The tetrad and hexad: Maximum beam separation as a starting point for noncoplanar 3D treatment planning: Prostate cancer as a test case

Sailer, Scott L.; Rosenman, Julian G.; Symon, James R.; Cullip, T; Chaney, Edward L.

doi:10.1016/0360-3016(94)90026-4

Cited by 41 publications

(19 citation statements)

References 21 publications

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“…Previous attempts to optimize beam orientations have included maximally separating treatment fields in 3D space, 12 using entropy, Fourier transform, simulated annealing or exhaustive search methods to select a few intensity-modulated fields, [13][14][15][16] the use of a ''path of least resistance'' to choose beams which experience minimal attenuation through the patient, 17 optimizing beam orientations using simulated annealing in the frequency domain 18 and optimization of figures of merit scores using a reduced search domain either by simple minimization 19 or genetic algorithms. 20 Planning aids, usually based on the ''beam's-eye view volumetrics'' have also been developed.…”

Section: Introductionmentioning

confidence: 99%

Improvements in prostate radiotherapy from the customization of beam directions

1998

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A methodology for optimizing the beam directions in radiotherapy treatment planning has been developed and tested on a cohort of twelve prostate patients. An optimization algorithm employing a an objective cost function was used, based on beam's-eye-view volumetrics but also employing a simple dose model and biological considerations for organs-at-risk (OARs). The cost function embodies information about the volume of OARs in a single field and their position relative to the planning target volume (PTV). The proximity of the PTV to the surface of the patient is also included. Within the algorithm "importance factor" were used to model the clinical importance of different organs-at-risk so that all organs-at-risk were included in a single objective score. "Gantry-angle-windows" were introduced to restrict the available beam directions. The methodology was applied to twelve prostate patients to determine the optimum beam directions for three-field direction plans. Orientation-optimized and standard treatment plans were compared via measures of tumor control probability (TCP) and normal tissue complication probability (NTCP). Standard plans had fixed beam directions whereas orientation-optimized plans contained beam directions chosen by the algorithm. The beam-weights of both the orientation-optimized and standard plans were optimized using a dose-based simulated annealing algorithm to allow the improvements by optimizing the beam directions to be studied in isolation. The results of the comparison show that optimization of the beam directions yielded better plans, in terms of TCP and NTCP, than the standard plans. When the dose to the isocenter was scaled to produce a rectal NTCP of 1%, the average TCP of the orientation-optimized plans was (5.7 +/- 1.4)% greater than that for the standard plans. In conclusion, the customization of beam directions in the treatment planning of prostate patients using and objective cost function and allowed gantry-angle-windows produces superior three-field direction plans compared to standard treatment plans.

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Section: Introductionmentioning

confidence: 99%

Improvements in prostate radiotherapy from the customization of beam directions

1998

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“…An anisotropic CTV to PTV margin (at least 10 mm) was added based on organ motion and set-up errors. A class solution with 4 non-coplanar fixed photon beams (plus 1-2 beams for isocenter verification) based on the tetrad configuration was used in all patients (17,18). The ESRT dose was prescribed to the isocenter (Fig.…”

Section: Methodsmentioning

confidence: 99%

Stereotactic radiotherapy in recurrent gynecological cancer: A case series

Deodato¹,

Macchia

Grimaldi

et al. 2009

Oncol Rep

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Abstract. Scarce data are available on the use of extracranial stereotactic radiotherapy in recurrent gynecological tumors. The aim of this report was to analyze the results of our preliminary experience with extracranial stereotactic radiotherapy in locally or distantly recurrent gynecological tumors. Extracranial stereotactic radiotherapy was planned by the Precise-Plan treatment planning system. Patients were immobilized using the Stereotactic Body-Frame. Five consecutive daily fractions were delivered; dose/ fraction and total dose were defined based on an institutional doseescalation protocol. A class solution with 4 non-coplanar fixed beams based on the tetrad configuration was used in all patients. Eleven patients (12 lesions), were included in the analysis. Stereotactic radiotherapy was delivered as first radiotherapy treatment (5 patients), or as retreatment (6 patients).Complete clinical response was achieved in 8/12 lesions (66.6%), while partial response was documented in 2/12 lesions (16.6%). With a median follow-up of 19 months (range, 2-37 months), 7 patients (63%) experienced local and/or distant progression of disease. The 2-year local progression-free survival was 81.8%, while the 2-year metastases-free survival was 54.4%. The 2-year overall survival was 63.6%. Acute and late toxicities were grade 2 or less. There was no difference in quality of life scores between the data collected before extracranial stereotactic radiotherapy and at first follow-up evaluation. Fractionated extracranial stereotactic radiotherapy administered up to a dose of 30 Gy in five fractions is well tolerated. Further studies of extracranial stereotactic radiotherapy and novel radiotherapy techniques are warranted in the challenging setting of recurrent gynecological tumors.

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“…CT simulation was performed by the spiral technique and by an acquisition of 3-mm-thick scans, with a 3-mm interval between scans at the target region of the body, and 10-mm-thick scans, with an interval between scans of 10 mm for the rest of SBF. For treatment plan, a class solution based on a tetrahedral static beam configuration was used in all patients (30,31). This 4 noncoplanar beam configuration was selected for maximal angular width between beams (approximately 109.5 • ), and thus, to achieve an optimal plan conformality.…”

Section: Introductionmentioning

confidence: 99%