Thermal grill conditioning: Effect on contact heat evoked potentials.

The 'thermal grill illusion' (TGI) is a unique cutaneous sensation of unpleasantness, induced through the application of interlacing warm and cool stimuli. While previous studies have investigated optimal parameters and subject characteristics to evoke the illusion, our aim was to examine the modulating effect as a conditioning stimulus. A total of 28 healthy control individuals underwent three testing sessions on separate days. Briefly, 15 contact heat stimuli were delivered to the right hand dorsum, while the left palmar side of the hand was being conditioned with either neutral (32 °C), cool (20 °C), warm (40 °C), or TGI (20/40 °C). Rating of perception (numeric rating scale: 0-10) and evoked potentials (i.e., N1 and N2P2 potentials) to noxious contact heat stimuli were assessed. While cool and warm conditioning decreased cortical responses to noxious heat, TGI conditioning increased evoked potential amplitude (N1 and N2P2). In line with other modalities of unpleasant conditioning (e.g., sound, visual, and olfactory stimulation), cortical and possibly sub-cortical modulation may underlie the facilitation of contact heat evoked potentials.

A novel infusion-drainage device to assess lower urinary tract function in neuro-imaging.

OBJECTIVE: To evaluate the applicability and precision of a novel infusion-drainage device (IDD) for standardized filling paradigms in neuro-urology and functional magnetic resonance imaging (fMRI) studies of lower urinary tract (LUT) function/dysfunction. SUBJECTS/PATIENTS AND METHODS: The IDD is based on electrohydrostatic actuation which was previously proven feasible in a prototype setup. The current design includes hydraulic cylinders and a motorized slider to provide force and motion. Methodological aspects have been assessed in a technical application laboratory as well as in healthy subjects (n=33) and patients with LUT dysfunction (n=3) undergoing fMRI during bladder stimulation. After catheterization, the bladder was pre-filled until a persistent desire to void was reported by each subject. The scan paradigm comprised automated, repetitive bladder filling and withdrawal of 100 mL body warm (37 °C) saline, interleaved with rest and sensation rating. Neuroimaging data were analysed using Statistical Parametric Mapping version 12 (SMP12). RESULTS: Volume delivery accuracy was between 99.1±1.2% and 99.9±0.2%, for different flow rates and volumes. Magnetic resonance (MR) compatibility was demonstrated by a small decrease in signal-to-noise ratio (SNR), i.e. 1.13% for anatomical and 0.54% for functional scans, and a decrease of 1.76% for time-variant SNR. Automated, repetitive bladder-filling elicited robust (P = 0.05, family-wise error corrected) brain activity in areas previously reported to be involved in supraspinal LUT control. There was a high synchronism between the LUT stimulation and the blood oxygenation level-dependent (BOLD) signal changes in such areas. CONCLUSION: We were able to develop an MR-compatible and MR-synchronized IDD to routinely stimulate the LUT during fMRI in a standardized manner. The device provides LUT stimulation at high system accuracy resulting in significant supraspinal BOLD signal changes in interoceptive and LUT control areas in synchronicity to the applied stimuli. The IDD is commercially available, portable and multi-configurable. Such a device may help to improve precision and standardization of LUT tasks in neuro-imaging studies on supraspinal LUT control, and may therefore facilitate multi-site studies and comparability between different LUT investigations in the future.

Design and Application of a New Automated Fluidic Visceral Stimulation Device for Human fMRI Studies of Interoception.

Mapping the brain centers that mediate the sensory-perceptual processing of visceral afferent signals arising from the body (i.e., interoception) is useful both for characterizing normal brain activity and for understanding clinical disorders related to abnormal processing of visceral sensation. Here, we report a novel closed-system, electrohydrostatically driven master-slave device that was designed and constructed for delivering controlled fluidic stimulations of visceral organs and inner cavities of the human body within the confines of a 3T magnetic resonance imaging (MRI) scanner. The design concept and performance of the device in the MRI environment are described. In addition, the device was applied during a functional MRI (fMRI) investigation of visceral stimulation related to detrusor distention in two representative subjects to verify its feasibility in humans. System evaluation tests demonstrate that the device is MR-compatible with negligible impact on imaging quality [static signal-to-noise ratio (SNR) loss <2.5% and temporal SNR loss <3.5%], and has an accuracy of 99.68% for flow rate and 99.27% for volume delivery. A precise synchronization of the stimulus delivery with fMRI slice acquisition was achieved by programming the proposed device to detect the 5 V transistor-transistor logic (TTL) trigger signals generated by the MRI scanner. The fMRI data analysis using the general linear model analysis with the standard hemodynamic response function showed increased activations in the network of brain regions that included the insula, anterior and mid-cingulate and lateral prefrontal cortices, and thalamus in response to increased distension pressure on viscera. The translation from manually operated devices to an MR-compatible and MR-synchronized device under automatic control represents a useful innovation for clinical neuroimaging studies of human interoception.

Risk to fragmented DNA in dry, wet, and frozen states from computed tomography: a comparative theoretical study.

Computed tomography represents the gold standard in forensic and palaeopathological diagnosis. However, the X-rays used may affect the DNA quality through fragmentation and loss of genetic information. Previous work showed that the effects of ionizing radiation on dry DNA are non-significant with P < 10(-8), which cannot be detected by means of polymerase chain reaction methods. In the present paper, complete analytical model that characterizes radiation effects on fragmented DNA in dry, wet, and frozen states is described. Simulation of radiation tracks in water phantom cells was performed using the Geant4-DNA toolkit. Cell hits by electrons with energies between 5 and 20 keV were simulated, and the formation of radiolytic products was assessed at a temperature of 298 K. The diffusion coefficient and the mean square displacement of reactive species were calculated by Stokes-Einstein-Smoluchowski relations at 273 K. Finally, DNA fragment damage was estimated using the density distribution of fragments calculated from atomic force microscopy images. The lowest probability of radiation-induced DNA damage was observed for dry state, with a range from 2.5 × 10(-9) to 7.8 × 10(-12) at 298 K, followed by that for frozen state, with a range from 0.9 to 4 × 10(-7) at 273 K. The highest probability of radiation-induced DNA damage was demonstrated for fragmented DNA in wet state with a range from 2 to 9 × 10(-7) at 298 K. These results significantly improve the interpretation of CT imaging in future studies in forensic and palaeopathological science.

Modeling ancient Egyptian mummification on fresh human tissue: macroscopic and histological aspects.

Many studies have been concerned with the ancient Egyptian mummification method; nevertheless, little effort has been made to explore it experimentally. The goal of this study is to apply evidence-based diagnostic criteria and state-of-the art methodology in order to improve knowledge on soft tissues preservation and postmortem alterations. Two human lower limbs (LL) from a female donor were (1) "naturally" mummified by dry heat and (2) artificially in natron. At specific time intervals a macroscopic and radiological examination of the LL was performed and skin and muscle samples were taken for histological and biomolecular analysis. Temperature, humidity, pH, and weight of the LL were systematically measured. The mummification by dry heat was stopped after 7 days due to unexpected lack of mummification progress. The mummification in natron was completed successfully after 208 days. The humidity, the external temperature, and the pH were proven with Pearson correlation and principal component analysis as important factors for the mummification process. The steady removal of water from the tissues through the natron has prevented the putrefaction. This is also evident in the absence of bacteria or fungi through the microbiological analysis. The histological analysis revealed very good preservation of the skin and the muscle tissues. In the muscular sample certain degree of structural disintegration can be seen, particularly affecting the epimysium whilst in the skin samples the epidermis, especially the stratum corneum, is mostly affected. The samples show better preservation compared with ancient Egyptian sections and other mummified tissues from historic or forensic context.

Design of an fMRI-compatible optical touch stripe based on frustrated total internal reflection.

Previously we developed a low-cost, multi-configurable handheld response system, using a reflective-type intensity modulated fiber-optic sensor (FOS) to accurately gather participants' behavioral responses during functional magnetic resonance imaging (fMRI). Inspired by the popularity and omnipresence of the fingertip-based touch sensing user interface devices, in this paper we present the design of a prototype fMRI-compatible optical touch stripe (OTS) as an alternative configuration. The prototype device takes advantage of a proven frustrated total internal reflection (FTIR) technique. By using a custom-built wedge-shaped optically transparent acrylic prism as an optical waveguide, and a plano-concave lens to provide the required light beam profile, the position of a fingertip touching the surface of the wedge prism can be determined from the deflected light beams that become trapped within the prism by total internal reflection. To achieve maximum sensitivity, the optical design of the wedge prism and lens were optimized through a series of light beam simulations using WinLens 3D Basic software suite. Furthermore, OTS performance and MRI-compatibility were assessed on a 3.0 Tesla MRI scanner running echo planar imaging (EPI) sequences. The results show that the OTS can detect a touch signal at high spatial resolution (about 0.5 cm), and is well suited for use within the MRI environment with average time-variant signal-to-noise ratio (tSNR) loss < 3%.

An fMRI-compatible multi-configurable handheld response system using an intensity-modulated fiber-optic sensor.

Functional magnetic resonance imaging (fMRI) data should be interpreted in combination and in the context of relevant behavioral measurements. However, the strong magnetic environment of MRI scanner and the supine position of participants in the scanner significantly limit how participants' behavioral responses are recorded. This paper presents the design of a low-cost handheld response system (HRS) with a multi-configurable optomechanical design that utilizes a reflective-type intensity modulated fiber-optic sensor (FOS) and a programmable visual interface to accurately gather participants' behavioral responses during an fMRI experiment. Considering the effects of an input unit design on the participants' performance efficiency across age groups and physical and neurological (dis)ability, the optomechanical system is designed to provide flexibility in the range of an input module with easy change-out feature. Specifically, the input unit can be configured as a binary module such as push buttons or as an analog input device including a scrolling wheel, and one-dimensional joystick (lever arm). To achieve MRI-compatibility, all parts of the unit that are used inside the scanner bore are built from nonferromagnetic and off-the-shelf plastic materials. The MRI compatibility was evaluated on a 3.0 Tesla MRI scanner running echo planar imaging (EPI) and the average time-variant signal-to-noise ratio (tSNR) loss is limited to 2%.

"Modeling ancient Egyptian embalming": radiological assessment of experimentally mummified human tissue by CT and MRI.

OBJECTIVE: To assess changes in different tissues during the process of artificial mummification by natron using computed tomography (CT) and magnetic resonance imaging (MRI), and to translate the results to image interpretation in paleoradiological studies of ancient mummies. MATERIALS AND METHODS: A human lower limb (LL) was amputated from a female donor 24 h post-mortem and mummified by artificial natron (54 % NaCl, 16 % Na2SO4, 18 % Na2CO3 12 % NaHCO3) in ancient Egyptian style. The LL was kept in a fume hood at 16-25 °C and 30-75 % relative humidity. CT and MRI were performed at specific intervals with quantitative evaluation of Hounsfield units (HU) and signal intensities (SI). RESULTS: Evaluated tissues showed different HU and SI changes during the experimental mummification. All tissues revealed an overall but varying increase of HU in CT examinations. All tissues except for the compact bone revealed an overall but varying decrease of SI in the IR and T2-weighted sequences of the MRI. Typical findings included a distinct increase of HU in the cutis at the end of the study and a temporary increase of SI in the IR and T2-weighted sequences in all muscle groups. CONCLUSIONS: Radiological findings showed a regular, controlled and effective dehydration by the applied natron without detectable putrefaction. Evaluated tissues revealed different radiological changes during the experiment, which altogether led to preservation of the tissues without radiologically identifiable destruction. The cutis revealed radiological signs of direct interaction with the natron in the form of covering and possibly permeation.

Direct action of radiation on mummified cells: modeling of computed tomography by Monte Carlo algorithms.

X-ray imaging is a nondestructive and preferred method in paleopathology to reconstruct the history of ancient diseases. Sophisticated imaging technologies such as computed tomography (CT) have become common for the investigation of skeletal disorders in human remains. Researchers have investigated the impact of ionizing radiation on living cells, but never on ancient cells in dry tissue. The effects of CT exposure on ancient cells have not been examined in the past and may be important for subsequent genetic analysis. To remedy this shortcoming, we developed different Monte Carlo models to simulate X-ray irradiation on ancient cells. Effects of mummification were considered by using two sizes of cells and three different phantom tissues, which enclosed the investigated cell cluster. This cluster was positioned at the isocenter of a CT scanner model, where the cell hit probabilities P(0,1,…, n) were calculated according to the Poisson distribution. To study the impact of the dominant physics process, CT scans for X-ray spectra of 80 and 120 kVp were simulated. Comparison between normal and dry tissue phantoms revealed that the probability of unaffected cells increased by 21 % following cell shrinkage for 80 kVp, while for 120 kVp, a further increase of unaffected cells of 23 % was observed. Consequently, cell shrinkage caused by dehydration decreased the impact of X-ray radiation on mummified cells significantly. Moreover, backscattered electrons in cortical bone protected deeper-lying ancient cells from radiation damage at 80 kVp X-rays.

Design and evaluation of a low-cost instrumented glove for hand function assessment.

BACKGROUND: The evaluation of hand function impairment following a neurological disorder (stroke and cervical spinal cord injury) requires sensitive, reliable and clinically meaningful assessment tools. Clinical performance measures of hand function mainly focus on the accomplishment of activities of daily living (ADL), typically rather complex tasks assessed by a gross ordinal rating; while the motor performance (i.e. kinematics) is less detailed. The goal of this study was to develop a low-cost instrumented glove to capture details in grasping, feasible for the assessment of hand function in clinical practice and rehabilitation settings. METHODS: Different sensor types were tested for output signal stability over time by measuring the signal drift of their step responses. A system that converted sensor output voltages into angles based on pre-measured curves was implemented. Furthermore, the voltage supply of each sensor signal conditioning circuit was increased to enhance the sensor resolution. The repeatability of finger bending trajectories, recorded during the performance of three ADL-based tasks, was established using the intraclass correlation coefficient (ICC). Moreover, the accuracy of the glove was evaluated by determining the agreement between angles measured with the embedded sensors and angles measured by traditional goniometry. In addition, the feasibility of the glove was tested in four patients with a pathological hand function caused by a cervical spinal cord injury (cSCI). RESULTS: A sensor type that displayed a stable output signal over time was identified, and a high sensor resolution of 0.5° was obtained. The evaluation of the glove's reliability yielded high ICC values (0.84 to 0.92) with an accuracy error of about ± 5°. Feasibility testing revealed that the glove was sensitive to distinguish different levels of hand function impairment in cSCI patients. CONCLUSIONS: The device satisfied the desired system requirements in terms of low cost, stable sensor signal over time, full finger-flexion range of motion tracking and capability to monitor all three joints of one finger. The developed rapid calibration system for easy use (high feasibility) and excellent psychometric properties (i.e. reliability and validity) qualify the device for the assessment of hand function in clinical practice and rehabilitation settings.

X-ray absorption-based imaging and its limitations in the differentiation of ancient mummified tissue.

OBJECTIVES: Differentiation of ancient tissues is of key importance in the study of paleopathology and in the evolution of human diseases. Currently, the number of imaging facilities for the non-destructive discrimination of dehydrated tissue is limited, and little is known about the role that emerging imaging technologies may play in this field. Therefore, this study investigated the feasibility and quality of dual-energy computed tomography (DECT) for the discrimination of dry and brittle soft tissue. Moreover, this study explored the relationship between morphological changes and image contrast in ancient tissue by using X-ray micro-tomography (micro-CT). MATERIALS AND METHODS: An Egyptian mummy head and neck was scanned with DECT at tube voltage/current of 140 kVp/27 mAs (tube A) and 100 kVp/120 mAs (tube B). The CT attenuation was determined by regions of interest (ROI) measurements of hard and soft tissue of the mummy skull. Finally, two samples from the posterior neck were dissected to acquire micro-CT images of shrunken dehydrated tissue. RESULTS: Dual-energy CT images demonstrated the high contrast resolution of surface structures from mummy skull. Bone density changes in the posterior skull base as well as soft-tissue alterations of the eyes and tongue were assessed. Micro-CT scans allowed the identification of morphological changes and the discrimination of muscle tissue from inorganic material in samples taken from the neck. CONCLUSIONS: Significant attenuation differences (p < 0.0007) were observed within 12 of the 15 ancient tissue groups and organic materials using DECT. We detected a correlation between X-ray scattering and image contrast reduction in dehydrated tissue with micro-CT imaging.

Enhancement of bend sensor properties as applied in a glove for use in neurorehabilitation settings.

Following hand function impairment caused by a neurological disorder, the functional level of the upper extremities has to be assessed in the clinical and rehabilitation settings. Current hand function evaluation tests are somewhat imprecise. Instrumented gloves allow finger motion monitoring during the performance of skilled tasks, such as grasping objects. As a result, they provide an objective tool for evaluating slight changes in the fine motor skills of the hand. Numerous gloves are based on resistive bend sensors, given that this is an easy to handle, low-cost, and reliable sensing element. When bending is not applied homogeneously along such a sensor, as is the case with finger-joint bending, its output response varies with the sensor's longitudinal position. Our goal is to determine the optimal sensor position with respect to the finger-joint in order to enhance the resolution of the sensors embedded in a glove. The validity of the integrated sensors is evaluated and the accuracy values are given.