Biomedical subjects

A Heuck

Publications and source records attributed to A Heuck.

At least 19 recordsLinked to original sources

PubMed2007

Directional mRNA transport in eukaryotes: lessons from yeast.

In eukaryotes, developmental processes and cell differentiation, as well as basic cellular functions require the propagation of information in an asymmetric manner. Localization of mRNA is a key mechanism to establish asymmetric cell fate. The first part of this review provides an overview of our current knowledge of motor protein-dependent mRNA transport in eukaryotes. The second part provides a more detailed description of the most comprehensively studied mRNA translocation complex to date: the ASH1 messenger ribonucleoprotein particle (mRNP) from Saccharomyces cerevisiae. During budding of yeast, the ASH1 mRNP transports cell fate determinants exclusively into the daughter cell. The core factors of the ASH1 mRNP have been identified, their interactions have been studied in detail, and the three-dimensional structure of its mRNA-binding protein, She2p, has been determined. Because no other mRNP has been studied in such detail, the ASH1 mRNP could serve as a model for asymmetric segregation of cell fate determinants in higher eukaryotes.

DNA-Binding Proteins↗

PubMed2006

[Meniscus and ligament injuries].

The knee is one of the major weight-bearing joints and is relatively exposed to trauma. Capsuloligamentous structures are essential to provide joint stability and -- in turn -- persistent instability bears a risk for osteoarthritis that needs timely and comprehensive diagnosis. Using MRI it may be beneficial to routinely apply (T)SE sequences in all three major planes as a basic protocol and to add additional sequences according to the clinical information available and imaging findings in the basic protocol. Especially fat-suppressed sequences (STIR, T2w/PDw FS TSE) are very useful because they sensitively depict bone marrow edema pattern (BMEP)-like changes. This finding often alerts the reader to -- sometimes only discrete -- underlying pathologies and may -- if found in typical locations -- give information about the mechanism of injury and thus lead the radiologist to look for specific concomitant capsuloligamentous, cartilage, and/or meniscal injury. BMEP is quite prominent in contusion injury, whereas often it is but discrete in avulsion lesions. There is extensive literature about the signs, possible pitfalls, and the accuracy of MRI for the diagnosis of specific pathologies such as meniscal tears or cruciate or collateral ligament ruptures. However, combined injuries of more than one structure are frequent and affect the therapeutic approach. Thus, the primary goal of the radiologist is to go beyond the description of any isolated lesion and to give a comprehensive description of (or to reliably exclude) any injury to other structures. A necessary prerequisite to accomplish this is a thorough knowledge of the -- in some locations -- complex anatomic relationships, pitfalls, and locations where lesions typically occur and where they may be overlooked.

Humans↗

PubMed2003

[MR imaging of prostate cancer].

PURPOSE: Accurate diagnosis and staging of prostate cancer (PC) is developing into an important health care issue in light of the high incidence of PC and the improvements in stage-adapted therapy. The purpose of this paper is to provide an overview on the current role of MR imaging and MR spectroscopy in the diagnosis and staging of PC. MATERIAL AND METHODS: Pertinent literature was searched and evaluated to collect information on current clinical indications, study techniques, diagnostic value, and limitations of magnetic resonance imaging and spectroscopy. RESULTS: Major indications for MR imaging of patients with suspected PC are to define tumor location before biopsy when clinical or TRUS findings are inconclusive, and to provide accurate staging of histologically proven PC to ascertain effective therapy. Current MR imaging techniques for the evaluation of PC include multiplanar high-resolution T2-weighted FSE and T1-weighted SE sequences using combined endorectal and phased-array coils. Using these techniques, the reported accuracy of MR imaging for the diagnosis of extracapsular tumor extension ranges between 82 and 88% with sensitivities between 80 and 95%, and specificities between 82 and 93%. Typical MR findings of PC in different stages of disease, as well as diagnostic problems, such as chronic prostatitis, biopsy-related hemorrhage and therapy-related changes of prostatic tissue are discussed. In addition, the current perspectives and limitations of MR spectroscopy in PC are summarized. CONCLUSIONS: Current MR imaging techniques provide important diagnostic information in the pretherapeutic workup of PC including a high staging accuracy, and is superior to TRUS.

Biopsy↗

PubMed2001

Contrast-enhanced MR angiography in patients after kidney transplantation.

The aim of this study was to investigate the value of a contrast-enhanced 3D MR angiography in detecting postoperative vascular complications after kidney transplantation in comparison with digital subtraction angiography (DSA). Forty-one patients who underwent a kidney transplantation were examined with MR angiography and DSA. Contrast-enhanced MR angiography was performed as a dynamic measurement with one precontrast and three postcontrast measurements. Maximum intensity projection reconstructions were performed for all postcontrast data sets after DSA. The results were evaluated by two independent observers who were unaware of the DSA results. Twenty-three hemodynamically significant arterial stenoses were identified with DSA in the iliac arteries ( n=7), the renal allograft arteries ( n=12), and in their first branches ( n=4). For a patient-based analysis the sensitivity and specificity, respectively, for observer 1 were 100 and 97%, and for observer 2, 100 and 93%. Respective data were 100 and 100% after a consensus evaluation by two observers. Complications involving the renal veins were detected in 2 cases and perfusion defects of the kidney parenchyma were detected in 4 cases. Contrast-enhanced MR angiography is a reliable method in identifying postoperative arterial stenoses after kidney transplantation. In addition, dynamic MR angiography can be helpful in detecting venous complications and perfusion defects in kidney allografts.

Adult↗

PubMed2001

[Benign bone-forming tumors].

Benign bone-forming tumors include osteomas, enostomas, osteoid osteomas, and osteoblastomas. These lesions are often characterized by typical imaging findings on radiographs, CT and MR imaging studies. Radiologic findings and additional clinical information allow for a specific diagnosis in most cases. This review article emphasizes the radiological patterns of benign bone-forming tumors as well as their epidemiological, clinical, and pathological characteristics. In addition, minimally invasive interventional procedures for the therapy of osteoid osteoma are reviewed.

Bone Neoplasms↗

PubMed2000

[The diagnosis of metastases in the bone marrow by MRT].

MRI plays an important role in the diagnostic workup of skeletal metastases. In principle two different applications of MRI can be distinguished: apart from the well known indications of clarifying uncertain lesions seen with other imaging modalities or demonstrating known osseous lesions with high resolution imaging for therapeutic planing, MRI can also be used as a primary screening modality for skeletal metastases. Besides the higher lesion detection rate the major advantage of MRI compared to bone scintigraphy lies in the demonstration of morphology which on the one hand exactly shows the extension of tumorous lesions and on the other hand clearly distinguishes between malign and benign processes. As unclear findings on bone scintigraphy often require additional imaging studies, especially in patients with clinical findings or lab results suggestive for metastatic disease, we think that whole-body-skeletal-MRI is not only an accurate but also a cost effective diagnostic modality in the detection and screening for skeletal metastases, if the indication for the examination is closely related to clinical findings and the therapeutic relevance of the imaging results.

Bone Marrow↗

PubMed2000

Tumors of the cardiac valves: imaging findings in magnetic resonance imaging, electron beam computed tomography, and echocardiography.

We describe the findings from various cross-sectional imaging modalities in patients with cardiac valve adherent masses. The techniques are discussed, and imaging findings are compared with the results of cardiac surgery. All three patients had neurological symptoms and/or cardiac murmurs. Transthoracic and/or transesophageal echocardiography revealed the cardiac mass in all three. For differentiation of thrombus and cardiac neoplasm magnetic resonance imaging (MRI) was also performed in all three patients and electron-beam computed tomography (EBCT) in two. Fast segmented cine gradient-echo MRI techniques provided mass depiction in all patients, while T1-weighted spin-echo imaging failed in mass detection in one patient. None of the patients showed evidence of valve regurgitation or stenosis in flow sensitive cine MRI. EBCT excluded mass calcifications in both patients and reliably demonstrated the valve attached lesions. Although echocardiography is the modality of choice in evaluating cardiac masses and especially valve attached masses, MRI and EBCT provide additional information about tissue characteristics and allows an excellent overview of the cardiac and paracardiac morphology. Fast segmented cine gradient-echo MRI is especially able to depict even small tumors attached to rapidly moving cardiac valves, and valve competence can be easily assessed within the same examination.

Adult↗

PubMed2000

A rare case of osteoporotic spine fracture associated with epidural lipomatosis causing paraplegia following long-term cortisone therapy.

Cushing's syndrome is frequently associated with osteoporosis. Therefore, the incidence of osteoporotic spine fractures is significant. They are a rare cause of paraplegic syndromes. Additionally, epidural lipomatosis may occur in those patients. The combination of both fracture and lipomatosis may cause neurological deficit. A case of a young patient suffering from drug-induced Cushing's syndrome is reported. She developed progressive paraplegia. Radiographs demonstrated kyphosis of the thoracic spine from T7 to T9 and pathologic fractures. Urgent operation was planned to stabilize and decompress the spinal cord in the area of the kyphosis. Fortunately, magnetic resonance imaging (MRI) was conducted first. It confirmed pathologic fractures of T7-9 but also showed massive epidural fat extending from the level of T1 to T9. As suspected, laminectomy alone in the area of the fracture proved to be insufficient, as shown by myelography during operation. For treatment of paraplegia in this case of symptomatic epidural lipomatosis, an expanded laminectomy was necessary to remove all the epidural fat. Having undergone this procedure, the patient is now recovering from paraplegia. Our experience suggests that care should be taken before operative treatment of patients with pathological fractures in combination with Cushing's syndrome. In addition to vertebral fractures, epidural lipomatosis has to be taken into consideration. Those patients with neurological deficits have to be treated by an extensive laminectomy.

Adult↗

PubMed2000

Focal liver lesions: evaluation of the efficacy of gadobenate dimeglumine in MR imaging--a multicenter phase III clinical study.

PURPOSE: To evaluate gadobenate dimeglumine (Gd-BOPTA) for dynamic and delayed magnetic resonance (MR) imaging of focal liver lesions. MATERIALS AND METHODS: In 126 of 214 patients, MR imaging was performed before Gd-BOPTA administration, immediately after bolus administration of a 0.05- mmol/kg dose of Gd-BOPTA, and 60-120 minutes after an additional intravenously infused 0.05-mmol/kg dose. In 88 patients, imaging was performed before and 60-120 minutes after a single, intravenously infused 0.1-mmol/kg dose. T1- and T2-weighted spin-echo and T1-weighted gradient-echo images were acquired. On-site and blinded off-site reviewers prospectively evaluated all images. Intraoperative ultrasonography, computed tomography (CT) during arterial portography, and/or CT with iodized oil served as the reference methods in 110 patients. RESULTS: Significantly more lesions were detected on combined pre- and postcontrast images compared with on precontrast images alone (P <. 01). All reviewers reported a decreased mean size of the smallest detected lesion and improved lesion conspicuity on postcontrast images. All on-site reviewers and two off-site reviewers reported increased overall diagnostic confidence (P <.01). Additional lesion characterization information was provided on up to 109 (59%) of 184 delayed images and for up to 50 (42%) of 118 patients in whom dynamic images were assessed. Gd-BOPTA would have helped change the diagnosis in 99 (47%) of 209 cases and affected patient treatment in 408 (23%) of 209 cases. CONCLUSION: Gd-BOPTA increases liver lesion conspicuity and detectability and aids in the characterization of lesions.

Adult↗

PubMed2000

Dynamic contrast-enhanced MR angiography from the distal aorta to the ankle joint with a step-by-step technique.

OBJECTIVE: The aim of this study was to visualize the arteries from the distal aorta to the ankle joint and to determine the accuracy of MR angiography for detecting stenoses and occlusions. SUBJECTS AND METHODS: Twenty-four patients with peripheral arterial occlusive disease underwent digital subtraction angiography and were examined on a 1.5-T MR scanner. The transit time for contrast material was determined with a test bolus injection. A T1-weighted three-dimensional gradient-echo sequence with short TR and TE was used for a dynamic measurement at the level of the iliac arteries, the upper leg, and the lower leg arteries. For each level a single dose of gadolinium was injected into an antecubital vein with an MR power injector. Maximal-intensity-projection reconstructions were calculated after subtraction of the first measurement at each level. Two experienced MR radiologists who were unaware of the digital subtraction angiography results interactively evaluated both the MIP reconstructions and the single slices on a workstation, first independently and then in a consensus interpretation. RESULTS: With digital subtraction angiography, 80 hemodynamically significant stenoses and 39 occlusions were detected. For the stenoses and occlusions, a sensitivity of 100% was found for MR angiography. The specificity for the assessment of stenoses and occlusions was 98% and 94%, respectively, for the iliac arteries; 98% and 94%, respectively, for the upper leg arteries; and 94% and 95%, respectively, for the lower leg arteries. Most false-positive findings of occlusion were due to metal stents present in the iliac (n = 3) and upper leg (n = 4) arteries. CONCLUSION: The MR imaging technique that we used revealed the arteries from the distal aorta to the ankle and proved to be reliable at showing arterial stenoses and occlusions.

Aged↗

PubMed2000

Effects of three different doses of a bolus injection of gadodiamide: assessment of regional cerebral blood volume maps in a blinded reader study.

BACKGROUND AND PURPOSE: Reconstruction of first-pass bolus information to derive regional cerebral blood volume (rCBV) maps is commonly performed in many centers; however, various protocols with different doses of paramagnetic contrast injections have been reported. We evaluated the dose dependency of rCBV maps in a brain tumor population by using three different doses of gadodiamide injection to evaluate their diagnostic accuracy in blinded reader sessions. METHODS: Eighty-three patients with intraaxial brain tumors (72 gliomas) were studied at three centers and randomized to receive a bolus injection of 0.1, 0.2, or 0.3 mmol/kg per body weight of gadodiamide. rCBV maps were generated from T2*-weighted gradient-echo echoplanar sequences at 1.5 T. Data processing was performed according to the indicator dilution theory. RESULTS: The mean contrast-to-noise ratio (CNR) was significantly different between gadodiamide doses of 0.1 and 0.2 mmol/kg (CNR = 8.7 and 15.7) and between 0.1 and 0.3 mmol/kg (CNR = 17.7). No significant difference was found between doses of 0.2 and 0.3 mmol/kg. Sensitivity for the differentiation of benign and malignant brain tumors was 80%, 95%, and 91%, and specificity was 45%, 54%, and 43% by blinded readings at 0.1, 0.2, and 0.3 mmol/ kg, respectively, as compared with histologic findings. Nonblinded readings had a sensitivity of 83%, 100%, and 90% and a specificity of 82%, 100%, and 73% at 0.1, 0.2, and 0.3 mmol/kg, respectively. CONCLUSION: A dose of 0.2 mmol/kg of gadodiamide is recommended for reconstruction of rCBV maps if data are acquired with the T2*-weighted protocol described.

Blood Volume↗

PubMed1999

T2-weighted breathold imaging of the liver: a quantitative and qualitative comparison of fast spin echo and half Fourier single shot fast spin echo imaging.

The imaging characteristics of two EPI-hybrid breath-hold sequences, T2-weighted fast spin-echo [FSE, effective echo time (TEeff) 138 ms] and half Fourier single shot turbo spin-echo (HASTE, TEeff 60 ms), were compared in hepatic imaging. A total of 111 patients with suspected hepatic disease were studied at 1.5 Tesla using a body phase-array coil. The signal-to-noise (S/N) and contrast-to-noise (C/N) ratios for organs and lesions were calculated and quantitatively compared. Organ delineation, visualization of anatomical structures and pathological lesions, artifacts, and total image quality were qualitatively assessed and statistically compared. The final diagnoses were metastases from colorectal, breast, and pancreatic cancer in 23/111, hepatocellular carcinoma in 15/111, cysts in 19/111, hemangiomas in 9/111, several other lesions in 7/111, and no lesions in 38/111 of the cases. A total of 139 lesion in 73% of the patients were seen while 85% of the lesions were at least 1.5 cm in size. Regarding S/Ns HASTE was significantly (P < 0.03) superior to FSE with only minor (P > 0.05) differences in C/Ns between the two sequences for anatomical and pathological structures. HASTE demonstrated in almost all (97.3%) of the cases no artifacts, while on fast SE imaging moderate to minor artifacts were present in 23.5-51.7% of the cases. The overall image quality and diagnostic confidence was rated significantly higher (good 43.2%, excellent 53.2%) for HASTE than for fast SE imaging (good 44.8%, excellent 17.6%). Providing comparable C/Ns for anatomical and pathological structures, breatheld HASTE imaging proved to be superior to fast SE in T2-weighted imaging of the upper abdomen regarding general image quality, and, with adequate technical prerequisites, may be a suitable substitute of fast T2-imaging techniques.

Evaluation Studies as Topic↗

PubMed1999

Evaluation of the carotid and vertebral arteries: comparison of 3D SCTA and IA-DSA-work in progress.

OBJECTIVE: The purpose of this study was to develop a method for three-dimensional (3D) visualization of the whole vascular system of the carotid and vertebral arteries using spiral computed tomographic angiography (SCTA), that allows accurate, qualitative and quantitative evaluation, of anatomical abnormalities, including detection of additional lesions, and estimation of degree of stenosis. MATERIALS AND METHODS: Fifteen patients with anatomical and pathological abnormalities of the arterial vascular system detected by color-coded duplex ultrasound were studied using intraarterial digital subtraction angiography (IA-DSA) with aortic arch injection, and SCTA. The carotid and vertebral arteries were segmented using an interactive threshold interval density volume-growing method and visualized with a color-coded shaded-surface display (SSD) rendering method. The adjacent bone structures were visualized using a transparent volume rendering method. RESULTS: In all cases, the entire volume of the vascular system of the carotid and vertebral arteries could be visualized on SCTA, and the anatomical and pathological abnormalities on 3D SCTA correlated well with that seen on IA-DSA. CONCLUSION: Results of 3D SCTA had a high degree of correlation with results of IA-DSA in the evaluation of the vascular system of the carotid and vertebral arteries. The 3D SCTA with a subsecond spiral CT scanner is useful for the visualization of anatomical and pathological abnormalities in the circulation in the carotid and vertebral arteries and offer a promising minimally invasive alternative compared with other diagnostic procedures.

Adult↗

PubMed1999

Magnetic resonance imaging of lateral epicondylitis of the elbow with a 0.2-T dedicated system.

The purpose of this study was to evaluate MR imaging findings of the common extensor tendon in patients with lateral epicondylitis and asymptomatic volunteers studied on a 0.2-T dedicated system. In 23 patients (age range 29-58 years, mean age 47 years) with clinical symptoms of lateral epicondylitis MR imaging was performed using T1-, T2- and contrast-enhanced T1-weighted spin-echo sequences. In addition, the elbows of seven healthy volunteers (age range 22-29 years, mean age 25 years) and the symptom-free contralateral elbow of 11 of the 23 patients (age range 29-58 years, mean age 47 years) were studied as controls. Five patients were surgically treated after the MR examination and the results of histopathology were correlated with MR findings. Of the patients, 95.6 % showed intratendinous signal intensity changes on T1-weighted images on the symptomatic side. In 69.6 % signal alterations were observed on T2-weighted sequences and in 56.5 % an intratendinous contrast enhancement was present. Histopathology showed fibrovascular proliferation and fatty degeneration in patients with distinct signal intensity changes and contrast enhancement. Patients with only minor signal intensity changes on T1- and T2-weighted sequences and no contrast enhancement demonstrated fibrosclerotic degeneration and intratendinous cartilage formation in histopathology. The contralateral elbow showed signal intensity changes in 6 of 11 (54.5 %) cases on T1-weighted images and in 3 of 11 (27.3 %) on T2-weighted images. In the group of healthy volunteers minor signal intensity changes of the common extensor tendon could be seen in only 1 case. In patients with lateral epicondylitis of the elbow the type and extent of pathologic changes within the common extensor tendon can be evaluated using a dedicated low-field MR system. On the basis of MR imaging findings a more specified therapy planning among the variety of treatment modalities can be achieved.

Adult↗

PubMed1999

MR findings in a patient with Kernicterus.

We report on a 2.5-year-old boy with severe mental retardation, choreoathetosis, dystonia, muscle rigidity, opisthotonus and severe hearing impairment. He had history of severe hyperbilirubinaemia immediately after birth presumably due to ABO incompatibility. The history and the clinical picture suggested the diagnosis of Kernicterus. The MR imaging examination upon admission revealed bilateral signal intensity increase in the globus pallidum on T2-weighted sequences. Additionally, our patient showed signal intensity changes within the subthalamic nuclei, which is known to be another characteristic area of bilirubin deposition in Kernicterus.

Abnormalities, Multiple↗

PubMed1999

[MRI of plantar fasciitis].

PURPOSE: The purpose of this study was to determine the type and frequency of characteristic bone and soft tissue changes on MRI of patients with a clinical diagnosis of plantar fasciitis. MATERIALS AND METHODS: 28 patients with a clinical diagnosis of plantar fasciitis underwent MR imaging. Besides T1- and T2-weighted sequences, short-tau-inversion-recovery sequences were used routinely. In 27 patients T1-weighted images after intravenous contrast injection were acquired additionally. As a control group the images of 15 patients without clinical signs for plantar fasciitis were evaluated. RESULTS: In 25 of 28 cases (89%) the clinical diagnosis of plantar fasciitis was established by MR imaging. The most common finding was a peritendinous edema at the calcaneal insertion site which was found in all 25 patients. In 19 of 25 cases (76%) a bone marrow edema of the calcaneus was present. In 14 of 25 cases (56%) an intratendinous signal intensity increase of the plantar fascia could be observed which showed contrast enhancement in 12 cases. Compared to the control group (mean thickness 3.3 mm) the plantar fascia showed significant thickening in the 25 MR positive patients (mean thickness 6.72 mm). DISCUSSION: Besides thickening of the plantar fascia and intratendinous signal intensity increase with contrast enhancement to some extent, bone marrow edema of the calcaneus and peritendinous edema close to the plantar fascia are characteristic signs of plantar fasciitis on MRI. Both signs can reliably be seen on STIR sequences only.

Adult↗

PubMed1999

Ferric ammonium citrate as a positive bowel contrast agent for MR imaging of the upper abdomen. Safety and diagnostic efficacy.

PURPOSE: To evaluate the safety and diagnostic efficacy of two different doses of ferric ammonium citrate as a paramagnetic oral contrast agent for MR imaging of the upper abdomen. MATERIAL AND METHODS: Ninety-nine adult patients referred for MR imaging for a known or suspected upper abdominal pathology were included in this randomized multicenter double-blind clinical trial. Imaging was performed with spin-echo (T1- and T2-weighted) and gradient-echo (T1-weighted) techniques before and after administration of either 1200 mg or 2400 mg of ferric ammonium citrate dissolved in 600 ml of water. Safety analysis included monitoring of vital signs, assessment of adverse events, and laboratory testing. Efficacy with regard to organ distension, contrast distribution, bowel enhancement and delineation of adjacent structures was graded qualitatively. RESULTS: No serious adverse events were reported for either of the two concentrations. A total of 31 minor side effects were noted, of which significantly more occurred in the higher dose group (p<0.01). The diagnostic confidence in defining or excluding disease was graded as better after contrast administration for 48% of all images. Marked or moderate enhancement of the upper gastrointestinal tract was achieved at both doses in 69.5% of cases with no evident difference between the two doses. The higher dose tended to show better results in terms of the contrast assessment parameters. CONCLUSION: Ferric ammonium citrate is a safe and effective oral contrast agent for MR imaging of the upper abdomen at two different dose levels. The higher dose showed a tendency toward better imaging results while the lower dose caused significantly fewer side effects. Therefore the 1200 mg dose can be recommended in view of the risk-to-benefit ratio.

Abdomen↗

PubMed1998

Hybrid rendering of the cervico-cranial arteries using spiral computed tomography.

PURPOSE: The purpose of this study was to develop a shaded-surface and volume display (hybrid rendering method) of the whole vascular system of the cervico-cranial arteries using spiral computed tomography (SCT). MATERIALS AND METHODS: We examined 12 patients with anatomic abnormalities and pathological conditions of the arterial vascular system. The cervico-cranial arteries were segmented using an interactive threshold interval density volume-growing method and visualized with a color-coded shaded-surface display (SSD) rendering method. The adjacent bone structures were visualized using a transparent volume rendering method. RESULTS: In all cases, the entire volume of the vascular system of the cervico-cranial arteries and the anatomic abnormalities and pathological conditions could be visualized. CONCLUSION: Hybrid rendering of the circulation of the cervico-cranial arteries using image data sets from a subsecond spiral CT scanner is useful for the visualization of anatomical and pathological abnormalities and offer a promising minimally invasive alternative compared with other diagnostic procedures.

Adult↗