ACC Logo Horizontal

Paul Ossi, M.D.

Radiation Oncologist
Drs. Ackerman and Ossi

Dr. Paul Ossi is a Board-Certified radiation oncologist who joined Ackerman Cancer Center after completing his residency at the University of Miami and Jackson Memorial Hospital. He previously served as the department chair of Radiation Oncology at St. Vincent’s Healthcare and remains actively involved in the St. Vincent’s Tumor Board.

Dr. Ossi is a member of the American College of Radiology, the American Society for Therapeutic Radiology and Oncology, the American Medical Association, the Duval County Medical Society, and the St. Johns County Medical Society. He serves as president of the Medical Excellence Committee at St. Vincent’s and is actively involved in the radiation safety program there. A Jacksonville native and graduate of Bishop Kenny High School, Dr. Ossi received both his Bachelor of Arts and his medical degree from Mercer University in Macon, Georgia. Outside of his clinical work and community involvement, he enjoys offshore fishing, water skiing, and spending time with his family.

Our Medical Team

Headshot Arlean Marcellus

Arlean Marcellus, BS

Physician Liaison

Arlean Marcellus joined Ackerman Cancer Center in March 2023 and leads physician outreach. She builds and strengthens meaningful partnerships with referring physicians, healthcare facilities, and medical groups, driving growth in patient referrals. Arlean holds a degree in Health Science with a concentration in Public Health from the University of North Florida. Beyond her work, she volunteers with Feeding Northeast Florida. In her free time, Arlean enjoys running, roller skating, and spending time with her family.
Headshot Shelby Goodman

Shelby Goodman, MSW

Oncology Social Worker

Shelby Goodman joined the Ackerman Cancer Center team in January 2023 as the oncology social worker. She earned her bachelor’s and master’s degrees in social work from the University of North Florida and went on to become a licensed clinical social worker (LCSW). With over five years of experience supporting individuals and families in the social work field, her practice focuses on psychosocial support, care coordination, and advocacy to enhance the quality of life for patients and their loved ones. Shelby is a member of the Florida Society of Oncology Social Workers (FSOSW). In her free time, she enjoys reading and spending time with her family and dog.
Headshot Kali Molter

Kali Molter, MBA

Community Relations Specialist

Kali Molter joined Ackerman Cancer Center in August 2024 and supports community outreach, marketing initiatives, and engagement efforts. She holds both a Master of Business Administration and a Bachelor of Business Administration in marketing from the University of North Florida. A Jacksonville native and Bishop Kenny alum, Kali is passionate about contributing to and strengthening the local community. She brings experience in hospitality and event management and serves on the Jacksonville Chamber’s NEXTUP JAX Professional Development and Community Engagement committees. Outside of work, Kali enjoys living at the beach, running and yoga, traveling, and is a lifelong Jacksonville Jaguars fan.

Ceilidgh O'Brien, BS

Patient Relations Manager

Ceilidgh O’Brien is the patient relations manager at Ackerman Cancer Center, where she leads the patient relations team and helps ensure every patient experience is organized, supportive, and welcoming. She oversees scheduling and communications and is passionate about creating efficient processes that help patients and staff feel informed, supported, and cared for. Ceilidgh earned a Bachelor of Science in health sciences from the University of South Florida in 2024 and values building strong, compassionate connections with both patients and colleagues. A Boston native, Ceilidgh traded snow for sunshine and now spends her free time running with friends and supporting the Jacksonville Humane Society.
Headshot Tiffany Vaughn

Tiffany Vaughn, RT (R)(T)

Manager, Radiation Therapy & Imaging

Tiffany Vaughn brings extensive experience and steady leadership to Ackerman Cancer Center, with 24 years of service to the practice. For the past 15 years, she has served in leadership roles, overseeing both radiation therapy and imaging departments with a focus on quality care, collaboration, and operational excellence. Tiffany is a proud member of the American Society of Radiologic Technologists and the American Registry of Radiologic Technologists. She earned her technologist degree from St. Vincent's Medical Center and completed radiation therapy training from Washburn University. Outside of work, Tiffany enjoys spending time with her family, relaxing in or around the water, and taking on hands-on projects around her home.
Vivienne Burnett Headshot

Vivienne Bennett, MS, RT(R)(M)​

Clinic Manager

Vivienne Bennett joined Ackerman Cancer Center in November 2013 as a mammography technologist and was promoted in 2021 to oncology clinic manager, overseeing clinical operations across all four locations. She provides leadership for daily clinic operations, supports multidisciplinary oncology teams, ensures regulatory and accreditation compliance, and implements operational strategies to improve quality, safety, and patient experience. Vivienne holds a master’s degree in medical radiation sciences from the University of Sydney in Australia and is a member of the American Registry of Radiologic Technologists (ARRT). Outside of work, she enjoys watching sports, walking, and spending time with friends and family.
Headshot Timothy Scott

Timothy Scott, RTR, RTT, CMD

Manager, Dosimetry, Facilities, & Research

Tim Scott joined Ackerman Cancer Center in 2003 and brings nearly 40 years of experience in radiation oncology and medical dosimetry operations. He oversees medical dosimetry, facilities, special projects, and research and has played a key role in nearly every building project and major technology launch at the center. Tim is passionate about innovation and the development, construction, and commissioning of advanced treatment technologies, including proton therapy. Beyond his professional work, Tim serves as a worship pastor and is a brass musician. In his free time, he enjoys restoring classic cars and spending time on the lake.
Headshot Grigoriy Sarkisov

Greg Sarkisov, BS

Director of Information Technology

Greg Sarkisov joined Ackerman Cancer Center in September 2019 and oversees all facets of information technology and information security within the organization. Greg has over twenty years of experience in information technology and security. With over six of those years in our practice, he has led initiatives to strengthen our core security and expand the use of various technologies to help aid our staff in providing effective and efficient patient care. Greg holds a Bachelor of Science degree in information systems security from ITT Technical Institute. Outside of work, he stays active in the community and is a member of the IT Council with the Jacksonville Chamber of Commerce. In his free time, Greg enjoys spending time with his family and friends.
Headshot Jennifer Zelaya

Jennifer Zelaya, MHA

Director of Human Resources

Jenny Zelaya is the director of human resources at Ackerman Cancer Center and Ackerman Urology, where she oversees all HR functions and fosters a positive, inclusive workplace culture. She holds a master’s degree in health administration from the University of Miami and brings extensive experience in talent management, employee engagement, and regulatory compliance. Fluent in Spanish, Jennifer enjoys staying active outside of work, playing pickleball, golfing with friends and family, and spending time with her golden retriever, Lenny.
Headshot Amy Mousa

Amy Mousa, CPA

Director of Finance and Accounting

Amy Mousa joined Ackerman Cancer Center in November 2021 and serves as the director of finance and accounting. In her role, she oversees financial operations and supports the organization’s strategic and operational goals. Amy holds a Florida CPA license and earned her Bachelor of Business Administration in accounting from the University of North Florida. Outside of work, she enjoys staying active, traveling, and spending quality time with her family.
Headshot Nelson Miksys

Nelson Miksys, PhD, MCCPM

Chief Medical Physicist

Nelson Miksys joined Ackerman Cancer Center in October 2019. As chief medical physicist, Nelson manages the medical physics department, which is responsible for
quality assurance of all patient treatment plans, calibration of the radiation therapy equipment, maintenance of the radiation safety program, integration of new technology
into the clinic, and providing clinical technical support across all aspects of the cancer center. Nelson has over ten years of experience as a medical physicist and comes to Ackerman Cancer Center from The Ottawa Hospital Cancer Centre (Ottawa, Canada). Nelson has a PhD in medical physics from Carleton University (Ottawa, Canada) and a
master’s degree in medical and health physics from McMaster University (Hamilton,
Canada). Outside of work, Nelson is actively involved in his children’s sports activities and community social events and is passionate about maintaining a healthy lifestyle through regular physical fitness and outdoor activities.

Headshot Robert Tokarz

Robert Tokarz, MS, DABR

Vice President, Technical Services

Rob Tokarz joined Ackerman Cancer Center in January 2014 and oversees the Physics, Dosimetry, Therapy, Imaging, IT, and Transcription departments. He holds a Bachelor of Science in physics from Notre Dame and a Master of Science in medical physics from Columbia University. Rob has worked in the field of medical physics for 25 years and has worked previously at Memorial Sloan Kettering Cancer Center. Prior to his career in medical physics, Rob was an officer in the United States Navy, where he attained the rank of lieutenant commander. As a naval aviator, he flew Seahawk
helicopters out of Naval Station Mayport and was stationed overseas in Bahrain.

Headshot Gigi Ackerman Schwartz

Gigi Ackerman Schwartz, MBA

Vice President, Operations

Gigi Ackerman Schwartz joined Ackerman Cancer Center in November 2020 and leads strategic planning initiatives across all departments, directs all aspects of revenue cycle management, and works to develop and maintain relationships with community partners. Gigi holds an MBA from Tulane University. A Jacksonville native, she is involved in several local charitable and civic organizations. She serves as chair of the Art in Public Places Committee for the Cultural Council of Greater Jacksonville, is a member of the National Young Leadership Cabinet, and is a trustee of the Jewish Community Alliance and Jacksonville Jewish Center. In her free time, Gigi enjoys playing mahjong, exploring new hobbies with friends, and spending time with her husband and two-year-old daughter.

close menu icon

SEARCH

Find information about cancer care, conditions we treat, our care providers, events, general wellness, and more.

Headshot Baylee Richter

Baylee Richter, BS

Community Relations Manager

Baylee Richter joined Ackerman Cancer Center in November 2024 and oversees digital campaigns, brand strategy, and community outreach and engagement. With more than eight years of experience in events and marketing, she has led initiatives that strengthen patient engagement, community awareness, and referral growth. Baylee holds a Bachelor of Science in hospitality and tourism management from Slippery Rock University of Pennsylvania. Outside of work, she stays actively involved in the community through her service on the board of the American Lung Association. She also supports the American Cancer Society’s Cowford Ball as a member of the children’s art project committee and contributes to the Jacksonville Chamber’s NEXTUP JAX program, serving on two committees. In her free time, Baylee enjoys spending time with her Australian Shepherd, Cooper, and cheering on the Pittsburgh Steelers.