Biomedical subjects
Publications and source records attributed to N Hosten.
The paper summarises imaging of orbital diseases by CT and MRI. As localisation is an important clue to differential diagnosis in orbital tumours, the different pathologies are described according to sites of prevalent occurrence. Morphological criteria of orbital pathology are described, and the more frequent entities are illustrated.
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Imaging findings of morphology and regional cerebral blood flow in two patients suffering from epileptic seizures are presented. CT and MRI revealed heterotopic gray matter as a probable structural correlate, causing the seizure disorder. 99mTc hexamethyl-propylenamine oxime (HM-PAO) SPECT demonstrated focally increased regional cerebral blood flow in both patients in the areas of their heterotopic lesions. Heterotopic and orthotopic gray matter seem to have similar features in terms of regional perfusion. A focally increased brain perfusion in interictal epileptic patients may indicate an underlying migration anomaly.
Anatomical specimens and normal persons were studied by gradient echo MR imaging to determine the influence of different echo times (TE) on bone marrow contrast. First of all, six normal persons were studied to determine specific echo times for in-phase and opposed-phase states. Using different sequences bone marrow contrast in isolated femoral bones was determined and compared to results of pathological exams. Red bone marrow had no signal on opposed-phase images; contrast between red and yellow marrow was higher on opposed-phase than on in-phase images. Bone marrow lesions can be expected to be visualised with high signal on opposed-phase images; this technique should be especially suited for MR imaging of bone marrow.
MR and CT examinations of 16 patients with lymphoma, pseudolymphoma and inflammatory pseudotumours were analysed to describe morphologic features of lymphocytic infiltration. Density and signal did not allow for differentiation, but localisation was the most important criterion: lymphoma and pseudolymphoma were located in the anterior superior orbit, inflammatory pseudotumours being retrobulbar lesions. Differentiation is of clinical importance, since both lymphoma and pseudolymphoma are accompanied by generalised malignant lymphoma while inflammatory pseudotumours are localised. Imaging of topographic relations of lens, optic nerve and lesion on sagittal MR images was found helpful for radiation therapy planning.
Preoperative evaluation of cervical lymph nodes by ultrasound and palpation was compared retrospectively in 123 patients with tumours on the head and neck. The diagnostic accuracy was higher by ultrasound (96.5%) than by palpation (85.5%). Hence, the sensitivity for detecting cervical metastases was also higher for ultrasound than for palpation (96% versus 83%), because of the reduced false negative findings. Specificity, however, was higher for palpation (82%) than for ultrasound (74%). Ultrasound was superior in delineating the relationship of metastases to adjacent tissues (vessels). Major disadvantages of ultrasound were the higher percentage of false positive findings (26%) and absence if delineation of the relationship to bony structures.
Multiplanar facilities of MR imaging allow for a detailed analysis of eye muscle enlargement. For taking full advantage of MRI's diagnostic possibilities, thorough knowledge of pathological anatomy is necessary. The paper describes examination technique and criteria for analysis. Diseases leading to eye muscle enlargement are illustrated by exemplary cases.
The diagnostic value of various doses of Gd-DTPA was compared intra-individually. Thirty-three patients with cerebral tumours were randomly allocated to three groups. Group 1 was given a dose of 0.025, group 2 a dose of 0.05 and group 3 a dose of 0.1 mmol GD-DTPA/kg body weight. Following administration of Gd-DTPA the average tumor/brain contrast in group 1 was -4.5%, in group 2 +8.4% and in group 3 +43.0%. Diagnostically useful tumour delineation was obtained in two out of 11 in group 1, in seven out of 11 in group 2 and in 10 out of 11 in group 3. A further increase in the dose to 0.2 mmol/kg body weight in group 3 resulted in a further increase in tumour/brain contrast of +62.5% and improved tumour delineation in one case. As a result of these findings a dose of 0.1 mmol Gd-DTPA/kg body weight is recommended for the routine investigation of intracranial tumours.
Sensitivity and specificity of plain T2-WI and Gd-DTPA enhanced T1-WI were compared by evaluating MR exams of 30 patients with brain metastases. Large lesions with high signal on T2-WI always enhanced (43/43) when a structure (perifocal edema, tumor tissue, central necrosis) was found. Large lesions nearly always enhanced (53/55) even if no such structure was found. 65% of small unstructured white matter lesions with high signal on T2-WI, which are generally considered vascular, did not enhance. Surprisingly, 35% did enhance. Demonstration of blood brain barrier disturbance in these lesions suggested a metastatic origin. In 3 patients with multiple metastases, Gd-DTPA enhanced T1-WI disclosed more than 140 lesions not seen on T2-WI. All of them were located in or adjacent to grey matter. Our results indicate that enhanced T1-WI should be obtained even if T1-WI are normal or show only small white matter lesions.
Renal clearance of 99mTc-mercaptoacetyltriglycine (MAG3) and 131J-orthoidohippurate (OIH) were compared by simultaneous measurement in 50 patients. Renal time-activity-curves of both radiopharmaceuticals were compared in 50 patients. With regard to the clearance, good correlation (r = 0.95) with a mean ratio MAG3-/OIH-clearance of 0.62 was found. No significant difference between patients with normal (n = 30) and impaired (n = 20) renal function could be demonstrated. Renal time activity curves and relative renal function showed good correspondence in patients with normal (n = 13) and impaired (n = 7) renal function. It is concluded that MAG3 may be used as substitute for OIH in patients with normal and impaired renal function.
In 50 patients with Graves' Ophthalmopathy and 9 controls both orbits were examined by MR Imaging at 0.5 Tesla using a surface coil. T1-weighted spin-echo images were obtained in transverse and coronal orientation; additionally, a T2-image was calculated from a multi-echo sequence (8 echoes). Signal intensity of eye muscles on both T1-weighted and T2-weighted MR images was evaluated qualitatively. T2-times were then calculated for all inferior rectus muscles. Eye muscle enlargement was found in 28 out of 50 patients. T2-times of inferior rectus muscles in stage III and IV patients were evaluated significantly (p less than 0.05). Areas of high signal intensity were accordingly found in enlarged eye muscles in 19 out of 50 patients; they were interpreted as edematous tissue changes. Areas of low signal intensity were found in enlarged eye muscles of 5 out of 50 patients; these eye muscles were considered fibrotic. Differentiation of eye muscle changes by MR imaging might help to decide between antiinflammatory medication and surgical therapy in patients with Graves' Ophthalmopathy.
Using labelled MAG3 (n = 172) or OIH (n = 102) the results of three different techniques of calculating renal clearance were compared. The following techniques were used: Tauxe (single plasma concentration determination), Oberhausen (modified, combined partial body and plasma disappearance clearance) and Winkler (partial body clearance). For OIH, linear regression analysis revealed a positive correlation of Tauxe and Oberhausen clearances with a correlation coefficient (r) of 0.90 and a mean ratio (mean) Oberhausen/Tauxe clearances of 1.03. For MAG3, the Oberhausen values were found to be significantly lower than the Tauxe values with an equally good correlation. For this radiopharmaceutical the Winkler values were significantly higher than the Tauxe and Oberhausen values. For OIH, no such difference was noted. However, the correlation coefficient was significantly lower. Whereas with the Tauxe method, a mean ratio MAG3-/OIH clearances of 0.62 was observed in an earlier investigation, from the present data a ratio of 0.53 is calculated for the Oberhausen clearance. The difference between the Tauxe and Oberhausen clearances with MAG3 is of importance when comparing clearance values obtained with clearance calculation techniques and for establishing normal values for the MAG3 clearance.
Thirty-nine patients with Graves ophthalmopathy were examined with magnetic resonance (MR) imaging at 0.5 T with use of a surface coil. T1- and T2-weighted spin-echo images were obtained, and T2 relaxation times of eye muscles and retrobulbar fat were calculated from a multiecho sequence. Normal values for T2 relaxation times of eye muscle were obtained by examining nine control subjects. MR imaging demonstrated eye muscle enlargement in 23 patients. Visual examination of T2-weighted and calculated T2 images showed areas of high signal intensity in enlarged eye muscles of 12 of 23 patients. Calculated T2 relaxation times of eye muscles differed significantly between control subjects and patients with stage III and IV disease. Signal intensity characteristics of these changes, as well as their correlation with well-known histologic findings, suggested their interpretation as edema caused by acute inflammation. Since computed tomography is not able to depict eye muscle edema, the MR findings of structural changes within enlarged eye muscles might have an impact on therapeutic decisions concerning the application of anti-inflammatory drugs.
Two woman patients with malignant melanoma of the skin known from their case history and with acutely emerging neurological symptoms were examined both by CT and by MR tomography (both plain and with intravenous contrast medium). The radiologically derived suspicion of meningioma could not be confirmed by intraoperatively performed histological examination. In both cases the patients had meningeal melanoma metastases with low melanin content and without noticeable bleeding into the metastases. MR diagnosis is rendered difficult by the absence of paramagnetic substances typical of melanoma metastases. Hence, if the case history is known, it should be considered whether there is meningeal metastasising with atypical histology.
Heterotopic grey matter is a rare cause of seizures. While lesions appear suspicious on CT because of equidensity to cortex, MR imaging can establish the diagnosis by demonstrating same signal intensity of heterotopia and grey matter on T1- and T2-weighted as well as inversion-recovery sequences.
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Fluoroimmunoassays appear to be an alternative to conventional radioimmunoassays and immunoradiometric assays because of the high specific activity of their label, thus promising high sensitivity and excellent precision. According to IFCC recommendations for the assessment of new laboratory methods, we evaluated precision, accuracy, linearity, lower detection limit and normal reference ranges of commercially available immunofluorometric assays of alpha-fetoprotein, choriongonadotropin and thyrotropin. In addition, thyrotropin content in sera of 147 patients was measured by immunofluorometric assay. Analysis of immunofluorometric assays gained performance data comparable to those of currently used immunoradiometric assays. Regression studies performed against currently employed methods showed accuracy of all three immunofluorometric assays. Results of immunofluorometric assay for thyrotropin demonstrated that sera of hyperthyroid subjects were distinguished from those of euthyroid subjects from basal thyrotropin alone. We conclude that immunofluorometric assays are an alternative to immunoradiometric assays which anybody concerned about the future of in vitro nuclear medicine should be aware of.