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Page 6 of 8 Yip et al. Hepatoma Res 2020;6:44 I http://dx.doi.org/10.20517/2394-5079.2020.30

[29]
significant correlations with ICG retention at 15 min (ICG-R15) (r = -0.84, P < 0.0001) and clinical Child-
[30]
Pugh status .

Hepatocyte-specific MRI contrast agents, such as gadoxetate acid (Gd-EOB DTPA), also have the potential
to provide information on liver function besides its role as a diagnostic tool in HCC [31,32] . The rate of
T1 relaxation time reduction and T1 map quantifications have been shown to correlate well with ICG
clearance [31-33] . However, its use in this setting requires additional research and validation.

We anticipate that functional liver imaging will play a complementary role to existing cirrhosis severity
evaluation criteria, particularly in providing valuable spatial information which can be used to guide HCC
treatment. One exciting area of research is the prospect of sparing functional liver as depicted on cross-
[34]
sectional imaging during radiation planning, which may allow us to reduce the risk of RILD even more .

PROPOSED IMAGING ALGORITHM
We propose that response evaluation should be performed at 3 months after SBRT using multi-phasic
CT or MRI. The latter should include DWI sequence and the use of hepatocyte-specific contrast agents
should be considered. This should continue 3 monthly in the first year, 3-6 monthly in the second year and
6-12 monthly in the subsequent years depending on the clinical needs. However, the absence of volumetric
shrinkage or presence of residual arterial enhancement in the first few months after SBRT should not be
deemed tumour relapse unless there are other unequivocal radiological and/or clinical signs of progression.
We suggest that early interval imaging should be performed in these cases to confirm disease progression if
clinical situation permits.

CONCLUSION
Early post-SBRT imaging features include hepatic and periportal oedema as well as reactive hyperaemia in
the surrounding irradiated liver parenchyma. The latter may mimic disease progression, although there is
usually no associated delayed washout observed in these cases. In the subsequent months after SBRT, there
is hepatic fibrosis which may be followed by atrophy and capsular retraction. PET imaging is currently not
18
routinely used in HCC, although F-FDG PET may have a role for extrahepatic staging, particularly in high-
99m
grade HCC. Tc-SC SPECT can also be considered to assess liver function before and after SBRT.
DECLARATIONS
Authors’ contributions
Made substantial contributions to conception, design of the study and performed data interpretation: Yip C
Made substantial contributions to the design of the study and data interpretation: Hennedige TP, Cook GJR,
Goh V

Availability of data and materials
Not applicable.

Financial support and sponsorship
None.

Conflicts of interest
All authors declared that there are no conflicts of interest.

Ethical approval and consent to participate
Not applicable.