AAPM Task Group Report 261: Comprehensive quality control methodology and management of dental and maxillofacial cone beam computed tomography (CBCT) systems.

Cone-beam computed tomography (CBCT) systems specifically designed and manufactured for dental, maxillofacial imaging (MFI) and otolaryngology (OLR) applications have been commercially available in the United States since 2001 and have been in widespread clinical use since. Until recently, there has been a lack of professional guidance available for medical physicists about how to assess and evaluate the performance of these systems and about the establishment and management of quality control (QC) programs. The owners and users of dental CBCT systems may have only a rudimentary understanding of this technology, including how it differs from conventional multidetector CT (MDCT) in terms of acceptable radiation safety practices. Dental CBCT systems differ from MDCT in several ways and these differences are described. This report provides guidance to medical physicists and serves as a basis for stakeholders to make informed decisions regarding how to manage and develop a QC program for dental CBCT systems. It is important that a medical physicist with experience in dental CBCT serves as a resource on this technology and the associated radiation protection best practices. The medical physicist should be involved at the pre-installation stage to ensure that a CBCT room configuration allows for a safe and efficient workflow and that structural shielding, if needed, is designed into the architectural plans. Acceptance testing of new installations should include assessment of mechanical alignment of patient positioning lasers and x-ray beam collimation and benchmarking of essential image quality performance parameters such as image uniformity, noise, contrast-to-noise ratio (CNR), spatial resolution, and artifacts. Several approaches for quantifying radiation output from these systems are described, including simply measuring the incident air-kerma (Kair) at the entrance surface of the image receptor. These measurements are to be repeated at least annually as part of routine QC by the medical physicist. QC programs for dental CBCT, at least in the United States, are often driven by state regulations, accreditation program requirements, or manufacturer recommendations.

AAPM MEDICAL PHYSICS PRACTICE GUIDELINE 5.b: Commissioning and QA of treatment planning dose calculations-Megavoltage photon and electron beams.

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized. The following terms are used in the AAPM practice guidelines: Must and Must Not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline. While must is the term to be used in the guidelines, if an entity that adopts the guideline has shall as the preferred term, the AAPM considers that must and shall have the same meaning. Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances.

Clinical commissioning of intensity-modulated proton therapy systems: Report of AAPM Task Group 185.

Proton therapy is an expanding radiotherapy modality in the United States and worldwide. With the number of proton therapy centers treating patients increasing, so does the need for consistent, high-quality clinical commissioning practices. Clinical commissioning encompasses the entire proton therapy system's multiple components, including the treatment delivery system, the patient positioning system, and the image-guided radiotherapy components. Also included in the commissioning process are the x-ray computed tomography scanner calibration for proton stopping power, the radiotherapy treatment planning system, and corresponding portions of the treatment management system. This commissioning report focuses exclusively on intensity-modulated scanning systems, presenting details of how to perform the commissioning of the proton therapy and ancillary systems, including the required proton beam measurements, treatment planning system dose modeling, and the equipment needed.

Image Guidance in Radiation Therapy: Techniques, Accuracy, and Limitations.

This book is a part of the proceedings of the American Association of Physicists in Medicine 2018 Summer School. It offers a comprehensive overview of the current technology, application, and development of image guidance in radiation therapy (IGRT). World experts in IGRT contributed chapters that address x-ray, surface, ultrasound, and magnetic resonance (MR) imaging applications in guiding radiotherapy, as well as touching on fundamental algorithms, on-going research, and future directions.

On-Treatment Verification Imaging.

The integration of on-board imaging (OBI) with linear accelerators paved the way for Image Guided Radiation Therapy (IGRT) as it is practiced today in the clinic. The advent of IGRT is a major milestone in the history of radiotherapy. The main goal of image guidance in radiotherapy is to improve radiation treatment delivery via superior localization and tracking of target cancer cells. IGRT is hence integral to accurate, precise and safe delivery of radiotherapy.

Dose, Benefit, and Risk in Medical Imaging, 1st Edition.

When interacting with colleagues, patients, and members of the public, medical physicists are frequently asked questions about radiation doses, clinical benefits, and biological risks of medical imaging. This book collects some of the latest data and understanding on these subjects into a single concise and well-organized volume and makes it accessible to a wide variety of potential readers. The editors and many of the chapter authors are from Memorial Sloan Kettering Cancer Center. Despite the variety of authors, the content is well-organized and fits together seamlessly.

AAPM Medical Physics Practice Guideline 5.a.: Commissioning and QA of Treatment Planning Dose Calculations - Megavoltage Photon and Electron Beams.

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education and professional practice of medical physics. The AAPM has more than 8,000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized. The following terms are used in the AAPM practice guidelines:• Must and Must Not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline.• Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances.

Early clinical outcomes for 3 radiation techniques for brain metastases: focal versus whole-brain.

PURPOSE: To present our novel technique for brain metastases (low-dose whole brain radiation therapy [WBRT] with simultaneous integrated boost (SIB) and focal, frameless stereotactic intensity modulated radiotherapy [IMRT]) in the context of patterns of failure, dosimetry, acute toxicity, and overall survival for 3 different radiation techniques. METHODS AND MATERIALS: We retrospectively reviewed 92 patients undergoing radiation for brain metastases via the following: (1) "prophylactic" WBRT to a low dose (median 30 Gy) with an SIB to the gross tumor volume plus 2-3 mm margin (median dose 45 Gy) in 10-15 fractions; (2) focal, frameless image-guided stereotactic IMRT (S-IMRT) in 5 fractions to tumor only (median 30 Gy); or (3) conventional (c)WBRT using 2 lateral opposed beams in 10-15 fractions (30-37.5 Gy). The primary endpoints were local (LBC), distant (DBC), and total brain control (TBC) for each of the 3 types of brain radiation. Survival, toxicity, and dosimetry were reported as secondary endpoints. RESULTS: LBC was achieved in 72%, 78%, and 56% for SIB, S-IMRT, and cWBRT, respectively. DBC (ie, no new brain metastases) was observed in 92%, 67%, and 81% for SIB, S-IMRT, and cWBRT, respectively. TBC (LBC + DBC) was 72%, 67%, and 56% for SIB, S-IMRT, and cWBRT, respectively. No statistical difference in overall survival was observed (P = .067), and only 1 patient experienced biopsy proven radionecrosis. CONCLUSIONS: TBC after low-dose WBRT with SIB was acceptable and at least comparable to S-IMRT and cWBRT. SIB seems to be a safe and effective treatment strategy for patients with brain metastases and may efficiently combine the benefits of cWBRT and stereotactic radiosurgery.

Superiority of equivalent uniform dose (EUD)-based optimization for breast and chest wall.

We investigate whether IMRT optimization based on generalized equivalent uniform dose (gEUD) objectives for organs at risk (OAR) results in superior dosimetric outcomes when compared with multiple dose-volume (DV)-based objectives plans for patients with intact breast and postmastectomy chest wall (CW) cancer. Four separate IMRT plans were prepared for each of the breast and CW cases (10 patients). The first three plans used our standard in-house, physician-selected, DV objectives (phys-plan); gEUD-based objectives for the OARs (gEUD-plan); and multiple, "very stringent," DV objectives for each OAR and PTV (DV-plan), respectively. The fourth plan was only beam-fluence optimized (FO-plan), without segmentation, which used the same objectives as in the DV-plan. The latter plan was to be used as an "optimum" benchmark without the effects of the segmentation for deliverability. Dosimetric quantities, such as V(20Gy) for the ipsilateral lung and mean dose (D(mean)) for heart, contralateral breast, and contralateral lung were used to evaluate the results. For all patients in this study, we have seen that the gEUD-based plans allow greater sparing of the OARs while maintaining equivalent target coverage. The average ipsilateral lung V(20Gy) reduced from 22 +/- 4.4% for the FO-plan to 18 +/- 3% for the gEUD-plan. All other dosimetric quantities shifted towards lower doses for the gEUD-plan. gEUD-based optimization can be used to search for plans of different DVHs with the same gEUDs. The use of gEUD allows selective optimization and reduction of the dose for each OAR and results in a truly individualized treatment plan.

Recommendations for clinical electron beam dosimetry: supplement to the recommendations of Task Group 25.

The goal of Task Group 25 (TG-25) of the Radiation Therapy Committee of the American Association of.Physicists in Medicine (AAPM) was to provide a methodology and set of procedures for a medical physicist performing clinical electron beam dosimetry in the nominal energy range of 5-25 MeV. Specifically, the task group recommended procedures for acquiring basic information required for acceptance testing and treatment planning of new accelerators with therapeutic electron beams. Since the publication of the TG-25 report, significant advances have taken place in the field of electron beam dosimetry, the most significant being that primary standards laboratories around the world have shifted from calibration standards based on exposure or air kerma to standards based on absorbed dose to water. The AAPM has published a new calibration protocol, TG-51, for the calibration of high-energy photon and electron beams. The formalism and dosimetry procedures recommended in this protocol are based on the absorbed dose to water calibration coefficient of an ionization chamber at 60Co energy, N60Co(D,w), together with the theoretical beam quality conversion coefficient k(Q) for the determination of absorbed dose to water in high-energy photon and electron beams. Task Group 70 was charged to reassess and update the recommendations in TG-25 to bring them into alignment with report TG-51 and to recommend new methodologies and procedures that would allow the practicing medical physicist to initiate and continue a high quality program in clinical electron beam dosimetry. This TG-70 report is a supplement to the TG-25 report and enhances the TG-25 report by including new topics and topics that were not covered in depth in the TG-25 report. These topics include procedures for obtaining data to commission a treatment planning computer, determining dose in irregularly shaped electron fields, and commissioning of sophisticated special procedures using high-energy electron beams. The use of radiochromic film for electrons is addressed, and radiographic film that is no longer available has been replaced by film that is available. Realistic stopping-power data are incorporated when appropriate along with enhanced tables of electron fluence data. A larger list of clinical applications of electron beams is included in the full TG-70 report available at http://www.aapm.org/pubs/reports. Descriptions of the techniques in the clinical sections are not exhaustive but do describe key elements of the procedures and how to initiate these programs in the clinic. There have been no major changes since the TG-25 report relating to flatness and symmetry, surface dose, use of thermoluminescent dosimeters or diodes, virtual source position designation, air gap corrections, oblique incidence, or corrections for inhomogeneities. Thus these topics are not addressed in the TG-70 report.

Measurements of primary off-axis ratios in wedged asymmetric photon fields: a formalism for dose and monitor unit calculations.

Asymmetric collimators or heavily blocked fields with physical wedges are still encountered in daily practice. In such cases, a reliable dosimetry system is necessary to perform manual dose and monitor unit calculations in order to independently verify the calculations of commercial treatment planning systems. In this work, primary wedged off-axis ratios (POAR(w)s) that account for changes in the beam intensity along both the wedge gradient and perpendicular directions of the photon field, when asymmetric collimators are applied, were measured experimentally at specific depths. The measurements were made in phantom with an ion chamber along the wedge gradient and the perpendicular directions under 'good geometry' conditions. A consistent formalism was presented that could easily be implemented in the clinical environment as an independent verification of the calculations by a treatment planning system. The accuracy of the method was found to be dependent on the specific wedge used, off-axis distance and depth in the phantom. In our study, the accuracy was within 2% in most cases for both energies. We concluded that the primary wedged off-axis ratios when used along with open symmetric field dosimetric parameters could provide adequate accuracy for manual monitor unit calculations.