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Biomedical subjects

K J Lehmann

Publications and source records attributed to K J Lehmann.

At least 19 recordsLinked to original sources
PubMed2000

Teleradiology requirements and aims in Germany and Europe: status at the beginning of 2000.

Specific radiological requirements have to be considered for realization of telemedicine. In this article the goals and requirements for an extensive implementation of teleradiology are defined from the radiological user's point of view. Necessary medical, legal and professional prerequisites for teleradiology are presented. Superior requirements, such as data security and privacy or standardization of communication, must be realized. Application specific requirements, e. g. quality and extent of teleradiological functions as well as technological alternatives, are discussed. Each project must be carefully planned in relation to one's own needs, extent of functions and system selection. Topics like legal acceptance of electronic documentation, reimbursement of teleradiology and liability must be clarified in the future.

Europe↗
PubMed2000

Evaluation of breath-hold contrast-enhanced 3D magnetic resonance angiography technique for imaging visceral abdominal arteries and veins.

RATIONALE AND OBJECTIVES: To evaluate the diagnostic value of breath-hold contrast-enhanced 3D magnetic resonance angiography (MRA) for assessment of the visceral abdominal arteries and veins in patients with suspected abdominal neoplasms. METHODS: Twenty-one patients underwent MR imaging on a 1.5 T unit using a body phased-array coil. MRA was performed with a 3D-FLASH sequence (TR 3.8 ms, TE 1.3 ms, flip angle 25 degrees, acquisition time 20 seconds), 8 to 12 seconds after an intravenous bolus injection of Gd-DTPA. The acquisition delay between the arterial and the portal venous phase was 12 seconds. The image quality and the degree of vascular involvement were evaluated using coronal source images and maximum intensity projection reconstructions. Diagnosis was confirmed by surgery/histology. RESULTS: Image quality was optimal in more than 85% of the patients (19/21 arterial phase and 17/21 portal venous phase). MRA correctly predicted vascular status in 20 of 21 patients (95%), with complete concordance between MRA results and surgical findings. In one patient with chronic pancreatitis, MRA demonstrated a false-positive finding that could not be confirmed surgically. CONCLUSIONS. Breath-hold contrast-enhanced 3D-MRA is a valuable technique for assessing visceral abdominal arteries and veins.

Abdomen↗
PubMed1999

First results of computerised tomographic angiography using electron beam tomography.

The aim of this study was to evaluate the suitability of electron beam tomography (EBT) with fast continuous volume scanning for CT angiography (CTA) in chest and abdomen. An Evolution XP EBT scanner with a new software version (12.34) was used. One hundred forty images per study can be acquired in 17 s using 3-mm collimation and overlapping image reconstruction. Study protocols for five different clinical applications of EBT CTA were established and evaluated. The EBT CTA technique was performed in 155 patients. High- and homogeneous density values were achieved along the whole course of the vessels; the mean density in the aorta was > 240 HU. Coeliac axis, superior and inferior mesenteric artery, renal and lumbar arteries were visualised in all cases. Maximum intensity projection and shaded surface display reconstruction demonstrated the relation between aneurysm and aortic branches very well due to an excellent resolution along the z-axis. In large scan volumes overlapping image reconstruction demonstrated better resolution along the z-axis than is available with helical CT. The EBT CTA technique proved to be very well suited excellent suitability for evaluation of pulmonary vessels. Compared with helical CT, EBT CTA offers a shorter scan time, which allows higher contrast enhancement in pulmonary vessels. The identification of intraluminal emboli and mural thrombi has improved. The EBT CTA technique is a very reliable tool for evaluation of aortic disease and pulmonary vessels.

Angiography↗
PubMed1999

[The role of electron beam CT in the diagnosis of acute pulmonary embolism--presenting a new examination protocol].

PURPOSE: To evaluate electron beam tomography in the detection of acute pulmonary embolism using a new acquisition protocol. MATERIALS AND METHODS: 65 patients underwent electron beam tomography (EBT) and v./p. scintigraphy. According to the inclusion criteria 46 patients participated in the study. Contrast enhancement and detectability of pulmonary arteries were scored on a 4 step scale for image quality. The results of prospective detection of pulmonary embolism were compared for both modalities (blinded reading). "Embolism", "questionable embolism" and "no embolism" were used as categories. RESULTS: 22/46 patients (48%) showed acute pulmonary embolism. EBT and scintigraphy were discordant in 24% of patients. In EBT 1 false positive and 1 false negative case occurred, scintigraphy demonstrated 2 false negative and 3 false positive cases. 6/9 patients with questionable findings in scintigraphy were correctly classified by EBT to a category "embolism" or "no embolism" as "suspected embolism", EBT displayed a sensitivity of 96.3% and a specificity of 94.7%. Scintigraphy evidenced a sensitivity of 93.7% and a specificity of 84.4%. CONCLUSIONS: EBT shows better results than scintigraphy for the detection of acute pulmonary emboli. The evaluated new acquisition protocol for EBT seems to be well suited. High vessel contrast and thin slices allow a reliable detection of segmental and subsegmental pulmonary arteries.

Acute Disease↗
PubMed1999

[The value of magnetic resonance tomography (MRT), magnetic resonance cholangiopancreatography (MRCP) and endoscopic retrograde cholangiopancreatography (ERCP) in the diagnosis of pancreatic tumors].

PURPOSE: To prospectively evaluate the role of MRI including MR cholangiopancreatography (MRCP) compared to endoscopic retrograde cholangiopancreatography (ERCP) in the diagnosis of pancreatic cancer. MATERIAL AND METHODS: ERCP and MRI including MRCP were performed in 52 patients with suspected pancreatic cancer. MRCP was obtained using a single-shot RARE technique. The results of axial images and MRCP were compared to concurrently performed ERCP examinations. The standards of reference were the surgical and pathological findings, respectively. Image quality of MRCP was assessed using a three-step-score (1 = good, 2 = fair, 3 = nondiagnostic). RESULTS: In 88% of the cases the MRCP was of good quality. Only in 4% was MRCP non-diagnostic. The combination of MRI and MRCP showed an overall accuracy of 88%, whereas the overall accuracies of MRCP alone and ERCP were 80%, and 85%, respectively. The positive predictive values of MRI/MRCP, MRCP alone, and ERCP were 91%, 85%, and 88%, respectively. CONCLUSION: For the detection of pancreatic cancer MRI including MRCP is comparable to ERCP and can be regarded as the method of choice in patients with suspected pancreatic cancer. ERCP is the procedure of choice in patients with contraindications to MRI and in patients in whom additional therapeutic procedures are performed.

Adenocarcinoma↗
PubMed1999

[Combined use of MRI and MR cholangiopancreatography and contrast enhanced dual phase 3-D MR angiography in diagnosis of pancreatic tumors: initial clinical results].

PURPOSE: To evaluate the accuracy of a non-invasive "all-in-one" staging MR method in patients with pancreatic tumors. MATERIAL AND METHODS: 46 patients were prospectively evaluated by a combined MR imaging protocol including breath-hold T1- and T2-weighted pulse sequence, MRCP using a breath-hold 2D-RARE sequence, and breath-hold gadolinium-enhanced dual-phase 3D-MR angiography. RESULTS: All pancreatic tumors were detected by the combination of cross-sectional imaging and MRCP. In spite of the use of MRCP, definitive differentiation between pancreatic carcinoma and chronic pancreatitis was not possible in 3 (6.5%) out of 46 cases. High quality 3D-MR angiograms were obtained in 43 (93.5%) cases. In 6 (13%) patients 3D-MRA showed an aberrant right hepatic artery. The overall accuracy of MRI in assessing extrapancreatic tumor spread, lymph node metastases, liver metastases, and vascular involvement was 95.7%, 80.4%, 93.5%, and 89.1%, respectively. CONCLUSION: Due to its high accuracy, the "all-in-one" MR protocol may become the most important modality after clinical examination and ultrasound in the diagnostic work-up for most patients with suspicion of pancreatic tumors.

Arteries↗
PubMed1999

Dose and image quality of electron-beam CT compared with spiral CT.

RATIONALE AND OBJECTIVES: To examine dose and image quality of electron-beam CT (EBCT) with continuous volume scan versus spiral CT. METHODS: An EBCT scanner was compared with a spiral CT (SCT) scanner. Three phantoms were used to measure low-contrast resolution, high-contrast resolution, slice width, and dose. RESULTS: The EBCT scans showed 30% lower high-contrast resolution for most settings. The dose was comparable to that of spiral CT with 3 mm collimation and 76%/106% higher with EBCT for 1.5 mm/6 mm collimation. Low-contrast resolution was comparable to that of spiral CT using 3 mm collimation, slightly worse for 1.5 mm, and bad for 6 mm EBCT collimation (four times higher dose to reach comparable contrast-to-noise ratio). CONCLUSIONS: Significant restrictions were found using EBCT with continuous volume scan. The authors found that 3 mm collimation can yield acceptable high-contrast resolution and good low-contrast resolution compared with spiral CT. The use of 6 mm or 1.5 mm collimation needs to be restricted to selected cases.

Evaluation Studies as Topic↗
PubMed1999

MR imaging of pancreatic lesions. Comparison of manganese-DPDP and gadolinium chelate.

RATIONALE AND OBJECTIVES: To compare manganese-DPDP-enhanced and gadolinium-DTPA-enhanced MR imaging in patients suspected of having pancreatic cancer. METHODS: Fifteen patients who underwent MR imaging for suspected pancreatic cancer and received gadolinium-DTPA took part in a clinical phase III trial in which the efficacy of manganese-DPDP for detection of pancreatic cancer was evaluated. T1-weighted gradient-echo (GRE) images with and without fat suppression were used. Signal-to-noise ratio and contrast-to-noise ratio were calculated before and after the administration of each contrast agent. Image quality was assessed using a four-step score; delineation of the normal pancreas was assessed by two readers in consensus. RESULTS: In terms of pancreatic signal-to-noise ratio, only gadolinium-DTPA-enhanced fat-suppressed and non-fat-suppressed GRE imaging showed a significant (P < 0.001) increase (72% and 61%, respectively). In the patients with a focal pancreatic lesion (n = 14), a significant increase in contrast-to-noise ratio was found only in manganese-DPDP-enhanced GRE imaging without (106%) and with (82%) fat saturation. Qualitative image analysis demonstrated a significant improvement of manganese-DPDP-enhanced fat-suppressed MR images in delineating the pancreatic parenchyma (P < 0.01) as well as pancreatic tumors (P < 0.01). CONCLUSIONS: T1-weighted manganese-DPDP-enhanced GRE imaging with fat saturation should be regarded as the most suitable combination for detecting a pancreatic lesion.

Adult↗
PubMed1999

Idiopathic myelofibrosis with extramedullary hematopoiesis in the kidneys.

Extramedullary hematopoiesis is a common finding in idiopathic myelofibrosis and is usually found in liver and spleen. We report on a patient with biopsy-proven myeloid metaplasia and fibrosis of the renal parenchyma as a rare cause of chronic renal failure. The renal biopsy specimen showed numerous infiltrates of hematopoietic cells expressing growth factors like M-CSF, GM-CSF, IL-1beta and PDGF while TGF-beta was not elevated. These findings suggest that hematopoietic growth factors play a key role in the pathogenesis of this condition causing proliferating fibrosis and enlargement of the kidneys.

Aged↗
PubMed1999

Economic analysis of teleradiology applications with KAMEDIN.

The teleradiology system KAMEDIN (German Telekom), installed on HP-Unix- and NT-Workstations, was evaluated in different scenarios and a cost-benefit-analysis was performed. CT examinations were transferred from a PACS workstation (GE) to KAMEDIN using DICOM-3 protocol. Teleconferences were realized with an intensive care unit by LAN, with a radiology department at 5 km. distance by ISDN, and with an on duty radiologist 22 km. away by ISDN. On average, 36 CT slices per patient were transferred. Overall costs (costs for hardware, software, support, ISDN-fees, and staff) were compared to possible cost reduction, mainly concerning transportation and films. These three scenarios could be realized during daily routine work. Differing in their amount of transportation cost reduction, two applications (intensive care unit, radiologist on duty) showed a break-even at 1817, respectively 528 teleconferences/year. Improvement of cost-effectiveness can be obtained on the conditions that existing hardware will be used and that the automatic data transfer will be improved. Combining all optimisation factors, the break-even decreased to a minimum of 167, respectively 77 teleconferences/year. The optimisation of patient management is an additional--but in this study, not yet counted--advantage of teleradiology.

Computer Communication Networks↗
PubMed1998

[Performance of electron-beam CT: continuous-volume-scan compared to spiral CT].

To compare patient dose and image quality of electron-beam-CT vs. spiral-CT by means of phantom measurements. An EBCT scanner (C-150 XP) and a spiral-CT scanner (GE HiSpeed Advantage) were used to scan three different phantoms. Administered dose, high contrast (HC) resolution, low contrast (LC) lesion detectability and the width of the radiation beams were measured. EBCT showed 25-35% lower HC resolution in comparison to spiral-CT. LC lesion detectability showed equivalent results for S/N vs. patient dose using 3 mm collimation with EBCT and spiral-CT, whereas spiral-CT was superior for 1.5 and 6 mm collimation. Dose measurements revealed a 2 fold higher patient dose using EBCT with 1.5 mm or 6 mm collimation compared to spiral-CT using equivalent scan parameters. No differences were seen using 3 mm collimation. Differences were due to insufficient beamside collimation of the EBCT. The use of EBCT with 6 mm collimation should be avoided, because of impaired performance. Using 3 mm collimation, EBCT showed comparable performance like state of the art spiral-CT despite lower HC resolution.

Algorithms↗
PubMed1998

[Electron-beam CT-angiography in abdominal aortic aneurysms. Initial results].

PURPOSE: To evaluate the suitability of ultrafast electron-beam tomography (EBT) for the investigation of abdominal aortic aneurysms using CTA. METHODS: Thirty-one patients with suspected abdominal aortic aneurysm were investigated with EBT using an Evolution XP scanner (Siemens, Erlangen) with the newest software version 12.34 with continuous volume scanning of 140 images in 17 s. Collimation was 3 mm, table increment 4 mm with overlapping image reconstruction every 2 mm, exposure time 200 ms (124 mAs), resulting in a scan-range of 28 cm. A quantity of 80 ml contrast material was administered (flow 4 ml/s). Visualization of the abdominal aorta and its branches was performed with MIPs and shaded surface display. Evaluation of image quality was based on a four-step classification scale (1 = good, 4 = insufficient) for the demonstration of the abdominal aorta and the visceral, renal and iliac arteries. RESULTS: All EBT examinations demonstrated high and homogeneous density values along the whole vessel course with a mean density value of 258.7 +/- 47.3 HU for the abdominal aorta and the iliac arteries. Quality evaluation for the vessel demonstration showed mean values between 1.22 and 1.57 for the abdominal aorta and the visceral, renal and iliac arteries. CONCLUSIONS: EBT with 140 slices and slice reconstruction every 2 mm offers a high z-axis resolution resulting in high-quality CT angiographies of the whole abdominal aorta and its branches.

Aged↗
PubMed1998

[Value of dual-phase-helical CT in the preoperative diagnosis of pancreatic cancer--a prospective study].

PURPOSE: A prospective study was performed to evaluate the accuracy of dual phase helical CT in suspected pancreatic cancer. METHODS: Within one year 136 patients underwent helical CT with arterial and portal venous scans after bolus tracking and NaCl bolus injection. Evidence of pancreatic cancer and assessment of resectability were recorded using a standardised protocol. Suspected benign disease was verified by follow-up examination and clinical data, suspected malignant disease was correlated with biopsy or surgery. RESULTS: For the detection of tumor the overall concordance was 92%, the sensitivity 98% and the specificity 70% (6 false positive, 1 false negative). Resectability was correctly assessed in 90% with a sensitivity of 92% and a specificity of 88% (4 false positive, 4 false negative). Vascular invasion was detected correctly in 91% (veins)-94% (arteries), lymph node invasion in 67% and liver metastasis in 94%. CONCLUSION: Dual phase helical CT is a very reliable tool in the assessment of resectability in pancreatic cancer.

Biopsy↗
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↗