In forty patients at early and advanced stages of HIV infection (Walter Reed stages I-IV) regional cerebral blood flow was determined by 99mTc-HMPAO SPECT, comparing the results with CT and MRI findings. All patients with HIV encephalopathy (AIDS dementia complex) had pathologic SPECT results (multilocular, patchy uptake defects), but also in earlier and even earliest stages of HIV infection positive SPECT findings were observed. Compared to functional SPECT imaging, morphologically orientated methods (CT, MRI) were insensitive in detecting HIV-induced foci: more than 50% of the patients with pathologic SPECT findings had negative CT or MRI scans. Most patients in advanced Walter Reed stages had neurological abnormalities accompanied by positive SPECT. Subtle alterations of HMPAO uptake were observed even in a few cases of early HIV infection without neurological CNS symptoms. The data presented suggest that HMPAO SPECT is highly sensitive in the detection of altered brain perfusion not only in advanced but also early stages of HIV infection. Changes in regional cerebral blood flow are present before noticeable structural defects may be observed. Thus, it is suggested to use HMPAO SPECT in the evaluation and monitoring of patients with, and particularly at risk for, HIV encephalopathy.

40 children and adolescents (aged 1–16 years) were examined by MRI at 1.0 T. Gd-DTPA was given intravenously at a dose of 0.1 mmol/kg body weight. In all cases T1-weighted SE sequences were used to demonstrate contrast enhancement. No adverse effects were seen. 30 patients had one or more lesions; in 20 patients contrast enhancement was seen. In 4 cases lesions were not observed by plain MRI and could only be detected after Gd-DTPA. In addition, contrast enhancement provided additional information about the differentiation of lesion from edema or necrosis in 13 patients. Normal brain matter did not show any changes in signal intensity. However, an age-dependent signal increase was found in the normal vertebral bone marrow in all children. Gd-DTPA should be used as a supplementary examination whenever a tumor or an infectious disease of the CNS is suspected and plain MRI is normal, or when origin and extent of a lesion cannot be adequately defined with plain MRI.

MRT is a highly sensitive method for the diagnosis of childhood tumours in the posterior fossa. Since it demonstrates tumour extent better than does CT, MRT is the method of choice for radiotherapy planning. The result of treatment can be judged morphologically and by measuring relaxation times. Changes due to treatment can be recognised more easily than by CT. A disadvantage of MRT is lack of specificity, since various processes may lead to an equal increase in T1 and T2 times.

Studies designed to optimise image contrasts of gradient echo sequences showed, that especially repetition times between 250 and 500 ms in combination with adequate echo times and flip angles provide new image contrasts. The clinical purpose of gradient echo sequences with longer TR was systematically evaluated in 450 patients. A major advantage of GE sequences was the low signal intensity of fat and bone tissue. On the other hand different pathologic changes showed a high signal intensity in comparison to T2 weighted spin echo sequences as well. With the possibility of multiple slices GE sequences were of outstanding diagnostic value especially in MR of soft tissue and of the musculoskeletal system. T2 weighted SE sequences provided no additional informations and could therefore be omitted in a great number of examinations.

The MRI findings in 149 patients with a clinical diagnosis of disseminated encephalomyelitis (D.E.) were related to the diagnostic criteria of McAlpine (definite, probable, possible). The most common pattern in all three groups was a mixed peri- and para-ventricular distribution of foci. The findings in 'possible' D.E., compared with 'definite' D.E., showed fewer confluent lesions, but were characterised by peri- and para-ventricular as well as solitary foci. The results of the present study permit better classification and evaluation of the MRI findings if the clinical diagnosis of D.E. is only suspected (probable or possible).

A total of 209 intracranial and spinal diseases were evaluated before and after administration of the paramagnetic contrast agent Gd-DTPA. The results justify the use of Gd-DTPA in intracranial and spinal tumors for better visualization of location and extent of a lesion and for better tissue differentiation. In inflammatory diseases Gd-DTPA allows the differentiation between active and chronic lesions.

7 cas. 3 types de kystes ont ete observes qui peuvent etre distingues par l'intensite de leur signal. Comparaison des resultats obtenus par RMN et par tomodensitometrie

Seven patients with confirmed craniopharyngiomas were examined via magnetic resonance imaging. The various tumour components (whether solid, cystic or calcified) were evaluated separately. Three types of cysts were observed that can be distinguished by their signal intensity in various pulse sequences. This could be explained largely by an analysis of the T1 and T2 image contrast. The reason for the various types of cysts is determined by their cholesterol content. MR imaging is not as useful as CT for demonstrating the solid and calcified portions of the tumour and this reduces its value in diagnosing the type of tumour. Against that, it is superior with regard to separating the tumour from its neighbouring structures. The differential diagnosis, which must be considered in using MR, is summarised in a table at the end of the paper.

The article describes imaging of cerebral alveolar echinococcosis via nuclear magnetic resonance. The results are correlated with surgical and CT findings.

Sixty patients with malignant testicular tumours were treated with bleomycin according to the Einhorn regime. Following treatment, pulmonary infiltrates were seen on the chest x-ray of three patients and the CT of six patients. Altogether 24 infiltrates resembling metastases were seen in five patients. Five round foci were combined with infiltrates in other parts of the lung. Regression of the infiltrates after stopping bleomycin, negative tumour markers, the timing of the development of the infiltrates and the regression of the infiltrates in three patients without treatment make it extremely unlikely that the appearances were due to metastases.

25 patients in whom a carcinoma of the urinary bladder had been confirmed, were examined preoperatively by means of computerised tomography, and the local size of the tumour was determined. These findings were compared postoperatively with the histopathological staging. The degree of tumour spread was verified exclusively via cystectomy. CT does not yield very relevant data in respect of the therapeutically important differentiation of the low tumour stages. However, CT is very well suited in the diagnosis of tumours which have penetrated the bladder wall; however, diagnostic relevance in respect of organ infiltration can be definitely limited by the overlapping of other organs.

During a controlled study, 55 patients who had an anterior resection of the rectum were thoroughly examined, including by computed tomography. The results verified the following statements: 1. The use of CT as a screening-method for early detection of local tumour recurrence following anterior resection of the rectum appears not to be justified. 2. CT is indicated: a) if there is a laboratory or clinical suspicion of recurrence, despite normal findings on proctoscopy; b) to clarify the question of extramural extension if recurrence has been established by proctoscopy. 3. Following anterior resection of the rectum, CT normally demonstrates no remarkable development of scar tissue, unless the anastomosis is inadequate. 4. Following anterior rectal resection every indefinable tissue thickening in the pelvis must be considered a possible tumour recurrence and must be further investigated by needle biopsy.