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H Imhof

Publications and source records attributed to H Imhof.

At least 55 records · Page 3Linked to original sources
PubMed2001

Left temporal and temporoparietal brain activity depends on depth of word encoding: a magnetoencephalographic study in healthy young subjects.

Using a 143-channel whole-head magnetoencephalograph (MEG) we recorded the temporal changes of brain activity from 26 healthy young subjects (14 females) related to shallow perceptual and deep semantic word encoding. During subsequent recognition tests, the subjects had to recognize the previously encoded words which were interspersed with new words. The resulting mean memory performances across all subjects clearly mirrored the different levels of encoding. The grand averaged event-related fields (ERFs) associated with perceptual and semantic word encoding differed significantly between 200 and 550 ms after stimulus onset mainly over left superior temporal and left superior parietal sensors. Semantic encoding elicited higher brain activity than perceptual encoding. Source localization procedures revealed that neural populations of the left temporal and temporoparietal brain areas showed different activity strengths across the whole group of subjects depending on depth of word encoding. We suggest that the higher brain activity associated with deep encoding as compared to shallow encoding was due to the involvement of more neural systems during the processing of visually presented words. Deep encoding required more energy than shallow encoding but for all that led to a better memory performance.

Adult↗
PubMed2001

[Non-neoplastic arthropathies of the temporomandibular joint].

The pathologic conditions that involve the TMJ are similar to those conditions that involve other joints in the body. Therefore, many of the radiologic characteristics are also similar. Nevertheless, because of the complex structure and function of this small joint, it is essential to know the variety of diseases that can involve the temporomandibular joint. It is also important to understand that functionally both TMJ's act as a single unit and that any alteration in function caused by a pathologic process on one side may lead to dysfunction on the contralateral side. It is essential that the radiologist is familiar with the principles of TMJ function as well as TMJ pathology.

Diagnosis, Differential↗
PubMed2001

[Diagnostic imaging of giant cell tumors].

Although classified as benign neoplasms, giant cell tumors are locally aggressive with a high recurrence rate of 30-50%. The histological appearance include osteoclast-like, multinucleated giant cells and round to spindle-shaped mono-nuclear stromal cells. These neoplasms predominately affect adults in the third and forth decades of life (70-80%). Giant cell tumors predominately arise in long tubular bones (75-95%) with the majority occurring around the knee (50%). The next most common site being the distal radius (10%). The epicenter of giant cell tumors is in the epiphysis. The radiographic signs of giant cell tumors are a geographical radiolucency with no internal mineralization, a thinning of the cortex, eccentric in the epiphysis of long bones. MRI signs of giant cell tumors are high signal intensity in T2-weighted images, high contrast media enhancement, fluid levels, signs according to haemorrhage and haemosiderin deposition. CT shows the expanded and thinned cortex. Plain radiographs remain the mainstay of diagnosis of giant cell tumors. MRI and CT are important for staging and therefore for surgical planning.

Bone Neoplasms↗
PubMed2001

[Diagnostic imaging of acute and chronic osteochondral lesions of the talus].

Acute fractures involving the articular surface of the talus run parallel to the surface and are confined to the cartilage and/or the immediate subchondral cancellous bone. Subchondral microfractures ("bone bruises"), osteochondral fractures and solely chondral fractures are different manifestations of impaction injuries that affect the articular surface. This article reviews the radiologic appearance of acute osteochondral lesions of the talus and comments on the role of the noninvasive imaging modalities. Conventional radiography and MRI provide the most relevant information and are widely discussed. A MRI classification is presented emphasizing the distinction between lesions with intact and disrupted cartilage. Osteochondrosis dissecans (OCD) is a chronic osteochondral lesion. It is diagnosed in most cases by conventional radiography. MRI has become a decisive tool in staging the lesions. Intact cartilage and contrast enhancement of the lesions are findings of MRI stage I. Cartilage defects with or without incomplete separation of the fragment, fluid around an undetached fragment, cysts larger than 5 mm in diameter and a dislodged fragment are MRI findings observed in stage II and operative treatment has to be considered.

Ankle Injuries↗
PubMed2001

CT and MR imaging of acquired abnormalities of the inner ear and cerebellopontine angle.

INTRODUCTION: Several entities of acquired lesions may affect the inner ear and cerebellopontine angle. The imaging of these lesions depends on the clinical history, and should be adapted to the lesion searched for and suspected by the otolaryngologist. In this paper, the modality of CT and MR imaging which is suited to delineate the acquired lesions of this region will be presented. MATERIALS AND METHODS: CT and/or MR imaging of the inner ear and cerebellopontine angle was performed in all cases in which an acquired lesion of this region was suspected by the otolaryngologist. CT was performed in the axial and coronal plane with the use of a high-resolution bone-window-level-setting. MRI was performed in the axial plane using high-resolution 3D T2-weighted fast spin echo sequences and 3D T1-weighted gradient echo sequences before and after the i.v. application of gadopentate dimeglumine. The obtained images were evaluated for the depiction of the acquired lesions. RESULTS: CT best depicted osseous lesions such as traumatic affections or lesions leading to ossification of the inner ear. Tumorous lesions were delineated in those cases in which they yielded to bony changes. Inflammatory or tumorous lesions not yielding to bony changes or intralabyrintine calicifications were not depicted. MRI delineated very well all lesions leading to soft tissue changes, and moderately depicted traumatic changes yielding to less severe fractures affecting the investigated region. CONCLUSION: CT and MR imaging are suited differently to delineate the acquired lesions of the inner ear and cerebellopontine angle. CT is excellently suited to depict osseous lesions, while MRI is excellently suited to delineate lesions affecting the soft tissue structures. These two imaging modalities should be used depending on the clinical question, and are supposed to be complementary methods.

Cerebellar Diseases↗
PubMed2001

False recognition depends on depth of prior word processing: a magnetoencephalographic (MEG) study.

Brain activity was measured with a whole head magnetoencephalograph (MEG) during the test phases of word recognition experiments. Healthy young subjects had to discriminate between previously presented and new words. During prior study phases two different levels of word processing were provided according to two different kinds of instructions (shallow and deep encoding). Event-related fields (ERFs) associated with falsely recognized words (false alarms) were found to depend on the depth of processing during the prior study phase. False alarms elicited higher brain activity (as reflected by dipole strength) in case of prior deep encoding as compared to shallow encoding between 300 and 500 ms after stimulus onset at temporal brain areas. Between 500 and 700 ms we found evidence for differences in the involvement of neural structures related to both conditions of false alarms. Furthermore, the number of false alarms was found to depend on depth of processing. Shallow encoding led to a higher number of false alarms than deep encoding. All data are discussed as strong support for the ideas that a certain level of word processing is performed by a distinct set of neural systems and that the same neural systems which encode information are reactivated during the retrieval.

Adult↗
PubMed2001

Whole-body vibration exercise leads to alterations in muscle blood volume.

Occupationally used high-frequency vibration is supposed to have negative effects on blood flow and muscle strength. Conversely, low-frequency vibration used as a training tool appears to increase muscle strength, but nothing is known about its effects on peripheral circulation. The aim of this investigation was to quantify alterations in muscle blood volume after whole muscle vibration--after exercising on the training device Galileo 2000 (Novotec GmbH, Pforzheim, Germany). Twenty healthy adults performed a 9-min standing test. They stood with both feet on a platform, producing oscillating mechanical vibrations of 26 Hz. Alterations in muscle blood volume of the quadriceps and gastrocnemius muscles were assessed with power Doppler sonography and arterial blood flow of the popliteal artery with a Doppler ultrasound machine. Measurements were performed before and immediately after exercising. Power Doppler indices indicative of muscular blood circulation in the calf and thigh significantly increased after exercise. The mean blood flow velocity in the popliteal artery increased from 6.5 to 13.0 cm x s(-1) and its resistive index was significantly reduced. The results indicate that low-frequency vibration does not have the negative effects on peripheral circulation known from occupational high-frequency vibration.

Adult↗
PubMed2001

Quantitative US of the calcaneus: cutoff levels for the distinction of healthy and osteoporotic individuals.

PURPOSE: To calculate cutoff levels for quantitative ultrasonography (US) performed to distinguish healthy individuals and those with osteoporosis identified with dual x-ray absorptiometry. MATERIALS AND METHODS: In 1,357 patients (856 females, aged 55.1 years +/- 15.4 [mean +/- SD]; 501 males, aged 50.4 years +/- 15), bone mineral density measurements of the lumbar spine (posteroanterior, L1 through L4) and femoral neck were obtained, and quantitative US was performed to determine the stiffness of the calcaneus. Individuals with a T score less than -2.5 (osteoporotic) at the spine and femur were identified, and upper T-score cutoff values (3 SDs from the mean) in the groups of male and female patients with osteoporosis were identified. RESULTS: Females with dual x-ray absorptiometric values that were indicative of osteoporosis of the spine had an upper T-score cutoff value of -1.0 (males, -0.2). Females who had femoral osteoporosis showed an upper quantitative US T-score cutoff value of -0.6 (males, 0). CONCLUSION: Cutoff values may permit the use of quantitative US to screen for the presence of osteoporosis in the spine and femur. Quantitative US will help to prevent unnecessary dual x-ray absorptiometric and conventional radiographic examinations.

Absorptiometry, Photon↗
PubMed2001

Diagnostic disagreement of imaging quantitative sonography of the calcaneus with dual X-ray absorptiometry of the spine and femur.

OBJECTIVE: This study evaluates the diagnostic agreement between imaging quantitative sonography of the calcaneus and dual X-ray absorptiometry of the spine and femur for diagnosing osteoporosis. MATERIALS AND METHODS: In 498 female patients (56 +/- 18 years old), bone mineral density measurements by dual X-ray absorptiometry of the lumbar spine (posteroanterior, L1--L4) and the proximal femur and imaging quantitative sonography of the calcaneus were performed. The percentage of patients having T-scores less than or equal to a threshold of -2.5 standard deviations below a young normal reference was used to compare quantitative sonography with dual X-ray absorptiometry. The diagnostic agreement was assessed using kappa scores. RESULTS: Approximately 30% of the patients had a T-score less than or equal to -2.5 standard deviations as assessed by imaging quantitative sonography (broadband ultrasound attenuation), 26.5% as assessed by dual X-ray absorptiometry of the spine, and 16.7--56.4% as assessed by dual X-ray absorptiometry of the different regions of interest at the femur. Kappa analysis showed that severe diagnostic disagreement exists among broadband ultrasound attenuation and dual X-ray absorptiometry (kappa = 0.28-0.42). CONCLUSION: Considerable diagnostic disagreement exists between imaging quantitative sonography and dual X-ray absorptiometry of the spine and femur. The disagreement is in the same range as that reported recently in comparisons of dual X-ray absorptiometry and nonimaging quantitative sonography. In general, no distinct advantage for imaging quantitative sonography could be found when compared with other techniques.

Absorptiometry, Photon↗
PubMed2001

[Tendon overuse syndrome: imaging diagnosis].

Injuries of muscles and tendons occur commonly during various sporting activities and in most cases the athletes feel such an accident to be sudden and unavoidable. The rupture of a tendon, however, has to be considered in many cases as the final stage of a long-standing progressive degeneration of collagen fibers. This process can be described as "tendon overuse syndrome (TOS)". Diagnostic imaging modalities, especially sonography and MRI, are suitable to detect and analyse the different stages of this syndrome and the degree of morphological abnormalities. The first stage is painful functional derangement, followed by tendovaginitis, peritendinitis, or bursitis. The third stage is tendinosis resulting from biomechanical or ischaemic injury of tendon fibers which may eventually be followed by partial or complete rupture. Regional or individual specifications of these four stages may occur at anatomically predisposing sites, so-called critical zones, or during periods of specific proneness, the vulnerable phases.

Athletic Injuries↗
PubMed2000

[Clinical management of acute head injury].

Patients after acute head injury are susceptible to secondary insults and therefore to secondary brain injury. A comprehensive approach, starting at the site of the accident, followed by emergency diagnosis and treatment in the appropriate emergency department of the trauma centre, intensive care and specific neurorehabilitation is the only way to minimise sequelae of primary brain lesions, prevent secondary brain damage and establish optimum frame conditions with respect to recovery from non-definite brain damage.

Accidents↗
PubMed2000

["Lines and tubes" in neonatal intensive care patients].

BACKGROUND: Central catheters in neonatological intensive care patients are used for the prolonged application of medication or parenteral infusions. Dislocations and septic and thromboembolic complications may occur. CONTROL OF POSITION: Radiologically, the correct position of the catheter must be proven. Dislocations or complications associated with central catheters must be diagnosed. For catheter monitoring plain film radiographs are the first line of investigation; however, sonography may be of additional assistance. Angiographic techniques should only be performed when conventional noninvasive methods do not supply satisfactory results. Special knowledge is necessary for monitoring catheters that are set via the umbilical artery or vein. The radiological applications for catheter monitoring in the neonate intensive care unit are discussed in this article.

Catheterization, Central Venous↗
PubMed2000

[Intraoperative navigation in paranasal sinus surgery with the Philips "Neuroguide" system].

OBJECTIVE: To investigate the feasibility, precision and usefulness of computer aided surgery in ENT-sinus surgery. MATERIAL AND METHODS: 5 Patients with chronic sinus pathology and an indication for sinus surgery were elected. For intraoperative navigation we used a Philips "NEUROGUIDE" system and surgical instruments with LED's. Navigation procedures are described in detail in the paper, the system's precision was measured by pointing at anatomical landmarks. The accuracy was measured as the distance in millimeter between the bony structures of the CT scan on screen and the haircross of the pointer's tip on the screen. Another parameter of the systems accuracy was calculated by the system itself as the root mean square error in millimeter (RMSE) between the registered markers position and the marker position in the CT data set. RESULTS: Axial 3/3/1 mm spiral CT provided sufficient resolution, data transfer via optical disk was practicable. Positioning of the navigation equipment required some experience and the registration of the patients head position needed attention, as the markers have to be pointed at precisely. During operation, the head tracking system must not change its position on the patients head to ensure a correct navigation display. The main advantage of the computed navigation system was the constant orientation during the sinus surgical procedure. Frontiers and critical anatomical structures could be identified in the corresponding CT data set, thus enabling the surgeon to decide on the further procedure. At present stage, the operation time was increased through the handling of the navigation system for at about 15 min, resulting in additional time of narcosis. CONCLUSION: We found the computed navigation system Philips "NEUROGUIDE" system to be an established technical aid, ready to use for ENT sinus surgery, in our cases with a precision between 1 and 3 mm. These results were similar to results obtained with a SPOCS Navigation System from Aesculap, as previously published by us [17].

Adult↗
PubMed2000

[The pharynx. The imaging of its normal anatomy].

BACKGROUND: The pharynx, being part of the digestive as well as the respiratory system, is embedded in the complex spatial anatomy of the neck and, due to its function and location, represents a very sophisticated region. DIAGNOSIS: Cross-sectional imaging with CT and MR imaging plays an indispensable complementary role to clinical work-up, as far as submucosal and deep cervical spaces are concerned. However, as dysphagia is a common symptom in clinical practice, interpretation of double contrast studies and videofluoroscopic investigations are also on frequent demand in the daily routine. CONCLUSION: Close interdisciplinary co-operation and the radiologist's familiarity with the anatomy of the region are required in order to use the diagnostic tools in an optimal fashion.

Cineradiography↗
PubMed2000

[The value of diffusion-weighted MRT in assessing the bone marrow changes in vertebral metastases].

AIM OF THE STUDY: The aim of the study was the evaluation of the diffusion coefficient (ADC) of vertebral metastasis and regular vertebral bodies with diffusion weighted MRI (DWI). DWI evaluates the tissue-specific molecular diffusion of protons. In tissues with high cell densities (neoplasm) a decreased ADC can be expected due to restricted diffusion according to an exaggerated amount of intra- and intercellular membranes (i.e. diffusion barriers). METHODS: In 5 breast cancer patients the ADC of both known vertebral metastases and of adjacent regular vertebral bodies were measured with DWI (1.0 T; Phased-Array-Body-Coil; b: 880 and 440 s/mm2). RESULTS: The ADC of regular vertebral bodies (1.3 +/- 0.23 x 10(-3) s/mm2) was significantly (p < or = 0.0002) higher than in vertebral metastases (0.39 +/- 0.11 x 10(-3) s/mm2). CONCLUSIONS: These data demonstrate that the ADC can be reliably measured in vertebral bodies. The quantitative evaluation of the ADC in vertebral bodies seems to be an objective and comparable parameter for differentiating malign from benign vertebral tissue.

Bone Marrow↗