Portaldosimetrie mit ´Portal Vision´
Var
i
an’
sQAsol
ut
i
on
VARIAN Medical Systems
© Varian Medical Systems, 2005
Die Vision

Goal
 Verify
the dose distribution

Each IMRT field, without patient in beam

PortalVision LC250 and aS500
 Increase
efficiency for the Physicist

Commission IMRT sooner

Ongoing pre-treatment QA
VARIAN Medical Systems

Reduce time to evaluate a plan

Less time/plan = Verify more plans
March 2005
Slide 2
Die Zukunft...
Focus
Asymmetric Jaws
MLC / Custom
Field Shaping

Quantitative dosimetric QA of
Patient Treatment, including
3D reconstruction of multi-field
IMRT
Patient
Central Dose
Absolute dose=
100 cGy delivered?
VARIAN Medical Systems
Treatment
Couch
March 2005
Slide 3
Traditional Dosimetry Tools

Measurement tools

VARIAN Medical Systems

Ion chamber

Diodes

Film

Analysis software
Challenges

Non-linear sensitometry of film

Image registration; accuracy variations

User errors

Labor intensive, time consuming (2-4 hr. / plan)
March 2005
Slide 4
Traditional Film Dosimetry
Expose film
Expose film
Process film
Process film
Scan film
Scan film
H&D curve
calibration
Calibration
VARIAN Medical Systems
Import dose image
Align images
Compare
results
Planned Field Analysis
March 2005
Slide 5
Portal Dosimetry
PV
Eclipse
Expose film
Expose
imager
Import
dose image
Process film
Process film
Scan film
Scan film
Align images
Calibrate
Imager
Compare
results
PV
Vision
Calibration
VARIAN Medical Systems
Planned Field Analysis
March 2005
Slide 6
Portal Dosimetry

Dosimetry is a Process

‘
Por
t
al
Dosi
met
r
y’i
sasystem capability (TPS, PV,
VarisVision)

‘
Dosi
met
r
yWor
kspace’access in PV (standalone)
and Vision Review

Portal Dosimetry is a set of capabilities which
provides

Accumulation of relative dose at the PV imager position

Dose evaluation, acquired dose vs. TPS-predicted dose

For the application of Pre-treatment QA
VARIAN Medical Systems

Beam through air only (thru phantom = future capability)

No patient in beam
March 2005
Slide 7
Focus
Portal Dosimetry
Dosimetry
Asymmetric Jaws
DMLC

Application


Pre-Treatment Verification
without Phantom
FDA 510(k)
Qualitative Comparison
Patient
Predicted
Portal Dose
Acquired
Portal Dose
Treatment
Couch
Portal Imager
VARIAN Medical Systems
March 2005
Slide 8
Portal Dosimetry Applications
The Future?
Machine QA
pre-Treatment QA
in vivo QA
Focus
Asymmetric Jaws
MLC / Custom
Field Shaping
Q
A
T
e
s
t
Consistency
P
l
a
n
Plan
vs
Actual
T
x
Patient
EPID/Film
Portal
Dose
VARIAN Medical Systems
Treatment
Couch
Portal
March 2005
Dose
Detector
Slide 9
Treatment Methods Supported
Treatment Type
Overall
Dose
Prediction
Dose
Acquisition
IMRT sliding windows
Yes
Yes
Yes
Step-and-shoot
Yes
Yes
Yes
Static field for machine QA
Yes
Yes
Yes
Dynamic wedge
No
No
Yes
VARIAN Medical Systems
March 2005
Slide 10
Varis/Vision
TPS
TPS
Fluence map
+ dose matrix
Dosimetric Image
VARIAN Medical Systems
USER
PROCESS
Vision
Vision
EPID
Portal Dose Prediction
March 2005
Slide 11
Eclipse (TPS) role in Dosimetry


Patient

Treatment Plan

Verification Plan

Dose prediction file for each field

Gantry 0 degrees for all fields (Plan angles possible)

User-defined imager position (SAD)
Result –predicted dose matrix ( image ) absorbed in
PV cassette in ABSOLUTE values
VARIAN Medical Systems
March 2005
Slide 12
Portal Vision ( EPID) role in Dosimetry


Calibration (Treat or Standalone PV)

Calibration of detector at each energy, dose rate, and
2 distances

Dose normalization for LC250
Acquisition (Treat or Standalone PV)

Integrated Image acquisition mode and sequence template

Automated Density Image to Dose Image conversion

Off-line integration of split fields (multiple image)
VARIAN Medical Systems
March 2005
Slide 13
Portal Vision (EPID) Acquisition

FDA 510(k) - Images courtesy of KFJ Hospital, Vienna Austria
VARIAN Medical Systems
March 2005
Slide 14
Portal Vision (EPID) Acquisition
Reference Image
VARIAN Medical Systems
Integrated Dose
March 2005
Slide 15
VarisVision (R&V) role in Dosimetry
 Dosimetry
workspace in Review (Vision or
Standalone PV)
 Dose

Image Display
Dose Images Alignment
 Dose
Measurement & Evaluation

Point dose

Line Profile

Dose difference

Gamma evaluation

Off-line integration of split fields (multiple image)
VARIAN Medical Systems
March 2005
Slide 16
Dosimetry Review: Dose Evaluation
Traditional Dose Evaluation Tools: Line Profile + Point Dose
VARIAN Medical Systems
March 2005
Slide 17
Dosimetry Review: Dose Evaluation
Gamma Evaluation showing good correlation
Gamma > 1
VARIAN Medical Systems
March 2005
Slide 18
Dosimetry Review: Dose Evaluation
Gamma Evaluation showing mismatch
GammaGamma
>1
>1
VARIAN Medical Systems
March 2005
Slide 19
Dosimetry Summary


IMRT adoption easier and faster

Facilitates IMRT QA

Confirms that Clinac delivers the planned dose

Pre-treatment QA in a fraction of the time vs. traditional methods
Advantages

Improved staff efficiency

Costs

Facilitates good patient care
VARIAN Medical Systems
, billings
March 2005
Slide 20
Conclusion

Acceptance testing, commissioning and QA of IMRT
involves new concepts specific to IMRT.

Standards and guidelines are not yet established.

Your clinical judgment is important to patient safety.

In general, you should expect IMRT planning and
delivery systems to perform as well as 3DCRT
planning and delivery systems.
VARIAN Medical Systems
March 2005
Slide 21
Vielen Dank für Ihre Aufmerksamkeit
VARIAN Medical Systems