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Surface brachytherapy is an effective method in the treatment of skin cancer. Current skin brachytherapy techniques are based on the placement of a source of gamma or X-ray photons in a close distance from the skin to irradiate the lesion. Due to the nature of photons, radiation dose in these methods may affect healthy tissue as well as sensitive structures around the target. In order to minimize unwarranted and incidental exposure, we propose a new skin brachytherapy applicator based upon beta particles which have penetration ranges of a few millimeters in tissue. The proposed concept is radioactive gel housed within a pre-designed tumor-specific applicator matching the topology of the skin lesion. The particles mixed with the gel showed a uniform distribution pattern, which is an essential prerequisite in having a uniform dose profile on the skin surface. Based on the dose calculation data from the proposed concept, the dose delivered to the depth of 4500 μm in skin tissue is 10% of the dose delivered to the surface of the tumor, making it suitable is treating thin skin tumors especially when located on top of the bone. Through the innovative combination of radioactive gel and tumor-specific applicator, the radiation entering the skin surface can be personalized while minimizing the adverse effects of undesired exposure to the surrounding healthy tissue.
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A new 3D printed applicator with radioactive gel for conformal
brachytherapy of superficial skin tumors
Ali Pashazadeh1, Axel Boese1, Nathan J. Castro2, Dietmar W. Hutmacher3, Michael Friebe1
Abstract Surface brachytherapy is an effective method in
the treatment of skin cancer. Current skin brachytherapy
techniques are based on the placement of a source of gamma
or X-ray photons in a close distance from the skin to irradiate
the lesion. Due to the nature of photons, radiation dose in
these methods may affect healthy tissue as well as sensitive
structures around the target. In order to minimize unwarranted
and incidental exposure, we propose a new skin brachytherapy
applicator based upon beta particles which have penetration
ranges of a few millimeters in tissue. The proposed concept
is radioactive gel housed within a pre-designed tumor-specific
applicator matching the topology of the skin lesion. The
particles mixed with the gel showed a uniform distribution
pattern, which is an essential prerequisite in having a uniform
dose profile on the skin surface. Based on the dose calculation
data from the proposed concept, the dose delivered to the
depth of 4500 µm in skin tissue is 10% of the dose delivered
to the surface of the tumor, making it suitable is treating
thin skin tumors especially when located on top of the bone.
Through the innovative combination of radioactive gel and
tumor-specific applicator, the radiation entering the skin surface
can be personalized while minimizing the adverse effects of
undesired exposure to the surrounding healthy tissue.
Basal cell carcinomas and squamous cell carcinomas are
by far the most widespread cancers in the world. According
to the American cancer society, the occurrence rate of skin
cancer is estimated to be 5.4 million per year [1]. The current
gold standard treatment for skin cancer patients is physical
removal of the lesion through the use of a surgical technique
called Mohs micrographic surgery [2]. In this technique,
the suspected site of skin tissue is excised in a layer-by-
layer fashion until the tumor is removed. Even though this
procedure yields excellent control rates, it is not applicable to
all skin cancer patients. Cosmetic issues and other potential
complications at the site of tumor excision as well as age
and health status of the patient are constraints to broaden-
ing the application of the surgical procedures. Therapeutic
methods based on ionizing radiation are efficient alternatives
to surgery which can be effective in the remediation of
superficial and deep cancerous cells. It has been shown that
*This work was partly funded by the German BMBF (grant
1Ali Pashazadeh, Axel Boese and Michael Friebe are with the chair
of Intelligent Catheter and Image Guided Procedures, Otto von Guericke
University Magdeburg, Germany
2Nathan J. Castro is with the Joint Quantum Institute and Physical
Measurements Laboratory, National Institute of Standards and Technology,
University of Maryland, College Park, Maryland 20742, USA
3Dietmar W. Hutmacher is with the Centre in Regenerative Medicine,
Institute of Health and Biomedical Innovation, Queensland University of
Technology, Kelvin Grove, Brisbane, QLD 4059, Australia
radiation has been associated with a favorable control rate
of malignancy [3], [4].
Currently, radiation therapy of skin cancer is performed using
established methods including orthovoltage therapy, electron
beam radiation therapy, high-dose-rate (HDR) brachytherapy
and electronic brachytherapy [5].
Orthovoltage therapy is a long-standing treatment which typ-
ically uses X-ray photon produced by electrons with kinetic
energies of 100-500 keV to deliver the radiation dose from
about 50 cm distance to tumors located up to 10 mm deep
[6], [7], [8]. In electron beam radiation therapy, normally the
tumor is irradiated using 4-25 MeV electrons produced by a
linear accelerator [8], [9]. Treatment based on electron beam
is usually prescribed when the skin tumor is large and located
in a flat area, but in small and irregular regions application
of this method is challenging.
HDR brachytherapy of skin tumor is based upon the use
of Iridium-192 (Ir-192) with an after-loader mechanism
contained within an applicator [10]. Ir-192 has a half-life of
73.8 days and effective photon energy of 380 keV delivering
a radiation dose at a rate of >12 Gy/h to the skin lesion.
Electronic brachytherapy systems are portable devices based
on a small X-ray source working at an energy of 50 or
69.5 kV[11]. Low energy radiation and the simple application
of these systems are the most significant advantages of these
In radiation therapy, the primary goal is to treat the tumor
while preventing undesired exposure to healthy tissue nearby
where incidental exposure may lead to complications such
as necrosis, fibrosis, and secondary skin cancer. In the case
of a skin tumor close to critical organs such as the eye or
ear, incidental irradiation may also cause ocular damage or
hearing loss. Therefore, protecting the normal and sensitive
structures around the tumor in a radiation therapy procedure
is highly important.
In the current study, we are introducing a new brachytherapy
device which utilizes beta particles instead of gamma or X-
ray photons to treat superficial skin tumors. The sharp dose
fall-off of beta particles in tissue may lead to minimal expo-
sure to the surrounding tissue and deep sensitive structures.
The two main components of the device are a three-
dimensional (3D) printed applicator, which can be person-
alized to the patient, and a radioactive gel (a mixture of
a gel and a beta-emitting isotope). While any clinically
approved beta-emitting isotope can theoretically be used,
in this applicator we selected Yttrium-90 (Y-90) due to its
interesting physical properties. Y-90 is generated through the
beta decay of Strontium-90 (Sr-90) and subsequently decays
to the stable isotope Zirconium-90 (Zr-90). It has a half-
life of 64 hours and emits beta particles with a maximum
energy of 2.27 MeV [12]. The emitted particles can penetrate
up to 11 mm in tissue, making this radioisotope suitable for
radiation therapy of small surface lesion of a few millimeters
in thickness.
Ongoing and successful clinical applications of Y-90 include
peptide receptor radionuclide therapy of neuroendocrine
tumors, radioimmunotherapy of non-Hodgkin’s lymphoma
and trans-arterial radioembolization therapy of hepatocellular
carcinoma have further encouraged us to consider this high-
energy beta-emitter in our proposed applicator [12].
In addition to developing a tangible prototype, the dose
distribution of the applicator with Y-90 radioisotope in skin
tissue was also calculated by using the VARSKIN electron
dosimetry code.
The applicator fabricated in the current study was designed
for a skin tumor of an arbitrary shape of about 20 mm in
diameter. For smaller or larger tumors, its design can be
scaled accordingly to better fit the dimension and shape of
a particular lesion.
A. Applicator fabrication
The device prototype can be fabricated individually based
on the morphology of the target skin tumor. After the tumor
is outlined on the skin surface, the resultant boundary is used
as the basis to design the shape and size of the digital model
of the cavity of the applicator. This cavity is then filled with
radioactive gel to have the source for the applicator. The
depth of the cavity used in the current design was 3 mm. The
thickness of the applicator was considered 10 mm to ensure
suitable shielding for the beta radiation of Y-90 in unwanted
directions. We used SolidWorks to design the applicator then
the computer-aided design (CAD) model was imported into
Slic3r to prepare for 3D printing. A 3D printer (Formlabs,
United States) was used to fabricate the physical model of
the applicator with methacrylate photopolymers.
B. Gel preparation
To prepare the source of beta radiation for this applicator,
we needed to mix the radioactive source with a gel. However,
as this was a proof-of-concept study to illustrate our pro-
posed applicator, the experiment was initially done using the
microspheres that were no longer radioactive. This allowed
us to work in a standard laboratory without the need to go
to a hot lab. Therefore, as a surrogate to the radioactive Y-
90, we utilized cooled microspheres of Y-90 (Sirtex Medical
Limited, Australia). The micrometer size of these particles
made it possible to visually verify the distribution of Y-90
particles in the gel using an optical microscope.
In order to prepare the gel for the applicator, gelatin powder
was mixed with water at a 1:10 ratio. 0.8 ml of water
was added to 0.2 ml of microspheres then the mixture was
added to the 5 ml of liquid gel. After the microspheres were
injected into the liquid gel, the mixture was triturated 3
times to ensure homogeneous distribution. Next, part of the
mixture was injected into the cavity of the applicator as a
representative of the radioactive gel with 1 mm in thickness.
Finally, the applicator was kept at a temperature of 14
celsius for 30 minutes allowing for the gel to solidify.
C. Verification of Y-90 distribution
Y-90 microspheres distribution was visually evaluated
using an optical microscope (SZ61, Olympus, Germany) to
assess their homogenous distribution in the gel. To this end,
the rest of the liquid gel was transferred into a 150 mm petri
dish to cover its surface. Then 16 microscopic photographs
were taken in randomly selected areas of the petri dish to
count the number of microspheres in each area.
To analyze the photographs and count the microspheres,
ImageJ was used. Each original microscopic image was im-
ported and processed to be prepared for automatic counting
by the software.
D. Dose calculation
Dose distribution from this applicator with the beta-
emitting radioactive gel was calculated using VARSKIN 6.2
code. VARSKIN is a computer code to calculate skin dose
caused during handling of, or contamination by, radioactive
sources [13]. The software allows to select one of 5 prede-
fined source geometries of point, disk, cylinder, sphere or
slab. For dose estimation, we approximated the shape of the
cavity to be a cylinder of 20 mm diameter. Then, the pattern
of dose distribution was calculated along the central axis
of the cavity and within the first 5000 µm of skin tissue at
500 µm steps. As the reference dose, dose rate at the shallow
depth of 70 µm was also calculated.
The applicator used in our study with its holding frame
is shown in Fig. 1. The cavity inside the applicator can
be designed for a patient-specific tumor further extending
its application. The two tongues seen in both sides of the
applicator are used to place it in the grooves of the holder,
which keeps the applicator in the tumor site.
Homogenous distribution of the radioactivity in the gel is
crucial to ensure uniform radiation from the applicator. As
Fig. 1. Custom-built applicator for beta radiation therapy of superficial
skin tumor
Image Number Counted Microspheres
1 1000
2 1117
3 994
4 1129
5 1098
6 1161
7 1085
8 1121
9 1076
10 1169
11 1116
12 1044
13 1115
14 1019
15 1049
16 981
we used nonradioactive Y-90, therefore distribution of micro-
spheres was assessed as an indicator of uniform distribution
of the activity. Number of microspheres counted by using an
optical microscope, in different areas of the gel is given in
Table I. The average of microspheres counted was 1080 with
standard deviation of 57. This observation indicated that the
microspheres inside the gel had a uniform 2D distribution.
The pattern of dose distribution from this applicator in
the skin tissue was calculated and is given in Fig. 2. As it is
seen in the figure, the dose rate at the shallow depth of 70 µm
drops by a factor of 10 at the depth of 4500 µm. The rapid
dose fall-off which is characteristic of beta radiation makes
the significant portion of the dose to be delivered within the
very first millimeters from the surface of the skin tissue.
In Fig. 3, a possible treatment workflow based on our
proposed applicator for a skin tumor is presented. Applica-
tion of a surface brachytherapy applicator is also shown for
comparison purpose.
Fig. 2. Calculated beta dose distribution in the skin tissue depth, from the
proposed applicator using VARSKIN code
Fig. 3. The workflow of the implementation of the treatment using the
proposed surface brachytherapy applicator. Top left: skin tumor delineation
including the safety margin, Top right: fixing the applicator holder in the site
of the tumor, Bottom left: placement of the surface applicator for treatment
delivery, Bottom right: Brachytherapy of a skin tumor using a conventional
surface applicator (for comparison)
Application of beta-emitting isotopes for possible radiation
therapy of very thin skin tumors has been assessed in
some studies, due to their capacity in protecting underlying
sensitive structures [14], [15], [16], [17], [18], [19]. In the
current study, a new skin brachytherapy device based on
beta radiation was designed and introduced which beside the
underlying sensitive structures can also protect the healthy
tissue around the tumor surface during the treatment proce-
The interesting feature of the applicator is that it is person-
alized. This means that the size of the applicator as well as
the shape of its cavity (containment of radioactive source)
are customizable to fit each specific tumor. Image of tumor,
which is obtained by using imaging modalities, can be used
to provide the basis for generating the digital model for the
3D printer. Manufacturing using a 3D printer provides an
opportunity for ease and quick preparation of this patient-
specific surface applicator. Therefore, using this individually-
fabricated applicator, radiation is shaped before entry the
skin, sparing healthy tissue around the tumor surface.
Microspheres showed a uniform 2D distribution pattern
inside the gel. This is an essential prerequisite in reliable
application of this applicator as a brachytherapy device.
When designing this applicator based on tumor shape and
size, safety margins around the tumor is also considered to
ensure that periphery of the tumor receives enough radiation
dose when treating with this applicator. The calculated dose
pattern of beta radiation emitted from our applicator showed
that the radiation dose beyond 3000-4000 µm from the skin
tissue drops to an insignificant level, making it a suitable
treatment for superficial skin tumors located right on top of
bone or other sensitive structures.
The amount of radioactivity, treatment time as well as the
dose needed to reach a desired therapeutic outcome depend
on the size and extension of the tumor. For a typical scenario
of a small nonmelanoma cancer with a diameter of 10 mm
located on a flat area, the prescribed dose of 20 Gy can treat
the tumor in one fraction [20]. There will be an additional
safety margin of 5 mm around the tumor to include micro-
scopic extension of the lesion. Therefore, with the proposed
applicator a cavity with a 20 mm diameter can be an option
for treating such a tumor. Considering the radioactive gel
containing 250 MBq Y-90 with 1 mm thickness, the treatment
time for a prescription depth of 2 mm will be about 70
minutes in a single fraction.
The concept of radioactive gel used in this study allows for
a high-energy beta-emitting isotopes of any half-life to be
a potential source of radiation for this applicator. Because
of the fast preparation of the radioactive gel, short half-life
beta emitters, besides the long half-life isotopes, can also be
utilized in this applicator.
Our proposed brachytherapy applicator fabricated with 3D
printing technology has also an advantage in terms of radi-
ation protection considerations. Due to the physics of inter-
action of the beta radiation with matter and its attenuation
in low atomic number materials, the material used for 3D
printing of the applicator can serve as shielding. Therefore,
during the treatment course with this brachytherapy appli-
cator, the staff is not needed to leave the treating room.
Additionally, low weight of the applicator allows to fix it
directly on the site of the skin tumor without the necessity
to use a supporting arm to hold the applicator which is the
case in some of the current skin brachytherapy methods.
It should be noted that the short range of beta particles
dictates to use a very thin layer of the radioactive hydrogel.
Our dose calculation was performed with radioactive gel of
1 mm thickness. Increasing the thickness of the radioactive
gel significantly increase the self-absorption of the radiation
inside the gel. As a result, a higher amount of radioactivity
will be needed to deliver the lethal dose to the lesion in a
time that is therapeutically reasonable.
The source of the radiation for the introduced applicator is
radioactive gel. However, as an alternative to the radioactive,
the cavity of the applicator can be filled with a radioactive
cream or synthetic resin, which has been recently used as a
treatment for skin cancer [21].
We illustrated a new surface brachytherapy applicator
for treating superficial skin tumors using a beta-emitting
radioisotope. Combination of beta radiation therapy and 3D
printing technology appears to well confine the radiation dose
to the thin skin tumor while protecting the surrounding sen-
sitive tissue. Next development will be adding the possibility
to the current concept to modulate the intensity of radiation
to further personalize the treatment for skin cancer patients.
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... A detailed description of the radioactive gel can be found in our previous work. 7 In the end, the applicator is placed into the template, which was previously fixed on the site of the grid. ...
... [18][19][20][21][22][23] They are mainly focused on creating planar sources of beta radiation applicable to skin tumors, with very few studies focusing on conforming the dose to the skin tumor shape. 7,24 The current multiwell brachytherapy applicator presents a simple method to conform the dose of beta radiation to the superficial skin tumors. As the applicator is fabricated using 3D printing technology and with plastic materials, the manufacturing process of the applicator body is quick and inexpensive. ...
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Background: Brachytherapy of thin skin tumors using beta particles can protect underlying sensitive structures such as the bone because of the rapid dose falloff of this type of radiation in tissue. The current work describes a skin brachytherapy applicator, based on beta radiation, that can provide the needed cell-killing radiation dose matched to the shape of individual skin tumors. Materials and methods: The applicator and its template were fabricated using 3D printing technology. Any clinically approved beta-emitting isotope in the form of a radioactive gel could theoretically be used in this applicator. Monte Carlo simulations were employed to study the capability of the applicator in conforming dose distribution based on the shape of the tumor. Dose profile in the shallow depth, transverse dose profiles at different depths, and the percent depth dose from this applicator were calculated. The radioisotope of choice for our calculations was Yttrium-90 (Y-90). Results: Using the proposed applicator, it is possible to create a desired dose profile matching the tumor surface shape. Conclusion: The short-range of the beta radiation, together with the dose conforming capability of the applicator, may lead to minimal interactions with the healthy tissue around the skin lesion.
... 3D-printed human skin can be a perfect option for researching chemicals and for creating new medical treatments. Through making a 3D skin with the patientÕs cells, a personalized treatment could also be developed and tested beforehand (Ref [102][103][104][105]. For the production of usable skin tissue and living cells behaving much like natural ones, 3D printing techniques will help to address some of these ethical problems. ...
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3D printing or additive manufacturing is an emerging technique for the fabrications of biomedical components. Several researchers are working on fabrications of the biomedical components, future prospective of implantation, and transplantation aspects. The current review presents a meticulous summary of research work done so far by the researchers in the view of design and fabrications about biomedical components by using 3D printing technology such as fused deposition modeling (FDM), inkjet printing, stereolithography, and selective laser sintering (SLS). The design and fabrications of biomedical components include 3D printing of bone, low-cost high-quality prosthetics, intervertebral disks, medical equipment, heart valve, building tissues using blood vessels and drugs. The objective of this review article is to explore different additive manufacturing processes, challenges, and future developments for 3D printing for biomedical components.
... Recently, there has been an interest in the use of betaemitting isotopes in treating superficial skin tumors, whose cell killing radiation does not extend very deep in tissue [2][3][4][5][6][7][8]. Beta particles emitted from these isotopes, in contrast to x-ray and gamma photons, penetrate the tissue usually only up to a maximum of around 10 mm depth and deposit their dose very locally. ...
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The short-range and sharp dose fall-off of beta particles in tissue make them an interesting option for use in the radiation therapy of superficial skin tumors. This can be used to protect bony or other sensitive structures located right beneath the tumor. In a previous study, we studied the feasibility of using 3D printing technology to create 2D radioactive models for the treatment of skin tumors. In the current study, the Monte Carlo method was used to simulate the transverse dose profile form 3D printed extruded line containing yttrium-90 (Y-90) particles. The time and activity required for treating a superficial skin tumor using these extruded lines were also calculated.
Brachytherapy is a mature treatment modality. The literature is abundant in terms of review articles and comprehensive books on the latest established as well as evolving clinical practices. The intent of this article is to part ways and look beyond the current state-of-the-art and review emerging technologies that are noteworthy and perhaps may drive the future innovations in the field. There are plenty of candidate topics that deserve a deeper look, of course, but with practical limits in this communicative platform, we explore four topics that perhaps is worthwhile to review in detail at this time. First, intensity modulated brachytherapy (IMBT) is reviewed. The IMBT takes advantage of anisotropic radiation profile generated through intelligent high-density shielding designs incorporated onto sources and applicators such to achieve high quality plans. Second, emerging applications of 3D printing (i.e., additive manufacturing) in brachytherapy are reviewed. With the advent of 3D printing, interest in this technology in brachytherapy has been immense and translation swift due to their potential to tailor applicators and treatments customizable to each individual patient. This is followed by, in third, innovations in treatment planning concerning catheter placement and dwell times where new modelling approaches, solution algorithms, and technological advances are reviewed. And, fourth and lastly, applications of a new machine learning technique, called deep learning, which has the potential to improve and automate all aspects of brachytherapy workflow, are reviewed. We do not expect that all ideas and innovations reviewed in this article will ultimately reach clinic but, nonetheless, this review provides a decent glimpse of what is to come. It would be exciting to monitor as IMBT, 3D printing, novel optimization algorithms, and deep learning technologies evolve over time and translate into pilot testing and sensibly phased clinical trials, and ultimately make a difference for cancer patients. Today's fancy is tomorrow's reality. The future is bright for brachytherapy.
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The aim of this work is to provide an overview of the current state of additive manufacturing (AM), commonly known as 3D printing, within superficial brachytherapy (BT). Several comprehensive database searches were performed to find publications linked to AM in superficial BT. Twenty-eight core publications were found, which can be grouped under general categories of clinical cases, physical and dosimetric evaluations, proof-of-concept cases, design process assessments, and economic feasibility studies. Each study demonstrated a success regarding AM implementation and collectively, they provided benefits over traditional applicator fabrication techniques. Publications of AM in superficial BT have increased significantly in the last 5 years. This is likely due to associated efficiency and consistency benefits; though, more evidences are needed to determine the true extent of these benefits.
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Radiation therapy is a valuable option for treatment of skin cancer. In order to deliver the radiation dose to the superficial skin tumor, an X-ray source, electron beam radiation therapy or a radioisotope is applied. The effectiveness of these procedures is well established in the literature. Findings of some recent studies have indicated that beta particles can be of particular interest in suppressing skin tumor growth. Betaemitting radioisotopes are favorable because of the short penetration depth of their emitted particles. Beta radiation can induce significant damage in superficial skin tumor, and at the same time, result in enhanced protection of the underlying healthy tissues. In this study, we propose the design of a patch that can be used in beta radiation therapy of skin cancer patients. For that, we describe the components of this radioactive patch, as well as a proposal for the subsequent clinical application procedure. A scaffold was used as a substrate for embedding the desired beta-emitting radioisotope, and two layers of hydrogel to provide protection and shielding for the radioactively labelled scaffold. The proposed design could provide a universal platform for all beta-emitting radioisotopes. Depending on the depth of the tumor spread, a suitable beta emitter for that specific tumor can be selected and used. This is of particular and critical importance in cases where the tumor is located directly on top of the bone and for which the depth of penetration of radiation should be limited to only the tumor volume. The proposed design has the mechanical flexibility to adapt to curved body regions so as to allow the use in anatomically challenging areas of the body.
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Purpose: To evaluate the possibility of utilizing the high-dose rate (HDR) (169) Yb and (60) Co sources, in addition to (192) Ir, for the treatment of skin malignancies with conical applicators. Methods: Monte Carlo (MC) simulations were used to benchmark the dosimetric parameters of single (169) Yb (4140), (60) Co (Co0.A86), and (192) Ir (mHDR-V2) brachytherapy sources in a water phantom and compared their results against published data. A standard conical tungsten alloy Leipzig-style applicator (Stand.Appl) was used for determination of the dose distributions at various depths with a single dwell position of the HDR sources. The HDR sources were modeled with its long axis parallel to the treatment plane within the opening section of the applicator. The source-to-surface distance (SSD) was 1.6 cm, which included a 0.1 cm thick removable plastic end-cap used for clinical applications. The prescription depth was considered to be 0.3 cm in a water phantom following the definitions in the literature for this treatment technique. Dose distributions generated with the Stand.Appl and the (169) Yb and (60) Co sources have been compared with those of the (192) Ir source, for the same geometry. Then, applicator wall thickness for the (60) Co source was increased (doubled) in MC simulations in order to minimize the leakage dose and penumbra to levels that were comparable to that from the (192) Ir source. For each source-applicator combination, the optimized plastic end-cap dimensions were determined in order to avoid over-dosage to the skin surface. Results: The normalized dose profiles at the prescription depth for the (169) Yb-Stand.Appl and the (60) Co-double-wall applicator were found to be similar to that of the (192) Ir-Stand.Appl, with differences <2.5%. The percentage depth doses (PDD) for the (192) Ir-, (169) Yb- and (60) Co-Stand.Appl were found to be comparable to the values with the (60) Co-double-walled applicator, with differences <1.7%. The applicator output-factors at the prescription depth were also comparable at 0.309, 0.316, and 0.298 (cGy/hU) for the (192) Ir-, (169) Yb-Stand.Appl, and (60) Co-double-wall applicators, respectively. The leakage dose around the Stand.Appl for distance >2 cm from the applicator surface was <5% for (192) Ir, <1% for (169) Yb, and <18% for (60) Co relative to the prescription dose. However, using the double-walled applicator for the (60) Co source reduced the leakage dose to around 5% of the prescription dose, which is comparable with that of the (192) Ir source. The optimized end-cap thicknesses for the (192) Ir-, (169) Yb-Stand.Appl and the (60) Co-double-wall applicator were found to be 1.1, 0.6, and 3.7 mm, respectively. Conclusions: Application of the (169) Yb (with Stand.Appl) or the (60) Co source (with double-wall applicator) has been evaluated as alternatives to the existing (192) Ir source (with Stand.Appl) for the HDR brachytherapy of skin cancer patients. These alternatives enable the clinics that may have (169) Yb or (60) Co sources instead of the (192) Ir source to perform the skin brachytherapy and achieve comparable results. The conical surface applicators must be used with a protective plastic end-cap to eliminate the excess electrons that are created in the source and applicator, in order to avoid skin surface over-dosage. The treatment times for the (60) Co source remain to be determined. Additionally, for (169) Yb, the source needs to be changed on monthly basis due to its limited half-life. This article is protected by copyright. All rights reserved.
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Introduction: Squamous cell carcinoma (SCC) is the second most common form of skin cancer in the United States. The efficacy of a pharmaceutically elegant radiotherapeutic bandage, previously described by us for application against SCC of the skin, was tested for the first time in vivo using a subcutaneous SCC mouse model and a therapeutically relevant radiation dose. Methods: Female athymic nude mice were injected with human Colo-16 SCC cells subcutaneously and after eight days (average tumor volume: 35±8.6mm(3)) received no treatment, or were exposed to non-radioactive or radioactive (92.5±18.5MBq) bandages for approximately 1h (n=10 per group). After treatment, tumors were measured over fifteen days, tumor volume ratios (TVRs) compared and histopathology performed. Results: Fifteen days after treatment, the TVR of the radioactive bandage treatment group was 3.3±4.5, while TVRs of the non-radioactive bandage treatment and no treatment control groups were 33.2±14.7 and 26.9±12.6, respectively. At the time of necropsy, there was mild focal epidermal hyperplasia surrounding a small area of epidermal ulceration in the radioactive bandage group. No other examined tissue (i.e., muscle, liver, kidney, lung, spleen and heart) showed significant lesions. Conclusions: Our radiotherapeutic bandage exhibits promising efficacy against SCC of the skin in a mouse model. It can be individually tailored for easy application on tumor lesions of all shapes and sizes, and could complement or possibly replace surgery in the clinic.
Nonmelanoma skin cancer (NMSC) is a major health concern due to its high incidence rate, its negative impact on the quality of life of patients as well as the associated economic burden to the healthcare system. Surgery is currently the primary treatment offered for skin cancer patients but not applicable or available in all cases. Radiation therapy (RT), with its long successful history in the management of cancer, has shown to be an effective alternative or complementary method in cutaneous oncology. Specifically, for dermatology applications, RT is very often the preferred option due to its favorable cosmetic results, besides the excellent control rate of the tumor. During the last 120 years since the introduction of treatments based on ionizing radiation, several techniques in this area have been developed. Radionuclide brachytherapy, electronic brachytherapy, X-ray therapies with kilovolt (KV) to megavolt (MV) photons and electron beam therapy are the established methods that are currently used on skin cancer patients. The purpose of this paper is to overview these techniques and discuss the pros and cons of these methods in dermatology practices. Additionally, a new approach of beta radiation therapy of superficial skin tumors is discussed, which may offer exciting features in the management of NMSC.
A new electron skin dosimetry model was developed for the VARSKIN 5 tissue dosimetry code. This model employs energy deposition kernels that provides for improved accuracy of energy deposition at the end of electron tracks. The Monte Carlo code EGSnrc was utilized to develop these energy deposition kernels such that scaling of electron energy loss is dependent on effective atomic number and density of the source material, electron range and conservation of energy. This work contrasts VARSKIN's electron dosimetry model to several existing deterministic and Monte Carlo dosimetry tools to determine the efficacy of these improvements. Comparison results are given for a wide range of scenarios that extend beyond the typical use of VARSKIN, including mono-energetic electrons and a homogenous water medium. For planar and point sources in contact with the skin, VARSKIN produces results equated to other dosimetry methods within 10%. However, it appears that VARSKIN is unable to account accurately for electron energy loss with the introduction of a cover material or an air gap. The comparisons herein confirm that VARSKIN provides accurate electron dose calculations for skin-contamination scenarios.
A system for the electron and photon therapy has been designed and developed at SAMEER, IITB, Mumbai. All the components of the system such as the 270° beam bending electromagnet, trim coils, magnet chamber, electron scattering foil, slits, applicators, etc., were designed and fabricated indigenously. The electrons of 6, 8, 9, 12, 15 and 18 MeV energies were provided by a linear accelerator, indigenously designed and made at SAMEER, IITB campus, Mumbai. The electron beam from the LINAC enters the magnet chamber horizontally, and after deflection and focusing in the 270° bending magnet, comes out of the exit port, and travels a straight path vertically down. After passing through the beryllium and tantalum scattering foils, the electron beam gets scattered and turns into a solid cone shape such that the diameter increases with the travel distance. The simulation results indicate that at the exit port of the 270° beam bending magnet, the electron beam has a divergence angle of ≤ 3 mrad and diameter ∼2–3 mm, and remains constant over 6–18 MeV. Normally, 6–18 MeV electrons are used for the electron therapy of skin and malignant cancer near the skin surface. On a plane at a distance of 100 cm from the scattering foils, the size of the electron beam could be varied from 10 cm × 10 cm to 25 cm × 25 cm using suitable applicators and slits. Different types of applicators were therefore designed and fabricated to provide required beam profile and dose of electrons to a patient. The 6 MeV cyclic electron accelerator called Race-Track Microtron of S. P. Pune University, Pune, was extensively used for studying the performances of the scattering foils, electron beam uniformity and radiation dose measurement. Different types of thermoluminescent dosimetry dosimeters were developed to measure dose in the range of 1–10kGy.
Techniques for intraoperative radiation therapy (IORT), the applications of tumor bed radiation immediately after surgery or utilising intracavitary access, have evolved in recent years. They are designed to substitute or complement conventional external beam radiation therapy in selected patients. IORT has become an excellent treatment option because of good long-term therapy outcomes. The combination of IORT with external beam radiation therapy has the potential to improve local control. The purpose of this paper is to present IORT techniques using gamma and electronic sources, as well as more conventional nuclide-based approaches and to evaluate their effectiveness. Common techniques for radiation of tumor cavities are listed and compared. Radionuclide IORT methods are represented by balloon and hybrid multi-catheter devices in combination with appropriate afterloaders. Electron beam therapy dedicated for use as intraoperative radiation system is reviewed and miniature x-ray sources in electronic radiation therapy are presented. These systems could further simplify IORT, because they are easy to use and require no shielding due to their relatively low photon energies. In combination with additional imaging techniques (MRI, US, CT and NucMed) the application of these miniature x-ray sources or catheter-based nuclide therapies could be the future of IORT.
Y-90, a beta emitting radionuclide, was immobilized in a bandage patch for possible application for the therapy of superficial maladies such as tumours and skin cancers. The aim was to prepare a radiation source that could deliver uniform dose within a short duration and avoid the inconveniences faced with the gamma sources used in teletherapy and brachytherapy. Y-90-ferric hydroxide macroaggregates were prepared, filtered and immobilized between two layers of gauze. When placed in saline, no radioactivity leached for 3 days, proving its safety for external application, Fibrosarcoma was induced in mice for checking the efficacy of Y-90 patches. Y-90 patches of various activities were prepared and applied on the tumours. The effect of time gap between inception and treatment of tumour, dose delivered and multiple application in fractionated doses was studied. In all the cases, tumour growth in the treated animals was considerably reduced in comparison with controls. It was concluded from the experiments that treatment should be started at the earliest stage possible, i.e. when the tumour is palpable. Delivery of dose from radioactive patches of approximately 90-100 MBq each, thrice at weekly intervals proved to be more effective for regression of tumour growth. ((C) 2002 Lippincott Williams Wilkins).
Aims: To report the local control and complication rates of orthovoltage radiotherapy in the management of medial canthal basal cell carcinoma (BCC). Methods: The medical records of all patients treated with medial canthal BCC between 1998 and 2010, with orthovoltage radiotherapy as primary treatment, adjuvant treatment after incomplete surgical excision, or for tumour recurrence following surgical excision, were retrospectively studied. The actuarial rates of tumour control and complications were calculated using Kaplan-Meier estimates. Main outcome measures were rates of tumour control and radiation complications. Results: 90 patients were included with a median follow-up of 80 months. Tumour control rate at 10 years for the entire cohort was 94% (95% CI 84% to 98%). Tumour control rates showed no statistically significant differences among different treatment intents or treatment radiation energies. Radiation-related complication rates included loss of eyelashes in 59% (95% CI 48% to 66%), epiphora 51% (95% CI 39% to 62%), dry eye 14% (95% CI 3% to 35%) and conjunctival scarring 11% (95% CI 1% to 33%). No patient developed long-term corneal complications. Conclusions: Orthovoltage radiotherapy can be a reliable therapeutic alternative for selected medial canthal BCCs, which can be contained within the prescribed radiation field, with anticipated radiation-related toxicities.