ARTICLE | doi:10.20944/preprints202104.0301.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Ultrasound; phantom; rectus femoris muscle; echogenicity; training
Online: 12 April 2021 (12:50:45 CEST)
Ultrasound has become widely used as a mean to measure the rectus femoris muscle in the acute and chronic phase of critical illness. Despite its noninvasiveness and accessibility, its accuracy highly depends on the skills of the technician. However, few ultrasound phantoms for the confirmation of its accuracy or to improve technical skills exist. In this study, we created a novel phantom model and used it for investigating the accuracy of measurements and for training. Study 1 investigated how various conditions affect ultrasound measurements such as thickness, cross-sectional area, and echogenicity. Study 2 investigated if the phantom can be used for training of various health care providers in vitro and vivo. Study 1 showed that thickness, cross-sectional area, and echogenicity were affected by probe compression strength, probe angle, phantom compression, and varying equipment. Study 2 in vitro showed that using the phantom for training improved the accuracy of the measurements taken within phantom, and Study 2 in vivo showed the phantom training had a short-term effect on improving the measurement accuracy in a human volunteer. The new ultrasound phantom model revealed that various conditions affected ultrasound measurements, and phantom training improved the measurement accuracy.
REVIEW | doi:10.20944/preprints201901.0293.v1
Subject: Behavioral Sciences, Behavioral Neuroscience Keywords: phantom limb, somatotopy, brachial plexus, deafferentation rehabilitation, anesthetic block.
Online: 29 January 2019 (09:46:09 CET)
Many neuropsychological theories agree that the brain maintains a relatively persistent representation of one’s own body, as indicated by vivid “phantom” experiences. It remains unclear how the loss of sensory and motor information contributes to the presence of this representation. Here, we focus on new empirical and theoretical evidence of phantom sensations following damage to or an anesthetic block of the brachial plexus. We suggest a crucial role of this structure in understanding the interaction between peripheral and central mechanisms in health and in pathology. Studies of brachial plexus function have shed new light on how neuroplasticity enables “somatotopic interferences,” including pain and body awareness. Understanding the relations among clinical disorders, their neural substrate, and behavioral outcomes may enhance methods of sensory rehabilitation for phantom limbs.
ARTICLE | doi:10.20944/preprints201809.0342.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: origami; percutaneous biopsy; computed tomography; radiologic phantom; 3D printing
Online: 18 September 2018 (10:32:24 CEST)
The objective of this study is to preliminarily evaluate a new CT-biopsy guidance device, an origami needle guide. The device is created by laser cutting the structure from a sheet of cardboard, 3D printing two radiocontrast agent grids on to the surface and folding the structure into a rectangular prism with a viewing window. An abdominal imaging phantom was used to evaluate the device through CT imaging and the targeting of lesions for needle insertion. The lesion targeting trials resulted in a mean targeting error of 1.88 mm with a standard deviation of 0.73 mm. The device attaches to the patient and is rigid enough to adequately support standard biopsy needles, reducing the effect of gravity and the risk of laceration by the needles, making it potentially advantageous for biopsy of superficial lesions and lesions approached from a horizontal orientation. The device supports insertion of multiple needles at once, making it particularly suitable for composite ablation using multiple needles. Another advantage of the device is that it can guide off-axial needle insertion. The low-cost and disposability of the device make it well-suited for the minimally invasive image guided therapy environment.
ARTICLE | doi:10.20944/preprints202208.0494.v1
Subject: Medicine & Pharmacology, Pediatrics Keywords: hydrocephalus; shunt failure; catheter occlusion; ventricular phantom; flow/pressure performance
Online: 29 August 2022 (12:45:35 CEST)
Objective: One of the major causes of cerebral ventricular shunt failure is proximal catheter occlusion. We describe a novel ventricular cerebrospinal fluid (CSF) flow replicating system that assesses pressure and flow responses to varied degrees of catheter occlusion. Methods: Ventricular catheter performance was assessed during conditions of partial and complete occlusion. The catheters were placed into a three-dimensionally printed phantom ventricular replicating system. Artificial CSF was pumped through the ventricular system at a constant rate of 1 ml/min to mimic CSF flow, with the proximal end of the catheter in the phantom ventricle. Pressure transducer and flow rate sensors were used to measure intra-phantom pressure, outflow pressure and CSF flow rates. The catheters were also inserted into silicone tubing and pressure was measured in the same manner for comparison with the phantom. Results: Pressure measured in the phantom ventricle did not change when the outflow of the ventricular catheter was partially occluded. However, the intraventricular phantom pressure significantly increased when the outflow catheter was 100% occluded. Flow through the catheter showed no significant difference in rate with any degree of partial occlusion of the catheter. At the distal end of the partially occluded catheters, there was less pressure compared with the nonoccluded catheters. This difference in pressure in partially occluded catheters correlated with the percentage of catheter hole occlusion. Conclusions: Our model mimics physiological dynamics of the CSF flow in partially and completely obstructed ventricular catheters. We found that partial occlusion of the catheter had no effect on CSF flow rate, but did reduce outflow pressure of the catheter.
ARTICLE | doi:10.20944/preprints202208.0136.v1
Subject: Physical Sciences, Astronomy & Astrophysics Keywords: Phantom energy; LRS Bianchi type-I; $f(R,T)$ theory; $5d$ spacetimes
Online: 8 August 2022 (08:11:41 CEST)
We obtain exact solutions to the field equations for 5 dimensional LRS Bianchi type-I spacetime in $f(R,T)$ theory of gravity where specifically the following three cases are considered: (i) $f(R,T)=\mu(R+T)$, (ii) $f(R,T)=R \mu + R T \mu^2$ and (iii) $f(R,T)=R+\mu R^2+\mu T$ where $R$ and $T$ respectively the Ricci scalar and trace of the energy-momentum tensor. It is found that the equation of state (EOS) parameter $w$ is governed by the parameter $\mu$ involved in the $f(R,T)$ expressions. We fine-tune the parameter $\mu$ to obtain effect of phantom energy in the model, however we also restrict this parameter to obtain a stable model of the universe. It is noted that the model isotropizes at finite cosmic time.
ARTICLE | doi:10.20944/preprints201812.0347.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: Nodules detection, neuromorphic touch, polymeric phantom, sensory augmentation, tactile telepresence, teleoperation, tele-palpation, vibro-tactile stimulation
Online: 28 December 2018 (12:31:26 CET)
The advancements in the study of the human sense of touch are fueling the field of haptics. This is paving the way for augmenting the sensory perception during objects palpation in tele-surgery, and reproducing the information through tactile feedback. Here, we present a novel tele-palpation apparatus that enables the user to detect nodules with various distinct stiffness buried in an ad-hoc polymeric phantom. The contact force measured by the platform was encoded using a neuromorphic model and reproduced on the index fingertip of a remote user through a haptic glove embedding a piezoelectric disk. We assessed the effectiveness of this feedback in allowing nodule identification under two experimental conditions of real-time telepresence: In Line of Sight (ILS), where the platform was placed in the visible range of a user; and the more demanding Not In Line of Sight (NILS), with the platform being 50 km apart. We found that the entailed percentage of identification was higher for stiffer inclusions with respect to the softer ones (average of 74% within the duration of the task), in both telepresence conditions evaluated. These promising results call for further exploration of tactile augmentation technology for telepresence in medical interventions.
ARTICLE | doi:10.20944/preprints201904.0013.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: cancer nodules detection; phantom; stiffness analysis; ultrasound analysis; visual analysis; automatic robotic platform; remote support for pathologists
Online: 1 April 2019 (13:26:13 CEST)
This study presents a platform for ex-vivo detection of cancer nodules, addressing automation of medical diagnoses in surgery and associated histological analyses. The proposed approach takes advantage of the property of cancer to alter the mechanical and acoustical properties of tissues, because of changes in stiffness and density. A force sensor and an ultrasound probe were combined to detect such alterations during force-regulated indentations. To explore the specimens, regardless of their orientation and shape, a scanned area of the test sample was defined using shape recognition applying optical background subtraction to the images captured by a camera. The motorized platform was validated using seven phantom tissues, simulating the mechanical and acoustical properties of ex-vivo diseased tissues, including stiffer nodules that can be encountered in pathological conditions during histological analyses. Results demonstrated the platform’s ability to automatically explore and identify the inclusions in the phantom. Overall, the system was able to correctly identify up to 90.3% of the inclusions by means of stiffness in combination with ultrasound measurements, paving pathway towards robotic palpation during intraoperative examinations.
ARTICLE | doi:10.20944/preprints201807.0597.v1
Subject: Materials Science, Polymers & Plastics Keywords: Keywords: Radiotherapy eye-phantom; radio-fluorogenic gel; x-ray beam imaging; 3D radiation imaging; polymer gel dosimetry.
Online: 30 July 2018 (15:41:48 CEST)
Abstract: We have filled a 24 mm diameter glass sphere with a transparent polymer-gel that is radio-fluorogenic, i.e. it becomes (permanently) fluorescent when irradiated, with an intensity proportional to the local dose deposited. The gel consists of >99.9% tertiary-butyl acrylate (TBA) pre-polymerized to ~15% conversion, and ~100 ppm maleimido-pyrene (MPy). Its dimensions and physical properties are close to those of the vitreous body of the human eye. We have irradiated the gel with a 3 mm diameter, 200 kVp X-ray beam with a dose rate of ~1 Gy/min. A 3D (video) view of the beam within the gel has been constructed from tomographic images obtained by scanning the sample through a thin sheet of UV light. To minimize optical artifacts, the cell was immersed in a square tank containing a refractive-index-matching medium. The 20%-80% penumbra of the beam was determined to be ~0.4 mm. The research was a preparatory investigation of the possibility of using the method to monitor the millimetre diameter proton pencil beams used in ocular radiotherapy.
ARTICLE | doi:10.20944/preprints201807.0053.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: Intra-body communication; path loss; microwave probes; channel characterization; fat tissue; ex-vivo; phantom; dielectric properties; topology optimization.
Online: 3 July 2018 (15:08:56 CEST)
In this paper, we investigate the use of fat tissue as a communication channel between in-body, implanted devices at R-band frequencies (1.7–2.6 GHz). The proposed fat channel is based on an anatomical model of the human body. We propose a novel probe that is optimized to efficiently radiate the R-band frequencies into the fat tissue. We use our probe to evaluate the path loss of the fat channel by studying the channel transmission coefficient over the R-band frequencies. We conduct extensive simulation studies and validate our results by experimentation on phantom and ex-vivo porcine tissue, with good agreement between simulations and experiments. We demonstrate a performance comparison between the fat channel and similar waveguide structures. Our characterization of the fat channel reveals propagation path loss of 1.4 dB and 3.8 dB per 20 mm for phantom and ex-vivo porcine tissue, respectively. These results demonstrate that fat tissue can be used as a communication channel for high data rate intra-body networks.