FDG-PET Imaging In Patients Research Articles

Imaging finding of renal masses associated with pathogenic variation in succinate dehydrogenase subunit B gene

PurposeSuccinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is a newly defined, rare subtype of renal cancer, associated with pathogenic variations in the Succinate Dehydrogenase Subunit B (SDHB) gene. Our aim is to investigate the imaging findings of SDHB-associated renal tumors, utilizing cross-sectional and FDG-PET imaging in patients with pathogenic variations in SDHB gene, to facilitate accurate tumor characterization. MethodsTwenty SDH-deficient tumors from 16 patients with pathogenic variations in SDHB gene were retrospectively evaluated using cross-sectional and FDG-PET imaging. Clinical findings such as demographics, family history, extra-renal findings and metastases were recorded. Tumor imaging characteristics on CT/MRI included were laterality, size, homogeneity, morphology, margins, internal content, T1/T2 signal intensity, enhancement features, and restricted diffusion. ResultsSixteen patients (median age 31 years, IQR 19–41, 8 males) were identified with 68.8 % of patients having a known family history of SDHB variation. 81.3 % of lesions were solitary and majority were solid (86.7 % on CT, 87.5 % on MRI) with well-defined margins in >62.5 % of lesions, without evidence of internal fat, calcifications, or vascular invasion. 100 % of lesions demonstrated restricted diffusion and avid enhancement, with degree >75 % for most lesions on CT and MRI. On FDG-PET, all renal masses showed increased radiotracer uptake. 43.8 % of patients demonstrated extra-renal manifestations and 43.8 % had distant metastasis. ConclusionSDHB-associated RCC is predominantly noted in young patients with no gender predilection. On imaging, SDH-deficient RCC are frequently unilateral, solitary, and solid with well-defined margins demonstrating avid enhancement with variability in enhancement pattern and showing restricted diffusion.

Low 18F-fluorodeoxyglucose dose positron emission tomography assisted by a deep-learning image-denoising technique in patients with lymphoma.

Patients with lymphoma receive multiple positron emission tomography/computed tomography (PET/CT) exams for monitoring of the therapeutic response. With PET imaging, a reduced level of injected fluorine-18 fluorodeoxyglucose ([18F]FDG) activity can be administered while maintaining the image quality. In this study, we investigated the efficacy of applying a deep learning (DL) denoising-technique on image quality and the quantification of metabolic parameters and Deauville score (DS) of a low [18F]FDG dose PET in patients with lymphoma. This study retrospectively enrolled 62 patients who underwent [18F]FDG PET scans. The low-dose (LD) data were simulated by taking a 50% duration of routine-dose (RD) PET list-mode data in the reconstruction, and a U-Net-based denoising neural network was applied to improve the images of LD PET. The visual image quality score (1 = undiagnostic, 5 = excellent) and DS were assessed in all patients by nuclear radiologists. The maximum, mean, and standard deviation (SD) of the standardized uptake value (SUV) in the liver and mediastinum were measured. In addition, lesions in some patients were segmented using a fixed threshold of 2.5, and their SUV, metabolic tumor volume (MTV), and tumor lesion glycolysis (TLG) were measured. The correlation coefficient and limits of agreement between the RD and LD group were analyzed. The visual image quality of the LD group was improved compared with the RD group. The DS was similar between the RD and LD group, and the negative (DS 1-3) and positive (DS 4-5) results remained unchanged. The correlation coefficients of SUV in the liver, mediastinum, and lesions were all >0.85. The mean differences of SUVmax and SUVmean between the RD and LD groups, respectively, were 0.22 [95% confidence interval (CI): -0.19 to 0.64] and 0.02 (95% CI: -0.17 to 0.20) in the liver, 0.13 (95% CI: -0.17 to 0.42) and 0.02 (95% CI: -0.12 to 0.16) in the mediastinum, and -0.75 (95% CI: -3.42 to 1.91), and -0.13 (95% CI: -0.57 to 0.31) in lesions. The mean differences in MTV and TLG were 0.85 (95% CI: -2.27 to 3.98) and 4.06 (95% CI: -20.53 to 28.64) between the RD and LD groups. The DL denoising technique enables accurate tumor assessment and quantification with LD [18F]FDG PET imaging in patients with lymphoma.

Matched FES and FDG PET imaging in patients with hormone receptor-positive, HER2+ advanced breast cancer.

1042 Background: The recently FDA approved 18F-Fluoroestradiol (FES) is a PET imaging tracer for characterizing disease in patients with ER+ breast cancer. As FES PET enters clinical practice it will be important to establish its utility in the full population of hormone-receptor positive patients, including those with HER2+ tumors. Historically the consensus around ER+/HER+ disease has been that these tumors are primarily driven by HER2, with therapies focused on targeting this pathway. Emerging research suggests that ER+ and HER2+ tumors represent a distinct phenotype, with bidirectional crosstalk between ER and HER2 pathways contributing to resistance to therapies targeting these critical pathways. Methods: Our cross-sectional database of patients with one or more FES scans stretches back to 1996. We selected all patients with HER2+ advanced breast cancer to determine whether ER is functional in the ER+/HER2+ subset. We examined paired FDG and FES scans and recorded SUVmax in matched lesions between the FDG and FES scans. We also looked at a subset of patients who underwent scans at more than one time-points and examined the clinical characteristics of these cases over time. Results: 36 patients with metastatic ER+, HER2+ breast cancer underwent concurrent FDG and FES PET scans between 1996 and 2013. 34 subjects (94%) were female; 32 (89%) were Caucasian, and 4 (11%) were Asian. Eight patients underwent serial scans. A total of 200 metastatic sites were recorded with the majority (67%) being bony lesions. No difference in quantitative FES avidity was observed between soft tissue and osseous sites. Six patients (16%) had negative FES scans despite displaying FDG avid lesions; three patients had at least one negative FES scan on serial scans, and two demonstrated FES-avid lesions with no FDG activity. Average FES SUVmax for positive scans was 3.5, with a range of 0.8 to 10.7. Among eight patients with multiple scans, half had 2 scans, three had 3 scans, and one had 4 scans. In 7/8 patients (88%) FES avidity increased over time even as FDG decreased or stayed stable with treatment; in one, both FES and FDG decreased on follow up scan. Conclusions: In a cohort of ER+, HER2+ patients undergoing FDG and FES PET scans, robust concordance between FDG and FES uptake was observed. FES avidity increased in patients with multiple scans, suggesting that the ER pathway remained active during treatment. The strong FES positivity in many HER2+ patients in this cohort suggests that FES PET could be used to guide patient selection for trials examining deescalated regimens employing a non-chemotherapy partner for HER2-directed therapy or emphasizing more ER-directed therapies such as CDK4/6 inhibitors, which are not currently approved in this population. With the ongoing development of HER2- PET imaging, combination scans could carry the potential for discrimination between sites, possibly serving as a tool to guide biopsy.

The Detection of Invisible Abnormal Metabolism in the FDG-PET Images of Patients With Anti-LGI1 Encephalitis by Machine Learning.

ObjectiveThis study aims to detect the invisible metabolic abnormality in PET images of patients with anti-leucine-rich glioma-inactivated 1 (LGI1) encephalitis using a multivariate cross-classification method.MethodsParticipants were divided into two groups, namely, the training cohort and the testing cohort. The training cohort included 17 healthy participants and 17 patients with anti-LGI1 encephalitis whose metabolic abnormality was able to be visibly detected in both the medial temporal lobe and the basal ganglia in their PET images [completely detectable (CD) patients]. The testing cohort included another 16 healthy participants and 16 patients with anti-LGI1 encephalitis whose metabolic abnormality was not able to be visibly detected in the medial temporal lobe and the basal ganglia in their PET images [non-completely detectable (non-CD) patients]. Independent component analysis (ICA) was used to extract features and reduce dimensions. A logistic regression model was constructed to identify the non-CD patients.ResultsFor the testing cohort, the accuracy of classification was 90.63% with 13 out of 16 non-CD patients identified and all healthy participants distinguished from non-CD patients. The patterns of PET signal changes resulting from metabolic abnormalities related to anti-LGI1 encephalitis were similar for CD patients and non-CD patients.ConclusionThis study demonstrated that multivariate cross-classification combined with ICA could improve, to some degree, the detection of invisible abnormal metabolism in the PET images of patients with anti-LGI1 encephalitis. More importantly, the invisible metabolic abnormality in the PET images of non-CD patients showed patterns that were similar to those seen in CD patients.

Accuracy of 18F-FDG PET/CT in patients with the suspicion of cardiac implantable electronic device infections

BackgroundUtility of 18F-FDG PET/CT in diagnosing infective endocarditis (IE) associated with cardiac implantable electronic devices (CIEDs) is not well established. Current ESC guidelines recommend the use of FDG-PET imaging in patients with CIEDs and positive blood cultures, but the number of studies evaluating the diagnostic performance of FDG-PET imaging in these patients remain limited. Our objective was to assess the diagnostic yield of 18F-FDG PET/CT in patients with suspected CIED infections, differentiating between pocket infection (PI) and lead infection (CIED-IE). Methods and ResultsFrom 2013 to 2018, all patients (n = 63) admitted to a hospital with suspected CIED infection were prospectively recruited, undergoing a diagnostic work-up including a PET/CT. Explanted devices and material from the pocket were cultured. 14 cases corresponded to isolated PI and 13 were categorized as CIED-IE. Considering radionuclide uptake in the intracardiac portion of the lead, sensitivity and specificity of PET/CT for CIED-IE were 38.5% and 98.0%, respectively. Positive (19.2) and negative (0.6) likelihood ratio values, suggest that a positive PET/CT is much more probable to correspond to a patient with CIED-IE, whereas it is not possible to exclude this diagnosis when negative. For PI, sensitivity and specificity were 72.2% and 95.6%, respectively. ConclusionsThe yield of 18F-FDG PET/CT for suspected CIED infections differs depending on the site of infection. Due to very high specificity but poor sensitivity, negative studies must be interpreted with caution if the suspicion of CIED-IE is high.

A physics-guided modular deep-learning based automated framework for tumor segmentation in PET

An important need exists for reliable positron emission tomography (PET) tumor-segmentation methods for tasks such as PET-based radiation-therapy planning and reliable quantification of volumetric and radiomic features. To address this need, we propose an automated physics-guided deep-learning-based three-module framework to segment PET images on a per-slice basis. The framework is designed to help address the challenges of limited spatial resolution and lack of clinical training data with known ground-truth tumor boundaries in PET. The first module generates PET images containing highly realistic tumors with known ground-truth using a new stochastic and physics-based approach, addressing lack of training data. The second module trains a modified U-net using these images, helping it learn the tumor-segmentation task. The third module fine-tunes this network using a small-sized clinical dataset with radiologist-defined delineations as surrogate ground-truth, helping the framework learn features potentially missed in simulated tumors. The framework was evaluated in the context of segmenting primary tumors in 18F-fluorodeoxyglucose (FDG)-PET images of patients with lung cancer. The framework’s accuracy, generalizability to different scanners, sensitivity to partial volume effects (PVEs) and efficacy in reducing the number of training images were quantitatively evaluated using Dice similarity coefficient (DSC) and several other metrics. The framework yielded reliable performance in both simulated (DSC: 0.87 (95% confidence interval (CI): 0.86, 0.88)) and patient images (DSC: 0.73 (95% CI: 0.71, 0.76)), outperformed several widely used semi-automated approaches, accurately segmented relatively small tumors (smallest segmented cross-section was 1.83 cm2), generalized across five PET scanners (DSC: 0.74 (95% CI: 0.71, 0.76)), was relatively unaffected by PVEs, and required low training data (training with data from even 30 patients yielded DSC of 0.70 (95% CI: 0.68, 0.71)). In conclusion, the proposed automated physics-guided deep-learning-based PET-segmentation framework yielded reliable performance in delineating tumors in FDG-PET images of patients with lung cancer.

Decreased Glucose Utilization Contributes to Memory Impairment in Patients with Glufosinate Ammonium Intoxication.

The symptoms of glufosinate ammonium (GLA) intoxication include gastrointestinal and neurologic symptoms, respiratory failure, and cardiovascular instability. Among these, neurologic symptoms including loss of consciousness, memory impairment, and seizure are characteristic of GLA poisoning. However, the mechanism of brain injury by GLA poisoning is still poorly understood. We investigated nine patients who had performed an F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) scan because of memory impairment caused by GLA ingestion. FDG-PET images of patients with GLA intoxication were compared with 24 age- and sex-matched healthy controls to evaluate whether the patients had abnormal patterns of glucose metabolism in the brain. Decreased glucose metabolism was observed in the inferior frontal and temporal lobes of these patients with GLA intoxication when compared with 24 age- and sex-matched healthy controls. Three patients performed follow-up FDG-PET scans. However, it was shown that the results of the follow-up FDG-PET scans were determined to be inconclusive. Our study showed that memory impairment induced by GLA intoxication was associated with glucose hypometabolism in the inferior frontal and temporal lobes in the brain.

Prognostic value of positron emission tomography and preoperative CA19-9 in patients treated on a prospective phase II trial of neoadjuvant therapy and surgery.

e15766 Background: The role of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in the staging of pancreatic cancer (PC) has not been well defined. We evaluated the prognostic value of FDG-PET imaging in patients with localized PC enrolled in a prospective trial of personalized molecular-directed neoadjuvant therapy. Methods: Pretreatment FDG-PET was classified as high or low based on a standardized uptake value (SUV) cutpoint of 7.2 (population median). Carbohydrate antigen 19-9 (CA19-9) was measured after the completion of neoadjuvant therapy (preoperative) and classified as normal (≤35 U/mL) or elevated. Results: Pretreatment FDG-PET imaging was performed on 100 consecutive patients; SUV was high in 50 and low in 50. Preoperative CA19-9 values were available in 99 of 100 patients; 54 (55%) were elevated and 45 (45%) were normal. Of the 100 patients, 81 completed neoadjuvant therapy and surgery, and 19 were not resected. Among the 81 resected patients, SUV was high in 37 (46%) and low in 44 (54%); preoperative CA19-9 was elevated in 40 (49%) and normal in 41 (51%). The median overall survival (OS) for all patients was 39 months; 45 months for who completed all intended neoadjuvant therapy and surgery and 9 months for patients who were not resected. The median OS for patients with normal CA19-9/low SUV, normal CA19-9/high SUV, elevated CA19-9/low SUV, and elevated CA19-9/high SUV were not reached, 35, 24, and 18 months, respectively (p = 0.0001). Conclusions: Pretreatment FDG-PET avidity and preoperative CA19-9 are important prognostic markers and may be used to estimate the anticipated benefit of surgery; information of immediate clinical significance for both treatment sequencing and the application of surgery to patients who are frequently of advanced age or high-risk.

Accuracy of Fluorodeoxyglucose-PET Imaging for Differentiating Benign From Malignant Pleural Effusions: A Meta-analysis

BACKGROUND The role of fluorodeoxyglucose (FDG)-PET imaging for diagnosing malignant pleural effusions is not well defined. The aim of this study was to summarize the evidence for its use in ruling in or out the malignant origin of a pleural effusion or thickening. METHODS A meta-analysis was conducted of diagnostic accuracy studies published in the Cochrane Library, PubMed, and Embase (inception to June 2013) without language restrictions. Two investigators selected studies that had evaluated the performance of FDG-PET imaging in patients with pleural effusions or thickening, using pleural cytopathology or histopathology as the reference standard for malignancy. Subgroup analyses were conducted according to FDG-PET imaging interpretation (qualitative or semiquantitative), PET imaging equipment (PET vs integrated PET-CT imaging), and/or target population (known lung cancer or malignant pleural mesothelioma). Study quality was assessed using Quality Assessment of Diagnostic Accuracy Studies-2. We used a bivariate random-effects model for the analysis and pooling of diagnostic performance measures across studies. RESULTS Fourteen non-high risk of bias studies, comprising 407 patients with malignant and 232 with benign pleural conditions, met the inclusion criteria. Semiquantitative PET imaging readings had a significantly lower sensitivity for diagnosing malignant effusions than visual assessments (82% vs 91%; P = .026). The pooled test characteristics of integrated PET-CT imaging systems using semiquantitative interpretations for identifying malignant effusions were: sensitivity, 81%; specificity, 74%; positive likelihood ratio (LR), 3.22; negative LR, 0.26; and area under the curve, 0.838. Resultant data were heterogeneous, and spectrum bias should be considered when appraising FDG-PET imaging operating characteristics. CONCLUSIONS The moderate accuracy of PET-CT imaging using semiquantitative readings precludes its routine recommendation for discriminating malignant from benign pleural effusions. The role of fluorodeoxyglucose (FDG)-PET imaging for diagnosing malignant pleural effusions is not well defined. The aim of this study was to summarize the evidence for its use in ruling in or out the malignant origin of a pleural effusion or thickening. A meta-analysis was conducted of diagnostic accuracy studies published in the Cochrane Library, PubMed, and Embase (inception to June 2013) without language restrictions. Two investigators selected studies that had evaluated the performance of FDG-PET imaging in patients with pleural effusions or thickening, using pleural cytopathology or histopathology as the reference standard for malignancy. Subgroup analyses were conducted according to FDG-PET imaging interpretation (qualitative or semiquantitative), PET imaging equipment (PET vs integrated PET-CT imaging), and/or target population (known lung cancer or malignant pleural mesothelioma). Study quality was assessed using Quality Assessment of Diagnostic Accuracy Studies-2. We used a bivariate random-effects model for the analysis and pooling of diagnostic performance measures across studies. Fourteen non-high risk of bias studies, comprising 407 patients with malignant and 232 with benign pleural conditions, met the inclusion criteria. Semiquantitative PET imaging readings had a significantly lower sensitivity for diagnosing malignant effusions than visual assessments (82% vs 91%; P = .026). The pooled test characteristics of integrated PET-CT imaging systems using semiquantitative interpretations for identifying malignant effusions were: sensitivity, 81%; specificity, 74%; positive likelihood ratio (LR), 3.22; negative LR, 0.26; and area under the curve, 0.838. Resultant data were heterogeneous, and spectrum bias should be considered when appraising FDG-PET imaging operating characteristics. The moderate accuracy of PET-CT imaging using semiquantitative readings precludes its routine recommendation for discriminating malignant from benign pleural effusions.

Prognostic Value of FDG PET Imaging in Patients with Laryngeal Cancer

Background and PurposeTo investigate the prognostic value of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in patients with laryngeal cancer.Materials and MethodsThe study included 51 patients of whom 30 underwent definitive radiotherapy with or without chemotherapy and 21 underwent radical surgery with or without adjuvant chemoradiation therapy. FDG uptake by both the primary lesion and the neck node was measured using the maximum standardized uptake value (SUVmax). The effects of clinicopathological factors including primary tumor SUVmax and nodal SUVmax on progression-free survival, local control, nodal progression-free survival, and distant metastasis-free survival were evaluated using the log-rank test and Cox method.ResultsThe median duration of follow-up was 48.6 months (range 8 to 82.1 months). Univariate analysis showed that nodal SUVmax, N status, and tumor TNM stage were significantly associated with recurrence, whereas primary tumor SUVmax, age, treatment strategy and T status were not. Multivariate analysis demonstrated that only the nodal SUVmax was a significantly unfavorable factor for progression-free survival (p = 0.029, hazard ratio 0.54, 95% CI 0.38-0.87) and nodal progression-free survival (p = 0.023, hazard ratio 0.51, 95% CI 0.34-0.81). ROC curve analysis and log-rank test showed that patients with a high nodal SUVmax (≧4) had a significantly lower progression-free survival rate than those with a low SUVmax (<4; p<0.0001).ConclusionsThe pretreatment SUVmax of nodal disease in patients with laryngeal cancer is prognostic for recurrence.

FDG-PET Imaging in Patients With Pulmonary Carcinoid Tumor

This study aimed to assess the imaging findings in patients with pathologically proven carcinoid tumors and determine if SUV can help to differentiate typical from atypical (more aggressive) pulmonary carcinoid tumors. A retrospective review of patients with a biopsy-proven diagnosis of a pulmonary carcinoid tumor at our institution from 2002 to 2010 that had a preoperative PET scan was performed after institutional review board approval was obtained. PET results, including SUV uptake and location, were recorded as well as all data from pathology reports. Carcinoids were considered to be more aggressive if they showed pathological diagnosis consistent with atypical carcinoid, lymph node invasion, poor histological grade (poorly differentiated), or evidence of systemic metastases. Atypical carcinoid pathology consisted of focal necrosis or a higher mitotic index (2-10 per square millimeter) with features of nests, trabeculae, pleomorphic cells, or dense hyperchromasia. SUV uptake was then evaluated and compared between the typical and atypical carcinoid groups using nonparametric statistical methods. We identified 29 patients from 2002 to 2010 at our institution with a pathological diagnosis of pulmonary carcinoid. Twenty-three were histopathologically typical, and the other 6 showed atypia. Mean (SD) nodule size was 2.4 (1.3) cm in the typical group versus 5.0 (3.2) cm in the atypical group (P = 0.065). Mean (SD) SUV uptake in the typical carcinoid group was 2.7 (1.6) and in the atypical group the SUV was 8.1 (4.1) (P < 0.01). A cutoff SUV of 6 or greater is predictive of malignancy (odds ratio, 23.6; P < 0.01), as well as a nodule size of 3.5 cm or greater (odds ratio, 5.1; P = 0.024). Preoperative PET imaging result is frequently positive in carcinoid tumors, and the biological behavior correlates well with SUV; however, size is not as strong of a predictor of malignancy. Size of 3.5 cm or greater and SUV of 6 or greater have a predictive value of greater than 95% for malignant histology.

Establishment of a UK-wide network to facilitate the acquisition of quality assured FDG–PET data for clinical trials in lymphoma

BackgroundMulticentre trials are required to determine how [fluorine-18]-2-fluoro-2-deoxy-D-glucose–positron emission tomography imaging can guide cancer treatment. Consistency in quality control (QC), scan acquisition and reporting is mandatory for high-quality results, which are comparable across sites. MethodsA national positron emission tomography (PET) clinical trials network (CTN) has been set up with a ‘core laboratory’ to coordinate QC and interpret scans. The CTN is involved in trials in Hodgkin’s lymphoma [Randomised Phase III trial to determine the role of FDG-PET Imaging in Clinical Stages IA/IIA Hodgkin's Disease (RAPID) and Randomised Phase III trial to assess response adapted therapy using FDG-PET imaging in patients with newly diagnosed, advanced Hodgkin lymphoma (RATHL)] and diffuse large B-cell lymphoma [Blinded evaluation of prognostic value of FDG-PET after 2 cycles of chemotherapy in diffuse large B-cell Non-Hodgkins Lymphoma, a sub-study of the R-CHOP-21 vs R-CHOP-14 trial (R-CHOP PET substudy)]. Approval to join requires scanner validation and agreement to follow a standard QC protocol. Scans are transferred to the core laboratory and reported centrally according to predetermined criteria. ResultsThe qualification procedure was carried out on 15 scanners. All scanners were able to demonstrate the necessary quantitative accuracy, and following modification of image reconstruction where necessary, scanners demonstrated comparable recovery coefficients (RCs) indicating similar performance. The average RC (±1 standard deviation) was 0.56±0.095 for the 13-mm sphere. Reports from 444 of 473 (94%) patients in RAPID and 67 of 73 (92%) patients in RATHL were available for randomisation of therapy. ConclusionsThe CTN has enabled consistent quality assured PET results to be obtained from multiple centres in time for clinical decision making. The results of trials will be significantly strengthened by this system.

Response to neoadjuvant chemotherapy as measured by PET predicts outcome after liver resection for colorectal metastases

3056 Background: Patients with hepatic colorectal metastases are often treated with neoadjuvant chemotherapy prior to liver resection. FDG PET is a standard imaging modality for such patients. We have shown the amount of FDG uptake in liver metastases is reduced by recent chemotherapy (chemo) administration and this is associated with a reduction in FDG uptake mediated by a reduction in hexokinase activity. We sought to determine if the amount of FDG uptake in the hepatic colorectal metastasis post chemo correlates with survival and to compare the prognostic significance of this single biologic scan to standard clinical predictors of outcome. Methods: A group of 149 patients enrolled in a prospective clinical trial examining the efficacy of FDG PET imaging in patients undergoing hepatic resection of colorectal cancer metastases to the liver formed the dataset. The maximal SUV within the liver was recorded for each patient, and the median of those maximums was determined across the patient group. Patients were then stratified by the median SUV, by the presence or absence of any chemo within 6 months of PET and by the clinical risk score (CRS) (a standard score for prognosis based on five clinical parameter (nodal status of primary, disease-free interval before liver metastases, size of largest liver tumor, number of tumors, and CEA). Multivariate analysis (MVA) and hazard ratios of death (HRD) were assessed. Results: The median of maximal SUVs was 7.9. In MVA in the patients without recent chemo, the CRS≥3 was an excellent predictor of survival (HRD=2.53; p=0.008), while SUV&gt;8 was not (HRD=1.02; p=0.96). Conversely, in patients who had chemo within 6 months, SUV&gt;8 (HRD 3.34; p=0.03) was a much superior predictor of outcome than CRS≥3 (HRD=1.25; p=0.57). Conclusions: In those patients without recent chemo CRS is the best predictor of survival confirming the utility of this scoring system, In those patients who had had chemo within 6 months of PET prior to surgery PET SUV was the best predictor of survival. No significant financial relationships to disclose.

F-18 FDG-PET imaging and correlation with CT in staging and follow-up of pediatric lymphomas

We hypothesized that F-18 FDG-PET could be a useful, functional imaging modality for assessing the initial staging, response to therapy and follow-up of children diagnosed with lymphoma. To assess the role of whole-body F-18 FDG-PET imaging in patients with lymphoma as an initial staging modality and to measure its predictive value for monitoring the response to therapy and disease recurrence compared to CT and clinical follow-up studies. As part of their routine clinical care, 24 patients with histologically proven lymphoma (18 Hodgkin disease and 6 non-Hodgkin lymphoma) underwent an F-18 FDG-PET and a CT scan. A total of 28 studies were performed and the entire set of scans retrospectively reviewed. Seven studies were performed for initial staging, 12 for monitoring therapy response and 9 for detecting recurrence. Initial diagnosis was confirmed by histopathology while the gold standard at follow-up was established by clinical follow-up, additional imaging modalities and/or biopsy. F-18 FDG-PET was visually compared to CT on a lesion-by-lesion basis. Fifteen anatomic regions (seven nodal and eight extranodal) were analyzed. Of the 414 regions analyzed, PET and CT were concordant in 366 (positive in 16 and negative in 350). Discordance was found in 48 regions. Overall sensitivities, specificities, and positive and negative predictive values were 78%, 98%, 94% and 90% for F-18 FDG-PET and 79%, 88%, 90% and 46% for CT, respectively. F-18 FDG-PET imaging is a useful technique for the staging and follow-up of pediatric patients with lymphoma.

Fluorodeoxyglucose positron emission tomography studies in the diagnosis and staging of clinically advanced prostate cancer.

To determine the value of 18F-fluoro-2-deoxyglucose (FDG) positron-emission tomography (PET) studies in evaluating patients with advanced prostate cancer. FDG-PET scans were taken in 30 patients with advanced prostate cancer 1 h after an injection with 555 MBq of FDG. Patients were scanned from the base of the skull to the inguinal region (including the pelvis). They were also assessed by computed tomography (CT) of the abdomen and pelvis, and bone scintigraphy, to evaluate them for metastases. Thirteen patients had locally extensive prostate cancer and 17 had metastatic disease. Twenty of the 30 patients were positive for radioisotope uptake in the prostate or extraprostatically. The patients with PET-detected prostate cancer were untreated (seven), treated hormonally while they had rising PSA levels (eight), or treated hormonally with a detectable but stable PSA (five). The remaining 10 patients were negative for FDG uptake in the prostate or any metastatic sites; these 10 patients were receiving hormone therapy, with undetectable PSA levels. FDG-PET imaging is not a useful test in evaluating advanced prostate cancer in patients being treated and who have an undetectable PSA level. Staging of advanced prostate cancer may be enhanced by FDG-PET imaging in patients who are untreated, who have had an incomplete response to therapy, or who have a rising PSA level despite treatment.

Positron emission tomography in the management of lymphomas.

Positron emission tomography is a functional imaging modality that capitalizes on biochemical changes within tumour cells to localize these changes within the body. As a functional imaging tool, unlike an anatomical imaging tool such as CT, it does not require enlargement of lymph nodes affected by disease but does require sufficient numbers of tumour cells to be present with altered biochemical function to visualize these disease sites. These changes are most commonly monitored using a glucose mimic fluorodeoxyglucose which is not only taken up into tumour cells but is trapped within these cells owing to alterations of the hexokinase and dephosphorylase enzymes. This review examines the current role of FDG PET imaging in patients with Hodgkins and Non-Hodgkins lymphoma and also speculates on future roles for this imaging modality.

Attenuation-Correction Induced Artifact in F-18 FDG PET Imaging Following Total Knee Replacement

Purpose: The clinical use of PET FDG in the work-up of patients with bone and soft tissue malignant tumors is rapidly increasing. The recognition of any source of artifact, therefore, is important to avoid interpretation pitfalls. Procedures: Two patients with complete knee joint replacement by metallic prosthesis in the course of their treatment for malignant bone and soft tissue sarcoma were evaluated by PET F-18 FDG imaging using a dual head coincidence gamma camera. Results: Both studies demonstrated in the attenuation-corrected images intense increase activity at the joint space between the metallic prosthetic surfaces at the level of the knee joint. No uptake, however, was noted in the same location on the non-attenuation-corrected images. Subsequent bone and thallium-201 scans confirmed the absence of tumor recurrence in the first patient. The second patient had multiple follow up F-18 FDG scans over a period of 16 months that show no changes from the baseline study. Conclusion: In the F-18 FDG PET images of patients with total knee metallic prosthesis, an intense activity tends to be seen in the joint space, only in the attenuation-corrected images. Such pattern of uptake is considered artifactual and should always be verified in the non-attenuated images.