C4 Imaging Announces Sirius Positive Signal MRI Marker Given FDA 510(k) Clearance for Use with Isoray’s Cesium-131 Brachytherapy Seeds to Treat Prostate Cancer

Jan 6, 2021

HOUSTON, TEXAS – January 05, 2021 – C4 Imaging LLC is pleased to announce that Isoray Medical, Inc. (NYSE American: ISR) has received U.S. Food and Drug Administration (FDA) 510(k) clearance for the use of C4 Imaging’s Sirius® positive-signal MRI (Magnetic Resonance Imaging) Markers with Isoray’s Cesium-131, brachytherapy seeds.

Sirius is implanted during the treatment of prostate cancer with brachytherapy and is used to facilitate brachytherapy seed localization within the prostate utilizing a single post-implant MRI procedure. This allows the benefits of MRI assisted brachytherapy, also known as MRI assisted radiosurgery or MARS™, to be made available to all prostate cancer patients treated with brachytherapy.

“This is a significant milestone,” said Andrew Bright, President and CEO of C4 Imaging. “Sirius MRI Markers will enable Isoray’s customers to fully utilize the benefits of MRI seed localization.” He added, “We’re delighted to partner with Isoray. They are leading innovators in the use of brachytherapy to treat prostate cancer, as well as other tumors, and recognize the potential of MRI to optimize treatment quality and patient care.”

Isoray CEO Lori Woods commented, “This achievement represents another step forward in Isoray’s leadership in providing effective prostate cancer therapeutic tools to patients and the doctors who treat them. We are excited to partner with C4 Imaging and bring together the benefits of their innovative technology and our proprietary isotope to achieve new strides in the ongoing fight against prostate cancer.”

Brachytherapy, or internal radiation therapy, is a leading, cost-effective option for the treatment of prostate cancer. Isoray is the world’s only producer of Cesium-131, commercially known as Cesium Blu™, brachytherapy seeds. Cesium-131 is a radioactive isotope that delivers a minimally invasive and highly targeted treatment to the site of the cancer preserving healthy tissue and organs. Patients benefit from the rapid resolution of their side effects allowing them to return to their normal lives quickly.


C4 Imaging: Andrew Bright (609) 933-5895, abright@c4imaging.com

Isoray: Media and Public Relations: Sharon Schultz (302) 539-3747
Isoray Investor Relations: Mark Levin (501) 255-1910


C4 Imaging develops medical devices that enable clinicians to more accurately perform image-guided procedures. The company’s proprietary technology, C4, has been developed as Sirius, the first Positive-Signal MRI Marker, as well as Orion™, an MRI Marker that enables accurate MRI–based treatment planning for cancer patients being treated with high dose rate (HDR) brachytherapy. Sirius® and Orion™ both enable the adoption of MARS – MRI-Assisted RadioSurgery. C4’s Multimodality Fiducial Marker was recently FDA cleared and will be launched in 2021; it will allow the benefits of positive-signal MRI to be offered to the hundreds of thousands of patients who receive radiotherapy each year. To learn more, please visit www.c4imaging.com. Join us on Facebook/siriusmri.

About Isoray

Isoray, Inc., through its subsidiary, Isoray Medical, Inc. is the sole producer of Cesium-131 brachytherapy seeds, which are expanding brachytherapy options throughout the body. Learn more about this innovative Richland, Washington company and explore the many benefits and uses of Cesium-131 by visiting www.isoray.com. Join us on Facebook/Isoray. Follow us on Twitter @Isoray.

Investor Relations:

Mark Levin

Global IR Group
(501) 255-1910

Media and Public Relations:

Sharon Schultz
Schultz Public Relations
(302) 539-3747