Cervical soft tissue imaging using a mobile CBCT scanner with a flat panel detector in comparison with corresponding CT and MRI data sets

OBJECTIVE: The aim of this study was to evaluate soft tissue image quality of a mobile cone-beam computed tomography (CBCT) scanner with an integrated flat-panel detector. STUDY DESIGN: Eight fresh human cadavers were used in this study. For evaluation of soft tissue visualization, CBCT data sets and corresponding computed tomography (CT) and magnetic resonance imaging (MRI) data sets were acquired. Evaluation was performed with the help of 10 defined cervical anatomical structures. RESULTS: The statistical analysis of the scoring results of 3 examiners revealed the CBCT images to be of inferior quality regarding the visualization of most of the predefined structures. Visualization without a significant difference was found regarding the demarcation of the vertebral bodies and the pyramidal cartilages, the arteriosclerosis of the carotids (compared with CT), and the laryngeal skeleton (compared with MRI). Regarding arteriosclerosis of the carotids compared with MRI, CBCT proved to be superior. CONCLUSIONS: The integration of a flat-panel detector improves soft tissue visualization using a mobile CBCT scanner.

Automated 3D Lumbar Intervertebral Disc Segmentation from MRI Data Sets

This paper proposed an automated 3D lumbar intervertebral disc (IVD) segmentation strategy from MRI data. Starting from two user supplied landmarks, the geometrical parameters of all lumbar vertebral bodies and intervertebral discs are automatically extracted from a mid-sagittal slice using a graphical model based approach. After that, a three-dimensional (3D) variable-radius soft tube model of the lumbar spine column is built to guide the 3D disc segmentation. The disc segmentation is achieved as a multi-kernel diffeomorphic registration between a 3D template of the disc and the observed MRI data. Experiments on 15 patient data sets showed the robustness and the accuracy of the proposed algorithm.

Fusion of fundus images and MRI data of the human eye

Purpose Ophthalmologists are confronted with a set of different image modalities to diagnose eye tumors e.g., fundus photography, CT and MRI. However, these images are often complementary and represent pathologies differently. Some aspects of tumors can only be seen in a particular modality. A fusion of modalities would improve the contextual information for diagnosis. The presented work attempts to register color fundus photography with MRI volumes. This would complement the low resolution 3D information in the MRI with high resolution 2D fundus images. Methods MRI volumes were acquired from 12 infants under the age of 5 with unilateral retinoblastoma. The contrast-enhanced T1-FLAIR sequence was performed with an isotropic resolution of less than 0.5mm. Fundus images were acquired with a RetCam camera. For healthy eyes, two landmarks were used: the optic disk and the fovea. The eyes were detected and extracted from the MRI volume using a 3D adaption of the Fast Radial Symmetry Transform (FRST). The cropped volume was automatically segmented using the Split Bregman algorithm. The optic nerve was enhanced by a Frangi vessel filter. By intersection the nerve with the retina the optic disk was found. The fovea position was estimated by constraining the position with the angle between the optic and the visual axis as well as the distance from the optic disk. The optical axis was detected automatically by fitting a parable on to the lens surface. On the fundus, the optic disk and the fovea were detected by using the method of Budai et al. Finally, the image was projected on to the segmented surface using the lens position as the camera center. In tumor affected eyes, the manually segmented tumors were used instead of the optic disk and macula for the registration. Results In all of the 12 MRI volumes that were tested the 24 eyes were found correctly, including healthy and pathological cases. In healthy eyes the optic nerve head was found in all of the tested eyes with an error of 1.08 +/- 0.37mm. A successful registration can be seen in figure 1. Conclusions The presented method is a step toward automatic fusion of modalities in ophthalmology. The combination enhances the MRI volume with higher resolution from the color fundus on the retina. Tumor treatment planning is improved by avoiding critical structures and disease progression monitoring is made easier.

3D documentation and visualization of external injury findings by integration of simple photography in CT/MRI data sets (IprojeCT).

This study evaluated the feasibility of documenting patterned injury using three dimensions and true colour photography without complex 3D surface documentation methods. This method is based on a generated 3D surface model using radiologic slice images (CT) while the colour information is derived from photographs taken with commercially available cameras. The external patterned injuries were documented in 16 cases using digital photography as well as highly precise photogrammetry-supported 3D structured light scanning. The internal findings of these deceased were recorded using CT and MRI. For registration of the internal with the external data, two different types of radiographic markers were used and compared. The 3D surface model generated from CT slice images was linked with the photographs, and thereby digital true-colour 3D models of the patterned injuries could be created (Image projection onto CT/IprojeCT). In addition, these external models were merged with the models of the somatic interior. We demonstrated that 3D documentation and visualization of external injury findings by integration of digital photography in CT/MRI data sets is suitable for the 3D documentation of individual patterned injuries to a body. Nevertheless, this documentation method is not a substitution for photogrammetry and surface scanning, especially when the entire bodily surface is to be recorded in three dimensions including all external findings, and when precise data is required for comparing highly detailed injury features with the injury-inflicting tool.

Automated 3D Lumbar Intervertebral Disc Segmentation from MRI Data Sets

This paper proposed an automated three-dimensional (3D) lumbar intervertebral disc (IVD) segmentation strategy from Magnetic Resonance Imaging (MRI) data. Starting from two user supplied landmarks, the geometrical parameters of all lumbar vertebral bodies and intervertebral discs are automatically extracted from a mid-sagittal slice using a graphical model based template matching approach. Based on the estimated two-dimensional (2D) geometrical parameters, a 3D variable-radius soft tube model of the lumbar spine column is built by model fitting to the 3D data volume. Taking the geometrical information from the 3D lumbar spine column as constraints and segmentation initialization, the disc segmentation is achieved by a multi-kernel diffeomorphic registration between a 3D template of the disc and the observed MRI data. Experiments on 15 patient data sets showed the robustness and the accuracy of the proposed algorithm.

Automated Intervertebral Disc Detection from Low Resolution, Sparse MRI Images for the Planning of Scan Geometries

Robust and accurate identification of intervertebral discs from low resolution, sparse MRI scans is essential for the automated scan planning of the MRI spine scan. This paper presents a graphical model based solution for the detection of both the positions and orientations of intervertebral discs from low resolution, sparse MRI scans. Compared with the existing graphical model based methods, the proposed method does not need a training process using training data and it also has the capability to automatically determine the number of vertebrae visible in the image. Experiments on 25 low resolution, sparse spine MRI data sets verified its performance.

Brain atrophy in pure and complicated hereditary spastic paraparesis: a quantitative 3D MRI study

Hereditary spastic paraparesis (HSP) is a heterogeneous group of neurodegenerative disorders with progressive lower limb spasticity, categorized into pure (p-HSP) and complicated forms (c-HSP). The purpose of this study was to evaluate if brain volumes in HSP were altered compared with a control population. Brain volumes were determined in patients suffering from HSP, including both p-HSP (n = 21) and c-HSP type (n = 12), and 30 age-matched healthy controls, using brain parenchymal fractions (BPF) calculated from 3D MRI data in an observer-independent procedure. In addition, the tissue segments of grey and white matter were analysed separately. In HSP patients, BPF were significantly reduced compared with controls both for the whole patient group (P < 0.001) and for both subgroups, indicating considerable brain atrophy. In contrast to controls who showed a decline of brain volumes with age, this physiological phenomenon was less pronounced in HSP. Therefore, global brain parenchyma reduction, involving both grey and white matter, seems to be a feature in both subtypes of HSP. Atrophy was more pronounced in c-HSP, consistent with the more severe phenotype including extramotor involvement. Thus, global brain atrophy, detected by MRI-based brain volume quantification, is a biological marker in HSP subtypes.

Postmortem imaging of blunt chest trauma using CT and MRI: comparison with autopsy

OBJECTIVE: Postmortem examination of chest trauma is an important domain in forensic medicine, which is today performed using autopsy. Since the implementation of cross-sectional imaging methods in forensic medicine such as computed tomography (CT) and magnetic resonance imaging (MRI), a number of advantages in comparison with autopsy have been described. Within the scope of validation of cross-sectional radiology in forensic medicine, the comparison of findings of postmortem imaging and autopsy in chest trauma was performed. METHODS: This retrospective study includes 24 cases with chest trauma that underwent postmortem CT, MRI, and autopsy. Two board-certified radiologists, blind to the autopsy findings, evaluated the radiologic data independently. Each radiologist interpreted postmortem CT and MRI data together for every case. The comparison of the results of the radiologic assessment with the autopsy and a calculation of interobserver discrepancy was performed. RESULTS: Using combined CT and MRI, between 75% and 100% of the investigated findings, except for hemomediastinum (70%), diaphragmatic ruptures (50%; n=2) and heart injury (38%), were discovered. Although the sensitivity and specificity regarding pneumomediastinum, pneumopericardium, and pericardial effusion were not calculated, as these findings were not mentioned at the autopsy, these findings were clearly seen radiologically. The averaged interobserver concordance was 90%. CONCLUSION: The sensitivity and specificity of our results demonstrate that postmortem CT and MRI are useful diagnostic methods for assessing chest trauma in forensic medicine as a supplement to autopsy. Further radiologic-pathologic case studies are necessary to define the role of postmortem CT and MRI as a single examination modality.

Chronometric features of processing unpleasant stimuli: a functional MRI-based transcranial magnetic stimulation study.

The quick identification of potentially threatening events is a crucial cognitive capacity to survive in a changing environment. Previous functional MRI data revealed the right dorsolateral prefrontal cortex and the region of the left intraparietal sulcus (IPS) to be involved in the perception of emotionally negative stimuli. For assessing chronometric aspects of emotion processing, we applied transcranial magnetic stimulation above these areas at different times after negative and neutral picture presentation. An interference with emotion processing was found with transcranial magnetic stimulation above the dorsolateral prefrontal cortex 200-300 ms and above the left intraparietal sulcus 240/260 ms after negative stimuli. The data suggest a parallel and conjoint involvement of prefrontal and parietal areas for the identification of emotionally negative stimuli.

Noninvasive pressure difference mapping derived from 4D flow MRI in patients with unrepaired and repaired aortic coarctation.

PURPOSE To develop a method for computing and visualizing pressure differences derived from time-resolved velocity-encoded three-dimensional phase-contrast magnetic resonance imaging (4D flow MRI) and to compare pressure difference maps of patients with unrepaired and repaired aortic coarctation to young healthy volunteers. METHODS 4D flow MRI data of four patients with aortic coarctation either before or after repair (mean age 17 years, age range 3-28, one female, three males) and four young healthy volunteers without history of cardiovascular disease (mean age 24 years, age range 20-27, one female, three males) was acquired using a 1.5-T clinical MR scanner. Image analysis was performed with in-house developed image processing software. Relative pressures were computed based on the Navier-Stokes equation. RESULTS A standardized method for intuitive visualization of pressure difference maps was developed and successfully applied to all included patients and volunteers. Young healthy volunteers exhibited smooth and regular distribution of relative pressures in the thoracic aorta at mid systole with very similar distribution in all analyzed volunteers. Patients demonstrated disturbed pressures compared to volunteers. Changes included a pressure drop at the aortic isthmus in all patients, increased relative pressures in the aortic arch in patients with residual narrowing after repair, and increased relative pressures in the descending aorta in a patient after patch aortoplasty. CONCLUSIONS Pressure difference maps derived from 4D flow MRI can depict alterations of spatial pressure distribution in patients with repaired and unrepaired aortic coarctation. The technique might allow identifying pathophysiological conditions underlying complications after aortic coarctation repair.

Detecting subarachnoid hemorrhage: Comparison of combined FLAIR/SWI versus CT

OBJECTIVES: Aim of this study was to compare the utility of susceptibility weighted imaging (SWI) with the established diagnostic techniques CT and fluid attenuated inversion recovery (FLAIR) in their detecting capacity of subarachnoid hemorrhage (SAH), and further to compare the combined SWI/FLAIR MRI data with CT to evaluate whether MRI is more accurate than CT. METHODS: Twenty-five patients with acute SAH underwent CT and MRI within 6 days after symptom onset. Underlying pathology for SAH was head trauma (n=9), ruptured aneurysm (n=6), ruptured arteriovenous malformation (n=2), and spontaneous bleeding (n=8). SWI, FLAIR, and CT data were analyzed. The anatomical distribution of SAH was subdivided into 8 subarachnoid regions with three peripheral cisterns (frontal-parietal, temporal-occipital, sylvian), two central cisterns and spaces (interhemispheric, intraventricular), and the perimesencephalic, posterior fossa, superior cerebellar cisterns. RESULTS: SAH was detected in a total of 146 subarachnoid regions. CT identified 110 (75.3%), FLAIR 127 (87%), and SWI 129 (88.4%) involved regions. Combined FLAIR and SWI identified all 146 detectable regions (100%). FLAIR was sensitive for frontal-parietal, temporal-occipital and Sylvian cistern SAH, while SWI was particularly sensitive for interhemispheric and intraventricular hemorrhage. CONCLUSIONS: By combining SWI and FLAIR, MRI yields a distinctly higher detection rate for SAH than CT alone, particularly due to their complementary detection characteristics in different anatomical regions. Detection strength of SWI is high in central areas, whereas FLAIR shows a better detection rate in peripheral areas.

The template of the primary lymphatic landing sites of the prostate should be revisited: results of a multimodality mapping study

OBJECTIVES: To map the primary prostatic lymphatic landing sites using a multimodality technique. METHODS: Thirty-four patients with organ-confined prostate cancer (cT1-cT2; cN0) underwent single-photon emission computed tomography fused with data from computed tomography (SPECT/CT) (n=33) or magnetic resonance imaging (SPECT/MRI) (n=1) 1h after ultrasound-guided intraprostatic injection of technecium (Tc-99m) nanocolloid. The presence of lymph nodes (LNs) containing Tc-99m was confirmed intraoperatively with a gamma probe. A backup extended pelvic lymphadenectomy (PLND) was performed to preclude missed primary lymphatic landing sites. The SPECT/CT/MRI data sets were used to generate a three-dimensional projection of each LN site. RESULTS: A total of 317 LNs (median, 10 per patient; range, 3-19) were detected by SPECT/CT/MRI, 314 of which were confirmed by gamma probe. With an "extended" PLND, two thirds of all primary prostatic lymphatic landing sites are resected compared with only one third with a "limited" PLND. CONCLUSIONS: The multimodality technique presented here enables precise mapping of the primary prostatic lymphatic landing sites. PLND for prostate cancer should include not only the external and obturator regions as well as the portions medial and lateral to the internal iliac vessels, but also the common iliac LNs at least up to the ureteric crossing, thus removing approximately 75% of all nodes potentially harbouring metastasis.

Postmortem multislice computed tomography and magnetic resonance imaging of odontoid fractures, atlantoaxial distractions and ascending medullary edema

Non-invasive imaging methods are increasingly entering the field of forensic medicine. Facing the intricacies of classical neck dissection techniques, postmortem imaging might provide new diagnostic possibilities which could also improve forensic reconstruction. The aim of this study was to determine the value of postmortem neck imaging in comparison to forensic autopsy regarding the evaluation of the cause of death and the analysis of biomechanical aspects of neck trauma. For this purpose, 5 deceased persons (1 female and 4 male, mean age 49.8 years, range 20-80 years) who had suffered odontoid fractures or atlantoaxial distractions with or without medullary injuries, were studied using multislice computed tomography (MSCT), magnetic resonance imaging (MRI) and subsequent forensic autopsy. Evaluation of the findings was performed by radiologists, forensic pathologists and neuropathologists. The cause of death could be established radiologically in three of the five cases. MRI data were insufficient due to metal artefacts in one case, and in another, ascending medullary edema as the cause of delayed death was only detected by histological analysis. Regarding forensic reconstruction, the imaging methods were superior to autopsy neck exploration in all cases due to the post-processing possibilities of viewing the imaging data. In living patients who suffer medullary injury, follow-up MRI should be considered to exclude ascending medullary edema.

Integration of merged delayed-enhanced magnetic resonance imaging and multidetector computed tomography for the guidance of ventricular tachycardia ablation: a pilot study

BACKGROUND Delayed enhancement (DE) MRI can assess the fibrotic substrate of scar-related VT. MDCT has the advantage of inframillimetric spatial resolution and better 3D reconstructions. We sought to evaluate the feasibility and usefulness of integrating merged MDCT/MRI data in 3D-mapping systems for structure-function assessment and multimodal guidance of VT mapping and ablation. METHODS Nine patients, including 3 ischemic cardiomyopathy (ICM), 3 nonischemic cardiomyopathy (NICM), 2 myocarditis, and 1 redo procedure for idiopathic VT, underwent MRI and MDCT before VT ablation. Merged MRI/MDCT data were integrated in 3D-mapping systems and registered to high-density endocardial and epicardial maps. Low-voltage areas (<1.5 mV) and local abnormal ventricular activities (LAVA) during sinus rhythm were correlated to DE at MRI, and wall-thinning (WT) at MDCT. RESULTS Endocardium and epicardium were mapped with 391 ± 388 and 1098 ± 734 points per map, respectively. Registration of MDCT allowed visualization of coronary arteries during epicardial mapping/ablation. In the idiopathic patient, integration of MRI data identified previously ablated regions. In ICM patients, both DE at MRI and WT at MDCT matched areas of low voltage (overlap 94 ± 6% and 79 ± 5%, respectively). In NICM patients, wall-thinning areas matched areas of low voltage (overlap 63 ± 21%). In patients with myocarditis, subepicardial DE matched areas of epicardial low voltage (overlap 92 ± 12%). A total number of 266 LAVA sites were found in 7/9 patients. All LAVA sites were associated to structural substrate at imaging (90% inside, 100% within 18 mm). CONCLUSION The integration of merged MDCT and DEMRI data is feasible and allows combining substrate assessment with high-spatial resolution to better define structure-function relationship in scar-related VT.

Grey matter volumetric changes related to recovery from hand paresis after cortical sensorimotor stroke

Preclinical studies using animal models have shown that grey matter plasticity in both perilesional and distant neural networks contributes to behavioural recovery of sensorimotor functions after ischaemic cortical stroke. Whether such morphological changes can be detected after human cortical stroke is not yet known, but this would be essential to better understand post-stroke brain architecture and its impact on recovery. Using serial behavioural and high-resolution magnetic resonance imaging (MRI) measurements, we tracked recovery of dexterous hand function in 28 patients with ischaemic stroke involving the primary sensorimotor cortices. We were able to classify three recovery subgroups (fast, slow, and poor) using response feature analysis of individual recovery curves. To detect areas with significant longitudinal grey matter volume (GMV) change, we performed tensor-based morphometry of MRI data acquired in the subacute phase, i.e. after the stage compromised by acute oedema and inflammation. We found significant GMV expansion in the perilesional premotor cortex, ipsilesional mediodorsal thalamus, and caudate nucleus, and GMV contraction in the contralesional cerebellum. According to an interaction model, patients with fast recovery had more perilesional than subcortical expansion, whereas the contrary was true for patients with impaired recovery. Also, there were significant voxel-wise correlations between motor performance and ipsilesional GMV contraction in the posterior parietal lobes and expansion in dorsolateral prefrontal cortex. In sum, perilesional GMV expansion is associated with successful recovery after cortical stroke, possibly reflecting the restructuring of local cortical networks. Distant changes within the prefrontal-striato-thalamic network are related to impaired recovery, probably indicating higher demands on cognitive control of motor behaviour.