of transmitted ultrasound data, it was determined that the probe can presently maintain intensity values up to 2.4 W/cm2 over indefinite times for therapeutic applications combined with intermittent 3D scanning to maintain targeting. These values were acquired using 8 cycle bursts at a prf of 6 kHz. Ex vivo heating experiments of excised pork tissue yielded a maximum temperature rises of 2.3 degrees C over 5 minutes of ultrasound exposure with an average rise of 1.8 +/- 0.2 degrees C over 5 trials. Modifications to the power supply and transducer array may enable us to reach the higher intensities required to facilitate drug delivery therapy.

Real-time three-dimensional transesophageal echocardiography for guiding interventional electrophysiology: feasibility study.

At present, there are limited methods of acquiring three-dimensional visualization of cardiac structure and function in real-time during interventional electrophysiology procedures. Images acquired for integration of computerized tomography and magnetic resonance imaging with electroanatomic mapping systems are static and are obtained earlier in time. The purpose of this study was to test the feasibility of real-time three-dimensional transesophageal echocardiography for the guidance of interventional electrophysiological studies. A matrix array transducer with 504 channels operating at 5 MHz in a 1 cm diameter steerable esophageal probe was used in conjunction with a scanner capable of real-time 3D scanning of pyramidal volumes from 65 degrees to 120 degrees at rates up to 30 volumes per second. This device has a spatial resolution of approximately 3 mm at 5 cm depth. The authors acquired real-time three-dimensional images of anatomic landmarks of value for electrophysiological procedures in five closed chest canines. Real-time, three-dimensional ultrasound imaging was also used for visualization and guidance of interventional catheter devices within the canine heart. Real-time three-dimensional images of the atria, pulmonary veins, and coronary sinus were acquired. Real-time 3-D color flow Doppler was employed to confirm patency. Multiple image planes of image volumes and rendered views were used to track catheter position and orientation. Images of left veno-atrial junctions have been confirmed by dissection. This study has demonstrated the feasiblity of using real-time three-dimensional transesophageal echocardiography for guiding interventional electrophysiology. The technology has the potential to fill a niche as an adjunct modality for cost-effective real-time interventional guidance and assessment, providing catheter and pacing lead visualization simultaneously with functional volumetric cardiac imaging.

Real-time 3D transesophageal echocardiography.

Transesophageal echocardiography (TEE) is an essential diagnostic tool in patients with poor transthoracic echocardiographic windows or when detailed imaging of structures distant from the chest wall is necessary. A real-time 3D TEE probe has been fabricated in our laboratory in order to increase the amount of information available during a transesophageal procedure. The 1 cm diameter esophageal probe utilizes a 2-dimensional, 5 MHz array at its tip with a 6.3 mm diameter aperture, including 504 active channels. The array has a periodic vernier geometry with an element pitch of 0.18 mm, built onto a multilayer flexible (MLF) interconnect circuit. In order to accommodate 504 channels within the device, a 1 m long Gore MicroFlat cable was utilized for wiring the MLF to the corresponding system connectors. Pulse-echo tests in a water tank have yielded a -6 dB bandwidth of 25.3%. Fully connected to the system through 3 m of cable, the probe shows an average 50 omega insertion loss of-85 dB with a standard deviation of 4 dB, as determined through pitch-catch measurements for a sampling of 10 elements. Using the completed 3D TEE probe with the Volumetrics Medical Imaging 3D scanner, real-time volumetric images of in vivo canine cardiac anatomy have been acquired, displaying atrial views, mitral valve function and interventional catheter guidance.