ANDERS BJO¨ RELAND
1, PETER LINDVALL2, ANNA KARLSSON3, HELEN
GUSTAVSSON
3, SVEN A°
J BA¨ CK
3, MIKAEL KARLSSON4 & TOMMY A. BERGENHEIM2
1
Department of Clinical Physiology and Radiation Physics, Sundsvall Hospital, Sundsvall, Sweden, 2Department of
Neurosurgery, Umea° University Hospital, Umea° , Sweden,
3Department of Radiation Physics, Lund University, Malmo¨
University Hospital, Malmo¨, Sweden and
4Department of Radiation Sciences, Umea° University Hospital, Umea°, Sweden
Abstract
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.
Hypofractionated conformal stereotactic radiotherapy
(HCSRT) is a method of delivering stereotactic
irradiation in a few fractions using a relocatable
stereotactic frame. This method is currently used for
the treatment of brain metastases and arteriovenous
malformations of the brain (AVMs) [1]. AVMs are
uncommon congenital lesions made up from clusters
of abnormal arteries and veins that shunt blood from
the arterial to the venous system. One treatment
option for AVMs is single fraction stereotactic radiosurgery
(SRS). However this treatment is mainly
used for smaller AVMs as it has been considered
difficult to treat AVMs larger than 10 cm
3 safely and
effectively with radiosurgery. For large AVMs, hypofractionated
stereotactic radiotherapy may be more
appropriate than SRS, allowing safe delivery of a
higher total dose of radiation than what is possible
with a single fraction [1]. Brain metastases is a
common manifestation of systemic cancer, and the
incidence has been reported to range from 20
40%
[2]. The most common treatment has been whole
brain radiotherapy (WBRT), but in recent years SRS
in combination with WBRT [3] or alone [4] has
been used widely with good results in terms of local
control and survival. The omission of whole brain
radiotherapy does not seem to compromise survival
and local control [5]. An alternative to SRS is
HCSRT. The results of HCSRT in terms of local
control and survival has been reported to be
equivalent to those of SRS [6]. Similarly to the
case with AVMs, HCSRT may allow treatment of
larger brain metastases than possible with SRS. In
addition it has been suggested that fractionated
stereotactic radiotherapy may provide a radiobiological
advantage over SRS [7].
At Umea° University Hospital, HCSRT has been
used for the treatment of AVMs and single or oligo
brain metastases since 1986. The results in terms of
Correspondence: Anders Bjo¨reland, Department of Clinical Physiology, and Radiation Physics
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