Spinal cord motion: influence of respiration and cardiac cycle.

PURPOSE: To assess physiological spinal cord motion during the cardiac cycle compared with the influence of respiration based on magnetic resonance imaging (MRI) measurements. MATERIALS AND METHODS: Anterior-posterior spinal cord motion within the spinal canal was assessed in 16 healthy volunteers (median age, 25 years) by cardiac-triggered and cardiac-gated gradient echo pulse sequence MRI. Image acquisition was performed during breath-holding, normal breathing, and forced breathing. Normal spinal cord motion values were computed using descriptive statistics. Breathing-dependent differences were assessed using the Wilcoxon signed-rank test and compared with the cardiac-based cord motion. RESULTS: A normal value table was set up for the spinal cord motion of each vertebral cervico-thoracic-lumbar segment. Significant differences in cord motion were found between cardiac-based motion while breath-holding and the two breathing modalities (P < 0.01 each). Spinal cord motion was found to be highest during forced breathing, with a maximum in the lower cervical spinal segments (C5; mean, 2.1 mm ±â€Š1.17). Image acquisition during breath-holding revealed the lowest motion. CONCLUSION: MRI permits the demonstration and evaluation of cardiac and respiration-dependent spinal cord motion within the spinal canal from the cervical to lumbar segments. Breathing conditions have a considerably greater impact than cardiac activity on spinal cord motion. KEY POINTS: • Cardiac-triggered and ECG-gated MRI allows for demonstration of the smallest spinal cord motions.• Respiratory influences seem to have the highest impact on spine motion.• In contrast, the influence of the cardiac cycle seems to be small.• The smallest spinal cord motions were measured during breath-hold.

[A false aneurysm as a rare complication of knee arthroscopy]. / Aneurysma spurium als seltene Komplikation einer Kniegelenksarthroskopie.

We present the rare case of a false aneurysm of the genus lat which occurred after knee arthroscopy. Apart from a pulse-synchronic swelling in close proximity to the former anterolateral portal there were no complaints and no pain. The diagnostic and therapeutic strategies - in this case performed with coiling of the involved vessel - are presented and discussed.

Current role and future perspective of MRI for diagnosis and characterization of renal cell carcinoma.

During the past years, magnetic resonance imaging (MRI) has been established as a reliable method for examination of the kidneys. Modern MRI systems enable to visualize renal masses with a high spatial resolution. This enables not only to differentiate between benign lesions and renal cancer but also to define the tumor stage with high accuracy. The impact of a precise preoperative staging has increased significantly due to stage adapted therapy approaches such as nephron sparing surgery or local ablative techniques (e.g. radiofrequency ablation). Tumor-related infiltration of the renal pelvis, infiltration of the perinephric fat or a tumor thrombus within the inferior caval vein has to be diagnosed with high accuracy to enable these stage adapted treatment regimens. This article introduces into clinically established "morphologic" MRI techniques for diagnosis and staging of renal cell carcinoma (RCC). Besides detection and staging of kidney cancer, the recent development of molecularly targeted therapies in patients with metastatic or non-operable tumors has led to novel diagnostic demands. To evaluate treatment efficiency, more information than just tumor morphology should be provided. Functional imaging techniques including dynamic contrast enhanced (DCE) MRI, diffusion weighted imaging (DWI), arterial spin labeling (ASL) and MR-spectroscopy are being investigated in preclinical and clinical trials. While some new techniques have shown promising results for a broad clinical application, others seem to be suited for dedicated questions only.

[Evaluation of an interactive breath-hold control system in CT-guided lung biopsy]. / Evaluation eines interaktiven Atemkontrollsystems bei der CT-gesteuerten Lungenbiopsie.

PURPOSE: In this study we assessed the effect of an interactive breath-hold control system on procedure time and technical success in transthoracic CT-guided lung biopsies. MATERIALS AND METHODS: In 36 patients (4 female, 32 male, mean age 65 years; range 33 - 88) with a pulmonary nodule, we performed CT-guided biopsy using a 18G Tru-cut needle (Cardinal Health, Dublin, UK) in a 64 row dual-source CT scanner (Somatom Definition, Siemens, Forchheim, Germany) using intermittent imaging of the needle. In half of the patients (2 female, 16 male, mean age 67 years), an interactive breath-hold control system (IBC) (Mayo Clinic Medical Devices, USA) was applied. No additional device was used in the control group. RESULTS: The biopsy was visually successful in all patients. The diameter of the target lesion was comparable in both groups (IBC: 30 +/- 19 mm; control: 28 +/- 15 mm). The number of imaging steps was significantly smaller (p < 0.05) and the intervention time was significantly shorter (p < 0.05) in the IBC group (IBC: 9 +/- 5 steps 17 +/- 10 min; control: 13 +/- 5 steps 26 +/- 12 min). CONCLUSION: Application of the IBC unit reduced the intervention time and radiation exposure in CT-guided Tru-cut biopsy of pulmonary nodules.

[Atrial tumors in cardiac MRI]. / Vorhoftumoren in der kardialen MRT.

Cardiac magnetic resonance imaging (MRI) is an important tool for the diagnosis of cardiac masses. Various cardiac tumors are predisposed to occurring in atrial structures. The aim of this review article is the description of atrial tumors and their morphological features in MRI. In general, cardiac tumors are rare: approximately 0.001 - 0.03 % in autopsy studies. About 75 % of them are benign. The most common cardiac tumor is the myxoma. They are predisposed to occur in the atria and show a characteristically strong hyperintense signal on T 2-wieghted images in MRI. In other sequences a heterogeneous pattern reflects its variable histological appearance. Lipomas exhibit a signal behavior identical to fatty tissue with a typical passive movement in cine imaging. Fibroelastomas are the most common tumors of the cardiac valves. Consisting of avascular fibrous tissue, they often present with hypointense signal intensities. Thrombi attached to their surface can cause severe emboli even in small tumors. Amongst primary cardiac malignancies, sarcomas are most common and favor the atria. Secondary malignancies of the heart are far more common than primary ones (20 - 40 times). In case of known malignancies, approximately 10 % of patients develop cardiac metastasis at the end of their disease. Lymphogenic metastases favor the pericardium, while hematogenic spread prefers the myocardium. Since they are not real atrial tumors, thrombi and anatomical structures of the atria have to be differentiated from other pathologies.

Comparison of image quality in magnetic resonance imaging of the knee at 1.5 and 3.0 Tesla using 32-channel receiver coils.

We examined to what degree the visualization of anatomic structures in the human knee is improved using 3.0-T magnetic resonance imaging (MRI) and many element RF receive coils as compared to 1.5 T. We imaged 20 knees at 1.5 and 3.0 T using T2-weighted STIR, T2-weighted gradient echo, T1-weighted spin-echo, true-FISP and T2-weighted fast spin echo techniques in conjunction with 32-element RF coil arrays. The 3.0-T examination was considerably faster than its 1.5-T counterpart. A superior subjective visibility at 3.0 T vs 1.5 T was found in 27 of 50 evaluated structures (meniscus, ligaments) with the exception of true-FISP techniques. The 3.0-T examination provided a better visibility (evaluated by blinded consensus-reading by two radiologists) of small structures such as the ligamentum transversum genu. Also, cartilage was better delineated at 3.0 T. A 23% increased average signal-to-noise ratio as assessed using a temporal filter was observed at 3.0 T as compared to 1.5 T. At 3.0 T, imaging of the human knee is faster and results in a subjective visibility of anatomic structures that is superior to and competitive with 1.5 T.

Diffusion tensor imaging in acquired blind humans.

Retinal implants as a future possible therapy of blindness rely on an intact neural transmission from the retina to the primary visual cortex. By now it remains unknown, in how far the absence of afferent input in blindness affects also the organization of the optic radiation. Using diffusion tensor imaging (DTI), the non-invasive evaluation of large fiber tracts including the optic radiation has become possible. This method is sensitive to changes of the axonal state such as wallerian degeneration. We have compared DTI data from 6 acquired blind patients with those of a group of 11 healthy control subjects. Neither the relative anisotropy quotient of the visual fiber tract and the pyramidal tract showed a statistically significant difference between the blind patients and the control group nor did the absolute values of the relative anisotropy in the pyramidal tract and the visual fiber tract. There was no axonal degeneration of the optic radiation in late onset acquired blindness. With the optic pathways remaining intact, transmitting electric signals of retinal implants to the visual regions of the human brain seems to be possible even after decades of acquired blindness.

Interneuronal systems of the cervical spinal cord assessed with BOLD imaging at 1.5 T.

The purpose of this study was to investigate if functional activity with spinal cord somatosensory stimulation can be visualized using BOLD fMRI. We investigated nine healthy volunteers using a somatosensory stimulus generator. The stimuli were applied in three different runs at the first, third, and fifth finger tip of the right hand, respectively, corresponding to dermatomes c6, c7, and c8. The stimuli gave an increase of BOLD signal (activation) in three different locations of the spinal cord and brain stem. First, activations could be seen in the spinal segment corresponding to the stimulated dermatome in seven out of nine volunteers for c6 stimulation, two out of eight for c7, and three out of eight for c8. These activations were located close to the posterior margin of the spinal cord, presumably reflecting synaptic transmission to dorsal horn interneurons. Second, activation in the medulla oblongata was evident in four subjects, most likely corresponding to the location of the nucleus cuneatus. The third location of activation, which was the strongest and most reliable observed was inside the spinal cord in the c3 and c4 segments. Activation at these spinal levels was almost invariably observed independently of the dermatome stimulated (9/9 for c6, 8/8 for c7, and 7/8 for c8 stimulation). These activations may pertain to an interneuronal system at this spinal level. The results are discussed in relation to neurophysiological studies on cervical spinal interneuronal pathways in animals and humans.