Fabrication Of Phantoms Research Articles

Fabrication and Characterization of Optical Tissue Phantoms Containing Macrostructure.

The rapid development of new optical imaging techniques is dependent on the availability of low-cost, customizable, and easily reproducible standards. By replicating the imaging environment, costly animal experiments to validate a technique may be circumvented. Predicting and optimizing the performance of in vivo and ex vivo imaging techniques requires testing on samples that are optically similar to tissues of interest. Tissue-mimicking optical phantoms provide a standard for evaluation, characterization, or calibration of an optical system. Homogenous polymer optical tissue phantoms are widely used to mimic the optical properties of a specific tissue type within a narrow spectral range. Layered tissues, such as the epidermis and dermis, can be mimicked by simply stacking these homogenous slab phantoms. However, many in vivo imaging techniques are applied to more spatially complex tissue where three dimensional structures, such as blood vessels, airways, or tissue defects, can affect the performance of the imaging system. This protocol describes the fabrication of a tissue-mimicking phantom that incorporates three-dimensional structural complexity using material with optical properties of tissue. Look-up tables provide India ink and titanium dioxide recipes for optical absorption and scattering targets. Methods to characterize and tune the material optical properties are described. The phantom fabrication detailed in this article has an internal branching mock airway void; however, the technique can be broadly applied to other tissue or organ structures.

3D프린터를 이용한 CT 선량측정 팬텀 제작 및 비교에 관한 연구

전산화 단층촬영 장치의 정 도관리 항목 중 하나인 환자 피폭선량 피폭 시험은 의료법 제38조 특수의료장비 설치 및 운영에 따라 1년마다 측정을 시행하고 기록을 보관해야 한다. 선량 측정을 위해 사용되고 있는 CT-Dose 팬텀은 정확한 선량 측정이 가능하지만 가격이 비싸다는 단점이 있다. 따라서 본 연구를 통해 기존의 CT-Dose 팬텀을 3D프린터로 유사하게 제작하여 기존의 팬텀과 비교 분석하고 유용성을 알아보았다. 기존의 CT-Dose팬텀과 동일한 팬텀을 제작하기위해 PLA 필라멘트를 이용하여 FFF 방식의 3D프린터를 이용하였으며, CTDIw 값을 산출하기 위해 팬텀의 주변부와 중앙부에 이온챔버를 삽입하여 각 10번씩 측정하였다. 측정결과 주변부는 CT-Dose팬텀 30.44 ± 0.31 mGy, 중앙부는 29.55 ± 0.34 mGy CTDIw값은 30.14 ± 0.30 mGy로 측정되었고, 3D프린터를 이용하여 제작된 팬텀은 주변부 30.59 ± 0.18 mGy, 중앙부 29.01 ± 0.04 mGy, CTDIw값은 30.06 ± 0.13 mGy로 측정되었다. SPSS 통계 프로그램의 Mann- Whiteney U-test를 사용하여 분석한 결과 중앙부의 결과 값은 통계적으로 유의한 차이가 있었지만 주변부와 CTDIw의 결과 값은 통계적으로 유의한 차이를 나타내지 않았다. 결론적으로, 3D프린터를 이용하여 제작된 팬텀으로 기존의 CT-Dose 팬텀과 유사한 선량측정 성능을 보였으며, 본 연구를 통해 3D프린터를 이용한 저비용의 팬텀 제작의 가능성을 확인할 수 있었다.

Characterization of the Optical Properties of Turbid Media by Supervised Learning of Scattering Patterns

Fabricated tissue phantoms are instrumental in optical in-vitro investigations concerning cancer diagnosis, therapeutic applications, and drug efficacy tests. We present a simple non-invasive computational technique that, when coupled with experiments, has the potential for characterization of a wide range of biological tissues. The fundamental idea of our approach is to find a supervised learner that links the scattering pattern of a turbid sample to its thickness and scattering parameters. Once found, this supervised learner is employed in an inverse optimization problem for estimating the scattering parameters of a sample given its thickness and scattering pattern. Multi-response Gaussian processes are used for the supervised learning task and a simple setup is introduced to obtain the scattering pattern of a tissue sample. To increase the predictive power of the supervised learner, the scattering patterns are filtered, enriched by a regressor, and finally characterized with two parameters, namely, transmitted power and scaled Gaussian width. We computationally illustrate that our approach achieves errors of roughly 5% in predicting the scattering properties of many biological tissues. Our method has the potential to facilitate the characterization of tissues and fabrication of phantoms used for diagnostic and therapeutic purposes over a wide range of optical spectrum.

Fabrication and characterization of biological tissue phantoms with embedded nanoparticles

Phantoms are imitations of biological tissue, which are used for modelling of the light propagation in biological tissues. Carrying out any biophysical experiments requires an indispensable constancy of the initial experiment conditions. The use of solid undegradable phantoms is the basis to obtain reliable reproducible experimental results. The fabrication of biological tissues phantoms containing high absorbance or fluorescence nanoparticles and corresponding to specific mechanical, optical properties is an actual task. This work describes development, fabrication and characterization of such solid tissue phantoms with embedded CdSe/ZnS quantum dots, gold and upconversion nanoparticles. Luminescence of samples with CdSe/ZnS quantum dots and upconversion nanoparticles were recorded. A sample of gold nanorods was analyzed using thermal gravimetric analysis. It can be concluded that the samples are well suited for experiments on laser thermolysis.

A Review on the 3D Printing of Functional Structures for Medical Phantoms and Regenerated Tissue and Organ Applications

Abstract Medical models, or “phantoms,” have been widely used for medical training and for doctor-patient interactions. They are increasingly used for surgical planning, medical computational models, algorithm verification and validation, and medical devices development. Such new applications demand high-fidelity, patient-specific, tissue-mimicking medical phantoms that can not only closely emulate the geometric structures of human organs, but also possess the properties and functions of the organ structure. With the rapid advancement of three-dimensional (3D) printing and 3D bioprinting technologies, many researchers have explored the use of these additive manufacturing techniques to fabricate functional medical phantoms for various applications. This paper reviews the applications of these 3D printing and 3D bioprinting technologies for the fabrication of functional medical phantoms and bio-structures. This review specifically discusses the state of the art along with new developments and trends in 3D printed functional medical phantoms (i.e., tissue-mimicking medical phantoms, radiologically relevant medical phantoms, and physiological medical phantoms) and 3D bio-printed structures (i.e., hybrid scaffolding materials, convertible scaffolds, and integrated sensors) for regenerated tissues and organs.

Abstract ID: 167 Assessing the CTDIVOL and SSDE from dose profiles in cylindrical phantoms of water equivalent materials

The assessment of the Computed Tomography (CT) radiation output has become a challenge to researchers and technicians due to the rapid evolution of the technology incorporated in CT machines. To guarantee the correct performance and to avoid accidents in CT examinations, the novel CT units require the use of specific phantoms for dosimetry and imaging evaluations. Nevertheless, such phantoms are expensive or they are unavailable in the market. In this work, water equivalent materials produced in the Medical Physics and Radiation Dosimetry Group of the University of Sao Paulo [1] will be evaluated in order to demonstrate their use in phantom fabrication for dosimetry and imaging purposes. Dose profiles along the central and peripheral axis of cylindrical phantoms of water equivalent material were computed in order to assess the quantities: volume CT Dose Index ( CTDI vol ) and Size Specific Dose Estimate (SSDE). The CTDI vol and SSDE are used as CT radiation output and patient dose descriptors, respectively. Three water equivalent materials: H2O_1 (Propylene + Chloroethylene + Sodium hydroxide), H2O_2 (Propylene + Phosphorous acid + Sodium hydroxide) and H2O_3 (Polyethylene + Sodium hydroxide + Calcium Fluoride) were evaluated in this work. X-ray source models based on phase space files generated by Monte Carlo simulation for 80, 100, 120 and 140 kV. The X-ray source model was implemented following the technical specification of the GE Lightspeed Ultra CT machine (General Electric Company, Boston, USA) and it incorporates the anode self-attenuation, anode tilt and the bowtie filters for head and body examination. The CTDI vol was computed in a cylindrical phantom of 15 cm length and the SSDE was achieved varying phantom diameters of 5–40 cm. CTDI vol and SSDE results were compared with literature data for reference materials. Finally, the results of this work will be used as reference to guarantee the usefulness of the materials developed in the GDFM in the manufacture of simulators for CT quality control.

Freeform fabrication of tissue-simulating phantom for potential use of surgical planning in conjoined twins separation surgery

Preoperative assessment of tissue anatomy and accurate surgical planning is crucial in conjoined twin separation surgery. We developed a new method that combines three-dimensional (3D) printing, assembling, and casting to produce anatomic models of high fidelity for surgical planning. The related anatomic features of the conjoined twins were captured by computed tomography (CT), classified as five organ groups, and reconstructed as five computer models. Among these organ groups, the skeleton was produced by fused deposition modeling (FDM) using acrylonitrile-butadiene-styrene. For the other four organ groups, shell molds were prepared by FDM and cast with silica gel to simulate soft tissues, with contrast enhancement pigments added to simulate different CT and visual contrasts. The produced models were assembled, positioned firmly within a 3D printed shell mold simulating the skin boundary, and cast with transparent silica gel. The produced phantom was subject to further CT scan in comparison with that of the patient data for fidelity evaluation. Further data analysis showed that the produced model reassembled the geometric features of the original CT data with an overall mean deviation of less than 2 mm, indicating the clinical potential to use this method for surgical planning in conjoined twin separation surgery.

Natural Rubber Nanocomposite with Human-Tissue-Like Mechanical Characteristic

The blends of synthetic rubber and natural rubber with nanosilica were prepared using a blending technique in presence of different filler volume fraction. The effect of filler on morphological and mechanical characteristics was studied. Utilization of human cadaver in means of medical study has been commonly used primarily as tools of medical teaching and training such as surgery. Nonetheless, human cadaver brought inevitable problems. So it is necessary to find a substitute material that can be used to replace cadavers. In orthopaedics, the materials that resemble in mechanical properties to biological tissues are elastomers such as natural rubber (latex) and synthetic rubber (polyurethanes, silicones). This substitution material needs to consider the potential of Indonesia to help the development of the nation. Indonesia is the second largest country producer of natural rubber in the world. This paper aims to contribute to adjusting the mechanical properties of tissue-mimicking materials (TMMs) to the recommended range of biological tissue value and thus allow the development of phantoms with greater stability and similarity to human tissues. Repeatability for the phantom fabrication process was also explored. Characteristics were then compared to the control and mechanical characteristics of different human body part tissue. Nanosilica is the best filler to produce the best nanocomposite similarities with human tissue. We produced composites that approaching the properties of human internal tissues.

Development of thin skin mimicking bilayer solid tissue phantoms for optical spectroscopic studies.

In vivo spectroscopic measurements have the proven potential to provide important insight about the changes in tissue during the development of malignancies and thus help to diagnose tissue pathologies. Extraction of intrinsic data in the presence of varying amounts of scatterers and absorbers offers great challenges in the development of such techniques to the clinical level. Fabrication of optical phantoms, tailored to the biochemical as well as morphological features of the target tissue, can help to generate a spectral database for a given optical spectral measurement system. Such databases, along with appropriate pattern matching algorithms, could be integrated with in vivo measurements for any desired quantitative analysis of the target tissue. This paper addresses the fabrication of such soft, photo stable, thin bilayer phantoms, mimicking skin tissue in layer dimensions and optical properties. The performance evaluation of the fabricated set of phantoms is carried out using a portable fluorescence spectral measurement system. The alterations in flavin adenine dinucleotide (FAD)-a tissue fluorophore that provides important information about dysplastic progressions in tissues associated with cancer development based on changes in emission spectra-fluorescence with varied concentrations of absorbers and scatterers present in the phantom are analyzed and the results are presented. Alterations in the emission intensity, shift in emission wavelength and broadening of the emission spectrum were found to be potential markers in the assessment of biochemical changes that occur during the progression of dysplasia.

Determination of effective atomic numbers from mass attenuation coefficients of tissue-equivalent materials in the energy range 60 keV-1.33 MeV

The main aim of this study was to establish a cost-effective tissue-equivalent material for phantom fabrication. Effective atomic numbers (Zeff) and effective electron densities (Neff) were calculated based on mass attenuation coefficient values. The linear and mass attenuation coefficients of two samples of paraffin wax and NaCl compositions were measured using Si detector for NaI (Tl) detector of 1.5” resources. Radioactive source was placed in front of detector and the sample was placed between the source and the photomultiplier tube (PMT) of the detector. The real time was set for 6000 seconds. The photopeak, full width at half maximum (FWHM) and net area of photopeak were measured using Meastro software. The attenuation coefficient values obtained from this study were used to calculate Zeff and Neff of paraffin wax and NaCl compositions. The measured results were compared with the theoretical values from XCOM and ICRU Report 44. The relative percentage difference of mass attenuation coefficients between experimental and human tissue for both paraffin wax and NaCl mixture are below 5%, whereas the relative percentage difference of Zeff and Neff are above 5%. The measured values of Zeff and Neff of paraffin wax and NaCl help us to establish the optimal mixtures to fabricate a cost-effective tissue-equivalent material.

A novelty technique for the fabrication of biomedical optics phantoms with cyst-mimicking inclusions

The construction of standardised phantoms for biomedical optics experiments is still a developing research field. Particularly, the application of diffusive optics techniques to tissues with low or non-scattering heterogeneities, such as cysts, where the diffuse approximation does not apply, has been studied during the last years. The reported phantoms for mimicking cysts have inclusions that consist of hollow cylinders filled with low or non-scattering fluids, being thus more representative of a 2D geometry rather than a 3D geometry. We present here an innovative proposal, to our knowledge not reported before, for the manufacture of solid diffusive phantoms with spherical, liquid inclusions, with low or non-scattering properties, intended to reproduce cysts. To this end, we used the inverse spherification technique from the molecular gastronomy. The constructed phantoms were optically characterised by two approaches, namely whole field continuous wave transmittance imaging and time-resolved experiments, both in the near infrared at λ = 785 nm. After optical characterisation, the phantoms were also dissected, showing that the inclusions remained in place and preserved their shape after the whole fabrication process. Some results were also validated by Monte Carlo simulations.

3D Printed Abdominal Aortic Aneurysm Phantom for Image Guided Surgical Planning with a Patient Specific Fenestrated Endovascular Graft System.

With training on the patient-specific 3D printed AAA phantom, the clinical team optimized their procedural strategy. Anatomical landmarks and all devices were visible under x-ray during the simulation mimicking the clinical environment. The actual patient procedure went without complications. With advances in 3D printing, fabrication of patient specific AAA phantoms is possible. Simulation with 3D printed phantoms shows potential to inform clinical interventional procedures in addition to CTA diagnostic imaging.

Fabrication of an Ultrasound Phantom with Blood Vessel Bifurcation Applicable for Both B- and Doppler-mode Imaging

Fabrication of an Ultrasound Phantom with Blood Vessel Bifurcation Applicable for Both B- and Doppler-mode Imaging

Natural Rubber Nanocomposite as Human-Tissue-Mimicking Materials for Replacement Cadaver in Medical Surgical Practice

The utilization of human cadaver in means of medical study has been common. Nonetheless, human cadaver brought inevitable problems. Thus a substitute material is necessary to diminish the usage ofa human cadaver. Substitute material needs to heed the potency of Indonesian resources to help the country's development. As the world knows, Indonesia is the world's second largest natural rubber producer. Hence natural rubber composite was chosen as the base material, blends with some silicone rubber. The purpose of this research is to synthesize nanocomposite that has a mechanical characteristic of thehuman tissue. The precursors will be made with some variations include theoptimization type of filler (nanosilica, caolin and CaCO3), and the optimization of filler nanosilica volume fraction. The composition of the materials used is also important to observe. Scattering properties are set by adding titanium dioxide, an inexpensive and widely available scattering agent which yields a wavelength dependent scattering coefficient similar to that observed in tissue in the near infrared. Repeatability for the phantom fabrication process will be presented. This research has produced some materials that have a similar mechanical characteristic with internal human tissue characteristic.

Fabrication of Two Flow Phantoms for Doppler Ultrasound Imaging.

Flow phantoms are widely used in studies associated with Doppler ultrasound measurements, acting as an effective experimental validation system in cardiovascular-related research and in new algorithm/instrumentation development. The development of materials that match the acoustic and mechanical properties of the vascular system is of great interest while designing flow phantoms. Although recipes that meet the flow phantom standard defined by the International Electrotechnical Commission 61685 are already available in the literature, the standard procedure for material preparations and phantom fabrications has not been well established. In this paper, two types of flow phantoms, with and without blood vessel mimic, are described in detail in terms of the material preparation and phantom fabrication. The phantom materials chosen for the two phantoms are from published phantom studies, and their physical properties have been investigated previously. Both the flow phantoms have been scanned by ultrasound scanners and images from different modes are presented. These phantoms may be used in the validation and characterization of Doppler ultrasound measurements in blood vessels with a diameter above 1 mm.

Fabrication and characterization of PVCP human breast tissue-mimicking phantom for photoacoustic imaging

Human tissue-mimicking phantoms are important for characterizing and optimizing ultrasound and photoacoustic imaging systems. We demonstrated the applicability of a polyvinyl chloride plastisol (PVCP) phantom to photoacoustic imaging studies. The acoustic properties of the fabricated PVCP phantom were measured to have a sound speed of 1370 m/s, attenuation coefficient of 0.71 dB/cm/MHz, and acoustic impedance of 1.39 Mrayl. Reduced scattering coefficients, absorption coefficient, and refractive index were obtained, as 1.31 mm-1, 0.001 mm-1, and 1.636 at 780 nm by optical measurements, respectively. Therefore, the PVCP phantom was found to be similar enough to human breast tissue in photoacoustic properties.

Fabrication of a compliant phantom of the human aortic arch for use in Particle Image Velocimetry (PIV) experimentation

Abstract Compliant phantoms of the human aortic arch can mimic patient specific cardiovascular dysfunctions in vitro. Hence, phantoms may enable elucidation of haemodynamic disturbances caused by aortic dysfunction. This paper describes the fabrication of a thin-walled silicone phantom of the human ascending aorta and brachiocephalic artery. The model geometry was determined via a meta-analysis and modelled in SolidWorks before 3D printing. The solid model surface was smoothed and scanned with a 3D scanner. An offset outer mould was milled from Ebalta S-Model board. The final phantom indicated that ABS was a suitable material for the internal model, the Ebalta S-Model board yielded a rough external surface. Co-location of the moulds during silicone pour was insufficient to enable consistent wall thickness. The resulting phantom was free of air bubbles but did not have the desired wall thickness consistency.

Fabrication and characterization of biotissue-mimicking phantoms in the THz frequency range

The study revealed the most promising candidates for phantoms mimicking different biological tissues in the terahertz frequency range. Closest to biological tissues in terms of the refractive index appeared to be gelatin-based gels; in terms of the absorption coefficient they were agar-based gels. Gelatin is more stable in time, but requires special storage conditions to limit water evaporation. The dense structure of the agar-based phantom allows its use without mold and risk of damage. However, agar is a nutrient medium for bacteria and its parameters degrade even when the phantom form and water content are retained. Use of liquid suspensions of lecithin and milk powder are found to be extremely limited.

Sci‐Sat AM: Radiation Dosimetry and Practical Therapy Solutions ‐ 04: On 3D Fabrication of Phantoms and Experimental Verification of Patient Dose Computation Algorithms

Purpose:Transport based dose calculation algorithm Acuros XB (AXB) has been shown to accurately account for heterogeneities mostly through comparisons with Monte Carlo simulations. This study aims at providing additional experimental verification for AXB for flattened and unflattened clinical energies in low density phantoms of the same material.Materials and Methods:Polystyrene slabs were created using a bench‐top 3D printer. Six slabs were printed at varying densities from 0.23 g/cm3 to 0.68 g/cm3, corresponding to different density humanoid tissues. The slabs were used to form different single and multilayer geometries. Dose was calculated with AXB 11.0.31 for 6MV, 15MV flattened and 6FFF (flattening filter free) energies for field sizes of 2×2 cm2 and 5×5 cm2. The phantoms containing radiochromic EBT3 films were irradiated. Absolute dose profiles and 2D gamma analyses were performed for 96 dose planes.Results:For all single slab, multislab configurations and energies, absolute dose differences between the AXB calculation and film measurements remained <3% for both fields, with slightly poor disagreement in penumbra. The gamma index at 2% / 2mm averaged 98% in all combinations of fields, phantoms and photon energies.Conclusions:The transport based dose algorithm AXB is in good agreement with the experimental measurements for small field sizes using 6MV, 6FFF and 15MV beams adjacent to low density heterogeneous media. This work provides sufficient experimental ground to support the use of AXB for heterogeneous dose calculation purposes.

Design and Fabrication of Kidney Phantoms for Internal Radiation Dosimetry Using 3D Printing Technology

A set of 4 single-compartment kidney phantoms with filling volumes between 8 and 123 mL was designed on the basis of the outer kidney dimensions provided by MIRD pamphlet 19. After the phantoms had been printed, SPECT/CT acquisitions of 3 radionuclides (99mTc, 177Lu, and 131I) were obtained and calibration constants determined for each radionuclide-volume combination. A set of additionally manufactured spheres matching the kidney volumes was also examined to assess the influence of phantom shape and size on the calibration constants. A set of refillable, waterproof, and chemically stable kidneys and spheres was successfully manufactured. Average calibration factors for 99mTc, 177Lu, and 131I were obtained in a large source measured in air. For the largest phantom (122.9 mL), the volumes of interest had to be enlarged by 1.2 mm for 99mTc, 2.5 mm for 177Lu, and 4.9 mm for 131I in all directions to obtain calibration factors comparable to the reference. Although partial-volume effects were observed for decreasing phantom volumes (percentage difference of up to 9.8% for the smallest volume [8.6 mL]), the difference between corresponding sphere-kidney pairs was small (<1.1% for all volumes). 3D printing is a promising prototyping technique for geometry-specific calibration of SPECT/CT systems. Although the underlying radionuclide and the related collimator have a major influence on the calibration, no relevant differences between kidney-shaped and spherically shaped uniform-activity phantoms were observed. With comparably low costs and submillimeter resolution, 3D printing techniques hold the potential for manufacturing individualized anthropomorphic phantoms in many clinical applications in nuclear medicine.