Impact of Dosimetric Compromises on Early Outcomes of Chordomas and Chondrosarcomas Treated With Image-guided Pencil Beam Scanning Proton Beam Therapy.

Purpose: To critically review the clinical factors, dosimetry, and their correlation with early outcomes in patients with chordomas and chondrosarcomas treated with pencil beam scanning (PBS) proton beam therapy (PBT).

Methods And Materials: Consecutive 64 patients diagnosed with chordoma or chondrosarcoma treated at our center were studied. Patient, tumor, and treatment-related factors including dosimetry were captured.

Generation and evaluation of anatomy-preserving virtual CT for online adaptive proton therapy.

Background: Daily CTs generated by CBCT correction are required for daily replanning in online-adaptive proton therapy (APT) to effectively deal with inter-fractional changes. Out of the currently available methods, the suitability of a daily CT generation method for proton dose calculation also depends on the anatomical site.

Purpose: We propose an anatomy-preserving virtual CT (APvCT) method as a hybrid method of CBCT correction, which is especially suitable for large anatomy deformations.

Benchmarking a New Circular Cone-based Radiosurgery System against Clinically Tested Radiosurgery System on the same Novel Digital Linear Accelerator Platform.

Objective: To examine the dosimetric characteristics of circular cones, the accuracy of dose modeling and overall treatment delivery of two radiosurgery systems integrated on a linear accelerator (Linac).

Materials And Methods: The dosimetric characteristics of circular cones (4-17.5 mm) from Varian (VC) and BrainLAB (BLC) were measured for 6 MV flattening filter free beam from Edge linac using stereotactic field diode and 0.

IMPT of head and neck cancer: unsupervised machine learning treatment planning strategy for reducing radiation dermatitis.

Radiation dermatitis is a major concern in intensity modulated proton therapy (IMPT) for head and neck cancer (HNC) despite its demonstrated superiority over contemporary photon radiotherapy. In this study, dose surface histogram data extracted from forty-four patients of HNC treated with IMPT was used to predict the normal tissue complication probability (NTCP) of skin. Grades of NTCP-skin were clustered using the K-means clustering unsupervised machine learning (ML) algorithm.

Dosimetric impact of random spot positioning errors in intensity modulated proton therapy plans of small and large volume tumors.

Objective: To study dosimetric impact of random spot positioning errors on the clinical pencil beam scanning proton therapy plans.

Methods And Materials: IMPT plans of 10 patients who underwent proton therapy for tumors in brain or pelvic regions representing small and large volumes, respectively, were included in the study. Spot positioning errors of 1 mm, -1 mm or ±1 mm were introduced in these clinical plans by modifying the geometrical co-ordinates of proton spots using a script in the MATLAB programming environment.

A novel hybrid 3D dose reconstruction approach for pre-treatment verification of intensity modulated proton therapy plans.

Aim: A novel hybrid three-dimensional (3D) dose reconstruction method, based on planar dose measured at a single shallower depth, was developed for use as patient-specific quality assurance (PSQA) of intensity modulated proton therapy (IMPT) plans. The accuracy, robustness and sensitivity of the presented method were validated for multiple IMPT plans of varying complexities.

Methods And Materials: An in-house MATLAB program was developed to reconstruct 3D dose distribution from the planar dose (GyRBE) measured at 3 g cm depth in water or solid phantom using a MatriXX PT ion chamber array.

Leaf open time sinogram (LOTS): a novel approach for patient specific quality assurance of total marrow irradiation.

There is no ideal detector-phantom combination to perform patient specific quality assurance (PSQA) for Total Marrow (TMI) and Lymphoid (TMLI) Irradiation plan. In this study, 3D dose reconstruction using mega voltage computed tomography detectors measured Leaf Open Time Sinogram (LOTS) was investigated for PSQA of TMI/TMLI patients in helical tomotherapy. The feasibility of this method was first validated for ten non-TMI/TMLI patients, by comparing reconstructed dose with (a) ion-chamber (IC) and helical detector array (ArcCheck) measurement and (b) planned dose distribution using 3Dγ analysis for 3%@3mm and dose to 98% (D) and 2% (D) of PTVs.

Ambient neutron and photon dose equivalent H*(10) around a pencil beam scanning proton therapy facility.

Objectives: To measure leakage ambient dose equivalent H*(10) from stray secondary neutron and photon radiation around proton therapy (PT) facility and evaluate adequacy of shielding design.

Methods And Materials: H*(10) measurement were carried out at 149 locations around cyclotron vault (CV), beam transport system (BTS) and first treatment room (GTR3) of a multiroom PT facility using WENDI-II and SmartIon survey meter. Measurement were performed under extreme case scenarios wherein maximum secondary neutrons and photons were produced around CV, BTS and GTR3 by stopping 230MeV proton of 300nA on beam degrader, end of BTS and isocenter of GTR3.

Physical and dosimetric characteristic of high-definition multileaf collimator (HDMLC) for SRS and IMRT.

Physical and dosimetric characteristics of HDMLC were studied for SRS6, 6, and 10 MV X-rays from Novalis Tx. This in-built tertiary collimator consists of 60 pairs (32 × 0.25 cm; 26 × 0.

Portal dosimetry for pretreatment verification of IMRT plan: a comparison with 2D ion chamber array.

Portal dosimetry (PD) was performed for 181 fields from 14 IMRT plans of various clinical sites at gantry zero and source-to-detector distance (SDD) of 100 cm. PD was realized using aSi1000 electronic portal imaging device (EPID) and portal dose prediction (PDP) algorithm implemented in Eclipse treatment planning system (TPS). Agreement of PDP predicted and EPID measured photon fluence/dose distribution were evaluated using gamma (γ) index set at 3% at 3 mm distance to point agreement (DTA).