Seminal vesicle intrafraction motion during the delivery of radiotherapy sessions on a 1.5 T MR-Linac

Abstract

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On-line daily plan optimization combined with a virtual couch shift procedure to address intrafraction motion in prostate magnetic resonance guided radiotherapy

“…For both groups, even larger outliers as an effect of unstable gas pockets with a tendency to push the prostate can be seen in the anterior and cranial translation direction. Similar effects of gas pockets on prostate intrafraction motion were reported in our previous study on seminal vesicle tracking [23] and in literature [24,25]. Obviously, the present ATP procedure cannot correct for such sudden events.…”

“…In our previous study including 50 patients we found drift to be the major intrafraction motion component in 30% of all fractions and during at least one fraction in 76% of all patients [23]. Intrafraction motion mainly caused by gas pockets was observed in 18% of all fractions and occurred in at least one fraction in 50% of all patients.…”

“…With only rotation about the left-right rotation axis the CTV (prostate corpus) may stay in the PTV. However, the effect of rotation about the left-right rotation axis was significantly larger if seminal vesicles were also (partially) included in the CTV [23].…”

Dosimetric Impact of Inter-Fraction Anatomical Changes in Carbon Ion Boost Treatment for High-Risk Prostate Cancer (AIRC IG 14300)

“…In our investigation, we focused exclusively on the residual inter-fraction anatomical variations after bony alignment and did not consider intra-fraction motion. However, several recent studies on cine-MR imaging extensively reported that prostate intrafraction motion could affect the target dose distribution (28,29). These studies concluded that 5-mm PTV margins were adequate to guarantee target coverage even during long-lasting treatments (>10 min).…”

Fast and accurate deformable contour propagation for intra-fraction adaptive magnetic resonance-guided prostate radiotherapy

“…Intra-fractional changes during radiotherapy delivery have become even more important with current interest in extremely-hypofractionated radiotherapy (i.e., ≤ 3 fractions) with larger fractional doses and therefore longer beam-on times [11] , [12] , [13] . Previously, we have presented intra-fraction motion results in prostate cancer (PCa) [1] , [14] . These results demonstrated that to guarantee target coverage with planning target volume (PTV) margins below 5 mm, workflows that allow intra-fraction adaptation are needed.…”