In response to the high prevalence of stroke, we propose a system for scanning simultaneously via both temporal bone windows. The characteristics of this window and system limitations guide the design of custom matrix arrays. We present operational arrays with a 7 dB increase in SNR made possible by an interconnect system that integrates the probes directly into the scanner, eliminating the lengthy cable common to most probes. In vivo volumes with color flow have been acquired using this system without contrast enhancement. Future transcranial array design improvements have also been illuminated by this process.

We have developed new miniature 2D array transducers integrated into a Cook Medical, Inc. vena cava filter deployment device. One transducer consists of 55 elements operating near 5 MHz. The interelement spacing is 0.20mm. It was constructed on a flat piece of copper clad polyimide and then wrapped around an 11 French catheter of a Cook, Inc. inferior vena cava (IVC) filter deployment device. We used a braided wiring technology from Tyco Electronics Corp. (Wilsonville, OR) to connect the elements to our real-time 3D ultrasound scanner. Typical measured transducer element bandwidth was 20% centered at 4.7 MHz and the 50 Ohm round trip insertion loss was -84 dB. The mean of the nearest neighbor cross talk was -37.0 dB. We have also built a transducer on a 46 cm long single layer flex circuit from MicroConnex (Snoqualmie, WA) which terminates in an interconnect that plugs directly into our system cable. This transducer consists of 70 elements at 0.157 mm interelement spacing operating at 4.8 MHz. Typical measured transducer element bandwidth was 29% and the 50 Ohm round trip insertion loss was - 94 dB. The mean of the nearest neighbor cross talk was -33.0 dB.

Transcranial Doppler imaging with contrast enhancement is a promising approach for visualizing a variety of cerebrovascular diseases requiring rapid treatment to minimize long-term effects. To address the time-sensitive nature of these diseases, we present a real-time 3D ultrasound scanner capable of simultaneously acquiring two trans-temporal volumes with color and spectral Doppler capabilities. To improve the clinical value of these scans, we also present fused, rendered 3D volumes and a rapid technique for registering these volumes. In an in vivo study, we were able to visualize blood flow in the internal carotid arteries, encouraging further development of this system. When combined with presented techniques for phase correction and instrumentation improvements, we envision these visualization techniques may potentially provide clinicians with a rapid, definitive tool to aid in diagnosis.

Contrast-enhanced (CE) transcranial ultrasound (US) and reconstructed 3D transcranial ultrasound have shown advantages over traditional methods in a variety of cerebrovascular diseases. We present the results from a novel ultrasound technique, namely real-time 3D contrast-enhanced transcranial ultrasound with phase aberration correction. Using real-time 3D (RT3D) ultrasound and micro-bubble contrast agent, we scanned 17 healthy volunteers via a single temporal window and 9 via the sub-occipital window and report our detection rates for the major cerebral vessels. In 82% of subjects, we identified the ipsilateral circle of Willis from the temporal window, and in 65% we imaged the entire circle of Willis. From the sub-occipital window, we detected the entire vertebrobasilar circulation in 22% of subjects, and in 50% the basilar artery. After performing phase aberration correction on one subject, we were able to increase the diagnostic value of the scan, detecting a vessel not present in the uncorrected scan. These preliminary results suggest that RT3D CE transcranial US with phase aberration correction has the potential to greatly impact the field of neurosonology.

The goal of this re search is to de ter mine the fea si bil ity of us ing a sin gle en do scopic probe for the com bined pur pose of real-time 3D (RT3D) ul tra sound im ag ing of a tar get or gan and the de liv ery of ul tra sound ther apy to fa cil i tate the ab sorp tion of com pounds for can cer treat ment. Re cent re search in ul tra sound ther apy has shown that ul tra sound-me di ated drug de liv ery im proves ab sorp tion of treat ments for pros tate, cer vi cal and esoph a geal can cer. The abil ity to com bine ul tra sound hyperthermia and 3D im ag ing could im prove vi su al iza tion and tar get ing of can cer ous tis sues. In this study, nu mer i cal mod el ing and ex per i men tal mea sure ments were de vel oped to de ter mine the fea si bil ity of com bined ther apy and im ag ing with a 1cm di am e ter en do scopic RT3D probe with 504 trans mit ters and 252 re ceive chan nels. This de vice op er ates at 5 MHz and has a 6.3 mm x 6.3 mm ap er ture to pro duce real time 3D py ram i dal scans of 60-120 de grees in cor po rat ing 64 x 64 = 4,096 im age lines at 30 vol umes/sec in ter leaved with a 3D steer able ther apy beam. A fi nite-el e ment mesh was con structed with over 128,000 el e ments in LS-DYNA to sim u late the in duced tem per a ture rise from our trans ducer with a 3 cm deep fo cus in tis sue. Quar ter-sym me try of the trans ducer was used to re duce mesh size and com pu ta tion time. Based on in ten sity val ues cal cu lated in Field II us ing the trans ducer’s ar ray ge om e try, a min i mum ISPTA of 3.6 W/cm 2 is re quired from our en do scope probe in or der to in duce a tem per a ture rise of 4oC within five min utes. Ex per i men tal mea sure ments of the ar ray’s power out put ca pa bil i ties were con ducted us ing a PVDF hydrophone placed 3 cm away from the face of the trans ducer in a watertank. Us ing a PDA14 Signatec data ac qui si tion board to cap ture full vol umes of trans mit ted ul tra sound data, it was de ter mined that the probe can pres ently main tain in ten sity val ues up to 2.4 W/cm over in def i nite times for ther a peu tic ap pli ca tions com bined with in ter mit tent 3D scan ning to main tain tar get ing. These val ues were ac quired us ing 8 cy cle bursts at a prf of 6 kHz. Ex vivo heat ing ex per i ments of ex cised pork tis sue yielded a max i mum tem per a ture rises of 2.3°C over 5 min utes of ul tra sound ex po sure with an av er age rise of 1.8 ± 0.2°C over 5 tri als. Mod i fi ca tions to the power sup ply and trans ducer ar ray may en able us to reach the higher in ten si ties re quired to fa cil i tate drug de liv ery ther apy.

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° to 120° 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.

We have previously described guidance of several interventional devices using a real time 3D (RT3D) ultrasound system with 3D color Doppler combined with the ColorMark technology. We then developed an analytical model for a vibrating needle to maximize the tip vibrations and improve the reliability and sensitivity of our technique. In this work, we use the analytical model and improved radiofrequency (RF) and color Doppler filters to detect two different vibrating devices in water tank experiments as well as in an in vivo canine experiment. An atrial septal puncture needle and an endomyocardial biopsy forceps, each vibrating at 1.3 kHz, were inserted into the vascular graft and were tracked using 3D color Doppler. Improved RF and wall filters increased the detected color Doppler sensitivity by 14 dB. In three simultaneous planes from the in vivo 3D scan, we identified both the septal puncture needle and the biopsy forceps within the right atrium using the 2.5 MHz probe. A display filter was used to suppress the unwanted flash artifact associated with physiological motion.

Ultrasound guidance of interventional devices during minimally invasive surgical procedures has been investigated by many researchers. Previously, we extended the methods used by the ColorMark tracking system to several interventional devices using a real-time 3D ultrasound system [Fronheiser, MP, et al., 2004; Smith, SW, et al., 2002]. These results showed that we needed to improve the efficiency and reliability of the tracking. Here, we describe an analytical model to predict the transverse vibrations along the length of an atrial septal puncture needle to enable design improvements of the tracking system. The initial results show an ability to predict the natural nodes and anti-nodes along the needle. Simulations show that applying a forcing function to the device at a natural anti-node yields an order of magnitude larger vibration than when driving the device at a node. 3D pulsed wave spectral Doppler data was acquired along the distal portion of the needle in a water tank using 3D transesophageal echocardiography (TEE) transducer probe. This data was compared to simulations of forced vibrations from the model. These initial results suggest that the model is a good first approximation of the vibrating device in a water tank. It is our belief that knowing the location of the natural nodes and anti-nodes will improve our ability to drive the device, which should improve our ability to track the device in vivo

The integration of real-time three-dimensional (RT3D) laparoscopic ultrasound with recent advances in robotic surgery can increase automation and ease of use for surgery in general, gynecological, and urological procedures. In this study, the 3D measurement system of the volumetric scanner used with a 1 cm diameter laparoscopic probe for RT3D imaging 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 3D laparoscopic ultrasound device, coordinates were acquired by the scanner and used to direct a robotically controlled needle towards desired in vitro targets. This system was also implemented for guiding a needle to organ boundaries in a post-mortem and an in vivo canine model. The RMS error for these measurements was 1.34 mm using optical alignment and 0.76 mm using ultrasound alignment

We have described and fabricated 2D array transducers for many real time volumetric imaging applications. These applications include transducers operating up to 5 MHz for transthoracic imaging, up to 15 MHz for intracardiac echocardiography (ICE), 5 MHz for transesophageal echocardiography (TEE) and 7 MHz for laparoscopic ultrasound imaging (LUS). We have recently adapted a transducer designed for TEE to be used for real time volumetric endoscopic imaging of the brain. The transducer consists of a 36 times 36 array with an interelement spacing of 0.18 mm. There are 508 transmitting and 256 receive channels placed in a regular pattern in the array. The operating frequency is 5 MHz with a -6 dB bandwidth of 30%. The transducer is fabricated on a 10 layer flexible circuit from MicroConnex (Seattle, WA). We bent the flexible circuit such that the finished transducer is in the forward viewing configuration. We used the Volumetrics Imaging (Durham, NC) 3D scanner to obtain our images in a canine model. In an intra-operative surgical procedure, a 10 mm burr hole was drilled through the skull of the canine. The hole was placed to one side of the midline and the transducer was placed up against the dura for endoscopic ultrasound imaging. Images of the lateral ventricles were produced , including real time 3D guidance of a needle puncture of one ventricle. In addition, contrast (Optison, Amersham) enhanced 3D Doppler color flow images have been made of the cerebral vessels including the complete Circle of Willis. Applications include real time 3D guidance of cerebral spinal fluid extraction from the lateral ventricles and bedside evaluation of critically ill patients where CT and MR imaging techniques are unavailable

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 hyperthermia to facilitate the absorption of compounds for cancer treatment. The ability to combine ultrasound hyperthermia and 3D imaging could improve visualization and targeting. In this study, numerical modeling and experimental measurements were developed to determine the feasibility of combined therapy and imaging with a 5 MHz, 1 cm diameter endoscopic RT3D probe with 504 active channels. 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. Based on intensity values calculated in Field II using the transducer's array geometry, a minimum I SPTA of 3.43 W/cm 2 is required in order to induce a temperature rise of 4 degC within 5 minutes. It was determined through dosimetry measurements that the probe can presently maintain intensity values up to 2.4 W/cm 2 over indefinite times for therapeutic applications combined with intermittent 3D scanning to maintain targeting. In vitro heating experiments of excised pork tissue yielded a maximum temperature rise of 2.3 degC over 5 minutes of ultrasound exposure with an average rise of 1.8 plusmn 0.2 degC 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

Modifications were made to a commercial real-time, three-dimensional (3-D) ultrasound system for near simultaneous 3-D scanning with two matrix array transducers. As a first illustration, a transducer cable assembly was modified to incorporate two independent, 3-D intra-cardiac echo catheters, a 7 Fr (2.3 mm O.D.) side scanning catheter and a 14 Fr (4.7 mm O.D) forward viewing catheter with accessory port, each catheter using 85 channels operating at 5 MHz. For applications in treatment of atrial fibrillation, the goal is to place the sideviewing catheter within the coronary sinus to view the whole left atrium, including a pulmonary vein. Meanwhile, the forward-viewing catheter inserted within the left atrium is directed toward the ostium of a pulmonary vein for therapy using the integrated accessory port. Using preloaded, phasing data, the scanner switches between catheters automatically, at the push of a button, with a delay of about 1 second, so that the clinician can view the therapy catheter with the coronary sinus catheter and vice versa. Preliminary imaging studies in a tissue phantom and in vivo show that our system successfully guided the forward-viewing catheter toward a target while being imaged with the sideviewing catheter. The forward-viewing catheter then was activated to monitor the target while we mimicked therapy delivery. In the future, the system will switch between 3-D probes on a line-by-line basis and display both volumes simultaneously.

We have previously described 2D array ultrasound transducers operating up to 13.5 MHz for applications including real time 3D transthoracic imaging, real time volumetric intracardiac echocardiography (ICE), real time transesophageal echocardiography (TEE) and real time 3D intravascular ultrasound (IVUS) imaging. We have recently built a pair of 2D array transducers for real time 3D laparoscopic ultrasound imaging. These transducers are intended to be placed down a trocar during minimally invasive surgery. Both transducers were built using Gore MicroFlat cables consisting of 18 wires spaced at 0.10 mm and attached to a polyimide backing. The first is a forward viewing 5 MHz, 19 x 11 array with 198 operating elements. It was built on an 8 layer multi-layer flex circuit. The interelement spacing is 0.20 mm yielding an aperture that is 2.2 mm x 3.8 mm. The O.D. of the completed transducer is 10.2 mm , and includes a 2 mm tool port. The average measured center frequency is 4.5 MHz, and the -6 dB bandwidth ranges from 15% to 30%. The 50 Ohm insertion loss, including the MicroFlat cabling, is -81.2 dB. The second transducer is a 7 MHz, 36 x 36 array with 504 operating elements. It was built upon a 10 layer multi-layer flex circuit. This transducer is in the forward viewing configuration, and the interelement spacing is 0.18 mm. The total aperture size is 6.48 mm x 6.48 mm. The O.D. of the completed transducer is 11.4 mm. The average measured center frequency is 7.2 MHz, and the -6 dB bandwidth ranges from 18% to 33%. The 50 Ohm insertion loss is -79.5 dB, including the MicroFlat cable. Real time in vivo 3D images of a canine heart have been made including an apical 4 chamber view from a substernal access with the first transducer to monitor cardiac function. In addition we produced real time 3D rendered images of the right pulmonary veins from a right parasternal access with the second transducer which would be valuable in the guidance of cardiac ablation catheters for treatment of atrial fibrillation.

We have previously described 2D array ultrasound transducers operating up to 10 MHz for applications including real time 3D transthoracic imaging, real time volumetric intracardiac echocardiography (ICE), real time 3D intravascular ultrasound (IVUS) imaging, and real time 3D transesophageal echocardiography (TEE). We have recently built a pair of 2D array transducers for real time 3D laparoscopic ultrasonography (3D LUS). These transducers are intended to be placed down a trocar during minimally invasive surgery. The first is a forward viewing 5 MHz, 11 times 19 array with 198 operating elements. It was built on an 8 layer multilayer flex circuit. The interelement spacing is 0.20 mm yielding an aperture that is 2.2 mm × 3.8 mm. The O.D. of the completed transducer is 10.2 mm and includes a 2 mm tool port. The average measured center frequency is 4.5 MHz, and the −6 dB bandwidth ranges from 15% to 30%. The 50 Ω insertion loss, including Gore MicroFlat cabling, is −81.2 dB. The second transducer is a 7 MHz, 36 times 36 array with 504 operating elements. It was built upon a 10 layer multilayer flex circuit. This transducer is in the forward viewing configuration and the interelement spacing is 0.18 mm. The total aperture size is 6.48 mm x 6.48 mm. The O.D. of the completed transducer is 11.4 mm. The average measured center frequency is 7.2 MHz, and the −6 dB bandwidth ranges from 18% to 33%. The 50 Ω insertion loss is −79.5 dB, including Gore MicroFlat cable. Real-time in vivo 3D images of canine hearts have been made including an apical 4-chamber view from a substernal access with the first transducer to monitor cardiac function. In addition, we produced real time 3D rendered images of the right pulmonary veins from a right parasternal access with the second transducer, which would be valuable in the guidance of cardiac ablation catheters for treatment of atrial fibrillation.

Wavefront distortion induced by the skull severely impacts transcranial ultrasound. In particular, the skull reduces the ability to monitor flow in the cerebral vasculature. We present B-scan and color flow images, aberratred with polymer casts of skull bone, that have been improved with near-field phase correction techniques. These algorithms rely on speckle targets for estimation of the phase profile. Real-time adaptive imaging experiements in tissue-mimicking phantoms with 4 mm spherical voids were performed using multi-lag cross-correlation and multi-lag speckle brightness phase correction algorithms. The real-time adaptive imaging was con- structed on a Siemens Antares TM scanner and used a custom 3.5 MHz, 1.75-D transducer (8×96 elements). Phase correction with the 1.75-D array was performed in a matter of a few seconds. The contrast-to-speckle (CSR) of the spherical voids improved from 1.16 ± 0.39 in the aberrated images to 1.52 ± 0.37 in the phase corrected images. Using a 2.5 MHz, 2-D array on a real time 3-D scanner similar experiments with spherical voids were performed. The CSR of the lesions on the 3-D scanner improved from 0.9 in the aberrated images to 1.6 in the phase corrected images. In addition, phase correction was shown to improve the estimation of 3-D color flow when the transducer was focused on a speckle target through the skull cast. I. INTRODUCTION Over the last decade, with the availability of color flow and power Doppler combined with safe, effective intravenous ultrasound contrast agents, a renaissance has occurred in the evaluation of cerebrovascular disease using transcranial ultrasound in spite of the image degrading properties of the skull. The standardized examination procedure for transcranial ultrasound uses a 2 MHz phased array applied to the acoustic windows of the skull combined with contrast agents and color flow Doppler and/or power Doppler. Extensive recent reviews have described the role of ultrasound in the evaluation of stroke and other pathologies of the intracranial vascular system (1, 2) as well as the brain parenchyma (3). Furthermore, there is continuing progress in the measurement of cerebral perfusion with new ultrasound contrast agents and harmonic imaging techniques (4). In 2004, we showed the feasibility of real-time 3-D tran- scranial ultrasound imaging (5). However, imaging the brain with ultrasound is a difficult process because the skull has a significantly higher speed of sound (approximately 3000 m/s) than soft tissues (nominally 1540 m/s). At such a large discrepancy in sound speed, the phase and amplitude of the ultrasound wave become severely distorted, resulting in significant degradation in beam focusing and image quality.

A method for simulating the temperature rise due to acoustic heating from an ablation transducer is introduced. The size of lesions produced by this temperature rise is also modeled. First the intensity from the transducer is calculated using Field II. This intensity is scaled to a measured value and converted into acoustic heat generation. Finite element analysis is then used to find the temperature rise in tissue from this heat generation. The thermal dose is calculated and from that the size of any lesions may be predicted. We validate the model by comparing simulated results to experimental results from an ablation ring transducer. Temperatures were within 2/spl deg/C of the experiment after a 2 minute ablation. The simulation predicted a lesion size of 1.75 mm deep by 5.5 mm in diameter. The experimental average of four lesions was 1.75 mm deep by 4.6 mm in diameter. The model was then used to predict the temperatures and lesions created by an 86 element linear array transducer in various configurations.

Real time 3D IVUS may require imaging depths of a few centimeters to look down the axis of a coronary vessel to view vulnerable atherosclerotic plaque. We have previously described 2D array transducers for forward looking real time 3D intravascular ultrasound (IVUS). We developed two transducers for different applications. Both transducers were constructed in the forward viewing configuration to allow simultaneous real time B-scans, G scans and volumetric rendering of vessels. vascular stents and other devices implanted in the peripheral vessels. The first is a 14 French catheter transducer intended to guide the placement and retrieval of devices in the peripheral vessels. It operates at 5 MHz and features 112 active channels in a 10 x 14 array. This transducer was originally designed for intracardiac echo applications. and has been previously reported. The second is a 5 French catheter transducer for use in smaller vessels. It operates at 10.0 MHz. and the array is 11 x 11 = 121 elements. We used non-coaxial cabling to obtain the needed number of conductors in the small lumen. In order to conform to the round aperture of the IVUS lumen. the corners were cut off resulting in a total of 97 signal channels. The 50 Ohm insertion loss is -83 dB and the -6 dB bandwidth is 25%. Average cross talk on nearest neighbor elements is -31.6 dB when loaded by 50 Ohms. However. our earlier processes led to poor yield and image quality. A new process. based on a custom fixture. improved the flatness of the wireguide. This improved our bonding and dicing techniques and increased our yield by 50%. Real time 3D images include tissue vascular phantoms with a 4.0 mm diameter lumen. a vascular stent before and after deployment in a tissue mimic phantom. and images of the aorta of an excised sheep heart. We have also pursued the fabrication of another 2D array transducer for IVUS that was constructed with non-rectilinear element placement. Using, the same cabling, 61 elements were diced out with a laser. Preliminary pulse and spectrum show a -6 dB bandwidth of 55% centered at 13 MHz.

We have previously described 2D arrays operating at up to 10.0 MHz consisting of several thousand elements for transthoracic cardiac imaging and over a hundred elements for intracardiac imaging using 7 Fr to 12 Fr catheters. We have begun to explore forward viewing real time 3D phased array intravascular ultrasound, which may require imaging depths of a few centimeters to look down the axis of a vessel to view vulnerable atherosclerotic plaque. We used a noncoaxial based cable technology that allowed 100 signal wires to be placed inside a 4.8 French IVUS lumen with an inner diameter of 1.3 mm. We pursued two different fabrication technologies for the building of the transducers. Each transducer was constructed in the forward viewing configuration to allow simultaneous real time B-scans, C-scans and volumetric rendering of vessels and vascular stents distal to the catheter tip. In order to obtain the desired penetration depth, each transducer was constructed to operate at 10.0 MHz. The first method included an ordered array of 11 × 11 = 121 elements. In order to conform to the round aperture of the IVUS lumen, the corners were cut off, resulting in a total of 97 signal channels. Real time images include a 4 mm diameter vessel in a tissue mimicking phantom, an expanded stent and a stent in an excised sheep aorta. The second method is based upon a laser dicing technique that cuts the individual elements in a random pattern. This resulted in 61 signal channels. Real time 3D images of the AIUM test object were made with this transducer.

The design, fabrication, and characterization of a 112 channel, 5 MHz, two-dimensional (2-D) array transducer constructed on a six layer flexible polyimide interconnect circuit is described. The transducer was mounted in a 7 Fr (2.33 mm outside diameter) catheter for use in real-time intracardiac volumetric imaging. Two transducers were constructed: one with a single silver epoxy matching layer and the other without a matching layer. The center frequency and -6 dB fractional bandwidth of the transducer with a matching layer were 4.9 MHz and 31%, respectively. The 50 /spl Omega/ pitch-catch insertion loss was 80 dB, and the typical interelement crosstalk was -30 dB. The final element yield was greater than 97% for both transducers. The transducers were used to acquire real-time, 3-D images in an in vivo sheep model. We present in vivo images of cardiac anatomy obtained from within the coronary sinus, including the left and right atria, aorta, coronary arteries, and pulmonary veins. We also present images showing the manipulation of a separate electrophysiological catheter into the coronary sinus.

Endoscopic optical coherence tomography (EOCT) is a medical imaging technique that uses infrared light delivered via an endoscope to produce high-resolution images of tissue microstructure of the gastrointestinal tract. A key component of an EOCT system is the method used to scan the infrared beam across the tissue surface. We have begun developing electrostatic MEMS micromirror devices for use in EOCT. These devices consist of 1 mm square gold-plated silicon mirrors on polyimide tables that tilt on 3 mum thick torsion hinges. The MEMS actuator used to tilt the mirror, the integrated forces array (IFA) is a thin (2.2 mum) polyimide membrane consisting of hundreds of thousands of deformable capacitors that can produce strains up to 20% and forces equivalent to 13 mg with applied voltages from 30-120 V. Measurements of optical deflections of these devices range from 18degrees at low frequencies to more than 120degrees near the resonant frequencies of the structures (30-60 Hz). The support structures, hinges, and actuators are fabricated from polyimide on silicon using photolithography. These electrostatic MEMS micromirrors were inserted into the scanning arm of an OCT imaging system to take in vitro images of porcine tissue and in vivo images of human skin at frame rates from 4-8 Hz. SLA probe tips were designed and fabricated to align the optics of the device and to protect the fragile polyimide devices during endoscopic imaging. In addition, devices are being fabricated that combine the IFA and mirror structures onto a single silicon wafer, reducing fabrication difficulty.