Abstract
IntroductionIn breast conserving radiotherapy differences of target volume delineations between observers do occur. We evaluated whether delineations based on co-registered computed tomography (CT) and magnetic resonance (MR) imaging may result in an improved consistency between observers. We used the delineation conformity index (CI) to compare clinical target volumes of glandular breast tissue (CTV breast) and lumpectomy cavity (LC) on both imaging modalities.Methods and materialsFour observers delineated CTV breast and LC on co-registered CTMR images in ten breast cancer patients. CIs were determined for CT and CTMR. Furthermore, the Cavity Visualization Score (CVS) of LC was taken into account.ResultsThe mean CI for CTV breast (CICT;CTV: 0.82 and CICT-CTMR;CTV: 0.80) and LC (CICT;LC: 0.52 and CICT-CTMR;LC: 0.48) did not differ significantly (p = 0.07 and p = 0.33, respectively). Taking CVS into account for the LC, with a CVS ≥ 4 the mean CI was 0.62 for both CICT;LC and CICT-CTMR;LC.ConclusionThe mean volume of the delineated glandular breast tissue based on CT was significantly larger compared to the volume based on CTMR. For patients with a CVS ≥ 4, the mean CIs of the LC were higher compared to CVS < 4 for volumes delineated on both CT as well as CTMR images. In our study cohort no significant differences between the CIs of the CTV breast and the LC delineated on CTMR co-registered images were found compared to the CIs on CT images only. Adding MR images does not seem to improve consistency of the delineation of the CTV breast and the LC, even though the volumes were copied from CT images. Since we included only ten patients, caution should be taken with regard to the results of our study.
Highlights
In breast conserving radiotherapy differences of target volume delineations between observers do occur
The mean volume of the delineated glandular breast tissue based on computed tomography (CT) was significantly larger compared to the volume based on CTMR
For patients with a Cavity Visualization Score (CVS) ≥ 4, the mean conformity index (CI) of the lumpectomy cavity (LC) were higher compared to CVS < 4 for volumes delineated on both CT as well as CTMR images
Summary
In breast conserving radiotherapy differences of target volume delineations between observers do occur. We evaluated whether delineations based on co-registered computed tomography (CT) and magnetic resonance (MR) imaging may result in an improved consistency between observers. We used the delineation conformity index (CI) to compare clinical target volumes of glandular breast tissue (CTV breast) and lumpectomy cavity (LC) on both imaging modalities. According to Jolicoeur et al, the use of MRI improved the level of agreement between observers delineating the lumpectomy cavity compared to CT [6]. We have evaluated the delineated clinical target volumes of the glandular breast tissue (CTV breast) and the lumpectomy cavity (LC) in ten patients referred for radiation therapy after breast conserving surgery
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