The document describes a study that used the MCNP5 Monte Carlo code to determine dosimetric quantities surrounding a 103Pd radioactive stent, according to AAPM TG-60 recommendations. The stent was modeled as a hollow cylinder coated with 103Pd. MCNP5 was used to calculate the dose deposited per photon, relative dose, anisotropy function F(r,h), and radial dose function gL(r) at various distances from the stent surface. The relative dose values calculated by MCNP5 agreed well with values from TG-43 and previous EGS4 simulations, with errors of less than 3%. The dosimetric parameters determined can be used in future treatment planning for intravascular brachytherapy.
THE USE OF ADAPTIVE STATISTICAL ITERATIVE RECONSTRUCTION (ASIR) ON IMAGE QUAL...AM Publications
Use of Adaptive Statistical Iterative Reconstruction (ASIR) on CT scan of thorax has been investigated. This study aims is to determine the effect of the use of ASIR on the radiation dose and image quality. The study was conducted using phantom anthropomorphic using CT Scan GE Optima 580 with setting ASIR Dose Reduction 0% - 50%. This study was carried out by using two parameters: fixed tube current and Tube Current Modulation (TCM). Analyzing of radiation dose is done by calculation of CTDIvol. While image quality are investigated by calculated Signal to Noise Ratio (SNR) and Contrast to Noise Ratio (CNR). There is a difference in the CTDIvol value, between the fixed tube current and TCM settings. At fixed tube current strength, the CTDIvol value is measured, starting from 0% to 50% ASIR, respectively: 48.60 mGy; 43.74 mGy; 38.88 mGy; 34.02 mGy; 29.16 mGy; and 24.30 mGy. While the CTDIvol value measured in TCM settings uses 0% to 50% ASIR as follows: 21.92 mGy; 20.09 mGy; 18.33 mGy; 16.51 mGy; 14.59 mGy; and 12.75 mGy. Using ASIR with TCM can produce CTDIvol values that are smaller than ASIR with fixed tube current. The difference in the average CTDIvol value is 51.80% between the use of TCM and fixed tube current. The greater the percentage of ASIR regulated, the greater the decrease in the CTDIvol dose. There is no significant difference in the SNR and CNR values produced by 0% to 50% ASIR with a fixed current strength. There is no significant difference in the SNR and CNR values produced by ASIR 0% to 50% with TCM. The average CNR value shown in TCM is higher than that of fixed tube current. The use of ASIR influence in dose radiation decreases without change the image quality.
Verification of a treatment planning system using an in-house designedtrunk p...IOSR Journals
This study is aimed at verifying the dosimetric performance of a treatment planning system (TPS)
and to as well compare the accuracy of the measured absorbed dose of the solid water phantom against the inhouse
phantom. In this study, a phantom for use in radiotherapy treatment planning of human trunk anatomical
region has been designed with six hollows for inserting materials mimicking different biological tissues and the
ionization chamber. For the trunk, pure Glycerolwas used for Muscle, 75% to 25% Glycerol-Water was used
for liver, Carboxyl-Methyl-Cellulose (CMC)was used for Lungs, 50% to 50% Glycerol-Water was used for
Adipose, Sodium Hypochlorite (soda bleach) for Bone and SodiumLaureth Sulphate (Texapon) was used for
Kidney. The phantom was scanned with Hi-Speed CT-scannerand images were transferred to a Precise PLAN
Treatment Planning System where appropriate beams were applied and verified before it was transferred to the
Elekta-Precise Clinical Linear Accelerator.Measurements of the Monitor Units (MU) were conducted using 6
MeV photon beams from the Elekta-Precise Clinical Linear Accelerator with iso-centric set up and the
corresponding doses were calculated. The test of the phantom was done using an Irregular Field Algorithm
(Clarkson Integration). The maximum standard deviation with large field size of22 × 24𝑐𝑚2for all
sixinhomogeneous inserts and bone only inhomogeneous inserts were −3.39% and 2.93% respectively. And
maximum standard deviation with small field size of 5 × 5𝑐𝑚2was−3.16%. Also, the percentage deviation for
the solid water phantom when compared with the in-house phantom with SSD of 85cm for both set-ups was
−2.09%. Theseresultsshow that irrespective of the field sizes and tissue equivalent materials, Irregular Field
Algorithm compensates for inhomogeneity.
THE USE OF ADAPTIVE STATISTICAL ITERATIVE RECONSTRUCTION (ASIR) ON IMAGE QUAL...AM Publications
Use of Adaptive Statistical Iterative Reconstruction (ASIR) on CT scan of thorax has been investigated. This study aims is to determine the effect of the use of ASIR on the radiation dose and image quality. The study was conducted using phantom anthropomorphic using CT Scan GE Optima 580 with setting ASIR Dose Reduction 0% - 50%. This study was carried out by using two parameters: fixed tube current and Tube Current Modulation (TCM). Analyzing of radiation dose is done by calculation of CTDIvol. While image quality are investigated by calculated Signal to Noise Ratio (SNR) and Contrast to Noise Ratio (CNR). There is a difference in the CTDIvol value, between the fixed tube current and TCM settings. At fixed tube current strength, the CTDIvol value is measured, starting from 0% to 50% ASIR, respectively: 48.60 mGy; 43.74 mGy; 38.88 mGy; 34.02 mGy; 29.16 mGy; and 24.30 mGy. While the CTDIvol value measured in TCM settings uses 0% to 50% ASIR as follows: 21.92 mGy; 20.09 mGy; 18.33 mGy; 16.51 mGy; 14.59 mGy; and 12.75 mGy. Using ASIR with TCM can produce CTDIvol values that are smaller than ASIR with fixed tube current. The difference in the average CTDIvol value is 51.80% between the use of TCM and fixed tube current. The greater the percentage of ASIR regulated, the greater the decrease in the CTDIvol dose. There is no significant difference in the SNR and CNR values produced by 0% to 50% ASIR with a fixed current strength. There is no significant difference in the SNR and CNR values produced by ASIR 0% to 50% with TCM. The average CNR value shown in TCM is higher than that of fixed tube current. The use of ASIR influence in dose radiation decreases without change the image quality.
Verification of a treatment planning system using an in-house designedtrunk p...IOSR Journals
This study is aimed at verifying the dosimetric performance of a treatment planning system (TPS)
and to as well compare the accuracy of the measured absorbed dose of the solid water phantom against the inhouse
phantom. In this study, a phantom for use in radiotherapy treatment planning of human trunk anatomical
region has been designed with six hollows for inserting materials mimicking different biological tissues and the
ionization chamber. For the trunk, pure Glycerolwas used for Muscle, 75% to 25% Glycerol-Water was used
for liver, Carboxyl-Methyl-Cellulose (CMC)was used for Lungs, 50% to 50% Glycerol-Water was used for
Adipose, Sodium Hypochlorite (soda bleach) for Bone and SodiumLaureth Sulphate (Texapon) was used for
Kidney. The phantom was scanned with Hi-Speed CT-scannerand images were transferred to a Precise PLAN
Treatment Planning System where appropriate beams were applied and verified before it was transferred to the
Elekta-Precise Clinical Linear Accelerator.Measurements of the Monitor Units (MU) were conducted using 6
MeV photon beams from the Elekta-Precise Clinical Linear Accelerator with iso-centric set up and the
corresponding doses were calculated. The test of the phantom was done using an Irregular Field Algorithm
(Clarkson Integration). The maximum standard deviation with large field size of22 × 24𝑐𝑚2for all
sixinhomogeneous inserts and bone only inhomogeneous inserts were −3.39% and 2.93% respectively. And
maximum standard deviation with small field size of 5 × 5𝑐𝑚2was−3.16%. Also, the percentage deviation for
the solid water phantom when compared with the in-house phantom with SSD of 85cm for both set-ups was
−2.09%. Theseresultsshow that irrespective of the field sizes and tissue equivalent materials, Irregular Field
Algorithm compensates for inhomogeneity.
APPLICATION OF PARTICLE SWARM OPTIMIZATION FOR ENHANCED CYCLIC STEAM STIMULAT...Zac Darcy
Three different variations of PSO algorithms, i.e. Canonical, Gaussian Bare-bone and Lévy Bare-bone
PSO, are tested to optimize the ultimate oil recovery of a large heavy oil reservoir. The performance of
these algorithms was compared in terms of convergence behaviour and the final optimization results. It is
found that, in general, all three types of PSO methods are able to improve the objective function. The best
objective function is found by using the Canonical PSO, while the other two methods give similar results.
The Gaussian Bare-bone PSO may picks positions that are far away from the optimal solution. The Lévy
Bare-bone PSO has similar convergence behaviour as the Canonical PSO. For the specific optimization
problem investigated in this study, it is found that the temperature of the injection steam, CO2 composition
in the injection gas, and the gas injection rates have bigger impact on the objective function, while steam
injection rate and the liquid production rate have less impact on the objective function.
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems...Pawan Kumar
Low dimensionality and high flexibility are key demands for flexible electronic semiconductor devices. SnIP, the first atomic‐scale double helical semiconductor combines structural anisotropy and robustness with exceptional electronic properties. The benefit of the double helix, combined with a diverse structure on the nanoscale, ranging from strong covalent bonding to weak van der Waals interactions, and the large structure and property anisotropy offer substantial potential for applications in energy conversion and water splitting. It represents the next logical step in downscaling the inorganic semiconductors from classical 3D systems, via 2D semiconductors like MXenes or transition metal dichalcogenides, to the first downsizeable, polymer‐like atomic‐scale 1D semiconductor SnIP. SnIP shows intriguing mechanical properties featuring a bulk modulus three times lower than any IV, III‐V, or II‐VI semiconductor. In situ bending tests substantiate that pure SnIP fibers can be bent without an effect on their bonding properties. Organic and inorganic hybrids are prepared illustrating that SnIP is a candidate to fabricate flexible 1D composites for energy conversion and water splitting applications. SnIP@C3N4 hybrid forms an unusual soft material core–shell topology with graphenic carbon nitride wrapping around SnIP. A 1D van der Waals heterostructure is formed capable of performing effective water splitting.
My co-authors and I have created an R package that allows the user to perform a fully quantitative analysis of DCE-MRI (dynamic contrast-enhanced magnetic resonance imaging) data. With applications in oncology in mind, users can interrogate the perfusion characteristics of tissue in order to compare between treatment groups and pre-/post-treatment.
Dose Evaluation in the Movement Couch of the Total Body Irradiation Technique...iosrjce
IOSR Journal of Applied Physics (IOSR-JAP) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Error Reduction in Parameter Estimation from the Segmented Intravoxel Incoher...asclepiuspdfs
The purpose of the study was to develop and evaluate a method aiming at reducing the estimation error of the intravoxel incoherent motion (IVIM) model parameters reduced-error IVIM (reIVIM) and to compare the estimated parameters to those measured using the conventional “segmented” IVIM (seIVIM) algorithm. Materials and Methods: The prospective clinical component of this study was approved by the Institutional Review Board; all patients signed informed consent. 10 patients who underwent pre-treatment magnetic resonance (MR) imaging between July 2014 and May 2015 at 3-Tesla as part of a prospective study of the effect of radiation treatment on IVIM parameters were included. Diffusion-weighted MR images at 17 b-values (0, 10, 40, 70, 90, 100, 110, 120, 170, 210, 240, 270, 390, 530, 620, 750, and 1000 s/mm2) were acquired at 4–8 consecutive time points. Using pre-treatment data, IVIM parameters (pseudo-diffusion D*, true diffusion D, and perfusion-fraction f) were estimated from tumor regions of interest using the seIVIM and reIVIM algorithms. The repeatability of IVIM parameters for each algorithm was evaluated through assessment of the coefficient of variation (CV). For simulated data, precision and accuracy were evaluated as a function of noise. Results: Differences in CV for D and f between seIVIM and reIVIM (mean ± standard deviation %: 5.95 ± 2.63 and 5.94 ± 2.78 for D and 13.26 ± 4.94 and 10.54 ± 3.83 for f, respectively) were not significant (P = 0.99 and P = 0.18 for D and f, respectively). Differences in CV for D* and f × D* between seIVIM and reIVIM (40.88 ± 14.80% and 20.51 ± 7.71% for D* and 45.10 ± 13.40% and 22.50 ± 8.48% for f × D*, respectively) were significant (P = 0.0003 and P = 0.0003 for D* and f × D*, respectively). Conclusion: The proposed approach to the voxel-wise analysis of IVIM data results in the improved estimation of the pseudo-diffusion parameter by reducing the variability of the measurement.
TOMOGRAPHY OF HUMAN BODY USING EXACT SIMULTANEOUS ITERATIVE RECONSTRUCTION AL...cscpconf
In this paper an Exact Simultaneous Iterative Reconstruction Algorithm is developed and applied on a large semi human size normal biological model and a diseased model (liver region affected) to verify the efficiency of the algorithm. The algorithm is successfully reconstructed the normal model having 15%-20% perturbation i.e. change in permittivity during disease. In diseased case, reconstructed imaginary part of complex permittivity clearly detects the affected zone and it may help the medical diagnosis. Hence it may be a powerful tool for early detection of cancerous tumors as the interrogating wave is a noninvasive one at the ultra high frequency range. The resolution of this system is increased with the reduction of
wavelength by immersing the antenna system and the model in saline water region. The advantage of this algorithm is that the calculation of cofactor are done offline to save the computational time and cofactors are expressed as a function of distances irrespective of their positions
Design of a Selective Filter based on 2D Photonic Crystals Materials IJECEIAES
Two dimensional finite differences temporal domain (2D-FDTD) numerical simulations are performed in cartesian coordinate system to determine the dispersion diagrams of transverse electric (TE) of a two-dimension photonic crystal (PC) with triangular lattice. The aim of this work is to design a filter with maximum spectral response close to the frequency 1.55 μm. To achieve this frequency, selective filters PC are formed by combination of three waveguides W 1 K A wherein the air holes have of different normalized radii respectively r 1 /a=0.44, r 2 /a=0.288 and r /a= 0.3292 (a: is the periodicity of the lattice with value 0.48 μm). Best response is obtained when we insert three small cylindrical cavities (with normalized radius of 0.17) between the two half-planes of photonic crystal strong lateral confinement.
APPLICATION OF PARTICLE SWARM OPTIMIZATION FOR ENHANCED CYCLIC STEAM STIMULAT...Zac Darcy
Three different variations of PSO algorithms, i.e. Canonical, Gaussian Bare-bone and Lévy Bare-bone
PSO, are tested to optimize the ultimate oil recovery of a large heavy oil reservoir. The performance of
these algorithms was compared in terms of convergence behaviour and the final optimization results. It is
found that, in general, all three types of PSO methods are able to improve the objective function. The best
objective function is found by using the Canonical PSO, while the other two methods give similar results.
The Gaussian Bare-bone PSO may picks positions that are far away from the optimal solution. The Lévy
Bare-bone PSO has similar convergence behaviour as the Canonical PSO. For the specific optimization
problem investigated in this study, it is found that the temperature of the injection steam, CO2 composition
in the injection gas, and the gas injection rates have bigger impact on the objective function, while steam
injection rate and the liquid production rate have less impact on the objective function.
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems...Pawan Kumar
Low dimensionality and high flexibility are key demands for flexible electronic semiconductor devices. SnIP, the first atomic‐scale double helical semiconductor combines structural anisotropy and robustness with exceptional electronic properties. The benefit of the double helix, combined with a diverse structure on the nanoscale, ranging from strong covalent bonding to weak van der Waals interactions, and the large structure and property anisotropy offer substantial potential for applications in energy conversion and water splitting. It represents the next logical step in downscaling the inorganic semiconductors from classical 3D systems, via 2D semiconductors like MXenes or transition metal dichalcogenides, to the first downsizeable, polymer‐like atomic‐scale 1D semiconductor SnIP. SnIP shows intriguing mechanical properties featuring a bulk modulus three times lower than any IV, III‐V, or II‐VI semiconductor. In situ bending tests substantiate that pure SnIP fibers can be bent without an effect on their bonding properties. Organic and inorganic hybrids are prepared illustrating that SnIP is a candidate to fabricate flexible 1D composites for energy conversion and water splitting applications. SnIP@C3N4 hybrid forms an unusual soft material core–shell topology with graphenic carbon nitride wrapping around SnIP. A 1D van der Waals heterostructure is formed capable of performing effective water splitting.
My co-authors and I have created an R package that allows the user to perform a fully quantitative analysis of DCE-MRI (dynamic contrast-enhanced magnetic resonance imaging) data. With applications in oncology in mind, users can interrogate the perfusion characteristics of tissue in order to compare between treatment groups and pre-/post-treatment.
Dose Evaluation in the Movement Couch of the Total Body Irradiation Technique...iosrjce
IOSR Journal of Applied Physics (IOSR-JAP) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Error Reduction in Parameter Estimation from the Segmented Intravoxel Incoher...asclepiuspdfs
The purpose of the study was to develop and evaluate a method aiming at reducing the estimation error of the intravoxel incoherent motion (IVIM) model parameters reduced-error IVIM (reIVIM) and to compare the estimated parameters to those measured using the conventional “segmented” IVIM (seIVIM) algorithm. Materials and Methods: The prospective clinical component of this study was approved by the Institutional Review Board; all patients signed informed consent. 10 patients who underwent pre-treatment magnetic resonance (MR) imaging between July 2014 and May 2015 at 3-Tesla as part of a prospective study of the effect of radiation treatment on IVIM parameters were included. Diffusion-weighted MR images at 17 b-values (0, 10, 40, 70, 90, 100, 110, 120, 170, 210, 240, 270, 390, 530, 620, 750, and 1000 s/mm2) were acquired at 4–8 consecutive time points. Using pre-treatment data, IVIM parameters (pseudo-diffusion D*, true diffusion D, and perfusion-fraction f) were estimated from tumor regions of interest using the seIVIM and reIVIM algorithms. The repeatability of IVIM parameters for each algorithm was evaluated through assessment of the coefficient of variation (CV). For simulated data, precision and accuracy were evaluated as a function of noise. Results: Differences in CV for D and f between seIVIM and reIVIM (mean ± standard deviation %: 5.95 ± 2.63 and 5.94 ± 2.78 for D and 13.26 ± 4.94 and 10.54 ± 3.83 for f, respectively) were not significant (P = 0.99 and P = 0.18 for D and f, respectively). Differences in CV for D* and f × D* between seIVIM and reIVIM (40.88 ± 14.80% and 20.51 ± 7.71% for D* and 45.10 ± 13.40% and 22.50 ± 8.48% for f × D*, respectively) were significant (P = 0.0003 and P = 0.0003 for D* and f × D*, respectively). Conclusion: The proposed approach to the voxel-wise analysis of IVIM data results in the improved estimation of the pseudo-diffusion parameter by reducing the variability of the measurement.
TOMOGRAPHY OF HUMAN BODY USING EXACT SIMULTANEOUS ITERATIVE RECONSTRUCTION AL...cscpconf
In this paper an Exact Simultaneous Iterative Reconstruction Algorithm is developed and applied on a large semi human size normal biological model and a diseased model (liver region affected) to verify the efficiency of the algorithm. The algorithm is successfully reconstructed the normal model having 15%-20% perturbation i.e. change in permittivity during disease. In diseased case, reconstructed imaginary part of complex permittivity clearly detects the affected zone and it may help the medical diagnosis. Hence it may be a powerful tool for early detection of cancerous tumors as the interrogating wave is a noninvasive one at the ultra high frequency range. The resolution of this system is increased with the reduction of
wavelength by immersing the antenna system and the model in saline water region. The advantage of this algorithm is that the calculation of cofactor are done offline to save the computational time and cofactors are expressed as a function of distances irrespective of their positions
Design of a Selective Filter based on 2D Photonic Crystals Materials IJECEIAES
Two dimensional finite differences temporal domain (2D-FDTD) numerical simulations are performed in cartesian coordinate system to determine the dispersion diagrams of transverse electric (TE) of a two-dimension photonic crystal (PC) with triangular lattice. The aim of this work is to design a filter with maximum spectral response close to the frequency 1.55 μm. To achieve this frequency, selective filters PC are formed by combination of three waveguides W 1 K A wherein the air holes have of different normalized radii respectively r 1 /a=0.44, r 2 /a=0.288 and r /a= 0.3292 (a: is the periodicity of the lattice with value 0.48 μm). Best response is obtained when we insert three small cylindrical cavities (with normalized radius of 0.17) between the two half-planes of photonic crystal strong lateral confinement.
Calculation of air-kerma strength and dose rate constant for new BEBIG 60Co H...Anwarul Islam
Calculation of air-kerma strength and dose rate constant for new BEBIG 60Co HDR brachytherapy source: an EGSnrc Monte Carlo study
M. Anwarul Islam, Medical Physicist
SQUARE Hospitals Ltd, Bangladesh
anwar.amch@yahoo.com
Characterization of Liquid Waste in Isotope production and Research Facilitiesiosrjce
IOSR Journal of Applied Physics (IOSR-JAP) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
1. M. Sadeghi and O. Kiavar
Dosimetric aspects of 103
Pd radioactive
stent source
This study aims to determine AAPM TG-60 dosimetric quanti-
ties in regions surrounding the 103
Pd stent wall by MCNP5
Monte Carlo code. The Palmaz-Schatz stent was modeled by
a hollow cylinder of 17.89 mm length (2 mm diameter) with
net surface very similar to real stent. The Dose deposited per
photon (Gy), relative dose, Anisotropy function, F(r,h), and ra-
dial dose function, gL(r), were described at AAPM TG-60 pro-
tocol were generated from these values and listed in tabular
format. For benchmarking, the relative dose values were veri-
fied with TG-43 and EGS4 code results at identical conditions,
relative to the radial distances from surface of the stent. There
were noticeable results. These physical dosimetric parameters
can be used in future treatment planning systems for IVBT.
Dosimetrische Aspekte radioaktiver 103
Pd Stents. Ziel dieser
Arbeit war die Bestimmung dosimetrischer Größen in der Um-
gebung von 103
Pd Stents gemäß den AAPM TG-60-Empfeh-
lungen mit Hilfe des MCNP5 Monte Carlo Rechencodes. Der
Palmaz-Schatz Stent wurde dabei modelliert durch einen
Hohlzylinder von 17.89 mm Länge (2 mm Durchmesser) mit
einer Netzoberfläche ähnlich der des realen Stents. Die pro
Photon erzeugte Dosis (Gy), die relative Dosis, die Anisotro-
piefunktion, F(r,h), und die radiale Dosisfunktion, gL(r), wur-
den wie im AAPM TG-60-Protokoll beschrieben aus diesen
Werten erzeugt und tabellarisch dargestellt. Zu Benchmarking-
zwecken wurden die relativen Dosiswerte verifiziert mit TG-43
und EGS4 Rechenergebnissen bei gleichen Bedingungen, rela-
tive zur radialen Entfernung von der Stentoberfläche. Die Er-
gebnisse sind bemerkenswert. Die dosimetrischen Parameters
können bei zukünftigen Therapieplanungssystemen für IVBT
verwendet werden.
1 Introduction
The doses given to the vessel wall are very crucial quantities
in intravascular brachytherapy (IVBT). When the concept of
using radiation to reduce the incidence of restenosis following
angioplasty was introduced, preclinical studies revealed pro-
mising results for both temporary catheter implants and per-
manently implanted radioactive stents [1]. The purpose of in-
travascular brachytherapy is to safely deliver a sufficient
radiation dose to the vessel wall while limiting dose to normal
tissues surrounding the vessel [2]. Current clinical trials are
showing that intravascular brachytherapy techniques effec-
tively reduce the occurrence of restenosis in humans [3, 4].
In addition, many dosimetry studies are being conducted to
determine which isotopes and delivery methods are best sui-
ted for inhibiting restenosis in human arteries.
This paper is a new study in which Monte Carlo code
(MCNP5) is employed to investigate the dosimetric character-
istics of a 103
Pd-implanted stent for the purpose of assessing
its potential use in IVBT [4, 5]. Because of the characteristic
low-energy X-rays that 103
Pd emits and the low activity re-
quired for intravascular brachytherapy, a 103Pd stent can be
handled safely with minimal shielding requirements. In addi-
tion, the short half-life of 103
Pd (T1/2 = 16.97 days) allows it
to deliver > 90% of its radiation over 2 months and also gives
it a reasonable shelf life [6]. Numerous other characteristics of
103
Pd make it an attractive choice for intravascular bra-
chytherapy.
By and large, the main aim of this study is to determine do-
simetric parameters of TG-60 protocol [7]. For benchmarking,
the relative doses around the stent are calculated by MCNP5
and the results are verified with previously published papers
data [8, 9]. It is worth noting that the all conditions in this re-
search are identical with the mentioned articles.
2 Methods
2.1 Stent description
An arbitrary stent design, closely matching that of a commer-
cial stent (Palmaz-Schatz) [8] was used for this work. The
stent was composed of 201 identical (316L) stainless steel
struts with a thin layer of 103
Pd on the stent. The stainless
steel had a density of 7.861 g/cm3
and was composed of 17%
Cr, 13% Ni, 2.5% Mo, 64.5% Fe and allowable maximums
of 1% Si and 2% Mn (Table 1) [10]. The 103
Pd is a photon
emitter and has a half life of almost 17 days with density of
12.023 g/cm3
(Table 2) [11–14]. Fig. 1 shows the diagram of
half stent geometry in simulation. To model the stent as it
might appear in a blood vessel, the stent was expanded to an
outer diameter of 2 mm and a length of 17.89 mm (18-mm un-
expanded length) [9, 17].
2.2 Monte Carlo calculation technique
The Monte Carlo N-Particle code (MCNP version 5) was used
for the dose calculations [15]. In this article it was tried to
KT_kt-110222 – 17.9.12/stm media köthen
M. Sadeghi and O. Kiavar: Dosimetric aspects of 103
Pd radioactive stent source
77 (2012) 5 Ó Carl Hanser Verlag, München 1
Table 1. Atomic numbers for 103
Pd, 316L stainless steel and a 1:1 mix-
ture [10, 11]
Material Z or Zeff
a)
103
Pd 46
Stainless steel 316L [Cr (17%), Ni (13%), Mo (2.5%),
Fe (64.5%), Si (1%), Mn (2%)]b)
27
1:1 Mixture of stainless steel and 103
Pd 39
a)
Zeff = (a1Z1
m
+ a2Z2
m
+ ... anZn
m
)1/m
; (m = 3.5)
2. KT_kt-110222 – 17.9.12/stm media köthen
simulate the geometry which is approximately similar to phys-
ical parameters of real stent, but simplification was inevitable
(Fig. 1). For geometry simulation the stent was covered longi-
tudinally and radially by 2 cm and 4.0 cm of water voxels, re-
spectively. The water detectors were also simulated in the
form of shells with 0.1 mm thickness and 0.2 mm height
(Fig. 1). The outputs of Monte Carlo simulation were the en-
ergy deposited (MeV) per photon, calculated by *F8 tallies.
Dose values can multiply by intensity factor (the number of
photons emitted per disintegration) and divided on mass of
each detector (kg) to give dose deposited per disintegration
(Gy). The number of photon histories was set at 4 · 107
in or-
der to obtain a relative statistical error not greater than 0.7%
for each of the tallies placed at angles of 08 and 908.
In this study the relative dose were obtained by volume-
averaging the dose values in the detectors only along the
transverse axis at radial distances of r = 0.5, 1, 1.5, 2, 2.5, 3,
3.5 and 4 cm from surface of stent and then normalizing them
by the volume-averaged dose value at 1 cm. For benchmark-
ing, the relative dose calculated by MCNP5, were compared
to those data at TG43 [16] and EGS4 (Monte Carlo) [9]. Ac-
cording to the protocol described in TG-60; F(r, h), gL(r) were
acquired in water using gamma emitter’s formula (Eq. (1) and
(2)). Ultimately, treatment planning and dose fall-off curves
were also calculated [7].
Fðt; hÞ ¼ Dðr; p=2ÞGðr; hÞ ð1Þ
gLðrÞ ¼
Dðr; p=2ÞGðr0; p=2Þ
Dðr0; p=2ÞGðr; p=2Þ
ð2Þ
Where: r = the distance from center of stent, r0= the reference
point for photons (1 cm), G(r, h) = geometry factor resulting
from spatial distribution of the radioactivity within the source.
For calculating G(r, h), employed the Monte Carlo F4 tally
with the mass densities of all materials within the entire com-
putational geometry set equal to zero so there were no inter-
action and particles streamed through the stent and water
geometry. This parameter based on TG-43 protocol was used
for removing the inverse square law, in computations of stated
F(r, h) and gL(r) factors [8].
3 Results and discussion
In this investigation, the dose distributions were calculated by
MCNP5 Monte Carlo code at definite points in transverse
M. Sadeghi and O. Kiavar: Dosimetric aspects of 103
Pd radioactive stent source
2 77 (2012) 5
Table 2. Statistical decay of 103
Pd radioisotope [16]
No Half life Rad. Type Energy
(keV)
Intensity
(%)
1 16.991 days Gamma 39.7480 0.0683
2 " " 53.2900 0
3 " " 62.410 0.001038
4 " " 241.880 0
5 " " 294.98 0.0028
6 " " 317.720 0
7 " " 357.450 0.02206
8 " " 443.790 0
9 " " 497.080 0.003961
10 " X L 2.7 8.80
11 " X KA2 20.0737 22.06
12 " X KA1 20.2161 41.93
13 " X KB 22.7 13.05
Fig. 1. The geometry and detectors simulations
with MCNP5 for half expanded stent (MCNP
plot)
Fig. 2. The dose fall-off of a 103
Pd stent per photon at the distance from
surface (Gy)
3. cross sections for per photon. Dose maps were plotted for dis-
tances ranging from contact to 0.7 cm radially out from the
stent surface (Fig. 2) and showed the fast dose fall-off of
photons. The curve decreases exponentially from surface
slightly and ultimately acquires the least value.
Table 3 shows our calculated relative-dose values com-
pared to the corresponding values calculated from tabulated
TG43 [8] and EGS4 data [9]. Regarding to the acquired dose
results, the mean averaged error, reported by MCNP5 was
less than 0.7%. The percent error between the previous calcu-
lated TG43 and EGS4 (Monte Carlo) data and MCNP5 (pres-
ent work) are also shown in Table 3.
According to American Association of Physicists in Medi-
cine (AAPM) Task Group No.60 recommendation, the an-
isotropy function (F(r, h)), the radial dose function, gL(r),
were calculated in water for gamma photons [7]. The detec-
tors were simulated at polar angles of 0–908 in 108 increase
and at radial distances of r = 0.18 to 0.9 cm relative to the
stent center (Fig. 1).
The 2-D anisotropy function describes the variation of
dose in the longitudinal plane of a brachytherapy source. For
calculation of the anisotropy function, the *F8 tally was used
to obtain dose per photon in contiguous annular disk shells
detectors by using gamma emitters formula (Eq. (1)) and the
KT_kt-110222 – 17.9.12/stm media köthen
M. Sadeghi and O. Kiavar: Dosimetric aspects of 103
Pd radioactive stent source
77 (2012) 5 3
Table 3. MCNP5 calculated relative dose versus TG-43 and EGS4 (Monte Carlo) along the transverse axis of a 103
Pd stent
Distance from surface
(cm)
TG-43
Relative dose [16]
Monte Carlo
Relative dose [9]
MCNP5
Relative dose
(present work)
MCNP5
error by TG-43
(%) [9]
MCNP5
error by MCNP5
(%) (present work)
0.50 4.97 4.90 4.821 2.9 –1.6
1.00 1.00 1.00 1.00 – –
1.50 0.343 0.333 0.351 2.3 5
2.00 0.145 0.146 0.149 2.7 2
2.50 0.069 0.071 0.066 –4.3 –7.02
3.00 0.035 0.036 0.034 –2.85 –5.5
3.50 0.019 0.0193 0.0198 4 2.5
4.00 0.010 0.0107 0.0106 5 –0.9
Table 4. Anisotropy function, F(r, h), for 103
Pd stent, used at coronary arteries
r (cm) 108 208 308 408 508 608 708 808 908
0.18 – – – – – 2.854 1.940 1.979 1
0.20 – – – – 2.815 2.909 1.965 1.988 1
0.22 – – – – 1.866 1.956 1.996 1.006 1
0.24 – – – 1.796 1.939 1.998 1.016 1.002 1
0.26 – – – 1.912 1.985 1.992 1.881 1.024 1
0.28 – – – 1.078 1.180 1.169 1.111 1.028 1
0.30 – – – 1.344 1.408 1.326 1.182 1.043 1
0.32 – – 1.491 1.856 1.862 1.618 1.311 1.081 1
0.34 – – 1.351 1.774 1.891 1.958 1.087 1.007 1
0.36 – – 1.345 1.829 1.926 1.896 1.796 1.167 1
0.38 – – 0.937 0.947 0.983 0.998 1.184 1.113 1
0.40 – – 0.600 0.788 0.852 0.892 0.931 1.168 1
0.45 – 0.825 0.98 0.991 1.002 1.038 1.231 1.033 1
0.50 – 0.652 0.823 0.906 0.941 0.964 0.994 1.012 1
0.60 – 0.515 0.728 0.865 0.916 0.964 0.982 1.052 1
0.70 – 0.504 0.721 0.854 0.930 0.960 0.955 0.987 1
0.80 – 0.505 0.722 0.854 0.91 0.964 0.945 0.985 1
0.90 0.418 0.612 0.754 0.857 0.921 0.954 0.978 1.012 1
4. KT_kt-110222 – 17.9.12/stm media köthen
results were presented in Table 4 [8, 13]. The anisotropy func-
tion, F(r, h), table, showed homogeneous doses scores near
the surface of stent. Notwithstanding, it is considerable that,
at some deep angles and near distances from surface of stent,
the F(r, h) values show variants values near 2.
The radial dose function, gL(r), was determined in order to
characterize the effects of absorption and scatter in the med-
ium along the reference radial (h0 = 908) axis of the source
(Eq. 2) [8]. Fig. 3 shows the radial dose function curve with
respect to the distance from surface of stent. It is clear from
the Fig. 3 that by increasing the distance from surface, the
gL(r) increases sharply and reaches the peak at 0.5 cm point.
This event can be because of the huge amount of energy
which the gamma photons deposit at nearby the source. At
the second step the gL(r) decreases steeply for the points be-
tween 0.5 and 1.5 and keeps its exponential fall-off after
1.5 cm. Regarding Fig. 3 it is obvious that g(r) = 1 where
r = 1 (reference point for gamma emitters). It can be justified
by considering the equivalence of the numerator and denomi-
nator of the mentioned fraction (Eq. (2)).
Finally the isodose curves plotted on transverse cross sec-
tion and the values of them demonstrated in percent scale
(Fig. 4). The isodose curves showed the detailed dose distribu-
tion in the arterial wall surrounding the stent. These curves
revealed the homogeneous treatment planning curves. The er-
rors of these points located at transverse cross section were
also reported (Fig. 5). It also should be added that all statisti-
cal uncertainness was less than 0.7% for this unique gamma
emitting source.
The American Association of Physicists in Medicine Task
Group No. 60 [7] has recommended specific radioactive-stent
dose prescriptions so that various studies can be compared.
Their recommendations, based on past preclinical studies
and the intimal proliferation mechanism of restenosis, specify
the dose delivered over 28 days at a depth of 0.5 mm along
the perpendicular bisector to the long axis of the stent from
its outer surface [7].
Our study showed well results in dose and comparative
dose rate computation by following the mentioned protocol
and these data were compared with both previous TG-43
and EGS4. From Table 3 it is conspicuous that the mean per-
cent error between the calculated relative doses by MCNP5
and TG43 values is almost 3.4% and for MCNP5 and EGS4
is about 3.5%. By considering Fig. 2, the curve decreases ex-
ponentially from surface slightly and ultimately acquires the
least value and this event is quite relevant by gamma behavior
through the tissue [4]. The anisotropy function according to
the TG-43 was calculated and listed in the Table 4. The men-
tioned occurrence of high values at some detectors must be
due to the natural behavior of photons which in these points
near to the stent deposit much more energy. This high dose
value (at numerator) compare with the dose at reference
angle (at denominator) can affect on the fraction of Eq. (1)
and increase it.
Owing to the complex geometry of stents, the ability to
model it in dose distributions using Monte Carlo calculations
is limited. The calculation technique we used to model a stent
and calculate the 3-D dose distribution surrounding it may
not perfectly match that of a commercial stent. Nevertheless,
at distances at least 0.5 mm from the surface of the stent, the
differences in calculation should be small and were showed.
4 Conclusions
Our technique provides a reasonable method for acquiring
the 3-D dose distribution around a stent and visualizing the
effects that the discrete stent structure has on the dose distri-
bution. Dosimetric parameters, including dose per photon,
relative dose, radial dose function, gL(r), and anisotropy func-
tion, F(r, h) of the 103
Pd stent have been calculated by using
M. Sadeghi and O. Kiavar: Dosimetric aspects of 103
Pd radioactive stent source
4 77 (2012) 5
Fig. 3. The radial dose function, gL(r), of a 103
Pd active stent from the
surface of stent
Fig. 4. The isodose curves (Percent scale) of a 103
Pd stent (X-Y cross sec-
tion)
Fig. 5. The standard errors calculated by MCNP5 at located detectors
(radial distances) (h0 = 90)
5. the MCNP5 Monte Carlo code [18, 19]. These calculations
were performed following the AAPM TG-60 task group re-
commendations. These values need to be determined inde-
pendently by several investigators to routinely calculate dose
in an artery in the clinical setting. More experimental dosime-
try is also essential to support these results. Future work, in-
cluding measuring dosimetry on a 103
Pd implanted stent, de-
termining the self-absorption of a 103
Pd implanted stent and
expanding the calculation to include plaque buildup in the ar-
tery wall, needs to be performed to fully assess the applicabil-
ity of a 103
Pd-implanted stent in intravascular brachytherapy.
These data by future experimental works lead us to have
promising results and plan more confident treatment [20, 21].
However, the use of this stent is still pending upon more bio-
logical scrutinizes.
Acknowledgement
The authors are thankful for all supports of Prof. Dr. Ali
S. Meigooni (Comprehensive Cancer Center of Nevada, Las
Vegas, Nevada, USA), and Prof. Dr. Claudio Tenreiro (De-
partment of Energy Science, SungKyunKwan University, Su-
won, Republic of Korea), and Milad Enferadi.
(Received on 28 December 2011)
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The authors of this contribution
Mahdi Sadeghi
Agricultural, Medical and Industrial Research School
Nuclear Science and Technology Research Institute
P.O. Box: 31485/498
Karaj, Iran
* Corresponding author. E-mail: msadeghi@nrcam.org
Omid Kiavar
Department of Biomedical Radiation Engineering
Science and Research Branch, Islamic Azad University
Tehran, Iran
You will find the article and additional material by entering
the document number KT110222 on our website at
www.nuclear-engineering-journal.com
KT_kt-110222 – 17.9.12/stm media köthen
M. Sadeghi and O. Kiavar: Dosimetric aspects of 103
Pd radioactive stent source
77 (2012) 5 5