Educational stereoscopic representation of a step-by-step brain white fiber dissection according to Klingler's method

BACKGROUND

Understanding and teaching the three-dimensional architecture of the brain remains difficult because of the intricate arrangement of grey nuclei within white matter tracts. Although cortical area functions have been well studied, educational and three-dimensional descriptions of the organization of deep nuclei and white matter tracts are still missing.

OBJECTIVE

We propose herein a detailed step-by-step dissection of the lateral aspect of a left hemisphere using the Klingler method and provide high-quality stereoscopic views with the aim to help teach medical students or surgeons the three-dimensional anatomy of the brain.

METHODS

Three left hemispheres were extracted and prepared. Then, according to the Klingler method, dissections were carried out from the lateral aspect. Photographs were taken at each step and were modified to provide stereoscopic three-dimensional views.

RESULTS

Gray and white structures were described: cortex, claustrum, putamen, pallidum, caudate nucleus, amygdala; U-fibers, external and internal capsules, superior longitudinal fasciculus, frontal aslant fasciculus, uncinate fasciculus, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, corticospinal fasciculus, corona radiata, anterior commissure, and optic radiations.

CONCLUSION

This educational stereoscopic presentation of an expert dissection of brain white fibers and basal ganglia would be of value for theoretical or hands-on teaching of brain anatomy; labeling and stereoscopy could, moreover, improve the teaching, understanding, and memorizing of brain anatomy. In addition, this could be also used for the creation of a mental map by neurosurgeons for the preoperative planning of brain tumor surgery.

Success rates, near-response patterns, and learning trends with free-fusion stereograms

Free-fusion stereograms are routinely used for demonstrating various stereoscopic effects. Yet, untrained observers find it challenging to perform this task. This study showed that only less than 1/3rd of sixty-one pre-presbyopic adults with normal binocular vision could successfully free-fuse random-dot image pairs and identify the stereoscopic shapes embedded in these patterns. Another one-third of participants performed the task with poor success rates, while the remaining could not perform the task. There was a clear dissociation of vergence and accommodative responses in participants who were successful with free-fusion, as recorded using a dynamic infrared eye tracker and photorefractor. Those in the unsuccessful cluster either showed strong vergence and accommodation or weak vergence and strong accommodation during the task. These response patterns, however, were specific to the free-fusion task because all these participants generated good convergence/accommodation to real-world targets and to conflicting vergence and accommodative demands stimulated with prisms or lenses. Task performance of the unsuccessful cluster also improved significantly following pharmacological paralysis of accommodation and reached the performance levels of the successful cluster. A minority of participants also appeared to progressively learn to dissociate one of the two directions of their vergence and accommodation crosslinks with repeated free-fusion trials. These results suggest that successful free-fusion might depend upon how well participants generate a combination of volitional and reflex vergence responses to large differences in disparity with conflicting static accommodative demands. Such responses would require that only one direction of the vergence-accommodation crosslinks be active at any given time. The sequence of near-responses could also be learnt through repeated trials to optimize task performance.

Glaucoma screening using an attention-guided stereo ensemble network

Glaucoma is a chronic eye disease, which causes gradual vision loss and eventually blindness. Accurate glaucoma screening at early stage is critical to mitigate its aggravation. Extracting high-quality features are critical in training of classification models. In this paper, we propose a deep ensemble network with attention mechanism that detects glaucoma using optic nerve head stereo images. The network consists of two main sub-components, a deep Convolutional Neural Network that obtains global information and an Attention-Guided Network that localizes optic disc while maintaining beneficial information from other image regions. Both images in a stereo pair are fed into these sub-components, the outputs are fused together to generate the final prediction result. Abundant image features from different views and regions are being extracted, providing compensation when one of the stereo images is of poor quality. The attention-based localization method is trained in a weakly-supervised manner and only image-level annotation is required, which avoids expensive segmentation labelling. Results from real patient images show that our approach increases recall (sensitivity) from the state-of-the-art 88.89% to 95.48%, while maintaining precision and performance stability. The marked reduction in false-negative rate can significantly enhance the chance of successful early diagnosis of glaucoma.

3D Exoscope System in Neurosurgery-Comparison of a Standard Operating Microscope With a New 3D Exoscope in the Cadaver Lab

BACKGROUND

For decades, the operating microscope has been the "gold standard" visualization device in neurosurgery. The development of endoscopy revolutionized different surgical disciplines, whereas in neurosurgery, the endoscope is commonly used as an additional device more than as single visualization tool. Invention of a 3D exoscope system opens new possibilities in visualization and ergonomics in neurosurgery.

OBJECTIVE

To assess the prototype of a 3D exoscope (3D exoscope, year of manufacture 2015, FA Aesculap, Tüttlingen, Germany) as neurosurgical visualization device in comparison to a standard operating microscope.

METHODS

A pterional approach was performed in 3 ETOH-fixed specimens (6 sides). A standard operating microscope was compared to a 3D exoscope prototype. Dimensions like visual field, magnification, illumination, ergonomics, depth effect, and 3D impression were compared.

RESULTS

In all approaches, the structures of interest could be clearly visualized with both devices. Magnification showed similar results. The exoscope had more magnification potential, whereas the visual quality got worse in higher magnification levels. The illumination showed better results in the microscope. Surgeons felt more comfortable with the 3D exoscope, concerning ergonomic considerations. Depth effect and 3D impression showed similar results. None of the surgeons felt uncomfortable using the exoscope.

CONCLUSION

The operating microscope is the gold standard visualization tool in neurosurgery because of its illumination, stereoscopy, and magnification. Nevertheless, it causes ergonomic problems. The prototype of a 3D exoscope showed comparable features in visual field, stereoscopic impression, and magnification, with a clear benefit concerning the ergonomic possibilities.

Learning curves, potential and speed in training of laparoscopic skills: a randomised comparative study in a box trainer

Background

The effectiveness of practical surgical training is characterised by an inherent learning curve. Decisive are individual initial starting capabilities, learning speed, ideal learning plateaus, and resulting learning potentials. The quantification of learning curves requires reproducible tasks with varied levels of difficulty. The hypothesis of this study is that the use of three-dimensional (3D) vision is more advantageous than two-dimensional vision (2D) for the learning curve in laparoscopic training.

Methods

Forty laparoscopy novices were recruited and randomised to a 2D Group and a 3D Group. A laparoscopy box trainer with two standardised tasks was used for training of surgical tasks. Task 1 was a positioning task, while Task 2 called for laparoscopic knotting as a more complex process. Each task was repeated at least ten times. Performance time and the number of predefined errors were recorded. 2D performance after 3D training was assessed in an additional final 2D cycle undertaken by the 3D Group.

Results

The calculated learning plateaus of both performance times and errors were lower for 3D. Independent of the vision mode the learning curves were smoother (exponential decay) and efficiency was learned faster than precision. The learning potentials varied widely depending on the corresponding initial values and learning plateaus. The final 2D performance time of the 3D-trained group was not significantly better than that of the 2D Group. The final 2D error numbers were similar for all groups.

Conclusions

Stereoscopic vision can speed up laparoscopic training. The 3D learning curves resulted in better precision and efficiency. The 3D-trained group did not show inferior performance in the final 2D cycle. Consequently, we encourage the training of surgical competences like suturing and knotting under 3D vision, even if it is not available in clinical routine.

Stereoscopic three-dimensional visualization: interest for neuroanatomy teaching in medical school

PURPOSE

The anatomy of both the brain and the skull is particularly difficult to learn and to teach. Since their anatomical structures are numerous and gathered in a complex tridimensional (3D) architecture, classic schematical drawing or photography in two dimensions (2D) has difficulties in providing a clear, simple, and accurate message. Advances in photography and computer sciences have led to develop stereoscopic 3D visualization, firstly for entertainment then for education. In the present study, we report our experience of stereoscopic 3D lecture for neuroanatomy teaching to early medical school students.

METHODS

High-resolution specific pictures were taken on various specimen dissections in the Anatomy Laboratory of the University of Lyon, France. Selected stereoscopic 3D views were displayed on a large dedicated screen using a doubled video projector. A 2-h stereoscopic neuroanatomy lecture was given by two neuroanatomists to third-year medicine students who wore passive 3D glasses. Setting up lasted 30 min and involved four people. The feedback from students was collected and analyzed.

RESULTS

Among the 483 students who have attended the stereoscopic 3D lecture, 195 gave feedback, and all (100%) were satisfied. Among these, 190 (97.5%) reported a better knowledge transfer of brain anatomy and its 3D architecture. Furthermore, 167 (86.1%) students felt it could change their further clinical practice, 179 (91.8%) thought it could enhance their results in forthcoming anatomy examinations, and 150 (76.9%) believed such a 3D lecture might allow them to become better physicians. This 3D anatomy lecture was graded 8.9/10 a mean against 5.9/10 for previous classical 2D lectures.

DISCUSSION-CONCLUSION

The stereoscopic 3D teaching of neuroanatomy made medical students enthusiastic involving digital technologies. It could improve their anatomical knowledge and test scores, as well as their clinical competences. Depending on university means and the commitment of teachers, this new tool should be extended to other anatomical fields. However, its setting up requires resources from faculties and its impact on clinical competencies needs to be objectively assessed.

tDCS recovers depth perception in adult amblyopic rats and reorganizes visual cortex activity

Amblyopia or lazy eye is a neurodevelopmental disorder that arises during the infancy and is caused by the interruption of binocular sensory activity before maturation of the nervous system. This impairment causes long-term deterioration of visual skills, particularly visual acuity and depth perception. Although visual function recovery has been supposed to be decreased with age as consequence of reduced neuronal plasticity, recent studies have shown that it is possible to promote plasticity and neurorestoration in the adult brain. Thus, transcranial direct current stimulation (tDCS) has been shown effective to treat amblyopia in the adulthood. In the present work we used postnatal monocular deprivation in Long Evans rats as an experimental model of amblyopia and the cliff test task to assess depth perception. Functional brain imaging PET was used to assess the effect of tDCS on cortical and subcortical activity. Visually deprived animals ability to perceive depth in the cliff test was significantly reduced in comparison to their controls. However, after 8 sessions of tDCS applied through 8 consecutive days, depth perception of amblyopic treated animals improved reaching control level. PET data showed 18F-FDG uptake asymmetries in the visual cortex of amblyopic animals, which disappeared after tDCS treatment. The possibility of cortical reorganization and stereoscopy recovery following brain stimulation points at tDCS as a useful strategy for treating amblyopia in adulthood. Furthermore, monocular deprivation in Long Evans rats is a valuable research model to study visual cortex mechanisms involved in depth perception and neural restoration after brain stimulation.

Stereoscopic versus monoscopic displays: Learning fine manual dexterity skills using a microsurgical task simulator

We investigated the learning of fine manual dexterity with a microsurgical instrument and a new simulator in a context of microsurgery. 30 subjects were divided into two groups. One (3D group) interacted with a stereoscopic and the other (2D group) with a monoscopic display. Visual information for the displays was captured from a surgical stereomicroscope. In 20 trials, both groups performed the repetitive tasks of picking up small rods from a funnel-shaped cavity and placing them outside. In analysing learning curves, we found that the initial learning process for hand-eye coordination is easier with a 3D display, and that performance persists at a higher level of proficiency than with the 2D display option. Thus stereoscopic displays can be especially beneficial for novices, for those learning new procedures, or for providing orientation to operators facing a new or altered spatial situation. Simulators with few reliefs or spatial textures should not be used for comparison between 3D and 2D viewing conditions.

Surface deformation tracking and modelling of soft materials

Many computer vision algorithms have been presented to track surface deformations, but few have provided a direct comparison of measurements with other stereoscopic approaches and physics-based models. We have previously developed a phase-based cross-correlation algorithm to track dense distributions of displacements over three-dimensional surfaces. In the present work, we compare this algorithm with one that uses an independent tracking system, derived from an array of fluorescent microspheres. A smooth bicubic Hermite mesh was fitted to deformations obtained from the phase-based cross-correlation data. This mesh was then used to estimate the microsphere locations, which were compared to stereo reconstructions of the microsphere positions. The method was applied to a 35 mm × 35 mm × 35 mm soft silicone gel cube under indentation, with three square bands of microspheres placed around the indenter tip. At an indentation depth of 4.5 mm, the root-mean-square (RMS) differences between the reconstructed positions of the microspheres and their identified positions for the inner, middle, and outer bands were 60 µm, 20 µm, and 19 µm, respectively. The usefulness of the strain-tracking data for physics-based finite element modelling of large deformation mechanics was then demonstrated by estimating a neo-Hookean stiffness parameter for the gel. At the optimal constitutive parameter estimate, the RMS difference between the measured microsphere positions and their finite element model-predicted locations was 143 µm.

Three-dimensional reconstruction and quantification of dislocation substructures from transmission electron microscopy stereo pairs

A great amount of material properties is strongly influenced by dislocations, the carriers of plastic deformation. It is therefore paramount to have appropriate tools to quantify dislocation substructures with regard to their features, e.g., dislocation density, Burgers vectors or line direction. While the transmission electron microscope (TEM) has been the most widely-used equipment implemented to investigate dislocations, it usually is limited to the two-dimensional (2D) observation of three-dimensional (3D) structures. We reconstruct, visualize and quantify 3D dislocation substructure models from only two TEM images (stereo pairs) and assess the results. The reconstruction is based on the manual interactive tracing of filiform objects on both images of the stereo pair. The reconstruction and quantification method are demonstrated on dark field (DF) scanning (S)TEM micrographs of dislocation substructures imaged under diffraction contrast conditions. For this purpose, thick regions (>300 nm) of TEM foils are analyzed, which are extracted from a Ni-base superalloy single crystal after high temperature creep deformation. It is shown how the method allows 3D quantification from stereo pairs in a wide range of tilt conditions, achieving line length and orientation uncertainties of 3% and 7°, respectively. Parameters that affect the quality of such reconstructions are discussed.

Stereoscopic Versus Monoscopic Viewing of Aneurysms: Experience of a Single Institution with a Novel Stereoscopic Viewing System

OBJECTIVE

Stereoscopic viewing of computed tomographic angiography (CT-A) or magnetic resonance angiograms might increase the diagnostic potential of these imaging techniques. Our aim was to evaluate the benefits of a novel stereoscopic viewing system for aneurysm detection compared with standard monoscopic viewing.

METHODS

Retrospective patient data were used for 2 different evaluations. First, monoscopic and stereoscopic CT-A viewing was compared by 14 clinicians in 10 patients with challenging (i.e., small and initially CT-A negative) aneurysms. Second, stereoscopic CT-As and the reference standard, digital subtraction angiography (DSA), were compared in 15 patients with randomly selected aneurysms by 12 clinicians. The study participants rated the presence and location of any aneurysm and its morphological characteristics. The detection rates and interrater reliability were calculated.

RESULTS

The first evaluation showed superior aneurysm detection in challenging cases using stereoscopic versus monoscopic CT-A viewing (median: monoscopic, 20%; interquartile range [IQR], 10%-32.5%; stereoscopic, 40%; IQR, 27.5%-42.5%). The interrater reliability analysis revealed good to excellent agreement among raters for aneurysm detection in both viewing modalities (monoscopic, intraclass correlation coefficient [ICC(2,1)], 0.798; 95% confidence interval [CI], 0.549-0.941; stereoscopic viewing, ICC(2,1), 0.895; 95% CI, 0.770-0.968). The second part demonstrated that stereoscopic CT-A viewing is comparable to DSA viewing for aneurysm detection (median: DSA, 80%; IQR, 73%-100%; stereoscopic CT-A, 87%; IQR, 87%-93%). The interrater reliability analysis revealed excellent absolute agreement in aneurysm detection between DSA and stereoscopic CT-A viewing (DSA: ICC(2,1), 0.971; 95% CI, 0.944-0.989; stereoscopic CT-A: ICC(2,1), 0.972; 95% CI, 0.945-0.989). The aneurysm detection rates correlated significantly with the participants' years of experience.

CONCLUSIONS

Stereoscopic viewing of CT-As increases the diagnostic accuracy and represents a promising technique to reduce the need for invasive DSA.

Superficial zone cellularity is deficient in mice lacking lubricin: a stereoscopic analysis

Background

Lubricin, a mucinous glycoprotein secreted by synoviocytes and chondrocytes plays an important role in reducing the coefficient of friction in mammalian joints. Elevated cartilage surface friction is thought to cause chondrocyte loss; however, its quantification and methodological approaches have not been reported. We adapted a stereological method and incorporated vital cell staining to assess cellular loss in superficial and upper intermediate zones in lubricin deficient mouse cartilage.

Methods

The femoral condyle cartilage of the intact knees from lubricin wild type (Prg4^+/+), heterozygote (Prg4^+/-), and knockout (Prg4^-/-) mice was imaged using fluorescein diacetate (FDA), propidium iodide (PI), and Hoechst staining, and confocal microscopy. Three dimensional reconstructions of confocal images to a depth of 14 μm were analyzed using Matlab to determine the volume fraction occupied by chondrocytes in cartilage of both medial and lateral femoral condyles. Living chondrocyte volume fraction was defined as FDA stained chondrocyte volume/total volume of superficial + upper intermediate zone. Living and dead (total) chondrocyte volume fraction was defined as FDA + PI stained chondrocyte volume/total volume of superficial + upper intermediate zone. MicroCT provided an orthogonal measure of cartilage thickness. Immunohistology for activated caspase-3 and TUNEL staining were performed to evaluate the presence of apoptotic chondrocytes in Prg4 mutant mice.

Results

Living chondrocyte volume fraction of the medial femoral condyle was significantly lower in Prg4^-/- mice compared to Prg4^+/+ (p = 0.002) and Prg4^+/- (p = 0.002) littermates. There was no significant difference in medial condyle chondrocyte volume fraction between Prg4^+/+ and Prg4^+/- mice (p = 0.82). No significant differences were observed for the chondrocyte volume fraction for the lateral condyle (p > 0.26). Cartilage thickness increased in the medial condyle for Prg4^-/- mice compared to Prg4^+/+ (p = 0.02) and Prg4^+/- (p = 0.03) littermates, and the lateral condyle for Prg4^-/- mice compared to Prg4^+/+ (p < 0.0001) and Prg4^+/- (p < 0.0001) littermates, indicating that a multi-dimensional increase in cartilage volume did not artifactually lower the chondrocyte volume fraction in the medial condyle. Significantly higher number of caspase-3 positive cells were observed in the superficial and upper intermediate zone cartilage of the medial femoral condyle of Prg4^-/- mice compared to Prg4^+/+ (p = 0.01) and Prg4^+/- (p = 0.04) littermates, and the lateral femoral condyle of Prg4^-/- mice compared to Prg4^+/+ (p = 0.02) and Prg4^+/- (p = 0.02) littermates. There were no significant differences in TUNEL staining among different Prg4 genotypes in both condyles (p > 0.05 for all comparisons).

Conclusions

Increased Caspase-3 activation is observed in Prg4 deficient mice compared to Prg4 sufficient littermates. Absence of Prg4 induces loss of chondrocytes in the superficial and upper intermediate zone of mouse cartilage that is quantifiable by a novel image processing technique.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-0967-4) contains supplementary material, which is available to authorized users.

Calibration-free quantitative surface topography reconstruction in scanning electron microscopy

This work presents a new approach to obtain reliable surface topography reconstructions from 2D Scanning Electron Microscopy (SEM) images. In this method a set of images taken at different tilt angles are compared by means of digital image correlation (DIC). It is argued that the strength of the method lies in the fact that precise knowledge about the nature of the rotation (vector and/or magnitude) is not needed. Therefore, the great advantage is that complex calibrations of the measuring equipment are avoided. The paper presents the necessary equations involved in the methods, including derivations and solutions. The method is illustrated with examples of 3D reconstructions followed by a discussion on the relevant experimental parameters.

Real-scale 3D models of the scoliotic spine from biplanar radiography without calibration objects

This paper presents a new method for modelling the spines of subjects and making accurate 3D measurements using standard radiologic systems without requiring calibration objects. The method makes use of the focal distance and statistical models for estimating the geometrical parameters of the system. A dataset of 32 subjects was used to assess this method. The results show small errors for the main clinical indices, such as an RMS error of 0.49° for the Cobb angle, 0.50° for kyphosis, 0.38° for lordosis, and 2.62mm for the spinal length. This method is the first to achieve this level of accuracy without requiring the use of calibration objects when acquiring radiographs. We conclude that the proposed method allows for the evaluation of scoliosis with a much simpler setup than currently available methods.

SU-E-J-79: Using the Distance of Closest Approach to Improve Compton Camera Image Quality

PURPOSE

The prompt gamma radiation emitted from tissue during proton therapy offers a means of beam range verification. Compton camera (CC) imaging systems offer high efficiency and 3D imaging capability. However, Doppler broadening and the inaccuracies in the measurement of the scattering positions and energies reduce the image resolution. The purpose of our study is to determine if removing events with a distance-of-closest-approach greater than a threshold value will improve the resolution of images reconstructed using the stochastic origins ensemble (SOE) algorithm.

METHODS

We first simulated a 3-stage CC detecting gammas from a 0.511 MeV point source. We then used SOE to reconstruct images from the point source and from a) all gammas, b) gammas with DCA < 3 mm, and c) gammas with DCA < 1 mm. We measured the point-spread-function for the point source for a), b), and c). Next, we simulated a 3-stage CC detecting prompt gammas emitted from tissue during proton therapy. We reconstructed the gammas using SOE and compared 2D images of all gammas, gammas with DCA < 3 mm, and gammas with DCA < 1 mm.

RESULTS

The FWHM of the PSF of the 0.511 MeV point source was reduced by 50% when DCA was required to be < 5 mm, and it was reduced by 65% when DCA was required to be < 3 mm. 2D images of a proton beam are of visibly higher quality as the DCA requirement is lowered.

CONCLUSIONS

The DCA for MC events can be used to identify the events with significant resolution loss due to the detector effects. Removing these events before running the reconstruction algorithm results in higher quality images. We discuss methods to predict the DCA based on the measured scatter data, so that a similar technique can be applied to data from real detectors. This work was supported by the National Institutes of Health through award number R21CA137362 from the National Cancer Institute.

SU-E-J-98: 3D Tracking of Interfraction Patient Setup Uncertainties Using Multiple Kinect Sensors

PURPOSE

On-board optical 3D imaging enables measuring daily setup patient uncertainties without involving any additional imaging-induced radiation dose to critical structures. We hypothesize that the tumor and normal organ deformation caused by routine patient head and neck misalignments can be determined by coupling a quantitative patient-specific biomechanical model with quantitative skin surface 3D imaging.

METHODS

A set of 3D cameras are used to track the patient anatomy externally. One of the cameras employed a marker less face recognition and tracking for delineating the region of the patient's face. The location of the face was then shared among the camera controllers in real-time and the anatomical contour that closely matches the face region is selected and integrated to form a single 3D anatomical representation. Patient surface aligning was performed between the patient's external surface obtained from a reference 3D anatomy (simulation CT, MRI, patient surface map from previous fraction) and the above-mentioned camera system to quantify the daily patient setup variations. For each of the 3D patient surface, a point feature histogram (PFH) was first generated. Once the PFH descriptors were generated, a non-rigid iterative closest point registration algorithm that minimizes the difference in the PFH descriptor aligns the patient surface to the reference 3D anatomy.

RESULTS

The proposed tracking system was able to track both the patient surface setup uncertainty and the internal anatomy when coupledwith a patient specific biomechanical head and neck model.

CONCLUSIONS

A 3D head and neck tracking system that monitors the interfraction patient setup uncertainties in the head and neck cancer patient is presented. The aligning process was shown to perform for cases with and without the head immobilization system. The external patient surface manifold and the motion vectors will be coupled to align the biomechanical model using model-guided techniques.

SU-E-J-05: Validation of an Iterative Tomosynthesis Algorithm for Low Dose on Board Cone Beam CT Patient Localization

PURPOSE

Cone beam CT (CBCT) is a well established technique to localize patients using bone and soft tissue anatomy. Current protocols are limited to one weekly CBCT due to the considerable imaging dose delivered to the patient. The purpose of this project is to develop and validate a low dose CBCT algorithm to reduce dose and imaging time of current 3D imaging localization procedures using a novel iterative tomosynthesis algorithm to allow daily CBCT for patient positioning and target localization.

METHODS

The algorithm is based on the combination of a tomosynthesis filtered back propagation (TFBP) acquisition geometry algorithm and a maximum likelihood expectation maximization (MLEM) iterative reconstruction. Circular or arc acquisition trajectory, projection number, and angular projection position are optimized according to the anatomical treatment site and region of interest. The TFBP method provides the first 3D image estimate, and the MLEM improves its quality. In this study, we focused on head and neck treatment localization imaging.

RESULTS

We studied the performance of our tomosynthesis algorithm imaging resolution on an anthropomorphic head and neck phantom to determine image quality as a function of dose reduction techniques. Reconstructed anatomy shows that a 1/8 dose reduction provides similar image quality and resolution as current CBCT protocols. Seven iterations show an optimal compromise between image quality and reconstruction time. Tomosynthesis images provide digitally reconstructed radiographs with similar resolution and contrast as full CBCT. We verified that the iterative process eliminates phantom images originated by the acquired sparse angular data projections.

CONCLUSIONS

We developed and validated an iterative algorithm for low dose cone beam CT based on circular or arc tomosynthesis geometries and iterative reconstruction techniques. The algorithm combines the strengths of both techniques to provide a novel low dose method to image patient anatomy for patient positioning and target localization.

WE-G-217A-05: Automatic Method for RF Coil Assessment in Clinical MRI: A Three-Dimensional Approach

PURPOSE

MRI RF coil assessment is usually evaluated with region-of-interest (ROI) analysis from a single 2D phantom image. This simple approach has worked well for large volume coils or phased-array coil with large receivers, but not the high density phased-array coils characterized by 3D array arrangement of their multiple receivers. This abstract proposes a novel approach for quantitative coil assessment based on 3D imaging and 3D ROI analysis.

METHODS

To characterize all receivers of the coil of interest, a large uniform phantom (preferably a corresponding anthropometric phantom) and a large 3D geometric coverage fully includes the coil sensitivity volume was applied during MR imaging. After imaging, data from all receivers were used to reconstruct a composite 3D image, and to reconstruct 3D images from each individual receiver, leading to a total of N+1 3D image datasets (where N is the number of coil channels). IDL programs were developed to automatically perform ROI analysis on the composite image and on the individual receiver images. Instead of choosing one single 2D slice out of each 3D dataset, the whole 3D dataset was treated as a 3D image, and 3D ROIs were automatically generated for coil assessment.

RESULTS

This 3D coil evaluation approach could be applied to all clinical coils including quadrature body/head coils, and phased-array coils with 2 to 32 channels. 3D sensitivity map could be generated to check receiver function visually. 3D mean SNR, max SNR, and uniformity could be obtained from composite and individual channel 3D images fully automatically. Coil/receiver performance assessment was very fast and straightforward, regardless of the number of receivers of the coil.

CONCLUSIONS

3D imaging in combination with 3D automatic ROI analysis is a fast, convenient, and less subjective approach for quantitative coil assessment, particularly for high density phased-array coils.