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Biomedical subjects

U Mödder

Publications and source records attributed to U Mödder.

At least 91 records · Page 5Linked to original sources
PubMed1999

[MR imaging-guided interventions].

The spectrum of MR imaging-guided interventions includes biopsies, thermal ablation modalities, vascular applications, MR endoscopy and intraoperative MR imaging. The concept of MR guidance is based on the excellent morphologic and functional imaging achieved by MR. The most important recently published experimental and clinical results are discussed. In the future, MR imaging will play an important role in interventional radiology, minimal invasive therapy and guidance of surgical procedures.

Biopsy↗
PubMed1999

Venous incompetence in erectile dysfunction: evaluation with color-coded duplex sonography and cavernosometry/-graphy.

The purpose of this study was to assess the accuracy of multi-parameter measurements with color-coded duplex sonography (CCDS) for the diagnosis of venous leakage in patients with erectile dysfunction. Sixty patients with repeated unsatisfactory reactions after intracavernous injection of vasoactive substances underwent CCDS. Following intracavernous injection of prostaglandin E1, peak systolic velocity (PSV), enddiastolic velocity (EDV), time averaged velocity (TAV), resistance index (RI), and pulsatility index (PI) were measured in the cavernous arteries over 30 min (one measurement per minute). The results were compared with independent measurements based on dynamic pharmaco-cavernosometry/cavernosography (DPCC). Dynamic pharmaco-cavernosometry/cavernosography revealed venous leakage in 33 patients. Of 48 patients with normal PSV ( > 25 cm/s), 25 had veno-occlusive dysfunction and the remainder presented normal venous function. No statistically significant differences between these groups were found in EDV, RI, and PI measurements. In contrast, differences in TAV were significant between patients with (mean 9.4 +/- 4.6 cm/s) and without venous leakage (mean 5.5 +/- 2.2 cm/s; p = 0.001). Analysis of relative frequencies revealed a broad overlap of EDV, TAV, RI, and PI measurements between both groups. Sensitivities and specificities determined from receiver-operating-characteristic curves were > 80 % and > 50% for a TAV threshold of 5 cm/s, and an RI threshold of 1.0. Measurements of EDV, TAV, RI, and PI in patients with repeated unsatisfactory reactions on intracavernous prostaglandin injection are poor predictors of venous leakage and should not replace DPCC in the investigation of vasculogenic impotence.

Adult↗
PubMed1999

Incidentally discovered pituitary lesions: high frequency of macroadenomas and hormone-secreting adenomas - results of a prospective study.

OBJECTIVE: With increasing use of computed tomography and magnetic resonance imaging, pituitary adenomas are being discovered incidentally with increasing frequency. However, limited data are available concerning the clinical importance and natural history of such 'incicentalomas'. We have undertaken a prospective study to investigate changes in adenoma size and endocrine and visual function in patients with incidentally discovered intrasellar masses. PATIENTS AND METHODS: Our study included 67 patients with incidentalomas of the pituitary gland during a 5-year period (1992-96). 50 of these patients were followed up prospectively over a mean period of 2.7 years. Initially, all patients underwent endocrine testing and ophthalmological examinations as well as magnetic resonance imaging or computed tomography scans. These investigations were repeated after 3 months and then annually. RESULTS: 42 (62.7%) out of 67 patients with incidentalomas had microadenomas whereas 37.3% had macroadenomas. Macroadenomas were found more frequently in men (52.2%). Visual field defects could be documented in 4.5% of the patients. Partial deficiency of anterior pituitary function was present in 14.9%. Eight patients (11.9%) had prolactinomas. An increase in adenoma size was detected in 3.2% of the microadenomas and in 26.3% of the macroadenomas within the follow-up period. CONCLUSION: Macroadenomas and hormone secreting adenomas are not uncommon in patients with pituitary incidentalomas. Macroadenomas should be closely monitored for tumour enlargement. All patients should undergo biochemical assessment and ophthalmological examination, since endocrine dysfunction or visual field defects may be present at the time a pituitary incidentaloma is detected.

Adenoma↗
PubMed1999

CT appearance of a renal aspergilloma in a patient with the acquired immunodeficiency syndrome.

The appearance of a unilateral renal aspergilloma on computed tomography is described in a 32-year-old man with acquired immunodeficiency syndrome (AIDS). Aspergillus infections are uncommon in the AIDS population. Only 9 cases of renal aspergilloma have been described in AIDS. The treatment performed was percutaneous drainage followed by antifungal drug administration and unilateral nephrectomy. This case report emphasizes the fact that renal fungal infections need to be considered in differential diagnosis of kidney infections in AIDS patients.

AIDS-Related Opportunistic Infections↗
PubMed1999

Diffusion- and perfusion-weighted MRI. The DWI/PWI mismatch region in acute stroke.

BACKGROUND AND PURPOSE: Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) are relatively new MR techniques increasingly used in acute stroke. During the first hours of stroke evolution, the regions with abnormal perfusion are typically larger than the DWI lesions, and this mismatch region has been suggested to be "tissue at risk." The aim of this study was to evaluate the PWI/DWI mismatch region in acute stroke patients and find parameters indicative of both infarct progression and functional impairment. METHODS: Twenty patients with nonlacunar ischemic stroke were imaged with DWI, PWI, and conventional MRI within 24 hours of symptom onset and after 1 week; in addition, the European Stroke Scale (ESS) score was recorded. With PWI, the volumes of regions with "time-to-peak" (TTP) delays of >/=2, 4, 6, 8, and 10 seconds were measured; these volumes were compared with the acute DWI lesion volumes, final infarct size, and ESS score. RESULTS: In 80% of patients the acute DWI lesion was surrounded by regions with abnormal TTP delays (PWI>DWI lesion). A TTP delay of >/=6 s in the mismatch region was found to be associated with lesion enlargement between the initial and follow-up MRI scans. Lesions increased in 9 of 12 patients (75%) in whom the area with TTP delay >/=6 s was larger than the DWI lesion, but they increased in only 1 of 8 (12.5%) of the remaining patients, in whom the area with a TTP delay >/=6 s was smaller than the DWI lesion. The volume of the regions with TTP delays of >/=4 s correlated better with ESS (r=-0.88, P<0.001) than other PWI (or DWI) volumes, which indicated that a TTP delay of approximately 4 s might be the threshold for functional impairment of brain tissue. CONCLUSIONS: Only patients with severe perfusion deficits in the PWI/DWI mismatch (TTP delays of >/=6 s) are at high risk of lesion enlargement. Functionally, more moderate perfusion deficits (TTP delays >/=4 and <6 s) appear to also contribute to the acute clinical deficit.

Acute Disease↗
PubMed1998

[Rational radiologic diagnosis of breast carcinoma].

For a favourable prognosis breast cancer must be diagnosed as early as possible. Among available imaging modalities (mammography, sonography, DAS, thermography, CT, MR) only mammography has been shown to produce a significant reduction in mortality, but unfortunately only for women above 50 years of age. The technical requirements, and the standard techniques and the appearance of benign and malignant breast tissues are described. The routine use of ultrasound in the evaluation of palpable masses remains controversial. Ultrasound technology is incapable of detecting early-stage cancers reliably. By "using dynamic MRM", i.e., repetitive imaging of the same slice before and at short time intervals after the injection of a contrast medium, high sensitivity and specificity is achieved in detecting breast cancer of different histologies. MR-mammography should be used in all cases where there is a discrepancy among radiographic, sonographic or clinical findings.

Adult↗
PubMed1998

[Interventional MR tomography. Current status and future perspectives].

The concept of MR guidance of invasive diagnostic and minimally invasive therapeutic procedures is based on the excellent morphologic and functional properties of MR imaging. Prerequisites are adequate patient monitoring and adherence to safety guidelines. Fast and ultrafast sequences, temperature quantification, visualization of intravascular devices, thermal stability of contrast media and thermosensitive contrast media are discussed. The spectrum of clinical applications includes biopsies, thermal ablation modalities, vascular applications, MR endoscopy and intraoperative MR imaging. The development of interventional MR imaging is still in its infancy. In the future, MR imaging may play an important role in interventional radiology and minimally invasive therapy.

Biopsy↗
PubMed1998

[The quality offensive in radiology].

The Institute of Diagnostic Radiology at the Heinrich-Heine-University Duesseldorf has recently defined and implemented more than thirty organizational changes as a result of a quality control project. The aim was to improve quality and efficiency of the Radiology service. The project was carried out in cooperation with an external consulting firm. To date the positive impact of this project on our work has been so profound that we would like to communicate some of the results in form of this report. During the first phase of the project quality circles were formed to define the various quality criteria and aims of a good service. Today these represent the core of a new quality policy for the Institute. In a second phase all members of staff cooperatively developed precise plans of action for implementation of the necessary changes. Main achievements are the reduction of organizational and communicational deficits obstructing the work process, enhancement of interaction between junior and senior medical staff, upgrading of the role and field of action of the radiography staff and last but not least improvements of cooperation between secretarial and medical staff.

Forecasting↗
PubMed1998

[B-mode ultrasound and modern Doppler ultrasound methods in diseases of the thyroid gland and parathyroid glands].

Color-coded duplex sonography is the main innovation in diagnostic ultrasound in recent years. It allows quantification of tissue vascularity and appreciation of vascular morphology. Due to the unique thyroid hypervascularity in Graves' disease this diagnosis can be made with color Doppler sonography alone. The decrease of vascularity during the course of disease is a relevant parameter throughout the follow-up. Hypervascularity is also observed within areas of inflammatory infiltration in thyroiditis, but the level is lower than in Graves' disease. Sonographic differentiation of benign from malignant thyroid nodules is not possible yet. Color-coded duplex sonography is not useful in the initial detection of parathyroid masses, but may be helpful in distinguishing parathyroid lesions from other cervical masses.

Diagnosis, Differential↗
PubMed1998

[Intraoperative findings and postoperative computer tomographic follow up of inflammatory aortic aneurysm].

PURPOSE: Retrospective evaluation of postoperative long-term results after surgery of inflammatory aortic aneurysms (IAAA) with computed tomography (CT). Findings in CT were analysed with particular attention to the development of inflammatory tissue adjacent to the aneurysm site. MATERIAL AND METHODS: Of 2101 patients operated on an aortic aneurysm 5.4% (114 patients) presented typical intraoperative features of inflammatory aortic aneurysms. 54 of these 114 patients (47%) were examined via computed tomography pre- and post-operatively. On an average the follow-up-study was performed 2.5 years postoperatively. RESULTS: All follow-up-studies revealed a correct location of the aortic prostheses. In 85.1% of the cases there was either no or negligible persisting inflammatory tissue with a diameter of less than 2 mm. 10.6% of the patients demonstrated remaining but reduced inflammatory tissue. In 4.3% of the cases the extent of the inflammatory tissue had not changed. Aneurysms of the anastomoses (n = 4), morphologic renal changes (n = 7) and an aorto-enteric fistula were demonstrated by CT as postoperative complications. CONCLUSIONS: In evaluating recurrence of the aneurysm and possible complications as well as the development of the inflammatory tissue, postoperatively performed computed tomography proved a reliable diagnostic method.

Aortic Aneurysm, Abdominal↗
PubMed1998

[Dosage measurements in spiral CT examinations of the head and neck region].

PURPOSE: In view of the increasing frequency of computed tomographic examinations the organ doses of the thyroid gland and the eye lenses in spiral CT examinations of the head and neck should be determined. MATERIAL AND METHODS: Standard CT-examinations of the neck, the paranasal sinuses in axial and coronal sections, and the mandibula were simulated by help of an Alderson-Rando phantom. Dose measurements were performed as well in 28 patients. The examinations were carried out in spiral mode ("Somatom AR.SP", "Picker PQ 2000", and "Toshiba Xpress SX") and conventional single slice technique ("Somatom Plus"). Three LiF-TLD were placed on each eyelid and three on the thyroid. RESULTS: With direct exposure to the x-ray-beam the organ doses did not exceed 64 mGy. When exposed by scatter radiation only, doses may be reduced by a factor of up to 10. The measurements in 28 patients showed similar results. CONCLUSIONS: The organ doses in spiral CT correspond with data known from conventional CT.

Head↗
PubMed1997

Determination of laser-induced temperature distributions using echo-shifted TurboFLASH.

An echo-shifted TurboFLASH sequence implemented on a clinical whole body MR scanner was used to determine thermal changes in tissue. With this snapshot-like data acquisition, temperature-related phase shifts were measured with a temporal resolution of 1.3 s. For different types of tissue (postmortem porcine brain, liver, and muscle) the temperature coefficients of the proton chemical shift were recorded during uniform heating of the specimen in a water bath. The specific temperature-dependent frequency shifts appeared similar to the proton chemical shift of free water (-0.01 ppm/degrees C). With this method, laser-induced ablation in postmortem porcine brain was monitored by temperature mapping. Comparison of the induced temperature profiles measured with NiCrNi-thermocouples with the MR calculated profiles demonstrated excellent temperature sensitivity and accuracy for this method of MR thermometry, with a maximum deviation of the determined temperatures of only 1.8 degrees C. This investigation was designed as a feasibility study for this rapid version of the phase mapping method, and no in vivo studies were performed.

Animals↗
PubMed1997

Early detection of avascular necrosis of the femoral head following renal transplantation.

This prospective study included 43 patients undergoing renal transplantations. Magnetic resonance imaging (MRI) and X-rays of the hip joints were produced 3 and 12 months after transplantation. In 6 hip joints of 4 patients (9.3%), we discovered femoral head necroses just 3 months after transplantation. Three of the hip joints affected were symptomatic and 3 painless. The MR images taken 12 months after transplantation revealed no additional femoral head necrosis. A core decompression was performed on 3 joints. In contrast to those with core decompression, the femoral heads without core decompression showed a progression of the necrosis in 2 of 3 cases. All 4 patients with femoral head necroses were younger than 50 years and exhibited a premature conversion of the haematopoietic marrow to fatty marrow in the area of the proximal femoral metaphysis. A similar premature conversion to fatty marrow was seen in 6 of the 22 (27.2%) patients younger than 50 years and without femoral head necroses. The doses in long-term steroid medication and the steroid doses during the rejection periods of the patients with femoral head necroses were not significantly higher than those for the patients with premature conversion to fatty marrow. The latter had also not received significantly higher doses than the patients whose MRI findings were inconspicuous.

Adult↗
PubMed1997

[Radiologic diagnosis of primary extranodal lymphoma manifestations].

Primary extranodal lymphoma manifestation in the narrow sense is the term used to define the primary organ manifestation of a malignant lymphoma, excluding the thymus, spleen, Waldeyer's tonsillar ring, the appendix and Peyer's patches. However, in the clinical routine the term is also used for the secondary organ manifestation of underlying lymphoproliferative disease. Primary extranodal lymphomas are mainly non-Hodgkin lymphomas; there is primary extranodal manifestation of Hodgkin's disease in only about 1% of the cases. Among the extranodal NHL, the highly malignant forms predominate. A major exception is MALT lymphomas, which mainly show low slow growth. In the past, they were considered to be pseudolymphomas because of their slow and localized tumor growth. They were included as an entity of their own for the first time in the Revised European American Lymphoma (REAL) classification of 1994. The incidence data vary between < 10% and 25% for primary extranodal manifestation. The major reason for this is the difference in extranodal regions because of classification. Secondary organ involvement of an NHL occurs in up to 40% of the cases in the long-term course of the disease in primary nodal lymphomas. Secondary organ involvement is frequently diagnosed in AIDS patients who develop an AIDS-related lymphoma (85% of cases). The following contribution reports on the radiological imaging of extranodal lymphoma manifestation in the thoracoabdominal region.

Diagnosis, Differential↗
PubMed1997

The value of new MRI techniques in adrenoleukodystrophy.

PURPOSE: To evaluate the significance of new techniques in MRI examinations of the brain in children with X-linked adrenoleukodystrophy (ALD). MATERIALS AND METHODS: Five patients aged between 2 and 15 years with childhood ALD were examined with MRI. Following conventional spin-echo (CSE) sequence, a fast spin-echo (FSE) sequence with T2 contrast was performed in four patients, an FSE turbo-inversion-recovery (TIR) sequence in two, magnetization transfer contrast (MTC) imaging in two, and localized proton spectroscopy (MRS) in four patients. RESULTS: FSE compared favorably with CSE with a time saving of 70%. On TIR images the contrast between normal and demyelinated white matter was greater than on CSE and FSE images. Calculated MTC values revealed a severe MTC loss within the demyelinated regions and a moderate reduction in the border zones. In this way, calculation of MTC might be useful to differentiate between edematous changes and areas of irreversible demyelination. MRS revealed a reduction in N-acetylaspartate and an elevation in choline (Cho). The degree of MRS changes paralleled the severity of demyelination. A Cho elevation may precede visible demyelination on T2-weighted images. CONCLUSIONS: T2-weighted FSE sequences can replace CSE without any disadvantages and with effective time saving. The indication for MTC imaging and MRS in children with ALD is not yet finally defined. These new techniques may reveal the earliest signs of cerebral involvement or of disease progression, a matter of great importance in selecting the optimal therapeutic approach.

Adolescent↗
PubMed1997

1H T1 and T2 measurements of the MR imaging contrast agents Gd-DTPA and Gd-DTPA BMA at 1.5T.

We report in vitro T1 and T2 relaxation studies for the open-chain complexes Gd-DTPA and Gd-DTPA BMA. Measurements were performed on phantoms containing aqueous and plasma solutions of different concentrations by MR imaging in a 1.5T superconducting whole-body scanner. Longitudinal relaxation times T1 were evaluated from serial turbo-FLASH experiments for concentrations less than 1 mM, whereas for larger concentrations the values were obtained from a standard inversion recovery (IR) sequence. Transverse relaxation times T2 were determined using multi-echo spin-echo MRI protocols. The T1 and T2 relaxivities of the nonionic Gd-DTPA BMA are similar to those of the Gd-DTPA. The temperature dependencies of the relaxivities were determined over a temperature interval ranging from 21 to 50 degrees C and were found to be slightly different for the two contrast agents. In the case of Gd-DTPA BMA a larger deviation of the expected temperature behavior of the relaxivities was observed as compared with Gd-DTPA. Deviations from a strictly linear dependence of relaxation times on temperature were found at lower concentrations in aqueous solutions. In plasma solutions a high T1/T2 ratio was observed for low concentrations, which decreased monotonically with increasing concentrations.

Contrast Media↗