Dental MRI using wireless intraoral coils.
Ontology highlight
ABSTRACT:
SUBMITTER: Ludwig U
PROVIDER: S-EPMC4810435 | biostudies-other | 2016 Mar
REPOSITORIES: biostudies-other
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Project description:ObjectivesTo facilitate dental disease screening program in prisoners by testing the diagnostic accuracy of teledentistry examination in comparison to direct oral examination by a dentist.Materials and methodsThis crossover study comprised three phases. Phase I, prisoner health volunteers (PHVs) enrolled teledentistry training for an intraoral camera (IOC) use. Phase II, the PHV used IOC for examining dental diseases of prisoners who reported dental-related problems, and captured symptomatic areas. The PHV and dentist independently determined tentative dental treatment need, comprising dental fillings, scaling, extraction, and surgical removal of impacted tooth. Phase III, another dentist performed direct oral examination of the prisoners who reported problems in phase II and determined dental treatment needs. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated, using direct oral examination by dentist as a true positive.ResultsDiagnostic accuracy was determined in 152 prisoners with 215 teeth. Sensitivity, specificity, PPV, and NPV of teledentistry and direct examination between two dentists were above 80%. The lowest sensitivity and specificity of teledentistry examination by the PHV were scaling and surgical removal.ConclusionsIOC use in teledentistry facilitates dentists in dental diseases screening for prisoners with acceptable diagnostic accuracy in identifying possible treatment needs. However, the imaging obtained from teledentistry is not adequate to accurately identify all dental treatment needs.
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Project description:IntroductionClinical photography in dentistry has become a vital part of dental education and clinical practice. Dental students seek demonstrations that help them visualize and understand new concepts and clinical procedures. Few multimedia resources are available that provide instruction regarding clinical photography for dental students. The concept videos serve as adjunctive teaching tools for predoctoral dental students in taking clinical photographs.MethodsI created the three concept videos on intraoral and extraoral photography by recording narrated PowerPoint slideshows. After sessions on basic photography concepts and digital camera operation, I used concept videos to show how to take comprehensive quality dental photographs in a step-by-step manner and to demonstrate positions of an operator and a patient. I collected feedback using an electronic survey sent to all 33 third-year dental students who participated.ResultsEleven students completed the survey; all students responded favorably to this method of instruction. Individual comments were also positive on helpfulness, conciseness, and applicability.DiscussionThese concept videos were shown to be a helpful resource for dental students in enhancing their knowledge and skills in obtaining dental photographs. Multimedia resources that helped provide students with practical tips and suggestions could supplement clinical chair-side teaching with faculty and further advance their knowledge and skills. Future studies could include more interactive platforms for better student utilization of the resource, and also compare students' performance before and after watching the videos.
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Project description:Magnetic resonance imaging is an inherently signal-to-noise-starved technique that limits the spatial resolution, diagnostic image quality and results in typically long acquisition times that are prone to motion artefacts. This limitation is exacerbated when receive coils have poor fit due to lack of flexibility or need for padding for patient comfort. Here, we report a new approach that uses printing for fabricating receive coils. Our approach enables highly flexible, extremely lightweight conforming devices. We show that these devices exhibit similar to higher signal-to-noise ratio than conventional ones, in clinical scenarios when coils could be displaced more than 18 mm away from the body. In addition, we provide detailed material properties and components performance analysis. Prototype arrays are incorporated within infant blankets for in vivo studies. This work presents the first fully functional, printed coils for 1.5- and 3-T clinical scanners.
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Project description:PurposeAsymmetric gradient coils introduce zeroth- and first-order concomitant field terms, in addition to higher-order terms common to both asymmetric and symmetric gradients. Salient to compensation strategies is the accurate calibration of the concomitant field spatial offset parameters for asymmetric coils. A method that allows for one-time calibration of the offset parameters is described.Theory and methodsA modified phase contrast pulse sequence with single-sided bipolar flow encoding is proposed to calibrate the offsets for asymmetric, transverse gradient coils. By fitting the measured phase offsets to different gradient amplitudes, the spatial offsets were calculated by fitting the phase variation. This was used for calibrating real-time pre-emphasis compensation of the zeroth- and first-order concomitant fields.ResultsImage quality improvement with the proposed corrections was demonstrated in phantom and healthy volunteers with non-Cartesian and Cartesian trajectory acquisitions. Concomitant field compensation using the calibrated offsets resulted in a residual phase error <3% at the highest gradient amplitude and demonstrated substantial reduction of image blur and slice position/selection artifacts.ConclusionsThe proposed implementation provides an accurate method for calibrating spatial offsets that can be used for real-time concomitant field compensation of zeroth and first-order terms, substantially reducing artifacts without retrospective correction or sequence specific waveform modifications.
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Project description:ObjectiveIn dental MRI, intraoral coils provide higher signal-to-noise ratio (SNR) than coils placed outside the mouth. This study aims to design an intraoral dipole antenna and demonstrates the feasibility of combining it with an extraoral coil.MethodsDipole antenna design was chosen over loop design, as it is open toward the distal; therefore, it does not restrain tongue movement. The dipole design offers also an increased depth-of-sensitivity that allows for MRI of dental roots. Different dipole antenna designs were simulated using a finite-difference-time-domain approach. Ribbon, wire, and multi-wire arms were compared. The best design was improved further by covering the ends of the dipole arms with a high-permittivity material. Phantom and in vivo measurements were conducted on a 3T clinical MRI system.ResultsThe best transmit efficiency and homogeneity was achieved with a multi-wire curved dipole antenna with 7 wires for each arm. With an additional high-permittivity cap the transmit field inhomogeneity was further reduced from 20% to 5% along the dipole arm. When combined with extraoral flexible surface-coil, the coupling between the coils was less than -32dB and SNR was increased.ConclusionUsing intraoral dipole design instead of loop improves patient comfort. We demonstrated feasibility of the intraoral dipole combined with an extraoral flexible coil-array for dental MRI. Dipole antenna enabled decreasing imaging field-of-view, and reduced the prevalent signal from tongue.SignificanceThis study highlights the advantages and the main challenges of the intraoral RF coils and describes a novel RF coil that addresses those challenges.
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