Biomedical subjects

Yuji Nakamoto

Publications and source records attributed to Yuji Nakamoto.

At least 37 records · Page 2Linked to original sources

PubMed2003

Diagnosis of pancreatic cancer using fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) --usefulness and limitations in "clinical reality".

The present review will provide an overview of the literature concerning the FDG PET diagnosis of pancreatic cancer and a summary from our experience of 231 cases of pancreatic lesions. FDG PET can effectively differentiate pancreatic cancer from benign lesion with high accuracy. Newly-developed PET scanners can detect small pancreatic cancers, up to 7 mm in diameter, by their high resolution, which could make a great contribution to the early detection of resectable and potentially curable pancreatic cancers. FDG PET is useful and cost-beneficial in the pre-operative staging of pancreatic cancer because an unexpected distant metastasis can be detected by whole-body PET in about 40% of the cases, which results in avoidance of unnecessary surgical procedures. FDG PET is also useful in evaluation of the treatment effect, monitoring after the operation and detection of recurrent pancreatic cancers. However, there are some drawbacks in PET diagnosis. A relatively wide overlap has been reported between semiquantitative uptake values obtained in cancers and those in inflammatory lesions. As for false-positive cases, active and chronic pancreatitis and autoimmune pancreatitis sometimes show high FDG accumulation and mimic pancreatic cancer with a shape of focal uptake. There were 8 false negative cases in the detection of pancreatic cancer by FDG PET, up to 33 mm in diameter, mainly because of their poor cellularity in cancer tissues. In addition, there are 19% of cancer cases with a decline in FDG uptake from 1 hr to 2 hr scan. FDG PET was recently applied to and was shown to be feasible in the differential diagnosis of cystic pancreatic lesions, such as intraductal papillary mucinous tumor of the pancreas. Further investigations are required to clarify the clinical value of FDG PET in predicting prognosis of the pancreatic patients.

Fluorodeoxyglucose F18↗

PubMed2003

Clinical value of FDG-PET in the follow up of post-operative patients with endometrial cancer.

OBJECTIVE: The clinical usefulness of FDG-PET in the follow up of post-operative patients with endometrial cancer was retrospectively evaluated. METHODS: Twenty-one post-operative patients with endometrial cancer received 30 FDG-PET examinations to evaluate recurrence or response to treatment. The findings of FDG-PET were compared with their serum levels of tumor markers, CT and/or MRI findings, and the final outcome. Results of FDG-PET were also correlated with the clinical course of each patient. RESULTS: In detecting recurrent lesions and evaluating treatment responses, FDG-PET, with the help in anatomic information by CT/MRI, showed better diagnostic ability (sensitivity 100.0%, specificity 88.2%, accuracy 93.3%) compared with combined conventional imaging (sensitivity 84.6%, specificity 85.7%, accuracy 85.0%) and tumor markers (sensitivity 100.0%, specificity 70.6%, accuracy 83.3%). FDG-PET had no false-negative results, suggesting the possibility of its use as the first-line examination in a patient's follow-up. FDG-PET could detect unknown lesions in 4 cases, and, as reported for other malignancies, FDG-PET affected the patient management in one-third of the cases. Furthermore, the results of FDG-PET correlated well with the clinical outcome of the patients, with patients with negative PET results tending to show disease-free courses. CONCLUSIONS: These results suggest that, despite the limited number of patients studied, FDG-PET was accurate in detecting recurrence and evaluating therapeutic response, and could afford important information in the management of post-operative patients with endometrial cancer. FDG-PET also appeared to have a possibility to predict the outcome of each patient.

Adult↗

PubMed2003

Optimal scan time for evaluating pancreatic disease with positron emission tomography using F-18-fluorodeoxyglucose.

OBJECTIVE: Image interpretation in positron emission tomography (PET) using F-18-fluoro-2-deoxy-D-glucose (FDG) is usually performed for images obtained at 1 h postinjection (PI) of FDG, but it remains unknown whether this is the optimal time for imaging patients with pancreatic disease. The aim of this study was to assess the optimal scan time for FDG-PET for patients suspected of having pancreatic cancer. PATIENTS AND METHODS: Forty-four patients with suspected pancreatic cancer underwent FDG-PET scans at both 1 h and 2 h PI. Tracer uptake in the pancreatic lesions and possible liver metastasis was interpreted qualitatively, using a 5-point grading system (0 = normal, 1 = probably normal, 2 = equivocal, 3 = probably abnormal, and 4 = definitely abnormal) by 4 nuclear medicine physicians independently, who were blind to all clinical information. Detection performance with each image was compared using receiver operating characteristic (ROC) analysis. An average score of the 4 readers for each patient was also defined as consensus average index (CAI) and compared between the two images. RESULTS: ROC results indicated no significant differences in detection performance (Averaged areas under ROC curves of 1 h vs. 2 h were 0.92 vs. 0.90 for primary tumor, and 0.81 vs. 0.85 for liver metastases). There were no significant differences in CAIs between 1 h and 2 h PI images in interpreting primary tumor and positive liver metastases, but a significant difference was observed for cases without liver metastases (p < 0.05). CONCLUSIONS: The certainty of excluding liver metastases was increased when the 2h image was used, although ROC analysis did not establish a difference between 1 h and 2 h imaging for differentiating malignant and benign lesions in primary pancreatic cancer or its liver metastases.

False Positive Reactions↗

PubMed2003

Tuberculous lymphadenitis as a cause of obstructive jaundice: report of a case.

We report a rare case of obstructive jaundice caused by enlarged tuberculous lymph nodes compressing the common bile duct in the retropancreatic region, mimicking pancreatic cancer. A 32-year-old man was admitted to our hospital with a 1-month of history of jaundice. An abdominal computed tomography (CT) scan showed a tumor in the pancreatic head, but an endoscopic retrograde cholangiopancreatogram (ERCP) showed a normal pancreatic duct system. Positron emission tomography with 2-[fluorine-18]-fluoro-2-deoxy- d-glucose (FDG-PET) revealed a hot spot only in the pancreatic head. Under a presumptive diagnosis of malignancy, a laparotomy was performed and an intraoperative biopsy specimen revealed epithelioid granuloma with caseous necrosis, which led us to suspect tuberculous lymphadenitis. This diagnosis was confirmed by culture, and antituberculous therapy was commenced postoperatively. The patient has not suffered any further episodes of obstructive jaundice. This case report demonstrates that positive FDG-PET results should be interpreted carefully when diagnosing tumors of the pancreatic head.

Adult↗

PubMed2003

Prevalence and patterns of bone metastases detected with positron emission tomography using F-18 FDG.

PURPOSE: The aim of this retrospective study was to report the prevalence and imaging characteristics of bone metastases detected with F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) and, when possible, compare these findings with the performance of bone scans in the same patients. METHODS: The reports of 403 patients with histologically proved malignant disease who underwent a PET scan for initial or post-therapeutic staging were reviewed for the presence of possible bone metastases. Based on the final diagnosis confirmed by histopathologic analysis or clinical follow-up, the PET findings of patients with positive bone metastases were evaluated in terms of location, intensity, and patterns. When the PET scan was positive, the PET results were compared with the findings of available bone scans. RESULTS: PET studies suggested the presence of bone metastases in 38 patients (9%). No follow-up data were available for 9 patients, and the remaining 29 were evaluated further. Of these patients, 6 had false-positive findings, whereas bone metastatic involvement was clinically confirmed in 23 patients. The primary malignant findings included lung cancer (n = 9), esophageal cancer (n = 3), lymphoma (n = 2), melanoma (n = 2), thyroid cancer (n = 2), breast cancer (n = 1), colon cancer (n = 1), prostate cancer (n = 1), testicular cancer (n = 1), and nasopharyngeal cancer (n = 1). On PET, 5 patients had a solitary metastatic focus (22%), and the remaining 18 patients had multiple lesions (78%). The vertebrae were the most frequently involved bones (74%), followed by pelvic bones (70%), ribs (65%), upper extremities including the scapula (48%), sternum (43%), and lower extremities (43%). The patterns of abnormal uptake were classified into three groups: focal (15 patients, 65%), diffuse (2 patients, 9%), and a mixed pattern (6 patients, 26%). Most of the lesions showed intense abnormal uptake (18 patients, 78%); 5 patients had both intense and moderate FDG uptake. Thirteen of the 23 patients with confirmed bone metastases also had a bone scan, which revealed positive bone disease in all of these patients. However, PET consistently revealed more metastatic foci than did the bone scan on a lesion basis. CONCLUSIONS: The most frequent pattern of detectable bone metastases with FDG-PET imaging was multiple foci of intense uptake. PET revealed more lesions than did bone scanning, independent of the type of cancer or location of bone involvement, in patients who were accurately diagnosed by FDG-PET imaging.

Adolescent↗

PubMed2003

Effects of nonionic intravenous contrast agents at PET/CT imaging: phantom and canine studies.

PURPOSE: To investigate the effects of intravenous contrast agents on quantitative values obtained with a combined positron emission tomographic (PET) and computed tomographic (CT) scanner by using several phantoms and a dog. MATERIALS AND METHODS: Fluorine 18 fluorodeoxyglucose (FDG) was mixed with different concentrations of contrast agent with the same syringe (phantom 1), and the phantom was scanned. After image reconstruction with various attenuation maps, radioactivity concentrations were compared. Then, FDG solutions with (phantom 2) or surrounded by (phantom 3) various concentrations of contrast agent were scanned repeatedly, and radioactivity concentration was compared. Finally, PET and CT with and without contrast agent were performed in a dog. PET images were reconstructed by using different attenuation maps, and radioactivity concentrations were compared. The radioactivity concentration on germanium 68 (68Ge)-based corrected images was regarded as standard, and percentage bias, defined as difference divided by measured activity of 68Ge-based corrected images, was assessed. The relationship between the concentration of contrast agent and the percentage bias was assessed with the Pearson coefficient r, and the significance of correlations was evaluated with the Fisher z test. RESULTS: All phantom studies demonstrated that presence of a contrast agent resulted in overestimation of emission data. CT numbers showed a strong positive correlation with the percentage bias in phantoms 2 (r = 0.999) and 3 (r = 0.987); the maximum percentage bias at 1,360 HU reached approximately 45%. These effects were independent of FDG concentration. In a canine model, presence of a contrast agent also increased emission activity, but the percentage bias was less than 15% in the liver and smaller in all other organs except the kidney (26%). CONCLUSION: High concentrations of a contrast agent caused considerable overestimation of apparent tracer activity in phantom studies; however, the emission bias was relatively modest in vivo, except in areas with very high contrast agent concentrations.

Animals↗

PubMed2003

Clinically significant inaccurate localization of lesions with PET/CT: frequency in 300 patients.

UNLABELLED: This study evaluated lesion mislocalization between PET and CT on PET/CT studies when CT instead of germanium is used for attenuation correction (AC). METHODS: PET/CT scans were obtained for 300 clinical patients. Both CT and germanium scans were used to correct PET emission data. Cases were noted of suspected inaccurate localization of lesions on any of the 5 sets of images (PET using germanium AC [GeAC] fused and not fused with CT, PET using CT AC fused and not fused with CT, and PET with no AC [NAC]). Independent CT or MRI was used to determine true lesion locations. RESULTS: Six of 300 patients (2%) had lesion mislocalization when CT was used for AC or fusion. True liver dome lesions were mislocalized to the right lung base on PET/CT, likely because of a respiratory motion difference between PET and CT. No mislocalization was present on NAC PET or non-CT-fused GeAC PET images. CONCLUSION: Serious lesion mislocalization on PET/CT studies may occur, albeit very infrequently, when CT is used for either AC or fusion.

Adult↗

PubMed2003

Initial experience with oral contrast in PET/CT: phantom and clinical studies.

UNLABELLED: The aims of the study were to evaluate the effects of oral contrast on apparent tracer activity measured with PET/CT when using CT attenuation correction and to report our initial experience in the use of oral contrast with PET/CT. METHODS: Phantom studies with (18)F activity and saline bags or syringes filled with barium or gastrografin of varying densities were performed using a PET/CT scanner (CT attenuation correction). In the study, 91 clinical patients received dilute oral contrast and were evaluated by whole-body (18)F-FDG PET. RESULTS: A phantom experiment with CT contrast (1.3% weight/volume [w/v] barium) showed a "cold" area in the cold stomach whereas a phantom with high-density barium (98% w/v) showed an artifactual focus of intense "activity" in the cold stomach. In clinical studies, stomach and right colon were opacified by CT contrast. Maximal measured contrast density was 239 Hounsfield units. CONCLUSION: High-density barium causes overestimation of tissue (18)F-FDG concentration. Low-density barium does not cause significant artifacts and appears suitable for clinical use.

Administration, Oral↗

PubMed2003

[Clinical application of FDG-PET for cancer diagnosis].

Positron emission tomography using 18F-FDG is accepted in clinical medicine as an imaging tool for the diagnosis and assessment of a large variety of cancers. Medicare reimbursement for these studies has been accepted in Japan since 2002. The number of requests for FDG-PET examinations has been increasing in institutions where a PET device is installed. PET is considered to be especially effective in re-staging and detecting recurrence of disease. In order to evaluate PET images properly, it is important to be familiar with the various physiological uptake patterns of FDG, and also to be alert to the possibility of false-positive and false-negative findings. Quantitative values obtained in PET images are widely used for the differentiation of benign and malignant tumors and for monitoring treatment; however, it should be kept in mind that these values may be influenced by many factors. To complement the poorer spatial resolution of PET, a combined PET/CT scanner has been created and its clinical application has begun. It is expected that this imaging tool will be useful and have a great effect on patient management.

Breast Neoplasms↗

PubMed2002

Impact of body habitus on quantitative and qualitative image quality in whole-body FDG-PET.

Obtaining consistent high image quality is desirable for clinical positron emission tomography (PET). Body morphology may impact image quality. The purpose of this study was to define the average and the range of body sizes in patients undergoing tumor PET studies in our center and to determine how the body habitus affects the statistical and visual quality of PET images. Height, weight, body surface area (BSA), and body mass index (BMI) were determined in 101 male and 101 female patients (group 1) referred for clinical PET. The summed total counts from three consecutive transaxial slices on non-attenuation-corrected (NAC) 2D fluorine-18 fluorodeoxyglucose (FDG) PET images, which included the largest liver section and no lesions, were determined and compared with body morphology and injected doses (ID) in a representative group of 30 male and 30 female patients (group 2) spanning a range of body morphologies. The visual quality of images was also evaluated using a scoring system by three readers. The average height, weight, and BSA were greater in male than in female patients, but the average BMI was not different between them in group 1. The largest value of weight or BMI was more than four times the smallest value in female patients. The total true counts were best correlated with ID/weight (mCi/kg) in group 2 ( r=0.929, P<0.0001). Intermediate to high total counts (930,000 or more) corresponded to ID/weight of 0.22 or higher. The average visual score was positively correlated with the total counts (rho=0.63, P<0.0001) and with ID/weight (rho=0.68, P<0.0001) on NAC images. The image quality in 22 (84.6%) of 26 patients with intermediate to high total counts was adequate to good, whereas that in 21 (61.8%) of 34 patients with lower total counts was suboptimal. A wide variety of body morphologies was observed in patients referred for clinical FDG-PET tumor studies in our center. The total counts and average image visual score were negatively correlated with weight. Counts in heavy patients were as low as one-fourth those in light patients. Adjusting injected FDG dose in each patient on the basis of body weight may be more appropriate to achieve consistent PET image quality than giving a fixed injected FDG dose.

Body Mass Index↗

PubMed2002

Prognostic value of positron emission tomography using F-18-fluorodeoxyglucose in patients with cervical cancer undergoing radiotherapy.

OBJECTIVE: The purpose of this study was to determine whether positron emission tomography (PET) using F-18-fluorodeoxyglucose (FDG) before and after radiotherapy would predict whether local control of cervical cancer had been achieved. METHODS: FDG-PET scans were performed prior to therapy and at a mean of 4.6 months after radiation in 20 patients (pts) with histologically proven uterine cervical cancer who were undergoing a "curative" course of radiation therapy. FDG uptake was interpreted visually by two readers using a 5-point grading system (0 = normal, 1 = probably normal, 2 = equivocal, 3 = probably abnormal, and 4 = definitely abnormal). The standardized uptake values corrected by lean body mass (SUL) were calculated for suspicious areas. The percentage of residual activity (%RA) for the posttherapy SUL was also evaluated as a percentage of the pretherapy SUL. RESULTS: At baseline before irradiation, 17 of 20 (85.0%) primary tumors were detected. Following irradiation, no or low (grade 0-2) uptake was observed in 9 pts, and none of these had local recurrence. Among the remaining 11 pts with grade 3 or 4 uptake, the correct diagnosis was made for 5 pts with active tumor; SULs (mean +/- SD = 4.17 +/- 2.52) and %RAs (57.9 +/- 16.8). Six patients without active tumor showed relatively low SULs (2.67 +/- 0.69) and %RAs (43.0 +/- 18.3). No significant differences were observed between the recurrent and nonrecurrent groups for these parameters. Overall, sensitivity, specificity, and accuracy were 100, 60, and 70%, respectively. CONCLUSION: These preliminary data indicate that FDG-PET is a sensitive tool for detecting active cervical cancer after radiation, however, the method, without anatomic correlation had suboptimal specificity.

Adult↗

PubMed2002

Reproducibility of common semi-quantitative parameters for evaluating lung cancer glucose metabolism with positron emission tomography using 2-deoxy-2-[18F]fluoro-D-glucose.

PURPOSE: Positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose (FDG) has been used for various cancers, but reproducibility of common utilized semi-quantitative parameters, such as the maximal single pixel standardized uptake value (SUV) and effective glycolytic volume (EGV), remains unknown. Knowledge of precision is essential for applying these parameters to treatment monitoring. The purpose of this investigation was to assess the precision of PET results obtained by repeated examinations of patients with untreated lung cancer. PATIENTS AND METHODS: Ten patients with lung cancer underwent two PET examinations within a week with no intervening treatment. The reproducibility of three parameters:((1) maximal SUV of 1 x 1 pixel anywhere in the tumor, calculated on the basis of predicted lean body mass [SULmax]; (2) highest average SUV at 4 x 4 pixels in the tumor adjusted by predicted lean body mass [SULmean]; and (3) EGV calculated by multiplying SUL by tumor volume), using PET images obtained at 50-60 min post-injection, were examined. Plasma glucose, insulin and free fatty acid levels were also monitored. RESULTS: The SULmax, SULmean, and EGV were measured with a mean +/- S.D. difference of 11.3% +/- 8.0, 10.1% +/- 8.2, and 10.1% +/- 8.0%, respectively. By multiplying SUL by plasma glucose concentration, the mean differences were slightly reduced to 7.2% +/- 5.8, 6.7% +/- 6.2, and 9.5% +/- 8.2, respectively. CONCLUSION: These data indicate that commonly used semi-quantitative indices of glucose metabolism on PET show high reproducibly. This supports their use in sequential quantitative analysis in PET, such as in treatment response monitoring.

Journal Article↗

PubMed2002

Comparison of attenuation-corrected and non-corrected FDG-PET images for axillary nodal staging in newly diagnosed breast cancer.

PURPOSE: The aim of this work is to compare the accuracy of non-attenuation-corrected (NAC) and attenuation-corrected (AC) PET images using 2-deoxy-2-[18F]fluoro-D-glucose (FDG) in assessment of the axilla in patients with newly-diagnosed, untreated, primary breast cancers, and to determine the frequency of extra-axillary findings. PATIENTS AND METHODS: FDG-PET was performed in 36 patients with breast cancer one hour following the intravenous injection of approximately 370 MBq of FDG. Patients were imaged prior to axillary dissection to prospectively confirm the presence or absence of axillary metastases. NAC and AC images were separately and independently reviewed in a blinded fashion by two readers. Imaging results were compared with final diagnoses obtained by surgery and pathology. RESULTS: Ninety-six positive axillary lymph nodes in 15 patients were histopathologically confirmed by surgery. The average areas under the ROC curve for NAC and AC image were 0.682 and 0.721, respectively. In patient-based analysis, the sensitivity in interpreting NAC images for the presence of metastases was low (53.3%) and comparable to that of AC images (46.7%). The specificity of NAC image was high (85.7%), but tended to be lower than that in AC (95.2%). The overall diagnostic accuracy for detecting axillary involvement in AC images (75.0%) was comparable to that of NAC images (72.2%). Extra-axillary disease was found in three patients. CONCLUSION: NAC images were comparable to AC images, although there were more false positive results with the NAC images. While AC PET has high specificity in this application, it appears insufficiently sensitive to use these methods to avoid axillary tissue sampling, when negative. Extra-axillary findings, while infrequent, may be quite important. Examination of both NAC and AC images is advised when assessing possible metastatic breast cancer to the axilla using PET.

Journal Article↗

PubMed2002

Quantitative evaluation of 2-deoxy-2-[18F] fluoro-D-glucose uptake in hepatic metastases with combined PET-CT: iterative reconstruction with CT attenuation correction versus filtered back projection with 68Germanium attenuation correction.

PURPOSE: Iterative reconstruction (IR) is a statistical reconstruction method that may be influenced by high background activity such as in the liver. Recently developed combined positron emission tomography (PET) and computerized tomography (CT) instrumentation utilizes CT attenuation correction that may also differ compared to 68Germanium (68Ge) segmented attenuation correction (IR SAC). Quantitative differences could affect the clinical interpretation of metastatic foci and subsequent response to therapy. The purpose of this study is to characterize potential quantitative differences specifically in hepatic metastases. PROCEDURES: Thirty-three metastatic liver lesions in 23 patients were evaluated. Whole-body 2-deoxy-2[18F]fluoro-D-glucose(FDG) PET images were obtained on a dedicated PET-CT device and reconstructed with IR and CT measured attenuation correction (IR CT MAC), IR and 68Ge segmented attenuation correction, and also with filtered back-projection and segmented attenuation correction (FBP SAC). Regions of interest over the liver lesions (L) and liver background (B) were drawn on FBP SAC images and superimposed on the co-registered IR CT MAC and IR SAC images for comparison. To identify the individual effects of IR and CT attenuation correction, IR SAC was first compared to FBP SAC, followed by a comparison of IR CT MAC and IR SAC. Differences were expressed as bias (%) and compared to FBP SAC. RESULTS: Compared to FBP SAC, IR SAC showed significantly lower liver lesion (mean bias -7.1%; P < 0.00001), significantly higher liver background (mean bias -3.5%; P = 0.005), and significantly lower L/B ratio (mean bias -10.1%; P < 0.00001). Compared to IR SAC, the IR CT MAC showed small but not statistically significant increases in liver lesion (mean bias 3.0%; P = 0.1) and liver background (mean bias 4.3%; P = 0.09), and no significant difference in L/B ratio (mean bias -1.3%; P = 0.5). The overall effect of IR CT MAC compared to FBP SAC was a significant decrease in liver lesion (mean bias -4.2%; P = 0.002), significant increase in liver background (mean bias 8.7%; P = 0.002), and significantly lower L/B (mean bias -11.1%; P < 0.00001) compared to FBP SAC. CONCLUSION: Compared to FBP, IR resulted in significantly lower mean hepatic tumor activity, higher mean liver background activity, and lower L/B activity, but these differences were modest. These differences were similarly seen in the CT corrected IR CT MAC when compared to FBP SAC. CT attenuation correction did not result in significant differences when compared to 68Ge correction. Although the differences in IR CT MAC were modest, consistent reconstruction methods are important to decrease the measurement variability and improve reproducibility.

Journal Article↗

PubMed2002

Relationship between retention index in dual-phase (18)F-FDG PET, and hexokinase-II and glucose transporter-1 expression in pancreatic cancer.

UNLABELLED: Recently, some studies have shown that delayed scanning with (18)F-FDG PET may help to differentiate malignant from benign pancreatic lesions. However, no study has evaluated the relationship between temporal changes in (18)F-FDG uptake and expression of hexokinase or glucose transporter. METHODS: Twenty-one consecutive patients with pancreatic cancer were studied preoperatively by dual-phase (18)F-FDG PET, performed 1 and 2 h after injection of (18)F-FDG. The standardized uptake value (SUV) of the pancreatic cancer was determined, and the retention index (RI) (%) was calculated by subtracting the SUV at 1 h (SUV1) from the SUV at 2 h (SUV2) and dividing by SUV1. The percentages of cells strongly expressing hexokinase type-II (HK-II) and glucose transporter-1 (GLUT-1) were scored on a 5-point scale (1 = 0%-20%, 2 = 20%-40%, 3 = 40%-60%, 4 = 60%-80%, 5 = 80%-100%) by visual analysis of immunohistochemical staining of paraffin sections from the tumor specimens using anti-HK-II and anti-GLUT-1 antibody (HK-index and G-index, respectively). RESULTS: SUV2 (mean +/- SD, 5.7 +/- 2.6) was higher than SUV1 (5.1 +/- 2.1), with an RI of 8.5 +/- 11.0. Four cases of cancer, in which SUV2 showed a decline from SUV1, showed a low HK-index (1.8 +/- 1.1), whereas 4 cases with an RI of > or =20 and 13 cases with an intermediate RI (0-20) showed significantly higher HK-indices (4.3 +/- 0.7 and 3.1 +/- 1.5, respectively; P < 0.05). RI showed a positive correlation with HK-index, with an R(2) of 0.27 (P < 0.05), but no significant correlation with the G-index. SUV1 showed no relationship with the HK-index but showed a weak positive correlation with the G-index, with an R(2) of 0.05 (P = 0.055). CONCLUSION: These preliminary findings suggest that the RI obtained from dual-phase (18)F-FDG PET can predict HK-II expression and that the SUV (at 1 h) has a positive correlation with GLUT-1 expression but not with HK-II expression.

Adenocarcinoma↗

PubMed2002

Increased (18)F-FDG uptake in a model of inflammation: concanavalin A-mediated lymphocyte activation.

UNLABELLED: The aim of this project was to study a mechanism that might explain the increased uptake of (18)F-labeled FDG seen in inflammation. The approach chosen was to examine the effect on (18)F-FDG uptake of acute activation of murine lymphocytes by concanavalin A (Con A). METHODS: Immunocompetent BALB/c mice and nude mice received an intravenous injection of 10 mg/kg Con A. Twenty-four hours later, the mice received an intravenous injection of 0.74 MBq (20 microCi) (18)F-FDG. One hour later, biodistribution was determined. The distribution of the radiolabel in the liver was also evaluated by autoradiography. In vitro (18)F-FDG uptake to splenocytes from BALB/c mice with and without Con A pretreatment were determined 30, 60, and 120 min after the splenocytes were mixed with (18)F-FDG (0.74 MBq [20 microCi]/200 microL). RESULTS: In immunocompetent BALB/c mice, pretreatment with Con A significantly increased (18)F-FDG uptake in the spleen and liver. Autoradiographs of the liver showed that pretreatment with Con A produced a specific localization of (18)F-FDG at periportal areas, where numerous sites of cellular infiltration were observed. In vitro binding of (18)F-FDG to the splenocytes was significantly higher for Con A-pretreated BALB/c mice than for control mice. CONCLUSION: This study showed that Con A increased (18)F-FDG uptake. Con A-activated lymphocytes actively took up (18)F-FDG both in vitro and in vivo, and (18)F-FDG specifically accumulated in Con A-mediated acute inflammatory tissues.

Animals↗

PubMed2002

PET/CT: comparison of quantitative tracer uptake between germanium and CT transmission attenuation-corrected images.

UNLABELLED: In PET, transmission scanning for attenuation correction has most commonly been performed with an external positron-emitting radionuclide source, such as (68)Ge. More recently, combined PET/CT scanners have been developed in which the CT data can be used for both anatometabolic image formation and attenuation correction of the PET data. The purpose of this study was to assess the quantitative differences between CT-based and germanium-based attenuation-corrected PET images. METHODS: Twenty-eight patients with known or suspected cancer underwent whole-body (18)F-FDG PET/CT scanning for clinical diagnostic purposes. For each patient, attenuation maps were obtained from both the CT scan and the (68)Ge transmission data, and 2 different attenuation-corrected emission datasets were produced. Measured activity concentrations (both mean and maximum) from identical regions of interest in representative normal organs and in 36 pathologic foci of uptake were compared. RESULTS: CT-corrected emission images generally showed slightly higher radioactive concentration values than did germanium-corrected images (P < 0.01) for all lesions and all normal organs except the lung. Mean and maximum radioactivity concentrations were 4.3%-15.2% higher for CT-corrected images than for germanium-corrected images. Calculated radioactivity concentrations were significantly greater in osseous lesions than in nonosseous lesions (11.0% vs. 2.3%, P < 0.05, for mean value; 11.1% vs. 2.1%, P < 0.01, for maximum value). A weak positive correlation was observed between the CT Hounsfield units within the regions of interest and the percentage difference in apparent tracer activity in the CT-corrected images. CONCLUSION: Although quantitative radioactivity values are generally comparable between CT- and germanium-corrected emission PET images, CT-based attenuation correction produced radioactivity concentration values significantly higher than the germanium-based corrected values. These effects, especially in radiodense tissues, should be noted when using and comparing quantitative PET analyses from PET and PET/CT systems.

Algorithms↗

PubMedDate not supplied

Synthesis and biodistribution of [11C]adenosine 5'-monophosphate ([11C]AMP).

PURPOSE: Imaging purine receptors and adenylate biodistribution in vivo may be of clinical importance not only for the investigation of normal adenylate metabolism but also in pathological conditions where adenylate uptake and/or release from certain tissues and organs may be altered, such as some types of cancer. In order to develop a tracer for positron emission tomography (PET) that would not be subject to loss of its radioisotope, adenosine 5'-monophosphate (AMP) was intrinsically labeled at the C-8 position with carbon-11. PROCEDURES: [11C]AMP was synthesized by reacting 5-amino-1-beta-D-ribofuranosylimidazole-4-carboxamidine-5'-phosphate with [11C]formaldehyde. The metabolism of [11C]AMP in human blood was determined in vitro both in the presence and absence of dipyridamole. The ex vivo biodistribution of [11C]AMP and its in vivo dosimetry were determined in normal mice. The effect of dipyridamole on the distribution of [11C]AMP in mice was also determined. RESULTS: [11C]AMP was reliably synthesized in 34 minutes (n = 7) with an average radiochemical yield of 2.4% and an average specific activity of 90.10 GBq/micromol (2435 mCi/micromol) at end of synthesis. In normal mice, the highest uptake of [11C]AMP was in the lungs, blood, and heart. The ex vivo mouse experiments showed that the uptake of 11C radiotracer in the lungs at 60 minutes postinjection was significantly lower for dipyridamole-treated animals than controls. Dosimetry showed that the critical organs for radiation dose burden are kidneys and bladder. CONCLUSIONS: Treatment with dipyridamole blocked the red blood cell uptake of extracellular adenosine and therefore its subsequent intracellular conversion to ATP. The biodistribution studies indicate that the tracer has substantial accumulation in the kidneys, lungs, heart, and blood. [11C]AMP is promising as a PET-imaging agent to trace adenylate biology in vivo.

Adenosine Monophosphate↗