[Creation of Stereo-paired Bone Anatomical Charts Using Human Bone Specimens for Radiation Education].

In radiological examinations of patients, we often take stacked images and three-dimensional (3D) images of human bone radiological images such as X-ray images and CT images. In general, learning of bone structure using specialized anatomy books is currently performed at medical radiological technologist education facilities. In the anatomy education of the medical school, in order to understand the structure of human and the individual bone shapes in detail, a real human bone specimen is used to gain knowledge of skeleton, bone shape, bone name and bone function. But it is actually difficult for a radiological technologist to obtain such learning opportunities. Therefore, we had to depend on two-dimensional information from an anatomical atlas so far. Therefore, as a method to solve this, we devised this stereo-paired bone anatomical chart by stereoscopic photography of a real human bone specimen that is available only in the anatomy laboratory. In classical anatomy textbooks, there are no figures that enable us to view 3D structures of human bones. Our stereo-paired bone anatomical charts make it possible to observe accurate bone structures three-dimensionally. In addition, we saved the data as a PDF file and uploaded to an internet server so that we can freely download and readily observe 3D images of human bones at all times and all places with a tablet or a PC monitor.

[Creation of Stereo Color Anatomical Charts Showing Nerve Fibers in the Cerebral Lobe and Gyrus of the Brain for Use in the MR Examination].

In anatomical charts in conventional books, the pathways of nerve fibers are drawn in illustrations. Conversely, with diffusion tensor tractography (DTT), we can visually understand the trajectory of nerve fibers through color. We created a stereo color anatomical chart of the nerve fibers that can be used for magnetic resonance (MR) examination to diagnose the pathway of nerve fibers and that can be used to explain the results of MR examination to visually understand how nerve fiber information is transmitted from the frontal lobe, parietal lobe, occipital lobe, temporal lobe, cerebellar lobe, and cerebral cortex.

Impact of Pelvic Rotational Setup Error on Lymph Nodal Dose in Whole Pelvic IMRT Using Fiducial Markers.

PURPOSE: The aim of this study was to investigate the impact of pelvic rotational setup error on lymph nodal dose in the whole pelvic intensity-modulated radiation therapy using the fiducial marker. METHODS: The dose differences of clinical target volume for pelvic lymph node (CTVLN) due to isocenter (IC) shift and pelvic rotation were evaluated using the radiation treatment planning system. The rotated computed tomography (CT) images were created for the simulation of the pelvic rotation. The original CT images were rotated around the IC of the original plan in the pitch and roll directions up to±3.0 deg. at 1.0 deg. intervals. As simulated plans, IC positions were shifted in the anterior-posterior and superior-inferior directions up to±10 mm at 2 mm intervals in the original and rotated CT images, and the dose distributions were calculated. The dose calculation was performed for each CT image while keeping the movement of multi leaf collimator and the monitor unit of the original plan. The differences between D98% of CTVLN in the original plan and simulated plans were calculated. RESULTS: In the posterior direction shifts of 4, 6, 8, and 10 mm, the dose reduction of 0.7, 2.1, 6.1, and 11.9% from the original plan were found for D98% of CTVLN, respectively. The dose reductions due to the rotation of pitch direction were greater than the rotation of roll direction. In the posterior direction shifts of 4, 6, 8, and 10 mm with 3.0 deg. rotation of pitch direction, the dose reduction of 2.2, 6.8, 12.8, and 19.0% from the original plan were found, respectively. CONCLUSION: The dose reduction of CTVLN might be occurred due to the rotational setup error of pitch direction.

[Investigation of the Administration Accuracy of an Auto Infusion Device in 18F-FDG PET].

PURPOSE: The administration accuracy of the automated infusion device for the positron emission radiopharmaceutical affects to calculation of the standardized uptake value (SUV) in 18F-fluorodeoxyglucose (18F-FDG) PET examination. The purpose of this study was to investigate the administration error in the clinical use of an automated infusion device for quantitative management in PET examination. METHODS: We assumed clinical use of the automated infusion device and investigated two types of administration errors. First, for investigating the administration error over time in a day (errorday), a total of 13 infusion works were performed every 30 minutes. Second, for investigating the long period administration error (errorperiod), the infusion work was performed once before clinical use of an automated infusion device. The dispensed radioactivity was set to 150 MBq. The administration error was calculated using output values from the automated infusion device and measured values from the dose calibrator. RESULTS: The administration errorday was 0.9±1.3%, and the maximum error was 2.7%. The administration errorperiod was 1.1±2.0%, and the maximum error was 5.9%. CONCLUSION: We investigated the administration error of the automated infusion device. We confirmed the approximately 1% administration error and high-accuracy injection in an automated-device method.

[11C-methionine positron emission tomography in nontumorous brain lesions].

Positron emission tomography (PET) with L-[methyl-11C]methionine (MET) provides information on the metabolism of brain tumor. MET uptake reflects amino acid active transport and protein synthesis and is proportional to the amount of viable tumor cells. However, MET uptake can be increased as a result of increased density of inflammatory cells and disruption of the blood brain barrier (BBB) in nontumorous brain lesions. From October 2005 through November 2009, 438 MET-PET studies were performed for various brain lesions at our institution. Among them, 27 (6%) were finally diagnosed to be nontumorous by surgical exploration or their clinical course. Nine of 10 intracerebral hemorrhages and all 4 cerebral infarctions demonstrated mild to moderate MET uptake in or surrounding the lesions in the subacute or chronic stage after the ictus. Moderately increased MET uptake was observed in all 3 patients with brain abscess. Active lesions in multiple sclerosis and Beçhet disease showed mild MET uptake. Idiopathic orbital and optic inflammations showed mildly increased MET uptake in the lesions. Finally, a case of hypertrophic cranial pachymeningitis exhibited strong MET uptake in the lesions. We should keep in mind that high MET uptake is frequently observed in nontumorous brain lesions. Although differentiation from tumorous lesions is usually possible by laboratory and morphological examinations, nontumorous lesions should be included in the differential diagnosis when encountering patients with high MET uptake.

Accuracy of target delineation by positron emission tomography-based auto-segmentation methods after deformable image registration: A phantom study.

PURPOSE: Diagnostic positron emission tomography and computed tomography (PET/CT) images can be fused to the planning CT images by a deformable image registration (DIR). The aim of this study was to evaluate the standardized uptake value (SUV) and target delineation on deformed PET images. METHODS: We used a cylindrical phantom and removable inserts of four spheres (16-38 mm in diameter) and three ellipsoids with a volume equal to the 38-mm-diameter sphere (S38) in each. S38 was filled with 18F-fluorodeoxyglucose activity, and then PET/CT images were acquired. The contours of S38 were generated using original PET images by PET auto-segmentation (PET-AS) methods of (1) SUV2.5, (2) 40% of maximum SUV (SUV40%max), and (3) gradient-based (GB), and were deformed to the other inserts by DIR. We compared the volumes and the SUVmax with the generated contours using the deformed PET images. RESULTS: The SUVmax was slightly decreased by DIR; the mean absolute difference was -0.10 ± 0.04. For SUV2.5 and SUV40%max, the differences in S38 volumes between the original and deformed PET images were less than 5%, regardless of deformation type. For the GB, the contoured volumes obtained from deformed PET images were larger than those of the original PET images for the deformation type of ellipsoids. When the S38 was deformed to the 16-mm-diameter sphere, the maximum volume difference was -22.8%. CONCLUSIONS: Although SUV fluctuations by DIR were negligible, the target delineation on deformed PET images by the GB should be carefully considered owing to the distortion of intensity profiles.

11C-methionine (MET) and 18F-fluorothymidine (FLT) PET in patients with newly diagnosed glioma.

PURPOSE: The purpose of this prospective study was to clarify the individual and combined role of L-methyl-(11)C-methionine-positron emission tomography (MET-PET) and 3'-deoxy-3'-[(18)F]fluorothymidine (FLT)-PET in tumor detection, noninvasive grading, and assessment of the cellular proliferation rate in newly diagnosed histologically verified gliomas of different grades. MATERIALS AND METHODS: Forty-one patients with newly diagnosed gliomas were investigated with MET-PET before surgery. Eighteen patients were also examined with FLT-PET. MET and FLT uptakes were assessed by standardized uptake value of the tumor showing the maximum uptake (SUV(max)), and the ratio to uptake in the normal brain parenchyma (T/N ratio). All tumors were graded by the WHO grading system using surgical specimens, and the proliferation activity of the tumors were determined by measuring the Ki-67 index obtained by immunohistochemical staining. RESULTS: On semiquantitative analysis, MET exhibited a slightly higher sensitivity (87.8%) in tumor detection than FLT (83.3%), and both tracers were 100% sensitive for malignant gliomas. Low-grade gliomas that were false negative on MET-PET also were false negative on FLT-PET. Although the difference of MET SUV(max) and T/N ratio between grades II and IV gliomas was statistically significant (P < 0.001), there was a significant overlap of MET uptake in the tumors. The difference of MET SUV(max) and T/N ratio between grades II and III gliomas was not statistically significant. Low-grade gliomas with oligodendroglial components had relatively high MET uptake. The difference of FLT SUV(max) and T/N ratio between grades III and IV gliomas was statistically significant (P < 0.01). Again, the difference of FLT SUV(max) and T/N ratio between grades II and III gliomas was not statistically significant. Grade III gliomas with non-contrast enhancement on MR images had very low FLT uptake. In 18 patients who underwent PET examination with both tracers, a significant but relatively weak correlation was observed between the individual SUV(max) of MET and FLT (r = 0.54, P < 0.05) and T/N ratio of MET and FLT (r = 0.56, P < 0.05). Total FLT uptake in the tumor had a higher correlation (r = 0.89, P < 0.001) with Ki-67 proliferation index than MET uptake (r = 0.49, P < 0.01). CONCLUSIONS: PET studies using MET and FLT are useful for tumor detection in newly diagnosed gliomas. However, there is no complimentary information in tumor detection with simultaneous measurements of MET- and FLT-PET in low grade gliomas. FLT-PET seems to be superior than MET-PET in noninvasive tumor grading and assessment of proliferation activity in gliomas of different grades.

Dual-time-point FDG-PET for evaluation of lymph node metastasis in patients with non-small-cell lung cancer.

OBJECTIVE: The objective of this study was to retrospectively evaluate whether delayed additional F-18-fluorodeoxyglucose positron emission tomography (FDG-PET) imaging can improve the certainty of this modality in evaluating lymph node metastasis in patients with non-small-cell lung cancer (NSCLC). METHODS: Eighty-three patients with NSCLC were examined. FDG-PET imaging (whole body) was performed at 1-h (early) post-FDG injection and repeated 2 h (delayed) after injection only in the thoracic area. The PET images were evaluated qualitatively for regions of focally increased metabolism. If a lymph node was visible on the PET image, the semi-quantitative analysis using the standardized uptake value (SUV) was determined for both early and delayed images (SUV(early) and SUV(delayed), respectively). Retention index (RI) was then calculated on the basis of the following equation: (SUV(delayed) - SUV(early)) x 100/SUV(early). The RI value of more than 0% was taken to be the PET criterion for malignancy. RESULTS: For early and delayed PET, sensitivities for lymph node staging were 54% and 62%, respectively, specificities were 89% for both, and accuracies were 78% and 81%, respectively. The results of combined delayed PET and RI showed a sensitivity of 62%, specificity of 96%, and accuracy of 86%. CONCLUSIONS: Dual-time-point FDG-PET (combined delayed PET and RI) showed better (although not statistically significant) specificity, positive predictive value, and accuracy than early or delayed PET alone for lymph node staging in NSCLC.

Comparison of early and delayed FDG PET for evaluation of biliary stricture.

OBJECTIVE: We assessed whether delayed FDG PET imaging is more useful for the evaluation of biliary stricture in differential diagnosis of malignancy from benign disease. METHODS: Thirty-seven patients who underwent FDG PET for differential diagnosis of the disease causing biliary stricture were included. FDG PET imaging was performed at 70+/-12 min (early) post FDG injection and repeated 188+/-27 min (delayed) after injection only in the abdominal region. Image analysis was performed with visual interpretation and using a semi-quantitative method if lesion was visible on the PET image. The semi-quantitative analysis using the standardized uptake value (SUV) was determined for both early and delayed images (SUVearly and SUVdelayed, respectively). The tumour-to-normal liver (T/L) ratio was also calculated. RESULTS: The final diagnosis was cholangiocarcinoma in 29 and benign disease in eight patients. In cases of cholangiocarcinoma, visual analysis of FDG PET using the delayed images, improve the diagnosis with one more patient correctly identified. For early and delayed FDG PET, sensitivities were 82.8% and 86.2%, respectively; specificities were 87.5% for both; and accuracies were 83.8% and 86.5%, respectively. Both SUV and T/L ratio derived from delayed images were significantly higher than those derived from early images for cholangiocarcinoma (P<0.0002 and P<0.0001, respectively). CONCLUSION: FDG PET could be useful for differential diagnosis of malignancy from benign disease in patients with biliary stricture. Especially, the delayed targeted FDG PET imaging can be recommended in those patients when early imaging is negative or equivalent, because of increased lesion uptake and increased lesion to background contrast ratio.

Dual-time-point 18F-FDG PET for the evaluation of gallbladder carcinoma.

UNLABELLED: Conventional imaging techniques such as ultrasonography, CT, and MRI are able to detect gallbladder abnormalities but are not always able to differentiate a malignancy from other disease processes such as cholecystitis. The purpose of the present study was to evaluate the efficacy of dual-time-point (18)F-FDG PET for differentiating malignant from benign gallbladder disease. METHODS: The study evaluated 32 patients who were suspected of having gallbladder tumors. (18)F-FDG PET (whole body) was performed at 62 +/- 8 min (early) after (18)F-FDG injection and was repeated 146 +/- 14 min (delayed) after injection only in the abdominal region. We evaluated the (18)F-FDG uptake both visually and semiquantitatively. Semiquantitative analysis using the standardized uptake value (SUV) was performed for both early and delayed images (SUV(early) and SUV(delayed), respectively). The retention index (RI) was calculated according to the equation (SUV(delayed) - SUV(early)) x 100/SUV(early). The tumor-to-liver ratio was also calculated. RESULTS: The final diagnosis was gallbladder carcinoma in 23 patients and benign disease in 9 patients. For visual analysis of gallbladder carcinoma, delayed (18)F-FDG PET images improved the specificity of diagnosis in 2 patients. When an SUV(early) of 4.5, SUV(delayed) of 2.9, and RI of -8 were chosen as arbitrary cutoffs for differentiating between malignant and benign conditions, sensitivity increased from 82.6% to 95.7% and 100% for delayed imaging and combined early and delayed imaging (i.e., RI), respectively. With the same criteria, specificity decreased from 55.6% to 44.4% for delayed imaging and combined early and delayed imaging, respectively. The specificity of (18)F-FDG PET improved to 80% in the group with a normal level of C-reactive protein (CRP) and decreased to 0% in the group with an elevated CRP level. For gallbladder carcinoma, both SUV and tumor-to-liver ratios derived from delayed images were significantly higher than the ratios derived from early images (P < 0.0001). CONCLUSION: Delayed (18)F-FDG PET is more helpful than early (18)F-FDG PET for evaluating malignant lesions because of increased lesion uptake and increased lesion-to-background contrast. However, the diagnostic performance of (18)F-FDG PET depends on CRP levels.

Magnetic resonance imaging and positron emission tomography findings in status epilepticus following severe hypoglycemia.

We recently experienced a case with asymmetrical cortical abnormality on MRI with focal status epilepticus following severe hypoglycemia. The cerebral blood flow and metabolisms for oxygen and glucose were determined using positron emission tomography (PET) during focal status epilepticus following severe hypoglycemia and at the follow-up period. Prolonged seizure activity produced profound glucose hypermetabolism and mild hyperemia in the region of the presumed cortical focus of epilepsy and in structures anatomically remote from the focus, corresponding to the areas of abnormal signal intensity on the MRI. The patient remained comatose and exhibited a diffuse hypoperfusion/hypometabolism and symmetrical brain atrophy on the follow-up PET and MRI, respectively. Cytotoxic brain edema due to profound glucose metabolism without compensatory increase of the blood flow during status epilepticus may account for the brain abnormality observed on the early MRI. Simultaneous examination of the cerebral blood flow and metabolism using PET can provide useful information about the pathology in patients with status epilepticus.

A case of non-hodgkin's lymphoma of the ovary: usefulness of 18F-FDG PET for staging and assessment of the therapeutic response.

Primary ovarian lymphoma as the initial manifestation is rare. A 27-year-old woman presented to our hospital with the symptoms of lower abdominal fullness and pollakisuria. CT scan and MRI revealed bilateral ovarian tumors, which showed heterogeneous masses. 18F-FDG PET revealed strong uptake by the abdominal masses, and the maximum standardized uptake value (SUVmax) was 12.5. Abnormal uptake was not shown by other regions. An exploratory laparotomy was performed. Histological findings revealed diffuse large B-cell lymphoma. The clinical stage was IV according to the Ann Arbor system. International prognostic index (IPI) was 3 (high-intermediate risk). Chemotherapy was administered consisting of three courses of an R-CHOP regimen, and 18F-FDG PET and CT scan revealed no signs of involvement 3 months after initiation of the chemotherapy. 18F-FDG PET was a useful method for staging and assessment of the therapeutic response in primary ovarian lymphoma.

FDG-PET findings of the brain in lymphomatoid granulomatosis.

A 44-year-old man with a history of sudden onset short-term disorientation was admitted to our hospital. T2-weighted fast spin-echo MR images of the head showed increased signal intensity in the bilateral frontal and parietal white matter. Gadolinium-enhanced T1-weighted spin-echo images showed multiple areas with punctate and linear enhancement scattered in the bilateral frontal and parietal white matter. Although 18F-fluorodeoxyglucose positron emission tomography ([18F]FDG-PET) did not display a significant increase in FDG accumulation in the bilateral frontal and parietal white matter, kinetic analysis of this scan showed increased hexokinase activity in the lesions compared to the unaffected occipital white matter. Diagnosis was made by open biopsy of the right frontal lobe and pathologic specimen was positive for lymphomatoid granulomatosis (LYG). The patient received high-dose methotrexate with CHOP (cyclophosphamide, doxorubicin hydrochloride, vincristine sulfate, and prednisolone) chemotherapy and follow-up MRI showed improvement of the lesions. [18F]FDG-PET study with kinetic analysis may be useful to diagnose LYG in the central nervous system.

Evaluation of delayed additional FDG PET imaging in patients with pancreatic tumour.

AIM: To evaluate whether delayed fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging is more helpful in differentiating between malignant and benign lesions and whether delayed FDG PET imaging can identify more lesions in patients in whom pancreatic cancer is suspected. METHODS: The study evaluated 86 patients who were suspected of having pancreatic tumours. FDG PET imaging (whole body) was performed at 1 h (early) post-injection and repeated 2 h (delayed) after injection only in the abdominal region. Qualitative and semi-quantitative evaluation was performed. The semi-quantitative analysis was performed using the standardized uptake value (SUV), obtained from early and delayed images (SUVearly and SUVdelayed, respectively). Retention index (RI) was calculated according to the equation: (SUVdelayed-SUVearly)x100/SUVearly. RESULTS: The final diagnosis was pancreatic cancer in 55 and benign disease in 31 patients. On visual and semi-quantitative analysis, the diagnostic accuracy of RI was the highest (88%). The differences between the SUVearly, SUVdelayed and RI value in both pancreatic cancer and benign disease were significant (P<0.01). The mean value of SUVdelayed was significantly higher than that of SUVearly (P<0.01) in pancreatic cancer. Furthermore, new foci of metastasis were seen in the liver in two patients and in the lymph node in one patient only on delayed images. CONCLUSIONS: The RI values obtained using early and delayed FDG PET may help in evaluating pancreatic cancer. Furthermore, addition of delayed FDG PET imaging is helpful to identify more lesions in patients with pancreatic cancer.

Contribution of whole body FDG-PET to the detection of distant metastasis in pancreatic cancer.

OBJECTIVE: Accurate baseline staging is necessary to appropriately treat pancreatic cancer. The present study was undertaken to evaluate the clinical contribution of whole body FDG-PET to the detection of distant metastasis in pancreatic cancer. METHODS: A total of consecutive 42 patients with previously untreated pancreatic cancer were examined. Whole body FDG-PET imaging for initial staging was performed with a 3D acquisition and iterative reconstruction on Siemens ECAT HR+ scanner at 1 hour post 185-200 MBq 18F-FDG injection. PET findings were correlated with clinical and radiological data to determine the impact of PET on staging. RESULTS: In 16 patients, there were one or more sites of metastasis based on clinical data. FDG-PET correctly identified the presence of metastasis in 13 of 16 patients and its absence in 23 of the remaining 26 patients. Thus, FDG-PET missed 4 metastatic sites in 4 patients (liver and lung metastasis). FDG-PET correctly identified 8 metastatic sites in 7 patients (peritoneal dissemination and liver, bone and supraclavicular lymph node metastasis), which were missed on CT imaging. Based on whole body FDG-PET, the clinical stage was changed in 5 of 42 patients (11.9%). CONCLUSIONS: These results suggest that FDG-PET and CT appear to have a complementary role in the detection of distant metastasis in patients with pancreatic cancer.

Applicability of emission-based attenuation map for rapid CBF, OEF, and CMRO2 measurements using gaseous (15)O-labeled compounds.

BACKGROUND: Cerebral blood flow (CBF), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO2) images have facilitated understanding of the pathophysiological basis of cerebrovascular disorders. Such parametric images can be rapidly, measured within around 15 min, using positron emission tomography (PET) with sequentially administered (15)O-labeled oxygen and water. For further shortening, one option is to eliminate the transmission scan by applying an emission-based attenuation correction. METHODS: The validity of the present method was tested by comparing parametric values with emission-based attenuation correction to those with transmission-based correction. This was applied to 27 subjects who were diagnosed with or without cerebrovascular disorders. All subjects received the rapid CBF/OEF/CMRO2 PET measurements. An emission-based attenuation map was generated by estimating the edge of the brain tissue contour on an obtained sinogram and by assuming the uniform tissue coefficient to be 0.1 cm(-1). Then images were reconstructed, and parametric images were computed. RESULTS: No difference was apparent between the emission- and transmission-based methods. Paired t-test showed no significant differences in CBF, OEF, or CMRO2 values between the emission- and transmission-based methods, except in the parietal and occipital and cerebellum and occipital regions, and the differences were less than 10%. The regression analysis showed a close correlation of r = 0.89 to 0.99. CONCLUSIONS: The present study revealed that the attenuation correction can be performed by the emission-based estimation method and clinical PET duration can be shortened for the CBF, OEF, and CMRO2 gas study.

Imaging of the appearance time of cerebral blood using [15O]H2O PET for the computation of correct CBF.

BACKGROUND: Quantification of cerebral blood flow (CBF) is important for the understanding of normal and pathologic brain physiology. Positron emission tomography (PET) with H215O (or C15O2) can quantify CBF and apply kinetic analyses, including autoradiography (ARG) and the basis function methods (BFM). These approaches, however, are sensitive to input function errors such as the appearance time of cerebral blood (ATB), known as the delay time. We estimated brain ATB in an image-based fashion to correct CBF by accounting for differences in computed CBF values using three different analyses: ARG and BFM with and without fixing the partition coefficient. METHODS: Subject groups included those with no significant disorders, those with elevated cerebral blood volume, and those with reduced CBF. All subjects underwent PET examination, and CBF was estimated using the three analyses. The ATB was then computed from the differences of the obtained CBF values, and ATB-corrected CBF values were computed. ATB was also estimated for regions of interest (ROIs) of multiple cortical regions. The feasibility of the present method was tested in a simulation study. RESULTS: There were no significant differences in the obtained ATB between the image- and ROI-based methods. Significantly later appearance was found in the cerebellum compared to other brain regions for all groups. In cortical regions where CBF was reduced due to occlusive lesions, the ATB was 0.2 ± 1.2 s, which was significantly delayed relative to the contralateral regions. A simulation study showed that the ATB-corrected CBF was less sensitive to errors in input function, and noise on the tissue curve did not enhance the degree of noise on ATB-corrected CBF image. CONCLUSIONS: This study demonstrates the potential utility of visualizing the ATB in the brain, enabling the determination of CBF with less sensitivity to error in input function.

Shortening the duration of [18F]FDG PET brain examination for diagnosis of brain glioma.

PURPOSE: Some patients cannot remain immobile for a long duration of 60 min, which is generally applied in the case of a 2-deoxy-2-[(18)F]fluoro-D-glucose ([(18)F]FDG) dynamic positron emission tomography (PET) scan. We investigated the change of the parametric values when the time duration of PET data was shortened. PROCEDURES: Eight normal subjects and four subjects with brain glioma were studied. The rate values of K(1), k(2), k(3), and K(i) parametric images were computed by changing the time duration from 20 to 60 min, and changes of those parametric values were compared. RESULTS: The change was 20-30% and 3-5% for k(3) and K(i), respectively, when the scan time was shortened from 60 to 40 min. The ratios of normal and disease regions in k(3) and K(i) values were similar, and contrasts of those images were not changed when the scan time was shortened to 40 min. CONCLUSIONS: These results demonstrate that the short time duration of [(18)F]FDG PET examination can provide an acceptable estimation of parametric k(3) and K(i) images.

Omission of [(15)O]CO scan for PET CMRO(2) examination using (15)O-labelled compounds.

OBJECTIVE: CBF, OEF and CMRO(2) provide us important clinical indices and are used for assessing ischemic degree in cerebrovascular disorders. These quantitative images can be measured by PET using (15)O-labelled tracers such as C(15)O, C(15)O(2) and (15)O(2). To reduce the time of scan, one possibility is to omit the use of CBV data. The present study investigated the influence of fixing the CBV to OEF and CMRO(2) values on subjects with and without cerebrovascular disorders. METHODS: The study consisted of three groups, namely, GROUP-0 (n = 10), GROUP-1 (n = 9), and GROUP-2 (n = 10), corresponding to--without significant disorder, with elevated CBV, and with reduced CBF and elevated OEF, respectively. All subjects received PET examination and using the PET data OEF and CMRO(2) images were computed by fixing CBV and with CBV data. The computed OEF and CMRO(2) values were compared between the methods. RESULTS: The OEF and CMRO(2) values obtained by fixing the CBV were around 10% underestimation against that with CBV data. The regression analysis showed that these values were comparable (r = 0.93-0.98, P < 0.001). The simulation showed that fixing of the CBV would not derive significant error in either OEF or CMRO(2) values, when changed from 0 to 0.08 ml/g. CONCLUSION: This study shows the feasibility of fixing the CBV value for computing OEF and CMRO(2) values in the PET examination, suggesting the CO scan could be eliminated.