Training Phantom Research Articles

Creating Custom Phantoms for Ultrasound-Guided Fine-Needle Aspiration Biopsy Training

Abstract Ultrasound-guided fine-needle aspiration (US-FNA) is superior to conventional fine-needle aspiration biopsies and when performed by cytopathologists yields higher diagnostic rates than when performed by nonpathologists. Ultrasound-guided fine-needle aspiration allows operators to perform targeted biopsies while avoiding critical nearby structures, decreasing the risk of procedural complications. Traditionally, cytopathology training programs have purchased costly commercial phantom models on which to train residents and fellows and provide opportunities for cytopathologists to practice their US-FNA technique. While phantoms are effective training tools, they are sold by several vendors at well over $1000 and have limited life spans as with continued use needle track marks obscure the ultrasound's view of practice targets. We developed and tested 2 cost-effective and easy-to-make recipes for creating your own US-FNA phantoms in-house. The first recipe features a gelatin-based phantom that can be made from ingredients available at any local grocery store. The second recipe for a silicon-based phantom is more durable but requires some ingredients that may be purchased online or at specialty costume shops. Finally, we share ideas and directions for making target lesions to be placed inside your phantoms and invite readers to harness their creativity to customize these phantom recipes to suit their practices' and trainees' needs.

Non-animal ultrasound phantoms for device testing and training

A phantom is a physical object to simplify device testing and clinical training. An industrial device is more reliable for device testing in quality control procedures, though it is expensive. When precision requirements are not so strict as it occurs in training, people prefer to use home-made phantoms, though many of these artisanal methods use animal products. The current paper illustrates a few alternative vegetal phantoms. Agar is a widely used material in laboratory investigations and can be used to contain ultrasound targets. Another quick and effective alternative is given by tofu. Target sizes and flow ultrasound measurements can be easily effected using a phantom and training can be planned and repeated as much as required. The current paper shows how low-cost animal phantoms can be perfectly replaced by low-cost vegetal ones for clinical and training purposes. Vegetal phantoms can be classified as possible realizations of the Replace, the 1st of the 3Rs pre-requisites for non-animal experiments.

Low-cost three-dimensional printed phantom for neuraxial anesthesia training: Development and comparison to a commercial model.

Neuraxial anesthesia (spinal and epidural anesthesia) procedures have significant learning curves and have been traditionally taught at the bed side, exposing patients to the increased risk associated with procedures done by novices. Simulation based medical education allows trainees to repeatedly practice and hone their skills prior to patient interaction. Wide-spread adoption of simulation-based medical education for procedural teaching has been slow due to the expense and limited variety of commercially available phantoms. Free/Libre/open-source (FLOS) software and desktop 3D printing technologies has enabled the fabrication of low-cost, patient-specific medical phantoms. However, few studies have evaluated the performance of these devices compared to commercially available phantoms. This paper describes the fabrication of a low-cost 3D printed neuraxial phantom based on computed tomorography (CT) scan data, and expert validation data comparing this phantom to a commercially available model.MethodsAnonymized CT DICOM data was segmented to create a 3D model of the lumbar spine. The 3D model was modified, placed inside a digitally designed housing unit and fabricated on a desktop 3D printer using polylactic acid (PLA) filament. The model was filled with an echogenic solution of gelatin with psyllium fiber. Twenty-two staff anesthesiologists performed a spinal and epidural on the 3D printed simulator and a commercially available Simulab phantom. Participants evaluated the tactile and ultrasound imaging fidelity of both phantoms via Likert-scale questionnaire.ResultsThe 3D printed neuraxial phantom cost $13 to print and required 25 hours of non-supervised printing and 2 hours of assembly time. The 3D printed phantom was found to be less realistic to surface palpation than the Simulab phantom due to fragility of the silicone but had significantly better fidelity for loss of resistance, dural puncture and ultrasound imaging than the Simulab phantom.ConclusionLow-cost neuraxial phantoms with fidelity comparable to commercial models can be produced using CT data and low-cost infrastructure consisting of FLOS software and desktop 3D printers.

Development of a Standardized Cranial Phantom for Training and Optimization of Functional Stereotactic Operations

Background: In recent years, simulations based on phantom models have become increasingly popular in the medical field. In the field of functional and stereotactic neurosurgery, a cranial phantom would be useful to train operative techniques, such as stereo-electroencephalography (SEEG), to establish new methods as well as to develop and modify radiological techniques. In this study, we describe the construction of a cranial phantom and show examples for it in stereotactic and functional neurosurgery and its applicability with different radiological modalities. Methods: We prepared a plaster skull filled with agar. A complete operation for deep brain stimulation (DBS) was simulated using directional leads. Moreover, a complete SEEG operation including planning, implantation of the electrodes, and intraoperative and postoperative imaging was simulated. Results: An optimally customized cranial phantom is filled with 10% agar. At 7°C, it can be stored for approximately 4 months. A DBS and an SEEG procedure could be realistically simulated. Lead artifacts can be studied in CT, X-ray, rotational fluoroscopy, and MRI. Conclusions: This cranial phantom is a simple and effective model to simulate functional and stereotactic neurosurgical operations. This might be useful for teaching and training of neurosurgeons, establishing operations in a new center and for optimization of radiological examinations.

A prototype assembled 3D-printed phantom of the glenohumeral joint for fluoroscopic-guided shoulder arthrography

To describe the methodology of constructing a three-dimensional (3D) printed model of the glenohumeral joint, to serve as an interventional phantom for fluoroscopy-guided shoulder arthrography training. The osseous structures, intra-articular space and skin surface of the shoulder were digitally extracted as separate 3D meshes from a normal CT arthrogram of the shoulder, using commercially available software. The osseous structures were 3D-printed in gypsum, a fluoroscopically radiopaque mineral, using binder jet technology. The joint capsule was 3D printed with rubber-like TangoPlus material, using PolyJet technology. The capsule was secured to the humeral head and glenoid to create a sealed intra-articular space. A polyamide mold of the skin was printed using selective laser sintering. The joint was stabilized inside the mold, and the surrounding soft tissues were cast in silicone of varying densities. Fluoroscopically-guided shoulder arthrography was performed using anterior, posterior, and rotator interval approaches. CT arthrographic imaging of the phantom was also performed. A life-size phantom of the glenohumeral joint was constructed. The radiopaque osseous structures replicated in-vivo osseous corticomedullary differentiation, with dense cortical bone and less dense medullary cancellous bone. The glenoid labrum was successfully integrated into the printed capsule, and visualized on CT arthrography. The phantom was repeatedly used to perform shoulder arthrography using all three conventional approaches, and simulated the in vivo challenges of needle guidance. 3D printing of a complex capsule, such as the glenohumeral joint, is possible with this technique. Such a model can serve as a valuable training tool.

Three-Dimensional Surface Point Cloud Ultrasound for Better Understanding and Transmission of Ultrasound Scan Information.

Ultrasound is notoriously plagued by high user dependence. There is a steep drop-off in information in going from what the sonographer sees during image acquisition and what the interpreting radiologist is able to view at the reading station. One countermeasure is probe localization and tracking. Current implementations are too difficult and expensive to use and/or do not provide adequate detail and perspective. The aim of this work was to demonstrate that a protocol combining surface three-dimensional photographic imaging with traditional ultrasound images may be a solution to the problem of probe localization, this approach being termed surface point cloud ultrasound (SPC-US). Ultrasound images were obtained of major vessels in an ultrasound training phantom, while simultaneously obtaining surface point cloud (SPC) 3D photographic images, with additional scanning performed on the right forearm soft tissues, kidneys, chest, and pelvis. The resulting sets of grayscale/color Doppler ultrasound and SPC images are juxtaposed and displayed for interpretation in a manner analogous to current text-based annotation or computer-generated stick figure probe position illustrations. Clearly demonstrated is that SPC-US better communicates information of probe position and orientation. Overall, it is shown that SPC-US provides much richer image representations of probe position on the patients than the current prevailing schemes. SPC-US turns out to be a rather general technique with many anticipated future applications, though only a few sample applications are illustrated in the present work.

Patient-specific cardiac phantom for clinical training and preprocedure surgical planning.

Minimally invasive mitral valve repair procedures including MitraClip® are becoming increasingly common. For cases of complex or diseased anatomy, clinicians may benefit from using a patient-specific cardiac phantom for training, surgical planning, and the validation of devices or techniques. An imaging compatible cardiac phantom was developed to simulate a MitraClip® procedure. The phantom contained a patient-specific cardiac model manufactured using tissue mimicking materials. To evaluate accuracy, the patient-specific model was imaged using computed tomography (CT), segmented, and the resulting point cloud dataset was compared using absolute distance to the original patient data. The result, when comparing the molded model point cloud to the original dataset, resulted in a maximum Euclidean distance error of 7.7mm, an average error of 0.98mm, and a standard deviation of 0.91mm. The phantom was validated using a MitraClip® device to ensure anatomical features and tools are identifiable under image guidance. Patient-specific cardiac phantoms may allow for surgical complications to be accounted for preoperative planning. The information gained by clinicians involved in planning and performing the procedure should lead to shorter procedural times and better outcomes for patients.

New approach of ultra-focal brachytherapy for low- and intermediate-risk prostate cancer with custom-linked I-125 seeds: A feasibility study of optimal dose coverage

PurposeTo present the feasibility study of optimal dose coverage in ultra-focal brachytherapy (UFB) with multiparametric MRI for low- and intermediate-risk prostate cancer. Methods and MaterialsUFB provisional dose plans for small target volumes (<7 cc) were calculated on a prostate training phantom to optimize the seeds number and strength. Clinical UFB consisted in a contour-based nonrigid registration (MRI/Ultrasound) to implant a fiducial marker at the location of the tumor focus. Dosimetry was performed with iodine-125 seeds and a prescribed dose of 160 Gy. On CT scans acquired at 1 month, dose coverage of 152 Gy to the ultra-focal gross tumor volume was evaluated. Registrations between magnetic resonance and CT scans were assessed on the first 8 patients with three software solutions: VariSeed, 3D Slicer, and Mirada, and quantitative evaluations of the registrations were performed. Impact of these registrations on the initial dose matrix was performed. ResultsMean differences between simulated dose plans and extrapolated Bard nomogram for UFB volumes were 36.3% (26–56) for the total activity, 18.3% (10–30) for seed strength, and 22.5% (16–38) for number of seeds. Registration method implemented in Mirada performed significantly better than VariSeed and 3D Slicer (p = 0.0117 and p = 0.0357, respectively). For dose plan evaluation between Mirada and VariSeed, D100% (Gy) for ultra-focal gross tumor volume had a mean difference of 28.06 Gy, mean values being still above the objective of 152 Gy. D90% for the prostate had a mean difference of 1.17 Gy. For urethra and rectum, dose limits were far below the recommendations. ConclusionsThis UFB study confirmed the possibility to treat with optimal dose coverage target volumes smaller than 7 cc.

Silicone-based composite materials simulate breast tissue to be used as ultrasonography training phantoms

A silicone-based composite breast phantom is fabricated to be used as an education model in ultrasonography training. A matrix of silicone formulations is tracked to mimic the ultrasonography and tactile response of human breast tissue. The performance of two different additives: (i) silicone oil and (ii) vinyl-terminated poly (dimethylsiloxane) (PDMS) are monitored by a home-made acoustic setup. Through the use of 75 wt% vinyl-terminated PDMS in two-component silicone elastomer mixture, a sound velocity of 1.29 ± 0.09 × 103 m/s and an attenuation coefficient of 12.99 ± 0.08 dB/cm—values those match closely to the human breast tissue—are measured with 5 MHz probe. This model can also be used for needle biopsy as well as for self-exam trainings. Herein, we highlight the fabrication of a realistic, durable, accessible, and cost-effective training platform that contains skin layer, inner breast tissue, and tumor masses.

Special Ultrasound Phantom for Interventional Training: Construction, Advantages, and Application.

Interventional radiology procedures are becoming more challenging over time; thus, there is a need for excellent and reliable training methods. Training on live patients is neither safe nor an ethical solution. Alternatives are many and varied, but the most popular is ultrasound guided simulators. This report shows how a simple, homemade, low-cost phantom material, and construction modules can provide several advantages over ordinary gelatin phantoms. A new layering technique and target synthesis are described for the biopsy phantom, including tips on decreasing the needle pass artifact as well as controlling the mixture echogenicity.

Cryogenic 3D Printing of Super Soft Hydrogels

Conventional 3D bioprinting allows fabrication of 3D scaffolds for biomedical applications. In this contribution we present a cryogenic 3D printing method able to produce stable 3D structures by utilising the liquid to solid phase change of a composite hydrogel (CH) ink. This is achieved by rapidly cooling the ink solution below its freezing point using solid carbon dioxide (CO2) in an isopropanol bath. The setup was able to successfully create 3D complex geometrical structures, with an average compressive stiffness of O(1) kPa (0.49 ± 0.04 kPa stress at 30% compressive strain) and therefore mimics the mechanical properties of the softest tissues found in the human body (e.g. brain and lung). The method was further validated by showing that the 3D printed material was well matched to the cast-moulded equivalent in terms of mechanical properties and microstructure. A preliminary biological evaluation on the 3D printed material, coated with collagen type I, poly-L-lysine and gelatine, was performed by seeding human dermal fibroblasts. Cells showed good attachment and viability on the collagen-coated 3D printed CH. This greatly widens the range of applications for the cryogenically 3D printed CH structures, from soft tissue phantoms for surgical training and simulations to mechanobiology and tissue engineering.

Pilot Investigation into the Use of an Anthropomorphic Breast Sonography Phantom as a Training and Assessment Tool

A device for the training and quantitative assessment of the competency of trainee radiologists in the technically challenging area of breast sonography was developed and evaluated. Currently, suitable commercially available devices are lacking, and there is a growing realization that the reliance on direct exposure to patients for learning may not represent best practice from either the trainees' or patients' perspective. Three devices (PI, PII and PIII) were designed to produce very realistic sonographic images of breast morphology with a range of embedded pathologies. The pilot evaluation used a case study research design to evaluate the role of the anthropomorphic breast sonography training device in training and assessment in a clinical environment. Through the case study, it was possible to evaluate the process and relationships when using this type of training intervention for a small group of radiology resident trainees. The investigation involved a baseline assessment of trainees' (n = 4) ability to detect and characterize all lesions in PI, followed by a 4-wk training period on PII and a post-training assessment using PIII. The evaluation revealed an improvement of 30% ± 8% in the trainee's performance from pre- to post-training. It was expected that the performance of the trainees would improve as the training phantom described in this study aligns with the learning theory of constructivism and fits the ideal specifications of a medical training device in terms of its realism and facilitation of self-directed learning and deliberate practice of the trainees. The device provides a useful platform upon which training and assessment can be facilitated.

An Easy-to-Make, Low-Cost Ultrasound Phantom for Simulation Training in Abscess Identification and Aspiration.

We have created a low-cost and easy to make phantom for abscess identification using point-of-care ultrasound. The phantom also allows needle tracking and abscess aspiration using ultrasound guidance.

Optical Guidance Systems for Epidural Space Identification

Epidurals are the most diffused loco-regional techniques for the relief of operative, postoperative, and chronic pain and are used for about 50% of deliveries. Currently, doctors still identify epidural space relying on subjective perception, by using “blind” manual techniques to which are associated failure rate up to 7%. In the last years, many systems aimed at assisting and guiding the placement of epidural needle have been proposed. In particular, optical systems basically rely on the integration inside the epidural needle lumen of optical fiber probes providing real-time discrimination of differing tissue types during needle penetration. In this study, aside of providing an exhaustive overview on the systems proposed so far, we also report on a novel sensorized medical needle, based on the judicious integration of a fiber Bragg grating sensor inside the epidural needle lumen. Our device, by providing continuous and real-time measurements of the pressure experienced by the needle tip during its advancement, is able to effectively detect the needle passage from one tissue to the other. A pilot study carried out on an epidural training phantom demonstrates the validity of our approach for making the needle placement into the epidural space easier and safer.

A training phantom for ultrasound-guided boiling histotripsy therapy

Boiling histotripsy (BH) uses millisecond-long focused ultrasound pulses with shocks to mechanically disrupt targeted tissue under real-time ultrasound monitoring. However, adipose tissue and ribs can interfere with BH therapy through aberration, absorption, and diffraction. Here we introduce a robust abdominal wall phantom that includes fat, muscle, and rib layers for demonstrating the use of BH and investigating the impact of anatomic structures on treatment success. The skin is a silicone sheet; the fat and muscle layers are poly-vinyl alcohol phantoms with irregular-shaped walls; the ribs are 3D-printed sections from a human model anatomically relevant to liver or kidney treatments. The target is a transparent alginate or polyacrylamide gel that allows visualization of the lesion. The pieces are assembled in a water-filled container providing coupling between layers and allowing components to be shifted in position relative to the transducer. A BH transducer (1.2 MHz, 12.5 cm focal length, f# = 1) containing an imaging probe in its central opening was used for initial phantom assessment. Preliminary results show that each layer impacts the beam in ways similar to observations from in vivo and ex vivo experiments. [Work supported by NSBRI through NASA NCC 9-58, NIH RO1EB007643, K01EB015745, and K01DK104854.]

3D printed ultrasound phantoms for clinical training

Ultrasound is a ubiquitous, portable structural imaging technique which is used to provide visual feedback for a range of diagnostic and surgical techniques. Training for these techniques demands a range of teaching models tailored for each application. Existing anatomical models are often overly simple or prohibitively expensive, causing difficulties in obtaining patient or procedure specific models. In this study we present ultrasonic rib phantoms for clinical teaching and training purposes, fabricated by three-dimensional (3D) printing technologies. Models were produced using freely available software and data, and their effectiveness as teaching phantoms evaluated using clinical ultrasound scans of the phantoms.

3D printed ultrasound phantoms for clinical training

Ultrasound is a ubiquitous, portable structural imaging technique which is used to provide visual feedback for a range of diagnostic and surgical techniques. Training for these techniques demands a range of teaching models tailored for each application. Existing anatomical models are often overly simple or prohibitively expensive, causing difficulties in obtaining patient or procedure specific models. In this study we present ultrasonic rib phantoms for clinical teaching and training purposes, fabricated by three-dimensional (3D) printing technologies. Models were produced using freely available software and data, and their effectiveness as teaching phantoms evaluated using clinical ultrasound scans of the phantoms.

Placenta Vasculature 3D Printed Imaging and Teaching Phantoms

Three-dimensional printing makes it possible to create patient-specific, complex anatomical geometries that can be used for training, teaching and surgical planning. The human placenta is a vital organ that transports nutrients from the mothers' uterine circulation to the fetus via a complex vasculature. Complications of the fetal vasculature are increasingly being imaged with ultrasound and treated before birth using invasive fetal therapy. There is a need for human placenta training phantoms such as placental anastomoses that occur in monochorionic twin pregnancy and can cause twin-to-twin transfusion syndrome and fetal death, if untreated. In this study we developed two phantoms based on the human placenta using 3D printing technology: an ultrasound imaging phantom and an anatomical teaching model.

Placenta Vasculature 3D Printed Imaging and Teaching Phantoms

Three-dimensional printing makes it possible to create patient-specific, complex anatomical geometries that can be used for training, teaching and surgical planning. The human placenta is a vital organ that transports nutrients from the mothers' uterine circulation to the fetus via a complex vasculature. Complications of the fetal vasculature are increasingly being imaged with ultrasound and treated before birth using invasive fetal therapy. There is a need for human placenta training phantoms such as placental anastomoses that occur in monochorionic twin pregnancy and can cause twin-to-twin transfusion syndrome and fetal death, if untreated. In this study we developed two phantoms based on the human placenta using 3D printing technology: an ultrasound imaging phantom and an anatomical teaching model.

Ultrasound Training Phantoms for Pathologist Performed Ultrasound-Guided Fine Needle Aspiration

Ultrasound Training Phantoms for Pathologist Performed Ultrasound-Guided Fine Needle Aspiration