WAM-B - Medical Health PhysicsRoom: B
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| Chair(s): John Jacobus, Michael Stabin
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WAM-B.1
Dealing with a Case of Deliberate Misuse of Radioactive Materials S. H. King, M.S. Hershey Medical Center
; K. L. Miller, M.S. Hershey Medical Center
Abstract: An incident occurred that involved the self-administration of a radiopharmaceutical by a technologist that did not have approval from an authorized user. After discovery, the incident was voluntarily reported to the U.S. Nuclear Regulatory Commission by the licensee. An ensuing fourteen month investigation by the NRC’s Office of Investigation (OI) determined that similar administrations had occurred on two additional occasions over the past ten years. The licensee was notified by the NRC of a possibility of three citations and escalated enforcement action. The licensee was offered a choice of either (1) attending a Pre-decisional Enforcement Conference, or (2) requesting Alternate Dispute Resolution (ADR) with the NRC in an attempt to resolve any disagreement on whether a violation occurred, the appropriate enforcement action, and the appropriate corrective actions. The licensee chose the Alternate Dispute Resolution. This presentation reviews this incident, the actions taken upon discovery, the results of in-house investigations and the subsequent modifications to policies, procedures and training programs. It also reviews the results of the ADR meeting, the agreement between NRC and the licensee and the follow-up actions taken.
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WAM-B.2
Photodynamically Inflicted Biomolecular Damage And Cell Death Of Malignant Melanoma Cells In Culture Abdel-Megid Mamoon, EAEA
; Tejas Telivala, BNL; Randy Smith, BNL; Q. Wang, BNL; Lisa Miller, BNL
Abstract: Malignant melanoma is a very serious skin cancer that if not discovered early and treated by surgery can become fatal. The incidence of the disease is increasing and is almost doubling every two decades. Photodynamic treatments have been found effective in the treatment of several skin conditions. Photodynamic treatment involves the use of an appropriate photosensitive dye that is not toxic by itself to living cells and is taken up by normal and malignant cells. The dye leaves the normal cells in a short time but stays longer in malignant cells. Light of appropriate wave length, which is maximally absorbed by the used dye, is shined at the cells from a laser resulting in the liberation of singlet oxygen which is very toxic to the cells. Experiments were carried out at Brookhaven National Laboratory and cultured human malignant melanoma cells were subjected to weak photodynamic treatment using the dye indocyanine green at a net concentration of 100 μM and using Ti-Sapphire laser (780 nm), with increasing light dose up to 150 joules. There was increasing melanoma cell death with dose as shown by the vital stain trypan blue. At an exposure of 150 joules there was 20% cell death compared to control cultures. Fourier Transform Spectromicroscopy using infra red radiation, from a synchrotron, was carried on control and treated melanoma cultures and revealed that there were changes in the spectra of biomolecules, the large effects being in the protein and nucleic acid components. These results hold promise for greater effects with stronger photodynamic treatments.
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WAM-B.3
Struggling With Radiation When The Subject Is Your Child Alan Fellman, Radiation Safety Academy, Inc.
Abstract: As an undergraduate and graduate student, I prepared for a career in radiation safety as a certified health physicist. This of course included significant training related to the health effects associated with ionizing radiation. In my role as an instructor, I have taught numerous radiation safety officers and radiation workers about the health effects of radiation. Indeed, I believe I can summarize the content of NRC Regulatory Guide 8.29 in my sleep. However, no amount of academic understanding of radiation health effects and radiobiology could fully prepare me to handle the issue as a father when I found myself confronted with deterministic radiation effects in my ten year old son.
What goes through the mind of an educated, experienced health physicist when his child's hair is on the bathroom floor? How does the book knowledge help? How does the book knowledge hinder? What questions are asked, and where can one find some answers? One remarkable on-going journey examining these questions is discussed.
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WAM-B.4
New Jersey's Quality Assurance Regulations: A Physicist's Perspective Ira Garelick, St. Barnabas Medical Center, Livingston, NJ
Abstract: In January 2001, the New Jersey Department of Environmental Protection enacted new regulations for
registrants of machine sources of radiation. These required all users of diagnostic x-ray equipment to implement and maintain a Quality Assurance program. A unique aspect was that "public" participation was used for drafting these regulations. The State DEP also implemented these regulations in a non-traditional manner. The goals of the Quality Assurance program are to reduce radiation exposure to patients and to improve the overall image quality. Conditions of this program include Quality Control tests of various frequencies that the site is required to perform. Tests are described for radiographic, fluoroscopic, and computed tomography systems. An annual medical physics survey is also required for each facility. This survey includes basic machine calibration evaluations, determination of representative entrance skin exposures, and a review of the site's QA program. Not surprisingly, large variations in program compliance have been observed. In general sites that have licensed x-ray technologists do very well, and sites that have physicians or non-technical staff performing tests do not. A review of these findings and an opinion of whether or not the program goals have been met will be presented. Suggestions for revisions to the program will also be discussed.
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WAM-B.5
Training program for occupational dose reduction in a positron emission tomography (PET) imaging facility A. Robert Schleipman, Brigham and Women's Hospital
Abstract: At our institution, the mean annual effective dose equivalent for nuclear medicine technologists has risen from 4.41 mSv in 2002 to 6.16 mSv in 2004. ALARA (As Low As Reasonably Achievable) I threshold warnings for staff are frequently submitted. The model procedures of the US Nuclear Regulatory Commission sets this dose value as an “action level” for which the Radiation Safety Officer should investigate, and formulate a plan to reduce the probability of reoccurrence. The trend is worrisome; particularly as the highest doses have been incurred by those performing positron-emission/computed tomography (PET/CT) scans, which have replaced many conventional scintigraphic exams. The implemented dose reduction plan has been to review and incorporate personnel monitor dose values, and real-time dosimetry for task-based and operator-specific measurements of exposure, into a training program that emphasizes optimal laboratory practices with radiobiology and PET-specific radiation protection principles. Our hypothesis that this will result in better outcomes is tested with pre-and post-training exams of staff, and comparison of their dosimetry results.
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WAM-B.6
Benchmark Data for Radiation Doses in Pediatric Cardiac Catheterization Procedures: Basis for Establishing Reference Dose Levels Abdalla Al-Haj, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
; Aida Lobriguito, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia; Walid Rafeh, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia; Abdulkarim Al-Humaidan, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
Abstract: Cardiac catheterization is among the interventional radiology procedures considered to give high doses to patients. These procedures are also performed on pediatric patients and there are limited published data on radiation doses. The study determines the dose area product values from records of pediatric patients in age group 0,1,5 and 10 years old at King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia. Four common procedures are selected, namely: diagnostic, pulmonary, COA dilatation and PDA occlusion. The average DAP and cumulative dose values per procedure for each age group are analyzed for correlation with patient equvalent cylindrical diameter, weight, and fluoroscopy time. Factors influencing the variation in doses are investigated. Results show that the kVp varies by +/- 1 kVp for AP projection and by +/- 3 kVp for lateral projection in all procedures. The mA for lateral and oblique is about 65% higher than for AP. The DAP values (cGy-cm2)for COA dilatation, diagnostic, PDA occlusion and pulmonary are 1765, 669, 2851 and 1326 respectively. The 5 year old age group has the highest DAP and cumulative dose values. In this group, 65% of the patients underwent COA and PDA procedures. The study aims to identify the procedures that give an estimated dose that approach the threshold value of 2 Gy for skin erythema; compare the estimated doses with published data and recommend dose reduction methods. It also aims to use the results of the dose assessment as the basis for establishing the reference dose levels.
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WAM-B.7
Calibration of Radiochromic Films for Patient Dosimetry in Interventional Radiology Abdalla Al-Haj, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
; Kostas Chantziantoniu, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia; Aida Lobriguito, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia; Nabil Iqeilan, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia; Charlie Lagarde, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
Abstract: Patient entrance skin dose assessment in interventional radiology procedures has been very complex because of varying projections that the procedures require. The use of verification films with extended dose range was recommended to generate the dose curves during patient irradiation. The use of radiochromic films when properly calibrated found numerous advantages in patient dosimetry in interventional radiology procedures because of the ability to give accurate dose measurements in the range of less than 1 Gy to about 8 Gy and do not require film processing. The study aims to analyze the effects of beam energy, dose fractionation and densitometer response on the calibration of radiochromic films. The International Specialty Products (ISP) GAFCHROMIC XR type R films were used in the study. The filmstrips were irradiated using a conventional radiograpy and an angiography unit at various doses ranging from 20 mGy to about 8 Gy. The beam quality in terms of the HVL was taken from the routine quality control test results. The air kerma was determined using a reference standard Radcal Model 9010 with Model 10X5-6 ionization chamber corrected for distance. A film and chamber holder was fabricated using a perspex material to ensure a fixed geometry. The filmstrips were irradiated using kVp settings of 65, 90, 100 kVp and above. Calibration curves were generated using the optical density (OD) readings. Results showed that the response of the film is not energy dependent for low doses ranging from 30 to 700 mGy where the coefficient of variation (COV) in OD is about 5 to 12% but starts to show a slight dependence for high doses above 2 Gy (COV=20%). The effect of dose fractionation was analyzed by comparing the film response for different doses using the conventional radiography unit where doses were delivered at about 10-min interval using 110 kVp setting with the response for doses delivered at one time using the angiography unit. Results showed no significant difference (5%) in the OD values. The calibration curves of the OD values versus the dose for all kVp settings were fitted and obtained the r2 value of 0.99. The minimum dose that the densitometer can give an OD value that is above the base+fog was about 50 mGy.
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WAM-B.8
Occupational Radiation Dose in Stress Myocardial Perfusion Imaging: Comparison Between 82Rb and 99mTc-MIBI A. Robert Schleipman, Brigham and Women's Hospital
; Frank Castronovo, Jr, Brigham and Women's Hospital, Harvard Medical School
Abstract: Prevailing wisdom indicates that PET imaging greatly increases radiation exposure for imaging staff, though the biophysical properties (and resultant radiation exposures) of positron-emitters vary considerably. We measured and compared the occupational dose burden associated with pharmacologic stress myocardial perfusion imaging using both 82Rb and 99mTc-MIBI. A pressurized ion chamber was used to monitor radiation exposure in 50 rest or pharmacologic stress exams. Staff exposure during pharmacologic stress in 20 other patients injected with 99mTc-MIBI was also measured. During 82Rb infusion and PET/CT acquisition the mean technologist dose was 0.45±0.25 µSv. For exercise staff performing stress testing at variable distances from the injected patient, exposure was equivalent to background. Exercise staff dose for stress testing at 0.5 m from the patient, commencing 7 minutes post 82Rb infusion, was estimated at 0.4 µSv. In comparison, dose for stress testing with 99mTc-MIBI, measured at variable distances from the patient was 1.07±0.32 µSv. Simulating response to medical emergency or close monitoring of acutely ill patients, the mean cumulative dose, measured at 0.5 m from the patient at 0-7 minutes of 82Rb infusion, totaled 19.1±5.8 µSv. Occupational radiation doses for all PET/CT imaging tasks, and routine stress testing patients are lower with 82Rb than measured or published values for 99mTc-MIBI. However, close proximity to the patient during or immediately following 82Rb infusion is not advised, as the radiation dose is significantly higher, thus underscoring the necessity for routine radiation protection practice of maintaining distance from the source.
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WAM-B.9
Factors Influencing the Radiation Doses in Pediatric CT Procedures Abdalla Al-Haj, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
; Aida Lobriguito, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
Abstract: The UNSCEAR 2000 Report has indicated that computed tomography (CT) procedures contribute to high population doses. In CT imaging different types of CT scaners are used for adult and pediatric patients. AT King Faisal Specialist Hospital & Research Centre,Riyadh, Saudi Arabia, there were about 2,600 pediatric patients that underwent chest and abdomen/pelvis CT procedures in the year 2004. A standard protocol is used for these two procedures where scan parameters vary with the weight of the patient. There are seven models in the protocol for weights ranging from 0 to 70 kg. This study was performed on Saudi children in age groups of 0, 1 and 5 years old. The mean weight data, the measured CTDI of 2 CT spiral units of different brands and models and the scan parameters in the standard protocol were used in the dose assessment. The effective dose for each age group was estimated by using the CT dosimetry excel program which utilizes the Monte Carlo normalized organ doses (NRPB SR 250) and the scaling factors of Le Heron.The effects of weight, equivalent cylindrical diameter and output of the CT units on doses were investigated.The estimated effecive dose of males for age group 1 year old was about 12% higher than the females for chest and about 5% for abdomen/pelvis. The 1 year old age group has an effective dose for chest procedure that is about 18% higher than the 5 years old age group. This study aims to determine the parameter that gives a high dose variation and recommend methods for dose reduction.
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WAM-B.10
A Novel Dosimetry Method for Cone Beam CT: Dose Comparison between Cone Beam CT and Conventional CT T. Yoshizumi, Duke University
; G. Toncheva, Duke University; G. Nguyen, Duke University; S. Yoo, Duke University; D. Godfrey, Duke University; P. Munro, Varian Medical System, Palo Alto, CA; F.-F. Yin, Duke University
Abstract: We have developed a new CTDI concept (ŕ la weighted CTDI; alaCTDIw), and have used this concept to measure and compare doses from cone-beam CT and conventional CT equipment. This new CT dose index (alaCTDIw) better accounts for scattered radiation in cone-beam CT geometry, but uses standard phantom geometry, which is important when comparing different CT systems. Dose measurements compared alaCTDIw between the cone beam CT system based on an On-Board Imager (Varian Medical System, Palo Alto, CA) and a conventional CT scanner (CT/i, GE Healthcare, Milwaukee, WI). Clinical scan protocols at our institution for head and body were used. For cone-beam CT, thermoluminescence dosimeters (Harshaw TLD-100, Thermo Electron, Santa Fe, NM) were employed. For CT scanner, high sensitivity MOSFET dosimeters (TN-1002RD, Thomson-Nielson, Ottawa, Canada) were used. Individual TLD chips were calibrated using simulated cone beam CT beams (HVL 5.5 mm Al @125 kVp); MOSFET detectors were calibrated with simulated CT beams (HVL 7.2 mm Al @120 kVp).For head scans, measured alaCTDIw were 8.97 +/- 0.40 cGy and 7.06 +/- 0.23 for Varian cone beam CT and GE CT/i respectively. For body scans they were 3.79 +/- 0.14 cGy and 4.31 +/- 0.29 cGy respectively. The proposed new alaCTDIw addressed the following: (a) large area cone beam geometry was incorporated in the measurements, (b) realistic scatter patterns from multi-slice helical CT beam were incorporated, (c) we observed that the cone beam alaCTDIw values were comparable to those from GE CT/i for our clinical head and body scan protocols at our institution, and (d) new definitions can be incorporated in clinical medical physics with MOSFET technology with little efforts.
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WAM-B.11
Radioactive Scorpion Venom Therapy Alan M Jackson, Henry Ford Health System
; Beth Harkness, Henry Ford Health System
Abstract: Scorpion venom is a neurotoxin and has been found to have an affinity for glioma cells (brain cancer). Based on that affinity, our site joined a phase 2 clinical trial in partnership with the Transmolecular Corporation using a synthetic version of the scorpion venom peptide labeled with I-131 (the 131I-TM-601 protocol). After resection of the tumor and selection for eligibility, patients are randomized into two groups. One group receives the therapy three times over a span of 3 weeks while the other group receives the therapy 6 times over a span of 6 weeks. The weekly administration amount, 1.48 GBq (40 mCi), is identical for each group but the patients enrolled in the six week trial receive twice the dose of the patient in the three week trial. This therapy is designed to be an outpatient procedure. Patient release presented a number of difficult challenges due to limited knowledge about the biological clearance of the compound and long time span of the therapy. Due to recent regulatory directives regarding dose to members of the public from radiation therapy, a special emphasis was placed on validating the dose to members of the public. Standard and electronic dosimetry was provided to family members to monitor their doses. Based on these results it is evident that patients in the six week trial must be carefully monitored and controlled.
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WAM-B.12
Iodine-131 Therapy And The Dialysis Patient M.J. Bohan, Yale-New Haven Hospital
; R.L. Richardson, Yale-New Haven Hospital
Abstract: The management of dialysis patients, who also have thyroid diseases requiring Iodine-131 therapy, will be presented. Patients with renal disease have a reduced ability to excrete Iodine-131. This change in excretion kinetics requires that standard administered doses must be modified to reduce needless whole body doses to these patients. In addition, dialysis patients present special problems to the Health Physicist in managing excretion waste byproducts. This paper will summarize the experience gained in treating thyroid disease patients on both hemodialysis and peritoneal dialysis.
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