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Another Device to Commission?
Begin
Commissioning AlignRT® with Minimal Disruption
DISCLOSURES
2
I have nothing to disclose
INTRODUCTION
3
• Technology and complexity in radiation oncology continues to grow at a fast pace
• The need for accurate implementation of SRS/SBRT QA programs is crucial
• Increased pressure to keep cost down and be more efficient
How can physicists provide increased value to clinics with increasing demands,
but maintain a high level of safety?
INTRODUCTION
4
• Combine tests to accomplish multiple QA procedures at one time
• Focus first on mission critical processes (think TG-100 and FMEA analysis)
• Use AAPM Task Groups as guidance when developing your program
Now, what about a technology that I don’t know? Like surface imaging?
COMMISSIONING SURFACE IMAGING
5
The approach is the same as every other modality in
radiation therapy
• Start out with the Task Group (AAPM TG-147)1 for
recommendations
• Discuss with your clinicians the goals of the system
(motion management for SRS, positioning for breast
patients, etc)
• Prioritize the QA in terms of the clinical need
– Do you need to perform all QA possible?
1 Willoughby, T., et al. “Quality assurance for nonradiographic radiotherapy localization and positioning systems: Report of Task Group 147.” 8 March 2012
6
THE TECHNOLOGY
• Stereoscopic camera system that is used for positioning and tracking
• Isocenter is determined from a novel calibration procedure2
• Triangulation provides a 3D reference frame using a speckle pattern on the
patient’s surface
ALIGNRT® INTRODUCTION
2 http://www.visionrt.com/content/core-technology
7
COMMON APPLICATION
• Intrafraction motion-management for SRS, SBRT, and respiratory cases
• Positioning for sites where the surface is a good surrogate for the target
– Breast, intracranial, extremities, etc
• General use for all patients
– Gross movements
• The beam can be held (automatically on most systems) when the registered
surfaces are out of the specified tolerance
ALIGNRT® INTRODUCTION
8
Start with the clinical use cases to establish QA procedures in conjunction with the
AAPM TG-147
One size may not fit all, and a good QA program will reflect the clinical need
• What site will be treated most often?
• Will it be used for motion-management, positioning, or both?
• Will the beam be held during treatment delivery (dynamic gating)?
• What tolerances will be needed during position and treatment delivery?
CLINICAL USE CASES
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Start by mapping out the workflow and establish an End-to-end test, which
incorporates the complete clinical use case
COMMISSIONING TESTS
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Try to create a test that mimics the clinical use case (E2E)
END-TO-END (E2E) TEST
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EQUIPMENT NEEDED
• Phantom (preferably anthropomorphic) that has a neutral surface for imaging
– Shouldn’t be a ball or cylinder, due to tracking difficulties
– MAX-HD® (Integrated Medical Technologies) a good choice
– STEEV SRS Phantom (CIRS)
– SRS Head Phantom from IROC (clear, so may need taped to image well)
• Detectors such as Gafchromic® film, microchambers/diodes, OSL/TLD
• Electrometer
• 3DOF Head Adjuster (provided by VisionRT) or 6DOF couch for accurate
positioning
END-TO-END (E2E) TEST
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END-TO-END (E2E) TEST
SAMPLE PHANTOMS
MAX-HD STEEV SRS (IROC) SRS Phantom
IMT CIRS IROC CIRS
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SOME NOTES ABOUT EQUIPMENT
• Detectors should be small enough to avoid partial volume effects, especially for
SRS
• Film scanning should use the right calibration procedure
• Make sure film is cut in such a way to ensure reproducibility and localization
– Laser cut films for the phantom are available
• Epson Perfection XL11000 (or the older XL10000) are good choices for film
scanning
END-TO-END (E2E) TEST
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CT SCANNING
• Use the highest resolution protocol possible (small slice thickness ~1mm, high
mAs, etc)
• Try and use the same immobilization techniques that would be used during
treatment
• Set your DICOM origin (CT origin) at a reproducible localization to minimize setup
errors
• If the phantom supports it, try multiple CT scans with different inserts and cubes
– Again, it’s important to know the origin with certainty for film scanning
END-TO-END (E2E) TEST
15
CONTOURING
• Many treatment planning systems automatically create the BODY contour, so
review for accuracy
• The Target Volume can be the sensitive volume of the detector or the center of
the film
END-TO-END (E2E) TEST
16
TREATMENT PLANNING
• Use a beam configuration that will test the system
– Couch kicks
– VMAT, if applicable, to block cameras
– Dose levels that mimic treatment time (don’t scale MU)
– Use a real plan if available
• Save for a baseline for routine QA
END-TO-END (E2E) TEST
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LOCALIZATION
• Use the AlignRT system to be the primary localization method
• Verify the positioning with CBCT and lasers
– There may be a small deviation with the DICOM because of the BODY
contour
– If so, position initially with CBCT, capture the reference, then reposition
with the AlignRT system
• Use a 6DOF localization technique to position the phantom
END-TO-END (E2E) TEST
18
DELIVERY
• Make note of gantry occlusion and deltas
– Some variation is acceptable during blockage, but extreme shifts may
indicate improper lighting, ROI, or calibration conditions
• Watch the deltas for drift over the course of the treatment at the couch base
• When rotating the couch, use the AlignRT readout, not the digital indicators, to
reposition
– Stereoscopic systems trump the internal readouts of the LINAC system,
hence the “STEREO” in stereotactic
– This is especially important in older systems, where couch tolerances are
looser
END-TO-END (E2E) TEST
19
ANALYSIS
• Temperature/pressure correct the chamber reading, and use a cross calibration
factor to calculate the ratio of charge/dose (traced by to your ASCL calibrated
detector)
• FilmQA® from Ashland is a good choice for film scanning
– FilmQA analyzes in all 3 RGB channels
– ImageJ is also available for free, but takes some effort to write code
• Always scan the film in the same orientation, and if the calibration films are not
done on the same day, wait a while for the film to develop
END-TO-END (E2E) TEST
20
WHAT AM I LOOKING FOR?
Depends on the clinical goals
• Breast patients could be passing 95% with a gamma index at 3%, 3mm with the
film analysis
• SRS programs treating trigeminal neuralgia cases may need 2%, 1mm
• Output measurements should be within 2% of the expected from the TPS, but
can be tough for small cones because of the output factors
If you pass the E2E, the commissioning process got a whole lot better. But…
END-TO-END (E2E) TEST
21
WHAT IF IT FAILS?
Start looking at each component of the system closer. You will need it for the
overall QA program anyways. Keep in mind:
1. TG-147 is just part of this. Since an E2E test checks the whole system, it could
be anything outlined in TG-40, TG-142, TG-66, etc
2. Focus on the components that are specific to TG-147, as to not get
overwhelmed
END-TO-END (E2E) TEST
22
• Do a “chart check” style review to make sure items transferred properly
– Patient ID
– Isocenter
– Contour (especially BODY)
– Scan orientation
• The coordinate system of the LINAC matches the TPS and DICOM transfer
– For example, the couch coordinates could be opposite if the coordinate
systems don’t match
COMMICATION BETWEEN SYSTEMS
23
• Do a “chart check” style review to make sure items transferred properly
– Patient ID
– Isocenter
– Contour (especially BODY)
– Scan orientation
• The coordinate system of the LINAC matches the TPS and DICOM transfer
– For example, the couch coordinates could be opposite if the coordinate
systems don’t match
• If using an interface for shifts, ensure that is correct by using lasers or another
surrogate to confirm AlignRT shifts performed by the LINAC console
COMMICATION BETWEEN SYSTEMS
24
• An accurate ROI gives stable real-time deltas for any phantom when there are no
occlusions. If the delta jump at couch base, and no blockage
– Ensure the ROI give a unique view
• I.e., not flat, symmetric, nor broken
– The underlying image is intact
• Check lighting condition or skin tone
• It is equally important to not make the ROI so big it doesn’t detect small
movements
– Like contouring the entire head for SRS – just use the small area in the
open mask
REGION OF INTEREST (ROI)
25
• In order to make sure the calibration (both the calibration plate and fine
isocenter) is correct, perform a series of shifts to known positions, and record
the deltas
– Shift 2mm, 1cm, 2cm, 5cm, 10cm in S/I, L/R, and A/P directions
– Kick the couch in increments of 45 degree, for example
– Move the phantom arbitrarily, and see if the 6DOF positioning can get
back to a zero baseline
• If greater than 1mm (for SRS) disagreement is seen, perform isocenter and
monthly calibrations again, and repeat
• Refer to the acceptance testing procedures for vendor baselines as well
SHIFTS
26
• With the camera system on for a significant period of time (like an hour or so),
turn the monitoring on and watch the deltas
• Record the values, and if large deviations are seen, repeat after a longer warm
up is achieved
• Compared to infrared based systems, the drift should be quite minimal
SHIFTS
27
• With the camera system on for a significant period of time (like an hour or so),
turn the monitoring on and watch the deltas
• Record the values, and if large deviations are seen, repeat after a longer warm
up is achieved
• Compared to infrared based systems, the drift should be quite minimal
SHIFTS
28
• With a simple motion phantom, try and move the phantom enough to hold the
beam
• Tighten tolerance to only beam on when the chamber is in position
• Use a simple test plan to isolate it just the motion of the phantom
• Measure with an ion chamber and record the results
– Should be very close to baseline, stationary reading, assuming the
phantom is not shifting during motion, and the gating is working
• This would also test spatial accuracy at the same time
DYNAMIC GATING
29
• As with all medical devices, it is up to the medical physicists to stay current with
the latest customer service bulletins and release notes
• The tests outlined are from a clinical medical physicist’s perspective, but are by
no means meant to be prescriptive
• Training and continuing education are equally, and maybe more, important than
a one-time commissioning – as is the continual QA program
VENDOR RECOMMENDATIONS
30
• VisionRT has already provided a nice workflow for QA
– DailyQA
• Uses the calibration plate, aligned by the therapists, and analyzes it
for constancy
– MonthlyQA
• Again, using the plate, but overrides the triangulated 3D position of
the system. To be done if the system appears to have changed
– Isocenter Calibration
• Using a phantom with fiducials that can be seen on CT/MV, with the
surface imaged, allows the isocenter of the imaging system to be
correlated to the MV isocenter
ESTABLISHING A QA PROGRAM
31
• In addition to the vendor provided phantoms and software, use the results from
the commissioning tests to create baselines for routine QA
ESTABLISHING A QA PROGRAM
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"If it's not written down, it didn't happen“
• Ensure all the tests you do during commissioning, QA, or anything concerning
the system are well documented
• Not only is it good to establish baselines and trends, it is very useful in helping
other centers when they go live with AlignRT
DOCUMENTATION
33
• Commissioning any system doesn’t have to be difficult, or even that time-
consuming, any long as the problem is well-defined
• By using clinical use cases as guidance, tests will solidify, and the project can be
focused
• By incorporated E2E tests, and grouping other QA procedures in an effective way,
commissioning and routine QA time can be reduced
CONCLUSIONS
34
THANK YOU!
www.alyzenmed.com
1801 South 54th StreetParagould, AR 72450
870.926.0894
Jonathan Rogers, MS, DABR