Integrated Endoscope for Real-Time 3D Ultrasound Imaging and Hyperthermia: Feasibility Study

Abstract

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.

Dual-Mode IVUS Transducer for Image-Guided Brain Therapy: Preliminary Experiments

“…Dual-mode ultrasound devices for image-guided therapy have been designed and implemented for many different applications using various approaches (Hynynen 1997; Wu et al 2001; Barthe et al 2004; Gentry and Smith 2004; Makin et al 2005; Ebbini et al 2006; Pua et al 2007; Bouchoux et al 2008; Bouchoux et al 2010). Intravascular ultrasound (IVUS) catheters, which are typically less than 4 Fr, were developed to navigate into coronary vessels to visualize and characterize atherosclerotic plaque (Fishbein and Siegel 1998; Mehran et al 1998; Nishioka et al 1998; Uren et al 1998a; Uren et al 1998b).…”

Dual-mode IVUS catheter for intracranial image-guided hyperthermia: Feasibility study

“…Dual-mode ultrasound devices for image-guided therapy have been designed and implemented for several thermal applications (e.g., treatment of cardiac arrhythmias and tumors of the liver, breast, biliary ducts, and prostate), using a catheter, endoscope, or extracorporeal approach with either single element or phased array transducers [40]–[45]. Ultrasound is an attractive modality for guidance, treatment, and monitoring because of its potential for inherent spatial registration between functions, as well as its low cost, portability, and high frame rate [43], [44], [46].…”

Dual-Mode Intracranial Catheter Integrating 3D Ultrasound Imaging and Hyperthermia for Neuro-oncology: Feasibility Study

“…[23][24][25][26][27] Dual-mode ul tra sound trans duc ers for im age-guided ther apy have been de signed and imple mented for sev eral ther mal ap pli ca tions, in clud ing treat ment of car diac arrhythmias and tu mors of the liver, breast, biliary ducts and pros tate. [28][29][30][31][32][33] These have been de vel oped with a cath e ter, en do scope or extracorporeal ap proach, us ing ei ther a sin gle el e ment or phased array for ther apy (phased ar rays al low for the most con trol over the en ergy de po si tion pat tern of ul tra sound). 34 When com pared with mag netic res o nance (MR) im ag ing, ultrasound is an at trac tive mo dal ity for guid ance and treat ment mon i tor ing, be cause of its low cost, por ta bility and high frame rate.…”