American Association Of Physicists In Medicine Research Articles

An analytical model to determine interseed attenuation effect in low‐dose‐rate brachytherapy

Brachytherapy treatment planning systems (BTPS) are employing the American Association of Physicists in Medicine (AAPM) Task Group 43 (TG‐43)‐recommended dosimetric parameters of sources, which are measured in water. The majority of brachytherapy implant volumes are not homogeneous media. Particularly, an implant with multiple seeds significantly changes homogeneity of the implant volume. Heterogeneities, such as attenuation by adjacent seeds or interseed attenuation (ISA), are neglected to this day in all BTPS. The goal of this project is to determine a novel analytical method to evaluate the impact of the dose perturbations (P‐value) and/or interseed attenuation effect (ISA‐value). This method will be validated for low‐ and high‐energy brachytherapy seeds such as 125I and 192Ir using Monte Carlo (MC) simulation techniques. In this analytical model, determination of dose perturbation and interseed attenuation in a multisource brachytherapy implant is based on MC‐simulated 3D kernels of P‐values and ISA data for single active and single dummy configurations, arranged at different distances and orientations relative to each other. The accuracy of the final model in multisource implant configurations has been examined by a comparison of the calculated P‐values and ISA‐values with full Monte Carlo water simulations (FMCWS). This model enabled us to determine the total perturbation and ISA values for any multisource implant, and the results are in excellent agreement with the FMCWS data. The advantage of this model to FMCWS for daily clinical application is the speed of the calculations and ease of the implementation. The new perturbation and ISA formulism have shown a better accuracy for 192Ir than 125I due to Compton scattering and its independence of the atomic number of the chemical composition of the phantom materials. The maximum difference between the ISA model and FMCWS for all cases was less than 5%. This new model can provide inputs for brachytherapy planning software to consider the ISA effect in dose calculations based on TG‐43U1 algorithm. This approach is applicable for energy range of 125I to 192Ir sources.PACS number: 87.53.Jw

Ethics and professionalism in medical physics: A survey of AAPM members

To assess current education, practices, attitudes, and perceptions pertaining to ethics and professionalism in medical physics. A link to a web-based survey was distributed to the American Association of Physicists in Medicine (AAPM) e-mail membership list, with a follow-up e-mail sent two weeks later. The survey included questions about ethics/professionalism education, direct personal knowledge of ethically questionable practices in clinical care, research, education (teaching and mentoring), and professionalism, respondents' assessment of their ability to address ethical/professional dilemmas, and demographics. For analysis, reports of unethical or ethically questionable practices or behaviors by approximately 40% or more of respondents were classified as "frequent." Partial or complete responses were received from 18% (1394/7708) of AAPM members. Overall, 60% (827/1377) of the respondents stated that they had not received ethics/professionalism education during their medical physics training. Respondents currently in training were more likely to state that they received instruction in ethics/professionalism (80%, 127/159) versus respondents who were post-training (35%, 401/1159). Respondents' preferred method of instruction in ethics/professionalism was structured periodic discussions involving both faculty and students/trainees. More than 90% (1271/1384) supported continuing education in ethics/professionalism and 75% (1043/1386) stated they would attend ethics/professionalism sessions at professional/scientific meetings. In the research setting, reports about ethically questionable authorship assignment were frequent (approximately 40%) whereas incidents of ethically questionable practices about human subjects protections were quite infrequent (5%). In the clinical setting, there was frequent recollection of incidents regarding lack of training, resources and skills, and error/incident reporting. In the educational setting, incidents of unethical or ethically questionable practices were only frequently recollected with respect to mentorship/guidance. With respect to professional conduct, favoritism, hostile work/learning environment, and maltreatment of subordinates and colleagues were frequently reported. A significantly larger proportion of women reported experiences with hostile work/learning environments, favoritism, poor mentorship, unfairness in educational settings, and concerns about student privacy and confidentiality. The survey found broad interest in ethics/professionalism topics and revealed that these topics were being integrated into the curriculum at many institutions. The incorporation of ethics and professionalism instruction into both graduate education and postgraduate training of medical physicists, and into their subsequent lifelong continuing education is important given the nontrivial number of medical physicists who had direct personal knowledge of unethical or ethically questionable incidents in clinical practice, research, education, and professionalism.

Report on the American Association of Medical Physics Undergraduate Fellowship Programs

The American Association of Physicists in Medicine (AAPM) sponsors two summer undergraduate research programs to attract top performing undergraduate students into graduate studies in medical physics: the Summer Undergraduate Fellowship Program (SUFP) and the Minority Undergraduate Summer Experience (MUSE). Undergraduate research experience (URE) is an effective tool to encourage students to pursue graduate degrees. The SUFP and MUSE are the only medical physics URE programs. From 2001 to 2012, 148 fellowships have been awarded and a total of $608,000 has been dispersed to fellows. This paper reports on the history, participation, and status of the programs. A review of surveys of past fellows is presented. Overall, the fellows and mentors are very satisfied with the program. The efficacy of the programs is assessed by four metrics: entry into a medical physics graduate program, board certification, publications, and AAPM involvement. Sixty‐five percent of past fellow respondents decided to pursue a graduate degree in medical physics as a result of their participation in the program. Seventy percent of respondents are currently involved in some educational or professional aspect of medical physics. Suggestions for future enhancements to better track and maintain contact with past fellows, expand funding sources, and potentially combine the programs are presented.PACS number: 01.10.Hx

A comparative study for different shielding material composition and beam geometry applied to PET facilities: simulated transmission curves

The aim of this work is to simulate transmission data for different beam geometry and material composition in order to evaluate the effect of these parameters on transmission curves. The simulations are focused on outgoing spectra for shielding barriers used in PET facilities. The behavior of the transmission was evaluated as a function of the shielding material composition and thickness using Geant4 Monte Carlo code, version 9.2 p 03.The application was benchmarked for barited mortar and compared to The American Association of Physicists in Medicine (AAPM) data for lead. Their influence on the transmission curves as well the study of the influence of the shielding material composition and beam geometry on the outgoing spectra were performed. Characteristics of transmitted spectra, such as shape, average energy and Half-Value Layer (HVL), were also evaluated. The Geant4 toolkit benchmark for the energy resulting from the positron annihilation phenomena and its application in transmission curves description shown good agreement between data published by American Association on Physicists in Medicine task group 108 and experimental data published by Brasil. The transmission properties for different material compositions were also studied and have shown low dependency with the considered thicknesses. The broad and narrow beams configuration presented significant differences on the result. The fitting parameter for determining the transmission curves equations, according to Archer model is presented for different material. As conclusion were defined that beam geometry has significant influence and the composition has low influence on transmission curves for shielding design for the range of energy applied to PET.

Cancer patients with cardiac pacemakers needing radiation treatment: A systematic review

With improving average life expectancy of individuals in most countries, there has been increase in the incidence of cardiovascular diseases and cancers. Radiation oncologists therefore are likely to encounter an increasing number of cancer patients with in situ cardiac pacemaker devices needing radiation treatments. Pacemaker technology has advanced rapidly in recent years. As a result, the potential interactions of these devices with radiation therapy have changed since American Association of Physicists in Medicine (AAPM) issued guidelines in 1994. Current approaches to treatment in patients who have these devices vary among radiation oncology centers. Furthermore, the recommendations given by the devices' manufacturers differ considerably. Common knowledge about pacemaker in radiation oncology community is vital as radiation management needs to be tailored to individual patients in accordance to the information of available for the device. Some general practical guidelines can be gleaned from the literature. It is felt that more robust information is required using web based database sharing to develop total safe practice guidelines in such patients. This article reviews the information available to help create such guidelines and presents recommendations for treatment in this increasingly common clinical situation.

Dosimetry of 125I and 103Pd COMS eye plaques for intraocular tumors: Report of Task Group 129 by the AAPM and ABS

Dosimetry of eye plaques for ocular tumors presents unique challenges in brachytherapy. The challenges in accurate dosimetry are in part related to the steep dose gradient in the tumor and critical structures that are within millimeters of radioactive sources. In most clinical applications, calculations of dose distributions around eye plaques assume a homogenous water medium and full scatter conditions. Recent Monte Carlo (MC)-based eye-plaque dosimetry simulations have demonstrated that the perturbation effects of heterogeneous materials in eye plaques, including the gold-alloy backing and Silastic insert, can be calculated with reasonable accuracy. Even additional levels of complexity introduced through the use of gold foil "seed-guides" and custom-designed plaques can be calculated accurately using modern MC techniques. Simulations accounting for the aforementioned complexities indicate dose discrepancies exceeding a factor of ten to selected critical structures compared to conventional dose calculations. Task Group 129 was formed to review the literature; re-examine the current dosimetry calculation formalism; and make recommendations for eye-plaque dosimetry, including evaluation of brachytherapy source dosimetry parameters and heterogeneity correction factors. A literature review identified modern assessments of dose calculations for Collaborative Ocular Melanoma Study (COMS) design plaques, including MC analyses and an intercomparison of treatment planning systems (TPS) detailing differences between homogeneous and heterogeneous plaque calculations using the American Association of Physicists in Medicine (AAPM) TG-43U1 brachytherapy dosimetry formalism and MC techniques. This review identified that a commonly used prescription dose of 85 Gy at 5 mm depth in homogeneous medium delivers about 75 Gy and 69 Gy at the same 5 mm depth for specific (125)I and (103)Pd sources, respectively, when accounting for COMS plaque heterogeneities. Thus, the adoption of heterogeneous dose calculation methods in clinical practice would result in dose differences >10% and warrant a careful evaluation of the corresponding changes in prescription doses. Doses to normal ocular structures vary with choice of radionuclide, plaque location, and prescription depth, such that further dosimetric evaluations of the adoption of MC-based dosimetry methods are needed. The AAPM and American Brachytherapy Society (ABS) recommend that clinical medical physicists should make concurrent estimates of heterogeneity-corrected delivered dose using the information in this report's tables to prepare for brachytherapy TPS that can account for material heterogeneities and for a transition to heterogeneity-corrected prescriptive goals. It is recommended that brachytherapy TPS vendors include material heterogeneity corrections in their systems and take steps to integrate planned plaque localization and image guidance. In the interim, before the availability of commercial MC-based brachytherapy TPS, it is recommended that clinical medical physicists use the line-source approximation in homogeneous water medium and the 2D AAPM TG-43U1 dosimetry formalism and brachytherapy source dosimetry parameter datasets for treatment planning calculations. Furthermore, this report includes quality management program recommendations for eye-plaque brachytherapy.

ACR–AAPM–SIIM Practice Guideline for Determinants of Image Quality in Digital Mammography

This guideline was developed collaboratively by individuals with recognized expertise in breast imaging, medical physics, and imaging informatics, representing the American College of Radiology (ACR), the American Association of Physicists in Medicine (AAPM), and the Society for Imaging Informatics in Medicine (SIIM), primarily for technical guidance. It is based on a review of the clinical and physics literature on digital mammography and the experience of experts and publications from the Image Quality Collaborative Workgroup [1–3]. For purposes of this guideline, digital mammography is defined as the radiographic examination of the breast utilizing dedicated electronic detectors to record the image (rather than screen film) and having the capability for image display on computer monitors. This guideline is specific to two-dimensional (2D) digital mammography since the vast majority of digital mammography performed in the USA is 2D. Although some three-dimensional technologies are in use, they are not addressed in this guideline since they continue to evolve and are not yet in widespread clinical use. In many parts of this guideline, the level of technical detail regarding the determinants of image quality for digital mammography is advanced, and is intended to provide radiologists, qualified medical physicists, regulators, and other support personnel directly involved in clinical implementation and oversight an expanded knowledge of the issues pertinent to assessing and maintaining digital mammography image quality from the acquisition, display, and data storage aspects of the process. Where basic technical requirements for digital mammography overlap with those for digital radiography in general, users are directed to consult the referenced ACR practice guidelines [4, 5]. All interested individuals are encouraged to review the ACR digital radiography guidelines. Additionally, this guideline includes input from industry, radiologists, and other interested parties in an attempt to represent the consensus of the broader community. It was further informed by input from another working group of the Integrating the Healthcare Enterprise (IHE) Initiative [6]. Furthermore, the ACR Subcommittee on Digital Mammography is developing a quality control (QC) manual for digital mammography. Analysis of image quality has meaning primarily in the context of a particular imaging task [7]. This guideline has been developed with reference to specific imaging tasks required by mammography, using the information available in the peer-reviewed medical literature regarding digital mammography acquisition, image processing and display, storage, transmission, and retrieval. Specifically, the imaging tasks unique to mammography that determine the essential characteristics of a high-quality mammogram are its ability to visualize the following features of breast cancer: The characteristic morphology of a mass. The shape and spatial configuration of calcifications. Distortion of the normal architecture of the breast tissue. Asymmetry between images of the left and right breast. The development of anatomically definable changes when compared with prior studies. The primary goal of mammography is to detect breast cancer, if it exists, by accurately visualizing these features. At the same time, it is important that these signs of breast cancer not be falsely identified if breast cancer is not present. Two aspects of digital image quality can be distinguished: technical and clinical. It is possible to make technical measurements describing the above attributes, and it may be possible to infer a connection between these technical measures and clinical image quality. The extent to which these features are rendered optimally with a digital mammography system using current technology depends on several factors and is the major focus of this guideline.

ACR–AAPM–SIIM Technical Standard for Electronic Practice of Medical Imaging

This technical standard has been revised by the American College of Radiology (ACR), the American Association of Physicists in Medicine (AAPM), and the Society for Imaging Informatics in Medicine (SIIM). For the purpose of this technical standard, the images referred to are those that diagnostic radiologists would normally interpret, including transmission projection and cross-sectional X-ray images, ionizing radiation emission images, and images from ultrasound and magnetic resonance modalities. Research, nonhuman and visible light images (such as dermatologic, histopathologic, or endoscopic images) are out of scope, though many of the same principles are applicable. Increasingly, medical imaging and patient information are being managed using digital data during acquisition, transmission, storage, display, interpretation, and consultation. The management of these data during each of these operations may have an impact on the quality of patient care. This technical standard is applicable to any system of digital image data management, from a single-modality or single-use system to a complete picture archiving and communication system (PACS) to the electronic transmission of patient medical images from one location to another for the purposes of interpretation and/or consultation. It defines goals, qualifications of personnel, equipment guidelines, specifications of data manipulation and management, and quality control and quality improvement procedures for the use of digital image data that should result in high-quality radiological care. A glossary of commonly used terminology (Appendix A) and a reference list are included. In all cases for which an ACR practice guideline or technical standard exists for the modality being used or the specific examination being performed, that practice guideline or technical standard will continue to apply when digital image data management systems are used. Digital mammography is outside the scope of this document. For further information, see the ACR–AAPM–SIIM Practice Guideline for Determinants of Image Quality in Digital Mammography. The goals of the electronic practice of medical imaging include, but are not limited to: Initial acquisition or generation and recording of accurately labeled and identified image data. Transmission of data to an appropriate storage medium from which it can be retrieved for display for formal interpretation, review, and consultation. Retrieval of data from available prior imaging studies to be displayed for comparison with a current study. Transmission of data to remote sites for consultation, review, or formal interpretation. Appropriate compression of image data to facilitate transmission or storage, without loss of clinically significant information. Archiving of data to maintain accurate patient medical records in a form that: May be retrieved in a timely fashion Meets applicable facility, state, and federal regulations Maintains patient confidentiality Promoting efficiency and quality improvement. Providing interpreted images to referring providers. Supporting telemedicine by making medical image consultations available in medical facilities without on-site medical imaging support. Providing supervision of off-site imaging studies. Providing timely availability of medical images, image consultation, and image interpretation by: Facilitating medical image interpretations in on-call situations Providing subspecialty support as needed. Enhancing educational opportunities for practicing radiologists. Minimizing the occurrence of poor image quality. Appropriate database management procedures applicable to all of the above should be in place.

ACR–AAPM–SIIM Practice Guideline for Digital Radiography

This guideline was developed collaboratively by the American College of Radiology (ACR), the American Association of Physicists in Medicine (AAPM), and the Society for Imaging Informatics in Medicine (SIIM). Increasingly, medical imaging and patient information are being managed using digital data during acquisition, transmission, storage, display, interpretation, and consultation. The management of these data during each of these operations may have an impact on the quality of patient care. “CR” and “DR” are the commonly used terms for digital radiography detectors. CR is the acronym for computed radiography, and DR is an acronym for digital radiography. CR uses a photostimulable storage phosphor that stores the latent image, which is subsequently read out using a stimulating laser beam. It can be easily adapted to a cassette-based system analogous to that used in screen-film (SF) radiography. Historically, the acronym DR has been used to describe a flat-panel digital X-ray imaging system that reads the transmitted X-ray signal immediately after exposure with the detector in place. Generically, the term CR is applied to passive detector systems, while the term DR is applied to active detectors. This guideline is applicable to the practice of digital radiography. It defines motivations, qualifications of personnel, equipment guidelines, data manipulation and management, and quality control (QC) and quality improvement procedures for the use of digital radiography that should result in high-quality radiological patient care. In all cases for which an ACR practice guideline or technical standard exists for the modality being used or the specific examination being performed, that guideline or standard will continue to apply when digital image data management systems are used.

Overview on the dosimetric uncertainty analysis for photon-emitting brachytherapy sources, in the light of the AAPM Task Group No 138 and GEC-ESTRO report

In 2011, the American Association of Physicists in Medicine (AAPM) and the Groupe Européen de Curiethérapie–European Society for Radiotherapy and Oncology (GEC-ESTRO) published a report pertaining to uncertainties in brachytherapy single-source dosimetry preceding clinical use. The International Organization for Standardization's Guide to the Expression of Uncertainty in Measurement and Technical Note 1297 by the National Institute of Standards and Technology are taken as reference standards for uncertainty formalism. Uncertainties involved in measurements or Monte Carlo methods to estimate brachytherapy dose distributions are provided with discussion of the components intrinsic to the overall dosimetric assessment. The uncertainty propagation from the primary calibration standard through transfer to the clinic for air-kerma strength is given with uncertainties in each of the brachytherapy dosimetry parameters of the AAPM TG-43 dose-calculation formalism. For low-energy and high-energy brachytherapy sources of low dose-rate and high dose-rate, a combined dosimetric uncertainty <5% (k = 1) is estimated, which is consistent with prior literature estimates. Recommendations are provided for clinical medical physicists, dosimetry investigators, and manufacturers of brachytherapy sources and treatment planning systems. These recommendations reflect the guidance of the AAPM and GEC-ESTRO for their members, and may also be used as guidance to manufacturers and regulatory agencies in developing good manufacturing practices for conventional brachytherapy sources used in routine clinical treatments.

Imaging system QA of a medical accelerator, Novalis Tx, for IGRT per TG 142: our 1 year experience

American Association of Physicists in Medicine (AAPM) task group (TG) 142 has recently published a report to update recommendations of the AAPM TG 40 report and add new recommendations concerning medical accelerators in the era of image‐guided radiation therapy (IGRT). The recommendations of AAPM TG 142 on IGRT are timely. In our institute, we established a comprehensive imaging QA program on a medical accelerator based on AAPM TG 142 and implemented it successfully. In this paper, we share our one‐year experience and performance evaluation of an OBI capable linear accelerator, Novalis Tx, per TG 142 guidelines.PACS numbers: 87.57.‐s, 87.57.C‐, 87.57.uq, 87.59.‐e, 87.59.bd

MO-D-211-01: Medical Physics Practice Guidelines - The Minimum Level of Medical Physics Support in Clinical Practice Settings.

1. Understand the concept and scope of MPPG from the AAPM 2. Understand the benefits and process of the development of MPPG by the AAPM 3. Understand the goals and methodology of the Therapy MPPG Task Group #14. 4. Understand the strategic plans from Professional Council towards the AAPM initiatives.

SU-E-T-501: Perturbation of TG-43 Parameters of the Brachytherapy Sources under Insufficient Scattering Materials.

According to the TG-43 recommendations of American Association of Physicist in Medicine (AAPM), the dosimetry parameters of brachytherapy sources are obtained in a water phantom with full scattering conditions. However, in many actual clinical treatments the source are not surrounded with sufficient tissue in all directions to provide the full scattering condition. HDR brachytherapy of the breast or 125I eye-plaque treatment of the ocular melanoma are among the treatment sites that fits this category. In this project, the impact of insufficient phantom material surrounding the 137Cs, 192Ir, and 103Pd brachytherapy source on their TG43 dosimetric characteristics has been investigated. In this study, the effect of the insufficient tissue (referred here as missing tissues) around the brachytherapy sources on their TG-43 dosimetric parameters have been investigated using MCNP5 Monte Carlo code. The brachytherapy sources were simulated in different locations inside a cubical water phantom with the dimensions of 30*30*30 cm3 . The variation of the dosimetric parameters of the three sources (i.e. Î>, g(r), and F(r,θ)) were compared to the values from full scattering conditions (i.e. source at the center of the phantom). The results of this study indicate the variation of g(r)and 2D anisotropy function of the brachytherapy sources as a function of the missing tissue thickness. These changes increase by decreasing the energy of the photons emitted by the brachytherapy sources. These differences are mainly due to the lack of full scattering condition for the points near the phantom boundary. Unlike the published data for symmetric, but insufficient phantom material around the source, the impact of asymmetric phantom materials have been evaluated on dosimetric characteristics of the brachytherapy sources.

SU-E-T-94: Multileaf Collimator Performance and Validation of Quality Control Tolerances.

The automated quality assurance system (AQUA) is a centralized quality control (QC) software designed to automate QC tests. Statistical analysis of AQUA results was performed to assess the geometric accuracy and long-term reproducibility of a commercially available multileaf collimator (MLC) and examine the applicability of the American Association of Physicists in Medicine (AAPM) tolerances for MLC QC. The MLC was first calibrated with AQUA by minimizing leaf-positioning errors on megavoltage images for 5 different leaf-bank positions (-60 to 100 mm from radiation isocenter). Leaf-positioning accuracy and reproducibility was assessed by repeating the AQUA test 5 times/week. The range of leaf-positioning error over leaf-bank positions and time was reported. Measured leaf-positioning errors were then separated into systematic and random error components. The systematic error corresponds to the variation (standard deviation) in mean positioning errors between leaves over leaf-bank positions and time. The random error quantifies the leaf position variations around its mean and is calculated as the root-mean-square of the individual leaf position standard deviations. To date, 2 different MLCs have been calibrated using AQUA and 9-18 datasets have been acquired to assess performance. For the unit with the longest follow up, the range of leaf-positioning errors was -0.62 to 0.85 mm and 98% of the measured leaf positions (n=7200) were within ±0.5 mm of the nominal position. The systematic error was the main error component (±0.15 to ±0.2 mm) and was attributed to the residual errors after calibration. The random error was ±0.07 mm for both units and demonstrated good leaf-positioning reproducibility and limited uncertainty of the AQUA measurements. Preliminary results show that after MLC calibration with AQUA, leaf-positioning errors on two different units are well within the AAPM-recommended ±1 mm tolerances. Additional MLC performance improvement is possible if residual errors after calibration can be reduced further as the MLC demonstrated high reproducibility. Funded in part by Elekta Inc.

Dose calculation for photon‐emitting brachytherapy sources with average energy higher than 50 keV: Report of the AAPM and ESTRO

Recommendations of the American Association of Physicists in Medicine (AAPM) and the European Society for Radiotherapy and Oncology (ESTRO) on dose calculations for high-energy (average energy higher than 50 keV) photon-emitting brachytherapy sources are presented, including the physical characteristics of specific (192)Ir, (137)Cs, and (60)Co source models. This report has been prepared by the High Energy Brachytherapy Source Dosimetry (HEBD) Working Group. This report includes considerations in the application of the TG-43U1 formalism to high-energy photon-emitting sources with particular attention to phantom size effects, interpolation accuracy dependence on dose calculation grid size, and dosimetry parameter dependence on source active length. Consensus datasets for commercially available high-energy photon sources are provided, along with recommended methods for evaluating these datasets. Recommendations on dosimetry characterization methods, mainly using experimental procedures and Monte Carlo, are established and discussed. Also included are methodological recommendations on detector choice, detector energy response characterization and phantom materials, and measurement specification methodology. Uncertainty analyses are discussed and recommendations for high-energy sources without consensus datasets are given. Recommended consensus datasets for high-energy sources have been derived for sources that were commercially available as of January 2010. Data are presented according to the AAPM TG-43U1 formalism, with modified interpolation and extrapolation techniques of the AAPM TG-43U1S1 report for the 2D anisotropy function and radial dose function.

KERMA ratios vs. SSDE: is one better at estimating pediatric CT radiation doses?

Reasonable estimates of pediatric CT radiation doses are necessary to better understand the potential radiation risks of this modality. This issue of Pediatric Radiology includes a paper titled “KERMA Ratios in Pediatric CT Dosimetry” [1] that presents a method to estimate organ doses in pediatric CT patients. In 2011, the American Association of Physicists in Medicine (AAPM) published a different approach to estimating pediatric radiation doses associated with CT scanning [2]. Is one of these methods better suited to the task or preferred over the other?

CT Scans: Balancing Health Risks and Medical Benefits

Computed tomography (CT) has been a boon for medical care. By generating detailed anatomical pictures, the technology can improve diagnoses, limit unneeded medical procedures, and enhance treatment. However, CT scans also dose patients with ionizing radiation, a known human carcinogen, posing a potential downside for public health. Mounting health worries over radiation risks are now driving efforts to limit avoidable CT scans and to reduce radiation doses where possible. “There’s a national focus on this issue right now,” says Marilyn Goske, a professor of radiology at Cincinnati Children’s Hospital Medical Center and chairwoman of the Image Gently campaign, a pediatric education and awareness campaign from the Alliance for Radiation Safety in Pediatric Imaging. In December 2011 the Institute of Medicine (IOM) published a report concluding that ionizing radiation contributes more to the development of breast cancer than any other type of routine environmental exposure.1 About half the U.S. annual exposure to ionizing radiation comes from natural sources, including cosmic rays, but most of the rest comes from medical imaging and from CT scans in particular.1 The IOM cited research by Amy Berrington de Gonzalez, a senior investigator in the Radiation Epidemiology Branch of the National Cancer Institute (NCI), whose calculations suggest that the CT scans performed in the United States in 2007 might produce up to 29,000 cancers in the future, about 6% of them in the breast and the remainder in the lungs, brain, and other organs.2 But the spotlight on CT safety has also drawn a backlash from those who say the risks are overblown. On 13 December 2011 the American Association of Physicists in Medicine (AAPM) issued a statement claiming that risks from CT imaging are “too low to be detectible and may be non-existent.”3 The AAPM added that “speculative predictions about cancer incidence and death” should be discouraged because they generate sensationalist media coverage that deters some patients who need CT scans from having them. Donald Miller, acting chief of the Diagnostic Devices Branch of the U.S. Food and Drug Administration (FDA) Center for Devices and Radiological Health, cites 2 basic principles for decreasing CT radiation risks. One is justification, which refers to prescribing a CT exam only when it is medically necessary. The other is optimization, which refers to adjusting and operating a CT scanner so that images adequate for diagnosis are obtained at the lowest possible dose. Justification is more difficult to address, Miller says, because it involves case-by-case decisions made by individual clinicians. More attention has been paid to optimization, he says, but both principles are equally important.

A Comparison of the Dosimetric Parameters of Cs-137 Brachytherapy Source in Different Tissues with Water Using Monte Carlo Simulation

Introduction After the publication of Task Group number 43 dose calculation formalism by the American Association of Physicists in Medicine (AAPM), this method has been known as the most common dose calculation method in brachytherapy treatment planning. In this formalism, the water phantom is introduced as the reference dosimetry phantom, while the attenuation coefficient of the sources in the water phantom is different from that of different tissues. The purpose of this study is to investigate the effects of the phantom materials on the TG-43 dosimetery parameters of the Cs-137 brachytherapy source using MCNP4C Monte Carlo code. Materials and Methods In this research, the Cs-137 (Model Selectron) brachytherapy source was simulated in different phantoms (bone, soft tissue, muscle, fat, and the inhomogeneous phantoms of water/bone) of volume 27000 cm3 using MCNP4C Monte Carlo code. *F8 tally was used to obtain the dose in a fine cubical lattice. Then the TG-43 dosimetry parameters of the brachytherapy source were obtained in water phantom and compared with those of different phantoms. Results The percentage difference between the radial dose function g(r) of bone and the g(r) of water phantom, at a distance of 10 cm from the source center is 20%, while such differences are 1.7%, 1.6% and 1.1% for soft tissue, muscle, and fat, respectively. The largest difference of the dose rate constant of phantoms with those of water is 4.52% for the bone phantom, while the differences for soft tissue, muscle, and fat are 1.18%, 1.27%, and 0.18%, respectively. The 2D anisotropy function of the Cs-137 source for different tissues is identical to that of water. Conclusion The results of the simulations have shown that dose calculation in water phantom would introduce errors in the dose calculation around brachytherapy sources. Therefore, it is suggested that the correction factors of different tissues be applied after dose calculation in water phantoms, in order to decrease the errors of brachytherapy treatment planning.

Controle de qualidade de monitores de diagnóstico por imagem e iluminância nos espaços de pós-processamento em serviços de imagiologia

OBJETIVO: Avaliar a qualidade dos monitores de diagnóstico e tratamento de imagem digital em radiologia convencional (raios X) com base nos níveis de luminância. Fez-se a medição da iluminância dos postos de trabalho onde estavam os monitores. MATERIAIS E MÉTODOS: A medição da luminância foi realizada usando-se um detector Unfors Xi Light em cinco instituições, com 23 monitores primários e 22 secundários, sendo 6 usados em urgência, seguindo o método descrito no relatório TG18 da American Association of Physicists in Medicine (AAPM). O instrumento de medida utilizado foi o Delta Ohm HD 9221 luximeter. RESULTADOS: Para as recomendações da AAPM, tanto monitores primários como secundários cumpriram, no geral, os níveis de tolerância. No caso dos níveis de iluminância, nos locais de trabalho dos monitores primários encontravam-se ligeiramente acima do intervalo recomendado. Quanto às recomendações do The Royal College of Radiologists (RCR), os monitores que respeitaram os níveis recomendados estavam em minoria, embora as diferenças não fossem significativas. CONCLUSÃO: Em geral, os resultados foram satisfatórios, embora os monitores não fossem adequados para atingir as recomendações exigentes do RCR. Os níveis de referência entre os monitores primários e secundários deveriam aproximar-se, de modo a garantir a qualidade de imagem. Os monitores para visualização e diagnóstico de imagens médicas devem ser regularmente avaliados para manter um sistema com a qualidade exigida, dada a função que desempenham.

Establishing the quality management baseline in the use of computed tomography machines in Kenya

The objective of this study was to assess the level of compliance to quality assurance and image quality standards in computed tomography facilities in Kenyan hospitals. A quality assurance inspection and physical image quality assessment in eighteen representative computed tomography facilities were completed. A quantitative method was developed and used to score the results obtained from the physical image quality measurements using the American Association of Physicists in Medicine (AAPM) water phantom. Inspection was done in order to establish the level of compliance with internationally recognized standards such as those stipulated in the European Guidelines Quality Criteria for Computed Tomography and the International Basic Safety Standards for Protection against Ionizing Radiation. The overall findings placed the national quality management performance at 50±3%, while image quality and quality assurance performance were 61±3% and 37±3%, respectively. The quality assurance assessment benchmarked the country's level of quality management system compliance in diagnostic radiology. During accreditation appraisal, the scrutiny of scores from each stage in the medical imaging chain per facility will encourage continual implementation of the quality improvement process.PACS number: 87.57.C, 87.57.cf, 87.57.cj, 87.57.cm, 87.57.cp, 87.57.Q, 87.55.N