|
|
Upstate |
Major Meeting Sponsor: Elekta
Inc.
12:00 pm – 5:00 pm Sponsoring Vendor Exhibits:
Elekta Inc.
North American Scientific
Impac Medical
Systems Upstate
Linac Services, LLC
Tomotherapy
Inc Sun Nuclear
Aktina, Inc
10:30 AM-11:30 AM
Business Meeting
12:00 Lunch Sponsored
by North
American Scientific
12:30 Refreshment
and Vendor Exhibit – Sengupta Room
Sponsored by Sun Nuclear
|
1:00 |
Meeting
Introduction |
Shivaji Deore UNYAPM President |
|
Vendor Session |
||
|
1:05 |
EPID for Absolute Dose Based IMRT QA” |
James Ernsberger, Sun Nuclear |
|
1:20 |
Discussion of Volumetric Modulated Arc Therapy |
Ed Hahn, Elekta, Inc. |
|
Proffered Paper Session |
||
|
1:35 |
A Genetic Algorithm and Distributed-Computing Approach to Beam Angle Optimization in IMRT |
Daryl P. Nazareth1, Stephen T. Brunner2, Matthew D. Jones3, Matthew B.
Podgorsak1, Michael R. Kuettel1 |
|
1:50 |
Beam Weight and Angle Optimization in Radiation Therapy using Coupled Monte Carlo and Genetic Algorithm Codes |
M Bakhtiari1, M D Jones2,
H K Malhotra1, M B Podgorsak1, and D |
|
2:05 |
Computer-aided detection of metastatic brain tumors using
automated 3-D template matching |
R. Ambrosini1,P. Wang2, B. Kolar3,
W. O’Dell1 |
|
2:20 |
The Solid-State
X-Ray Image Intensifier (SSXII): The Next Generation of X-Ray Imagers |
Andrew
Kuhls-Gilcrist, Amit Jain, Daniel R Bednarek, Stephen Rudin, |
|
2:35 |
Estimating Effective
Dose in Radiostereometric Analysis of the Lumbar Spine |
Kerry Greene-Donnelly, Kent Ogden, Nat Ordway, Jerry Calabrese,
Marsha Roskopf |
|
2:50 |
Refreshment , Vendor
Exhibits and Poster Viewing* – Sengupta Room Sponsored
by
Sun Nuclear, |
|
|
3:20 |
An IMRT planning method for limiting spinal cord to tolerable
levels with unintended field overlaps at the supra-clavicular junction plane
of head and neck radiotherapy |
Steven de Boer,
Osama Hassad*, Wainwright
Jaggernauth |
|
3:35 |
A Guidance System for Optical Patient Alignment during
breast radiotherapy |
Jonathan
Schmitta, Kenneth Hoffmanb, Mohammad Bakhtiaria,
Harish Malhotraa, Daryl Nazaretha |
|
Invited Speaker Sessions |
||
|
3:50 |
Experience in Development
of clinical SBRT Program |
Harish K Malhotra, Roswell Park Cancer Institute, Bufflao,NY |
|
4:10 |
The Past,
Present, and Future in Medical Physics |
Prof. Jake Van Dyk |
|
4:50 |
Frederick Faw Memorial Award Presentation |
Dan Bednarek & Steve de Boer |
*Poster Presentations:
1. Accuracy
in the dose delivery of IMRT as a function of Gantry and Collimator Angles,
Jubei
Liu, Zhou Wang, Matthew B. Podgorsak, Steven
F. de Boer, Lalith Kumaraswamy,
Harish Malhotra, Department
of Radiation Medicine, Roswell Park Cancer Institute, Elm & Carlton
Streets,
2. Dosimetric Analysis of the
Effect of Tungsten Shields in a Fletcher-suit Delclos Applicator in High-
Dose-Rate brachytherapy using Gafchromic Film,
Thomas R. Stanley, Mohammad Bakhtiari, M B,Podgorsak, Wainwright Jaggernauth &
Malhotra
HK, Roswell Park Cancer Institute,
ADJOURN
Driving Directions to
Directions (to
From the West:
From
From the East:
From the South: 390 North to 590 North to 104 West to
Parking is available on 3rd and 4th floors. After parking, please take Elevator to Hospital Main Entrance. The TWIG auditorium is located right after front desk.
UNYAPM
SPRING MEETING PROCEEDINGS
May 22, 2008
EPID for Absolute Dose Based
IMRT QA
Benjamin Nelms, James Ernsberger
Sun Nuclear Corporation,
The Electronic Portal Imaging Device (EPID) has become a common linac accessory, and there is great interest in the adoption of the Mega-voltage (MV) EPID for use in routine IMRT QA. There are several benefits to this technology, most particularly: high data density, good resolution (small pixels), large area, and workflow efficiency (online and electronic). However, the EPID is not a dosimeter, it is essentially a camera, and it is paramount to keep IMRT QA in a “dose-based” strategy. In order to fully audit both the delivery system and the TPS calculation, a measured absolute dose plane must be compared with a TPS calculated absolute dose plane (i.e. image-to-predicted image strategies do not audit fully the TPS calculation). EPIDoseTM, part of the MapCHECKTM suite of QA tools, was recently commercialized, making it possible to convert, via an algorithm, EPID images into QA absolute dose planes. The EPIDose model is commissioned vs. absolute dose diode array planes, and then used thereafter for comparison directly with TPS calculated planar dose fields. The EPIDose solution is highly efficient, planning system independent, allows calculation accuracy to be verified by a trusted dosimetry standard and no part of the planning delivery system is left out of the QA routine. In this presentation, clinical IMRT plans will be presented illustrating the accuracy and power of EPIDose.
__________________________________________________________________________________________________________________________________________________________________________
Discussion of Volumetric
Modulated Arc Therapy
Ed Hahn, Elekta, Inc.
Volumetric Modulated Arc
Therapy (VMAT) technology provides a simultaneous control of the linear
accelerator gantry position and speed, the leaves and angle of the multileaf
collimator and dose rate. This flexibility enables highly conformal cancer
treatments, as well as optimal sparing of the healthy tissue around the target.
In addition, VMAT significantly reduces patient treatment times, leading to
greater patient comfort and stillness for a more efficient and precise
treatment.
The clinical benefits of VMAT that are seen by our customers who are utilizing this technology with CE Designation in Europe are as follows: Smooth automatic delivery in one automatic sequence, fast, accurate and efficient beam delivery, optimal tumor conformity, increased patient through put, reduced interplane dose and the ability for treatment of pediatric tumors.
With VMAT from Elekta,
customers are able to utilize non-coplanar techniques (up to 12 degrees) as we
have the smallest Linac head diameter.
By being able to kick the table this further improves conformity to PTV
and reduces dose to critical structures.
As Elekta has been working
on this technology (beginning with Intensity Modulated Arc Therapy, IMAT) for
ten years and holds the patent on multiple arc delivery. This enables the option deliver with more
than one arc. Complicated head and neck
IMRT plans may have much better plans if the first arc rotated around the table
at 0 degrees, and then rotated back with the table shifted at a 10 degree
angle.
*Elekta Volumetric Intensity
Modulated Arc Therapy (VMAT) is pending regulatory approvals in certain
markets, including 510(k) clearance in the US, and is not yet available for commercial
sale in the US.
__________________________________________________________________________________________________________________________________________________________________________
A Genetic Algorithm and
Distributed-Computing Approach to Beam Angle Optimization in IMRT
Daryl P. Nazareth1, Stephen T.
Brunner2, Matthew D. Jones3, Matthew B. Podgorsak1,
Michael R. Kuettel1
1Roswell Park Cancer Institute,
3University at
Purpose: IMRT treatment planning involves the selection of gantry angles, as
well as the specification of structures and constraints employed in the
optimization process. Including these
angles in the combinatorial search space vastly increases the computational
burden, and therefore the gantry angle selection is normally performed manually
by a clinician, based on clinical experience.
We have investigated the use of a genetic algorithm (GA) and
distributed-computing platform to optimize the gantry angle parameters and to
provide insight into additional structures which may be necessary in the dose
optimization process to produce optimal IMRT treatment plans.
Method and Materials: For an IMRT prostate patient, we produced
the first generation of 40 samples, each of five gantry angles, by selecting
from a uniform random distribution, subject to certain adjacency and opposition
constraints. The dose optimization was
performed by distributing the forty-plan workload over several machines running
a commercial treatment planning system.
A score was assigned to each resulting plan, based on how well it
satisfied clinically-relevant constraints.
The second generation of 40 samples was produced by combining the
highest-scoring samples using the techniques of crossover and mutation. The process was repeated until the sixth
generation, and the results compared with a clinical (equally-spaced) gantry
angle configuration
Results: In the sixth generation, 34 of the 40 GA samples achieved better
scores than the clinical plan, with the best plan showing an improvement of
84%. Moreover, the resulting
configuration of beam angles tended to cluster toward the patient’s sides,
indicating where the inclusion of additional structures in the dose
optimization process may avoid dose hot spots.
Conclusion: Gantry angle optimization in IMRT involves
a large-scale computational problem. We
have demonstrated that the GA combined with a distributed-computing platform
can be applied to optimize gantry angle selection within a reasonable amount of
time.
__________________________________________________________________________________________________________________________________________________________________________
Beam Weight and Angle
Optimization in Radiation Therapy using Coupled
M Bakhtiari1, M D Jones2,
H K Malhotra1, M B Podgorsak1, and D Nazareth1
1Roswell Park Cancer Institute,
2Center for Computational Research, University at
Purpose:
Monte Carlo (MC)
algorithms remain the gold standard in dose calculation routines. However, their long calculation times
generally make them infeasible for clinical implementation, especially for IMRT
optimization which requires rapid pencil-beam dose computation. In a
preliminary study, we are investigating how high-throughput computing may be
employed to perform MC dose calculations, beam weight optimization, and in
conjunction with a genetic algorithm (GA), beam orientation optimization.
Method and Materials: Two non-commercial software packages were
used for this project, VMC++ and CERR.
VMC++ is an MC dose calculation package which is more efficient than
general-purpose MC routines due to its use of variance reduction techniques,
making it approximately 50 times faster than the BEAMnrc code. CERR is an open-source environment for
radiotherapy calculations. We used the
data-importation and beam-shaping features of CERR in conjunction with the
dose-calculation routines of VMC++ to perform dose computation on a 5-field 3D
CRT prostate case as the inner loop of our method. We then optimized the beam
weights using DVH-based constraints and the Nelder-Mead simplex technique, a
multidimensional unconstrained nonlinear minimization algorithm. The results served as input for a GA run in
the outer loop. Each generation of the
GA involved 40 plans. The calculations
were performed using the computational resources of the Center for
Computational Research, an academic supercomputing facility.
Results: The dose calculation and optimization involved several million
particle histories, and required about two hours for each generation of the
genetic algorithm. The resulting plan
was optimal based on the constraints provided to the system.
Conclusion: We have shown that, using a
distributed-computing platform, MC and GA routines may be coupled and employed
for treatment planning in a reasonable amount of time. This work will be
extended to IMRT and beam-angle optimization by combining a variety of techniques.
__________________________________________________________________________________________________________________________________________________________________________
The Solid-State X-Ray Image
Intensifier (SSXII): The Next Generation of X-Ray Imagers
Andrew Kuhls-Gilcrist, Amit Jain, Daniel R
Bednarek, Stephen Rudin
University at
Buffalo, Buffalo, NY.
Purpose: The solid-state x-ray image intensifier (SSXII) is an EMCCD-based x-ray detector designed to satisfy an increasing need for high-resolution real-time images, while offering significant improvements over current flat panel detectors (FPDs) and x-ray image intensifiers (XIIs). FPDs are replacing XIIs because they reduce/eliminate veiling glare, pincushion or s-shaped distortions and are physically flat. However, FPDs suffer from excessive lag and ghosting and their performance has been disappointing for low-exposure-per-frame procedures due to excessive instrumentation-noise. XIIs and FPDs both have limited resolution capabilities of ~3 cycles/mm.
Method and Materials: To overcome these limitations a prototype SSXII module has been developed, consisting of a 1k x 1k, 8 µm pixel EMCCD with a fiber-optic input window, which views a 350 µm thick CsI(Tl) phosphor via a 4:1 magnifying fiber-optic-taper (FOT). Arrays of such modules will provide a larger field-of-view. Detector MTF, DQE, and instrumentation-noise equivalent exposure (INEE) were measured to evaluate the SSXIIs performance using a standard x-ray spectrum (IEC RQA5), allowing for comparison with current state-of-the-art detectors.
Results: The MTF was 0.20 at 3 cycles/mm, comparable to standard detectors, and better than 0.05 up to 7 cycles/mm, well beyond current capabilities. DQE curves indicate no degradation from high-angiographic to low-fluoroscopic exposures (< 2% deviation in overall DQE from 1.3 mR to 2.7 µR), demonstrating negligible instrumentation-noise, even with low input signal intensities. An INEE of < 0.2 µR was measured for the highest-resolution mode (32 µm effective pixel size). Comparison images between detector technologies qualitatively demonstrate these improved imaging capabilities provided by the SSXII.
Conclusion: Initial use of the solid-state x-ray image intensifier has shown that this technology has great promise to be the next generation dynamic x-ray imager, providing significant improvements over current state-of-the-art detectors for applications such as fluoroscopy and angiography requiring high frame rates, resolution, dynamic range and sensitivity while maintaining essentially no lag and very low INEE.
__________________________________________________________________________________________________________________________________________________________________________
Accuracy in the dose delivery
of IMRT as a function of Gantry and Collimator Angles
Jubei Liu, Zhou Wang, Matthew B. Podgorsak, Steven F. de Boer, Lalith Kumaraswamy, Harish Malhotra
Department of
Radiation Medicine, Roswell Park Cancer Institute, Elm & Carlton Streets,
Purpose: Sliding window IMRT is the most
demanding in terms of quality assurance requirement because of the coordination
of the MLC positioning with the machine output.
Because of their weight, MLC leaves may experience significant
gravitational force particularly when moving against gravity. Traditionally IMRT beam data as well as
patient specific IMRT QA is performed with gantry in straight condition which
does not reflect the actual beam and collimator angle used in a patient. Thus it is important to study the accuracy in
dose delivery due to MLC motions as a function of gantry and collimator angles.
Material & Methods: We
have taken 3 IMRT treatment fields representing minimally, moderately and
heavily modulated fluences, respectively.
The dose plans were generated for a Varian Trilogy unit employing a
millennium MLC. All the treatment fields
had 320 control points for IMRT delivery.
MapCHECK along with 3 cm buildup material, in its isocentric fixture,
was mounted in the linac accessory tray to hold it precisely at 100 cm SAD. Both gantry and collimator angle were varied
in intervals of 30° though collimator angles were restricted from 270°-90°. This resulted in 72 combinations of gantry
and collimator measurements per fluence.
Plans were evaluated using standard 3%/3mm criteria.
Results: The pass rate of each
measurement was calculated and normalized over the result of 0o
gantry and 0o collimator. The
variation in the pass-rate was independently studied as function of gantry
angle and collimator angle but no systematic dependence on either of them was
seen. Worst variation of 6% in
moderately modulated field at 270o gantry and 90o collimator
was observed. The overall average and
standard deviations were within 3%.
Conclusion: Our study has given a
confidence that the sliding window IMRT dose delivery technique does not
demonstrate significant gantry and collimator angle dependence due to MLC for
the linac studied.
__________________________________________________________________________________________________________________________________________________________________________
An IMRT planning method for
limiting spinal cord to tolerable levels with unintended field overlaps at the
supraclavicular junction plane of head and neck radiotherapy.
Steven de Boer, Osama Hassad*, Wainwright Jaggernauth
Department of
Radiation Medicine, Roswell Park Cancer Institute,
Purpose: Head and neck cancers can be treated with an upper intensity modulation
radiation therapy (IMRT) plan matched with a lower supraclavicular anterior
field. A small spinal cord block is
traditionally placed in the supraclavicular field to shield to protect the
spinal cord from excess dose due to unintended field overlaps. This block can shield targeted tissue. This study describes a method that keeps the
cord dose within tolerance and still delivers dose to targeted tissues.
Method and Materials:
Radiotherapy plans were created with 7 coplanar IMRT fields matched to
the anterior supraclavicular field. IMRT
optimization is then used to reduce the dose to levels that would result in
tolerable spinal cord doses when field misalignments occur. A structure, named
“cord junction”, was defined as the spinal cord that extends 2.1 cm superiorly
and inferiorly to the junction plane.
The IMRT plan was optimized junction cord tolerances of 5, 10, 20, and
45 Gy. Each of these plans were then summated with the supraclavicular field
with field misalignments of 0, 2, 5, 10 and 20 mm.
Results: As
the overlap increases the maximum “junction cord” dose increases. Larger overlaps are tolerable when the
junction cord was reduced. The 45 Gy
junction cord limit is exceeded for overlaps of 2 mm (junction constraint of 45
Gy), 10 mm (junction constraint of 20 Gy or 10 Gy) and an over 20 mm overlap
was tolerable when the cord junction constraint was 5 Gy. The planning target volume (PTV) coverage was
maintained for each optimization with D95 values of 98%.
Conclusion: This
study has addressed a common concern among clinicians of the need to not shield
areas of possible disease yet ensure a safe spinal cord dose in the case of
small positional errors in the radiation beam.
__________________________________________________________________________________________________________________________________________________________________________
Estimating Effective Dose in
Radiostereometric Analysis of the Lumbar Spine
Kerry Greene-Donnelly, Kent Ogden, Nat
Ordway, Jerry Calabrese, Marsha Roskopf
Purpose: To determine the effective dose
of patients undergoing radiostereometric analysis (RSA) of the lumbar spine
Method and Materials: 12
patients with total disk replacement prosthetic devices in the lumbar spine
participated in an IRB approved study to follow the sagittal and coronal range
of motion using RSA. Image pairs were
obtained at 6 weeks, and then 3, 6, 12, 18 and 24 months. Five image pairs were acquired at each visit
(neutral, flexion, extension, and left and right lateral bend). Radiographic techniques were recorded for all
acquired images. Patient mass was used
to estimate abdominal AP thickness. Tube
output and half value layers were measured at the appropriate tube accelerating
potentials. This information was used
with the image geometry to calculate the entrance kerma-area product (KAP)
incident on the patients. The KAP and
patient thickness were then used to estimate the energy imparted to the
patients and the resulting effective dose.
Results:
The average
technique used was 141 kVp and 11.6 mAs.
The mean effective dose per image pair was 0.304 mSv, and the mean per
visit (5 image pairs) was 1.52 mSv with a standard deviation of 0.7 mSv. The average for the entire two year study was
approximately 9.1 mSv. This compares
very favorably with the value of 18 mSv reported in the 2000 UNSCEAR report for
a single diagnostic lumbar spine study.
Conclusion:
Image quality
requirements for RSA are not the same as for general diagnostic imaging. The use of high kV techniques that would
result in unacceptable low contrast images for general diagnostic purposes are
adequate for visualizing fiducial beads used in RSA. Low doses allow for the acquisition of
multiple image sets to detect motion of prosthetic devices with total effective
doses that are much lower than a typical diagnostic lumbar spine examination.
__________________________________________________________________________________________________________________________________________________________________________
Computer-aided detection of metastatic brain
tumors using automated 3-D template matching
R. Ambrosini1, P. Wang2, B. Kolar3,
and W. O’Dell1,4
Departments of 1Biomedical Engineering, 3Radiology,
and 4Radiation Oncology,
2Department of Radiation Oncology,
Purpose: The development of metastases to the
brain is a common and frequently devastating complication for patients with
extracranial primary tumors. However,
the generally poor prognosis of patients with brain metastases can be improved
with early detection and treatment with stereotactic radiosurgery, as performed
routinely at our institution. We have
developed a novel small tumor detection algorithm based on 3-D template
matching that will enhance the accuracy and
efficiency of radiologists by allowing them to focus upon locations of high
suspicion for metastatic brain tumors without having to spend time reviewing
every image slice.
Methods and Materials: Spherical tumor appearance models were created to match the expected geometry of the small tumors of interest and accounting for offsets due to the cut of MRI sampling planes. A 3-D normalized cross-correlation coefficient (NCCC) between the brain volume and spherical templates was calculated using a fast frequency domain algorithm.
Results: The data collected on 22 patient datasets consisting of 1320 coronal MR slices containing 161 total nodules shows that we can achieve currently a sensitivity of 87.6% with a false positive rate of 0.58 per image slice.
Conclusion: Our results demonstrate that the 3-D
template matching method can be an effective, fast, and accurate tool for
automated detection of tumors in brain MRIs.
Through the optimization of parameters such as
zero padding and NCCC thresholding, we believe our algorithm has the potential
to develop into a clinically useful tool to assist radiologists in providing
earlier and more definitive diagnoses of metastases within the brain.
__________________________________________________________________________________________________________________________________________________________________________
A
Guidance System for Optical Patient Alignment During Breast Radiotherapy
Jonathan Schmitta, Kenneth Hoffmanb, Mohammad Bakhtiaria, Harish Malhotraa, Daryl Nazaretha
a.) Roswell Park Cancer Institute b.)
Purpose: Breast radiotherapy, particularly IMRT, involves large dose gradients and difficult patient positioning problems. A critical requirement for successful treatment is accurate reproduction of the patient’s position assumed during CT simulation and planning. We have developed an image-guided technique, which assists in accurately and reproducibly positioning the patient, by displaying her real-time optical image superimposed on a perspective projection image of her 3D CT data.
Methods. The Single Projection Technique (SPT) accurately determines the 3-D position and orientation of a camera from a single image acquired of a known model. A calibration jig, composed of ten identifiable points, was constructed and CT imaged to provide this model. The 3D coordinates of each point were indicated and recorded using treatment planning software. In a preliminary study, a regular digital camera was installed in the treatment suite and used to obtain an optical image of the jig. The SPT then provided the coordinates and orientation of the camera. Using this information, 3D CT patient data could then be projected onto the camera’s imaging plane, superimposed on the real-time patient image using standard graphical software and displayed on a monitor. This would enable the therapist to view both the patient’s current and desired positions, and guide the patient into assuming the correct position.
Results: The SPT can determine the position and orientation of the camera to an accuracy of 0.2 cm and 0.3°, respectively, using an optical digital image of the calibration jig. This allows an estimated accuracy of 5 mm in the fidelity of the patient’s external anatomy to the surface CT data. This includes anatomical points not easily positioned properly, such as the raised arm and breast skin surface.
Conclusion: We have developed a method to superimpose a perspective projection of a CT image on a patient’s real-time optical image. Displaying this visual information will assist in accurate setup during breast radiotherapy.
__________________________________________________________________________________________________________________________________________________________________________
Dosimetric Analysis of the
Effect of Tungsten Shields in a Fletcher-suit Delclos Applicator in
High-Dose-Rate brachytherapy using Gafchromic Film
Thomas R. Stanley, Mohammad Bakhtiari, M B Podgorsak, Wainwright Jaggernauth & Harish K Malhotra
Roswell Park Cancer Institute,
Purpose: To study the effect of tungsten shields in the radiation dose delivery in a Fletcher-Suit Delclos applicator in high-dose-rate (HDR) brachytherapy using gafchromic film dosimetry.
Methods and Materials: A gadget for rigidly and reproducibly mounting a Fletcher-Suit Delclos (FSD) tandem and ovoid applicator along with an attachment to hold a set of gafchromic films in relation to the applicator in a conventional water phantom was designed and fabricated. The gadget allowed placing 14 films anterior to the tandem and another 14 posterior to the ovoids at a distance of 6.025 mm from each other. The gadget has a provision of 5 fiducial marks per film for spatial registration with the orthogonal films acquired in a simulator. A treatment plan delivering 700 cGy to the pseudo point A was designed. The plan does not account for tungsten shields in the ovoids. After the films were put in place, lasers were used as guides to mark the central axis of each film with respect to the tandem (to establish spatial coordination between both). Once the films were properly aligned, the water phantom was filled with water. The applicator was connected to the Micorselectron HDR treatment unit and the treatment plan was delivered. Each gafchromic film was removed, marked for its location in the pack, dried, and scanned using a Vidar VXR-16 scanner for analysis using RIT software. Using a measured H&D curve for calibration of the gafchromic films, the dose distributions on each film was evaluated and compared to the corresponding distributions produced from the treatment planning system.
Results: An analysis of the data revealed a reduction in dose measured by the gafchromic film over the calculated values from the treatment planning system in the area covered by the solid angle subtended by the tungsten shields in the ovoids. This seems to follow logically considering the treatment planning algorithm does not account for the tungsten shields within each ovoid. The details of the results will be presented.
Conclusion: The growing trend in brachytherapy procedures of this nature is to use CT/MR compatible tandem and ovoid applicators which do not provide any shielding for the bladder and rectum within the ovoids. Thus, it is very important to understand the true radiation doses being delivered to these critical structures when the original treatment has used a shielded applicator.
__________________________________________________________________________________________________________________________________________________________________________
Experience in the development
of clinical SBRT Program
Harish K Malhotra
Asst. Professor,
Dept. of Radiation Medicine, Roswell Park Cancer Institute,
Recently Stereotactic body radiotherapy [SBRT] has been finding wide clinical acceptance for certain type of tumors. Though initially started only for non-operable tumors with a palliative intent, recent interest is also to use it with curative intent irrespective of the operable status of certain tumors. The ablative nature of the high doses associated with SBRT necessitate that this rapidly evolving modality for cancer treatment is implemented in a manner which ensures safe delivery of radiation dose to patients. The present talk will focus on the clinical implementation of a SBRT program using Varian’s Trilogy linear accelerator. The linear accelerator is equipped with KV-imager and has ability to KV-KV, KV-MV and CBCT acquisitions including KV-fluoroscopy mode. It also comes with an optical guidance platform to assist in the patient setup using infrared fiducial markers. Both single slice CT scanner as well as 16-slice CT scanners were used for the CT simulation of these patients. A number of additional quality assurance steps were added at each phase of the treatment including simulation, immobilization, initial setup verification, treatment planning, pre-treatment QA for the linear accelerator as well as the process to determine the setup shifts and during the actual treatment delivery. More than 30 patients have been treated so far since the starting of the program at Roswell Park Cancer Institute since February’07. Details of our experience in the development of our clinical SBRT program will be discussed.
__________________________________________________________________________________________________________________________________________________________________________
The Past, Present, and Future
in Medical Physics
Jacob (Jake) Van Dyk
Manager, Physics and Engineering
Professor,
Departments of Oncology, Medical Biophysics, Diagnostic Imaging and Nuclear
Medicine, and Physics and Astronomy,
790 Commissioners Rd E, London, Ontario,
Canada
The discovery of “a new kind of ray” by Roentgen in 1895 spawned a new era for medicine and a new discipline known as “Medical Physics”. With the evolution of new technologies, medical physics has developed subspecialties in Radiation Oncology, Diagnostic Radiology and Nuclear Medicine. Progress in radiation oncology can be divided into five distinct phases. The advances in the last four decades have largely been in parallel with advances in computer capabilities. In the last two decades, we have experienced a revolution in radiation delivery technologies such that intensity modulated radiation therapy (IMRT) has become routine. Furthermore, enhancement of imaging technologies with the use of CT simulation, MRI, PET and combined PET/CT allows for 3-D viewing of targets and critical structures, with the addition of functional, disease-related information. At the same time, new imaging capabilities on radiation therapy machines provide the location of the “target of the day” and are moving us towards the routine use of image-guided adaptive radiation therapy. With 4-D imaging and 4-D treatment capabilities now possible, we can expect, in the not too distant future, to get daily 4-D imaging of the patient in treatment position and real-time optimization of an updated treatment plan to deal with the anatomy of the day. With developments in new technologies, heavy particle therapy will become more economically viable. In addition, radiobiological modeling and optimization will become routine. A little further forward, nanotechnology and molecular biology will become significant components of both diagnostic imaging and therapy, not only for cancer but for other diseases as well. With these continuous advancements in technology and the increased information base, medical physics continues to have a bright future.
__________________________________________________________________________________________________________________________________________________________________________