Subtle Medical is building an AI layer for medical images that increases efficiency for healthcare providers and benefits patients.
Health systems and imaging centers are facing increased medical imaging workloads due to outdated technology and limited scanner capacity. Imaging tests are usually long and uncomfortable for patients.
Menlo Park, California-based Subtle Medical aims to address these challenges with AI-powered image processing software that reduces manual labor and enables faster, higher-quality medical image processing. Long scan times can reduce image quality, delay diagnosis, and limit scanner capacity. Subtle Medical’s AI software improves image quality and speeds up scanning on existing imaging systems, allowing providers to increase throughput without purchasing new hardware.
The company’s technology also improves patient experience by reducing MRI scan times and improves patient safety by reducing radiation exposure.
The startup was born out of Stanford University by founders Greg Zakarchuk, MD, a neuroradiologist and professor at Stanford University, and deep learning scientist Enhao Gong, PhD. The company has developed a vendor-neutral software solution built on machine learning and generative AI. This improves image quality for regular and fast imaging protocols, allowing radiologists to expedite patient care.
Preparing for the next phase of commercial growth, Subtle Medical has secured $33 million in growth capital through Series C financing led by funds managed by Morgan Stanley Expansion Capital. The funding included participation from South Korea-based Shinhan Venture Investment and existing investors Fusion Fund, EnvisionX, BRV, and Samsung Ventures. The company has raised $86 million to date.
Subtle Medical will use the new capital to accelerate product development, expand commercial adoption globally, and expand its vendor-neutral AI imaging platform across MRI, PET, and CT workflows.
In addition to the funding announcement, Subtle Medical has named medical imaging executive Ohad Arazi as its new chief executive officer, replacing Gong as co-founder and CEO. Mr. Gong will now serve as chief scientific officer, leading the company’s science roadmap and continuing to support business operations and strategic partnerships in China.
“Subtle Medical was founded to make advanced imaging faster, safer and more accessible,” Gong said in a statement. “As we enter this next phase, I am excited to welcome Ohad and continue to advance the science behind our platform while expanding its impact across global imaging workflows.”
Subtle’s AI solutions are deployed on more than 1,300 scanners in major imaging networks, academic medical centers, and healthcare systems around the world. Customers such as Mount Sinai, RadNet, and Radiology Partners report measurable improvements in throughput, efficiency, and patient experience. The company has received 11 Food and Drug Administration (FDA) approvals and published more than 25 peer-reviewed papers.
On the right is an MRI image enhanced with SubtleHD (MR) (Subtle Medical)
Subtle Medical has developed a suite of deep learning technologies to improve MRI image quality, reduce exam time and reduce manual labor. This allows providers to extend the lifespan of their existing scanners while delivering sharper images and more efficient workflows. The company’s SubtlePET AI software improves PET image quality and enables faster, lower-dose PET scans, supporting a safer and more comfortable patient experience without compromising diagnostic accuracy.
SubtleMR uses AI to denoise and sharpen MRI scans, allowing facilities to run scans up to 80% faster. The company’s solutions help hospitals and imaging centers around the world achieve faster, higher-quality image processing without the need for new hardware investments.
“We use software that overlays existing equipment, so you don’t have to upgrade the scanner. We take a copy of those images and send them to the cloud, and we use AI to remove noise and neural networks to fill in the blanks. So we can get higher-resolution images than we could get with a standard scan, even with a much shorter scan time,” Arazi told Fierce Healthcare.
Arazi brings decades of experience across digital health, medical imaging, and healthcare IT as an entrepreneur, investor, and public company executive. He has held CEO and leadership roles in AI-powered ultrasound diagnostics company Clarius, Zebra Medical Vision, Genoox, TELUS Health, and PACS businesses at McKesson/Change Healthcare.
Subtle Medical is positioning itself as an essential AI infrastructure layer for modern radiology, Arazi said.
“I have to say that in my 20 years in the medical technology field, I have never come across a value proposition so clear and clearly articulated,” he told Fierce Healthcare. He said the company’s use of AI improves patient experience and healthcare provider efficiency.
“Most hospitals are still in the red in the post-COVID reality, and essentially what we’re doing, in addition to improving patient experience by increasing patient comfort and reducing anxiety, we’re also addressing challenges related to movement. It’s an incredible value proposition for providers because a typical MRI in the United States processes about 14 patient slots per day per scanner, so they book about 14 patients per appointment. By adding about four to five slots per day per scanner, using a provider’s existing equipment, existing shift lengths, and existing technology resources, in an eight-hour shift or a 10-hour shift, it’s a significant revenue increase for the hospital, which of course reduces patient wait times and reduces imaging wait times,” Arazi said.
Ohad Alazi (Subtle Medicine)
Subtle Medical is expanding its multimodality AI imaging portfolio across MRI, PET, and CT. The company’s Imaging Hub is an integrated platform that gives medical systems central control over imaging performance across scanners, regardless of manufacturer. Instead of managing scanners for AI tools by scanner or by modality, providers can improve image quality, standardize output, and streamline workflows across their infrastructure in real-time. Unlike OEM-native AI tied to specific equipment or fragmented point solutions that address one modality at a time, Subtle Medical’s hub operates simultaneously across MRI, PET, and CT environments.
“Subtle Medical solves a real operational problem in the health care system: the imaging backlog that slows treatment and limits capacity,” Kevin Hung, executive director of Morgan Stanley Expansion Capital, said in a statement. “We are excited to support Subtle Medical in its next phase of growth to help improve the patient experience in medical imaging.”
Subtle is also advancing AI-powered contrast enhancement imaging through strategic partnerships, including Bracco Imaging on AiMIFY for AI-powered contrast enhancement. The company is also developing SubtleGAD, a technology designed to enable gadolinium-enhanced MRI, which can reduce the dose of gadolinium contrast agent by up to 90% for safer medical imaging.
The company has also developed an AI imaging solution for CT imaging that is pending FDA approval. AI-powered image enhancement software reduces noise and improves contrast-to-noise ratio.
Over the past nine years, Gong and Zaharchuk have built Subtle Medical into an AI-powered medical imaging software provider that is well established in the scientific community, Arazi said.
“They focused on publications and research to build trust with clinicians to say, ‘I feel safe reading this image.’ This is a huge step forward in terms of building trust, and that’s where the founders were really great. What’s important now is to take that scientific direction. “It’s about how do we take that and put some commercial rocket fuel into it by developing new channels, entering new markets, learning to maybe tell that story in a slightly different way and overcoming some of the visibility challenges,” he said.
Subtle Medical raised $12.2 million in Series A investment in 2020 and $30 million in Series B funding in 2024.
The company is experiencing accelerating growth and aims to achieve breakeven profits within the next 24 months.
“We basically think this is the last capital going into the company. This will probably be enough of a catalyst for whatever this company does next. Our focus is to grow commercially into new areas, new types of customers, and they’re moving away from traditional imaging center groups to more hospitals,” Alazi said.
