VARIAN Medical Systems

Portaldosimetrie mit ´Portal Vision´

© Varian Medical Systems, 2005

Varian’s QA solution

VARIAN Medical Systems March 2005 Slide 2

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

Reduce time to evaluate a plan

Less time/plan = Verify more plans

VARIAN Medical Systems March 2005 Slide 3

Die Zukunft...Asymmetric Jaws

Focus

MLC / CustomField Shaping

Patient

TreatmentCouch

Quantitative dosimetric QA ofPatient Treatment, including3D reconstruction of multi-fieldIMRT

Central Dose

Absolute dose=100 cGy delivered?

VARIAN Medical Systems March 2005 Slide 4

Traditional Dosimetry Tools

Measurement tools 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)

VARIAN Medical Systems March 2005 Slide 5

Traditional Film Dosimetry

Expose film

Process film

Scan film

H&D curvecalibration

Expose film

Process film

Scan film

Compareresults

Import dose image

Align images

Calibration Planned Field Analysis

VARIAN Medical Systems March 2005 Slide 6

Portal Dosimetry

CalibrateImager

Exposeimager

Compareresults

Importdose image

Align images

Expose film

Process film

Scan film

Process film

Scan film

Calibration Planned Field Analysis

PV

Vision

Eclipse

PV

VARIAN Medical Systems March 2005 Slide 7

Portal Dosimetry

Dosimetry is a Process

‘Portal Dosimetry’ is a system capability (TPS, PV,VarisVision)

‘Dosimetry Workspace’access in PV (standalone)and Vision Review

Portal Dosimetry is a set of capabilities whichprovides Accumulation of relative dose at the PV imager position

Dose evaluation, acquired dose vs. TPS-predicted dose

For the application of Pre-treatment QA

Beam through air only (thru phantom = future capability)

No patient in beam

VARIAN Medical Systems March 2005 Slide 8

Portal Imager

Asymmetric Jaws

Focus

DMLC

Dosimetry

Patient

TreatmentCouch

Portal Dosimetry

Application

Pre-Treatment Verificationwithout Phantom

Qualitative Comparison

FDA 510(k)

PredictedPortal Dose

AcquiredPortal Dose

VARIAN Medical Systems March 2005 Slide 9

The Future?Machine QA pre-Treatment QA in vivo QA

Portal Dosimetry Applications

EPID/Film

Q

A

Test

Detector

Asymmetric Jaws

Focus

MLC / CustomField Shaping

Patient

TreatmentCouch

PortalDose

Tx

Plan

Planvs

ActualConsistency

PortalDose

VARIAN Medical Systems March 2005 Slide 10

Treatment Methods Supported

Treatment Type Overall Dose DosePrediction 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 11

EPID

TPS

Varis/Vision

Dosimetric Image

Visio

n

Visio

nTP

S

Fluence map+ dose matrix

Portal Dose Prediction

USERPROCESS

VARIAN Medical Systems March 2005 Slide 12

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 inPV cassette in ABSOLUTE values

VARIAN Medical Systems March 2005 Slide 13

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 14

FDA 510(k) - Images courtesy of KFJ Hospital, Vienna Austria

Portal Vision (EPID) Acquisition

VARIAN Medical Systems March 2005 Slide 15

Portal Vision (EPID) AcquisitionIntegrated DoseReference Image

VARIAN Medical Systems March 2005 Slide 16

VarisVision (R&V) role in Dosimetry

Dosimetry workspace in Review (Vision orStandalone 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 17

Dosimetry Review: Dose EvaluationTraditional Dose Evaluation Tools: Line Profile + Point Dose

VARIAN Medical Systems March 2005 Slide 18

Dosimetry Review: Dose EvaluationGamma Evaluation showing good correlation

Gamma > 1

VARIAN Medical Systems March 2005 Slide 19

Dosimetry Review: Dose EvaluationGamma Evaluation showing mismatch

Gamma > 1Gamma > 1

VARIAN Medical Systems March 2005 Slide 20

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 , billings

Facilitates good patient care

VARIAN Medical Systems March 2005 Slide 21

Conclusion

Acceptance testing, commissioning and QA of IMRTinvolves 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 anddelivery systems to perform as well as 3DCRTplanning and delivery systems.

VARIAN Medical Systems

Vielen Dank für Ihre Aufmerksamkeit