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Biomedical subjects

N Hosten

Publications and source records attributed to N Hosten.

At least 37 records · Page 2Linked to original sources
PubMed2001

Intraocular metastases: differential diagnosis from uveal melanomas with high-resolution MRI using a surface coil.

Magnetic resonance imaging with dedicated surface coils plays a pivotal role in differential diagnosis and staging of intraocular tumors. The purpose of this study was to establish MRI criteria for the differential diagnosis of uveal melanomas and intraocular metastases. In a prospective study 44 eyes in 36 patients with intraocular metastases and 200 patients with uveal melanomas were investigated with MRI using a 1.5-T scanner and a 5-cm surface coil. Both quantitative and qualitative evaluation of the resulting images was performed. The MR signal intensities typically expected for metastases (slightly hyperintense on non-contrast T1-weighted images and hypointense on T2-weighted images compared to the vitreous body) were seen in only 23.1%. The typical melanoma signal of either moderate or strong hyperintensity on T1-weighted images and hypointensity on T2-weighted images was seen in 69.4% of the proven melanomas. Contrast enhancement was observed in both metastases and melanomas. Morphological differences between metastases and melanomas were detected in tumor size, shape, position, frequency of retinal detachment, and homogeneity of the tumor. Differentiation between intraocular metastases and uveal melanoma is limited by overlap of signal intensities. Some improvement is achieved with morphologic criteria.

Adult↗
PubMed2001

Quantification of morphologic and hemodynamic severity of coarctation of the aorta by magnetic resonance imaging.

OBJECTIVE: As the morpholgic severity of coarctation of the aorta is difficult to assess, especially after previous repair, the value of the technique of multiplanar reconstruction of magnetic resonance imaging data to achieve a 3-dimensional reconstruction of the aortic arch was evaluated and compared to hemodynamic measurements. METHODS AND RESULTS: We performed 30 examinations in 27 patients aged from 6 to 54 years, with a mean of 21 years, by magnetic resonance imaging using a 1.5Tesla scanner with a standard body coil. Measurements of flow across the coarctation were performed using phase shift velocity mapping, and peak velocity was calculated at the site of stenosis. Aortic cross-sectional area before, at, and beyond the stenosis was reconstructed 3-dimensionally to calculate a percentage degree of stenosis. Morphologic severity of stenosis was correlated to invasively assessed hemodynamic gradients and morphologic data from biplane angiography in 23 patients. Among the 30 examinations, 24 patients had been previously treated by either surgery, in 17 patients, or balloon dilation, while 6 had native coarctation. 3-dimensional reconstruction was possible in all and better delineated the anatomy concerning the hemodynamic relevance of stenoses even as compared with biplane angiography. The correlation between severity of narrowing assessed by diameter measurements in the biplane angiography and 2-dimensional magnetic resonance imaging was r = 0.94, and multiplanar reformation with 2-dimensional magnetic resonance imaging was r = 0.87 with a tendency of higher grading with the 3-dimensional technique (p = 0.0001). The correlation of 2-dimensional magnetic resonance imaging with invasively measured hemodynamic gradients was r = 0.67 versus r = 0.74 for the areas assessed by multiplanar reformation, indicating that the hemodynamic relevance of a morphological approach to evaluate the degree of a stenosis should better be assessed 3-dimensionally. CONCLUSIONS: The 3-dimensional reconstruction of the morphologic severity of coarctation offers additional information over conventional imaging especially in patients with kinking, complex geometry, or collaterals, in whom hemodynamic measurements can become unreliable.

Adolescent↗
PubMed2001

Intraoperative computed tomography with the mobile CT Tomoscan M during surgical treatment of orbital fractures.

Up to now it has only been possible to monitor the alignment of orbital floor fractures postoperatively with a computed tomography (CT) examination with coronal sectioning. If this showed an incorrect positioning, renewed surgery and anaesthetics were often required. The purpose of this study was the implementation and definition of the spectrum of indications for intraoperative CT examinations while keeping patient radiation exposure to a minimum. Thirty-two orbital fracture cases were examined pre- and intraoperatively using the mobile computer tomograph Tomoscan M in coronal sectioning. In this patient collective, 12 cases showed an isolated orbital floor fracture and twenty cases an orbital floor fracture associated with a zygomatic fracture. The technical prerequisite for these examinations was the construction of a suitable radiolucent operating table which permitted coronal sections to be made with the CT-Gantry tilted. The authors aimed to reduce radiation exposure by optimizing the technical setting parameters and closely defining the scan region for the operator. In three of 32 cases there were no surgical indications following clinical and preoperative CT examination. In three of the 20 cases with associated zygomatic fracture a closed reduction with a reduction hook was carried out, and no revision was necessary after the intraoperative CT examination. In 26 cases an open reduction was carried out. Of these open reduced fractures, four had to be revised after intraoperative CT monitoring; one of the isolated orbital floor fractures and three of those associated with a zygomatic fracture. Intraoperative CT monitoring of orbital floor fractures is considered a useful surgical aid. Its advantages are immediate monitoring of the surgical reduction, the presence of the surgeon during scanning enabling him to determine directly the relevant sections to scan, and the resulting radiation exposure.

Adult↗
PubMed2001

[Laser-induced thermotherapy (LITT). Use of round and pointed laser applicator systems--initial results].

PURPOSE: To assess the advantages and disadvantages by using round and sharp laser application systems during laser-induced thermotherapy. METHOD: 6 in vitro examinations were performed and 12 patients with liver metastases of colorectal carcinoma were treated with laser-induced thermotherapy. All lesions were closely localised to the diaphragm, liver capsule and large intrahepatic vessels. Five patients were treated with the sharp and 7 patients with the round applicator system. After CT-guided insertion of the catheter system into the metastasis laser therapy was performed under MRI control (approx. 25 W, 20 min). RESULTS: Reduction of the distance between the laser applicator and rounded laser catheter tipp (approx. 0.5-1 cm) leads to better placement of the laser applicator in metastases located near the diaphragm, liver capsule and large intrahepatic vessels. Improved therapy results due to complete ablation of metastases were obtained. All patients treated with the round system had complete ablation of metastasis. In 3 of 5 patients treated with the sharp system, MRI control 2 days after therapy showed a residual tumour margin close to the diaphragm or to an intrahepatic vessel. DISCUSSION: Improved ablation can be obtained by closer placement of a round laser catheter in liver metastasis located near the diaphragm, liver capsule and large intrahepatic vessels.

Adult↗
PubMed2001

[Radiological-guided liver-port implantation: Evaluation, technical approach, interventional procedure and follow up].

UNLABELLED: Radiological-guided liver-port implantation: Evaluation, technical approach, interventional procedure and follow up. PURPOSE: Description of evaluation, technical approach, interventional procedure and follow up of radiological-guided liver-port implantation. METHOD: Percutaneous implantation of a liver-port system was performed in twelve patients through a transfemoral approach and in one patient via the superficial epigastric artery after surgical exploration. In four patients we used port systems which are accessible via ventral puncture. Strecker-port systems were implanted in the remaining nine patients. RESULTS: The liver-port implantation was technically successful in all cases. No dislocation of the distal catheter tip, no thrombosis of the hepatic or splenic artery, no leakage near connections of the catheters or connections of catheter and port system and no thrombosis of the femoral arteries were observed. Correction of a kink in the catheter was performed in one patient. Another patient showed prolonged healing of the subcutaneous pocket. CONCLUSIONS: Interventional liver-port implantation is a safe procedure and leads to good clinical results. From the view of the radiologist the Strecker-system shows a good performance. The approach via the superficial epigastric artery demands excellent interdisciplinary cooperation.

Angiography↗
PubMed2001

Hemorrhagic cavernoma or ruptured dermoid of the orbit: Diagnosis with MRI.

MRI is a useful tool to study space-occupying lesions of the orbit. We present two cases of intraorbital lesions that were found to be a hemorrhagic cavernous hemangioma and a ruptured dermoid, respectively. The difficulties in arriving at the diagnosis of these rare entities with MRI are discussed. In general, dermoids are characterized by a peripheral, extra-conal location in the immediate vicinity of an orbital suture, while cavernous hemangiomas tend to be intraconal. Secondary complications of both entities, such as hemorrhage or rupture, may alter the characteristic MRI signal patterns found in uncomplicated lesions. Inflammatory reactions may be observed. The signal of the fatty dermoid and the hemorrhagic part of a cavernoma are both of high intensity on the T1-weighted images, and this may lead to diagnostic difficulties.

Journal Article↗
PubMed2001

Histopathological correlation to MRI findings during and after laser-induced thermotherapy in a pig pancreas model.

RATIONALE AND OBJECTIVES: To investigate whether percutaneous laser-induced thermotherapy (LITT) with continuous magnetic resonance (MR) monitoring of thermal effects within the pancreas is feasible in a porcine model. METHODS: Laser applicators were placed in the pancreas of 15 female pigs. A temperature-sensitive (thermo--fast low-angle shot) sequence was used for continuous monitoring of thermal effects during LITT at 1.5 T. Follow-up MR images were acquired, the pigs were observed for 7 days, and then a pathological examination was performed after sacrifice. RESULTS: Continuous MR monitoring visualized thermal effects in pancreatic tissue and thermal damage of the spleen (n = 1), the left kidney (n = 1), and peripancreatic fat (n = 4) but missed the thermal damage of the duodenum (n = 2). Thermal-induced lesions (10--32-mm diameter) were clearly visualized on contrast-enhanced T1-weighted images. CONCLUSIONS: Laser-induced thermotherapy of pancreatic tissue was feasible in this porcine model, and online monitoring was practicable. Further studies are necessary to increase the accuracy of online MR imaging of thermal effects.

Amylases↗
PubMed2000

Combined imaging techniques for pancreatic cancer.

Advanced pancreatic cancer has a poor prognosis. Early detection with imaging techniques can, however, improve the outlook for patients who undergo surgical resection, the only potential curative treatment. Individual techniques, however, have poor sensitivity for small masses and cannot easily differentiate tumour tissue from pancreatic masses associated with chronic pancreatitis. We combined biochemical detection on positron emission tomography with the anatomical accuracy of computed tomography and were able to improve accuracy of interpretation of imaging for patients with pancreatic cancer.

Aged↗
PubMed2000

MRI and 18F-fluorodeoxyglucose positron emission tomography in hemimegalencephaly.

We report hemimegalencephaly in a 44-year-old woman with mental retardation, epilepsy and a mild hemiparesis. In addition to typical findings on MRI, 2-deoxy-2[18F]fluorodeoxyglucose positron-emission tomography (PET) demonstrated glucose hypometabolism of the affected hemisphere. The results of PET have been coregistered with morphological information from the MRI studies by image fusion.

Adult↗
PubMed2000

MRI in decompression illness.

We report a case of decompression illness in which the patient developed paraparesis during scuba diving after rapid ascent. MRI of the spine revealed a focal intramedullary lesion consistent with the symptoms. The pathophysiological and radiological aspects of spinal decompression illness are discussed.

Adult↗
PubMed2000

Primary and secondary hepatic manifestation of neuroendocrine tumors.

BACKGROUND: In comparison with most other malignancies, in the treatment of metastatic neuroendocrine tumors one also has to consider endocrine symptoms and natural progression of disease. Since hepatic metastasis predominates and endocrine symptoms correlate with functional tumor mass, hepatic resection may improve prognosis or even cure patients. PATIENTS AND METHODS: We reviewed 41 consecutive patients with metastatic neuroendocrine tumors and four patients with primary hepatic disease presenting between 1989 and 1999. The neuroendocrine tumors were classified according to their origin, pattern of metastasis, endocrine activity, and histology. Operative therapy including hepatic resections of different extent, liver transplantation, and removal of the primary tumor was analyzed. The median survival after initial diagnosis and after hepatic resection were major parameters of outcome. RESULTS: There were 26 low-grade malignant, 12 high-grade malignant, 2 biphasically differentiated neuroendocrine carcinomas, and 5 pancreatic endocrine tumors. Hepatic resections were performed in 25 patients, resections of the primary tumor in 40 patients. The median survival after initial diagnosis was 49 months; 50.5 months in patients with hepatic resection versus 47 months in those with no liver surgery. CONCLUSION: Hepatic resection improved the outcome of patients with liver metastasis due to neuroendocrine tumors tendentiously but not significantly.

Adult↗
PubMed2000

[The T2-weighted half-Fourier acquired single-shot turbo-spin-echo technic compared to the conventional T2-weighted turbo-spin-echo technic for cerebral magnetic resonance tomography. A sequence comparison].

PURPOSE: To compare a T2-weighted half-fourier acquired single-shot turbo spin-echo (HF-TSE) sequence (HA-STE-sequence) for cerebral MRI with a standard T2-weighted fast spin-echo (TSE) sequence. MATERIALS AND METHODS: Signal-to-noise (SNR) and contrast-to-noise ratios (CNR) for different cerebral structures, and intracerebral lesions as well as the detectability of intracerebral lesions depending on size and relaxation properties were evaluated on cranial MR examinations of 46 patients with both a TSE and a HF-TSE sequence. RESULTS: SNR and CNR were found to be significantly higher with the TSE sequence for all normal structures and lesions except CSF, and lesions with short relaxation time T2 (p < 0.001). The number of detected lesions larger than 10 mm was similar with both sequences. Thirty-six (TSE) and 34 (HF-TSE) hyperintense, and 7 (TSE) and 2 (HF-TSE) hypointense lesions of at least 5 mm but less than 10 mm in size were detected. Thirty-three (TSE) and 10 (HF-TSE) hyperintense, and 2 (TSE) and no (HF-TSE) hypointense lesions smaller than 5 mm were detected. CONCLUSION: Due to its short acquisition time, the HF-TSE sequence is an alternative for MR examinations of non-compliant or claustrophobic patients. The low SNR and CNR relative to the TSE-technique are limiting factors as to the detectability of small lesions or lesions with low contrast to surrounding structures, with the risk of an increasing number of false negative results in lesions with short T2 relaxation time smaller than 10 mm.

Artifacts↗
PubMed2000

[Fusion of CT and PET data: methods and clinical relevance for planning laser-induced thermotherapy of liver metastases].

AIM: Catheter-placement in liver metastases is difficult when the lesions are not visible on plain images. We evaluated the use of image fusion using CT and PET data, providing information on anatomy and liver lesions, respectively. METHODS: Plain CT of the liver and whole body FDG-PET were performed in 28 patients with colorectal carcinoma in preparation for laser-induced thermotherapy. Fusions of image data and 2D-visualisation were performed and evaluated with regard to quality of the registration, number of detected lesions and influence of the procedure on laser-induced thermotherapy. Image fusion was performed using an algorithm which was developed by our group. RESULTS: 84 focal liver lesions were visible on CT, 107 on PET images. This means that CT guided catheter placement would have to be performed "blindly" in 23 lesions. In 6 patients previously unknown extra-hepatic tumor deposits were seen on PET images (local recurrence, 2 extrahepatic metastases, 2 second primaries). CONCLUSION: Hot spots from metastases, which are difficult to locate on PET images alone, may be identified on images generated by fusion of CT and PET data. These images facilitate an interventional approach to liver lesions which are not visible on plain CT. As PET allows for whole body screening, it helps identifying patients who would not profit from laser-induced thermotherapy.

Algorithms↗
PubMed2000

[Imaging of intra-arterial hepatic port catheter systems by power-doppler sonography using contrast media--preliminary results].

AIM: This study was designed to determine whether intra-arterial hepatic port catheter systems can be adequately detected by contrast-enhanced power-Doppler sonography. METHOD: 15 patients with a liver port system were investigated before chemotherapy. Examinations were performed with short bolus injections of the contrast medium Levovist in addition to angiographic imaging. RESULTS: Liver port systems were easily detected by the contrast-enhanced power-Doppler method. In 11 out of 15 patients a correct flow of the contrast medium via the port system was seen with both examination methods. One partially occluded hepatic artery was not identified by power-Doppler despite correct flow of the contrast fluid. In one of three patients showing an incorrect flow of the contrast medium the blood circulated primarily through the splenic artery due to a dislocation of the catheter tip. Circulation through both the hepatic and the splenic arteries was shown in a second patient and an occluded right hepatic artery was demonstrated in a third. All these findings were observed with both examination techniques. CONCLUSION: Power-Doppler sonography provides a reliable image of the port catheter system. This method can be used as a follow-up procedure to determine the state of arterial hepatic circulation during chemotherapy.

Aged↗
PubMed2000

Arterial switch procedure for D-transposition of the great arteries: quantitative midterm evaluation of hemodynamic changes with cine MR imaging and phase-shift velocity mapping-initial experience.

PURPOSE: To evaluate cine magnetic resonance (MR) imaging and phase-shift velocity mapping for assessment of the hemodynamic relevance of stenotic segments or specific hemodynamic changes in the great vessels after an arterial switch procedure for correction of D-transposition of the great arteries. MATERIALS AND METHODS: Twenty consecutive patients (age range, 2-17 years) with an acoustic window that was insufficient for Doppler transthoracic echocardiography were included in the study. Flow and diameter measurements of the pulmonary arterial trunk and its primary branches were performed with phase-shift velocity mapping and cine MR imaging. RESULTS: There were good correlations between pressure gradients in the pulmonary arteries estimated with MR imaging and those measured with Doppler echocardiography (r = 0.83, n = 15) and cardiac catheterization (r = 0.90, n = 13). Cine MR imaging revealed that the diameters of the right and left pulmonary arteries decreased with the expansion of the aorta during systole, which increased the peak velocity. This temporary stenosis was more severe in the right than in the left pulmonary artery and was accompanied by a significantly (P <.05) lower volume flow in the right artery. CONCLUSION: The anatomic situation after arterial switch repair tended to produce temporary stenoses in the primary pulmonary arterial branches, with significant changes in hemodynamics. These changes may affect the long-term outcome and go undetected with other imaging modalities.

Adolescent↗