Comparison between bone matching and marker matching for evaluation of intra- and inter-fractional changes in accumulated dose of carbon ion radiotherapy for hepatocellular carcinoma

Abstract

Background and purpose: To determine whether bone matching (BM) or marker matching (MM) is the better positioning technique for carbon ion radiotherapy (CIRT) of primary hepatocellular carcinoma (HCC), we prospectively evaluated accumulated dose distributions with respect to intra- and inter-fractional anatomical changes.

Materials and methods: The accumulated doses in ten patients with HCC were evaluated, with the doses being calculated with respect to inter-fractional changes (InterDose) on treatment-room CT images on day 1 or day 2 of therapy (RefCT). This was accomplished by warping 3-day CT dose distributions to the RefCT through deformable registration. The accumulated doses were also calculated with respect to intra-fractional change (IntraDose) calculated by warping dose distributions for three 4DCT phases to the RefCT. Each dose was evaluated using dose-volume parameters for the clinical target volume (CTV) percentages receiving greater than 95% of the prescription dose (V₉₅).

Results: The InterDose CTV V₉₅ values (mean [range]) were BM: 98.74% (95.62-100%), MM: 99.79% (98.55-100%), and the IntraDose values were BM: 99.46% (98.10-100%), MM: 99.74% (98.91-100%). Although all cases were acceptable with either matching method, MM provided better values than BM.

Conclusion: MM is a better positioning technique than BM for ensuring the target dose during and between fractions of CIRT. However, further analysis is required as our study included only a low number of cases.

Keywords: Accumulated dose distribution; Bone matching; Carbon ion radiotherapy; Hepatocellular carcinoma; Intra- and inter-fractional anatomical change; Tumor matching.