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Biomedical subjects

K Oberholzer

Publications and source records attributed to K Oberholzer.

18 recordsLinked to original sources
PubMed2003

Rapid musculoskeletal magnetic resonance imaging using integrated parallel acquisition techniques (IPAT)--initial experiences.

PURPOSE: To investigate the feasibility of using multiple receiver coil elements for time saving integrated parallel imaging techniques (iPAT) in traumatic musculoskeletal disorders. MATERIAL AND METHODS: 6 patients with traumatic derangements of the knee, ankle and hip underwent MR imaging at 1.5 T. For signal detection of the knee and ankle, we used a 6-channel body array coil that was placed around the joints, for hip imaging two 4-channel body array coils and two elements of the spine array coil were combined for signal detection. All patients were investigated with a standard imaging protocol that mainly consisted of different turbo spin-echo sequences (PD-, T (2)-weighted TSE with and without fat suppression, STIR). All sequences were repeated with an integrated parallel acquisition technique (iPAT) using a modified sensitivity encoding (mSENSE) technique with an acceleration factor of 2. Overall image quality was subjectively assessed using a five-point scale as well as the ability for detection of pathologic findings. RESULTS: Regarding overall image quality, there were no significant differences between standard imaging and imaging using mSENSE. All pathologies (occult fracture, meniscal tear, torn and interpositioned Hoffa's cleft, cartilage damage) were detected by both techniques. iPAT led to a 48 % reduction of acquisition time compared with standard technique. Additionally, time savings with iPAT led to a decrease of pain-induced motion artifacts in two cases. CONCLUSION: In times of increasing cost pressure, iPAT using multiple coil elements seems to be an efficient and economic tool for fast musculoskeletal imaging with diagnostic performance comparable to conventional techniques.

Adolescent↗
PubMed2002

[Positron emission tomography for the preoperative staging of esophageal carcinoma].

BACKGROUND AND OBJECTIVE: Exact preoperative staging is a prerequisite for the indication as well as the choice of the appropriate operative technique for patients with esophageal carcinoma. In this prospective study we assessed whether positron emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) increases the accuracy of staging compared to standard computer tomography (CT) and leads to a different therapeutic approach. PATIENTS AND METHODS: 30 patients (25 men, 5 women, median age 63 years) with histologically identified carcinoma of the esophagus (n =29) and the cardia (n = 1), respectively, were studied. All patients underwent FDG-PET imaging of the neck, chest, and abdomen as well as CT of the chest and abdomen. Sensitivity, specificity and accuracy were calculated for FDG-PET and CT to evaluate the detection of histologically identified lymph node metastases and distant metastatic disease. RESULTS: FDG-PET showed higher specificity whereas the accuracy of the CT proved to be higher not only for the detection of abdominal lymph node metastases (67 % vs. 46 %), but also for lymph node metastases of the thorax (71 % vs. 50 %). Furthermore, the accuracy of the CT for the detection of blood-bone and lymphatic distant metastases was also higher than that of FDG-PET (72 % vs. 68 %). FDG-PET was more specific (100 % vs. 71 %) albeit less sensitive than CT-imaging (27 % vs. 73 %). CONCLUSION: In our study, FDG-PET did not increase the accuracy of standard staging (CT) in patients with carcinoma of the esophagus. Therefore, no new consequences resulted for the operative indication as well as therapeutic procedure. Due to the high costs involved with PET investigation, this form of staging is momentarily indicated mainly for use in clinical studies, and in cases where CT does not offer unequivocal results. Increase in sensitivity of the already advantageous whole-body FDG-PET imaging by means of tumor-affinitive radiopharmaceuticals as well as optimized apparatus resolution could lead to new indications for this staging procedure.

Carcinoma↗
PubMed2002

[The current value of percutaneous transhepatic biliary drainage].

Percutaneous transhepatic biliary drainage (PTBD) is a well established method in the treatment of obstructive jaundice. Major indications are malignant diseases. PTBD may be necessary preoperatively in cases with severe jaundice or cholangitis or as part of palliative treatment concepts. In the past, it has been proposed that a period of preoperative PTBD may improve the morbidity rates of surgery. Various studies could not prove this theory. The significance of preoperative PTBD has changed, as observed during a 15 years period in our own institution, the indications for preoperative PTBD have decreased by half. At present, the majority of treatments with PTBD are palliative (almost 70 % of all procedures). The diagnostic opportunities of the transhepatic approach (intraductal sonography, cholangioscopy, biopsy) are exploited only in few selected cases. Since the radiological approach ist considered to be invasive and related to serious complications most patients are being referred to endoscopic drainage first. Radiologists are consulted in complicated cases of jaundice and when endoscopic approaches have failed. The retrospective evaluation of more than 1000 procedures over a period of 16 years demonstrates good results with a low rate of serious complications. During the two observed periods of nine and seven years, respectively, there occurred complications like sepsis in 1.9 %/0.5 %, peritonitis in 0.5 %/0.7 %, severe bleeding in 0.5 %/1.5 %, procedure-related death in 0.8 %/0.7 %. The overall rate of serious complications was 5 %/3.4 %. These results are comparable to those of the endoscopic approach with a complication rate of 3.6-14 % and a mortality rate of 0.5 %.

Cholangiography↗
PubMed2002

[Cardiac MRI in suspected myocarditis].

PURPOSE: To evaluate the potential of ECG-gated breath-hold MRI in diagnosing acute myocarditis. MATERIAL AND METHODS: Cardiac MRI was performed on 21 consecutive patients with suspected myocarditis. ECG-gated breath-hold T2-weighted images with fat suppression were acquired in 3 standard views. T1-weighted imaging (FLASH) was performed 10 min after IV administration of Gd-DTPA. Laboratory data included creatine kinase, troponin T and serological tests, ECG findings and echocardiography. Imaging findings were retrospectively compared to the discharge diagnoses. Signal alterations were semiquantitatively classified. RESULTS: Acute myocarditis was diagnosed in 9 patients and cardiac sarcoidosis in 2 patients. Late enhancement was observed in 4 patients with acute myocarditis and in both patients with cardiac sarcoidosis. Semiquantitative evaluation revealed 9 true positive, 9 true negative, 1 false positive and 2 false negative results. CONCLUSION: Cardiac MRI has the potential to detect acute myocarditis and to diagnose cardiac sarcoidosis. Late enhancement of Gd-DTPA can be found in both viral myocarditis and cardiac sarcoidosis.

Acute Disease↗
PubMed2001

[Contrast-enhanced three-dimensional MR angiography of the carotid artery at 1.0 Tesla compared to i.a. DSA: is the method suitable for the diagnosis of carotid stenosis?].

PURPOSE: To evaluate the efficacy of three-dimensional, contrast-enhanced magnetic resonance angiography (CE-MRA) of the carotid artery with a 1.0 T system in comparison to intra-arterial conventional angiography (i.a.CA) for the assessment of carotid artery disease. METHOD: 55 patients with suspected stenosis of the carotid artery were examined with a 3 D-CE gradient-echo sequence on a 1.0 T scanner (TR/TE = 6.2/2.2 ms) and a selective DSA i.a. angiography. Image quality was evaluated by estimating the arterial contrast and venous enhancement. Morphological pathologies were registered for all arteries, stenoses of the internal carotid artery were graded by applying the NASCET criteria. RESULTS: Sensitivity and specificity of MRA in detecting high-grade stenosis (> or = 70%) and occlusion of the extracranial internal carotid artery were 97.7 and 94.0%. Therapeutic relevant misinterpretations were mostly based on overestimating the stenoses. CONCLUSION: The applied CE-MRA technique with a 1.0 T system is suitable for the assessment of carotid artery stenoses. In case of a therapeutically relevant stenosis revealed by MRA, however, verification of the diagnosis by i.a. CA is recommended.

Aged↗
PubMed2001

[Hydro-MRI for abdominal diagnostics in children].

PURPOSE: A clinical evaluation of hydro-MRI as an alternative method to barium studies in children with abdominal pain of unknown origin is presented. PATIENTS AND METHODS: 20 children with abdominal pain of unknown origin aged from 9 - 16 years were examined after oral bowel opacification using 1000 ml of 2.5 % mannitol solution with a 1.0 T MRI system. The investigation was done in 2 planes (coronal and axial) under breath-hold conditions. Imaging procedures included various sequences (T2W HASTE + FS, contrast-enhanced T1W FLASH FS). Suspicious findings in bowel segments and extra-intestinal changes were assessed. RESULTS: In 21/24 examinations the small bowel was completely visualized, in 15/24 cases colon segments were identified. An accurate assessment of the terminal ileum was not possible in 3/24 procedures. Breathing artefacts occurred in 3/24 examinations. Signs of Crohn's disease were found in 4 examinations, inflammatory changes of the ileum were detected in 3 cases. Inflammation of the colon was demonstrated in 2 children. Furthermore, pathological findings included constipation in one child and inflammation of the ileo-colic and mesenterial lymph nodes were found in another child. Extra-intestinal changes in 3 children were caused by ovarian cysts, and in one case by pleural effusion. In 4 examinations we detected ascites in the absence of other pathological findings. In 5 children there was no pathological correlation in the bowel or extra-intestinal region for the complaints. The children tolerated the hydro-MRI very well. There were no side effects using oral mannitol. CONCLUSION: Hydro-MRI is a valuable non-invasive method in the diagnosis of abdominal pain of unknown origin. In children it should be the method of choice because it further offers the advantage of the absence of ionizing radiation. Patient compliance is a prerequisite for this new examination. In our experience this requirement was met in children older than 9 years. Further studies should prove the necessity of conventional radiology following negative hydro-MRI.

Abdominal Pain↗
PubMed2000

[Contrast-enhanced MR angiography of abdominal vessels using a 1.0 T system].

PURPOSE: To evaluate the efficacy of breath-hold, three-dimensional, contrast-enhanced magnetic resonance angiography with a 1.0 T system for imaging the abdominal vessels in comparison to conventional arteriography (CA). METHODS: The abdominal aorta and visceral arteries were studied in 54 patients (60 examinations) on a 1.0 T scanner using an ultrafast gadolinium-enhanced gradient-echo sequence with the following parameters: TR/TE = 3.8/1.4 ms, flip angel 25 degrees, matrix 198 x 256, field 380-420 mm, pixel size 1.9 x 1.48 mm2, slice thickness 1.5-2.5 mm, acquisition time 22-26 sec. Individual circulation times were determined by a test bolus before each MR angiography. Conventional arteriography was performed in 23 of the 60 cases. RESULTS: 172 vessel segments of 23 MR angiographies were compared with CA, sensitivity and specificity were 96.4% and 97.2%. Over-estimations of stenoses or occlusions (n = 4) were caused by the limited resolution of small vessel branches and one stent artifact. CONCLUSION: Contrast-enhanced MR angiography of the abdominal vessels may replace invasive digital subtraction angiography in certain cases like perioperative or peri-interventional diagnostics. Imaging of small peripheral vessels remains a problem and limits use of the method.

Abdomen↗
PubMed2000

[Contrast media-enhanced 3D MR angiography of peripheral arteries using an automatic tracking technique at 1.0 Tesla].

PURPOSE: Assessment of the value of contrast-enhanced MR angiography (ceMRA) using an automatic tracking technique at 1.0 Tesla in comparison with digital subtraction angiography (DSA) of the pelvic and lower limb arteries. MATERIALS AND METHODS: In 15 patients with peripheral arterial occlusive disease a ceMRA (3D FLASH, TR/TE = 6.2/2.3 ms, Flip angle alpha = 30 degrees, Matrix 170 x 256) using a new automatic tracking technique was accomplished. The reference method was DSA. Twenty-one vessel segments of each patient were graded as normal, stenosed (> 50%) or occluded. Image material was evaluated independently by two radiologists. RESULTS: In comparison, the interobserver agreement showed a good (Cohen's kappa > 71%) concordance for 38% of the 21 vessel segments, a moderate (Cohen's kappa between 31%-70%) for 21% and a poor (Cohen's kappa < 30%) concordance for 38% of the 21 vessel segments. Regarding the MRA and DSA results, a good concordance was achieved for 62% of the 21 vessel segments, 14% showed a moderate concordance and 24% only a poor concordance. CONCLUSION: In patients with peripheral arterial occlusive disease ceMRA using an automatic tracking technique enables a reliable evaluation of pelvis and upper limb arteries at 1.0 Tesla. However, a reliable evaluation of lower limb arteries is not yet possible.

Aged↗
PubMed2000

Hydro-MRI in Crohn's disease: appraisal of disease activity.

RATIONALE AND OBJECTIVES: To appraise the value of hydro-MRI in the assessment of activity in Crohn's disease. METHODS: After bowel opacification with 1000 mL of an orally administered 2.5% mannitol solution was achieved, axial and coronal breath-hold sequences (T2-weighted half-Fourier acquisition single-shot turbo spin-echo sequences with or without fat saturation, dynamic T1-weighted fast low-angle shot sequences, and contrast-enhanced T1-weighted fast low-angle shot with fat saturation sequences) were acquired in 82 patients with proved Crohn's disease at 1.0 T. Enhancement of the bowel wall was correlated with other MRI findings, with the Crohn's disease activity index (CDAI), and with levels of C-reactive protein (CRP). RESULTS: In Crohn's disease, contrast enhancement of the affected bowel wall was markedly increased in comparison with the normal bowel wall (+80% +/- 22% versus +43% +/- 12%; P = 3 x 10(-15)). Positive correlations could be established between the increase in bowel wall enhancement and many other MRI findings. Between the increase in bowel wall enhancement and the CDAI, only a poor correlation was found (r = 0.25, P = 0.02). There was no statistical correlation between the increase in bowel wall enhancement and CRP. CONCLUSIONS: Hydro-MRI seems to be superior to the CDAI and CRP for the registration of Crohn's disease activity. In particular, differentiation between an active and an inactive (scarred) stenosis, which is crucial for the choice of therapeutic procedures, seems to be more reliable by the interpretation of several morphological and functional parameters on hydro-MRI than by the use of CDAI and CRP.

Adult↗
PubMed1999

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

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

Angiography, Digital Subtraction↗
PubMed1998

[The "nutcracker syndrome" of the renal vein (superior mesenteric artery syndrome) as the cause of gastrointestinal complaints].

HISTORY AND CLINICAL FINDINGS: Since the age of 19 a now 22-year-old man had complained of intermittent abdominal pain, irregular stools and paroxysmal tachycardia. The only preceding illness had been a single episode of iron-deficiency anemia. A laparoscopy, done 8 months after the onset of symptoms, had revealed an inflamed Meckel's diverticulum which was surgically removed. After transient improvement the symptoms recurred 5 months postoperatively. On admission to clarify the cause of the symptoms he had discrete abdominal pain on pressure, but physical examination was otherwise unremarkable. INVESTIGATIONS: Routine biochemical tests and endoscopy were normal. Abdominal computed tomography was suspicious of severe narrowing of the left renal artery by a crossing superior mesenteric artery. As a result the left testicular vein and the peripelvic venous network were markedly dilated by retrograde congestion, strongly suggesting the "nutcracker syndrome" of obstruction of the left renal vein. This diagnosis was confirmed by selective renal phlebography and pressure measurement. TREATMENT AND COURSE: The vascular anomaly was corrected surgically by reimplanting the left renal vein into the inferior vena cava 3-4 cm further caudally. The patients has been completely symptom-free since then. CONCLUSIONS: The nutcracker-syndrome is a rare cause of hematuria. The coexistence of this anomaly with gastrointestinal symptoms has not been previously described, but it is likely that congestion of the splanchnic veins by obstruction of the left renal vein was at least partly responsible for them, in view of the postoperative relief.

Abdominal Pain↗
PubMed1998

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

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

Adolescent↗
PubMed1997

Pneumomediastinum and pneumopericardium due to malignant subcarinal lymphadenopathy: CT demonstration.

A 52-year-old man had been treated for oral cancer T3 N0 M0 by radical surgery, neck dissection on the right and cervical irradiation (60 Gy). Two months after therapy he presented with dysphagia and hemoptysis. Admission chest X-ray revealed a pneumopericardium. It was caused by a bronchomediastinal fistula due to necrotic metastatic lymph nodes as shown by CT, which also revealed a concomitant pneumomediastinum. The patient died 10 days later from pneumonia. The CT findings were confirmed at autopsy. We conclude that malignant mediastinal lymphadenopathy is a potential cause of pneumopericardium and pneumomediastinum.

Bronchial Fistula↗
PubMed1997

[Clinical relevance of CT of paranasal sinuses prior to bone marrow transplantation].

PURPOSE: To investigate the clinical necessity of CT of the paranasal sinuses before bone marrow or peripheral blood stem cell transplantation. PATIENTS AND METHODS: 80 patients with malignant disease underwent coronal CT of the paranasal sinuses prior to transplantation to exclude sinusitis. RESULTS: CT revealed sinusitis requesting therapy in 17/80 patients (21%). Patients with leukaemia and non-Hodgkin lymphoma were significantly more affected. Chronic sinusitis was found in two patients, mucosal swelling not requesting therapy in 22, and normal findings in 39. CONCLUSION: CT of the paranasal sinuses is advised in patients suffering haemoblastoses with an increased risk of infectious complications during the transplantation phase, because pathological findings can be expected in 21% of the patients. Diagnosis and therapy of an infectious focus within the paranasal sinuses is especially important prior to allogenous bone marrow transplantation.

Adolescent↗
PubMed1996

[Radiologically assisted percutaneous gastro-/enterostomy--a retrospective analysis of 90 procedures].

PURPOSE: To analyse retrospectively the indications, technique and results of radiologically induced gastrostomies or enterostomies. PATIENTS AND METHOD: Radiologically assisted gastrostomies or enterostomies were induced in 90 patients, mostly with high grade obstructions due to head and neck tumours or oesophageal tumours. 19/90 patients had had previous resection of the oesophagus or gastric operations. RESULTS: A catheter was successfully introduced in all patients. In 11/90 patients this was followed by a two-stage procedure. In 16/90 patients puncture was performed under CT control because of some anatomical peculiarity. Serious complication occurred in 9/90 patients but in only one was surgery necessary. There were no deaths resulting from the procedure but mortality after 30 days was 6.7%. CONCLUSION: Radiologically assisted gastrostomies or enterostomies are a reliable and effective form of treatment even amongst difficult patients. The results and complications are comparable to those from endoscopic procedures.

Adult↗