Three-dimensional Imaging Modalities Research Articles

Stationary intraoral digital tomosynthesis using a carbon nanotube X-ray source array.

Intraoral dental tomosynthesis and closely related tuned-aperture CT (TACT) are low-dose three-dimensional (3D) imaging modalities that have shown improved detection of multiple dental diseases. Clinical interest in implementing these technologies waned owing to their time-consuming nature. Recently developed carbon nanotube (CNT) X-ray sources allow rapid multi-image acquisition without mechanical motion, making tomosynthesis a clinically viable technique. The objective of this investigation was to evaluate the feasibility of and produce high-quality images from a digital tomosynthesis system employing CNT X-ray technology. A test-bed stationary intraoral tomosynthesis unit was constructed using a CNT X-ray source array and a digital intraoral sensor. The source-to-image distance was modified to make the system comparable in image resolution to current two-dimensional intraoral radiography imaging systems. Anthropomorphic phantoms containing teeth with simulated and real caries lesions were imaged using a dose comparable to D-speed film dose with a rectangular collimation. Images were reconstructed and analysed. Tomosynthesis images of the phantom and teeth specimen demonstrated perceived image quality equivalent or superior to standard digital images with the added benefit of 3D information. The ability to "scroll" through slices in a buccal-lingual direction significantly improved visualization of anatomical details. In addition, the subjective visibility of dental caries was increased. Feasibility of the stationary intraoral tomosynthesis is demonstrated. The results show clinical promise and suitability for more robust observer and clinical studies.

Imagerie peropératoire tridimensionelle de la réduction et de l’ostéosynthèse des fractures du scaphoïde

IntroductionWe examined the clinical benefit of 2 intraoperative three-dimensional imaging modalities for reduction and fixation of scaphoid fractures. HypothesisOur hypothesis was that three-dimensional imaging will aid in operative care in comparison with standard fluoroscopy. MethodsIn 25 consecutive patients treated for fractures, after satisfactory reduction and fixation was obtained with a single Kirschner wire using fluoroscopy, intraoperative three-dimensional visualization was performed. The quality of fracture reduction, wire position and extrusion of the wire were examined. ResultsIn two of the 25 cases, after three-dimensional visualization, malreduction of the fracture was seen and the reduction revised. Artifact and the dependency on technologist performance limited the use of these modalities to locate the wire accurately. DiscussionDiagnosis of malreduction of a scaphoid fracture is possible with 3-dimensional modalities. Utilization of these systems is still limited by technical factors. Level of evidenceLevel IV. Retrospective study.

Enhanced patient care through collaborative team play: An orthodontist and an OMF.Radiologist’s collective perspective

The overarching theme of patient-centric care should serve as the fundamental basis for our treatment plans. Treatment plans that best utilize knowledge; training and technology must be developed on current evidence that rests on soundly researched principles. In orthodontics, the evolution of cone beam computed tomography as a new three-dimensional imaging modality has brought a paradigm shift in the radiographic evaluation of the maxillofacial structures. However, the coming of new technology does not warrant its use in routine practice and tight imaging protocols must be developed to include and promote the evidence-based patient-centric approach. This principle is best approached if the effort is a collaborative one. Collaboration between all the disciplines that contribute to patient care must act as a unified force to deliver superior care. In this editorial, we present a successful collaborative effort between orthodontics and oral and maxillofacial radiology that have engaged in collaborative efforts to deliver superior patient care, better predoctoral and postdoctoral training programs and how this effort has yielded excellent contribution to research.

Intraoperative 3-dimensional imaging of scaphoid fracture reduction and fixation

IntroductionWe examined the clinical benefit of two intraoperative three-dimensional imaging modalities for reduction and fixation of scaphoid fractures. HypothesisOur hypothesis was that three dimensional imaging will aid in operative care in comparison with standard fluoroscopy. MethodsIn 25 consecutive patients treated for fractures, after satisfactory reduction and fixation was obtained with a single Kirschner wire using fluoroscopy, intraoperative three-dimensional visualization was performed. The quality of fracture reduction, wire position and extrusion of the wire were examined. ResultsIn two of the 25 cases, after three-dimensional visualization, malreduction of the fracture was seen and the reduction revised. Artifact and the dependency on technologist performance, limited the use of these modalities to locate the wire accurately. DiscussionDiagnosis of malreduction of a scaphoid fracture is possible with 3-dimensional modalities. Utilization of these systems is still limited by technical factors. Level of evidenceLevel IV. Retrospective study.

Digital panoramic radiography for diagnosis of the temporomandibular joint: CBCT as the gold standard.

Three-dimensional imaging modalities have been reported to be more accurate than panoramic radiographs (PR) for the assessment of bone components of the temporomandibular joint (TMJ). No exact prior information is available that demonstrates which specific limitations occur in terms of TMJ diagnosis when using PR for this purpose. This study aimed to assess the clinical validity of digital panoramic radiography (DPR) when diagnosing morphological disorders of the TMJ using cone-beam computed tomography (CBCT) images as the gold standard. A sample composed of TMJ images (N = 848), including 212 DPR and 212 CBCT images obtained from the same patient, was used to assess any morphological changes in the TMJ. Four appraisers diagnosed all of the DPR images, whereas the CBCT images were used to establish the gold standard. The reliability of each appraiser's response pattern was analyzed using the Kappa test (κ), and diagnostic tests were performed to assess each appraiser's performance using a significance level setting of 5% (α = 0.05). Reliability of each appraiser's response pattern compared to the gold standard ranged from a slight-to-moderate agreement (0.18 ≤ κ ≤ 0.45); and among the different appraisers, the response pattern showed a fair agreement (0.22 ≤ κ ≤ 0.39). Diagnostic tests showed a wide range among the different possible morphological changes diagnosed. DPR does not have validity when diagnosing morphological changes in the TMJ; it underestimates the radiological findings with higher prevalence, and thus, it cannot be used effectively as a diagnostic tool for bone components within this region.

Noninvasive mapping of ventricular arrhythmias.

Several decades of research has led to the development of a 252-lead electrocardiogram-based three-dimensional imaging modality to refine noninvasive diagnosis and improve the management of heart rhythm disorders. This article reviews the clinical potential of this noninvasive mapping technique in identifying the sources of electrical disorders and guiding the catheter ablation of ventricular arrhythmias (premature ventricular beats and ventricular tachycardia). The article also briefly refers to the noninvasive electrical imaging of the arrhythmogenic ventricular substrate based on the electrophysiologic characteristics of postinfarction ventricular myocardium.

Three-dimensional Intraoperative Imaging Modalities in Orthopaedic Surgery: A Narrative Review.

Intraoperative imaging and navigation systems have revolutionized orthopaedic surgery for the spine, joints, and orthopaedic trauma. Imaging modalities such as the isocentric C-arm, O-arm imaging, and intraoperative MRI or navigation systems allow the visualization of surgical instruments and implants relative to a three-dimensional CT image or MRI. Studies show that these technologies lower the rates of implant misplacement and inadequate fracture reduction, thereby improving surgical outcomes and reducing reoperation rates. An additional benefit is reduced radiation exposure compared with that for conventional fluoroscopy. Concerns surrounding adoption of these technologies include cost and increased operating times, but improvements in design and protocol may improve the integration of these imaging modalities into the operating room.

Insights gained from three-dimensional imaging modalities for closure of ventricular septal defects.

Ventricular septal defects (VSDs) are the commonest group of congenital heart lesions, accounting for ≈30% of congenital heart defects in liveborn infants.1 Defects in the ventricular septum are classified according to their position when the ventricular septum is viewed from the right ventricle and these may vary in their location, size, and number.2,3 VSDs can occur as isolated lesions or as part of more complex disease, for example, transposition of the great arteries or double outlet right ventricle, where the location and size of such defects assume great importance in planning the optimal mode of surgical repair.4 In most cases, surgical closure remains the mainstay treatment for VSDs, but selected lesions may be amenable to catheter closure.5,6 Cross-sectional echocardiography is the most commonly used noninvasive diagnostic method to delineate the position of a VSD before surgery.7 Multiple sonographic cuts and cross-sectional sweeps of the region of interest are used to build a virtual reconstruction of the three-dimensional (3D) anatomy in the mind of the echocardiographer. However, for the surgeon who deals solely with 3D images there can remain an element of uncertainty when called to operate on the patient. The number, size, location of VSDs, and their relationship to adjacent structures are central for selecting whether the defects might be best closed via the tricuspid valve, via the semilunar valves, or via a ventriculotomy or whether these might not be readily approachable and a palliative pulmonary artery banding is desirable.8,9 In this review, we present key 3D echocardiographic projections and examples of different types of VSDs where the images have a direct effect on the approach taken to VSD closure. Comparison of 3D echocardiography (3DE) with other 3D imaging modalities is also described. Images are presented in an …

Three-dimensional Echocardiographic Analysis of left Atrial size and Volumetric Function — Clinical Implications and Comparison with Other Imaging Modalities

Since a number of imaging approaches are used to measure left atrial volume, it is important to know whether values obtained by different imaging modalities or by the same imaging modality using different measurement algorithms are interchangeable. This is particularly relevant for follow-up examinations. The advent of real-time full-volume three-dimensional echocardiography allows rapid measurement of chamber volume without making geometric assumptions. Furthermore, the semiautomatic methods allow repeat measurement of volume changes during the cardiac cycle thus permitting volumetric quantification of atrial function. Although three-dimensional imaging modalities including magnetic resonance imaging and computed tomography are considered as non-invasive reference methods for cardiac chamber volume determination they are less available, more costly, more time consuming and have other specific limitations, and therefore are less suitable for atrial volume and function measurement in daily clinical practice. In this article we provide a critical review of available literature validating and comparing different non-invasive three-dimensional imaging modalities and measurement algorithms used for determination of left atrial volumes with special reference to three- dimensional echocardiography.

Image reconstruction for digital breast tomosynthesis (DBT) by using projection-angle-dependent filter functions

Digital breast tomosynthesis (DBT) is considered in clinics as a standard three-dimensional imaging modality, allowing the earlier detection of cancer. It typically acquires only 10–30 projections over a limited angle range of 15–60° with a stationary detector and typically uses a computationally-efficient filtered-backprojection (FBP) algorithm for image reconstruction. However, a common FBP algorithm yields poor image quality resulting from the loss of average image value and the presence of severe image artifacts due to the elimination of the dc component of the image by the ramp filter and to the incomplete data, respectively. As an alternative, iterative reconstruction methods are often used in DBT to overcome these difficulties, even though they are still computationally expensive. In this study, as a compromise, we considered a projection-angle-dependent filtering method in which one-dimensional geometry-adapted filter kernels are computed with the aid of a conjugate-gradient method and are incorporated into the standard FBP framework. We implemented the proposed algorithm and performed systematic simulation works to investigate the imaging characteristics. Our results indicate that the proposed method is superior to a conventional FBP method for DBT imaging and has a comparable computational cost, while preserving good image homogeneity and edge sharpening with no serious image artifacts.

Recent developments and best practice in brachytherapy treatment planning.

Brachytherapy has evolved over many decades, but more recently, there have been significant changes in the way that brachytherapy is used for different treatment sites. This has been due to the development of new, technologically advanced computer planning systems and treatment delivery techniques. Modern, three-dimensional (3D) imaging modalities have been incorporated into treatment planning methods, allowing full 3D dose distributions to be computed. Treatment techniques involving online planning have emerged, allowing dose distributions to be calculated and updated in real time based on the actual clinical situation. In the case of early stage breast cancer treatment, for example, electronic brachytherapy treatment techniques are being used in which the radiation dose is delivered during the same procedure as the surgery. There have also been significant advances in treatment applicator design, which allow the use of modern 3D imaging techniques for planning, and manufacturers have begun to implement new dose calculation algorithms that will correct for applicator shielding and tissue inhomogeneities. This article aims to review the recent developments and best practice in brachytherapy techniques and treatments. It will look at how imaging developments have been incorporated into current brachytherapy treatment and how these developments have played an integral role in the modern brachytherapy era. The planning requirements for different treatments sites are reviewed as well as the future developments of brachytherapy in radiobiology and treatment planning dose calculation.

Photonic integrated Mach-Zehnder interferometer with an on-chip reference arm for optical coherence tomography.

Optical coherence tomography (OCT) is a noninvasive, three-dimensional imaging modality with several medical and industrial applications. Integrated photonics has the potential to enable mass production of OCT devices to significantly reduce size and cost, which can increase its use in established fields as well as enable new applications. Using silicon nitride (Si3N4) and silicon dioxide (SiO2) waveguides, we fabricated an integrated interferometer for spectrometer-based OCT. The integrated photonic circuit consists of four splitters and a 190 mm long reference arm with a foot-print of only 10 × 33 mm(2). It is used as the core of a spectral domain OCT system consisting of a superluminescent diode centered at 1320 nm with 100 nm bandwidth, a spectrometer with 1024 channels, and an x-y scanner. The sensitivity of the system was measured at 0.25 mm depth to be 65 dB with 0.1 mW on the sample. Using the system, we imaged human skin in vivo. With further optimization in design and fabrication technology, Si3N4/SiO2 waveguides have a potential to serve as a platform for passive photonic integrated circuits for OCT.

Three-dimensional imaging modalities in endodontics.

Recent research in endodontics has highlighted the need for three-dimensional imaging in the clinical arena as well as in research. Three-dimensional imaging using computed tomography (CT) has been used in endodontics over the past decade. Three types of CT scans have been studied in endodontics, namely cone-beam CT, spiral CT, and peripheral quantitative CT. Contemporary endodontics places an emphasis on the use of cone-beam CT for an accurate diagnosis of parameters that cannot be visualized on a two-dimensional image. This review discusses the role of CT in endodontics, pertaining to its importance in the diagnosis of root canal anatomy, detection of peri-radicular lesions, diagnosis of trauma and resorption, presurgical assessment, and evaluation of the treatment outcome.

The role of imaging in radiation therapy planning: past, present, and future.

The use of ionizing radiation for cancer treatment has undergone extraordinary development during the past hundred years. The advancement of medical imaging has been critical in helping to achieve this change. The invention of computed tomography (CT) was pivotal in the development of treatment planning. Despite some disadvantages, CT remains the only three-dimensional imaging modality used for dose calculation. Newer image modalities, such as magnetic resonance (MR) imaging and positron emission tomography (PET), are also used secondarily in the treatment-planning process. MR, with its better tissue contrast and resolution than those of CT, improves tumor definition compared with CT planning alone. PET also provides metabolic information to supplement the CT and MR anatomical information. With emerging molecular imaging techniques, the ability to visualize and characterize tumors with regard to their metabolic profile, active pathways, and genetic markers, both across different tumors and within individual, heterogeneous tumors, will inform clinicians regarding the treatment options most likely to benefit a patient and to detect at the earliest time possible if and where a chosen therapy is working. In the post-human-genome era, multimodality scanners such as PET/CT and PET/MR will provide optimal tumor targeting information.

Total liquid ventilation: a new approach to improve 3D OCT image quality of alveolar structures in lung tissue

Little is known about mechanical processes of alveolar tissue during mechanical ventilation. Optical coherence tomography (OCT) as a three-dimensional and high-resolution imaging modality can be used to visualize subpleural alveoli during artificial ventilation. The quality of OCT images can be increased by matching the refractive index inside the alveoli to the one of tissue via liquid-filling. Thereby, scattering loss can be decreased and higher penetration depth and tissue contrast can be achieved. We show the liquid-filling of alveolar structures verified by optical coherence tomography and intravital microscopy (IVM) and the advantages of index matching for OCT imaging of subpleural alveoli in a mouse model using a custom-made liquid ventilator.

Three-dimensional stereoscopic imaging modality based on a single optical channel and detector

A three-dimensional stereoscopic imaging modality (3D-SIM) based on a single optical channel and detector was developed to overcome some of the limitations of conventional 3D-SIM. It produces 3-D stereoscopic images by adjusting the angle of a transparent rotating deflector (TRD) to generate disparity between left and right images. The angular effect of the TRD was demonstrated to investigate the feasibility of the proposed method in 3-D stereoscopic image generation. Results indicate that image disparity increased as a function of the rotation angles of the TRD, while maintaining adequate 3-D perception. These results are expected to facilitate the practical use of a 3D-SIM in medicine.

Generation of voxelized breast phantoms from surgical mastectomy specimens.

In the research and development of dedicated tomographic breast imaging systems, digital breast object models, also known as digital phantoms, are useful tools. While various digital breast phantoms do exist, the purpose of this study was to develop a realistic high-resolution model suitable for simulating three-dimensional (3D) breast imaging modalities. The primary goal was to design a model capable of producing simulations with realistic breast tissue structure. The methodology for generating an ensemble of digital breast phantoms was based on imaging surgical mastectomy specimens using a benchtop, cone-beam computed tomography system. This approach allowed low-noise, high-resolution projection views of the mastectomy specimens at each angular position. Reconstructions of these projection sets were processed using correction techniques and diffusion filtering prior to segmentation into breast tissue types in order to generate phantoms. Eight compressed digital phantoms and 20 uncompressed phantoms from which an additional 96 pseudocompressed digital phantoms with voxel dimensions of 0.2 mm(3) were generated. Two distinct tissue classification models were used in forming breast phantoms. The binary model classified each tissue voxel as either adipose or fibroglandular. A multivalue scaled model classified each tissue voxel as percentage of adipose tissue (range 1%-99%). Power spectral analysis was performed to compare simulated reconstructions using the breast phantoms to the original breast specimen reconstruction, and fits were observed to be similar. The digital breast phantoms developed herein provide a high-resolution anthropomorphic model of the 3D uncompressed and compressed breast that are suitable for use in evaluating and optimizing tomographic breast imaging modalities. The authors believe that other research groups might find the phantoms useful, and therefore they offer to make them available for wider use.

Reliability of clinically relevant 3D foot bone angles from quantitative computed tomography.

BackgroundSurgical treatment and clinical management of foot pathology requires accurate, reliable assessment of foot deformities. Foot and ankle deformities are multi-planar and therefore difficult to quantify by standard radiographs. Three-dimensional (3D) imaging modalities have been used to define bone orientations using inertial axes based on bone shape, but these inertial axes can fail to mimic established bone angles used in orthopaedics and clinical biomechanics. To provide improved clinical relevance of 3D bone angles, we developed techniques to define bone axes using landmarks on quantitative computed tomography (QCT) bone surface meshes. We aimed to assess measurement precision of landmark-based, 3D bone-to-bone orientations of hind foot and lesser tarsal bones for expert raters and a template-based automated method.MethodsTwo raters completed two repetitions each for twenty feet (10 right, 10 left), placing anatomic landmarks on the surfaces of calcaneus, talus, cuboid, and navicular. Landmarks were also recorded using the automated, template-based method. For each method, 3D bone axes were computed from landmark positions, and Cardan sequences produced sagittal, frontal, and transverse plane angles of bone-to-bone orientations. Angular reliability was assessed using intraclass correlation coefficients (ICCs) and the root mean square standard deviation (RMS-SD) for intra-rater and inter-rater precision, and rater versus automated agreement.ResultsIntra- and inter-rater ICCs were generally high (≥ 0.80), and the ICCs for each rater compared to the automated method were similarly high. RMS-SD intra-rater precision ranged from 1.4 to 3.6° and 2.4 to 6.1°, respectively, for the two raters, which compares favorably to uni-planar radiographic precision. Greatest variability was in Navicular: Talus sagittal plane angle and Cuboid: Calcaneus frontal plane angle. Precision of the automated, atlas-based template method versus the raters was comparable to each rater’s internal precision.ConclusionsIntra- and inter-rater precision suggest that the landmark-based methods have adequate test-retest reliability for 3D assessment of foot deformities. Agreement of the automated, atlas-based method with the expert raters suggests that the automated method is a valid, time-saving technique for foot deformity assessment. These methods have the potential to improve diagnosis of foot and ankle pathologies by allowing multi-planar quantification of deformities.

Cone Beam Computed Tomography in Dental Education: A Survey of U.S., U.K., and Australian Dental Schools

Cone beam computed tomography (CBCT) is an excellent three-dimensional (3D) imaging modality. Traditional dental education has focused on teaching conventional (2D) imaging. The aims of this survey-based study were therefore to evaluate the incorporation of CBCT teaching in both the predoctoral/undergraduate (D.D.S./D.M.D./B.D.S.) and postgraduate/residency specialty training curricula in dental schools in the United States, the United Kingdom, and Australia. A nine-question survey form was electronically mailed to fifty-seven schools in the United States, sixteen schools in the United Kingdom, and seven schools in Australia. Fifty U.S. dental schools (89 percent), ten U.K. dental schools (62.5 percent), and one Australian dental school (14 percent) presently have CBCT equipment. The majority of responding schools do not include instruction in higher level use of this technology for undergraduate/predoctoral students, raising questions as to whether these students are adequately trained on qualification. Larger numbers of schools reported providing this training to residents in specialty programs. A similar trend was noticed in U.S., British, and Australian dental education. If general dentists are to be permitted to purchase and use CBCT equipment, inclusion of CBCT in dental education is an absolute requirement to prepare future dental practitioners to apply 3D imaging appropriately for diagnosis and treatment planning.

An Improved Tamper Detection and Localization Scheme for Volumetric DICOM Images

The development of teleradiology brings the convenience of global medical record access along with the concerns over the security of medical images transmitted over the open network. With the prevailing adoption of three-dimensional (3-D) imaging modalities, it is vital to develop a security mechanism to provide large volumes of medical images with privacy and reliability. This paper presents the development of a new and improved method of implementing tamper detection and localization based on a fully reversible digital watermarking scheme for the protection of volumetric DICOM images. This tamper detection and localization method utilizes the 3-D property of volumetric data to achieve much faster processing time at both sender and receiver sides without compromising tamper localization accuracy. The performance of the proposed scheme was evaluated by using sample volumetric DICOM images. Results show that the scheme achieved on average about 65 % and 72 % reduction in watermarking and dewatermarking processing time, respectively. For cases where the images had been tampered, it is possible to detect and localize the tampered areas with improved localization resolution in the images using the scheme.