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M Völk

Publications and source records attributed to M Völk.

At least 19 recordsLinked to original sources
PubMed2006

[Diagnostic imaging of splenic disease].

Primary diseases of the spleen are relatively rare. More frequently, the spleen is involved secondarily in hematological, oncological, infectious, immunological, vascular, and other systemic diseases. The spleen is the most commonly injured organ in blunt abdominal trauma. Anatomical and physiological basics are explained, in addition to embryological facts with resulting abnormalities, such as accessory and "wandering" spleen, and polysplenia. The most frequent primary and secondary diseases of the spleen, including rare diagnoses, are presented and illustrated. Hemangioma represents the most common primary benign tumor, and lymphoma the most common primary malignant tumor of the spleen. Diagnostic imaging does not a allow safe differentiation between Hodgkin's and non-Hodgkin's lymphoma. One section deals with the clinical value and diagnostic workup of incidentally detected lesions. Simple cysts and calcifications need neither clarification nor a follow-up examination. Atypical cysts should be controlled within 3-6 months. Additional clarification using CT or MRT should be reserved for cases with a strong suspicion of clinically relevant primary or secondary splenic disease.

Diagnosis, Differential↗
PubMed2005

Intra-arterial magnetic resonance angiography of the iliac arteries: clinical experience using two different protocols.

PURPOSE: To assess the feasibility of intra-arterial magnetic resonance angiography (iaMRA) with two different protocols. MATERIAL AND METHODS: Twenty patients were prospectively examined after digital subtraction angiography. Contrast-enhanced iaMRA was performed using a 1.5T magnetic resonance imaging (MRI) system. Contrast agent (gadodiamide) was injected through a conventional angiography catheter placed in the abdominal aorta. The patients were randomized into two groups each comprising 10 patients. Group 1 was examined with a FLASH-3D (fast low-angle shot) sequence, allowing the center of the k-space to be acquired 0.5 s after initiation of the measurement. Group 2 was examined with the identical sequence, but the center of the k-space was acquired after 8.7 s. The increase in the intravascular signal intensity was determined and the diagnostic value of the angiograms was independently scored by 4 investigators using a 5-point scale. RESULTS: Nineteen of 20 MRAs were scored as diagnostic; only 1 was scored as non-diagnostic by 2 observers. The diagnostic value of the angiograms of group 2 was judged superior to that of group 1 owing to a more homogeneous intravascular contrast distribution. CONCLUSION: Intra-arterial MRA is feasible. The diagnostic value of angiograms using a flash sequence with center of the k-space acquisition after 8.7 s ranged from good to excellent. This sequence is appropriate for iaMRA of iliac arteries to support MR guided intervention.

Adult↗
PubMed2005

Comparison of magnetic resonance imaging colonography with conventional colonoscopy for the assessment of intestinal inflammation in patients with inflammatory bowel disease: a feasibility study.

AIM: Magnetic resonance imaging (MRI) based colonography represents a new imaging tool which has mainly been investigated for polyp screening. To evaluate this approach for patients with inflammatory bowel disease (IBD), we compared MRI based colonography with conventional colonoscopy for assessing the presence and extent of colonic inflammation. PATIENTS AND METHODS: In 22 consecutive patients with suspected or known IBD, MRI colonography was performed immediately before conventional colonoscopy. After bowel cleansing, a T1 positive contrast agent was applied rectally. In addition to T2 weighted sequences, T1 weighted two dimensional and three dimensional Flash acquisitions as well as volume rendered virtual endoscopy were performed. All images were evaluated with regard to typical MRI features of inflammation. The results were compared with colonoscopy findings. RESULTS: Distension and image quality was assessed as good to fair in 97.4% of all colonic segments. Only four of 154 segments were considered non-diagnostic. With colonoscopy serving as the gold standard, the sensitivity for correctly identifying inflammation on a per segment analysis of the colon was 31.6% for Crohn's disease (CD) and 58.8% for ulcerative colitis (UC). In CD, in most cases mild inflammation was not diagnosed by MRI while in UC even severe inflammation was not always depicted by MRI. Virtual endoscopy did not add any relevant information. CONCLUSION: MRI based colonography is not suitable for adequately assessing the extent of colonic inflammation in patients with IBD. Only severe colonic inflammation in patients with CD can be sufficiently visualised.

Adult↗
PubMed2004

Feasibility of MR-guided angioplasty of femoral artery stenoses using real-time imaging and intraarterial contrast-enhanced MR angiography.

PURPOSE: To show the feasibility of magnetic resonance (MR) for guided interventional therapy of femoral and popliteal artery stenoses with commercially available materials supported by MR real-time imaging and intraarterial MR angiography. MATERIALS AND METHODS: Three patients (1 female, 2male), suffering from symptomatic arterial occlusive disease with stenoses of the femoral (n = 2) or popliteal (n = 1) arteries were included. Intraarterial digital subtraction angiography was performed in each patient pre- and post-interventionally as standard of reference to quantify stenoses. The degree of the stenoses reached from 71 - 88 %. The MR images were acquired on a 1.5 T MR scanner (Magnetom Sonata; Siemens, Erlangen, Germany). For MR-angiography, a Flash 3D sequence was utilized following injection of 5 mL diluted gadodiamide (Omniscan; Amersham Buchler, Braunschweig, Germany) via the arterial access. Two maximum intensity projections (MIP) were used as road maps and localizer for the interactive positioning of a continuously running 2D-FLASH sequence with a temporal solution of 2 images per second. During the intervention, an MR compatible monitor provided the image display inside the scanner room. Safety guidelines were followed during imaging in the presence of a conductive guidewire. The lesion was crossed by a commercially available balloon catheter (Wanda, Boston Scientific; Ratingen, Germany), which was mounted on a 0.035" guidewire (Terumo; Leuven, Belgium). The visibility was provided by radiopaque markers embedded in the balloon and was improved by injection of 1 mL gadodiamide into the balloon. After dilation, the result was checked by intraarterial MR angiography and catheter angiography. RESULTS: The stenoses could be correctly localized by intraarterial MR angiography. There was complete correlation between intraarterial MR angiography and digital subtraction angiography. The combination of guidewire and balloon was visible and the balloon was placed correctly to cover the entire stenoses. Balloon dilation reduced the degree of stenosis about 45 % on average. A prolonged dilation was necessary in one patient due to a relevant residual stenosis, which was recognized by intraarterial MR angiography. CONCLUSION: MR-guided balloon dilatation of femoral and popliteal artery stenoses supported by real time imaging and intraarterial MR angiography is feasible with commercially available materials in the above mentioned way.

Aged↗
PubMed2004

[Reimbursement of radiologically guided vascular interventions within the DRG-system: what will change?].

PURPOSE: To evaluate reimbursement within the DRG-system ("diagnosis-related groups") compared with traditional reimbursement for interventional therapy of hospitalized patients. MATERIALS AND METHODS: Reimbursement calculation was prospectively analyzed in two respects for 30 consecutive patients who underwent percutaneous transluminal angioplasty (PTA) of the lower extremity arteries: (1) based on the DRG-system; (2) based on the traditional system. Additional evaluation was performed for five further, typical vascular procedures on the basis of real documentation and calculation data (stenting of the carotid artery, fibrinolytic therapy of basilar artery occlusion, stenting of renal artery stenosis, angioplasty of hemodialysis-shunt stenosis and aspiration thrombectomy of an infrapopliteal arterial occlusion). RESULTS: In our hospital, the introduction of the DRG system would reduce reimbursement by approximately 1100 euro per PTA patient. However, the other vascular radiological procedures can be expected to increase the payments by up to 4500 euro. CONCLUSION: To minimize imminent reduction of reimbursement for patients with peripheral PTA, complete documentation and economical patient management is mandatory. Payment may increase significantly for patients with the other reported vascular interventional procedures.

Adult↗
PubMed2004

[In vitro examination of the visibility of 11 stent catheters with real-time MR imaging].

PURPOSE: To evaluate artifacts of unexpended stents and to determine their exact position for MR-guided percutaneous transluminal angioplasty using real-time sequences. MATERIALS AND METHODS: By using an in vitro model, 11 unexpended stents - 9 nitinol, 1 stainless steel, and 1 cobalt alloy - were investigated by MR. Each stent was studied in a vessel-phantom filled with saline solution. Imaging was performed using five different real-time sequences: fast low angle shot (Flash 2D), fast imaging with steady precession (true FISP, FISP, interactive true FISP) and segmented echo planar imaging (seg. EPI). Artifacts of the introducer system and the stent were calculated by four blinded radiologists (scale: 1 - artifacts, making an excellent contribution to visualization; 2 - artifacts, making mainly a contribution to visualization; 3 - artifacts, making no contribution to visualization). Furthermore, an evaluation of the visibility of the tip of the stent-catheter and the proximal and distal end of the stent was performed using a four-point scale (very good visibility to invisible). RESULTS: The artifacts of the introducer system and stent were rated best for Omnilink (1.3 +/- 0.47), Wallstent (1.6 +/- 0.5), Jostent (1.65 +/- 0.5) and Luminexx (1.65 +/- 0.5). The differences between Omnilink and Jostent as well as Omnilink and Luminexx were significant. A very good to good visibility of the catheter tip was observed with a mean of 1.7 +/- 0.66 for Omnilink followed by the Jostent (1.95 +/- 0.69), by the Wallstent(R) (2.1 +/- 0.72) and by Luminexx (2.5 +/- 1.14). Differences between Omnilink and Luminexx were significant. The visibility of the proximal and distal end of the stent was evaluated as very good to good in 4 stent catheters (Omnilink, Wallstent, Jostent, Luminexx). However, the differences between Omnilink and Jostent as well as between Omnilink and Luminexx, and between Wallstent and Luminexx were significant. For all evaluation criteria, the segmented EPI and the interactive true FISP were rated to be most suitable for visualization. There were no significant differences in the evaluation of these two sequences. CONCLUSION: Omnilink stent, Jostent, Wallstent, and Luminexx stent are suitable for MR-angioplasty due to their good visibility in MR. Segmented EPI- and a newly developed interactive true FISP-sequence enable an effective visualization of these stent-catheters.

Alloys↗
PubMed2003

[Evaluation of radiological teaching programs in the Internet].

PURPOSE: Evaluation of web based training programs, which can be contacted from the homepages of radiological departments of German universities. MATERIAL AND METHOD: From June 2000 to January 2002 the 75 web based training programs of 57 providers,which can be contacted from the web pages of the radiological departments of German universities were evaluated in a prospective study. A medical student experienced in using the world wide web examined each training program three times in an interval of six months using the following criteria: availability of the web sites, target group, kind of training program, contents and structure and the technical solution. RESULTS: 51 of the 57 the homepages were fully available at each visit. 64 of the 75 web based training programs which could be connected from these sites were available at all three visits.One program was only partially available at one spot check. 8 of the 75 programs were designed for physicians and medically trained personal, 23 were made for medical students and 44 addressed both target groups (partially more than once mentioned). The number of the presented cases ranged between one single and 3700. In 31 of 75 training programs links to other teaching files were found. A complete presentation of cases was presented by 48 of the 75 web sites.5 of the 75 web sites offered physiological images for comparison. In 20 training programs the pathological changes were optically marked in the x-ray images. A logical and didactical structure was found in 24 teaching files, 14 gave the possibility to check the learning results. No provider made use of the possibility to pass credits to the students or physicians account with regard to official training programs. Multimedia techniques were used in 15 training programs.43 sites used data reduced preview images (thumbnails). The latest update of the site is mentioned in 55 of the 75 web sites. 19 of 57 providers had either no possibility of contact or did not answer to an e-mail. CONCLUSION: From the homepages of the departments of diagnostic radiology of German universities 75 teaching files can be contacted. There is a great variety in quantity and quality. Most sites offer collections of cases. A web based training program which is comparable in quality to a CD-ROM teaching program could not be found. No program used the possibility to give credits to the users with regard to official training programs.

Computer-Assisted Instruction↗
PubMed2002

[Evaluation of the Internet presence of diagnostic radiology units at German universities].

PURPOSE: Analyzing the availability and the contents of the internet homepages of the radiological departments of German universities. MATERIAL AND METHOD: In June and July 2001 the internet homepages of 36 radiological departments of German universities were evaluated in a study. A medical student experienced in using the world wide web examined the websites concerning the following criteria: research, teaching, informations for patients, clinical topics and general information. Additionally an evaluation of the technical standard of the presentation was performed. RESULTS: 31 of the 36 radiological departments presented a homepage in the world wide web. The subject research was presented by 29 institutes. Also 29 departments provided information concerning teaching in their presentations. In 24 cases informations especially for patients were given. In all topics there is a huge variety of the quality and quantity of the provided information throughout the different institutions. 21 homepages available without restriction during the study period; 3 were nearly completely under construction. Multimedia techniques were only used in 2 homepages. The structural hierarchy of the webpages was in the average only two or three levels. Only 6 providers presented an additional version of their homepage in english. CONCLUSION: In the moment the possibility of internet-presentation is sub-optimal used by the responsible persons of the radiological institutions. The main emphasis is on research and teaching. There is nearly no use of multimedial elements in the presentations. Only a minority of the homepages can be read by international viewers because of the lack of an english version of the pages.

Germany↗
PubMed2002

[Intraoperative spinal sonography].

AIM: Our intention was to examine the value of ultrasonography in the case of spinal stenosis caused by bony fragments or a tumour. Pre- and postoperative computed tomographies were compared with intraoperative ultrasound images. METHOD: Intraoperative sonography during spinal surgery was used after laminotomy or laminectomy in twenty patients with a stenosis of the spinal canal, caused by fragments or tumours. RESULTS: The posterior vertebral wall as well as tumour-tissue and myelon can be well distinguished by sonography. The dural sheath remains sonographically visible as a white line between tumour-tissue and myelon even in the case of immense compression. Small bony fragments or herniated disc material are also visible in the spinal canal. Thin surgical instruments can be guided into their target region under ultrasonographic control. When the restored epidural space can be demonstrated sonographically, this proves complete decompression of the spinal cord. CONCLUSION: Intraoperative ultrasound is an unrestricted repeatable real-time method for the surgeon to control the restoration and the width of the spinal canal. The extent of the operation depends on the results of the intraoperative sonography.

Constriction, Pathologic↗
PubMed2002

[Cost analysis of radiological interventional procedures and reimbursement within a clinic].

PURPOSE: Analysis of costs for vascular radiological interventions on a per patient basis and comparison with reimbursement based on GOA (Gebührenordnung für Arzte) and DKG-NT (Deutsche Krankenhausgesellschaft-Nebenkostentarif). MATERIAL AND METHODS: The ten procedures most frequently performed within 12 months were evaluated. Personnel costs were derived from precice costs per hour and estimated procedure time for each intervention. Costs for medical devices were included. Reimbursement based on GOA was calculated using the official conversion factor of 0.114 DM for each specific relative value unit and a multiplication factor of 1.0. The corresponding conversion factor for DKG-NT, determined by the DKG, was 0.168 DM. RESULTS: A total of 832 interventional procedures were included. Marked differences between calculated costs and reimbursement rates were found. Regarding the ten most frequently performed procedures, there was a deficit of 1.06 million DM according GOA data (factor 1.0) and 0.787 million DM according DKG-NT. The percentage of reimbursement was only 34.2 (GOA; factor 1.0) and 51.3 (DKG-NT), respectively. CONCLUSION: Reimbursement of radiological interventional procedures based on GOA and DKG-NT data is of limited value for economic controlling purposes within a hospital.

Angioplasty, Balloon↗
PubMed2002

MR imaging of cranial nerve lesions using six different high-resolution T1- and T2(*)-weighted 3D and 2D sequences.

PURPOSE: To find a suitable high-resolution MR protocol for the visualization of lesions of all 12 cranial nerves. MATERIAL AND METHODS: Thirty-eight pathologically changed cranial nerves (17 patients) were studied with MR imaging at 1.5 T using 3D T2*-weighted CISS, T1-weighted 3D MP-RAGE (without and with i.v. contrast medium), T2-weighted 3D TSE, T2-weighted 2D TSE and T1-weighted fat saturation 2D TSE sequences. Visibility of the 38 lesions of the 12 cranial nerves in each sequence was evaluated by consensus of two radiologists using an evaluation scale from 1 (excellently visible) to 4 (not visible). RESULTS: The 3D CISS sequence provided the best resolution of the cranial nerves and their lesions when surrounded by CSF. In nerves which were not surrounded by CSF, the 2D T1-weighted contrast-enhanced fat suppression technique was the best sequence. CONCLUSIONS: A combination of 3D CISS, the 2D T1-weighted fat suppressed sequence and a 3D contrast-enhanced MP-RAGE proved to be the most useful sequence to visualize all lesions of the cranial nerves. For the determination of enhancement, an additional 3D MP-RAGE sequence without contrast medium is required. This sequence is also very sensitive for the detection of hemorrhage.

Contrast Media↗
PubMed2002

Evaluation of arterial bypass grafts of the pelvic and lower extremities with gadolinium-enhanced magnetic resonance angiography: comparison with digital subtraction angiography.

RATIONALE AND OBJECTIVES: The aim of this study was to compare contrast-enhanced magnetic resonance angiography (CE MRA) with digital subtraction angiography (DSA) in the assessment of patency and stenoses in bypass grafts. METHODS: Fifteen patients were examined with both CE MRA and DSA. Fifteen bypass grafts were evaluated by four readers for potential stenosis in five locations. The stenoses were classified in five types: 1 (0% to 24% stenosis), 2 (25% to 49%), 3 (50% to 74%), 4 (75% to 99%), and 5 (occlusion). RESULTS: Using both techniques, 70 of 75 evaluated locations (93.3%) were classified identically. This included six stenoses < 50% and six stenoses > 50%, respectively. Four of five overestimations of stenoses were scaled in DSA as stenoses type 1. One stenosis was categorized as type 3 in DSA. Sensitivity for CE MRA for detecting stenoses >or= 25% was 100% and the specificity 90%. Interobserver agreement for all evaluations was 0.77 (Spearman rank correlation test). CONCLUSION: In the assessment of low-grade stenosis in bypass grafts, CE MRA overestimates stenoses slightly but yields good results in comparison with DSA.

Angiography, Digital Subtraction↗
PubMed2001

Frequency of benign hepatic lesions incidentally detected with contrast-enhanced thin-section portal venous phase spiral CT.

PURPOSE: To evaluate the frequency of benign focal hepatic lesions incidentally detected at contrast-enhanced thin-section portal venous phase spiral CT. MATERIAL AND METHODS: Between January 1998 and February 1999, contrast-enhanced hepatic spiral CT examinations were performed in 1,892 patients. Out of these, only 100 patients fulfilled the following inclusion criteria: No underlying malignant disease, no liver cirrhosis, no suspected or known focal liver lesions. Standardized spiral CT parameters were applied. All CT studies were reviewed retrospectively by one radiologist. Any focal lesion was recorded and classified. Lesion size and number were noted. RESULTS: A total of 108 hepatic lesions were reported in 33 out of 100 patients (80 cysts; 18 hemangiomas; 3 focal fatty infiltrations; 2 focal non-tumorous perfusion defects; 1 calcification; and 4 non-classified lesions). The average lesion size was 9.4 mm (< or =5 mm: n=40; 6-10 mm: n=30; 11-15 mm: n=28; >15 mm: n=10). CONCLUSION: Benign liver lesions are probably a frequent incidental finding at abdominal spiral CT.

Adult↗
PubMed2001

[Percutaneous transpapillary extraction of biliary calculi for symptomatic choledocholithiasisafter unsuccessful endoscopic treatment].

PURPOSE: Evaluation of a percutaneous transhepatic treatment of symptomatic choledocholithiasis in bile ducts that cannot be reached with the endoscope. METHODS: From January 1996 to August 2000 a transhepatic extraction of biliary calculus was performed in four patients. Endoscopic retrograde cholangiography (ERC) was not successful in any of the cases. Clinical symptoms were icterus in four cases, additional cholangitis or colics in two cases. First, a balloon dilation of the papilla was performed by a percutaneous transhepatic approach. For removal of bile duct stones, occlusion catheters and Dormia baskets were used. Technical success was defined as complete removal of bile duct stones. Clinical success was defined as normalization of cholestasis and inflammation parameters. In the follow-up an ultrasound examination was performed and blood samples were taken for control of cholestasis parameters. RESULTS: In all four cases treatment was technically and clinically successful. For complete removal of biliary calculus a second intervention was necessary in two cases. In each case an internal to external drainage was left over a mean of 7 days (3-13 days). In the mean follow-up of 30.5 months (6-50 months) all patients had persistent relief of symptoms. No further interventions were necessary. No complications were present. CONCLUSION: Percutaneous transpapillary extraction of biliary calculus is an effective alternative to surgery in patients with bile ducts, that cannot be reached with the endoscope.

Aged↗