Radiation Oncology最新文献

Objective: To minimize the radiation injury for white matter (WM) pathways during brain arteriovenous malformation (bAVM) stereotactic radiosurgery (SRS), the WM tractography is integrated into treatment planning to identify WM pathways and restrict receiving dose. Manual segmentation of eloquent bAVM adjacent to WM pathways is time-consuming and prone to substantial inter-practitioner variability due to intricate entanglement within eloquent brain areas. The objective of this study is to develop and evaluate a deep learning (DL) system for the segmentation of eloquent bAVM in a clinical setting.

Methods: A total of 191 eloquent bAVM patients who underwent WM tractography and 3D time-of-flight magnetic resonance angiography (TOF-MRA) images were enrolled. 153 patients were used to construct a two-stage DL bAVM segmentation ensemble (TBASE) consisting of 2D detection and 3D segmentation models to segment the bAVM, the other 38 to test performance. Comparative experiments with ResNet and U-Net were conducted to validate the effectiveness of the proposed network. A randomized multi-reader evaluation was then conducted to assess the impact of TBASE assistance for bAVM segmentation using ten algorithm-unseen cases. Six medical professionals contoured the same series of cases in both assisted and unassisted modes, with a 6-week memory washout period between each session. The aided and unaided Dice Similarity Coefficients (DSC), Hausdorff Distance (HD), along with contouring times were compared.

Results: The mean values and standard deviations for DSC and HD of TBASE are 0.87 ± 0.03 and 3.51 ± 0.26, respectively, while Res-Net and U-Net results are 0.75 ± 0.12 and 4.14 ± 0.99, 0.77 ± 0.09 and 3.94 ± 0.82, respectively. The average volume difference across all patients in test dataset is 0.25 ± 1.39 cc, with no statistically significant variation observed. With TBASE assistance, the mean DSC of readers improved from 0.76 ± 0.07 to 0.86 ± 0.05 (P < 0.001), with corresponding values of mean HD reducing from 4.31 ± 0.68 to 3.35 ± 0.17 (P < 0.001) and a mean time saving of 52.15% ± 13.85% per patient. Less-experienced readers achieved greater improvements in contouring accuracy compared to specialists (DSC increase: 0.15 ± 0.11 vs. 0.06 ± 0.09; P < 0.001), while demonstrating similar reductions in contouring time as specialists (50.68% ± 14.62% vs. 55.1% ± 11.98%; P = 0.217).

Conclusions: The reliable eloquent bAVM automated-segmentation method has been validated in clinical workflow. The TBASE assistance improved the accuracy and efficiency of the eloquent bAVM manual delineation while considering WM pathway protection.

Clinical trial number: Not applicable.

Background: Dose escalation in rectal radiotherapy shows promise for improving complete response rates and organ preservation, yet optimal expansion margins for rectal lesions remain unclear. This study aims to utilize high-resolution real-time imaging from MR-guided radiotherapy to characterize rectal motion uncertainties, optimize planning target volume (PTV) margins, and validate dosimetric outcomes, thereby enhancing the precision in rectal cancer dose escalation.

Methods: A cohort of 22 advanced rectal cancer patients undergoing neoadjuvant radiotherapy on a 1.5T MR-Linac. Pre-treatment, intra-fraction, and post-treatment MR images were acquired for each fraction, with the rectum delineated according to the distance from the anus (upper, middle, lower). Inter- and intrafractional margins were determined by isotropic expansion of the segmented clinical target volume (CTV), with adequacy defined as covering 95% of the CTV volume in 90% of all fractions. Dosimetric validation was performed on 15 patients (10 internal, 5 external), comparing the segmental margins with literature-based uniform margins to assess target coverage and organs at risk (OARs) sparing.

Results: Rectal motion variability was segment-dependent, with the upper rectum requiring the largest margins and the lower rectum the smallest. Interfractional margins for the upper, middle, and lower rectum were 13 mm, 7 mm, and 6.5 mm, respectively. Intrafractional analysis revealed that treatment duration also influenced margin requirements, with 7 mm for the upper rectum and 3 mm for the middle and lower rectum sufficient for durations under 30 min; longer durations necessitated slightly larger margins. Dosimetric analysis confirmed that the segmented margin expansion strategy achieves adequate target coverage while substantially sparing OARs with dose reductions ranging from 7.4% to 44.5%.

Conclusions: Segment-specific margin expansion suggest a potential improvement for rectal radiotherapy, ensuring target coverage while reducing OAR dose, thereby facilitating organ and function preservation.

Clinical trial number: Not applicable.