Dosimetric impact of intrafraction motion on boosts on intraprostatic lesions: a simulation based on actual motion data from real time ultrasound tracking

Abstract

Background Intrafraction motion is particularly problematic in case of small target volumes and narrow margins. Here we simulate the dose coverage of intraprostatic lesions (IPL) by simultaneous integrated boosts (SIB). For this purpose, we use a large sample of actual intrafraction motion data. Methods Fifty-three h of intra-fraction motion of the prostate were recorded in real-time by 4D ultrasound (4DUS) during 720 fractions in 28 patients. We simulate spherical IPLs with 3, 5, and 7 mm radius and matching spherical SIBs with 0, 2, and 5 mm safety margins. The volumetric overlap between IPLs and SIBs is calculated. Dose volume histograms (DVH) are estimated by Monte Carlo simulation. Results On average, the distance of the prostate was 1.3 mm from its initial position over all fractions and patients. Average volumetric overlap was 73, 82, and 87% of IPL volume in case of 3, 5, and 7 mm IPLs and SIBs without safety margins. These improved to 95% or more in case of 2 mm safety margins and 98% or more in case of 5 mm safety margins. DVHs showed that 80% of the IPL volume received 60, 72, and 79% of maximum dose in case of 3, 5, and 7 mm IPLs and SIBs without safety margins. These improved to 94% or more given moderately sized safety margins of 2 mm. Conclusions On average over all fractions and patients, the dose coverage would have been acceptable even for small target volumes such as IPLs of radius 3 to 7 mm and narrow fields. Moderate safety margins of 2 mm could have ensured a delivery of 90% or more of the SIB dose to the IPL. In this case, SIB volume would have been considerably larger than IPL volume, but still considerably smaller than the overall PTV of the prostate. Electronic supplementary material The online version of this article (10.1186/s13014-019-1285-1) contains supplementary material, which is available to authorized users.

Dosimetric Uncertainties in Dominant Intraprostatic Lesion Simultaneous Boost Using Intensity Modulated Proton Therapy

“…Ballhausen et al reported a simulation study for the dosimetric impact from intrafraction motion on the DIL boost treatment using EBPT and found that the DILs can be covered by 90% of SIB doses with 2mm margin on them. (36) Advanced IMPT provides much better dosimetry than the EBPT, thanks to the sharp distal falloff from the proton brag peak. However, IMPT is sensitive to range/setup uncertainties and anatomy changes.…”

“…Ballhausen et al reported a simulation study for the dosimetric impact from intrafraction motion on the DIL boost treatment using XRT and found that the DILs can be covered by 90% of SIB doses with 2 mm margin on them. 36 …”

The ProMotion LMU dataset (2022 edition), prostate intra-fraction motion recorded by transperineal ultrasound

“…The data we acquired was used to validate the random walk model of intra-fraction motion 1 , investigate a potential impact of patient couch shifts on intra-fraction motion 2 , to estimate the impact of ultrasound probe pressure on intra-fraction drift of the prostate 3 , to show that a shorter treatment time reduces the severity of intra-fraction motion 4 and to estimate the dosimetric impact of intra-fraction motion on boosts on intra-prostatic lesions 5 .…”

The ProMotion LMU dataset, prostate intra-fraction motion recorded by transperineal ultrasound

“…The data we acquired was used to validate the random walk model of intra-fraction motion 1 , investigate a potential impact of patient couch shifts on intra-fraction motion 2 , to estimate the impact of ultrasound probe pressure on intra-fraction drift of the prostate 3 , to show that a shorter treatment time reduces the severity of intra-fraction motion 4 and to estimate the dosimetric impact of intra-fraction motion on boosts on intra-prostatic lesions 5 .…”