Cryoablation, a cancer treatment that destroys tumors by freezing them, may soon be planned by more than the shape of the visible ice ball. A new analytical model proposes measuring the biological effect of cold as a cumulative dose, combining temperature, exposure time, tissue sensitivity and repeated freeze cycles. The approach, described by Francois H. Cornelis, Arthur A. Cornelis and Stephen B. Solomon in CVIR Oncology, is intended to help clinicians estimate whether tissue has received enough lethal cold while keeping the treatment within the boundaries imposed by nearby nerves, blood vessels or other critical structures. The authors call the metric cumulative cold dose, or CCD. Their model does not yet represent a validated clinical standard, but it offers a framework for turning cryoablation from a largely geometry-driven procedure into one that also accounts for how long cells remain below a lethal temperature. That distinction could be important in the thin transition zone between a frozen tumor and surrounding tissue, where temperatures may be damaging without immediately killing every cell.
In current practice, the ice ball created by a cryoablation probe is a central visual guide. Imaging can show the approximate volume of frozen tissue, allowing operators to position applicators and judge whether the tumor is covered. Yet the outer boundary of an ice ball does not necessarily reveal the distribution of temperatures inside it. The temperatures commonly used as lethal benchmarks, around −20 °C to −40 °C, cannot be directly visualized in routine treatment images. As power is reduced to prevent the ice from reaching a vulnerable structure, the overall ice ball may remain similar in size while its colder internal isotherms contract. The result can be a larger marginal zone, spanning temperatures from roughly 0 °C to the lethal threshold, where cells experience sublethal stress and may recover. The CCD model is designed to address that uncertainty by asking not simply whether a location lies inside the ice ball, but whether it has accumulated sufficient time at or below the cell type’s lethal threshold.
The researchers developed the model through a systematic review conducted under PRISMA 2020 guidelines. Searches of PubMed, Embase and Web of Science, covering the available literature through March 2025, identified studies reporting the effects of freeze duration, cell-specific lethal thresholds, lethal isotherm ratios or outcomes associated with particular treatment protocols. Two reviewers independently screened the records, and 43 studies met the inclusion criteria. The evidence base comprised 24 in vitro studies, nine in vivo studies, seven clinical studies and three reviews. CCD was defined as the total time tissue remains at or below its cell-type-specific lethal threshold across all freeze cycles, excluding the intervals used for thawing. For modeling purposes, a point was considered lethally dosed when its accumulated exposure corresponded to a probability of at least 80 percent cell death. The authors describe that level as a conservative lower bound for anatomically constrained treatments, while noting that procedures performed with curative intent and unconstrained margins may require higher targets.
The model’s duration component was calibrated using data from an in vitro study of the transition zone. In that source study, extending exposure from 60 seconds to 120 seconds increased marginal-zone cell death from 42.5 percent to 84.8 percent. The researchers fitted those two points to a logistic curve, using a growth parameter of 0.0538 and a midpoint of 86 seconds. The resulting calculation estimated that a single freeze cycle would need at least 120 seconds to reach the model’s 80-percent cell-death target. Repeating the freeze changed the estimated requirement because processes such as ice recrystallization and incomplete membrane repair during passive thaw can amplify injury between cycles. Under the model’s conservative amplification assumption, the minimum exposure fell to 50 seconds per cycle for a double-cycle protocol and 31 seconds per cycle for a triple-cycle protocol. These values describe effective dose targets in the model, not universally established treatment instructions.
The review also examined how treatment power and ice-ball size affect the spatial distribution of cold. The analysis modeled three cryoablation systems, four ice-ball sizes ranging from 25 to 40 millimeters and power settings between 40 and 100 percent. The calculations assumed that the lethal zone shrinks proportionally as power decreases, although the authors emphasized that this linear relationship has not been fully validated. At 40 percent power, the −20 °C isotherm contracted to approximately 25 to 30 percent of the total ice-ball width. This contraction expanded the marginal zone by as much as 3.9-fold. A visible ice ball could therefore occupy the intended treatment volume while containing a much smaller region exposed to temperatures expected to cause direct lethal injury. Sensitivity analyses using more conservative and more optimistic scaling assumptions changed CCD targets by about 15 to 25 percent, highlighting the uncertainty surrounding the geometry calculations.
The predicted consequences differed according to how resistant the target tissue was to cold. For cold-sensitive tissues, the model found that double-cycle protocols could maintain an adequate cumulative dose across all tested power levels, with estimated exposures of 50 to 125 seconds per cycle. For cold-resistant phenotypes, which may require temperatures near −40 °C for direct lethal injury, most configurations required escalation to triple-cycle protocols, multi-probe overlap or reliance on additional mechanisms of tissue destruction. The analysis found that double cycling increased renal cell lethality from 22 to 62 percent at −10 °C and from 63 to 89 percent at −15 °C in the underlying evidence. It also noted that a meta-analysis involving 786 patients had associated longer freeze duration with better local tumor control. That clinical association supports the importance of time, but it does not by itself prove that the CCD model accurately predicts outcomes for individual patients.
The model offers a practical way to interpret multi-cycle treatment. Under its proposed logic, the first cycle can establish the desired treatment geometry, while later cycles deliver additional biological dose without necessarily expanding the ice ball beyond an anatomical boundary. The source article illustrates this concept with a palliative cryoablation procedure for a 25-millimeter ovarian metastasis near the left psoas, between the L2 and L3 nerve roots. A single applicator was operated at 30 to 40 percent power to constrain the ice ball, and a triple-cycle protocol with passive thawing was used to compensate for the reduced internal isotherms. The first cycle lasted five minutes at 30 percent power, followed by seven minutes at 40 percent and five minutes at 30 percent. The reported procedure produced no observed nerve damage during follow-up. The example demonstrates how the model could rationalize repeated freezing, although one case cannot establish efficacy or safety for broader clinical use.
Important biological limitations remain. Measurements derived from cultured cells cannot be transferred directly to living tumors, where blood flow can carry heat into the treatment margin and shorten the effective duration of cold exposure. This heat-sink effect may be partly offset in later cycles if the first freeze damages blood vessels and reduces local perfusion. Cell type, tissue composition, tumor architecture and temperature history can also influence the response. CCD currently counts time below a fixed threshold rather than assigning a continuous weight to different subzero temperatures. In that respect, it is simpler than the cumulative equivalent minutes at 43 °C model used for hyperthermia, which weights time and temperature continuously. The present calibration relies on only two duration points, the validated duration range is limited to 60 to 120 seconds, and the assumed relationship between power reduction and isotherm contraction remains unconfirmed. The authors therefore present CCD as a structured, testable hypothesis. Prospective studies combining real-time thermometry with volumetric treatment outcomes will be needed before it can guide routine care. If those studies confirm the predictions, cumulative cold dose could give interventional radiologists a quantitative language for choosing freeze duration, cycle number and probe arrangement—especially when tumor control must be balanced against the safety of nearby healthy tissue.
A further implication of the proposed framework is that treatment adequacy would have both spatial and volumetric dimensions. It would not be enough for a few sampled locations to exceed a CCD threshold; the threshold would need to be achieved across a prespecified fraction of the treatment volume. This distinction matters because temperature gradients are steep near the ice-ball margin, and a treatment could contain highly dosed central tissue alongside underdosed peripheral tissue. In principle, thermometry or validated thermal modeling could generate a three-dimensional map of accumulated dose rather than relying on a single visible boundary.
The model also separates the size of the frozen region from its spatial efficiency. The lethal isotherm ratio, or LIR, estimates the proportion of ice-ball width occupied by a selected lethal isotherm. In the reviewed comparisons, the liquid-nitrogen system had the highest reported ratios for a 25-millimeter ice ball, including an approximately 82.6% ratio at −20 °C and 63.3% at −40 °C. By contrast, a larger clustered configuration could produce a greater absolute lethal-zone width while having lower spatial efficiency. These measures therefore answer different planning questions: whether a system can reach a required temperature, how much of the target can be exposed to it, and whether additional cycles or overlapping probes are needed.
CCD may ultimately support adaptive treatment rather than a fixed protocol selected before the procedure. A clinician could begin with a geometry-limited freeze, use measured temperatures or system-specific isotherm estimates to identify underdosed regions, and then adjust cycle duration, power or probe overlap. Such an approach would require reliable calibration for each device and tissue context, because the review combined heterogeneous experimental and clinical evidence. The authors also tested inter-cycle amplification across a broad range and used the conservative end for their principal recommendations, underscoring that the benefit attributed to repeated freezing is not a single settled biological constant. Prospective validation would need to compare predicted dose maps with biopsy, imaging, local-control and toxicity outcomes while accounting for blood flow and temperature measurement error.
Subject of Research: Cumulative cold-dose modeling for cryoablation treatment planning
Article Title: A cumulative cold dosimetry model for cryoablation: from geometry to dose-time planning
Article References: Cornelis, F. H., Cornelis, A. A., & Solomon, S. B. (2026). A cumulative cold dosimetry model for cryoablation: from geometry to dose-time planning. CVIR Oncology, 2(1), Article 20. https://doi.org/10.1007/s44343-026-00058-y
Image Credits: AI Generated
DOI: 10.1007/s44343-026-00058-y
Keywords: cryoablation, cumulative cold dose, cancer treatment, dosimetry, thermal isotherms, cell death, interventional radiology, tumor ablation, cumulative, cold, model, geometry
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Scienmag. “New Cold-Dose Model Could Make Cryoablation More Precise.” Scienmag, 28 August 2026, https://scienmag.com/new-cold-dose-model-could-make-cryoablation-more-precise/. Accessed 28 August 2026.
Scienmag. “New Cold-Dose Model Could Make Cryoablation More Precise.” Scienmag. August 28, 2026. https://scienmag.com/new-cold-dose-model-could-make-cryoablation-more-precise/
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