Computational human phantom
Encyclopedia
Computational human phantoms
are models of the human body
used in computerized analysis
. Since the 1960s, the radiological science
community has developed and applied these models for ionizing radiation
dosimetry
studies. These models have become increasingly accurate with respect to the internal structure of the human body. As computing evolved, so did the phantoms. Graduating from phantoms based on simple quadratic equation
s to voxel
ized phantoms, which were based on actual medical images
of the human body, was a major step. The newest models are based on more advanced mathematics, such as Non-Uniform Rational B-Splines (NURBS) and polygon mesh
es, which allow for 4-D
phantoms where simulations can take place not only 3-dimensional space
but in time
as well. Phantoms have been developed for a wide variety of humans, from children to adolescents to adults, male and female, as well as pregnant women. With such a variety of phantoms, many kinds of simulations
can be run, from dose
received from medical imaging procedures to nuclear medicine
. Over the years, the results of these simulations have created an assortment of standards that have been adopted in the International Commission on Radiological Protection (ICRP)
recommendations.
doses
from internally deposited radioactive materials in workers and patients. Until the late 1950s, the ICRP
still used very simple models. In these calculations, each organ of the body was assumed to be represented as a sphere
with an “effective radius
.” The radionuclide
of interest was assumed to be located at the center of the sphere and the “effective absorbed energy
” was calculated for each organ. However, scientists attempted to model individual organs of the body and ultimately the entire human body in a realistic manner, the efforts of which led to stylized anthropomorphic phantoms—those resemble the human anatomy
.
In general, stylized computational phantom is a mathematical representation of the human body, when coupled with a Monte Carlo
radiation transport
computer code
, can be used to track the radiation interactions and energy deposition in the body. The feature of stylized computational phantom is finely tuned by adjusting individual parameters of the mathematical equations, which describes the volume
, position
, and shape
of individual organ
s. Stylized computational phantom has a long history of development through the 1960s to 1980s.
in 1960s with 22 internal organs and more than 100 sub-regions. It is the first anthropomorphic phantom representing a hermaphrodite
adult
for internal dosimetry
.
unknown by the mainstream radiation protection dosimetry community, etc.
, and medical imaging
, one cannot overcome its inborn limitation. The representation of internal organs in this mathematical phantom was crude, by capturing only the most general description of the position
and geometry
of each organ. With the powerful computer and tomographic
imaging technologies became available in the late 1980s, the history launched a new era of voxel
phantoms.
The stylized phantoms provided only basic information with a large degree of error. More accurate methods of simulating a human body were necessary to advance. To allow further research, the computer technology had to become more powerful and more readily available. This did not occur until the 1980s. The real breakthrough occurred when CT (Computed Tomography)
and MRI (Magnetic Resonance Imaging)
devices could generate highly accurate images of internal organs in three dimensions and in digital
format. Researchers discovered that they could take that diagnostic data and transform it into a voxel (volumetric pixel)
format, essentially re-creating the human body
in digital form in 3D. Today there are over 38 human phantoms in voxel format, for many different uses.
Two major issues with development of the reference phantoms are difficulty in obtaining useful images and handling the large amount of data
created from these images. CT scans give the human body a large dose
of ionizing radiation
– something the computational phantom was designed to circumvent in the first place. MRI images take a long time to process. Furthermore, most scans of a single subject cover only a small portion of the body, whereas a full scan series is needed for useful data. Handling this data is also difficult. While the newer computers had hard drives large enough to store the data, the memory
requirements for processing the images to the desired voxel size were often too steep.
While there have been many voxel phantoms developed, they have all followed a similar path to completion. First, they must obtain the raw data
, from CT scans, MRI imaging, or direct imaging through photography
. Second, the components of the body must be segmented, or identified and separated from the rest. Third, the density of each component must be identified, along with the composition of each. Lastly, the data must be unified into a single 3D structure so it may be used for analysis
.
The earliest work on voxelized phantoms occurred independently at about the same time by Dr. Gibbs, of Vanderbilt University
, and Dr. Zankl at the National Research Center for Environment and Health (GSF) in Germany. This occurred about 1982. Dr. Gibb’s work started with X-ray
images, not CT
or MRI
images, for the reconstruction of a human phantom which was used for medical dose
simulations
. M. Zankl and team did use CT imaging to create 12 phantoms, ranging from BABY to VISIBLE HUMAN.
Since voxel
phantoms have been superseded by mesh- and NURBS-based phantoms, there has been limited development in the past few years. Many of the advancements have come through manipulations of current phantoms to correct for height and weight variations of the population.
In 2009, the International Commission on Radiological Protection (ICRP) and the International Commission on Radiation Units and Measurements (ICRU) adopted voxel-based adult male and female reference computational phantoms for the computation of organ dose coefficients .
phantoms are computational human models that contain exterior and interior anatomical features
of a human body
using boundary representation
method. In the realm of health and medical physics
they are primarily used for ionizing radiation
dosimetry
.
In the development of computational human phantoms, of particular interest is the concept of a “deformable” phantom whose geometry
can be conveniently transformed to fit particular physical organ
shape
s, volume
s, or body postures. Design of this type of phantom is realized by Non-Uniform Rational B-Spline (NURBS) method or polygonal mesh method, which are usually collectively called BREP methods. Compared to the voxel phantoms, BREP phantoms are better suited for geometry deformation and adjustment, because a larger set of computerized operations are available, such as extrusion
, chamfering, blending, drafting
, shelling
and tweaking
. A major advantage of BREP phantoms is their ability to morph into an existing reference phantom or into the anatomy of a real worker or patient, which makes individual-specific dose calculation possible.
s which are formulated by a set of control points. The shape and volume of a NURBS surface vary with the coordinates of control points. This feature is useful in designing a time-dependent 4D
human body
modeling. An example is given by NCAT phantoms by Segars et al, which is used to simulate cardiac and respiratory motions with more realistic modeling of the cardiac system.
, edges
, and faces
that specify the shape of a polyhedral object
in 3D space
. The surfaces of the phantom are defined by a large amount of polygonal meshes, most commonly triangle
s. The polygonal mesh has three remarkable advantages in developing whole-body phantoms. Firstly, mesh surfaces depicting human anatomy can be conveniently obtained from real patient images or commercial human anatomy mesh models. Secondly, the polygonal mesh-based phantom has considerable flexibility in adjusting and fine-tuning its geometry, allowing the simulation of very complex anatomies. Thirdly, many commercial computer aided design (CAD)
software, such as Rhinoceros
, AutoCAD
, Visualization Toolkit (VTK)
, provide built-in functions able to rapidly convert polygonal mesh into NURBS.
described the method of developing a dynamic NURBS-based cardiac-torso (NCAT) phantom in detail. The phantom has a 4D beating heart
model which was derived from 4D tagged magnetic resonance image (MRI)
data. The remaining organs in the torso of the phantom were designed based on the Visible Human Project
CT data set and were composed of 3D NURBS surfaces. Respiratory motion was also incorporated into this phantom.
In 2005, Xu et al. at Rensselaer Polytechnic Institute (RPI)
used the 3D VIP-Man phantom to simulate respiratory motions by adopting the gated respiratory motion data of the NCAT phantom. The 4D VIP-Man Chest phantom was used to study external-beam treatment
planning for a lung cancer
patient. In 2007, Xu’s research group reported creation of a series of polygon
-based phantoms representing a pregnant woman and her fetus
at the end of 3, 6, and 9 month gestation
s (RPI Pregnant Females). The mesh data were initially obtained from separate anatomical information sources including a non-pregnant female, a 7-month pregnant woman CT data set, and a mesh model of the fetus. In 2008, two triangular mesh-based phantoms were created, named as RPI Deformable Adult Male and Female (RPI-AM, RPI-FM). The anatomic parameters of the phantoms were made consistent with two datasets: the mass
and density
of internal organs originated from ICRP-23 and ICRP-89, and the whole-body height and weight percentile data were obtained from the National Health and Nutrition Examination Survey (NHANES 1999-2002)
. Later on, to study the relationship between breast size and lung dosimetry
, a new group of phantoms were produced by altering the breast geometry
of RPI-AF.
From 2006 to 2009, Bolch et al. at University of Florida (UF)
designed a total of twelve “hybrid” male and female phantoms, representing newborn, 1, 5, 10, 15-year old and adult male/females. The phantoms are addressed as “hybrid” because most organs and tissues were modeled by NURBS surfaces whereas the skeleton, brain and extra-thoracic airways were modeled by polygonal surfaces. Anatomic parameters of the phantoms were adjusted to match 4 reference datasets, i.e., standard anthropometric
data
, reference organ masses from ICRP
Publication 89, reference elemental compositions provided in ICRP 89 as well as ICRU Report 46, and reference data on the alimentary tract organs given in ICRP Publications 89 and 100.
In 2008, Stabin et al. at Vanderbilt University
, in collaboration with Segars from Duke University
, developed a family of adult and pediatric phantoms by adapting the NURBS-based NCAT adult male and female phantoms. ICRP-89 reference body and organ values were used to adjust NURBS surfaces.
In 2009 Cassola et al at the Federal University of Pernambuco
, Brazil, developed a pair of polygonal mesh-based phantoms in standing posture, FASH (Female Adult meSH) and MASH (Male Adult meSH). The methodology is very similar but not entirely identical to the one implemented in the designing of RPI-AM and RPI-FM.
In 2010, based on existing RPI-AM, Xu et al. continued to create 5 more phantoms with different Body Mass Index (BMI)
ranging from 23 to 44 kg∙m-2. These phantoms are used to study the correlation between BMI and organ doses
resulting from CT and PET
examinations.
In 2011 Kim et al. at Hanyang University
, Korea, reported a polygon-surface reference Korean male phantom (PSRK-Man). This phantom was constructed by converting the Visible Korean Human-Man (VKH-man) into a polygonal mesh-based phantom. The height, weight, geometry of organs and tissues were adjusted to match the Reference Korean data. Without voxel
ization the PSRK-man could be directly implemented in Geant4
Monte Carlo
simulation
using a built-in function, but the computation
time was 70~150 times longer than that required by High Definition Reference Korean-Man (HDRK-Man), a voxelized phantom derived also from VKH-man.
Imaging phantom
Imaging phantoms, or simply "phantoms", are specially designed objects that are scanned or imaged in the field of medical imaging to evaluate, analyze, and tune the performance of various imaging devices. These objects are more readily available and provide more consistent results than the use of...
are models of the human body
Human body
The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs.By the time the human reaches adulthood, the body consists of close to 100 trillion cells, the basic unit of life...
used in computerized analysis
Computation
Computation is defined as any type of calculation. Also defined as use of computer technology in Information processing.Computation is a process following a well-defined model understood and expressed in an algorithm, protocol, network topology, etc...
. Since the 1960s, the radiological science
Radiology
Radiology is a medical specialty that employs the use of imaging to both diagnose and treat disease visualized within the human body. Radiologists use an array of imaging technologies to diagnose or treat diseases...
community has developed and applied these models for ionizing radiation
Ionizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...
dosimetry
Dosimetry
Radiation dosimetry is the measurement and calculation of the absorbed dose in matter and tissue resulting from the exposure to indirect and direct ionizing radiation...
studies. These models have become increasingly accurate with respect to the internal structure of the human body. As computing evolved, so did the phantoms. Graduating from phantoms based on simple quadratic equation
Quadratic equation
In mathematics, a quadratic equation is a univariate polynomial equation of the second degree. A general quadratic equation can be written in the formax^2+bx+c=0,\,...
s to voxel
Voxel
A voxel is a volume element, representing a value on a regular grid in three dimensional space. This is analogous to a pixel, which represents 2D image data in a bitmap...
ized phantoms, which were based on actual medical images
Medical imaging
Medical imaging is the technique and process used to create images of the human body for clinical purposes or medical science...
of the human body, was a major step. The newest models are based on more advanced mathematics, such as Non-Uniform Rational B-Splines (NURBS) and polygon mesh
Polygon mesh
A polygon mesh or unstructured grid is a collection of vertices, edges and faces that defines the shape of a polyhedral object in 3D computer graphics and solid modeling...
es, which allow for 4-D
Spacetime
In physics, spacetime is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space as being three-dimensional and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions...
phantoms where simulations can take place not only 3-dimensional space
Three-dimensional space
Three-dimensional space is a geometric 3-parameters model of the physical universe in which we live. These three dimensions are commonly called length, width, and depth , although any three directions can be chosen, provided that they do not lie in the same plane.In physics and mathematics, a...
but in time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....
as well. Phantoms have been developed for a wide variety of humans, from children to adolescents to adults, male and female, as well as pregnant women. With such a variety of phantoms, many kinds of simulations
Computer simulation
A computer simulation, a computer model, or a computational model is a computer program, or network of computers, that attempts to simulate an abstract model of a particular system...
can be run, from dose
Absorbed dose
Absorbed dose is a measure of the energy deposited in a medium by ionizing radiation per unit mass...
received from medical imaging procedures to nuclear medicine
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...
. Over the years, the results of these simulations have created an assortment of standards that have been adopted in the International Commission on Radiological Protection (ICRP)
International Commission on Radiological Protection
The International Commission on Radiological Protection is an advisory body providing recommendations and guidance on radiation protection; It was founded in 1928 by the International Society of Radiology and was then called the ‘International X-ray and Radium Protection Committee’...
recommendations.
Stylized (First-Generation) Computational Phantoms
The very first generation computational phantoms were developed for the needs to better assess organOrgan (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
doses
Absorbed dose
Absorbed dose is a measure of the energy deposited in a medium by ionizing radiation per unit mass...
from internally deposited radioactive materials in workers and patients. Until the late 1950s, the ICRP
International Commission on Radiological Protection
The International Commission on Radiological Protection is an advisory body providing recommendations and guidance on radiation protection; It was founded in 1928 by the International Society of Radiology and was then called the ‘International X-ray and Radium Protection Committee’...
still used very simple models. In these calculations, each organ of the body was assumed to be represented as a sphere
Sphere
A sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...
with an “effective radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
.” The radionuclide
Radionuclide
A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...
of interest was assumed to be located at the center of the sphere and the “effective absorbed energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
” was calculated for each organ. However, scientists attempted to model individual organs of the body and ultimately the entire human body in a realistic manner, the efforts of which led to stylized anthropomorphic phantoms—those resemble the human anatomy
Human anatomy
Human anatomy is primarily the scientific study of the morphology of the human body. Anatomy is subdivided into gross anatomy and microscopic anatomy. Gross anatomy is the study of anatomical structures that can be seen by the naked eye...
.
In general, stylized computational phantom is a mathematical representation of the human body, when coupled with a Monte Carlo
Monte Carlo method
Monte Carlo methods are a class of computational algorithms that rely on repeated random sampling to compute their results. Monte Carlo methods are often used in computer simulations of physical and mathematical systems...
radiation transport
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
computer code
Computer simulation
A computer simulation, a computer model, or a computational model is a computer program, or network of computers, that attempts to simulate an abstract model of a particular system...
, can be used to track the radiation interactions and energy deposition in the body. The feature of stylized computational phantom is finely tuned by adjusting individual parameters of the mathematical equations, which describes the volume
Volume
Volume is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance or shape occupies or contains....
, position
Position
Position may refer to:* Position , a player role within a team* Position , the orientation of a baby prior to birth* Position , a mathematical identification of relative location...
, and shape
Shape
The shape of an object located in some space is a geometrical description of the part of that space occupied by the object, as determined by its external boundary – abstracting from location and orientation in space, size, and other properties such as colour, content, and material...
of individual organ
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
s. Stylized computational phantom has a long history of development through the 1960s to 1980s.
MIRD Phantom
The MIRD phantom was developed by developed by Fisher and Snyder at Oak Ridge National Laboratory (ORNL)Oak Ridge National Laboratory
Oak Ridge National Laboratory is a multiprogram science and technology national laboratory managed for the United States Department of Energy by UT-Battelle. ORNL is the DOE's largest science and energy laboratory. ORNL is located in Oak Ridge, Tennessee, near Knoxville...
in 1960s with 22 internal organs and more than 100 sub-regions. It is the first anthropomorphic phantom representing a hermaphrodite
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
adult
Adult
An adult is a human being or living organism that is of relatively mature age, typically associated with sexual maturity and the attainment of reproductive age....
for internal dosimetry
Dosimetry
Radiation dosimetry is the measurement and calculation of the absorbed dose in matter and tissue resulting from the exposure to indirect and direct ionizing radiation...
.
Phantoms derived from MIRD
Based on MIRD phantom, many derivations of phantoms were developed for the following decades. The major types of phantom include: stylized “Family” phantom series developed in 1980s by Cristy and Eckerman; “ADAM and EVA” developed by GSF, Germany; CAM (Computerized Anatomical Man) phantom developed by NASANASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
unknown by the mainstream radiation protection dosimetry community, etc.
Limitation on stylized phantom
Although many efforts were undertaken to diversify and extend its applications in radiation protection, radiation therapyRadiation therapy
Radiation therapy , radiation oncology, or radiotherapy , sometimes abbreviated to XRT or DXT, is the medical use of ionizing radiation, generally as part of cancer treatment to control malignant cells.Radiation therapy is commonly applied to the cancerous tumor because of its ability to control...
, and medical imaging
Medical imaging
Medical imaging is the technique and process used to create images of the human body for clinical purposes or medical science...
, one cannot overcome its inborn limitation. The representation of internal organs in this mathematical phantom was crude, by capturing only the most general description of the position
Position
Position may refer to:* Position , a player role within a team* Position , the orientation of a baby prior to birth* Position , a mathematical identification of relative location...
and geometry
Geometry
Geometry arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the study of numbers ....
of each organ. With the powerful computer and tomographic
Tomography
Tomography refers to imaging by sections or sectioning, through the use of any kind of penetrating wave. A device used in tomography is called a tomograph, while the image produced is a tomogram. The method is used in radiology, archaeology, biology, geophysics, oceanography, materials science,...
imaging technologies became available in the late 1980s, the history launched a new era of voxel
Voxel
A voxel is a volume element, representing a value on a regular grid in three dimensional space. This is analogous to a pixel, which represents 2D image data in a bitmap...
phantoms.
Voxel (Second-Generation) Phantoms
The stylized phantoms provided only basic information with a large degree of error. More accurate methods of simulating a human body were necessary to advance. To allow further research, the computer technology had to become more powerful and more readily available. This did not occur until the 1980s. The real breakthrough occurred when CT (Computed Tomography)
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
and MRI (Magnetic Resonance Imaging)
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
devices could generate highly accurate images of internal organs in three dimensions and in digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
format. Researchers discovered that they could take that diagnostic data and transform it into a voxel (volumetric pixel)
Voxel
A voxel is a volume element, representing a value on a regular grid in three dimensional space. This is analogous to a pixel, which represents 2D image data in a bitmap...
format, essentially re-creating the human body
Human body
The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs.By the time the human reaches adulthood, the body consists of close to 100 trillion cells, the basic unit of life...
in digital form in 3D. Today there are over 38 human phantoms in voxel format, for many different uses.
Challenges for implementation
Two major issues with development of the reference phantoms are difficulty in obtaining useful images and handling the large amount of data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
created from these images. CT scans give the human body a large dose
Absorbed dose
Absorbed dose is a measure of the energy deposited in a medium by ionizing radiation per unit mass...
of ionizing radiation
Ionizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...
– something the computational phantom was designed to circumvent in the first place. MRI images take a long time to process. Furthermore, most scans of a single subject cover only a small portion of the body, whereas a full scan series is needed for useful data. Handling this data is also difficult. While the newer computers had hard drives large enough to store the data, the memory
Computer memory
In computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which are fast In computing, memory refers to the...
requirements for processing the images to the desired voxel size were often too steep.
Basic development process of a voxel phantom
While there have been many voxel phantoms developed, they have all followed a similar path to completion. First, they must obtain the raw data
Raw data
'\putang inaIn computing, it may have the following attributes: possibly containing errors, not validated; in sfferent formats; uncoded or unformatted; and suspect, requiring confirmation or citation. For example, a data input sheet might contain dates as raw data in many forms: "31st January...
, from CT scans, MRI imaging, or direct imaging through photography
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...
. Second, the components of the body must be segmented, or identified and separated from the rest. Third, the density of each component must be identified, along with the composition of each. Lastly, the data must be unified into a single 3D structure so it may be used for analysis
Analysis
Analysis is the process of breaking a complex topic or substance into smaller parts to gain a better understanding of it. The technique has been applied in the study of mathematics and logic since before Aristotle , though analysis as a formal concept is a relatively recent development.The word is...
.
Early developments
The earliest work on voxelized phantoms occurred independently at about the same time by Dr. Gibbs, of Vanderbilt University
Vanderbilt University
Vanderbilt University is a private research university located in Nashville, Tennessee, United States. Founded in 1873, the university is named for shipping and rail magnate "Commodore" Cornelius Vanderbilt, who provided Vanderbilt its initial $1 million endowment despite having never been to the...
, and Dr. Zankl at the National Research Center for Environment and Health (GSF) in Germany. This occurred about 1982. Dr. Gibb’s work started with X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
images, not CT
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
or MRI
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
images, for the reconstruction of a human phantom which was used for medical dose
Absorbed dose
Absorbed dose is a measure of the energy deposited in a medium by ionizing radiation per unit mass...
simulations
Computer simulation
A computer simulation, a computer model, or a computational model is a computer program, or network of computers, that attempts to simulate an abstract model of a particular system...
. M. Zankl and team did use CT imaging to create 12 phantoms, ranging from BABY to VISIBLE HUMAN.
Advancements in voxel phantom design by country
- United StatesUnited StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
- Dr. Zubal and team at Yale UniversityYale UniversityYale University is a private, Ivy League university located in New Haven, Connecticut, United States. Founded in 1701 in the Colony of Connecticut, the university is the third-oldest institution of higher education in the United States...
developed the VoxelMan phantom in 1994. This phantom was complete only from head-to-torso, and was designed specifically for improving nuclear medicine. - In 2000, Dr. George XuGeorge XuXie George Xu is a professor with the at Rensselaer Polytechnic Institute. After receiving a PhD. in Nuclear Engineering from Texas A&M University, he joined RPI in 1995, where he soon received the NSF in 1999...
and two students at Rensselaer Polytechnic Institute (RPI)Rensselaer Polytechnic InstituteStephen Van Rensselaer established the Rensselaer School on November 5, 1824 with a letter to the Rev. Dr. Samuel Blatchford, in which van Rensselaer asked Blatchford to serve as the first president. Within the letter he set down several orders of business. He appointed Amos Eaton as the school's...
created the VIP-Man phantom from data retrieved from the National Library of Medicine’s (NLM) Visible Human Project (VHP)Visible Human ProjectThe Visible Human Project is an effort to create a detailed data set of cross-sectional photographs of the human body, in order to facilitate anatomy visualization applications. A male and a female cadaver were cut into thin slices which were then photographed and digitized. The project is run by...
. This phantom was the most complex model to date, with over 3.7 billion voxels. This model was used in many studies concerning health physics and medical physics. - Dr. Bolch and team at the University of FloridaUniversity of FloridaThe University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...
created a set of pediatric phantoms from 2002 to 2006. Child computational phantoms had been severely underrepresented until this point. The team developed models ranging from newborn to mid-teens.
- Dr. Zubal and team at Yale University
- BrazilBrazilBrazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
- Dr. Kramer in Brazil improved on the data from the Yale Zubal team in an attempt to create a phantom similar to ICRPInternational Commission on Radiological ProtectionThe International Commission on Radiological Protection is an advisory body providing recommendations and guidance on radiation protection; It was founded in 1928 by the International Society of Radiology and was then called the ‘International X-ray and Radium Protection Committee’...
requirements, and created the MAX phantom.
- Dr. Kramer in Brazil improved on the data from the Yale Zubal team in an attempt to create a phantom similar to ICRP
- United KingdomUnited KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
- The NORMAN phantom was developed by a team led by Dr. Dimbylow. This was created by analyzing MRMagnetic resonance imagingMagnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
images of a human male in 1996. In 2005, the team created a female phantom.
- The NORMAN phantom was developed by a team led by Dr. Dimbylow. This was created by analyzing MR
- AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
- At Flinders University, Dr. Caon and team created a torso phantom to simulate a teenage girl in 1999. The name of the phantom was ADELAIDE. This was the only teenage female phantom for a number of years.
- JapanJapanJapan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
- The first Asian phantom was developed by Dr. Saito and team at the Japanese Atomic Energy Research Institute (JAERI)Japan Atomic Energy Research InstituteThe Japan Atomic Energy Research Institute is a former semi-governmental organization that existed for the purpose of further nuclear power in Japan. It was created June 1956 by the Atomic Energy Basic Law...
in 2001. This was primarily used for radiation dosimetry studies. - Another group, led by Dr. Nagaoka at the National Institute of Information and Communications Technology (NIICT)National Institute of Information and Communications TechnologyThe National Institute of Information and Communications Technology is Japan's national research institute for information and communications...
, created a male and female phantom around the same time period as the JAERI group. These were created from MR images.
- The first Asian phantom was developed by Dr. Saito and team at the Japanese Atomic Energy Research Institute (JAERI)
- KoreaKoreaKorea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
- Many computational phantoms have been created in Korea since 2004 by Drs. Lee and Kim. Both male and female phantoms have been created. The High-Definition Reference Korean (HDRK) was created by color pictures of a cadaver, similar to the construction of the VIP-Man phantom from RPI.
- ChinaChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
- In the mid-2000s, the Chinese government authorized the creation of their own version of the VHP. The data was used by Dr. Zhang and team at the China Institute for Radiation Protection to create the CNMAN phantom, the most accurate computational phantom to date.
- GermanyGermanyGermany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
- M. Zankl and co-workers used CT images to construct a variety of individual voxel phantoms, including three paediatric ones and a woman in the 24th week of pregnancy.
Recent developments
Since voxel
Voxel
A voxel is a volume element, representing a value on a regular grid in three dimensional space. This is analogous to a pixel, which represents 2D image data in a bitmap...
phantoms have been superseded by mesh- and NURBS-based phantoms, there has been limited development in the past few years. Many of the advancements have come through manipulations of current phantoms to correct for height and weight variations of the population.
In 2009, the International Commission on Radiological Protection (ICRP) and the International Commission on Radiation Units and Measurements (ICRU) adopted voxel-based adult male and female reference computational phantoms for the computation of organ dose coefficients .
Statistical phantom
A computational framework was presented, based on statistical shape modelling, for construction of race-specific organ models for internal radionuclide dosimetry and other nuclear-medicine applications. The proposed technique used to create the race-specific statistical phantom maintains anatomic realism and provides the statistical parameters for application to radionuclide dosimetry.Boundary Representation (BREP) phantom
Boundary representation (BREP)Boundary representation
In solid modeling and computer-aided design, boundary representation—often abbreviated as B-rep or BREP—is a method for representing shapes using the limits...
phantoms are computational human models that contain exterior and interior anatomical features
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
of a human body
Human body
The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs.By the time the human reaches adulthood, the body consists of close to 100 trillion cells, the basic unit of life...
using boundary representation
Boundary representation
In solid modeling and computer-aided design, boundary representation—often abbreviated as B-rep or BREP—is a method for representing shapes using the limits...
method. In the realm of health and medical physics
Medical physics
Medical physics is the application of physics to medicine. It generally concerns physics as applied to medical imaging and radiotherapy, although a medical physicist may also work in many other areas of healthcare...
they are primarily used for ionizing radiation
Ionizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...
dosimetry
Dosimetry
Radiation dosimetry is the measurement and calculation of the absorbed dose in matter and tissue resulting from the exposure to indirect and direct ionizing radiation...
.
In the development of computational human phantoms, of particular interest is the concept of a “deformable” phantom whose geometry
Geometry
Geometry arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the study of numbers ....
can be conveniently transformed to fit particular physical organ
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
shape
Shape
The shape of an object located in some space is a geometrical description of the part of that space occupied by the object, as determined by its external boundary – abstracting from location and orientation in space, size, and other properties such as colour, content, and material...
s, volume
Volume
Volume is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance or shape occupies or contains....
s, or body postures. Design of this type of phantom is realized by Non-Uniform Rational B-Spline (NURBS) method or polygonal mesh method, which are usually collectively called BREP methods. Compared to the voxel phantoms, BREP phantoms are better suited for geometry deformation and adjustment, because a larger set of computerized operations are available, such as extrusion
Extrusion
Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section...
, chamfering, blending, drafting
Engineering drawing
An engineering drawing, a type of technical drawing, is used to fully and clearly define requirements for engineered items.Engineering drawing produces engineering drawings . More than just the drawing of pictures, it is also a language—a graphical language that communicates ideas and information...
, shelling
Shelling (topology)
In mathematics, a shelling of a simplicial complex is a way of gluing it together from its maximal simplices in a well-behaved way. A complex admitting a shelling is called shellable.-Definition:...
and tweaking
Tweaking
Tweaking refers to fine-tuning or adjusting a complex system, usually an electronic device. Tweaks are any small modifications intended to improve a system....
. A major advantage of BREP phantoms is their ability to morph into an existing reference phantom or into the anatomy of a real worker or patient, which makes individual-specific dose calculation possible.
NURBS-based phantom
Surfaces of a NURBS-based phantom are defined by NURBS equationEquation
An equation is a mathematical statement that asserts the equality of two expressions. In modern notation, this is written by placing the expressions on either side of an equals sign , for examplex + 3 = 5\,asserts that x+3 is equal to 5...
s which are formulated by a set of control points. The shape and volume of a NURBS surface vary with the coordinates of control points. This feature is useful in designing a time-dependent 4D
Spacetime
In physics, spacetime is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space as being three-dimensional and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions...
human body
Human body
The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs.By the time the human reaches adulthood, the body consists of close to 100 trillion cells, the basic unit of life...
modeling. An example is given by NCAT phantoms by Segars et al, which is used to simulate cardiac and respiratory motions with more realistic modeling of the cardiac system.
Polygonal mesh-based phantom
A polygonal mesh is composed of a set of verticesVertex (geometry)
In geometry, a vertex is a special kind of point that describes the corners or intersections of geometric shapes.-Of an angle:...
, edges
Edge (geometry)
In geometry, an edge is a one-dimensional line segment joining two adjacent zero-dimensional vertices in a polygon. Thus applied, an edge is a connector for a one-dimensional line segment and two zero-dimensional objects....
, and faces
Face (geometry)
In geometry, a face of a polyhedron is any of the polygons that make up its boundaries. For example, any of the squares that bound a cube is a face of the cube...
that specify the shape of a polyhedral object
Polyhedron
In elementary geometry a polyhedron is a geometric solid in three dimensions with flat faces and straight edges...
in 3D space
Three-dimensional space
Three-dimensional space is a geometric 3-parameters model of the physical universe in which we live. These three dimensions are commonly called length, width, and depth , although any three directions can be chosen, provided that they do not lie in the same plane.In physics and mathematics, a...
. The surfaces of the phantom are defined by a large amount of polygonal meshes, most commonly triangle
Triangle
A triangle is one of the basic shapes of geometry: a polygon with three corners or vertices and three sides or edges which are line segments. A triangle with vertices A, B, and C is denoted ....
s. The polygonal mesh has three remarkable advantages in developing whole-body phantoms. Firstly, mesh surfaces depicting human anatomy can be conveniently obtained from real patient images or commercial human anatomy mesh models. Secondly, the polygonal mesh-based phantom has considerable flexibility in adjusting and fine-tuning its geometry, allowing the simulation of very complex anatomies. Thirdly, many commercial computer aided design (CAD)
Computer-aided design
Computer-aided design , also known as computer-aided design and drafting , is the use of computer technology for the process of design and design-documentation. Computer Aided Drafting describes the process of drafting with a computer...
software, such as Rhinoceros
Rhinoceros 3D
Rhinoceros is a stand-alone, commercial NURBS-based 3-D modeling tool, developed by Robert McNeel & Associates. The software is commonly used for industrial design, architecture, marine design, jewelry design, automotive design, CAD / CAM, rapid prototyping, reverse engineering as well as the...
, AutoCAD
AutoCAD
AutoCAD is a software application for computer-aided design and drafting in both 2D and 3D. It is developed and sold by Autodesk, Inc. First released in December 1982, AutoCAD was one of the first CAD programs to run on personal computers, notably the IBM PC...
, Visualization Toolkit (VTK)
VTK
The Visualization Toolkit is an open-source, freely available software system for 3D computer graphics, image processing and visualization. VTK consists of a C++ class library and several interpreted interface layers including Tcl/Tk, Java, and Python. Kitware, whose team created and continues to...
, provide built-in functions able to rapidly convert polygonal mesh into NURBS.
Development
Segars was the precursor of applying NURBS to phantom design. In 2001 his doctoral thesisThesis
A dissertation or thesis is a document submitted in support of candidature for an academic degree or professional qualification presenting the author's research and findings...
described the method of developing a dynamic NURBS-based cardiac-torso (NCAT) phantom in detail. The phantom has a 4D beating heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
model which was derived from 4D tagged magnetic resonance image (MRI)
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
data. The remaining organs in the torso of the phantom were designed based on the Visible Human Project
Visible Human Project
The Visible Human Project is an effort to create a detailed data set of cross-sectional photographs of the human body, in order to facilitate anatomy visualization applications. A male and a female cadaver were cut into thin slices which were then photographed and digitized. The project is run by...
CT data set and were composed of 3D NURBS surfaces. Respiratory motion was also incorporated into this phantom.
In 2005, Xu et al. at Rensselaer Polytechnic Institute (RPI)
Rensselaer Polytechnic Institute
Stephen Van Rensselaer established the Rensselaer School on November 5, 1824 with a letter to the Rev. Dr. Samuel Blatchford, in which van Rensselaer asked Blatchford to serve as the first president. Within the letter he set down several orders of business. He appointed Amos Eaton as the school's...
used the 3D VIP-Man phantom to simulate respiratory motions by adopting the gated respiratory motion data of the NCAT phantom. The 4D VIP-Man Chest phantom was used to study external-beam treatment
External beam radiotherapy
External beam radiotherapy or teletherapy is the most common form of radiotherapy. The patient sits or lies on a couch and an external source of radiation is pointed at a particular part of the body...
planning for a lung cancer
Lung cancer
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...
patient. In 2007, Xu’s research group reported creation of a series of polygon
Polygon
In geometry a polygon is a flat shape consisting of straight lines that are joined to form a closed chain orcircuit.A polygon is traditionally a plane figure that is bounded by a closed path, composed of a finite sequence of straight line segments...
-based phantoms representing a pregnant woman and her fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
at the end of 3, 6, and 9 month gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
s (RPI Pregnant Females). The mesh data were initially obtained from separate anatomical information sources including a non-pregnant female, a 7-month pregnant woman CT data set, and a mesh model of the fetus. In 2008, two triangular mesh-based phantoms were created, named as RPI Deformable Adult Male and Female (RPI-AM, RPI-FM). The anatomic parameters of the phantoms were made consistent with two datasets: the mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
and density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
of internal organs originated from ICRP-23 and ICRP-89, and the whole-body height and weight percentile data were obtained from the National Health and Nutrition Examination Survey (NHANES 1999-2002)
National Health and Nutrition Examination Survey
The National Health and Nutrition Examination Survey is a survey research program conducted by the National Center for Health Statistics to asses the health and nutritional status of adults and children in the United States, and to track changes over time. The survey combines interviews and...
. Later on, to study the relationship between breast size and lung dosimetry
Dosimetry
Radiation dosimetry is the measurement and calculation of the absorbed dose in matter and tissue resulting from the exposure to indirect and direct ionizing radiation...
, a new group of phantoms were produced by altering the breast geometry
Geometry
Geometry arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the study of numbers ....
of RPI-AF.
From 2006 to 2009, Bolch et al. at University of Florida (UF)
University of Florida
The University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...
designed a total of twelve “hybrid” male and female phantoms, representing newborn, 1, 5, 10, 15-year old and adult male/females. The phantoms are addressed as “hybrid” because most organs and tissues were modeled by NURBS surfaces whereas the skeleton, brain and extra-thoracic airways were modeled by polygonal surfaces. Anatomic parameters of the phantoms were adjusted to match 4 reference datasets, i.e., standard anthropometric
Anthropomorphism
Anthropomorphism is any attribution of human characteristics to animals, non-living things, phenomena, material states, objects or abstract concepts, such as organizations, governments, spirits or deities. The term was coined in the mid 1700s...
data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
, reference organ masses from ICRP
International Commission on Radiological Protection
The International Commission on Radiological Protection is an advisory body providing recommendations and guidance on radiation protection; It was founded in 1928 by the International Society of Radiology and was then called the ‘International X-ray and Radium Protection Committee’...
Publication 89, reference elemental compositions provided in ICRP 89 as well as ICRU Report 46, and reference data on the alimentary tract organs given in ICRP Publications 89 and 100.
In 2008, Stabin et al. at Vanderbilt University
Vanderbilt University
Vanderbilt University is a private research university located in Nashville, Tennessee, United States. Founded in 1873, the university is named for shipping and rail magnate "Commodore" Cornelius Vanderbilt, who provided Vanderbilt its initial $1 million endowment despite having never been to the...
, in collaboration with Segars from Duke University
Duke University
Duke University is a private research university located in Durham, North Carolina, United States. Founded by Methodists and Quakers in the present day town of Trinity in 1838, the school moved to Durham in 1892. In 1924, tobacco industrialist James B...
, developed a family of adult and pediatric phantoms by adapting the NURBS-based NCAT adult male and female phantoms. ICRP-89 reference body and organ values were used to adjust NURBS surfaces.
In 2009 Cassola et al at the Federal University of Pernambuco
Federal University of Pernambuco
The Federal University of Pernambuco is a public university located in Recife, Brazil, and established in 1946. UFPE has 70 undergraduate courses and 175 postgraduate courses. As of 2007, UFPE had near 35,000 students and about 2,000 professors. The university has three campuses: Recife, Vitória...
, Brazil, developed a pair of polygonal mesh-based phantoms in standing posture, FASH (Female Adult meSH) and MASH (Male Adult meSH). The methodology is very similar but not entirely identical to the one implemented in the designing of RPI-AM and RPI-FM.
In 2010, based on existing RPI-AM, Xu et al. continued to create 5 more phantoms with different Body Mass Index (BMI)
Body mass index
The body mass index , or Quetelet index, is a heuristic proxy for human body fat based on an individual's weight and height. BMI does not actually measure the percentage of body fat. It was invented between 1830 and 1850 by the Belgian polymath Adolphe Quetelet during the course of developing...
ranging from 23 to 44 kg∙m-2. These phantoms are used to study the correlation between BMI and organ doses
Absorbed dose
Absorbed dose is a measure of the energy deposited in a medium by ionizing radiation per unit mass...
resulting from CT and PET
Positron emission tomography
Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...
examinations.
In 2011 Kim et al. at Hanyang University
Hanyang University
Hanyang University is one of the most prestigious universities in South Korea. In particular, Hanyang's School of Engineering is one of the oldest engineering schools in Korea. The main campus is Hanyang University at Seoul, located in the Seoul, with its branch campus, the ERICA campus , located...
, Korea, reported a polygon-surface reference Korean male phantom (PSRK-Man). This phantom was constructed by converting the Visible Korean Human-Man (VKH-man) into a polygonal mesh-based phantom. The height, weight, geometry of organs and tissues were adjusted to match the Reference Korean data. Without voxel
Voxel
A voxel is a volume element, representing a value on a regular grid in three dimensional space. This is analogous to a pixel, which represents 2D image data in a bitmap...
ization the PSRK-man could be directly implemented in Geant4
Geant4
Geant4 is a platform for "the simulation of the passage of particles through matter," using Monte Carlo methods. It is the successor of the GEANT series of software toolkits developed by CERN, and the first to use Object oriented programming . Its development, maintenance and user support are...
Monte Carlo
Monte Carlo method
Monte Carlo methods are a class of computational algorithms that rely on repeated random sampling to compute their results. Monte Carlo methods are often used in computer simulations of physical and mathematical systems...
simulation
Computer simulation
A computer simulation, a computer model, or a computational model is a computer program, or network of computers, that attempts to simulate an abstract model of a particular system...
using a built-in function, but the computation
Computation
Computation is defined as any type of calculation. Also defined as use of computer technology in Information processing.Computation is a process following a well-defined model understood and expressed in an algorithm, protocol, network topology, etc...
time was 70~150 times longer than that required by High Definition Reference Korean-Man (HDRK-Man), a voxelized phantom derived also from VKH-man.