Quantitative imaging with the positron emitter (86)Y is the method of choice to determine the uptake and dosimetry of (90)Y-labelled radiopharmaceuticals. To examine the quantitative accuracy of positron emission tomography findings with (86)Y, this non-pure positron emitter was evaluated in a cylindrical phantom with rods of Teflon, water and air and measured with three different scanners: ECAT EXACT (2D/3D), ECAT HR+ (2D/3D) and PC4096+ (2D). After standard reconstruction, (86)Y radioactivity measured with the ECAT EXACT and related to the true radioactivity varied between 0.84 and 0.99 in 2D and between 0.93 and 1.20 in 3D from the first to the last acquisition (eight half-life times later). The water and Teflon rods exhibited considerable amounts of reconstructed radioactivity-21% in 2D and 67% in 3D for water and 65% and 147%, respectively, for Teflon-compared with the actual (86)Y radioactivity of the phantom. For the ECAT HR+ similar results were obtained in 3D, but there were even greater overestimations in 2D. Measurements with the PC4096+ showed rather small errors, with 10% for water and 20% for Teflon. To correct for the background of gamma-coincidences, sinograms were analysed and an experimental percentage of the background was subtracted from the sinograms. In order to minimise the errors in reconstructed radioactivity, the subtraction value had to be different for the individual scanners and modes. Our results demonstrate that (90)Y/(86)Y-based dosimetry for bone and red marrow must be regarded with caution if it is derived from regions of interest over the bone, the density of which is similar to that of Teflon. To obtain more reliable estimates, an appropriate background correction must be applied and tailored individually with respect to the scanner and acquisition mode.

Fusion of morphology and function has been shown to improve diagnostic accuracy in many clinical circumstances. Taking this into account, a number of instruments combining computed tomography (CT) with positron emission tomography (PET) or single-photon emission tomography (SPET) are appearing on the market. The aim of this study was to evaluate a simple and cost-effective approach to generate fusion images of similar quality. For the evaluation of the proposed approach, patients with neuroendocrine abdominal tumours with liver metastases were chosen, since the exact superimposition in the abdomen is more difficult than in other regions. Five hours following the injection of 110 MBq (111)In-DTPA-octreotide, patients were fixed in a vacuum cushion (MED-TEC, Vac-Loc) and investigated with helical CT in a mid-inspiration position ( n=14). Directly following the CT, a SPET study (SPET1) of the abdominal region was performed without changing the position of the patient. A second SPET study (SPET2), 24 h p.i., was acquired after repositioning the patient in his or her individually moulded vacuum cushion. A total of nine markers suitable for imaging with CT and SPET were fixed on the cushion. Datasets were fused by means of internal landmarks (e.g. metastases or margin of abdominal organs) or by the external markers. Image fusion using external markers was fast and easy to handle compared with the use of internal landmarks. Using this technique, all lesions detectable by SPET ( n=28) appeared exactly superpositioned on the respective CT morphology by visual inspection. Image fusion of CT/SPET1 and CT/SPET2 showed a mean deviation of the external markers that in the former case was smaller than the voxel size of 4.67 mm: 4.17+/-0.61 (CT/SPET1; +/-SD) and 5.52+/-1.56 mm (CT/SPET2), respectively. Using internal landmarks, the mean deviation of the chosen landmarks was 6.47+/-1.37 and 7.78+/-1.21 mm. Vector subtraction of corresponding anatomical points of the CT and the re-sampled SPET volume datasets resulted in a similar accuracy. Vector subtraction of the metastases showed a significantly less accurate superimposition when internal landmarks were used ( P<0.001). The vacuum cushion did not affect the image quality of CT and SPET. The proposed technique is a simple and cost-effective way to generate abdominal datasets suitable for image fusion. External markers positioned on the cushion allow for a rapid and robust overlay even if no readily identifiable internal landmarks are present. This technique is, in principle, also suitable for CT/PET fusion as well as for fusions of MRI data with PET or SPET.

Objectives-The pathophysiology of dysarthria can preferentially be studied in patients with the rare lacunar stroke syndrome of "isolated dysarthria". Methods-A single study was carried out on seven consecutive patients with sudden onset of isolated dysarthria due to single ischaemic lesion. The localisation of the lesion was identified using MRI. The corticolingual, cortico-orofacial, and corticospinal tract functions were investigated using transcranial magnetic stimulation. Corticopontocerebellar tract function was assessed using 99m Tc hexamethylpropylene amine oxime-single photon emission computerised tomography (HMPAO-SPECT) in six patients. Sensory functions were evaluated clinically and by somatosensory evoked potentials. Results-Brain MRI showed the lesions to be located in the corona radiata (n=4) and the internal capsule (n=2). No morphological lesion was identified in one patient.Corticolingual tract function was impaired in all patients. In four patients with additional cortico-orofacial tract dysfunction, dysarthria did not diVer from that in patients with isolated corticolingual tract dysfunction. Corticospinal tract functions were normal in all patients. HMPAO-SPECT showed no cerebellar diaschisis, suggesting unimpaired corticopontocerebellar tract function. Sensory functions were not aVected. Conclusion-Interruption of the corticolingual pathways to the tongue is crucial in the pathogenesis of isolated dysarthria after extracerebellar lacunar stroke. (J Neurol Neurosurg Psychiatry 1999;66:495-501)

Our results suggest that a possible antipsychotic activity of EMD 57445 in schizophrenia is not necessarily attributable to its affinity for sigma receptors, but could be simply due to the potent antidopaminergic effects of EMD 59983, its main metabolite.

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