ABSTRACT: BACKGROUND: [11C]methionine (MET) has been used to monitor amino acid metabolism in tumors, the pancreas, liver, and myocardium. The aim of the present study was to standardize [11C]MET positron emission tomography (PET) by optimizing the timing of initiation of the scan and applying correction to the plasma concentrations of neutral amino acids (NAAs), where necessary. METHODS: Sequential whole-body MET PET/computed tomography (CT) was performed in 11 normal adults after they had fasted for at least 4 h. After whole-body CT for attenuation correction and intravenous bolus injection of MET, the subjects were scanned from the parietal to the groin. The scanning was repeated six to seven times. Decay of radioactivity during the PET scan was corrected to the time of initiation of the first scan. The standardized uptake values (SUVs) were evaluated in various organs by setting regions of interest on the tomographic images. Plasma concentrations of NAAs were examined in relation to the SUV values. RESULTS: The SUVs in the pancreas reached their plateau from 6.5 to 11 min after the MET injection, and in the brain, lung, and myocardium, they reached their plateau from 19.6 to 24.1 min. The MET uptake in the spleen and kidney peaked early after the injection and steadily decreased thereafter. The SUVs in the liver and stomach wall rapidly increased during the first 0 to 4.5 min and gradually elevated thereafter during the scan period. Urinary radioactivity in the bladder reached its plateau from 26.1 to 30.6 min after the MET injection. There were no correlations between the plasma concentrations of NAAs and the maximal SUV in any organs. CONCLUSIONS: The present study revealed the times taken to reach the plateau of MET uptake in various important organs, and little effects of the plasma neutral amino acid concentrations on the SUVs in PET studies conducted after the patients had fasted for at least 4 h. In the MET PET study, 4 h fasting period before MET administration and the scan initiation 20 min after MET administration provide the SUV values independent of scan initiation time and the plasma neutral amino acid concentrations.
EJNMMI research. 04/2013; 3(1):27.
ABSTRACT: PET with (15)O gas has been used for the quantitative measurement of cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO(2)), oxygen extraction fraction (OEF), and cerebral blood volume (CBV) in humans. However, several technical difficulties limit its use in experiments on small animals. Herein, we describe the application of the (15)O gas steady-state inhalation method for normal anesthetized rats. METHODS: Eight normal male Sprague-Dawley rats (mean body weight ± SD, 268 ± 14 g) under anesthesia were investigated by (15)O-labeled gas PET. After tracheotomy, an airway tube was placed in the trachea, and the animals were connected to a ventilator (tidal volume, 3 cm(3); frequency, 60/min). The CBF and OEF were measured according to the original steady-state inhalation technique under artificial ventilation with (15)O-CO(2) and (15)O-O(2) gases delivered through the radioactive gas stabilizer. CBV was measured by (15)O-CO gas inhalation and corrected for the intravascular hemoglobin-bound (15)O-O(2). Arterial blood sampling was performed during each study to measure the radioactivity of the whole blood and plasma. MR image was performed with the same acrylic animal holder immediately after the PET. Regions of interest were placed on the whole brain of the PET images with reference to the semiautomatically coregistered PET/MR fused images. RESULTS: The data acquisition time for the whole PET experiment in each rat was 73.3 ± 5.8 (range, 68-85) min. In both the (15)O-CO(2) and the (15)O-O(2) studies, the radioactivity count of the brain reached a steady state by approximately 10 min after the start of continuous inhalation of the gas. The quantitative PET data of the whole brain were as follows: CBF, 32.3 ± 4.5 mL/100 mL/min; CMRO(2), 3.23 ± 0.42 mL/100 mL/min; OEF, 64.6% ± 9.1%; and CBV, 5.05 ± 0.45 mL/100 mL. CONCLUSION: Although further technical improvements may be needed, this study demonstrated the feasibility of quantitative PET measurement of CBF, OEF, and CMRO(2) using the original steady-state inhalation method of (15)O-CO(2) and (15)O-O(2) gases and measurement of CBV using the (15)O-CO gas inhalation method in the brain of normal anesthetized rats.
Journal of Nuclear Medicine 01/2013; · 6.38 Impact Factor
ABSTRACT: Purpose: The simultaneous measurement of PET and magnetic resonance imaging (MRI) is an emerging field for molecular imaging research. Although optical fiber based PET∕MRI systems have advantages on less interference between PET and MRI, there is a drawback in reducing the scintillation light due to the fiber. To reduce the problem, the authors newly developed flexible optical fiber bundle based block detectors and employed them for a high resolution integrated PET∕MRI system.Methods: The flexible optical fiber bundle used 0.5 mm diameter, 80 cm long double clad fibers which have dual 12 mm × 24 mm rectangular inputs and a single 24 mm × 24 mm rectangular output. In the input surface, LGSO scintillators of 0.025 mol.% (decay time: ∼31 ns: 0.9 mm × 1.3 mm × 5 mm) and 0.75 mol.% (decay time: ∼46 ns: 0.9 mm × 1.3 mm × 6 mm) were optically coupled in depth direction to form depth-of-interaction detector, arranged in 11 × 13 matrix and optically coupled to the fiber bundle. The two inputs of the bundle are bent for 90°, bound to one, and are optically coupled to a Hamamatsu 1-in. square position sensitive photomultiplier tube.Results: Light loss due to the fiber bundle could be reduced and the performance of the block detectors was improved. Eight optical fiber based block detectors (16 LGSO blocks) were arranged in a 56 mm diameter ring to form a PET system. Spatial resolution and sensitivity were 1.2 mm full-width at half-maximum and 1.2% at the central field-of-view, respectively. Sensitivity change was less than 1% for 2 °C temperature changes. This PET system was integrated with a 0.3 T permanent magnet MRI system which has 17 cm diameter hole at the yoke area for insertion of the PET detector ring. There was no observable interference between PET and MRI. Simultaneous imaging of PET and MRI was successfully performed for small animal studies.Conclusions: The authors confirmed that the developed high resolution PET∕MRI system is promising for molecular imaging research.
Medical Physics 11/2012; 39(11):6660-71. · 2.83 Impact Factor
ABSTRACT: Purpose: Recently, photomultiplier tubes (PMTs) and position sensitive PMTs (PSPMTs) with higher quantum efficiencies (HQE) have been developed. However, it remains unclear whether they actually improve such performances as the energy and spatial resolution for PET and SPECT detectors.Methods: The authors evaluated the quantum efficiencies (QEs) for PMTs and PSPMTs and measured the energy resolution of a 3-in. round HQE PMT combined with various scintillators and compared the results with a conventional normal quantum efficiency (NQE) PMT of the same type. The authors also measured the position and energy performance of a 2-in. square HQE PSPMT combined with scintillator blocks and compared them with a NQE PSPMT of the same size.Results: The energy resolution of the 3-in. round HQE PMT showed higher energy resolution than the NQE with all scintillators. The improvement of the energy resolution was smaller, for all measurements, than the expected value from the quantum efficiency of the PMT but was higher for the scintillators with smaller light outputs. The energy and position performance of the HQE PSPMT based block detectors showed higher position and energy performance than those with NQE.Conclusions: From these results, the authors conclude that both HQE PMT and PSPMT contribute to improve the energy and position performance for PET and SPECT detectors. Significant performance improvements will be expected in PET and SPECT systems by the use of the HQE PMTs or PSPMTs.
Medical Physics 11/2012; 39(11):6900-7. · 2.83 Impact Factor
ABSTRACT: Background: Previous findings on neural correlates of delusion in Alzheimer's disease (AD) have been inconsistent because of methodological issues, such as treating multiple delusions as a single entity. In this retrospective study, we classified AD delusions and investigated their neural correlates by using single-photon emission computed tomography data. Methods: We selected AD patients with delusions from our consecutive outpatients from 2004 to 2010. In this study, eight types of delusions were evaluated with Neuropsychiatric Inventory and classified by factor analysis. Twenty-five of the patients also had single-photon emission computed tomography data, which we used to assess the relationships between cerebral regions of hypoperfusion and hyperperfusion and each classified delusion. The relations were assessed using Statistical Parametric Mapping with normalization to the white matter cerebral blood flow. Results: The delusions were classified into three factors. Factor 1 consisted of a belief that his/her house is not his/her home, phantom boarder symptom, delusion of abandonment, and belief that one's spouse or others are not who they claim to be. Factor 1 was related to hypoperfusion in the right temporal pole and hyperperfusion in the medial frontal and precentral regions. Factor 2 consisted of delusion relating to the television and delusion of persecution. Factor 2 was related to hypoperfusion in the precuneus and hyperperfusion in the insula and thalamus. Factor 3 consisted of delusion of abandonment and delusional jealousy. Factor 3 was related to hypoperfusion in the right inferior temporal and frontal regions and hyperperfusion in the middle frontal gyrus, insula and posterior cingulate gyrus. Delusion of theft was not included in any factors, and it was related to hypoperfusion in the bilateral thalami and left posterior cingulate gyrus and hyperperfusion in the left inferior frontal regions and anterior cingulate gyrus. Conclusions: Delusions in AD were classifiable, and each classified delusion was related to different neural networks.
Psychogeriatrics 09/2012; 12(3):200-10. · 1.21 Impact Factor
ABSTRACT: To investigate involvement of extrafocal regions in mesial temporal lobe epilepsy (MTLE), we retrospectively explored abnormalities in distribution of iomazenil (IMZ) activity by identifying interhemispheric asymmetry on IMZ-SPECT images of patients with MTLE. Fourteen MTLE patients in whom a good surgical outcome was achieved were included in the study. Voxel-based (VB) analysis and volume-of-interest (VOI) analysis with predefined VOIs were applied to compare IMZ binding between the hemispheres ipsilateral and contralateral to the epileptic focus. VB analysis showed significant decreases in iomazenil binding not only in the ipsilateral anterior temporal lobe including the mesial temporal structures but also in the ipsilateral extratemporal region including the insula, putamen, and medial occipital lobe. VOI analysis showed similar significant decreases in the ipsilateral parahippocampal gyrus, amygdala, putamen, lateral temporal lobe, and lateral occipital lobe. Results of the SPECT analyses suggest that decreased or dysfunctional IMZ activity extends from the mesial temporal lobe to the ipsilateral extrafocal region in patients with MTLE.
Epilepsy research 07/2012; · 2.48 Impact Factor
ABSTRACT: Esophageal cancer is a highly aggressive disease, and improved modalities for its treatment are needed. We performed chemoimmunotherapy involving the intratumoral administration of 111In-labeled dendritic cells (DC) in combination with preoperative chemotherapy in 5 esophageal cancer patients. Mature DC were generated and traced by scintigraphy after their administration. No adverse events that were directly related to the intratumoral DC administration were observed. Delayed-type hypersensitivity skin tests against keyhole limpet hemocyanin, which was added to the culture medium, detected a positive response in 3 patients, and keyhole limpet hemocyanin antibody production was observed in 4 patients, suggesting that intratumorally administered DC migrate to the lymph nodes, where they function as antigen-presenting cells. However, scintigraphic images obtained after the DC administration demonstrated that the DC remained at the esophageal tumor injection sites in all cases, and no DC accumulation was observed elsewhere. The accumulation of CD83+ cells in the primary tumor was also observed in 2 out of 4 patients in an immunohistochemical analysis using surgically resected specimens. Although the induction of tumor-specific immune responses during chemoimmunotherapy was also analyzed in enzyme-linked immunosorbent assay against 28 tumor antigens, none of the antibodies against the antigens displayed enhanced titers. No changes of NY-ESO-1-specific cellular immune response was observed in a patient who displayed NY-ESO-1 antibody production before the DC administration. These results suggest that the intratumoral administration of 111In-labeled mature DC during chemotherapy does not lead to detectable DC migration from the primary tumor to the draining lymph nodes, and therefore, might not achieve an optimal clinical response.
Journal of immunotherapy (Hagerstown, Md.: 1997) 07/2012; 35(6):513-21. · 3.20 Impact Factor
ABSTRACT: Recently, PET response criteria in solid tumors (PERCIST) have been proposed as a new standardized method to assess chemotherapeutic response metabolically and quantitatively. The aim of this study was to evaluate therapeutic response to neoadjuvant chemotherapy for locally advanced esophageal cancer, comparing PERCIST with the currently widely used response evaluation criteria in solid tumors (RECIST).
Fifty-one patients with locally advanced esophageal cancer who received neoadjuvant chemotherapy (5-fluorouracil, adriamycin, and cisplatin), followed by surgery were studied. Chemotherapeutic lesion responses were evaluated using (18)F-FDG PET and CT according to the RECIST and PERCIST methods. The PET/CT scans were obtained before chemotherapy and about 2 wk after completion of chemotherapy. Associations were statistically analyzed between survival (overall and disease-free survival) and clinicopathologic results (histology [well-, moderately, and poorly differentiated squamous cell carcinoma], lymphatic invasion, venous invasion, clinical stage, pathologic stage, resection level, reduction rate of tumor diameter, reduction rate of tumor uptake, chemotherapeutic responses in RECIST and PERCIST, and pathologic response).
There was a significant difference in response classification between RECIST and PERCIST (Wilcoxon signed-rank test, P < 0.0001). Univariate analysis showed that lymphatic invasion, venous invasion, resection level, pathologic stage, and PERCIST were significant factors associated with disease-free or overall survival in this study. Although multivariate analysis demonstrated that venous invasion (disease-free survival: hazard ratio [HR] = 4.519, P = 0.002; overall survival: HR = 5.591, P = 0.003) and resection level (disease-free survival: HR = 11.078, P = 0.001) were the significant predictors, PERCIST was also significant in noninvasive therapy response assessment before surgery (disease-free survival: HR = 4.060, P = 0.025; overall survival: HR = 8.953, P = 0.034).
RECIST based on the anatomic size reduction rate did not demonstrate the correlation between therapeutic responses and prognosis in patients with esophageal cancer receiving neoadjuvant chemotherapy. However, PERCIST was found to be the strongest independent predictor of outcomes. Given the significance of noninvasive radiologic imaging in formulating clinical treatment strategies, PERCIST might be considered more suitable for evaluation of chemotherapeutic response to esophageal cancer than RECIST.
Journal of Nuclear Medicine 05/2012; 53(6):872-80. · 6.38 Impact Factor
ABSTRACT: ObjectiveCardiac 15O-water PET studies provide an accurate quantitation of regional myocardial blood flow (rMBF). We developed a motion correction
system using an optical motion-tracking device to detect a subject’s global movement for cardiac study.
MethodsPET studies were carried out on a cardiac phantom and a healthy volunteer at rest. The three-dimensional locations of the
markers attached to the subjects during scans were measured using an optical motion-tracking system. In the phantom study,
we performed a transmission scan and seven 18F emission scans of a baseline and with artificial misalignment of shifts and rotations. The correlation coefficients between
the baseline and the other images before and after the corrections for the misalignment were calculated. In the human study,
we performed a 15O-water dynamic scan with a transmission and axially 30mm-shifted transmission scans. Motion of the subject was estimated
by the information from the system, and was corrected on each sinogram using attenuation maps realigned to dynamic frames.
Reconstructed dynamic images were then realigned to the transmission data. We calculated rMBF values for nine segments and
myocardial images from the emission images, which were reconstructed with the first attenuation map (reference) and with the
misaligned attenuation map before and after our corrections.
ResultsIn the phantom study, the correlation coefficients were improved from 0.929±0.022 to 0.987±0.010 (mean±SD) after the
corrections. In the human study, the global and cyclic movements were detected. The cyclic movement due to respiration was
smoothed by frame-averaging, and reasonable information of the global movement was obtained. The rMBF value (mean±SD) was
0.94±0.12mL/min/g for the reference. The rMBF values using the misaligned attenuation map changed from 1.03±0.21 to 0.93±0.11mL/min/g
after the correction, and spurious defects in myocardial images were also recovered.
ConclusionsOur technique provided reasonable information for correcting the global movement of the subject. It was shown that this system
was applicable to detect and correct subject movement in cardiac PET studies at rest.
Annals of Nuclear Medicine 04/2012; 24(1):1-11. · 1.50 Impact Factor
ABSTRACT: ObjectiveStatistical parametric mapping (SPM) was employed to investigate the regional decline in cerebral blood flow (rCBF) as measured
by99mTc-hexamethyl propylene amine oxime (HMPAO) single photon emission computed tomography (SPECT) in mild Alzheimer’s disease
(AD). However, the role of the post reconstruction image processing on the interpretation of SPM, which detects rCBF pattern,
has not been precisely studied. We performed99mTc-HMPAO SPECT in mild AD patients and analyzed the effect of linearization correction for washout of the tracer on the detectability
of abnormal perfusion.
MethodsEleven mild AD (NINCDS-ADRDA, male/female, 5/6; mean ± SD age, 70.6 ± 6.2 years; mean ± SD mini-mental state examination score,
23.9 ± 3.41; clinical dementia rating score, 1) and eleven normal control subjects (male/female, 4/7; mean ± SD age, 66.8
± 8.4 years) were enrolled in this study.99mTc-HMPAO SPECT was performed with a four-head rotating gamma camera. We employed linearization uncorrected (LU) and linearization
corrected (LC) images for the patients and controls. The pattern of hypoperfusion in mild AD on LU and LC images was detected
by SPM99 applying the same image standardization and analytical parameters. A statistical inter image-group analysis (LU vs.
LC) was also performed.
ResultsClear differences were observed between the interpretation of SPM with LU and LC images. Significant hypoperfusion in mild
AD was found on the LU images in the left posterior cingulate gyrus, right precuneus, left hippocampus, left uncus, and left
superior temporal gyrus (cluster level, corrected p < 0.005). With the LC images, significant hypoperfusion in AD was found
only in the bilateral posterior cingulate gyrus and left precuneus (cluster level, corrected p < 0.005). A pattern of greater
rCBF distribution at the high flow cortices and low flow cortices was observed on LC and LU images, respectively, in the case
of both controls and mild AD patients.
ConclusionHippocampal hypoperfusion could be detected by means of SPM in the LU images but not in the LC images. The results of SPM
may vary in99mTc-HMPAO SPECT with or without linearization correction, which should be carefully evaluated when interpreting the pattern
of rCBF changes in mild Alzheimer’s disease.
Annals of Nuclear Medicine 04/2012; 20(8):511-517. · 1.50 Impact Factor
ABSTRACT: ObjectiveThe objective of this study was to prospectively investigate the relationship between high accumulation of 2-deoxy-2-[18F] fluoro-d-glucose (FDG) in the oral cavity and dental infections on positron emission tomography/computed tomography (PET/CT).
MethodsFDG-PET/CT scans of 103 patients who underwent a health screening were evaluated. The dental examination was performed prior
to each PET/CT scan, and dental infections were assessed. Dental infections were classified into six blocks. The severity
of dental caries was classified into five grades, and periodontal disease and apical periodontitis were classified into three
grades. Two radiologists classified the PET images in the same manner as the dental examination. They evaluated the intensity
of FDG uptake by a four-point visual PET image score for each block. The comparison of the dental examination, as a gold standard,
and the visual PET image score was performed on a patient or block basis.
ResultsOn a patient-based analysis, 21 of 103 patients (20.4%) showed PET positive findings in the oral cavity; 18 of the 21 patients
(85.7%) had dental infections. On a block-based analysis, 25 of 605 blocks (4.1%) showed PET positive findings in the oral
cavity; 22 of the 25 blocks (88.0%) had dental infections. On a detailed block-based analysis, a significant difference was
observed between the presence of periodontal disease, or apical periodontitis and the positivity of the visual PET image findings
(P < 0.01). Their severity correlated with the visual PET image score (P < 0.05).
ConclusionsPeriodontal disease or apical periodontitis, but not dental caries, caused FDG accumulation in the oral cavity. This finding
should be taken into account when a head and neck FDG-PET study is interpreted.
Annals of Nuclear Medicine 04/2012; 22(7):587-593. · 1.50 Impact Factor
ABSTRACT: ObjectiveIodine-123 (123I)-labeledN-isopropyl-4-iodoamphetamine (IMP) has been used as a cerebral blood flow (CBF) tracer for single-photon emission computed
tomography (SPECT). An autoradiographic (ARG) method has been developed for the quantitation of CBF by IMP and SPECT. Two
IMPs (IMPA and IMPB) produced by different radiopharmaceutical companies are marketed in Japan. In the present study, whole-body distributions
including brain and blood of the two IMPs were compared in the same human subjects.
MethodsTwo brain SPECT studies using IMPa or IMPb were performed on separate days in six young healthy men. Whole-body scans were
also obtained with a large field-of-view single-head gamma camera. One-point arterial blood sampling was performed at 10 min
after injection of IMP to measure both the radioactivity concentrations of whole blood and of octanol-extracted components.
ResultsNo significant differences between the two tracers were observed in body distribution, tracer kinetics in brain, or regional
distribution in brain. However, the octanol extraction fraction in blood was significantly different between the two tracers.
Radiochemical purity was slightly but significantly different between the tracers.
ConclusionsIn the ARG method, arterial input function is determined by calibration of a standard input function with the radioactivity
concentration of arterial whole blood. Because the standard input function in the ARG method was obtained using IMPa, the
standard input function obtained for IMPb should be used when CBF is calculated by the ARG method with IMPB
Annals of Nuclear Medicine 04/2012; 20(7):493-498. · 1.50 Impact Factor
ABSTRACT: PurposeOur aim was to determine dual-phase 18F-FDG PET imaging features for various subtypes of thymic epithelial tumors based on the World Health Organization classification.
MethodsForty-six patients with histologically verified thymic epithelial tumors [23 with low-risk tumors (4 with type A, 16 with
AB, and 3 with B1) and 23 with high-risk tumors (7 with B2, 5 with B3, and 11 with thymic carcinoma] were enrolled in this
study. All patients were injected with 18F-FDG.; after 1 h, they underwent scanning; after 3 h, 23 patients underwent an additional scanning. The maximum standard
uptake value (SUVmax) and the retention index (RI%) of the lesions were determined.
ResultsThe early and delayed SUVmax values in the patients with high-risk tumors [early SUVmax (mean: 6.0) and delayed SUVmax (mean: 7.4)] were both significantly larger than those in patients with low-risk tumors [early SUVmax (mean: 3.2) and delayed SUVmax (mean: 3.4)] (P < 0.05). Early SUVmax values of greater than 7.1 differentiated thymic carcinomas from other types of tumors. For the histological differentiation
between high-risk tumors and low-risk tumors, an early SUVmax value of 4.5 was used as the cutoff. The sensitivity, specificity, and accuracy were 78.3, 91.3, and 84.8%, respectively.
ConclusionHigh SUV values (early SUV > 4.5) suggest the presence of high-risk tumors. A very high SUV value (early SUV > 7.1) is useful
for the differentiation of thymic carcinomas from other types of tumors. The delayed SUV values were higher than the early
SUV values in all types of tumors.
European journal of nuclear medicine and molecular imaging 04/2012; 36(8):1219-1225. · 4.99 Impact Factor
ABSTRACT: Cerebral blood flow (CBF) can be quantified non-invasively using the brain perfusion index (BPI), which is determined using
radionuclide angiographic data obtained through the use of technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO). The BPI is generally calculated using graphical analysis (GA). In this study, BPI was measured using spectral analysis
(SA), and the usefulness of SA was compared with that of GA. Thirteen patients with various brain diseases and four healthy
male volunteers were examined using radionuclide angiography with99mTc-HMPAO. The BPI was measured for each subject using both SA and GA. In the four healthy volunteers, the BPI was examined
at rest and after the intravenous administration of 1 g of acetazolamide (ACZ). An H2
15O PET examination was also performed in the 13 patients; the BPIS and BPIG values were compared with the CBF measurements obtained using H2
15O PET (CBFPET). The BPI values obtained by SA (BPIS) (x) and by GA (BPIG) (y) were correlated (y = 0.568x + 0.055, r = 0.901) in the 13 patients and four healthy volunteers at rest, although the BPIG values were underestimated by 36.1 ± 7.5% (mean ± SD) compared with the BPIS values. The degree of underestimation tended to increase with increasing BPIS values. The increase in the BPIS was 32.1 ± 8.0% after the intravenous administration of ACZ, while the increase in BPIG was only 8.1 ± 2.8%. This discrepancy was considered to be the result of the BPIG values being affected by the first-pass extraction fraction of the tracer. Although both BPIS and BPIG values were significantly correlated with the CBFPET values, the correlation coefficient for BPIS was higher than that for BPIG (BPIS: r = 0.881; BPIG: r = 0.832). These results suggest that SA produces a more reliable BPI for quantifying CBF using99mTc-HMPAO than the conventional method using GA. The SA method should be especially useful for activation studies involving
pharmacological intervention and/or clinical cases with an increased CBF.
Annals of Nuclear Medicine 04/2012; 18(3):243-249. · 1.50 Impact Factor
ABSTRACT: To evaluate the usefulness of a combination of linearization and seatter-attenuation correction on99mTc-bicisate (ECD)-single photon emission tomographic (SPECT) images, both cerebral blood flow (CBF)-positron emission tomographic
(PET) images and ECD-SPECT images from fifteen patients with chronic cerebral infarction were acquired. We measured radioactivity
counts in regions of interest (ROIs) on all sets of both images and obtained a 2D scattered graph between ECD-SPECT and CBF-PET
data. To evaluate diagnostic accuracy, the sensitivity, specificity and accuracy of ECD-SPECT images were calculated by means
of discriminant analysis. The same analysis was also performed on the ECD-SPECT images corrected by a combination of linearization
and scatter-attenuation correction. An overall nonlinear relationship was observed between ECD-SPECT and CBF-PET. The sensitivity,
specificity, and accuracy of ECD-SPECT images were 69.6%, 91.4% and 73.0%, and those of ECD images corrected by the combination
of linearization and scatter-attenuation correction were 79.5%, 95.7% and 82.0% respectively. The clinically diagnostic accuracy
of ECD-SPECT images corrected by the combined method apparently increased. So that the linearization with the scatter-attenuation
method is useful for improving the diagnostic accuracy of ECD-SPECT images.
Annals of Nuclear Medicine 04/2012; 15(2):123-129. · 1.50 Impact Factor
ABSTRACT: The aim of this study is to develop a non-invasive procedure for quantitative assessment of regional cerebral blood flow using IMP and SPECT. A technique to utilize a population-based standardized arterial input function has been evaluated for the normal data base obtained from 3 institutions, which employed different SPECT device configurations. In total, data from 39 subjects were analyzed. Due to the unique feature of the QSPECT reconstruction software program, images are quantitative providing units of Bq/ml. Thus, the well counter values can be converted to absolute radioactivity concentration. The blood-to-whole-body average partition coefficient was 343.8 +/- 65.0 and did not show significant difference among the three institutions. The estimated blood counts agreed with those assessed by the well counter in all institutions, thus the arterial input function can be estimated with the unique conversion factor for all institutions. This feature may allow a large scale multi-center investigation, which may contribute to improve the non-invasive protocol.
Kaku igaku. The Japanese journal of nuclear medicine 03/2012; 49(2):49-58.
ABSTRACT: OBJECTIVE: We recently developed an integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) (iPET/MRI) scanner for small animals, which had relatively large field-of-view (FOV) covering up to the size of a rat body. The purpose of this study was to report results of simultaneous PET/MRI of a rat body using this scanner with some radiotracers. METHODS: C-11-methionine (MET), F-18-fluorodeoxyglucose (FDG), or F-18-sodium fluoride (NaF) was injected as a radiotracer for PET portion in addition to gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid, a hepatobiliary contrast agent, for MRI portion. Simultaneous PET/MRI was performed in normal rats. PET, MRI, and co-registered fusion images were evaluated regarding image quality and feasibility for rat imaging studies. RESULTS: MET uptake was clearly shown in the liver and pancreas, which was confirmed with magnetic resonance (MR) and fused PET/MR images. PET/MR images depicted intense FDG uptake in the brain, Harderian glands, and myocardium. NaF uptake was observed in all bones and joints within FOV, except in ribs, which was well recognized with the help of MR and fused PET/MR images. CONCLUSION: This study demonstrated that simultaneous PET/MRI with an integrated dual-modality molecular imaging scanner was a feasible technique for imaging studies targeting on a rat body. However, further developments including attenuation correction methods are required to use this technique routinely in rat imaging studies.
Annals of Nuclear Medicine 02/2012; · 1.50 Impact Factor
ABSTRACT: Patient movement has been considered an important source of errors in cardiac PET. This study was aimed at evaluating the effects of such movement on myocardial blood flow (MBF) and perfusable tissue fraction (PTF) measurements in intravenous ¹⁵O-water PET.
Nineteen ¹⁵O-water scans were performed on ten healthy volunteers and three patients with severe cardiac dysfunction under resting conditions. Motions of subjects during scans were estimated by monitoring locations of markers on their chests using an optical motion-tracking device. Each sinogram of the dynamic emission frames was corrected for subject motion. Variation of regional MBF and PTF with and without the motion corrections was evaluated.
In nine scans, motions during ¹⁵O-water scan (inter-frame (IF) motion) and misalignments relative to the transmission scan (inter-scan (IS) motion) larger than the spatial resolution of the PET scanner (4.0 mm) were both detected by the optical motion-tracking device. After correction for IF motions, MBF values changed from 0.845 ± 0.366 to 0.780 ± 0.360 mL/minute/g (P < .05). In four scans with only IS motion detected, PTF values changed significantly from 0.465 ± 0.118 to 0.504 ± 0.087 g/mL (P< .05), but no significant change was found in MBF values.
This study demonstrates that IF motion during ¹⁵O-water scan at rest can be source of error in MBF measurement. Furthermore, estimated MBF is less sensitive than PTF values to misalignment between transmission and ¹⁵O-water emission scans.
Journal of Nuclear Cardiology 02/2012; 19(3):524-33. · 2.67 Impact Factor
ABSTRACT: Immunotherapy targeting the Wilms tumor 1 (WT1) gene product is a promising treatment modality for patients with malignant gliomas, and there have been reports of encouraging results. It has become clear, however, that Gd-enhanced MR imaging does not reflect prognosis, thereby necessitating a more robust imaging evaluation system for monitoring response to WT1 immunotherapy. To meet this demand, the authors performed a voxel-wise parametric response map (PRM) analysis of (11)C-methionine PET (MET-PET) in WT1 immunotherapy and compared the data with the overall survival after initiation of WT1 immunotherapy (OS(WT1)).
Fourteen patients with recurrent malignant glioma were included in the study, and OS(WT1) was compared with: 1) volume and length change in the contrast area of the tumor on Gd-enhanced MR images; 2) change in maximum uptake of (11)C-methionine; and 3) a more detailed voxel-wise PRM analysis of MET-PET pre- and post-WT1 immunotherapy.
The PRM analysis was able to identify the following 3 areas within the tumor core: 1) area with no change in (11)C-methionine uptake pre- and posttreatment; 2) area with increased (11)C-methionine uptake posttreatment (PRM(+MET)); and 3) area with decreased (11)C-methionine uptake posttreatment. While the results of Gd-enhanced MR imaging volumetric and conventional MET-PET analysis did not correlate with OS(WT1) (p = 0.270 for Gd-enhanced MR imaging length, p = 0.960 for Gd-enhanced MR imaging volume, and p = 0.110 for MET-PET), the percentage of PRM(+MET) area showed excellent correlation (p = 0.008) with OS(WT1).
This study describes the limited value of Gd-enhanced MR imaging and highlights the potential of voxel-wise PRM analysis of MET-PET for monitoring treatment response in immunotherapy for malignant gliomas. Clinical trial registration no.: UMIN000002001.
Journal of Neurosurgery 01/2012; 116(4):835-42. · 2.96 Impact Factor
ABSTRACT: In quantitative measurements of small animal PET studies, blood sampling is limited due to the small amounts of blood such animals can provide. In addition, injection doses are quite limited. In this situation, a high-sensitivity well counter would be useful for reducing the amount of the blood sample needed from small animals. Bismuth germinate (BGO) has a high stopping power for high-energy gamma rays compared to NaI(Tl), which is commonly used for conventional well counters. We have developed a BGO well counter and have tested it for blood-sampling measurements in small animals. The BGO well counter uses a square BGO block (59 × 59 × 50 mm) with a square open space (27 × 27 × 34 mm) in the center of the block. The BGO block was optically coupled to a 59-mm square-shaped photomultiplier tube (PMT). Signals from the PMT were digitally processed for the integration and energy window setting. The results showed that the energy spectrum of the BGO well counter measured with a Na-22 point source provided counts that were about 6 times higher for a 1022-keV (511 keV × 2) gamma peak than the spectrum of a 2-in. NaI(Tl) well counter. The relative sensitivity of the developed BGO well counter was 3.4 times higher than that of a NaI(Tl) well counter. The time activity curve of arterial blood was obtained successfully with the BGO well counter for a F-18-FDG study on rat. The BGO well counter will contribute to reducing the amount of sampled blood and to improving the throughput of quantitative measurements in small animal PET studies.
Radiological Physics and Technology 01/2012; 5(1):59-62.