MRI-based brain volumetry in chronic whiplash patients: no evidence for traumatic brain injury

INTRODUCTION: Cognitive complaints, such as poor concentration and memory deficits, are frequent after whiplash injury and play an important role in disability. The origin of these complaints is discussed controversially. Some authors postulate brain lesions as a consequence of whiplash injuries. Potential diffuse axonal injury (DAI) with subsequent atrophy of the brain and ventricular expansion is of particular interest as focal brain lesions have not been documented so far in whiplash injury. OBJECTIVE: To investigate whether traumatic brain injury can be identified using a magnetic resonance (MR)-based quantitative analysis of normalized ventricle-brain ratios (VBR) in chronic whiplash patients with subjective cognitive impairment that cannot be objectively confirmed by neuropsychological testing. MATERIALS AND METHODS: MR examination was performed in 21 patients with whiplash injury and symptom persistence for 9 months on average and in 18 matched healthy controls. Conventional MR imaging (MRI) was used to assess the volumes of grey and white matter and of ventricles. The normalized VBR was calculated. RESULTS: The values of normalized VBR did not differ in whiplash patients when compared with that in healthy controls (F = 0.216, P = 0.645). CONCLUSIONS: This study does not support loss of brain tissue following whiplash injury as measured by VBR. On this basis, traumatic brain injury with subsequent DAI does not seem to be the underlying mechanism for persistent concentration and memory deficits that are subjectively reported but not objectively verifiable as neuropsychological deficits.

Impact of a self-developed planning and self-constructed navigation system on skull base surgery: 10 years experience

CONCLUSION: Our self-developed planning and navigation system has proven its capacity for accurate surgery on the anterior and lateral skull base. With the incorporation of augmented reality, image-guided surgery will evolve into 'information-guided surgery'. OBJECTIVE: Microscopic or endoscopic skull base surgery is technically demanding and its outcome has a great impact on a patient's quality of life. The goal of the project was aimed at developing and evaluating enabling navigation surgery tools for simulation, planning, training, education, and performance. This clinically applied technological research was complemented by a series of patients (n=406) who were treated by anterior and lateral skull base procedures between 1997 and 2006. MATERIALS AND METHODS: Optical tracking technology was used for positional sensing of instruments. A newly designed dynamic reference base with specific registration techniques using fine needle pointer or ultrasound enables the surgeon to work with a target error of < 1 mm. An automatic registration assessment method, which provides the user with a color-coded fused representation of CT and MR images, indicates to the surgeon the location and extent of registration (in)accuracy. Integration of a small tracker camera mounted directly on the microscope permits an advantageous ergonomic way of working in the operating room. Additionally, guidance information (augmented reality) from multimodal datasets (CT, MRI, angiography) can be overlaid directly onto the surgical microscope view. The virtual simulator as a training tool in endonasal and otological skull base surgery provides an understanding of the anatomy as well as preoperative practice using real patient data. RESULTS: Using our navigation system, no major complications occurred in spite of the fact that the series included difficult skull base procedures. An improved quality in the surgical outcome was identified compared with our control group without navigation and compared with the literature. The surgical time consumption was reduced and more minimally invasive approaches were possible. According to the participants' questionnaires, the educational effect of the virtual simulator in our residency program received a high ranking.

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.

Virtopsy, a new imaging horizon in forensic pathology: virtual autopsy by postmortem multislice computed tomography (MSCT) and magnetic resonance imaging (MRI)--a feasibility study

Using postmortem multislice computed tomography (MSCT) and magnetic resonance imaging (MRI), 40 forensic cases were examined and findings were verified by subsequent autopsy. Results were classified as follows: (I) cause of death, (II) relevant traumatological and pathological findings, (III) vital reactions, (IV) reconstruction of injuries, (V) visualization. In these 40 forensic cases, 47 partly combined causes of death were diagnosed at autopsy, 26 (55%) causes of death were found independently using only radiological image data. Radiology was superior to autopsy in revealing certain cases of cranial, skeletal, or tissue trauma. Some forensic vital reactions were diagnosed equally well or better using MSCT/MRI. Radiological imaging techniques are particularly beneficial for reconstruction and visualization of forensic cases, including the opportunity to use the data for expert witness reports, teaching, quality control, and telemedical consultation. These preliminary results, based on the concept of "virtopsy," are promising enough to introduce and evaluate these radiological techniques in forensic medicine.

Safety of Active Implantable Devices during MRI Examinations: A Finite Element Analysis of an Implantable Pump

The goal of this study was to propose a general numerical analysis methodology to evaluate the magnetic resonance imaging (MRI)-safety of active implants. Numerical models based on the finite element (FE) technique were used to estimate if the normal operation of an active device was altered during MRI imaging. An active implanted pump was chosen to illustrate the method. A set of controlled experiments were proposed and performed to validate the numerical model. The calculated induced voltages in the important electronic components of the device showed dependence with the MRI field strength. For the MRI radiofrequency fields, significant induced voltages of up to 20 V were calculated for a 0.3T field-strength MRI. For the 1.5 and 3.0T MRIs, the calculated voltages were insignificant. On the other hand, induced voltages up to 11 V were calculated in the critical electronic components for the 3.0T MRI due to the gradient fields. Values obtained in this work reflect to the worst case situation which is virtually impossible to achieve in normal scanning situations. Since the calculated voltages may be removed by appropriate protection circuits, no critical problems affecting the normal operation of the pump were identified. This study showed that the proposed methodology helps the identification of the possible incompatibilities between active implants and MR imaging, and can be used to aid the design of critical electronic systems to ensure MRI-safety

Oxygen-sensitive 3He-MRI in bronchiolitis obliterans after lung transplantation

Oxygen-sensitive 3He-MRI was studied for the detection of differences in intrapulmonary oxygen partial pressure (pO2) between patients with normal lung transplants and those with bronchiolitis obliterans syndrome (BOS). Using software developed in-house, oxygen-sensitive 3He-MRI datasets from patients with normal lung grafts (n = 8) and with BOS (n = 6) were evaluated quantitatively. Datasets were acqiured on a 1.5-T system using a spoiled gradient echo pulse sequence. Underlying diseases were pulmonary emphysema (n = 10 datasets) and fibrosis (n = 4). BOS status was verified by pulmonary function tests. Additionally, 3He-MRI was assessed blindedly for ventilation defects. Median intrapulmonary pO2 in patients with normal lung grafts was 146 mbar compared with 108 mbar in patients with BOS. Homogeneity of pO2 distribution was greater in normal grafts (standard deviation pO2 34 versus 43 mbar). Median oxygen decrease rate during breath hold was higher in unaffected patients (-1.75 mbar/s versus -0.38 mbar/s). Normal grafts showed fewer ventilation defects (5% versus 28%, medians). Oxygen-sensitive 3He-MRI appears capable of demonstrating differences of intrapulmonary pO2 between normal lung grafts and grafts affected by BOS. Oxygen-sensitive 3He-MRI may add helpful regional information to other diagnostic techniques for the assessment and follow-up of lung transplant recipients.

Application and assessment of a robust elastic motion correction algorithm to dynamic MRI

The purpose of this study was to assess the performance of a new motion correction algorithm. Twenty-five dynamic MR mammography (MRM) data sets and 25 contrast-enhanced three-dimensional peripheral MR angiographic (MRA) data sets which were affected by patient motion of varying severeness were selected retrospectively from routine examinations. Anonymized data were registered by a new experimental elastic motion correction algorithm. The algorithm works by computing a similarity measure for the two volumes that takes into account expected signal changes due to the presence of a contrast agent while penalizing other signal changes caused by patient motion. A conjugate gradient method is used to find the best possible set of motion parameters that maximizes the similarity measures across the entire volume. Images before and after correction were visually evaluated and scored by experienced radiologists with respect to reduction of motion, improvement of image quality, disappearance of existing lesions or creation of artifactual lesions. It was found that the correction improves image quality (76% for MRM and 96% for MRA) and diagnosability (60% for MRM and 96% for MRA).

Projector-based augmented reality for intuitive intraoperative guidance in image-guided 3D interstitial brachytherapy

PURPOSE: The aim of this study is to implement augmented reality in real-time image-guided interstitial brachytherapy to allow an intuitive real-time intraoperative orientation. METHODS AND MATERIALS: The developed system consists of a common video projector, two high-resolution charge coupled device cameras, and an off-the-shelf notebook. The projector was used as a scanning device by projecting coded-light patterns to register the patient and superimpose the operating field with planning data and additional information in arbitrary colors. Subsequent movements of the nonfixed patient were detected by means of stereoscopically tracking passive markers attached to the patient. RESULTS: In a first clinical study, we evaluated the whole process chain from image acquisition to data projection and determined overall accuracy with 10 patients undergoing implantation. The described method enabled the surgeon to visualize planning data on top of any preoperatively segmented and triangulated surface (skin) with direct line of sight during the operation. Furthermore, the tracking system allowed dynamic adjustment of the data to the patient's current position and therefore eliminated the need for rigid fixation. Because of soft-part displacement, we obtained an average deviation of 1.1 mm by moving the patient, whereas changing the projector's position resulted in an average deviation of 0.9 mm. Mean deviation of all needles of an implant was 1.4 mm (range, 0.3-2.7 mm). CONCLUSIONS: The developed low-cost augmented-reality system proved to be accurate and feasible in interstitial brachytherapy. The system meets clinical demands and enables intuitive real-time intraoperative orientation and monitoring of needle implantation.

Functional imaging of the parotid glands using blood oxygenation level dependent (BOLD)-MRI at 1.5T and 3T

PURPOSE: To evaluate the function of the parotid glands before and during gustatory stimulation, using an intrinsic susceptibility-weighted MRI method (blood oxygenation level dependent, BOLD-MRI) at 1.5T and 3T. MATERIALS AND METHODS: A total of 10 and 13 volunteers were investigated at 1.5T and 3T, respectively. Measurements were performed before and during gustatory stimulation using ascorbate. Circular regions of interest (ROIs) were delineated in the left and right parotid glands, and in the masseter muscle for comparison. The effects of stimulation were evaluated by calculating the difference between the relaxation rates, DeltaR(2)*. Baseline and stimulation were statistically compared (Student's t-tests), merging both parotid glands. RESULTS: The averaged DeltaR(2)* values prestimulation obtained in all parotid glands were stable (-0.61 to 0.38 x 10(-3) seconds(-1)). At 3T, these values were characterized by an initial drop (to -2.7 x 10(-3) seconds(-1)) followed by a progressive increase toward the baseline. No significant difference was observed between baseline and parotid gland stimulation at 1.5T, neither for the masseter muscle at both field strengths. A considerable interindividual variability (over 76%) was noticed at both magnetic fields. CONCLUSION: BOLD-MRI at 3T was able to detect DeltaR(2)* changes in the parotid glands during gustatory stimulation, consistent with an increase in oxygen consumption during saliva production.

Periprocedural embolic events related to carotid artery stenting detected by diffusion-weighted MRI: comparison between proximal and distal embolus protection devices

PURPOSE: To evaluate and compare the efficacy of proximal versus distal embolus protection devices (EPD) during carotid artery angioplasty/stenting (CAS) based on diffusion-weighted magnetic resonance imaging (DW-MRI). METHODS: Forty-four patients (31 men; mean age 68 years, range 48-85) underwent protected CAS and had DW-MRI before and after the intervention. The cohort was analyzed according to the type of EPD used: a proximal EPD was deployed in 25 (56.8%) patients (17 men; mean age 66 years, range 48-85) and a distal filter in 19 (14 men; mean age 70 years, range 58-79). Fifteen (60.0%) patients with proximal protection were symptomatic of the target lesion; in the distal protection group, 10 (52.6%) were symptomatic. RESULTS: New lesions were seen on the postinterventional DW-MRI in 28.0% (7/25) of the proximal EPD group versus 32.6% (6/19) of those with a distal filter (p = NS). The majority were clinically silent. The new lesions in the vascular territory of the stented carotid artery in the group as a whole and per patient were fewer in the proximal EPD group (p = NS). No significant differences were noted in the T(2) appearance of the new lesions or the number of new lesions observed away from the vascular territory of the stented artery. CONCLUSION: Proximal embolus protection devices show a nonsignificant trend toward fewer embolic events, which warrants large-scale studies. Furthermore, proximal protection devices can be useful to control and treat acute in-stent thrombosis.

Ultrasound-guided blocks for the treatment of chronic pain

Ultrasound (US) is an emerging imaging technique in interventional pain management. The main advantages are the identification of soft tissues, vessels, and nerves, without exposing patients and personnel to radiation, the possibility to perform continuous imaging, and the visualization of the fluid injected in a real-time fashion. Possible applications are nerve blocks of the cervical and lumbar zygapophysial joints, stellate ganglion block, intercostal nerve blocks, occipital nerve blocks, blocks of the inguinal nerves, peripheral nerve blocks of the extremities, blocks of painful stump neuromas, caudal epidural injections, and injections of tender points. US may also be used for destructive procedures, such as cryoanalgesia, radiofrequency lesions, or chemical neurolysis. The increasing published data available suggest that US has a potential usefulness in interventional pain management, but also limitations. There is still a need for clinical trials investigating efficacy and safety of US-guided pain procedures. Until these studies are made, fluoroscopy or computed tomography remain the gold standard for most interventional pain procedures.