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Reproducibility and geometric accuracy of the Fixster system during hypofractionated stereotactic radiotherapy.
Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurosurgery.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
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2008 (English)In: Radiation Oncology, ISSN 1748-717X, Vol. 3, no 16Article in journal (Refereed) Published
Abstract [en]

BACKGROUND:

Hypofractionated radiotherapy has been used for the treatment of AVMs and brain metastases. Hypofractionation necessitates the use of a relocatable stereotactic frame that has to be applied on several occasions. The stereotactic frame needs to have a high degree of reproducibility, and patient positioning is crucial to achieve a high accuracy of the treatment.

METHODS:

In this study we have, by radiological means, evaluated the reproducibility of the isocenter in consecutive treatment sessions using the Fixster frame. Deviations in the X, Y and Z-axis were measured in 10 patients treated with hypofractionated radiotherapy.

RESULTS:

The mean deviation in the X-axis was 0.4 mm (range -2.1 - 2.1, median 0.7 mm) and in the Y-axis -0.3 mm (range -1.4 - 0.7, median -0.2 mm). The mean deviation in the Z-axis was -0.6 (range -1.4 - 1.4, median 0.0 mm).

CONCLUSION:

There is a high degree of reproducibility of the isocenter during successive treatment sessions with HCSRT using the Fixster frame for stereotactic targeting. The high reducibility enables a safe treatment using hypofractionated stereotactic radiotherapy.

Place, publisher, year, edition, pages
2008. Vol. 3, no 16
Identifiers
URN: urn:nbn:se:umu:diva-10199DOI: doi:10.1186/1748-717X-3-16PubMedID: 18507861OAI: oai:DiVA.org:umu-10199DiVA: diva2:149870
Available from: 2008-06-30 Created: 2008-06-30 Last updated: 2011-08-30Bibliographically approved
In thesis
1. Hypofractionated conformal stereotactic radiotherapy in the treatment of AVMs and cerebral metastases
Open this publication in new window or tab >>Hypofractionated conformal stereotactic radiotherapy in the treatment of AVMs and cerebral metastases
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Hypofractionated conformal stereotactic radiotherapy (HCSRT) has been used for the treatment of AVMs at the Umeå University Hospital since 1986. From this year and onwards an increasing number of patients with single or oligo brain metastases have also been treated using this technique.

In paper I we have retrospectively evaluated our treatment results of AVMs in terms of obliteration and complications. The rates of obliteration and complications seem to be comparable with SRS even if the AVM volumes in our series were larger than in most series with SRS. In paper II we have retrospectively evaluated the results in terms of local control, survival and complications in two groups of patients with single or oligo brain metastases. One group was treated with HCSRT alone and the other group was treated with whole brain radiotherapy in combination with a stereotactic boost. Controversy still exists concerning the benefit of additional use of WBRT in combination with stereotactic irradiation. The survival times were equal in the two groups and no significant difference in local control was observed. The omission of WBRT seems to carry a higher risk for development new brain metastases distant from the irradiated area. In paper III we report the treatment results in a subgroup of AVMs treated with a combination of embolisation and HCSRT. We also focus on the reduction of vascular density within the nidus of an AVM and propose a method to digitally compare images and more objectively assess a reduction in vascular density following embolisation. Obliteration rates seem comparable with other series using a combination of SRS and embolisation even if our rate of complications was higher than what is usually reported. Using luminescence as measure of vascular density all AVMs seemed to be less dense after embolisation.

Treatment accuracy in terms of reproducibility of the isocenter in consecutive treatment sessions is crucial in fractionated radiotherapy. In paper IV we have radiologically evaluated the reproducibility of the isocenter in successive treatment sessions using the non invasive relocatable Fixster frame. There was a high degree of reproducibility and only small errors that most likely is of no clinical importance.

A reliable dose plan is equally important as a tool to predict the dose delivered inside and outside the target volume. In paper V we have evaluated the reliability of treatment plans in HCSRT for targets of different geometry and size. A liquid ion chamber and gel dosimeter was used for assessment of dose distribution and absorbed dose. The doseplanning system proved to be accurate in predicting the absorbed dose and dose distribution for the different targets.

Publisher
91 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1042
Keyword
arteriovenous malformations, brain metastases, hypofractionation, stereotactic radiotherapy, LINAC, embolisation
Research subject
Clinical Neurophysiology
Identifiers
urn:nbn:se:umu:diva-864 (URN)91-7264-135-5 (ISBN)
Public defence
2006-10-13, Sal B, plan 9, 1D, Tandläkarhögskolan, Umeå, 09:00 (English)
Opponent
Available from: 2006-09-18 Created: 2006-09-18 Last updated: 2009-10-09Bibliographically approved

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Bergström, PerHenriksson, RogerBergenheim, A Tommy

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