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Biomedical subjects

G P Krestin

Publications and source records attributed to G P Krestin.

At least 19 recordsLinked to original sources
PubMed2005

[Adrenal incidentaloma: a clinical problem related to imaging].

Two female patients, 68 and 67 years of age, were referred for right abdominal pain and pyelonephritis, respectively. During the diagnostic work-up, an unsuspected adrenal mass was found in both patients. Hormonal evaluation and imaging showed a benign non-hyperactive functioning adenoma in one patient and a pheochromocytoma in the other. Both patients were successfully treated with endoscopic adrenalectomy. Wider application and improvement of abdominal imaging procedures have caused an increase of incidentally detected adrenal masses, posing a common clinical problem. Typically, a diagnosis can be made on the basis of the characteristic radiological image. The exact nature of the defect is often unclear and further evaluation is required to determine functionality and possible malignancy. An algorithm is presented for the management of adrenal incidentalomas.

Abdominal Pain↗
PubMed2005

In vitro imaging of single living human umbilical vein endothelial cells with a clinical 3.0-T MRI scanner.

Iron oxide-labelled, single, living human umbilical vein endothelial cells (HUVECs) were imaged over time in vitro using a clinical 3.0-T magnetic resonance (MR) microscopy system. Labelling efficiency, toxicity, cell viability, proliferation and differentiation were assessed using flow cytometry, magnetic cell sorting and a phenanthroline assay. MR images were compared with normal light and fluorescence microscopy. Efficient uptake of iron oxide into HUVECs was shown, although with higher label uptake dose-dependent cytotoxic effects were observed, affecting cell viability. For MR imaging, a T2* weighted three-dimensional protocol was used with in-plane resolution of 39 x 48 microm2 and 100-microm slices with a scan time of 13 min. MRI could detect living cells in standard culture dishes at single-cell resolution, although label loss was observed that corresponded with the intracellular iron measurements. MR microscopy using iron oxide labels is a promising tool for studying HUVEC migration and cell biology in vitro and in vivo, but possible toxic effects of label uptake and loss of label over time should be taken into account.

Cell Proliferation↗
PubMed2005

Non-invasive coronary angiography with 64-slice computed tomography.

Multislice computed tomography is a rapidly emerging technique for the non-invasive visualization of coronary arteries. Over the past 5 years several scanner generation were introduced with a progressive improvement in the diagnostic accuracy in the detection of coronary artery stenosis in selected patients populations. The introduction of 64-slice technology has further improved the diagnostic performance. This technique is at the edge of clinical implementation and, even though large clinical trials are still missing, an increased demand for these type of studies is observed all over the world. We describe our experience of more than 1 year with 64-slice CT coronary angiography providing clues on reasonable clinical applications.

Coronary Angiography↗
PubMed2004

High-resolution magnetic resonance imaging of iron-labeled myoblasts using a standard 1.5-T clinical scanner.

Myoblast transplantation is a promising means of restoring cardiac function in infarcted areas. For optimization of transplant protocols, tracking the location and fate of the injected cells is necessary. An attractive imaging modality for this is magnetic resonance imaging (MRI) as it is noninvasive and as iron-labeled myoblasts provide a signal attenuation in T2*-weighted protocols. The aim of this study was to develop an efficient iron-labeling protocol for myoblasts and to visualize single-labeled cells using a clinical 1.5-T scanner. Pig myoblasts were labeled with a superparamagnetic iron oxide (SPIO) agent using a liposome transfection agent. Labeling efficiency, toxicity, cell viability, and proliferative capacity were measured for 10 days. Magnetic resonance (MR) of myoblast cultures used a T2*-weighted three-dimensional protocol with a maximum in-plane resolution of 19.5 x 26.0 microm2 and 50 microm slices. Use of liposomes improved SPIO labeling efficiency. Labeling did not induce toxicity or affect cell viability or proliferation. The cell distribution as observed with light and fluorescence microscopy matched the signal voids observed in the MRI datasets. Liposomes promote fast, nontoxic and efficient SPIO labeling of myoblasts that can be tracked by MRI microscopy in clinical scanners using susceptibility-weighted protocols.

Animals↗
PubMed2004

Dynamic contrast-enhanced MRI using macromolecular contrast media for monitoring the response to isolated limb perfusion in experimental soft-tissue sarcomas.

The objective of this study was to evaluate the potential of dynamic contrast-enhanced MRI for quantitative characterization of tumor microvessels and to assess the microvascular changes in response to isolated limb perfusion with TNF-alpha and melphalan. Dynamic contrast-enhanced MRI was performed in an experimental cancer model, using a macromolecular contrast medium, albumin-(Gd-DTPA)45. Small fragments of BN 175, a soft-tissue sarcoma, were implanted in 11 brown Norway (BN) rats. Animals were assigned randomly to a control (Haemaccel) or drug-treated group (TNF-alpha/melphalan). MRI was performed at baseline and 24 h after ILP. The transendothelial permeability (K(PS)) and the fractional plasma volume (fPV) were estimated from the kinetic analysis of MR data using a two-compartment bi-directional model. K(PS) and fPV decreased significantly in the drug-treated group compared to baseline (p<0.05). In addition, K(PS) post therapy was significantly lower (p<0.05) in the drug-treated group than in the control group. There was no significant difference in fPV between the drug-treated and the control group after therapy. Tumor microvascular changes in response to isolated limb perfusion can be determined after 24 h by dynamic contrast-enhanced MRI. The data obtained in this experimental model suggest possible applications in the clinical setting, using the appropriate MR contrast agents.

Albumins↗
PubMed2004

Surgical validation of unenhanced helical computed tomography in acute appendicitis.

BACKGROUND: Surgery for pain in the right lower quadrant of the abdomen remains a clinical dilemma. This prospective study assessed the accuracy of preoperative unenhanced helical computed tomography (CT) in the evaluation of patients with suspected acute appendicitis. METHODS: One hundred and three adult patients with suspected acute appendicitis underwent unenhanced helical CT of the abdomen. Subsequently, all patients underwent laparoscopic inspection of the abdominal cavity by a surgeon who was blinded to the diagnosis suggested by CT. Patients underwent appropriate surgical therapy accordingly. Follow-up was at least 6 weeks. RESULTS: Appendicitis was diagnosed by CT in 83 patients (80.6 per cent). Acute appendicitis was identified during laparoscopy in 87 patients (84.5 per cent). Prospective interpretation of CT images yielded a sensitivity of 95.4 per cent and a specificity of 100 per cent for the diagnosis of acute appendicitis. There were four false-negative scans. In 12 of 20 patients without signs of appendicitis on CT, the scan established the presence of other pathology. At operation no additional pathology was observed in this group and all other diagnoses proved to be correct. CONCLUSION: Plain helical CT in patients with suspected acute appendicitis provides an accurate diagnosis without the disadvantages of contrast enhancement.

Abdominal Pain↗
PubMed2003

Non-invasive angiography of the coronary arteries with multislice computed tomography: state of the art and future prospects.

Until now conventional angiography has represented the only technique for assessing the coronary arteries. During the last decade, attempts have been made to validate a non-invasive technique for the study of coronary arteries. In particular, Electron-beam Tomography and Magnetic Resonance Imaging have been used for this purpose, even though they have not become clinical tools. More recently, spiral computed tomography (CT) technology, improved by the use of multiple slices and 500ms gantry rotation times, has shown a good potential without entering routine clinical practice. The introduction of multislice technology with 16 rows and rotation times below 500ms has yielded such good results in detecting significant (>50%) coronary artery stenosis that it has been proposed as a clinical tool. This paper describes the examination technique and the results achieved in CT angiography of the coronary arteries.

Coronary Angiography↗
PubMed2002

Bilateral adrenal swelling as a cause of chest, back, and upper abdominal pain in essential thrombocythemia and polycythemia vera is due to microvascular ischemic thrombosis rather than to hemorrhage.

Bilateral massive adrenal swelling (BAS) on computed tomography (CT) scan with no enhancement after injection of intravenous contrast media has been observed in two completely different clinical settings. On the one hand, BAS is the result of ischemic necrosis and subsequent hemorrhagic infarction in patients with sepsis and hypotension in critically ill situations. On the other hand, BAS is the result of microvascular thrombosis, ischemia, and secondary inflammatory swelling in the setting of thrombotic conditions such as antiphospholipid syndrome (APS), heparin-induced thrombocytopenia and thrombosis (HITT), and thrombocythemia. In this study we present evidence that the etiology of unilateral or BAS in reported cases of essential thrombocythemia (ET) and polycythemia vera (PV) is similar to the etiology of microvascular circulation disturbances in thrombocythemia caused by platelet-mediated inflammation and thrombosis in the peripheral, cerebral, and/or coronary endarterial microvascular circulation.

Abdominal Pain↗
PubMed2002

Contrast medium extravasation injury: guidelines for prevention and management.

Extravasation of contrast material is a well-recognized complication of contrast-enhanced imaging studies. The management of this complication is contentious; therefore, the Contrast Media Safety Committee of The European Society of Urogenital Radiology decided to review the literature and issue guidelines. A comprehensive literature search was carried out. The resulting report was discussed at the 8th European Symposium on Urogenital Radiology in Genoa, Italy. Automated power injection may result in extravasation of large volumes and may or can lead to severe tissue damage. Infants, young children and unconscious and debilitated patients are particularly at risk of extravasation during contrast media injection. Fortunately, most extravasations result in minimal swelling or erythema, with no long-term sequelae; however, severe skin necrosis and ulceration may occur. Large volumes of high osmolar contrast media are known to induce significant tissue damage. Compartment syndrome may be seen associated with extravasation of large volumes. Conservative management is often adequate, but in serious cases the advice of a plastic surgeon is recommended. Based on the review simple guidelines for prophylaxis and management of contrast medium extravasation injuries are proposed.

Adult↗
PubMed2002

Non-invasive coronary angiography with multislice spiral computed tomography: impact of heart rate.

OBJECTIVE: To evaluate the impact of heart rate on the diagnostic accuracy of coronary angiography by multislice spiral computed tomography (MSCT). DESIGN: Prospective observational study. PATIENTS: 78 patients who underwent both conventional and MSCT coronary angiography for suspicion of de novo coronary artery disease (n=53) or recurrent coronary artery disease after percutaneous intervention (n=25). SETTING: Tertiary referral centre. METHODS: Intravenously contrast enhanced MSCT coronary angiography was done during a single breath hold, and ECG synchronised images were reconstructed retrospectively. All coronary segments of > or = 2.0 mm without stents were evaluated by two investigators and compared with quantitative coronary angiography. Patients were classified according to the average heart rate (mean (SD)) into three equally sized groups: group 1, 55.8 (4.1) beats/min; group 2, 66.6 (2.8) beats/min; group 3, 81.7 (8.8) beats/min. RESULTS: Image quality was sufficient for analysis in 78% of the coronary segments in patients in group 1, 73% in group 2, and 54% in group 3 (p < 0.01). The sensitivity and specificity for detecting significant stenoses (> or = 50% lumen reduction) in these assessable segments were: 97% (95% confidence interval (CI) 84% to 100%) and 96% in group 1; 74% (52% to 89%) and 94% in group 2; and 67% (33% to 90%) and 94% in group 3 (p < 0.05). Accounting for all segments of > or = 2.0 mm, including lesions in non-assessable segments as false negatives, the sensitivity decreased to 82% (28/34 lesions, 95% CI 69% to 91%), 61% (14/23 lesions, 42% to 77%), and 32% (6/19 lesions, 15% to 50%), respectively (p < 0.01). CONCLUSIONS: MSCT allows reliable coronary angiography in patients with low heart rates.

Confidence Intervals↗
PubMed2001

Superparamagnetic iron oxide contrast agents: physicochemical characteristics and applications in MR imaging.

Superparamagnetic iron oxide MR imaging contrast agents have been the subjects of extensive research over the past decade. The iron oxide particle size of these contrast agents varies widely, and influences their physicochemical and pharmacokinetic properties, and thus clinical application. Superparamagnetic agents enhance both T1 and T2/T2* relaxation. In most situations it is their significant capacity to reduce the T2/T2* relaxation time to be utilized. The T1 relaxivity can be improved (and the T2/T2* effect can be reduced) using small particles and T1-weighted imaging sequences. Large iron oxide particles are used for bowel contrast [AMI-121 (i.e. Lumirem and Gastromark) and OMP (i.e. Abdoscan), mean diameter no less than 300 nm] and liver/spleen imaging [AMI-25 (i.e. Endorem and Feridex IV, diameter 80-150 nm); SHU 555A (i.e. Resovist, mean diameter 60 nm)]. Smaller iron oxide particles are selected for lymph node imaging [AMI-227 (i.e. Sinerem and Combidex, diameter 20-40 nm)], bone marrow imaging (AMI-227), perfusion imaging [NC100150 (i.e. Clariscan, mean diameter 20 nm)] and MR angiography (NC100150). Even smaller monocrystalline iron oxide nanoparticles are under research for receptor-directed MR imaging and magnetically labeled cell probe MR imaging. Iron oxide particles for bowel contrast are coated with insoluble material, and all iron oxide particles for intravenous injection are biodegradable. Superparamagnetic agents open up an important field for research in MR imaging.

Contrast Media↗
PubMed1999

FDG PET-negative liver metastases of a malignant melanoma and FDG PET-positive hurthle cell tumor of the thyroid.

A Hurthle cell tumor (oncocytoma) of the thyroid presented as a hypermetabolic focus in a fluorodeoxyglucose positron emission tomography (FDG PET) study which was performed as staging procedure in a patient with malignant melanoma. This finding led to the initial diagnosis of a metastasis. In contrast, multiple liver metastases, seen on MRI and sonography, did not show any increased FDG uptake. Cytology results of one liver mass confirmed a melanoma metastasis, and of the neck mass, a Hurthle cell tumor. The Hurthle cell tumor was, based on clinical evidence, thought to be benign. This is the first description of a FDG PET-positive benign Hurthle cell tumor, with FDG PET-negative liver metastases of a malignant melanoma, in the same patient.

Adenoma, Oxyphilic↗
PubMed1999

Genitourinary MR: kidneys and adrenal glands.

Due to its high tissue contrast and multiplanar imaging capabilities, MRI provides a detailed display of renal and adrenal anatomy. Recent technical developments overcoming the problem of respiration induced motion artifacts and the use of paramagnetic contrast agents have further improved the performance of MRI which has now evolved as an alternative or complementary imaging modality to ultrasound, excretory urography and computed tomography. Dynamic contrast-enhanced studies will usually allow to detect even small enhancing solid areas within the cyst wall. Use of a fast (turbo) spoiled gradient echo sequence allows for assessment of contrast enhancement dynamics in renal and adrenal masses. For tumor staging, the multiplanar imaging capabilities of MRI are advantageous. Perinephric extent is best detected using opposed-phase GRE images resulting in an artificial accentuation of renal contours. Extension into venous structures is best diagnosed by using a GRE sequence allowing for distinction between flowing blood and tumor thrombus. Noninvasive differentiation of adrenal lesions can be performed with an unprecedented accuracy using chemical-shift imaging.

Adrenal Gland Diseases↗
PubMed1998

Detection of breast cancer with conventional mammography and contrast-enhanced MR imaging.

The aim of this study was to compare the diagnostic performance of conventional mammography and dynamic contrast-enhanced fast 3D gradient-echo (GRE) MRI regarding the detection and characterization of breast lesions relative to histopathologic analysis and to assess the results of a combined evaluation of both methods. fifty consecutive patients with 63 histopathologically verified breast lesions underwent dynamic contrast-enhanced GRE MRI in addition to routine conventional mammography. All lesions were classified by both methods on a five-point scale as benign or malignant, and the results were correlated to histopathology. Conventional mammography and dynamic MRI yielded a sensitivity and specificity of 82 and 64 %, and 92 and 76 %, respectively. The difference between the results was statistically not significant (p > 0.05) with areas under the receiver-operating-characteristics curves of 0.807 for mammography and 0.906 for MR imaging. Combination of the results of both methods slightly increased the sensitivity for detection of breast cancer to 95 % but decreased specificity to 52 %. In this selected patient subset, including only patients referred for excisional biopsy, contrast-enhanced dynamic MRI proved more sensitive and specific than conventional mammography regarding the detection of malignancy. While a combination of both methods yields a slightly improved sensitivity, specificity is vastly reduced.

Adult↗
PubMed1998

Magnetic resonance in the assessment of renal function.

The kidneys are the most important organs to maintain homeostasis. In the assessment of renal functional disorders laboratory tests offer only indirect hints on location of the disease; radionuclide nephrography is hampered by low spatial resolution and radiologic methods provide only limited quantitative information. The MRI technique with fast pulse sequences and renally eliminated contrast agent has the capability of combining both anatomic and functional information. This article gives an overview on functional MRI of the kidneys with its possibilities and limitations. The clinical application of functional MRI allows a better understanding of some pathologic conditions such as urinary tract obstruction, renal insufficiency, effects of extracorporeal shock wave lithotripsy, different states of hydration, effects of drugs, vascular disorders, and effects of transplantation.

Contrast Media↗