Verification of Accuracy of Treatment Delivery in Serial Tomotherapy

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Verification of Accuracy of Treatment Delivery in
Serial Tomotherapy
M. Al-Ghazi, R. Yakoob, H. Chung, T. Lau and R.
Sanford
Department of Radiation Oncology University of
California, Irvine 101 The City Drive Orange, CA
92868
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Presentation Outline

• Purpose and Background
• Patient Population Studied
• Materials and Methods
• Patient Immobilization
• CT Imaging
• Field Placement Verification
• Results
• Conclusion

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Purpose of the Study

• Describe a method for verifying field placement
  in serial tomotherapy (ST)
• Quantify the extent of patient movement during a
  fractionated course of ST

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CT Imaging

IMRT Inverse Planning
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(No Transcript)
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Dosimetric Consequences of Field Placement Errors
in ST/IMRT

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Patient Population Studied

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Patient Immobilization
CNS Mask
Prostate Mask

Lead markers are used to level the patient in 3
planes.
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ICRU 42 Patient Coordinate System

AP/PA /- Z, R/L Lat /-X, Cranio-Caudal (CC)
/-Y
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AP LAT Scouts

Transverse cut at the level of planning origin
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Determination of Field Position

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Determination of Field Position (Contd)

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Lateral Verification Port
Field Center
Sella Turcica

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Anatomical Landmarks used for Field Placement
Verification

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Results

AP/PA /- Z, R/L Lat /-X, Cranio-Caudal (CC)
/-Y
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Conclusions

• Patient position variability can reach a maximum
  of 8.5 mm for a thoracic lesion in the
  cranio-caudal (CC) direction and up to 5 mm for
  other directions and sites.
• Daily portal verification and adjustment of
  patient position is critical for accuracy of
  treatment delivery during fractionated serial
  tomotherapy (ST).
• Use of appropriate bony anatomical landmarks, as
  a reference is essential. This is in addition to
  surface marks and lead markers placed on an
  immobilization cast.

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Acknowledgements
The authors are grateful to the Departments
radiation oncologists and therapists for
facilitating implementation of this verification
procedure. Dr. Daniel Low (Mallinckrodt
Institute of Radiology) has kindly supplied the
plastic insert used in this study.