Giving Radiologists and Other Clinicians the Tools to Identify Radiation Effects on Imaging Studies

Liver magnetic resonance imaging for evaluation of response to treatment after stereotactic body radiation therapy of hepatocellular carcinoma

BACKGROUND

Although stereotactic body radiation therapy (SBRT) is increasingly used, its application has not yet been regulated by the main international guidelines, leaving the decision to multidisciplinary teams.

AIM

To assess magnetic resonance imaging (MRI) features of hepatocellular carcinoma (HCC) treated with SBRT, highlighting the efficacy of the treatment and the main aspects of the lesion before and after the procedure.

METHODS

As part of a retrospective study, 49 patients who underwent SBRT for HCC between January 2013 and November 2019 were recruited. Each patient underwent a pre-treatment MRI examination with a hepatospecific contrast agent and a similar follow-up examination within 6 mo of therapy. In addition, 22 patients underwent a second follow-up examination after the first 6 mo. The following characteristics were analysed: Features analysed compared to pre-treatment MRI examination, presence or absence of infield and outfield progression, ring-like enhancement, signal hyperintensity in T2-weighted sequences in the perilesional parenchyma, capsular retraction, and "band" signal hypointensity in T1-weighted gradient echo fat saturated sequences obtained during hepatobiliary excretion.

RESULTS

Signal hyperintensity in the T2-weighted sequences showed a statistically significant reduction in the number of lesions at the post-SBRT first control (P = 0.0006). Signal hyperintensity in diffusion-weighted imaging-weighted sequences was decreased at MRI first control (P < 0.0001). A statistically significant increase of apparent diffusion coefficient values from a median of 1.01 to 1.38 at the first post-control was found (P < 0.0001). Capsular retraction was increased at the late evaluation (P = 0.006). Band-like signal hypointensity in the hepatobiliary phase was present in 94% at the late control (P = 0.006). The study of the risk of outfield progression vs infield progression revealed a hazard ratio of 9.

CONCLUSION

The efficacy of SBRT should be evaluated not in the first 6 mo, but at least 9 mo post-SBRT, when infield progression persists at very low rates while the risk of outfield progression increases significantly.

Feasibility and clinical utility of a workflow interfacing radiation oncology lung stereotactic body radiotherapy treatment planning and diagnostic radiology

Stereotactic body radiotherapy (SBRT) is commonly used to treat early stage non-small cell lung cancer (NSCLC). SBRT beam arrangements include multiple entry/exit pathways resulting in irregular low dose distributions within normal lung parenchyma. An improved understanding of post-treatment radiographic changes may improve the ability to predict clinical complications including radiation pneumonitis as well as assist in early detection of local failures. Radiation treatment planning is conducted using software systems separate from diagnostic radiology, often not accessible to the diagnostic radiologist. We developed a workflow for interfacing radiation dose information from lung SBRT treatments with diagnostic radiology picture archiving and communication system (PACS). In an anonymized PACS study folder, SBRT dose maps depicting high dose, low dose, and non-irradiated lung volumes were viewable side-by-side with pretreatment and follow up diagnostic CT scans. Clinical utility was evaluated by two thoracic diagnostic radiologists reviewing post-treatment diagnostic follow up scans in PACS both with and without radiation dose maps available. The addition of the biologically effective dose (BED) map did not significantly change identification rates of radiation induced lung injury (RILI) (92% vs. 95%, p=0.32) but did significantly decrease radiologic suspicion for LR (22% vs. 8%, p=0.003). The addition of BED maps significantly increased confidence in calling RILI (7.75 vs. 8.82, p=0.004) and LR (5.5 vs 6.6, p=0.005). Recommendation for additional workup was not significantly different (10% vs 7%, p=0.41). We demonstrated the feasibility and clinical utility of a workflow generating simplified radiation dose maps that are viewable within PACS for diagnostic radiology review.