Comparison of Magnetic Resonance Imaging and Computed Tomography for Breast Target Volume Delineation in Prone and Supine Positions

Abstract

Purpose/Objective(s): MRI provides no ionizing radiation dose (allowing inter and intra fraction imaging), improved soft tissue contrast and potentially improved conformity in delineation than CT. This study aimed to determine if T2 weighted magnetic resonance imaging improves seroma cavity (SC) and Whole Breast (WB) inter-observer conformity for radiotherapy purposes compared with the gold standard of CT, both in the prone and supine positions. Results: Imaging modality did not affect inter-observer variation for WB CTVs. Prone WB CTVs were larger in volume and more conformal than Supine CTVs (on both MRI and CT). SC volumes were larger on CT than MRI. SC volumes proved to be comparable in inter-observer conformity in both modalities (VOI of 0.57±0.03 for CT supine, 0.52±0.04 for MR supine, 0.56±0.03 for CT prone and 0.55±0.04 for MR prone) however after registering modalities together the inter-modality variation (DSC of 0.41±0.05 for supine and 0.38±0.04 for prone) was larger than the inter-observer variability for SC despite the location typically remaining constant.Conclusions: MRI inter-observer variation was comparable to CT for the WB CTV and SC delineation, in both prone and supine positions. Whilst the CVS and inter-observer concordance M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 3 was not significantly higher for MRI than CT, the SCs were smaller on MRI, potentially due to clearer SC definition, especially on T2-weighted MR images.

The impact of different simulation modalities on target volume delineation in breast-conserving radiotherapy

“…Furthermore, we found that as CVS increased, interobserver consistency increased while dCOM showed a decreasing trend. Similar to our findings, a study comparing CT and MR images from 33 patients delineated by 11 observers, reported a negative correlation between the CVS and IOV parameters [26]. Two previous studies also revealed a positive association between the CVS and CI gen [15,18], but neither reported a correlation coefficient or P values as we have done in the current study.…”

Breast tumor movements analysis using MRI scans in prone and supine positions

“…The MRI scan at the supine position is also difficult to perform due to low accuracy of tumor diagnosis due to motion artifacts and low contrast in MRI. Telegrafo et al 4 showed that a key issue for clinical use of pre-operative breast MRI is how to transfer the three-dimensional (3D) information obtained from the patient in prone position to the operating room, since the surgical treatment is performed in the supine position 4,10 . If the location of MRI-detected tumors in the supine position could be predicted, those predicted positions could be used as a surgical planning guide for the surgeon 11,12 , which could then promote a decrease in the re-excision rate of BCS.…”

Optimizing MR-Guided Radiotherapy for Breast Cancer Patients

“…Second, studies have shown both a significant increase as well as a decrease in the target volume when either a preoperative or postoperative MRI scan was available for delineation in addition to a postoperative planning CT (20,21,34,50). Third, in three separate studies, MRI did not lead to a reduction in interobserver variation (20,24,50). However, in a more recent larger study, a significant reduction in interobserver variation was reported for delineation on MRI in patients without surgical clips (51).…”

“…In studies that evaluated prone breast MRI for RT, a dedicated breast coil is usually used (19,22,24). While this coil provides optimal image quality for the breasts, it cannot capture the full body contour and all organs at risk (OARs) with adequate quality (Figure 2).…”

“…For use of MRI in the adjuvant breast RT setting, use of T1-weighted 3D sequences without fat suppression resulted in the best visualization of surgical clips, whereas T1-weighted images with fat suppression (e.g., mDixon) best enabled differentiation between glandular breast tissue and seroma ( 9 , 20 , 34 ). Two-dimensional or 3D T2-weighted MRI with fat suppression [e.g., Short inversion time inversion recovery (STIR) or water selective excitation] or without fat suppression was preferred for visualization of lumpectomy cavity and associated seroma and for discrimination between glandular breast tissue and tumour bed ( 17 , 19 , 21 , 22 , 24 ).…”