Strategy for online correction of rotational organ motion for intensity-modulated radiotherapy of prostate cancer.

PURPOSE To develop and evaluate a correction strategy for prostate rotation using gantry and collimator angle adjustments. METHODS AND MATERIALS Gantry and collimator angle adjustments were used to correct for prostate rotation without rotating the table. A formula to partially correct for left-right (LR) rotations was derived through geometric analysis of rotation-induced clinical target volume (CTV) beam's-eye-view shape changes. For 10 prostate patients, intensity-modulated radiotherapy (IMRT) plans with different margins were created. Simulating CTV LR rotation and correcting each beam by a collimator rotation, the corrected CTV dose was compared with the original and uncorrected dose. Effects of residual geometric uncertainties were assessed using a Monte Carlo technique. A large number of treatments representative for prostate patients were simulated. Dose probability histograms of the minimum CTV dose (D min) were derived, with and without online correction, resulting in a more realistic margin estimate. RESULTS Dosimetric analysis of all IMRT plans showed that, with rotational correction and a 2-mm margin, D min was constant to within 3% for LR rotations up to +/-15 degrees . The Monte Carlo dose probability histograms showed that, with correction, a margin of 4 mm ensured that 90% of patients received a D min >or=95% of the prescribed dose. Without correction a margin of 6 mm was required. CONCLUSIONS We developed and tested a practical method for (online) correction of prostate rotation, allowing safe and straightforward implementation of margin reduction and dose escalation.

[1]  D Yan,et al.  An off-line strategy for constructing a patient-specific planning target volume in adaptive treatment process for prostate cancer. , 2000, International journal of radiation oncology, biology, physics.

[2]  M. V. van Herk,et al.  The probability of correct target dosage: dose-population histograms for deriving treatment margins in radiotherapy. , 2000, International journal of radiation oncology, biology, physics.

[3]  Raj Shekhar,et al.  Direct aperture deformation: an interfraction image guidance strategy. , 2006, Medical physics.

[4]  J. Siebers,et al.  A dynamic compensation strategy to correct patient-positioning errors in conformal prostate radiotherapy. , 2006, Medical physics.

[5]  Jan-Jakob Sonke,et al.  Automatic prostate localization on cone-beam CT scans for high precision image-guided radiotherapy. , 2005, International journal of radiation oncology, biology, physics.

[6]  Eugene Wong,et al.  Dosimetric evaluation of daily rigid and nonrigid geometric correction strategies during on-line image-guided radiation therapy (IGRT) of prostate cancer. , 2006, Medical physics.

[7]  David Jaffray,et al.  Online image-guided intensity-modulated radiotherapy for prostate cancer: How much improvement can we expect? A theoretical assessment of clinical benefits and potential dose escalation by improving precision and accuracy of radiation delivery. , 2004, International journal of radiation oncology, biology, physics.

[8]  John Wong,et al.  Assessment of residual error for online cone-beam CT-guided treatment of prostate cancer patients. , 2004, International journal of radiation oncology, biology, physics.

[9]  K L Lam,et al.  A mathematical model for correcting patient setup errors using a tilt and roll device. , 1999, Medical physics.

[10]  J. Wong,et al.  Flat-panel cone-beam computed tomography for image-guided radiation therapy. , 2002, International journal of radiation oncology, biology, physics.

[11]  Joos V Lebesque,et al.  Inclusion of geometric uncertainties in treatment plan evaluation. , 2002, International journal of radiation oncology, biology, physics.

[12]  Qiuwen Wu,et al.  Geometric and dosimetric evaluations of an online image-guidance strategy for 3D-CRT of prostate cancer. , 2006, International journal of radiation oncology, biology, physics.

[13]  Joos V Lebesque,et al.  Reduction of rectal dose by integration of the boost in the large-field treatment plan for prostate irradiation. , 2002, International journal of radiation oncology, biology, physics.

[14]  Joos V Lebesque,et al.  Strategies to reduce the systematic error due to tumor and rectum motion in radiotherapy of prostate cancer. , 2005, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[15]  He Wang,et al.  An automatic CT-guided adaptive radiation therapy technique by online modification of multileaf collimator leaf positions for prostate cancer. , 2005, International journal of radiation oncology, biology, physics.

[16]  Ravinder Nath,et al.  A method to implement full six-degree target shift corrections for rigid body in image-guided radiotherapy. , 2005, Medical physics.

[17]  He Wang,et al.  Use of deformed intensity distributions for on-line modification of image-guided IMRT to account for interfractional anatomic changes. , 2005, International journal of radiation oncology, biology, physics.

[18]  M van Herk,et al.  3-D portal image analysis in clinical practice: an evaluation of 2-D and 3-D analysis techniques as applied to 30 prostate cancer patients. , 2000, International journal of radiation oncology, biology, physics.

[19]  K L Lam,et al.  A tilt and roll device for automated correction of rotational setup errors. , 1998, Medical physics.

[20]  Joos V Lebesque,et al.  An adaptive off-line procedure for radiotherapy of prostate cancer. , 2007, International journal of radiation oncology, biology, physics.

[21]  R L Siddon,et al.  Solution to treatment planning problems using coordinate transformations. , 1981, Medical physics.

[22]  Marcel van Herk,et al.  Quantification of shape variation of prostate and seminal vesicles during external beam radiotherapy. , 2005, International journal of radiation oncology, biology, physics.