Detection of liver metastases from pancreatic cancer using FDG PET.

We evaluated the potential of the glucose analog [18F]fluorodeoxyglucose (FDG) as a PET tracer for the hepatic staging in 168 patients designated for resective pancreatic surgery. METHODS: Metastatic liver disease was confirmed or excluded during surgery or with CT follow-up for at least 6 mo. Proven metastases were then retrospectively identified on preoperative CT (gold standard). Hepatic PET scans of all patients were interpreted blindly. Any focal FDG uptake was considered malignant. Both proven hepatic metastases and suspicious hepatic PET lesions were then compared, lesion by lesion, with CT. Standardized uptake values (SUV) and tumor-to-liver ratios (T/L) were determined for the most intense lesion of each patient. RESULTS: Sensitivity of FDG PET was 68% (15 of 22 patients). The lesion detection rate was 97% (28 of 29 metastases) for lesions >1 cm and 43% (16 of 37 metastases) for lesions < or = 1 cm. Specificity was 95% (138 of 146 patients). Six of eight patients with false-positive results had marked intrahepatic cholestasis (versus 3 of 15 patients with true-positive lesions), one had an infrahepatic abscess and one had a right basal pulmonary metastasis. The SUV and T/L were 4.6+/-1.4 and 2.3+/-1.1, respectively, for malignant lesions and 4.1+/-1.5 and 1.9+/-0.3, respectively, for false-positive lesions and therefore are of limited value. CONCLUSION: FDG PET provides reliable hepatic staging for lesions >1 cm. False-positive results are associated with the presence of marked intrahepatic cholestasis. For lesions < or = 1 cm, FDG PET can define malignancy in 43% of suspicious CT lesions in the absence of dilated bile ducts.     

Diagnostic usefulness of FDG PET for pancreatic mass lesions

The purpose of this study was to investigate the feasibility of [18F]2-deoxy-2-fluoro-D-glucose (FDG) positron emission tomography (PET) in patients with a pancreatic mass by comparing the results with those of X-ray computed tomography (CT) and magnetic resonance (MR) imaging. METHODS: Eighty-six patients with pancreatic lesions, included 65 malignant tumors and 21 benign masses (55 masses were proven histologically and the others were diagnosed clinically), were studied. The diagnostic factors of CT and MR imaging were evaluated, and those of FDG PET were also evaluated for malignant and benign masses by visual interpretation and quantitative interpretation with the standardized uptake value (SUV) and SUVgluc which was designed to reduce the effects of a high blood sugar level. Visual interpretations were evaluated only in FDG PET images, and quantitative interpretations were evaluated by referring to CT and/or MR imaging. The correlation between SUV and the degree of histological differentiation in pancreatic ductal adenocarcinoma was investigated. RESULTS: Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy for CT imaging were 91, 62, 88, 68 and 84%, and for MR imaging 78, 70, 88, 54 and 76%, respectively. In visual interpretation of FDG PET images, the sensitivity, specificity, PPV, NPV and accuracy were 82, 81, 93, 59 and 81%, respectively. Significant differences between malignant and benign lesions existed in SUV and SUVgluc (p < 0.0001, each). With the cutoff value of SUV as 2.1 and SUVgluc as 2.2, the accuracy of diagnosis was maximal. With that cutoff value, the sensitivity, specificity, PPV, NPV and accuracy for SUV were 89, 76, 92, 70 and 86%, and for SUVgluc 91, 76, 92, 73 and 87%, respectively. The sensitivity and NPV of SUVgluc were higher than those of SUV, which suggests that SUVgluc may be more useful in reducing the number of overlooked malignant tumors. The specificity and PPV of FDG PET were superior to those of CT and MR imaging. There were no significant differences between the SUVs of moderately differentiated adenocarcinomas and those of well differentiated adenocarcinomas. CONCLUSION: To improve the diagnostic procedure for classifying masses, FDG PET with not only SUV but also SUV corrected by the blood sugar level is required in addition to morphological diagnosis by CT and/or MR imaging.     

Evaluation of recurrent squamous cell carcinoma of the head and neck with FDG positron emission tomography

PURPOSE: This study compared the effectiveness of fluorodeoxyglucose (FDG) positron emission tomography (PET) with computed tomography (CT), magnetic resonance imaging (MRI), or both for the assessment of recurrent squamous cell carcinoma of the head and neck. The value of quantifying the standardized uptake values (SUV) to distinguish recurrent neoplasm from inflammatory lesions and normal structures was also evaluated. METHODS: Forty-three patients with head and neck cancer were examined with F-18 FDG PET at least 4 months after their last course of radiation therapy (mean, 11 months). The SUVs were measured in visually identified regions of abnormally increased activity and were compared with the values in normal mucosa, the base of the tongue, and the hard palate to determine if an optimal cutoff value exists for diagnosing recurrence of malignant lesions. The final diagnosis of recurrence was made based on biopsy or at least 6 months' clinical follow-up. RESULTS: FDG PET correctly detected recurrence in 20 of 22 patients who had 45 discrete lesions located in the field of the upper aerodigestive tract. Two false-negative and three false-positive results were identified. The accuracy of FDG PET was 88% (38 of 43 patients), compared with 66% (25 of 38 patients) for CT, MRI, or both. Although there was a significant difference of SUVs (P = 0.0036) between the recurrent lesions and normal structures, the optimal cutoff values were difficult to define. CONCLUSIONS: Visual analysis of FDG PET is significantly more accurate in the diagnosis of recurrent squamous cell cancer of the head and neck than are CT or MRI. However, single SUV quantification does not significantly enhance efficacy.     

Incidental colonic focal lesions detected by FDG PET/CT

OBJECTIVE: The aim of this study was to assess the performance of FDG PET/CT for the detection of colonic lesions, especially advanced neoplasms (villous or >10-mm adenomas, carcinomas). Because of 18F FDG accumulation in adenomatous polyps, PET using FDG can detect early premalignant colorectal lesions. MATERIALS AND METHODS: FDG PET/CT studies performed for a 1-year period in 1,716 consecutive patients with various malignant diseases, except colorectal cancer, were retrospectively reviewed. PET images obtained 1 hr after FDG injection and non-contrast CT images used for attenuation correction were fused for analysis. Of 45 patients showing intense focal colonic FDG uptake, 20 patients (with 21 foci) underwent a colonoscopic investigation, and, when necessary, polyp resection. The intensity of FDG uptake was quantified using the standardized uptake value (SUV(max)). RESULTS: The FDG colonic foci were associated with 18 colonoscopic abnormalities in 15 patients, with no colonic abnormality detected in five patients (false-positive [FP] results). Histopathologic findings revealed advanced neoplasms in 13 patients (13 villous adenomas and three carcinomas) and two cases of hyperplastic polyps. A difference in the mean SUV(max) was found between FP and true-positive colonic FDG foci but was not statistically significant (p = 0.14). CONCLUSION: Presence of a focal colonic FDG uptake incidental finding on a PET/CT scan justifies a colonoscopy to detect (pre-)malignant lesions. The fusion of PET and CT images allows an accurate localization of the lesions. PET/CT is a useful tool to differentiate pathologic from physiologic FDG uptake.     

Ki-67 immunostaining in pancreatic cancer and chronic active pancreatitis: does in vivo FDG uptake correlate with proliferative activity?

PET with 18F-FDG has been shown to be useful in the detection and staging of pancreatic cancer. However, whether FDG uptake is dependent on proliferative activity is still unclear. The aim of this prospective study was to evaluate a probable correlation between FDG uptake and proliferative activity in benign and malignant pancreatic tumors. METHODS: Our series consisted of 23 patients with pancreatic cancer and 9 patients with chronic active pancreatitis (CAP). FDG PET was performed within 2 wk before surgery, and standardized uptake values (SUVs) were calculated for benign and malignant pancreatic tumors. Patients were selected when focally increased FDG uptake in previously known pancreatic tumors was present. Proliferation fraction was measured in tissue specimens using the anti-Ki-67 antibody MIB-1. A computer-assisted imaging system was used for quantification of nuclear Ki-67 immunostaining. Immunohistochemical findings were correlated to SUVS: RESULTS: Pancreatic cancer showed both intense nuclear staining of Ki-67 (39% +/- 16%) and high FDG uptake (SUV = 3.6 +/- 1.6). However, no significant correlation was found between in vivo FDG uptake and Ki-67 immunoreactivity (P = 0.65). By contrast, Ki-67 nuclear staining was significantly lower (3.8% +/- 2.7%, P < 0.05) in CAP, whereas FDG uptake was in the same range as for pancreatic cancer (SUV = 3.5 +/- 1.8). CONCLUSION: FDG uptake did not correlate with proliferative activity in pancreatic cancer. Proliferative activity was tenfold higher in malignant pancreatic tumors than in benign tumors associated with CAP, whereas FDG uptake in vivo did not differ significantly. Thus, a PET tracer indicating cellular proliferation should better differentiate between cancer and inflammatory lesions than do metabolic markers such as FDG.     

Impact of FDG PET on patients with differentiated thyroid cancer who present with elevated thyroglobulin and negative 131I scan.

FDG PET is increasingly performed in patients with differentiated thyroid cancer who present with elevated human thyroglobulin (hTG) levels and negative 131I scan. The aim of this study was to evaluate the impact of FDG PET on treatment in these patients. METHODS: A total of 118 FDG PET studies were performed on 64 patients, and follow-up data were available for all patients. Whole-body images were acquired 1 h after intravenous injection of 370 MBq (10 mCi) FDG using a PET scanner with an axial field of view of 16.2 cm. Tumor-suspicious FDG PET studies were evaluated by histology, cytology, 131I uptake, CT or MRI, and follow-up of hTg levels. The therapeutic consequence was noted for each patient. Moreover, results of FDG PET were correlated with hTg levels. RESULTS: Forty-four patients had positive scans, which were proven to be true-positive in 34 patients, whereas 7 patients had false-positive findings. Two patients exhibited a secondary malignancy. One patient did not fit in any category, having true-positive, false-positive, and false-negative findings. On the other hand, 20 patients had negative scans. These were true-negative findings in 5 patients, whereas the remaining 15 patients had false-negative results. Accordingly, the positive predictive value of FDG PET was 83% (34/41), whereas the negative predictive value was 25% (5/20). Treatment was directly changed in 19 of 34 patients with true-positive PET studies: 18 patients had further surgery, and 4 patients were referred for external irradiation, 3 of them after incomplete removal of local recurrences. FDG PET showed widespread disease in 7 patients; thus, palliative treatment, rather than curative therapy, was initiated. True-positive FDG PET findings were correlated positively with increasing hTg levels (i.e., FDG PET was true-positive in 11%, 50%, and 93% of patients with hTg levels of <10, 10-20, and >100 microg/L, respectively). CONCLUSION: FDG PET is a valuable diagnostic tool in patients with differentiated thyroid cancer who present with increased hTg levels and negative 131I scans because it permits selection of patients for surgery, which may be curative. FDG PET is most promising at hTg levels of >10 microg/L.     

18F-FDG PET/CT in the evaluation of adrenal masses.

Our purpose was to evaluate the performance of (18)F-FDG PET/CT, using data from both the PET and the unenhanced CT portions of the study, in characterizing adrenal masses in oncology patients. METHODS: One hundred seventy-five adrenal masses in 150 patients referred for (18)F-FDG PET/CT were assessed. Final diagnosis was based on histology (n = 6), imaging follow-up (n = 118) of 6-29 mo (mean, 14 mo), or morphologic imaging criteria (n = 51). Each adrenal mass was characterized by its size; its attenuation on CT, expressed by Hounsfield units (HU); and the intensity of (18)F-FDG uptake, expressed as standardized uptake value (SUV). Receiver operating characteristic curves were drawn to determine the optimal cutoff values of HU and SUV that would best discriminate between benign and malignant masses. RESULTS: When malignant lesions were compared with adenomas, PET data alone using an SUV cutoff of 3.1 yielded a sensitivity, specificity, positive predictive value, and negative predictive value of 98.5%, 92%, 89.3%, 98.9%, respectively. For combined PET/CT data, the sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 98%, 97%, 100%, respectively. Specificity was significantly higher for PET/CT (P < 0.01). Fifty-one of the 175 masses were 1.5 cm or less in diameter. When a cutoff SUV of 3.1 was used for this group, (18)F-FDG PET/CT correctly classified all lesions. CONCLUSION: (18)F-FDG PET/CT improves the performance of (18)F-FDG PET alone in discriminating benign from malignant adrenal lesions in oncology patients.     

<Superscript>18</Superscript>FDG PET scanning of benign and malignant musculoskeletal lesions

OBJECTIVE: To describe the technique, applications and advantages of (18)FDG PET scanning in detection, analysis and management of musculoskeletal lesions. DESIGN AND PATIENTS: Forty-five patients (19 males,26 females) aged 9 to 81 years had radiographs, routine radionuclide scans, CT and/or MRI of clinically suspected active benign or malignant musculoskeletal lesions. (18)FDG scans with a Siemens ECAT EXACT 921 dedicated PET unit (Knoxville, Tenn.) and FWH=6 mm images acquired as a 5-6 bed examination (6 min emission and 4 min transmission) used OSEM iterative reconstruction with segmented transmission attenuation correction and a Gaussian filter (cutoff 6.7 mm). Region of interest (ROI) 3x3 pixel image analysis based on transverse whole body images (slice thickness 3.37 mm) generated Maximum Standard Uptake Values (Max SUV) with a cutoff of 2.0 used to distinguish benign and malignant lesions. RESULTS: Thirty-nine studies were available for SUV ROI analysis. Overall sensitivity for differentiating malignant from benign osseous and non-osseous lesions was 91.7% (22/24), overall specificity was 100% (11/11) with an accuracy of 91.7%. All aggressive lesions had a Max SUV >2.0. Data separating benign from malignant lesions and aggressive from benign lesions were statistically significant ( P<0.001) in both categories. There was no statistically significant difference in distinguishing aggressive from malignant lesions ( P, ns). CONCLUSION: (18)FDG PET contributes unique information regarding metabolism of musculoskeletal lesions. By supplying a physiologic basis for more informed treatment and management, it influences prognosis and survival. Moreover, since residual, recurrent or metastatic tumors can be simultaneously documented on a single whole body scan, PET may theoretically prove to be cost-effective.     

2. Diagnostic Utility of FDG-PET in the Clinical Management of Patients with Suspected Recurrent Pancreatic Carcinoma after Whipple Procedure

Purpose: We evaluated the usefulness of FDG-PET in the assessment of patients with suspected pancreatic carcinoma who have previously undergone a Whipple procedure.Methods and Materials: Attenuation-corrected FDG-PET was performed in 11 patients (5 males, 6 females, age range 52-76 years), with suspected recurrent pancreatic carcinoma after Whipple procedure. Recurrence was suspected based on clinical, laboratory (CA19-9 serum tumor marker level), or abdominal CT findings. Diagnostic validation was by histology in 2 patients and radiologic or clinical follow-up (5 to 48 months) in 9 patients. Changes in therapeutic management that were prompted by PET were tabulated.Results: PET was concordant with the findings of abdominal CT in 7 patients (6 true-positive, 1 true-negative). PET detected unsuspected lung lesions in 1 of these patients that was subsequently confirmed by a chest CT. PET was discordant with abdominal CT in 4 patients. PET detected tumor recurrence in 3 of 4 patients in this group (27% of total) who had non-diagnostic CT and elevated CA19-9 serology. Chemotherapy was initiated in 2 of these 3 patients (18% of total), while the other patient died shortly after the PET study from pneumonia and recurrent tumor was confirmed at autopsy. The remaining 1 of 4 patients in the discordant group had a false-positive PET study due to relatively high FDG localization in a displaced loop of bowel.Conclusion: PET is useful in localizing the tumor in post-Whipple patients with suspected recurrent pancreatic carcinoma and can impact their clinical management.     

Fluorodeoxyglucose positron emission tomography in pancreatic cancer: an unsolved problem

The aim of this study was to examine the significance and problems of 2-[fluorine-18]-2-deoxy-d-glucose (FDG) positron emission tomography (PET) in diagnosing pancreatic cancer and mass-forming pancreatitis (MFP). PET, X-ray computed tomography (CT) and magnetic resonance (MR) imaging were performed in 15 patients with pancreatic cancer and nine patients with MFP. The areas of the PET scan were determined according to the markers drawn on the patients at CT or MR imaging. Regions of interests (ROIs) were placed by reference to the CT or MR images corresponding to the PET images. Tissue metabolism was evaluated by the differential absorption ratio (DAR) at 50 min after intravenous injection of FDG [DAR = tissue tracer concentration/(injected dose/body weight). The DAR value differed significantly . in pancreatic cancer (mean±SD, 4.64±1.94) and MFP (mean±SD, 2.84±2.22) (P<0.05). In one false-negative case (mucinous adenocarcinoma), the tumour contained a small number of malignant cells. In one false-positive case, lymphocytes accumulated densely in the mass in the pancreatic head. Further studies are necessary to investigate the histopathological characteristics (especially the cellularity) and other factors affecting the FDG DAR on PET images.     

Use of a corrected standardized uptake value based on the lesion size on CT permits accurate characterization of lung nodules on FDG-PET

The purpose of this study was to determine the actual standardized uptake value (SUV) by using the lesion size from computer tomography (CT) scan to correct for resolution and partial volume effects in positron emission tomography (PET) imaging. This retrospective study included 47 patients with lung lesions seen on CT scan whose diagnoses were confirmed by biopsy or by follow up CT scan when the PET result was considered negative for malignancy. Each lesion's FDG uptake was quantified by the SUV using two methods: by measuring the maximum voxel SUV (maxSUV) and by using the lesion's size on CT to calculate the actual SUV (corSUV). Among small lesions (2.0 cm or smaller on CT scan), ten were benign and 17 were malignant. The average maxSUV was 1.43+/-0.77 and 3.02+/-1.74 for benign and malignant lesions respectively. When using an SUV of 2.0 as the cutoff to differentiate benignity and malignancy, the sensitivity, specificity, and accuracy were 65%, 70%, and 67% respectively. When an SUV of 2.5 was used for cutoff, the sensitivity, specificity, and accuracy were 47%, 80%, and 59% respectively. The average corSUV was 1.65+/-1.09 and 5.28+/-2.71 for benign and malignant lesions respectively. Whether an SUV of either 2.0 or 2.5 was used for cutoff, the sensitivity, specificity, and accuracy remained 94%, 70%, and 85% respectively. The only malignant lesion that was falsely considered benign with both methods was a bronchioalveolar carcinoma which did not reveal any elevated uptake of fluorine-18 fluorodeoxyglucose (FDG). Of the large lesions (more than 2.0 cm and less than 6.0 cm), one was benign and 19 were malignant and the corSUV technique did not significantly change the accuracy. It is concluded that measuring the SUV by using the CT size to correct for resolution and partial volume effects offers potential value in differentiating malignant from benign lesions in this population. This approach appears to improve the accuracy of FDG-PET for optimal characterization of small lung nodules.     

18F-FDGPET／CT联合腹部增强CT对诊断胰腺癌及评估肿瘤可切除性的临床应用

目的评价18F-脱氧葡萄糖（FDG）PET／CT联合腹部增强CT对诊断胰腺癌、鉴别诊断胰腺良恶性病变以及评估肿瘤可切除性的临床应用价值。方法回顾性分析行18F—FDGPET／CT和腹部增强CT检查并经病理检查或临床等方法证实的48例原发性胰腺病变患者的资料,其中胰腺癌34例,胰腺良性病变14例。对胰腺癌和胰腺良性病变患者最大标准摄取值（SUVmax）进行t检验;比较分析单独PET、腹部增强CT、PET／CT、PET／CT联合腹部增强CT4种方法的图像特征和诊断价值,对灵敏度和准确性进行x2检验,对特异性进行Fisher确切概率法检验。结果34例胰腺癌患者与14例胰腺良性病变患者的SUVmax（5．91±2．90和2．24±1．13）差异有统计学意义（t=4．56,P〈0．01）。PET／CT联合腹部增强CT诊断胰腺癌的灵敏度、特异性和准确性分别为97．1％（33／34）、92．9％（13／14）和95．8％（46／48）,与单纯PET的88．2％（30／34）、64．3％（9／14）和81．2％（39／48）相比,x2=0．863和P=0．352,P=0．038,X2=5．031和P=0．024;与腹部增强CT的76．5％（26／34）、71．4％（10／14）和75．0％（36／48）相比,x2=6．274和P=0．012,P=0．042,x2=8．362和P=0．003;与PET／CT的88．2％（30／34）、78．6％（11／14）和85．4％（41／48）相比,x2=0．863和P=0．352,P=0．048,x2=3．928和P=0．047。PET／CT全身显像几乎发现了全部转移灶,使14例胰腺癌患者避免了不必要的外科手术;PET／CT可对单独PET显像诊断的胰腺癌患者胰腺外假阳性病灶进行正确诊断,使1例胰头癌患者分期下调,进行了外科手术。腹部增强CT通过多期显像,可以准确判断肿瘤对胰腺周围主要血管的侵犯程度,腹部增强CT按血管受侵程度评估肿瘤可切除性的准确性为83．3％（15／18）,不可切除的准确性为9／9。结论PET／CT联合增强CT对于诊断胰腺癌、鉴别胰腺良恶性病变及评估肿瘤的可切除性准确性有一定临床价值。     

Evaluation of intraoperative radiation therapy for unresectable pancreatic cancer with FDG PET.

This investigation was undertaken to evaluate 18F-labeled fluorodeoxyglucose (FDG) PET in monitoring patients after intraoperative radiotherapy (IORT) for unresectable pancreatic cancer and to compare its usefulness with CT. METHODS: FDG PET was performed in 12 consecutive unresectable ductal adenocarcinoma patients before (n = 12) and after IORT (0.7-11.9 mo, n = 14). In the follow-up period, FDG PET results after IORT were divided into three groups: early (0-2.0 mo after IORT, n = 7), intermediate (2.1-4.0 mo, n = 5) and delayed period (4.1 mo or later, n = 2). FDG uptake at 60 min after injection of 185 MBq FDG under fasting conditions was analyzed with standardized uptake value (SUV). Three parameters, the highest SUV in the tumor, the area of tumor showing SUV of more than 2.0 and the average SUV in the tumor area were calculated. Ratios of each parameter after IORT to that before IORT were defined as residual uptake ratio (RUR)-1, -2 and -3, respectively. Tumor regression after IORT was evaluated with CT as tumor size ratio (TSR) every 2 mo. RESULTS: Results of RUR-1 and -3 were consistent with tumor size measured by CT. They decreased in 10 patients with partial response and increased in 2 patients with no change, although these 2 patients had abscesses. RUR-3 decreased consistently as 0.65+/-0.33 in 2 mo, 0.51+/-0.39 in 4 mo and 0.24 in 4 mo or later after IORT, respectively. RUR-1 decreased in early period, but demonstrated no change through the remaining periods. There were discrepancies between the results of RUR-2 and those of the other RURs. CT results revealed a slow decrease in tumor size, because TSR was 0.91 +/-0.10, 0.76+/-0.11 and 0.70+/-0.18 in 2, 4 and 6 mo after IORT, respectively. RUR-3 was smaller than TSR at 2 mo (P < 0.05) and 4 mo (P = 0.056). These results indicate that the measurement of the average SUV in the tumor area with FDG PET could evaluate the local response of pancreatic cancer after IORT earlier and more markedly than with CT. CONCLUSION: FDG PET was useful in monitoring patients after IORT, because the decrease of metabolism in pancreatic tumor could be detected earlier than the decrease in tumor size.     

Comparison of 18F-FLT PET and 18F-FDG PET in esophageal cancer.

18F-FDG PET has gained acceptance for staging of esophageal cancer. However, FDG is not tumor specific and false-positive results may occur by accumulation of FDG in benign tissue. The tracer 18F-fluoro-3'-deoxy-3'-L-fluorothymidine (18F-FLT) might not have these drawbacks. The aim of this study was to investigate the feasibility of 18F-FLT PET for the detection and staging of esophageal cancer and to compare 18F-FLT PET with 18F-FDG PET. Furthermore, the correlation between 18F-FLT and 18F-FDG uptake and proliferation of the tumor was investigated. METHODS: Ten patients with biopsy-proven cancer of the esophagus or gastroesophageal junction were staged with CT, endoscopic ultrasonography, and ultrasound of the neck. In addition, all patients underwent a whole-body 18F-FLT PET and 18F-FDG PET. Standardized uptake values were compared with proliferation expressed by Ki-67 positivity. RESULTS: 18F-FDG PET was able to detect all esophageal cancers, whereas 18F-FLT PET visualized the tumor in 8 of 10 patients. Both 18F-FDG PET and 18F-FLT PET detected lymph node metastases in 2 of 8 patients. 18F-FDG PET detected 1 cervical lymph node that was missed on 18F-FLT PET, whereas 18F-FDG PET showed uptake in benign lesions in 2 patients. The uptake of 18F-FDG (median standardized uptake value [SUV(mean)], 6.0) was significantly higher than 18F-FLT (median SUV(mean), 3.4). Neither 18F-FDG maximum SUV (SUV(max)) nor 18F-FLT SUV(max) correlated with Ki-67 expression in the linear regression analysis. CONCLUSION: In this study, uptake of 18F-FDG in esophageal cancer is significantly higher compared with 18F-FLT uptake. 18F-FLT scans show more false-negative findings and fewer false-positive findings than do 18F-FDG scans. Uptake of 18F-FDG or 18F-FLT did not correlate with proliferation.     

The possible role of F-18 FDG positron emission tomography in the differential diagnosis of focal pancreatic lesions

PURPOSE: To compare the diagnostic values of different methods for the differentiation of malignant from benign pancreatic lesions. METHODS: In 22 patients with focal pancreatic lesions, the carbohydrate antigen (CA) 19-9 level was measured; abdominal ultrasound (US), computed tomography (CT), endoscopic retrograde cholangiopancreatography (ERCP), and F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) were performed; and the value of these methods were analyzed for their use in cancer diagnosis. RESULTS: Malignant lesions were identified in six patients and verified by surgery or clinical follow-up. The CA 19-9 level was elevated in four of the five patients examined (sensitivity, 80%). In all six cases, US and CT revealed hypoechogenic and hypodense areas (sensitivity, 100%). In one patient, ERCP was unsuccessful but yielded true-positive results in three others (sensitivity, 60%). The sensitivity of FDG PET was 100%. Sixteen focal cases of pancreatic disease proved to be benign. The CA 19-9 level was elevated in four of them (specificity, 73%). Hypoechogenic and hypodense areas were evident on US and CT in eight patients. The specificity of CT was 50% (8 of 16 cases). The specificity of US was 47% (7 of 15 cases). The specificity of successful ERCP was 92%. Fourteen negative FDG-PET results were truly negative. In two patients, however, the PET findings proved to be falsely positive (specificity, 88%). CONCLUSIONS: FDG-PET is an effective tool to differentiate malignant from benign focal pancreatic lesions. In persons with focal pancreatic hypoechogenic or hypodense lesions detected by CT or US and an elevated CA 19-9 level, FDG PET should be the next step in the diagnostic strategy.     

Diagnostic accuracy of 18F-FDG PET in restaging patients with medullary thyroid carcinoma and elevated calcitonin levels.

Medullary thyroid carcinoma (MTC) is a rare endocrine tumor arising from the C-cells of the thyroid gland. Calcitonin is the principal serum tumor marker. A rising calcitonin level after total thyroidectomy for localized disease generally indicates residual, recurrent, or metastatic disease. The role of (18)F-FDG PET in MTC remains somewhat unclear. We reviewed our own experience with (18)F-FDG PET in postthyroidectomy MTC patients with elevated calcitonin. METHODS: From our database, we identified patients with suspected residual, recurrent, or metastatic MTC and elevated calcitonin who had been referred for (18)F-FDG PET between January 2000 and October 2005. (18)F-FDG PET findings were classified as positive or negative on the basis of visual interpretation of the scan. Standardized uptake values (SUVs) were also calculated. The (18)F-FDG PET findings were verified by histopathologic examination, when available, or other imaging studies and clinical follow-up. Any negative (18)F-FDG PET result was considered false-negative. RESULTS: Twenty-eight patients underwent a total of 38 (18)F-FDG PET studies. Calcitonin levels ranged from 106 to 541,000 pg/mL (median, 7,260 pg/mL). There were 23 true-positive, 1 false-positive, and 14 false-negative (18)F-FDG PET scans, yielding an overall sensitivity of 62%. There was no true-positive finding when calcitonin levels were below 509 pg/mL (n = 5). Using an arbitrary cutoff of 1,000 pg/mL, we found that the sensitivity in scans with calcitonin levels greater than 1,000 pg/mL increased to 78% (21/27; 95% confidence interval, 58%-91%). The mean SUV of all lesions with (18)F-FDG uptake was 5.3 +/- 3.2 (range, 2.0-15.9). Among the 14 patients with false-negative (18)F-FDG PET findings, 8 had concurrent anatomic imaging studies and only 2 of these had positive findings. CONCLUSION: (18)F-FDG PET can detect residual, recurrent, or metastatic MTC with a reasonable sensitivity of 78% when the calcitonin level is above 1,000 pg/mL but appears of limited use if the calcitonin level is below 500 pg/mL.     

动态18F-FDG PET定量分析用于骨病变鉴别诊断

目的 评价^18F-脱氧葡萄糖（FDG）PET在骨骼病变中的诊断价值。谅研究对象为40例原发性骨骼病变患者。所有患者在注射示踪剂后立即开始动态PET采集，持续60min。对动态PET图像进行半定量分析，分别计算平均和最大标准摄取值（SUVaver和SUVmax)，病灶SUV／肌肉SUV比值（T／M），病灶60min SUV/30min SUV比值（SUVaver60/30min和SUVmax60/30min）等。采用Patlak作图分析法对动态图像数据进行拟合计算，得出摄入常数（Ki），计算FDG代谢率（MRFDG）。根据接受器工作特性曲线（ROC）确定各定量指标的诊断阈值，并比较其鉴别良恶性病变的灵敏度和特异性。结果 经病理检查证实恶性病变21例，良性病变19例。恶性病变的MRFDG和SUV值高于良性病变，但各种指标的数值分布均存在交叉重叠。SUVaver与MRFDG呈正相关（r=0.67)。以SUV值≥1.8作为阈值时，鉴别良恶性病变的灵敏度和特异性分别为85．0％和82．4％，以MRFDG（1．1）为阈值时的灵敏度（82．4％）与SUV相近，而特异性（92．9％）较高。同时采用SUV（1．8）和SUVaver60/30min(1.1)作为鉴别标准时，较之单独有用SUV特异性可改善为93．3％，灵敏度略有降低（81．3％）。结论 骨骼良恶性病变之间存在葡萄糖代谢率差异。单用静态FDG PET获取SUV值不能很好鉴别骨骼良恶性病变。动态显像定量分析可提供更有价值的信息。根据动态图像进行半定量分析获取可反映动态过程的摄取指标，可能是一种较简便和有价值的鉴别方法。     

Comparison of 3′-deoxy-3′-[18F]fluorothymidine positron emission tomography (FLT PET) and FDG PET/CT for the detection and characterization of pancreatic tumours

Purpose

Despite recent advances in clinical imaging modalities, differentiation of pancreatic masses remains difficult. Here, we tested the diagnostic accuracy of molecular-based imaging including 3′-deoxy-3′-[¹⁸F]fluorothymidine (FLT) positron emission tomography (PET) and [¹⁸F]fluorodeoxyglucose (FDG) PET/CT in patients with suspected pancreatic masses scheduled to undergo surgery.

Methods

A total of 46 patients with pancreatic tumours suspicious for malignancy and scheduled for resective surgery were recruited prospectively. In 41 patients, FLT PET and FDG PET/CT scans were performed. A diagnostic CT performed on a routine basis was available in 31 patients. FLT PET and FDG PET/CT emission images were acquired according to standard protocols. Tracer uptake in the tumour [FDG and FLT standardized uptake value (SUV)] was quantified by the region of interest (ROI) technique. For FDG PET/CT analysis, correct ROI placement was ensured via side-by-side reading of corresponding CT images.

Results

Of 41 patients, 33 had malignancy, whereas 8 patients had benign disease. Visual analysis of FDG and FLT PET resulted in sensitivity values of 91% (30/33) and 70% (23/33), respectively. Corresponding specificities were 50% (4/8) for FDG PET and 75% (6/8) for FLT PET. In the subgroup of patients with contrast-enhanced CT (n?=?31), sensitivities were 96% (PET/CT), 88% (CT alone), 92% (FDG PET) and 72% (FLT PET), respectively. Mean FLT uptake in all malignant tumours was 3.0 (range SUV_max 1.1–6.5; mean FDG SUV_max 7.9, range 3.3–17.8; p?Conclusion For differentiation of pancreatic tumours, FDG PET and FDG PET/CT showed a higher sensitivity but lower specificity than FLT PET. Interestingly, visual analysis of FLT PET led to two false-positive findings by misinterpreting physiological bowel uptake as pathological FLT uptake in the pancreas. Due to the limited number of patients, the clinical value of adding FLT PET to the diagnostic workup of pancreatic tumours remains to be determined.     

Positron emission tomographic imaging with<Superscript>11</Superscript>C-choline in differential diagnosis of head and neck tumors: comparison with<Superscript>18</Superscript>F-FDG PET

The aim of this study was to evaluate the clinical value of positron emission tomography (PET) with¹¹C-labeled choline (CHOL) for the differential diagnosis of malignant head and neck tumors from benign lesions as compared with¹⁸F-fluorodeoxyglucose PET.Methods: We studied 45 patients (28 males, 17 females, age range, 29-84 years) with suspected lesions in the head and neck region using both CHOL and FDG PET within a 2-week period on each patient. All patients fasted for at least 6 hours for both the CHOL and FDG studies. PET imaging was performed 5 min and 50-60 min after intravenous injection of CHOL and FDG, respectively. After data acquisition, PET images were corrected for attenuation, and the reconstructed images were analyzed by visual interpretation. Then, the standardized uptake value (SUV) was calculated for semiquantitative evaluation of tumor tracer uptake. Finally the results of PET scans were compared with the histological diagnoses from surgical specimens or biopsies.Results: With CHOL PET, malignant tumors were correctly detected in 24 (96%) of 25 patients, and benign lesions in 14 (70%) of 20 patients with an accuracy of 84.4%. With FDG PET, malignancy was correctly diagnosed in 23 (92%) of 25 patients, and benign lesions in 13 (65%) of 20 patients resulting an accuracy of 80%. A significant positive correlation between CHOL and FDG SUVs was found for all lesions (r = 0.677, p = 0.004, n = 45). Malignant tumors showed significantly higher tracer accumulation than the benign lesions in both CHOL and FDG studies (5.69 ± 1.61, n = 25 vs. 2.98 ± 2.13, n = 20, p < 0.0001; 9.21 ± 4.23, n = 25 vs. 3.60 ± 2.57, n = 20, p < 0.0001). The cutoff SUV for differentiating malignant and benign lesions was 3.5 for CHOL and 3.9 for FDG. CHOL showed slightly better differentiation between malignant and benign lesions than FDG although some overlap existed on both studies. But the difference was not statistically significant.Conclusion: The results of this study indicate that CHOL PET may be feasible clinically for head and neck tumor imaging. PET imaging with CHOL seems to be able to detect malignant head and neck tumors as effectively as FDG PET. The advantages of CHOL PET were shorter examination period and low uptake in the muscle. However, both CHOL and FDG have some limitations in the evaluation of salivary gland lesions.     

11C-choline PET for the detection of bone and soft tissue tumours in comparison with FDG PET

We assessed and compared the usefulness of C-choline positron emission tomography (PET) with that of 2-[ F]fluoro-2-deoxy-D-glucose (FDG) PET for the differentiation between benign and malignant bone and soft tissue tumours. A total of 43 patients with 45 lesions were included. C-choline PET and FDG PET were performed from 5 and 40 min, respectively, after injection of 275-370 MBq tracer. PET data were evaluated by using the standardized uptake value (SUV) and were analysed according to the pathological data. C-choline uptake in malignancies was 4.9+/-2.1 (n=14), which was significantly higher than that in benign lesions (2.5+/-1.7, n=31) (P <0.0001). The sensitivity, specificity and accuracy of C-choline PET were 100%, 64.5% and 75.6%, respectively, when 2.59 of the SUV was used as the cut-off value. The FDG uptake in malignancies was 5.1+/-4.2 (n=14) and was also significantly larger than that in benign lesions 2.9+/-2.9 (n=31) (P<0.003). The sensitivity, specificity and accuracy of FDG PET were 85.7%, 41.9% and 55.6%, respectively (cut-off=1.83). The C-choline uptake in the lesions correlated with FDG uptake ( r=0.61, P<0.003). In receiver operating characteristic (ROC) analysis, the area under the ROC curve for C-choline PET (area=0.847) was higher than that for FDG PET (area=0.717). This study showed that C-choline PET was superior to FDG PET in differentiation between malignant and benign lesion in bone and soft tissue tumours. C-choline PET might be useful as a screening method for malignant bone and soft tissue tumours.