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Biomedical subjects

H Imhof

Publications and source records attributed to H Imhof.

At least 73 records · Page 4Linked to original sources
PubMed2000

[Magnetic resonance tomography (MRI) of joint cartilage. Current status of knowledge and new developments].

MRI is the most accurate noninvasive technique available for assessment of normal articular cartilage and cartilage lesions. MRI cannot only provide morphologic information about the area of damage, but can also provide unique insight into the biochemical composition of the articular cartilage. New image processing techniques such as three-dimensional mapping of cartilage thickness will help to establish automated analysis of cartilage loss. Theses techniques are ideally suited for monitoring patients who undergo treatment with new chondroregenerative drugs.

Cartilage, Articular↗
PubMed2000

[Radiologic quantification of joint changes. A methodological overview].

Osteoarthritis as well as rheumatoid arthritis lead to chronical progressive destruction of diseased joints. As aggressive new treatments need to be evaluated, plenty of (semi-) quantitative methods for the radiological joint evaluation had been developed. They lack sufficient reproducibility due to their low objectivity. Modern approaches of computer-assisted radiological quantification should increase the reproducibility and efficiency of radiological scoring. Automatically calculated, computer-assisted measurements of joint space, cartilage- and synovial volume, periarticular assessment of bone mineral density and quantitative analysis of the subchondral plate will have major impact on the radiological routine of the future.

Arthritis, Rheumatoid↗
PubMed2000

[Diagnostic imaging in femur head necrosis].

Diagnosis of avascular necrosis (AVN) of the hip has been improved by the technical progress of imaging modalities during the last decade. For a long period, only plain radiographs had been available. Scintigraphy and computed tomography contributed to differential diagnosis and early detection of bone necrosis. In the meantime, MR imaging has gained special value in the evaluation of AVN. It is now the method of choice for early detection as well as for assessment in later stage disorders. Using the ARCO system, all imaging modalities and their diagnostic viability are described. Findings regarding the different stages of AVN are correlated to tissue-specific changes.

Diagnostic Imaging↗
PubMed2000

Subchondral bone and cartilage disease: a rediscovered functional unit.

The role of subchondral bone in the pathogenesis of cartilage damage has likely been underestimated. Subchondral bone is not only an important shock absorber, but it may also be important for cartilage metabolism. Contrary to many drawings and published reports, the subchondral region is highly vascularized and vulnerable. Its terminal vessels have, in part, direct contact with the deepest hyaline cartilage layer. The perfusion of these vessels accounts for more than 50% of the glucose, oxygen, and water requirements of cartilage. Bony structure, local metabolism, hemodynamics, and vascularization of the subchondral region differ within a single joint and from one joint to another. Owing to these differences, repetitive, chronic overloading or perfusion abnormalities may result in no pathological reaction at all in one joint, while in another joint, these same conditions may lead to osteonecrosis, osteochondritis dissecans, or degenerative changes. According to this common etiological root, similar pathological reactions beginning with marrow edema and necrosis and followed by bone and cartilage fractures, joint deformity, and insufficient healing processes are found in osteonecrosis, osteochondritis dissecans, and degenerative disease as well.

Biomechanical Phenomena↗
PubMed2000

Magnetic resonance imaging of articular cartilage and evaluation of cartilage disease.

Clinical magnetic resonance imaging of articular cartilage is possible by using techniques that offer high contrast between articular cartilage and adjacent structures in reasonable examination times. The fat-suppressed, three-dimensional, spoiled gradient-echo sequence has been reported to be accurate and reliable, and the addition of this sequence to a routine examination does not significantly compromise patient throughput. Fast spin-echo imaging also shows promise in the clinical evaluation of articular cartilage, because the newer, stronger-gradient systems allow thinner slice acquisition with two-dimensional sequences. Together, these sequences allow the evaluation of intrachondral lesions and surface defects. Furthermore, quantitative measurements of cartilage volume for follow-up studies are possible with the use of the fat-suppressed, three-dimensional, spoiled gradient-echo sequence.

Cartilage Diseases↗
PubMed2000

Peripheral quantitative CT of the forearm: scanner cross-calibration using patient data.

Bone density measurements by peripheral quantitative CT (pQCT) of the distal radius in 87 women (age 38.4 +/- 12.3 years) were obtained on a both a Stratec XCT 900 and an updated version XCT 1400. Axial area, and total and trabecular bone mineral density (BMD) results from both scanners were compared for all patients using linear regression analysis. To achieve scanner calibration we used the intercept and slope of the patients' correlations. The correlations of the patients' values were good for area (r = 0.83) as well as total BMD (r = 0.90) and excellent for trabecular BMD (r = 0.97). The cross-calibration approach in our study provided compatibility of pQCT for trabecular and total ROIs, the clinically mostly utilized volumes of measurement.

Adult↗
PubMed1999

The role of relaxation times in monitoring proteoglycan depletion in articular cartilage.

Various proton relaxation times (T2, T1rho, and gadolinium-diethylene triamine pentaacetic acid [Gd-DTPA]-enhanced T1) were measured in articular cartilage in vitro at 3 T to assess their role in visualizing proteoglycan depletion. Cartilage-bone specimens were obtained from patients who underwent total joint replacement and got a double dose of Gd-DTPA 2 hours prior surgery. In these specimens, regions of mechanically undamaged cartilage having a decreased content of proteoglycans showed about 15% lower T1 values compared with apparently normal cartilaginous tissue. The expected increase of the T2 relaxation time was not observed in these regions. On the other hand, the T2 and, to a lower degree, T1 relaxation times were found to be increased in regions of cartilage fibrillation. The T1rho relaxation times obtained were slightly longer than the corresponding T2 values, but both parameters showed almost identical spatial distributions. J. Magn. Reson. Imaging 1999;10:497-502.

Cartilage, Articular↗
PubMed1999

[MRI of the ankle joint. Comparison of the 1.0-T and the 0.2-T units].

PURPOSE: Comparison of ankle joint injuries with different MR systems and at different field strengths. METHOD: Ten patients with acute ankle injuries were examined using mid-field (1.0 T) and dedicated low-field (0.2 T) MR units. Findings of ligamentous injury, sinus tarsi involvement, bone injury, and tendon injury were correlated. RESULTS: There was no significant difference between mid- and low-field MR imaging for ligamentous injuries (chi 2 = 0.0395), sinus tarsi changes bone injuries (chi 2 = 0.0507; critical value = 5,991). CONCLUSION: This study showed good agreement in pathological findings in ankle injury on mid-field and low-field MR imaging.

Acute Disease↗
PubMed1999

[MRI arthrography of the ankle joint].

Due to its superior soft tissue contrast conventional MRI is the imaging method of choice in the evaluation of ankle joint disorders. Conventional MR imaging can accurately demonstrate normal or acutely injured ligaments; however, in subacute and chronic injury joint fluid necessary for delineation of injured ligaments is absent and MR arthrography should be performed. MR arthrography uses the intraarticular injection of contrast material to distend the joint, yielding improved discrimination of intraarticular structures. This joint distension with MR arthrography is also helpful in the staging of osteochondritis dissecans, since in cases of unstable lesions tracking of contrast material into the interface can be more easily demonstrated. Finally, high contrast and joint distension by MR arthrography improves the detection of intraarticular loose bodies, which often require surgery. MR arthrography, although invasive, may provide additional information in various ankle joint disorders.

Ankle Injuries↗
PubMed1999

[Clinical application of densitometry].

An early diagnosis of osteoporosis and an accurate estimation of treatment outcome are the focus of the radiological efforts. The most commonly applied methods for the evaluation of the peripheral and axial skeleton are dual x-ray absorptiometry, quantitative computed tomography, and quantitative ultrasound. Data of an individual are generally compared to an age-, sex-, and ethically-matched control population. The bone mass measurement predict a patients future risk of fracture and the presence of osteoporosis can be diagnosed even in the absence of prevalent fractures. Fracture risk increases approximately 1.5-2.5 times for every 1.0 standard deviation an individual's bone mass is below the mean peak mass of healthy young individuals (T-score). The choice of the appropriate measurement sites may vary depending on the specific circumstances of the patient. The choice of the appropriate technique in any given clinical circumstance should be based on the strength and limitations of the different techniques.

Absorptiometry, Photon↗
PubMed1999

[Filmless magnetic resonance tomography. Advantages and disadvantages in comparison with film reports].

At our hospital, an average MRI examination comprises 170 images. These examinations were evaluated exclusively on digital reporting systems with two high-resolution monitors for a period of 1 year. A retrospective analysis of this reporting method in comparison with films on a conventional viewing wall was performed with subjective and objective data. Radiologists and technicians were requested to evaluate the system on a subjective scale from 1 to 5 for seven topics (image analysis, inspection, time for reporting, handling, comparison with previous reports, quality of PC laser prints, training period). Moreover, personal interviews were conducted and protocols taken. Patient and image frequency, film costs, data transfer time and amount of system failures were evaluated as objective data. The most important results were: Two thirds of the film checking radiologists prefer the conventional viewing walls over the computer monitors. However, 70% of the residents prefer using the computer monitor for reporting. Seventy percent of the interviewed radiologists considered comparison with former examinations on film very difficult. Digitizing of former MRI examinations was not a convincing method; printing on a standard PC laser printer was considered to yield insufficient quality. The different acceptance between radiologists and residents seems to be related to different experiences. The reduction in film costs (48.6%) will improve further with complete PACS installation in the whole hospital. Data transfer rates are still poor; further improvement of network performance is necessary for convenient work. One whole MRI examination and report could be stored on CD-ROM for a cost of less than 2 euros. This could be a future means of cheap archiving and documentation suitable for viewing on any PC with DICOM III viewer. Images and reports could stay with the patients as in the past.

Computer Peripherals↗
PubMed1999

[Teleradiology in dentistry].

Teleradiology is a means of electronically transmitting radiographic patient images and consultative text. This offers a new way to communicate with other radiologists and transferring clinicians. Different applications of teleradiology, such as on-call services for emergency departments or rural regions, as well as expert consultation (second opinion) already have been realized. Especially in concern of dental radiography, analog (film-based) imaging gets progressively replaced by digital imaging. The combination with ultrafast data transfer offers an increasing efficacy in diagnosis and therapy, acceleration of communication and new means of quality assessment in patient care. Various applications of teleradiology concerning dental medicine are discussed.

Humans↗
PubMed1999

Imaging of trabecular bone structure in osteoporosis.

Osteoporosis is a metabolic bone disorder that is characterized by reduced bone mass and a deterioration of bone structure which results in an increased fracture risk. Since the disease is preventable, diagnostic techniques are of major importance. Standard techniques determine bone mineral density, whereas some of the newer techniques focus on trabecular structure. This article reviews structure analysis techniques in the diagnosis of osteoporosis. Imaging techniques applied to the assessment of trabecular bone structure include conventional radiography, magnification radiography, high-resolution CT (HRCT) and high-resolution MR imaging (HRMRI). The best results were obtained using high-resolution tomographic techniques. The highest spatial resolutions in vivo were achieved using HRMRI. The most common texture analysis techniques that have been used are morphological parameters (analogous to bone histomorphometry). Fractal dimension, co-occurrence matrices, mathematical filter techniques and autocorrelation functions are more complex techniques. Most of the studies evaluating structure analysis show that texture parameters and bone mineral density both predict bone strength and osteoporotic fractures, and that combining both techniques yields the best results in the diagnosis of osteoporosis.

Bone Density↗
PubMed1999

Discrimination between fluid, synovium, and cartilage in patients with rheumatoid arthritis: contrast enhanced Spin Echo versus non-contrast-enhanced fat-suppressed Gradient Echo MR imaging.

PURPOSE: The aim of this study was to compare fat-suppressed T1-weighted 3D-Gradient Echo (GE)-images and conventional T1-weighted contrast-enhanced SE images in the assessment of patients with rheumatoid arthritis in an attempt to improve discrimination of inflamed synovium, joint fluid, and cartilage. PATIENTS AND METHODS: 28 knee joints in 20 patients with rheumatoid arthritis were examined with a 3 D-GE-T1 weighted sequence with frequency-selective fat suppression (Flash 3D fat sat) and T1-weighted SE-sequences after intravenous gadolinium-containing contrast agent administration using a 1.5T system. Differentiation of cartilage, synovium, and joint effusion was assessed on both sequences qualitatively by two observers and quantitatively by signal intensity measurements. RESULTS: Qualititative analysis revealed higher grading rates for cartilage/fluid differentiation with fat-suppressed T1-weighted GE images than contrast enhanced T1-SE images. Quantitative analysis by measurements of contrast-to-noise ratios revealed significantly higher rates for the Flash 3D fat sat with regard to cartilage/fluid discrimination, significantly higher rates for T1-SE post-contrast for cartilage/synovium discrimination, and significantly higher rates for T1-SE post-contrast for synovium/fluid discrimination. CONCLUSION: 3D-GE-imaging with fat-suppressed T1 weighted sequences allows sufficient differentiation of cartilage and joint fluid in patients with rheumatoid arthritis without application of contrast agents and may assist in monitoring disease progression and response to therapy. The higher contrast to noise ratios of cartilage/synovium and synovium/fluid on T1-SE images following administration of gadolinium-containing contrast agents may improve detection of disease activity.

Adult↗
PubMed1999

Comparison of low field (0.2T) and high field (1.5T) MR imaging in the differentiation of torned from intact menisci.

PURPOSE: To evaluate the usefulness of a low field MRI system (0.2T; Esaote, Biomedica) for the evaluation of meniscal tears with regard to anatomic site, and to compare the results with findings from a high field unit (1.5T; Siemens, Erlangen). MATERIAL AND METHODS: MRI was performed in 25 patients in a low field (0.2T; Esaote, Biomedica), and a high field (1.5T; Siemens, Erlangen) MRI unit. The images were analyzed for the presence or absence of meniscal tears and the confidence of decision making. Results were further analyzed for the number of identical and unidentical findings on both imaging modalities. In seven patients, arthroscopy was performed and the findings compared with the results from MR imaging. Statistical analysis was performed by chi 2-test, Wilcoxon test and Friedman analysis. RESULTS: Qualitative evaluation of the level of confidence in decision making was significantly superior on high field strength images. When comparing the evaluations from both image modalities in 21 of 25 patients (84%), the diagnosis concerning the presence or absence of meniscal tears was identical. CONCLUSION: Although low field MR imaging might offer diagnostic potential concerning the presence or absence of meniscal tears, the level of confidence in decision making is significantly superior with high field strength imaging, probably reflecting the higher conspicuity of lesions from high field strength units.

Adult↗