Computational human phantom
The newest models are based on more advanced mathematics, such as non-uniform rational B-spline (NURBS) and polygon meshes, 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.
[1] The very first generation computational phantoms were developed to address the need to better assess organ doses from internally deposited radioactive materials in workers and patients.
The MIRD phantom[7] was developed by Fisher and Snyder at Oak Ridge National Laboratory (ORNL) in the 1960s with 22 internal organs and more than 100 sub-regions.
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.
CT scans give the human body a large dose of ionizing radiation – something the computational phantom was designed to circumvent in the first place.
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.
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.
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.
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.
[39][40] 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).
[40] From 2006 to 2009, researchers at the University of Florida designed a total of twelve "hybrid" male and female phantoms, representing newborn, 1-, 5-, 10-, and 15-year-old and adult male/females.
In 2010, based on existing RPI-AM, researchers at RPI continued to create 5 more phantoms with different body mass index (BMI) ranging from 23 to 44 kg∙m-2.
[46] These phantoms are used to study the correlation between BMI and organ doses resulting from CT and positron emission tomography (PET) examinations.
In 2012, researchers at RPI developed the Computational Human for Animated Dosimetry (CHAD) phantom, structured such that its posture could be adjusted in conjunction with data obtained using a motion capture system.
[50] A collection of animal models (rodents, pigs, and monkeys) have also been developed for research on non-ionizing dosimetry and its associated risk of cancer.
