Measurement-guided volumetric dose reconstruction for helical tomotherapy.

It was previously demonstrated that dose delivered by a conventional linear accelerator using IMRT or VMAT can be reconstructed - on patient or phantom datasets - using helical diode array measurements and a technique called planned dose perturbation (PDP). This allows meaningful and intuitive analysis of the agreement between the planned and delivered dose, including direct comparison of the dose-volume histograms. While conceptually similar to modulated arc techniques, helical tomotherapy introduces significant challenges to the PDP formalism, arising primarily from TomoTherapy delivery dynamics.

Incidental radiation to uninvolved internal mammary lymph nodes in breast cancer.

Routine treatment of clinically uninvolved internal mammary nodes in breast cancer patients requiring post-mastectomy radiation therapy is controversial. The purpose of this study was to measure the incidental radiation dose to the internal mammary lymph nodes not included in the planning target volume (PTV) in women with breast cancer receiving post-mastectomy radiation therapy. This retrospective protocol utilized CT-based 3D conformal treatment plans.

Motion as perturbation. II. Development of the method for dosimetric analysis of motion effects with fixed-gantry IMRT.

Purpose: In this work, the feasibility of implementing a motion-perturbation approach to accurately estimate volumetric dose in the presence of organ motion--previously demonstrated for VMAT--is studied for static gantry IMRT. The method's accuracy is improved for the voxels that have very low planned dose but acquire appreciable dose due to motion. The study describes the modified algorithm and its experimental validation and provides an example of a clinical application.

Evaluation of semiempirical VMAT dose reconstruction on a patient dataset based on biplanar diode array measurements.

We report the results of a preclinical evaluation of recently introduced commercial tools for 3D patient IMRT/VMAT dose reconstruction, the Delta4 Anatomy calculation algorithm. Based on the same initial measurement, volumetric dose can be reconstructed in two ways. Three-dimensional dose on the Delta4 phantom can be obtained by renormalizing the planned dose distribution by the measurement values (D4 Interpolation).

Cross-validation of two commercial methods for volumetric high-resolution dose reconstruction on a phantom for non-coplanar VMAT beams.

Background And Purpose: Delta(4) (ScandiDos AB, Uppsala, Sweden) and ArcCHECK with 3DVH software (Sun Nuclear Corp., Melbourne, FL, USA) are commercial quasi-three-dimensional diode dosimetry arrays capable of volumetric measurement-guided dose reconstruction. A method to reconstruct dose for non-coplanar VMAT beams with 3DVH is described.

Validation of measurement-guided 3D VMAT dose reconstruction on a heterogeneous anthropomorphic phantom.

3DVH software (Sun Nuclear Corp., Melbourne, FL) is capable of generating a volumetric patient VMAT dose by applying a volumetric perturbation algorithm based on comparing measurement-guided dose reconstruction and TPS-calculated dose to a cylindrical phantom. The primary purpose of this paper is to validate this dose reconstruction on an anthropomorphic heterogeneous thoracic phantom by direct comparison to independent measurements.

Evaluation of inhomogeneity correction factors for 6 MV flattening filter-free beams with brass compensators.

The 6 MV flattening filter-free (FFF) beam has been commissioned for use with compensators at our institution. This novel combination promises advantages in mitigating tumor motion due to the reduced treatment time made possible by the greatly increased dose rate of the FFF beam. Given the different energy spectrum of the FFF beam and the beam hardening effect of the compensator, the accuracy of the treatment planning system (TPS) model in the presence of low-density heterogeneities cannot be assumed.

Motion as a perturbation: measurement-guided dose estimates to moving patient voxels during modulated arc deliveries.

Purpose: To present a framework for measurement-guided VMAT dose reconstruction to moving patient voxels from a known motion kernel and the static phantom data, and to validate this perturbation-based approach with the proof-of-principle experiments.

Methods: As described previously, the VMAT 3D dose to a static patient can be estimated by applying a phantom measurement-guided perturbation to the treatment planning system (TPS)-calculated dose grid. The fraction dose to any voxel in the presence of motion, assuming the motion kernel is known, can be derived in a similar fashion by applying a measurement-guided motion perturbation.

VMAT QA: measurement-guided 4D dose reconstruction on a patient.

Purpose: To develop and validate a volume-modulated arc therapy (VMAT) quality assurance (QA) tool that takes as input a time-resolved, low-density (∼10 mm) cylindrical surface dose map from a commercial helical diode array, and outputs a high density, volumetric, time-resolved dose matrix on an arbitrary patient dataset. This first validation study is limited to a homogeneous "patient."

Methods: A VMAT treatment is delivered to a diode array phantom (ARCCHECK, Sun Nuclear Corp.

Evaluating dosimetric accuracy of flattening filter free compensator-based IMRT: measurements with diode arrays.

Purpose: Compensator-based IMRT coupled with the high dose rate flattening filter free (FFF) beams offers an intriguing possibility of delivering an intensity modulated radiation field in just a few seconds. As a first step, the authors evaluate the dosimetric accuracy of the treatment planning system (TPS) FFF beam model with compensators.

Methods: A 6 MV FFF beam from a TrueBeam accelerator (Varian Medical Systems, Palo Alto CA) was modeled in PINNACLE TPS (v.

Commissioning compensator-based IMRT on the Pinnacle treatment planning system.

We present a systematic approach to commissioning of the compensator-based IMRT in Pinnacle treatment planning system for commercially manufactured brass compensators. Some model parameters for the beams modulated by the variable-thickness compensators can only be associated with a single compensator thickness. To intelligently choose that thickness for beam modeling, we empirically determined the most probable filter thickness occurring within the modulated portion of the compensators typically used in clinics.

Evaluation of a biplanar diode array dosimeter for quality assurance of step-and-shoot IMRT.

In this paper, we described and characterized a novel biplanar diode array, and demonstrated its applicability to dosimetric QA of the step-and-shoot IMRT. It is the first commercially available device of its kind specifically designed for measurements at varying gantry angles. The detector consists of a cylindrical PMMA phantom with two orthogonal detector boards.

Use of electric cell-substrate impedance sensing to assess in vitro cytotoxicity.

In vitro assessment of cytotoxicity based on electrochemical impedance spectroscopy (EIS) needs more quantitative methods to analyze the alteration of cell morphology and motility, and hence the potential risk to human health. Here, we applied electric cell-substrate impedance sensing (ECIS) to evaluate dose-dependent responses of human umbilical vein endothelial cells exposed to cytochalasin B. To detect subtle changes in cell morphology, the frequency-dependent impedance data of the cell monolayer were measured and analyzed with a theoretical cell-electrode model.