Y. Popowski et al., INTRAARTERIAL (90)Y BRACHYTHERAPY - PRELIMINARY DOSIMETRIC STUDY USING A SPECIALLY MODIFIED ANGIOPLASTY BALLOON, International journal of radiation oncology, biology, physics, 33(3), 1995, pp. 713-717
Citations number
9
Categorie Soggetti
Oncology,"Radiology,Nuclear Medicine & Medical Imaging
Purpose: Irradiation has been shown to be effective in preventing rest
enosis after dilatation in human peripheral arteries, We have develope
d a dedicated system for coronary intraarterial irradiation using a Y-
90 pure beta-emitting source inside a specially modified angioplasty b
alloon. This paper presents a preliminary dosimetric evaluation of thi
s system. Methods and Materials: Specially fabricated titanium-covered
and activated yttrium wires (outer diameter 0.32 mm) were used for th
ese studies, Dosimetry was performed using small thermoluminescent dos
imeters (TLDs) placed on the surface of the 2-cm long angioplasty ball
oons, inflated with contrast medium to a diameter of 2.5, 3, 3.5, and
4 mm. Radioactive Y-90 wires were left in the inner balloon catheter a
nd the surface dose rate was measured and extrapolated to 72 h after a
ctivation to allow a comparison between the values obtained. After obs
erving the poor centering of the source within the standard angioplast
y balloon, a new centering balloon was developed. A conventional ballo
on was subdivided into four evenly spaced interconnecting chambers, th
us assuring adequate centering of the inner catheter. Thermoluminescen
t dosimetric measurements were performed with a 3.5 mm centering ballo
on to evaluate the homogeneity of the surface doses compared to those
measured with the conventional balloon. Results: Thermoluminescent dos
imetric measurements using the standard balloons filled with contrast
medium were plotted semilogarithmically as a function of distance from
the balloon surface. The logarithms of the measured doses fit a strai
ght line as a function of depth. The doses at 1 mm and 3 mm are approx
imately 50 and 10% of the surface dose, respectively. Due to the poor
centering of the source in the conventional balloons, the dispersion a
nd standard deviations (SDs) of the measured surface doses increased p
roportionally to the balloon diameter (SDs are 1.89, 5.52, 5.79, and 6
.46 Gy for 2.5, 3, 3.5, and 4 mm balloon diameters, respectively). For
the 3.5 mm centering and conventional balloons the respective mean, m
inimum, and maximum surface doses were 8.41 Gy (min. 7.26; max. 9.46)
and 7.89 Gy (min. 2.18; max. 16.06) and their standard deviations were
0.66 and 5.79 Gy, respectively. Conclusions: Conventional angioplasty
balloons cannot ensure a homogeneous dose delivery to an arterial wal
l with an intralumenal Y-90 beta source. Preliminary dosimetric result
s using a modified centering balloon show that it permits improved sur
face dose distribution (axial and circumferential homogeneity), making
it suitable for clinical applications,