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Upstate Roswell Park Cancer Institute Elm and |
Sponsoring Vendor
Exhibits:
LACO Inc & PTW, ACCURAY Inc., Upstate
Linac Services, VARIAN, ELEKTA, TomoTherapy,
Velocity Medical Solutions, SUN Nuclear, VisionRT,
BARD, ScandiDos
MEETING SPONSOR
VARIAN
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10:30 |
Business
Meeting |
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11:45 |
Lunch Sponsored by Upstate
Linac Services and ELEKTA |
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12:50 |
Meeting Introduction |
Iris Wang Ph.D., UNYAPM President |
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Vendor Session |
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1:00 |
4D
Quality Assurance |
PTW Regional Product Manager |
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1:15 |
The Cyberknife Radiosurgery System – Technology Update |
Vance Sorell, Accuray Inc. |
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Proffered Paper Session |
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1:45 |
Investigating the
Usability of BIM (Brain Imaging Material) as a Water Equivalent Material in
Neurovascular Imaging Studies |
Brendan Loughran TSRC, University at |
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2:00 |
Increasing x-ray tube output while maintaining the
small effective focal spot for the Microangiographic
Fluoroscope (MAF) System |
Sandesh
Gupta TSRC,
University at |
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2:15 |
The
Optimization of Stereotactic Body Radiation Therapy (SBRT) from a Simple
Field Order Rearrangement |
Jonathan Schmitt Roswell Park Cancer
Institute |
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2:30 |
Dose Reduction technique
for Image Guided Neurovascular Intervention |
Setlur Nagesh, Swetadri
Vasan Dept of E.E., TSRC, University at |
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2:45 |
Competency and Credentialing: Current AAPM
Initiatives |
Daniel C. Pavord |
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3:00 |
Refreshments and Vendor Exhibits Sponsored by Upstate Linac Services and ELEKTA |
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Invited Talk |
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3:20 |
Lifetime Achievement Award presentation |
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3:30-4:30 |
Cancer Imaging for Radiotherapy |
Thomas Rockwell Mackie, Ph.D. FAAPM |
ADJOURN
UNYAPM 2011 FALL MEETING PROCEEDINGS
ABSTRACTS
1) Investigating the Usability of BIM (Brain Imaging
Material) as a Water Equivalent Material in Neurovascular Imaging Studies
Brendan Loughran, Ciprian N Ionita, Daniel R Bednarek, Stephen Rudin
Purpose: We investigated a homemade putty or BIM as a tissue
equivalent attenuator in neurovascular stent imaging studies. Previously, the standard AAPM lateral head
phantom was used to conduct preliminary technique parameter estimations prior
to clinical research and it was found that the technique parameters were
severely underestimated. This is likely
because most neurovascular stenting procedures
require imaging at the portion of the brain which is at the bony base of the
skull. Therefore, to improve preliminary
technique parameter estimations, the use of an anatomical head phantom and BIM
is beneficial. The BIM should be
somewhat water equivalent and must easily conform to the irregular interior
regions of the skull.
Methods: The BIM was made from salt, water, and flour. X-rays at technique parameters of 74 kVp and 0.02 mAs were then passed
through the BIM. The exposure was
recorded by a PTW chamber and electrometer at the entrance of the material,
after 1 inch, and after 2 inches. The
same was done with water equivalent plastic and the exposures were
compared.
Results: The entrance exposure for both the BIM and water
equivalent plastics was 38.1 µR/frame. The exposures at 1 inch
and 2 inches of BIM were 14.0 µR/frame and 5.83 µR/frame,
respectively. The exposures at 1 inch and 2 inches of water equivalent plastic were 17.5
µR/frame and 9.25 µR/frame, respectively.
The percent difference between the BIM and the water equivalent plastic
was 20.0% at 1 inch and 37.0% at 2 inches.
Conclusion: We find that the BIM conforms better to the complex
and irregular portions of the interior of the anatomical head phantom than the
water equivalent plastic. The differences in attenuation between the BIM and the water
equivalent plastic have been quantified.
For our purposes, the BIM adequately mimics the physical and attenuation
characteristics of brain tissue.
Therefore, we can conclude that the BIM is a useful tissue approximating
material.
2) Increasing x-ray tube
output while maintaining the small effective focal spot for the Microangiographic Fluoroscope (MAF) System
S Gupta, A Jain, DR Bednarek,
Purpose: High-resolution region-of-interest (ROI) imaging
requires the use of a small effective focal-spot with sufficient output to
maintain spatial and contrast resolution for endovascular-image-guided
interventions (EIGIs). We investigate two possible
methods to increase the x-ray output while maintaining the effective focal-spot
size for the Microangiographic Fluoroscope (MAF)
System.
Materials and Methods: In the first method, we evaluated the increase in
tube output for the MAF made possible by reducing the anode angle and
lengthening the filament for the small focal -spot to maintain a constant
effective focal-spot size while assuming flux density and heat distribution as
unchanged. “Spek Calc” software was used to calculate
the change in inherent tube filtration and in x-ray spectrum and intensity as a function of anode angle. In the second
method, generalized MTF (GMTF), generalized NNPS (GNNPS) and generalized NEQ
(GNEQ) were calculated for the MAF at a fixed object magnification of 1.11 for
the medium and small focal-spots on the central axis and the medium focal spot
on the anode side.
Results: The x-ray output could be increased by 3.3 times with
a 2-degree anode angle compared to the standard 8-degree target with an
increase of 4 times in filament length, following the first method. The GNEQ of
medium focal spot with at the anode side is higher at all frequencies below the
Nyquist due to the reduced effective focal spot size,
following the second method.
Conclusions: For EIGIs where high
resolution is essential but only over a small FOV, higher tube output while maintaining
a small focal-spot should be achievable with only small modification of
standard x-ray tube geometry. Furthermore, there is a clear benefit to
utilizing the increased tube output for the medium focal-spot, while decreasing
the effective anode angle to reduce focal-spot size for the MAF.
Support: NIH Grants R01-EB008425, R01-EB002873
3) The Optimization of Stereotactic Body Radiation Therapy (SBRT) from a Simple Field Order Rearrangement
Jonathan Schmitt, Graham Warren, Iris Wang
Roswell Park Cancer Institute
Purpose:
Stereotactic Body Radiation Therapy (SBRT) uses high dose fractions with
multiple co-planar and non-coplanar beams. Due to the large fractional doses,
SBRT treatments are typically protracted and the number of fields is greater than
a conventional radiation treatment. We demonstrate a temporal optimization
method could be applied to SBRT treatments to enhance biological effectiveness.
Methods:
Clinically treated SBRT cases were studied. Using the Lea-Catcheside
protraction factor (G-value), we cycled through possible field-order
permutations for each treatment plan, and determined an optimal and a
least-favorable field order. For comparison, clinically delivered field orders
were also included. We utilized the Lethal Potential Lethal (LPL) model to
quantify the difference in survival fraction. To acquire the parameters needed
by the LPL model we fit the data to three non-small cell lung cancers (NSCLC):
H460, H660, and H157. The results are expressed as the ratios 
and 
,
where N is the number fractions in
the SBRT protocol.
Results: Our
results verified that maximization of cell kill is achieved by orienting the
fields in a D pattern, where the
fields with greatest dose are positioned in the center. Minimization of cell
kill occurred when fields with smallest dose were positioned centrally and
higher dose fields were placed in the beginning and end of the fraction. This
orientation resembled a V shape. The
survival fraction ratios calculated using the LPL model showed that regardless
of the cell type the D shape had lower cell survival fractions compared to both the clinical
example (C) and the V arrangement. For example, results of
H460 cell line, with T1/2 = 0.25 h, showed the D pattern is approximately 10 times more effective than
a clinical field order, after 5 fractions.
Conclusion:
Using theoretical models we have shown that rearrangement of the field orders
for a SBRT treatment could optimize cell kill and potentially affect overall
treatment outcome.
4) Dose Reduction technique for Image Guided Neurovascular Intervention
S.N Swetadri Vasan1,2,
A. Panse2 ,A. Jain2,
P. Sharma1,2, Ciprian N. Inonita2, A.H. Titus1,2,
A.N.
Cartwright1,2, D.R Bednarek2,
1Department of Electrical
Engineering, University at
X-ray
endovascular image-guided interventions are carried out using the insertion and
navigation of catheters through the vasculature under fluoroscopic image
guidance. Once the catheter is guided closer to the site of the pathology to be
treated, the need for detailed image information outside this region is reduced
and the dose to the patient can be reduced. In this paper we present a novel
approach to achieve patient dose reduction, by reducing the dose outside the
treatment area. A material x-ray region of interest (ROI) attenuator is used to
reduce the dose incident to the patient. The region of the image under the
attenuator has fewer x-ray quanta reaching the detector, hence noisier, as
compared to the non attenuating region with less noise. This results in an
image with differential brightness.
First
the image is equalized in brightness by post processing and then a spatially
different temporal filter with higher weight is applied to the high attenuating
region to reduce the noise at the cost of some loss in temporal resolution,
however a lower temporal weight is used inside the region of interest to
preserve temporal resolution. A simulation of this technique on an image
sequence obtained from a Neurovascular intervention is presented.
5) Competency and Credentialing: Current AAPM Initiatives
Daniel C. Pavord
Ensuring the competency of
staff in radiation oncology is critical to providing safe and effective patient
care. To help achieve this, there are
three initiatives in process within AAPM to provide guidance and resources to
clinical staff in this area.
First, a subcommittee of the
Clinical Practice Committee on Competency and Credentialing has been
formed. This group has produced a
guidance report that is in the approval process in Professional Council. The scope of the report is:
- A framework to develop medical physics
competencies in a variety of situations: a. Solo physicist vs. larger
group, b. Experienced physicist vs. new graduate, c. Initial competency
evaluation (credentialing) vs. ongoing competency evaluation, d.
Implementation of new procedures or technology.
- A set of criteria for physicians and
administrators to evaluate the content of a competency program.
Specific
areas to be addressed are: Policies and procedures, New staff evaluation,
Existing staff evaluation, Outside reviews, Training, and Staffing.
Secondly, a task group on
simulation training has been formed.
This group will produce a white paper on the use of simulation training
in radiation oncology. Many areas such
as the airline industry have shown this type of training to be highly effective
in improving safety.
Lastly, a proposal has been
submitted to develop an online system for the documentation of competency for
specific procedures. From the proposal: Derek Brown, Peter Dunscombe and
colleagues have created a pilot system called the RTP Learning Centre [Med.
Phys. 38, 3829 (2011)]. This system comprises four specific levels for
attaining and maintaining competency in special procedures. The proposed
pathway would involve the general steps toward competency in a specific area
being determined from Practice Guidelines from AAPM, ASTRO, ACR, etc. by CPC
subcommittee on Competency and Credentialing. One of the methods to attain
competency would be through the use of simulation training as described by
TG194. The proposed system would be the framework that would standardize
competency and credentialing in Medical Physics with extension to other members
of the Radiation Oncology team.
Vendor’s session
1) 4D Quality Assurance - The PTW OCTAVIUS 4D allows for true independent verification of IMRT
Planning.
By: PTW Regional Product Manager
2)
The Cyberknife Radiosurgery System –
Technology Update
By: Vance Sorell, Accuray
Inc.
A
presentation on the basic components of the Cyberknife
Radiosurgery system with a focus on the unique use of
the 3D space around the patient. The
robotic mechanism provides an advantage for radiation therapy treatments by targeting
volumes and minimizing or eliminating the placement of beams through the organs
at risk. This generates treatment plans
with radiosurgery margins and high dose conformality with rapid dose fall-off. The robotic movement uniquely allows for real
time tumor tracking by correcting beam placement through imaging and motion
correlation.
Keynote Speaker –
2011 UNYAPM Lifetime Achievement Award Honoree
Thomas Rockwell Mackie,
Ph.D., Dr. Thomas “Rock” Mackie has a
bachelor degree in Physics from the
Cancer Imaging for Radiotherapy
Thomas Rockwell Mackie, Ph.D., FAAPM, Professor
Other than the first Co-60 cancer therapy unit, the
most important advance in the management of cancer with radiotherapy has come
about because of improvements in imaging. More than 25 years ago conventional
planar x-rays were the main tool used to image a radiation therapy
patient. Conventional x-rays can
accurately reveal the location of bone and lung in two dimensions, but most
cancer involves soft tissue not bone and the exact shape and extent of lung
cancer in three dimensions is poorly determined. X-rays were only useful for
localizing the general anatomical site of the disease not the exact site to be
treated. This meant that very large
treatment margins were used, thereby limiting the dose to the tumor to avoid
normal tissue complications. The advent
of the computed tomographic (CT) scanner revealed
soft tissue structures with millimeter precision in three-dimensions that could
theretofore only be visualized during surgery.
At the same time the availability of relatively inexpensive computers
enabled the CT images to be used to visualize where beams of radiation could be
applied to the tumor in ways which would avoid as much as possible harm to
normal sensitive tissue. This treatment
planning process also included a more accurate calculation of the radiation
dose to be delivered to the patient using methods that were largely developed
by Canadian medical physicists. These
developments allowed higher doses of radiation to be more safely delivered.
Today, all radiotherapy clinics have CT scanners specialized for planning treatments. Scanning before each treatment ensures the
tumor is being adequately covered and the normal tissue not receiving too much
radiation. The use of conventional
x-rays has been nearly completely replaced by CT scanners for use in
radiotherapy, however, planar x-rays still have a very important role in
specialized diagnostic exams for cancer.
Medical imaging for cancer is evolving rapidly. Magnetic resonance imaging (MRI) reveals some
soft tissue structures with more specificity and at higher resolution than a CT
scanner can. A positron emission tomographic (PET) scanner is able to reveal not only
anatomy but the uptake of tracers that can signal the location of rapidly
growing or metabolizing cells - the hallmark of cancer. In the
With increased use of modern imaging systems, cancer
will be made a chronic disease for those that fail the first round of
treatment. Patients should be followed
up often after treatment using appropriate imaging resources. If there is residual disease even at distance
anatomic sites, additional treatments are appropriate, so long as the risk of
complications can remain low. The
earlier the recurrence is detected and therefore the smaller it is, the more
likely a single convenient and cost-effective dose of radiation can be safely
administered. Finding the recurrence
early often means the disease can be eliminated at that site. Careful
accounting of, and minimizing, the dose to healthy tissue will keep the quality
of life high. Imaging will also reveal
if the disease is so extensive that intervention could not be safely
administered. It is highly likely that the number of years patients survive
with a high quality of life, will steadily increase over the next 25 years as
imaging for cancer becomes less expensive and even more capable.
Directions (to Roswell Park Cancer Institute):
From points east, west, north and south of
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