Phantom structure

Phantom structures are artificial structures designed to emulate properties of the human body in matters such as, including, but not limited to, light scattering and optics, electrical conductivity, and sound wave reception. Phantoms have been used experimentally in lieu of, or as a supplement to, human subjects to maintain consistency, verify reliability of technologies, or reduce experimental expense.[1] They also have been employed as material for training technicians to perform imaging.[2]

## Contents

* 1 Optical phantoms
* 1.1 Composite Materials
* 2 Computational phantoms
* 3 Physiological models
* 3.1 Phantom head
* 3.2 Phantom prostate
* 3.3 Phantom ear
* 3.4 Phantom skin
* 3.5 Phantom breast
* 3.6 Phantom muscle
* 4 References

## Optical phantoms

Main article: Imaging phantom

Optical tissue phantoms, or imaging phantoms, are reported to be used largely for three main purposes: to calibrate optical devices, record baseline reference measurements, and for imaging the human body.[3] Optical tissue phantoms may have irregular shape of body parts.[4]

### Composite Materials

Optical phantoms can be made from a number of materials. These are including but not limited to:

* homogenized milk[3]
* non-dairy creamer[3]
* wax[3]
* blood and yeast suspension[3]
* water-soluble dye (India ink)[3]
* intralipid[3]
* latex microspheres[3]
* solid epoxy[4][3]
* liquid rubber[4]
* silicone[3]
* polyester[3]
* polyurethane[3]

## Computational phantoms

Main article: Physics:Computational human phantom

Computational human phantoms have many uses, including but not limited to, biomedical imaging computational modeling and simulations, radiation dosimetry, and treatment planning.[5]

## Physiological models

### Phantom head

While using research oriented and Commercial Off The Shelf (COTS) EEG technologies built for monitoring brain activity, scientists established the need for a benchmark reading of neural electrical activity.[1] EEG readings’ strong dependency on mechanical contact makes the technology sensitive to movement.[6] This and a high responsivity to environmental conditions may lead to signal noise. Without a baseline, it is hard to interpret whether abnormal clinical data is a result of faulty technology, patient inconsistency or noncompliance, ambient noise, or an unexplained scientific principle.[1]

A phantom head was described by researchers in 2015. This head was developed at the U.S. Army Research Laboratory.[1] Reported intent for the engineering of this phantom head was to “accurately recreate real and imaginary scalp impedance, contain internal emitters to create dipoles, and be easily replicable across various labs and research groups.” [7]

The scientists used an inverse 3D printed mold that was reproduced an anonymized MRI image. The head consisted of ballistics gel with a composition that included salt in order to conduct electricity like human tissue.[8] Ballistics gelatin was chosen because it conducts electricity,[8] while also possessing mechanical properties similar to living tissue.[9][10] Multiple electric wires within the Army’s phantom head carried electric current. A CT scan was used to verify proper electrode placement.[8] The limitations of this phantom was that the material was not sufficiently durable.[1][8] The refrigerated gel degraded relatively quickly, by approximately .3% each day.[8]

Other reported models had been made of saline filled spheres.[11]

### Phantom prostate

In 2013, a patent submission for a prostate phantom was reported. The prostate was composed of three separate phantom layers of prostate, perineal gland, and skin tissue and developed for the study of prostate cancer brachytherapy. The scientists claimed that the phantom emulates the imaging and mechanical properties of the prostate and surrounding tissues.[12]

### Phantom ear

In 2002, researchers proposed an ear phantom for experimental studies on sound absorbance rates of cellular emissions.[13]

### Phantom skin

Several designs of phantom skin have been developed for various uses including, but not limited to, studying skin lesion therapy, applications of narrowband and ultra-band microwaves (like breast cancer detection),[14] and imaging fingernails and underlying tissues.[15]

### Phantom breast

Ultrasound tissue elastography is a method to determine tissue health, as pathologies have been noted to increase the elasticity of tissue. In 2015, a tissue-like agar-based phantom had been reported to be useful in compression elastographical diagnosis of breast cancer. The scientists replicated the clinical appearance of conditions such as fibroadenoma and invasive ductal carcinoma in the phantom breast and compared elastographic and sonographic images.[2]

Additionally, a recipe for the formation of a semi-compressible phantom breast with liquid rubber has been reported.[4]

### Phantom muscle

There have been many fabrication methods developed on muscle phantoms over the years, and the research is still going on. Still, here in the year 2020, researchers have developed muscle phantoms to implicate or act as tumors in breast imaging for cancer detection.[16]

## References

1. ↑ 1.0 1.1 1.2 1.3 1.4 "'Phantom head' may one day take guesswork out of EEG monitoring" (in en). www.army.mil. https://www.army.mil/article/158604/phantom_head_may_one_day_take_guesswork_out_of_eeg_monitoring.
2. ↑ 2.0 2.1 "Development of a training phantom for compression breast elastography-comparison of various elastography systems and numerical simulations". Journal of Medical Imaging 2 (4): 047002. October 2015. doi:10.1117/1.JMI.2.4.047002. PMID 26697511.
3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 "Project: Optical Phantoms" (in en). https://omlc.org/~prahl/projects/phantoms.html.
4. ↑ 4.0 4.1 4.2 4.3 "Photon Migration Imaging Lab". http://www.nmr.mgh.harvard.edu/PMI/research/phantom-recipes.htm.
5. ↑ "6th International Workshop on Computational Human Phantoms | August 27 – 30, 2017 in historic Annapolis, MD, USA" (in en). http://www.cpworkshop.org/.
6. ↑ "Carbon nanofiber-filled conductive silicone elastomers as soft, dry bioelectronic interfaces". PLOS ONE 13 (2): e0189415. 2018-02-06. doi:10.1371/journal.pone.0189415. PMID 29408942. Bibcode: 2018PLoSO..1389415S.
7. ↑ Hairston, W David; A. Slipher, Geoffrey; B. Yu, Alfred (2016-09-24). Ballistic gelatin as a putative substrate for EEG phantom devices. Bibcode: 2016arXiv160907691H. https://www.researchgate.net/publication/308646583.
8. ↑ 8.0 8.1 8.2 8.3 8.4 "Summer student's EEG research continues to develop at ARL | U.S. Army Research Laboratory" (in en). https://www.arl.army.mil/www/default.cfm?article=2644.
9. ↑ Richler, D; Rittel, D (2014-06-01). "On the Testing of the Dynamic Mechanical Properties of Soft Gelatins". Experimental Mechanics 54 (5): 805–815. doi:10.1007/s11340-014-9848-4. https://www.researchgate.net/publication/271573856.
10. ↑ "Characterization and evaluation of tissue-mimicking gelatin phantoms for use with MRgFUS". Journal of Therapeutic Ultrasound 3: 9. 2015-06-16. doi:10.1186/s40349-015-0030-y. PMID 26146557.
11. ↑ Collier, T. J.; Kynor, D. B.; Bieszczad, J.; Audette, W. E.; Kobylarz, E. J.; Diamond, S. G. (2012). "Creation of a Human Head Phantom for Testing of Electroencephalography Equipment and Techniques - IEEE Journals & Magazine" (in en-US). IEEE Transactions on Bio-Medical Engineering 59 (9): 2628–34. doi:10.1109/TBME.2012.2207434. PMID 22911537.
12. ↑ "U.S. Patent No. US 8,480.407 B2" (issued Jul.9, 2013)
13. ↑ Gandhi, Om P.; Kang, Gang (2002). "Some present problems and a proposed experimental phantom for SAR compliance testing of cellular telephones at 835 and 1900 MHz" (in en). Physics in Medicine and Biology 47 (9): 1501–18. doi:10.1088/0031-9155/47/9/306. ISSN 0031-9155. PMID 12043816. Bibcode: 2002PMB....47.1501G.
14. ↑ "Tissue-mimicking phantom materials for narrowband and ultrawideband microwave applications". Physics in Medicine and Biology 50 (18): 4245–58. September 2005. doi:10.1088/0031-9155/50/18/001. PMID 16148391. Bibcode: 2005PMB....50.4245L. https://www.researchgate.net/publication/7614358.
15. ↑ "Finger tissue model and blood perfused skin tissue phantom". Dynamics and Fluctuations in Biomedical Photonics VIII (SPIE) 7898: 78980Z. 2011-02-10. doi:10.1117/12.881604. Bibcode: 2011SPIE.7898E..0ZT.
16. ↑ Joseph, Laya; Asan, Noor Badariah; Ebrahimizadeh, Javad; Chezhian, Arvind Selvan; Perez, Mauricio D.; Voigt, Thiemo; Augustine, Robin (March 2020). "Non-Invasive Transmission Based Tumor Detection Using Anthropomorphic Breast Phantom at 2.45 GHZ". 2020 14th European Conference on Antennas and Propagation (EuCAP). Copenhagen, Denmark: IEEE. pp. 1–5. doi:10.23919/EuCAP48036.2020.9135953. ISBN 978-88-31299-00-8. https://ieeexplore.ieee.org/document/9135953.

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