slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
AIR CORE SCINTILLATION DOSIMETER PowerPoint Presentation
Download Presentation
AIR CORE SCINTILLATION DOSIMETER

Loading in 2 Seconds...

play fullscreen
1 / 1

AIR CORE SCINTILLATION DOSIMETER - PowerPoint PPT Presentation


  • 149 Views
  • Uploaded on

Cerenkov-free Scintillation Dosimeter for use in External Beam Radiotherapy. David R. McKenzie 1 , Natalka Suchowerska 1,2 , Jamil Lambert 1,2 , YongBai Yin 1 , Sue Law 1 , 1 Royal Prince Alfred Hospital, Sydney, Australia 2 University of Sydney, Sydney, Australia. SUMMARY

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'AIR CORE SCINTILLATION DOSIMETER' - akio


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Cerenkov-free Scintillation Dosimeter for use in External Beam Radiotherapy

David R. McKenzie1,Natalka Suchowerska1,2 , Jamil Lambert1,2, YongBai Yin1, Sue Law1,

1Royal Prince Alfred Hospital, Sydney, Australia

2University of Sydney, Sydney, Australia

SUMMARY

We have shown that Cerenkov light can be reduced to a negligible level in scintillation dosimetry by using an air core light guide to transport the scintillation light signal out of the radiation primary beam. This novel design has favourable characteristics for megavoltage photon and electron beam dosimetry, with high spatial resolution and fast readout speed, critical for applications such as stereotactic radiosurgery and IMRT.

AIR CORE SCINTILLATION DOSIMETER

The Challenge

Current methods of transmitting the scintillation light to a remote detector use a solid core optical fibre. When exposed to radiation, these fibres generate an unwanted Cerenkov light as a background. The background can exceed the scintillation signal at characteristic angles.

The Solution

Our new scintillation dosimeter design does not produce any Cerenkov signal in the air core. This design has a small detection volume which is tissue equivalent, it is energy and dose rate independent and provides real time dose readings with high reproducibility and linearity.

PERFORMANCE

CERENKOV SIGNAL – ANGULAR DEPENDENCE

Figure 2.

Solid core

  • The angular dependence of dosimeter performance was measured (Figure 1).
  • Dose readings were taken as a function of angle, integration time 0.5s
  • Air core dosimeter readings were within 2% (0.7%) for all angles
  • Solid core dosimeter exhibited a Cerenkov signal 2.5 times the magnitude of the radiation induced light signal.
  • All scintillation dosimeters should be tested in this worst case situation to validate performance.

Cerenkov

background

Figure 1. Experimental design

SIGNAL:NOISE

DEPTH DEPENDENCE

  • Table 1 shows the signal with and without a scintillator (signal and background respectively), when the scintillator axis is at 90 to the beam central axis
  • Cerenkov generates 26% of the signal in PMMA fibre
  • Signal is reduced by the air core, but the signal to background ratio is vastly improved.
  • Percentage depth dose for 6MV photon beam and 9MeV electron beam were measured in water using the air core dosimeter (Figure 3)
  • For photons, measured dose agreed with 0.125cc SEMI-FLEX (PTW 31010) ionisation chamber readings to within 1.5% (0.3%)
  • For electrons, measured dose agreed with Advanced Markus ionisation chamber readings to within 3% for depths 1.5 to 54 mm

FIELD SIZE DEPENDENCE

  • The reading of the air core dosimeter with 1x5mm scintillator is shown as a function of field size in the range 1x1cm to 10x10 cm in a 6MV photon beam.
  • The results agree with a 0.125cc SEMI-FLEX (PTW 31010) ionisation chamber
  • Note that the diamond detector readings departs from both of the other detectors at 1x1cm fields.

Figure 3. Measured % depth dose

  • CONCLUSION

The Air core scintillation dosimeter eliminates Cerenkov background light and is tissue equivalent. This feature, combined with its other characteristics of dose rate independence, high spatial resolution, energy independence and fast response, make the Air core scintillation dosimeter a promising new tool for complex dosimetry applications, such as IMRT and stereotactic radiosurgery.

REFERENCES

Lambert J, YinY., McKenzie D., Suchowerska N., Cerenkov free scintillation dosimetry in external beam radiotherapy with an air core light guide, Physics in Medicine and Biology(53) 3071-3080, 2008

Elsey, J, McKenzie, DR, Lambert, J, Suchowerska, N, Law, S, Fleming, S Optimal Coupling of Light from a Cylindrical Scintillator into an Optical Fibre, Applied Optics, 46 397-404, 2007

SH Law, N Suchowerska, DR McKenzie, SC Fleming, T Lin, The transmission of Čerenkov radiation in optical fibers, Optics Letters 32, (10), 1205-1207, 2007

Law, SH, Fleming, SC, McKenzie, DR, Suchowerska, N, Transmission of Čerenkov radiation generated in the core of an optical fiber, Applied Optics 32[10] 2007