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LI-RADS 2024 radiation and nonradiation treatment response algorithms: what's new?
After six years of using the 2018 LI-RADS Treatment Response Assessment (LI-RADS TRA) algorithm, multiple questions and limitations have emerged. Consequently, evidence-based studies have been conducted for validation. Following this research, several key statements can be made regarding the updates to the 2024 LI-RADS Treatment Response Assessment Algorithm.
Key Findings and Limitations of Previous Versions
Research indicates that APHE is the only imaging feature that has demonstrated a true diagnostic yield in confirming viability. While the LI-RADS algorithm has shown good reliability in classifying patients treated with locoregional therapies into viable and non-viable categories, the LR-TR Equivocal category has poor interobserver agreement. Studies have demonstrated that a significant number of patients classified as Equivocal had an incomplete response on pathological examination. Furthermore, arterial mass-like hyperenhancement is a common finding in patients treated with radiation therapy and can persist for up to 3–6 months, increasing the number of patients incorrectly classified as LR-TR Viable.
Changes in the 2024 LI-RADS TRA Algorithm
In response to these limitations, the LI-RADS Committee has introduced the following changes in the 2024 version:
- Washout and enhancement similar to pretreatment are no longer considered viability characteristics.
- Ancillary features (AF), such as T2 hyperintensity and restricted diffusion, can now be used to upgrade patients from LR-TR Equivocal or LR-TR Non-progressing to LR-TR Viable.
- Two separate cores for treatment evaluation have been introduced: one for patients treated with locoregional therapies and one for patients treated with radiation therapies.
- The LI-RADS TR radiation core incorporates a watch-and-wait strategy.
LI-RADS TRA 2024 Category Definitions
The following table summarizes the four main categories applicable to treatment response assessment:
| Category | Definition and Features |
|---|---|
| LR-TR Non-evaluable | The presence of mass-like enhancement cannot be assessed due to image degradation or omission. |
| LR-TR Nonviable | No mass-like enhancement (of any degree, in any phase) is identified within the treated lesion or along its margins. Includes smooth perilesional enhancement or perfusional parenchymal changes. |
| LR-TR Viable | A mass-like enhancement (of any degree, in any phase) is classified as a viable lesion. Mass-like enhancement includes nodular, irregular, or smooth enhancement within the treated lesion or along its margins. |
| LR-TR Equivocal | This category is reserved for small enhancing areas that may harbour viable tumour but are not large enough to be confidently diagnosed. Current definition is uncertainty about mass-like enhancement (its presence or morphology). |
Implementation: Non-Radiation vs. Radiation Cores
LI-RADS Non-Radiation TRA Version 2024
This version must be used for lesions treated with surgery or locoregional therapies. Normal expected findings along the margins of the treated lesion now have a clearer definition, such as smooth perilesional enhancement and perfusional parenchymal changes without mass-like enhancement. In these patients, short-interval follow-up with imaging every three months is recommended. Most of these will eventually be diagnosed as LR-TR Viable on follow-up studies.
LI-RADS Radiation TRA Version 2024
This version must be used for lesions treated with radiation therapies, such as TARE and SBRT. The definition for LR-TR Non-evaluable remains the same as in LI-RADS Non-Radiation. Expected findings along the margins of the treated lesion are the same as those in non-radiation LI-RADS. For example, after TARE, perfusional changes typically exhibit a wedge-shaped morphology.