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Objective: The dependent-density of computed tomography (CT) images of positron emission tomography (PET)/CT is sometimes difficult to distinguish from chronic interstitial lung disease (ILD) when it accompanies increased (18)F-fluorodeoxy-D: -glucose ((18)FDG) uptake. Though the possible utility of (18)FDG-PET for the diagnosis of active ILD has been reported, the clinical relevance of mild lung (18)FDG uptake in ILD cases without signs and symptoms suggesting acute progression has not been described. This study aimed to test relationships between (18)FDG uptake and lung density on CT using PET/CT in patients with normal lung as well as clinically stable chronic ILD. Methods: Thirty-six patients with normal lungs (controls) and 28 patients with chronic ILD (ILD cases) without acute exacerbation were retrospectively selected from (18)FDG-PET/CT scans performed in examination of malignant neoplasms. Elliptical regions of interest (ROIs) were placed on the lung. The relationships between CT density and (18)FDG uptake between the control and ILD cases were tested. Results: The CT density and (18)FDG uptake had a linear correlation in both the controls and the ILD cases without a difference in their regression slopes, and they were overlapped between the controls and the ILD cases with higher mean values in the ILD cases. Conclusions: Lung (18)FDG uptake was considered to reflect a gravity-dependent tissue density in the normal lung. Though the lung (18)FDG uptake as well as the CT density tended to be higher in chronic ILD patients, it may be difficult to distinguish them in normal dependent regions from those related to chronic ILD in some cases. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the normal distribution patterns of 99mTc-HMPAO (HMPAO) in young and aged normal individuals and to clarify differences between the distribution patterns of the two groups by means of an anatomical standardization technique. The tracer distribution was measured with HMPAO and SPECT in 18 normal subjects; age range 20-81 yrs. SPECT images were globally normalized by averaging whole brain radioactivity counts to 100 counts/voxel. The SPECT images for each subject were transformed into the standard brain anatomy by means of a computerized brain atlas, together with each subject's CT images. Mean and SD images for young (28.8 +/- 6.4 yrs) and aged groups (62.3 +/- 10.2 yrs) were then calculated on a voxel-by-voxel basis. Statistically significant differences between young and aged groups were observed in the relative tracer distribution patterns. In the aged group, relative decreases were found in the cortical areas of the frontal and temporal lobes, limbic areas and basal ganglia regions. The results, as visualized changes in tracer distribution patterns with aging, may contribute to more accurate clinical diagnosis. [ABSTRACT FROM AUTHOR]

Objective: In clinical positron emission tomography (PET) studies for oncology, it is occasionally required to differentiate a diffuse increase in bone marrow (BM) F-18 fluoro-2-deoxyglucose (FDG) uptake due to the involvement of malignancy or hematopoietic disease and that due to the administration of hematopoietic cytokines, an inflammation reaction, or stimulation by some types of malignancy. The objectives of this study were to clarify the relationships between BM F-18 FDG uptake and blood parameters as well as age, and also to determine the degree of F-18 FDG accumulation that constitutes an abnormal level referring to blood parameters., Methods: Records of 65 patients, 32 with benign diseases and 33 with malignancies without metastasis in bone and liver until a half year after the PET examination, were analyzed retrospectively. Regions of interest were placed on the liver and the lower thoracic and lumbar vertebrae to measure the standardized uptake value (SUV), and vertebral SUVs were averaged as the BM SUV(mean). The BM SUV(mean) was divided by the liver SUV to calculate the BM/liver ratio. The relationships among the BM SUV(mean), or BM/liver ratio, and blood parameters and age were tested using multiple regression analysis., Results: In both patients with and without malignancy, a multiple regression model using the BM/liver ratio showed a higher coefficient of determination value than that using the BM SUV(mean), indicating that the correction by the liver SUV reduced the interindividual variation in the BM SUV(mean). The BM/liver ratio was negatively correlated with age (beta = -0.41 and -0.43, respectively) and positively correlated with serum C-reactive protein (CRP) level (beta = 0.39 and 0.46, respectively) in both groups of patients. Every patient with benign disease who had a ratio greater than or equal to 1 had an increased CRP level., Conclusions: The BM F-18 FDG uptake depends on the patient's age and serum CRP level, both with and without malignancy. A BM F-18 FDG uptake greater than or equal to that of the liver may indicate BM activation.

The vertebral spine is frequently affected by the SAPHO (synovitis, acne, pustulosis, hyperostosis, and osteitis) syndrome. We report the collective imaging findings of hybrid F-18 fluorodeoxyglucose-positron emission tomography/computed tomography (18FDG-PET/CT), as well as bone scans and magnetic resonance imaging, in a patient who had suspected metastatic vertebral bone tumors. 18FDG-PET/CT can be utilized to exclude metastatic vertebral tumors, as well as identifying stable lesions, by demonstrating active inflammatory lesions with accurate anatomic localization through the convergence of the functional information from 18FDG uptake with the anatomic information of CT.

Objective: We compared the diagnostic accuracy achieved by a human observer (nuclear medicine physician) and a channelized Hotelling (CH) observer on the basis of receiver-operating characteristics (ROC) curve for the differential diagnosis of Alzheimer's disease (AD) from SPECT images., Methods: The I-123-IMP brain perfusion SPECT images of 42 subjects (21 AD patients and 21 healthy controls) were used for an interpretation study and those of 10 healthy subjects were for a normal database. SPECT images were processed into four types: original SPECT images, three-dimensional stereotactic surface projection (3DSSP) images derived from them, Z-scores of SPECT images, and Z-scores of 3DSSP images. Five nuclear medicine physicians evaluated the test dataset sequentially as to whether the presented images were those of AD patients, which were rated using five categories of certainty: definitely, possibly, equivocally, possibly not, and definitely not. The test statistics (lambda) of the dataset generated by the CH observer were rated for ROC analysis. The areas under the ROC curves (Az) for the four image types interpreted by the human and CH observers were estimated and compared., Results: Among the four image types, the best performance based on Az obtained by both the CH and human observers was observed for the Z-score of 3DSSP images, and the lowest was for the original SPECT images., Conclusions: The performance of the CH observer was similar to that of the human observers, and both were dependent on the image type. This indicates that the CH observer may predict human performance in discriminating Alzheimer's dementia and can be useful for comparing and optimizing image processing methods of brain perfusion SPECT without human observers.

Objectives: Three accumulative tracers, iodine-123-labeled N-isopropyl-p-iodoamphetamine (I-123-IMP), technetium-99m-labeled hexamethylpropyleneamineoxime (Tc-99m-HMPAO), and technetium-99m-labeled ethyl cysteinate dimer (Tc-99m-ECD) are widely used to measure cerebral blood flow (CBF) in single-photon emission computed tomography (SPECT). In the present study, normal regional distribution of CBF measured with three different SPECT tracers was entered into a database and compared with regional distribution of CBF measured by positron emission tomography (PET) with H2(15)O. The regional distribution of tissue fractions of gray matter determined by voxel-based morphometry was also compared with SPECT and PET CBF distributions., Methods: SPECT studies with I-123-IMP, Tc-99m-HMPAO, and Tc-99m-ECD were performed on 11, 20, and 17 healthy subjects, respectively. PET studies were performed on 11 healthy subjects. Magnetic resonance (MR) imaging studies for voxel-based morphometry were performed on 43 of the 48 subjects who underwent SPECT study. All SPECT, PET, and MR images were transformed into the standard brain format with the SPM2 system. The voxel values of each SPECT and PET image were globally normalized to 50 ml/100 ml/min. Gray matter, white matter, and cerebrospinal fluid images were segmented and extracted from all transformed MR images by applying voxel-based morphometry methods with the SPM2 system., Results: Regional distribution of all three SPECT tracers differed from that of H2150 in the pons, midbrain, thalamus, putamen, parahippocampal gyrus, posterior cingulate gyrus, temporal cortex, and occipital cortex. No significant correlations were observed between the tissue fraction of gray matter and CBF with any tracer., Conclusion: Differences in regional distribution of SPECT tracers were considered to be caused mainly by differences in the mechanism of retention of tracers in the brain. Regional distribution of CBF was independent of regional distribution of gray matter fractions, and consequently the blood flow per gray matter volume differed for each brain region.

Unlabelled: The limited spatial resolution of SPECT causes a partial volume effect (PVE) and can lead to the significant underestimation of regional tracer concentration in the small structures surrounded by a low tracer concentration, such as the cortical gray matter of an atrophied brain. The aim of the present study was to determine, using 123I-IMP and SPECT, normal CBF of elderly subjects with and without PVE correction (PVC), and to determine regional differences in the effect of PVC and their association with the regional tissue fraction of the brain., Methods: Quantitative CBF SPECT using 123I-IMP was performed in 33 healthy elderly subjects (18 males, 15 females, 54-74 years old) using the autoradiographic method. We corrected CBF for PVE using segmented MR images, and analyzed quantitative CBF and regional differences in the effect of PVC using tissue fractions of gray matter (GM) and white matter (WM) in regions of interest (ROIs) placed on the cortical and subcortical GM regions and deep WM regions., Results: The mean CBF in GM-ROIs were 31.7 +/- 6.6 and 41.0 +/- 8.1 ml/100 g/min for males and females, and in WM-ROIs, 18.2 +/- 0.7 and 22.9 +/- 0.8 ml/100 g/min for males and females, respectively. The mean CBF in GM-ROIs after PVC were 50.9 +/- 12.8 and 65.8 +/- 16.1 ml/100 g/min for males and females, respectively. There were statistically significant differences in the effect of PVC among ROIs, but not between genders. The effect of PVC was small in the cerebellum and parahippocampal gyrus, and it was large in the superior frontal gyrus, superior parietal lobule and precentral gyrus., Conclusion: Quantitative CBF in GM recovered significantly, but did not reach values as high as those obtained by invasive methods or in the H2(15)O PET study that used PVC. There were significant regional differences in the effect of PVC, which were considered to result from regional differences in GM tissue fraction, which is more reduced in the frontoparietal regions in the atrophied brain of the elderly.

Objectives: Single-photon emission computed tomography (SPECT) with iodine-123 (123I)-labeled N-isopropyl-p-iodoamphetamine (IMP) is widely used in measuring the cerebral blood flow (CBF) response to acetazolamide stress for assessment of cerebral vascular reserve. To quantitate CBF by means of SPECT with IMP, an autoradiographic (ARG) method has been developed and is widely used. Because the relation between the brain counts on the SPECT scan and CBF is not linear in the ARG method, a mixture of gray and white matter in a pixel causes errors in the calculation of CBF. In the present study, errors in the calculation of CBF and vascular response to acetazolamide stress by the ARG method due to tissue heterogeneity were estimated by simulation study. Correction for effects of tissue heterogeneity in SPECT data was also attempted., Methods: Images of gray and white matter fraction were obtained by voxel-based morphometry analysis of magnetic resonance (MR) imaging data set. Ideal CBF images, which were generated from gray and white matter fraction images with assumed blood flow values for gray and white matter, were compared to CBF images generated by the ARG method. Correction for effects of tissue heterogeneity in SPECT data was performed with gray and white matter fraction data obtained from MR images., Results: Systematic underestimation of CBF due to tissue heterogeneity was observed in all brain regions. In the neocortical regions, underestimation by -21% to -16%, -26% to -20%, -31% to -24%, and -35% to -27% was observed for gray and white matter blood flow of 80 and 20, 100 and 25, 120 and 30, and 140 and 35 ml/100 ml/min, respectively. Vascular response was also systematically underestimated in most brain regions. Vascular responses in the neocortical regions ranged from 17% to 20%, from 31% to 37%, and from 42% to 52% when ideal vascular responses were 25%, 50%, and 75%, respectively. After correction for the effects of tissue heterogeneity, values of vascular response to acetazolamide stress ranged from 64% to 116% in the neocortical regions, whereas values obtained by the ARG method ranged from 48% to 52%., Conclusion: Underestimation of the vascular response to acetazolamide stress due to tissue heterogeneity should be considered in the estimation of cerebral vascular reserve.

Several studies using single photon emission tomography (SPECT) have shown changes in cerebral blood flow (CBF) with age, which were associated with partial volume effects by some authors. Some studies have also demonstrated gender-related differences in CBF. The present study aimed to examine age and gender effects on CBF SPECT images obtained using the 99mTc-ethyl cysteinate dimer and a SPECT scanner, before and after partial volume correction (PVC) using magnetic resonance (MR) imaging. Forty-four healthy subjects (29 males and 15 females; age range, 27-64 y; mean age, 50.0 +/- 9.8 y) participated. Each MR image was segmented to yield grey and white matter images and coregistered to a corresponding SPECT image, followed by convolution to approximate the SPECT spatial resolution. PVC-SPECT images were produced using the convoluted grey matter MR (GM-MR) and white matter MR images. The age and gender effects were assessed using SPM99. Decreases with age were detected in the anterolateral prefrontal cortex and in areas along the lateral sulcus and the lateral ventricle, bilaterally, in the GM-MR images and the SPECT images. In the PVC-SPECT images, decreases in CBF in the lateral prefrontal cortex lost their statistical significance. Decreases in CBF with age found along the lateral sulcus and the lateral ventricle, on the other hand, remained statistically significant, but observation of the spatially normalized MR images suggests that these findings are associated with the dilatation of the lateral sulcus and lateral ventricle, which was not completely compensated for by the spatial normalization procedure. Our present study demonstrated that age effects on CBF in healthy subjects could reflect morphological differences with age in grey matter.

Objectives: Iodine-123 (123I)-labeled N-isopropyl-p-iodoamphetamine (IMP) has been used as a cerebral blood flow (CBF) tracer for single-photon emission computed tomography (SPECT), and measurements of the CBF response to acetazolamide stress by SPECT with IMP are widely used to assess cerebral vascular reserve. To quantitate CBF by means of SPECT with IMP, an autoradiographic (ARG) method has been developed and is widely used. In the ARG method, CBF is calculated from the brain counts of the SPECT scan with an assumed distribution volume value of IMP (Vd). However, differences between true Vd and assumed Vd results in errors in calculated CBF. In the present study, errors in the CBF response to acetazolamide stress as calculated by the ARG method were investigated., Methods: SPECT studies were performed on 12 patients with steno-occlusive lesions of the major cerebral artery. Two studies were performed on separate days. The first study was performed at rest (baseline), and the second during acetazolamide stress. SPECT scans were performed at 40 min (early scan) and 180 min (delayed scan) after intravenous injection of IMP., Results: Although a simulation study showed that errors in calculated changes in CBF in response to acetazolamide stress, which result from differences between the true Vd and the assumed Vd, were larger when the baseline CBF and change in CBF were larger, values calculated by the ARG method with an assumed Vd were in good agreement with those calculated with true Vd obtained from early and delayed scan data., Conclusion: These data indicate that errors in the calculated CBF response to acetazolamide stress as calculated by the ARG method are negligible even at high CBF responses. The ARG method is therefore reliable for measurement of CBF response to acetazolamide stress.

Objective: Two methods of quantitating cerebral blood flow (CBF) with iodine-123-labeled N-isopropyl-p-iodoamphetamine (I-123 IMP) and a two-compartment model had been proposed; one is the table look-up (TLU) method and the other is the autoradiographic (ARG) method. The TLU method provides values of the cerebral blood flow (CBF) values and distribution volume of I-123 IMP (Vd) independently. In the ARG method, a fixed Vd is applied for the entire brain to calculate CBF. Our purpose was to evaluate regional differences in Vd in the human brain, or possible effects of regional differences in Vd on CBF calculated by the ARG method., Methods: In the present study, two SPECT scans were acquired from each of eight normal subjects (aged 44.0 +/- 16.7) at 40 min and 180 min of mid-scan-time after intravenous 1 min infusion of 111 MBq IMP. A single arterial blood sampling was performed 10 min after the IMP infusion. All images were anatomically normalized and analyzed with SPM99 and Matlab. We generated CBF and Vd images for each subject by the TLU method and evaluated differences in Vd among brain structures. We subsequently generated another set of CBF images by the ARG method and examined differences between CBF calculated by the TLU method and that by the ARG method., Results: Significant main effects of subject and brain structure in Vd were observed (two-way ANOVA). Vd values were higher in the deep gray matter than in the cerebral cortical regions. Among the cerebral cortical regions, no significant difference in Vd was observed. In spite of the significant differences in Vd among the brain structures, the voxel-by-voxel analyses as well as the ROI analyses revealed no statistically significant difference between CBF calculated by the TLU method and that by the ARG method., Conclusions: Although regional differences in Vd were observed, the present results support the assumption that a fixed Vd does not cause significant error in the calculation of CBF by the ARG method.

Iodine-123-iomazenil (Iomazenil) is a ligand of central type benzodiazepine receptors for single photon emission computed tomography (SPECT). Previously we reported a simple, table look-up method for quantification of its binding potential (BP) by using two SPECT scans and calibrated standard input function with one blood sampling. This method is based on a two-compartment model (K1: influx rate constant; k2: efflux rate constant; Vd (= K1/k2): the total distribution volume corresponding BP), and requires two SPECT scans for calculating both K1 and Vd values. If the K1 value in the two-compartment model can be assumed to be constant, the radioactivity of one SPECT scan at 180 min after injection can be considered to tabulate as a function of Vd for a given K1 value and a given input function, and a table look-up procedure provides the corresponding Vd value. The purpose of this study was to develop a simple, autoradiographic method for quantification of BP by using one SPECT scan and calibrated standard input function with one blood sampling. SPECT studies were performed on 14 patients. A dynamic SPECT scan was initiated following an intravenous bolus injection of Iomazenil. A static SPECT scan was performed at 180 min after the injection. Frequent blood sampling from the brachial artery was performed on all subjects to determine the arterial input function. Simulation studies revealed that errors in calculated Vd values were around +/-10-15% for varied K1 values. A good correlation was observed between total distribution volume values calculated by three-compartment model analysis and those calculated by the present method (r = 0.90), supporting the validity of this method. The present method is simple and applicable for clinical use, and will be able to provide images of BP.

The chemical properties of 99mTc-DL-homocysteine (99mTc-Hcy) showing high accumulation in several experimental tumors were investigated. The form of tumor-tropic 99mTc-Hcy was a polymeric complex which appeared at void volume on Sephadex G-15 by eluting with 5 mM Hcy. This complex changed into smaller complexes of ca. 600 molecular weight in the presence of 150 mM NaCl and 5 mM Hcy, suggesting that 99mTc-Hcy was a complex composed of smaller polymers which are weakly bound together by an ionic bond. The complex showed a negative charge. The Hcy/Tc molar ratio in the complex was approximately 2 and no Sn was detected.