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Biomedical subjects

C D Claussen

Publications and source records attributed to C D Claussen.

At least 19 recordsLinked to original sources
PubMed2006

Unusual distribution of red marrow mimicking chloroma in a patient with acute myelogenous leukemia.

We present a case of unusual distribution of red marrow in a patient with extramedullary acute myelogenous leukemia (AML). In adults, hematopoietic marrow is usually located in the axial skeleton and the proximal aspects of the limbs, except for the epiphyses. Nodular islets of red marrow located in the epiphyseal and distal parts of the limbs may mimic tumoral infiltration and be mistaken for chloroma in a patient with AML.

Aged↗
PubMed2006

Differentiation between malignant and benign solitary pulmonary nodules with proton density weighted and ECG-gated magnetic resonance imaging.

OBJECTIVE: To estimate performance of MRI for differentiating malignant from benign solitary pulmonary nodules (SPN) using morphological characteristics. MATERIAL AND METHODS: MRI in 46 patients with SPN (mean diameter: 19 mm) was carried out on 1.0 Tesla scanner using ECG-gated, gradient echo sequence. Morphological signs of SPN were determined and compared with previously performed helical-CT, where final diagnosis served as reference with 52% frequency of malignancy. Furthermore, three observers evaluated all images. RESULTS: Significant differences between the two groups were found for nodules shape, margin, inhomogeneity and the vessel-sign in MRI, nodules shape, margin, the vessel-sign, and presence of spicules in CT. Using these signs, AUC were 0.746 for MRI and 0.765 for CT. The mean sensitivity, specificity, and accuracy of observers for MRI/CT were 89%/95%, 42%/41%, 66%/68%, respectively. CONCLUSIONS: Despite discrepancies in morphologic appearance, no significant difference of accuracy between MRI and CT was determined. Further investigations are necessary to demonstrate the clinical use in combination with functional parameters, establishing MRI as a comprehensive diagnostic modality for SPN.

Adult↗
PubMed2006

Differences and similarities of cytomegalovirus and pneumocystis pneumonia in HIV-negative immunocompromised patients thin section CT morphology in the early phase of the disease.

The purpose of this study was to assess CT morphology of pneumocystis pneumonia (PcP) and cytomegalovirus (CMV) pneumonia for specific characteristic features, similarities as well as differences, which might contribute to an early diagnosis and, therefore, influence patient management 58 patients were included, 31 with CMV pneumonia and 27 with PcP. All patients with CMV pneumonia had underlying haematological malignancies (n = 31) mainly treated by haematopoietic cell transplantation (HCT) (n = 26). Patients with PcP had haematological malignancies (n = 17) treated by HCT in 6, solid tumours (n = 5) and corticosteroid therapy (n = 5). Thin section CTs were analysed retrospectively by two radiologists. 18 CT morphological criteria were evaluated for presence or absence. Significance was calculated by chi2 test. Interobserver correlation was tested by kappa-statistic (K) Only 5 of the 18 features were found to have significantly different frequencies in the two entities. Apical distribution (p<0.01), mosaic pattern (p<0.01) and homogeneous structure of ground-glass opacities (GGO) (p<0.05) were found more frequently in PcP (each K: 0.7-0.9), whereas small nodules or unsharp demarcation of GGO and consolidation were typical of CMV pneumonia (p<0.05). Peripheral sparing, consolidation and septal thickening inter alia were found equally in both groups In conclusion analysis of craniocaudal distribution, demarcation and structure of infiltrates may be helpful in prioritizing differential diagnosis of CMV pneumonia or PcP. However, some features thought typical for one or the other entities appear with similar frequency in both groups in HIV-negative patients.

Adult↗
PubMed2006

[Evaluation of different breathing and contrast-protocols concerning quality and alignment in 18F-FDG PET/CT].

PURPOSE: The purpose of this study was to establish a reliable and simple parameter for alignment evaluation and the evaluation and optimization of state-of-the-art contrast-enhanced examination protocols for (18)F FDG-PET/CT. MATERIALS AND METHODS: 44 consecutive patients were referred to 4 examination protocols. Group A and B underwent single-phase, contrast-enhanced CT (90 s delay) performed either during free shallow breathing (FA; group A) or normal expiration (NormExp; group B). Groups C and D underwent arterial and portal venous multiphase examinations performed during FA (group C) or during NormExp (group D) followed by a low-dose CT scan for attenuation correction. Organ displacement in the cranio-caudal direction was correlated with a 3D-vectorial shift. For alignment evaluation discrepancies with respect to size and liver location, the spleen and kidneys were calculated. Additionally, the groups were compared with regard to the presence of CT artifacts. RESULTS: Cranio-caudal organ shift and 3D-vectorial shift showed a high correlation (r > 0.8). Single-phase CT scans performed during NormExp yielded better image quality (p < 0.001) and alignment (p < 0.01 for liver, spleen and right kidney) than those performed during FA. Differences in organ size did not differ during FA and NormExp. Depending on the evaluated organ, breathing and contrast protocol misalignment was in the cranio-caudal direction 0-27 mm (mean: 6.8; standard deviation: +/- 4.9) in multiphase CT compared to 0 - 11 mm (mean: 4.5 +/- 2.3) in single-phase examinations. CONCLUSION: 1. Organ shift in the cranio-caudal direction is a good and simple parameter for alignment evaluation. 2. Alignment and CT quality are best in expiration protocols. 3. Despite comparatively low alignment quality, integrated multiphase CT examinations show acceptable quality and alignment.

Aged↗
PubMed2006

Magnetic resonance imaging for hepatic radiofrequency ablation.

Image-guided radiofrequency (RF) ablation is a minimally invasive therapy option in the treatment of primary and secondary hepatic malignancies. Magnetic resonance (MR) imaging offers an accurate pre-interventional imaging having important impact on patient selection and planning of the ablation procedure. Peri-interventional imaging is used for targeting, monitoring, and controlling of the ablation procedure. Due to a high soft-tissue contrast offering delineation of tumor tissue and the surrounding anatomy, coupled with multiplanar capabilities, MR imaging is an advantageous targeting technique compared with ultrasonography (US) or computed tomography (CT). MR imaging is sensitive to thermal effects enabling a monitoring of ablation therapy subsequently being supportive to control the ablation procedure. Therefore, MR imaging can fulfil the conditions for overlapping ablations by enabling a precise repositioning of the MR compatible RF applicator if required. Thus, the probability of achieving complete coagulation in larger tumors within a single therapy session is potentially increased. A monitoring of thermal effects is moreover essential in order to prevent unintended tissue damage from critical structures in the surrounding of the target tissue. Post-interventional imaging is performed to assess treatment response after RF ablation and has prognostic impact, as an early detection of treatment failure, e.g. residual tumor tissue, enables immediate therapy. Nevertheless, differential diagnostic difficulties arise from benign periablational enhancement which may cover tumor tissue. Hence, further evaluation and improvement in the assessment of treatment response is essential.

Catheter Ablation↗
PubMed2006

Effect of concentration of SH U 555A labeled human melanoma cells on MR spin echo and gradient echo signal decay at 0.2, 1.5, and 3T.

In the current study the effect of increasing concentrations of superparamagnetic iron oxide labeled cells on the MRI signal decay at magnetic field strengths of 0.2, 1.5, and 3 T was evaluated. The spin echo and gradient echo cellular transverse relaxivity was systematically studied for various concentrations (N = 1, 5, 10, 20, 40, and 80 cells/microl(gel)) of homogeneously suspended SH U 555A labeled SK-Mel28 human melanoma cells. For all field strengths investigated a linear relationship between cellular transverse relaxation enhancement and cell concentration was found. In the spin echo case, the cellular relaxivities [i.e., d(deltaR2)/dN] were determined to 0.12 s(-1) (cell/microl)(-1) at 0.2 T, 0.16 s(-1) (cell/microl)(-1) at 1.5 T, and 0.17 s(-1) (cell/microl) at 3 T. In the gradient echo case, the calculated cellular relaxivities (i.e., d(deltaR2*)/dN) were 0.51 s(-1) (cell/microl)(-1) at 0.2 T, 0.69 s(-1) (cell/microl)(-1) at 1.5 T, and 0.71 s(-1) (cell/microl)(-1) at 3 T. The proposed preparation technique has proven to be a simple and reliable approach to quantify effects of magnetically labeled cells in vitro. On the basis of this quantification well suited tissue specific models can be derived.

Artifacts↗
PubMed2006

Non-invasive coronary angiography with 16-slice spiral computed tomography: image quality in patients with high heart rates.

The purpose of this study was to assess segment image quality at high heart rates using 16-slice computed tomography and differential reconstruction for major coronary vessels. According to the following protocol, 16-slice CT coronary angiography in 46 patients with a mean heart rate of 86.3+/-11.8 was reconstructed. At three transverse planes, preview series were obtained and motion artifacts evaluated in 5% increments from 0-95% within the cardiac cycle. Relying on image quality in the previews, reconstructions were performed at three z-positions for each patient. Segment image quality was assessed in terms of artifacts and visibility. The effects of heart rate and trigger delay on image quality were analyzed. Optimal image quality was achieved at 25 to 35% of the cardiac cycle for the left circumflex (CX) and right coronary artery (RCA) or 30 to 40% for the left main (LM) and left anterior descending artery (LAD). Sixteen-slice CT and differential reconstruction produced good image quality with a low percentage of motion-degraded proximal and middle segments (8.8%). Grades were 1.5 for the LM, 1.9 for the LAD, 2.0 for the CX and 2.3 for the RCA. At high heart rates, good image quality of the coronary arteries is achieved by 16-slice CT and a sophisticated reconstruction strategy at peak to late systole.

Algorithms↗
PubMed2006

[Cardiac MR tagging: optimization of sequence parameters and comparison at 1.5 T and 3.0 T in a volunteer study].

PURPOSE: The aim of this study was the optimization of a gradient echo (GRE) MR tagging sequence at 3.0 T in comparison to 1.5 T in order to obtain the best image contrast between the myocardium, tag lines and blood signal. Theoretically expected improvements of signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were also calculated. MATERIALS AND METHODS: 14 healthy volunteers (8 male, 6 female; mean age 43.4 +/- 10.3 years) were scanned using a 3.0 T as well as a 1.5 T whole-body system. A GRE flash-2 D tagging sequence was evaluated (midventricular short axis view) by varying the flip angle (8 - 16 degrees ), slice thickness (4 - 8 mm; fixed flip angle 1.5/3.0 T: 12 degrees /8 degrees , tag size 8 mm) and tag size (4 - 8 mm, fixed flip angle 1.5/3.0 T: 12 degrees /8 degrees , slice thickness 6 mm). The field of view, acquisition time and temporal resolution (45 ms) were kept constant. Qualitative and quantitative image analysis was performed by calculating the SNR, CNR (tag) as well as the relative contrast between the myocardium and tag lines (RCMT). RESULTS: Based on individual comparison, the best imaging protocol was found at a slice thickness of 6 mm, tag size of 8 mm, optimized flip angle of 8 degrees (3.0 T) and 12 degrees (1.5 T), respectively. Compared to 1.5 T, a significantly higher overall image score was determined (mean +/- sd; 3.2 +/- 0.2 vs. 2.7 +/- 0.4) and a strong correlation between the CNR (tag) and RCMT for flip angle alpha and the slice thickness was found. A higher field strength resulted in an 80 % increase in the CNR (tag) compared to 1.5 T (mean 10.7/6.1). Furthermore, the SNR was improved by 35 % (mean 20.6/15.3) and the RCMT by 35 % (mean 0.47/0.35). CONCLUSION: Myocardial tagging at 3.0 T has shown superior image quality in comparison to 1.5 T due to a higher baseline SNR and an improved CNR as well as RCMT. The suppressed fading of the tags enables the accessibility to the diastolic phase of the cardiac cycle.

Adult↗
PubMed2006

[CT-based assessment score after ventral spondylodesis for thoracolumbar spine fracture].

BACKGROUND: Dorsoventral stabilization is a common procedure to treat thoracolumbar spine fractures. Especially in respect of the evaluation of alternative procedures to autogenous bone graft, a standardized evaluation score for ventral spondylodesis is necessary. PATIENTS AND METHODS: In a group of 44 patients a follow-up CT scan was evaluated with a standardized scoring system by four different independent evaluators (a trauma surgeon, an orthopedic surgeon, and two radiologists). The score is based on the morphologic classification of the region between graft and vertebral body. It allows a classification of the spondylodesis as sufficient, partial, and not sufficient. RESULTS: The statistical evaluation of the classification of the different evaluators shows very good interobserver agreement in monosegmental fusion and good agreement in bisegmental fusion. CONCLUSION: The demonstrated score is easy to handle, does not need special equipment for CT scans, and shows good interobserver agreement in the classification of spinal fusion after ventral spondylodesis for thoracolumbar spine fracture.

Adolescent↗
PubMed2006

[Volumetry of the human tongue by MRI].

AIM: The purpose of this study was to determine the volume of the tongue using MRI. The correlation of the individual volume of the tongue and the size of the oral cavity was to be investigated. MATERIAL AND METHODS: To analyze the tongue volume we combined coronal and sagittal data acquisition, which divided the tongue virtually into two lateral and one medial part. This procedure helped to decrease artefacts by partial volume effect. In 20 probands (m/f 7/13, average age of 36.3 years) the volume of the tongue was determined. Imaging protocol: Magnetom 63 SP (Siemens, Erlangen), T1-weighted sequences (TR/TE 500 ms/10 ms), slice thickness 5 mm, matrix 256 x 256, FOV 250 mm. RESULTS: There was a significant linear regression between the tongue volume and height of the mouth cavity. This correlation can be used to calculate the normal volume of a patient's tongue. DISCUSSION: Volumetry of the tongue can be carried out by means of MRI without application of injurious X-rays. It can be employed before as well as after tongue reduction surgeries for therapy control. The individual ideal tongue volume can be determined easily by determination of the height of the oral cavity.

Adult↗
PubMed2006

Image quality and diagnostic accuracy of 16-slice multidetector computed tomography for the detection of coronary artery disease in obese patients.

BACKGROUND: Cardiac multislice spiral computed tomography (MSCT) scanners permit visualization of the coronary arteries with an overall good sensitivity (sens) and specificity (spec). However, in obese patients (pts), who are at higher risk to develop coronary artery disease (CAD), image quality of MSCT is supposed to be limited. At present, there are no data whether the accuracy of MSCT depends on the body mass index (BMI). Thus, we compared the catheter-controlled MSCT results from normal weight and obese pts in a cohort of 117 pts with regard to sens, spec, positive predictive value (PPV), negative predictive value (NPV) and image quality. METHODS AND MATERIAL: In all, 21 normal weight pts (group I: BMI<25, 64.6+/-11.1 years, number of risk factors 2.1+/-1.1), 60 pts with mild overweight (group II: BMI 25-30, 64.6+/-8.9 years, number of risk factors 3.4+/-1.0) and 36 obese pts (group III: BMI >30, 63.0+/-8.5 years, number of risk factors 3.4+/-0.9) were examined by MSCT (Sensation 16 Speed 4 D((R)), Siemens, Germany, gantry rotation time 375 ms) and invasive coronary angiography. MSCT results were compared blinded to the results of the coronary angiography with regard to the presence or absence of a significant stenosis (>50%) in a modified AHA 13 segment (sgt) model. Image quality was assessed on a qualitative scale between 1 (very good) and 5 (insufficient image quality) for each sgt. RESULTS: Sens, spec, PPV and NPV were statistically not different in all three groups (I: 0.88/0.97/0.91/0.96, II: 0.83/0.97/0.88/0.95, III: 0.87/0.99/0.96/0.96). 3 pts (group I 1, group II 2) had to be excluded from analysis due to technical problems. Group I had significantly less risk factors (P < 0.001) and image quality was significantly better than in group II and III (P < 0.05). Group II and III did not differ with regard to risk factors or image quality. CONCLUSIONS: Overweight and obesity have an impact on MSCT image quality but did not hamper the diagnostic accuracy. Thus, MSCT is a noninvasive method to detect or rule out CAD also in pts with higher BMI. These retrospective data have to be confirmed in larger prospective trials.

Aged↗
PubMed2006

[Cardiovascular whole-body MR imaging in patients with symptomatic peripheral arterial occlusive disease].

PURPOSE: To examine patients with peripheral-arterial-occlusive-disease (PAOD) for systemic effects associated with atherosclerosis using a comprehensive state-of-the-art whole-body MR examination protocol. The protocol comprises the assessment of the complete arterial vasculature (except coronary arteries), the brain, and the heart. MATERIALS AND METHODS: Multi-station whole-body 3D MR angiography was performed in sixty consecutive patients with clinical suspicion for PAOD at 1.5 T (Magnetom Avanto, Siemens, Erlangen, Germany). Functional and delayed enhancement cardiac images were acquired, as well as FLAIR images of the brain and TOF angiography of intracranial vessels. MR and DSA images were assessed by independent observers for atherosclerotic manifestations and other pathology. Sensitivity and specificity for the detection of vascular pathology was calculated for MR data using conventional DSA of the symptomatic region as standard-of-reference. RESULTS: Sensitivity and specificity for the detection of significant vascular stenosis (> 70 % luminal narrowing) was 94 % and 96 % (PPV 87 %, NPV 98 %). Significant microangiopathic tissue alterations (n = 7) and/or cerebral infarction (n = 18) were diagnosed in 23/60 patients. Thirty-eight of 60 patients presented with systolic left ventricular wall motion abnormalities. In 24 patients subendocardial or transmural delayed enhancement was detected in corresponding regions, indicating prior myocardial infarction. CONCLUSION: For patients with PAOD and suspected systemic atherosclerotic disease a comprehensive diagnosis of accompanying cardiovascular pathology and therefore staging of systemic atherosclerotic disease is feasible within one MR examination.

Aged↗
PubMed2006

3D imaging of the whole spine at 3T compared to 1.5T: initial experiences.

PURPOSE: To describe our first experiences with a recently introduced 3T system for T2-weighted isotropic 3D whole-spine imaging. MATERIAL AND METHODS: Magnetic resonance imaging of the whole spine was performed by implementing an isotropic 3D fast spin-echo sequence with variable flip-angle refocusing pulses at 3T and 1.5T. Signal-to-noise ratio (SNR) was compared on both systems in eight subjects. RESULTS: Mean values for SNR were significantly higher at 3T (346+214) for 1.0 mm voxel size compared to 1.5T (202 +/- 41), but showed considerably higher variability at 3T. At 3T, measurements with 0.9 mm voxel size were possible with similar SNR as with 1.0 mm voxel size at 1.5T. CONCLUSION: High-resolution 3D imaging of the whole spine is feasible at 3T with an increased SNR compared to 1.5T. Signal gain at 3T can be used to further increase spatial resolution. Pronounced interpatient variability of SNR at 3T may be a result of inhomogeneous RF deposition due to dielectric effects.

Adult↗
PubMed2006

Disseminated mucormycosis in haematological patients: CT and MRI findings with pathological correlation.

Disseminated mucormycosis is a rare, mostly fatal infectious complication in immunocompromised haematological patients. The purpose of our study was to describe the multiorgan manifestations of disseminated mucormycosis documented at CT and MRI in four patients and correlate these with the pathological findings and patient outcome. Irrespective of the site of infection, infarction or haemorrhage are the constant features of invasive mycosis. Identification of one or both of these two major imaging findings in immunocompromised patients should be regarded as an indicator of possible infection by angiotropic fungi, including the genre Mucorales.

Adult↗
PubMed2006

Percutaneous vascular interventions in the superficial femoral artery. A review.

The superficial femoral artery (SFA) is a frequent target of atherosclerotic disease predominantly in the proximal section near the bifurcation to the deep femoral artery and in the distal section where the adductor muscles tend to compress the artery. In the past, SFA revascularization was the domain of vascular surgery (femoropopliteal and femorodistal bypasses). However, with the development of endovascular treatment and advancing techniques as well as more sophisticated stenting material and balloons, endovascular treatment is nowadays not just a treatment option but, in most cases, preferable at least as initial revascularization procedure in the treatment of peripheral artery vascular disease. In the last years, many efforts have been made to fight restenosis in revascularized artery segments after stenting and/or angioplasty. This article aims to give a review on this topic including the most recent experience with the various latest revascularization techniques such as drug eluting stents, coated stent grafts, brachytherapy, cryoplasty, cutting balloons, and drug coated balloons.

Angioplasty, Balloon↗
PubMed2005

Age and gender related effects on adipose tissue compartments of subjects with increased risk for type 2 diabetes: a whole body MRI/MRS study.

Quantitative measurement of adipose tissue (AT) compartments in the entire body and of lipids in muscle and liver cells by means of MRI and MRS. Assessment of age and gender related differences in AT compartments and determination of cross-correlations between AT compartments in a heterogeneous cohort at increased risk for metabolic diseases. One hundred and fifty healthy volunteers with increased risk to type 2 diabetes were examined. T1-weighted MRI was applied for whole-body adipose tissue quantification. Adipose tissue compartments were subdivided in lower extremities, trunk (abdominal subcutaneous (SCAT) and visceral (VAT) adipose tissue), and upper extremities. Intrahepatocellular lipids (IHCL) and intramyocellular lipids (IMCL) in tibialis anterior and soleus muscle were determined by volume selective MRS. Females are characterized by lower %VAT (2.8+/-1.3% vs. 4.6+/-1.4%, p<0.001) and higher %SCAT (14.7+/-3.9% vs. 9.3+/-2.9%, p<0.001). There is a strong correlation between %VAT and age (r=0.64/0.60 for females/males), whereas %SCAT remained virtually unchanged in males (r=-0.09) and was only slightly increaseding in females (r =0.30, p<0.01). For IHCL, age related differences were observed in females with significantly increased IHCL in the older women, but not in males. IMCL contents in both muscles were found almost independent of age in both, males and females. Furthermore, VAT and IHCL show significant correlations in both groups. Assessed age and gender related differences, especially the age related significant increase of VAT and IHCL, as well as cross-correlations between different lipid compartments might contribute to a better understanding of the lipid metabolism under normal and pathologic metabolic conditions in humans.

Adipose Tissue↗
PubMed2005

Dual-phase multidetector thin-section CT in detecting duodenal gastrinoma.

Preoperative localization of gastrinomas, especially of extrapancreatic origin, remains a challenge to the radiologist. Most patients with extrapancreatic gastrinomas undergo surgery without preoperative identification of the primary tumor. The appropriate imaging modality to localize gastrinomas is under continuing debate. We report a case of a duodenal gastrinoma with regional lymph node metastases that presented with Zollinger-Ellison syndrome. The small primary tumor was detected noninvasively by dual-phase multidetector thin-section computed tomography with adequate bowel distention and confirmed by endoscopy and histopathologic examination. The case illustrates that appropriate computed tomographic technique and scanning protocol are crucial for success in localizing extrapancreatic gastrinoma.

Contrast Media↗