[Gd-DTPA-supported magnetic resonance tomographic perfusion follow-up of shockwave-treated tumors]

The signal characteristics of 14 shockwave-treated and 14 solid control tumors were studied before and after injection of Gd-DTPA in an animal model. T1-weighted images of shockwave-treated tumors documented no significant signal intensity increase after contrast media injection in comparison with the untreated control tumors. The reduction of perfusion in shockwave-treated tumors can be documented in vivo by the signal intensity changes of the tumors after contrast media injection.

Detection and quantification of chronic cerebrovascular disease: comparison of MR imaging, SPECT, and CT

Twenty patients with angiographically proved occlusion of the internal carotid artery (ICA) (19 unilateral, one bilateral) were studied with magnetic resonance (MR) imaging, iodine-123 iodoamphetamine (IMP) single photon emission computed tomography (SPECT), xenon-133 SPECT, and computed tomography (CT). All patients had a history of stroke or prolonged reversible ischemic neurologic deficit for more than 4 weeks. By regions of interest, T1, T2, regional cerebral blood flow (rCBF), and the number and size of the lesions were determined. The data were expressed as interhemispheric ratios (diseased/nondiseased). The highest ratios obtained were for MR imaging (T1, 2.60 +/- 0.42; T2, 1.61 +/- 0.22 [mean +/- standard deviation]) followed by Xe-133 SPECT (0.58 +/- 0.13) and IMP SPECT (0.56 +/- 0.13). Correlation coefficients for MR imaging (1/T1, 1/T2) and IMP SPECT were below .21. The lesion size was greatest on IMP SPECT images, intermediate on MR images, and least on CT scans. However, MR imaging was superior in detection of pathologic areas (detection rates: MR, 100%; IMP SPECT, 91%; CT, 79%). Relaxation times do not correlate with rCBF.

[In vivo 31P magnetic resonance spectroscopy and MRI in patients with superficial tumors]

Simultaneous 31P-MR spectroscopy (MRS) and MR imaging (MRI) of 10 patients suffering from superficial tumours like carcinoma, lymphoma and adenoma, revealed significantly enhanced concentrations of phosphomonoester, phosphodiester and inorganic phosphorus in the tumour, whereas the concentration of phosphocreatine was lower in comparison to muscle tissue. In all tumours the pH showed a slight alkaline shift. The existing of necrotic regions detected by MRI was accompanied by an increase of inorganic phosphorus in the spectra. A follow-up study of a patient with a lymphoma during chemotherapy showed a tumour regression, whereas the spectra indicated a continuous approach of tumour values to the muscle values.

[Diseases of the lymphatic system of the head and neck region. A comparative study of MRI and CT]

The diagnostic possibilities of magnetic resonance imaging compared with computed tomography in lymphomas and pathological enlargement of the lymph nodes in the head and neck region are presented. Whereas plain MRI examinations showed the same diagnostic sensitivity as CT, application of the paramagnetic contrast medium Gd-DTPA in 50 of 87 patients clearly increased diagnostic accuracy. Signal intensities of T1- or T2-weighted images before therapy (operation, chemotherapy, radiotherapy) and after administration of Gd-DTPA were enhanced, compared with posttherapeutic and plain examinations. An increase after therapy in two patients signalled a relapse or residual tumour tissue; a decrease in three cases was evaluated as response to therapy. Other differential diagnostic processes such as lipomas, neurinomas, glomus tumours etc. were differentiated with the help of signal intensity curves after administration of contrast media and the use of a gradient echo sequence TR/TE = 30/12 msec with a flip angle of 30 degrees. Differentiation of tissue based on morphological criteria such as homogeneity of tumour tissue or the delineation against surrounding tissue structures showed in the case of Hodgkin's disease and inflammatory diseases mainly homogeneous elements without ring-shaped structure. Non-Hodgkin lymphomas had a predominantly homogeneous structure. In squamous cell carcinomas MR revealed in two cases a ring-shaped enhancement.

[Allergic bronchopulmonary aspergillosis with hay dust-induced alveolitis and bronchial asthma]

A 55-year-old female farmer had all the clinical, biochemical and radiological signs diagnostic of allergic bronchopulmonary aspergillosis. Remarkably she also had symptoms of farmer's lung and exogenous allergic bronchial asthma with specific types I and III sensitisation due to Aspergillus antigens inhaled with straw-dust. In addition to the usual asthma treatment she also received antimycotic agents and corticosteroids. Antigen exposure was strictly avoided. These measures brought about lasting regression of the disease manifestations and of the high concentrations of IgE and IgG antibodies against many Aspergillus antigens.

[Gd-DTPA contrast enhancement in the nuclear magnetic resonance tomographic diagnosis of thoracic space-occupying lesions]

The optimal technique for examining mediastinal masses is the use of T1 weighted spin-echo sequences (TR 500 msec/TE 17 msec) in transverse and coronal slice orientation pre and post contrast application. This setup provides an excellent morphological depiction of anatomy and pathology as well as T2 comparable information about tumor structure without the disadvantage of a reduction of the signal-to-noise ratio.

Fragmentation of gallstones using extracorporeal shock waves: an in vitro study

Eighty in vitro experiments were performed with single (n = 51) or multiple (n = 29) gallstones in order to find out which parameters are of prime importance for their disintegration by extracorporeal shock waves. A Dornier lithotripter and an upper limit of 1,500 discharges were employed. Although computed tomography density was significantly lower in cholesterol stones than in the noncholesterol stones (p less than 0.0001) and although the latter were significantly more often radiopaque (p less than 0.0001), we found no clear-cut correlation between the cholesterol content or computed tomography density and the degree of fragmentation of the stones. The most important variable which limited successful disintegration was the total stone volume. In stones with a mean total volume of 0.83 ml +/- 0.25 S.E. (diameter for single stones = 11.5 +/- 0.9 mm), none of the fragments exceeded 2 mm, whereas in stones with a mean volume of 3.6 ml +/- 0.64 (diameter = 17.2 +/- 1.5 mm) at least one fragment larger than 2 mm remained (p less than 0.002). Under the in vitro conditions, fragmentation was similar in multiple and solitary stones, provided the volume of the stones was comparable. These data show that, in general, the number and size of the stones, i.e. their total volume, and much less significantly their chemical composition are the major determinants of fragmentation by extracorporeal shock waves.

[NMR tomography of lunate malacia]

Conventional radiographs are not always able to exclude ischemic necrosis of the lunate in the early stages of the disease. Tomograms on two planes have a higher sensitivity than radiographs in two planes. Sensitivity during middle and late stages of ischemic necrosis of the lunate is approximately the same as that of magnetic resonance imaging. MRI is indicated if conventional techniques are negative or doubtful and where there are clinical signs of malacia (Decoulx stages 0 to 1). For these indications MRI is a justifiable additional method for diagnosing ischemic necrosis of the lunate.

[Value of magnetic resonance tomography in the diagnosis of diseases of the thoracic aorta]

MRI with imaging in the frontal and axial planes can replace, in most cases, CT as well as angiography. By limiting oneself to these planes, the examination can be carried out on patients with acute symptoms. If the findings on MRI are indefinite due to movement or flow artifacts, angiography can be carried out immediately. This may not be possible after CT, due to limitation of contrast volumes. With the exception of patients being ventilated after multiple trauma, MRI should nowadays be the primary form of examination, particularly in high risk patients.

[Intraneuronal ganglia: value of diagnostic radiologic possibilities]

This report describes two cases of intraneuronal ganglia cysts with degeneration of the peroneal and suprascapular nerve. In addition to standard radiographs other diagnostic studies such as CT and MRI may be required to ascertain the extent of the lesion. Histopathologic information is derived from biopsy.

[Value of nuclear magnetic resonance tomography in the staging of tumors of the urinary bladder]

The accuracy of magnetic resonance imaging (MRI) and computed tomography (CT) in the staging of bladder tumors was evaluated in 46 patients. In the T-staging MRI was superior to CT. With MRI 38 out of the 46 tumors were correctly staged into the four groups T0, T1-T3a, T3b and T4. With CT this classification was only possible in 28 cases. The main advantages of MRI were the capability for multiplanar imaging, which improved evaluation of the bladder base and the bladder dome, as well as a better differentiation between tumor recurrency and fibrosis. In the evaluation of adenopathy MRI and CT proved to be equal and demonstrated a sensitivity of 50%.

MRI of the breast--histopathologic correlation

132 solid breast masses have been examined at our institution by MR and have consequently been histopathologically correlated. T1- and T2-weighted SE and multi-echo sequences have been evaluated visually. It was found that signal intensities of tissues on T2-weighted images correlated with the contents of fibrosis, cells or water. Thus in some lesions (which consisted of different tissue components), a characteristic internal structure was visible on T2-weighted images, reflecting their histopathologic structure. Corresponding to their different composition, differences of signal intensity have also been noted between those fibroadenomas with a high contents of fibrosis and all other well-circumscribed breast lesions (fibroadenomas, carcinomas). However, for the majority of lesions with irregular contours a discrimination based on signal intensities or calculated T1- and T2-values did not seem possible. This overlap can also be explained by the macroscopically similar composition (amount of fibrosis, water or cells) of benign and malignant irregular lesions.

[Determination of T2-times of tumor and muscle tissue by nuclear magnetic resonance tomography and resonance spectroscopy--results of a comparative study]

In 13 patients the T2 values of muscular and various tumor tissues was determined by MR under in-vivo conditions. The tumors were confirmed by surgery. In 5 cases there was a neurinoma of the acoustic nerve, in 3 cases a lateral neck cyst, a granuloma of the larynx and some other pathological processes. Intraoperatively the tissues are biopsied and the T2* time is determined by spectroscopy in vitro. Both the muscular and the tumor tissue show higher mean values or standard deviations in MR measurements than in measurements by spectroscopy. The relations between muscular and tumor tissue (quotients) are comparable in neurinomas of the acoustic nerve (n. vestibulo-cochlearis) and lateral neck cysts, the granuloma of the larynx and lymph nodes of the neck, using both examination methods. Calculations of the correlation coefficients of T2 values and quotients of the muscular and tumor tissue point to tissue-specific connections between in-vivo and in-vitro measurements.

[Imaging of the Achilles tendon using magnetic resonance tomography]

The Achilles tendon and pre-achillean space of 30 patients was studied by MRI. A surface coil (Helmholtz' principle) was applied and all patients were examined with a superconducting magnet operating at 1.0 Tesla field strength. The purpose of the study was to illustrate pathological changes of the tendon and the surrounding soft tissue. In 3 cases MRI diagnosed a total rupture of the Achilles tendon. Furthermore, the strain of the tendon and side effects of an inflammatory process could be demonstrated. The use of a surface coil yields a high resolution of the normal anatomy of the region and of the pathological changes of the tendon and the surrounding soft tissue structures. The advantages of MRI for Achilles tendon diagnostics against competitive modalities are excellent soft tissue contrast, multiplanar imaging, as well as exact delineation and visualisation of the lesion.

[Value of high-resolution CT and nuclear magnetic resonance tomography compared to the standard procedures in the diagnosis of meniscal lesions]

The knees of 20 patients with evidence of meniscal tears were examined via high-resolution computed tomography (HRCT); 10 of these were studied by MRI. The HRCT study was performed directly after double-contrast arthrography (AG). For comparison with HRCT, slice orientation for MRI examination was in transverse view; gradient echo sequences using the FISP technique were applied instead of spin echo sequences. All results were correlated to the arthroscopy (AS) findings. In 95% of the cases AG and AS results agreed, HRCT/AS in 85% and MRI/AS in 70%. In certain cases HRCT provided additional information which influenced appropriate surgical treatment. MRI is a noninvasive nonionising method but gives a less exact documentation of the lesion than AG and HRCT. The gradient echo mode is superior to the SE mode in respect of outlining meniscal structures, at least in transverse view.