Dual Time Point Research Articles

Comparative evaluation of SUV, tumor-to-blood standard uptake ratio (SUR), and dual time point measurements for assessment of the metabolic uptake rate in FDG PET.

BackgroundWe have demonstrated recently that the tumor-to-blood standard uptake ratio (SUR) is superior to tumor standardized uptake value (SUV) as a surrogate of the metabolic uptake rate Km of fluorodeoxyglucose (FDG), overcoming several of the known shortcomings of the SUV approach: excellent linear correlation of SUR and Km from Patlak analysis was found using dynamic imaging of liver metastases. However, due to the perfectly standardized uptake period used for SUR determination and the comparatively short uptake period, these results are not automatically valid and applicable for clinical whole-body examinations in which the uptake periods (T) are distinctly longer and can vary considerably. Therefore, the aim of this work was to investigate the correlation between SUR derived from clinical static whole-body scans and Km-surrogate derived from dual time point (DTP) measurements.MethodsDTP 18F-FDG PET/CT was performed in 90 consecutive patients with histologically proven non-small cell lung cancer (NSCLC). In the PET images, the primary tumor was delineated with an adaptive threshold method. For determination of the blood SUV, an aorta region of interest (ROI) was delineated manually in the attenuation CT and transferred to the PET image. Blood SUV was computed as the mean value of the aorta ROI. SUR values were computed as ratio of tumor SUV and blood SUV. SUR values from the early time point of each DTP measurement were scan time corrected to 75 min postinjection (SURtc). As surrogate of Km, we used the SUR(T) slope, Kslope, derived from DTP measurements since it is proportional to the latter under the given circumstances. The correlation of SUV and SURtc with Kslope was investigated. The prognostic value of SUV, SURtc, and Kslope for overall survival (OS) and progression-free survival (PFS) was investigated with univariate Cox regression in a homogeneous subgroup (N=31) treated with primary chemoradiation.ResultsCorrelation analysis revealed for both, SUV and SURtc, a clear linear correlation with Kslope (P<0.001). Correlation SUR vs. Kslope was considerably stronger than correlation SUV vs. Kslope (R2=0.92 and R2=0.69, respectively, P<0.001). Univariate Cox regression revealed SURtc and Kslope as significant prognostic factors for PFS (hazard ratio (HR) =3.4/ P=0.017 and HR =4.3/ P=0.020, respectively). For SUV, no significant effect was found. None of the investigated parameters was prognostic for OS.ConclusionsScan-time-corrected SUR is a significantly better surrogate of tumor FDG metabolism in clinical whole-body PET compared to SUV. The very high linear correlation of SUR and DTP-derived Kslope (which is proportional to actual Km) implies that for histologically proven malignant lesions, FDG-DTP does not provide added value in comparison to the SUR approach in NSCLC.

Dual time-point FDG PET/CT and FDG uptake and related enzymes in lymphadenopathies: preliminary results.

The purpose of this study was to determine the ability of dual time-point (DTP) PET/CT with (18)F-FDG to discriminate between malignant and benign lymphadenopathies. The relationship between DTP FDG uptake and glucose metabolism/hypoxia markers in lymphadenopathies was also assessed. Patients with suspected lymphoma or recently diagnosed treatment-naive lymphoma were prospectively enrolled for DTP FDG PET/CT (scans 60min and 180min after FDG administration). FDG-avid nodal lesions were segmented to yield volume and standardized uptake values (SUV), including SUVmax, SUVmean, cSUVmean (with partial volume correction), total lesion glycolysis (TLG) and cTLG (with partial volume correction). Expression of glucose transporter-1 (GLUT-1), hexokinase-II (HK-II), glucose-6-phosphatase (G6Pase) and hypoxia-inducible factor-1alpha (HIF-1alpha) were assessed with immunohistochemistry and enzyme activity was determined for HK and G6Pase. FDG uptake was assessed in 203 lesions (146 malignant and 57 benign). Besides volume, there were significant increases over time for all parameters, with generally higher levels in the malignant lesions. The retention index (RI) was not able to discriminate between malignant and benign lesions. Volume, SUVmax, TLG and cTLG for both scans were able to discriminate between the two groups statistically, but without complete separation. Glucose metabolism/hypoxia markers were assessed in 15 lesions. TLG and cTLG were correlated with GLUT-1 expression on the 60-min scan. RI-max and RI-mean and SUVmax, SUVmean and cSUVmean on the 60-min scan were significantly correlated with HK-II expression. RI was not able to discriminate between malignant and benign lesions, but some of the SUVs were able to discriminate on the 60-min and 180-min scans. Furthermore, FDG uptake was correlated with GLUT-1 and HK-II expression.

Diagnostic value of F-18 FDG PET/CT in patients with spondylodiscitis: Is dual time point imaging time worthy?

PurposeIn this retrospective study, we aimed to investigate the value of FDG-PET/CT in the diagnosis of spondylodiscitis (SD), the significance of dual time point imaging (DTPI) for SD diagnosis and the worth of SUVmax data for distinguishing tuberculous vs. non-tuberculous SD. Materials and methods32 patients with suspected SD were scanned with FDG-PET/CT. For quantitative analysis maximum standardized uptake value (SUVmax) of the lesion area was measured. Nineteen patients had DTPI of FDG-PET/CT. The final diagnoses were achieved by histopathological, microbiological, and clinical results. ResultsSpecific pathogens were isolated in 21 patients; other patients were accepted as nonspecific bacterial SD. In all patients, FDG-PET/CT results were compatible with SD diagnosis. The SUVmax data for tuberculous and non-tuberculous SD and DTPI results were statistically insignificant. ConclusionFDG-PET/CT is a successful modality for SD diagnosis; additionally, DTPI protocol for FDG-PET/CT in SD diagnosis and SUVmax data for differentiation between non-tbc SD and tbc SD are useless.

Basal 18F-FDG PET/CT as a predictive biomarker of tumor response for neoadjuvant therapy in breast cancer

PurposeTo explore the relation between tumor kinetic assessed by 18F-FDG PET and final neoadjuvant chemotherapy (NC) response within a molecular phenotype perspective. Material and MethodsProspective study included 144 women with breast cancer. All patients underwent a dual-time point 18F-FDG PET/CT previous to NC. The retention index (RI), between SUV-1 and SUV-2 was calculated.Molecular subtypes were re-grouped in low, intermediate and high-risk biological phenotypes.After NC, all residual primary tumor specimens were histopathologically classified in tumor regression grades (TRG) and response groups.The relation between SUV-1, SUV-2 and RI with the TRG and response groups was evaluated in all molecular subtypes and in accordance with the risk categories. ResultsResponder's lesions showed significant greater SUVmax compared to non-responders. The RI value did not show any significant relation with response.Attending to molecular phenotypes, statistical differences were observed with greater SUV for responders having high-risk molecular subtypes. ConclusionGlycolytic tumor characteristics showed a significant correlation with NC response and dependence of risk phenotype.

Dual time-point (18)F-FDG PET/CT to assess response to radiofrequency ablation of lung metastases.

To establish the usefulness of dual time-point PET/CT imaging in determining the response to radiofrequency ablation (RFA) of solitary lung metastases from gastrointestinal cancer. This prospective study included 18 cases (3 female, 15 male, mean age 71±15 yrs) with solitary lung metastases from malignant digestive tract tumors candidates for RFA. PET/CT images 1h after injection of 4.07MBq/kg of (18)F-FDG (standard images) were performed at baseline, 1 month, and 3 months after RFA. PET/CT images 2h after injection centered in the thorax at 1 month after RFA were also performed (delayed images). A retention index (RI) of dual time-point images was calculated as follows: RI=(SUVmax delayed image-SUVmax standard image/SUVmax standard image)*100. Pathological confirmation of residual tumor by histology of the treated lesion was considered as local recurrence. A negative imaging follow-up was considered as complete response. Local recurrence was found in 6/18 lesions, and complete response in the remaining 12. The mean percentage change in SUVmax at 1 month and at 3 months showed a sensitivity and specificity for PET/CT of 50% and 33%, and 67% and 92%, respectively. The RI at 1 month after RFA showed a sensitivity and specificity of 83% and 92%, respectively. Dual time point PET/CT can predict the outcome at one month after RFA in lung metastases from digestive tract cancers. The RI can be used to indicate the need for further procedures to rule out persistent tumor due to incomplete RFA.

Dual-time point 18FDG-PET/CT imaging may be useful in assessing local recurrent disease in high grade bone and soft tissue sarcoma.

Sarcomas comprise 1% of malignant tumors in adults but represent a significant diagnostic and therapeutic challenge. Molecular imaging with ¹⁸FDG PET/CT is a powerful modality in oncology. Its use for initial assessment, evaluation of response to therapy and recurrent disease in most tumors is essential for therapeutic decisions. Its indication in sarcomas is still controversial. One of the indications for PET/CT in sarcomas is detection of recurrences. Nowadays magnetic resonance tomography (MRT) has a crucial role in identification of local recurrences in soft tissue and bone sarcoma. ¹⁸FDG-PET/CT may serve as a complementary method. Dual time point imaging (DTPI) has been studied for most tumors as a method for differentiating benign from malignant lesions. There is limited data on DTPI in sarcomas. Therefore we studied prospectively patients with suspected local recurrences in the treated area and used DTPI as a method for differentiating benign from malignant tissue. of this study was to evaluate the ability of dual-time point PET/CT to enhance sensitivity, specificity, PPV, NPV and accuracy of ¹⁸FDG PET/CT in high grade and low grade sarcomas. We conducted a dual-time PET/CT in 15 patients with suspected locally recurrent disease. The delayed scan was conducted on the 120th min in the suspected region. The interpretation of PET/CT was made both upon CT scan and metabolic scans. The percentage change over time per lesion was calculated (%DSUV). The increase in SUVmax with %DSUV > 10% in the late scanning was considered as indicative for malignancy. We assessed the sensitivity, specificity, accuracy, positive and negative predicting value of the interpretation of PET/CT at 60 min and 120 min. All of the patients were followed up for a period of 1-3 years after our examination, either with histologic results, or with an MRT scans. The received sensitivity, specificity and accuracy of ¹⁸FDG PET/CT interpretation at 120 min in high grade sarcomas were respectively 100%, 80% and 89%. By comparison, in low grade tumors at 120 min scan, these parameters were 50%, 75% and 66%. These preliminary data suggests that dual-time imaging in sarcomas improves sensitivity and accuracy in identification of local recurrent disease in high grade sarcomas and have limited role in low grade sarcomas. Further research is necessary to confirm these results.

Delayed Dual-Time Point Imaging Protocol Improving Myocardial Uptake of 18-Fluorine Flouro Deoxyglucose (18F-FDG) During Viability Screening of Diabetes Mellitus Type 2 Patients Using Integrated Positron Emission Tomography/Computed Tomography (PET/CT) Imaging

Aims: To investigate the effect of delayed imaging protocol and hypoglycemic agent on quantitative values obtained during myocardial viability

A meta-analysis to evaluate the diagnostic value of dual-time-point F-fluorodeoxyglucose positron emission tomography/computed tomography for diagnosis of pulmonary nodules.

This meta-analysis aimed at evaluating the efficacy of dual-time-point (DTP) F-fluorodeoxyglucose (F-FDG) positron emission tomography/computed tomography (PET/CT) in diagnosing pulmonary nodules. Using computer and manual search, the current research about the efficacy of DTP F-FDG PET/CT in diagnosing pulmonary nodules was collected. According to the evaluation criteria of Quality Assessment of Diagnostic Accuracy Studies Scale, the data from 13 studies were analyzed by Meta-DiSc software, and the sensitivity (Sen), specificity (Spe), diagnostic odds ratios (DOR), positive likelihood ratios (LR+), and negative likelihood ratios (LR-) were summarized. A total of 13 articles were included in this study, involving 962 patients. The meta-analysis showed that the rough Sen of DTP PET/CT was 0.80 (95% confidence interval [CI] 0.76-0.84, I2 = 83.2%), the summary Spe was 0.75 (95% CI 0.71-0.79, I2 = 89.3%), the summary LR + and LR- were 2.57 (95% CI 1.54-4.29) and 0.28 (95% CI 0.16-0.5), respectively, and DOR was 10.01 (95% CI 3.83-26.18). DTP F-FDG PET/CT has similar Sen and Spe, with single-time-point PET/CT in diagnosing pulmonary nodules. Further high-quality research is required to explore the potential value of DTP F-FDG PET/CT.

The application of positron emission tomography (PET/CT) in diagnosis of breast cancer. Part II. Diagnosis after treatment initiation, future perspectives.

Similarly to the applications described in the first part of this publication, positron emission tomography with computed tomography (PET/CT) is also gaining importance in monitoring a tumour's response to therapy and diagnosing breast cancer recurrences. This is additionally caused by the fact that many new techniques (dual-time point imaging, positron emission tomography with magnetic resonance PET/MR, PET/CT mammography) and radiotracers (16α-18F-fluoro-17β-estradiol, 18F-fluorothymidine) are under investigation. The highest sensitivity and specificity when monitoring response to treatment is achieved when the PET/CT scan is made after one or two chemotherapy courses. Response to anti-hormonal treatment can also be monitored, also when new radiotracers, such as FES, are used. When monitoring breast cancer recurrences during follow-up, PET/CT has higher sensitivity than conventional imaging modalities, making it possible to monitor the whole body simultaneously. New techniques and radiotracers enhance the sensitivity and specificity of PET and this is why, despite relatively high costs, it might become more widespread in monitoring response to treatment and breast cancer recurrences.

PET/CT Dual Time Point Scanning in Evaluation of Malignant Lymphoma

Purpose: The purpose of the present study is to evaluate the value of dual-time-point F-18 FDG PET/CT imaging in malignant lymphoma (ML) to differentiate between benign lesions and residual or relapsing malignant lesions. Patients and methods: This prospective study included 252 lymph nodes in 60 patients. F-18 FDG PET/CT scan was performed at 50 min (early scan) and at 100 min (delayed scan) after the injection. The maximum standardized uptake value (SUV max) of each lesion was calculated at early and delayed scans. We estimated the difference between early and delayed SUV max (D-SUV max) and the retention index (RI-SUV max) to evaluate the change of tracers handling in the lesions. Also, the early lesion/liver ratio and delayed lesion/liver ratio were calculated. Then their cut-off values were evaluated using receiver operating characteristic analysis. Correlations of these cutoff values with different clinico-pathological parameters were done. Results: The cut-off value in Early-SUV max was 4.05, Delayed-SUV max were 4.45, D-SUV max was 0.45, RISUV max was 0.155, Early lesion/liver ratio was 1.25 and in Delayed lesion/liver ratio was 1.35. The delayed-SUV max had the highest sensitivity and specificity of 85.3% and 92.6% respectively. The overall result of DTP PET/CT showed sensitivity of 95.3%, specificity of 76.4%, accuracy of 86.1%, and positive predictive value of 80.9% and negative predictive value of 94% respectively. Based on a total of true and false results in early and delayed PET/CT imaging, there was significant improvement in specificity in the delayed PET/CT imaging compared to the early PET/CT imaging. Correlation of DTP cut off value with the different clinico-pathological parameters showed that nodular sclerosis and lymphocytic predominance pathological subtypes had the highest sensitivity of 100%, while mixed cellularity showed the lowest sensitivity of 64.3%. In Hodgkin lymphoma lesions, cervical sites showed the lowest sensitivity and specificity 90.2% & 61.4% respectively.Conclusions: The dual time point FDG PET/CT scan is useful to differentiate between post-therapy changes as benign lesions and residual or relapsing malignant lesions in malignant lymphoma.

Biphasic 68Ga-PSMA-HBED-CC-PET/CT in patients with recurrent and high-risk prostate carcinoma

Binding of (68)Ga-PSMA-HBED-CC ((68)Ga-PSMA) at prostate cancer (PC) cells increases over time. A biphasic protocol may help separating benign from tumor lesions. The aim of this study was the retrospective evaluation of a diagnostic incremental value of a dual-time point (biphasic) (68)Ga-PSMA-PET/CT in patients with prostate cancer. Retrospective analysis of 35 consecutive patients (49-78 years, median 71) with newly diagnosed PC (12/35) or recurrence of PC (23/35). PET/CT (Gemini TF16, Philips) was acquired 1 h and 3 h p. i. of 140-392 MBq (300 MBq median) (68)Ga-PSMA, followed by a diagnostic contrast CT. PET findings were correlated with histology or unequivocal CT findings. Semiquantitative PET data (SUVmax, SUV mean) were acquired and target-to-background-ratios (T/B-ratio) were calculated for benign and malign lesions for both time points. Size of lymph nodes (LN) on diagnostic CT was recorded. Statistical analysis was performed for assessment of significant changes of semiquantitative PET-parameters over time and for correlation of size and uptake of lymph nodes. One hundred and four lesions were evaluated. Sixty lesions were referenced by histology or unequivocal CT findings, including eight (13.3 %) histopathologically benign lymph nodes, 12 (20 %) histopathologically lymph node metastases, 12 (20 %) primary tumors, three (5 %) local recurrences, and 25 (41.7 %) bone metastases. Forty-four lesions were axillary LN with normal CT-appearance. Benign lesions had significantly lower SUVmax and T/B-ratios compared with malignant findings. Malign lesions showed a significant increase of both parameters over time compared to benign findings. There was no correlation between LN size and SUVmax. The sensitivity, specificity, the positive predictive value and negative predictive value of PET/CT regarding pelvic LN was 94 %, 99 %, 89 %, and 99.5 %, respectively. In contrast to benign tissues, the uptake of proven tumor lesions increases on (68)Ga-PSMA-PET/CT over time. A biphasic PET-study may lead to a better detection of tumor lesions in unequivocal findings.

Dual time point imaging for F18-FDG-PET/CT does not improve the accuracy of nodal staging in non-small cell lung cancer patients.

To analyze the diagnostic performance of dual time point imaging (DTPI) for pre-therapeutic lymph node (LN) staging in non-small cell lung cancer (NSCLC). This was a retrospective analysis of 47 patients with NSCLC who had undergone DTPI by PET (early + delayed) using F18-fluorodeoxyglucose (FDG). PET raw data were reconstructed iteratively (point spread function + time-of-flight). LN uptake in PET was assessed visually (four-step score) and semi-quantitatively (SUVmax, SUVmean, ratios LN/primary, LN/liver, and LN/mediastinal blood pool). DTPI analyses included retention indices (RIs), Δ-ratios and changes in visual score. Histology or cytology served as standards of reference. Accuracy was determined based on ROC analyses. Thirty-six of 155 LNs were malignant. DTPI accuracy was low for all measures (visual assessment, 24.5%; RI SUVmax, 68.4%; RI SUVmean, 65.8%; Δ-ratios, 63.9-76.1%) and significantly inferior to early PET. Accuracies of early (range, 86.5-92.9%) and delayed PET (range, 85.2-92.9%) were comparable. At early PET, accuracy of the visual score (92.9%) was similar or superior to semi-quantitative analyses (range, 86.5-92.3%). Using a modern PET/CT device and novel image reconstruction, neither additional delayed PET nor DTPI analyses improved the accuracy of PET-based LN staging. Dedicated visual assessment criteria performed very well. • DTPI did not improve accuracy of PET-based LN staging in NSCLC. • Analyzed SUV ratios were not superior to LN SUVmax or SUVmean. • A four-step visual score may allow highly accurate, standardized LN assessment.

Basal (18)F-FDG PET/CT as a predictive biomarker of tumor response for neoadjuvant therapy in breast cancer.

To explore the relation between tumor kinetic assessed by (18)F-FDG PET and final neoadjuvant chemotherapy (NC) response within a molecular phenotype perspective. Prospective study included 144 women with breast cancer. All patients underwent a dual-time point (18)F-FDG PET/CT previous to NC. The retention index (RI), between SUV-1 and SUV-2 was calculated. Molecular subtypes were re-grouped in low, intermediate and high-risk biological phenotypes. After NC, all residual primary tumor specimens were histopathologically classified in tumor regression grades (TRG) and response groups. The relation between SUV-1, SUV-2 and RI with the TRG and response groups was evaluated in all molecular subtypes and in accordance with the risk categories. Responder's lesions showed significant greater SUVmax compared to non-responders. The RI value did not show any significant relation with response. Attending to molecular phenotypes, statistical differences were observed with greater SUV for responders having high-risk molecular subtypes. Glycolytic tumor characteristics showed a significant correlation with NC response and dependence of risk phenotype.

The Sum of Tumour-to-Brain Ratios Improves the Accuracy of Diagnosing Gliomas Using 18F-FET PET.

Gliomas are common brain tumours, but obtaining tissue for definitive diagnosis can be difficult. There is, therefore, interest in the use of non-invasive methods to diagnose and grade the disease. Although positron emission tomography (PET) with 18F-fluorethyltyrosine (18F-FET) can be used to differentiate between low-grade (LGG) and high-grade (HGG) gliomas, the optimal parameters to measure and their cut-points have yet to be established. We therefore assessed the value of single and dual time-point acquisition of 18F-FET PET parameters to differentiate between primary LGGs (n = 22) and HGGs (n = 24). PET examination was considered positive for glioma if the metabolic activity was 1.6-times higher than that of background (contralateral) brain, and maximum tissue-brain ratios (TBRmax) were calculated 10 and 60 min after isotope administration with their sums and differences calculated from individual time-point values. Using a threshold-based method, the overall sensitivity of PET was 97%. Several analysed parameters were significantly different between LGGs and HGGs. However, in a receiver operating characteristics analysis, TBR sum had the best diagnostic accuracy of 87% and sensitivity, specificity, and positive and negative predictive values of 100%, 72.7%, 80%, and 100%, respectively. 18F-FET PET is valuable for the non-invasive determination of glioma grade, especially when dual time-point metrics are used. TBR sum shows the greatest accuracy, sensitivity, and negative predictive value for tumour grade differentiation and is a simple method to implement. However, the cut-off may differ between institutions and calibration strategies would be useful.

Clinical significance of dual-time-point 18F-FDG PET imaging in resectable non-small cell lung cancer.

ObjectiveThe maximal standardized uptake value (SUVmax) of pulmonary lesions on dual-time-point (DTP) fluorodeoxyglucose positron emission tomography (FDG-PET) has been shown to be useful for differentiation between malignant and non-malignant pulmonary lesions, and also to be of value for intrathoracic nodal staging of non-small cell lung cancer (NSCLC). However, a few NSCLC lesions have been found to show decreased FDG uptake on delayed images, and the significance of this finding remains unknown.Patients and methodsWe conducted a retrospective review of the data of 284 patients with NSCLC who underwent DTP FDG-PET before surgery. Cases of adenocarcinoma in situ and minimally invasive adenocarcinoma were excluded, because these lesions show little FDG uptake. Each patient was scanned at 60 min (early acquisition; SUV-E) and 115 min (delayed acquisition; SUV-D) after the radiopharmaceutical injection. The intratumoral retention index (RI) of 18F-FDG was measured for each examination by the DTP method. Recurrence-free survival (RFS) was determined by the Kaplan–Meier method and compared in relation to the SUV-E, SUV-D, and RI by univariate and multivariate analysis using models including the clinico-pathological prognostic factors.ResultsOf the 284 cases, the RI ≤ 0 was in 49 cases (17.3 %). This group of patients showed lower values of SUV-E and SUV-D, a smaller tumor size, and a lower rate of lymphatic invasion or vascular invasion. It was particularly noteworthy that lymph node metastasis was not histopathologically confirmed in any of these patients. Univariate analysis identified the RI, SUV-E and SUV-D, besides age, tumor size, lymph node metastasis, and tumor differentiation grade as predictors of the RFS. On the other hand, multivariate analysis identified the RI and lymph node metastasis, but not the SUV-E and SUV-D, as independent predictors of the RFS.ConclusionsThis study demonstrated that DTP FDG-PET of the primary tumor in NSCLC can be useful to predict the RFS of the patients. In addition, this method may also be useful to predict the presence/absence of intrathoracic lymph node metastasis in these patients.

Evaluation of Dual Time Point Imaging 18F-FDG PET/CT in Differentiating Malignancy From Benign Gastric Disease.

To assess the clinical value of dual time point imaging (DTPI) fluorine-18fludeoxyglucose (18F-FDG) positron emission tomography (PET)/CT in differentiating malignancy and benign disease of patients with focally increased gastric uptake.Patients who present focally increased 18F-FDG uptake in gastric wall on conventional PET/CT imaging received delayed imaging. PET/CT scans were acquired at 1 and 2 hours (early and delayed imaging) after 18F-FDG injection. The maximum standardized uptake value (SUV) was calculated. The SUVmax of the early and delayed imaging acquisition were signed S1 and S2, respectively. The receiver operating characteristic curve (ROC) of the S1, S2, and the retention index (RI) were drawn to find the best cut-off point value for differential diagnosis. Sensitivity, specificity, Youden index, and the area under the curve (AUC) were calculated, respectively.From September 2010 to May 2015, 74 patients (56 male and 18 female; age of 57 ± 12 years; range, 32–86 years) referring for areas of focally increased uptake of 18F-FDG in gastric wall received delayed imaging. The S1 was 5.0 ± 1.4 (range, 1.9–11.3), and S2 was 5.9 ± 2.7 (range, 1.0–16.3). The SUVmax were increased in 52 patients in delayed imaging, with 85% (44/52 cases) appeared malignant; decreased in 20 patients, and 90% (18/20 cases) were benign; 2 patients of benign had not changed. The change of SUVmax between malignant and benign was significant difference (t = −5.785, P = 0.000).Taking the S1, S2, and RI higher than 4.6%, 5.1%, and 13% as positive diagnostic criteria, the sensitivity were 65.2%,87.0%, and 87.0%, respectively; the specificity were 64.3%, 82.1%, and 89.3%; the Youden index were 0.332, 0.693, and 0.770; AUC were 0.635 (95% confidence intervals (95% CI) 0.507–0.764), 0.873 (95% CI, 0.786–0.961), and 0.923 (95% CI, 0.854–0.992).DTPI is more precise to distinct malignant from benign gastric diseases compared with conventional imaging, and it is readily accessible.

Quantifying [18F]fluorodeoxyglucose uptake in the arterial wall: the effects of dual time-point imaging and partial volume effect correction

The human arterial wall is smaller than the spatial resolution of current positron emission tomographs. Therefore, partial volume effects should be considered when quantifying arterial wall (18)F-FDG uptake. We evaluated the impact of a novel method for partial volume effect (PVE) correction with contrast-enhanced CT (CECT) assistance on quantification of arterial wall (18)F-FDG uptake at different imaging time-points. Ten subjects were assessed by CECT imaging and dual time-point PET/CT imaging at approximately 60 and 180 min after (18)F-FDG administration. For both time-points, uptake of (18)F-FDG was determined in the aortic wall by calculating the blood pool-corrected maximum standardized uptake value (cSUVMAX) and cSUVMEAN. The PVE-corrected SUVMEAN (pvcSUVMEAN) was also calculated using (18)F-FDG PET/CT and CECT images. Finally, corresponding target-to-background ratios (TBR) were calculated. At 60 min, pvcSUVMEAN was on average 3.1 times greater than cSUVMAX (P < .0001) and 8.5 times greater than cSUVMEAN (P < .0001). At 180 min, pvcSUVMEAN was on average 2.6 times greater than cSUVMAX (P < .0001) and 6.6 times greater than cSUVMEAN (P < .0001). This study demonstrated that CECT-assisted PVE correction significantly influences quantification of arterial wall (18)F-FDG uptake. Therefore, partial volume effects should be considered when quantifying arterial wall (18)F-FDG uptake with PET.

Diagnostic value of 18F-FDG PET/CT in patients with pancreatic neoplasm

Objective To evaluate the diagnostic value of 18F-FDG PET/CT in patients with pancreatic neoplasm. Methods Fifty-three patients (36 males, 17 females; age:(60.3±8.9) years) who underwent 18F-FDG PET/CT examination for suspected pancreatic tumor were retrospectively analyzed. Thirty-two of them underwent dual-time point imaging. The characteristics of PET/CT images and serum CA19-9 were reviewed. Pathological results were used as a gold standard for evaluating the diagnostic value of PET/CT. Two-sample t test, paired t test and ROC curve analysis were used for data analysis. Results Thirty-nine patients were finally diagnosed with pancreatic cancer and the other fourteen patients with benign disease. With SUVmax cutoff value of 3.13, the sensitivity and specificity of single-time point 18F-FDG PET/CT for diagnosis of pancreatic cancer were 92.3%(36/39) and 9/14, respectively. The SUVmax was significant different between pancreatic cancer group and benign disease group (6.16±2.89 vs 3.37±1.58; t=4.46, P 0.05). With the SUVmax cutoff value of 3.3, the sensitivity, specificity and accuracy in the early scan were 87.0%(20/23), 6/9 and 81.2%(26/32), respectively. While with the SUVmax cutoff value of 3.0, the sensitivity, specificity and accuracy in the delayed scan were 95.7%(22/23), 5/9 and 84.4%(27/32), respectively. Conclusion 18F-FDG PET/CT is a useful tool in the differential diagnosis of benign from malignant pancreatic diseases. Key words: Pancreatic neoplasms; Tomography, emission-computed; Tomography, X-ray computed; Deoxyglucose

PET/CT Imaging of Tuberculosis with 68ga-Citrate

Objective: The impact of tuberculosis (TB) on mortality and morbidity is indisputable worldwide and even more so in countries with a high prevalence of Human Immunodeficiency Virus (HIV) co-infection. The development of a non-invasive diagnostic tool that is capable of early and accurate detection, staging and follow-up evaluation of tuberculosis is crucial in minimizing its devastating effects. We evaluated PET/CT imaging with a novel tracer, 68Ga-citrate,in this setting. Methods: Thirteen patients with tuberculosis were included in this prospective pilot study and were imaged with 68Gacitrate. A diagnosis of TB was reached with bacteriological or histopathology studies (n=8) or based on a combination of clinical data, biochemistry and imaging (n=5). PET images were acquired at 60 minutes (and 120 minutes where possible) and analyzed qualitatively (relative to the liver) and semi-quantitatively (using SUVmax and change in SUVmax). PET findings were also compared to that of CT. Results: All 13 patients demonstrated abnormal tracer accumulation in the lungs or extra-pulmonary or both. 68Ga-citrate accumulated in every lung lesion noted on CT in six cases (46%). In seven cases (54%) some of the lung lesions noted on CT were not 68Ga-citrate avid, which is suggestive of non-active tuberculosis lesions. Ten patients (77%) demonstrated extrapulmonary involvement, which included various lymph node groups, skeletal lesions, pleural-, splenicand gastro-intestinal tract involvement. More extra-pulmonary lesions were detected on PET compared to CT in eight cases (80%). The results of dual-time point imaging varied significantly amongst study participants. Conclusion: Pulmonary and extra-pulmonary tuberculosis lesions demonstrate 68Ga-citrate accumulation; with more extrapulmonary lesions detected on PET compared to CT. 68Ga-citrate PET may also provide a way of distinguishing active from inactive lesions for treatment response evaluation.

Standardization of dual time point [18F] 2-Deoxy-2-fluoro-D-glucose-positron emission tomography performed with different positron emission tomography scanners using partial volume correction

Standardization of dual time point [18F] 2-Deoxy-2-fluoro-D-glucose-positron emission tomography performed with different positron emission tomography scanners using partial volume correction