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Twenty surgically proven pituitary microadenomas were examined with MR imaging and CT. MR demonstrated 20 of 20 microadenomas: 90% of the tumors were hypointense on T1-weighted images before Gd-DTPA administration and in 45% the tumors were more clearly delineated postcontrast. CT demonstrated 19 of 20 diagnosed microadenomas: showing low attenuation in 85% of the tumors precontrast. Iohexol facilitated delineation of the tumors in 45%. Focal enlargement of the gland and diaphragma sellae convexity were more useful than infundibular tilting and sellar—floor erosion as ancillary findings supporting the diagnosis. In general, CT and MR agreed regarding the microadenomas' size and location, measurement of enlarged intrasellar contents, detection of the diaphragma sellae bulge, and demonstration of infundibulum abnormality. CT was more sensitive than MR in identifying sellar—floor erosion. We suggest that CT be the first method for demonstration of microadenomas.

Continuous recording of vital physiological variables and sequential MR imaging were performed simultaneously during continuous expansion of an epidural rubber balloon over the left hemisphere in anaesthetised dogs. Balloon expansion led to a progressive and slightly nonlinear rise in intracranial CSF pressures and a fall in local perfusion pressures. Changes in systemic arterial pressure, pulse rate, and respiration rate usually appeared at a balloon volume of 4% to 5% of the intracranial volume (reaction volume), together with a marked transtentorial pressure gradient and MR imaging changes consistent with tentorial herniation. Respiratory arrest occurred at a balloon volume of approximately 10% of the intracranial volume (apnoea volume), which was associated with occlusion of the cisterna magna, consistent with some degree of foramen magnum herniation. Increase in tissue water was observed beginning at approximately the reaction volume, presumably due to ischaemic oedema, due to the fall in perfusion pressures.

Eight patients with liver metastases from endocrine gastrointestinal tumours were examined with magnetic resonance imaging of the liver before and during treatment with interferon. T1, T2 and tumour size were measured and compared with tumour marker levels and symptomatic improvement or deterioration. Before therapy all tumours showed a long T1 and T2, in comparison to normal liver and fat, and during therapy they all showed a decrease in T1. As no change in liver T1 and fat T1 occurred, the decreased tumour T1 is considered to be a therapy effect. This cannot be fully explained but is possibly due to a reduction in tumour growth rate during interferon treatment. There was no certain correlation between tumour T1 and tumour marker levels or symptomatic changes.

A method has been developed to estimate the dipolar hyperfine interaction for 19F in fluorinated radicals based on INDO theory. The dipolar integrals have been calculated using Slater-type orbitals. Careful selection of effective nuclear charges, different from those obtained by Slater's rules, and adjustment for the valence electron distribution proved necessary in order to obtain agreement between theory and experiment. The method has been applied to a prototype system, the ·CF3 radical. The results confirm a pyramidal structure with an F-C-F bond angle θ = 109·5° - 112·0° and a C-F bond length of 1·30-1·35 Å. With θ=111·1° the dipolar tensor is calculated to be (122·2, -55·5, -66·7) G, close to the experimental result (120·0, -56·5, -63·5) G.An ambiguity in the determination of the sign of the angle α' between the 120·0 G component and the C3v symmetry axis was found to occur experimentally but not theoretically.According to experiment α' = ± 17·8°, where the negative sign corresponds to an axis perpendicular to the C-F bond. INDO theory gives α' = 26·8°. Ab initio theory confirms the pyramidal structure with θ = 111° and α' = 19·7°. Thus the 120 G component is believed not to be perpendicular to the C-F bond, but to make an angle of about 54° with the bond axis. This result is explained by the contribution to the dipolar couplings from spin density in 19F 2p orbitals. In this instance bond directions cannot be obtained from E.S.R. data without detailed analysis of the electronic structure.