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T Helmberger

Publications and source records attributed to T Helmberger.

At least 37 records · Page 2Linked to original sources
PubMed2000

Segmental and subsegmental pulmonary arteries: evaluation with electron-beam versus spiral CT.

PURPOSE: To compare contrast agent-enhanced spiral and electron-beam computed tomography (CT) for the analysis of segmental and subsegmental pulmonary arteries. MATERIALS AND METHODS: CT angiography of the pulmonary arteries was performed in 56 patients to rule out pulmonary embolism. Electron-beam CT was performed in 28 patients. The other 28 patients underwent spiral CT with comparable scanning protocols. The depiction of segmental and subsegmental arteries was analyzed by three independent readers. The contrast enhancement in the main pulmonary artery was measured in each patient. RESULTS: Analysis was performed in 1,120 segmental and 2, 240 subsegmental arteries. One segmental (RA7, P =.010) and two subsegmental (LA7b, P =.029; RA6a+b, P =.038) arteries in paracardiac and basal segments of the lung were depicted significantly better with electron-beam CT. There was no statistically significant difference between electron-beam and spiral CT in the total number of analyzable peripheral arteries depicted. The mean contrast enhancement in the main pulmonary artery was 362 HU in electron-beam CT studies versus 248 HU in spiral CT studies. CONCLUSION: Detailed visualization of peripheral pulmonary arteries is well within the scope of advanced CT techniques. Electron-beam CT has minor advantages in analyzing paracardiac arteries, probably because of reduction of motion artifacts and higher contrast enhancement. Further studies are needed to establish whether electron-beam CT allows a more confident diagnosis of emboli in these vessels.

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↗
PubMed1999

[Diagnosis and staging of liver metastases with imaging methods].

Liver metastases are much more common than primary hepatic malignancies and may occur in up to 80% of patients with extrahepatic malignancies. To optimize the patient's management, precise detection or exclusion of liver metastases, as well as assessment of their number and extent, is indispensable. For imaging of liver metastases, ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), scintigraphy, and angiography can be utilized. All these methods have been technically improved with benefits for diagnostic utility. Biphasic contrast-enhanced spiral CT (SCT) and MRI with modern pulse sequences and tissue-specific contrast agents are superior to other imaging modalities in terms of diagnostic efficacy and reproducibility of results. With SCT and MRI sensitivities and specificities in the diagnosis of focal hepatic disease are in the range of 80-95%. Moreover, their non-invasiveness is a strong advantage. The diagnostic strategy in the assessment of liver metastases has to take into account both the strengths and limitations of the respective method. Additionally, the clinical situation of a particular patient has to be considered, and conclusive diagnostic results have to be achieved in a short time in order to ensure a favourable cost-effectiveness relation.

Colorectal Neoplasms↗
PubMed1999

[Computed tomography of the abdomen with multidetector-array CT].

BACKGROUND: The advent of multidetector CT (MDCT) constitutes a quantum leap creating a wealth of new opportunities in medical imaging. However, while the basic principles of spiral CT still apply, we are now challenged to rethink our strategies in planning a CT study to take full advantage of the increased capabilities of MDCT. MATERIALS AND METHODS: We report here our preliminary experiences with MDCT for abdominal CT imaging within a 5-month period. During this time, suitable protocols for investigation of the abdomen using MDCT were developed. The capabilities of MDCT allow for tailoring dedicated CT protocols for routine applications as well as for biphasic liver studies and CT angiography of the aorta and abdominal vessels. RESULTS: The speed of MDCT can either be used to reduce the time needed to cover a given volume, or to use narrower beam collimations to increase the resolution of detail along the z-axis and reduce volume averaging. Higher scan speed allows reduction of the amount of contrast material in vascular applications and suppression of motion artifacts. Higher spatial resolution with thinner collimations reduces volume averaging and improves the detection of small hepatic and pancreatic lesions. Detailed analysis of vascular structures and high-quality three-dimensional reformations become feasible. New problems arise from the large amount of data generated by MDCT. CONCLUSIONS: MDCT offers a wealth of new opportunities that help us to come to a fast and accurate diagnosis in suspected abdominal disease. Traditional indications for performing CT are reemphasized and new clinical applications can be exploited.

Abdomen↗
PubMed1999

[New techniques and pulse sequences in MRI of the liver].

PURPOSE: The MRI techniques which have contributed to increasing utilization of MRI for abdominal imaging are described and recent advances addressed. METHODS: For breath-hold examinations of the abdomen, two basic techniques are required: array coil technology and fast and ultrafast pulse sequences providing T1 and T2 contrast. RESULTS: Circular polarized array coils render high signal-to-noise ratios (SNR) within large imaging volumes. With fast gradient-echo sequences the liver can be scanned with or without fat saturation within one breath-hold. When adequate parameters are selected, T2-weighted fast (turbo) spin-echo sequences allow high contrast between normal liver tissue and focal liver lesions, even if breath-hold acquisition is applied. Moreover, good soft tissue contrast can also be achieved with ultrafast single-shot sequences. Based on this sequence type, MRCP with a 512 matrix could be performed. The "TRUE FISP" allows for high resolution visualisation of vessels without contrast media. Three-dimensional T1-weighted sequences allow for scanning the upper abdomen with a slice thickness of 3 mm within one breath-hold. Diffusion-weighted sequences contribute to the characterisation of focal liver lesions. DISCUSSION: Modern MRI technology including phase-array coils and high-performance gradient systems made it possible to perform all examinations in breath-hold techniques, reducing motion artifacts.

Humans↗
PubMed1999

[Comparison of dual-phase helical CT with native and ferum oxide-enhanced magnetic resonance imaging in detection and characterization of focal liver lesions].

PURPOSE: Evaluation of the diagnostic efficacy of contrast-enhanced, dual-phase spiral CT and MRI before and after administration of SPIO particles in focal hepatic disease with previously uncertain diagnosis. MATERIAL AND METHODS: In 46 patients in whom primary or secondary hepatic malignancy was suspected, dual-phase spiral CECT and breath-held T1-weighted gradient-echo and T2-weighted fast spin-echo MRI (1.5 T, body-phased-array coil) before and after SPIO administration were compared. The indications for the subsequent MRI studies were based on ambiguous findings on CECT. The number of hepatic lesions, the overall lesion detection and characterization was evaluated by consensus and compared to the gold standard (histological proof in 30/46 of the cases, long-term follow-up in 16/46 of the cases). RESULTS: In 34 of 46 cases the correct diagnoses were established by CECT (sensitivity 96%, specificity 48%) revealing significantly less lesions than MRI. Unenhanced MRI had sensitivity of 93% and specificity of 71%, whereas SPIO-enhanced MRI had sensitivity of 97% and specificity of 88%. The differences between the modalities were even more pronounced in the detection of lesions smaller than 10 mm with SPIO-MRI as the most sensitive method. CONCLUSIONS: In this problem-oriented scenario, SPIO-enhanced MRI was superior to spiral CT and unenhanced MRI regarding the diagnostic efficacy in the pre-operative work-up of focal liver lesions. SPIO-enhanced MRI can be recommended as a problem-solving tool for the clinical routine.

Adult↗
PubMed1999

[Percutaneous interventional radiologic implantation of intravenous port-catheter systems].

PURPOSE: Percutaneous interventional radiologic and surgical techniques of port-catheter implantation are described and compared with regard to the technical procedure and results. MATERIALS AND METHODS: In 53 patients with various malignancies interventional radiologic implantation of port-catheter systems into the subclavian vein was performed to provide long-term intravenous access for chemotherapy. The technical procedure, operation time, complication rates and long-term patency were compared with those of surgically implanted systems. RESULTS: Implantation was successful in all cases. Mean operation time was 36 min (range 20-55 min). Mean function time was 189 days (range 7-518). Primary patency rate was 92.5% with a total complication rate of 15% (8/53). In three patients (5.7%) pneumothorax was observed but did not require further treatment. In two cases (3.8%) local infection occurred, and in one patient (1.8%) a non-complicated wound dehiscence. In 12/53 patients (22.6%) the system was withdrawn. Among these, withdrawal was due to complications in 4/53 (7.6%) cases. CONCLUSIONS: Interventional radiologic implantation of long-term intravenous port-catheter systems is comparable to surgical placement with regard to both complication rate and long-term patency.

Adult↗
PubMed1999

[Evaluation of right heart load with spiral CT in patients with acute lung embolism].

PURPOSE: Purpose of this study was to evaluate whether spiral-CT allows judgment of right ventricular failure in patients with acute pulmonary embolism. MATERIALS AND METHODS: 61 patients underwent spiral-CT due to suspicion of acute pulmonary embolism. Patients with pulmonary embolism were divided into subpopulations according to the severity of pulmonary embolism in the CT scan. Cardiac measurements were performed on axial spiral-CT images and compared to those of patients without suspicion of pulmonary embolism or cardiac diseases. RESULTS: In 30 patients spiral-CT revealed acute pulmonary embolism. Significant differences in cardiac measurements in patients with severe and less severe pulmonary embolism were found on comparing the following dimensions: left ventricular width (p = 0.0003), left (p = 0.008) and right (p = 0.009) ventricular cross-sectional area, proportion of right to left ventricular width (p = 0.0003) and proportion of right to left ventricular cross-sectional area (p = 0.0001). The proportion of the cross-sectional areas (r = 0.65) and the proportion of the width (r = 0.60) of both ventricles correlated well with the severity of central pulmonary embolism. CONCLUSION: Besides reliable assessment of pulmonary embolism spiral-CT allows the evaluation of cardiac dimensions for judgment of right ventricular failure.

Adult↗
PubMed1999

Effective contrast use in CT angiography and dual-phase hepatic CT performed with a subsecond scanner.

OBJECTIVE: To deduce an optimal injection protocol for CT angiography and fast dual-phase hepatic CT. METHODS: Fifty-two patients underwent fast dual-phase hepatic CT using one of three different injection protocols: A (0.9 g/sec iodine injection rate, 36 g dose); B (1.35 g/sec, 30 g); C (1.6 g/sec, 40 g). Aortic attenuation time curves as well as aorta-to-liver contrast and hepatic enhancement time curves obtained by region of interest measurements along the helical axis were analyzed. RESULTS: Protocol C revealed a significantly higher peak in aortic attenuation and hepatic enhancement than the other protocols. Approximately 50 seconds after the bolus injection, hepatic enhancement declined to a plateau similar to that seen with the other protocols. In terms of the areas under the curves of the aorta-to-liver contrast and hepatic enhancement dynamics, protocol C was significantly superior to the other protocols. CONCLUSIONS: A high iodine injection rate realized by a high iodine concentration in conjunction with fast dual-phase scanning (total scan time < 50 seconds) promises to enhance CT angiography and contrast of liver lesions.

Angiography↗
PubMed1999

New formula for quantification of pleural effusions from computed tomography.

The authors develop a method to accurately and easily estimate the volume of pleural effusions with computed tomography (CT). In 15 patients with either simple or loculated pleural effusions (14 right-sided and 11 left-sided), routine helical CT examinations of the thorax were obtained. Two experienced radiologists visually estimated the volume of the effusions. Three-dimensional reconstructions of the pleural effusions were performed from the helical CT examinations, and the volumes of the effusions were calculated. Effusion volumes were also estimated using the formula d2 x l (d = greatest depth of the effusion on a single CT image, l = greatest length of the effusion). The computer calculated the estimated volumes and they were then statistically compared. The coefficient of correlation between the estimation by measurement and calculated volumes of all effusions was 0.908 (p<0.0001) for the right side, and 0.849 for the left side (p<0.002). Excluding the loculated effusions, the coefficient of correlation was 0.969 for the right side and 0.949 for the left side (p<.001). The volume estimation by visual inspection was also correlated to the calculated volumes (0.84 on the left and 0.85 on the right, p<0.008), but resulted in a consistent overestimation by 300 ml to 500 ml. Although pleural effusion volumes can be estimated by visual inspection with good correlation, some overestimation is consistently seen. Use of the formula d2 x l readily enables estimation of pleural effusion volume from CT, from two simple measurements. This formula-based method of volume estimation provides an accurate and easily measured means of estimation that is readily obtained from routine CT of the chest.

Humans↗
PubMed1999

Electrocardiographically gated thin-section CT of the lung.

PURPOSE: To determine whether electrocardiographic (ECG) gating improves image quality of thin-section computed tomographic (CT) scans of the lung obtained with a subsecond CT scanner. MATERIALS AND METHODS: Thin-section CT was performed in 35 patients by using standard techniques. Three additional sections were obtained in each patient with prospective ECG gating at corresponding levels of the paracardiac lung parenchyma. Non-ECG-gated and ECG-gated sections were then rated in blinded fashion by three experienced radiologists for overall image quality, spatial resolution, and diagnostic value and for different types of respiratory and cardiac motion artifacts. RESULTS: ECG gating helped significantly reduce artifacts caused by cardiac motion (i.e., distortion of pulmonary vessels, double images, or blurring of the cardiac border) (P < .05). ECG gating did not reduce respiratory motion artifacts. In patients with heart rates of less than 76 beats per minute, ECG gating significantly improved overall image quality (P = .041). ECG gating was not perceived to increase the diagnostic value of thin-section CT scans. CONCLUSION: ECG gating improves image quality of thin-section CT scans of the lung by reducing cardiac motion artifacts that may mimic disease. It must be established whether ECG gating can help increase the diagnostic accuracy of thin-section CT for the evaluation of subtle parenchymal disease.

Adult↗
PubMed1998

Comparison of sequences for depicting bone marrow alterations in osteomyelitis applied in a low field strength magnetic resonance imaging system.

OBJECTIVE/PATIENTS: To investigate the efficacy of standard sequences of a low field system for the detection of osteomyelitis, we tested T1wI pre and post i.v. contrast, T2w and fat suppressed IR sequences. DESIGN: On the basis of clinical and laboratory evidence, pathology reports, and three phase granulocyte scintigraphy, osteomyelitis was diagnosed in 18 of 21 patients with Charcot's joints. A consecutive low and high field magnetic resonance (MR) scan confirmed osteomyelitic bone marrow changes in the same osseous regions. These 18 diabetic patients were then studied on a 0.2 Tesla dedicated MR system (Esaote ArtoScan) using T1wI (SE: relaxation time (TR) 520/echo time (TE) 24: axial and coronal) before and after i.v. application of 0.1 mmol/l Gd-DTPA/kg BW, T2w imaging (TSE: TR 3500/TE 80 or TR 2000/TE 120: axial), and fat suppressed inversion recovery (IR) imaging (short tau inversion recovery (STIR): TR 3000/TE 30/TI 80 or inversion recovery gradient echo (IRGE)/fat suppressed IRGE (GEFS): TR 1000/TE 16m 80: coronal). RESULTS: The SE T1w sequence showed a significantly higher contrast-to-noise ratio (CNR) before administration of i.v. contrast. The TSE T2w pulse sequence demonstrated bone marrow changes superiorily utilizing a TE of 120 ms (CNR = 16.5+/-2.7 compared to 5.5+/-2.5 with TE = 80 ms). The IRGE showed a higher CNR than the standard STIR (CNR = 19.2+/-2.5 compared to 12.4+/-2.9). CONCLUSION: Fat suppressed IRGE imaging and longer TE in T2w TSE sequences result in a significantly better CNR in osteomyelitis. This way, using optimized sequences, low field systems are apt to depict bone marrow changes in the course of osteomyelitis.

Adolescent↗
PubMed1998

[MRI of the small intestine with rapid MRI sequences in Crohn disease after enteroclysis with oral iron particles].

PURPOSE: To evaluate the efficacy of breathhold MRI following enteroclysis with addition of oral magnetic particles to study the extension, detection of stenoses and extraluminal manifestations in Crohn's disease. MATERIAL AND METHODS: 18 patients with Crohn's disease and potential of surgical intervention were studied with enteroclysis with addition of oral magnetic particles. T1-/T2-weighted breathhold MRI w/o spectral fat suppression w/o i.v. Gd-DTPA was applied. RESULTS: Typical findings were marked bowel wall thickening with strong contrast enhancement. 95.8% of affected small bowel segments and 94.7% of stenoses were correctly detected by MRI. All four fistulas were detected and important extraluminal findings were seen in 6/18 patients. Additionally, one ileoileal and two ileosigmoidal adhesions, two extraluminal abscesses and affection of the right ureter were delineated. CONCLUSION: MRI in Crohn's disease offers the potential to avoid radiation exposure in this relatively young patient group. Important additional findings relevant to indication of surgery are seen in approximately one third of cases. The replacement of transduodenal intubation by oral contrast application remains to be further studied.

Administration, Oral↗
PubMed1998

[Focal liver diseases].

INTRODUCTION: Advanced therapies are improving significantly the survival of patients with malignant focal liver disease. For efficient implementation of these surgical and interventional techniques a clear concept of the diagnostic procedure is mandatory. METHODS: Based on a review of the current literature, the different imaging modalities, including ultrasound, computed tomography, magnetic resonance tomography, nuclear medicine and angiography, are discussed and evaluated for their diagnostic efficacy in focal hepatic disease. RESULTS: Considering clinical, diagnostic, and economical appropriateness, recommendations for diagnostic strategies in different clinical scenarios regarding focal heptic disease are presented. CONCLUSION: If the power of specific imaging methods are relevant clinical information is known, problem-based diagnostic strategies help to avoid unnecessary, expensive and time-consuming studies in the work-up of focal liver lesions.

Carcinoma, Hepatocellular↗
PubMed1998

[Vena cava filter. Indications, complications, clinical evaluation].

INTRODUCTION: Pulmonary embolism is the third leading cause of death in the western countries. If anticoagulation fails or is contra-indicated, or if the risk for pulmonary embolism is increased for other reasons, the percutaneous implantation of a vena cava filter should be considered. METHODS: The available filters can be differentiated by the design (cone, basket, net-types), by the material, and by their removability. The rate of complications (caval thrombosis, fracture of filter) and the in vitro efficacy in trapping thrombotic clots is dependent on the specific filter type. RESULTS: In clinical practice there is no evidence for significant differences in trapping efficacy among the different filters. About 4% of all patients treated by caval filters still can have pulmonary embolism, and 1% will have a fatal outcome. Dependent on the filter type, the most common complication is caval thrombosis, in up to 25% of cases. CONCLUSION: The percutaneous implantation of caval filters can readily be performed by interventional radiologists. However, randomized clinical studies failed to clearly document efficacy of caval filters. Therefore, indication has to be considered carefully.

Humans↗
PubMed1998

[Diagnosis of pulmonary embolism with spiral and electron-beam CT].

PURPOSE: To compare spiral (SCT) and electron-beam CT (EBT) for the diagnosis of pulmonary embolism (PE). MATERIALS AND METHODS: From June 1997 to June 1998 188 patients with suspected acute or chronic thromboembolism of the pulmonary arteries were examined. A total of 108 patients were scanned using SCT and 80 patients using EBT. On each scanner two different scan protocols were evaluated. RESULTS: PE was diagnosed in 38 patients using EBT and in 49 patients using SCT. Especially with EBT, isolated peripheral emboli could be confidently diagnosed. When EBT and SCT were compared for the analysis of peripheral pulmonary arteries, some paracardiac segmental and subsegmental vessels were significantly better analyzable with EB. Additional or diseases other than PE were diagnosed in 112 patients. Other diagnoses included bronchial carcinoma and aortic dissection. CONCLUSIONS: Advanced CT scanning techniques allow the highly accurate diagnosis of central and peripheral PE. Other potentially life-threatening underlying diseases are also readily recognized.

Aortic Dissection↗