Incorporating Treatment Time into Butterfly Optimization to Reduce Total Treatment Time for Vaginal Cylinder Brachytherapy.

Purpose For patient comfort and safety, irradiation times should be kept at a minimum while maintaining high treatment quality. In this study of high dose rate (HDR) therapy with a vaginal cylinder, we used the butterfly optimization algorithm (BOA) to simultaneously optimize individual dwell times for precise dose conformity and for the reduction of total dwell time. Material and methods BOA is a population-based, meta-heuristic algorithm that averts local minima by conducting intensive local and global searching based on switching probability.

Tumour-specific amplitude-modulated radiofrequency electromagnetic fields induce differentiation of hepatocellular carcinoma via targeting Ca3.2 T-type voltage-gated calcium channels and Ca influx.

Background: Administration of amplitude modulated 27·12 MHz radiofrequency electromagnetic fields (AM RF EMF) by means of a spoon-shaped applicator placed on the patient's tongue is a newly approved treatment for advanced hepatocellular carcinoma (HCC). The mechanism of action of tumour-specific AM RF EMF is largely unknown.

Methods: Whole body and organ-specific human dosimetry analyses were performed.

Optical surface guidance for submillimeter monitoring of patient position during frameless stereotactic radiotherapy.

Purpose: To evaluate the accuracy of monitoring intrafraction motion during stereotactic radiotherapy with the optical surface monitoring system. Prior studies showing a false increase in the magnitude of translational offsets at non-coplanar couch positions prompted the vendor to implement software changes. This study evaluated two software improvements intended to address false offsets.

Stereotactic radiosurgery with MLC-defined arcs: Verification of dosimetry, spatial accuracy, and end-to-end tests.

Purpose: To measure dosimetric and spatial accuracy of stereotactic radiosurgery (SRS) delivered to targets as small as the trigeminal nerve (TN) using a standard external beam treatment planning system (TPS) and multileaf collimator-(MLC) equipped linear accelerator without cones or other special attachments or modifications.

Methods: Dosimetric performance was assessed by comparing computed dose distributions to film measurements. Comparisons included the γ-index, beam profiles, isodose lines, maximum dose, and spatial accuracy.

The virtual cone: A novel technique to generate spherical dose distributions using a multileaf collimator and standardized control-point sequence for small target radiation surgery.

Purpose: The study aimed to develop and demonstrate a standardized linear accelerator multileaf collimator-based method of delivering small, spherical dose distributions suitable for radiosurgical treatment of small targets such as the trigeminal nerve.

Methods And Materials: The virtual cone is composed of a multileaf collimator-defined field with the central 2 leaves set to a small gap. For 5 table positions, clockwise and counter-clockwise arcs were used with collimator angles of 45 and 135 degrees, respectively.

Use of non-ionizing electromagnetic fields for the treatment of cancer.

Cancer treatment and treatment options are quite limited in circumstances such as when the tumor is inoperable, in brain cancers when the drugs cannot penetrate the blood-brain-barrier, or when there is no tumor-specific target for generation of effective therapeutic antibodies. Despite the fact that electromagnetic fields (EMF) in medicine have been used for therapeutic or diagnostic purposes, the use of non-ionizing EMF for cancer treatment is a new emerging concept. Here we summarize the history of EMF from the 1890's to the novel and new innovative methods that target and treat cancer by non-ionizing radiation.

A novel phantom and procedure providing submillimeter accuracy in daily QA tests of accelerators used for stereotactic radiosurgery*.

Stereotactic radiosurgery (SRS) places great demands on spatial accuracy. Steel BBs used as markers in quality assurance (QA) phantoms are clearly visible in MV and planar kV images, but artifacts compromise cone-beam CT (CBCT) isocenter localization. The purpose of this work was to develop a QA phantom for measuring with sub-mm accuracy isocenter congruence of planar kV, MV, and CBCT imaging systems and to design a practical QA procedure that includes daily Winston-Lutz (WL) tests and does not require computer aid.

End-to-end test of spatial accuracy in Gamma Knife treatments for trigeminal neuralgia.

Purpose: Spatial accuracy is most crucial when small targets like the trigeminal nerve are treated. Although current quality assurance procedures typically verify that individual apparatus, like the MRI scanner, CT scanner, Gamma Knife, etc., are meeting specifications, the cumulative error of all equipment and procedures combined may exceed safe margins.

Beam geometry selection using sequential beam addition.

Purpose: The selection of optimal beam geometry has been of interest since the inception of conformal radiotherapy. The authors report on sequential beam addition, a simple beam geometry selection method, for intensity modulated radiation therapy.

Methods: The sequential beam addition algorithm (SBA) requires definition of an objective function (score) and a set of candidate beam geometries (pool).

Patient safety considerations concerning the scheduling of emergency-off system tests.

Emergency-off systems (EOS) are essential to the safe operation of medical accelerators and other high-risk equipment. To assure reliable functioning, some states require weekly tests; others permit monthly, tri-monthly or even six-monthly tests, while some do not specify test intervals. We investigate the relative safety of the various test schedules by computing the fraction of time during which a nonfunctional state of the EOS may remain undetected.

Targeted treatment of cancer with radiofrequency electromagnetic fields amplitude-modulated at tumor-specific frequencies.

In the past century, there have been many attempts to treat cancer with low levels of electric and magnetic fields. We have developed noninvasive biofeedback examination devices and techniques and discovered that patients with the same tumor type exhibit biofeedback responses to the same, precise frequencies. Intrabuccal administration of 27.

SU-E-J-141: Assessment of the Magnitude and Impact of Trigger Delay in Respiratory Triggered Real-Time Imaging during Radiotherapy.

Purpose: To assess the trigger delay in respiratory triggered real-time imaging and its impact on image guided radiotherapy (IGRT) with Varian TrueBeam System.

Methods: A sinusoidal motion phantom with 2cm motion amplitude was used. The trigger delay was determined directly with video image, and indirectly by the distance between expected and actual triggering phantom positions.

TU-E-BRB-11: End-To-End Positioning Quality Assurance for Image-Guided Radiosurgery of Multiple Targets Using a Single-Isocenter.

Purpose: Using a single isocenter significantly reduces delivery times in radiosurgery involving multiple targets. However, because not every target can be placed at isocenter with this type of treatment, a conventional Winston-Lutz test cannot be used. We describe a novel Winston-Lutz like mulitarget test (MTT) for verifying accurate positioning.

SU-E-T-538: Evaluation of IMRT Dose Calculation Based on Pencil-Beam and AAA Algorithms.

Purpose: To evaluate the accuracy of dose calculation for intensity modulated radiation therapy (IMRT) based on Pencil Beam (PB) and Analytical Anisotropic Algorithm (AAA) computation algorithms.

Methods: IMRT plans of twelve patients with different treatment sites, including head/neck, lung and pelvis, were investigated. For each patient, dose calculation with PB and AAA algorithms using dose grid sizes of 0.

MO-D-BRB-06: JUNIOR INVESTIGATOR WINNER - Fast and Accurate Patient Specific Collision Detection for Radiation Therapy.

Purpose: To develop a fast and generalizable method which can identify all possible hardware collisions specific to a given patient setup before treatment planning.

Methods: An anthropomorphic phantom placed in a typical breast setup using a wingboard was simulated on a CT scanner and the phantom body contour, table, and gantry geometry were made into polygon meshes using 3D modeling software. In the treatment room, a limited physical search of the collision positive zones was performed using the positioned phantom.

SU-E-T-631: Beam Geometry Selection Using Sequential Beam Addition.

Purpose: To investigate a beam geometry selection algorithm based on sequential addition of beams.

Methods: The sequential beam addition algorithm (SBA) requires an objective function (score) and a set of candidate beam geometries (pool). The optimal score is determined for each beam in the pool and the best beam selected.

SU-E-T-433: Pear-Shaped Based Dose Optimization for HDR Intracavitary Brachytherapy for Cervical Cancer Patients with Small Uterus.

Purpose: Currently, CT has been widely used for HDR planning as MRI is not widely available for tumor imaging. Conventional pear-shaped isodose distribution may not be discarded completely because of possible microscopic diseases into parametrium/uterus. For patients with small uterus, organs at risk (OARs) can fall inside 100% conventional pear-shaped isodose-line.

Cancer cell proliferation is inhibited by specific modulation frequencies.

Background: There is clinical evidence that very low and safe levels of amplitude-modulated electromagnetic fields administered via an intrabuccal spoon-shaped probe may elicit therapeutic responses in patients with cancer. However, there is no known mechanism explaining the anti-proliferative effect of very low intensity electromagnetic fields.

Methods: To understand the mechanism of this novel approach, hepatocellular carcinoma (HCC) cells were exposed to 27.

Dynamic MLC leaf sequencing for integrated linear accelerator control systems.

Purpose: Leaf positions for dynamic multileaf collimator (DMLC) intensity modulated radiation therapy must be closely synchronized with MU delivery. For the Varian C3 series MLC controller, if the planned trajectory (leaf position vs. MU) requires velocities exceeding the capability of the MLC, the leaves fall behind the planned positions, causing the controller to momentarily hold the beam and thereby introduce dosimetric errors.

Treatment of advanced hepatocellular carcinoma with very low levels of amplitude-modulated electromagnetic fields.

Background: Therapeutic options for patients with advanced hepatocellular carcinoma (HCC) are limited. There is emerging evidence that the growth of cancer cells may be altered by very low levels of electromagnetic fields modulated at specific frequencies.

Methods: A single-group, open-label, phase I/II study was performed to assess the safety and effectiveness of the intrabuccal administration of very low levels of electromagnetic fields amplitude modulated at HCC-specific frequencies in 41 patients with advanced HCC and limited therapeutic options.

RapidArc radiation therapy: first year experience at the University of Alabama at Birmingham.

Purpose: To evaluate treatment planning and delivery for patients treated during our initial year of experience with RapidArc radiation therapy.

Methods And Materials: RapidArc was used to treat 52 patients at The University of Alabama at Birmingham between May 2008 and April 2009. A single ionization chamber phantom with film and a two-dimensional ionization chamber array were used for quality assurance measurements.

Performance of a commercial Macro Monte Carlo dose calculation algorithm for determining output factors of clinical electron fields.

We compare measured output factors of clinical electron fields to those calculated by a commercial treatment planning system based on an electron Monte Carlo algorithm. The measured data is comprised of 195 fields with energies 6 to 18 MeV, applicator sizes 6 x 6 cm(2) to 25 x 25 cm(2), and source to surface distances (SSDs) of 97 to 107 cm. Due to a scarcity of clinical fields for the highest energies and the largest applicator sizes, additional measurements were made at arbitrarily chosen large field sizes at previously not used energies, for a total of 223 output factors.

Development of an accelerated GVF semi-automatic contouring algorithm for radiotherapy treatment planning.

Fast contouring is important in image-guided radiation therapy (IGRT) and adaptive radiation therapy (ART) where large computed tomography (CT) volumes have to be segmented. In this study, a modified active contour (also called snake) segmentation method based on a faster gradient-vector-flow (GVF) calculation algorithm is proposed. The accelerated method was tested on multiple organs, including lung, right ventricle, kidney and prostate.