Kim Butts Pauly, PhD, Professor, Program co-Director and Steering Committee
Professor, Department of Radiology
Dr. Butts Pauly’s research interests are in the area of image-guided minimally invasive therapies. Dr. Butts Pauly has developed innovative methods for monitoring temperature in the prostate, in the liver during free breathing, for monitoring High Intensity Focused Ultrasound (HIFU) with MR-acoustic radiation force imaging (MR-ARFI), and for monitoring the temperature of frozen prostate tissue during cryoablation. MR-ARFI is an exciting new technique that might be used for MR monitoring of mechanical mode ultrasound therapy (e.g. Drug deliver via liposomes or opening of the BBB with HIFU). Example MR-ARFI images (Figure 3) demonstrate improvements in Fig 3. MR-ARFI setup and sample images (Dr. Butts Pauly) SNR (right image). In collaboration with Drs. Pelc and Fahrig, Dr. Butts Pauly has also worked contributed toward the fully integrated X-rayand MRI system with the development of X-ray compatible MR coils.
Norbert Pelc, ScD, Co-Director
Professor, Department of Radiology
Professor and Chair, Department of Bioengineering
Dr. Pelc has been active in diagnostic imaging research for more than 40 plus years.Although he is best known for his work in Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), he has also worked in nuclear medicine, x-ray, and ultrasound imaging. During his graduate training, he was one of the first to work in "fully 3D" PET. His early contributions in CT include theoretical research on quantum noise and practical work including the first demonstration of "bone detail" reconstructions and illumination of the source of several image artifacts. In the early 1980's Dr. Pelc's research included high impact work on digital and dual energy x-ray imaging. In MRI, he contributed to the development of hardware systems, including quadrature excitation and advanced transceivers, to imaging methods including cardiac cine, MR angiography, respiratory compensation, single and half-NEX imaging, and motion studies based on velocity mapping. He worked on hybrid imaging in collaboration with Drs. Butts Pauly, Fahrig, and Daniel, especially x-ray/MR systems for guiding minimally invasive procedures.
Recently, his interests have returned to CT imaging. Computed tomography has made phenomenal technical advances since its introduction in the early 1970s. As an example, Fig 4 shows the progress in clinical CT scanning speed since the earliest systems. Evolution of CT speed This, combined with improvements in spatial and contrast resolution, have made CT a powerful tool in diagnosis and management of patients. The growth in the utilization of CT is evidence of its success. However, even though the dose per slice is decreasing, the dose to the population is significant, which is roughly half of that due to natural sources, has raised concerns. While the benefits from clinically indicated CT exams far outweigh any risk from radiation, it is prudent to reduce CT radiation dose as much as physically possible, and NIBIB has encouraged the scientific and medical community to develop further reductions in CT radiation dose. Dr. Pelc has contributed to this effort in several ways. He developed the concept of “inverse geometry” CT, a system design that can lead to improved volumetric imaging and significant dose reduction through precise control of the x-ray field illuminating the patient, but is very difficult to implement.
More recently, his group proposed a more feasible way to achieve the dose reduction, through control of the illuminating field using a dynamic piece-wise linear pre-patient attenuator comprising triangular wedges (“dynamic bowtie”, Fig 5). Dynamic bowtie Computer simulations predict that a dynamic bowtie can reduce dose by 30-40% in conventional studies and even more in exams where only a fraction of the in-plane field of view is of clinical interest. With funding from NIBIB, an initial feasibility model is being built and tested (Fig 5). Of importance to the current proposal, these projects led to the dissertations of 4 PhD students.
Along with his excellent research track record, Dr. Pelc is a highly regarded teacher of both pre-doctoral and post-doctoral trainees (including physicians). Dr. Pelc was the principal advisor of 14 PhD students, 11 of whom have completed their studies. He has been the primary or co-advisor of 17 postdoctoral fellows. His students have gone on to successful careers in academia and industry in roughly equal numbers. They have won recognition for their research with awards that include two ISMRM Young Investigator winners, five RSNA research fellow prizes, and one AAMI Young Investigator award. Dr. Pelc has served on the admissions committees of two degree-granting programs at Stanford (Bioengineering and Biophysics) and has been a secondary advisor or on the thesis committees of many doctoral students. He has advised graduate students in six degree granting programs (EE, ME, BioE, Physics, Applied Physics, and Biophysics) at Stanford, an indication of his experience and ability to work closely with the programs and departments that are linked to the training program.
Amin Arbabian PhD, Assistant Professor, Preceptor
Department of Electrical Engineering
Dr. Arbabian is the director of the THz lab in the Electrical Engineering department of Stanford University. His group works in the area of high-frequency systems and electromagnetic interfaces. Research topics include microwave and millimeter-wave circuits and systems for high-speed communication and medical imaging applications, integrated antennas and antenna arrays, and ultra-low power electronics. On the biomedical front his research explores system design for emerging and hybrid medical imaging modalities, applies advanced electrical/electromagnetic interface solutions to bio-sensing applications, and investigates new technologies for wireless implants.
Jeremy Dahl, PhD, Associate Professor, Preceptor
Department of Radiology
Dr. Dahl’s research involves ultrasound imaging techniques to improve the quality of diagnostic ultrasound images, particularly those in the difficult-to-image category. These techniques involve beamforming and adaptive beamforming methods to reduce and compensate for acoustic noise and its sources, such as diffuse reverberation and aberration. One of these methods, called SLSC Power Doppler imaging, is insensitive to the thermal noise that often accompanies traditional Power Doppler imaging and requires fewer pulses per ensemble. Dr. Dahl also has interest in ultrasonic radiation force based imaging methods to generate images of the mechanical contrast of tissue. Power Doppler vs. SLSC Power Doppler
Bruce Daniel, MD, Professor, Secondary Mentor
Department of Radiology
Section of Abdominal Imaging
Dr. Daniel is a world leader in the development of MR-guided breast imaging (Figure 7) and biopsy techniques. As a result, Stanford has become a regional referral center for the care of high risk breast patients. In addition, Dr. Daniel’s research in MR-guided cryoablation of the prostate has resulted Fig. 7. Bilateral breast MRI (Drs. Daniel and Hargreaves)in innovative imaging techniques, such as ultrashort TE (UTE) MRI that has demonstrated that frozen tissue signal can be related to tissue temperature, and temperature mapping techniques can be developed in frozen tissue.
Adam de la Zerda, PhD Assistant Professor, Preceptor
Departments of Structural Biology and Electrical Engineering
Dr. de la Zerda's research focuses on the development of new molecular imaging technologies to visualize and interrogate biomolecules in living subjects. He is the co-developer of photoacoustic molecular imaging, a technique that is using light excitation and ultrasound emission for molecular detection of biomolecules in deep tissues. The figure shows a carbon nanotube particle that is targeted to alpha-v-beta-3 integrin on tumor neovascularization. The carbon nanotube absorbs light pulses and emit ultrasound waves in return, allowing the photoacoustic instrument to create a high resolution image of alpha-v-beta-3 distribution in the tumor (green signal) and display it on top of an ultrasound image (gray signal) that visualizes the tissue anatomy.
Daniel Ennis, PhD, Associate Professor of Radiology, Steering Committee
Department of Radiology
Research in Dr. Ennis’s lab focuses on the development of advanced MRI acquisition and analysis methods with a focus on cardiac structure, function, flow, and remodeling. Current translational applications include: 1) characterizing several cardiac MRI biomarkers to detect the cardiomyopathy associated with Duchenne Muscular Dystrophy; and 2) developing MRI methods and a computational modeling framework to estimate changes in passive ventricular stiffness in patients with Heart Failure with Preserved Ejection Fraction (HFpEF). An In vivo cardiac diffusion tensor image obtained using convex optimized diffusion encoding is shown. A central technical focus of our current work is the development of an open source gradient waveform optimization toolbox. The toolbox enables the development of MRI pulse sequences that make optimal use of the available MRI gradient hardware to improve acquisition efficiency and mitigate measurements errors. Dr. Ennis is also the Director of Radiology research for the Veterans Affairs Palo Alto Health Care System.
Katherine Ferrara, PhD, Professor of Radiology, Steering Committee
Department of Radiology
Dr. Ferrara’s laboratory works in the areas of ultrasound imaging and therapy and drug and gene delivery. Her early work has involved the development of imaging strategies for ultrasound contrast agents including phase inversion and radiation force-based strategies. She developed early molecularly-targeted ultrasound contrast agents. She has developed strategies for nanoparticle labeling for positron emission tomography, synthesizing and evaluating new therapeutics and nanoparticles, and creating methods for enhancing therapeutic delivery. She has recently developed multiple methods for cell transfection and method to label gene delivery vehicles.
Sanjiv (Sam) Gambhir, MD, PhD, Professor, Preceptor
Departments of Radiology, Bioengineering, and Materials Science and Engineering
Professor and Chair of Radiology, is an internationally recognized researcher in molecular imaging research, clinical nuclear medicine, and training in both areas. He is also the director of the Molecular Imaging Program at Stanford (MIPS), is PI in both the Center of Cancer Nanotechnology Excellence and Translation (CCNE-T) and the In Vivo Cellular and Molecular Imaging Center (ICMIC). Dr. Gambhir also leads his own lab that focuses on interrogating fundamental molecular events in living subjects. He has developed and clinically translated several multimodality molecular imaging strategies including imaging of gene and cell therapies with PET. He has also developed strategies for Raman and Photoacoustic multimodality molecular imaging. He has developed clinical management algorithms for cost-effective management of cancer patients with PET and continues to develop and translate PET tracers for clinical use.
Gary Glover, PhD, Professor, Preceptor
Department of Radiology
Dr. Glover is the Director of the Lucas MRI Center (a campus Service Center). He has more than 40 years of medical imaging experience, which spans the development and implementation of new technologies in MRI, ultrasound, and computed tomography in industry as well as at Stanford. He is well known for his research on pulse sequence and reconstruction developments for rapid MRI, with nearly 400 published papers in medical imaging. He has been involved in research on fMRI since its inception in 1992, an example of which is shown in the figure. This work is from one of his graduate students, now an assistant professor
Garry Gold, MD, Professor, Preceptor and Steering Committee
Department of Radiology
Section of Musculoskeletology
Dr. Gold’s research is in the application of new MR imaging technology to musculoskeletal problems. His current projects include rapid MRI for osteoarthritis, weight-bearing cartilage imaging with MRI, MRI-based models of muscle, sodium imaging (Figure 12), and imaging around metallic implants. Dr. Gold currently works to develop the application of new MR imaging techniques such as rapid imaging, real-time imaging, and short echo time imaging to learn more about biomechanics and pathology of bones and joints. His training in engineering, medicine, and radiology makes him a strong advocate for translating Fig. 12. MRI of the knee (Drs. Gold and Hargreaves).bench top research into clinical use. Dr. Gold has also developed courses for graduate students and has received the Resident’s Teaching Award.
Edward Graves, PhD, Associate Professor, Preceptor
Department of Radiation Oncology
Division of Radiation Physics
The laboratory of Dr. Graves is focused on applications of emerging functional and molecular imaging techniques in radiation therapy of cancer. This includes the development of novel clinical and preclinical imaging and radiotherapy techniques as well as their application to study tumor and normal tissue radiobiology. Ongoing research projects include that address these issues and Dr. Graves’s interests include 1) engineering of clinically-relevant small animal conformal radiotherapy systems; 2) development and validation of multimodal molecular imaging techniques for preclinical and clinical imaging of tumor radiosensitivity and radiation response; 3) design of software for multimodal image analysis; and 4) characterization of the role of circulating tumor cells in cancer response and recurrence. A collimator for preclinical radiotherapy developed by Dr. Graves is shown.
Brian Hargreaves, PhD, Professor, Preceptor
Department of Radiology
Dr. Hargreaves is interested in magnetic resonance imaging (MRI) applications including cardiovascular, abdominal, breast and musculoskeletal imaging. These applications require development of faster and more efficient MRI methods that provide improved diagnostic contrast compared with current methods. His work includes novel excitation schemes, efficient imaging methods and reconstruction tools. One area of particular excitement Fig.14. Preliminary comparison at spin echo (SE) and our method, SEMAC, in the spine of a volunteer with steel hardware, seen in pro- jection X-rays (top right) shows the reduction of distortion and other metal-induced artifacts. Axial and sagittal CT scans show severe streaking artifacts (Dr. Hargreaves).is the development of an MR method that can provide robust assessment around metallic implants (Figure 14).
Robert Herfkens, MD, Professor, Secondary Mentor
Department of Radiology
Section of MR Imaging
Dr. Herfkens is the director of the body MRI section in the Department of Radiology and has more than 25 years of experience in MRI and MR spectroscopy (MRS). He has an extensive background in the development, testing, and clinical aspects of cardiovascular and breast MRI, an example of which is shown in Figure 15. He is a past president of the ISMRM. In addition, he is an expert on MR safety and serves on the ISMRM safety committee. Fig.15. Water and fat images of a patient with a pericardial effusion (Dr. Herfkens).
Aya Kamaya, MD, Assistant Professor, Secondary Mentor
Department of Radiology
Dr. Kamaya's research focuses on photoacoustic imaging of cancer. In collaboration with Professor Khuri-Yakub, she is developing and testing photoacoustic imaging devices made with capacitive micromachined ultrasonic transducers for improved imaging of breast cancer . Her research collaborations and interests also include perfusion imaging of tumors, ultrasound, thyroid imaging, gynecologic imaging and hepatic imaging. Dr Fig. 17. Photoacoustic image (Dr. Kamaya).Kamaya is an outstanding mentor and teacher, having been awarded the teacher of the year award twice by popular vote of the radiology residents at Stanford University,
Butrus (Pierre) Khuri-Yakub, PhD, Professor, Steering Committee and Preceptor
Department of Electrical Engineering
Prof. Khuri-Yakub is the Deputy Directory of the Edward L. Ginzton Laboratory within the Department of Electrical Engineering. His current research interests include medical ultrasound and photoacoustic imaging and therapy, micromachined ultrasonic transducers, chemical/biological sensors, smart bio-fluidic channels, microphones, ultrasonic fluid ejectors, and ultrasonic nondestructive evaluation, imaging and microscopy. He is well-known for his research in capacitive micromachined ultrasonic transducers (CMUTs), including MR-compatible Fig. 18. CMUT schematic (Dr. Khuri-Yakub)CMUTs for MR-guided HIFU. A CMUT (Figure 18) is a vacuum-gap capacitor in which the top membrane is free to move with applied voltage. Many membranes are connected in parallel to form a large area transducer. Dr. Khuri-Yakub has authored over 400 publications and has been the principal or co-inventor of 76 U.S. and international issued patents.
Maarten Lansberg PhD, Assistant Professor, Secondary Mentor
Department of Neurology and Neurosurgery
Dr. Arbabian is the director of the THz lab in the Electrical Engineering department of Stanford University. His group works in the area of high-frequency systems and electromagnetic interfaces. Research topics include microwave and millimeter-wave circuits and systems for high-speed communication and medical imaging applications, integrated antennas and antenna arrays, and ultra-low power electronics. On the biomedical front his research explores system design for emerging and hybrid medical imaging modalities, applies advanced electrical/electromagnetic interface solutions to bio-sensing applications, and investigates new technologies for wireless implants.
Craig Levin, PhD, Professor, Preceptor and Steering Committee
Department of Radiology
Division of Nuclear Medicine and Molecular Imaging
Dr. Levin’s research involves the development of novel instrumentation and software algorithms for the in vivo imaging of molecular signatures of disease in humans and small animals. These new cameras efficiently image radiation emissions in the form of positrons, annihilation photons, gamma rays, and light from molecular
Fig. 19. Schematic of a 1 mm3 PET system using 3D positioning detectors (Dr. Levin).probes developed to target molecular processes from deep within the tissue of living subjects. The objectives of the instrumentation projects are to push the sensitivity and spatial, spectral, and/or temporal resolutions as far as physically possible. The algorithm goals are to understand the physical system comprising the subject tissues, radiation transport, and imaging system, as well as to provide the best available image quality and quantitative accuracy. The ultimate goal of Dr. Levin’s work is to introduce new imaging tools into studies of molecular mechanisms and treatments of disease within living subjects.
Jennifer McNab, PhD, Assistant Professor, Preceptor
Department of Radiology
Dr. McNab’s research is centered on the development of MRI contrast mechanisms and acquisition strategies that yield new and/or improved diagnostic or prognostic information about disorders of the human brain. Over the past decade, Dr. McNab has developed numerous MRI pulsesequences, with her primary contributions being in the field of diffusion MRI, including approaches to improving resolution, measuring cortical diffusion anisotropy, mapping axon diameter distributions and imaging of postmortem brain specimens. Dr. McNab has extensive experience with the most cutting-edge MRI technology, including the world’s strongest human-MRI gradients (300 mT/m), highly-parallelized phased-array RF coils (64-channels) and ultra-highmagnetic field (7T). Currently, Dr. McNab’s group has a strong focus on the development of neuroimaging methods for 7T MRI including high-spatial and temporal resolution resting-state function MRI.
Michael Moseley, PhD, Professor, Preceptor
Department of Radiology
Division of Cardiovascular Medicine
Dr. Moseley’s interests involve research for better diagnosis of disease states using new techniques of magnetic resonance imaging (MR). Mapping brain water diffusion has revolutionized our knowledge of the onset and evolution of cerebral stroke, making the MR scanner a potential "operating room" of choice for early and effective treatment of vascular Fig. 21. Diffusion and Perfusion MRI of Acute Clinical Stroke. Row A: Diffusion DWI, B: Time-to-Peak Perfusion MRI. C: Quantitative Arterial Spin-Labeling (ASL) CBF blood flow.disease. Because these diffusion and blood flow maps can be rapidly acquired, rapid identification of tissues that are in need of thrombolytic therapy or cytotoxic protection in the first critical hours following stroke or during surgery can be made. The diffusion brain images in row A clearly show brain that is destined to die a few hours after stroke (bright regions). Row B is a perfusion image showing sharp delays in blood flow (red) to the affected areas and slowed flow to other surrounding tissues. Row C is a new quantitative method to quickly measure the decreased CBF blood flow to the area showing pronounced (bright) alternate routes.
Sandy Napel, PhD, Professor, Preceptor
Department of Radiology
Dr. Napel codeveloped the ”electron beam” CT technique and has had extensive experience in image reconstruction and 3D rendering. His current interests include developing diagnostic and therapy-planning applications and strategies for the acquisition, visualization, and quantitation of multi-dimensional medical imaging data. Prof. Napel has also been involved in developing and evaluating techniques for exploring cross- sectional imaging data from an internal perspective, i.e., virtual endoscopy (including colonoscopy, angioscopy, and bronchoscopy), and in the quantitation of structure parameters, e.g., volumes, lengths, medial axes, and curvatures.
Dr. Napel's most recent focus includes making image features computer-accessible, to facilitate content-based retrieval of similar lesions, and prediction of molecular phenotype, response to therapy, and prognosis from imaging features (Figure 22). He is co-director of the Radiology 3D and Quantitative Imaging Lab, providing clinical service to the Stanford and local community, and co-Director of IBIIS (Integrative Biomedical Imaging Informatics at Stanford), whose mission is to advance the clinical and basic sciences in radiology, while improving understanding of biology and the manifestations of disease, by pioneering methods in the information sciences that integrate imaging, clinical and molecular data.
Fig. 22. Linking image features to gene expression in lung cancer (Dr. Napel)
Dwight Nishimura, PhD, Professor, Preceptor
Department of Electrical Engineering
Dr. Nishimura is Co-Director of the Magnetic Resonance Systems Research Laboratory (MRSRL). He has over 30 years of research experience in medical imaging systems, primarily MRI, developing new acquisition and processing method for improved diagnostic imaging. He is internationally known for his work in MR vascular imaging. His principal interests are in MR Fig. 23. MR Angio (Dr. Nishimura)coronary artery imaging and non-contrast peripheral angiography, an example of which is shown in Figure 23. In addition, his research includes studies in fast MRI, image contrast mechanisms, and image reconstruction. He is an outstanding teacher and teaches several of the core biomedical imaging courses at Stanford.
John Pauly, PhD, Professor, Preceptor
Department of Electrical Engineering
Dr. Pauly is Co-Director of the Magnetic Systems Research Laboratory along with Dwight Nishimura. He has worked in many areas of MRI, including RF selective excitation, real-time interactive imaging, and image reconstruction. He teaches classes in medical image reconstruction (EE369C), RF pulse design for MRI (EE469C), as well as introductory courses in signal processing (EE102A,B) and medical imaging (EE169). Some of his current Fig. 25. A parallel transmit system developed and built by the MRSRL. Top left is a complete scalable MR console, that works as a USB peripheral. Top center are four RF amplifiers, and top right is a four channel RF transmit coil. Measured transmit patterns for each channel are shown below.interests include MR systems for image guided interventions, parallel transmit systems for MRI, the safety of implanted devices with MRI, and the use of balanced SSFP for functional magnetic resonance imaging of brain activation. A parallel transmit system developed by the MRSRL is shown in Fig. 25.
Guillem Pratx, PhD, Assistant Professor of Radiation Oncology, preceptor
Department of Radiation Oncology
Dr. Pratx’ research is aimed at developing new ways of imaging the biological and physical characteristics of cancer initiation, progression, and treatment. Novel approaches that utilize the complementary interaction of ionizing interaction and light are being developed for interrogating biological and molecular processes, either pre-clinically in small animals and cell cultures, or clinically in patients. Ongoing research projects include radioluminescence microscopy, a novel technique that can measure the uptake of radionuclide probes with high resolution in cancer models, optical imaging methods for visualizing therapeutic radiation beams, and novel radionuclide probes and algorithms for tracking cell migration in vivo, with single-cell resolution (see figure).
Brian Rutt, PhD, Preceptor
Department of Radiology
Dr. Rutt is an established researcher in the area of MRI technology and applications development. He focuses on hardware development, such as radio frequency and gradient systems engineering, as well as high-field and high-resolution MRI development. Applications of his research include Fig. 26. Novel field-cycling hardware (Dr. Rutt).neuro and cardiovascular diseases and cancer.
Mark Schnitzer, PhD, Associate Professor, Preceptor
Departments of Biology and Applied Physics
Dr. Schnitzer’s research in neural circuit dynamics and optical imaging has three major research efforts: in vivo fluorescence imaging and behavioral studies of cerebellar-dependent motor control and motor learning, development and application of fiber-optic fluorescence microendoscopy imaging techniques for studies of learning and memory in behaving mice and for clinical uses in humans, and development of high-throughput, massively parallel imaging techniques for studying brain function in large numbers of Drosophila concurrently.
Olav Solgaard, PhD, Professor, Preceptor
Department of Electrical Engineering
Prof. Solgaard is the Director of the Edward L. Ginzton Laboratory and the Associate Chair of Graduate Education in the Department of Electrical Engineering. His current research interests include optical MEMS, Photonic Crystals, optical sensors, microendoscopy, atomic force microscopy, and solar energy conversion. He is wellknown for his research on miniaturized optical systems, including fiber-coupled Photonic Crystal sensors. The figure shows a multifunctional photonic crystal sensor mounted on a the facet of an optical fiber. Prof. Solgaard has authored more than 350 technical publications and holds 60 patents.
Dan Spielman, PhD, Professor, Preceptor
Department of Radiology
Dr. Spielman’s research interests are in the field of medical imaging, particularly magnetic resonance imaging and in vivo spectroscopy. His current research focuses on novel techniques for producing clinically valuable images of important metabolic components such as lactate and choline. Applications of Dr. Spielman’s work include cancer diagnosis, treatment monitoring, and prediction of response to therapy. Current projects include MRI and MRS at high magnetic fields and metabolic imaging using hyperpolarized 13C-labeled MRS. His experience training students in spectroscopy provides a unique opportunity in the expanding applications of MR imaging and spectroscopy.
Fig. 28. Pyruvate in the rat kidney, with conversion to lactate and alanine (Dr. Spielman)
Shreyas Vasanawala, MD, PhD, Asociatet Professor, Preceptor
Department of Radiology
Section of Pediatric Radiology
Dr. Vasanawala’s work is focused on developing new MRI techniques for body imaging, in particular, for pediatric imaging. His research focuses on a number of projects including: 1) increasing the speed of MRI, 2) developing novel MR methods of probing metabolism, 3) new MRI techniques for body imaging, and most importantly, 4) pursuing imaging related research projects with the promise of reducing risks to pediatric patients. Figure 29 shows a new RF coil configuration under development for pediatric imaging.
Fig. 29. (a) Custom high-density pediatric phased array coil design. (b) Prototype of anterior elements of the coil. (c) Resulting highly-accelerated MR angiogram on a six year old girl (Dr. Vasanawala).
Lei Xing, PhD, Professor, Preceptor
Department of Radiation Oncology
Division of Radiation Physics
In imaging related projects, Dr. Xing’s group is developing novel radiation dose reduction and image enhancement techniques for four-dimensional (4D) CT, cone beam CT, and PET. The focus of his dose optimization research is on the effective utilization and integration of clinical outcome results and data from various new imaging modalities. The new treatment planning framework has resulted in substantial improvement in enhancing tumor control probability while sparing more sensitive organs. His group is also actively working on the real-time guidance of radiation delivery with the aid of optical and projection X-ray images (Figure 31)
Fig. 31. A fiducial detection algorithm for motion tracking (Dr. Xing).
Greg Zaharchuk, MD, PhD, Assistant Professor, Preceptor
Department of Radiology
Section of Neuroradiology
Dr. Zaharchuk’s research includes the use of tomographic imaging techniques, particularly CT and MRI, to further both the basic physiological understanding of cerebral ischemia and to diagnose, treat, and monitor clinical patients with cerebrovascular disease. His current research and clinical interests include acute imaging of stroke, focusing on identifying Fig. 32. Perfusion-diffusion mismatch in acute ischemic stroke using multimodality MRI. (a) Diffusion shows a small left MCA stroke. (b) Bolus contrast perfusion-weighted imaging (PWI) shows a larger region at-risk of infarction. (c) Noncontrast arterial spin labeling (ASL) shows a similar large area ofperfusion abnormality with high signal in feeding arteries consistent with collateral flow. Such a patient might benefit from reperfusion therapy outside the standard 4.5 hr time window.collateral flow; imaging of brain function, blood flow, and oxygenation; advanced diffusion imaging of the spinal cord, spinal cord injury; and the study and imaging of chronic ischemia and Moyamoya disease.