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WE‐C‐AUD C‐07: Expected Clinical Impact of the Differences Between Planned and Delivered Dose Distributions in Helical Tomotherapy
Author(s) -
Papanikolaou N,
Stathakis S,
Mavroidis P
Publication year - 2008
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2962704
Subject(s) - tomotherapy , nuclear medicine , medicine , dosimetry , radiation treatment planning , radiation therapy , radiology
Purpose: To investigate the effectiveness of highly conformal radiation modalities in conjunction with a patient setup correction method, Helical Tomotherapy (HT) was employed using the Helical Megavoltage CT (MVCT) scanner of the tomotherapy unit. Any discrepancy between the planned and delivered dose distributions would likely affect the clinical outcome. Method and Materials: The case of a head and neck cancer was used to evaluate the accuracy of dose delivery. The right parotid, left parotid and spinal cord are the primary organs at risk proximal to the target volume. MVCT images were taken before and after the patient setup correction. MVCT images of the patient were acquired daily. The three dose distributions (planned, with and without patient setup correction) were compared by using the complication‐free tumor control probability ( P + ) and the biologically effective uniform dose (BEUD) concepts. Results: For the computerized treatment plan, the maximum value of P + is 88.3%, the total control probability, P B is 97.3% and the total risk for complications, P I is 9.3%. For the delivered dose distribution without patient setup correction, the value of P + is 79.8% and the probabilities P B and P I are 83.6% and 3.8%, respectively. Finally, for the delivered dose distribution with patient setup correction in every fraction the value of P + is 87.2% and the probabilities P B and P I are 92.7% and 5.5%, respectively. The expected clinical effectiveness dropped by a Δ P + of 1.1% and 8.5% in the cases with and without patient setup correction. Conclusion: Highly conformal treatment plans can deliver higher doses to the target allowing for increased control rates for the same or a reduced risk for complications. The results show that the effectiveness of the applied dose distribution drops between the treatment plan and the dose delivery with and without patient setup correction.