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F Schweden

Publications and source records attributed to F Schweden.

At least 19 recordsLinked to original sources
PubMed2003

[Percutaneous radiofrequency ablation of liver tumors using the LeVeen 4 cm array probe].

BACKGROUND: The purpose of this study was to evaluate safety and efficacy of a radiofrequency ablation system in clinical practice. METHODS: In 35 patients (age 63,9 +/- 12,6 years, range 22 - 83) a total of 65 liver tumors were percutaneously treated using a 200 watt radiofrequency generator and a LeVeen 4 cm array probe (RF3000, Boston Scientific). The interventions were performed under CT guidance in local anaesthesia and sedation. Adapted to the tumor size, the LeVeen Probe was repositioned during the procedure with an additional safety margin of 1 cm. Primary tumors were colorectal in 22, and mamma tumors (n = 4), zystic pancreas tumors (n = 2), gastric cancer (n = 1), zystadenocarcinoma of the liver (n = 1), lung cancer (n = 1), gastrointestinal stroma tumor (n = 1), duodenal carcinoma (n = 1), cholangiocellular carcinoma (n = 1) and hepatocellular carcinoma (n = 1). Post interventional control and follow-up was performed with multislice-CT (collimation 2.5 mm, unenhanced and contrast enhanced, arterial and portal filling) at 4 weeks, and every three months. RESULTS: One to 4 metastases were treated per patient during one or up to 4 procedure sessions. Mean lesion size was 2,3 +/- 1,2 cm (range 0,2 to 7,0). The corresponding size of the necrosis achieved was 4,6 +/- 1,4 cm (range 2,0 - 8,2). Primary technical success with complete tumor ablation was reached in 60 of 65 lesions. In 4 cases two treatment sessions were necessary in order to achieve the intended results. In one case the procedure was aborted because of a close relationship between lesion and right colon. 63 tumors were treated in sedation and local anesthesia. General anesthesia was necessary in two cases, in one who refused intervention in sedation, and in another case with insufficient analgetic effect. Morbidity was 9.2 %: Bleeding complications (n = 3, one arterial bleeding from the ablation tract, two intrahepatic bleedings with extrahepatic hematoma) were confirmed by selective angiography of the hepatic artery and were treated with coil embolisation of the respective segmental arteries. One case with subcapsular tumor ablation suffered from a large subcapsular hematoma requiring a blood transfusion. In one case with a subphrenic location of the metastasis, the needle electrode had passed the costophrenic recessus and resulted in an hematothorax. This patient was treated by pleural drainage for two days. One patient suffered from fever up to 39 degrees C and inflammation of the biliary tract and received a cholecystectomy 22 days post interventionally. There was no peri interventional mortality. Mean follow-up is 5,6 +/- 3,3 months (range 0 to 13). 21 of 35 patients showed no evidence of tumor recurrence. One case is scheduled for a second treatment session for complete tumor ablation. 13 of 35 patients suffered from tumor recurrence, either local recurrences and/or new metastases. At the sites of prior RF-ablation 9 local recurrences were detected in 7 patients, two cases with isolated local recurrences and 5 cases with local recurrences and new metastases. 6 Patients showed no evidence for local recurrences but new metastases. In these 11 cases a total of 37 metastases were found at new locations. In three patients tumor recurrence was treated by means of a second RF-ablation. The remaining 10 patients received chemotherapy. CONCLUSION: RF-ablation can be performed in local anaesthesia and sedation with low peri interventional morbidity and mortality. Using the LeVeen probe and a 200 watt generator, appropriate necroses can be achieved. CT follow-up is required every three months because of the tumor recurrence rate and reinterventions may be required.

Adult↗
PubMed2002

[Chronic thromboembolic pulmonary hypertension: diagnostic impact of Multislice-CT and selective Pulmonary-DSA].

PURPOSE: To evaluate the diagnostic impact of multislice-CT and selective pulmonary DSA in chronic thromboembolic pulmonary hypertension (CTEPH). METHODS: 994 vessel segments of 14 consecutive patients with CTEPH were investigated with multislice-CT (slice thickness 3 mm, collimation 2.5 mm, reconstruction intervall 2 mm) and selective pulmonary DSA (posterior-anterior, 45 degrees oblique, and lateral projection. Analysis was performed by 2 investigators independently for CT and DSA. Diagnostic criteria were occlusions and non-occlusive changes like webs and bands, irregularities of the vessel wall, diameter reduction and thromboembolic depositions at different levels from central pulmonary arteries to subsegmental arteries. Reference diagnosis was made by synopsis of CT and DSA by consensus. RESULTS: Concerning patency CT and DSA showed concordant findings overall in 88.9 %, 92.9 % for segmental arteries and 85.4 % for subsegmental arteries. Concerning any thromboembolic changes, multislice-CT was significantly inferior to selective DSA (concordance 67.0 % overall, 70.4 % for segments and 63.6 % for subsegments). Non-occlusive changes of the vessels were significantly underdiagnosed by CT (concordance of CT versus DSA: 23.1 %). CONCLUSION: Multislice-CT and selective pulmonary DSA are equivalent for diagnosis of vessel occlusions at the level of segmental and subsegmental arteries. However, for visualisation of the non-occlusive thromboembolic changes of the vessel wall selective pulmonary DSA is still superior compared to multislice-CT. Multislice-CT and selective pulmonary DSA are complementary tools for diagnosis and treatment planning of chronic thromboembolic pulmonary hypertension (CTEPH).

Angiography, Digital Subtraction↗
PubMed2001

Identification of unknown dead bodies by X-ray image comparison of the skull using the X-ray simulation program FoXSIS.

The aim of the study was to improve the objectivity of X-ray image comparison for the identification of unknown dead individuals. CT-data were collected for 30 macerated skulls. An already presented computer program which uses CT data to establish virtual X-ray images was used to obtain X-rays with different beam angulations simulating rotation, dorsal flexion, and ventral flexion. Specific parameters were measured on the simulated images. The frontal sinus reveals the highest variability not only between the individual skulls but also within an individual skull in different positions. The most consistent parameters with respect to different positions were the skull breadth, the biorbital breadth and the bizygomatic breadth. In a blind study, three out of 24 skulls could clearly be identified just by measured distances although the positions were different and unknown to the investigator. The dimensions of the frontal sinus do not correlate with the other skull parameters (analysis of covariance). Based on the presented results, we propose a method that will calculate the probability of identity. The presented results demonstrate that the comparison of X-ray images can be undertaken in an objective way by quantifying the probability of identity even when the comparative images were made under different conditions.

Adult↗
PubMed1998

Pulmonary nodules: detection with low-dose vs conventional-dose spiral CT.

The purpose of the study was the evaluation of low-dose spiral CT in the detection and assessment of contours of pulmonary nodules. In a prospective investigation 71 consecutive chest CT examinations were acquired both at 30 and 200 mA. Films were interpreted independently by two radiologists. According to the size, nodules were divided into four categories: </= 3, 4-5, 6-10, and > 10 mm; nodule shape was registered. With both protocols, 240 nodules were detected. The correlation coefficient for both methods was 0.89. Discrepancies were found most frequently in nodules near to pulmonary vessels. Nodule size estimation did not differ more than one size category. Eight spiculated nodules were identified by both techniques. Low-dose spiral CT of the chest has a high sensitivity in the detection of pulmonary nodules. If clinical circumstances require dose minimization, low-dose spiral CT may be advocated as an alternative screening method to conventional dose spiral CT.

Adolescent↗
PubMed1998

[Dosimetry in conventional and spiral CT in 8 spiral CT scanners of the latest generation].

PURPOSE: Measurement of scanner-dependent differences in PCTDI for conventional and spiral CT and evaluation of PCTDI/100 mAs in eight spiral CT scanners of the latest generation. METHODS: Central PCTDI was evaluated in a PMMA phantom for different scan lengths of conventional and spiral CT in four scanners. Central and peripheral PCTDI/100 mAs, average dose and the quotient between peripheral and central PCTDI/100 mAs were measured with a dedicated 10 cm ionisation chamber positioned within a PMMA phantom using the parameters of a standardised liver protocol and a high-resolution inner ear protocol for eight spiral CT scanners. RESULTS: Depending on scanner type and scan length PCTDI for the spiral mode is in a range between 11.3% higher and 4.3% lower than that for the conventional mode. PCTDI/100 mAs varies considerably between different CT scanners. For the standardised liver protocol PCTDI/100 mAs varies up to a factor of 2, for the inner ear protocol up to a factor of 4. CONCLUSION: Even in comparable modern CT scanners there are considerable protocol and scanner-dependent differences in PCTDI/100 mAs. The values for his own scanner should be known to each CT user so that he can develop a dose-optimised, patient and problem-orientated examination strategy.

Ear, Inner↗
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

Radiation dose and image quality in spiral computed tomography: multicentre evaluation at six institutions.

The purpose of this study was to evaluate the correlation of radiation dose with image quality in spiral CT. Seven clinical protocols were measured in six different radiological departments provided with four different types of high specification spiral CT scanners. Central and surface absorbed doses were measured in acrylic. The practical CT dose index (PCTDI) was calculated for seven clinical examination protocols and one standardized protocol using identical parameters on four different spiral CT scanners with a dedicated ionization chamber inserted into PMMA phantoms. For low contrast measurements, a cylindrical three-dimensional (3D) phantom (different sized spheres of defined contrast) was used. Image noise was measured with a cylindrical water phantom and high contrast resolution with a Perspex hole phantom. Image quality phantoms were scanned using the parameters of the clinical protocols. Images were randomized, blinded and read by six radiologists (one from each institution). PCTDI values for four different scanners varied up to a factor between 1.5 (centre) and 2.2 (surface) for the standardized protocol. A greater degree of variation was observed for seven clinical examination protocols of the six radiological departments. For example, PCTDI varied up to a factor between 1.7 (cerebrum protocol) and 8.3 (abdomen paediatric protocol). Low contrast resolution correlates closely with dose. An improvement in detection from 8 mm to 4 mm sized spheres needs approximately a ten-fold increase in dose. Noise shows a moderate correlation with PCTDI. High contrast resolution of clinical protocols is independent of PCTDI within a certain range. Differences in modern CT scanner technology seem to be of less importance for radiation exposure than selection of protocol parameters in different radiological institutes. Future discussion on guidelines regarding optimal (patient adapted) tube current for clinical protocols is desirable.

Brain↗
PubMed1998

[MRI in typical and atypical aortic dissection].

PURPOSE: To determine the value of MRI in typical and atypical aortic dissections. METHODS: MRI investigations on 16 patients with aortic dissections were analysed retrospectively; for 8 patients CT investigations carried out at almost the same time were available for comparison. RESULTS: In all cases the diagnosis of aortic dissection was possible from MRI and CT. If a dissection membrane and a double lumen were present these were detected in all patients by both methods. In three patients with atypical dissections, only an asymmetrical abnormal wall thickening as sole sign for the presence of an aortic dissection was seen. A differentiation between true and false lumen was possible in 16 of 17 MRI investigations and in 5 of 8 CT investigations on the basis of differing blood flow velocities or, respectively, the detection of a thrombus in the false lumen. The relationship of the dissection membrane to the large aortic branches as well as the determination of the branch vessel origin with regard to true or false lumen could be evaluated better with MRI than with CT. CONCLUSIONS: Thus MRI has a significant role in the diagnosis and follow-up of aortic dissections. The advantage in comparison to the alternative spiral CT technique is, in addition to the absence of radiation exposure, the better analysis of the extent of the dissection as a result of the multi-planar slice orientation (especially in the region of the aortic arch and the arch vessel origins) without the necessity to administer iodine-containing contrast media.

Adult↗
PubMed1998

[Clinical relevance of thoracic CT in intensive care and emergency medicine].

PURPOSE: Evaluation of the impact, indications, and therapeutic efficiency of chest CT in intensive-care and emergency patients. MATERIALS AND METHODS: Retrospective assessment of 741 consecutive chest CT, or which 74% were acquired in the spiral technique, in intensive-care and emergency patients. Chest CT scans and respective clinical data were compared. RESULTS: 16% of all examinations were indicated to resolve questions arising from the chest radiogram, 10% to confirm or exclude pulmonary embolisms and 10% to confirm or exclude aortic dissection. In 10% a focus of infection was sought. 57% of all CT examinations had an impact on therapy, in 7% further diagnostic tests were prompted. Among a total of 588 clinical decisions based upon chest CT, the most frequent therapeutic conclusions consisted in: minimally invasive CT guided interventions in 17%. A new drug was administered in 13%, surgical intervention was performed in 13%, bed-side interventions such as insertion of a drainage tube in 13%, and a given pharmacological therapy was continued in 11%. CONCLUSION: Chest CT has a strong impact on patient management in emergency and critical-care medicine. CT guided interventions are frequently used in critically-ill patients. The introduction of the spiral technique has led to important new CT indications in the field of non-invasive vascular diagnosis, namely the assessment of pulmonary embolism and aortic dissection.

Critical Care↗
PubMed1997

[Whole body spiral CT in primary diagnosis of patients with multiple trauma in emergency situations].

PURPOSE: The aim of this study was to evaluate the role of a fast whole body helical CT scanner for primary diagnosis in trauma patients. METHODS: 27 severely injured patients (9 women, 18 men; mean age 43 years) were first examined with a helical CT scanner allowing for digital radiograms up to a length of 1024 mm and continuous helical scans of up to 70 seconds (slice thickness 3 to 10 mm, pitch factor up to 2). The primary CT diagnosis was verified either by x-ray after the CT examination or during the subsequent days, by abdominal ultrasound, by additional CT scans in the following days, and by clinical follow-up. RESULTS: CT showed all clinically relevant injuries of the head, spine, chest, abdomen and pelvis. The diagnosis and classification of vertebral fractures was performed immediately. 4% of the fractures of the extremities and the ribs were not seen primarily. 6% of the injuries were outside the CT scan field. CONCLUSION: Helical CT is a reliable and fast method to obtain vital information and to improve management planning in severely injured patients. It reduces the number of conventional x-ray examinations. In certain cases, additional x-rays of extremity fractures may be required.

Abdominal Injuries↗
PubMed1997

[The algorithm of imaging diagnostics of pulmonary embolism: is it time for a new definition?].

Acute pulmonary embolism (PE) is an increasing and underdiagnosed cause of mortality and morbidity in hospitalised patients: pulmonary hypertension based on chronic pulmonary embolism is an uncommon, but severe and surgically curable complication. Since clinical signs might be silent or unspecific, both acute and chronic PE require imaging methods for diagnosis and treatment planning. Chest radiographic findings are usually non-specific. Scintigraphy provides a high sensitivity for PE, but lacks anatomic resolution and sufficient specificity. Pulmonary angiography, albeit accurate, is an invasive procedure associated with low but still not negligible morbidity and mortality. Hence, non-invasive methods offer advantages. Spiral CT, for example, is most reliable in the diagnosis of acute and chronic PE: Such fast CT techniques provide a non-invasive means to detect and differentiate acute emboli and organised thrombi, as well as perfusion abnormalities and other concomitant findings. MRI offers both morphological and functional information on lung perfusion and right heart function, but its image quality still needs improvement to be comparable with CT. Thus, while MRI must still be tested in clinical studies. CT is recommended as a screening method in acute and chronic pulmonary embolism.

Algorithms↗
PubMed1997

[Computerized tomography of the epiphyseal union of the medial clavicle: an auxiliary method of age determination during adolescence and the 3d decade of life?].

PURPOSE: To establish a reference population for the stages of epiphyseal union of the medical clavicle determined by CT. MATERIAL AND METHODS: Retrospectively, the thoracic CTs of patients under 30 years of age were reevaluated. Basic conditions were the lack of a bone development disorder and a sufficient assessment of the medial clavicle in a bone window setting. The stages of epiphyseal union were categorized as follows: Stage 1 refers to nonunion without ossification of the epiphysis, Stage 2 to nonunion with a separate and ossified epiphysis, Stage 3 to partial, and Stage 4 to complete union. RESULTS: Up to now, 279 individuals could be included in the study. Stage 1 was observed till age 16, Stage 2 occurred from ages 13 through 22, Stage 3 was found from ages 16 through 26. Stage 4 was first noted at age 22, and in 100% of the sample at age 27. CONCLUSIONS: CT is well suitable to determine the stages of epiphyseal union of the medial clavicle. It may become a generally accepted method of age identification during adolescence and the 3rd decade of life. The presented data serve as a reference population at least for white Europeans.

Adolescent↗
PubMed1997

[CT angiography in arterial occlusive disease: comparison of 3 rendering techniques].

PURPOSE: To evaluate different rendering techniques of CT data for the assessment of long vessel segments in peripheral vascular occlusive disease. MATERIAL AND METHODS: 40 CT angiograms (aortoiliac: n = 20, leg arteries: n = 20) were viewed using three different rendering techniques: 1, maximum intensity projection (MIP); 2, volume rendering (VR); 3, shaded surface display (SSD). CT angiograms were obtained in 6 or 8 projections. Axial cross-section images were analysed using an interactive cine mode. Intraarterial DSA was the standard in all cases. RESULTS: The sensitivities for the diagnosis of occlusive disease were 100% (cross-section images), 94% (MIP), 91% (VR) and 93% (SSD). The specificities were 100%, 99%, 99% and 99%, respectively. For the accurate grading of high-grade (> 75%) stenoses, the sensitivities were 85% (cross-section images), 62% (MIP), 44% (VR) and 35% (SSD). Specificity was 99% for all techniques. CONCLUSIONS: CTA is accurate in occlusive disease. Interactive viewing of cross-section images is the most accurate technique. MIP is superior to VR in the imaging of high-grade stenoses because contrast-to-noise ratio is high and thresholding is not necessary.

Angiography, Digital Subtraction↗
PubMed1997

Spiral CT of pulmonary hypertension and chronic thromboembolism.

Pulmonary hypertension caused by chronic pulmonary embolism (PE) represents an uncommon, but severe and surgically curable complication of recurrent acute embolism. Because clinical signs might be silent or nonspecific, chronic PE requires imaging methods for diagnosis and treatment planning. Chest radiographic findings are usually nonspecific. Scintigraphy provides a high sensitivity for PE, but lacks anatomic resolution and sufficient specificity. Pulmonary angiography, albeit accurate, is an invasive procedure associated with low but still considerable morbidity and mortality. Thus, noninvasive methods are required. Most reliably in the diagnosis of acute and chronic PE, fast computed tomography (CT) techniques like spiral CT provide noninvasive means to detect and differentiate organized mural thrombi, as well as perfusion abnormalities and concomitant findings. Magnetic resonance imaging offers morphologic as well as functional information on lung perfusion and right heart function, but image quality needs improvement to be comparable with spiral CT. Thus, although spiral CT is recommended as the screening method for acute and chronic PE, magnetic resonance imaging might be the method of the future.

Chronic Disease↗
PubMed1997

CT angiography versus intraarterial digital subtraction angiography for assessment of aortoiliac occlusive disease.

OBJECTIVE: The purpose of this study was to evaluate the accuracy of CT angiography (CTA) with a single helical acquisition for assessment of stenoses and occlusions of the iliac arteries. SUBJECTS AND METHODS: In our prospective study, intraarterial digital subtraction angiography and IV CTA were performed from the suprarenal aorta to below the femoral bifurcation in 30 patients with vascular occlusive disease. Maximum-intensity-projection images in multiple views were also obtained. The accuracy of CTA with and without analysis of axial images was determined. RESULTS: Sensitivity and specificity of CTA were 100% for iliac artery occlusions with a confidence interval 85-100% and 97-100%, respectively. When axial scans were interpreted, 14 of 15 high-grade (> 75%) stenoses were recognized. Sensitivity and specificity of CTA were 93% (range, 68-100%) and 99% (range, 97-100%), respectively. When maximum intensity projections alone were analyzed, sensitivity for the diagnosis of 15 high-grade stenoses was only 53% (range, 27-79%) because calcified plaques obscured six stenoses. CONCLUSIONS: CTA accurately reveals iliac artery occlusions. Observers of CT angiograms may overlook short stenoses in rare instances. Calcified plaques limit the use of maximum-intensity-projection images.

Angiography↗
PubMed1997

Non invasive evaluation of the inflammatory activity in sarcoidosis with high-resolution computed tomography.

PURPOSE: The value of high resolution computed tomography (HR-CT) in the recognition of pathologic changes of the lung parenchyma, especially in the diagnosis of sarcoidosis, is well established. The importance of these findings in regard to the inflammatory activity is not sufficiently documented, also because a direct histologic correlation is seldom possible. METHOD: In a prospective study twenty-one patients with suspected or known sarcoidosis were evaluated. The diagnostic work up comprised the clinical examination, lung function tests, the radiological evaluation, including GH-CT, and bronchoscopy for bronchoalveolar lavage (BAL) and transbronchial biopsy. RESULTS: The comparison of the HR-CT findings, like pathologic appearance of the bronchovascular bundle and intraparenchymal nodules, with serologic and BAL-parameters yielded high correlation coefficients with the total cell count in BAL and sIL-2R, and moderate correlations with the lavage lymphocyte count and the activity markers, like T4/T8 ratio, IL-2R and HLA-DR expression. CONCLUSION: As a non invasive method, HR-CT depicts pathologic findings of the lung parenchyma which are associated with the inflammatory activity of sarcoidosis.

Adult↗