Liquid Water: A Single Approach to Its Two Continuous Phase Transitions

In this paper, we show that both continuous phase transitions of liquid water, the liquid-gas and the liquid-liquid, can be articulated within a single thermodynamic analytical formalism. This result follows from a combination of the two-liquid model (TLM), recently confirmed for water, with the idea of a thermal-dependent excluded volume, v_e, concept introduced by van der Waals, in his famous state equation. Starting from the fundamentals of thermodynamics, it will be shown that the TLM naturally leads to the idea of an extensive thermal-dependent v_e that acts as a parameter of the sample thermodynamic potentials. This procedure effectively separates the thermodynamics of the system into two parts: the first concerns the clusters' thermodynamics, taken as wandering particles, and the second concerns the thermal behavior of its internal structure (geometry and number of particles). From this result, we demonstrate that the condition of mechanical instability leads to not one but two critical points, each happening in one of the above-described parts of the system.

Thermal diffusivity and the conformal transformation on nematic liquid crystals

In this paper, we will study theoretically and experimentally the anisotropy of the thermal diffusivity in nematic liquid crystals. We will show that the Baalss-Hess conformal transformation [D. Baalss and S. Hess, Phys. Rev. Lett. 57, 86 (1986)], can be used to obtain a free of adjustable parameters equation that describes the anisotropy of the heat diffusion in these materials. The results of this theory will be compared with experimental data. This study will partially confirm the widely known experimental evidences that indicate that the thermal diffusivity is larger in the director direction than in the one perpendicular to it. For calamitic nematic phases this is true; for discotic nematic ones the reverse situation would be found; the diffusivity would become larger in the direction perpendicular to the director. We will also present experimental data supporting this theoretical prediction. The data comprehend the calamitic and discotic nematic lyotropic phases and a nematic thermotropic phase.

[MRT, CT and sonography in the preoperative assessment of the primary tumor spread in malignant pleural mesothelioma]

PURPOSE

Evaluation of the diagnostic value of the imaging modalities computed tomography (CT), magnetic resonance imaging (MRI), and thoracic sonography in the preoperative staging of malignant pleural mesothelioma.

MATERIALS AND METHODS

The diagnostic accuracy of CT (n = 41), MRI (n = 24), and thoracic sonography (n = 37) were evaluated in 51 patients with histologically proven diffuse malignant pleural mesothelioma. Values of sensitivity, specificity, positive and negative predictive values, and accuracy were calculated for the assessment of the diaphragm, lung, thoracic wall, pericardial wall, myocardium, and (retro)peritoneal space.

RESULTS

The accuracy rates for CT were 85%, 98%, 83%, 73%, 71%, and 83%. MRI had an accuracy of 71%, 92%, 71%, 83%, 71%, and 96%, the thoracic ultrasound examinations of 76%, 63%, 51%, 60%, 71%, and 89%.

CONCLUSIONS

According to these results CT remains the method of choice in the preoperative assessment of T-stage of malignant pleural mesothelioma. MRI is of nearly the same value, but is not a must. Sonography may be supplementary method for operation planning.

Magnetic resonance imaging to detect bone marrow metastases in the initial staging of small cell lung carcinoma and breast carcinoma

BACKGROUND

Bone marrow is a common site of metastases in patients with small cell lung carcinoma (SCLC) and female breast carcinoma (FBC). Metastatic bone marrow involvement is found in approximately 50% of SCLC patients and up to 85% of FBC patients at autopsy. Initial staging procedures detect malignant bone marrow lesions in only 2-30% of patients with these tumors. This study was performed to assess whether MRI can improve the detection rate of bone marrow metastases in tumors with a high incidence of skeletal involvement.

METHODS

Fifty-two patients with histologically verified SCLC (25 with limited stage disease and 27 with extensive stage disease) and 33 women with FBC were entered into a prospective study. The MRI protocol was comprised of coronal slices in the pelvic region and sagittal slices of the whole spine utilizing a T1-weighted spin echo sequence with a field of view of 50 cm. All patients underwent initial routine diagnostic staging procedures including bone scintigraphy, unilateral crest biopsy, and plain film radiography of suspicious skeletal areas.

RESULTS

Only in two SCLC patients, MRI was positive in 25 cases. All SCLC patients with bone marrow lesions histologically verified, diagnosed by crest biopsy (six patients) or by bone scan (seven patients) had the correct diagnosis of metastases by MRI. In addition MRI revealed hypointense bone marrow foci in 14 cases. In contrast, 28 of 33 FBC patients examined during the initial staging procedure showed no evidence of bone marrow involvement. MRI was not superior compared with bone scintigraphy in FBC patients.

CONCLUSIONS

The staging results obtained in SCLC and FBC patients are different, although both tumors have a high incidence of bone marrow metastases. It may be assumed that the biologic behavior of these tumors is reflected by the initial bone marrow involvement. Because of its superiority compared with biopsy and bone scan, the authors believe MRI should become an integral part of the initial staging procedures in patients with SCLC. When staging patients with FBC, MRI should be applied only in clinically indicated cases.

[Therapy of acute traumatic vascular injuries using covered stents]

PURPOSE

Evaluation of percutaneously implanted covered stents in acute vascular bleeding as therapeutic alternative to conventional surgical treatment.

MATERIALS AND METHODS

8 patients aged 26 to 83 years with acute vascular lesions caused by traumas, and subsequent haemorrhage, were transferred to our department. Because of general inoperability or difficult surgical access, interdisciplinary evaluation favoured an interventional treatment. In 6 patients stents could be placed percutaneously to the aorta, subclavian and iliac arteries. In one case we had to implant three stents into the thoracic aorta.

RESULTS

In 7 interventionally treated patients the stents could be placed exactly on the lesions (88%). The bleeding could be stopped immediately in 6 cases (75%). In one patient we had to implant successfully two more stents in reintervention (12%). In another patient the available prosthesis was too short, so that the patient had to be referred to the OR for surgical treatment (12%). There were no complications during the treatment.

CONCLUSION

First results in the use of covered stents as interventional treatment of acute vascular lesions are encouraging and may represent a possible alternative to surgical therapy in locally limited bleedings, presupposing that all different types and sizes of industrially produced covered stents are available. Further investigations to compare surgical and interventional techniques are warranted.

Diagnostic value of MR imaging in comparison to CT in the detection and differential diagnosis of renal masses: ROC analysis

The aim of this work was to compare MR imaging and CT in the detection of renal masses and in the differential diagnosis between benign and malignant lesions. In 33 patients with 54 renal lesions CT and MR images were evaluated by four readers with regard to tumor detection and characterization using a receiver-operating-characteristics (ROC) analysis. The MRI protocol consisted of a T1-weighted spin-echo (SE) sequence (TR/TE: 300/10 ms) before and after contrast administration and a heavily T2-weighted turbo-SE (TSE) sequence (TR/TE: 5500/150 ms). Az values for the area under the ROC curves for lesion detection were 0.92 +/- 0.04 for CT and 0.91 +/- 0.05 for MRI, respectively, which was not statistically different. The MRI technique was slightly, but not significantly, better than CT in the overall characterization (accuracy in differentiation between benign and malignant) of renal lesions with an Az value of 0.90 +/- 0.05 compared with 0.88 +/- 0.06 for CT. The MRI technique proved to be statistically superior to CT (p < 0.01) in the correct characterization of benign renal lesions. MRI equals CT in the overall detection and differential diagnosis of renal masses. MRI is very helpful for further differential diagnosis of lesions which are equivocal on CT especially in the differentiation between complicated cysts and cystic or hypovascular renal cell carcinoma.

Atrophy of hippocampus in patients with Alzheimer's disease and other diseases with memory impairment

In clinical practice, Alzheimer's disease (AD), multi-infarct Dementia (MID) and depression are often difficult to differentiate and may coexist. This study reports the findings of CT and MRI focused on hippocampal atrophy (HA). Quantitative volumetric MRI measurements of the hippocampus showed a reduced volume in AD patients compared to normal controls with no overlap. CT studies reported a significant widening of the hippocampal fissure in AD patients. Because volumetric measurements are not available for routine examinations, so far we are required to use the finding of hippocampal lucency in CT and dilatation of the directly visible hippocampal fissure in coronal MRI scans as criteria for HA. These findings were visually classified on a 4-point scale by 2 neuroradiologists, who had no knowledge of the clinical diagnosis. The examinations of 80 patients (42 with AD, 22 with major depression, 3 with MID, 6 classified as age-associated memory impairment (AAMI) and 8 'normals' with only subjective memory impairment) showed that the HA strongly supports the diagnosis of AD, by correctly identifying 95% of the AD patients and 47.8% of the patients without AD. These results suggest that CT and MRI examinations of the hippocampus are capable of demonstrating HA in clinical practice, which is strongly correlated with the diagnosis of AD.

[Magnetic resonance tomography of the kidney: the testing of new pulse sequences and comparison with CT in the differential diagnosis of space-occupying lesions]

PURPOSE

To evaluate new pulse sequences (turbo-spin-echo [TSE] and turbo-field-echo [TFE] sequences) for study protocol optimisation and to assess the role of MRI in the differential diagnosis of renal tumours.

METHODS

In six volunteers MRI of the kidney was performed at 0.5 T using a conventional T2 weighted spin-echo (SE) sequence (TR/TE 1800/90 ms) and three different TSE sequences (TR 1800-5000 ms, TE 90-150 ms). Additionally CT and MRI was performed in 34 patients with 41 renal masses. Two readers evaluated both images regarding the differentiation between malignant and benign masses.

RESULTS

The pilot study showed that the heavily T2-weighted TSE sequence (TR/TE 5500/150 ms) was superior to other sequences with regard to image quality and differentiation of the corticomedullary junction. In the clinical study malignant tumours were correctly classified with CT and MRI in 86.4% and 95.5% of the cases, whereas the accuracy in the diagnosis of benign lesions of CT and MRI was 73.7% and 89.5%, respectively.

CONCLUSION

Using new puls sequences MRI is superior to CT in the differential diagnosis of renal tumours. MRI is superior to CT in the differentiation between complicated cysts and cystic or hypovascular renal cell carcinomas.

[Intra-arterial treatment of therapy-resistant residual tumors of the pelvis]

PURPOSE

Evaluation of intraarterial cancer treatment in recurrent pelvic tumors, which were resistent to other treatment modalities.

PATIENTS AND METHODS

Ninety-seven patients suffering from pelvic recurrences originating from bladder (n = 40), rectum (n = 19), cervix (n = 21) oder other organs (n = 17) were treated by intraarterial chemotherapy (111 times) or transcatheter embolisation (52 times).

RESULTS

Less than 20% of our patients had remission of the tumor burden but tumor symptoms (especially pain and bleeding) could be controlled in 35 to 87% of the patients. The main complication was a muscle necrosis after intraarterial chemotherapy because of recurrent bladder cancer.

CONCLUSION

Intraarterial cancertherapy is a useful procedure for symptomatic treatment of tumor symptoms especially in case of bleeding. Local tumor control can only be achived in a minority of the patients.

[MR mammography at 0.5 tesla. I. Comparison of image quality and sensitivity of MR mammography at 0.5 and 1.5 T]

PURPOSE

To determine whether dynamic MR mammography is possible on midfield systems without loss of diagnostic sensitivity when compared to the standard highfield technique.

MATERIALS AND METHODS

42 consecutive patients were examined twice: Once using the standard dynamic 2D gradient echo technique at 1.5 T; a second examination was performed on a 0.5 T system. For the midfield examinations a 3D sequence with optimized T1 contrast was used to compensate for the shorter T1 relaxation times at 0.5 T. Subtraction images were calculated to improve detectability of enhancing lesions.

RESULTS

Image quality was comparable on both systems. Mean enhancement of lesions was higher at 0.5 T/3D as compared to 1.5 T/2D (161% versus 112%). In malignant lesions, enhancement at 0.5 T/3D surpassed that at 1.5 T/2D in 88% of cases; average maximum signal intensity increase of cancers was significantly higher at 0.5 T/3D as compared to 1.5 T/2D (183% versus 108% relative to baseline). One satellite lesion of a recurrent carcinoma was detected on the 0.5 T/3D images only.

CONCLUSION

A 3D gradient echo pulse sequence can be used to compensate for the T1 shortening effect of the lower field strength. With a 3D sequence, sensitivity of MRM at 0.5 T is even superior to that of the standard 2D highfield technique.

[Spiral computerized tomography, multiplane transesophageal echocardiography and magnetic resonance imaging in the diagnosis of thoracic aortic dissection]

The aim of this study was the evaluation of spiral computed tomography (Spiral-CT), multiplane transesophageal echocardiography (multiplane TEE) and magnetic resonance imaging (MRI) in the diagnosis of thoracic aortic dissection. 41 patients were examined: 30 with clinically suspected acute aortic dissection (14 Stanford A, 7 Stanford B), 11 with aortic repair (7/11 with persisting distal dissection). In 14 patients there was involvement of the supraaortic vessels. Sensitivity of Spiral-CT, multiplane TEE and MRI in the detection of aortic dissection was 100%, specificity was 100, 92, and 91%. In the assessment of involvement of aortic arch vessels sensitivity was 100, 67, and 60%, specificity was 100, 95, and 90%. The new imaging modalities Spiral-CT and multiplane TEE are equal to MRI in the detection of aortic dissection. In the assessment of the supraaortic branches Spiral-CT is superior to multiplane TEE and MRI and might become the method of choice.

[DIL vena cava filter. Initial experiences in 15 patients]

DIL filters were permanently inserted through the cubital vein, using a 7-F catheter, in 15 patients and were followed up for six months in 12 patients. One filter could not be opened and 4 others were only partly open. Clinically there were no recurrences of pulmonary emboli. There were no complications from the correctly placed filters. Amongst the 4 incompletely expanded filters, two caused perforation of the cava, in one the cava thrombosed and in another the filter migrated to the bifurcation of the pulmonary artery. It follows that unexpanded filters should not be placed in the cava. Measurements in 10 patients showed the cava reduced to less than 10 mm lumen. In two cases the reduction of lumen was only slight, measuring more than 15 mm. The effect of the reduction in the lumen remains to be compared with that achieved by other filters.

[Diagnostic imaging in primary hepatobiliary cystadenoma of the liver]

The clinical and radiological findings of 5 patients with a total of 7 hepatobiliary cystadenomas are reported. In all cases sonography and computed tomography were performed, in three cases angiography was carried out, and in one case magnetic resonance imaging was used. On sonography and computed tomography hepatobiliary cystadenomas exhibit relatively typical findings as a multicystic, space-occupying lesion with septation and papillary mucosal nodes; hence the diagnosis can be made preoperatively in most cases. For differential diagnosis, the malignant form, hepatobiliary cystadenocarcinoma has to be considered which can only be distinguished from the benign form by histology.

[Evaluation of rapid gradient-echo and turbo-spin-echo sequences in MRT of focal liver lesions using 0.5 tesla]

The value of rapid T1- and T2-weighted fast field (T1-FFE, T2-FFE) gradient-echo sequences and T2 weighted turbo-spin echo (TSE) sequences in the diagnosis of focal liver lesions using 0.5 Tesla was compared with conventional spin-echo sequences (SE). Amongst 88 liver lesions T1-SE sequences showed 98%, T2-TSE sequences showed 92%, T2-SE sequence showed 84%, T1-FFE sequence showed 78% and T2-FFE sequence showed 69%. Direct comparison has shown that TSE sequences are able to demonstrate significantly more lesions (p < 0.05) than T2-SE sequences. Quantitative assessment has shown that the tumor/liver contrast/noise ratio in the T1-SE sequence was 118% higher than in the T1-FFE sequence (p < 0.001). Comparison of T2 weighted sequences has shown that the tumour/liver contrast/noise ratio was 45% higher in the TSE sequence than in the T2-SE and 239% higher than in the T2-FFE sequence (p < 0.001). The results indicate that the TSE sequence should be used instead of the conventional T2-SE sequence because of the reduced time (about 40%), due to improved image quality and increased demonstration rate of liver lesions. Neither T1-FFE nor T2-FFE are suitable, when using moderate field strength, to replace T1-SE or TSE sequences.

[The nitinol stent as a palliative measure in inoperable carcinoma of the esophagus and cardia. Possibilities and limitations of the procedure]

Nitinol stents were used in ten patients as palliative treatment for carcinoma of the esophagus and the cardia. Following insertion of the stent the severity of dysphagia decreased on average from 3.2 to 1.5 (on a scale from 0-4). Difficulties with stent opening and passage through the gut were found particularly in the region of metal sutures at esophago-jejunal anastomoses. One stent, which had been obstructed by mucosal folds, had to be removed and replaced. One stent which had been incorrectly placed was extended by introducing a second stent by a coaxial technique. During the period of observation, six patients died after an average of 4.6 months. The palliative effect of the stent lasted on average for eleven weeks. In two patients the tumour grew beyond the stent and in three there was tumour growth into the stent.

[MR tomography and bone marrow scintigraphy in the screening of skeletal metastases in patients with breast carcinoma]

46 patients with recently diagnosed carcinoma of the breast were included in a prospective comparative study of MRI and bone marrow scintigraphy. The aim of the study was to compare these procedures within a histologically unified patient collective. It was shown that MRI was superior to bone marrow scintigraphy in respect of sensitivity (92% vs 58%) and specificity (97% vs. 85%), although only about three quarters of the marrow spaces are examined by MRI screening. Bone marrow scintigraphy suffered particularly from a relatively high number of false positive findings (haemangiomas, degenerative changes). MRI remains the method of choice for investigating the bone marrow.

[The role of MRT in detecting the cause of therapy-refractory partial complex epilepsy]

MRT is of considerable significance in the investigation of epilepsy because of its ability to render soft tissue contrast for the demonstration of structural lesions. The present retrospective study consists of an analysis of MRT findings in operatively confirmed, circumscribed temporal tumours and in hippocampal sclerosis. The examinations were performed under standard conditions using T1- and T2-weighted spin-echo sequences of the head and coronal T2-weighted gradient-echo sequences of the brain stem. The diagnosis of tumours was extremely accurate (22/23) and specific (18/23) whereas hippocampal sclerosis could not be satisfactorily demonstrated (5/18). The use of intravenous contrast medium did not provide any advantages.

[Hemophiliac arthropathy of the knee joint. Gd-DTPA-enhanced MRI; clinical and roentgenological correlation]

17 patients with hemophilic arthropathy of the knee joint were studied with static and dynamic MRT before and after i.v. bolus injection of Gadolinium-DTPA (0.1 mmol/kg body weight). After contrast enhancement, synovial proliferations exhibited an increase of signal intensity (SI) on FFE and SE images of 47.7% and 37.4% respectively, whereas muscle and fatty tissue, tendons, bone marrow and joint effusion revealed only minor increase in SI. The gradient of signal intensity (ratio SI/time) of pannus was 39.6%/min. Gd-DTPA enhanced MRI studies delineate and quantify the synovial proliferations in hemophilic arthropathy. Dynamic studies in hemophilic arthropathy do not provide qualitative assessment of the inflammatory process.

[Primary amyloid tumor of the lung]

Primary idiopathic amyloidosis may be a diagnostic problem because of its low incidence and its variable manifestations. The clinical and radiographic findings in a patient with accidentally discovered primary amyloidosis of the lung are presented. The extensive mediastinal and hilar lymph-node enlargement was striking. Peripheral bronchial carcinoma was initially suspected because of the radiographic and CT findings. Various patterns of pulmonary amyloidosis have to be considered in the differential diagnosis of nodules and interstitial changes of the lung.

[Manganese-DPDP in the MR tomography of malignant liver tumors. The initial results with a new hepatobiliary contrast agent]

The new hepatobiliary contrast agent Mangan-DPDP, unlike extracellular Gd-DTPA, leads to a constant increase in signal intensity of normal liver tissue in MR imaging of the liver which lasts at least for 30 minutes. In 19 patients with malignant liver tumors there was no difference in the contrast between tumor and liver when using a dose of 5 or 10 mumol/kg. Contrast enhanced T1-w SE- and T1-w GE sequences show a significant increase in tumor/liver contrast compared with T1-weighted unenhanced sequences. This increase was also significant when compared with T2-w SE sequences. In 16% additional focal lesions were detected on the enhanced scan.

Pneumocystis carinii pleuropneumonia after aerosolized pentamidine prophylaxis

We observed an atypical Pneumocystis infection with spontaneous pneumothorax, bronchopleural fistulae, an apical cyst and Pneumocystis pleuritis after aerosolized pentamidine prophylaxis in an AIDS patient. These findings suggest a failure of pentamidine aerosol in controlling active Pneumocystis infection in peripheral pulmonary areas. A relapse of Pneumocystis carinii pneumonia (PCP) must be suspected when pneumothorax occurs during secondary prophylaxis with aerosolized pentamidine. It should always be confirmed by bronchoalveolar lavage or transbronchial or open biopsy. Cases presenting as atypical Pneumocystis pneumonia may additionally reveal extrapulmonary dissemination of Pneumocystis infection.

[Progressive cytomegalovirus encephalitis in successful ganciclovir therapy of cytomegalovirus retinitis in an AIDS patient]

We describe a case of an HIV-infected intravenous drug-abuser who died of progressive cytomegalovirus encephalitis despite successful treatment of cytomegalovirus retinitis with ganciclovir. On autopsy, complete remission of retinitis and widespread cytomegalovirus-encephalitis could be demonstrated. Therapeutic failure therefore seems attributable to insufficient CNS-distribution of ganciclovir rather than to ganciclovir-resistant cytomegalovirus strains.

[Course and diagnosis of pulmonary Kaposi sarcoma in patients with AIDS]

Diagnosis of pulmonary Kaposi's sarcoma can be difficult. Clinical findings and chest X-rays are non-specific and endobronchial diagnostic in about 50% of cases. Additional concomitant infectious complications are frequent. Symptomatic pulmonary Kaposi's sarcoma most oftenly is progressive and has a poor prognosis. Preliminary data suggest effective palliation with radio- and chemotherapy and an improved survival time in selected cases. We present six cases of proven pulmonary Kaposi's sarcoma and discuss clinical course and diagnostic difficulties. Based on this view we propose a diagnostic approach to warrant therapeutic success.

[Non-selective digital subtraction angiography of aortocoronary bypasses]

Intra-arterial DSA was performed on 225 patients with a total of 552 coronary bypasses (515 aorto-coronary venous bypasses and 37 internal mammary artery bypasses). Four hundred and ninety-five bypasses were examined in the four weeks following surgery; of these, 428 (85.9%) were patent. Demonstration of the distal anastomosis was obtained in 40.4% of bypasses of the right anterior interventricular artery and in 36.1% of the right coronary artery, at least in their proximal parts. Bypasses of smaller branches showed filling in 12.8 to 19.2%. Because of the unsatisfactory demonstration of distal vessels by non-selective intra-arterial DSA, this method is suitable only for showing the patency of a bypass in the postoperative phase, but should not be used for investigating cardiac signs and symptoms following a bypass examination.

[Cardiomyopathy in progressive muscular dystrophy]

A dilated cardiomyopathy with clear signs of left-ventricular functional abnormalities occurred in a 21-year-old man with known Duchenne's progressive muscular dystrophy. Echocardiography and magnetic resonance imaging delineated the regional disorder of ventricular wall motion and defined its segmental extent. With neither method was it possible to analyse texture with demonstration of differential regional involvement. As a noninvasive method echocardiography is suitable for diagnosing Duchenne's cardiomyopathy and monitoring its progression.

[Computed tomography in orbital trauma]

The results of CT in 104 patients with traumatic lesions of the orbits have been analysed retrospectively. Eighty-four fractures of the orbital skeleton were diagnosed in 58 patients; in 18 cases there was peri-orbital, retrobulbar or intrabulbar bleeding and two patients had a ruptured globe. A foreign body was demonstrated in 20 cases. Additional fractures of neighbouring paranasal sinuses were present in 22 cases. Mucosal swelling or bleeding in the sinus was found in 59 cases and orbital emphysema in 22 patients. The particular value of CT in the diagnosis of orbital trauma lies in the certainty with which bony injury of the orbit and peri-orbital structures can be demonstrated.

[In vivo measurement of tissue relaxation times using localized 31P and 1H MR spectroscopy]

Methods of in vivo determination of 31P longitudinal relaxation times within image-determined volume selected MRI spectroscopy have been investigated. T1 values for phosphor compounds in skeletal muscle and in brain have been measured. The 1H relaxation times of T1 and T2 of diffuse parenchymal liver disease, using inversion recovery and spin echo sequences were compared with quantitative MR tomography. Clinically, spectroscopic techniques are particularly useful where there is superimposition of water and lipid signals during MR imaging.

[Qualitative control over quantitative MR tomography: in vitro and in vivo checks on relaxation time measurements]

In-vivo and in-vitro checks on measurements of relaxation times in MRI have been carried out as part of quality control. For the in-vitro experiments we used 13 reagents consisting of varying concentrations of copper sulphate manganese sulphate, gadolinium solutions and various oils as well as water. For in-vivo measurements we used liver parenchyma and fat in three subjects. Eight different sequences were performed; intra- and interindividual variations and comparison of three similar MRI units showed average variations of 2-3% for T1 and 3-4% variations for T2 relaxation times. This margin of error makes quantitative MRI acceptable for clinical use.

[Qualitative and quantitative NMR tomographic findings in focal nodular hyperplasia of the liver]

The qualitative and quantitative MRI findings in 16 patients with focal nodular hyperplasia (FNH) of the liver are described; nine of these were confirmed histologically. A central scar is typical of FNH and provides a reliable diagnosis. This finding was seen in half the cases. If the scar is not demonstrable, the following features suggest the diagnosis: smooth margins, homogeneous signal distribution, increased signal intensity in T2-weighted spin-echo images and reduced signal intensity in inversion-recovery sequences. The T1 and T2 relaxation times in FNH are increased by about 30% compared with normal liver tissue.

[Relaxation time measurements in the differential magnetic resonance tomographic diagnosis of liver tumors]

T1-weighted IR sequences and T2-weighted SE sequences and combined SE/IR sequences were carried out in 62 patients with malignant and 50 patients with benign liver tumours and the T1 and T2 relaxation times were measured. IR sequences proved the most sensitive method for imaging focal liver lesions and providing good contrast between liver tissue and tumour. For lesions above 1.5 cm, quantitative MRI achieved an accuracy better than 95% in distinguishing between haemangiomas and malignant lesions. Routine quantitative measurements of relaxation times were sufficiently reproducible for clinical use.

[MR tomography, CT and angiography of vascular malformations of the central nervous system]

The findings on MR tomography in 31 vascular malformations of the central nervous system are described; 26 of these had angiography and 24 were examined by CT. There were 19 A-V angiomas, 7 cavernomas and 5 large aneurysms. MRT provided a correct diagnosis in 29 out of 31 cases, angiography succeeded in 19 out of 26 cases and CT in 20 of 24. MRT was superior to CT and angiography. Nevertheless, it cannot replace arteriography, since this is the only method for demonstrating the vascular supply of angiomas and small aneurysms can be demonstrated only by arteriography.

[CT portography in malignant space-occupying lesions of the liver]

CT portography was performed in 32 patients with liver tumours and in four patients with cirrhosis of the liver, but without evidence of tumour, after angiographic injection of contrast into the superior mesenteric or splenic arteries. Compared with CT using no contrast, or contrast by intravenous injection, CT portography has the following advantages: better tumour detection, better detection of tumour size, better demarcation and localisation of tumours, better demonstration of the portal system, more inhomogeneity of the parenchyma. Of 12 patients with a number of tumours shown on CT, CT portography demonstrated tumours in four cases, which could not be shown by any other imaging method. Problems concerning CT portography in patients with cirrhosis of the liver are discussed.

Cerebral sarcoidosis presenting as supranuclear gaze palsy with hypokinetic rigid syndrome

A 31-year-old man with histologically documented pulmonary sarcoidosis developed a severe hypokinetic rigid syndrome with a supranuclear gaze palsy following recurrent lymphocytic meningitis and occlusive hydrocephalus. Magnetic resonance imaging (MRI) showed multiple hyperintense foci in the CNS, not detectable by computed tomography (CT). Long-term steroid therapy led to clinical complete remission.

[MR tomography of hepatic hemangioma]

MR tomography of the liver using 1.5 T has been carried out in 63 patients with focal lesions in order to demonstrate haemangiomas and to differentiate these from primary and secondary malignant liver tumours. This differentiation was possible in all patients, using conventional spin echo and inversion recovery sequences in combination with sonography. Accuracy was much less good when using gradient echo sequences. With sufficiently large tumours, measurement of relaxation time made possible diagnosis of all the 22 haemangiomas.

[Artifact reduction via motion-compensating gradient shifting in MR tomography]

In 62 patients spinecho or gradientecho sequences compensated for motion were compared with corresponding non-compensated sequences. Compensation during MRT reduces those artifacts which are caused by regular motion. This is particularly effective during examination of the brain stem, spinal canal and the heart. The improved demonstration of the morphology of normal and diseases organs simplifies the analysis of the types of movement.