UNYAAPMmeetingletterhead

Upstate New York Association of Physicists in Medicine, Inc.      (A Chapter of the AAPM)

Fall Meeting – October 6, 2010

Bone and Joint Center

6620 Fly Road, Suite 100

East Syracuse, New York 13057

 

12:00 pm – 4:00 pm    Sponsoring Vendor Exhibits:

Elekta, Sun Nuclear, Laco, Inc., Core Oncology, Upstate Linac Services, LLC        

                       

10:30

Business Meeting

12:00

Lunch                                              Sponsored by  Upstate Linac Services & Sun Nuclear

12:30

Refreshment and Vendor Exhibit – Whipple Auditorium

1:00

Meeting Introduction

Michael Schell Ph.D., UNYAPM President

Proffered Paper Session (13 minute talks, 2 min QA)

Proffered Paper Session

1:05

Stereotactic Radiosurgery and How to Stay out of the New York Times

Michael C. Schell and Douglas Clark

1:20

Dosimetric variations in treatment planning caused by image artifact from extended field-of-view of a widebore CT simulator

Vincent Wu, Iris Z Wang*, Tuan-Anh Tran, Harish K Malhotra, Matthew B Podgorsak

1:35

An interesting artifact in bilateral breast radiation therapy

Dinko Plenkovich

1:50

Using EPID for patient specific VMAT quality assurance

M Bakhtiari, L Kumaraswamy, D W Bailey, S de Boer, H K Malhotra, and M B Podgorsak

2:05

Intraoperative Radiation for Treatment of Breast Cancer

Dan Pavord

2:20

Examining the off-axis dosimetric response of two commercial EPID systems

D. Bailey, L. Kumaraswamy, H. Malhotra, M. Podgorsak

2:35

Realistic simulated lung nodule dataset for testing CAD detection and sizing

R.D. Ambrosini and W.G. O’Dell

2:50

Refreshments and Vendor Exhibits

                                                       

3:20

Invited Speaker Radiation Dose Reduction and Image Quality in Diagnostic Imaging—Easily and Inexpensively

Joel E. Gray, Ph.D., FAAPM, FACMP Professor Emeritus, Mayo Clinic College of Medicine And President and Consulting Medical Physicist, DIQUAD, LLC

 

ADJOURN

Driving Directions to the Bone and Joint Center

From the New York State Thruway

From either direction on the Thruway (90), take exit 34A. Go through the tollbooth and merge onto 481 South

toward Syracuse/Fairgrounds/Binghamton. Take exit 5W for Kirkville Road West. Merge onto KirkvilleRoad.

Turn right onto Fly Road (CR-77), proceed 0.9 mile, then turn right into the business park. (You will see a

median with a sign forCampus East).

From 481 North or South

From either direction on 481, take exit 5W for Kirkville Road West. Merge onto Kirkville Road. Turn right

onto Fly Road (CR-77), proceed 0.9 mile, then turn right into the business park. (You will see a

median with a sign for Campus East).

From Downtown Syracuse

Take 690 East and merge onto 481 North via the exit on the left toward the Thruway. Take exit 5W for

Kirkville Road West. Merge onto Kirkville Road. Turn right onto Fly Road (CR-77) proceed 0.9 mile, then turn

right into the business park. (You will see a median with a sign for Campus East)

Enter the main entrance of the Bone and Joint Center. At the main atrium, turn left. An elevator is on your left.

Take the elevator to the 3rd (top) floor. Upon exiting elevator, enter the first door on the left, to arrive at the

main vestibule of the conference center. Vendors should set up anywhere in the main vestibule using the tableson-

wheels located throughout the conference center. The presentations will take place in the conference/class

room adjacent to the food area.


                                      

UNYAPM FALL 2010 MEETING PROCEEDINGS

 

 

UNYAPM SPRING MEETING PROCEEDINGS

Bone and Joint Center, Syracuse, NY

October 06, 2010

Invited Speaker: Joel E. Gray, Ph.D

Radiation Dose Reduction and Image Quality in Diagnostic Imaging—

Easily and Inexpensively

Joel E. Gray, Ph.D., FAAPM, FACMP

Professor Emeritus, Mayo Clinic College of Medicine

And President and Consulting Medical Physicist, DIQUAD, LLC

Optimizing dose and image quality in diagnostic radiology is one of the most helpful aspects of all responsibilities of the diagnostic

medical physicist. Dose reductions on the order of a factor of two are readily achievable, often times with improvements in image

quality. Such reductions in dose are truly appreciated by radiologists and radiology staff today, especially with the sensitivity of

public to radiation doses in medicine.

Dose and image quality are closely, though often inversely, related, i.e., in many cases high patient doses mean poor image quality.

Doses and image quality can be optimized easily and inexpensively, often at little or no cost to the department. Diagnostic reference

levels and achievable doses will be discussed along with easy and inexpensive optimization methods.

Stereotactic Radiosurgery and How to Stay out of the New York Times

Michael C. Schell and Douglas Clark,

JP Wilmot Cancer Center, University of Rochester, Rochester, NY

Purpose: Review SRS procedures and minimize risk to the patient. Recent New York Times articles have focused on tragic events in

radiation oncology. The New York Times reports will be reviewed and related to SRS procedures.

Method and Materials: The SRS procedure is analyzed with the goal of minimizing the risk of human error in all aspects. Methods

of risk reduction will be presented and applied to typical SRS procedures.

Results: The application of risk analysis, check lists and time outs have a role in error reduction. These techniques are valuable for

stable staffing and complex procedures. These are inadequate when the procedure rate is low, where staffing rotates and when the

procedure technology changes. The role of training and re-training will be presented. Training must be augmented by internal and

external program reviews and audits. Finally, the quality and frequency of training will be proposed.

Conclusion: The medical field needs to re-invent the safety programs to minimize the error rate in patient care.

Dosimetric variations in treatment planning caused by image artifact from extended field-of-view of a wide-bore

CT simulator

Vincent Wu, Iris Z Wang*, Tuan-Anh Tran, Harish K Malhotra, Matthew B Podgorsak

Roswell Park Cancer Institute

The purpose of this study was to evaluate the dosimetric impact of image artifact from an extended field-of-view (FOV)

reconstruction with a wide-bore CT scanner in radiotherapy (RT) treatment planning (TP). Since traditional RT CT scanners typically

provide a FOV of 50 cm diameter and a limited bore size that can not accommodate very large sized patients or extended simulation

setup such as respiratory gated simulation, wide-bore scanners with increased bore size and extended FOV reconstruction were

developed to address these needs. Images of subjects that are extended outside the standard scan FOV for extended FOV

reconstruction may generate image artifacts due to truncated projection data, which distort CT numbers and structure contours,

especially in the region beyond the standard FOV. A GE wide-bore LightSpeed™ RT scanner and the Eclipse™ TP system were used

to study the potential inaccuracy of dose calculation that may be introduced by the extended FOV artifacts. Results from water

phantom and CT phantom (of equivalent tissues) studies show that both body contour and CT number are altered by image artifact in

extended FOV reconstruction. CT number distortion of up to 356 HU or 115% was observed. Lung and pelvis anthropomorphic

phantom studies with several standard beam configurations show that body contour distortion causes tumor dose reduction of 3% and

1.9% for 6 MV and 23 MV x-rays, respectively. With heterogeneity correction, the distortion of CT number causes tumor dose

increase of 1.6% and 1.3% for the 6 MV and 23 MV x-rays, respectively. The two competing effects can partially cancel each other

out in treatment planning resulting in small error (less than 1 percent) in dose calculation

An interesting artifact in bilateral breast radiation therapy

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

Purpose: Breast is among the most frequently treated sites in a typical radiation oncology department. Occasionally, both breasts are

treated at the same time. Dose considerations and some peculiar dose artifacts in the Plan Sum will be discussed. Method and

Materials: Two 6 MV tangentional breast treatment plans were produced, one for the right breast, and the other one for the left

breast. A gap was left between the medial tangents to assure that no point, in the patient’s body, receives the primary radiation from

both plans. A 300 wedge was inserted in each tangentional field, the Anisotropic Analytical Algorithm (Version 8.2.23) was used, and

the heterogeneity correction was turned ON. The Plan Sum was formed by adding the radiation dose from the right and left breast

plans together. Results: The 3D dose maximum in the right breast plan was 108.7%, and in the left breast plan 107.9%. Due to the

scattered radiation, the maximum dose in the Plan Sum was 113.6%. While the distribution of radiation dose in the individual breast

plans was fairly uniform, in the Plan Sum the anterior aspects of both breasts receive more dose than their lateral aspects. In addition

to this, some interesting dose artifacts have been discovered in the Plan Sum, which are, usually, not noticed in the unilateral breast

plans. Conclusion: When treating the patient with more than one treatment plan, the effect of scatter from one plan into the other has

to be taken into consideration. The sources of dose artifacts noticed in the Plan Sum, but, most of the time, overlooked in the

individual treatment plans will be analyzed.

Using EPID for patient specific VMAT quality assurance

M Bakhtiari, L Kumaraswamy, D W Bailey, S de Boer, H K Malhotra, and M B Podgorsak

Roswell Park Cancer Institute, Buffalo, NY

Purpose: A patient specific quality assurance (QA) method was developed to verify gantry-specific individual Multi-Leaf Collimator

(MLC) apertures (control points) in Volumetric Modulated Arc Therapy (VMAT) plans using an Electronic Portal Imaging Device

(EPID).

Methods: VMAT treatment plans were generated on Eclipse treatment planning system (TPS). DICOM Images from a Varian EPID

(aS1000) acquired in continuous acquisition mode were used for pretreatment QA. Each DICOM file contains the grey scale image of

the MLC aperture related to its specific control point and the corresponding gantry angle information. The TPS MLC file of this

RapidArc plan contains the leaf positions for all 177 control points (gantry angles). In-house software was developed that interpolates

the measured images based on the gantry angle and overlays them with the MLC pattern for all control points. The 35% isodose line was

used to detect the edge of the MLC leaves on the portal images. The software generates graphs and tables that provide analysis for the

number of mismatched leaf positions for a chosen distance to agreement (DTA) at each control point and the frequency in which each

particular leaf mismatches for the entire arc.

Results: Seven patient plans were analyzed using this method. Even for a very complex plan, 80% of the active leaves passed the 3 mm

DTA criteria. The leaves with the highest mismatched rate were found to be treatment plan dependent.

Conclusions: This in-house software can be used to automatically verify the MLC leaf positions for all control points of VMAT plans

using cine images acquired by EPID.

Intraoperative Radiation for Treatment of Breast Cancer

Dan Pavord,

Chief Medical Physicist, Vassar Brothers Medical Center

Purpose: Recent studies have shown the equivalence at 4 years follow up of a single dose of radiation delivered in the OR at the time

of lumpectomy to the conventional 6 weeks of external beam radiation delivered post surgically. The treatment of a single large dose

of radiation requires a strict safety program to ensure an accurate delivery. The process from acceptance of the equipment, calculation

of treatment times, placement of the applicator within the patient, monitoring of the dose rate during the treatment, and verification of

the delivered dose are discussed.

Methods and Materials: At our institution we use the Intrabeam system from Zeiss. The manufacturer’s data for absolute dose rate

and depth dose were verified using parallel plate and cylindrical chambers in water and in plastic water. Based on our institutions

prescription of 600cGy at 1cm from the surface, independent treatment time tables were generated to confirm the console values for

each treatment. The position of the applicator, tissue conformance, and proper skin distance is verified with ultrasound prior to

treatment. One Dose mosfet detectors are placed at the closest point on the skin to the applicator and on the contralateral breast.

During the treatment, the internal radiation monitor on the Intrabeam system tracks the dose rate to confirm accurate delivery.

Results: The manufacturer’s data was confirmed to within 5%/1mm for dose rate and depth dose. The skin doses measured with the

mosfet detectors agreed with calculated values within 20%. This is reasonable given the uncertainty in the exact placement of the

device. The average contralateral breast dose was 2.4 cGy, minimum and maximum were 1.2 and 4.7 cGy.

Conclusion: All results have agreed well with calculated values.

Examining the off-axis dosimetric response of two commercial EPID systems

D. Bailey, L. Kumaraswamy, H. Malhotra, M. Podgorsak

Purpose: In recent years, MV electronic portal imaging devices (EPIDs) have proven useful for pre-treatment IMRT dosimetric

verification. The Varian PortalDosimetry system (Palo Alto CA), which compares an EPID calibrated image to a predicted EPID

image calculated by the TPS, is documented in the literature as producing good results with central fields but overresponse at off-axis

distances greater than 10cm. A newer EPID dosimetry system, EPIDose by Sun Nuclear Corporation (Melbourne FL), which converts

raw EPID images into dose planes for direct comparison to TPS cross-sections calculated in water, has previously been studied with

prostate and head/neck IMRT fluences but no examination has been documented concerning off-axis response. This study compares

the off-axis dosimetric response of these EPID systems.

Methods and Materials: We have commissioned both Varian Portal Dosimetry and Sun Nuclear EPIDose for use with a Varian

Trilogy accelerator and aS1000 Portal Vision EPID. The EPIDose algorithm was optimized for EPID response to MLC transmission,

EPID response to varying field size, and dose kernel redistribution (accounting for scattering characteristics dependent on depth) using

sample prostate and head/neck fluences. No model optimization is currently recommended for the Varian portal prediction system.

EPID images (both raw and calibrated) and MapCHECK dose planes were measured for 30 off-axis, asymmetric breast tangent

electronic compensation fluences. PortalDosimetry predictions and calculated water dose planes were exported for comparison of the

measurements to the TPS.

Results and Conclusions: PortalDosimetry and EPIDose perform with similar results for centrally located fields (e.g. prostate and

head/neck), as expected from the current literature. However, PortalDosimetry shows marked disagreement with TPS predictions for

off-axis, asymmetric fields (e.g. breast tangents), with an average gamma evaluation pass rate of 79% (3%,3mm, 10% threshold).

Results for the same fluences with MapCHECK and EPIDose (as compared to TPS water calculations) are much better, averaging

gamma pass rates of 97% and 95%, respectively. The improved performance of the EPIDose system over the PortalDosimetry system

for these types of fluences is evidently the result of the EPIDose model optimization procedures, including a correction factor for

EPID response to MLC transmitted radiation (a factor not accounted for by the PortalDosimetry system and largely responsible for its

off-axis overresponse, as documented in the literature).

Realistic simulated lung nodule dataset for testing CAD detection and sizing

R.D. AMBROSINI1 AND W.G. O’DELL1,2

Departments of 1Biomedical Engineering and 2Radiation Oncology, University of Rochester, Rochester, NY

The development of computer-aided diagnosis (CAD) methods for the processing of CT lung scans continues to become increasingly

popular due to the potential of these algorithms to reduce image reading time, errors caused by user fatigue, and user subjectivity

when screening for the presence of malignant lesions. This study seeks to address the critical need for a realistic simulated lung

nodule CT image dataset based on real tumor morphologies that can be used for the quantitative evaluation and comparison of these

CAD algorithms. The manual contouring of 17 different lung metastases was performed and reconstruction of the full 3D surface of

each tumor was achieved through the utilization of an analytical equation comprised of a spherical harmonics series. 2D nodule slice

representations were then computed based on these analytical equations to produce realistic simulated nodules that can be inserted into

CT datasets with well-circumscribed, vascularized, or juxtapleural borders and also be scaled to represent nodule growth. The 3D

shape and intensity profile of each simulated nodule created from the spherical harmonics reconstruction was compared to the real

patient CT lung metastasis from which its contour points were derived through the calculation of a correlation coefficient, producing

an average value of 0.8897 (±0.0609). This database of realistic simulated nodules can fulfill the need for a reproducible and reliable

gold standard for CAD algorithms with regards to nodule detection and nodule sizing, especially given its virtually unlimited capacity

for expansion to other nodule shape variants, organ systems, and imaging modalities.