Current Role at Stanford

•Original research focusing on applications of MR guided Focused Ultrasound (MRgFUS) for ablative treatments of cancer and trans-cranial neurosurgical treatment of tremor.
•Developing new MRI imaging strategies and pulse sequence development of non-ablative applications of focused ultrasound, including MR Acoustic Radiation Force Imaging.
•Medical Physicist including ultrasound treatment planning and MRI imaging specialist of multiple ongoing human clinical trials, as well as clinical treatments at SHC, to image, treat, and monitor MRgFUS of bone metastases, soft tissue tumors of the extremities, uterine fibroids, and trans-cranial MRgFUS treatment of essential tremor.
•Bridge technical and clinical communication as a go between in collaborations with clinicians, interventional radiologists, imaging technologists, medical device companies, and research scientists, graduate students, and faculty.

Honors & Awards

  • NIH LRP Award for Clinical Research, National Institutes of Health (2014)
  • Magna Cum Laude Merit Award, International Society of Magnetic Resonance in Medicine - 20th Annual Symposium (2012)
  • Postdoctoral Fellowship Award, California Breast Cancer Research Program (2010-2012)
  • Member, Tau Beta Pi Engineering Honor Society (2000)

Education & Certifications

  • Ph.D., University of Southern California, Biomedical Engineering (2008)
  • M.S., University of Southern California, Biomedical Engineering (2005)
  • B.S., University of South Florida, Electrical Engineering (2002)


Professional Affiliations and Activities

  • Director, Radiological Sciences Laboratory Trainee Council (2012 - 2014)
  • Member, International Society of Magnetic Resonance in Medicine (2009 - Present)


All Publications

  • Correcting Heat-Induced Chemical Shift Distortions in Proton Resonance Frequency-Shift Thermometry MAGNETIC RESONANCE IN MEDICINE Gaur, P., Partanen, A., Werner, B., Ghanouni, P., Bitton, R., Pauly, K. B., Grissom, W. A. 2016; 76 (1): 172-182

    View details for DOI 10.1002/mrm.25899

    View details for Web of Science ID 000384996900016

  • Correcting heat-induced chemical shift distortions in proton resonance frequency-shift thermometry. Magnetic resonance in medicine Gaur, P., Partanen, A., Werner, B., Ghanouni, P., Bitton, R., Butts Pauly, K., Grissom, W. A. 2016; 76 (1): 172-182


    To reconstruct proton resonance frequency-shift temperature maps free of chemical shift distortions.Tissue heating created by thermal therapies such as focused ultrasound surgery results in a change in proton resonance frequency that causes geometric distortions in the image and calculated temperature maps, in the same manner as other chemical shift and off-resonance distortions if left uncorrected. We propose an online-compatible algorithm to correct these distortions in 2DFT and echo-planar imaging acquisitions, which is based on a k-space signal model that accounts for proton resonance frequency change-induced phase shifts both up to and during the readout. The method was evaluated with simulations, gel phantoms, and in vivo temperature maps from brain, soft tissue tumor, and uterine fibroid focused ultrasound surgery treatments.Without chemical shift correction, peak temperature and thermal dose measurements were spatially offset by approximately 1 mm in vivo. Spatial shifts increased as readout bandwidth decreased, as shown by up to 4-fold greater temperature hot spot asymmetry in uncorrected temperature maps. In most cases, the computation times to correct maps at peak heat were less than 10 ms, without parallelization.Heat-induced proton resonance frequency changes create chemical shift distortions in temperature maps resulting from MR-guided focused ultrasound surgery ablations, but the distortions can be corrected using an online-compatible algorithm. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.25899

    View details for PubMedID 26301458

  • Magnetic resonance-guided focused ultrasound treatment of extra-abdominal desmoid tumors: a retrospective multicenter study. European radiology Ghanouni, P., Dobrotwir, A., Bazzocchi, A., Bucknor, M., Bitton, R., Rosenberg, J., Telischak, K., Busacca, M., Ferrari, S., Albisinni, U., Walters, S., Gold, G., Ganjoo, K., Napoli, A., Pauly, K. B., Avedian, R. 2016: -?


    To assess the feasibility, safety and preliminary efficacy of magnetic resonance-guided focused ultrasound (MRgFUS) for the treatment of extra-abdominal desmoid tumours.Fifteen patients with desmoid fibromatosis (six males, nine females; age range, 7-66 years) were treated with MRgFUS, with seven patients requiring multiple treatments (25 total treatments). Changes in viable and total tumour volumes were measured after treatment. Efficacy was evaluated using an exact one-sided Wilcoxon test to determine if the median reduction in viable tumour measured immediately after initial treatment exceeded a threshold of 50 % of the targeted volume. Median decrease after treatment of at least two points in numerical rating scale (NRS) worst and average pain scores was tested with an exact one-sided Wilcoxon test. Adverse events were recorded.After initial MRgFUS treatment, median viable targeted tumour volume decreased 63 %, significantly beyond our efficacy threshold (P = 0.0013). Median viable total tumour volume decreased (105 mL [interquartile range {IQR}, 217 mL] to 54 mL [IQR, 92 mL]) and pain improved (worst scores, 7.5 ± 1.9 vs 2.7 ± 2.6, P = 0.027; average scores, 6 ± 2.3 vs 1.3 ± 2, P = 0.021). Skin burn was the most common complication.MRgFUS significantly and durably reduced viable tumour volume and pain in this series of 15 patients with extra-abdominal desmoid fibromatosis.• Retrospective four-centre study shows MRgFUS safely and effectively treats extra-abdominal desmoid tumours • This non-invasive procedure can eradicate viable tumour in some cases • Alternatively, MRgFUS can provide durable control of tumour growth through repeated treatments • Compared to surgery or radiation, MRgFUS has relatively mild side effects.

    View details for PubMedID 27147222

  • Is MR-guided High-intensity Focused Ultrasound a Feasible Treatment Modality for Desmoid Tumors? CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Avedian, R. S., Bitton, R., Gold, G., Butts-Pauly, K., Ghanouni, P. 2016; 474 (3): 697-704


    MR-guided high-intensity focused ultrasound is a noninvasive treatment modality that uses focused ultrasound waves to thermally ablate tumors within the human body while minimizing side effects to surrounding healthy tissues. This technology is FDA-approved for certain tumors and has potential to be a noninvasive treatment option for extremity soft tissue tumors. Development of treatment modalities that achieve tumor control, decrease morbidity, or both might be of great benefit for patients. We wanted to assess the potential use of this technology in the treatment of extremity desmoid tumors.(1) Can we use MR-guided high-intensity focused ultrasound to accurately ablate a predetermined target volume within a human cadaver extremity? (2) Does MR-guided high-intensity focused ultrasound treatment stop progression and/or cause regression of extremity desmoid tumors?Simulated tumor volumes in four human cadavers, created by using plastic markers, were ablated using a commercially available focused ultrasound system. Accuracy was determined in accordance with the International Organization of Standards location error by measuring the farthest distance between the ablated tissue and the plane corresponding to the target. Between 2012 and 2014, we treated nine patients with desmoid tumors using focused ultrasound ablation. Indications for this were tumor-related symptoms or failure of conventional treatment. Of those, five of them were available for MRI followup at 12 months or longer (mean, 18.2 months; range, 12-23 months). The radiographic and clinical outcomes of five patients who had desmoid tumors treated with focused ultrasound were prospectively recorded. Patients were assessed preoperatively with MRI and followed at routine intervals after treatment with MRI scans and clinical examination.The ablation accuracy for the four cadaver extremities was 5 mm, 3 mm, 8 mm, and 8 mm. Four patients' tumors became smaller after treatment and one patient has slight progression at the time of last followup. The mean decrease in tumor size determined by MRI measurements was 36% (95% confidence interval, 7%-66%). No patient has received additional adjuvant systemic or local treatment. Treatment-related adverse events included first- and second-degree skin burns occurring in four patients, which were managed successfully without further surgery.This preliminary investigation provides some evidence that MR-guided high-intensity focused ultrasound may be a feasible treatment for desmoid tumors. It may also be of use for other soft tissue neoplasms in situations in which there are limited traditional treatment options such as recurrent sarcomas. Further investigation is necessary to better define the indications, efficacy, role, and long-term oncologic outcomes of focused ultrasound treatment.Level IV, therapeutic study.

    View details for DOI 10.1007/s11999-015-4364-0

    View details for Web of Science ID 000370150000018

    View details for PubMedID 26040967

  • Improving thermal dose accuracy in magnetic resonance-guided focused ultrasound surgery: Long-term thermometry using a prior baseline as a reference. Journal of magnetic resonance imaging Bitton, R. R., Webb, T. D., Pauly, K. B., Ghanouni, P. 2016; 43 (1): 181-189


    To investigate thermal dose volume (TDV) and non-perfused volume (NPV) of magnetic resonance-guided focused ultrasound (MRgFUS) treatments in patients with soft tissue tumors, and describe a method for MR thermal dosimetry using a baseline reference.Agreement between TDV and immediate post treatment NPV was evaluated from MRgFUS treatments of five patients with biopsy-proven desmoid tumors. Thermometry data (gradient echo, 3T) were analyzed over the entire course of the treatments to discern temperature errors in the standard approach. The technique searches previously acquired baseline images for a match using 2D normalized cross-correlation and a weighted mean of phase difference images. Thermal dose maps and TDVs were recalculated using the matched baseline and compared to NPV.TDV and NPV showed between 47%-91% disagreement, using the standard immediate baseline method for calculating TDV. Long-term thermometry showed a nonlinear local temperature accrual, where peak additional temperature varied between 4-13°C (mean = 7.8°C) across patients. The prior baseline method could be implemented by finding a previously acquired matching baseline 61% ± 8% (mean ± SD) of the time. We found 7%-42% of the disagreement between TDV and NPV was due to errors in thermometry caused by heat accrual. For all patients, the prior baseline method increased the estimated treatment volume and reduced the discrepancies between TDV and NPV (P = 0.023).This study presents a mismatch between in-treatment and post treatment efficacy measures. The prior baseline approach accounts for local heating and improves the accuracy of thermal dose-predicted volume. J. MAGN. RESON. IMAGING 2016;43:181-189.

    View details for DOI 10.1002/jmri.24978

    View details for PubMedID 26119129

  • MR-acoustic radiation force imaging (MR-ARFI) and susceptibility weighted imaging (SWI) to visualize calcifications in ex vivo swine brain JOURNAL OF MAGNETIC RESONANCE IMAGING Bitton, R. R., Butts, K. R. 2014; 39 (5): 1294-1300


    To present the use of MR-acoustic radiation force imaging (MR-ARFI) and susceptibility weighted imaging (SWI) to visualize calcifications in ex vivo brain tissue as a planning indicator for MR-guided focused ultrasound (MRgFUS).Calcifications were implanted in ex vivo swine brain and imaged using SWI, MR-ARFI, and computed tomography (CT). SWI-filtered phase images used 3D gradient recalled echo (GRE) images with a Fourier-based unwrapping algorithm. The MR-ARFI pulse sequence used a 2DFT spin-echo with repeated bipolar encoding gradients in the direction of the longitudinal ultrasound beam. MR-ARFI interrogations scanned a subregion (14 × 10 × 12 mm) of the brain surrounding the calcification. They were combined into a single displacement weighted map, using the sum of squares method. Calcification size estimates were based on image profiles plotted along the ±x and ±z direction, at the full-width half-maximum.Both MR-ARFI and SWI were able to visualize the calcifications. The contrast ratio was 150 for CT, 12 for SWI, and 12 for MR-ARFI. Profile measures were 1.35 × 1.28 mm on CT, 1.24 × 1.73 mm on SWI, and 2.45 × 3.02 mm on MR-ARFI. MR-ARFI displacement showed a linear increase with acoustic power (20-80W), and also increased with calcification size.The use of SWI-filtered phase and MR-ARFI have the potential to provide a clinical indicator of calcification relevance in the planning of a transcranial MRgFUS treatment.J. Magn. Reson. Imaging 2013. © 2013 Wiley Periodicals, Inc.

    View details for DOI 10.1002/jmri.24255

    View details for Web of Science ID 000333984700028

    View details for PubMedID 24123504

  • Toward MR-guided high intensity focused ultrasound for presurgical localization: Focused ultrasound lesions in cadaveric breast tissue JOURNAL OF MAGNETIC RESONANCE IMAGING Bitton, R. R., Kaye, E., Dirbas, F. M., Daniel, B. L., Pauly, K. B. 2012; 35 (5): 1089-1097


    To investigate magnetic resonance image-guided high intensity focused ultrasound (MR-HIFU) as a surgical guide for nonpalpable breast tumors by assessing the palpability of MR-HIFU-created lesions in ex vivo cadaveric breast tissue.MR-HIFU ablations spaced 5 mm apart were made in 18 locations using the ExAblate2000 system. Ablations formed a square perimeter in mixed adipose and fibroglandular tissue. Ablation was monitored using T1-weighted fast spin echo images. MR-acoustic radiation force impulse (MR-ARFI) was used to remotely palpate each ablation location, measuring tissue displacement before and after thermal sonications. Displacement profiles centered at each ablation spot were plotted for comparison. The cadaveric breast was manually palpated to assess stiffness of ablated lesions and dissected for gross examination. This study was repeated on three cadaveric breasts.MR-ARFI showed a collective postablation reduction in peak displacement of 54.8% ([4.41 ± 1.48] ?m pre, [1.99 ± 0.82] ?m post), and shear wave velocity increase of 65.5% ([10.69 ± 1.60] mm pre, [16.33 ± 3.10] mm post), suggesting tissue became stiffer after the ablation. Manual palpation and dissection of the breast showed increased palpability, a darkening of ablation perimeter, and individual ablations were visible in mixed adipose/fibroglandular tissue.The results of this preliminary study show MR-HIFU has the ability to create palpable lesions in ex vivo cadaveric breast tissue, and may potentially be used to preoperatively localize nonpalpable breast tumors.

    View details for DOI 10.1002/jmri.23529

    View details for Web of Science ID 000302721800011

    View details for PubMedID 22170814

  • A 3-D High-Frequency Array Based 16 Channel Photoacoustic Microscopy System for In Vivo Micro- Vascular Imaging IEEE TRANSACTIONS ON MEDICAL IMAGING Bitton, R., Zemp, R., Yen, J., Wang, L. V., Shung, K. K. 2009; 28 (8): 1190-1197


    This paper discusses the design of a novel photoacoustic microscopy imaging system with promise for studying the structure of tissue microvasculature for applications in visualizing angiogenesis. A new 16 channel analog and digital high-frequency array based photoacoustic microscopy system (PAM) was developed using an Nd:YLF pumped tunable dye laser, a 30 MHz piezo composite linear array transducer, and a custom multichannel receiver electronics system. Using offline delay and sum beamforming and beamsteering, phantom images were obtained from a 6 mum carbon fiber in water at a depth of 8 mm. The measured -6 dB lateral and axial spatial resolution of the system was 100+/-5 microm and 45+/-5 microm, respectively. The dynamic focusing capability of the system was demonstrated by imaging a composite carbon fiber matrix through a 12.5 mm imaging depth. Next, 2-D in vivo images were formed of vessels around 100 mum in diameter in the human hand. Three-dimensional in vivo images were also formed of micro-vessels 3 mm below the surface of the skin in two Sprague Dawley rats.

    View details for DOI 10.1109/TMI.2008.2011899

    View details for Web of Science ID 000268525500005

    View details for PubMedID 19131292

  • Realtime Photoacoustic Microscopy of Murine Cardiovascular Dynamics OPTICS EXPRESS Zemp, R. J., Song, L., Bitton, R., Shung, K. K., Wang, L. V. 2008; 16 (22): 18551-18556


    Non-invasive visualization of cardiovascular dynamics in small animals is challenging due to their rapid heart-rates. We present a realtime photoacoustic imaging system consisting of a 30-MHz ultrasound array transducer, receive electronics, a high-repetition-rate laser, and a multicore-computer, and demonstrate its ability to image optically-absorbing structures of the beating hearts of young athymic nude mice at rates of approximately 50 frames per second with 100 microm x 25 microm spatial resolution. To our knowledge this is the first report of realtime photoacoustic imaging of physiological dynamics.

    View details for Web of Science ID 000260865900140

    View details for PubMedID 18958134

  • Realtime photoacoustic microscopy in vivo with a 30-MHz ultrasound array transducer OPTICS EXPRESS Zemp, R. J., Song, L., Bitton, R., Shung, K. K., Wang, L. V. 2008; 16 (11): 7915-7928


    We present a novel high-frequency photoacoustic microscopy system capable of imaging the microvasculature of living subjects in realtime to depths of a few mm. The system consists of a high-repetition-rate Q-switched pump laser, a tunable dye laser, a 30-MHz linear ultrasound array transducer, a multichannel high-frequency data acquisition system, and a shared-RAM multi-core-processor computer. Data acquisition, beamforming, scan conversion, and display are implemented in realtime at 50 frames per second. Clearly resolvable images of 6-microm-diameter carbon fibers are experimentally demonstrated at 80 microm separation distances. Realtime imaging performance is demonstrated on phantoms and in vivo with absorbing structures identified to depths of 2.5-3 mm. This work represents the first high-frequency realtime photoacoustic imaging system to our knowledge.

    View details for Web of Science ID 000256469900038

    View details for PubMedID 18545502

  • Design of a high frequency array based photoacoustic Microscopy system for micro-vascular Imaging 2007 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-16 Bitton, R., Zerrip, R., Yen, J., Wang, L. H., Shung, K. K. 2007: 2175-2178


    The rapidly expanding field of photoacoustic imaging includes a technique called photoacoustic microscopy. Photoacoustic microscopy is a hybrid imaging modality with sub-millimeter resolution that possesses the contrast benefit of optical imaging and the resolution benefit of ultrasonic imaging. This technique can be used to image the structure and dynamics of microvessels involved in angiogenesis within biological tissue. In this paper we present results of a new high frequency array based photoacoustic microscopy system (PAM) using an Nd:YLF pumped tunable dye laser, a 30MHz piezo composite linear array and a custom multi-channel receiver system. Using offline delay and sum beamforming and beamsteering, phantom images were obtained from a 6microm carbon fiber in water at a depth of 8mm. The measured axial and lateral spatial resolution of the system was 103+/-5microm and 45+/-5microm, respectively. In vivo B-scans were obtained from vessels within a human hand as well as 3D photoacoustic images of vessels 3mm below the skin surface in a Sprague Dawley Rat.

    View details for Web of Science ID 000253467001228

    View details for PubMedID 18002420

  • Photoacoustic imaging of the microvasculature with a high-frequency ultrasound array transducer JOURNAL OF BIOMEDICAL OPTICS Zemp, R. J., Bitton, R., Li, M., Shung, K. K., Stoica, G., Wang, L. V. 2007; 12 (1)


    Visualization of microvascular networks could provide new information about function and disease. We demonstrate the capabilities of a 30-MHz ultrasound array system for photoacoustic microscopy of small (< or = 300 microm) vessels in a rat. 3D images obtained by translating the array in the elevation direction are compared with photographs of excised skin. The system is shown to have 100-microm lateral resolution, 25-microm axial resolution, and 3-mm imaging depth. To our knowledge this is the first report on photoacoustic microscopy of the microvasculature with a high-frequency array transducer. It is anticipated that the system can be used for studying and diagnosing a number of diseases including cancer, atherosclerosis, dermatological disorders, and peripheral microvascular complications in diabetes.

    View details for DOI 10.1117/1.2709850

    View details for Web of Science ID 000245505400001

    View details for PubMedID 17343475

  • Photoacoustic Microscopy with a 30MHz Array and Receive System Proc IEEE Ultrasonics Symposium 2006 Bitton R, Zemp R, Li M.L., Yen J., Wang L.H., Shung K.K. 2006: 389-392