Management of radiotherapy patients with implanted cardiac pacemakers and defibrillators: A Report of the AAPM TG-203.

Managing radiotherapy patients with implanted cardiac devices (implantable cardiac pacemakers and implantable cardioverter-defibrillators) has been a great practical and procedural challenge in radiation oncology practice. Since the publication of the AAPM TG-34 in 1994, large bodies of literature and case reports have been published about different kinds of radiation effects on modern technology implantable cardiac devices and patient management before, during, and after radiotherapy. This task group report provides the framework that analyzes the potential failure modes of these devices and lays out the methodology for patient management in a comprehensive and concise way, in every step of the entire radiotherapy process.

Image guidance doses delivered during radiotherapy: Quantification, management, and reduction: Report of the AAPM Therapy Physics Committee Task Group 180.

Background: With radiotherapy having entered the era of image guidance, or image-guided radiation therapy (IGRT), imaging procedures are routinely performed for patient positioning and target localization. The imaging dose delivered may result in excessive dose to sensitive organs and potentially increase the chance of secondary cancers and, therefore, needs to be managed.

Aims: This task group was charged with: a) providing an overview on imaging dose, including megavoltage electronic portal imaging (MV EPI), kilovoltage digital radiography (kV DR), Tomotherapy MV-CT, megavoltage cone-beam CT (MV-CBCT) and kilovoltage cone-beam CT (kV-CBCT), and b) providing general guidelines for commissioning dose calculation methods and managing imaging dose to patients.

Addendum to brachytherapy dose-volume histogram commissioning with multiple planning systems.

The process for validating dose-volume histogram data in brachytherapy software is presented as a supplement to a previously published article. Included is the DVH accuracy evaluation of the Best NOMOS treatment planning system called "Best TPS VolumePlan." As done previously in other software, a rectangular cuboid was contoured in the treatment planning system.

Radiation Testing of the GERD Stimulation Therapy System Using a Particle Accelerator.

Objective: This testing was conducted to determine if exposure from a particle accelerator used to treat cancer patients would alter the performance of the EndoStim® neurostimulator when programmed either passively or actively and while being irradiated.

Methods: A total of 12 EndoStim Lower Esophageal Sphincter (LES) Stimulation System implantable neurostimulators were investigated in this research. Included were six each of the EndoStim I and EndoStim II.

Brachytherapy dose-volume histogram commissioning with multiple planning systems.

The first quality assurance process for validating dose-volume histogram data involving brachytherapy procedures in radiation therapy is presented. The process is demonstrated using both low dose-rate and high dose-rate radionuclide sources. A rectangular cuboid was contoured in five commercially available brachytherapy treatment planning systems.

Vagus nerve stimulator stability and interference on radiation oncology x-ray beams.

Five different models of Cyberonics, Inc. vagus nerve stimulation (VNS) therapy pulse generators were investigated for their stability under radiation and their ability to change the absorbed dose from incident radiation. X-ray beams of 6 MV and 18 MV were used to quantify these results up to clinical doses of 68-78 Gy delivered in a single fraction.

Evaluation of a ventricular assist device: stability under x-rays and therapeutic beam attenuation.

Improved outcomes and quality of life of heart failure patients have been reported with the use of left ventricular assist devices (LVADs). However, little information exists regarding devices in patients undergoing radiation cancer treatment. Two HeartWare Ventricular Assist Device (HVAD) pumps were repeatedly irradiated with high intensity 18 MV x-rays to a dosage range of 64-75 Gy at a rate of 6 Gy/min from a radiation oncology particle accelerator to determine operational stability.

A novel phantom model for mouse tumor dose assessment under MV beams.

In order to determine a mouse's dose accurately and prior to engaging in live mouse radiobiological research, a tissue-equivalent tumor-bearing phantom mouse was constructed and bored to accommodate detectors. Comparisons were made among four different types of radiation detectors, each inserted into the mouse phantom for radiation measurement under a 6 MV linear accelerator beam. Dose detection response from a diode, thermoluminescent dosimeters, and metal-oxide semiconductor field-effect transistors were used and compared to that of a reference pinpoint ionization chamber.

Design of site-specific prognostic morbidity-mortality studies and internal outcome focus studies in radiation oncology.

This research focuses on morbidity-mortality reviews and internal outcome focus studies. Definitions are provided as well as a complete discussion of the ideal parameters to consider when constructing each of these. The implementation of the design characteristics used may be of assistance to a center pursuing achievement of these requirements toward accreditation to exemplify continuous quality improvement in external-beam radiation therapy.

Radiation therapy in cochlear implant recipients.

Hypothesis: Processes of scattering and attenuation were investigated to determine the consequence on dose distributions by having a cochlear implant in the field of therapeutic radiation.

Background: Radiation oncology medical accelerator beams of 6- and 18-MV x-ray energy were used. Five cochlear implants were investigated.

Beam profile disturbances from implantable pacemakers or implantable cardioverter-defibrillator interactions.

The medical community is advocating for progressive improvement in the design of implantable cardioverter-defibrillators and implantable pacemakers to accommodate elevations in dose limitation criteria. With advancement already made for magnetic resonance imaging compatibility in some, a greater need is present to inform the radiation oncologist and medical physicist regarding treatment planning beam profile changes when such devices are in the field of a therapeutic radiation beam. Treatment plan modeling was conducted to simulate effects induced by Medtronic, Inc.

Effects on radiation oncology treatments involving various neuromodulation devices.

Object: Where no society-based or manufacturer guidance on radiation limits to neuromodulation devices is available, this research provides the groundwork for neurosurgeons and radiation oncologists who rely on the computerized treatment plan clinically for cancer patients. The focus of the article is to characterize radiation parameters of attenuation and scatter when an incident therapeutic x-ray beam is directed upon them. At the time of this writing, manufacturers of Neuromodulation products do not recommend direct exposure of the device in the beam nor provide guidance for the maximum dose for these devices.

Dose-volume histogram quality assurance for linac-based treatment planning systems.

Dose-volume histograms provide key information to radiation oncologists when they assess the adequacy of a patient treatment plan in radiation therapy. It is important therefore that all clinically relevant data be accurate. In this article we present the first quality assurance routine involving a direct comparison of planning system results with the results obtained from independent hand calculations.

Providing solid angle formalism for skyshine calculations.

We detail, derive and correct the technical use of the solid angle variable identified in formal guidance that relates skyshine calculations to dose-equivalent rate. We further recommend it for use with all National Council on Radiation Protection and Measurements (NCRP), Institute of Physics and Engineering in Medicine (IPEM) and similar reports documented. In general, for beams of identical width which have different resulting areas, within ± 1.

Radiation skyshine from a 6 MeV medical accelerator.

This study assesses the dose level from skyshine produced by a 6 MeV medical accelerator. The analysis of data collected on skyshine yields professional guidance for future investigators as they attempt to quantify and qualify radiation protection concerns in shielding therapy vaults. Survey measurements using various field sizes and at varying distances from a primary barrier have enabled us to identify unique skyshine behavior in comparison to other energies already seen in literature.

Analytical correction of an extension of the "MU Fraction Approximation" for Varian enhanced dynamic wedges.

The most common method to determine enhanced dynamic wedge factors begins with the use of segmented treatment tables. These segmental dose delivery values set as a function of upper jaw position are the backbone of a calculation process coined the "MU Fraction Approximation." Analytical and theoretical attempts have been made to extend and alter the mathematics for this approximation for greater accuracy.

Establishing radiation therapy treatment planning effects involving implantable pacemakers and implantable cardioverter-defibrillators.

Recent improvements to the functionality and stability of implantable pacemakers and cardioverter-defibrillators involve changes that include efficient battery power consumption and radiation hardened electrical circuits. Manufacturers have also pursued MRI-compatibility for these devices. While such newer models of pacemakers and cardioverter-defibrillators are similar in construction to previously marketed devices - even for the recent MRI-compatible designs currently in clinical trials - there is increased interest now with regard to radiation therapy dose effects when a device is near or directly in the field of radiation.

Dosimetric impact of surgical clips in electron beam treatment of breast cancer.

Titanium clips are commonly used to delineate the location of the tumor bed during breast cancer surgery. Electron beams are frequently used to boost radiation dose to the breast cavity. This research investigated the effect on such boost treatments as a result of metallic clip perturbation potentially exhibited through attenuation and scatter processes using measurements with Gafchromic film and treatment planning simulation with both generalized Gaussian pencil beam and electron Monte Carlo algorithms.

Dosimetric effects near implanted vascular access ports: an examination of external photon beam calculation.

Vascular access ports are used widely in the administering of drugs for radiation oncology patients. Their dosimetric effect on radiation therapy delivery in photon beams has not been rigorously established. In this work the effects on external beam fields when any of a variety of vascular access ports is included in the path of a high energy beam are studied.

Correlation between detector array measurements and a computer algorithm for enhanced dynamic wedge profiles.

Verification of dosimetric data computed by a treatment planning system is necessary in the commissioning process for any clinical software, just as it is necessary for any annual quality assurance testing. Direct verification of the dosimetric data is achievable when calculating the enhanced dynamic wedge (EDW) off-axis ratio at each point of interest. As mathematical models for hand-calculating such factors are still evolving, measurement of these external beam arrangements has proven significantly more accurate.