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Treatment of Liver Metastases Using an Internal Target Volume Method for Stereotactic Body Radiotherapy
Published on: May 8, 2018
Improved target volume delineation for stereotactic radiosurgery in brain metastases using post-contrast 3D T1 TSE
Zhao Hui Chen Zhou1, Rafael D Ambrosi2, Amaya Hilario1
1Neuroradiology Section, Department of Radiology, Hospital Universitario 12 de Octubre, Madrid, Spain.
Background:
Accurate delineation of brain metastases is essential for the success of stereotactic radiosurgery (SRS). This study aimed to compare the morphological and volumetric characteristics of brain metastases using post-contrast 3D T1 gradient-recalled echo (GRE) and 3D T1 black-blood turbo-spin-echo (TSE) sequences. The hypothesis was that gross tumor volumes (GTV) and planning target volumes (PTVs) would be larger on black-blood sequences.
Methods:
A retrospective review was conducted on 74 adult patients with untreated brain metastases who underwent MRI during a 12-month period. Post-contrast 3D T1 GRE and black-blood TSE sequences were acquired using a 1.5 T MRI. A total of 167 brain metastases were delineated separately by a neuroradiologist and a radiation oncologist, who then determined the consensus GTV and PTV (2 mm). The volumes were then statistically compared using Wilcoxon matched-pairs tests.
Results:
The inter-observer agreement (DICE index) was higher for black-blood sequences (0.84) than for GRE sequences (0.76). The mean GTV increased significantly from 1.84 cc on GRE sequences to 2.16 cc on black-blood sequences (a 29.8% increase, P < .001). Similarly, the mean PTV increased from 3.30 to 3.77 cc (a 32.5% increase; P < .001). Black-blood sequences depicted larger volumes in 80% of metastases, showing superior visualization of lesion margins and reduced artifacts (P < .001).
Conclusion:
Post-contrast black-blood sequences produce a significantly larger GTV and PTV than GRE, thereby improving target delineation for SRS. These findings suggest that black-blood MRI should be incorporated into routine planning to optimize treatment accuracy.
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