Measurement-based study on characterizing symmetric and asymmetric respiratory motion interplay effect on target dose distribution in the proton pencil beam scanning.
This study evaluated the measurements of proton pencil beam scanning delivery made with a 2D ion chamber array in solid water on a 1D motion platform, where respiratory motion was simulated using sine and cosine4 waves representing sinusoidal symmetric and realistic asymmetric breathing motions, respectively. Motion amplitudes were 0.5 cm and 1 cm corresponding to 1 cm and 2 cm of maximum respiratory excursions, respectively, with 5 sec fixed breathing cycle. The treatment plans were created to mimic spherical targets of 3 cm or 10 cm diameter located at 5 cm or 1 cm depth in solid water phantom. A reference RBE dose of 200 cGy per fraction was delivered in 1, 5, 10, and 15 fractions for each dataset. We evaluated dose conformity and uniformity at the center plane of targets by using the Conformation Number and the Homogeneity Index, respectively. Results indicated that dose conformity as well as homogeneity was more affected by motion for smaller targets. Dose conformity was better achieved for symmetric breathing patterns than asymmetric breathing patterns regardless of the number of fractions. The presence of a range shifter with shallow targets reduced the motion effect by improving dose homogeneity. While motion effects are known to be averaged out over the course of multifractional treatments, this might not be true for proton pencil beam scanning under asymmetrical breathing pattern. PMID: 32170992 [PubMed - as sup...
Discussion: Incorporation of PBT into our existing cancer center allowed for multidisciplinary oncologic treatment of a diverse population of patients. Insurance coverage for PBT presents as a significant hurdle and improvements are needed to provide more timely access to necessary oncologic care.
Whole-pelvis pencil beam scanning (PBS) proton therapy is utilized in both the intact and post-operative settings in patients with prostate cancer. As whole pelvis prostate radiotherapy has traditionally been delivered with standard photon beams, limited evidence and technical descriptions have been reported regarding the use of proton therapy. Here we present two robust three-field treatment planning approaches utilized to maximize target coverage in the presence of anatomic and delivery uncertainties.
Conclusions: The SPArc_seq optimization algorithm could effectively reduce the BDT compared to the original SPArc algorithm. The improved efficiency of the SPArc_seq algorithm has the potential to increase patient throughput, thereby reducing the operation cost of proton therapy. PMID: 32421375 [PubMed - as supplied by publisher]
ConclusionsRe-irradiation with proton therapy is a safe and effective treatment in patients with recurrent glioblastoma. Proton therapy does not negatively effect on HRQOL, but rather it seems to preserve HRQOL until the time of disease progression.
CONCLUSION: The GPR and SNN models outperformed the EM in terms of prediction accuracy. Machine and deep learning algorithms predicted the output factor and MU for USPT with higher predictive accuracy than EM. In our clinic, these models have been adopted as a secondary check of MU or output factors. PMID: 32419245 [PubMed - as supplied by publisher]
Skull base chordomas are rare and heterogeneously behaving tumors. Though still classified as benign they can grow rapidly, are locally aggressive, and have the potential to metastasize. To adapt the treatment...
Radiation-induced cerebral vasculopathy (RICV) has been described in paediatric patients after radiation therapy (RT) for tumours of optic tracts, hypothalamus, and suprasellar region [1,2]. Delayed RICV mainly results from an accelerated arteriosclerosis process of small and medium sized vessels within the radiation field [3,4]. This complication can present as moyamoya syndrome, which results from stenosis or occlusion of large and intermediate cerebral arteries . The real incidence of RT-induced stenosis of carotid arteries and intracerebral arteries is however not well established.
CONCLUSIONS: For children with and without RICVs, quantitative analysis showed a significant correlation with LETd average/maximum values in vascular structures, whilst no correlation was found on dosimetric parameters. PMID: 32387488 [PubMed - as supplied by publisher]
In conclusion, the choice of detector configuration as well as the amount and the complexity of the considered anatomical changes determine the minimum number of radiographies to be used. PMID: 32365335 [PubMed - as supplied by publisher]
CONCLUSION: Organ-matching may be a better setup correction technique than BM for both photon therapy and IMPT plans. However, in some beam arrangements of IMPT, the dose distribution may be somewhat worse using OM, due to interfractional anatomical variation. Therefore, it is important to choose beam angles that are less likely to be influenced by changes in the gastrointestinal gas volume, especially in IMPT plans. PMID: 32350969 [PubMed - as supplied by publisher]