The effects of non-centred catheter and guidewire on the dose distribution around source in catheter-based intravascular brachytherapy with 90Sr/90Y beta source
ABSTRACT Recently, animal experiments and clinical studies indicate that rates of restenosis can be significantly reduced by short-range ionizing radiation in the dose range of 15–30 Gy applied locally. In the irradiation system with seed form, a manual afterloading device brings the sources to the end of a closed-end catheter by hydraulic pressure in the treatment. The 5 French (5F) catheters contain three lumens for guidewire, radioactive seeds and provides a mean of hydraulic fluid return. Because the lumen for radioactive seeds is not in the centre of the delivery catheter, the dose distribution around the source train may be disturbed. Attenuation of beta rays in the medium is very rapid and the absorption of the beta rays is tightly dependent on the atomic number of the medium. Therefore, the presence of a metallic guidewire inside the target region may disturb the dose distribution behind the guidewire. The aim of this work is to investigate the dose distribution around 90Sr/90Y source train with and without the guidewire at a radial distance 2 mm from the catheter centre using the radiochromic film dosimetry. We measured dose variations up to 25% caused by non-centred catheter and 35% dose reduction by the guidewire. The results of this study show that an acceptable homogeneous dose distribution around the 90Sr/90Y beta source cannot be achieved, in case of a non-centred catheter and a significant underdose region behind the guidewire may have occurred in the presence of guidewire inside the target region.
- Medical Physics 01/2004; 31(5). · 2.91 Impact Factor
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ABSTRACT: Ionizing gamma radiation has been shown to reduce neointimal formation and the incidence of restenosis after balloon angioplasty and stenting in clinical trials. However, the long-term effects of this therapy are unknown. The first cohort of patients to receive intracoronary gamma radiation after balloon angioplasty for the prevention of restenosis have completed a 5-year angiographic and clinical follow-up. The outcome of these patients is presented and discussed. Twenty-one patients with unstable angina (22 arteries) underwent standard balloon angioplasty. Intracoronary radiation therapy was performed immediately after the intervention using an Iridium-192 source wire hand-delivered to the angioplasty site. All patients were followed clinically and Quantitative Coronary Analysis (QCA) was performed at 6, 24, 36 and 60 months. Target lesion revascularization occurred in six lesions, three of which were total occlusions (two early within 30 days and one occurred at 2 years), and one patient had a myocardial infarction attributable to a nontarget vessel. Serial QCA detected a binary restenosis rate of 28.6% (n=6) at 6 months. The late loss (0.29 mm) and loss index (0.25) remained low at 2, 3 and 5 years. Angiographic complications included four aneurysms (two procedure related and two occurring within 3 months). At 2 years, only one aneurysm increased in size (46 vs. 27 mm(2)); and at 3 and 5 years, all aneurysms remained unchanged. No other angiographic complications were observed. The early clinical and angiographic effects of intracoronary gamma radiation were maintained at 5 years without further increase in the aneurysm formation or apparent new adverse effects related to the radiation therapy between 2 and 5 years.Cardiovascular Radiation Medicine 04/2002; 3(2):74-81.
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ABSTRACT: The dose response of high-sensitivity GafChromic film to photons from 125I seeds for doses up to 200 Gy was established. The optical densities were measured using two types of densitometers: (a) a Macbeth spot densitometer with broadband light spectrum, and (b) an LKB He-Ne laser scanning microdensitometer with red light of wavelength 632.8 nm. The net optical density was found to be a power function of dose with exponents of 0.858 and 0.997, for the Macbeth and LKB densitometers, respectively. Film sensitivity with the LKB densitometer was about double of that with the Macbeth densitometer. The dose measurements were performed using the high-sensitivity GafChromic films for 125I model 6702 seed in solid water phantom. Each film was positioned parallel to the seed's long axis and centered at the seed's transverse axis. Films were exposed at various distances, ranging from contact to 3 cm from the seed center. The radiation dose delivered to the film center varied from 7 to 50 Gy, depending on the distance. The optical density at the film center was measured using both types of densitometers. Dose conversion was achieved with the established dose response curves for the respective densitometers. The dose values, along the seed's transverse axis obtained using both densitometers, were compared with each other, and also compared with published thermoluminescent dosimeter (TLD) data and Monte Carlo results. General agreement was found. It was concluded that the high-sensitivity GafChromic film measurement is a feasible method for 125I seed dosimetry in solid water phantom.(ABSTRACT TRUNCATED AT 250 WORDS)Medical Physics 06/1994; 21(5):651-7. · 2.91 Impact Factor
Radiation Measurements 41 (2006) 317–322
Bayram Demira,∗, Mustafa Demirb,Asm SabbirAhmedb
aIstanbul University, Science Faculty, Physics Department, Istanbul, Turkey
bIstanbul University, Cerrahpasa Medical Faculty, Nuclear Medicine Department, Istanbul, Turkey
Received 28 March 2005; accepted 24 June 2005
Recently, animal experiments and clinical studies indicate that rates of restenosis can be significantly reduced by short-
range ionizing radiation in the dose range of 15–30Gy applied locally. In the irradiation system with seed form, a manual
afterloading device brings the sources to the end of a closed-end catheter by hydraulic pressure in the treatment. The 5 French
(5F) catheters contain three lumens for guidewire, radioactive seeds and provides a mean of hydraulic fluid return. Because
the lumen for radioactive seeds is not in the centre of the delivery catheter, the dose distribution around the source train may
be disturbed. Attenuation of beta rays in the medium is very rapid and the absorption of the beta rays is tightly dependent on
the atomic number of the medium. Therefore, the presence of a metallic guidewire inside the target region may disturb the
dose distribution behind the guidewire. The aim of this work is to investigate the dose distribution around90Sr/90Y source
train with and without the guidewire at a radial distance 2mm from the catheter centre using the radiochromic film dosimetry.
We measured dose variations up to 25% caused by non-centred catheter and 35% dose reduction by the guidewire. The results
of this study show that an acceptable homogeneous dose distribution around the90Sr/90Y beta source cannot be achieved, in
case of a non-centred catheter and a significant underdose region behind the guidewire may have occurred in the presence of
guidewire inside the target region.
© 2005 Elsevier Ltd. All rights reserved.
Keywords: Intravascular brachytherapy; Non-centred catheter; Guidewire; Radiochromic film dosimetry
Restenosis after stent implantation in patients with coro-
nary artery disease is caused primarily by an intimal hy-
perplastic response (Liu et al., 1989). Previous studies have
shown that radiation may inhibit cellular hyperplasia by
either killing progenitor cells or limiting their replicative
∗Corresponding author. Tel.: +902124555700;
E-mail address: email@example.com (B. Demir).
1350-4487/$-see front matter © 2005 Elsevier Ltd. All rights reserved.
capacity, thus reducing the number of clonal populations
(Condado et al., 2002; Waksman et al., 1995). In general,
the isotopes that are preferred for intravascular brachyther-
apy (IVBT) are beta emitters because of their suitable
features for this therapy (Amols et al., 1996). One of the
IVBT irradiation system using beta emitter radioisotope is
catheter-based Novoste Beta-Cath.This irradiation system is
formed with seeds, and a manual afterloading device brings
the sources to the end of a closed-end delivery catheter by
hydraulic pressure in the treatment. The cardiologist propels
the radioactive seeds down the delivery catheter using a
B. Demir et al. / Radiation Measurements 41 (2006) 317–322
sterile water-filled syringe. Thus, an effectively continuous
and flexible line source is provided inside the injured vessel
region. The delivery catheter used in this irradiation system
contains three lumens for guidewire, radioactive seeds and
provides a mean of hydraulic fluid return. Because of the
delivery catheter’s design, the lumen for radioactive seeds is
not in the centre of the catheter and a distance of 0.39mm
separates the source lumen centre from the catheter’s centre.
Due to a short range of beta rays in the tissue, this distance
between the centres may have caused an in-homogenous
A metallic guidewire is used in an angioplasty applica-
tion to place the balloon and other intracoronary catheters.
High torquability and steerability properties of these metal-
lic guidewires are very useful for the cardiologist to nav-
igate the balloon and other intracoronary catheters inside
the vessel. Besides, the same guidewire is used in an IVBT
procedure when the delivery catheter is put into the exact
place to irradiate the injured vessel part with the sufficient
radiation doses. These guidewires are produced using heavy
metal like stainless steel and they have rather higher atomic
number than the tissue. On the other hand, attenuation of
beta rays in the medium is very rapid and the absorption of
the beta rays is tightly dependent on the atomic number of
the medium. Therefore, the presence of a metallic guidewire
inside the target region, may disturb the dose distribution
behind the guidewire.
There are several physical reasons,whichmayhavecaused
an unwanted in-homogenous dose distribution around the
source in catheter-based IVBT using beta emitter radioiso-
tope with short therapeutic range, and to provide a homo-
geneous dose distribution around the source is difficult.
Previous studies have shown that major deviations on the
dose distribution may be caused because of (i) source cen-
tering and residual plaque (Sehgal et al., 2001), (ii) lateral
and longitudinal displacement in case of cardiac motions
or calcified plaques (Chibani and Li, 2002), (iii) the off-
centring of the source train lumen within the catheter (Roa
et al., 2002), (iv) high absorption of the beta rays by metal-
lic guidewire (Li and Shih, 2001; Shih et al., 2002), and
(v) metallic stent (Nath et al., 1999b). In the present study,
we ignored all the movements of the catheter inside the
vessel, instead we investigated the effect of a non-centred
catheter and a guidewire on the circumferential dose distri-
bution around the source in the catheter-based IVBT with
90Sr/90Y beta emitter using radiochromic film dosimetry
in a homogeneous stable phantom, which was made of
polymethyl methacrylate (PMMA) in our department.
2. Materials and methods
2.1. The90Sr/90Y source train
The90Sr/90Y source (Beta-Cath System, Novoste Cor-
poration) used for IVBT to prevent restenosis is a pure beta
emitter radionuclide with emissions at average energies of
and 2226keV, respectively) with a half-life of 28.5years.
The source train consists of 16 radioactive seeds in the form
of steel cylinders containing strontium titanate ceramic and
two non-active radiopaque marker seeds at each end. The
seeds are 2.5mm × 0.64mm of size (length × diameter)
and the total active source length is 40mm. When not in
use, the source train is stored inside a shielding container,
in which they are shielded by acrylic plastic. With the sys-
tem, dose calculations are made according to the reference
vessel diameter and the mean treatment times are 3–4min.
2.2. The delivery catheter and the guidewire
In this irradiation system, a manual afterloading device
brings the sources to the end of a closed-end catheter by
hydraulic pressure in the treatment. The cardiologist pro-
pels the radioactive seeds down the delivery catheter using a
sterile water-filled syringe. There are two radiopaque mark-
ers near the distal tip of the delivery catheter that define the
treatment length as shown in Fig. 1a. The 5 French (5F)
(1 French = 0.318mm) delivery catheters have an outer di-
ameter of 1.6mm and it contains three lumens for guidewire,
radioactive seeds and provides a mean of hydraulic fluid re-
turn as shown in Fig. 1b. The shortest distance between the
source axis and the catheter’s surface is 0.41mm, and the
farthest distance between the source axis and the catheter’s
surface is 1.19mm, while the distance between the source
axis and the centre of the catheter is 0.39mm.The guidewire
used in this study is 180cm long, 0.014in. (0.0356cm) in
diameter and was made of stainless steel.
2.3. Radiochromic film measurements
Recently, several studies have shown that the ra-
diochromic film dosimetry is ideally in the dosimetry of the
brachytherapy sources (McLaughlin et al., 1991; Chiu-Tsao
et al., 1994) because it is nearly tissue equivalent and has
a near-linear response of optical density vs. dose. The ra-
diochromic film is a thin, almost colourless polyester sheet
embedding a chromophore that changes dark blue under
the influence of radiation. Typically, the radiochromic film
is calibrated in a known radiation field and the relationship
between the dose and the film response is determined. The
radiochromic film used in the study is known as HD-810
(Nuclear Associates) and has a single layer of radiosen-
sitive material of thickness 7?m on a 100-?m polyester
base. HD-810 films are mainly used for dose mapping in
the range of 50–2500Gy. To obtain more information about
radiochromic films, readers are referred to the AAPM task
group report no. 55 (Niroomand-Rad et al., 1998).
The treatment depth of a coronary artery in IVBT is
2mm and the dose rate for beta emitter IVBT sources with
catheter-based system is measured at a reference point lo-
cated at a radial distance of 2mm from the source axis as
B. Demir et al. / Radiation Measurements 41 (2006) 317–322
Cross sectional view
Catheter Radioactive Seeds
Radiopaque MarkerGold Marker Guidewire
Fig. 1. The non-centred delivery catheter, seeds and guidewire. The 5 French delivery catheter has an outer diameter of 1.6mm, the active
source lumen has a 0.81mm inner diameter and seeds have a 0.64mm outer diameter. The guidewire has a 180cm long, 0.014in. (0.0356cm)
diameter. (a) Lateral view and (b) cross-sectional view.
recommended by the AAPM task group no. 60 (Nath et al.,
1999a).Therefore, dosimetric effects of a non-centred cathe-
ter and a guidewire were investigated at a radial distance of
2mm from the geometric centre of the catheter using the
radiochromic film dosimetry.
The measurements with non-centred delivery catheter
were performed in a specially manufactured phantom,
which was made of PMMA in our department. A 5F deliv-
ery catheter was placed in a hole (with diameter of 1.7mm)
that was drilled into a cylindrical PMMA phantom (inner
block) with a diameter of 4mm and 6cm long. Also, a
radiochromic film with the size of 1.2×6cm2was covered
around the inner block so that its sensitive side was facing
to the source. Then, the inner block and the radiochromic
film were placed in a hole (with diameter of 4.2mm) that
was drilled into a PMMA block (outer block) so that the
distances from the catheter’s centre to the radiochromic
film’s surface are exactly 2mm. Thus, a centering prob-
lem due to the non-centred catheter was generated in a
stable phantom as shown in Fig. 2. The radiochromic films
were irradiated with and without the guidewire using the
90Sr/90Y source train with the set-up as shown in Fig. 2.
In order to obtain the best optical density on the films, the
irradiation time were 25min (about 186Gy according to the
manufacturer’s certificates). The radiochromic films irradi-
ated with and without guidewire were presented in Fig. 3.
The optical densities on the films were carefully read be-
tween 0◦and 345◦the using a transmission densitometer
and, the absorbed doses on the films were calculated using
the dose–response curve (described below). Then, the rela-
tive dose profiles created from these films as a function of
degrees were presented in Fig. 4.
Cross sectional view of the tissue equivalent PMMA phantom.
Fig. 2. Experimental set-up used in this study to measure the
dosimetric effects of non-centred delivery catheter and guidewire.
Without guidewire With guidewire
Fig. 3. The irradiated radiochromic films as a circumferential using
the90Sr/90Y source train without and with guidewire at 2mm
radial distance from the geometric centre of the catheter during a
period of 25min. The films were scanned from 0◦to 345◦.
B. Demir et al. / Radiation Measurements 41 (2006) 317–322
0 45 90135 180 225270 315360
Circumferential Angle (Degrees)
Fig. 4. The dose profiles obtained from radiochromic films in Fig. 3. Doses are normalized to the dose at 0◦.
Because the radiochromic film has been shown to have
the same response to the electron beams as the60Co gamma
rays (to within 3%) (McLaughlin et al., 1991), radiochromic
films in the same day were calibrated using60Co beams
with 50, 100, 150, 200Gy doses at 5cm depth using solid
water phantom (20×30×30cm3of size), which was large
of radiochromic films were determined after 24h and the
and doses. The densitometer (Densitometer PTW-DensiX,
PTW-Freiburg) uses a standard fluorescent light (broadband)
to measure the density.
3. Results and discussion
When an electron penetrates into the medium, it loses
its energy with two types of interactions. One of them is
collisional interaction between the initial electron and the
other is the interaction which results in the bremsstrahlung
irradiations between the initial electron and the nucleus of
the medium atoms (radiation losses). During these interac-
tions, the medium atoms cause the electron to slow down
and change their direction. Eventually, it will lose all of
its kinetic energy within a finite distance, which is called
the range of the electron, and comes to rest. Because, elec-
trons have a negative electric charge, their interactions prob-
ability with the medium atoms increases with an increased
atom number of the medium. Especially, for heavy met-
als like stainless steel, attenuation of electron beams in the
medium is very rapid due to their high electron density
(2.30×1024e−/cm3) and high mass density (8.1gr/cm3),
compared to the tissue (3.43×1023e−/cm3and 1gr/cm3)
(Johns and Cunningham, 1983).
In the present study, we investigated the effect of a non-
centred catheter and a guidewire on the circumferential dose
distribution around the source in a catheter-based IVBT with
the90Sr/90Y beta emitter. The above effects related to elec-
tron absorption in any medium were clearly seen on the films
in Fig. 3. There are major optical density variations on the
films that depend on the distance between the source axis
and the surface of the film. As might be expected, the parts
of the film closer to the source received more radiation and
thus, the optical density was higher than the parts further
away. Also, the effect of the guidewire on the second film
that was irradiated with the stainless steel guidewire can be
seen. The optical density behind the guidewire was clearly
reduced because of high absorption of the guidewire.
For the numerical analysis of the films, the results of the
study were presented as a graphic in Fig. 4 which shows a
plot of the relative dose vs. the circumferential angle. When
the effects of the non-centred catheter on the circumferential
dose profile in Fig. 4 were examined, important variations on
the dose profile were seen. For example, we have determined
a dose rate of 10.63cGy/min at pointA (the shortest distance
between the source axis and the film’s surface = 1.61mm)
and 13.29cGy/min at point B (farthest distance between
the source axis and the film’s surface = 2.39mm), whereas
12.50cGy/min at 2mm from the source axis. Thus, because
of the non-centred catheter, the doses between points A and
B can differ as much as 25%.
Similar studies were done by Roa et al. (2002, 2004)
who measured the dose rates at only point C (the shortest
distance between the source axis and 5F catheter’s surface
is 0.41mm) and D (the farthest distance between source
axis and 5F catheter’s surface is 1.19mm) for 3cm long
90Sr/90Y source train within the 5F catheter using radio-
choromic film dosimetry. They have reported a dose rate of
5.2cGy/min at point C and 6.0cGy/min at point D, whereas
dose rates of 5.45cGy/min that is given at 2mm have been
reported by Novoste. According to their dose rate values,
a discrepancy of 15.4% between points C and D occurred
due to the non-centred catheter. The difference between our
B. Demir et al. / Radiation Measurements 41 (2006) 317–322
and their results could have arised because of the distance
from the source axis to the distances of the measurement
points. Although, they studied at a distance of 0.8mm from
the catheter’ centre, we investigated the dose distributions
around the source train at a distance of 2mm from the
catheter’s centre. The results of these studies have shown
that the effects of the non-centred catheter on the dose dis-
tribution have become clearer with increasing distance from
the catheter’s centre.
On the other hand, when the dose profile with the
guidewire in Fig. 4 were examined, it can be seen that there
was a dose reduction behind the stainless steel guidewire
up to 35% at 1.3mm distance behind the 0.014in. stain-
less steel guidewire located at ∼ 0.8mm distance from the
source axis, compared to the dose distribution without the
guidewire. Although there is not any experimental study
that shows the effect of the guidewire on the dose distribu-
tion of90Sr/90Y source train, previous Monte Carlo studies
have shown that attenuation of the stainless steel guidewire
for beta sources can be increased 20–55% depending on the
guidewire positions (Li and Shih, 2001; Shih et al., 2002).
According to Monte Carlo calculations, at 1.3mm distance
behind the 0.014in. stainless steel guidewire located at
1mm distance from the source axis during irradiation with
the90Sr/90Y source train, there was a dose reduction of
30% caused by the guidewire. The discrepancy of 5% be-
tween our experimental result and the Monte Carlo result
could have arised due to either the difference (∼ 0.2mm)
between the locations of the guidewire from the source axis
or due to our experimental errors.
90Sr/90Y beta source has many advantages in terms of
specific activity and dose rate. The high activity of the
source permits short irradiation times (3–4min) to the ap-
plication of therapeutic doses of 15–30Gy at depths of
1–2mm. The usage of90Sr/90Y sources with the seed form
in a catheter-based IVBT procedure is rather easy and the
average treatment procedure for IVBT using the Novoste
model irradiation system takes 20–25min. Besides, the sys-
tem is very economical due to their half-life with 28.5
years and because of the limited range of beta rays, treat-
ments could be carried out in the cardiology laboratory
with minimal radiation protection during the IVBT proce-
dure (Nath et al., 1999a). In spite of these advantages, our
results show that an acceptable homogeneous dose distri-
bution [within ±10% as recommended by the AAPM task
group report no. 60 (Nath et al., 1999a)] for IVBT sources
around the90Sr/90Y beta source in case of the non-centred
catheter cannot be achieved. Also, a significant underdose
region, behind the guidewire may have occurred in the
presence of the guidewire inside the target region. There-
fore, for a better dose distribution around the vessel wall
in the treatment, the guidewire should be retracted outside
the target region after the catheter is put carefully into the
This work was supported by the Research Fund of the
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