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The clock drawing (CD) task involves visual integration skills associated with parietal lobe function. Seven mild Alzheimer's Disease (AD) patients and 11 healthy elderly controls (EC) underwent functional magnetic resonance imaging (fMRI) scanning while viewing a radial motion (RM) task. This RM task in EC activated the bilateral secondary visual cortex and parietal regions, whereas AD patients activated only the right-sided secondary visual cortex. The magnitude of the fMRI signal in the left superior parietal lobe was positively correlated with performance on the CD task in AD patients. These findings suggest that complex visuospatial processing impairments reflect the underlying AD neuropathology in parietal regions.

Free association has been central to psychoanalytic theory and practice for over a century, yet its physiology has largely been ignored. When viewed from a cognitive neurobiological perspective, the process resembles a minimally constrained executive task, one that might engage the left dorsolateral prefrontal cortex. To test this hypothesis, we used functional magnetic resonance imaging to detect neural activity while subjects performed overt, vocal free association in the scanner. Twelve healthy subjects performed three active tasks—vocal free association, orthographic (letter) fluency, and semantic (category) fluency—alternating with a baseline condition, word repetition. Stimulus administration and overt response performance occurred during periods of scanner silence. Each subject was scanned three times, the order of conditions counterbalanced across scans. Statistical parametric mapping was used to perform a mixed-effects analysis of those images acquired. We found that, in common with both verbal f...

A method of image guidance for neurosurgery using the surgeon's binocular depth perception is described. Magnetic resonance volume acquisitions and surface rendering software were used to produce stereoscopic pairs of images of the surface of the heads of patients with brain tumours. Stereoscopic pairs of the surface rendering of the tumour were also produced. The two pairs of images were colour-coded and combined into one pair of 35-mm slides. A stereoscopic viewer was constructed to allow simultaneous viewing of the pair of slides and the patient's head. Registration was achieved by moving the stereoscope in space until the virtual images of the rendered surface of the head coincided with the real head. The stereoscope was then locked in position and the virtual image of the tumour was projected 'into' the patient's head to allow the surgeon to locate the tumour. The instrument was used in six cases. A lateral accuracy of 10-15 mm was achieved and a depth accuracy of 5-10 mm.

The purpose of this study was to determine whether short echo-time proton magnetic resonance spectroscopy (H-MRS) could detect mobile lipid resonances attributable to myelin breakdown products in the deep cerebral white matter of patients with AIDS who have severe diffuse/patchy white matter hyperintensity on T2-weighted magnetic resonance imaging (MRI). Seven patients with AIDS and clinical HIV-associated dementia complex (HADC) and 12 male controls were studied at 1.5T using a single 8 ml voxel, gradient localised, stimulated echo acquisition mode (STEAM) spectroscopy sequence. Spectra were acquired at an echo time of 20 ms with a repetition time of 5000 ms. No spectroscopic peaks were identified at 0.9 ppm and 1.3 ppm (corresponding to lipid resonances) in 6 of the 7 patients with AIDS or in any of the controls. Lipid resonances were identified in 1 patient who had been taking anti-retroviral therapy for 8 weeks. Follow up MRI/H-MRS, performed after a further 14 weeks of anti-retroviral therapy, showed partial resolution of white matter hyperintensity and lipid resonances were not detectable. These data suggest that mobile lipids are only rarely detected by H-MRS in patients with HADC and abnormalities on MRI and that their presence may be transitory.

SummaryAim - To correlate the magnetic resonance imaging signal changes observed during interstitial laser photocoagulation (ILP) therapy with histopatho-logical analysis of tissue necrosis. A 1.5T MR system was used. Lesions were produced with a diode laser (805 nm) in the liver of normal Wistar rats at laparotomy under general anaesthesia and imaged during treatment. Seventeen lesions were monitored with a T1-weighted spin echo (T1WSE) sequence, and 15 with a FLASH sequence. Treated tissue was removed and stained for NADPH-diaphorase to determine the extent of devitalization. Per-procedural T1WSE showed an expanding area of low signal which developed a high signal rim as ILP progressed. FLASH imaging showed an expanding area of low intensity which was replaced by a complex region of signal change as treatment progressed. Good imaging-histopathological correlation was shown: for T1WSE, r2=0.88 (P < 0.001) and for FLASH, r2=0.95 (P < 0.001). MR imaging during hepatic ILP accurately shows the extent of tis...

SummaryInterstitial laser photocoagulation (ILP) is currently limited by deficient per-procedural monitoring. The purpose of this study was to evaluate MR control of ILP of hepatic metastases. Twenty-two laser activations were used to treat eight metastases in seven patients under local anaesthesia and sedation. Laser energy was delivered via optical fibres positioned in the tumour under ultrasound guidance. T1-weighted FLASH and spin-echo sequences were used to monitor the procedure. Enhanced CT was performed at 24 h to assess thermal necrosis. FLASH imaging showed an enlarging area of signal change during ILP. The final extent of this correlated closely with the extent of tissue necrosis on CT. Spin-echo imaging was disappointing because of poor contrast between the treated tissue and normal liver/untreated tumour. Per-procedural MR imaging accurately and reliably depicts ILP-induced necrosis. MR control may permit more widespread application of ILP to the treatment of hepatic tumours.

The purpose of this study was to examine by proton spectroscopy for any difference in cerebral metabolites in patients taking part in the Concorde study (comparing the efficacy of immediate versus deferred treatment with zidovudine on asymptomatic HIV infected individuals). Forty seven HIV positive male patients [29 immediate, 18 deferred zidovudine] were examined in the last 9 months of the therapeutic trial. Magnetic resonance imaging and proton spectroscopy were performed at 1.5 Tesla using a single voxel placed in the parieto-occipital white matter. No significant difference was found in metabolite ratios comparing immediate versus deferred zidovudine (NA/NA+Cho+Cr 0.52 vs. 0.52). High quality spectra were acquired in relatively large numbers of patients and logistically spectroscopy may be applied to clinical therapeutic studies.