A presentation from Jonathan Rogers, Senior Medical Physicist at Alyzen Medical Physics, at ASTRO 2015.

1. Another Device to Commission?
Begin
Commissioning AlignRT® with
Minimal Disruption

2. DISCLOSURES
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I have nothing to disclose

3. INTRODUCTION
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• 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?

4. INTRODUCTION
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• 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?

5. COMMISSIONING SURFACE IMAGING
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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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• 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

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• 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

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• 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)

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• 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

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• 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

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• 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

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• 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

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• 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

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• 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

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• 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

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• 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

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THANK YOU!
www.alyzenmed.com
1801 South 54th Street
Paragould, AR 72450
870.926.0894
jrogers@alyzenmed.com
Jonathan Rogers, MS, DABR