Medical Staff

Richard Rosenthal, M.D

Richard Rosenthal, M.D. is a world renowned Pain Medicine Physician who has incorporated regenerative injection therapies into his everyday pain medicine practice. He is board certified in Anesthesiology, Pain Medicine, Addiction Medicine and Interventional Pain Medicine. He graduated from the University of Utah medical school in 1985. In 1993 he graduated from an anesthesia residency at the University of Texas at San Antonio Medical Center. He is the Founder, President, and Medical Director of Nexus Pain Specialists.
Dr. Rosenthal has distinguished himself as a leader in educating and training medical professionals in the fields of Interventional Pain and Regenerative Medicine. He is the editor of the interventional pain section of the widely read journal, Practical Pain Management.  He developed a one-year pain medicine fellowship which teaches young physicians the skills in Interventional Pain and Regenerative Medicine. Dr. Rosenthal is a master instructor for the prestigious organization the Spinal Intervention Society.  He has taught physicians in both the United States and Europe how to correctly perform various spinal procedures.  He has authored several scientific articles and book chapters on topics in the specialty of pain medicine. He is also involved in clinical research and has served as an expert witness in malpractice cases. His clinic was awarded the Excellence in Multi-disciplinary Pain Care Award by the World Institute of Pain (one of only 4 clinics in the United States to receive the award in 2011).
Dr. Rosenthal has been practicing Regenerative Medicine for the past several years. He has acted as Course Director for more than 30 Regenerative Medicine courses and has also lectured at several national conferences.  He specializes in the use of stem cells and platelet rich plasma for the treatment of painful joints, including the knee, hip and shoulder. His treatments are based on a comprehensive approach to relieving pain and improving function.  Dr. Rosenthal has lectured on the topic of Regenerative Medicine, especially Platelet Rich Plasma and Stem Cells treatments, for such prestigious organizations as the American Society of Interventional Pain Physicians and the Society for Pain Practice Management.

George Chang Chien, DO

George C. Chang Chien, D.O. specializes in musculoskeletal medicine and comprehensive pain management. He was trained in Physical Medicine & Rehabilitation at the Rehabilitation Institute of Chicago, the #1 Ranked Rehabilitation Hospital in the United States since 1991.  After completion of his Physiatry training, he completed fellowship training in comprehensive pain medicine at the prestigious Cleveland Clinic Anesthesiology Institute.

Dr. Chang Chien has authored over 50 manuscripts on the treatment of pain and musculoskeletal conditions and has been a collaborator on multiple multi-center drug studies. His current research involves the use of ultrasound in the diagnosis and treatment of shoulder and hip pain.

His professional ultrasound teaching experience in musculoskeletal and interventional pain management includes: ultrasound course Director at the Cleveland Clinic, Regenerative Medicine Course Director for American Society of Interventional Pain Physicians, American Society of Regional Anesthesia, Apex Biologix, and the Society for Pain Practice Management.

Dr. Chang Chien specializes in non-surgical orthopedic care.  He practices regenerative medicine with expertise in platelet rich plasma (PRP), bone marrow aspiration for stem cells (BMAC), and adipose-derived stem cells (ADSC).

He is currently the Medical Director for Pain Management at Ventura County Medical Center and the Director for the Center for Regenerative Medicine at Southern California University. He serves in the editorial board for Pain Physician medical journal and is the section editor for Regenerative Medicine.

To learn more about Dr. George C. Chang Chien, you can visit his website at

Aaron Calodney, MD

Dr. Calodney earned his medical degree from the University of Missouri School of Medicine and completed a family medicine internship at St Joseph’s Hospital in Syracuse, New York. His residency in anesthesiology and subsequent interventional pain management fellowship was completed at the University of Texas Health Science Center at Houston. He subsequently completed a fellowship in pediatric anesthesia at the Denver Children’s Hospital. After spending several years as a faculty member in the Department of Anesthesiology at the UT medical school in Houston, Dr. Calodney moved to East Texas where he has practiced since 1991.

With particular interest in Spine and special interests including Neuromodulation and Intrathecal Drug Delivery, Biological treatment of the painful degenerative disc, Peripheral nerve injury, and Radiofrequency ablation, Dr. Calodney has presented and published many articles and textbook chapters. He is actively involved in clinical research and has delivered over 250 invited lectures in the US and abroad. Dr. Calodney also specializes in treating pain through the use of regenerative medicine and implements these techniques, when applicable, into his practice.

Dr. Calodney is a member of the American Society of Anesthesiologists, American Society of Regional Anesthesia and Pain Medicine, International Spine Intervention Society, International Neuromodulation Society, American Society of Interventional Pain Physicians, North American Neuromodulation Society, Texas Pain Society, Texas Medical Association, Texas Society of Anesthesiology, and the Smith County Medical Society.

Arthur Watanabe, MD

Dr. Watanabe graduated from the University of California with a Doctor of Pharmacy degree and from the University of Cincinnati with a Doctor of Medicine degree. He successfully completed an internal medicine internship and diagnostic radiology residency at the University of Utah Medical Center. He completed a neuroradiology fellowship at Long Beach Memorial Medical Center. He is sub-specialized in the practice of interventional pain management and has been practicing in this specialty since 1997. He is board certified by the American Board of Radiology and a member of the International Spinal Intervention Society, American Society of Interventional Pain Physicians and the American Society of Spine Radiologists as well as the Spokane County Medical Society and Washington State Medical Association.

Steve Aydin, DO

Dr. Aydin is Chief of Physical Medicine and Rehabilitation and Interventional Pain Management at Kayal Orthopaedic Center, as well as Clinical Assistant Professor at Hofstra – Northwell Health. In, 2010 after completing an anesthesia-based pain management fellowship at the University of Michigan Health System, he joined Manhattan Spine and Pain, and was appointed clinical assistant professor of PMR in 2013.

In addition to specializing in pain management, Dr. Aydin is board-certified in physical medicine and rehabilitation. He completed his training at the Kessler Institute for Rehabilitation, in New Jersey. He took an avid interest in pain management early in his training, and worked to address it in patients with traumatic brain injury, stroke, and spinal cord injury. “Physical medicine and rehabilitation focuses on musculoskeletal medicine—the body’s interconnected system of nerves, muscles and bones,” said Dr. Aydin. “This training offers a better understanding of how an injury or problem in one part of the body can affect other parts, which is important when developing nonsurgical strategies to help people regain normal function and pain control.”

Matt Murphy, PhD

Dr. Murphy designs and implements new strategies for the isolation and application of autologous stem cells for spine, orthopedics, and cardiovascular therapies. Dr. Murphy was a senior researcher at Methodist Hospital Research Institute in Houston, Texas, where he focused on the combination of adult stem cells and biomaterials for regenerative medical applications in orthopedics, spine, pancreatic, and soft tissue repair. At Rice, he researched novel biomaterials for bone and cartilage regeneration and developed targeted drug delivery strategies. He also worked at NASA on the design of new spacesuits for travel to the moon and Mars as part of the Constellation Program. He has authored twelve peer-reviewed publications and two textbook chapters related to tissue engineering and drug delivery. Dr. Murphy holds a Ph.D. in Bioengineering from Rice University and a B.S. in Chemical Engineering from The University of Texas at Austin.

Sudhir Diwan, MD

Dr. Sudhir Diwan is a top-rated, highly sought after pain management specialist and serves as the executive director of Manhattan Spine & Pain Medicine. Dr. Diwan is well-known for treating the most complex and challenging cases of chronic pain through numerous interventional procedures and is a leading specialist in regenerative medicine.

Dr. Diwan has provided his expertise in pain medicine to articles appearing in leading newspapers including The New York Times and The Los Angeles Times, and has made various television appearances including Fox 5’s Good Day New York and Health Headlines on CBS for the latest research on radiofrequency lesioning for chronic back pain.

In addition to his busy pain management practice, Dr. Diwan lectures extensively and interacts regularly with experts in the field of pain medicine nationally and internationally. He has been a guest speaker for many noteworthy organizations including the American Cancer Society, the American Society of Anesthesiology, the American Society of Regional Anesthesia and Pain Medicine, the World Institute of Pain, and numerous pain specialty societies and congresses in Europe. He is also a regular speaker for the New York State Society of Anesthesiologists on the topic of pain management and management of cancer pain.

Sireen Gopal, MD

Dr. Sireen Gopal has been triple board certified in the areas of Physical Medicine & Rehabilitation, Pain Medicine, and Neuromuscular Medicine. Dr. Gopal is President and Founder of both New York Spine & Sports Rehabilitation Medicine PC and New York Advanced Surgical Interventions Care PLLC. Both of his clinics provide advanced regenerative medicine therapies with refined techniques and experience.

Dr. Gopal is a specialist in the non-operative management of Spine and Musculoskeletal Disorders. His practice has a novel approach to treating musculoskeletal pain early with multidisciplinary options as needed. He also specializes in interventional pain treatments for several conditions and incorporates regenerative medicine in his private practice when applicable.

Dr. Gopal’s scientific work includes a Chapter on the “Work up of Neck Pain and Low Back Pain” published in the Physical Medicine and Rehabilitation Clinics of North America, Volume 8, No 1 February 1997. Dr. Gopal is a dynamic and personable instructor for regenerative medicine courses.

Douglas Spiel, MD

Dr. Spiel’s unique clinical background has enabled him to view the practice of interventional pain through a broader perspective. By elevating the diagnosis and treatment of those in pain to an art form, he is uniquely qualified to blend the objective and subjective components of a patient’s signs and symptoms to arrive at a plausible and treatable diagnosis.

Dr. Spiel is widely recognized as an expert in numerous treatment modalities and has lectured both throughout the country and abroad. He credits the numerous physicians worldwide that he has studied with providing him with the necessary scaffold to build his current diverse skill set. Dr. Spiel believes that “only by cross-training with multiple specialties can anyone physician bridge the necessary knowledge required to effectively treat the complexities of the human condition.”

The American Board of Interventional Pain Physicians examines and certifies appropriate applicants as diplomats in interventional pain procedures. Dr. Spiel was the first among the few radiologist and interventional pain specialists on the list to be certified by this prestigious board.

Orlando G. Florete, Jr, MD

Orlando G. Florete, Jr, MD, has received numerous scholarships and awards, among them the Winthrop Stearns Scholarship Award and the Community Service Award from the Department of Anesthesiology at the University of Florida College of Medicine. In 2011, Dr. Florete was recognized by the International Association of Anesthesiologists as one of the Leading Physicians of the World.

Dr. Florete is a highly esteemed and frequently invited speaker at both national and international symposia, lecturing on pain management and treatment algorithms.He is a member of several professional organizations, including the American Academy of Pain Medicine, the American Academy of Pain Management, American Society of Anesthesiologists, International Anesthesia Research Society, the American Pain Society, the Florida Academy of Pain Management, and others; he is a life member of the Winthrop Stearns Fellows and Scholars Association. Dr. Florete's research has been extensively published, with numerous book chapters and journal articles to his credit, as well as abstracts and teaching materials.

Dr. Florete received his medical degree from the Cebu Institute of Medicine in Cebu City, Philippines.He performed his internship and residency at the University of Philippines College of Medicine as well as a residency in Anesthesiology at the University of Florida College of Medicine. His postgraduate training includes fellowships in cardiology (University of Philippines) and critical care medicine (University of Florida) as well as additional pain management training at the University of Virginia and the University of Kentucky for his board certification.

Amy Killen, MD

Amy Killen M.D. received her Bachelor’s degree in Biomedical science from Texas A&M University and then her M.D. from UT Southwestern Medical School. She completed an Emergency Medicine residency at the University of Arizona and worked for many years in Austin, Texas as a board certified emergency physician before moving to Portland and becoming medical director of an anti-aging specialty clinic.

Now in Utah, Dr. Killen embraces bio-identical hormone therapy and personalized medicine and offers aesthetics services including Botox, Fillers, and Micro-needling. Dr Killen is also very enthusiastic about cutting-edge regenerative medicine techniques, using Platelet Rich Plasma (PRP) for skin rejuvenation, hair restoration, urinary incontinence, and sexual dysfunction.