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Hypofractionated conformal stereotactic radiotherapy in the treatment of AVMs and cerebral metastases
Umeå University, Faculty of Medicine, Pharmacology and Clinical Neuroscience.
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.

Place, publisher, year, edition, pages
2006. , 91 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1042
Keyword [en]
arteriovenous malformations, brain metastases, hypofractionation, stereotactic radiotherapy, LINAC, embolisation
Research subject
Clinical Neurophysiology
Identifiers
URN: urn:nbn:se:umu:diva-864ISBN: 91-7264-135-5 (print)OAI: oai:DiVA.org:umu-864DiVA: diva2:144786
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
List of papers
1. Hypofractionated conformal stereotactic radiotherapy for arteriovenous malformations
Open this publication in new window or tab >>Hypofractionated conformal stereotactic radiotherapy for arteriovenous malformations
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2003 (English)In: Neurosurgery, ISSN 0148-396X, E-ISSN 1524-4040, Vol. 53, no 5, 1036-1042 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:umu:diva-5303 (URN)10.1227/01.NEU.0000088566.82699.E6 (DOI)
Available from: 2006-09-18 Created: 2006-09-18 Last updated: 2017-12-14Bibliographically approved
2. Hypofractionated conformal stereotactic radiotherapy alone or in combination with whole-brain radiotherapy in patients with cerebral metastases
Open this publication in new window or tab >>Hypofractionated conformal stereotactic radiotherapy alone or in combination with whole-brain radiotherapy in patients with cerebral metastases
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2005 (English)In: International Journal of Radiation Oncology, Biology, Physics, ISSN 0360-3016, E-ISSN 1879-355X, Vol. 61, no 5, 1460-1466 p.Article in journal (Refereed) Published
Keyword
Brain metastases, radiotherapy, stereotactic, hypofractionation, whole-brain radiotherapy
Identifiers
urn:nbn:se:umu:diva-14189 (URN)doi:10.1016/j.ijrobp.2004.08.027 (DOI)15817351 (PubMedID)
Available from: 2007-11-29 Created: 2007-11-29 Last updated: 2017-12-14Bibliographically approved
3. Combined effects of embolisation and hypofractionated conformal stereotactic radiotherapy in arteriovenous malformations of the brain
Open this publication in new window or tab >>Combined effects of embolisation and hypofractionated conformal stereotactic radiotherapy in arteriovenous malformations of the brain
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2005 (English)In: INTERVENTIONAL NEURORADIOLOGY, ISSN 1123-9344, Vol. 11, no 3, 223-229 p.Article in journal (Refereed) Published
Abstract [en]

There are three major treatment options for cerebral AVMs; surgery, embolization and radiosurgery. Embolization may be effective to reduce the size and density but completely obliterates AVMs only in a minority of cases. Radiosurgery may be an alternative to resection, especially in smaller AVMs. Large AVMs have been considered difficult to treat safely and effectively with single fraction radiosurgery. Hypofractionated conformal stereotactic radiotherapy (HCSRT)alone or in combination with embolization may be an alternative treatment. Embolization may reduce the volume and density of AVMs, followed by HCSRT, allowing a safe delivery of a higher total dose of radiation than possible with a single fraction. Sixteen patients with AVMs were treated with embolization and HCSRT. Embolization was performed in 1-6(median 2) sessions. HCSRT was delivered in 5fractions with 6-7 Gy each to the total dose of30–35 Gy. Cerebral angiographies before and after embolization were digitally compared for calculation of volume reduction and luminescence as a measure of AVM density. The mean AVM volume in 15 patients was reduced from11.9 ± 2.1 (1-29, median 10.0) ml to 6.5 ± 2.0(0.5–28, median 3) ml by embolization. The luminescence for all AVMs was significantly higher after than before embolization, indicating that all AVMs were less dense after embolization. Thirteen out of 16 patients (13/16, 81%) treatedwith embolization and HCSRT have so farshown obliteration of their AVMs 2-9 (median4) years after HCSRT. Three patients experienced neurological sequele after embolization, and three patients developed radionecrosis after HCSRT. Using a new method to compare cerebral angiographies in AVMs we report reduction in density and volume after embolization. The obliteration rate of a combined treatment with embolization and HCSRT seems comparable with single fraction radiosurgery although the AVMs in our series are larger than reported in most series treated with single fraction radiosurgery.

Place, publisher, year, edition, pages
Milan, Udine, Italy: Edizioni del Centauro, 2005
Keyword
AVM, embolization, stereotactic, radiotherapy
Identifiers
urn:nbn:se:umu:diva-5305 (URN)
Available from: 2006-09-18 Created: 2006-09-18 Last updated: 2017-12-14Bibliographically approved
4. Reproducibility and geometric accuracy of the Fixster system during hypofractionated stereotactic radiotherapy.
Open this publication in new window or tab >>Reproducibility and geometric accuracy of the Fixster system during hypofractionated stereotactic radiotherapy.
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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.

Identifiers
urn:nbn:se:umu:diva-10199 (URN)doi:10.1186/1748-717X-3-16 (DOI)18507861 (PubMedID)
Available from: 2008-06-30 Created: 2008-06-30 Last updated: 2011-08-30Bibliographically approved
5. Liquid ionization chamber calibrated gel dosimetry in conformal stereotactic radiotherapy of brain lesions
Open this publication in new window or tab >>Liquid ionization chamber calibrated gel dosimetry in conformal stereotactic radiotherapy of brain lesions
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2008 (English)In: Acta Oncologica, ISSN 0284-186X, E-ISSN 1651-226X, Vol. 47, no 6, 1099-1109 p.Article in journal (Refereed) Published
Abstract [en]

Hypofractionated conformal stereotactic radiotherapy (HCSRT) is an established method of treating brain lesions such as arteriovenous malformations (AVMs) and brain metastases. The aim of this study was to investigate the reliability of treatment plans in the terms of dose distribution and absorbed dose for HCSRT.

Methods and materials. Treatment plans for three different clinical intracerebral targets, AVMs, were transferred to a CT study of a spherical water filled phantom simulating the human head and recalculated for the phantom geometry using a standard treatment planning system utilizing a pencil beam algorithm for dose calculation. The calculated absorbed dose, relative three dimensional (3D) dose distribution and dose conformity were investigated using gel dosimetry normalized to liquid ionization chamber (LIC) measurements.

Results. The measured absorbed dose to the dose reference point was found to be within 2% of the calculated dose for all three targets. The measured dose distribution was found to be within 3% and 2 mm of the calculated dose for more than 93% of all points in the target volume for all three targets.

Conclusions. The results show that the investigated standard treatment planning system can correctly predict the absorbed dose and dose distribution in different types of intracerebral targets and that the treatment can be delivered according to the plan.

Identifiers
urn:nbn:se:umu:diva-10573 (URN)10.1080/02841860801888781 (DOI)18607837 (PubMedID)
Available from: 2008-10-01 Created: 2008-10-01 Last updated: 2017-12-14Bibliographically approved

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