Computed Tomography Imaging Assessment of Postexternal Beam Radiation Changes of the Liver

Abstract

Radiation is being used for patients with primary and secondary liver cancers, as a rapidly evolving treatment. However, postradiation imaging changes of the liver are not well understood and therefore challenging to interpret. Distinguishing normal radiation changes from residual or recurrent disease is difficult. Size and contrast enhancement have been used to guide interpretation and clinical recommendations, but normal radiation changes can make interpretation difficult and are not accounted for in available guidelines. Knowledge of dose- and time-dependent changes in addition to imaging findings, such as morphological and enhancement patterns, provides useful differentiating parameters. This paper reviews recent studies using computed tomography that can guide interpretation and help differentiate tumor from benign changes after external beam radiation.

In vitro and in vivo evaluation of the safety and efficacy of a novel liquid fiducial marker for image‑guided radiotherapy

“…The authors attributed this to the degree of tissue condensing following injection, wherein tissue volumetric integrity was better preserved and an improved representation of the tumor border was observed. Other studies have demonstrated that a large volume of liquid material leads to hardened artifacts and results in decreased imaging quality, rendering the radiotherapy unprecise (12,48). In the present study, the injection volume of 0.15 ml was not shown to reduce the CT imaging quality.…”

Imaging Evaluation Following 90Y Radioembolization of Liver Tumors: What Radiologists Should Know

“…Imaging features of radiation effect on hepatic parenchyma after radioembolization have not yet been well described. However, radiation-induced changes in the liver after external radiation have been reported in the previous studies ( 54 55 56 ) and can be applied in the interpretation of post-radioembolization examinations with caution. After external radiation therapy, the irradiated hepatic parenchyma frequently shows arterial hyper-enhancement on an early follow-up until 6 months which may interfere with accurate assessment of tumor response in HCC ( 54 ).…”

“…Lack of washout appearance on the delayed phase can be helpful in differentiating radiation effect from tumor progression ( 54 ). On the portal venous phase and delayed phase images, the irradiated hepatic parenchyma can present various enhancement patterns according to the radiation dose and time interval after the treatment ( 55 ). Typical time-dependent changes are as follows: type I (within 3 months), hypo-attenuation on the portal venous phase and iso-attenuation on the delayed phase ( Fig.…”

“…7C ) ; type III (after 6 months), iso- or hyper-attenuation on the portal venous phase and hyper-attenuation on the delayed phase ( Fig. 8C ) ( 55 ). Type I and II enhancement patterns may be explained by the radiation-induced acute veno-occlusive disease, resulting in delayed contrast inflow without and with reduced contrast clearance ( 56 ).…”

“…Type I and II enhancement patterns may be explained by the radiation-induced acute veno-occlusive disease, resulting in delayed contrast inflow without and with reduced contrast clearance ( 56 ). Type III enhancement patterns may be related to distortion of the liver architecture and fibrotic change ( 55 ). By reflecting the time-dependent changes, serial imaging studies may show a shift in the enhancement patterns.…”