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Biomedical subjects

H Imhof

Publications and source records attributed to H Imhof.

At least 163 records · Page 9Linked to original sources
PubMed1995

[Tarsal tunnel syndrome. MRI diagnosis].

Clinical findings and symptoms of tarsal tunnel are commonly vague and diffuse and electrodiagnostic studies do not provide definitive diagnosis. MR imaging with its excellent soft tissue contrast can demonstrate clearly the anatomy of the tarsal tunnel and its contents. MRI is able to demonstrate a space-occupying lesion and its relationship to the posterior tibial nerve and its branches. This information aids in surgical planning by determining the extent of the decompression required. MR imaging may also be used to follow up non-surgical causes of tarsal tunnel syndrome such as tenosynovitis.

Diagnosis, Differential↗
PubMed1995

[Ultrasound diagnosis of the popliteal fossa].

Sonography of the knee is a well-established method for the diagnosis of palpable tumors. However, evaluation of the menisci, cruciate ligaments, and hyaline cartilage is controversial. Despite the variable echogenicity and extension of different diseases, many distinct sonographic signs are different in cysts, solid neoplasms, and vascular diseases. The investigator must be familiar with various patterns of popliteal cyst formation: crescent-shaped, cross-shaped, slitlike, and grape-like cysts. Because of diagnostic and economic reasons the following concept should provide guidance when diagnosing lesions of the popliteal fossa: the first step of diagnostic imaging should include plain film radiography and sonography. In a second step MRI and/or arthroscopy should be performed.

Aneurysm↗
PubMed1995

[Ultra-short turbo-spin echo in comparison with turbo-spin echo. Possible applications in the musculoskeletal system].

Ultrashort turbo spin-echo sequence (TSE) has the advantage of shorter scan times, minimizing motion artifacts, but has the disadvantage of a lower signal-to-noise ratio and suffers from different artifacts. T2-weighted ultrashort TSE (echo train 24) and TSE (echo train 11) were compared in degenerative lesions of the spine (n = 9) and ligamentous lesions associated with sprained ankle injuries (n = 5). The imaging quality of ultrashort TSE was very similar to TSE. There was no difference in diagnostic reliability with ultrashort TSE compared to TSE in the spine or ankle. With regard to contrast properties a higher signal intensity of fatty bone marrow was obtained with ultrashort TSE, with consecutive lower contrast between fluid and edema on the one hand and fatty tissue on the other.

Ankle Injuries↗
PubMed1995

[MR-pool: the "Vienna blend". An interactive computer-assisted teaching system for MRI].

Advances in the field of computer technology have facilitated the development of computer-assisted instruction. In this paper we present an interactive computer-based MR teaching system for education in radiology. Our program contains 120 teaching files. Various MR sequences can be displayed and compared to conventional X-ray images, CT, angiography and scintigraphy. Using a text field, additional clinical and diagnostic hints are offered. This teaching file can be easily upgraded and distributed on CD-ROM. Furthermore, we compare computer-assisted teaching in general to other conventional instruction media.

Austria↗
PubMed1995

[New approaches to computer-assisted diagnosis of rheumatologic diseases].

UNLABELLED: Since the 1960s, several knowledge-based systems for computer-assisted diagnosis in radiology have been developed. The great majority of these tools has been implemented as off-line systems. This requires interaction with the system solely for the purpose of consultation and therefore interrupts the radiologist's work flow. This and inadequate man-machine interfaces may have inhibited the routine clinical use of such systems. The goal of this paper is to describe the current research toward the development of the on-line expert system Cadiag-4/Rheuma-Radio. The underlying fundamentals of the system design, including client/server architecture, communication interfaces, and fuzzy set theory and fuzzy logic as methods for knowledge representation and interference, are presented. METHODS: In radiology today, computers are routinely used to acquire radiological images in hospital and radiology information systems (HIS/RIS) and picture archiving and communication systems (PACS). In our approach, we make use of pre-existent sources of information to build an expert system that minimizes the interaction between radiologists and the computer. To handle uncertainty and vagueness of medical knowledge, fuzzy set theory and fuzzy logic are used. Given data of a specific case, a deductive inference procedure combines the observed radiological signs, establishes confirmed and excluded diagnoses as well as diagnostic hypotheses, and provides explanations for these conclusions. Furthermore, proposals for confirmation or exclusion of diagnostic hypotheses are offered. RESULTS: For evaluation purposes, an early prototype of Cadiag-4/Rheuma-Radio was tested on radiological disorders of the hip joint related to rheumatological diseases. Twenty radiological cases were used as test cases, reaching a diagnostic accuracy of about 80%. CONCLUSION: The first results are acceptable and encourage further work to cover the whole area of rheumatologically relevant radiological signs and diagnoses. Furthermore, research into the development of user-oriented data acquisition tools will be carried out.

Arthritis, Rheumatoid↗
PubMed1994

[Magnetic resonance imaging of breast implants. Significance compared to mammography and ultrasonography].

Magnetic resonance imaging (MRI), mammography and ultrasonography were performed in 44 consecutive women (mean age 45 [29-70] years) with a total of 73 silicone breast implants. The implant had been inserted after mastectomy for cancer in 15 patients, for cosmetic breast augmentation in 29. MRI proved to be superior to the other two imaging modalities with respect to assessing implant content, capsule and surrounding tissues. In 39 patients MRI clearly demarcated the implant from the residual breast tissue. But in four patients the lateral MRI assessment was impaired by phase artefact and in one other by movement artefacts in a restless patient. Implant thickness was underestimated by mammography and ultrasonography compared with MRI. In nine cases mammography showed retromammary parenchyma, while MRI did so in 20. The posterior wall of the implant was visualized by mammography in only one patient, but in all of them by MRI. Ultrasonography failed in all patients to show the entire implant circumference. In three cases MRI was the only imaging method which revealed a defect in the implant capsule with extrusion of silicone.

Adult↗
PubMed1994

Method for the quantitative assessment of contrast agent uptake in dynamic contrast-enhanced MRI.

In previous papers relative signal intensity increase was used as a quantitative assessment parameter for contrast uptake in contrast-enhanced MRI. However, relative signal intensity increase does not only reflect contrast uptake but depends also on tissue parameters (native T1 relaxation time) and sequence parameters (repetition time and flip angle); thus, the contrast uptake cannot be assessed accurately using relative signal intensity increase. Based on an analysis of the contrast behavior of spoiled gradient echo sequences, a method is described in this paper that overcomes the limitations of relative signal intensity increase measurement. A parameter, called "enhancement factor" (EF) is introduced that approximates differential T1 relaxation rate. The enhancement factor scales linearly with contrast uptake and is independent of tissue and sequence parameters. The additional measurement time involved in determining the enhancement factor is less than 1 min and computation is straightforward. The practicality of the new method was confirmed by phantom measurements using T1-weighted and proton density-weighted spoiled gradient echo sequences (FLASH-2D). Enhancing tissues were simulated by water phantoms doped with increasing concentrations of Gd-DTPA.

Algorithms↗
PubMed1994

Magnetic resonance angiography and selective angiography following extra-intracranial bypass operations.

Magnetic resonance angiography (MRA) was compared with conventional angiography in 14 patients following extra-intracranial arterial anastomosis. In 13 patients the bypass was shown by MRA and confirmed by conventional angiography. In five of these, the anastomosed vessels, in particular the superficial temporal artery, was of the same calibre or smaller than the same vessels on the contralateral, healthy side. In one patient no anastomosis could be shown by MRA, and occlusion of the bypass was confirmed by conventional angiography. Absence of dilatation of the anastomotic vessels may indicate insufficient bypass function due to stenosis or an incorrect indication for surgery.

Adult↗
PubMed1994

Effect of lung transplantation on right and left ventricular volumes and function measured by magnetic resonance imaging.

To evaluate the effect of lung transplantation on right ventricular (RV) and left ventricular (LV) volumes and function, magnetic resonance imaging (MRI) was performed in 11 patients before and 6 to 24 months after single (n = 7) or double (n = 4) lung transplantation as well as in 15 healthy control subjects. Prior to transplantation, RV end-diastolic (RVEDVI, ml/m2) and end-systolic (RVESVI, ml/m2) volume indices were significantly increased in patients compared with those in control subjects. RV ejection fraction (RVEF, %), although within the lower normal range, was significantly reduced. In contrast, LV volume indices (ml/m2) were significantly smaller in patients than in control subjects, whereas LV ejection fraction (LVEF, %) was not different from that in normal subjects. After lung transplantation, MRI revealed a significant reduction in RVEDVI from 73 +/- 29 to 54 +/- 14 (p = 0.03) and RVESVI from 38 +/- 23 to 20 +/- 6 (p = 0.01) with a concomitant significant increase in RVEF from 48 +/- 14 to 63 +/- 6 (p = 0.01). Consecutively, the LV expanded to normal (LVEDVI from 49 +/- 12 to 65 +/- 14, p = 0.01; LVESVI from 23 +/- 9 to 28 +/- 7, p = 0.05), whereas LVEF remained unchanged (55 +/- 9 versus 56 +/- 8).

Adult↗
PubMed1994

Preoperative staging of osteosarcoma: efficacy of MR imaging in detecting joint involvement.

OBJECTIVE: Selecting the appropriate surgical procedure for treatment of patients with osteosarcoma requires accurate preoperative evaluation of tumor extent. Establishing the presence or absence of joint involvement is particularly important. Accordingly, we studied the efficacy of MR imaging for detecting joint involvement in 46 patients with osteosarcoma around joint spaces. SUBJECTS AND METHODS: Preoperative MR examinations were performed in 46 consecutive patients with osteosarcoma whose tumors were located around the knee (n = 33), the hip (n = 8), or the shoulder (n = 5). T2-weighted and unenhanced and contrast-enhanced T1-weighted spin-echo MR images were obtained for all patients. We assessed the presence or absence of tumor invasion of the intracapsular-intrasynovial joint space, either by disruption of the joint capsule or by intraarticular destruction of the cortical bone and articular cartilage or the intracapsular-extrasynovial cruciate ligaments of the knee. All patients subsequently had surgery. The MR findings were correlated with findings from macroscopic and microscopic pathologic examinations. RESULTS: All 10 patients who subsequently proved to have tumor involvement of the joint were correctly identified (sensitivity, 100%). The tumor involved the knee joint in seven patients, the hip joint in two, and the shoulder joint in one. However, the MR diagnosis was false-positive in another 11 patients who did not have joint involvement at surgery (specificity, 69%). In the knee, MR imaging was more accurate in identifying tumor extension to the cruciate ligaments than to the intrasynovial joint space. Post-contrast T1-weighted images were most useful in detecting joint involvement. CONCLUSION: MR imaging is highly sensitive for detecting joint invasion of osteosarcoma. However, false-positive diagnoses may lead to overstaging of tumor and result in unnecessarily radical surgical procedures.

Adolescent↗
PubMed1994

[The traumatized and surgically treated spine. Current diagnostic imaging].

In trauma patients X-ray and CT are the important imaging modalities for detecting instability of the spine and determining the cause of a spinal cord lesion. MRI should be done to demonstrate the spinal cord lesion itself. Operations on spinal injuries are based on X-ray films and CT. Polydirectional tomography is valuable in the assessment of bone healing, determining osteomyelitis with fistulae, pseudarthrosis and imaging of bone graft fusion in the presence of metallic fixation devices. MRI is indicated for diagnosis and ascertaing the prognosis of spinal cord lesions. In the long-term follow-up syrinx, myelomalacia and atrophy can be differentiated. MRI can also be done for osteomyelitis and complications of bone graft fusion.

Diagnostic Imaging↗
PubMed1994

[Basics of MRI technique and MRI image interpretation].

Today magnetic resonance imaging (MRI) is an important routine diagnostic tool in orthopaedics. It is based on the nuclear magnetic resonance phenomenon: "free" hydrogen atoms (mainly from water) become field-parallel in a strong outer magnetic field. They reach a higher energy level by application of an additional electromagnetic field. After shutdown of this outer field the atoms send out electromagnetic waves (radiowaves), representing the MR signal. Different amounts of "free" water result in various image characteristics. Typically, a higher tissue water content is represented by high MR signals, e.g. in blastomas, inflammations and degenerative changes. Waterless structures such as calcified or fibrous tissues, tendons and ligaments show low MR signals. Fatty structures have high signals; proteins dissolved in "free" water change the water signal dramatically. Besides these basic parameters, para-, ferro- and super-paramagnetic materials--ether naturally present in the human body, such as methemoglobin, or artificially introduced, such as MR contrast media--and flow are responsible for different grey shades in MRI. MRI is not associated with ionizing radiation and allows imaging in all planes without changing the patient's position. Disadvantages of MRI are high costs and low availability. Future technical developments will result in shorter imaging times and broadening of the application spectrum, leading towards "MR fluoroscopy" and MR interventions.

Adolescent↗
PubMed1994

[Bone inflammation (including spondylitis)].

MRI diagnosis of bony inflammations has sensitivity of up to 96%, but specificity of only 70-87%. The most common reasons for false-positive results are fractures, infarctions, neoplasms, septic arthritis and aggressive metastasis. Early MRI diagnosis is based on bone marrow oedema, which is hypointense on T1-weighted images, hyperintense on T2-weighted images. Reactive fibrovascular tissue and hyperaemia lead to contrast enhancement. Necrosis, calcification and sequestra show low signal intensities. Increasing calcifications and restructuring of spongiosa are not well visualized in MRI. In spondylitis, fat conversion is a good marker for healing. Complications of osteomyelitis (e.g. soft tissue abscesses) can be diagnosed by MRI with high sensitivity. In the primary diagnosis and follow-up of osteomyelitis (spondylitis), standard X-ray exams should be performed first. In the initial studies MRI can replace bone scintigraphy, which has poor morphological resolution. Semiquantitative follow-up studies can be done by MRI or scintigraphy.

Adolescent↗
PubMed1994

[Osteonecrosis].

The causes of osteonecrosis are varied. The pathogenesis of osteonecrosis subsequent to trauma is well known. Furthermore, an association of this disorder with cortisone, haemoglobinopathies, rare metabolic diseases, and risk factors seems to be evident. However, a sizable proportion of patients have osteonecrosis in which none of these associations exists, referred to as idiopathic osteonecrosis. Generally, intraosseous vascularization represents the common pathway for the various causes of the disease. The prognosis is influenced by the age of the patient, the location of the necrosis and the stage of the disease at the time of diagnosis. In recent times diagnosis has been improved by the use of modern imaging modalities, and MR imaging is now widely accepted as the imaging method of choice. It not only allows early diagnosis but also yields exact staging information in advanced disease, which is a requirement for adequate therapy.

Adult↗
PubMed1994

[Conventional roentgen diagnosis of the salivary glands. Still of clinical value or "traditional care"-].

This paper reviews the examination technique, normal findings, and pathological findings in conventional radiographic diagnosis of the salivary glands. The clinical importance of plain radiographs and sialography today despite the availability of modern imaging modalities is discussed. Of the ultrasound equipment is adequate and the examiner has enough experience in small-parts ultrasonography, application of conventional X-ray methods should be limited to confirmation of ultrasonographic suspicion of sialolithiasis or tumor-erosion of adjacent bone, especially the mandible (plain films), further imaging of extra- and intraglandular salivary duct abnormalities in chronic inflammatory salivary gland disease, and demonstrating salivary gland involvement in special entities, such as sialadenosis (pseudo)cystica in Sjögren-syndrome by sialography.

Humans↗
PubMed1994

[The non-traumatic femur head necrosis in the adult. II: radiologic diagnosis and staging].

In recent years diagnosis, and in particular early diagnosis, of osteonecrosis of the hip has been much improved by modern imaging modalities. Magnetic resonance imaging is widely accepted as the primary imaging modality for the early detection of this disorder and can help to facilitate the therapeutic management in later stages. However, plain radiographs, bone scans and computed tomography are still important techniques, which cannot be avoided in most cases. This paper describes the relative values of the different modalities. The staging system used is the international ARCO system.

Adult↗