Quantification of the margin required for treating intraprostatic lesions

Abstract

Advances in magnetic resonance imaging (MRI) sequences allow physicians to define the dominant intraprostatic lesion (IPL) in prostate radiation therapy treatments allowing for dose escalation and potentially increased tumor control. This work quantifies the margin required around the MRI‐defined IPL accounting for both prostate motion and deformation. Ten patients treated with a simultaneous integrated intraprostatic boost (SIIB) were retrospectively selected and replanned with incremental 1 mm margins from 0‐5 mm around the IPL to determine if there were any significant differences in dosimetric parameters. Sensitivity analysis was then performed accounting for random and systematic uncertainties in both prostate motion and deformation to ensure adequate dose was delivered to the IPL. Prostate deformation was assessed using daily CBCT imaging and implanted fiducial markers. The average IPL volume without margin was 2.3% of the PTV volume and increased to 11.8% with a 5 mm margin. Despite these changes in volume, the only statistically significant dosimetric difference was found for the PTV maximum dose, which increased with increasing margin. The sensitivity analysis demonstrated that a 3.0 mm margin ensures >95% IPL coverage accounting for both motion and deformation. We found that a margin of 3.0 mm around the MRI defined IPL is sufficient to account for random and systematic errors in IPL position for the majority of cases.PACS number(s): 87.55.de

Turbo Gradient and Spin Echo PROPELLER-Diffusion Weighted Imaging for Orbital Tumors: A Comparative Study With Readout-Segmented Echo-Planar Imaging

“…Minimized geometric distortion is of critical importance to avoid excessive radiation dose to healthy tissues ( Bergen et al, 2020 ). According to several published literatures ( Chen et al, 2006 ; McPartlin et al, 2016 ; Studenski et al, 2016 ; Bergen et al, 2020 ), approximately 3 mm distortion would increase the doses in RT, and it would lead to significant dose errors if more than 1 cm and even affects the treatment outcomes. Results of the current study showed the superiority of TGSE-PROPELLER-DWI with minimized distortions and susceptibility artifacts, indicating the potential to be implemented in RT management.…”