Estimation of post-therapeutic liver reserve capacity using 99mTc-GSA scintigraphy prior to carbon-ion radiotherapy for liver tumors.

BACKGROUND: There is currently no established imaging method for assessing liver reserve capacity prior to carbon-ion radiotherapy (CIRT) for liver tumors. In order to perform safe CIRT, it is essential to estimate the post-therapeutic residual reserve capacity of the liver. PURPOSE: To evaluate the ability of pre-treatment 99mTc-galactosyl human serum albumin (99mTc-GSA) scintigraphy to accurately estimate the residual liver reserve capacity in patients treated with CIRT for liver tumors. MATERIALS AND METHODS: This retrospective study evaluated patients who were performed CIRT for liver tumors between December 2018 and September 2020 and underwent 99mTc-GSA scintigraphy before and 3 months after CIRT, and gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI within 1 month before CIRT were evaluated. The maximal removal rate of 99mTc-GSA (GSA-Rmax) was analyzed for the evaluation of pre-treatment liver reserve capacity. Then, the GSA-Rmax of the estimated residual liver (GSA-RL) was calculated using liver SPECT images fused with the Gd-EOB-DTPA-enhanced MRI. GSA-RL before CIRT and GSA-Rmax at 3 months after CIRT were compared using non-parametric Wilcoxon signed-rank test and linear regression analysis. RESULTS: Overall, 50 patients were included (mean age ± standard deviation, 73 years ± 11; range, 29-89 years, 35 men). The median GSA-RL was 0.393 [range, 0.057-0.729] mg/min, and the median GSA-Rmax after CIRT was 0.369 [range, 0.037-0.780] mg/min (P = .40). The linear regression equation representing the relationship between the GSA-RL and GSA-Rmax after CIRT was y = 0.05 + 0.84x (R2 = 0.67, P < .0001). There was a linear relationship between the estimated and actual post-treatment values for all patients, as well as in the group with impaired liver reserve capacity (y = - 0.02 + 1.09x (R2 = 0.62, P = .0005)). CONCLUSIONS: 99mTc-GSA scintigraphy has potential clinical utility for estimating the residual liver reserve capacity in patients undergoing carbon-ion radiotherapy for liver tumors. TRIAL REGISTRATION: UMIN000038328, https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000043545 .

Automated semi-quantitative amyloid PET analysis technique without MR images for Alzheimer's disease.

OBJECTIVE: Although beta-amyloid (Aß) positron emission tomography (PET) images are interpreted visually as positive or negative, approximately 10% are judged as equivocal in Alzheimer's disease. Therefore, we aimed to develop an automated semi-quantitative analysis technique using 18F-flutemetamol PET images without anatomical images. METHODS: Overall, 136 cases of patients administered 18F-flutemetamol were enrolled. Of 136 cases, five PET images each with the highest and lowest values of standardized uptake value ratio (SUVr) of cerebral cortex-to-pons were used to create positive and negative templates. Using these templates, PET images of the remaining 126 cases were standardized, and SUVr images were produced with the pons as a reference region. The mean of SUVr values in the volume of interest delineated on the cerebral cortex was compared to those in the CortexID Suite (GE Healthcare). Furthermore, centiloid (CL) values were calculated for the 126 cases using data from the Centiloid Project ( http://www.gaain.org/centiloid-project ) and both templates. 18F-flutemetamol-PET was interpreted visually as positive/negative based on Aß deposition in the cortex. However, the criterion "equivocal" was added for cases with focal or mild Aß accumulation that were difficult to categorize. Optimal cutoff values of SUVr and CL maximizing sensitivity and specificity for Aß detection were determined by receiver operating characteristic (ROC) analysis using the visual evaluation as a standard of truth. RESULTS: SUVr calculated by our method and CortexID were highly correlated (R2 = 0.9657). The 126 PET images comprised 84 negative and 42 positive cases of Aß deposition by visual evaluation, of which 11 and 10 were classified as equivocal, respectively. ROC analyses determined the optimal cutoff values, sensitivity, and specificity for SUVr as 0.544, 89.3%, and 92.9%, respectively, and for CL as 12.400, 94.0%, and 92.9%, respectively. Both semi-quantitative analyses showed that 12 and 9 of the 21 equivocal cases were negative and positive, respectively, under the optimal cutoff values. CONCLUSIONS: This semi-quantitative analysis technique using 18F-flutemetamol-PET calculated SUVr and CL automatically without anatomical images. Moreover, it objectively and homogeneously interpreted positive or negative Aß burden in the brain as a supplemental tool for the visual reading of equivocal cases in routine clinical practice.

Topics of nuclear medicine research in Europe.

Last year in the European Journal of Nuclear Medicine and Molecular Imaging, we introduced some recent nuclear medicine research conducted in Japan. This was favorably received by European readers in the main. This year we wish to focus on the Annals of Nuclear Medicine on some of the fine nuclear medicine research work executed in Europe recently. In the current review article, we take up five topics: prostate-specific membrane antigen imaging, recent advances in radionuclide therapy, [18F]fluorodeoxyglucose positron-emission tomography (PET) for dementia, quantitative PET assessment of myocardial perfusion, and iodine-124 (124I). Just at the most recent annual meeting of the European Association of Nuclear Medicine 2016, Kyoto was selected as the host city for the 2022 Congress of the World Federation of Nuclear Medicine and Biology. We hope that our continuous efforts to strengthen scientific cooperation between Europe and Japan will bring many European friends and a great success to the Kyoto meeting.

The cingulate island sign within early Alzheimer's disease-specific hypoperfusion volumes of interest is useful for differentiating Alzheimer's disease from dementia with Lewy bodies.

BACKGROUND: In addition to occipital hypoperfusion, preserved metabolism of the posterior cingulate gyri (PCG) relative to the precunei is known as the cingulate island sign (CIS) in the patients with dementia with Lewy bodies (DLB). CIS has been detected using [(18)F]fluorodeoxyglucose positron emission tomography but not using brain perfusion single-photon emission computed tomography (SPECT). The purpose of this study was to optimize brain perfusion SPECT to enable differentiation of DLB from Alzheimer's disease (AD) using CIS and occipital hypoperfusion. Eighteen patients with probable DLB and 17 age-matched Pittsburgh compound B-positive patients with AD underwent technetium-99m ethyl cysteinate dimer SPECT. SPECT Z-score maps were generated using the easy Z-score imaging system (eZIS) analysis software (Matsuda H, Mizumura S, Nagao T, Ota T, Iizuka T, Nemoto K, Takemura N, Arai H, Homma A, AJNR Am J Neuroradiol 28(4):731-6, 2007), which included volumes of interest (VOIs) in which a group comparison between patients with AD and cognitively normal subjects revealed significant relative hypoperfusion. We used the Montreal Neurological Institute (MNI) space anatomical border to divide the bilateral PCG to precunei VOIs into two parts, the PCG and precunei. Z-scores in the PCG, precunei, and occipital areas and ratios were analysed and compared with receiver operating characteristic (ROC) curve analyses. RESULTS: The largest area under the curve (AUC) value for use in differentiating DLB from AD with the ratio of PCG to medial occipital was 0.87; the accuracy, sensitivity, and specificity were 85.7, 88.9, and 82.4 %, respectively. The AUC with the ratio of PCG to the precuneus was smaller, and it was 0.85, though no significant difference was observed between these two AUCs. CONCLUSIONS: The Z-score ratio of the PCG within the early-AD-specific VOI to medial-occipital area is clinically useful in discriminating demented patients with DLB from those with AD.

Report of a nationwide survey on actual administered radioactivities of radiopharmaceuticals for diagnostic reference levels in Japan.

OBJECTIVE: The optimization of medical exposure is one of the major issues regarding radiation protection in the world, and The International Committee of Radiological Protection and the International Atomic Energy Agency recommend establishing diagnostic reference levels (DRLs) as tools for dose optimization. Therefore, the development of DRLs based on the latest survey has been required for nuclear medicine-related societies and organizations. This prompted us to conduct a nationwide survey on the actual administered radioactivity to adults for the purpose of developing DRLs in nuclear medicine. METHODS: A nationwide survey was conducted from November 25, 2014 to January 16, 2015. The questionnaire was sent to all of the 1249 nuclear medicine facilities in Japan, and the responses were collected on a website using an answered form. RESULTS: Responses were obtained from 516 facilities, for a response rate of 41 %. 75th percentile of (99m)Tc-MDP and (99m)Tc-HMDP: bone scintigraphy, (99m)Tc-HM-PAO, (99m)Tc-ECD and (123)I-IMP: cerebral blood flow scintigraphy, (99m)Tc-Tetrofosmin, (99m)Tc-MIBI and (201)Tl-Cl; myocardial perfusion scintigraphy and (18)F-FDG: oncology PET (in-house-produced or delivery) in representative diagnostic nuclear medicine scans were 932, 937, 763, 775, 200, 831, 818, 180, 235 and 252, respectively. More than 90 % of the facilities were within the range of 50 % from the median of these survey results in representative diagnostic nuclear medicine facilities in Japan. Responses of the administered radioactivities recommended by the package insert, texts and guidelines such as 740 MBq ((99m)Tc-MDP and (99m)Tc-HMDP: bone scintigraphy), 740 MBq ((99m)Tc-ECD and (99m)Tc-HM-PAO: cerebral blood flow scintigraphy) and 740 MBq ((99m)Tc-Tetrofosmin and (99m)Tc-MIBI: myocardial perfusion scintigraphy), etc. were numerous. The administered activity of many radiopharmaceuticals of bone scintigraphy ((99m)Tc-MDP and (99m)Tc-HMDP), cerebral blood flow scintigraphy ((99m)Tc-HM-PAO) and myocardial perfusion scintigraphy ((99m)Tc-Tetrofosmin and (99m)Tc-MIBI), etc. were within the range of the EU DRLs and almost none of the administered radioactivity in Japan exceeded the upper limit of SNMMI standard administered radioactivity. CONCLUSIONS: This survey indicated that the administered radioactivity in diagnostic nuclear medicine in Japan had been in the convergence zone and nuclear medicine facilities in Japan show a strong tendency to adhere to the texts and guidelines. Furthermore, the administered radioactivities in Japan were within the range of variation of the EU and the SNMMI administered radioactivities.

Concordance between (99m)Tc-ECD SPECT and 18F-FDG PET interpretations in patients with cognitive disorders diagnosed according to NIA-AA criteria.

OBJECTIVES: The purpose of this study was to clarify the concordance of diagnostic abilities and interobserver agreement between 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and brain perfusion single photon-emission computed tomography (SPECT) in patients with Alzheimer's disease (AD) who were diagnosed according to the research criteria of the National Institute of Aging-Alzheimer's Association Workshop. METHODS: Fifty-five patients with "AD and mild cognitive impairment (MCI)" (n = 40) and "non-AD" (n = 15) were evaluated with 18F-FDG PET and (99m)Tc-ethyl cysteinate dimer (ECD) SPECT during an 8-week period. Three radiologists independently graded the regional uptake in the frontal, temporal, parietal, and occipital lobes as well as the precuneus/posterior cingulate cortex in both images. Kappa values were used to determine the interobserver reliability regarding regional uptake. RESULTS: The regions with better interobserver reliability between 18F-FDG PET and (99m)Tc-ECD SPECT were the frontal, parietal, and temporal lobes. The (99m)Tc-ECD SPECT agreement in the occipital lobes was not significant. The frontal, temporal, and parietal lobes showed good correlations between 18F-FDG PET and (99m)Tc-ECD SPECT in the degree of uptake, but the occipital lobe and precuneus/posterior cingulate cortex did not show good correlations. The diagnostic accuracy rates of "AD and MCI" ranged from 60% to 70% in both of the techniques. CONCLUSIONS: The degree of uptake on 18F-FDG PET and (99m)Tc-ECD SPECT showed significant correlations in the frontal, temporal, and parietal lobes. The diagnostic abilities of 18F-FDG PET and (99m)Tc-ECD SPECT for "AD and MCI," when diagnosed according to the National Institute of Aging-Alzheimer's Association Workshop criteria, were nearly identical.

18F-fluorodeoxyglucose positron emission tomography optimizes neoadjuvant chemotherapy for primary breast cancer to achieve pathological complete response.

BACKGROUND: To assess the usefulness of positron emission tomography combined with computed tomography using (18)F-fluorodeoxyglucose (FDG PET/CT) for optimizing chemotherapy during neoadjuvant chemotherapy for primary breast cancer. METHODS: One hundred and eight patients (110 tumors) with breast cancer (≥2 cm, stages II and III) received neoadjuvant chemotherapy consisting of an anthracycline-based regimen and taxane. The maximal value of the baseline standardized uptake value (SUV) and the change in SUV after four cycles of an anthracycline-based regimen relative to baseline SUV were assessed for predicting pathological complete response (pCR) after sequential taxane. RESULTS: Tumors with pCR had significantly higher baseline SUV (9.3 ± 3.7 SD) compared to those with non-pCR (7.2 ± 3.8 SD) (p = 0.02), but there was a considerable overlap between two groups. On PET scan after four cycles of chemotherapy, thirty-three patients (33.7%) with a 72.1% or greater reduction in SUV were considered as responders and the performance in predicting pCR had a sensitivity of 88.9% and specificity of 78.7%. CONCLUSION: The baseline SUV could not be a useful indicator for predicting pCR due to the wide range in sensitivity. On the other hand, a relative change in SUV after completion of an anthracycline-based regimen could be useful for predicting pCR.

Preoperative 18[F]-fluorodeoxyglucose positron emission tomography/computed tomography predicts early recurrence after pancreatic cancer resection.

BACKGROUND: An important step in deciding the treatment strategy for pancreatic cancer is to preoperatively predict the possibility of early recurrence. We reviewed whether 18[F]-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) before pancreatic cancer resection could predict tumor recurrence in the early postoperative period. METHODS: FDG-PET/CT was performed preoperatively on 56 patients with pancreatic cancer. The maximum standardized uptake (SUV(max)) values obtained by FDG-PET/CT were compared between two groups: patients with and without recurrence within the first 6 postoperative months. SUV(max) analyses were also performed to determine whether age, sex, CA 19-9 values, the operative method, and portal vein resection were also predictive of recurrence within less than 6 months after tumor resection. RESULTS: The median SUV(max) values of the recurrence group and no-recurrence group were 7.9 and 4.2, respectively (P = 0.0042). The SUV(max) was the only risk factor for recurrence in the first 6 postoperative months identified by multivariate analysis (P = 0.0062). CONCLUSIONS: Preoperative SUV(max) was higher in the recurrence group during the early postoperative period, and a high SUV(max) was a risk factor for early postoperative recurrence. Based on these results, we conclude that FDG-PET/CT is predictive of the recurrence of pancreatic cancer in the early postoperative period.

Evaluation of both perfusion and atrophy in multiple system atrophy of the cerebellar type using brain SPECT alone.

BACKGROUND: Partial volume effects in atrophied areas should be taken into account when interpreting brain perfusion single photon emission computed tomography (SPECT) images of neurodegenerative diseases. To evaluate both perfusion and atrophy using brain SPECT alone, we developed a new technique applying tensor-based morphometry (TBM) to SPECT. METHODS: After linear spatial normalization of brain perfusion SPECT using 99mTc-ethyl cysteinate dimer (99mTc-ECD) to a Talairach space, high-dimension-warping was done using an original 99mTc-ECD template. Contraction map images calculated from Jacobian determinants and spatially normalized SPECT images using this high-dimension-warping were compared using statistical parametric mapping (SPM2) between two groups of 16 multiple system atrophy of the cerebellar type (MSA-C) patients and 73 age-matched normal controls. This comparison was also performed in conventionally warped SPECT images. RESULTS: SPM2 demonstrated statistically significant contraction indicating local atrophy and decreased perfusion in the whole cerebellum and pons of MSA-C patients as compared to normal controls. Higher significance for decreased perfusion in these areas was obtained in high-dimension-warping than in conventional warping, possibly due to sufficient spatial normalization to a 99mTc-ECD template in high-dimensional warping of severely atrophied cerebellum and pons. In the present high-dimension-warping, modification of tracer activity remained within 3% of the original tracer distribution. CONCLUSIONS: The present new technique applying TBM to brain SPECT provides information on both perfusion and atrophy at the same time thereby enhancing the role of brain perfusion SPECT.

A comparison of the respiratory signals acquired by different respiratory monitoring systems used in respiratory gated radiotherapy.

PURPOSE: Respiratory monitoring systems are used to detect the respiratory phase of patients during the planning and administration of respiratory gated radiotherapy by using four-dimensional computed tomography (4DCT) or 4D positron-emission tomography/CT (4DPET/CT) and the linear accelerator (linac), respectively. Generally, identical respiratory monitoring systems are used for 4DCT, 4DPET/CT, and linac. However, different systems are sometimes used in combination because the accessibility of the respiratory monitoring systems may differ by manufacturer. The combined use of different respiratory monitoring systems in phase-based gating is of concern because the differences in the timing of tags (end-respiration signals algorithmically determined by the respiratory monitoring system), defined by the two systems, may result in phase differences, The purpose of this study is to estimate this difference and evaluate its effect on 4DCT data. METHODS: Ten patients (seven men and three women) with a median age of 75 yr (range: 57-84 yr) were treated by gated stereotactic body radiation therapy between April and December 2009. Two types of respiratory monitoring systems--RPM (Varian Medical Systems) and AZ-733V (Anzai MEDICAL)--were placed on the abdominal surface of the patients, and the respiratory signals were acquired by both systems. The relationship between the amplitude peak and the tag obtained by each respiratory system was analyzed for each patient. Further, the 4DCT images were reconstructed by using the signals obtained from both the RPM and the AZ-733V systems, and the tumor volumes and the tumor centroid positions in the craniocaudal plane were analyzed for each patient. RESULTS: The correlation factor between the respiratory signals from the RPM system and AZ-733V system was 0.990 (range: 0.940-0.994). The amplitude peak of the RPM system corresponded well with that of the AZ-733V system. The median +/- standard deviation of the phase difference for all the patients ranged from -4.3 +/- 7.1% to 3.5 +/- 2.2%. In the case of some patients, differences were noted between the two systems in the estimation of the tumor centroid position and tumor shape. CONCLUSIONS: The estimation of the position of the tumor centroid and tumor shape may vary with the use of different respiratory monitoring systems. This implies that it is preferable to use the same respiratory monitoring system with 4DCT, 4DPET-CT, and linac.

Contribution of subtraction ictal SPECT coregistered to MRI to epilepsy surgery: a multicenter study.

OBJECTIVE: A multicenter prospective study was performed to assess the additional value of a subtraction ictal SPECT coregistered to MRI (SISCOM) technique to traditional side-by-side comparison of ictal- and interictal SPECT images in epilepsy surgery. METHODS: One hundred and twenty-three patients with temporal and extratemporal lobe epilepsy who had undergone epilepsy surgery after evaluation of scalp ictal and interictal electroencephalogram (EEG), MRI, and ictal and interictal SPECT scans were followed up in terms of postsurgical outcome for a period of at least 1 year. Three reviewers localized the epileptogenic focus using ictal and interictal SPECT images first by side-by-side comparison and subsequently by SISCOM. Concordance of the localization of the epileptogenic focus by SPECT diagnosis with the surgical site and inter-observer agreement between reviewers was compared between side-by-side comparison and SISCOM. Logistic regression analysis was performed in predicting the surgical outcome with the dependent variable being the achievement of a good postsurgical outcome and the independent variables using the SISCOM, side-by-side comparison of ictal and interictal SPECT images, MRI, and scalp ictal EEG. RESULTS: The SISCOM presented better concordance in extratemporal lobe epilepsy and less concordance in temporal lobe epilepsy than side-by-side comparison. Inter-observer concordance was higher in SISCOM than in side-by-side comparison. Much higher concordance of the epileptogenic focus by SPECT diagnosis with the surgical site was obtained in patients with good surgical outcome than in those with poor surgical outcome. These differences in concordance between good and poor surgical outcomes were greater in SISCOM than in side-by-side comparison. Logistic regression analysis showed the highest odds ratio of 12.391 (95% confidence interval; 3.319, 46.254) by SISCOM evaluation for concordance of the epileptogenic focus with the surgical site in predicting good surgical outcome. CONCLUSIONS: A SISCOM technique of ictal and interictal SPECT images provides higher predictive value of good surgical outcome and more reliability on the diagnosis of the epileptogenic focus than side-by-side comparison in medically intractable partial epilepsy.

Brown adipose tissue demonstrating intense FDG uptake in a patient with mediastinal pheochromocytoma.

We present an interesting case with a central mediastinal pheochromocytoma showing intense F-18 fluorodeoxyglucose (FDG) uptake in tumor and systemic brown adipose tissue (BAT) mimicking metastases. The findings of hypertension and high plasma catecholamine concentration suggested the presence of pheochromocytoma. Mediastinal tumor showed intense FDG uptake and faint uptake of I-131 metaiodobenzylguanidine. Intense FDG uptake was demonstrated in cervical, paravertebral, mediastinal, and perirenal regions. Positron emission tomography and computed tomography (PET/CT) revealed uptake in a fat density area suggesting that the FDG uptake had occurred in BAT. The mediastinal tumor was resected along with an adhesion to the left atrial wall and pathologically confirmed as pheochromocytoma. The plasma catecholamine concentration and blood pressure then reverted to normal. The FDG uptake in BAT disappeared after tumor resection.

Effect of nilvadipine on regional cerebral blood flow in a patient with early Alzheimer disease.

Hypertension in an 83-year-old woman with early Alzheimer disease was treated with a calcium channel blocker, nilvadipine, for 3 months. Before and after nilvadipine treatment, global and regional cerebral blood flow (gCBF and rCBF) were measured using Tc-99m ethyl cysteinate dimer SPECT. This treatment elevated both the Mini-Mental State Examination score from 23 to 27 and gCBF from 37.6 to 42.0 mL/100 g/min. This treatment also elevated rCBF prominently in the bilateral frontal cortex, right parietal cortex, and posterior cingulate cortex. These areas with rCBF increase generated by subtraction of pretreatment SPECT from post-treatment SPECT were demonstrated on a coregistered MRI.

Gender difference in brain perfusion 99mTc-ECD SPECT in aged healthy volunteers after correction for partial volume effects.

BACKGROUND: Previous reports have yielded controversial results concerning gender differences in regional cerebral blood flow (rCBF). To elucidate this issue, we compared 99mTc ethyl cysteinate dimer single photon emission computed tomography (SPECT) images for brain perfusion between aged-matched healthy men and women after correction for partial volume effects (PVEs). METHODS: Brain perfusion SPECT in the resting state was performed on 40 healthy, right-handed subjects, 20 men and 20 women, with an age range of 58-86 years, who did not differ sociodemographically. PVE correction was performed using grey matter volume measured by magnetic resonance imaging. Statistical parametric mapping was used for the analysis of the adjusted rCBF images of relative flow distribution. RESULTS: The PVE correction revealed that women had higher rCBF in left inferior frontal gyrus, bilateral middle temporal gyri, and left superior temporal gyrus. Men had higher rCBF in left superior frontal gyrus, right medial frontal gyrus, right superior parietal lobule, right postcentral gyrus, right cerebellum, right middle frontal gyrus, right fusiform gyrus, and right precuneus. CONCLUSION: Significant gender differences in rCBF existed in these healthy volunteers. The PVE correction of SPECT images revealed gender differences that were consistent with the universal findings of better performance on verbal tasks in women and on visuospatial tasks in men.

Correction for partial-volume effects on brain perfusion SPECT in healthy men.

UNLABELLED: The limited spatial resolution of SPECT scanners does not allow an exact measurement of the local radiotracer concentration in brain tissue because partial-volume effects (PVEs) underestimate concentration in small structures of the brain. The aim of this study was to determine which brain structures show greater influence of PVEs in SPECT studies on healthy volunteers and to investigate aging effects on SPECT after the PVE correction. METHODS: Brain perfusion SPECT using (99m)Tc-ethylcysteinate dimer was performed in 52 healthy men, 18-86 y old. The regional cerebral blood flow (rCBF) was noninvasively measured using graphical analysis. SPECT images were corrected for PVEs using gray-matter volume, which was segmented from coregistered MR images and convoluted with spatial resolution of SPECT scanners. Absolute rCBF data were measured using a 3-dimensional (3D) stereotactic template for regions of interest on anatomically standardized SPECT. We examined correlation of advancing age with rCBF before and after the PVE correction. To validate the correction method for PVEs, a Hoffman 3D brain phantom experiment was also performed. RESULTS: The PVE correction remarkably reduced the coefficient of variation for SPECT counts in the whole phantom. The PVE correction made the rCBF distribution more homogeneous throughout the brain with less intersubject variation than the original distribution. There were significant negative correlations between age and adjusted rCBF in the bilateral perisylvian and medial frontal areas. These correlations remained significant after the PVE correction. Instead of a positive correlation in the medial temporal structures between age and adjusted rCBF before the PVE correction, the sensorimotor and parietal areas mainly showed positive correlations after the correction. CONCLUSION: SPECT data reflect both brain volume loss and functional changes. Use of the PVE correction in brain perfusion SPECT provides a more accurate determination of rCBF even in healthy volunteers.

Functional connectivity revealed by single-photon emission computed tomography (SPECT) during repetitive transcranial magnetic stimulation (rTMS) of the motor cortex.

OBJECTIVE: In the present study, we studied effects of 1 Hz repetitive transcranial magnetic stimulation (rTMS) over the left primary motor cortex (M1) on regional cerebral blood flow (rCBF) using single-photon emission computed tomography (SPECT). METHODS: SPECT measurements were carried out under two experimental conditions: real and sham stimulation. In sham stimulation, to exclude other components besides currents in the brain in rTMS, we applied sound and electrical stimulation to the skin of the head. 99mTc-ethyl cysteinate dimer was injected during the real or sham stimulation. Images were analyzed with the statistical parametric mapping software (SPM99). Relative differences in adjusted rCBF between two conditions were determined by a voxel-by-voxel paired t test. RESULTS: 1 Hz rTMS at an intensity of 1.1 x active motor threshold evoked increase of rCBF in the contralateral (right) cerebellar hemisphere. Reduction of rCBF was observed in the contralateral M1, superior parietal lobule (most probably corresponding to PE area in the monkey) (Rizzolatti G, Luppino G, Matelli M. Electroenceph clin Neurophysiol 1998;106:283-296), inferior parietal lobule (PF area in the monkey (Rizzolatti et al., 1998)), dorsal and ventral premotor areas (dPM, vPM) and supplementary motor area (SMA). CONCLUSIONS: Increase of rCBF in the contralateral cerebellum must reflect facilitatory connection between the motor cortex and contralateral cerebellum. Reduced rCBF in the contralateral M1 may be produced by transcallosal inhibitory effect of the left motor cortical activation. CBF decrease in the right PM, SMA and parietal cortex may reflect some secondary effects. Low frequency rTMS at an intensity of around threshold for active muscles can evoke rCBF changes. SIGNIFICANCE: We demonstrated that rCBF changes could be elicited even by low frequency rTMS at such a low intensity as the threshold for an active muscle. Combination of rTMS and SPECT is one of powerful tools to study interareal connection within the human brain.

Brain SPET abnormalities in Alzheimer's disease before and after atrophy correction.

The aim of this study was to determine which brain structures show the greatest influence of partial volume effects (PVE) in single-photon emission tomography (SPET) studies on Alzheimer's disease (AD). Brain perfusion SPET was performed in 30 patients with probable AD and 62 age-matched healthy volunteers. SPET images were corrected for PVE using grey matter volume segmented from magnetic resonance images. The most prominent changes after PVE correction were observed in the medial temporal structures. The PVE correction revealed a selective decrease in regional cerebral blood flow (rCBF) in the parahippocampal gyrus of AD without rCBF decreases in the hippocampus, which had been observed before correction. This correction seems to be essential in order to achieve accurate measurements of rCBF in SPET, which has limited spatial resolution.