18F-FDG accumulation with PET for differentiation between benign and malignant lesions in the thorax.

Recent reports have indicated the value and limitations of (18)F-FDG PET and (201)Tl SPECT for determination of malignancy. We prospectively assessed and compared the usefulness of these scintigraphic examinations as well as (18)F-FDG PET delayed imaging for the evaluation of thoracic abnormalities. METHODS: Eighty patients with thoracic nodular lesions seen on chest CT images were examined using early and delayed (18)F-FDG PET and (201)Tl-SPECT imaging within 1 wk of each study. The results of (18)F-FDG PET and (201)Tl SPECT were evaluated and compared with the histopathologic diagnosis. RESULTS: Fifty of the lesions were histologically confirmed to be malignant, whereas 30 were benign. On (18)F-FDG PET, all malignant lesions showed higher standardized uptake value (SUV) levels at 3 than at 1 h, and benign lesions revealed the opposite results. Correlations were seen between (18)F-FDG PET imaging and the degree of cell differentiation in malignant tumors. No significant difference in accuracy was found between (18)F-FDG PET single-time-point imaging and (201)Tl SPECT for the differentiation of malignant and benign thoracic lesions. However, the retention index (RI) of (18)F-FDG PET (RI-SUV) significantly improved the accuracy of thoracic lesion diagnosis. Furthermore, (18)F-FDG PET delayed imaging measuring RI-SUV metastasis was useful for diagnosing nodal involvement and it improved the specificity of mediastinal staging. CONCLUSION: No significant difference was found between (18)F-FDG PET single-time-point imaging and (201)Tl SPECT for the differentiation of malignant and benign thoracic lesions. The RI calculated by (18)F-FDG PET delayed imaging provided more accurate diagnoses of lung cancer.     

The Clinical Role of Dual-Time-Point 18F-FDG PET/CT in Differential Diagnosis of the Thyroid Incidentaloma

Thyroid incidentalomas are common findings during imaging studies including ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) for cancer evaluation. Although the overall incidence of incidental thyroid uptake detected on PET imaging is low, clinical attention should be warranted owing to the high incidence of harboring primary thyroid malignancy. We retrospectively reviewed 2,368 dual-time-point ¹⁸F-FDG PET/CT cases that were undertaken for cancer evaluation from November 2007 to February 2009, to determine the clinical impact of dual-time-point imaging in the differential diagnosis of thyroid incidentalomas. Focal thyroid uptake was identified in 64 PET cases and final diagnosis was clarified with cytology/histology in a total of 27 patients with ¹⁸F-FDG-avid incidental thyroid lesion. The maximum standardized uptake value (SUVmax) of the initial image (SUV1) and SUVmax of the delayed image (SUV2) were determined, and the retention index (RI) was calculated by dividing the difference between SUV2 and SUV1 by SUV1 (i.e., RI = [SUV2 - SUV1]/SUV1 × 100). These indices were compared between patient groups that were proven to have pathologically benign or malignant thyroid lesions. There was no statistically significant difference in SUV1 between benign and malignant lesions. SUV2 and RI of the malignant lesions were significantly higher than the benign lesions. The areas under the ROC curves showed that SUV2 and RI have the ability to discriminate between benign and malignant thyroid lesions. The predictability of dual-time-point PET parameters for thyroid malignancy was assessed by ROC curve analyses. When SUV2 of 3.9 was used as cut-off threshold, malignancy on the pathology could be predicted with a sensitivity of 87.5 % and specificity of 75 %. A thyroid lesion that shows RI greater than 12.5 % could be expected to be malignant (sensitivity 88.9 %, specificity 66.3 %). All malignant lesions showed an increase in SUVmax on the delayed images compared with the initial images. But in the group of benign lesions, 37.5 % (6/16) showed a decrease or no change in SUVmax. Dual-time-point ¹⁸F-FDG PET/CT, obtaining additional images 2 h after injection, seems to be a complementary method for the differentiation between malignancy and benignity of incidental thyroid lesions.     

Evaluation of delayed18F-FDG PET in differential diagnosis for malignant soft-tissue tumors

OBJECTIVE: Positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) has been used for the evaluation of soft-tissue tumors. However, the range of accumulation of 18F-FDG for malignant soft-tissue lesions overlaps with that of benign lesions. The aim of this study is to investigate the usefulness of delayed 18F-FDG PET imaging in the differentiation between malignant and benign soft-tissue tumors. METHODS: Fifty-six patients with soft-tissue tumors underwent whole body 18F-FDG PET scan at 1 hour (early scan) and additional scan at 2 hours after injection (delayed scan). The standardized uptake value (SUV(max)) of the tumor was determined, and the retention index (RI) was defined as the ratio of the increase in SUV(max) between early and delayed scans to the SUV(max) in the early scan. Surgical resection with histopathologic analysis confirmed the diagnosis. RESULTS: Histological examination proved 19 of 56 patients to have malignant soft-tissue tumors and the rest benign ones. In the scans of all 56 patients, there was a statistically significant difference in the SUV(max) between malignant and benign lesions in the early scan (5.50 +/- 5.32 and 3.10 +/- 2.64, respectively, p < 0.05) and in the delayed scan (5.95 +/- 6.40 and 3.23 +/- 3.20, respectively, p < 0.05). The mean RI was not significantly different between malignant and benign soft-tissue tumors (0.94 +/- 23.04 and -2.03 +/- 25.33, respectively). CONCLUSIONS: In the current patient population, no significant difference in the RI was found between malignant and benign soft-tissue lesions. Although the mean SUV(max) in the delayed scan for malignant soft-tissue tumors was significantly higher than that for benign ones, there was a marked overlap. The delayed 18F-FDG PET scan may have limited capability to differentiate malignant soft-tissue tumors from benign ones.     

双时相18F-FDG PET显像用于肿瘤良恶性鉴别诊断

目的探讨双时相^18F-FDG PET显像在肿瘤良恶性鉴别中的临床价值。方法52例单次显像难以鉴别病变性质的患者行双时相全身^18 F-FDG PET／CT显像，将显像结果与病理学检查结果对照。结果43例延迟显像SUV升高的患者中有39例经病理检查证实为恶性病变，4例为良性病变；9例延迟显像SUV降低的患者中有7例经病理检查证实为良性病变，2例为恶性病变。灵敏度为95．1％，准确性为88．5％，特异性为63．6％，阳性预测值为90．7％，阴性预测值为7／9例。结论双时相^18F—FDG PET对良恶性病变的鉴别具有较高的灵敏度和准确性。     

18F-FDG PET-CT双时相显像结合高分辨率CT诊断孤立性肺结节的价值

目的 探讨18F-FDG PET-CT双时相显像结合高分辨率CT (HRCT)对孤立性肺结节(SPN)的鉴别诊断价值。方法 经CT证实符合SPN的病例173例,应用PET-CT技术对SPN病例进行双时相显像及同机HRCT,早期显像于注射18F-FDG后50 ～60min,并行HRCT,延迟显像于注射后2～2.5 h进行...     

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.     

18F-FDG PET/CT联合肺动脉灌注成像指数在单发肺结节中的应用价值

目的探讨18F-FDG PET/CT联合320容积CT双入口灌注成像(DI-CTP)肺动脉灌注指数(PPI)对单发性肺结节的鉴别诊断价值。方法搜集经病理证实40例单发性肺结节患者的18F-FDG PET/CT及320排CT灌注成像影像资料(恶性结节24例、良性结节16例),PET/CT以结节18F-FDG摄取值SUV≥2.5为诊断恶性结节阈值,18F-FDG PET/CT联合PPI则在SUV≥2.5诊断阈值的基础上综合PPI<50%判定,并分析SUV与PP均值在良恶性结节间差异性及相关性。结果PET/CT联合PPI正确诊断38例,其中恶性结节22例、良性结节16例,误诊2例。18F-FDG PET/CT联合PPI诊断肺单发结节的敏感性91.6%,特异性100%,准确性95.0%;18F-PDG摄取值SUV在良、恶性结间差异无统计学意义(t=1.66,P>0.05),而PPI均值在良、恶性结节间差异有统计学意义(t=-3.14,P<0.01);SUV与PPI间相关性无统计学意义(r=0.20,P>0.05)。结论18F-FDG PET/CT联合PPI可以提高诊断肺单发肺结节敏感性、特异性和准确性,减少误诊率。     

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.     

^18F-FDG PET／CT双时相显像对肺部病灶的定性诊断价值

目的探讨^18F-脱氧葡萄糖（FDG）PET／CT双时相显像在肺部病灶良恶性鉴别诊断中的临床应用价值。方法78例临床疑诊肺癌患者,均行早期和延迟^18F—FDG PET／CT显像。计算早期及延迟显像最大标准摄取值（SUVmax）,并计算2次显像SUVmax变化率（ASUV）。以SUVmax〉2．5和ASUV〉20％作为诊断肺癌的标准。患者最终诊断均经组织病理学、细菌学或治疗后随访证实。采用SPSS13．0软件,SUV组间比较用t检验,用受试者工作特征（ROC）曲线评价SUVmax、ASUV对肺部病灶的定性诊断价值。结果（1）78例患者中肺癌60例,良性病变18例（增殖性病变16例,占88．89％）。肺癌组（9．92±5．33和7．94±4．17,t=10．19）和良性病变组（8．54±6．61和7．21±5．74,t=8．23,P均〈0．01）延迟SUVmax均明显高于早期SUVmax;肺癌组与良性病变组间早期和延迟显像SUVmax差异均无统计学意义（t=0．60和-0．91,P均〉0．05）;肺癌组与良性病变组ASUV差异也无统计学意义[（26．04±14．73）％和（18．09±24．09）％,t=1．67,P〉0．05]。18例良性病变患者中有2例延迟显像SUVmax较早期减低,而肺癌患者延迟显像SUVmax均无减低。（2）以SUVmax〉2．5和ASUV〉20％为诊断肺癌的标准,其灵敏度、特异性、准确性、阳性预测值和阴性预测值分别为93．33％（56／60）和63．33％（38／60）、22．22％（4／18）和50．00％（9／18）、76．92％（60／78）和60．26％（47／78）、80．00％（56／70）和80．85％（38／47）、50．00％（4／8）和70．97％（22／31）;根据SUVmax和ASUV得到的ROC曲线下面积分别为0．61（Z=1．38,P〉0．05）和0．56（Z=0．65,P〉0．05）,差异均无统计学意义。结论对肺部病灶临床疑诊为肺癌的患者,如良性病变以增殖性病变为主,则^18F—FDG PET双时相显像良恶性鉴别诊断临床应用价值不大;但延迟SUVmax减低可能?     

18F-FDG PET显像在胰腺恶性病变鉴别诊断及转移灶探查中的应用价值

目的研究18F-FDGPET显像在胰腺恶性肿瘤诊断与鉴别诊断中的应用价值。方法 40例临床疑为胰腺恶性病变的患者均行18F-FDGPET显像,对显像结果进行目测法及SUV值半定量分析,并结合CT,MRI等影像学检查进行综合诊断,最后诊断根据手术病理或经4个月以上随访证实。结果如果以SUV为2.5作为鉴别诊断胰腺病灶良恶性的阈值,24例证实为胰腺癌患者中18F-FDGPET显像正确诊断22例,16例胰腺良性病变患者18F-FDGPET检出13例,其灵敏度、特异度及准确性分别为91.7%（22/24）,81.3%（13/16）及87.5%（35/40）;而结合CT,MRI等其他检查结果进行综合诊断,其诊断灵敏度、特异度及准确性分别为91.7%（22/24）、87.5%（14/16）及90%（36/40）。恶性病变的SUV平均值为4.6±2.6,良性病变的SUV平均值为2.3±1.5,良恶性病变间SUV平均值差异有统计学意义（P〈0.01）。在转移灶的检出中,18F-FDGPET显像发现了全部38处转移灶,并发现6处CT,MRI未能发现的远处转移病灶,排除了1例CT认为是胰周转移性淋巴结肿大的病例。结论 18F-FDGPET对鉴别诊断胰腺良恶性肿瘤的灵敏度、特异性较高,尤其在远处转移灶的探查中有较高应用价值。     

Focal thyroid lesions incidentally identified by integrated 18F-FDG PET/CT: clinical significance and improved characterization.

In this retrospective study, we investigated whether the (18)F-FDG uptake pattern and CT findings improved the accuracy over the standardized uptake value (SUV) for differentiating benign from malignant focal thyroid lesions incidentally found on (18)F-FDG PET/CT. We also defined the prevalence of these lesions and their risk for cancer. METHODS: (18)F-FDG PET/CT was performed on 1,763 subjects without a previous history of thyroid cancer from May 2003 to June 2004. Two nuclear medicine physicians and 1 radiologist interpreted PET/CT images, concentrating on the presence of focal thyroid lesions, the maximum SUV of the thyroid lesion, the pattern of background thyroid (18)F-FDG uptake, and the CT attenuation pattern of the thyroid lesion. RESULTS: The prevalence of focal thyroid lesions on PET/CT was 4.0% (70/1,763). Diagnostic confirmation was done on 44 subjects by ultrasonography (US)-guided fine-needle aspiration (n = 29) or US with clinical follow-up (n = 15). Among 49 focal thyroid lesions in these 44 subjects, 18 focal thyroid lesions of 17 subjects were histologically proven to be malignant (papillary cancer in 16, metastasis from esophageal cancer in 1, non-Hodgkin's lymphoma in 1). Therefore, the cancer risk of focal thyroid lesions was 36.7% on a lesion-by-lesion basis or 38.6% on a subject-by-subject basis. The maximum SUV of malignant thyroid lesions was significantly higher than that of benign lesions (6.7 +/- 5.5 vs. 10.7 +/- 7.8; P < 0.05). When only the maximum SUV was applied to differentiate benign from malignant focal thyroid lesions for the receiver-operating-characteristic curve analysis, the area under the curve (AUC) of PET was 0.701. All 16 focal thyroid lesions with very low attenuation or nonlocalization on CT images, or with accompanying diffusely increased thyroid (18)F-FDG uptake, were benign. When those lesions were regarded as benign lesions, irrespective of the maximum SUV, the AUC of PET/CT was significantly improved to 0.878 (P < 0.01). CONCLUSION: Focal thyroid lesions incidentally found on (18)F-FDG PET/CT have a high risk of thyroid malignancy. Image interpretation that includes (18)F-FDG uptake and the CT attenuation pattern, along with the SUV, significantly improves the accuracy of PET/CT for differentiating benign from malignant focal thyroid lesions.     

Accuracy of PET for diagnosis of solid pulmonary lesions with 18F-FDG uptake below the standardized uptake value of 2.5.

Benign and malignant pulmonary lesions usually are differentiated by 18F-FDG PET with a semiquantitative 18F-FDG standardized uptake value (SUV) of 2.5. However, the frequency of malignancies with an SUV of <2.5 is significant, and pulmonary nodules with low 18F-FDG uptake often present diagnostic challenges. METHODS: Among 360 consecutive patients who underwent 18F-FDG PET to evaluate pulmonary nodules found on CT, we retrospectively analyzed 43 who had solid pulmonary lesions (excluding lesions with ground-glass opacity, infiltration, or benign calcification) with an SUV of <2.5. The uptake of 18F-FDG was graded by a visual method (absent, faint, moderate, or intense) and 2 semiquantitative methods (SUV and contrast ratio [CR]). Final classification was based on histopathologic findings or at least 6 mo of clinical follow-up. RESULTS: We found 16 malignant (diameter, 8-32 mm) and 27 benign (7-36 mm) lesions. When faint visual uptake was the cutoff for positive 18F-FDG PET results, the receiver-operating-characteristic (ROC) analysis correctly identified all 16 malignancies and yielded false-positive results for 10 of 27 benign lesions. Sensitivity was 100%, specificity was 63%, and the positive and negative predictive values were 62% and 100%, respectively. When an SUV of 1.59 was the cutoff for positive 18F-FDG PET results, the ROC analysis revealed 81% sensitivity, 85% specificity, and positive and negative predictive values of 77% and 89%, respectively. At a cutoff for positive 18F-FDG PET results of a CR of 0.29, the ROC analysis revealed 75% sensitivity, 82% specificity, and positive and negative predictive values of 71% and 85%, respectively. The areas under the curve in ROC analyses did not differ significantly among the 3 analyses (visual, 0.84; SUV, 0.81; and CR, 0.82). Analyses of intra- and interobserver variabilities indicated that visual and SUV analyses were quite reproducible, whereas CR analysis was poorly reproducible. CONCLUSION: These results suggested that for solid pulmonary lesions with low 18F-FDG uptake, semiquantitative approaches do not improve the accuracy of 18F-FDG PET over that obtained with visual analysis. Pulmonary lesions with visually absent uptake indicate that the probability of malignancies is very low. In contrast, the probability of malignancy in any visually evident lesion is about 60%.     

Solid splenic masses: evaluation with 18F-FDG PET/CT.

Our objective was to assess the role of (18)F-FDG PET/CT in the evaluation of solid splenic masses in patients with a known malignancy and in incidentally found lesions in patients without known malignancy. METHODS: Two groups of patients were assessed: (a) 68 patients with known malignancy and a focal lesion on PET or a solid mass on CT portions of the PET/CT study; and (b) 20 patients with solid splenic masses on conventional imaging without known malignancy. The standard of reference was histology (n = 16) or imaging and clinical follow-up (n = 72). The lesion size, the presence of a single versus multiple splenic lesions, and the intensity of (18)F-FDG uptake expressed as a standardized uptake value (SUV) were recorded. The ratio of the SUV in the splenic lesion to the background normal splenic uptake was also calculated. These parameters were compared between benign and malignant lesions within each of the 2 groups of patients and between the 2 groups. RESULTS: The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of (18)F-FDG PET/CT in differentiating benign from malignant solid splenic lesions in patients with and without malignant disease were 100%, 100%, 100%, and 100% versus 100%, 83%, 80%, and 100%, respectively. In patients with known malignant disease, an SUV threshold of 2.3 correctly differentiated benign from malignant lesions with the sensitivity, specificity, PPV, and NPV of 100%, 100%, 100%, and 100%, respectively. In patients without known malignant disease, false-positive results were due to granulomatous diseases (n = 2). CONCLUSION: (18)F-FDG PET can reliably discriminate between benign and malignant solid splenic masses in patients with known (18)F-FDG-avid malignancy. It also appears to have a high NPV in patients with solid splenic masses, without known malignant disease. (18)F-FDG-avid splenic masses in patients without a known malignancy should be further evaluated as, in our series, 80% of them were malignant.     

双时相18F-FDG PET/CT显像在胰腺良恶性病变鉴别诊断中的应用

目的 探讨双时相18F-FDG PET/CT对胰腺良恶性病变鉴别诊断的价值.方法 回顾性分析2011年9月～2012年6月在我院行双时相18F-FDG PET/CT全身检查的胰腺病变患者41例,分别测定病灶早期及延迟标准摄取值（SUVmax）,计算18F-FDG的滞留指数（retention index,RI）;以病理及临床随访结果作为诊断标准,绘制SUVmax早期及RI的ROC曲线,寻找最佳诊断界值,分别计算SUVmax早期、RI为标准诊断胰腺癌敏感性、特异性及准确性.结果 41例胰腺病变患者中,恶性组（26例）SUVmax早期、SUVmax延迟、RI分别为8.2±2.7、10.5±4.1、（24.1±22.6）％,良性组（15例）SUVmax早期、SUVmax延迟、RI分别为4.0±3.7、4.3±3.8、（8.5±14.1）％;胰腺恶性病变SUVmax延迟较SUVmax早期明显升高（P＜0.001）,胰腺良性病灶延迟显像前后SUVmax差异无统计学意义（P=0.068）,胰腺良恶性组间RI差异有统计学意义（P=0.004）.本试验根据ROC曲线观察发现以SUV max=3.4为界值,诊断胰腺癌的敏感性、特异性及准确性分别为92.3％、66.7％、82.9％;以RI=9.1％为界值,诊断胰腺癌的敏感性、特异性及准确性分别为76.9％、73.3％及73.2％;SUVmax≥3.4结合RI≥9.1％诊断胰腺癌敏感性、特异性及准确性分别为88.5％、86.7％及87.8％.结论 应用双时相18F-FDG PET/CT显像能提高胰腺癌诊断特异性及准确性,但炎性（包括肿块型胰腺炎、自身免疫性胰腺炎、结核）延迟显像也可明显升高.     

Utility of 18F-FDG PET/CT uptake patterns in Waldeyer's ring for differentiating benign from malignant lesions in lateral pharyngeal recess of nasopharynx.

Focally increased (18)F-FDG uptake in the lateral pharyngeal recess (LPR) of the nasopharynx due to a benign or malignant lesion is not an uncommon finding on PET images. The aim of this study was to evaluate whether, on PET/CT images, (18)F-FDG uptake occurs with characteristic patterns and intensities in various regions of Waldeyer's ring that can improve our ability to differentiate benign from malignant lesions. METHODS: Data generated from the (18)F-FDG PET/CT images of 1,628 subjects in our cancer-screening program were analyzed. Increased uptake in the LPR was observed in 80 subjects (4.9%) presenting with benign lesions, including 53 subjects without and 27 subjects with symptoms of upper airway discomfort. In addition, 30 healthy controls and 21 patients with newly diagnosed nasopharyngeal carcinoma were recruited for this study. Visual uptake, measurements of the lesions' standardized uptake value (SUV), and any abnormalities on PET/CT were evaluated. The receiver-operating-characteristic curve and area under the curve were applied to evaluate the discriminating power. RESULTS: Increased (18)F-FDG uptake (SUV, mean +/- SD) was found in the LPR, with a statistically significant (P < 0.001) difference between benign lesions (3.0 +/- 1.16) and malignant lesions (7.03 +/- 3.83). However, associated increased uptake exclusively in the palatine tonsil, lingual tonsil, and submandibular gland was found in both asymptomatic and symptomatic subjects. The ratio of LPR uptake to palatine tonsil uptake (N/P ratio) in benign lesions (0.81 +/- 0.37) was significantly (P < 0.001) lower than that in malignant lesions (2.30 +/- 1.62). Higher incidences of asymmetric (18)F-FDG LPR uptake, cervical lymph node uptake, and asymmetric wall thickening of the LPR on CT were observed in patients with nasopharyngeal carcinoma. When an SUV of less than 3.9 and an N/P ratio of less than 1.5 were used as cutoff points in subjects showing the combination of symmetric uptake in the LPR and normal or symmetric wall thickening, and detectable lymph node uptake, the area under the curve for benign lesions on PET/CT was 0.932 +/- 0.042 (95% confidence interval, 0.86-0.98), with a sensitivity of 90.4% and a specificity of 93.8%. CONCLUSION: The intensity and patterns of (18)F-FDG uptake in various regions of Waldeyer's ring along with CT scan findings provide a feasible modality to differentiate benign from malignant nasopharyngeal lesions.     

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

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.     

11C-胆碱与18F-FDG双时相PET显像在孤立性肺结节鉴别诊断中的应用

目的 比较^11C-胆碱、18F-脱氧葡萄糖（FDG）和^18F-FDG双时相PET显像对鉴别肺部孤立性结节良恶性的价值。方法16例临床疑为肺肿瘤的患者进行^18F-FDGPET显像（注药后1h显像，2h后行延迟显像）、^11C-胆碱PET显像（3d内，于注药后10min进行）。图像判断以标准摄取值（SUV）作为半定量指标，异常放射性浓聚灶以SUV〉2．5为葡萄糖代谢增高，^18F-FDG延迟显像SUV上升≥10％为恶性病变（阳性），如下降或升高〈10％为良性病变（阴性）；^11C-胆碱异常摄取灶以SUV〉2．0为阳性。所有病例进行随访，以显像诊断是否符合病理检查结果作为判断标准。结果病理检查结果证实12例肺癌，3例结核，1例结节病。^11C-胆碱PET显像确诊了12例肿瘤中的ll例，而^18F-FDG PET显像确诊10例（10／12例），双时相^18F-FDG PET显像确诊11例。4例良性病变者，^11C-胆碱PET显像能较好鉴别；而^18F-FDG PET显像2例假阳性，结合延迟显像仅1例假阳性。结论 ^11C-胆碱和^18F-FDG PET显像均能较好地鉴别肺部良恶性肿瘤。但^11C-胆碱和双时相^18F-FDGPET显像优于常规^18F-FDGPET显像，三者联合能提高对肺部病变的诊断效率。     

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.     

Optimizing delayed scan time for FDG PET: comparison of the early and late delayed scan

OBJECTIVES: Although dual-time-point scans have been widely used to improve the diagnostic efficacy of FDG PET in differentiating between malignant and benign lesions, no optimized delayed scan time-point has yet been recommended in clinical practice. Our study aimed to explore the most appropriate time for a delayed scan by comparing early and late delayed scans. METHODS: Eighty patients with suspected malignancy were given a three-phase (64 min, 110 min, 233 min after FDG injection) PET/CT scan. The maximum standardized uptake values (SUVs) in the three-phase scans were recorded as SUV1, SUV2 and SUV3, respectively, and compared among three-phase imaging. Retention indices (RIs) of each lesion in two delayed phases were calculated according to the formulae: RI1=SUV2-SUV1/SUV1 x100% and RI2=SUV3-SUV1/SUV1 x100%. RI1 and RI2 in both malignant and benign groups were assessed through correlation analysis. The diagnostic values of two delayed scans were compared through the analysis of the receiver operating characteristic curves. RESULTS: One hundred and nine of 148 lesions were malignant, and 39/148 lesions benign, which were verified by pathological, clinical, laboratory or radiological examination. RI1 and RI2 in malignancy were 14.8+/-13.1% and 10.8+/-20.5% respectively, and the correlation coefficient was 0.6 (P=0.0001). RI1 and RI2 in benign lesions were 11.3+/-28.2% and 9.3+/-42.4%, respectively, and the correlation coefficient was 0.6 (P=0.0001). The area under the ROC curve for RI1 was 0.627+/-0.050 (null hypothesis: true area=0.5, P=0.0130); whereas the area under the ROC curve for RI2 was 0.563+/-0.052 (null hypothesis: true area=0.5, P=0.2321), suggesting that the late delayed scan may have no diagnostic value. CONCLUSION: The retention index values in the two delayed phases have good relativity. The diagnostic value of early delayed imaging is higher than that of late delayed imaging. An early delayed scan, according to our research, should be recommended in clinical practice.     

The role of gastric distention in differentiating recurrent tumor from physiologic uptake in the remnant stomach on 18F-FDG PET.

Physiologic (18)F-FDG uptake in the stomach can often cause false-positive results and lowers the usefulness of (18)F-FDG PET in evaluating the remnant stomach. We assessed the role of gastric distension to see whether it is beneficial for the differentiation of recurrent tumors from physiologic (18)F-FDG uptake in the remnant stomach. METHODS: Thirty patients (22 men and 8 women; age range, 27-80 y; mean age, 58.3 y) with a history of subtotal gastrectomy for gastric cancer underwent (18)F-FDG PET for various clinical indications. After whole-body imaging, the patients were asked to drink water, and then spot imaging of the stomach was performed. (18)F-FDG uptake in the remnant stomach was considered positive for malignancy if it was persistently increased, whether focal or diffuse, after water ingestion. We used 2 standardized uptake value (SUV) criteria to differentiate benign from malignant uptake. First, a lesion was considered benign if its SUV was less than 2 on whole-body imaging. Second, for a lesion with an SUV of 2 or above, it was classified as benign if SUV decreased by more than 10% after water ingestion. RESULTS: Visual analysis of whole-body images produced 9 true-negative, 4 false-positive, 16 true-positive, and 1 false-negative results. Use of additional spot images produced 12 true-negative, 1 false-positive, 15 true-positive, and 2 false-negative results. When an SUV cutoff of 2 was applied for malignancy before water ingestion, all 17 patients with local recurrence were correctly identified, but 11 of the 13 patients without local recurrence were falsely considered to have a recurrent tumor in the remnant stomach. To reduce the false-positive results, we used the second SUV criterion after water ingestion. Use of that criterion produced 4 false-negative results although it correctly identified the 11 false-positive results as true negative. CONCLUSION: Gastric distension by having patients drink a glass of water seems to be a simple, cost-effective way of improving the diagnostic accuracy of (18)F-FDG PET in patients with suspected recurrence in the remnant stomach. Visual analysis with special attention to the configuration of (18)F-FDG activity after water ingestion seems to be more useful than the change in SUV in evaluating the remnant stomach.