Use of reduced dose rate when treating moving tumors using dynamic IMRT

The purpose was to evaluate the effect of dose rate on discrepancies between expected and delivered dose caused by the interplay effect. Fifteen separate dynamic IMRT plans and five hybrid IMRT plans were created for five patients (three IMRT plans and one hybrid IMRT plan per patient). The impact of motion on the delivered dose was evaluated experimentally for each treatment field for different dose rates (200 and 400 MU/min), and for a range of target amplitudes and periods. The maximum dose discrepancy for dynamic IMRT fields was 18.5% and 10.3% for dose rates of 400 and 200 MU/min, respectively. The maximum dose discrepancy was larger than this for hybrid plans, but the results were similar when weighted by the contribution of the IMRT fields. The percentage of fields for which 98% of the target never experienced a 5% or 10% dose discrepancy increased when the dose rate was reduced from 400 MU/min to 200 MU/min. For amplitudes up to 2 cm, reducing the dose rate to 200 MU/min is effective in keeping daily dose discrepancies for each field within 10%. PACS number: 87.55Qr

[1]  Ross Berbeco,et al.  Management of the interplay effect when using dynamic MLC sequences to treat moving targets. , 2008, Medical physics.

[2]  L. Court,et al.  Development and Experimental Evaluation of Guidelines for Planning and Treating Moving Tumors using Dynamic IMRT , 2008 .

[3]  K. Langen,et al.  Organ motion and its management. , 2001, International journal of radiation oncology, biology, physics.

[4]  Steve B. Jiang,et al.  An experimental investigation on intra-fractional organ motion effects in lung IMRT treatments. , 2003, Physics in medicine and biology.

[5]  R. Mohan,et al.  Quantifying the effect of intrafraction motion during breast IMRT planning and dose delivery. , 2003, Medical physics.

[6]  D A Jaffray,et al.  The effects of intra-fraction organ motion on the delivery of dynamic intensity modulation. , 1998, Physics in medicine and biology.

[7]  Steve B. Jiang,et al.  Measurement of the interplay effect in lung IMRT treatment using EDR2 films , 2006, Journal of applied clinical medical physics.

[8]  Charles S Mayo,et al.  Hybrid IMRT for treatment of cancers of the lung and esophagus. , 2008, International journal of radiation oncology, biology, physics.

[9]  Ross Berbeco,et al.  Evaluation of the interplay effect when using RapidArc to treat targets moving in the craniocaudal or right-left direction. , 2009, Medical physics.

[10]  H Paganetti,et al.  Effects of organ motion on IMRT treatments with segments of few monitor units. , 2007, Medical physics.

[11]  Jay Burmeister,et al.  Effect of respiratory motion on the delivery of breast radiotherapy using SMLC intensity modulation. , 2006, Medical physics.

[12]  M. V. van Herk,et al.  Precise and real-time measurement of 3D tumor motion in lung due to breathing and heartbeat, measured during radiotherapy. , 2002, International journal of radiation oncology, biology, physics.

[13]  Steve B. Jiang,et al.  Effects of intra-fraction motion on IMRT dose delivery: statistical analysis and simulation. , 2002, Physics in medicine and biology.

[14]  Jun Duan,et al.  Dosimetric and radiobiological impact of dose fractionation on respiratory motion induced IMRT delivery errors: a volumetric dose measurement study. , 2006, Medical physics.

[15]  J Debus,et al.  Influence of intra-fractional breathing movement in step-and-shoot IMRT. , 2004, Physics in medicine and biology.

[16]  R. Jeraj,et al.  Confirmation, refinement, and extension of a study in intrafraction motion interplay with sliding jaw motion. , 2005, Medical physics.

[17]  David S Followill,et al.  Technical note: Heterogeneity dose calculation accuracy in IMRT: study of five commercial treatment planning systems using an anthropomorphic thorax phantom. , 2008, Medical physics.