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Upstate TWIG Auditorium |
12:00 pm – 5:00 pm Sponsoring
Vendor Exhibits:
Upstate Linac Services, Sun Nuclear, Resonant Medical Inc., Vision RT., Elekta, BrainLAB AG, CIVCO Medical Solution, LACO Inc, PTW, BARD, Accuray Inc., RAD Technology Medical Systems, IBA Dosimetry , MIM Software Inc.
MEETING SPONSOR
Upstate Linac
Services
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10:00 |
Business Meeting
(Sengupta Room ) |
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11:30 |
Lunch Sponsored by Sun
Nuclear & Elekta |
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12:20 |
Meeting Introduction |
Iris Wang Ph.D., UNYAPM President |
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Vendor Session |
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12:20-12:40 |
Novel Cylindrical 3D
Scanner - A fresh new approach - Less subjectivity |
Jim Ernsberger Sun Nuclear Corporation |
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Proffered Paper Session |
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12:50 |
Study of High-Resolution (HR) and High-Light (HL)
Phosphors in the Micro-Angiographic Fluoroscope (MAF) using Generalized
Linear Systems Analyses |
Sandesh K. Gupta, Amit Jain,
Daniel R. Bednarek, Stephen Rudin |
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1:05 |
Estimation
of confidence intervals for pass rates of low-density 2D IMRT QA planes |
D.
Bailey, B. Nelms, L. Kumaraswamy,
M. Podgorsak |
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1:20 |
Adaptive Temporal Filtering Based On
the Motion of an Object of Interest for Image Guided Procedures Using the
High Resolution Microangiographic Fluoroscope (MAF) |
A. Panse, A. Jain, C.
Ionita, D. Bednarek, S. Rudin |
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1:35 |
A novel hybrid radiotherapy technique combining a
VMAT arc with beam angle optimized IMRT fields |
Jason Spaans, Lalith
Kumaraswamy, Harish Malhotra, Mohammad Bakhtiari, Matthew Podgorsak, and
Daryl Nazareth |
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1:50 |
Dose
Calculation with MCNP5 in the Buildup Region for 6MV photon beams |
Hassan Abbas, Jahangir Satti and C. A. MacDonald |
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2:05 |
Evaluation
of the Accuracy in the Algorithm used for Optical Patient Alignment. |
Juan Carlos Paz Lozada,
Daryl Nazareth, and Harish Malhotra |
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2:20 |
Attention on Details in Radiation Medicine |
Dinko Plenkovich |
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2:35 |
Refreshments and Vendor Exhibits –
Vestibule Sponsored by Sun Nuclear
& Elekta |
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Invited
Talk |
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3:00-4:00 |
SBRT: A paradigm shift from conventional
radiotherapy |
Harish Malhotra, PhD Roswell Park Cancer Institute |
UNYAPM SPRING 2010 MEETING PROCEEDINGS
ABSTRACTS
1) Study of High-Resolution (HR) and High-Light (HL) Phosphors in the Micro-Angiographic Fluoroscope (MAF) using Generalized Linear Systems Analyses
Sandesh K. Gupta, Amit Jain, Daniel R. Bednarek, Stephen Rudin
Purpose: To investigate if
the high light (HL) phosphor with its higher screen efficiency could be
replaced with the high resolution (HR) phosphor to achieve improved resolution
that is essential for neurovascular procedures without increase in noise
resulting from the HR’s decreased light-photon yield.
Methods and Materials: We designated the detectors MAF-HR and MAF-HL
based on the imaging phosphor HR and HL, respectively, and compared them with a
commercial flat panel detector (FPD) (194 micron pixel pitch and 600 micron
thick CsI(Tl)). For this
comparison, we used the generalized linear-system metrics of GMTF, GNNPS and
GDQE which are more realistic measures of total system performance since they
include the effect of scattered radiation, focal spot distribution, and
geometric un-sharpness. Magnifications (1.05-1.15) and scatter fractions (0.28
and 0.33) characteristic of a standard head phantom were used. Results:
In this study, we evaluated the imaging characteristics of the high-resolution,
high-sensitivity micro-angiographic fluoroscope (MAF) with 35-micron
pixel-pitch when used with different commercially-available 300 micron thick
phosphors: the high resolution (HR) and high light (HL) from
2)
Estimation of confidence intervals for pass rates of
low-density 2D IMRT QA planes
D. Bailey, B. Nelms, L. Kumaraswamy,
M. Podgorsak
Roswell Park Cancer Institute
Purpose: The most common metric for comparing measured to calculated dose for
IMRT QA is a pass rate (%) calculated by percent difference (%Diff) and/or
distance-to-agreement (DTA). However, for many dosimeters, the grid of analyzed
points corresponds to a low-density 2D or 3D array (of diodes or ion
chambers). In these cases the pass rates for any given %Diff/DTA criteria
are not absolute, as they exhibit statistical variability that is a function,
in part, on the detector sampling geometry. In this work, we analyze the
statistics of various methods commonly used to calculate pass rates, and
propose methods for establishing confidence intervals for pass rates obtained
with low-density arrays.
Methods and Materials: Dose planes were acquired for 10 prostate IMRT fields
and 10 head and neck fields via diode array and EPID. Respective calculated
dose planes were created by the TPS. The pass rate for each measured vs.
calculated plane pair (both centered to the CAX) was calculated with several
common comparison methods: %Diff/DTA composite analysis and gamma evaluation,
using both local and global normalization. Specialized software was designed to
selectively sample the EPID response (very high data density) down to discrete
points to simulate low-density measurements (such as those acquired via diode
or ion chamber arrays). The software was used to realign the simulated detector
grid at many simulated positions with respect to the CAX, thereby altering the
low-density sampled grid. Simulations were repeated with 100 positional
iterations using a 1 detector/cm uniform grid, a 2 detector/cm uniform grid,
and similar random detector grids (to examine any potential biases introduced
by a simple orthogonal low-density grid). For each simulation, composite
analysis pass rates were calculated with various %Diff/DTA criteria and for
both local and global %Diff normalization techniques.
Results and Conclusions: For both the prostate cases and the H&N cases, the
average pass rate obtained with gamma analysis is 2%-5% higher than respective
composite analysis, depending on DTA/%Diff tolerances, but regardless of
normalization. Meanwhile, the average pass rate obtained via local
normalization was 2%-6% lower than global maximum normalization, again
depending on tolerance criteria. Repositioning of simulated low-density
sampling grids leads to a distribution of possible pass rates for each given QA
pair. These distributions can be predicted using a binomial distribution, which
can be used to establish confidence intervals that should accompany each
analysis. The confidence interval of each pass rate depends largely on the
sampling density and the observed pass rate (i.e. the degree of difference
between measured and calculated). Any passing rate for a low-density
measurement array should be accompanied by a confidence interval indicating the
statistical uncertainty of that pass rate.
3)
Adaptive Temporal Filtering Based On the Motion
of an Object of Interest for Image Guided Procedures Using the High Resolution Microangiographic Fluoroscope (MAF)
A. Panse, A. Jain, C. Ionita, D. Bednarek, S. Rudin
Purpose: To study the effect of temporal filtering on accuracy of localization for static and moving objects and to implement real-time adaptive temporal filtering based on amount of motion detected for the object of interest during fluoroscopy.
Method and Materials: A phantom consisting of two stents (stainless steel and nitinol) mounted on a stepper motor controlled linear stage, and a stationary third stent (nitinol stent with platinum markers) was assembled. The stent strut sizes ranged between 80 to 100 micron. The new high resolution 35- micron-pixel Microangiographic Fluoroscope (MAF) was used for imaging the stent as it was moved forward 7500 steps and brought back to the original position. Object detection algorithm available in LabVIEW IMAQ Vision software was used to localize the stent using different temporal filtering weights. A real time adaptive temporal filter was developed. Depending on the amount of motion the weight was reduced; more the motion, lesser the weight.
Results: For fixed exposure, stationary object localization accuracy is improved by a factor of 5 for higher temporal filtering compared to no temporal filtering; however, for moving objects the error in localization increased 50 percent due to motion blurring when the filter weight was increased from 4 to 8. Without temporal filtering, the nitinol stent could not be seen. When the stents were stationary, and the temporal filter weight was increased, the nitinol stent could be clearly visualized due to the quantum noise reduction. When the stents were moving, the filter weight was reduced thus reducing the motion blur and improving the visualization of the stainless steel stent struts.
Conclusions: Motion based adaptive temporal filtering can be implemented to aid during interventional procedures by tracking the motion of the high contrast interventional device to improve the visualization of lower contrast neurovascular objects.
4)
A novel hybrid radiotherapy
technique combining a VMAT arc with beam angle optimized IMRT fields
Jason Spaans, Lalith Kumaraswamy, Harish Malhotra, Mohammad Bakhtiari,
Matthew Podgorsak, and Daryl Nazareth
Roswell Park Cancer Institute
Purpose: To develop a new radiotherapy delivery technique, which combines the superior dose conformality of an IMRT technique and the efficiency of a VMAT technique.
Methods
and Materials: A simple
beam angle optimization algorithm was developed based on field weight, MLC
modulation, and patient anatomy to determine the optimal gantry position for
placement of IMRT fields. The use of one, two, or three IMRT fields was
investigated. A VMAT plan was then generated and optimized with the IMRT
plan as the base plan. The resultant VMAT plan delivery was manually
merged with the IMRT plan that was initially generated. This resulted in
a single intensity modulated arc which incorporated the additional IMRT fields
in static gantry positions. The resulting hybrid technique delivers dose
continuously using an arc technique, and the gantry pauses during its rotation,
to deliver each IMRT field.
Results: In a retrospective study of prostate and head
& neck cases, the new method was evaluated by comparison with clinical VMAT
plans. The hybrid plan, consisting of two optimized IMRT fields and a
single arc, provided the best trade-off between low MU’s
and favorable dose distribution. The new technique demonstrated greater
sparing of OAR’s than VMAT, with similar coverage of
target structures. For example, the new technique delivered 9% less dose
to 40% of the bladder, 13% less dose to 40% of the rectum, and required 10%
fewer MU’s. In addition, the hybrid plan could
theoretically be loaded onto the treatment machine as a single arc field.
Conclusions: This work indicates a new treatment delivery
method incorporating both IMRT and VMAT techniques, that results in the
efficient delivery of radiation therapy plans. In comparison with
existing treatment techniques, this hybrid technique provides comparable
coverage of target volumes with increased sparing of OAR’s
and more efficient treatment delivery.
5) Dose Calculation with MCNP5 in the Buildup Region for 6MV photon beams
Hassan Abbas1, Jahangir Satti2 and C. A.
MacDonald1
1. Center for X-Ray
Optics, Physics Department, University at
2. Department of Radiation
Oncology,
Purpose:
Cylindrical ion chamber measurements are known to overestimate the dose in the
build up region. Several authors have investigated different measurement
methods and MC simulations for accurate PDD predictions in the buildup region.
The potential of MCNP5 to provide accurate dose calculations in the buildup
region for 6 MV photon beams was studied.
Method:
MCNP5 was used to model a 6 MV photon beam for a Varian linear accelerator.
Modeling geometry was based on the vendor provided specifications with the
primary collimator corrections proposed by Chibani
and Ma. Percentage dose depth ionization (PDIs)
curves and cross dose profiles were measured using a Farmer ionization chamber
for 10×10 and 30×30 cm2 field sizes. The MCNP5 model was benchmarked
by comparison with measurements. Dose in the buildup region (at depths ≤
1.5cm) was calculated with MCNP5 for 2 mm depth voxels
for the 10×10 cm2 field size. In order to calculate the dose at
clinically significant depths shallower than 2 mm, a polynomial fit of degree 6
was used on MCNP5 computations in the build up region. Dose calculations in the
buildup region are compared with reported measurements and MC simulations with
other codes.
Results:
Depth dose calculations and cylindrical ion chamber PDI measurements agree
within 2% beyond dmax for 10×10 and 30×30
cm2 field sizes. Beam profile calculations and measurements at dmax~1.5
cm and at a depth of 10 cm agree within 2% for flat region of the
cross profile for both field sizes. MCNP5 calculated PDDs
vary from 16.78% to 41.62% within 1 mm from surface for 10×10 cm2
field size for the 6 MV photon beam. These calculations are comparable to
accurate measurements and MC simulations reported in literature.
Conclusion:Accurate
dose in the buildup region can be calculated by MCNP5.
6)
Evaluation
of the Accuracy in the Algorithm used for Optical Patient Alignment.
Juan Carlos Paz Lozada, Daryl Nazareth, and Harish Malhotra
Roswell Park Cancer
Institute
Purpose: To analyze and evaluate the intrinsic
precision of an optical patient alignment system, which we are currently
developing, to assist in patient positioning during breast radiotherapy. Since the breast is a deformable organ of
variable size and shape, standard setup procedures may be inadequate to
position the breast properly for treatment.
Methods and Materials: This method employs a standard digital
camera, and an in-house constructed calibration phantom (CP), composed
of ten identifiable reflecting spheres, mounted on a wooden platform.
Results: A set of 300 simulated images with different rotation angles and translations were created to evaluate the accuracy of the model. Once the simulated data was obtained we applied the optimization algorithm to calculate the rotation and translation and compared with the known values. The results showed errors of less than 1 mm in translation and less than 1 degree in rotation.
Conclusion: It suggests that theoretically the system would be a useful tool that can be used to minimize errors due to inconsistent position during breast radiotherapy.
7) Attention on Details in Radiation Medicine
Dinko Plenkovich
Roswell Park Cancer
Institute,
Purpose: Between January 23, 2010 and February 27, 2011, the New York Times investigative reporter, Walt Bogdanich, published a series of excellent articles about errors which occurred in radiation medicine. ECRI Institute, a non-profit healthcare research organization, ranked “Radiation Overdose and Other Dose Errors during Radiation Therapy” the top healthcare technology hazard for 2011. Attention on details during beam output calibration, radiation therapy simulation, treatment planning, patient setup, and treatment delivery can prevent errors and reduce their severity. Method and Materials: We have reviewed Mr. Bogdanich’s reports and devised procedures to prevent the errors described in them. The first article discusses the tragic events pertaining to the head-and-neck IMRT patient who was treated for three days with the multileaf collimator fully open. The radiation oncologist should have allowed sufficient time for the revision and QA of the IMRT plan. Results: We have implemented a visual reminder for the radiation therapists to place the bolus on the patient. Our method of marking the patient’s skin or the head immobilization mask has greatly reduced the frequency of errors. Displaying the carina on digitally reconstructed radiographs of the chest patients helps in verification of portal images. Conclusion: The use of modern record-and-verify systems has permitted radiation delivery on an “auto pilot.” Just as an airline pilot has to monitor the instruments and look through the window of the cockpit, the radiation therapist must pay attention to the details of the treatment console and CCTV monitors throughout the treatment. Just as there are a pilot and copilot in every commercial airplane, there should be two radiation therapists at the controls of a linear accelerator, and there is plenty of work for both of them.
Vendor’s session
(15 – 30 min)
Novel Cylindrical 3D
Scanner - A fresh new approach - Less subjectivity
Jim Ernsberger
Sun Nuclear Corporation
Invited talk (60
min)
SBRT: A paradigm shift
from conventional radiotherapy
Harish Malhotra, PhD
Medical Physicist, Assistant Professor
Roswell Park Cancer Institute
Directions (to
From the West:
From
From the East:
From the South: 390 North to 590 North to 104 West to
Please
park in the Portland Ramp (1425 Portland Av). Enter the hospital on the
star (*) floor from the visitor elevator. Thus you will enter the Polessini Pavilion. The meeting rooms are on the left hand
side.
Vendor exhibits will be
in the Atrium. The Atrium is a 20 second
(maybe less) walk from the Twig aud and the meeting
rooms