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Biomedical subjects

P Mildenberger

Publications and source records attributed to P Mildenberger.

At least 19 recordsLinked to original sources
PubMed2000

Focal airtrapping at expiratory high-resolution CT: comparison with pulmonary function tests.

This study was undertaken to determine prevalence, extent, and severity of focal airtrapping at expiratory high-resolution CT, and to compare focal airtrapping with age, gender, pulmonary function tests, and blood gas analysis. Two-hundred seventeen patients with and without pulmonary disease underwent paired inspiratory/expiratory high-resolution CT. Six scan pairs with corresponding scan levels were visually assessed for focal--not diffuse--airtrapping using a four-point scale. Pulmonary function tests and blood gas analysis were available for correlation in all patients (mean interval 5 days). Focal airtrapping with lower lung predominance was observed in 80% of patients. Twenty-six of 26 patients with restrictive lung function impairment exhibited focal airtrapping (mean score 2.4), whereas only 72 of 98 (74%) patients with obstruction did (mean score 1.5; p < 0.05). Fifty-eight of 70 (83%) patients with normal lung function (mean score 1.8) and 19 of 23 (83%) patients with mixed impairment (mean score 1.8) had focal airtrapping. Focal airtrapping showed negative correlations with static lung volumes (-0.27 to -0.37; p < 0.001) in all patients and moderate positive correlations with dynamic parameters (0.3-0.4; p < 0.001) in patients with obstruction. No significant correlations were found with age, gender, and blood gas analysis. Visual assessment of focal--not diffuse--airtrapping at expiratory high-resolution CT does not correlate with physiological evidence of obstruction as derived from pulmonary function tests since the perception of focal airtrapping requires an adequate expiratory increase in lung density.

Adolescent↗
PubMed2000

[Segmental anatomy of the liver in computed tomography: do we localize the lesion accurately?].

PURPOSE: To evaluate if Couinaud's model using the planes of the major veins is an adequate tool for the presurgical localization of focal liver lesions. METHODS: Biphasic helical CT scans were performed on patients evaluated for liver resection using an increased IV bolus of contrast medium (180 ml lopamidol) and 2 mm image reconstruction increments. During the first evaluation, all liver lesions were localized in the conventional way using the planes of the 3 major hepatic veins and the portal trunks as segmental boundaries. In a second review, all lesions were attributed to the nearest peripheral portal branches. The path and the segmental attribution of the portal branches were analysed. Evaluations were performed using an interactive cine mode as well as three-dimensional reconstructions. RESULTS: 20 of 126 (16%) liver lesions had a different segmental location if the individual anatomy of the peripheral portal branch was used instead of the conventional technique. These different locations were due to the path of the portal trunks or the path of the peripheral portal branches crossing the planes of the major hepatic veins. CONCLUSION: The segmental anatomy of the liver using the planes of hepatic veins and portal trunks according to Couinaud is not an accurate tool for the presurgical localization of liver lesions in many cases.

Carcinoma, Hepatocellular↗
PubMed2000

[Rational diagnostic imaging of pelvic and acetabulum injuries].

In spite of the widespread availability of CT scanners, conventional X-ray radiographs remain the basic imaging modality in patients with pelvic and/or acetabular trauma. However, the extent of their use will depend on local utilities (e.g., availability of CT scanners) and on the patient's clinical condition. Regarding the inaccuracy of conventional radiography in the diagnosis of injuries of the dorsal pelvic ring and of the acetabulum, computed tomography represents the most important imaging modality in the clinically stable patient. CT provides an exact staging of the extent of trauma and allows for differentiation of pelvic instabilities. CT clearly demonstrates the severity of acetabular trauma and is superior in the detection of local complicating factors, i.e., impressions fractures and (sub-)luxations of the femoral head as well as free intraarticular fragments. CT findings provide the basis for definite treatment regimens of the injured patient. By extension of the examination, all relevant organs and systems (craniospinal, cardiovascular, gastrointestinal, respiratory, genitourinary) can be imaged during one session. The speed of spiral CT scanners and their diagnostic accuracy will play a major role in the management of, especially, polytraumatized patients. The indication for angiography with the option of therapeutic embolization exists if a pelvic bleeding persists even after reposition and operative fixation of the injury.

Acetabulum↗
PubMed1999

[Use of the DICOM standard in a heterogenous environment. Incompatibility or inoperability?].

PURPOSE: The DICOM standard, introduced in 1993, is now established in many of today's image modalities. Experiences with DICOM implementations and requirements for future developments are described. METHODS: First a brief summary of the development of the DICOM standard is given. Based on general observations, different problems with installation, programming and maintenance are outlined. RESULTS: The standard consists of mandatory and optional information models and functionalities to enable the use and development of a broad spectrum of applications. But the available options lead to specific applications not compatible with the basic idea of the standard. DISCUSSION: For functional communication distinct DICOM services are necessary. This includes DICOM Basic Worklist, Storage Commitment and Performed Procedure Step. A constructive way to achieve inter-operability through voluntary arrangements between manufactures and users will be shown.

Diagnostic Imaging↗
PubMed1999

[MR angiography of peripheral vessels with automatic tracking table technique at 1.0 in comparison with intra-arterial digital subtraction angiography].

PURPOSE: Contrast-enhanced (CE) 3D-MR angiography of peripheral arteries was performed in 8 patients with peripheral arterial occlusive disease by applying a new tracking technique on a 1.0 T system (Magnetom Harmony, Siemens). The studies were compared with intra-arterial digital angiography as gold standard. MATERIALS AND METHODS: Imaging of the distal aorta, pelvis, upper and lower limb arteries was accomplished with a Flash-3D-sequence (TR/TE = 6.2/3.2 ms) within 26 s acquisition time of each region after a single bolus of 30 ml contrast agent. Individual circulation time was determined by a test bolus before each examination. RESULTS: 112 vessel segments were evaluated. MR angiography achieved a sensitivity of 89% and a specificity of 100% for detecting high grade stenoses and vessel occlusions. CONCLUSIONS: Tracking CE 3D-MR angiography with a 1.0 T MR imager proved to be a promising method in evaluating hemodynamically significant stenoses and occlusions of peripheral arteries. However, its definite role in the diagnostic work-up of peripheral arterial occlusive disease has to be evaluated in larger prospective studies.

Angiography, Digital Subtraction↗
PubMed1999

[Color-coded volume reconstruction for 3-dimensional presentation of CT data].

PURPOSE: To evaluate a technique of colored three-dimensional reconstructions without segmentation. MATERIAL AND METHODS: Color-coded volume rendered images were reconstructed from the volume data of 25 thoracic, abdominal, musculoskeletal, and vascular helical CT scans using commercial software. The CT volume rendered voxels were encoded with color in the following manner. Opacity, hue, lightness, and chroma were assigned to each of four classes defined by CT number. Color-coded reconstructions were compared to the corresponding grey-scale coded reconstructions. RESULTS: Color coded volume rendering enabled realistic visualisation of pathologic findings when there was sufficient difference in CT density. Segmentation was necessary in some cases to demonstrate small details in a complex volume. CONCLUSION: Color coded volume rendering allowed lifelike visualisation of CT volumes without the need of segmentation in most cases.

Abdominal Neoplasms↗
PubMed1999

Pneumonia in febrile neutropenic patients and in bone marrow and blood stem-cell transplant recipients: use of high-resolution computed tomography.

PURPOSE: To obtain statistical data on the use of high-resolution computed tomography (HRCT) for early detection of pneumonia in febrile neutropenic patients with unknown focus of infection. MATERIALS AND METHODS: One hundred eighty-eight HRCT studies were performed prospectively in 112 neutropenic patients with fever of unknown origin persisting for more than 48 hours despite empiric antibiotic treatment. Fifty-four of these studies were performed in transplant recipients. All patients had normal chest roentgenograms. If pneumonia was detected by HRCT, guided bronchoalveolar lavage was recommended. Evidence of pneumonia on chest roentgenograms during follow-up and micro-organisms detected during follow-up were regarded as documentation of pneumonia. RESULTS: Of the 188 HRCT studies, 112 (60%) showed pneumonia and 76 were normal. Documentation of pneumonia was possible in 61 cases by chest roentgenography or micro-organism detection (54%) (P < 10(-6)). Sensitivity of HRCT was 87% (88% in transplant recipients), specificity was 57% (67%), and the negative predictive value was 88% (97%). A time gain of 5 days was achieved by the additional use of HRCT compared to an exclusive use of chest roentgenography. CONCLUSION: The high frequency of inflammatory pulmonary disease after a suspicious HRCT scan (> 50%) proves that pneumonia is not excluded by a normal chest roentgenogram. Given the significantly longer duration of febrile episodes in transplant recipients, HRCT findings are particularly relevant in this subgroup. Patients with normal HRCT scans, particularly transplant recipients, have a low risk of pneumonia during follow-up. All neutropenic patients with fever of unknown origin and normal chest roentgenograms should undergo HRCT.

Adult↗
PubMed1998

[Magnetic resonance imaging (MRI) of liver and brain in hematologic-oncologic patients with fever of unknown origin].

PURPOSE: To examine the advantage of liver and brain MRI in clinically anomalous haematological patients with fever of unknown origin. MATERIAL AND METHODS: Twenty liver MRI (T2-TSE, T2-HASTE, T1-FLASH +/- Gd dynamic) and 16 brain MRI (T2-TSE, FLAIR, T1-TSE +/- Gd) were performed searching for a focus of fever with a suspected organ system. Comparison with clinical follow-up. RESULTS: A focus was detected in 11/20 liver MRI. Candidiasis (n = 3), mycobacteriosis (n = 2), relapse of haematological disease (n = 3), graft versus host disease (n = 1), non-clarified (n02). The remaining 9 cases with normal MRI were not suspicious of infectious hepatic disease during follow-up. In brain MRI, 3/16 showed a focus (toxoplasmosis, aspergillosis, mastoiditis). Clinical indication for an infectious involvement of the brain was found in 4/16 cases 2-5 months after initially normal brain MRI. No suspicion of an infectious involvement of brain was present in the remaining 9/16 cases. CONCLUSION: In case of fever of unknown origin and suspicion of liver involvement, MRI of the liver should be performed due to data given in literature and its sensitivity of 100%. Because of the delayed detectability of cerebral manifestations, in cases of persisting suspicion even a previously normal MRI of the brain should be repeated.

Aspergillosis↗
PubMed1998

[3D CT of fractures: comparison of volume and surface reconstruction].

PURPOSE: The comparison of volume rendering (VR) and surface rendering (SSD) for demonstrating fractures from spiral-CT data. MATERIALS AND METHODS: Standardized VR and SSD projections were produced from 50 spiral CT scans of 50 consecutive patients with fractures. Appropriate multiplanar reformattings (MPR) were used as the standard. RESULTS: SSD provided sufficient information in 31/50 cases. Results of VR were not significantly different (33/50). VR was superior in demonstrating 6/7 craniofacial fractures and 3/3 calcaneal fractures. SSD was superior for visualizing 2/3 shoulder fractures and 2/2 elbow fractures. CONCLUSION: VR is a flexible technique for the depiction of fractures and the assessment of spongiosa and articular surfaces at one setting. SSD is superior in the delineation of small dislocated fragments.

Calcaneus↗
PubMed1998

[Diagnosis of primary sclerosing cholangitis: prospective comparison of MR cholangiography with endoscopic retrograde cholangiography].

PURPOSE: To assess the accuracy of MR cholangiography (MRC) in the diagnosis of primary sclerosing cholangitis (PSC) in comparison to endoscopic retrograde cholangiography (ERC). METHOD: 20 patients with PSC were examined by ERC and MRC (1.0 T, HASTE sequence). Visualization and pathologic changes of the extra- and intrahepatic bile ducts were evaluated with both methods. RESULTS: Mural irregularities of the common bile duct were seen with MRC in 6/7 cases, stenoses and dilatation of the common bile duct were detected correctly in all patients. Diffuse, multifocal strictures of the intrahepatic bile ducts were the most common intrahepatic findings and correctly diagnosed in almost all patients. Mural irregularities of the intrahepatic ducts in early stages may be missed by MRC because of the limited spatial resolution. MRC is superior to ERC in visualization of nonopacified intrahepatic ducts. CONCLUSIONS: MRC is a reliable, non-invasive method to detect typical diagnostic features of PSC. It should be considered as an adjunct to ERC in patients with suspected PSC for primary diagnosis and as an alternate method for follow-up studies.

Adolescent↗
PubMed1998

[Value of spirometry-gated high resolution computerized tomography of the lung during inspiration and expiration].

PURPOSE: To compare mean lung density (MLD) of paired inspiratory and expiratory thin-section CT scans acquired after patient instruction or using spirometric gating. MATERIALS AND METHODS: 21 patients (13 m, 8 f. median age 59 years, two with normal lung function, 15 with obstructive, 4 with restrictive impairment) underwent thin-section CT. Paired inspiratory and expiratory scans were performed in the upper, middle and lower lung fields. They were acquired after automatic patient instruction with constant intervals between instruction and scan. Spirometrically gated scans were acquired within 4 days at 80% and 20% of vital capacity (VC) which has been determined on the CT scanner in supine position directly prior to the examination using the built-in spirometric option. Semiautomatic segmentation of the lung was performed and MLD was calculated. VC of pulmonary function testing was available for correlation. RESULTS: Inspiratory MLD was -828 +/- 71 HU with spirometric gating and -818 +/- 87 HU without. Expiratory MLD was -750 +/- 119 HU (increase 78 +/- 58 HU) with spirometric gating and -748 +/- 119 HU (increase 70 +/- 46 HU) without. All differences were non-significant. Intraindividual differences were 10 +/- 21 HU for inspiration and 2 +/- 36 HU for expiration. VC under CT-conditions was significantly smaller than that known from pulmonary function tests (1.9 +/- 0.71 vs. 2.7 +/- 0.81, p < 0.005). CONCLUSION: Spirometric gating does not lead to different results for MLD as compared with acquisition of paired inspiratory and expiratory thin-section CT after automatic patient instruction.

Absorptiometry, Photon↗
PubMed1998

Assessment of lung volumes using helical CT at inspiration and expiration: comparison with pulmonary function tests.

OBJECTIVE: This study was designed to determine lung volumes using inspiratory and expiratory helical CT with two-dimensional (2D) and three-dimensional (3D) postprocessing and to compare the accuracy of those measurements with pulmonary function test results. SUBJECTS AND METHODS: Seventy-two patients with suspected pulmonary disease underwent unenhanced helical CT (slice thickness, 8 mm; pitch, 2; increment, 8 mm) at deep inspiration and expiration. Lung volumes were determined using either a 2D approach (semiautomatic segmentation; thresholds, -1024 and -200 H) or a 3D technique (double-threshold seeded volumes of interest; thresholds, -1024 H [lower] and -900, -500, 400, -300, or -200 H [upper]). Pulmonary function tests were available for correlation in all cases. RESULTS: Using inspiratory helical CT, we underestimated total lung capacity by 12%, which had a good correlation (r = .89) with static lung volumes. Volume revealed by expiratory helical CT was equivalent to intrathoracic gas volume, which also exhibited a good correlation (r = .88). However, using expiratory helical CT, we overestimated residual volume by 850 ml with a rather good correlation (r = .77). An emphysema index revealed moderate correlation with the relative forced expiratory volume in 1 sec (inspiration, r = -.66; expiration, r = -.54), whereas the expired volume showed a moderate correlation with the absolute forced expiratory volume in 1 sec (r = .65). The 2D approach showed lower absolute volumes than the 3D technique (mean, 3.6%; r = .99). In the 3D technique, lower upper thresholds led to reduced volumes (170 ml/100 H). CONCLUSION: Inspiratory and expiratory helical CT show high correlation with static lung volumes. The 3D technique (-1024 to -200 H) is recommended for absolute estimation of lung volumes.

Female↗
PubMed1997

[CT-angiography in carotid stenosis].

PURPOSE: Prospective evaluation of the accuracy of CT angiography (CTA) with different postprocessing for extracranial carotid artery in comparison with DSA. METHOD: One hundred patients were studied with standardized CTA. For postprocessing, MPR, MIP, and 3D reconstruction based on segmentation with upper and lower threshold were used. Intravascular density profiles were considered. All CTA studies were correlated with intra-arterial angiography. The degree and classification of stenoses was determined using the guidelines established by the NASCET collaborators. RESULTS: Measurement of stenosis was possible by MPR in 82.5%, by MIP in 85%, and 3D in 100%. Correct classification was found in 65.5% for MPR, 66% for MIP and 88.5% for 3D. The sensitivity for severe stenoses was 74% for MPR, 82% for MIP, and 93% for 3D. The specificity of these methods was 98%, 96%, and 97%, respectively. All carotid occlusions were correctly identified, no carotid artery was wrongly classified as occluded. CONCLUSIONS: CT angiography allows reliable examinations in carotid artery stenoses and occlusions. 3D reconstruction based on threshold segmentation is superior to MPR and MIP. In some circumstances, e.g., carotid occlusion, further investigation by invasive procedures is not necessary.

Angiography↗
PubMed1997

Aneurysms complicating inflammatory diseases in immunocompromised hosts: value of contrast-enhanced CT.

We studied the value of contrast-enhanced CT in the detection of aneurysms in immunocompromised patients suffering from inflammatory diseases eventually complicated by hemorrhage. Contrast-enhanced spiral CT was applied in three patients with immunocompromise due to chemotherapy, alcohol abuse or HIV. They suffered from invasive aspergillosis, chronic pancreatitis with pseudocyst formation, and acute pancreatitis together with HIV-associated lymphadenopathy. Complicating hemorrhage was present in two cases. Contrast-enhanced CT showed aneurysms complicating the underlying inflammatory disease in all three cases. The feeding vessels were identified and the patients with signs of bleeding were subsequently referred for angiography and embolization. Contrast-enhanced spiral CT is suited to detect aneurysms in immunocompromised patients suffering from inflammatory disease. It is recommended in these patients prior to angiography and intervention.

Adult↗
PubMed1997

Automatic detection of ground glass opacities on lung HRCT using multiple neural networks.

The purpose of this study was to implement neural networks and expert rules for the automatic detection of ground glass opacities (GG) on high-resolution computed tomography (HRCT). Different approaches using self-organizing neural nets as well as classifications of lung HRCT with and without the use of explicit textural parameters have been applied in preliminary studies. In the present study a hybrid network of three single nets and an expert rule was applied for the detection of GG on 120 HRCT scans from 20 patients suffering from different lung diseases. Single nets alone were not capable to reliably detect or exclude GG since the false-positive rate was greater than 100 % with regard to the area truly involved, more than 50 pixels throughout, and the true-positive rate was greater than 95 %. The hybrid network correctly classified 91 of 120 scans. Mild GG was false positive in 15 cases with less than 50 pixels, which was judged not clinically relevant. The pitfalls were: partial volume effects of bronchovascular bundles and the chest wall. Motion artefacts and diaphragm were responsible for 11 misclassifications. Hybrid networks represent a promising tool for an automatic pathology-detecting system. They are ready to use as a diagnostic assistant for detection, quantification and follow-up of ground glass opacities, and further applications are underway.

Expert Systems↗
PubMed1997

[Spiral CT and 3-D reconstruction of the tracheobronchial tree for the selection of the proper double-lumen tubes before individual lung ventilation].

PURPOSE: To assess the potential of 3-D spiral CT in the selection of adequate double-lumen tubes (DLT) for one-lung-ventilation. MATERIALS AND METHODS: 3-D spiral CT of eight different DLTs was performed with standardized acquisition parameters: section thickness 4 mm, table speed 6 mm/s, increment 3 mm and standardised thresholds, window settings and magnification zoom. The accuracy was confirmed by measuring 3-D objects on screen and original DLTs by vernier caliper. 3-D spiral CT was performed in 20 patients preoperatively with slice thickness 4-8 mm, pitch 1-1.5, increment 4-8 mm. To select the adequate DLT size the 3-D reconstructions of the patient's tracheobronchial tree and of the DLT were superimposed by templates or computer animation. The accuracy was controlled by endoscopic and clinical measurements. RESULTS: The accuracy of the 3 D spiral CT was nearly 0.1 mm. The superimposition with templates was easy and reliable. The 3-D spiral CT determined DLTs were shown to fit perfectly by clinical and endoscopic measurements in all cases. CONCLUSION: 3-D reconstructions of the tracheobronchial tree obtained from routine preoperative spiral CT scans allow for an easy and accurate individual selection of double-lumen tubes.

Adult↗