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Updated: Jul 19, 2026
Stereotactic Radiosurgery for Gynecologic Cancer
Published on: April 17, 2012
Impact of target point deviations on control and complication probabilities in stereotactic radiosurgery of AVMs and
Harald Treuer1, Martin Kocher, Moritz Hoevels
1Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Germany. harald.treuer@uk-koeln.de
Objective:
Determination of the impact of inaccuracies in the determination and setup of the target point in stereotactic radiosurgery (SRS) on the expectable complication and control probabilities.
Methods:
Two randomized samples of patients with arteriovenous malformation (AVM) (n=20) and with brain metastases (n=20) treated with SRS were formed, and the probability for complete obliteration (COP) or complete remission (CRP), the size of the 10 Gy-volume in the brain tissue (VOI10), and the probability for radiation necrosis (NTCP) were calculated. The dose-effect relations for COP and CRP were fitted to clinical data. Target point deviations were simulated through random vectors and the resulting probabilities and volumes were calculated and compared with the values of the treatment plan.
Results:
The decrease of the relative value of the control probabilities at 1mm target point deviation was up to 4% for AVMs and up to 10% for metastases. At 2 mm the median decrease was 5% for AVMs and 9% for metastases. The value for the target point deviation, at which COP and CRP decreased about 0.05 in 90% of the cases, was 1.3 mm. The increase of NTCP was maximally 0.0025 per mm target point deviation for AVMs and 0.0035/mm for metastases. The maximal increase of VOI10 was 0.7 cm(3)/mm target point deviation in both patient groups.
Conclusions:
The upper limit for tolerable target point deviations is at 1.3mm. If this value cannot be achieved during the system test, a supplementary safety margin should be applied for the definition of the target volume. A better accuracy level is desirable, in order to ensure optimal chances for the success of the treatment. The target point precision is less important for the minimization of the probability of radiation necroses.
Insights
Target point accuracy in stereotactic radiosurgery (SRS) is crucial for treatment success. Deviations over 1.3mm significantly reduce control probabilities for brain arteriovenous malformations (AVMs) and metastases.
Area of Science:
- Neurosurgery
- Radiation Oncology
- Medical Physics
Background:
- Stereotactic radiosurgery (SRS) requires precise targeting for effective treatment of brain arteriovenous malformations (AVMs) and metastases.
- Inaccuracies in target point determination and setup can impact treatment outcomes and complication probabilities.
Purpose of the Study:
- To determine the impact of target point inaccuracies in SRS on expected complication and control probabilities.
- To establish tolerable limits for target point deviations in SRS procedures.
Main Methods:
- Two patient groups (AVM n=20, brain metastases n=20) treated with SRS were analyzed.
- Simulations of target point deviations were performed to calculate probabilities for complete obliteration/remission (COP/CRP), radiation necrosis (NTCP), and 10 Gy-volume (VOI10).
Main Results:
- A 1.3 mm target point deviation was identified as the threshold where COP/CRP decreased by approximately 0.05 in 90% of cases.
- Control probabilities decreased by up to 10% with a 2 mm deviation.
- Increases in NTCP and VOI10 were observed per mm of target point deviation.
Conclusions:
- An upper limit of 1.3 mm for tolerable target point deviations in SRS is recommended.
- If system tests cannot achieve this precision, a supplementary safety margin for target volume definition is advised.
- Enhanced accuracy is essential for optimal treatment success, though target point precision is less critical for minimizing radiation necrosis.
