Improved Multiscale Entropy Technique with Nearest-Neighbor Moving-Average Kernel for Nonlinear and Nonstationary Short-Time Biomedical Signal Analysis.

Analysis of biomedical signals can yield invaluable information for prognosis, diagnosis, therapy evaluation, risk assessment, and disease prevention which is often recorded as short time series data that challenges existing complexity classification algorithms such as Shannon entropy (SE) and other techniques. The purpose of this study was to improve previously developed multiscale entropy (MSE) technique by incorporating nearest-neighbor moving-average kernel, which can be used for analysis of nonlinear and non-stationary short time series physiological data. The approach was tested for robustness with respect to noise analysis using simulated sinusoidal and ECG waveforms. Feasibility of MSE to discriminate between normal sinus rhythm (NSR) and atrial fibrillation (AF) was tested on a single-lead ECG. In addition, the MSE algorithm was applied to identify pivot points of rotors that were induced in ex vivo isolated rabbit hearts. The improved MSE technique robustly estimated the complexity of the signal compared to that of SE with various noises, discriminated NSR and AF on single-lead ECG, and precisely identified the pivot points of ex vivo rotors by providing better contrast between the rotor core and the peripheral region. The improved MSE technique can provide efficient complexity analysis of variety of nonlinear and nonstationary short-time biomedical signals.

Novel approaches for quantitative electrogram analysis for intraprocedural guidance for catheter ablation: A case of a patient with persistent atrial fibrillation.

PURPOSE: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia that causes stroke affecting more than 2.3 million people in the US and is increasing in prevalence due to ageing population causing a new global epidemic. Catheter ablation with pulmonary vein isolation (PVI) to terminate AF is successful for paroxysmal AF but suffers limitations with persistent AF patients as current mapping methods cannot identify AF active substrates outside of PVI region. Recent evidences in the mechanistic understating of AF pathophysiology suggest that ectopic activity, localized re-entrant circuit with fibrillatory propagation and multiple circuit re-entries may all be involved in human AF. The authors developed novel electrogram analysis methods and validated using optical mapping data from isolated rabbit hearts to accurately identify rotor pivot points. The purpose of this study was to assess the feasibility of generating patient-specific 3D maps for intraprocedural guidance for catheter ablation using intracardiac electrograms from a persistent AF patient using novel electrogram analysis methods. METHODS: A persistent AF patient with clinical appointment for AF ablation was recruited for this study with IRB approval. 1055 electrograms throughout the left and right atrium were obtained for offline analysis with the novel approaches such as multiscale entropy, multiscale frequency, recurrence period density entropy, kurtosis and empirical mode decomposition to generate patient specific 3D maps. 3D Shannon Entropy, Renyi Entropy and Dominant frequency maps were also generated for comparison purposes along with local activation time and complex fractionated electrogram analysis maps. RESULTS: Patient specific 3D maps were obtained for each of the different approach. The 3D maps indicate potential active sites outside the PVI region. However, presence of rotors cannot be confirmed and validation of these approaches is required on a larger dataset. CONCLUSIONS: Conventional catheter mapping system can be used for generating patient specific 3D maps with short time series analysis using the novel approaches.

A comparative evaluation of the diagnostic efficacy of film and digital sensors for detection of simulated periapical lesions.

OBJECTIVE: The purpose of this study was to evaluate the diagnostic efficacy of Ektaspeed Plus film (EPF), a charge-coupled device (CCD), and photostimulable phosphor (PSP)-based digital images for detection of simulated periapical lesions. STUDY DESIGN: Lesions were simulated in the periapical areas of 24 human mandibular sections invested in acrylic using burs of sizes #1, 2, 4, and 6 and imaged using EPF, CCD, and PSP sensors. Percent correct response scores, sensitivity, and specificity values were computed for all variables. Repeated-measures analysis of variance and post hoc testing were performed to determine the effects of imaging modality, observer, and lesion sizes with respect to lesion detection. RESULTS: EPF displayed the highest sensitivity and specificity, followed by PSP and CCD images (P <.001). Percent correct score was the highest for 3 of 4 observers when EPF was used. Analysis of variance revealed significance (P <.001) with respect to all variables. Observers with experience in digital image-viewing performed better than those without such experience (P <.001). Intraobserver agreement was fair (kappa = 0.5). CONCLUSIONS: EPF outperformed CCD and PSP images when observers could manipulate image characteristics.

Updated quality assurance self-assessment exercise in intraoral and panoramic radiography. American Academy of Oral and Maxillofacial Radiology, Radiology Practice Committee.

This updated self-assessment exercise for the dental team by the Radiology Practice Committee of the American Academy of Oral and Maxillofacial Radiology is intended to produce the highest quality diagnostic radiographs while keeping patient exposure as low as is reasonably achievable. To continue to provide the best radiographic services to patients, those involved in dental radiography need to be aware of the latest changes and advances in dental radiography and need to use them in their practice.

Conventional linear tomography: protocol for assessing endosseous implant sites.

Proper implant dimension and implant site selection are two major factors that affect the eventual prosthodontic rehabilitation and long-term serviceability of the implant and prosthesis. Conventional linear tomography permits accurate measurements and assessment of available bone for both factors. A protocol for the use of conventional linear tomography for diagnostic assessment, evaluation of proposed implant sites, and the selection of proper implant type and dimension is presented.

Assessing condylar changes with digital subtraction radiography.

Transcranial radiographs of the temporomandibular joint with and without simulated pathology were compared with digital subtracted and histogram equalized images of the same joints. Subtracted images had specificity and sensitivity values of 0.83 and 0.76 respectively, compared with values of 0.42 and 0.54 for conventional radiographs. It was concluded that digital subtraction radiography has the potential to increase the diagnostic yield of transcranial temporomandibular radiography for bony changes to the condylar head.

Exposure reduction in panoramic radiography.

Increased receptor speed in panoramic radiography is useful in reducing patient exposure if it doesn't substantially decrease the diagnostic quality of the resultant image. In a laboratory investigation four rare earth screen/film combinations were evaluated ranging in relative speed from 400 to 1200. The results indicated that an exposure reduction of approximately 15 percent can be achieved by substituting a 1200 speed system for a 400 speed system without significantly affecting the diagnostic quality of the image.

Digital subtraction radiography for detecting cortical and cancellous bone changes in the periapical region.

Previous studies have found that bony lesions cannot be visualized on conventional radiographs unless there is cortical plate involvement. The aim of this project was to compare the sensitivity of digital subtraction to conventional radiography for detecting periapical changes in cortical and cancellous bone. Using a long source-to-object X-ray technique and E-speed film, serial radiographs of a dry skull mandible were obtained. Two bone lesions per radiograph were simulated using #1 to 8 round burs. Conventional and digitally subtracted images were evaluated for lesion presence by a board of reviewers. The results demonstrated greater sensitivity scores for digitally subtracted images in identifying cortical and cancellous bone changes. The lower limit of detection was less for digitally subtracted images in cortical and cancellous bone as well.

A clinical comparison of image quality and patient exposure reduction in panoramic radiography with heavy metal filtration.

Laboratory and clinical studies with the use of rare earth intensifying screens and four different forms of heavy metal elements serving as additional beam filtration were performed for panoramic radiography to identify the most efficacious system. Balanced density images were evaluated for contrast indices, resolution, relative dose reduction, and subjective image quality. Clinical studies were performed with a standard calcium tungstate imaging system and the four most promising experimental imaging systems that showed improvement over the standard system. Dosimetric studies were performed with the use of ionization chambers and thermoluminescent dosimetry (TLD) dosimeters. Exposure reductions of 34% to 79%, depending on the anatomic site and the imaging system used, were achieved. Subjective image quality was evaluated and analyzed statistically. This study concluded that the use of a Kodak Lanex regular screen/T-Mat G film with either Lanex screen or yttrium added beam filtration results in reduced patient exposure in panoramic radiography while image quality is maintained or improved.