PURPOSE: Without a clear definition of an optimal treatment plan, no optimization model can be perfect. Therefore, instead of automatically finding a single “optimal” plan, finding multiple, yet... Show morePURPOSE: Without a clear definition of an optimal treatment plan, no optimization model can be perfect. Therefore, instead of automatically finding a single “optimal” plan, finding multiple, yet different near-optimal plans, can be an insightful approach to support radiation oncologists in finding the plan they are looking for. METHODS AND MATERIALS: BRIGHT is a flexible AI-based optimization method for brachytherapy treatment planning that has already been shown capable of finding high-quality plans that trade-off target volume coverage and healthy tissue sparing. We leverage the flexibility of BRIGHT to find plans with similar dose-volume criteria, yet different dose distributions. We further describe extensions that facilitate fast plan adaptation should planning aims need to be adjusted, and straightforwardly allow incorporating hospital-specific aims besides standard protocols. RESULTS: Results are obtained for prostate (n=12) and cervix brachytherapy (n=36). We demonstrate the possible differences in dose distribution for optimized plans with equal dosevolume criteria. We furthermore demonstrate that adding hospital-specific aims enables adhering to hospital-specific practice while still being able to automatically create cervix plans that more often satisfy the EMBRACE-II protocol than clinical practice. Finally, we illustrate the feasibility of fast plan adaptation. CONCLUSIONS: Methods such as BRIGHT enable new ways to construct high-quality treatment plans for brachytherapy while offering new insights by making explicit the options one has. In particular, it becomes possible to present to radiation oncologists a manageable set of alternative plans that, from an optimization perspective are equally good, yet differ in terms of coverage-sparing trade-offs and shape of the dose distribution Show less
Ende, R.P.J. van den; Ercan, E.; Keesman, R.; Kerkhof, E.M.; Marijnen, C.A.M.; Heide, U.A. van der 2020
PURPOSE: The individual channels in an endorectal applicator for high-dose-rate endorectal brachytherapy are not visible on standard MRI sequences. The aim of this study was to test whether an... Show morePURPOSE: The individual channels in an endorectal applicator for high-dose-rate endorectal brachytherapy are not visible on standard MRI sequences. The aim of this study was to test whether an ultrashort echo time (UTE) MRI sequence could be used to visualize the individual channels to enable MR-only treatment planning for rectal cancer.METHODS AND MATERIALS: We used a radial three-dimensional (3D) UTE pulse sequence and acquired images of phantoms and two patients with rectal cancer. We rigidly registered a UTE image and CT scan of an applicator phantom, based on the outline of the applicator. One observer compared channel positions on the UTE image and CT scan in five slices spaced 25 mm apart. To quantify geometric distortions, we scanned a commercial 3D geometric quality assurance phantom and calculated the difference between detected marker positions on the UTE image and corresponding marker positions on two 3D T-1-weighted images with opposing readout directions.RESULTS: On the UTE images, there is sufficient contrast to discern the individual channels. The difference in channel positions on the UTE image compared with the CT was on average -0.1 +/- 0.1 mm (left-right) and 0.1 +/- 0.3 mm (anteroposterior). After rigid registration to the 3D T-1-weighted sequences, the residual 95th percentile of the geometric distortion inside a 550-mm-diameter sphere was 1.0 mm (left-right), 0.9 mm (anteroposterior), and 0.9 mm (craniocaudal).CONCLUSIONS: With a UTE sequence, the endorectal applicator and individual channels can be adequately visualized in both phantom and patients. The geometrical fidelity is within an acceptable range. (C) 2020 The Authors. Published by Elsevier Inc. on behalf of American Brachytherapy Society. Show less
Heerden, L.E. van; Wieringen, N. van; Koedooder, K.; Rasch, C.R.N.; Pieters, B.R.; Bel, A. 2018
PURPOSE: Structure-based deformable image registration (DIR) can be used to calculate accumulated dose volume histogram parameters for cervical cancer brachytherapy (BT). The purpose of this study... Show morePURPOSE: Structure-based deformable image registration (DIR) can be used to calculate accumulated dose volume histogram parameters for cervical cancer brachytherapy (BT). The purpose of this study is to investigate dose warping uncertainties for the accumulated dose to the 2 cm(3) receiving the highest dose (D-2 cm(3)) in the rectal wall, using a physically realistic model (PRM) describing rectal wall deformation.METHODS AND MATERIALS: For 10 patients, treated with MRI-guided pulsed dose rate BT (two times 24 x 0.75 Gy, given in two applications BT1 and BT2), the planning images were registered with structure-based DIR. The resulting transformation vectors were used to accumulate the total rectum dose from BT. To investigate the dose warping uncertainty, a PRM describing rectal deformation was used. For point pairs on rectum(BTl) and rectum(BT2) that were at the same location according to the PRM, the dose for BT1 and BT2 was added (D-PRM) and compared to the DIR-accumulated dose (D-DIR) in the BT2 point. The remaining distance after DIR between corresponding point pairs, defined as the residual distance, was calculated.RESULTS: For points within the D-2 cm(3) volume, more than 75% was part of the D-2 cm(3) volume according to both PRM and DIR. The absolute dose difference was <7.3 Gy(EQD2), and the median (95th percentile) of the residual distance was 8.7 (22) mm.CONCLUSIONS: DIR corresponded with the PRM for on average 75% of the D-2 cm(3) volume. Local absolute dose differences and residual distances were large. Care should therefore be taken with DIR for dose-warping purposes in BT. (C) 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved. Show less
Ende, R.P.J. van den; Rijkmans, E.C.; Kerkhof, E.M.; Nout, R.A.; Ketelaars, M.; Laman, M.S.; ... ; Heide, U.A. van der 2018
PURPOSE: To quantify distortions on MR images of the Utrecht interstitial CT/MR applicator at a field strength of 3T using an MRI-only method.MATERIALS AND METHODS: An MR-compatible phantom... Show morePURPOSE: To quantify distortions on MR images of the Utrecht interstitial CT/MR applicator at a field strength of 3T using an MRI-only method.MATERIALS AND METHODS: An MR-compatible phantom suspending the applicator in water was built and imaged on a Philips Ingenia 3T MRI scanner. A map of the magnetic field (B-0) was calculated from multiecho images and used to quantify the field inhomogeneity. The expected displacements of the applicator could be quantified using the measured field inhomogeneity and sequence bandwidth. Additionally, two scans were acquired using opposing readout gradients. These scans were rigidly matched and their displacement was compared with the expected displacements from the B-0 map.These same methods were applied in 4 patients. By rigid matching of the scans acquired with opposing readout direction the applicator displacement due to image distortion from B-0 inhomogeneity as well as patient movement and organ deformation was determined.RESULTS: According to the B-0 map, the displacement on the intrauterine device of the plastic brachytherapy applicator was <0.4 mm for both the phantom and patients. Displacements obtained by the opposing readout method were <= 0.8 mm for each patient with a mean +/- SD over the patients of 0.3 +/- 0.1 mm.CONCLUSION: The results of our study indicate that the B-0 method agrees with the opposing readout method. Displacements caused by magnetic field inhomogeneity on 3T MRI were small compared with displacements due to patient movement and organ deformation. (C) 2016 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved. Show less
Jongkamp, V.G.; Roeloffzen, E.M.A.; Monninkhof, E.M.; Leeuw, J.R.J. de; Nijeholt, A.A.M.L.A.; Vulpen, M. van 2012
