Tiny Coils and Software Help Doctors Destroy Liver Tumors Without Contrast Dye

Interventional radiologists at Wake Forest University School of Medicine have reported a technique that could change how doctors treat large liver tumors in patients who cannot receive contrast dye. In a case report published in CVIR Oncology, Benjamin Daniel and Brian Kouri describe how they used six tiny metallic coils, cone-beam computed tomography, and predictive ablation software to completely destroy a 4.5-centimeter hepatocellular carcinoma without any intravenous contrast administration. The patient, a 72-year-old man with cirrhosis and stage 4 chronic kidney disease who refused contrast, remains free of disease more than two years after the procedure. The achievement matters because contrast agents, which are normally essential for visualizing liver tumors during image-guided therapy, are dangerous for patients with impaired kidney function and are sometimes declined outright by patients wary of allergic reactions.

Hepatocellular carcinoma is the most common form of primary liver cancer and ranks third among all cancers in worldwide mortality. For tumors caught at an early stage, percutaneous thermal ablation, in which a needle-like antenna delivers heat to cook the tumor away, is considered the optimal minimally invasive locoregional therapy. But the technique depends entirely on the operator’s ability to see the tumor. At most institutions, tumors between 3 and 5 centimeters are typically treated with radiation segmentectomy or with transarterial chemoembolization combined with microwave ablation. Both approaches rely on catheters threaded into the arteries feeding the tumor, and both depend on iodinated contrast to map the tumor’s blood supply. When contrast is off the table, those pathways close.

The patient in this report faced exactly that dilemma. His tumor board determined he was ineligible for transplantation, surgical resection, or stereotactic body radiotherapy because of regional lymph node metastases and compromised liver function, classified as Child-Pugh B7 cirrhosis. His stage 4 chronic kidney disease made contrast-enhanced procedures hazardous, and he refused contrast administration altogether. That ruled out radiation segmentectomy, transarterial chemoembolization, and cone-beam CT arteriography, the contrast-enhanced imaging technique that normally guides such procedures in the angiography suite. After extensive discussion, he agreed to a novel alternative: microwave ablation guided by ultrasound-placed fiducial markers and non-contrast cone-beam CT with trajectory planning software.

The technique began with the placement of six radio-opaque fiducial markers, short pushable coils measuring 2 millimeters, delivered through a 15-centimeter, 20-gauge needle under ultrasound guidance. Each coil was positioned at one of the tumor’s anatomic boundaries: cranial, caudal, medial, lateral, anterior, and posterior. Ultrasound and fluoroscopic imaging confirmed that all six markers sat satisfactorily around the lesion. The concept is elegantly simple. Because the tumor itself was poorly visible on non-contrast imaging, the team created an artificial outline of it, framing the cancer with metal beacons that any X-ray-based imaging system could detect. The coils effectively drew the tumor’s borders in a language the treatment equipment could read.

With the tumor framed, the team advanced a microwave antenna under ultrasound guidance until its tip abutted the first fiducial marker. A planning cone-beam CT confirmed the probe’s position, and the images were exported to a standalone desktop running ablation visualization software. That software calculated the maximal yet safe ablation zone for the probe’s position, predicting the volume of tissue that a given energy delivery would destroy, and computed the resulting ablation margin, the buffer of treated tissue extending beyond the tumor edge. The team targeted margins of 0.5 to 1 centimeter, the standard needed to eliminate microscopic tumor extensions that imaging cannot see.

What followed was a carefully choreographed sequence of overlapping ablations. After the first burn, a second probe trajectory was planned using the post-placement cone-beam CT, and the antenna was repositioned with the help of a planned trajectory overlaid on live fluoroscopic guidance. A repeat cone-beam CT verified the new position, the planning software extrapolated the residual tumor still to be treated, and the next trajectory was calculated accordingly. The team worked through the fiducials one by one, ultimately performing eight fiducial-targeted ablations plus two additional burns to confirm adequate margins using the cumulative ablation zones displayed by the software and verified on post-ablation imaging. Because the software mapped every zone and cone-beam CT followed each ablation, no additional immediate postoperative imaging was needed.

The technical footprint of the procedure was modest. Total fluoroscopic time was 18.5 minutes, with a cumulative radiation dose of 1405 milligray. There were no intraoperative or immediate complications. The patient experienced only mild epigastric pain for one week after the procedure and reported no complaints at one-month follow-up. Most strikingly, the initial post-procedural MRI and the most recent 26-month follow-up MRI both demonstrated complete response of the target lesion by modified RECIST criteria, the standardized imaging assessment used to judge treatment success in liver cancer trials. For a tumor larger than 3 centimeters treated without contrast, that durability is the report’s central evidence.

The authors acknowledge meaningful limitations. This is a single-patient retrospective case report, and skeptics could argue that the same outcome might have been achieved with ultrasound or conventional CT alone. But the authors counter that the tumor’s size demanded multiple probe placements and overlapping ablations, which would have been impossible to verify with ultrasound alone because the ablation planning software requires cross-sectional imaging to confirm sufficient coverage. Non-contrast conventional CT, meanwhile, would have limited the precise oblique probe trajectories needed to cover the entire lesion while protecting adjacent bowel. Out-of-plane needle placements are more accurate with the trajectory planning and real-time fluoroscopic guidance that cone-beam CT uniquely provides. The fundamental weakness of non-contrast cone-beam CT is its limited soft tissue resolution, which is precisely the problem the fiducials were designed to solve.

Fiducial markers are not new to interventional radiology. They have previously been used to guide ablation of colorectal metastases, particularly for lesions that disappear on imaging after chemotherapy, leaving nothing visible to target. But little research exists on fiducial placement for prospective ablation guidance in hepatocellular carcinoma, and the authors argue that the effectiveness and reproducibility of this approach make it a worthy addition to the literature. They also sketch a more refined evolution of the technique: a staged workflow in which fiducials are placed first, a preoperative CT or MRI is then acquired, and that study is uploaded and overlaid on the patient in the procedure room. A single fiducial would serve as an internal control for respiration and patient positioning, allowing the ablation zone to be planned from preoperative imaging alone.

The broader significance of the report lies in what it demonstrates about adaptability in image-guided medicine. Predictive ablation software, originally developed to help operators estimate burn volumes in conventional settings, proved capable of anchoring an entire treatment plan around metal markers instead of a contrast-visible tumor. The approach preserves three advantages that are usually lost when contrast is unavailable: accurate margin assessment, safe probe trajectories through difficult anatomy, and confidence that overlapping ablations have covered the target completely. The authors are careful to note that future prospective studies are needed before the technique can be considered standard practice, and a single case cannot establish safety across diverse patients and tumor geometries. Still, for the growing population of patients with liver cancer and kidneys that cannot tolerate contrast, the report offers a concrete, technically grounded path forward, one in which six small coils and clever software stand in for the contrast dye that medicine long took for granted.

Subject of Research: Fiducial marker-assisted, contrast-free microwave ablation of hepatocellular carcinoma using cone-beam CT guidance and ablation predictive software

Article Title: Fiducial marker-assisted microwave ablation of hepatocellular carcinoma: achieving margins without contrast

Article References: Daniel, B., & Kouri, B. (2025). Fiducial marker-assisted microwave ablation of hepatocellular carcinoma: achieving margins without contrast. CVIR Oncology, 1(1), Article 16. https://doi.org/10.1007/s44343-025-00013-3

Image Credits: AI Generated

DOI: 10.1007/s44343-025-00013-3

Keywords: hepatocellular carcinoma, microwave ablation, fiducial markers, cone-beam CT, interventional radiology, ablation predictive software, contrast contraindication, liver cancer, trajectory planning, cirrhosis, mRECIST, case report