bluuebunny/crossref_metadata_2025_split huggingface dataset:
Risk of Pregnancy‐Related Hypertension Within 5 Years of Exposure to Drinking Water Contaminated With Escherichia coli O157:H7
Authors: Moist Louise , Sontrop Jessica M. , Garg Amit X. , Clark William F. , Suri Rita S , Gratton Robert , Salvadori Marina , Nevis Immaculate , Macnab Jennifer J. 
Published: April 2010

J Clin Hypertens(Greenwich). 2010;12:613–620. © 2010 Wiley Periodicals, Inc.The authors evaluated the risk for pregnancy‐related hypertension among previously healthy women who conceived within 5 years of exposure to drinking water contaminated with Escherichia coli O157.H7 in Walkerton, Canada (2000). Chronic hypertension was defined as systolic/diastolic blood pressure ≥140/90 mm Hg before 20 weeks gestation; gestational hypertension was defined as new onset systolic/diastolic blood pressure ≥140/90 mm Hg ≥20 weeks gestation. The incidence of hypertension was compared between women who were asymptomatic during the outbreak to those who experienced acute gastroenteritis. Blood pressure data were available for 135 of 148 eligible pregnancies. The adjusted relative risks for chronic and gestational hypertension were 1.5 (95% confidence interval [CI]: 0.3–7.7) and 1.0 (95% CI: 0.4–2.5), respectively. Mean arterial pressure before 20 weeks gestation was 2.7 mm Hg higher in women who had acute gastroenteritis (95% CI: 0.05–5.4). A trend toward higher chronic hypertension and mean arterial pressure in early pregnancy was observed among women who experienced gastroenteritis after exposure to bacterially‐contaminated drinking water.
SU‐AA‐BRD‐02: Licensure and the Practicing Medical Physicist: AAPM Licensure Regulations Guidance Document
Authors: Pizzutiello R 
Published: April 2010

AAPM has made a significant commitment of priorities and resources to advance licensure in the 46 states that do not presently license medical physicists. Pending federal legislation may motivate States to implement licensure on a short timetable.The AAPM Licensure Regulations Guidance Document is among the significant steps in this effort completed by the Joint Medical Physics Licensure Sub‐Committee (JMPLSC). This document was created modeled after the licensure laws in Texas, New York and Florida.This session will review the big picture of how licensure is accomplished, and how licensure will affect the practicing medical physicist. Key provisions of the Guidance document will be presented with an emphasis on practical implementation issues.
SU‐AA‐BRD‐03: A New “CARE” and a New Focus
Authors: Fairobent L 
Published: April 2010

As you are aware we have a new administration and a new congress and health care reform is a priority of both. On July 15, 2008 the Medicare Improvements for Patients and Providers Act of 2008 (MIPPA) was enacted making changes to the Medicare program. There has been a lot of confusion over MIPPA and how it relates to the goals we have for the “CARE” legislation (which stands for Consistency, Accuracy, Responsibility, and Excellence in Medical Imaging and Radiation Therapy (CARE) Act of 2009”). Questions have been raised do we still need to pursue the CARE legislation. This session will review the relationship between MIPPA, proposed CARE legislation and the overall AAPM and ACMP efforts to efforts to ensure that medical physics is performed by Qualified Medical Physicists.Learning Objectives:1. To review the provisions of the Medicare Improvements for Patients and Providers Act of 2008 (MIPPA).2. To discuss the between MIPPA and the proposed “Consistency, Accuracy, Responsibility, and Excellence in Medical Imaging and Radiation Therapy (CARE) Act of 2009.”3. To review the overall AAPM and ACMP efforts to ensure that medical physics is performed by Qualified Medical Physicists.
SU‐DD‐A3‐01: Swallowing‐Induced Target Motion and Dosimetric Impact for Head and Neck Cancer Radiotherapy as Assessed by Dynamic MRI
Authors: Paulson E , Bradley J , Ahunbay E , Wang D , Li X 
Published: April 2010

Purpose: Deglutition (i.e., swallowing) results in dynamic changes in the geometry of aerodigestive tract anatomy, which may affect the doses delivered to targets and critical structures in head and neck cancer radiotherapy. The purpose of this study was to determine (1) whether MRI could be used to capture the motion of swallowing, (2) the geometrical variation induced by deglutition, and (3) the dosimetric impact of deglutition on head and neck cancer radiotherapy. Method and Materials: Five patients with aerodigestive tract cancer were imaged in treatment position on a 3.0T Siemens Verio scanner. Two time series of single‐slice sagittal images were acquired using a 2D FLASH sequence (6.667 frames/sec with and 3.257 frames/sec without parallel imaging). Swallowing frequency and duration were determined from time series data and motion was assessed using contours of gross tumor volumes (GTV) drawn during one swallowing event. Using each patient's IMRT plan and swallowing frequency and duration results, dosimetric impact was assessed by worst‐case scenario of the GTV moving completely out of the treatment field during deglutition. Results: Deglutition was non‐periodic, with frequency and duration ranging from 2.89–24.18 mHz and 3.86–6.10 sec. Dynamic changes in GTV position, size, and shape resulted from deglutition, ranging from 0–28.36mm and 0–60% change in area of GTV projection. Deglutition resulted in a 1.4–14.3% reduction in dose delivered to GTV. Conclusion: MRI is able to capture the motion of swallowing with or without the use of parallel imaging. Deglutition is non‐periodic, and results in dynamic changes in GTV position, size, and shape. The overall impact of deglutition on dose delivery for head and neck cancer, although generally insignificant, can be non‐negligible for patients with extremely high swallowing frequency and long duration.Conflict of Interest: Partially supported by Siemens Healthcare and the MCW Cancer Center Meinerz Fellowship.
SU‐FF‐I‐31: A Novel Application of MRI‐Polymer Gel Dosimeter for Measurement of CTDI On X‐Ray 64 Slices CT Scanner
Authors: Riyahi‐Alam N , Karimiafshar L , Ay M , Pourfallah T Alahvirdi , Allahverdi M 
Published: April 2010

The purpose of this study is to measure the Computed Tomography Dose Index (CTDI) of GE multi‐slice CT scanner(64‐slice) using polymer gel dosimetry based on MRI imaging (MRPD). CTDI is the sum of point doses along the central axis and estimates the average patient dose during CT scanning.For measuring CTDI, after designing and fabricating the phantom and preparing MAGIC‐gel, MRI imaging using 1.5 T Siemens MRI scanner was performed with imaging parameters of ST=2mm, NEX=1, TE=20–640 ms and TR=2000 ms. CTDI was measured with a 100 mm ion chamber (CTDI100) and also MAGIC gel with MRPD method for 10 mm and 40 mm CT scan nominal width.With measuring CTDI100 for 10 mm and 40 mm nominal slice width of multi‐slice scanner with the use of both ion chamber and MAGIC gel, the results showed that ion chamber underestimates CTDI100 by 28.71% and 14.03% compared to gel respectively for 10 mm and 40 mm.It was concluded from this study that gel dosimeters have the capability to measure CTDI in wide beams of multi‐slice CT scanners whereas 100 mm standard ion chamber due to its limited length is not reliable even for 10 mm beam width. In addition, due to 3 dimensional nature of gel dosimetry, by using MAGIC polymer gel it is possible to obtain a lot of important information from the mentioned profiles such as the actual slice thickness and z axis geometric efficiency. In addition to the stated parameters, the percent of the total homogeneity and partial homogeneity in the slice plane can be obtained only from the gel dosimetry. The results of this study show that MAGIC polymer gel based on MRI can be used as a supplementary method in measuring conventional ion chambers dosimetry especially in measurements of more than 2 mm slice width.
SU‐FF‐I‐69: Monte‐Carlo Evaluation of the Backscattering Shielding of Two EPIDs
Authors: Wang S , Gordon J , Gardner J , Siebers J 
Published: April 2010

Purpose: To evaluate two possible designs to shield the imaging panel from radiation backscattered from objects downstream of the imager. Method and Materials: Two EPID panel variants, panel 1 and panel 2, are prototyped with an in‐house EGSnrc Monte Carlo code module. These panels differ from commercial panels via the addition of composite materials within the detector panel, designed to shield the detection screen from radiation backscattered. No, medium, and strong backscattering materials are simulated via the addition of 10 cm vacuum, water and lead respectively beneath the imager geometry. Poly‐energetic energy deposition kernels for 6 and 18 MV photon beams are calculated using Monte Carlo simulation. The integrated energy is used to evaluate the signal enhancement due to the backscattering. Each kernel is convolved with 5×5, 10×10, 15×15, and 25×25 cm2 fluence profiles to determine the maximum backscatter signal deviation attributable to the added materials as a function of field size. Results: The largest signal enhancements for poly‐energetic irradiations are 2.87% and 3.07% for panel 1 and panel 2 respectively, which occur with the 18 MV incident energy and the lead backscatter. For water, the maximum enhancement is 0.74% and 1.08%. The back‐scatter signal induced deviation decreases with field size. Conclusions: Both prototype imaging panels will reduce the maximum backscatter signal enhancement to <3.1%. For typical clinical field sizes and backscattering materials, the signal enhancement should be <1%. Use of these panels could reduce the backscattering induced uncertainties and improve the reliability of measurements.Conflict of Interest: This work was funded in part by Varian Medical Systems.
SU‐FF‐I‐114: Effects of Exposure Level and Anatomical Background On Detection of Simulated Microcalcifications in Digital Mammography
Authors: Lai C , You Z , Zhong Y , Shen Y , Chen L , Liu X , Han T , Ge S , Yi Y , Geiser W , Whitman G , Yang W , Shaw C 
Published: April 2010

Purpose: To assess the influence of quantum and anatomic noises on the detection of simulated microcalcifications (MCs) on digital mammograms. Materials and Methods: Images of an anthropomorphic breast phantom (RMI 169) overlapping with simulated MCs ranging from 160 to 224 micron in size placed at various locations were acquired with an aSi/aSe flat panel based digital mammography system (Selenia) operated with Mo‐Mo target/filter combination at 28 kVp. These mammograms were exposed with 10, 20, 40, 80, 160, and 325 mAs. All images were displayed randomly on a review workstation and reviewed by five readers independently. The readers were asked to count the number of visible MCs. The ratio of visible MCs was computed for each different combination of MC size, reader and mAs setting. The performance differences in the ratios averaged from all readers between mAs levels was assessed by performing Student t‐test to compute the p values. Results: It was found that in the dense tissue region the visibility reached 90% at 10, 33 and 37 mAs for 200–212, 160–180 and 180–200 micron MCs, respectively; and at 10 mAs for 180–200 and 200–212 micron MCs and at 15 mAs for 160–180 micron MCs in the fatty region. The lower visibility in the dense tissue region may be due to the fact that the photon flux was lower in the dense tissue regions therefore requiring higher mAs setting to achieve sufficient image SNRs for detection of MCs. Our results also show that in the dense tissue region, the visibility of 180–200 micron MCs stayed at 90% at 80 mAs. This may indicate that the anatomical noise was limiting the detectability of 180–200 micron MCs.This work was supported in part by grants CA104759 and CA124585 from NIH‐NCI, a grant EB00117 from NIH‐NIBIB, and a subcontract from NIST‐ATP.
SU‐FF‐J‐06: Off‐Axis Variation of the Varian OBI Photon Spectrum and Impact On Cone‐Beam CT Image Quality
Authors: Zhang L , Lazos D , Zheng D , Pokhrel D , Williamson J 
Published: April 2010

Purpose: Bow‐tie filters used in CBCT image acquisition alter photon spectra across the radiation field. Furthermore, incident spectra vary along the longitudinal direction of an X‐ray tube due to the anode‐heel effect. The goal of this study is to characterize off‐axis spectral variation of a Varian® on‐board kV imager and to investigate its impact on the quality of reconstructed images. Method and Materials: Spectra were derived by fitting the semi‐empirical Birch‐Marshall (BM) model to narrow‐beam aluminum transmission data measured with a parallel‐plate ion‐chamber at different locations along the transverse axes of the OBI field. Photon spectra with and without filtration of the full and half bow‐tie filters were measured. Simple analytical models for deriving off‐axis spectra at arbitrary detector locations from the central‐axis spectrum were developed and validated against the measured spectra. Images reconstructed from synthetic datasets with constant and spatially variant photon spectra were used to assess both bow‐tie filter and anode‐heel spectral hardening effects on image quality. Results: The derived spectra accurately reproduced the transmission measurements with mean and maximum deviations of 0.6% and 2.5%, respectively. The anode‐heel effect is insignificant at small off‐axis angles. The variation of aluminum HVLs of spectra is less than 0.5 mm within 3° off‐axis angles. Bow‐tie filters significantly alter photon off‐axis spectra. The mean photon energies at 5° off‐axis angle with the full bow‐tie and the half bow‐tie filter are 78.7 keV and 67.6 keV, respectively, compared to the centralaxis mean energy of 60.0 keV. Conclusion: Our investigation demonstrates the feasibility of using narrow‐beam transmission measurements in conjunction with the BM model to characterize relative small off‐axis spectral variations. The spectra at arbitrary off‐axis angles can be adequately characterized by hardening the central‐axis spectra. The anode‐heel effect does not significantly alter beam‐hardening artifacts in the reconstructed images.Supported by Varian Medical Systems
SU‐FF‐J‐26: Multimodal Sono‐Contrast NIR Spectroscopy System for Breast Cancer Diagnosis
Authors: Yan K , Podder T , Huang K , Hu Y , Li J , Liao L , Yu Y 
Published: April 2010

Purpose: To present a multimodal imaging system that combines three modalities, optical spectroscopy, ultrasonography and acoustic radiation force (ARF) for improved diagnosis of breast cancer based on noninvasive interrogation of vasculature. Method and Materials: The scanhead incorporates two 1MHz focused transducers aligned orthogonally to deliver ARF in a 2.4cm region. A commercial ultrasound probe is positioned to image the focal plane. The ultrasound probe and focused transducers have two degrees‐of‐freedom, so that the focal zone can be scanned in tissue depth‐wise and laterally. Three force sensors are mounted on the breast compression plate to ensure consistent, slight compression. A fiber array (6 sources and 12 detectors) connects to the concave bottom plate of the scanhead. Sources are illuminated by two laser diodes (680 and 830nm) through a multi‐channel optical switch. Diffuse reflectance signals are collected by 12 detectors, amplified by avalanche photodiodes, and transmitted through a multi‐channel data acquisition card for analysis. The scanhead is mounted on a 360° ring gantry, which can rotate around the breast and move towards or away from the patient. A software system was implemented in Visual C++ to perform real‐time tasks, including acquisition of optical and force signals, control of optical switch and function generator, and data display. Results: The maximum exposure to laser was controlled within 0.2W⋅cm−2 (ANSI Z136.1). The ARF fields were maintained below FDA diagnostic limits (0.72W⋅cm−2) for manipulating blood flow and oxyhemoglobin concentrations at the time and location of detection, causing measurable differences in the dynamic behavior of tissue blood supply as reported by optical spectroscopy. This technique was demonstrated to be highly diagnostic in a murine tumor model. Conclusions: A multimodal system incorporating ARF, optical spectroscopy and ultrasonography has been developed to characterize breast cancers. Pilot clinical study is being carried out.Acknowledgement: Work supported by NCI Grant CA107860.
SU‐FF‐J‐36: Efficient 4D Treatment Planning Using CT Datasets Synthesized Via Deformable Image Registration
Authors: Zhong H , Fragoso M , Chetty I 
Published: April 2010

Purpose: 4D treatment planning is often a time‐intensive process, requiring a series of procedures on multiple (up to 10) CT‐datasets. We hypothesize that more efficient strategies exist for lung cancer, 4D planning, and that dosimetrically, these methods are equivalent to plans based on the typical 4D process. Method and Materials: Three strategies were tested: (a) Exhale and Inhale CT‐datasets were registered using deformable image registration (ITK “demons”) and the resulting displacement vector field (DVF) was used to “synthesize” 8 additional CT datasets, at equally spaced phases between inhale and exhale. A single dataset, based on average CT‐number of the 10 datasets was then generated for planning purposes, CTAVE_SYN. (b) Ten CT‐datasets were retrospectively reconstructed during a patient 4D scan, and an average dataset was generated for planning purposes, CTAVE_4D. (c) Dose is computed on each of the ten datasets independently, dose accumulation is performed (trilinear interpolation), to yield a “warped” 4D, benchmark dataset, CTWARPED_4D. A step‐and‐shoot IMRT plan was developed and applied to the CTAVE_SYN, CTAVE_4D, and CTWARPED_4D datasets. Dose calculations were performed using Monte Carlo (BEAMnrc/DOSXYZnrc) integrated with Pinnacle. Doses were mapped to the reference image dataset (end‐exhale) for dosimetric comparison. Results: PTV and ITV mean doses generated using the CTAVE_SYN and CTAVE_4D datasets agreed within 0.5% of each other. Mean doses generated using CTWARPED_4D agreed with the CTAVE_SYN and CTAVE_4D datasets within 1% and 1.5% for the ITV and PTV, respectively. Biological dose indices, including EUD (ITV and PTV), and NTCP and mean lung dose (normal lung tissue) were within 1% agreement for treatment plans using all 3 datasets. Conclusion: Results are suggestive that 2 CT‐datasets used to synthesize an average 4D dataset (via a DVF and CT‐number averaging) may be a feasible approach, offering the potential for improved efficiency in the lung cancer 4D planning process.Acknowledgement_NIH‐R01CA106770
SU‐FF‐T‐29: Application of Optically‐Stimulated‐Luminescence Dosimeters in Partial‐Breast‐Irradiation Brachytherapy
Authors: Paliza M Morales , Ding G , Coffey C 
Published: April 2010

Purpose: To study the application of in‐vivo optically‐stimulated‐luminescence (OSL) dosimeters in high‐dose‐rate (HDR) partial‐breast‐irradiation (PBI) brachytherapy. Methods and Materials: In PBI brachytherapy treatment planning using HDR Ir‐192, one of the organs at risk is the skin. With the recent clinical introduction of multi‐dwell position and multi‐lumen PBI treatment devices, optimization dose algorithms allow improved treatment volume (PTV‐EVAL) dose distributions. However this gain in improved tumor volume coverage may oftentimes be at the risk of increasing the overlying skin tissues to radiation tolerance doses. Hence, there is increasing concern to validate the calculated skin dose with experimental in‐vivo determinations. Using Landauer OSL chip dosimeters, we clinically measured the dose to a reference point in the skin surface and correlated this measured dose with our treatment planning computer predictions. Location of calculation points was validated using surface markers via computed tomography. Care was taken to provide 1‐cm thickness of 4 × 4‐cm2‐area backscatter‐factor material. Results: The chip dosimeters were calibrated using a 6‐MV‐linear‐accelerator‐photon beam. Mean dose measured values on two patients to date were within 3% of error with respect to the planned values. Conclusions: OSL dosimetry provided a direct way to measure in‐vivo doses for HDR brachytherapy procedures, verifying accuracy for 380‐keV average photon energy. Our treatment protocol now includes these dosimeters for estimation of skin dose. We will discuss specific energy response differences and dose calibration procedures for the OSL dosimeter for application using HDR Ir‐192 brachytherapy. Accuracy, versatility of placement and straightforward way of reading these dosimeters make them a valuable alternative to thermo‐luminescence, diode and MOSFET‐based dosimeters.Conflict of interest: This study is sponsored by Landauer, Inc., Glenwood, Illinois
SU‐FF‐T‐39: Investigating Thermal Properties of a Thermobrachytherapy Radioactive Seed for Concurrent Brachytherapy and Hyperthermia Treatments: Design Considerations
Authors: Shvydka D , Gautam B , Parsai E , Feldmeier J 
Published: April 2010

Purpose: Hyperthermia has been demonstrated to be one of the most effective radiation sensitizers. It offers significant improvement in both tumor control and survival rate after radiation therapy without considerable increase in side effects. Previous studies show that the time interval between administrations of both modalities has to be rather short, preferably, within an hour. We propose a new Thermobrachytherapy radioactive seed model, serving as a heat source for concurrent administration of brachytherapy and hyperthermia.Method and Materials: A new combination seed is based on the BEST Model , where tungsten marker core is replaced with a ferromagnetic material, capable of producing heat when subjected to external alternating electro‐magnetic field. Such a replacement does not noticeably change the dose rate distribution, and has only minor effect on the radiographic properties of the seed. A finite‐element partial differential equation solver package “COMSOL Multiphysics” was used to evaluate thermal distribution of the heat induced in the ferromagnetic core. Results: The induction heat source has relatively low efficiency due to losses associated with a considerable distance between the ferromagnetic core and induction coil. However, the temperature distribution is tunable based on the number of seeds used during the treatment, their locations, coil diameter, and the frequency of the electro‐magnetic field. A model with a solid radiographic marker is preferable for the proposed application since it offers the highest heat output. We found that the implementation of the proposed seed will require only small changes in the internal structure of a standard commercial model, and will not affect significantly the dose rate and other TG43 factors characterizing radiation distribution. Conclusion: We will present the radiation and thermal properties of the new seed model which has high potential for implementation of concurrent brachytherapy and hyperthermia.