CT/MRI LI-RADS 2024 Update: Treatment Response Assessment

Abstract

With the rising incidence of hepatocellular carcinoma, there has been increasing use of local-regional therapy (LRT) to downstage or bridge to transplant, for definitive treatment, and for palliation. The CT/MRI Liver Imaging Reporting and Data System (LI-RADS) Treatment Response Assessment (TRA) algorithm provides guidance for step-by-step tumor assessment after LRT and standardized reporting. Current evidence suggests that the algorithm performs well in the assessment of tumor response to arterial embolic and loco-ablative therapies and fair when assessing response to radiation-based therapies, with limited data to validate the latter. Both evidence-based and expert-based refinements of the algorithm are needed to improve its diagnostic accuracy after varying types of LRT. This review provides an overview of the challenges and limitations of the LI-RADS TRA algorithm version 2017 and discusses the refinements introduced in the updated 2024 LI-RADS algorithm for CT/MRI.

Graphical abstract

Figure 1:

CT/MRI Liver Imaging Reporting and Data System (LI-RADS) Treatment Response Assessment (TRA) algorithm, version 2024 (v2024), for (A) nonradiation treatment and (B) radiation-based treatment. LRT = local-regional therapy, LR-TR = LI-RADS treatment response. * = Examples include complete lesion disappearance, no lesional enhancement, smooth perilesional enhancement, or parenchymal perfusional changes without masslike enhancement.

Figure 2:

Liver Imaging Reporting and Data System (LI-RADS) treatment response (LR-TR) Nonviable after microwave ablation (MWA). MRI scans in a 62-year-old male patient with cirrhosis who presented with a 2.4-cm LI-RADS 5 observation in segment V show (A) arterial phase hyperenhancement (arrow) and (B) portal venous phase washout with capsule (arrow). (C) Patient underwent microwave ablation, and MRI scan 3 months later shows a 3.2-cm treatment cavity demonstrating intrinsic T1 precontrast hyperintense signal secondary to coagulation necrosis (red arrow). Note the treatment cavity is 8–10 mm larger than the tumor itself to ensure adequate treatment of microscopic disease surrounding the tumor. (D) Arterial phase MRI scan shows no intralesional masslike enhancement and smooth perilesional enhancement, categorized as LR-TR Nonviable (arrow). Note the surrounding perfusional changes.

Figure 3:

Liver Imaging Reporting and Data System (LI-RADS) treatment response (LR-TR) Viable after transarterial chemoembolization. MRI scans in a 75-year-old male patient with hepatitis C–related cirrhosis show (A) a 3.3-cm observation in segment II of the liver that demonstrates arterial phase hyperenhancement (arrow), plus washout and capsule (not shown), categorized as LI-RADS 5. (B) Arterial phase MRI scan 1 month after transarterial chemoembolization shows no residual intralesional enhancement (arrow), and (C) there is smooth perilesional enhancement without masslike areas of enhancement (arrow), yielding LR-TR Nonviable. One year following transarterial chemoembolization, (D) noncontrast MRI scan shows a new 4.5 × 1.0-cm area of irregular T1 hypointense signal (arrows) with (E) masslike enhancement (arrows) and (F) washout and capsule (arrows) along the margin of the previous transarterial chemoembolization–treated hepatocellular carcinoma, yielding LR-TR Viable.

Figure 4:

Liver Imaging Reporting and Data System (LI-RADS) treatment response (LR-TR) Equivocal after microwave ablation. MRI scans in a 76-year-old female patient with alcohol-related cirrhosis show a 1.7-cm segment VI observation demonstrating (A) arterial phase hyperenhancement (arrow), (B) washout and capsule (arrow), (C) mild T2 hyperintense signal (arrow), and (D) restricted diffusion (arrow), categorized as LI-RADS 5. (E) MRI scan 3 months after microwave ablation shows irregular perilesional rim enhancement on arterial phase (arrow), while the (F) corresponding portal venous phase image shows no finding (arrow). (G) T2-weighted image shows subtle corresponding mild hyperintense signal (arrow) with (H) restricted diffusion (arrow). In Treatment Response Assessment version 2017, this would be LR-TR Equivocal; however, in version 2023, this can be upgraded to LR-TR Viable based on the presence of ancillary features. (I) Precontrast T1-weighted MRI scan 6 months after microwave ablation shows central coagulation necrosis (arrow), with (J) increasing nodular masslike enhancement along the margin (arrow), which demonstrates (K) corresponding mild T2 hyperintense signal (arrow) and (L) restricted diffusion (arrow), yielding LR-TR Viable. The patient was re-treated with microwave ablation.

Figure 5:

Liver Imaging Reporting and Data System (LI-RADS) treatment response (LR-TR) Nonviable after transarterial radioembolization. Arterial phase MRI scans in a 48-year-old female patient show a LI-RADS 5 observation (circle) in segment VII/VI of the liver ([A] arterial phase hyperenhancement and [B] washout and capsule). Arterial phase MRI scans (C) 3 months, (D) 9 months, and (E) 15 months after transarterial radioembolization show no masslike intralesional enhancement and smooth perilesional rim enhancement (arrow), yielding LR-TR Nonviable at all time points. Note the surrounding wedge-shaped parenchymal perfusional changes corresponding to the vascular distribution, compatible with radiation fibrosis and the slowly developing parenchymal atrophy from fibrosis.

Figure 6:

Liver Imaging Reporting and Data System (LI-RADS) treatment response (LR-TR) Viable after transarterial radioembolization. MRI scans in a 58-year old male patient with (A) biopsy-proven LR-M (peripheral rim enhancement at arterial phase with progressive enhancement at portal venous and delayed phase) hepatocellular carcinoma in segment VIII (arrow). Arterial phase images (B) 3 months and (C) 9 months after transarterial radioembolization show no intralesional enhancement and smooth perilesional rim enhancement without masslike enhancement (arrow), yielding LR-TR Nonviable. (D) MRI scans 15 months after transarterial radioembolization show a new nodular area of arterial phase hyperenhancement along the 7 o’clock aspect of the treatment cavity (arrow), which demonstrates (E) washout (arrow) on the portal venous phase image, yielding LR-TR Viable.

Figure 7:

Liver Imaging Reporting and Data System treatment response (LR-TR) Viable after stereotactic body radiation therapy (SBRT). Pretreatment MRI scans in an 89-year-old female patient with hepatitis C–related cirrhosis presenting with 3.6-cm biopsy-proven hepatocellular carcinoma show (A) arterial phase peripheral rim enhancement and heterogeneous central enhancement (arrow), with (B) restricted diffusion (arrow) and (C) mild hyperintense T2-weighted signal (arrow), yielding category LR-M. (D–F) MRI scans acquired 3 months after stereotactic body radiation therapy show the treated lesion measuring 2.0 cm, with (D) persistent irregular masslike enhancement in the lesion with surrounding parenchymal perfusional changes related to postradiation changes (arrow), (E) mild restricted diffusion (arrow), and (F) mild persistent T2-weighted hyperintense signal (arrow), yielding LR-TR Nonprogressing. On MRI scans (G) 6 and (J) 12 months after stereotactic body radiation therapy, the treated observation measures 1.4 cm and 1.5 cm, respectively, with no intralesional enhancement but increasing parenchymal fibrosis (arrow), (H, K) loss of restricted diffusion (arrow), and (I, L) decreasing T2-weighted hyperintensity (arrow), yielding LR-TR Nonviable at both time points. (M–O) Fifteen-month follow-up MRI scans show interval increase in size of the treatment cavity, measuring 2.7 cm with (M) new intralesional enhancement (arrow), (N) areas of increased restricted diffusion (arrow), and (O) T2-weighted hyperintense signal corresponding to the areas of new internal enhancement (arrow), yielding LR-TR Viable.

Figure 8:

Liver Imaging Reporting and Data System (LI-RADS) treatment response (LR-TR) Nonprogressing. Images in a 54-year-old male patient with hepatitis C and alcohol-related cirrhosis presenting with an α-fetoprotein level of 143 ng/mL and a 3.8-cm segment IV observation with (A) arterial phase hyperenhancement (arrow) and washout and capsule (not shown), categorized as LI-RADS 5. (B) MRI arterial phase scan 1 month after transarterial radioembolization, with an α-fetoprotein level of 12.5 ng/mL, shows minimal residual intralesional enhancement (11 o’clock position) and smooth perilesional rim enhancement (arrow), yielding LR-TR Nonprogressing. (C) On the MRI arterial phase scan 5 months after transarterial radioembolization, the treatment cavity was smaller, with decreasing intralesional enhancement and smooth perilesional rim enhancement (arrow), yielding LR-TR Nonprogressing. (D) On the MRI arterial phase scan 18 months after transarterial radioembolization, there was no residual intralesional enhancement, and the treatment cavity had decreased in size (arrow), yielding LR-TR Nonviable. Note the overlying capsular retraction from radiation fibrosis, an expected finding after transarterial radioembolization.

Figure 9:

Liver Imaging Reporting and Data System treatment response (LR-TR) Nonprogressing. MRI arterial phase scan in a 74-year-old male patient with history of right segmentectomy for hepatocellular carcinoma, presenting with a new 1.4-cm observation in the caudate, shows (A) arterial phase hyperenhancement (arrow); washout was also observed (not shown). (B) MRI arterial phase scan 3 months after stereotactic body radiation therapy shows persistent irregular masslike enhancement of the treated lesion with associated parenchymal perfusional enhancement (arrow), yielding LR-TR Nonprogressing. (C) MRI arterial phase 6-month follow-up scan shows decreasing size and enhancement of the treated observation with surrounding parenchymal perfusional changes (arrow), consistent with expected postradiation fibrosis, yielding LR-TR Nonprogressing. (D) MRI arterial phase 12-month follow-up scan shows progressive atrophy of caudate with no intralesional enhancement (arrow), yielding LR-TR Nonviable.