Portal Imaging Introduction (Portal Vision)
Portal Imaging Introduction (Portal Vision)
Portal Imaging Introduction (Portal Vision)
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•<br />
<strong>Portal</strong> <strong>Imaging</strong> <strong>Introduction</strong> (<strong>Portal</strong> <strong>Vision</strong>)<br />
This presentation is only for internal Varian<br />
training and not for customer presentations<br />
Peter Munro, Ph.D.<br />
Palo Alto, USA
Acknowledgements<br />
• Cal Huntzinger<br />
• Richard Stark<br />
• Lisa Hampton<br />
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Agenda<br />
• What is <strong>Portal</strong> <strong>Imaging</strong>?<br />
• Why Do We Image the Treatment <strong>Portal</strong>s?<br />
• A Brief History of … <strong>Portal</strong> <strong>Imaging</strong><br />
• <strong>Portal</strong> <strong>Imaging</strong> Technology<br />
• Why use electronic images?<br />
• Improved clinical process<br />
• Solve important clinical problems<br />
• Summary<br />
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<strong>Portal</strong> <strong>Imaging</strong><br />
x ray source<br />
Image<br />
receptor<br />
Accelerator gantry<br />
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Glossary<br />
• EPID – electronic portal imaging device<br />
(image receptor)<br />
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<strong>Portal</strong> <strong>Imaging</strong> with <strong>Portal</strong><strong>Vision</strong> (PV)<br />
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Patient Set-up Errors<br />
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<strong>Imaging</strong> Objective<br />
CTV<br />
CTV<br />
PTV<br />
Without<br />
<strong>Imaging</strong><br />
PTV<br />
With<br />
<strong>Imaging</strong><br />
CTV – volume containing disease<br />
PTV – volume that needs to be irradiated to ensure CTV is always treated<br />
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•<br />
<br />
A Brief History of … <strong>Portal</strong> <strong>Imaging</strong>
Television-Roentgen Systems<br />
• 200 kVp; Jubilee Clinic, Göteborg (1958)<br />
x-ray tube<br />
• 2 MeV; NIH (1958)<br />
Van de Graaff generator<br />
• 30 MeV; Jubilee Clinic, Göteborg (1962)<br />
betatron<br />
• 5 MeV; Jubilee Clinic, Göteborg (1967)<br />
linear accelerator<br />
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• 200 kVp X-rays<br />
Strandquist, et. al., Brit.J.Radiol. 31:513-514 (1958)<br />
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• 2 MeV Roentgen Therapy<br />
Andrews, et.al., Am.J. Roentgenol. 79:74-78 (1958)<br />
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“Modern” Electronic <strong>Portal</strong> <strong>Imaging</strong> Devices<br />
(EPIDs )<br />
• Scanning diode arrays (1982)<br />
• Scanning scintillating arrays (1984)<br />
• TV camera-based systems (1980 …)<br />
• Liquid ionization chamber (1985)<br />
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• Modern EPIDs<br />
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“Really Modern” Electronic <strong>Portal</strong> <strong>Imaging</strong><br />
Devices (EPIDs )<br />
• Amorphous silicon flat panel image receptors<br />
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a-Si Schematic<br />
Photon Beam<br />
Metal<br />
Phosphor Screen<br />
a-Si Sensor<br />
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a-Si Sensor<br />
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a-Si – Image Receptor<br />
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Clinical Images<br />
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Technology Evolution<br />
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Why Use Electronic <strong>Imaging</strong>?<br />
• Improved clinical process<br />
• Solve important clinical problems<br />
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• More Convenient Acquisition<br />
EPIDs save effort and time<br />
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• More Convenient Image Distribution<br />
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• Measurement tools<br />
Film<br />
Varian EPIDs have tools to to measure set-up errors<br />
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<strong>Portal</strong> <strong>Imaging</strong> Applications<br />
• Plan verification<br />
• Improve patient set-up<br />
• Measure patient set-up errors<br />
• Correct patient set-up errors<br />
• Dosimetry -> IMRT Q/A<br />
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Measure Set-up Errors<br />
X= 0.0; y= 0.0<br />
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Image Registration<br />
X= 0.2; y= 0.0<br />
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Image Registration<br />
X= 0.4; y= 0.2<br />
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Image Registration<br />
X= 0.4; y= 0.6<br />
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Glossary - Patient Correction Strategies<br />
• Off-line corrections (correct early in a course<br />
of therapy)<br />
• Random errors<br />
• Systematic errors<br />
• On-line corrections (correct before each daily<br />
treatment)<br />
• Random errors<br />
• Systematic errors<br />
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Off-Line Correction<br />
Random Errors<br />
Systematic Errors<br />
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Off-Line Correction<br />
Random Errors<br />
Systematic Errors<br />
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Off-Line Correction<br />
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On-Line Correction<br />
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On-Line Correction<br />
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On-Line Correction<br />
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On-Line Correction<br />
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On-Line Correction<br />
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On-Line Correction<br />
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On-Line Correction<br />
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EPID versus Film<br />
• No lifting/carrying of cassettes<br />
• Fast acquisition<br />
• No technique charts needed<br />
• Always get a good exposure with an EPID<br />
• Image display and distribution<br />
• Set-up error measurement tools<br />
• Clinical applications for aS500<br />
• Evaluate new immobilization techniques<br />
• Dose escalation/IMRT<br />
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Conclusions<br />
• Acquiring images during patient treatment is a<br />
well established clinical task<br />
• <strong>Imaging</strong> hardware has improved – over a<br />
very long period of time<br />
• There are a variety of applications for the<br />
images:<br />
• Plan Verification<br />
• Reduce patient set-up errors<br />
• Dosimetry -> IMRT Q/A<br />
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