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Biomedical subjects

A J Aschoff

Publications and source records attributed to A J Aschoff.

At least 19 recordsLinked to original sources
PubMed2005

[An unusual foreign body in the upper gastrointestinal tract causing nonspecific abdominal pain].

The risk of penetration of vena cava filters through the wall of the vena cava is estimated to be as high as 25%, although clinical symptoms are observed far less frequently in patients with this complication. Due to the close relationship between vena cava and duodenum, the latter can be injured by dislocated filters. We describe the presentation, evaluation, and treatment of a patient with a cava filter protruding into the duodenum, and we review the literature.

Abdominal Pain↗
PubMed2005

[GI hemorrhage with fulminant shock induced by jejunal gastrointestinal stromal tumor (GIST) coincident with duodenal neuroendocrine carcinoma (NET) + neurofibromatosis (NF) -- case report and review of the literature].

BACKGROUND: The incidence of neuroendocrine tumors (NET) and of gastrointestinal stromal tumors (GIST) is 0.5 and 1 - 2 in 100,000; the prevalence of neurofibromatosis is 1 in 3000 live births in Western countries. CASE REPORT: A 43-year-old white woman with a six-month history of meleana, paleness, vertigo and fatigue was not referred to any gastrointestinal doctor for diagnostic work-up. Finally, she collapsed and was admitted to hospital because of an acute gastrointestinal bleeding. Endoscopically the source of bleeding could not be localized while blood in the duodenum and proximal jejunum was demonstrable. The source of bleeding could not be identified by endoscopy, CT scan or angiography. The patient developed a fulminant gastrointestinal hemorrhage with hemoglobin levels below 3.5 g %. An emergency laparotomy and pylorus-preventing Whipple operation was performed. Pathological studies showed a GIST with 3.5 cm diameter of the proximal jejunum which was the source of bleeding. Coincidentally a neuroendocrine carcinoma of the duodenum was found. CONCLUSION: This case is the first presentation of the coincidence of a neuroendocrine carcinoma of the duodenum with a jejunal bleeding gastrointestinal stromal tumor in neurofibromatosis type1 which led to hemorrhagic shock. In neurofibromatosis -- even if non-symptomatic -- the increased incidence of tumor needs to be considered.

Adult↗
PubMed2005

[Local radiofrequency ablation of liver lesions--possibilities and limitations].

Radiofrequency ablation (RFA) is currently the most established technique for the local destruction of tumors within the liver. It is technically straightforward, can be repeated and combines a high efficiency in tissue destruction with a low to moderate incidence of complications. This review explains the principle of RFA and lists currently available systems. In addition, the rationale behind RFA is discussed, and an overview of clinical indications, results and complications is presented. One of the main problems in assessing the clinical value of RFA is the fact that no large and controlled randomized studies are available, while the number of ablations and treated tumor entities are steadily increasing. From a technical point of view, the major problem is the still limited volume of necrosis that is achievable. The indication for RFA has to be discussed as interdisciplinary. A complete tumor necrosis should be the aim of all ablations, with the exception of symptomatic metastases of neuroendocrine tumors. The value of additional chemotherapy to RFA is still unclear, especially in the treatment of liver metastases.

Animals↗
PubMed2005

A retrospective evaluation of patient acceptance of computed tomography colonography ("virtual colonoscopy") in comparison with conventional colonoscopy in an average risk screening population.

PURPOSE: To evaluate patient acceptance of computed tomography (CT) colonography compared with conventional colonoscopy by means of a self-assessed questionnaire. MATERIAL AND METHODS: Four-hundred-and-one patients with valid address information from our patient collective were preselected. Patient acceptance was evaluated retrospectively using a self-assessed questionnaire. The patients underwent CT colonography in our institution using 4x or 16x multi-detector row (MDR) CT. Two-hundred-and-forty-six patients returned a completed questionnaire, 157 of these indicating that they had undergone both virtual and conventional colonoscopy. RESULTS: One-hundred-and-twenty (76.4%) of the 157 patients would undergo another CT colonography if necessary, while only 14 patients would not. One-hundred-and-sixteen (73.9%) patients favored the actual examination procedure of CT colonography (P<0.0001), while only 6.4% preferred the conventional method. Preparation prior to CT colonography was experienced as more convenient than preparation prior to conventional colonoscopy (52.2% versus 14%). CONCLUSION: CT colonography was preferred in terms of both preparation and the actual procedure itself.

Adult↗
PubMed2004

[Abdominal trauma. Injury oriented management].

Successful management of abdominal trauma is characterized by efficient emergency-room work-up aimed at immediate determination of the prognosis by rational use of diagnostic techniques. The purposes of any conservative and/or surgical procedures are the preservation of organ function and low mortality and morbidity in multiply injured patients. State-of-the-art computed tomography with fast trauma scanning has become well accepted among patients with multiple trauma. Organ resections are becoming less common, except in the case of bowel injuries. The surgical treatment of hepatobiliary, splenic and large-vessel trauma is still challenging, as it involves the risk of life-threatening bleeding, while in the case of pancreatic and bowel injuries the challenge lies in the avoidance of septic complications. Interdisciplinary management of complex injuries with application of the "damage control" concept contributes to high-quality results in abdominal trauma.

Abdominal Injuries↗
PubMed2004

[CT colonography --"virtual colonoscopy"--a current review].

This article reviews published data regarding CT colonography and discusses both technical and medical aspects of its development over the last 10 years. Although colonography can be performed using MRI instead of CT, mainly CT aspects are dealt with. The technical development of CT to the current generation of Multi-detector-row-CT is explained, and the influence of various factors (slice thickness, dose, patient preparation, post processing) is discussed. The method has a high sensitivity and specificity as well as a high negative predictive value for the detection of polyps > or = 1 cm, but is currently still insufficient in the detection of polyps < 5 mm. It is a valid alternative after incomplete optical colonoscopy and an alternative in patients with "high-risk" for conventional endoscopy. In the future it may become an alternative for conventional endoscopy in screening programs for colorectal cancer.

Clinical Trials as Topic↗
PubMed2004

[Non-invasive, multi detector row (MDR) CT based computational fluid dynamics (CFD) analysis of hemodynamics in infrarenal abdominal aortic aneurysm (AAA) before and after endovascular repair].

PURPOSE: Simulation, description and analysis of dynamic pressure in infrarenal abdominal aortic aneurysms (AAA) before and after endovascular repair. MATERIALS AND METHODS: During March 1996 and May 2001, 13 patients with AAA underwent endovascular treatment. The MDR-CT scans of these patients were used for the non-invasive analysis of the hemodynamics in the aorta with CFD software before and after endovascular repair. One pre-interventional and three post-interventional CT scans were analyzed for each patient. RESULTS: Compared to the pre-interventional simulation, endovascular treatment led to an average dynamic pressure decrease of 1057 Pa in 10 of 13 patients. During the subsequent course, the median of the dynamic pressure decreased in 8 of 13 patients. Vulnerable regions initially identified as high-pressure regions, like the docking area or the second stent limb, adapted to the pressure in the surrounding tissue in the course of time. CONCLUSION: CFD-based blood flow simulation offers the opportunity to analyze dynamic pressure in AAA before and after endovascular repair and allows a prognostic statement as to the possible homogenization of the pressure in abdominal stent-grafts.

Aortic Aneurysm, Abdominal↗
PubMed2004

Numerical simulation of air temperature and airflow patterns in the human nose during expiration.

Recovery of heat and water during expiration is an important but not yet fully understood function of the nose. The presented study investigated cooling of the expiratory air for heat recovery within the human nose applying numerical simulation. A numerical simulation in a bilateral three-dimensional model of the human nose based on computed tomography was employed. Temperature distribution and airflow patterns during expiration were displayed. Cooling of the expiratory air primarily takes place in the areas of inferior and middle turbinate. Areas of the highest decrease in temperature are characterized by turbulent airflow with vortices of low velocity. Numerical results showed good concordance with experimental in vivo temperature measurements. Heating of inspired air not only depends on inspiration but also on expiration. Cooling the warm expiratory air may be regarded as an important factor for heat recovery. Furthermore, the results demonstrate the close relation between heat exchange and airflow patterns.

Exhalation↗
PubMed2004

Effect of iodine concentration of contrast media on contrast enhancement in multislice CT of the pancreas.

The purpose of this study was to determine the influence of two different iodine concentrations of the non-ionic contrast agent, Iomeprol, on contrast enhancement in multislice CT (MSCT) of the pancreas. To achieve this MSCT of the pancreas was performed in 50 patients (mean age 57+/-14 years) with suspected or known pancreatic tumours. The patients were randomly assigned to group A (n=25 patients) or group B (n=25 patients). There were no statistically significant differences in age, height or weight between the patients of the two groups. The contrast agent, Iomeprol, was injected with iodine concentrations of 300 mg ml(-1) in group A (130 ml, injection rate 5 ml s(-1)) and 400 mg ml(-1) in group B (98 ml, injection rate 5 ml s(-1)). Arterial and portal venous phase contrast enhancement (HU) of the vessels, organs, and pancreatic masses were measured and a qualitative image assessment was performed by two independent readers. In the arterial phase, Iomeprol 400 led to a significantly greater enhancement in the aorta, superior mesenteric artery, coeliac trunk, pancreas, pancreatic carcinomas, kidneys, spleen and wall of the small intestine than Iomeprol 300. Portal venous phase enhancement was significantly greater in the pancreas, pancreatic carcinomas, wall of the small intestine and portal vein with Iomeprol 400. The two independent readers considered Iomeprol 400 superior over Iomeprol 300 concerning technical quality, contribution of the contrast agent to the diagnostic value, and evaluability of vessels in the arterial phase. No differences were found for tumour delineation and evaluability of infiltration of organs adjacent to the pancreas between the two iodine concentrations. In conclusion the higher iodine concentration leads to a higher arterial phase contrast enhancement of large and small arteries in MSCT of the pancreas and therefore improves the evaluability of vessels in the arterial phase.

Adult↗
PubMed2004

Topography of cerebral atrophy in early Huntington's disease: a voxel based morphometric MRI study.

OBJECTIVES: To analyse grey matter changes in early stages of Huntington's disease using magnetic resonance imaging (MRI) and the technique of voxel based morphometry (VBM). METHODS: Forty four patients with a molecularly confirmed clinical diagnosis of Huntington's disease based on the presence of motor signs were included in the study. Patients were clinically rated using the Unified Huntington's Disease Rating Scale; all were in early clinical stages of the disease (that is, Shoulson stages I and II). High resolution volume rendering MRI scans (MP-RAGE) were acquired. MRI data were volumetrically analysed in comparison to an age matched normal database by VBM, using statistical parametric mapping (SPM99). RESULTS: In Huntington's disease, robust regional decreases in grey matter density (p<0.001, corrected for multiple comparisons)-that is, atrophy-were found bilaterally in striatal areas as well as in the hypothalamus and the opercular cortex, and unilaterally in the right paracentral lobule. The topography of striatal changes corresponded to the dorso-ventral gradient of neuronal loss described in neuropathological studies. Stratification according to clinical severity showed a more widespread involvement extending into the ventral aspects of the striatum in the group of more severely affected patients. CONCLUSIONS: The topography of cerebral volume changes associated with Huntington's disease can be mapped using VBM. It can be shown that cerebral grey matter changes co-vary with clinical severity and CAG repeat length.

Adult↗
PubMed2003

[ECG-triggered MDR-CT for the detection of pulmonary metastases].

PURPOSE: Comparison of multidetector-row CT (MDR-CT) of the chest with and without ECG triggering for the detection of pulmonary metastases. MATERIALS AND METHODS: Fifty patients with malignant tumors underwent CT of the chest. The unenhanced phase was performed with ECG-triggered MDR-CT and the contrast-enhanced phase with helical MDR-CT. The ECG-triggered and standard helical scans were interpreted in separate sessions, with the analysis determining the number and demarcation of the intrapulmonary nodules and the delineation of the mediastinal structure (rated 1 = excellent to 5 = poor). RESULTS: ECG-MDR-CT images detected 38 % more pulmonary nodules than MDR-CT. The detection rate for tumors < 5 mm was 64 % higher in ECG-triggered scans. The median demarcation rating of all pulmonary findings was 2 for ECG-MDR-CT and 3 for MDR-CT. The median demarcation rating of tumors < 5 mm was 3 for ECG-MDR-CT and 4 for MDR-CT. Mediastinal structures were better delineated by ECG-triggering. The median demarcation rating of the vessels and left bronchus was 2 for ECG-MDR-CT and 4 for MDR-CT. Detection rate and demarcation rating of pulmonary tumors and the delineation of mediastinal structures were not significant different for either CT technique. CONCLUSION: Our study indicates superiority for ECG-MDR-CT.

Adult↗
PubMed2002

Transient Global Amnesia. Evidence against vascular ischemic etiology from diffusion weighted imaging.

The etiology of Transient Global Amnesia (TGA) is still obscure. Diffusion-Weighted-Imaging (DWI) provides conflicting evidence concerning a possible vascular ischemic cause in mesiotemporal structures including the hippocampal region. The question remains open whether conflicting observations resulted from different observation times. DWI was performed at a time interval with known sensitivity for detection of ischemia. Ten patients (5 male, 5 female; mean age of 63 +/- 9, range 41-71 years) with typical TGA were investigated at an average delay of 18 hours (range 6 to 44 hours) between onset of symptoms and magnetic resonance imaging (transversal DW-, T1W- and T2W-MRI). Five patients received apparent-diffusion-coefficient (ADC)-mapping. Cerebrovascular studies (ECG, TTE and extra/transcranial dopplersonographic and duplexultrasonic investigation) and EEG were normal in all patients. DW-MRI-sequences and ADC-maps, if performed, were normal in all patients. Conventional T2W-MRI in 3 out of 10 patients showed microangiopathic subcortical changes and lacunar strokes of older origin. We conclude that TGA does not result from a vascular ischemic etiology in the majority of cases.

Adult↗
PubMed2002

[The contribution of MRI to the detection of endovascular aneurysm repair].

PURPOSE: Evaluation of MR-imaging in the follow-up of patients after endovascular repair of abdominal aortic aneurysms concerning detection of endoleaks. MATERIALS AND METHODS: In the postoperative follow-up after endovascular repair of aortic aneurysms, 10 consecutive patients (mean age: 68 years) were suspected to have an endoleak by helical CT and were scheduled for conventional angiography, preceded by supplemental MR-imaging to confirm or refute the diagnosis. The images of helical CT and MRI were evaluated by two independent readers concerning leak, feeding vessel and artifacts. RESULTS: The follow-up MRI was able to detect all endoleaks (type 1 endoleak, n = 7; type 2 endoleak, n = 3) compared to all but one detected by helical CT. Of the 10 patients with an endoleak, MR-angiography visualized the feeding vessel in 7 patients and CT in one patient. MRI did show fewer metal artifacts from the stent wire than CT. For the visualization of feeding vessels and endoleaks, MRA achieved statistically significant superiority. In a single case, helical-CT was not reliable because of strange metal artefacts after previous coil embolization. CONCLUSION: MRI is comparable to helical-CT in detecting endoleaks and superior to CT in demonstrating the anatomy of the feeding vessel after endovascular repair of aortic aneurysms. The major advantages are fewer artifacts after coil embolization and absent radiation exposure.

Aged↗
PubMed2001

Radial keyhole sequences for low field projection reconstruction interventional MRI.

Interventional magnetic resonance imaging (IMRI) is a rapidly emerging application for MRI in which diagnostic and therapeutic procedures are performed with MR image guidance. Real-time or near-real-time image acquisition and relative insensitivity to motion are essential for most intraoperative, therapeutic, and diagnostic procedures performed under MR guidance. The purpose of this work was to demonstrate the development and utility of two alternative rapid acquisition strategies during IMRI that are analogous to computed tomography fluoroscopy or keyhole MRI in a radial rather than rectilinear coordinate frame. The two strategies discussed here, interleaved projection reconstruction and continuous projection reconstruction, are compared and the feasibility of their application in experimental interventional applications is studied. J. Magn. Reson. Imaging 2001;13:142-151.

Animals↗
PubMed2001

How does alteration of hepatic blood flow affect liver perfusion and radiofrequency-induced thermal lesion size in rabbit liver?

The purpose of this study was to test the hypothesis that decreasing liver perfusion in rabbits results in an increase in thermal lesion size and that these effects can be accurately monitored using magnetic resonance imaging (MRI). We additionally tested the hypothesis that the increase in thermal lesion size would depend on the particular vessel or vessels occluded (hepatic artery, portal vein, or both). Using an Institutional Animal Care and Use Committee approved protocol, 20 New Zealand white rabbits were randomly assigned to four treatment groups (five in each group): control and ligation of portal vein (PV), hepatic artery (HA), or both PV and HA (HAPV). Surgical ligation of the appropriate vessel was performed under general anesthesia. Immediately after ligation, the rabbits were placed in a 0.2-T open MR system, and an 18-G copper radiofrequency (RF) electrode with a 2-cm exposed tip was inserted into the liver. RF was applied for 10 minutes with the tip temperature maintained at 90 degrees +/- 2 degrees C. Before and after ablation, perfusion data were obtained for 90 seconds using 30 3-second sequential single oblique-slice fast imaging with steady-state progression (FISP) acquisitions after injection of gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) via the inferior vena cava. Postablation scanning included axial and oblique turbo spin-echo (TSE) T2-weighted (T2w), STIR, and Gd-enhanced T1w sequences. Lesion size was determined perpendicular to the RF electrode using software calipers on the imager. The rabbits were sacrificed after completion of the post-therapy scans, and their livers were harvested for histologic analysis. The liver showed a mean increase in signal amplitude (SA) of 76% 24 seconds after Gd contrast injection in the control group. After contrast injection, the SA increased to a mean of only 66% in the group with ligated hepatic arteries, with no difference in the time to peak compared with the control group. No significant SA increase over baseline could be found in the groups with ligated PV or ligated PV and HA. T2-weighted images demonstrated the highest lesion-to-liver contrast-to-noise ratios (CNRs; mean -5.5) on postprocedure images, followed by STIR images (mean -2.2) in the control group. The lesions were poorly delineated on the Gd-enhanced images. Average maximum lesion sizes (mean +/- 95% confidence interval) were 22 +/- 4.3 mm after ligation of PV, 22 +/- 2.6 mm after ligation of both PV and HA, 14 +/- 2.0 mm after ligation of HA, and 13 +/- 1.9 mm in the control group. We accept the hypothesis that the diameter of the region of coagulation necrosis achieved by standardized RF ablation in the liver increases with reduced organ perfusion and that this effect can be accurately monitored using MRI. The major factor influencing the size of the coagulation area is the portal venous flow. Occlusion of the hepatic artery alone does not significantly increase lesion size. T2w sequences are best suited for postprocedure imaging due to the high lesion-to-liver CNR in rabbits with normal hepatic perfusion. J. Magn. Reson. Imaging 2001;13:57-63.

Animals↗
PubMed2001

A multielement RF coil for MRI guidance of interventional devices.

Accurate localization of minimally invasive devices is critical to the success of interventional procedures. Device orientation and tip position are two of the most important pieces of information needed to define device location for magnetic resonance imaging (MRI)-guided interventional procedures. While a single one-element micro coil incorporated into an interventional device has proven to be effective in some applications, it can only supply tip position information. However, multiple positions on the device are necessary to also determine its orientation. For this purpose, a novel single micro coil design with three separate winding elements that provides both the device orientation and tip position is described in this study. Definition of MR scan planes, by using the device orientation and the target tissue location, permits automatic tracking of the insertion of the device. Furthermore, devices that include this coil design are permitted to bend to a limited extent. This makes the micro coil design appropriate for many flexible interventional devices. Reliable near-real-time tracking of three points on an interventional device is demonstrated on a 0.2T MRI system with modest gradient performance. Phantom and in vivo animal experiments are used to demonstrate the utility of this new coil design.

Animals↗