UNYAAPMmeetingletterhead

Upstate New York Association of Physicists in Medicine, Inc.      (A Chapter of the AAPM)
Fall Meeting –Wednesday  November  18, 2009,

Loretta C. Ford Education Wing Auditorium, Helen Wood Hall

University of Rochester Medical Center,

255 Crittenden Blvd., Rochester NY 14642

 

12:00 pm – 5:00 pm    Sponsoring Vendor Exhibits:

Resonant Medical Inc.                    Varian Medical Systems                             TomoTherapy, Inc.

BrainLAB AG          CIVCO Medical Solutiosn           Upstate Linac Services, LLC                 Sun Nuclear        

                       

10:00

Business Meeting

11:30

Lunch                                                    Sponsored by  Upstate Linac Services, LLC

12:00

Refreshments and Vendor Exhibits – Sengupta Room        Sponsored by Sun Nuclear

12:25

Meeting Introduction

Walter O’Dell Ph.D., UNYAPM President

Vendor Session

12:30

Virtual Environment Radiotherapy Training (VERT)

Andy Beavis, Ph.D., Vertual Ltd.

12:45

Modern Rotational Dosimetry: 2D and 4D

Jie Shi, Ph.D., SUN Nuclear

Proffered Paper Session

1:00

The development of a region of interest (ROI) angiography system for clinical use.

Weiyuan Wang, C Ionita, C Keleshis, A Kuhls, A Jain, D Bednarek, S Rudin

1:15

Flow analysis of aneurysms treated with self-expanding asymmetric vascular stents (SAVS) using digital subtracted angiography

Ciprian Ionita, W Wang, D Bednarek, S Rudin

1:30

Task Group proposal for Simulation Training and Error Reduction in Medical Physics

Michael C. Schell, P Halverson,

D VerEllen, and A Beavis

1:50

Refreshments and Vendor Exhibits – Vestibule        Sponsored by Sun Nuclear

2:30

Demonstration and comparison of contrast and spatial resolution between Single Photon Counting and Energy Integrating modes for the newly developed high-resolution Micro-Angiographic Fluoroscopic detector

Amit Jain, A. Kulhs-Gilcrist, D. Bednarek, S. Rudin

2:48

Measuring the MTF without slits, edges, or other test objects

 

Andrew Kuhls-Gilcrist, A Jain,

D Bednarek, S Rudin

3:06

Dosimetric Correction for Lung Aperature used in Mouse Irradiation Experiments for a 250 kVp Orthovoltage Unit

 

Cameron D. Arndt, Z. Wang, N. Saito, M.B. Podgorsak

3:24

External Beam Dose Perturbation from Implanted Seeds, Fiducial Markers and Surgical Clips for Radiotherapy

 

James P. Steinman, HK Malhotra

 

3:42

An alternative method for beam output constancy measurements

Dinko Plenkovich

4:00

Refreshments and Vendor Exhibits – Vestibule        Sponsored by Sun Nuclear

                                                          Invited Speaker Session

4:25

Life time achievement award winner Introduction

Michael Schell Ph.D.,

UNYAPM President-Elect

4:30

 

David Rogers Ph.D.

5:30

Award Presentation

Walter O’Dell Ph.D., UNYAPM President


Driving Directions to the University of Rochester Medical Center, Helen Wood Hall, 255 Crittenden Blvd

Google map link

 

From the West:  New York State Thruway to Exit 47.

  -  Take exit #47/LEROY (RT-19)/ROCHESTER onto I-490 E (Toll applies) - go 19.63 mi

  -  Take exit #9B/AIRPORT onto I-390 S - go 2.9

  -  Take exit #17/SCOTTSVILLE RD. - go 0.2 mi

  -  Turn Left on SCOTTSVILLE RD(RT-383) - go 0.6 mi

  -  Bear Right on ELMWOOD AVE - go 0.7 mi

  -  Turn Right on Kendrick Rd - go 0.2 mi

  -  Turn Left on Crittenden Blvd - go 0.2 mi

Parking is available in the Visitors lot next to Helen Wood Hall, and also in Ramp Garage.

 

From Rochester Airport (ROC):

  -  Take exit #9B/AIRPORT onto I-390 S - go 2.9

  -  Take exit #17/SCOTTSVILLE RD. - go 0.2 mi

  -  from there follow the directions as above

 

From the East: New York State Thruway to Exit 46.

  -  Take exit #46/ROCHESTER/CORNING onto I-390 N toward ROCHESTER (Toll applies) - go 6.9mi

  -  Take exit #16/E HENRIETTA RD/W HENRIETTA RD (RT-15) - go 0.2 mi

  -  Turn Right on E HENRIETTA RD(RT-15A) - go 0.9 mi

  -  Bear Right on MT HOPE AVE(RT-15) - go 0.2 mi

  -  Turn Left on Crittenden Blvd - go 0.3 mi

 

From the South:  390 North and follow the directions above when coming from the East.

 

 

 

Text Box: Visitor
Parking

 

                                       

UNYAPM FALL 2009 MEETING PROCEEDINGS

University of Rochester Medical Center, Helen Wood Hall, Rochester, NY

November 18, 2009

 

Virtual Environment Radiotherapy Training (VERT)

Andy Beavis, Ph.D., Vertual Ltd.

                                                                                                                              

 

The development of a region of interest (ROI) angiography system for clinical use

Weiyuan Wang, Ciprian Ionita, Christos Keleshis, Andrew Kuhls, Amit Jain, Daniel Bednarek, Stephen Rudin

Toshiba Stroke Research Center, SUNY Buffalo, Buffalo NY

Due to the high-resolution needs of angiographic and interventional vascular imaging, a Micro-Angiographic Fluoroscope (MAF) detector with a Control, Acquisition, Processing, and Image Display System (CAPIDS) was installed on a detector changer which was attached to the C-arm of a clinical angiographic unit.  The MAF detector provides high-resolution and real-time imaging and consists of a 300 µm CsI phosphor, a dual stage micro-channel plate light image intensifier (LII) coupled to a fiber optic taper (FOT), and a fast-frame-rate, progressive-scan, frame-transfer CCD camera providing 1024x1024 pixels with 12 bit depth.  The changer allows the MAF or a Solid-State X-ray Image Intensifier (SSXII) region-of-interest (ROI) detector to be inserted in front of the standard flat-panel detector (FPD) when higher resolution is needed during angiographic or interventional vascular imaging procedures.  The CAPIDS developed and implemented using LabVIEW software provides a user-friendly interface that allows control of several clinical radiographic imaging modes using the MAF or SSXII including: fluoroscopy, roadmapping, radiographic mode, and digital-subtraction-angiography (DSA).  Additional features of CAPIDS, including recursive filtering, contrast enhancement, patient registry and image archival have been implemented and should facilitate the clinical use of the MAF- or SSXII-based dual-detector system.  The total system has been used for image guidance during endovascular image-guided interventions (EIGI) using prototype self-expanding asymmetric vascular stents (SAVS) in over 10 rabbit aneurysm creation and treatment experiments which have demonstrated the system's potential capability for future clinical use.

                                                                                                                              

Flow analysis of aneurysms treated with self-expanding asymmetric vascular stents (SAVS) using digital subtracted angiography

Ciprian N. Ionita, Weiyuan Wang, Daniel R. Bednarek, Stephen Rudin

Department of Neurosurgery, SUNY Buffalo, Buffalo NY

Purpose: To quantify hemodynamic modification in animal model aneurysms caused by image-guided deployment of a new self-expanding asymmetric vascular stent (SAVS) using x-ray contrast digital subtraction angiography (DSA) thus providing an indication of expected treatment outcome.

Materials and Methods: A nitinol-SAVS containing a low porosity patch to cover only the aneurysm neck was used to treat five rabbit-model aneurysms. Contrast flow in the aneurysm dome was recorded before-treatment, and after-treatment, using rapid-sequence (15 fps) DSA. The DSAs were analyzed using time-density curves (TDC) measuring the contrast in the aneurysm as a function of frame-time for each case. The TDCs were normalized to the maximum value of the initial curve (before-treatment).

Results: Before-treatment TDC’s showed clearance of the contrast from the aneurysm dome in less than 3 seconds indicating strong blood flow in the dome. Post-treatment TDC’s showed in 3 of 5 cases negligible contrast entering the aneurysms (almost 100% drop in the TDC peak), 1 of the 5 had strong inflow followed by prologue contrast residence in the dome, and the last of the 5 had moderately reduced flow (75% of the initial peak), fast clearance, however only a remnant neck was observed at 30 day follow-up.  TDC’s generated from the DSA acquisitions of the Nitinol-SAVS-treated aneurysms indicated drastic reduction of the hemodynamic flow in the aneurysm dome and completely successful treatment except for the one case where incomplete treatment was predicted by only moderate flow modification.

Conclusions: Changes in angiographically derived TDC’s appear to be a very useful tool to predict treatment outcome. Based on TDC-analysis, the new Nitinol-SAVS is a very promising option for treatment of intracranial aneurysms. (Support: NIH-R01NS43924, NIH-R01EB002873)

                                                                                                                              

Task Group proposal for Simulation Training and Error Reduction in Medical Physics

Michael C. Schell, Per Halverson, Dirk VerEllen, and Andrew Beavis

Department of Radiation Oncology, University of Rochester Medical Center, Rochester NY

According to IAEA Safety Report Series No. 17(1) and the Radiation Risk Profile by the WHO(2), lack of training plays a key role in many misadministrations in radiation oncology. Error reduction is greatly enhanced by training on all levels. It is assumed that the physicist fulfills the basic AAPM definition of a credentialed medical physicist and is board certified by the American Board of Medical Physics or the American Board of Radiology. Requisite training on all technology is an obvious requirement.

One aspect of training is frequently overlooked. Ongoing training is essential to error reduction and a safe treatment environment. The medical field focuses on continuing medical education (CME) to ensure competence. CME can be fulfilled by quizzes and journal reading and meeting attendance. CME does not test on actual performance of professionals in the workplace in stressful conditions where procedures fail. Consider the training policy of a nuclear power plant, such as the Ginna nuclear power plant in upstate New York. The technologists and engineers receive two full weeks of training each year. The training includes simulator training that tests the personnel for the proper response to various failure modes. The nuclear power plant operators train every sixth week for every possible operation. A professional fireman typically receives two weeks training per year. In contrast to these training policies, how does any medical field fare? Training and testing of medical professionals in simulated conditions is at best amateurish. Ongoing training typically is 2 days per year for a few departmental clinicians rather than the entire department. Thus weak or non-existent ongoing training erodes the infrastructure of the department as memories fade and personnel turnover takes it toll.

The Task Group goals and an overview of simulation training will be presented.

                                                                                                                              

 

Demonstration and comparison of contrast and spatial resolution between Single Photon Counting (SPC) and Energy Integrating (EI) modes for the newly developed high-resolution Micro-Angiographic Fluoroscopic (MAF) detector

Amit Jain, A. Kulhs-Gilcrist, D. R. Bednarek, S. Rudin

Toshiba Stroke Research Center, University at Buffalo, Buffalo 14214 NY

Abstract: Although in radiological imaging, the prevailing mode of acquisition is to integrate the energy deposited by all x-rays absorbed by the imaging detector, much improvement in image spatial and contrast resolution could be achieved if each individual x-ray photon were detected and counted separately. In this work we compare the conventional energy integration (EI) mode with the new single photon counting (SPC) mode for a recently developed high-resolution Micro-Angiographic Fluoroscopic (MAF) detector, which is uniquely capable of both modes of operation.

      The MAF has 1024x1024 pixels of 35 microns effective size and is capable of real-time imaging at 30 fps. The large variable gain of its light image intensifier (LII) provides quantum limited operation with essentially no additive instrumentation noise and enables the MAF to operate in both EI and the very sensitive low-exposure SPC modes. We used high LII gain with very low exposure (<1 x-ray photon/pixel) per frame for SPC mode and higher exposure with lower gain for EI mode. Multiple signal-thresholded frames were summed in SPC mode to provide an integrated frame with the same total exposure as EI mode. A heavily K-edge filtered x-ray beam (average energy of 31 keV) was used to provide a nearly monochromatic spectrum.

      The MTF measured using a standard slit method showed a dramatic improvement for the SPC mode over the EI mode at all frequencies. Images of a line pair phantom also showed improved spatial resolution with 11 lp/mm visible in SPC mode compared to only 8 lp/mm in EI mode. In SPC mode, images of human distal and middle phalanges showed the trabecular structures of the bone with far better contrast and detail. This improvement with the SPC mode should be advantageous for clinical applications where high resolution is essential such as in mammography and extremity imaging as well as for dual modality applications, which combine nuclear medicine and x-ray imaging using a single detector.

 

                                                                                                                              

Measuring the MTF without slits, edges, or other test objects

Andrew Kuhls-Gilcrist, Amit Jain, Danial R. Bednarek, and Stephen Rudin

SUNY Buffalo, Buffalo NY

Purpose: To provide a new method for measurement of the modulation transfer function (MTF) using the noise response of digital radiography systems.

Method and Materials: Cascaded linear system methods have been used for several decades to accurately predict the signal and noise performance of a wide variety of digital x-ray imaging technologies including x-ray image intensifiers, direct and indirect flat-panel detectors (FPDs), and CCD/EMCCD-based detectors. The noise response of such imagers inherently incorporates the detector resolution response, i.e. the detector MTF. In this work, a generalized linear systems analysis was used to derive an exact relationship. The two-dimensional noise power spectrum (NPS) was plotted versus the mean signal level, for all spatial-frequencies. A linear regression was fitted to this data to isolate the quantum-noise component, the shape of which depends in part on the system resolution. The spatial-frequency response of the resulting slopes was then used to obtain the MTF. The accuracy of this method was investigated using simulated images from a simple detector model, based on high-resolution EMCCD detectors, in which the MTF was known exactly. Measurements were also done on a FPD and the results were compared using the standard edge response method.

Results: The MTF measured from the noise response of the simulated detector system showed exceptional agreement with the “true MTF” at both low and high spatial-frequencies. Differences of 0.3%, 1.8% and 6.1% were observed at 5, 10 and 15cycles/mm, respectively. The FPD MTF obtained using the noise and edge response methods were also shown to agree within experimental uncertainty.

Conclusions: Initial results indicate that the noise response method is a simple technique which can be used to accurately measure the MTF (in all directions simultaneously) of digital x-ray imagers, alleviating the burdens of development and implementation of precision edge or slit devices.

                                                                                                                              

 

Dosimetric Correction for Lung Aperature used in Mouse Irradiation Experiments for a 250 kVp Orthovoltage Unit

Cameron D. Arndt, Z. Wang, N. Saito, M. B. Podgorsak,

Roswell Park Cancer Institute, Buffalo, NY

Purpose: Mice lung irradiation experiments are being carried out to investigate radiation induced pulmonary fibrosis. The irradiation setup involved a mouse pie cage device to irradiate 10 mice simultaneously and radiation shields to protect critical organs. The objective of this study was to evaluate the dosimetric effect of a lung aperture located at an off-axis location.

Method and Materials: The irradiator is a Philips RT 250 orthovoltage unit with a 12.5 cm diameter cone and 250 kVp X-rays which were used for irradiation. We used Gafchromic EBT-2 film as the relative dose measurement tool in this study. To ensure Gafchromic film measurement is accurate, we first compared percentage depth dose (PDD) measurements to ion chamber measured beam data. The concentric radiation shields were made of 0.5 cm thick Cerrobend, which leaves only the mice lung regions open with a 1.2 cm width ring. The lung aperture is approximately 4.5 cm away from the center of the cone. Effects of a 1-cm airgap, off-axis effects and shielding effects were studied.

Results: The PDDs measured using Gafchromic films matched well with the ion chamber data with very minimal errors when depth < 2 cm (essentially thickness of a typical mouse in the AP/PA direction), which validated the Gafchromic film dose measurement accuracy. The effects of the 1 cm space were 7% drop in dose, essentially inverse square fall off. There was 7% drop in dose from off-axis effects, and shielding further dropped the dose 6%. The off-axis PDD curves also showed a 4% decrease within the first 2 cm in depth with the ring-shape aperture.

Summary: The dose to the lungs of the mouse from the effects mentioned above was a 24% decrease in dose. More accurate dose delivery will be achieved when the correction factors are applied.

 

                                                                                                                              

External Beam Dose Perturbation from Implanted Seeds, Fiducial Markers and Surgical Clips in Radiotherapy

James P. Steinman, H.K. Malhotra

Roswell Park Cancer Institute, SUNY Buffalo, Buffalo NY

Purpose:  Suboptimal dose distributions from brachytherapy seed implants are often salvaged by additional radiation using 3DCRT/IMRT. External beam therapy often follows surgery which may involve many surgical clips.  Fiducial markers are used in defining the tumor site or as a surrogate in imaging for tumor localization.   In standard treatment planning, the dosimetric perturbations by the seeds/fiducial markers/surgical clips are usually ignored.  Present study aims at characterizing these perturbations for 6MV and 18MV beams within a phantom setting immediately above and below non-radioactive I-125, Pd-103, Cs-131 seeds, Gold fiducial markers, Copper, Aluminum, and Titanium clips. 

Methods and Materials: A seed/fiducial marker/clip was placed on a Lucite plate at 100cm SSD on 10cm Solid Water.  Two Kodak X-Omat V films were placed on top of the Lucite beneath 5cm Solid Water.  A 1cmx1cm field was irradiated with 10MU at 6MV and 18MV.  For measurements behind the seed, the setup was similar but three films placed underneath the Lucite plate.  Control field was irradiated with no seed.  The films were scanned using a Vidar VXR-16 scanner and analyzed using RIT 113 Version 5.1.   All films were taken from the same batch and processed together. 

Results:  For I-125 seeds, dose enhancement upstream was found to be 6.3% while dose attenuation downstream was -10.9% compared with no seed on the films touching the seed at 6MV.  The greatest effect was by the Gold Markers where the perturbation was 27.8% and -24.7% and least by Aluminum, 3.0% and -8.6%.  The dose perturbation fell rapidly with distance and nearly vanished beyond ~2 mm.   

Conclusion:  The dose perturbation caused by the seeds, markers and clips is significant at close proximity and varies greatly on the material.   Depending upon the treatment planning system accuracy in predicting dose in inhomogeneous media, this effect may not be fully observed.                           

 

 

An alternative method for beam output constancy measurements      

Dinko Plenkovich, Roswell Park Cancer Institute, WCA Cancer Treatment Center, Jamestown, NY

Purpose:  After the completion of the absolute TG-51 calibration in water, measurements are, usually, taken in a plastic phantom, and the beam-output-constancy coefficients are calculated.  It is important to perform these measurements in plastic immediately after the absolute TG-51 calibration.   An alternative method is proposed, which does not require any measurements after the completion of the absolute TG-51 calibration. 

Method and Materials:  The dose per monitor unit can be expressed in the form Dose/MU = coefficient * PTP *Mraw.  The coefficients, for various photon and electron energies, are calculated from the TG-51 worksheets.  For the constancy measurement of the beam output, the same ionization chamber, cable, electrometer, water phantom, and setup are used as for the absolute TG-51 calibration.  Only the temperature inside the ionization chamber, the atmospheric pressure, and the collected electric charge, Mraw, for the polarity of the ionization chamber ADCL calibration, need to be measured.  For each of the photon and electron energies, the ionization chamber is placed at the same depth, in water, as during the absolute TG-51 calibration. 

Results: If one has a water phantom in which the depth of the ionization chamber in water can be controlled from the treatment unit console, the measurement time is shorter than with the plastic phantom, whose slabs have to be rearranged for different photon and electron energies.  When performing the next TG-51 calibration, the newly measured beam output can be, easily, compared with the output calculated using the previously calculated beam-output-constancy coefficients, without the need to perform any measurement in plastic. 

Conclusion:  The accuracy of the beam-output-constancy measurement is higher in the water phantom because the conclusions do not need to be inferred from water to plastic during the determination of the beam-output-constancy coefficients and back from plastic to water during the interpretation of the output-constancy results.