[Quality assurance in radiology].
Explore the source record for details and available documents.
Germany↗
Biomedical subjects
U Mödder
Publications and source records attributed to U Mödder.
[MR tomographic temperature quantification at 1.5 T in vitro: a comparison of fast T1 maps and a phase-sensitive sequence].
PURPOSE: To determine the value of fast T1-maps and a phase-sensitive sequence for temperature quantification with MR imaging. MATERIAL AND METHODS: The experimental setup allowed both homogeneous heating as well as laser-induced interstitial thermotherapy (Nd:YAG, 1064 nm) of tissue specimens (pig brain, liver and muscle) in vitro. A total of 60 experiments were performed. T1-maps were calculated by means of a multi-point-turbo-FLASH sequence. Additionally, the temperature dependent phase shift was determined with a 2D-FLASH sequence. RESULTS: The T1-relaxation times of four different aqueous solutions of gadolinium-DTPA (0.125-1.0 mmol/l) varied by less than 5%. During homogeneous heating, the T1-maps revealed a linear correlation (r > 0.98) between temperature and T1-relaxation times. The temperature coefficients were 11.0 +/- 0.42 ms/degree C. Variations of the linear correlation were observed during laser irradiation. There was only slight variation of the temperature coefficients of the chemical shift during homogeneous heating of different tissues (brain: 0.0098 +/- 0.0002 ppm/degree C; muscle: 0.0109 +/- 0.0003 ppm/degree C; liver: 0.0093 +/- 0.0002 ppm/degree C). The temperatures calculated during laser therapy based on the phase shift correlated strongly (r = 0.99) to the measured temperatures. CONCLUSION: Due to the considerable tissue independence and high accuracy, the phase mapping method is superior to T1-maps for monitoring thermal therapy modalities at 1.5 T in vitro.
Animals↗
[Value of the esophagogram in preoperative assessment of esophageal carcinoma].
PURPOSE: In this study we utilized barium swallows exhaustively in each patient. After that we compare the results with the intraoperative findings. The goal is to select those criteria which contribute to the preoperative clinical staging of esophageal carcinoma. METHODS: In a retrospective study we examined the esophagograms of 65 tumor patients. We evaluated the location and length of the tumor, the deformation of the esophageal axis, stenosis, dilatation, and the radiological type of the tumor. All characteristics were correlated with the pathologically determined TNM-criteria, the stage of the tumor, and the palliative or curative type of resection. RESULTS: We found the following significant correlations: localisation/T-criterion, radiological type/T-and M-criteria, stenosis/type of resection, deformation of the axis, stenosis and radiological type/tumor stage. CONCLUSION: In the sense of a checklist the stenosis, the deformation of the esophageal axis and the radiological type of the tumor should be carefully evaluated and included in the report. With these data, the clinical stage of the tumor can be estimated.
Adenocarcinoma↗
[Dependence of axis deviation in the esophagram on computerized tomography determined wall thickness and its value in assessing depth of invasion of esophageal carcinoma].
PURPOSE: In this study we compared the abnormalities of the esophageal axis seen in the esophagogram with the thickness of the esophageal wall measured by computed tomography. We have investigated, how exactly both methods assess the local tumor invasion according to the TNM criteria and whether there is a relation between the esophageal axis and the wall thickness. METHODS: In a retrospective study we examined the esophagograms of 65 tumor patients. Computed tomography examinations were available in 40 cases. Using a graphical method the wall thickness was transferred to the esophagograms under consideration of the different scales of the images. RESULTS: There is no correlation between the different types of distortion of the esophageal axis and the wall thickness in computed tomography. However, it can be demonstrated that the distortion results from specific fixation effects with the surrounding tissue. CONCLUSIONS: Both radiological methods cannot determinate the tumor invasion correctly.
Adult↗
Fast spin-echo MR imaging of the pediatric brain.
On a 1.5-T MR unit conventional spin-echo (CSE) and fast spin-echo (FSE) images were obtained in 70 consecutive children ranging from 4 days to 13 years in age. They suffered from developmental retardation, neurodegenerative, ischemic or inflammatory diseases. In our prospective study artifacts, lesion conspicuity and general impression were compared between double-echo (proton density- and T2-weighted) CSE and single-echo (T2-weighted) FSE images. Phase artifacts from flowing blood were seen rarely on the FSE images, while motion artifacts appeared more frequently. Assessment of myelination in 43 children with unfinished myelination revealed no difference between FSE and CSE. The lesion conspicuity in 20 children with focal abnormalities compared favorably between FSE and CSE. There was no diagnostically relevant difference between FSE and CSE, although in FSE spin density images were missing. FSE sequences can be used in MR imaging of the pediatric brain without disadvantage and with a time reduction of 67-75%.
Artifacts↗
[Laser-induced interstitial induced hyperthermia of cerebral tumors with nuclear magnetic resonance tomography control].
PURPOSE: The purpose of our study was to determine the value of MRI in monitoring laser-induced interstitial thermotherapy (LITT) of cerebral neoplasms. MATERIALS AND METHODS: Sixteen patients with brain tumors were treated with LITT. The laser irradiation was performed within the MR unit and monitored with a temperature-sensitive T1-weighted 2D-FLASH sequence. RESULTS: During irradiation a gradually increasing central zone of high signal intensity was surrounded by an increasing area of reduced signal intensity. After therapy, the diameter of an enhancing rim at the outer border of the peripheral zone indicated total lesion size. On T2-weighted images the signal intensities were reversed. Total lesion size decreased during follow-up. CONCLUSION: MRI is suitable for monitoring LITT. However, the role of LITT in the treatment of brain tumors has still to be defined.
Adult↗
[MRI tomographic blood volume measurements in the diagnosis of a stroke: the results of a clinical pilot study].
PURPOSE: In this study the sensitivity of proving a stroke using regional cerebral blood volume (rCBV) maps were investigated. Another aim was to evaluate the strength of the ischaemia. METHODS: Seven patients were examined during the acute phase of a stroke, eight during the subacute or chronically stage. To calculate rCBV-maps of one slice low dosed Gd-DTPA was injected as a bolus. Using the relaxation-effect the obtained signal intensity-time curves were converted pixel-wise to rCBV images. For the region of the infarction rCBV ratios were calculated relative to the corresponding area in the contralateral hemisphere. RESULTS: Only 63% of the investigations carried out during the acute phase were utilizable. In all those cases a decrease of rCBV was found. The infarct area could only visually recognized if the rCBV ratio was lower than 0.7. The ratios of completely and partial necrotic areas of the infarctions were 0.481 and 1.028 respectively. With a p = 0.0015 these values are even statistically different. CONCLUSIONS: During the acute stage the sensitivity of the rCBV measurement was not as high as that of morphological MR imaging. However, rCBV maps make it possible to estimate the strength of the ischaemia even during the first hours.
Adult↗
[Gadodiamide and gadolinium-DTPA as intravenous media in computed tomography].
PURPOSE: To evaluate the effect of intravenously applied gadolinium-based contrast medium in computed tomographic (CT) studies. MATERIAL AND METHODS: Serial dilutions of iohexol 300, Gd-DTPA and gadodiamide were scanned with CT in a phantom study using water filled tubes. For quantification of x-ray attenuation, the mean Hounsfield units (HU) were calculated from the CT scans. Five patients with contraindications against iodine contrast agents were examined with abdominal or thoracic CT before and after application of 0.2 mmol/kg body weight of a gadolinium-based contrast agent. In these patients attenuation values were obtained in ROI from unenhanced and enhanced CT scans. RESULTS: The phantom study revealed a 38.4% enhancement for Gd-DTPA and a 35.7% enhancement for gadodiamide scaled on the reference measurements with iohexol 300. Thus, 130.2 ml Gd-DTPA or 140.1 ml gadodiamide are needed to achieve the same attenuation as an i.v. injection of 50 ml iohexol 300. Consequently the corresponding dose of 1 mmol/kg body weight would exceed the manufacturer's recommended dose. In four patients with complete thoracic or abdominal CT, i.v. applied gadolinium-based contrast medium (0.2 mmol/kg) yielded no visible advantage. In these patients parenchymal enhancement did not exceed 25%. Dynamic CT of a patient with focal liver lesion revealed an arterial enhancement peak of 75%. CONCLUSION: Sufficient parenchymal enhancement in CT studies cannot be achieved with the available gadolinium-based contrast mediums. They might be helpful if only short time vascular enhancement is required.
Contraindications↗
[Ileocecal invagination in a patient with HIV infection and non-Hodgkin's lymphoma].
Explore the source record for details and available documents.
Adult↗
Mapping of the cortical motor hand area with functional MR imaging and MR imaging-guided laser-induced interstitial thermotherapy of brain tumors. Work in progress.
PURPOSE: To localize the cortical motor hand area with functional magnetic resonance (MR) imaging before and after MR imaging--guided laser-induced interstitial thermotherapy of tumors in the precentral brain region to control energy delivery and to improve safety. MATERIALS AND METHODS: Functional MR images were obtained in eight patients (five men, three women; aged 27-63 years) while they flexed their fingers. MR imaging--guided laser-induced interstitial thermotherapy was terminated when there was less than 8-12 mm between the border of the laser-induced lesion and the motor hand area anterior aspect. RESULTS: Seven patients had a statistically significant localized change in signal intensity in the central region of the contralateral hemisphere. This area was a spotlike circumscribed focus in three patients and scattered over a larger zone in four patients. Persistent deficits did not occur after thermotherapy in any patient. In three patients, onset of reversible perifocal edema in the motor hand area coincided with the development of hemiparesis, which completely resolved. No patient had activity within the tumor on functional MR images. CONCLUSION: Functional MR imaging findings can be used to prevent neurologic damage during MR imaging--guided laser-induced interstitial thermotherapy.
Adult↗
[Use of an image serve for external communication in a radiologic department].
UNLABELLED: In radiology picture information is increasingly acquired digitally. Image postprocessing is sometimes carried out via the picture archiving and communication system (PACS). In this paper we present a strategy for the simple implementation of an external picture communication system. METHODS: Image transfer for the entire radiology department is carried out through a single image server, which physically and logically separates the PACS from the external network. The server is organized as an image mailbox system. For each user the images can be transferred to their respective mailbox from the radiology department. However, direct access to the image archive is prevented by the system. RESULTS: Because the networks are separate, a high degree of access security is guaranteed. New users can easily be added to the server without additional configuration of the PACS. System usage has received wide acceptance within the department and with external users. CONCLUSIONS: The integration of an image server into a PACS has proved to be non-problematic. The concept allows for more effective information sharing in the field of teleradiology.
Computer Communication Networks↗
Measurement of cerebral blood volume via the relaxing effect of low-dose gadopentetate dimeglumine during bolus transit.
PURPOSE: To quantify regional cerebral blood volume (rCBV) on the basis of the enhancement of blood proton relaxation rates after intravenous administration of gadopentetate dimeglumine. METHODS: A series of sequential MR images on one section was recorded during bolus transit with a standard fast low-angle shot sequence. The signal-intensity curves were converted into corresponding concentration-time curves from which rCBV images were calculated. RESULTS: The functional parameter images of rCBV were calculated pixel-by-pixel for two patients who had received a 1-second bolus injection of 1 mmol of gadopentetate dimeglumine. In a larger series of 62 patients, a mean blood volume of 4.6 +/- 1.6 vol% was determined for normal brain tissue. CONCLUSIONS: The relaxing effect of a contrast agent can be used to determine blood volume quantitatively. The results are in agreement with those obtained by nuclear medicine techniques. The proposed method requires no special hardware, and can thus be implemented on clinical MR scanners.
Aged↗
Intracranial stenoocclusive disease: MR angiography with magnetization transfer and variable flip angle.
PURPOSE: To assess time-of-flight MR angiography that uses magnetization transfer contrast (MTC) pulses, tilted optimized nonsaturating excitation (TONE), and a 256 x 512 image matrix for the detection of small intracranial arteries and for the detection and quantification of intracranial arterial stenoocclusive disease. METHODS: To assess anatomic sensitivity, six interpreters, in a blinded fashion, reviewed the MTC/TONE MR angiograms and selective intraarterial angiograms obtained in 70 patients within a mean interval of 5.5 days (SD, 1.5). In addition, all intracranial angiograms were evaluated with regard to presence and degree of arterial stenosis and anatomic variants. RESULTS: Interobserver correlations for determining vessel length were comparably high for both methods. A strong correlation was found between measurements obtained on MR angiograms and those obtained on intraarterial angiograms. The mean vascular length averaged across all arteries was 34.8 mm (SD, 28.1) on MR angiograms and 53.2 mm (SD, 36.8) on intraarterial angiograms. Forty-one stenoses and occlusions and 30 anatomic variants were identified with intraarterial angiography. All arterial variants and 100% of occluded vessels were graded correctly. Moreover, 80% of stenoses greater than 70% and 88% of stenoses less than 70% were quantified correctly at MR angiography. Specificity for identifying stenotic disease was 99%. CONCLUSION: Despite inferior display of vessel length, MTC/TONE MR angiography with increased spatial resolution was able to show the vast majority of high grade lesions visible at selective intraarterial angiography and may suffice for clinical decision making in many patients.
Adolescent↗
[Arachnoid cyst as the differential diagnosis of ischemic optic neuropathy in type-II diabetes].
HISTORY AND CLINICAL FINDINGS: A 71-year-old woman, a diabetic (type IIb) for 27 years, developed bilateral hemianopsia over a period of about 2 years. A few weeks before hospital admission the defect in her visual fields increased more rapidly and double vision occurred intermittently. The hemianopsia was demonstrated by finger perimetry. There was no evidence of heart failure or peripheral vascular disease. Muscle reflexes were normal, but there was a decrease in vibratory sensation in both feet. The cause of the visual disturbance was at first thought to be an ischaemic optic neuropathy. INVESTIGATIONS: Biochemical tests showed an HbA1 of 12.8%, blood sugar levels were between 230 and 359 mg/dl, and there was increased intravascular platelet activation. Ophthalmological examination confirmed bitemporal hemianopsia and early retinopathy. Magnetic resonance imaging of the skull revealed an intra- and suprasellar cystic space-occupying lesion extending to the right optic chiasma. These findings, taken together, indicated an arachnoidal cyst. TREATMENT AND COURSE: After the diabetic metabolic state had been normalized with insulin treatment (average of 30 IU of an intermediary insulin) and dietary measures, the cyst was evacuated stereotactically. The hemianopsia quickly improved markedly and the patient was discharged 4 days after the operation with her vision nearly fully restored.
Aged↗
[Contrast-enhanced color-coded duplex ultrasound of high grade carotid stenoses].
PURPOSE AND METHODS: The usefulness of SH-U-508A (Laevovist) in the quantification of high-grade internal carotid stenosis (ICA) is assessed in this study. 32 patients with high-grade ICA stenosis (> = 70%) or occlusion are examined using colour Doppler-assisted duplex imaging (CDDI) before and after injection of SH-U-508A. RESULTS: The SH-U-508A-induced increase in blood echogenicity started at 9.8 s (mean; SD: 2.2) after bolus injection and peaked at 21 dB (mean; SD: 1.9; n = 12) after 14.8 s (mean; SD: 2.9). In addition, SH-U-508A led to a significant increase in systolic peak velocity determined in the common carotid artery, by 26% (mean; SD: 9; p < 0.05). Significant differences between non-enhanced and enhanced CDDI were found for the visualisation of the entire length of the intrastenotic residual lumen (43% vs 83%; p < 0.01). Correlations between non-enhanced and enhanced CDDI were high (r > 0.9) for the determination of cross-sectional area reduction and plaque length. CONCLUSION: SH-U-508A may be useful in quantifying high-grade ICA stenoses with insufficient delineation at non-enhanced CDDI.
Aged↗
[Radiation exposure of radiologists during angiography: dose measurements outside the lead apron].
The aim of this study was to provide practical information to angiographers concerning radiation exposure to body parts not covered by lead aprons. Individual doses to the neck and hands of radiologists measured in micro-Sieverts were obtained during the course of 80 angiographies of various types. The number of diagnostic and interventional procedures, which might lead to exceeding permissible doses, have been calculated. Possibilities of estimating doses during angiography by means of parameters such as screening times were examined statistically. Especially with regard to the hands, estimations of the doses are insufficient (correlation r = 0.21). Radiologists who undertake much angiographic and particularly interventional work may reach exposure levels requiring protective measures in addition to lead aprons.
Angiography↗
[Follow-up and diagnosis of recurrence of malignant head and neck tumors after radiochemotherapy. Comparison of computed tomography and magnetic resonance tomography].
339 CT and 95 MRT examinations in 210 patients were evaluated retrospectively to determine the value of CT and MRT for follow-up of head and neck tumors and for diagnosing recurrences. Semi-quantitative evaluation of tumor extent during and after radiotherapy showed advantages for MRT since changes induced by treatment, particularly oedema, produced less contrast loss in the images. CT had a sensitivity of 81% for the recognition of recurrences; this was 92% for MRT. Specificity for CT was 76% and for MRT 86%. Concerning the reliability of individual diagnostic criteria, space occupying lesions were the most valuable in CT diagnosis. For MRT, space occupying lesions and infiltration into neighbouring structures were of equal value. Because of differences in the nature of the signals, MRT proved better than CT in characterising recurrent masses and this improved the differentiation between scarring and local tumour recurrence.
Combined Modality Therapy↗
[Magnetic resonance tomography and localized proton spectroscopy in 2 siblings with Canavan's disease].
We present the findings of magnetic resonance imaging (MRI) and localised 1H magnetic resonance spectroscopy (MRS) in two brothers with Canavan's disease, a rare autosomal recessive leukodystrophy. Urine specimens of one child were evaluated by MRS. All examinations were performed in the same whole body 1.5 T superconducting magnet. MRI revealed the typical pattern of leukodystrophy including a more severe demyelination in the older child. The younger brother showed additional high signal lesions in the globi pallidi on T2-weighted images. MRS of the brain had an elevated ratio of N-acetyl-aspartate (NAA)/phosphocreatin + creatin (Cr) while the ratio of Cholin/Cr was reduced. in urine spectroscopy the concentration of NAA was markedly increased. The ratio of NAA/creatin + creatinin was 880 +/- 10% mmol/mol (normal: 5-21 mmol/mol). Diagnosis of Canavan's disease was supported by gas chromatographic urine examination with an 80-100 fold elevation of NAA concentration. Hence, the diagnosis of Canavan's disease could be established by increased ratio of NAA/Cr and decreased ratio of Cho/Cr relation in brain spectroscopy and high NAA concentration in urine spectroscopy.
Aspartic Acid↗