Cone-beam System Research Articles

Multi-pass approach to reduce cone-beam artifacts in a circular orbit cone-beam CT system.

We propose a multi-pass approach to reduce cone-beam artifacts in a circular orbit cone-beam computed tomography (CT) system. Employing a large 2D detector array reduces the scan time but produces cone-beam artifacts in the Feldkamp, Davis, and Kress (FDK) reconstruction because of insufficient sampling for exact reconstruction. While the two-pass algorithm proposed by Hsieh is effective at reducing cone-beam artifacts, the correction performance is degraded when the bone density is moderate and the cone angle is large. In this work, we treated the cone-beam artifacts generated from bone and soft tissue as if they were from less dense bone objects and corrected them iteratively. The proposed method was validated using a numerical Defrise phantom, XCAT phantom data, and experimental data from a pediatric phantom followed by image quality assessment for FDK, the two-pass algorithm, the proposed method, and the total variation minimization-based iterative reconstruction (TV-IR). The results show that the proposed method was superior to the two-pass algorithm in cone-beam artifact reduction and effectively reduced the overcorrection by the two-pass algorithm near bone regions. It can also be observed that the proposed method produced better correction performance with fewer iterations than the TV-IR algorithm. A qualitative evaluation with mean-squared error, structural similarity, and structural dissimilarity demonstrated the effectiveness of the proposed method.

Geometric Calibration Based on a Simple Phantom for Multi-Lens Microscopic CT

In multi-lens microscopic cone-beam CT system, different resolutions can be achieved by tuning different objective lens with different magnifications, following the scan field of view (FOV) changed. By this multi-FOV/resolution acquisition strategy, many applications like truncation problem can be solved successfully. However, in order to achieve high-resolution image, the microscopic cone-beam CT system should comply with its geometrical restrictions accordingly, which are not only for that of conventional cone-beam system but also for that of multiple objective lens. Hence, compared with the existed cone-beam system calibration, a specific united calibration method is proposed in this paper. A set of geometrical parameters is presented, which can fully describe whole geometry of conventional cone-beam system as well as multi-lens. By taking use of projective data of circular trajectory of one single ball phantom, a cost function with the described arguments based on the projective lines of the phantom is built up. After solving the cost function, the calibration parameters can be determined optimally. The simulated and experimental results demonstrate that the proposed method shows significant improvements in robustness, precision and implementation.

Computed Laminography of CFRP Using an X-Ray Cone-Beam and Robotic Sample Manipulator Systems

Carbon fiber-reinforced polymers (CFRPs) are of interest to the aerospace sector for meeting future CO2 emission targets due to their weight reduction potential. However, the detection of structural and matrix defects is crucial for determining the performance and suitability of CFRPs in current and future generations of aircraft. Computed laminography (CL), a well-established nondestructive testing method, is well suited to the scanning of CFRP components with large aspect ratios, for which the conventional computed tomography (CT) is less suitable. Utilizing an existing Nikon Metrology custom build X-ray CT scanner, two lift-in lift-out robotic sample manipulator systems are used to extend the capability of the system and allow the exploration of atypical scanning geometries. Implementing raster and limited angle trajectories, reconstructions using the ASTRA Tomography Toolbox and the Simultaneous Iterative Reconstruction Technique algorithm are able to show structural defects in CFRPs, despite the reduced information inherent with CL systems. This paper reports on the system design and initial experiments that demonstrate benefits and drawbacks of different design options and scanning trajectory choices.

Filter-based energy-resolved X-ray computed tomography with a clinical imager

ABSTRACT Filter-based energy-resolved X-ray computed tomography (CT) is an approach for implementing energy-resolved CT imaging using a flat-panel-detector-based cone-beam system. In this study, we performed experiments with a 20-cm-diameter phantom on a clinical X-ray imager. The material density results showed good agreement with the ideal values. We also propose an improved method for obtaining the detector response function and the X-ray spectrum, which requires fewer measurements and will be practical for future clinical use. Issues such as scatter and image noise remain to be addressed.

A Hybrid Approach to Reduce Cone-Beam Artifacts for a Circular Orbit Cone-Beam CT System

In a cone-beam computed tomography (CT) system, the Feldkamp, Davis, and Kress (FDK) algorithm produces cone-beam artifacts due to insufficient object sampling in the missing cone region of frequency space. While total variation minimization-based iterative reconstruction (TV-IR) may reduce cone-beam artifacts by filling in the missing cone region, it introduces image blurring or noise increase depending on the regularization parameter. In this paper, we propose a method to reduce cone-beam artifacts through an optimal combination of FDK and TV-IR images. The method utilizes FDK (TV-IR) data outside (inside) the missing cone region, which enables to keep the original image quality of the FDK image and preserve the advantages of the TV-IR image for cone-beam artifact reduction. To validate the proposed method, we used numerical phantoms composed of Defrise disks, vertical plates, and star objects and assessed the image quality of FDK, TV-IR, and the proposed method using the mean squared error, contrast to noise ratio, and structural similarity with different TV-IR regularization parameters. Experimental validation was also conducted using a spine phantom with a bench-top cone-beam CT system. The results showed that the performance of the cone-beam artifacts reduction in TV-IR depended on the value of the regularization parameter, which often produced suboptimal image quality for different imaging tasks. However, the proposed method provided good image quality regardless of the regularization parameter values.

Clinical investigation of the Nucleus Slim Modiolar Electrode

Aims: The Nucleus CI532 cochlear implant incorporates a new precurved electrode array, i.e., the Slim Modiolar electrode (SME), which is designed to bring electrode contacts close to the medial wall of the cochlea while avoiding trauma due to scalar dislocation or contact with the lateral wall during insertion. The primary aim of this prospective study was to determine the final position of the electrode array in clinical cases as evaluated using flat-panel volume computed tomography. Methods: Forty-five adult candidates for unilateral cochlear implantation were recruited from 8 centers. Eleven surgeons attended a temporal bone workshop and received further training with a transparent plastic cochlear model just prior to the first surgery. Feedback on the surgical approach and use of the SME was collected via a questionnaire for each case. Computed tomography of the temporal bone was performed postoperatively using flat-panel digital volume tomography or cone beam systems. The primary measure was the final scalar position of the SME (completely in scala tympani or not). Secondly, medial-lateral position and insertion depth were evaluated. Results: Forty-four subjects received a CI532. The SME was located completely in scala tympani for all subjects. Pure round window (44% of the cases), extended round window (22%), and inferior and/or anterior cochleostomy (34%) approaches were successful across surgeons and cases. The SME was generally positioned close to the modiolus. Overinsertion of the array past the first marker tended to push the basal contacts towards the lateral wall and served only to increase the insertion depth of the first electrode contact without increasing the insertion depth of the most apical electrode. Complications were limited to tip fold-overs encountered in 2 subjects; both were attributed to surgical error, with both reimplanted successfully. Conclusions: The new Nucleus CI532 cochlear implant with SME achieved the design goal of producing little or no trauma as indicated by consistent scala tympani placement. Surgeons should be carefully trained to use the new deployment method such that tip fold-overs and over insertion may be avoided.

Research progress of X-ray luminescence optical tomography

Recently, X-ray luminescence optical tomography (XLOT) has been proposed as a promising optical molecular imaging modality. XLOT, or equivalently, X-ray luminescence computed tomography (XLCT), is a tomography imaging technique based on the X-ray excited nanophosphors (NPs). Briefly, when NPs in imaged object are irradiated with X-ray, NPs will emit visible or near infrared (NIR) luminescence. By mathematically modeling the light transportation and solving an inverse problem, the three dimensional (3D) distribution of NPs in imaged object can be recovered. Compared with the conventional optical molecular imaging modalities, XLOT has ability to eliminate the autofluorescence and provide the increased penetration depth in tissues. As a result, the imaging technique is well suited for biomedical researches. Especially, XLOT provides the potential for clinical applications due to the increased penetration depth. Based on the excitation patterns of X-ray beams, the current XLOT imaging systems can be classed into three types, i.e., the pencil-beam system, the fan-beam system, and the cone-beam system. Among these systems, the pencil-beam XLOT has the highest spatial resolution and the lowest time resolution. In contrast, the cone-beam XLOT system, especially the single-view cone-beam XLOT system, has the shortest data acquisition time. But, the imaging quality is relatively lower compared to the pencil-beam system. Hence, there is a tradeoff between the spatial resolution and time resolution for XLOT imaging technique. After acquring the measurement data by the above XLOT system, the 3D distribution of NPs in imaged object can be recovered by the reconstruction methods. For XLOT reconstruction, there are two types of methods, i.e., the filtered back projection (FBP) method and the reconstruction method based on photon migration model. For the pencil-beam XLOT system, the reconstruction is generally performed by FBP method, which is similar to XCT reconstruction method. For the cone-beam XLOT system, the NPs in imaged object are generally resolved by using the method based on photon migration model. It is worth noting that the reconstruction based on migration mode is a high ill-posed problem due to the high scattering of light in biological tissues. To alleviate the ill-posedness, the compressive sensing technique and a priori information method (e.g., excitation a priori information) can be used. In addition, the imaging probes play an important role in XLOT imaging. Currently, the rare-earth nanophosphors have be widely used in XLOT due to their optical properties. Of course, the rare-earth nanophosphors are not sole NPs for XLOT imaging. Other NPs, e.g., quantum dots and gold nanoclusters, have also been used as the imaging probes. Further, with the advances in NPs, more applications would be expected in bio-medical researches. To sum up, for XLOT excellent performances, during the last few years, the continuous research efforts have been made to develop new imaging systems, build robust reconstruction methods, design efficient NPs, and expand the applications of XLOT. This paper reviews the developments of XLOT, including the basic imaging principles, system compositions, and advantages and disadvantages of different XLOT imaging systems. Subsequently, the corresponding reconstruction methods and the imaging probes are classified and summarized. Finally, we discuss the applications of XLOT in the preclinical diagnosis, and the future research direction of XLOT.

An iterative weighted method based on YALL1 for cone-beam X-ray luminescence optical tomography imaging: A phantom experimental study.

Cone-beam X-ray luminescence optical tomography (CB-XLOT) plays an important role in in vivo small animal imaging study, which can non-invasively image the three-dimensional (3-D) distribution of x-ray-excitable nanophosphors deeply embedded in imaged object. However, CB-XLOT suffers from a low spatial resolution due to the ill-posed nature of optical reconstruction. To alleviate the ill-posedness of reconstruction and improve the imaging performance of XLOT, in this paper, we propose an iterative weighted L1 minimization method which is achieved by incorporating YALL1 (Your algorithm for L1 norm problems). The physical phantom experiment was conducted to evaluate the performance of the proposed method, where a custom-made cone-beam XLOT system was used as the imaging platform. The experimental results indicate that by applying the proposed iterative weighted strategy to YALL1 method, the reconstruction performance of XLOT can be improved when compared with the conventional YALL1 method.

Quantitative image quality evaluation for kV cone-beam CT-based IGRT

The objective of this study is to quantitatively evaluate the image quality of a kV cone-beam CT-based IGRT system (Elekta, XVI) using two commercial CT image quality phantoms, Catphan-600 and CIRS-062QA. Both phantoms consist of similar image quality test modules (uniformity, CT linearity and spatial resolution) but each phantom has different diameter and test pattern design. Each test module was imaged separately using an optimised cone-beam CT imaging parameter. The quality metrics of the reconstructed images were analysed using algorithms developed with MatLab. The image uniformity and the spatial resolution measured with Catphan were of 4% and 40% greater respectively, compared to those measured with CIRS phantom. The differences were due to the beam scattering and hardening originated from the CIRS phantom holder. The contrast-to-noise ratio (CNR) values measured with CIRS phantom were at least 2% higher than that of Catphan. The diameter of CIRS phantom is smaller and resulted in lower beam attenuation. The quantitative image quality assessment algorithms developed for both phantoms provided a phantom-specific set of reference values for a cone-beam CT imaging system as recommended by AAPM TG-142. Further investigation will be performed to resolve beam hardening issue arising from the CIRS phantom holder.

Initial Experience with a Cone-beam Breast Computed Tomography-guided Biopsy System.

Objective:To evaluate our initial experience with a cone-beam breast computed tomography (BCT)-guided breast biopsy system for lesion retrieval in phantom studies for use with a cone-beam BCT imaging system.Materials and Methods:Under the Institutional Review Board approval, a phantom biopsy study was performed using a dedicated BCT-guided biopsy system. Fifteen biopsies were performed on each of the small, medium, and large anthropomorphic breast phantoms with both BCT and stereotactic guidance for comparison. Each set of the 45 phantoms contained masses and calcification clusters of varying sizes. Data included mass/calcium retrieval rate and dose and length of procedure time for phantom studies.Results:Phantom mass and calcium retrieval rate were 100% for BCT and stereotactic biopsy. BCT dose for small and medium breast phantoms was found to be equivalent to or less than the corresponding stereotactic approach. Stereotactic-guided biopsy dose was 34.2 and 62.5 mGy for small and medium breast phantoms, respectively. BCT-guided biopsy dose was 15.4 and 30.0 mGy for small and medium breast phantoms, respectively. Both computed tomography biopsy and stereotactic biopsy study time ranged from 10 to 20 min.Conclusion:Initial experience with a BCT-guided biopsy system has shown to be comparable to stereotactic biopsy in phantom studies with equivalent or decreased dose.

Noise Power Characteristics of a Micro-Computed Tomography System.

The aim of this study was to investigate the noise power properties of a micro-computed tomography (micro-CT) system under different operating conditions. A commercial micro-CT was used in the study that used a flat panel detector with a 127-μm-pixel pitch and a micro-focus x-ray tube. Conical tubes of various diameters were used under different acquisition conditions. Multidimensional noise power spectrums were used as a metric to investigate the noise properties of the system. Noise power spectrum was calculated from the difference data generated by subtraction of 2 identical scans. The noise properties with respect to various parameters that include the impact of number of projections, x-ray spectra, milliampere-second, slice location, object diameter, voxel size, geometric magnification (M), back-projection filters, and reconstruction magnification (Mrecon) were studied. At a same isocentric exposure rate of 270 mR/s, the noise power was much lower for the image reconstructed with 3672 views (122 seconds) as compared with the 511 views (17 seconds), whereas at a fixed isocentric exposure of 4600 mR, the noise power levels were almost similar. Image noise with a 50-kV beam was higher as compared with the 90-kV beam at a same isocentric exposure. Image noise from a 16-mm-diameter conical tube was much lower as compared with the 28- and 56-mm tubes under identical isocentric exposures. The choice of back-projection filter influences noise power spectrum curves in terms of width and amplitudes. Reconstruction magnification applied during the reconstruction process increased the noise power at lower spatial frequencies but reduced the noise power at higher spatial frequencies. It can be established that, for small details corresponding to high spatial frequencies, reconstruction magnification can provide an improved signal-to-noise ratio. At all spatial frequencies, the in-plane images had lower noise power levels as compared with the z-plane images. The noise power properties investigated in this study provide important image quality references for refined cone beam system development, optimization, and operations.

Technical Note: Robust measurement of the slice-sensitivity profile in breast tomosynthesis.

The purpose of this work is to improve the repeatability of the measurement of the slice-sensitivity profile (SSP) in reconstructed breast tomosynthesis volumes. A grid of aluminum ball-bearings (BBs) within a PMMA phantom was imaged on breast tomosynthesis systems from three different manufacturers. The full-width half-maximum (FWHM) values were measured for the SSPs of the BBs in the reconstructed volumes. The effect of transforming the volumes from a Cartesian coordinate system (CCS) to a cone-beam coordinate system (CBCS) on the variability in the FWHM values was assessed. Transforming the volumes from a CCS to a CBCS before measuring the SSPs reduced the coefficient of variation (COV) in the measurements of FWHM in repeated measurements by 56% and reduced the dependence of the FWHM values on the location of the BBs within the reconstructed volume by 76%. Measuring the SSP in the volumes in a CBCS improves the robustness of the measurement.

TH-AB-209-01: Making Benchtop X-Ray Fluorescence Computed Tomography (XFCT) Practical for in Vivo Imaging by Integration of a Dedicated High-Performance X-Ray Source in Conjunction with Micro-CT Functionality

Purpose: To make benchtop x-ray fluorescence computed tomography (XFCT) practical for routine preclinical imaging tasks with gold nanoparticles (GNPs) by deploying, integrating, and characterizing a dedicated high-performance x-ray source and addition of simultaneous micro-CT functionality. Methods: Considerable research effort is currently under way to develop a polychromatic benchtop cone-beam XFCT system capable of imaging GNPs by stimulation and detection of gold K-shell x-ray fluorescence (XRF) photons. Recently, an ad hoc high-power x-ray source was incorporated and used to image the biodistribution of GNPs within a mouse, postmortem. In the current work, a dedicated x-ray source system featuring a liquid-cooled tungsten-target x-ray tube (max 160 kVp, ∼3 kW power) was deployed. The source was operated at 125 kVp, 24 mA. The tube's compact dimensions allowed greater flexibility for optimizing both the irradiation and detection geometries. Incident x-rays were shaped by a conical collimator and filtered by 2 mm of tin. A compact “OEM” cadmium-telluride x-ray detector was implemented for detecting XRF/scatter spectra. Additionally, a flat panel detector was installed to allow simultaneous transmission CT imaging. The performance of the system was characterized by determining the detection limit (10-second acquisition time) for inserts filled with water/GNPs at various concentrations (0 and 0.010–1.0 wt%) and embedded in a small-animal-sized phantom. The phantom was loaded with 0.5, 0.3, and 0.1 wt% inserts and imaged using XFCT and simultaneous micro-CT. Results: An unprecedented detection limit of 0.030 wt% was experimentally demonstrated, with a 33% reduction in acquisition time. The reconstructed XFCT image accurately localized the imaging inserts. Micro-CT imaging did not provide enough contrast to distinguish imaging inserts from the phantom under the current conditions. Conclusion: The system is immediately capable of in vivo preclinical XFCT imaging with GNPs. Micro-CT imaging will require optimization of irradiation parameters to improve contrast. Supported by NIH/NCI grant R01CA155446; This investigation was supported by NIH/NCI grant R01CA155446

TH-AB-204-10: Drastic Performance Improvement of a Polychromatic Cone- Beam X-Ray Fluorescence Computed Tomography (XFCT) System Using a Kilowatt-Range X-Ray Source

Purpose: To demonstrate drastic performance improvement of a polychromatic cone-beam x-ray fluorescence computed tomography (XFCT) system using a kilowatt-range x-ray source. Methods: An experimental polychromatic cone-beam XFCT system capable of imaging gold nanoparticles (GNPs) within small-animal-sized objects by stimulating K-shell XRF from gold and detection using a cadmium-telluride detector has been under development. Originally configured with a low-power (∼50 W) x-ray source (105 kVp, 0.45 mA, 0.9-mm tin filter), the system has now been retrofitted with a high-power (∼3 kW) source, operated at 125 kVp, 25 mA. The higher flux allowed the use of a 2-mm tin filter to harden the incident x-ray spectrum, thereby optimizing XRF production. The material detection limit was determined at these settings using GNP/water-containing calibration phantoms (0, 0.1, 0.5, 1, 2 wt. % of GNPs). Subsequently, a 3-cm-diameter PMMA phantom with 0.2, 0.5, and 1 wt. % GNP/water inserts was imaged. The image reconstruction algorithm was modified with Compton-scatter-based background fitting for accurate XRF signal extraction and empirical attenuation correction. Results: Under the optimized conditions, the detection limit was remarkably lower (factor of 2.5), compared to the original configuration, allowing imaging of GNP concentrations as low as 0.2 wt. %. The reconstructed image demonstrated accurate localization of all inserts. Scan time was drastically decreased (factor of 4), enabling imaging of the phantom in 1.5 hours with just one detector translated 11 times. By reverting to the 0.9-mm filter, as used previously, scan time could be lowered to 30 minutes, at the expense of sensitivity. Implementation of additional/array detectors for parallel data acquisition will lower scan time further. Conclusion: By adopting a high-power source for the XFCT system, dramatic improvements were made, while meeting realistic constraints. This work shows the practicality of performing XFCT for routine preclinical ex-/in-vivo imaging using GNPs.

X-ray microtomographic confirmation of the reliability of CBCT in identifying the scalar location of cochlear implant electrode after round window insertion

Cone-beam computed tomography (CBCT) plays a key role in cochlear implantation in both planning implantation before surgery and quality control during surgery due to the high spatial resolution and convenience of application in the operation theater. We recently designed a novel, highresolution cone-beam acquisition system that has been tested in temporal bones with cochlear implantation to identify the scalar localization of the electrode arrays. The current study aimed to verify the reliability of the experimental CBCT set-up using high-resolution in vitro X-ray microtomography (μCT) imaging as a reference. Nine human temporal bones were studied by inserting a straight electrode of a cochlear implant using the round window approach followed by sequential imaging using experimental CBCT and μCT with and without 1% iodine as the contrast agent. In the CBCT images, the electrodes were located in the scala tympani and near the lateral wall in all temporal bones. In the μCT images, the cochlear fine structures, including Reissner's membrane, stria vascularis, spiral ligament, basilar membrane, spiral limbus, osseous spiral lamina, and Rosenthal's canal that hosts the spiral ganglion cells, were clearly delineated; the electrode array avoided the lateral wall of the scala tympani in the hook region and then ran along the lateral wall of the scala tympani without any exception, a feature that was also detected in a temporal bone with ruptures in the basilar and Reissner's membranes. In conclusion, the current in vitro μCT imaging system produced high-quality images that could demonstrate the fine cochlear structures faithfully and verify the reliability of a novel experimental CBCT set-up aimed for clinical application in identifying the scalar localization of the electrode array. The straight electrode is safe for cochlear structures with low risk of translocation and is suitable for atraumatic implantation, although a large gap between the contacts and the modiolus exists.

PD-0143: 4D cone-beam computed tomography combining total variation regularization and motion compensation

Breathing motion affects the image guidance of lung tumors when projection images are acquired using a slowly rotating cone-beam (CB) CT X-ray system while the patient breathes. Advanced methods have been developed to achieve streak-free and blur-free reconstructions, most of which are either based on motion compensation, or on regularization using some a-priori information. This paper introduces a method that combines both approaches, called Motion Compensated RecOnstructiOn using Spatial and Temporal Regularization (MC ROOSTER), and describes how it compares with its regularization-only counterpart (ROOSTER), with Motion Compensated FDK (MC FDK), and with respiration-correlated FDK.

A breast-specific, negligible-dose scatter correction technique for dedicated cone-beam breast CT: a physics-based approach to improve Hounsfield Unit accuracy

The purpose of this research was to develop a method to correct the cupping artifact caused from x-ray scattering and to achieve consistent Hounsfield Unit (HU) values of breast tissues for a dedicated breast CT (bCT) system. The use of a beam passing array (BPA) composed of parallel-holes has been previously proposed for scatter correction in various imaging applications. In this study, we first verified the efficacy and accuracy using BPA to measure the scatter signal on a cone-beam bCT system. A systematic scatter correction approach was then developed by modeling the scatter-to-primary ratio (SPR) in projection images acquired with and without BPA. To quantitatively evaluate the improved accuracy of HU values, different breast tissue-equivalent phantoms were scanned and radially averaged HU profiles through reconstructed planes were evaluated. The dependency of the correction method on object size and number of projections was studied. A simplified application of the proposed method on five clinical patient scans was performed to demonstrate efficacy. For the typical 10–18 cm breast diameters seen in the bCT application, the proposed method can effectively correct for the cupping artifact and reduce the variation of HU values of breast equivalent material from 150 to 40 HU. The measured HU values of 100% glandular tissue, 50/50 glandular/adipose tissue, and 100% adipose tissue were approximately 46, −35, and −94, respectively. It was found that only six BPA projections were necessary to accurately implement this method, and the additional dose requirement is less than 1% of the exam dose. The proposed method can effectively correct for the cupping artifact caused from x-ray scattering and retain consistent HU values of breast tissues.

Automatic calibration method of voxel size for cone-beam 3D-CT scanning system

For a cone-beam three-dimensional computed tomography (3D-CT) scanning system, voxel size is an important indicator to guarantee the accuracy of data analysis and feature measurement based on 3D-CT images. Meanwhile, the voxel size changes with the movement of the rotary stage along X-ray direction. In order to realize the automatic calibration of the voxel size, a new and easily-implemented method is proposed. According to this method, several projections of a spherical phantom are captured at different imaging positions and the corresponding voxel size values are calculated by non-linear least-square fitting. Through these interpolation values, a linear equation is obtained that reflects the relationship between the voxel size and the rotary stage translation distance from its nominal zero position. Finally, the linear equation is imported into the calibration module of the 3D-CT scanning system. When the rotary stage is moving along X-ray direction, the accurate value of the voxel size is dynamically exported. The experimental results prove that this method meets the requirements of the actual CT scanning system, and has virtues of easy implementation and high accuracy.

Reporte clínico: Registro piezográfico de la zona neutra, en un paciente con espasmos musculares involuntarios

Every function of the stomatognathic system involves the synergistic action of the musculature around the prosthesis, consisting of complex and individual structures such as tongue, lips, cheeks and mouth floor. When planning and making complete prostheses, the muscular dynamic is not always considered. This can generate instability of the device during function, the location of the artificial teeth is made arbitrarily on the top and middle parts of the flange, and the configuration of the polished areas is made according to mechanistic concepts. This factor takes more relevance in patients with severe atrophy of their residual flanges, where the prosthetic stability can be a decisive factor between the success or failure of the rehabilitation. It is known that the osseointegrated implants provide retention, support and stability. However, there are special situations in which it is not possible to access to this type of treatment, both for medical surgical reasons or associated costs. In this study, a Piezographyc record of the Neutral Zone was used in a patient with facial nerve involvement generating involuntary muscle spasms of the affected side. A prosthetic rehabilitation based on the appropriate relation between external prosthetic surface and surrounding tissues was obtained, improving functional requirements such as retention and stability. The computerized tomographic Cone Beam system was used, with the objective to show the piezographic record. The results obtained with these piezographic prostheses prove to be superior in factors like comfort and speech articulation, but inferior in masticatory efficiency, where the conventional technique is still better.

Reporte clínico: Registro piezográfico de la zona neutra, en un paciente con espasmos musculares involuntarios

Every function of the stomatognathic system involves the synergistic action of the musculature around the prosthesis, consisting of complex and individual structures such as tongue, lips, cheeks and mouth floor. When planning and making complete prostheses, the muscular dynamic is not always considered. This can generate instability of the device during function, the location of the artificial teeth is made arbitrarily on the top and middle parts of the flange, and the configuration of the polished areas is made according to mechanistic concepts. This factor takes more relevance in patients with severe atrophy of their residual flanges, where the prosthetic stability can be a decisive factor between the success or failure of the rehabilitation. It is known that the osseointegrated implants provide retention, support and stability. However, there are special situations in which it is not possible to access to this type of treatment, both for medical surgical reasons or associated costs. In this study, a Piezographyc record of the Neutral Zone was used in a patient with facial nerve involvement generating involuntary muscle spasms of the affected side. A prosthetic rehabilitation based on the appropriate relation between external prosthetic surface and surrounding tissues was obtained, improving functional requirements such as retention and stability. The computerized tomographic Cone Beam system was used, with the objective to show the piezographic record. The results obtained with these piezographic prostheses prove to be superior in factors like comfort and speech articulation, but inferior in masticatory efficiency, where the conventional technique is still better. Rev. Clin. Periodoncia Implantol. Rehabil. Oral Vol. 6(3); 134-137, 2013.