TAM-B - Medical Health Physics Part 1 Orlando V 08:00 - 11:15
|
| Chair(s): John Hackett, Joseph Ring
|
| |
TAM-B.1
08:00 Testing the IAEA TRS483 Code of Practice for Small Fields Dosimetrynat King Faisal Specialist Hospital and Research Centre M Arib*, King Faisal Specialist Hospital and Research Centre
; A Nobah, King Faisal Specialist Hospital and Research Centre; A Alkafi, King Faisal Specialist Hospital and Research Centre; F Alzorkani, King Faisal Specialist Hospital and Research Centre; M Shehadeh, King Faisal Specialist Hospital and Research Centre; U Mwedu, King Faisal Specialist Hospital and Research Centre; W Alnajjar, King Faisal Specialist Hospital and Research Centre; B Moftah, King Faisal Specialist Hospital and Research Centre; F Mayhoub, King Faisal Specialist Hospital and Research Centre; O Noor, King Faisal Specialist Hospital and Research Centre
Abstract: The radiotherapy treatment is nowadays performed using modern treatment machines capable of delivering beams as small as 5 mm x 5 mm. In addition to the fact that the dosimetry of such small field sizes is subject to an increased uncertainty due to the weakness of traceability to reference dosimetry based on conventional Dosimetry Codes of Practice, accidents have occurred in some radiotherapy centres for having used dosimetry methods recommended by these conventional codes of practice that are not applicable to small fields. The new code of practice TRS 483, jointly published by the IAEA and the AAPM, is aiming at helping medical physicists performing the dosimetry of small static photon fields with energies less than 10 MV. The present work describes the methodology followed at King Faisal Specialist Hospital and Research Centre for testing this code of practice. The results of the measurements performed using a Cyberknife (twelve circular field sizes from 6 cm to 0.5 cm diameter) and a Tomotherapy ( seven rectangular field sizes from 5 x 40 cm² to 1 x 0.625 cm.
Four detectors were used, PTW Pin point 31016 3D and semi flex 31010, IBA CC01, and a Sun Nuclear Edge Detector. Measurements were performed in solid water phantom using the SAD and SSD configurations.
It shown that the determination of the Quality index TPR20,10(10) from measurements using small fields and applying the Palmans formalism, gave consistent results within 0.3% for the cyberknife and 0.6% for the tomotherapy.
For the determination of the field output factors, it is shown that the application of the field output correction factors published in the TRS 483 reduced the spread observed for the normal output factors from 16.6%, 8.9 % and 3.94 % to 4.2 %,1.71% and 1.81 % at 0.75 cm, 1 cm and 1.25 cm diameter for the cyberknife. For Tomotherapy the standard deviations of the mean for the Field Output Factors are respectively 4.09% and 3.24% for the SAD configuration and the smallest field sizes and 1.73% and 1.65% for the SSD configuration.
|
TAM-B.2
08:15 Development of Novel Nano-Fiber Optic Detector Technology for Real-time Detection of Beta Energy in a Pure Beta Emitter (P-32) BR Smiley*, Duke University
; NA Petry; R Gunasingha; M Therien; T Yoshizumi
Abstract: At the present time there is no real-time beta particle detection system for radioactive solutions. Our laboratory has developed a novel nano-particle based radiation detection system called a nano-fiber optic detector (nano-FOD). The purpose of this study was two-fold: (1) to test the feasibility of pure beta particle detection with P-32 (1.710 MeV max) and (2) to derive dose conversion factors using Monte Carlo simulations. A glass vial containing the P-32 sealed with a plastic screw cap was placed inside a modified lead pig with a 1mm diameter hole drilled through the tops of each to allow for insertion of the nano-FOD. Measurements were taken by submerging the nano-FOD into liquid P-32 with a 36.1 mCi/mL initial concentration and collecting the produced voltage output signal. For P-32, this was done over a 45-day period to estimate the lower limit of detection and to determine the half-life over time. From the data collected, the net signal and signal-to-noise ratio (SNR) were calculated and plotted as a function of days. The experimental half-life (13.46 ± 0.87 days) agreed well to the published half-life of P-32 (14.02 days). The dose conversion factor was computed as 0.025 ± 0.002 cGy/s per mV. The results confirmed that the nano-FOD system can be utilized as a real time beta detector in liquid solution. We believe that this technology can be utilized in small animal radiation dosimetry with beta emitters in the future. We are also actively engaged in the development of dosimetry technology where mixed beta and gamma emitters such as I-131 and Lu-177 are used.
|
TAM-B.3
08:30 Dosimetry In Pulsed Radiation Fields – Features And Measurement Data Of An Innovative Active Alarming Personal Dosimeter MA Iwatschenko-Borho*, Thermo Fisher Scientific Messtechnik GmbH
; N Trost, Thermo Fisher Scientific Messtechnik GmbH
Abstract: Today nearly all medical X-ray devices operate in a pulsed mode with a pulse length typically in the order of several milliseconds. Accelerator-based therapy involves pulses of a few microseconds and nondestructive testing (NDT) flash-radiography devices operate with even shorter pulse widths in the 10 to 50 nanosecond range. Passive dosimeters, such as film or TLD, are not affected by the time structure of these radiation fields and can correctly register the accumulated dose, but do not yield any real time dose and dose-rate information and cannot provide an alarm signal to the wearer of the dosimeter. Sensitive active alarming dosimeters on the other hand typically operate in a counting mode and may experience saturation effects during the duration of the radiation field pulse. These transient over-range events and related saturation effects may remain undetected if the electronic counters are read in macroscopic time intervals (e.g. seconds). Therefore the new Thermo Fisher Scientific TruDose personal dosimeter can operate on millisecond cycles. Consequently the transient doserate of pulsed medical X-ray devices can be correctly analyzed and eventually be dead time corrected. Temporary over-range conditions are as well discovered on a millisecond scale. Corresponding test results according to IEC 62743:2012 in pulsed radiation fields as specified in ISO 18090-1 (2015) are presented. For shorter radiation field pulses in the sub-microsecond range, special circuitry detects over-range conditions and provides an instantaneous alarm signal to alert the wearer of the dosimeter. Unnecessary dose exposure e.g. during operation of a X-ray flash device can thus be avoided.
|
TAM-B.4
08:45 Dose Analysis & Comparison For Landauer Personnel Dosimetry & Philips Dose-Wise Dose Management System D Pringle, University of Alabama at Birmingham
; S Yates, University of Alabama at Birmingham; L Johnson*, University of Alabama at Birmingham
Abstract: Direct beam contact and scatter radiation while using a regular C-arm fluoroscopic x-ray system can result in high exposure rates to those working in the operating room. Establishing an effective ALARA program that is both balanced and coherent across modalities, software and x-ray devices provides a serious challenge for the radiation safety program managers at any location. The goal is to compare and analyze results from Landauer dosimetry badges to data results from the Phillips Dose-Wise output programs. Dosimetry is placed in various spaces within the suite and then compared and analyzed to documented output data after 30 days of use. This analysis hopes to supply information that will direct the development of efficient techniques to reduce radiation exposure. Reducing unnecessary radiation exposure during medical imaging is paramount. This study trends modality and usage of X-Ray radiation at our institution.
|
TAM-B.5
09:00 Selective-reconstruction Methods and A Microscopic-system Design for Spectral Computed Tomography Q Wang*, University of Massachusetts Lowell
Abstract: Spectral CT is proposed by extending the conventional CT along the energy dimension. The state-of-the-art photon-counting-detector-based spectral CT scanners can collect photons to various energy bins. Although it has superior energy-resolution, it meanwhile suffers seriously increased noise, which not only degrades the quality of reconstructed images but also decreases the material-decomposition accuracy. In this talk, first, I would like to illustrate some constrained-optimization-based one-and two-step selective-reconstruction methods. For one-step selective-reconstruction methods, we innovatively employ a locally linear transform to convert the structural similarity as three-dimensional gradient sparsity, and correspondingly develop the optimization methods with various sparsity descriptions. For two-step selective-reconstruction methods, we establish a general multi-domain constraint based optimization framework, and concretize it with Kullback-Leibler divergence measurement in photon domain and Mumford-Shah smoothness constraint in material-image domain. In addition, we design a spectral micro-CT system with both optical-magnification and energy-identification mechanism, and correspondingly develop the high-resolution spectral-imaging methods.
|
TAM-B.6
09:15 Dosimetric Characterization of a High Efficiency Gaseous Neutron Dosemeter Consisting of 95 Multi-elements JY Kim*, McMaster University
Abstract: We present dosimetric characterization of a high efficiency gaseous neutron dosemeter consisting of 95 multi-elements using the Thick Gas Electron Multiplier (THGEM) technology. The traditional tissue-equivalent proportional counters have low detection efficiency and therefore, suffers from very low count rates for weak neutron fields. To overcome the low efficiency problem, THGEM based multi-element tissue-equivalent neutron dosemeters have been under active development at McMaster University. The multi-element detectors subdivide a gaseous sensitive volume into many smaller volumes, which increases the effective surface area of detector and hence the neutron detection efficiency in principle. Founded on our prototype multi-element detector [1] consisting of 21 sensitive volumes, we recently built a more efficient multi-element detector with 95 sensitive volumes. In order to investigate the variation in gas multiplication gain, the responses of individual single sensitive volumes as well as groups of sensitive volumes were investigated using a 238PuBe neutron source. A full dosimetric characterization of the new multi-element detector is currently underway using the McMaster Tandetron 7Li(p,n) neutron field.
[1] Z. Anjomani, Development of a thick gas electron multiplier-based multi-element microdosimetric detector, McMaster University, 2017. Available at http://hdl.handle.net /11375/21428
|
TAM-B.7
10:00 A New Era of Medical Radiation Shielding: Environmentally Friendly Lead-Free Alternate for the Attenuation of X- and Gamma Rays PJ Fenelon, Artemis Shielding,LLC
; MD Liverett, Versant Medical Physics and Radiation Safety; SE Konerth*, Versant Medical Physics and Radiation Safety
Abstract: Background and Purpose. As a byproduct of silver mining, lead has been used for many years in various different materials such as batteries, bullets, and containers. Lead’s unique properties of high density, inertness to oxidation, and abundance helped to make it a material of choice for radiation shielding. By the turn of the twentieth century the occupational toxicity was becoming widely recognized and the worldwide public health strategy recommended completely banning the use of lead where appropriate replacement is available. With the rapid growth of radiation produced diagnostic imaging and radiation-induced therapy, companies are interested in finding an alternative, non-toxic options for the attenuation of X- and gamma rays for patient and personal safety as well as internal shielding for equipment.
Methods. Artemis materials have been tested by K&S Associates, Inc. to confirm HVL attenuation by multiple x-ray beam energies following published procedures for X-rays and radioisotopes using both narrow and a modified broad beam geometry according to procedures published by AAPM and IEC 61331-1.
A chart will be presented which shows this data, additional data will also be given which gives exposure rates (attenuation) measured clinically and in the field.
Conclusions. The Artemis material exhibits good attenuation properties across multiple energies. This has been shown through lab testing and experimental exposure rate measurements. This material can be successfully used in clinics and industry to replace traditional lead shielding
|
TAM-B.8
10:15 The Radiation Safety Officer as an Advocate for Patient Safety TL Morgan*, Versant Medical Physics
Abstract: The role of a Radiation Safety Officer (RSO) is to maintain radiation exposures As Low as Reasonably Achievable (ALARA). Traditionally, the focus has been on reducing or eliminating unnecessary exposure of employees, visitors and members of the public to ionizing radiation generated by the licensee’s operations. Over the last three decades there has been increasing concern raised in the biomedical literature on the potential risks of radiation exposure to patients undergoing diagnostic medical imaging procedures. This paper will discuss the need for and processes by which RSOs can expand the focus of a medical radiation safety program to include advocacy for applying the principles and practices of ALARA to patient safety. The presentation will focus on a proactive approach that includes self-education of RSOs about online educational resources, active engagement with senior management, education of stakeholders including physicians, administrators and technologists, and training. The goal is to develop an organizational safety culture that applies the traditional radiation protection principles of justification, optimization and dose limitation to patients undergoing diagnostic imaging procedures.
|
TAM-B.9
10:30 Simplifying the Identification and Management of Radiation Protective Apparel JP Ring*, Beth Israel Deaconess Medical Center
; J Jozokos, Beth Israel Deaconess Medical Center; J Mungia, Beth Israel Deaconess Medical Center; J Bohn, Tego, Inc
Abstract: Managing Radiation Protective Apparel (RPA) at a large academic medical center can be difficult and is even more so with The Joint Commissions (TJC) increased attention. Most RPA are not assigned a unique identification number or permanent identification marker making it difficult to track inspection history. The use conditions and RPA fabric make it difficult to fix labels that identify the RPA or the most recent testing. Many of the labeling systems used either fall off, wear out or scratch and cut the user. To further complicate reliable testing, users may store RPA in personal lockers or move them from clinic to clinic making it difficult to locate a piece for testing. As a result, it is necessary to visually inspect most surfaces of each RPA numerous times a year to identify pieces that need to be tested.
To address these issues, we worked with a vendor specializing in digital asset management. The vendor developed an intelligent high-memory-RFID tagging solution, complete with a cloud data hub. The vendors smart tag stores the inspection history of each RPA, has a QR code that can be used to confirm inspection status by a layperson, and a reliable tag adhesive with durable outer protective layer to protect the identification number and QR code. With this system, a handheld RFID scanner paired to a smart phone or tablet runs an application that enables users to identify RPAs on a rack or in lockers that need to be tested. When the scanner finds a piece that is either due or past due for inspection, an alert is displayed next to the RPAs swatch making it easier for the user to collect the piece for testing. Detailed information on the specific RPA piece and the entire testing history is stored in the RFID tag and synched to the cloud data hub. The data accessibility makes it easy to report testing metrics, performance history and develop trending metrics. The data hub can be used to report the history of a piece of RPA for TJC inspectors and clinic staff can use a smartphone QR code reader to show the current status.
|
TAM-B.11
10:45 131I-Iomab-B Blood Sample Handling and Occupational Radiation Extremity Exposures F Safavi, Actinium Pharmaceuticals, Inc.
; DR Fisher*, Versant Medical Physics and Radiation Safety; S Konerth, Versant Medical Physics and Radiation Safety; Q Liang, Actinium Pharmaceuticals, Inc.; V Reddy, Actinium Pharmaceuticals, Inc.; MS Berger, Actinium Pharmaceuticals, Inc.
Abstract: Background and Purpose. Elderly leukemia patients are being treated using high-dose radioimmunotherapy with iodine-131-anti-CD45-Apamistamab (Iomab-B, Actinium Pharmaceuticals, Inc). This SIERRA trial phase III clinical trial is currently being conducted at 19 major medical centers in the U.S. and Canada. Treatment involves intravenous infusion of 12.9 to 38.1 GBq of the I-131 pharmaceutical, which results in I-131 activity in blood samples that are collected at various times post-infusion. Nursing staff often express concerns about handling radioactive samples. The purpose of this work was to evaluate occupational radiation exposures to the hands and fingers of clinical staff involved in collecting and handling radioactive blood specimens from patients. Methods. Radiation doses were calculated to hands of health care personnel involved in specimen collection. Doses to skin were calculated using VARSKIN4 based on the known infused activities, retention half-times in patient blood, time spent during handling, and specimen geometry, container thickness, density, and distances. Results. Calculated radiation doses to hands of nursing personnel involved in multiple sample collections were insignificant to small (less than 0.1 mGy). For comparison, the 10CFR20 regulatory limit (occupational) for extremities is 500 mSv. Conclusions. This work showed that radiation exposures to hands for clinical staff involved in blood sample collections from patients infused with I-131-Iomab-B in the SIERRA trial is minimal and is not a safety concern. Support. Actinium Pharmaceuticals, Inc., New York, New York.
|
TAM-B.12
11:00 Evaluating Feline Release Criteria Following Iodine-131 Treatment For Hyperthyroidism AD Davila*, Louisiana State University
; JF Fletcher, Louisiana State University; KM Matthews, Louisiana State University School of Veterinary Medicine; WW Wang, Louisiana State University
Abstract: Hyperthyroidism is a common endocrine disorder for both humans and cats. Of the treatment options available (i.e., medication, radionuclide therapy, surgery, and dietary therapy), radionuclide therapy with iodine-131 is the treatment of choice. However, the eight-day half-life of iodine-131 makes the patient a possible radiation health risk to others. Despite receiving lower doses, typically 2-4 mCi, feline patients require mandatory hospitalization following administration. In contrast, human patients are typically released on the same day of treatment if the administered dose is less than 33 mCi. In addition, the release criteria of human patients are specified in 10 CFR 35.75, which mandates a limit of 5 mSv (total effective dose equivalent) to the maximally exposed person of the general public. The release of feline patients is regulated by 10 CFR 20.1301, which mandates a limit of 1 mSv (total effective dose equivalent). This discrepancy between humans and cats is not explicitly explained or justified in the available literature. The more restrictive release criteria can place a burden on both the veterinary staff and the pet owner. By measuring the exposure rates on the cats, determining potential removable contamination from the cats, and estimating excreting activity of the litter and feces of the cats, the current release criteria for feline patients can be adequately evaluated.
|
TAM-B.14
11:15 Health Physics Analysis of Cs-131 Mesh Implants for Colorectal Cancer LA Chang*, Houston Methodist HospitalH
; P Patel, Houston Methodist Hospital; H Alvarez, Houston Methodist Hospital; EM Quan, Houston Methodist Hospital
Abstract: In November 2018, Houston Methodist performed two Cs-131 mesh implants for colorectal cancer patients. One was performed robotically, while another was performed as part of an open-cavity surgery. This latter procedure was amongst the first ever performed of such complexity which also included kidney replacement and vascular reconstruction. Open-cavity surgery presents a unique opportunity to assess radiation dose to the surgeons in the operating room. The mesh had to be cut before insertion adding radioactive dose concerns as well as potential written directive changes. In this presentation, we assess the pre-, in-, and post-procedure steps that were taken from a health physics perspective for these implants. Pre-procedure steps included license compliance and floor training. Because of the nature of the procedure, training needed to be performed for floors that had no prior exposure to radiation procedures. During the procedure, the radiation safety team was in the operating room during the insertion and present radiation safety observations and measurements taken in the room to assess dose to the surgery team. We also review post-implant follow-up measurements including nurse and public exposure, detailing potential complications such as the patient being unable to turn over when the mesh was towards the back of his body. Cs-131 implant release limits were not available in Nuclear Regulatory Commission Guide 8.39 and thus had to be calculated. The open-cavity patient never exceeded these thresholds post-operation and if not for the complex nature of the surgery was able to be released from a radiation standpoint. Over 95 percent of the personal dosimeters came out minimal as did area badges on the final nursing unit the patient stayed at. Another issue that developed was the patient who received the mesh implant robotically was rejected from another hospital because of the radioactivity inside the patients body.
|
