Cochlea-sparing acoustic neuroma treatment with 4π radiation therapy.

PurposeThis study investigates whether 4π noncoplanar radiation therapy can spare the cochleae and consequently potentially improve hearing preservation in patients with acoustic neuroma who are treated with radiation therapy.Methods and materialsClinical radiation therapy plans for 30 patients with acoustic neuroma were included (14 stereotactic radiation surgery [SRS], 6 stereotactic radiation therapy [SRT], and 10 intensity modulated radiation therapy [IMRT]). The 4π plans were created for each patient with 20 optimal beams selected using a greedy column generation method and subsequently recalculated in Eclipse for comparison. Organ-at-risk (OAR) doses, homogeneity index, conformity, and tumor control probability (TCP) were compared. Normal tissue complication probability (NTCP) was calculated for sensorineural hearing loss (SNHL) at 3 and 5 years posttreatment. The dose for each plan was then escalated to achieve 99.5% TCP.Results4π significantly reduced the mean dose to both cochleae by 2.0 Gy (32%) for SRS, 3.2 Gy (29%) for SRT, and 10.0 Gy (32%) for IMRT. The maximum dose to both cochleae was also reduced with 4π by 1.6 Gy (20%), 2.2 Gy (15%), and 7.1 Gy (18%) for SRS, SRT, and IMRT plans, respectively. The reductions in mean/maximum brainstem dose with 4π were also statistically significant. Mean doses to other OARs were reduced by 19% to 56% on average. 4π plans had a similar CN and TCP, with a significantly higher average homogeneity index (0.93 vs 0.92) and significantly lower average NTCP for SNHL at both 3 years (30.8% vs 40.8%) and 5 years (43.3% vs 61.7%). An average dose escalation of approximately 116% of the prescription dose achieved 99.5% TCP, which resulted in 32.6% and 43.4% NTCP for SNHL at 3 years and 46.4% and 64.7% at 5 years for 4π and clinical plans, respectively.ConclusionsCompared with clinical planning methods, optimized 4π radiation therapy enables statistically significant sparing of the cochleae in acoustic neuroma treatment as well as lowering of other OAR doses, potentially reducing the risk of hearing loss

Feasibility of automated 3-dimensional magnetic resonance imaging pancreas segmentation.

PurposeWith the advent of MR guided radiotherapy, internal organ motion can be imaged simultaneously during treatment. In this study, we evaluate the feasibility of pancreas MRI segmentation using state-of-the-art segmentation methods.Methods and materialT2 weighted HASTE and T1 weighted VIBE images were acquired on 3 patients and 2 healthy volunteers for a total of 12 imaging volumes. A novel dictionary learning (DL) method was used to segment the pancreas and compared to t mean-shift merging (MSM), distance regularized level set (DRLS), graph cuts (GC) and the segmentation results were compared to manual contours using Dice's index (DI), Hausdorff distance and shift of the-center-of-the-organ (SHIFT).ResultsAll VIBE images were successfully segmented by at least one of the auto-segmentation method with DI >0.83 and SHIFT ≤2 mm using the best automated segmentation method. The automated segmentation error of HASTE images was significantly greater. DL is statistically superior to the other methods in Dice's overlapping index. For the Hausdorff distance and SHIFT measurement, DRLS and DL performed slightly superior to the GC method, and substantially superior to MSM. DL required least human supervision and was faster to compute.ConclusionOur study demonstrated potential feasibility of automated segmentation of the pancreas on MRI images with minimal human supervision at the beginning of imaging acquisition. The achieved accuracy is promising for organ localization

Molecular docking of HSPs (heat shock proteins) from rice seed

The expression of heat shock proteins (HSPs) is an essential part of the heat shock response in plants where HSPs act as chaperones that help in protein folding and unfolding mechanism. This project focuses on determining the docking mechanism and conformation stability of HSPs from rice seed at several simulated temperatures. HSP20 was selected from previously isolated rice seed proteins and the sequence was used for homology modelling. The suitable model of this sequence was then selected to undergo molecular dynamics simulation and docking procedure with the targeted proteins. The simulated environmental temperature was set as 37oC and 100oC during the simulation process. Model for the selected HSP20 protein was generated successfully via I-Tasser server. The results of 50ns simulation at 310K and 373K for selected model were plotted in the graphs of RMSD, RMSF, hydrogen bonding number and radius of gyration. The RMSD result showed that HSP20 model was more stable at simulated temperature of 37oC as compared to 100oC. Whereas for the RMSF graph visualization, two significant loops of this model were found in the same position of its 3D structure as corresponded in both 37oC and 100oC results. For the results of hydrogen bonding number and radius of gyration, the mean numbers were around 102 and 1.6 respectively for 37oC and 100oC simulations. These findings indicated the responsible stability and flexibility of the model’s 3D structure in terms of its secondary structure, folding pattern and loops location. Molecular docking of this HSP20 model with the selected proteins: TPR and SGT1 was carried out successfully with ZDock server. The docked structures generated were used to understand the docking mechanism and protein-protein interactions between these proteins. Further study of these protein models is required for understanding on the roles of binding conformation between them as well as possible protein-protein interaction of HSP20 with other co-chaperones