Dynamic Single-photon Emission Tomography Research Articles

Aerosol deposition and clearance measurement: a novel technique using dynamic SPET.

Planar gamma camera scintigraphy is a well-established technique for characterising the deposition and clearance of radiolabelled aerosols. While single-photon emission tomography (SPET) can offer superior assessment of radioaerosol deposition and better differentiation between peripheral and central deposition, the long acquisition times of single-headed SPET have largely prevented its use for measuring clearance or deposition of fast-clearing radioaerosols. This study investigated the feasibility of fast dynamic SPET imaging (1 min/frame) using a three-headed gamma camera to assess the regional and total deposition and clearance of different radioaerosols over a period of 26 min. Six subjects inhaled nebulised technetium-99m diethylene triamine penta-acetic acid radiolabelled aerosols with small and large droplet sizes [mass median aerodynamic diameter (MMAD) 3.2 +/- 0.2 and 6.5 +/- 0.2 microm, span 1.8 and 1.7, respectively] and in normal (0.9%) or hypertonic (7%) saline with controlled breathing on four separate occasions. The penetration indices (PIs) calculated from the SPET data for normal saline were 0.50 +/- 0.04 and 0.36 +/- 0.02 for the small and large droplet sizes, respectively. Consistent with the hygroscopic growth of the hypertonic aerosols, the PIs for hypertonic saline were lower, at 0.43 +/- 0.02 and 0.34 +/- 0.02 for the small and large droplet sizes, respectively. PIs calculated from the planar data showed similar trends, but failed to detect the significant difference seen with SPET between small normal and small hypertonic saline radioaerosols. In conclusion, the feasibility of using fast dynamic SPET for imaging radioaerosol deposition and associated radiolabel clearance in the lung has been successfully demonstrated. The fast SPET was able to reveal important differences in aerosol deposition that were not detected by planar imaging.

Dynamic 99Tcm-HIDA SPET: non-invasive measuring of intrahepatic bile flow. Description of the method and a study in primary sclerosing cholangitis.

In this study dynamic 99Tcm-HIDA single photon emission tomography (SPET) was performed in patients with primary sclerosing cholangitis and normal test subjects. The method offers the possibility of functional analysis of individual liver segments. After injection of 120 MBq of 99Tcm-HIDA, 12 consecutive SPET examinations were performed at 6-min intervals. The segmental borders of liver segments as seen on computed tomography or magnetic resonance examinations were superimposed on the scintigraphic images allowing placement of regions of interest (ROIs) in specific liver segments. Sampling from the same ROIs in consecutive SPET images enabled creation of time-activity curves for individual liver segments. A range of normal values was created by quantitative analysis of normal volunteer studies. Results of the studies in patients correlated well with cholangiographic extent of disease, liver function tests and histological stage. The technique may have particular value in diseases that affect the liver in a nonhomogenous or segmental fashion. Giving an indication of bile clearance from individual liver segments, it can quantify the functional importance of radiologically detected strictures. Percutaneous liver biopsy can be directed to the worst affected parts of the liver, making biopsy more representative. Sequential studies may allow monitoring of disease progression, aiding in selection and timing of therapeutic procedures.

Simplified quantification of dopamine transporters in humans using [99mTc]TRODAT-1 and single-photon emission tomography.

Quantification of dopamine transporters (DAT) using [99mTc]TRODAT-1 and single-photon emission tomography (SPET) requires full kinetic modeling of the data, using complex and invasive arterial blood sampling to provide an input function to the model. We have shown previously that a simpler reference tissue model provides accurate quantitative results, using a reference region devoid of DAT as the input to the model and thereby obviating the need for blood sampling. We now extend this work into humans, and develop further simplifications to make the imaging protocol much more practical as a routine procedure. Fourteen healthy subjects (age 29.8 +/- 8.4 years, range 18.7-45.5 years) underwent dynamic SPET for 6 h following injection of 752 +/- 28 MBq [99mTc]TRODAT-1. The kinetic data were analyzed using nonlinear regression analysis (NLRA) and Logan-Patlak graphical analysis. In addition, simple average ratios of striatal-to-background counts were obtained for three 1-h periods (3-4 h, 4-5 h, 5-6 h), and compared against the kinetic models. All methods gave an index of specific binding, proportional to the binding potential, known as the distribution volume ratio (DVR). The reference tissue NLRA gave mean values of k3=0.013 +/- 0.003 min(-1), k4=0.011 +/- 0.002 min(-1), and DVR=2.29 +/- 0.17. Graphical analysis gave a value of DVR=2.28 +/- 0. 16, and the three ratio values of DVR were: 3-4 h, 2.18 +/- 0.15; 4-5 h, 2.34 +/- 0.13; and 5-6 h, 2.46 +/- 0.19. Graphical analysis was highly correlated with NLRA (R2=0.91, slope=0.90 +/- 0.08). The ratio methods correlated well with NLRA (3-4 h, R2=0.71, slope= 0.73 +/- 0.13; 4-5 h, R2=0.86, slope=0.73 +/- 0.09; 5-6 h, R2=0.80, slope=1.00 +/- 0.15), and also with graphical analysis (3-4 h, R2=0.65, slope=0.74 +/- 0.16; 4-5 h, R2=0.85, slope=0.78 +/- 0.09; 5-6 h, R2=0.88, slope=1.11 +/- 0.12). The optimum equilibrium time point for obtaining a simple ratio was approximately 4.5-5.5 h. In conclusion, the simple ratio techniques for obtaining a quantitative measure of specific binding correlated well with the reference tissue kinetic models, using both NLRA and graphical analysis. The optimum time for obtaining a ratio appeared to be in the range 4.5-5.5 h. Earlier time points, while still relatively accurate, had a lower sensitivity and may not be optimized for measuring small changes in DAT concentrations.

Relative preservation of peripheral lung function in smoking-related pulmonary emphysema: assessment with 99mTc-MAA perfusion and dynamic 133Xe SPET.

In this study the cross-sectional functional differences between the central and peripheral lung in smokers with pulmonary emphysema were evaluated by lung perfusion and dynamic xenon-133 single-photon emission tomography (SPET). The subjects were 81 patients with a long-term smoking history and relatively advanced emphysema, 17 non-smoker patients with non-obstructive lung diseases and six healthy non-smokers. Regional lung functional difference between the peripheral and central lung was assessed in the upper, middle and lower lung zones by technetium-99m macroaggregated albumin SPET and dynamic 133Xe SPET. The distribution of emphysematous changes was assessed by density-mask computed tomography (CT) images which depicted abnormally low attenuation areas (LAAs) of less than -960 Hounsfield units. Two hundred and eighty-eight (59.2%) lung zones of 63 (77.7%) patients with pulmonary emphysema showed relative preservation of lung function in the peripheral lung, with a curvilinear band of normal perfusion (a stripe sign) and a significantly faster 133Xe half-clearance time (T(1/2)) than in central lung (P<0.0001). Of these lung zones, 256 (88.8%) showed central-dominant LAA distributions on density-mask CT images, but the remaining 32 zones did not show any regional preference in LAA distribution. Conversely, 117 (24.0%) lung zones of 19 (23.4%) patients showed periphery-dominant perfusion defects and LAA distributions, with significantly prolonged T(1/2) in the peripheral lung area (P<0.0001). The remaining 81 lung zones of the patients with pulmonary emphysema and all the lung zones of the healthy subjects and patients with non-obstructive lung diseases did not show a stripe sign, and no differences were observed in T(1/2) values and LAA distributions between the central and peripheral lung. Relative preservation of peripheral lung function seems to be a characteristic feature in smoking-related pulmonary emphysema, and may indicate a lower susceptibility of peripheral parenchyma to the development of this disease.

Automatic segmentation of dynamic neuroreceptor single-photon emission tomography images using fuzzy clustering.

The segmentation of medical images is one of the most important steps in the analysis and quantification of imaging data. However, partial volume artefacts make accurate tissue boundary definition difficult, particularly for images with lower resolution commonly used in nuclear medicine. In single-photon emission tomography (SPET) neuroreceptor studies, areas of specific binding are usually delineated by manually drawing regions of interest (ROIs), a time-consuming and subjective process. This paper applies the technique of fuzzy c-means clustering (FCM) to automatically segment dynamic neuroreceptor SPET images. Fuzzy clustering was tested using a realistic, computer-generated, dynamic SPET phantom derived from segmenting an MR image of an anthropomorphic brain phantom. Also, the utility of applying FCM to real clinical data was assessed by comparison against conventional ROI analysis of iodine-123 iodobenzamide (IBZM) binding to dopamine D2/D3 receptors in the brains of humans. In addition, a further test of the methodology was assessed by applying FCM segmentation to [123I]IDAM images (5-iodo-2-[[2-2-[(dimethylamino)methyl]phenyl]thio] benzyl alcohol) of serotonin transporters in non-human primates. In the simulated dynamic SPET phantom, over a wide range of counts and ratios of specific binding to background, FCM correlated very strongly with the true counts (correlation coefficient r2>0.99, P<0.0001). Similarly, FCM gave segmentation of the [123I]IBZM data comparable with manual ROI analysis, with the binding ratios derived from both methods significantly correlated (r2=0.83, P<0.0001). Fuzzy clustering is a powerful tool for the automatic, unsupervised segmentation of dynamic neuroreceptor SPET images. Where other automated techniques fail completely, and manual ROI definition would be highly subjective, FCM is capable of segmenting noisy images in a robust and repeatable manner.

Simplified reference region model for the kinetic analysis of [99mTc]TRODAT-1 binding to dopamine transporters in nonhuman primates using single-photon emission tomography.

Accurate quantification of neuroreceptors requires full kinetic modeling of the dynamic single-photon emission tomography (SPET) or positron emission tomography (PET) images, with highly invasive arterial blood sampling. This study investigated the application of a reference region kinetic model to the dynamics of [99mTc]TRODAT-1 in nonhuman primates, obviating the need for blood sampling. A series of dynamic SPET scans were performed on two baboons following the injection of approximately 700 MBq of [99mTc]TRODAT-1. Rapid arterial blood samples were taken automatically during scanning. Reconstructed SPET images were coregistered with magnetic resonance imaging (MRI) scans of the baboons, and regions of interest (ROIs) placed on the striatum, cerebellum and cerebral hemispheres. The ROI data were combined with metabolite-corrected blood data, and fitted to a three-compartment kinetic model using nonlinear least squares techniques. The same data were also used in a simplified reference region model, in which the input function was derived from the nondisplaceable tissue compartment. In addition, semiquantitative blinded analysis was performed by three raters to determine the point of transient equilibrium in the specific binding curves. All methods generated values for the ratio of the kinetic rate constants k3/k4, which gives an estimate of the binding potential, BP. These were compared with the full kinetic model. The mean values of k3/k4 for the three different analysis techniques for each baboon were: 1.17 +/- 0.21 and 1.12 +/- 0.13 (full kinetic model), 0.93 +/- 0.13 and 0.90 +/- 0.07 (reference region model), and 0.97 +/- 0.18 and 0.92 +/- 0.08 (equilibrium method). The reference region method gave significantly lower results than the full kinetic model (P = 0.01), but it also produced a much smaller spread and better quality fits to the kinetic data. The reference region model results for k3/k4 correlated very strongly with the full kinetic analysis (r2 = 0.992, P < 0.001), and with the equilibrium model (r2 = 0.88, P = 0.002). The subjectivity inherent in the equilibrium method produces inferior results compared with both kinetic analyses. It is suggested that the self-consistency of the reference region model, which requires no arterial blood sampling, provides a more precise and reliable estimate of the binding of [99mTc]TRODAT-1 to dopamine transporters than full kinetic modeling. The reference region method is also better suited to a routine clinical environment, and would be able to distinguish smaller differences in dopaminergic function between patient groups.

Quantification of cerebral blood flow using technetium-99m ethyl cysteinate dimer and single-photon emission tomography.

The aim of this study was to develop a new method for quantifying regional cerebral blood flow (rCBF) with technetium-99m ethyl cysteinate dimer (ECD) and single-photon emission tomography (SPET). Employing a three-compartment model, we introduced a parameter, regional brain fractionation index (BFI), that reflects rCBF values and is obtained by a single SPET scan at optimum time T (min) after tracer injection and the integral of arterial input. By analysing the dynamic SPET and arterial blood sampling data of 15 subjects, including the results of acetazolamide challenges, with the graphical plot method, optimum time T was determined to be approximately 20 min post injection. Regional BFI values of each subject were calculated from the single SPET data at 20 min and arterial input. The relationship between the values of regional BFI and rCBF obtained by xenon-133 inhalation SPET was analysed by approximation with an exponential function, resulting in good agreement (r = 0.907). In the present method, rCBF values were determined from regional BFI values by using the inverse exponential function as a non-linear regression curve. To validate the method, we applied it to six other subjects, in whom acetazolamide challenges were also performed. In comparing rCBF values thus obtained and those obtained by 133Xe inhalation SPET, we found a good correlation (r = 0.901) with an inclination approximating 1 (= 1.02) and without underestimation of rCBF in the high-flow range. Since the present method does not require dynamic planar imaging or dynamic SPET scanning, it can be applied to any type of SPET scanner and is useful in clinical SPET studies.

A case of marked cerebellar atrophy in a woman with anorexia nervosa and cerebral atrophy and a review of the literature

While cerebral atrophy has been shown in patients with anorexia nervosa, cerebellar atrophy has never been reported in these patients. We report a case of cerebral atrophy with marked cerebellar atrophy in a 20-year-old woman with anorexia nervosa admitted to our hospital for severe weight loss. Neuroradiological examinations of the patient showed morphological brain alteration without focal parenchymal lesions. Cranial computerized tomography (CCT) showed an enlargement of the external cerebrospinal fluid spaces, especially those close to the cerebellar cistern. A brain magnetic resonance imaging (MRI) study confirmed the results of the CCT and dynamic single-photon emission tomography (d-SPECT) showed a reduced perfusion of the left brain areas. The reported case shows that some forms of anorexia nervosa have a concomitant presence of cerebral and cerebellar morphological anomalies. At present, it is not possible to demonstrate the whole correlation between the imaging reports and the clinical or neurological symptomatology. Some forms of brain alteration could be secondary to undernutrition; on the other hand, cerebral and cerebellar atrophy and eating disorders are far from clear and may also be an expression of an unknown common denominator. © 1998 by John Wiley & Sons, Inc. Int J Eat Disord 24: 443–447, 1998.

Evaluation of abnormal regional ventilation in patients with lung cancer using three-dimensional display of dynamic 133Xe SPET.

Preliminary studies were carried out of regional ventilation in lung cancer using three-dimensional (3D) display of dynamic pulmonary 133Xe single photon emission tomography (SPET). Transaxial equilibrium and washout images were obtained from SPET data acquired with an acquisition time of 30 s using a triple-detector SPET system in 39 patients with lung cancer. After reconstructing colour-illuminated, surface-rendered 3D images of equilibrium and 3-min washout (WO3), a single 3D fusion display was created from these two different time-course image sets, in which the 3D WO3 image indicating 133Xe retention was visible through the 3D equilibrium image delineating lung contours. The extent of retention was assessed using the 133Xe retention index, defined as the ratio of summed pixels of the segmented WO3 data to those of the segmented equilibrium data. 133Xe SPET was highly sensitive and specific for the presence of regional ventilation abnormalities associated with endobronchial tumour or bronchial compression due to enlarged lymph nodes. These abnormalities were demonstrated irrespective of the presence or absence of secondary changes distal to the tumour on the chest computed tomography scan. The geometrically realistic 3D fusion display enhanced anatomic localization of the regional ventilation abnormalities compared to the information from multislice tomograms, and the 133Xe retention index correlated well with %FEV1 (r = 0.828). This topographic 3D display for 133Xe SPET allows better perception of anatomic localization and extent of 133Xe retention. It will be useful for assessing regional ventilatory function in patients with lung cancer.

Index for predicting post-operative residual liver function by pre-operative dynamic liver SPET.

To predict residual liver function before hepatic resection, we devised a predictive index by combining clearance values with functional liver volume measured by liver dynamic single photon emission tomography (SPET). Forty-seven patients with liver disease underwent liver dynamic SPET with 99Tcm-Sn colloid before hepatic resection. There were no operation-related deaths. Three patients died from hepatic failure more than 1 month following the operation. Their predictive indices were 0.24, 0.33 and 0.34. When the predictive index was above 0.35, no patient had symptoms of hepatic failure or died. Our data suggest that when the predictive index is above 0.35, there is a low probability of hepatic failure after hepatectomy.

Initial evaluation of123I-5-I-R91150, a selective 5-HT2A ligand for single-photon emission tomography, in healthy human subjects

The mapping of 5-HT2 receptors in the brain using functional imaging techniques has been limited by a relative lack of selective radioligands. Iodine-123 labelled 4-amino-N-[1-[3-(4-fluorophenoxy)propyl]-4-methyl-4-piperidinyl]-5-iodo-2-methoxybenzamide (123I-5-I-R91150 or123I-R93274) is a new ligand for single-photon emission tomography (SPET), with high affinity and selectivity for 5-HT2A receptors. This study reports on preliminary123I-5-I-R91150 SPET, wholebody and blood distribution findings in five healthy human volunteers. Maximal brain uptake was approximately 2% of total body counts at 180 min post injection (p.i.). Dynamic SPET sequences were acquired with the brain-dedicated, single-slice multi-detector system SEM-810 over 200 min p.i. Early peak uptake (at 5 min p.i.) was seen in the cerebellum, a region free from 5HT2A receptors. In contrast, radioligand binding in the frontal cortex increased steadily over time, up to a peak at approximately 100–120 min p.i. Frontal cortex-cerebellum activity ratios reached values of 1.4, and remained stable from approximately 100 min p.i. onwards. Multi-slice SPET sequences showed a pattern of regional variation of binding compatible with the autoradiographic data on the distribution of 5-HT2A receptors in (cerebral cortex>striatum>cerebellum). These findings suggest that123I-5-I-R91150 may be used for the imaging of 5-HT2A receptors in the living human brain with SPET.

Initial evaluation of 123I-5-I-R91150, a selective 5-HT2A ligand for single-photon emission tomography, in healthy human subjects.

The mapping of 5-HT2 receptors in the brain using functional imaging techniques has been limited by a relative lack of selective radioligands. Iodine-123 labelled 4-amino-N-[1-[3-(4-fluorophenoxy)propyl]-4-methyl-4-piperidinyl]-5-io do-2-methoxybenzamide (123I-5-I-R91150 or 123I-R93274) is a new ligand for single-photon emission tomography (SPET), with high affinity and selectivity for 5-HT2A receptors. This study reports on preliminary 123I-5-I-R91150 SPET, whole-body and blood distribution findings in five healthy human volunteers. Maximal brain uptake was approximately 2% of total body counts at 180 min post injection (p.i. ). Dynamic SPET sequences were acquired with the brain-dedicated, single-slice multi-detector system SME-810 over 200 min p.i. Early peak uptake (at 5 min p.i.) was seen in the cerebellum, a region free from 5HT2A receptors. In contrast, radioligand binding in the frontal cortex increased steadily over time, up to a peak at approximately 100-120 min p.i. Frontal cortex-cerebellum activity ratios reached values of 1.4, and remained stable from approximately 100 min p.i. onwards. Multi-slice SPET sequences showed a pattern of regional variation of binding compatible with the autoradiographic data on the distribution of 5-HT2A receptors in humans (cerebral cortex>striatum>cerebellum). These findings suggest that 123I-5-I-R91150 may be used for the imaging of 5-HT2A receptors in the living human brain with SPET.

Quantitative analysis of scatter- and attenuation-compensated dynamic single-photon emission tomography for functional hepatic imaging with a receptor-binding radiopharmaceutical.

A new method for quantitative liver study was developed using the tracer technetium-99m diethylene triamine penta-acetic acid-galactosyl human serum albumin (99mTc-GSA), an analog ligand of the asialoglycoprotein receptor, which is a hepatocyte surface receptor specific for galactose-terminated glycoproteins. For quantitative dynamic single-photon emission tomographic (SPET) studies, attenuation compensation using transmission computed tomography (TCT) and the triple energy window (TEW) scatter compensation method were evaluated. As the TCT source, we used an uncollimated multi-tube source with the TEW scatter compensation method. To verify the accuracy of cross-calibrated SPET values as compared with measured radioactivities, we performed SPET of a cylindrical water pool phantom which contains seven hot rods filled with different concentrations of 99mTc activities, simulating the scan conditions in human studies. The results of the phantom studies showed good linearity and accuracy of the SPET values, with R2=0.993 and a regression line of y=0.941x+5.48. From the analysis of a kinetic model based on a one-compartment model, focussing on the initial stage of several minutes after 99mTc-GSA injection and taking the physiological expression presented in a three-compartment analysis into account, we introduced the Rutland equation (Patlak plot) in the 99mTc-GSA study by which the overall and regional effective hepatic blood flow (EHBF) and hepatic blood pool volume were determined. Preliminary clinical evaluations were performed for four normal male subjects (23-35 years of age) and one patient. Forty sequential 30-s dynamic SPET acquisitions were obtained for a period of 20 min following the intravenous injection of 99mTc-GSA with venous blood sampling at 10 min. After scatter compensation, the SPET images were reconstructed with attenuation compensation using an attenuation map obtained from TCT. The average normal value for the total EHBF was 468+/-83 ml/min and that for the hepatic blood pool volume, 777+/-123 ml. Functional images of the distribution of regional values of EHBF (ml/min/voxel) and hepatic blood pool volume (ml/voxel) were also generated corresponding to the original SPET images. The EHBF images showed regional liver function, higher in the right lobe than the left lobe in the normal cases, and the heptic blood pool volume images showed the distribution of intensified high values along major vascular structures. Receptor imaging with 99mTc-GSA using the Rutland method and dynamic SPET with scatter and attenuation compensation is an effective technique that allows the evaluation of total and regional hepatic functional parameters (EHBF, hepatic blood pool) in vivo.

A simple method for the quantification of benzodiazepine receptors using iodine-123 iomazenil and single-photon emission tomography

Iodine-123 iomazenil (Iomazenil) is a ligand for central type benzodiazepine receptors that is suitable for single-photon emission tomography (SPET). The purpose of this study was to develop a simple method for the quantification of its binding potential (BP). The method is based on a two-compartment model (K1, influx rate constant; k2', efflux rate constant; VT' (=K1/k2'), the total distribution volumes relative to the total arterial tracer concentration), and requires two SPET scans and one blood sampling. For a given input function, the radioactivity ratio of the early to delayed scans can be considered to tabulate as a function of k2', and a table look-up procedure provides the corresponding k2' value, from which K1 and VT' values are then calculated. The arterial input function is obtained by calibration of the standard input function by the single blood sampling. SPET studies were performed on 14 patients with cerebrovascular diseases, dementia or brain tumours (mean age+/-SD, 56.0+/-12.2). None of the patients had any heart, renal or liver disease. A dynamic SPET scan was performed following intravenous bolus injection of Iomazenil. A static SPET scan was performed at 180 min after injection. Frequent blood sampling from the brachial artery was performed on all subjects for determination of the arterial input function. Two-compartment model analysis was validated for calculation of the VT' value of Iomazenil. Good correlations were observed between VT' values calculated by three-compartment model analysis and those calculated by the present method, in which the scan time combinations (early scan/delayed scan) used were 15/180 min, 30/180 min or 45/180 min (all combinations: r=0.92), supporting the validity of this method. The present method is simple and applicable for clinical use.

Regional ventilatory evaluation using dynamic SPET imaging of xenon-133 washout in obstructive lung disease: an initial study

Regional ventilatory abnormalities in obstructive lung disease were evaluated by dynamic single-photon emission tomography (SPET) of pulmonary washout of xenon-133 (133Xe) gas. The subjects included seven healthy volunteers. 17 patients with obstructive lung disease, and seven patients with restrictive lung disease. Following 6 min of inhalation of 133Xe gas (60-72 MBq/l), equilibrium and subsequent washout SPET images during spontaneous breathing were sequentially acquired every 30 s for 6-7 min, using a triple-head SPET system with the return mode of continuous repetitive rotating acquisition. A gravity-induced gradient of ventilation was demonstrated in the volunteers' lungs. Compared with the normal subjects, all the patients with obstructive disease showed abnormal 133Xe retention on the washout SPET images, with or without abnormalities on chest X-ray computed tomography, whereas the patients with restrictive disease did not show any significant delays in washout. This modality may assist in the evaluation of the three-dimensional dynamic process of ventilatory abnormalities in obstructive lung disease.

Brain morphology and regional cerebral blood flow in anorexia nervosa

Cranial computed tomography (CT) was performed in 12 patients with anorexia nervosa, revealing that the majority of the patients displayed ventricular dilatation and/or sulcal widening. In addition, regional cerebral blood flow (rCBF) was measured at admission and once again after weight gain, using xenon-133 dynamic single-photon emission tomography (dSPECT). The mean flow rates assessed at the first examination did not significantly differ from those assessed at the second examination and from those of a control group. There was a significant inverse relationship between the size of the cerebrospinal fluid spaces and the cerebral blood flow in the anorectics; a decrease in ventricular size after weight gain was associated with an increase in cerebral blood flow in this area. This finding, however, has to be interpreted with caution, as partial volume effects render the flow rates ambiguous in brain areas, which, in addition to neuronal tissue, also include ventricular and sulcal structures.

Monitoring CBF in clinical routine by dynamic single photon emission tomography (SPECT) of inhaled xenon-133.

A very simple and low-cost brain dedicated, rapidly rotating Single Photon Emission Tomograph SPECT is described. Its use in following patients with ischemic stroke is illustrated by two middle cerebral artery occlusion cases, one with persistent occlusion and low CBF in MCA territory, and one with early lysis of the occlusion having high CBF (massive luxury perfusion) for some weeks. Evidence of this kind may be essential in the evaluation of therapeutic measures in ischemic stroke.

Normal distribution of regional cerebral blood flow measured by dynamic single-photon emission tomography.

Regional CBF (rCBF) was measured quantitatively using the inert-gas washout technique with xenon-133 and single-photon emission computed tomography. Tomographic data were reconstructed by filtered back projection, and flow was calculated according to the double-integral method. Ninety-seven subjects ranging in age from 20 to 59 years received a single examination; eight of these received a second examination within 1 h of the first; seven others received a second examination separated from the first by 1-10 days. Transverse-section images were obtained at 2, 6, and 10 cm above and parallel to the canthomeatal line (CML). Cortical gray matter flows were obtained from 12 brain regions in the slice 6 cm above the CML, and cerebellar and inferior cerebral gray matter flows were obtained from 4 regions in the slice 2 cm above the CML. Mean gray matter flow was 72 +/- 12 ml/min/100 g, with highest flows in the parietal lobes and visual cortex. No significant differences in rCBF occurred when a second study followed the first by 30 min to 10 days. Right-sided rCBF was slightly higher than left in all regions except frontal and parietal lobes where there was no difference. Flow was higher in women than in men and declined mildly with age for both sexes (slope = -0.33 ml/min/100 g/year; p less than 0.05).