Neoplasma Vol.52, p.325-329, 2005
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Title: The efficacy and reliability of lung protection during total body
irradiation of patients with disseminated malignancies
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Author: J., MALICKI
; A., SKROBALA
; G., KOSICKA
; J., WACHOWIAK
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Abstract: The main problem in total body irradiation (TBI) is obtaining a
homogenous dose distribution inside the whole irradiated
body and ensuring appropriate dose reduction in the lungs. The
process of irradiation should be comfortable for the patients
and repeatable despite the size and age diversity among patients.
The aim of this paper was 1) to check accuracy of the applied dose
algorithm and reliability of the measurement technique
used in the lung region during TBI taken alternatively on a Cobalt-
60 unit and on 15MVlinear accelerators, and 2) to check
if the described methodology made it possible to obtain
reproducibly of the lowered level of the dose to the lungs for a
diverse
group of patients.
TBI was performed as a preparatory regiment in children and adults
with disseminated malignancies undergoing bone
marrow transplantation (a dose of 12.6 Gy in the midline/central
beam axis). Two consecutive groups of patients were retrospectively
included in the study: 15 irradiated with Cobalt-60 and 15 with 15
MV photons. The doses were evaluated for
three sections passing through the middle of the lungs and at
their upper and lower sides. Two types of detectors: semiconductor
and thermoluminescent ones were used simultaneously. The measured
doses were evaluated statistically to reveal
agreement between readings of the two types of detectors and
agreement between the measured doses and those previously
calculated.
The results of measurements exhibited a not Gaussian-type
distribution (dissymmetry). The Wilcoxon-type test revealed
compliance between the doses measured with thermoluminescent (TL)
and semiconductor (SEM) detectors for all sections
passing through the lungs (p>0.05), excluding the lung exit
(middle and lower sides) with the Cobalt therapy. The t-Student
test used to compare the measured doses with those previously
calculated revealed agreement (p>0.05) between the measured
doses and those calculated for all lung sections for the
15MVphoton therapy, while for Cobalt therapy such an agreement
was at some points doubtful.
The calculation algorithm and measurement techniques have proved
to be correct, which was revealed by agreement between
the doses measured and those calculated. The shielding of the
lungs during both types of fields was effective and reproducible
as indicated by agreement between the doses measured with the two
types of detectors. Better agreement between
the measured and calculated doses was found for 15 MV photons than
for the Cobalt unit.
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Keywords: in-vivo dose measurements, TBI, dose accuracy, leukemia
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Year: 2005, Volume: 52, Issue: |
Page From: 325, Page To: 329 |
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