Performance of 11C-Pittsburgh Compound B PET Binding Potential Images in the Detection of Amyloid Deposits on Equivocal Static Images.

UNLABELLED: The goal of this study was to clarify whether binding potential (BP) images using (11)C-Pittsburgh compound B ((11)C-PiB) and dynamic PET can reliably detect cortical amyloid deposits for patients whose (11)C-PiB PET static images are ambiguous and whether visual ratings are affected by white matter retention. METHODS: Static and BP images were constructed for 85 consecutive patients with cognitive impairment after (11)C-PiB dynamic PET. Cortical uptake was visually assessed as positive, negative, or equivocal for both types of images. Quantitatively, the standardized uptake value ratio (SUVR) from the static image, the nondisplaceable BP from the dynamic image for mean gray matter uptake, and the ratio of gray matter uptake to white matter retention were compared among (11)C-PiB-positive, (11)C-PiB-equivocal, and (11)C-PiB-negative groups. RESULTS: Forty-three scans were visually assessed as (11)C-PiB-positive in both the static and the BP images. Ten scans were (11)C-PiB-equivocal in the static images. In 8 of them, the BP images were (11)C-PiB-positive, whereas the other 2 were (11)C-PiB-equivocal. Thirty-two scans were assessed as (11)C-PiB-negative in the static images. In the BP images, 4 were (11)C-PiB-positive and 2 were (11)C-PiB-equivocal. The mean gray matter uptake of (11)C-PiB in SUVR and nondisplaceable BP, respectively, showed statistically significant differences among the (11)C-PiB-positive, (11)C-PiB-equivocal, and (11)C-PiB-negative groups. The ratio of gray matter uptake to white matter retention was lower in the BP images than static images from the (11)C-PiB-negative and (11)C-PiB-equivocal groups, whereas it was higher in the (11)C-PiB-positive group. CONCLUSION: (11)C-PiB PET BP images can clarify visual interpretation of clinical static (11)C-PiB-equivocal images by reducing the interference of nonspecific white matter retention. We conclude that (11)C-PiB-equivocal PET findings on static images reflect cortical amyloid deposits, which can be verified using BP images. Furthermore, quantitative assessments, such as SUVR and nondisplaceable BP, are of no use for correctly rating equivocal visual findings.

Investigation of (11)C-PiB equivocal PET findings.

OBJECTIVE: We have encountered occasional equivocal findings when assessing cerebral cortical amyloid retention with (11)C-Pittsburgh compound B (PiB) PET. We investigated the diagnostic significance of equivocal PiB PET findings. METHODS: This retrospective study included 101 consecutive patients complaining of cognitive disorders (30 Alzheimer's disease, 25 mild cognitive impairment, 8 Lewy body disease, 7 frontotemporal lobar degeneration, 31 others) who underwent both (11)C-PiB PET and (18)F-fluorodeoxy-D-glucose (FDG) PET. We visually classified PiB-positive, PiB-equivocal or PiB-negative ratings according to cortical uptake. For quantitative assessments of PiB PET, standard uptake values referred to cerebellar cortex (SUVR) were calculated in regional template volume of interests (frontal, temporoparietal, precuneus/posterior cingulate cortex, cerebral white matter and cerebellar cortex). The results of visual assessment were compared with the regional and mean cortical SUVRs and cortical-to-white matter ratio of PiB uptake, as well as clinical and FDG PET findings. RESULTS: Among the 101 scans, 41 were PiB negative, 11 were PiB equivocal, and 49 were rated PiB positive in the visual assessments. The mean cortical SUVR and cortical-to-white matter ratio were 0.97 ± 0.07 and 0.57 ± 0.21 in PiB-negative, 1.51 ± 0.17 and 0.75 ± 0.06 in PiB equivocal and 2.10 ± 0.33 and 0.97 ± 0.11 in PiB-positive group, respectively. Nine of 11 subjects with PiB-equivocal findings had cognitive impairments and FDG distribution compatible with Alzheimer's disease or dementia with Lewy bodies. CONCLUSIONS: We considered equivocal visual findings on PiB PET equivalent to PiB-positive with slight cortical uptake. In addition, slight cortical amyloid deposits were considered to cause cerebral metabolic abnormality and cognitive impairment. Although mean cortical SUVR was more sensitive than visual assessment because of low cortical-to-white matter contrast due to non-specific accumulation in white matter, it is important not to overlook small amounts of cortical uptake of PiB in visual inspection for exact diagnosis.

Regional glucose metabolic reduction in dementia with Lewy bodies is independent of amyloid deposition.

PURPOSE: There is evidence that some cases of patients with dementia with Lewy bodies (DLB) can demonstrate Alzheimer disease (AD) like reduced glucose metabolism without amyloid deposition. The aim of this study was to clarify whether regional hypometabolism is related to amyloid deposits in the DLB brain and measure the degree of regional hypometabolism. METHODS: Ten consecutive subjects with DLB and 10 AD patients who underwent both Pittsburgh compound B (PiB)-PET and (18)F-fluoro-2-deoxyglucose (FDG)-PET were included in this study. Regional standardized uptake value ratio (SUVR)s normalised to cerebellar cortices were calculated in the FDG- and PiB-PET images. RESULTS: All AD patients and five DLB patients showed amyloid deposits (PiB positive). In the DLB group the parietotemporal and occipital metabolism were significantly lower than those in the AD group but there was no difference between the posterior cingulate hypometabolism between DLB and AD groups. There were no differences in regional glucose metabolism between PiB positive and negative DLB patients. CONCLUSIONS: In the DLB brain, it is suggested that decreased regional glucose metabolism is unrelated to amyloid deposits, although the hypometabolic area overlaps with the AD hypometabolic area and the degree of parietotemporal and occipital hypometabolism in DLB brain is much larger than that in AD brain.

Dynamic sequence respiratory gated perfusion pulmonary SPECT without external tracking device.

OBJECTIVE: The purpose of this study was to develop and evaluate a new method for respiratory gated pulmonary perfusion SPECT (RGPS) based on dynamic acquisition without using an external tracking device (ETD) or list-mode data acquisition. METHODS: In the phantom study, our method used a dynamic sequence technique, which was specified by sequences of 50-ms acquisition during 30 s per view of SPECT instead of using an ETD. For this purpose, we created a computer program that identified respiratory phases by calculating the center of activity (COA) in each dynamic frame image. We compared RGPS using the dynamic sequence acquisition (RGPS-DS) and RGPS using ETD (RGPS-ETD) in phantom studies employing a cylinder phantom filled with technetium-99m solution attached to an instrument providing a simple harmonic motion. In the patient study, RGPS-DS was applied to data collected from 3 patients during a routine study of Tc-MAA pulmonary perfusion SPECT. RESULTS: In the phantom study, the calculation of COA indicated a good agreement between RGPS-DS and RGPS-ETD. With an oscillatory phantom movement amplitude of 30 mm, the amplitudes determined by RGPS-DS and RGPS-ETD (28.36 and 27.58 mm, respectively) were identical on considering a pixel size of 4.66 mm for reconstructed SPECT images. In the patient study, applicability of our method to patient data was demonstrated. CONCLUSIONS: We have showed the feasibility of our method to obtain RGPS without ETD, and conclude that RGPS-DS may be an innovative and efficient technique in respiratory gated pulmonary perfusion SPECT. Further studies with a larger number of patients should demonstrate the accuracy of our method.

[Evaluation of patient dose from diagnostic X-ray using glass badges].

Radiography is used in medical practices based on the principles of justification and optimization. Patients' exposure doses should be kept as low as still allows for image quality that does not disturb the diagnostic processes. To optimize diagnostic radiological procedures, the international commission on radiological protection (ICRP) advocated the establishment of diagnosis reference levels (DRLs) in the new basic recommendation (Publication 103) in 2007 by stating that "The DRL should be expressed as a readily measurable patient-dose-related quantity for the specified procedure." In this context, a simple and standardized dosimetric method is needed to verify the adaptability of a radiation dose to the DRLs. As a measuring instrument that has good availability, high accuracy, and easy operability, we adopted the glass badge system, which has been used for individual exposure dose management. We evaluated the accuracy of the system as a tool of simplified dosimetry of diagnostic X-rays by comparing it to the standard dosimetry of an ionization chamber. In an energy range of 50 to 140 kV for X-ray exposure, the glass badge showed values within 7% of or closer to those measured by the standard ionization chamber. Moreover, the glass badge measurement was independent of the rectification modes of the X-ray tubes. In conclusion, glass badge measurement is feasible for verifying diagnostic X-ray doses in relation to DRLs and can be widely used in hospitals and clinics.

Fluorodeoxyglucose uptake in the bone marrow after granulocyte colony-stimulating factor administration in patients with non-Hodgkin's lymphoma.

PURPOSE: To clarify the change in the fluorodeoxyglucose (FDG) uptake by the bone marrow over time after administration of granulocyte colony-stimulating factor (G-CSF), we evaluated the correlation between the interval from the last day of administration of G-CSF to positron emission tomography/computed tomography (PET/CT) study and spinal bone marrow accumulation in patients with non-Hodgkin's lymphoma. METHODS: A total of 127 patients with confirmed non-Hodgkin's lymphoma who underwent FDG PET within 60 days from the last administration of G-CSF were retrospectively reviewed. Thirty age-matched and sex-matched healthy controls were also included to evaluate physiological FDG uptake. PET/CT examinations were retrospectively reviewed, and maximum standardized uptake value (SUVmax) was measured by placing volumetric regions of interest over each thoracic and lumbar vertebra on PET images referring to CT images. Bone marrow SUV was defined as the mean SUVmax of the vertebra. The correlation between the interval after G-CSF and the bone marrow SUV was plotted and analyzed with polynomial approximation. RESULTS: In controls, physiological bone marrow SUV of the spine was determined. In patients with lymphoma, bone marrow SUV decreased over time and reached a plateau at about 14 days after G-CSF administration, and this was higher by 5% than the plateau at 10 days. SUV declined to the 'physiological range', that is, mean+1 standard deviation of patients, at about 7 days. CONCLUSION: For a PET/CT study, an interval of 10 days after G-CSF administration is recommended to minimize the influence of G-CSF on the bone marrow when evaluating treatment response in patients with non-Hodgkin's lymphoma.

Decreased brain FDG uptake in patients with extensive non-Hodgkin's lymphoma lesions.

OBJECTIVE: Faint brain [(18)F]fluoro-2-deoxyglucose (FDG) uptake has sporadically been reported in patients with FDG-avid large or diffusely extended tumors. The purpose of this study was to investigate whether there is a correlation between massive tumor uptake and decreased brain uptake on FDG positron emission tomography/computed tomography (PET/CT). METHODS: Sixty-five patients with histologically confirmed non-Hodgkin's lymphoma who underwent FDG-PET/CT were enrolled. Thirty control subjects were also included to evaluate normal brain FDG uptake. PET/CT examinations were retrospectively reviewed. The volumetric regions of interest were placed over lesions by referring to CT and PET/CT fusion images to measure mean standardized uptake value (SUVavg). The products of SUVavg and tumor volume were calculated as total glycolytic volume (TGV). The maximum SUV (SUVmax) and SUVavg were measured in the cerebrum and cerebellum. The values of TGV and brain FDG uptake were plotted and analyzed with a linear regression method. RESULTS: In the lymphoma patients, there were statistically significant negative correlations between TGV and brain SUVs. CONCLUSION: Demonstrating a significant negative correlation between TGV and brain uptake validated the phenomenon of decreased brain FDG uptake. Diversion of FDG from the brain to the lymphoma tissue may occur during the FDG accumulation process. Recognition of this phenomenon prevents unnecessary further neurological examinations in such cases.