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Biomedical subjects

G Adam

Publications and source records attributed to G Adam.

At least 55 records · Page 3Linked to original sources
PubMed2004

Evaluation of balanced steady-state free precession (TrueFISP) and K-space segmented gradient echo sequences for 3D coronary MR angiography with navigator gating at 3 Tesla.

PURPOSE: To test the feasibility of k-space segmented gradient-echo pulse sequences for free-breathing coronary magnetic resonance angiography (cMRA) on a clinical 3T system. MATERIALS AND METHODS: T2-prepared, fat-suppressed turbo field echo (TFE, turboFLASH, SFPGR) as well as balanced TFE (b-TFE, trueFISP, FIESTA, segmented SSFP) sequences with navigator gating for prospective motion correction were applied on a 3T system equipped with a six-element phased-array cardiac coil. In 15 healthy volunteers, the right coronary artery (RCA) was examined with TFE and b-TFE sequences. Due to examination time limitations, the left coronary artery (LM/LAD) was examined exclusively with the TFE sequence in ten volunteers. Image quality was graded on a five point scale (0 = not visualized to 4 = excellent). The length, diameter and sharpness of the vessels and the contrast-to-noise ratios (CNR) were measured. RESULTS: 98 % of all major segments (proximal/middle/distal) of the RCA could be seen with the TFE sequence and 82 % with the b-TFE sequence. The image quality for the three segments was graded higher for the TFE sequence (2.7/2.7/1.5) than for the b-TFE sequence (1.9/1.6/0.9) with P: (< or = 0.001/< or = 0.004/< or = 0.056). The kappa of the interobserver variability was 0.75 for the TFE sequence and 0.8 for the b-TFE sequence. The measured vessel lengths were longer for the TFE sequence (95 +/- 22 mm) than for the b-TFE sequence (80 +/- 40 mm; P < or = 0.115). No significant changes (P < or = 0.074, P < or = 0.145) in diameter and vessel sharpness of the RCAs were observed between the TFE (2.4 +/- 0.3 mm, 60 % +/- 5) and b-TFE sequences (2.4 +/- 0.3 mm, 62 % +/- 6). The CNR was higher for the TFE sequence (10.1 +/- 3.4) than for the b-TFE sequence (6.6 +/- 2.1; P < or = 0.014). All ten main and proximal segments of the LM/LAD, which were examined exclusively with the TFE sequence, were visible with grade 2.5 and 2.1. The middle segment was visible in seven cases with grade 1.3. In three cases, the distal segment was visible with grade 0.5. The vessel length was 78 +/- 27 mm and the CNR 11.9 +/- 2.4. CONCLUSION: The conventional TFE technique has demonstrated good feasibility for cMRA at 3T. In its operational availability at 3T, the b-TFE sequence is inferior to the TFE sequence.

Adult↗
PubMed2004

[Multislice CT of the pelvis: dose reduction with regard to image quality].

PURPOSE: To optimize the examination protocols of multislice CT (MSCT) of the pelvis for dose reduction with regard to image quality. MATERIALS AND METHODS: MSCT of the pelvis was performed on 5 cadaver specimens with stepwise reduction of the tube current at 140 kV (250, 200, 150, 100, 75, 50, 35, 25 mAs) and 120 kV (50, 27 mAs). The remaining scan parameters like collimation (4 x 1 mm) and table speed of 4 mm per rotation remained unchanged. Axial sections and coronal reconstructions were used to evaluate cortex, trabecular structures, subjective image quality, image noise and detail detectability (pelvis and SI joint), with evaluation performed independently by four blinded experienced radiologists on a 5-point scale. Kappa coefficient, accuracy of the observers to sort the films with regard to dose reduction and mean scores of image evaluation were determined for statistical analysis. RESULTS: The deterioration of the image quality was most pronounced for all criteria between 75 mAs and 50 mAs at 140 kV. Good results with adequate image quality were obtained for detail detectability at 50 mAs and 140 kV (effective dose [E]: 3.3 mSv) and for the remaining four criteria at 75 mAs (E: 4.9 mSv). There was a moderate agreement between the four observers (kappa coefficient: 0.27). All observers were excellent in arranging the images according to the increasing dose reduction. CONCLUSIONS: Image quality of MSCT of the pelvis appears to be acceptable at 75 mAs and 140 kV with the dose reduced to 46% of the average value of the nation-wide survey of the German Roentgen Society in 1999 for this type of examination.

Acetabulum↗
PubMed2004

[Clinical relevance of computed tomography under emergency conditions--diagnostic accuracy, therapeutic consequences].

PURPOSE: To evaluate the diagnostic accuracy and therapeutic consequences of computed tomography performed on an emergency basis in a primary care hospital. MATERIAL AND METHODS: In 418 patients, 463 computed tomographies (thorax, abdomen, pelvis, spine, aorta, neck and extremities) were performed with-in 12 months, providing 999 diagnoses. The computed tomography diagnoses were retrospectively evaluated and correlated to surgery and discharge diagnoses. Therapeutical consequences were analyzed and allocated to a time period < 36 h (urgent) and > or = 36 - 72 h (elective). Average age was 49 (1 - 94) years (41% female and 59% male). Discharge diagnosis was defined as gold standard, provided that it was supported by clinical, blood chemical, diagnostic and possible surgical data. RESULTS: In 176 of 999 diagnoses (18%), the diagnoses were classified as "non-correlatable". Of the 823 correlated diagnoses, 431 were true positive, 14 false positive, 66 false negative and 312 true negative. Sensitivity, specificity and diagnostic accuracy of computed tomography was 87, 96 and 90%. Computed tomography had therapeutic consequences (surgery, drainage, puncture, reposition, thrombolytic therapy, chemotherapy, bronchoscopy, endoscopy, percutaneous transluminal angioplasty, coiling etc.) in 57% and no direct therapeutic interventions in 43%. Computed tomography excluded the suspected diagnosis in 36% and resulted in a conservative therapeutic regiment in 7%. Surgery was performed on 134 of the 418 patients (32%) who underwent computed tomography, with the surgery urgent in 71 (17%) and elective in 63 (15%) of the 418 patients. CONCLUSION: The high diagnostic accuracy and consecutive therapeutic consequences of computed tomography in establishing a precise, timely and reproducible diagnosis confirm its important role as primary diagnostic method on an emergency basis.

Adolescent↗
PubMed2004

[MRI of congenital heart disease in childhood].

MRI provides a non-invasive diagnostic tool complementing echocardiography on one hand, and showing advantages over echocardiography, on the other hand, especially after corrective procedures. The multiple different MRI sequences need to be adapted to examinations of children and patients with congenital heart disease (CHD), and can be used to detect morphologic changes, blood-flow in the heart and thoracic vessels and diastolic or systolic function of myocardium. Several factors determine the success of the examination of a complex congenital heart disease or a postoperative situs. Pediatric radiologists and radiologists experienced in congenital heart diseases have to work in close cooperation. Echocardiography should be performed before MRI. The results of prior examinations and the clinical history of the patients, including possible palliative or reconstructive operations, must be available before MRI to guide the planning of the examination. With a systematic segmental approach to the situs, to the atrial and ventricular morphology, and to the visceroatrial, atrioventricular and ventriculoarterial connections, most CHDs can be diagnosed correctly. With appropriate knowledge, MRI can also be performed quite accurately after complex operations and may avoid or delay invasive diagnostic procedures. The aim of this article is to impart knowledge, to mention problems and to provide guidance in the performance of cardiac MRI in patients with CHD.

Adolescent↗
PubMed2004

Radiation exposure during midfacial imaging using 4- and 16-slice computed tomography, cone beam computed tomography systems and conventional radiography.

OBJECTIVES: Radiation doses were determined to balance risks against usefulness of the different modalities available for the imaging of the facial skeleton. METHODS: An Alderson Rando Phantom, armed with lithium fluoride thermoluminescent dosemeters (TLDs) was exposed using a set of four conventional radiographs (orbital view, modified Waters view, orthopantomography, skull posterior--anterior 0 degrees ), two different cone beam computed tomography (CBCT) (NewTom 9000 and Siremobil Iso-C3D), and multislice computed tomography (CT) modalities (Somatom VolumeZoom and Somatom Sensation 16). TLDs from 14 well defined anatomical sites lying within the primary beam as well as the TLD corresponding to the thyroid gland were evaluated. RESULTS: Multislice CT showed the highest exposure values. Exposure levels of the CBCT systems lay between CT and conventional radiography. Dose measurement for the 16-slice CT revealed nearly the same radiation exposure as the 4-slice system when adapted examination protocols were used. CONCLUSIONS: Selection of the most appropriate imaging modality should be performed in view of the delivered doses, required image quality and information and the clinical circumstances.

Facial Bones↗
PubMed2003

An unusual large intergenic region in the S-RNA of a Bulgarian tomato spotted wilt virus isolate.

The complete S-RNA sequences of four Bulgarian and one German isolate of tomato spotted wilt tospovirus were determined. All isolates show a high conservation in their N proteins, while the NSs proteins and the intergenic regions (IGR) are more variable. The Bulgarian isolate 10HK96 has the largest S-RNA (3364 nucleotides) among tomato spotted wilt viruses reported so far. The enlargement is based on an insertion of 365 nts in the IGR that may have resulted from stuttering of the viral polymerase or non-homologous recombination. This insertion is present in the N protein gene subgenomic messenger, upstream of a proposed transcription termination signal.

Amino Acid Sequence↗
PubMed2003

[Multislice CT (MSCT) in the detection and classification of pelvic and acetabular fractures].

PURPOSE: To assess the usefulness of MSCT in the detection and classification of pelvic and acetabular fractures. MATERIALS AND METHODS: Routine radiographs and MSCT of the pelvis with sagittal and coronal multiplanar reconstruction (MPR) were performed in 50 patients with clinically suspected pelvic or acetabular fractures. One trauma surgeon and a radiologist evaluated routine radiographs and CT images in terms of fracture detection, classification and visualization. The AO classification of fractures was used. RESULTS: MSCT excluded a suspected fracture in 15 patients. In the remaining 35 patients, 19 anterior pelvic ring fractures, 10 anterior and posterior pelvic ring fractures, 8 acetabular fractures and 4 sacral fractures were diagnosed. All MSCT diagnoses were made from the axial source images. In 7 (17 %) patients, MSCT detected additional fractures (2 acetabular and 5 posterior pelvic ring fractures) not seen on conventional radiographs. In 3 other patients, MSCT changed the fracture classification by delineating the full extent of the fracture. MPR visualized 7 acetabular and 4 sacral fractures better than the axial source images. CONCLUSIONS: MSCT of the pelvis is needed for correct fracture detection and classification and has therapeutic consequences.

Acetabulum↗
PubMed2003

[MR imaging of lung ventilation with aerosolized gadolinium-chelates].

PURPOSE: To evaluate the feasibility of magnetic resonance assessment of human lung ventilation with aerosolized Gd-chelates in healthy volunteers. MATERIALS AND METHODS: Five healthy adults (mean age 37 years) were studied with a 1.5 T unit. The volunteers were instructed to inhale the aerosol through an airtight facial mask for 10 minutes. The aerosol was generated with a jet-type small particle nebulizer with attached heater. Ventilation imaging was performed using a respiration-gated dynamic T1-weighted turbo spin echo sequence (T(R) = 199 ms, T(E) = 8.5 ms, 12 signal averages, slice thickness 10 mm). Pulmonary signal intensity changes were calculated before and after nebulization. RESULTS: The investigation was successfully carried out in all volunteers. An acute or delayed allergic reaction to the aerosolized contrast medium was not observed. In 4 of 5 experiments (80 %), a homogeneous signal intensity increase was readily visualized with an average signal increase of 35 % after 10 minutes; in one experiment, the aerosol distribution was slightly heterogeneous. CONCLUSION: The results of the presented phase I clinical study demonstrate the feasibility of human ventilation imaging with aerosolized Gd-chelates for the first time. More trials with a larger number of healthy subjects and patients are needed before the clinical introduction of Gd-based ventilation MR imaging of the lungs.

Adult↗
PubMed2003

[MR-guided coil embolisation of renal arteries in an animal model].

PURPOSE: To test the feasibility of MR-guided coil embolization with passive visualization in an animal model. MATERIALS AND METHODS: All experiments were performed on a 1.5 T interventional MR-scanner (Gyroscan ACS-NT, Philips, Netherlands). A gradient echo sequence was combined with radial k-space acquisition and sliding window reconstruction technique to calculate the raw data with a specially designed back projector, yielding a frame rate of 20 images per second. The images were directly displayed on LCD-screens next to the MR scanner. A multipurpose catheter with dysprosium markers was placed into the renal arteries of two pigs under MR guidance, and a nitinol coil and platinum coil each were deployed. The position of the coils was verified with magnetic resonance angiography and conventional angiography. RESULTS: MR-guided catheterization of renal arteries with subsequent coil embolization was successfully carried out but the configuration of the coils could not be visualized on the MR images. CONCLUSION: MR-guided coil embolization of renal arteries is feasible. Exact guidance of coil deployment is not attainable with passive visualization.

Angiography, Digital Subtraction↗
PubMed2003

[Comparison of an edema-sensitive HASTE-TIRM sequence with delayed contrast enhancement in acute myocardial infarcts].

GOAL: Comparison between a fluid-sensitive (HASTE-TIRM)-sequence and delayed contrast-enhancement in patients with acute myocardial infarct (AMI) in MRI. MATERIAL AND METHODS: 32 patients with AMI were imaged 7 +/- 4 days after the time of infarction with a 1.5 T unit using a T2 HASTE-TIRM and a contrast-enhanced (CE) T1 turbo FLASH sequence. A threshold method (>2 SD in comparison with normal myocardium) was used to quantify the hyperintense zones in both sequences. The transmurality of the hyperintense regions was measured on a segmental basis. RESULTS: The hyperintense areas were larger on the HASTE-TIRM sequence with 29.6 +/- 13.2 % of the left ventricular (LV) area as compared to the CE-MRI with 19.2 +/- 10 % of the LV area (p < 0.0001). The measured transmurality was higher with the HASTE-TIRM sequence than with the CE-MRI (p < 0.0001). While the correlation between CE-MRI and peak creatine kinase (CK max) was good (r = 0.59, p < 0.001), no correlation was found between the HASTE-TIRM sequence and CK max (r = 0.29, p = ns). CONCLUSIONS: The peri-infarct edema can be depicted with a HASTE-TIRM sequence in addition to the non-viable infarct zone. The HASTE-TIRM sequence shows a higher transmurality of the hyperintense regions than the CE-MRI. The additional area depicted by the HASTE-TIRM sequence could represent functionally impaired but viable myocardium).

Adult↗
PubMed2003

[MRCP in primary sclerosing cholangitis].

PURPOSE: Evaluation of MR-cholangiopancreaticography (MRCP) for the diagnosis of primary sclerosing cholangitis (PSC) in correlation with endoscopic retrograde cholangiopancreaticography (ERCP) and in comparison to the diagnostic accuracy of various T2-weighted sequences. METHODS AND MATERIALS: Fifty-five patients (34 males, 21 females; mean age 40 years, range 16 to 65 years) with suspected PSC were examined in a 1.5 T MR unit (Magnetom Vision, Siemens, Erlangen), using breath-hold transverse and coronal HASTE, paracoronal RARE and thin-sliced HASTE (TS-HASTE) sequences. Applying a five-point-scale, two blinded investigators assessed the image quality for ROC analysis. Morphologic criteria of PSC were documented and correlated with ERCP, which served as the gold standard, and sensitivity, specificity and diagnostic accuracy were calculated. RESULTS: PSC was confirmed in 40 of 55 patients (ERCP 55 of 55, liver biopsy 37 of 55), with concomitant chronic ulcerative colitis in 27 and Crohn's disease in 6 of the 40 patients. Qualitative analysis of the image quality showed no significant difference between RARE, HASTE and thin-sliced HASTE sequences (3.4/3.5/3.2). The RARE sequence had the highest sensitivity (97 %), specificity (64 %) and accuracy (84 %) for the detection of PSC. The difference between HASTE and thin-sliced HASTE was statistically significant (p < 0.01). Of the 40 patients with confirmed PSC, 29 were followed by MRI and 3 underwent a liver transplantation within the follow-up period. A Klatskin tumor, which was misdiagnosed by MRCP, was diagnosed by brush biopsy in 1 of the 40 patients. Interobserver variability was adequate to good (kappa 0.4 to 0.7), depending on the chosen sequence. CONCLUSION: MRCP seems to be a reliable non-invasive imaging method to diagnose and follow PSC. The RARE sequence showed the highest diagnostic accuracy of the T2-weighted sequences.

Adolescent↗
PubMed2003

[MR-urography and CT-urography: principles, examination techniques, applications].

MR-urography (MRU) and CT-urography (CTU) provide refined imaging of the upper urinary tract not achievable with conventional intravenous urography (IVU). The traditional MR-urographic technique utilizes unenhanced, heavily T2 -weighted turbo spin-echo sequences for obtaining static fluid images of the urinary tract independent of the excretory renal function. T2 -weighted MR-urograms have proved to be excellent in visualizing the dilated urinary tract, even in non-excreting kidneys. In contrast, T1 -weighted MRU reflects the excretory renal function and displays the urine flow through the upper tract after renal excretion of an intravenously administered gadolinium chelate. The gadolinium-enhanced urine is visualized with fast T1 -weighted 3D-gradient-echo sequences. The combination of gadolinium and low-dose furosemide (5 - 10 mg) is the key for achieving a uniform distribution of gadolinium in the collecting system and for avoiding susceptibility artifacts (T2*-effects) in the urine. T1 -weighted excretory MRU provides impressive urograms of both non-dilated and obstructed collecting systems in patients with normal or moderately impaired renal function. Multislice-CT-urography (MS-CTU) is also an excretory urography like T1 -weighted MRU. Furthermore, MS-CTU can be combined with low-dose furosemide for accelerated passage of excreted contrast material obviating the need for abdominal compression. CT-urography is limited by its radiation burden and the nephrotoxicity of radiographic contrast media. Combining MRU or MS-CTU with conventional MRI or CT offers several applications, e.g., diagnosis of intrinsic and extrinsic tumors. Meanwhile, MRU has replaced IVU in pediatric uroradiology and is also recommended for the assessment of renal transplants. MS-CTU may provide valuable information in chronic urolithiasis, especially if associated with a distorted urinary tract anatomy. Both MRU and MS-CTU will play an important role in modern uroradiology.

Adolescent↗
PubMed2003

[Establishing a quality management system according to DIN EN ISO 9001:2000 in an academic radiological department].

PURPOSE: Establishing a quality management (QM) system according the guidelines of DIN EN ISO 9001:2000 in an academic radiological department. MATERIALS AND METHODS: To fulfill the requirements of an academic radiological department a quality management system according the guidelines of DIN EN ISO 9001 : 2000 has been established within one year. All important educational, research and patient care issues have been discussed in plenary sessions of all employees of the department twice a week. All core processes of the department have been documented as process instructions and standard operation procedures. RESULTS: Supported by the staff unit "quality assurance" of the university hospital, the QM system has been established during one year. Assisted by all parties of the department, obliging regulations have been established which are well accepted in the daily routine clinical work but also in research and education. The implementation of the QM system caused an additional work load. However, spreading the work load by a consequent responsibility assignment, it could be reduced effectively. CONCLUSION: The implementation of a QM system within the daily routine work of an academic radiological department is feasible. It allows the installation of generally accepted rules which regulate the principal tasks of research and education, and patient care.

Diagnostic Imaging↗
PubMed2003

[Transjugular liver biopsy: trucut or aspiration biopsy with modified Ross needles?].

PURPOSE: The transjugular liver biopsy is performed in patients with coagulopathy to evaluate diffuse hepatopathies. Using a jugular venous access, a liver vein is cannulated and a transvascular biopsy taken. The two techniques in use are the aspiration biopsy with a modified 15G or 16G Ross needle used for TIPS and the core biopsy with a Trucut needle. The sampling is quite similar for these techniques, but the costs are significantly different. This study is a meta-analysis of data published on both techniques to search for clinical evidence that justifies the use of the more expensive Trucut needle or that finds aspiration with the less expensive Ross needle equivalent. MATERIALS AND METHODS: The study includes 16 publications that were published between 1996 and 2002 and provided reliable information on technical success rate, complications and adequate histology. The data on 1374 procedures were analyzed, comprising 436 aspiration biopsies and 938 Trucut biopsies. RESULTS: Considering both procedures together, 95.9 % of the procedures were technically successful and 92.2% of the histologic samples diagnostically adequate. The technical success rate was 96.7 % for the Trucut-biopsies and 94.4 % for the aspiration biopsies. The corresponding rates of obtaining diagnostically adequate histologic samples were 92.5 % and 91.5 %, respectively. The complication rate of the entire population studied was 0.65 % without significant difference found between the two methods. With a list price of 420 Euro, the Trucut system costs about 200 Euro more than the Ross needle, which is listed as approximately 220 Euro. CONCLUSION: In the absence of any significant differences between both techniques for transjugular liver biopsies, economic considerations make the aspiration biopsy with the modified Ross needle preferable over the Trucut needle biopsy.

Biopsy, Needle↗
PubMed2003

[Radiation exposure of the head, midface and pelvis in multi-slice CT (MSCT): comparison with single-slice CT (SSCT)].

PURPOSE: Comparison of the radiation exposure of the head, midface and pelvis in multi-slice CT (MSCT) and single-slice CT (SSCT) for manufacturer-implemented standard protocols. MATERIALS AND METHODS: An anthropomorphic Alderson-Rando phantom equipped with LiF-thermoluminescent dosimeters in the head, neck and pelvic region was examined with different MSCT and SSCT protocols, and the measured organ doses were compared. RESULTS: In comparison with the SSCT protocols, the MSCT protocols delivered about twice the organ dose to the head and pelvis and about eight times the organ dose to the midface. The comparison indicates that the parameters (slice collimation, mAs, pitch) used for the MSCT protocols deliver increased radiation doses. CONCLUSIONS: The current standard MSCT protocols generally lead to higher organ doses to the head, midface and pelvis than the SSCT protocols, raising the question whether using the MSCT protocols recommended by the manufacturer can be justified. The dose parameters should be optimized to achieve an acceptable balance of dose reduction and adequate image quality.

Equipment Design↗