Clinical Implementation and Initial Experience of Real-Time Motion Tracking With Jaws and Multileaf Collimator During Helical Tomotherapy Delivery.

Purpose: This work reports the clinical implementation of a real-time motion tracking and correction system using dynamic multileaf collimator and jaws during helical tomotherapy delivery (Synchrony on Radixact; Accuray, Inc).

Methods And Materials: The first clinical Synchrony on Radixact system was recently installed and tested at our institution. Various clinical workflows, including fiducial implantation, computed tomography simulation, treatment planning, delivery quality assurance, treatment simulation, and delivery, for both fiducial-free and fiducial-based motion tracking methods were developed.

4D-MRI driven MR-guided online adaptive radiotherapy for abdominal stereotactic body radiation therapy on a high field MR-Linac: Implementation and initial clinical experience.

Background And Purpose: In this report, we describe our implementation and initial clinical experience using 4D-MRI driven MR-guided online adaptive radiotherapy (MRgOART) for abdominal stereotactic body radiotherapy (SBRT) on the Elekta Unity MR-Linac.

Materials And Methods: Eleven patients with abdominal malignancies were treated with free-breathing SBRT in three to five fractions on a 1.5 T MR-Linac.

Technical Note: Comprehensive performance tests of the first clinical real-time motion tracking and compensation system using MLC and jaws.

Purpose: To evaluate the performance of the first clinical real-time motion tracking and compensation system using multileaf collimator (MLC) and jaws during helical tomotherapy delivery.

Methods: Appropriate mechanical and dosimetry tests were performed on the first clinical real-time motion tracking system (Synchrony on Radixact, Accuray Inc) recently installed in our institution. kV radiography dose was measured by CTDIw using a pencil chamber.

Reducing radiation dose and enhancing imaging quality of 4DCT for radiation therapy using iterative reconstruction algorithms.

Purpose: Four-dimensional computed tomography (CT) images are typically used to quantify the necessary internal target volumes for thoracic and abdominal tumors. However, 4-dimensional CT is typically associated with excessive imaging dose to patients and the situation is exacerbated when using repeat 4-dimensional CT imaging on a weekly or daily basis throughout fractionated therapy. The aim of this work is to evaluate an iterative reconstruction (IR) algorithm that helps reduce the imaging dose to the patient while maintaining imaging quality as quantified by point spread function and contrast-to-noise ratios (CNRs).

Technical Note: Dose effects of 1.5 T transverse magnetic field on tissue interfaces in MRI-guided radiotherapy.

Purpose: The integration of MRI with a linear accelerator (MR-linac) offers great potential for high-precision delivery of radiation therapy (RT). However, the electron deflection resulting from the presence of a transverse magnetic field (TMF) can affect the dose distribution, particularly the electron return effect (ERE) at tissue interfaces. The purpose of the study is to investigate the dose effects of ERE at air-tissue and lung-tissue interfaces during intensity-modulated radiation therapy (IMRT) planning.

Technical Note: Development and performance of a software tool for quality assurance of online replanning with a conventional Linac or MR-Linac.

Purpose: To develop an integrated quality assurance (QA) software tool for online replanning capable of efficiently and automatically checking radiation treatment (RT) planning parameters and gross plan quality, verifying treatment plan data transfer from treatment planning system (TPS) to record and verify (R&V) system, performing a secondary monitor unit (MU) calculation with or without a presence of a magnetic field from MR-Linac, and validating the delivery record consistency with the plan.

Methods: The software tool, named ArtQA, was developed to obtain and compare plan and treatment parameters from both the TPS and the R&V system database. The TPS data are accessed via direct file reading and the R&V data are retrieved via open database connectivity and structured query language.

A planning comparison of 7 irradiation options allowed in RTOG 1005 for early-stage breast cancer.

This study compared the 7 treatment plan options in achieving the dose-volume criteria required by the Radiation Therapy Oncology Group (RTOG) 1005 protocol. Dosimetry plans were generated for 15 representative patients with early-stage breast cancer (ESBC) based on the protocol-required dose-volume criteria for each of the following 7 treatment options: 3D conformal radiotherapy (3DCRT), whole-breast irradiation (WBI) plus 3DCRT lumpectomy boost, 3DCRT WBI plus electron boost, 3DCRT WBI plus intensity-modulated radiation therapy (IMRT) boost, IMRT WBI plus 3DCRT boost, IMRT WBI plus electron boost, IMRT WBI plus IMRT boost, and simultaneous integrated boost (SIB) with IMRT. A variety of dose-volume parameters, including target dose conformity and uniformity and normal tissue sparing, were compared for these plans.

A planning and delivery study of a rotational IMRT technique with burst delivery.

Purpose: A novel rotational IMRT (rIMRT) technique using burst delivery (continuous gantry rotation with beam off during MLC repositioning) is investigated. The authors evaluate the plan quality and delivery efficiency and accuracy of this dynamic technique with a conventional flat 6 MV photon beam.

Methods: Burst-delivery rIMRT was implemented in a planning system and delivered with a 160-MLC linac.

An on-line replanning scheme for interfractional variations.

Ability of online adaptive replanning is desirable to correct for interfraction anatomic changes. A full-scope replanning/reoptimization with the current planning techniques takes too long to be practical. A novel online replanning strategy to correct for interfraction anatomic changes in real time is presented.

Automated computer optimization for 3D treatment planning of breast irradiation.

A software package, capable of optimizing beam energy and weight and wedge angle and orientation in conjunction with commercial treatment planning system, has been developed to effectively generate three-dimensional conformal radiation therapy (3DCRT) plans for breast irradiation with complicated dosimetry requirements. A nonlinear optimization procedure was utilized for the optimization. The study with 15 patient cases shows that the technique can reduce treatment planning time and effort significantly and can give comparable or slightly better dosimetry results.

Development of an inverse optimization package to plan nonuniform dose distributions based on spatially inhomogeneous radiosensitivity extracted from biological images.

An inverse optimization package which is capable of generating nonuniform dose distribution with subregional dose escalation is developed to achieve maximum equivalent uniform dose (EUD) for target while keeping the critical structure doses as low as possible. Relative cerebral blood volume (rCBV) maps obtained with a dynamic susceptibility contrast-enhanced MRI technique were used to delineate spatial radiosensitivity distributions. The voxel rCBV was converted to voxel radiosensitivity parameters (e.

Direct aperture optimization-based intensity-modulated radiotherapy for whole breast irradiation.

Purpose: To investigate the technical and dosimetric advantages and the efficacy of direct aperture optimized intensity-modulated radiation therapy (DAO-IMRT) over standard (e.g., beamlet optimized) IMRT and conventional three-dimensional conformal radiotherapy (3D-CRT) for whole breast irradiation in supine and prone positions.