Accuracy of 18F-FDG PET/CT in detection and restaging of recurrent ovarian cancer

Purpose

To estimate the accuracy of 18FDG PET/CT in detection of recurrent cancer ovary and to describe the localization of metastases for restaging.

Performance of integrated FDG-PET/contrast-enhanced CT in the staging and restaging of colorectal cancer: Comparison with PET and enhanced CT

Objective

The purpose of this study was to assess the diagnostic value of PET/CT as a one step examination in patients with colorectal cancer. Therefore we proved whether diagnostic PET/CT adds information over PET or contrast-enhanced CT alone for staging or restaging of patients with colorectal cancer.

Methods

Seventy-three patients (46 males and 27 females; age range: 50-81 years; mean age: 67 years) with known colorectal cancer underwent 18F-FDG-PET/CT for staging or restaging.

Results

Of the 73 patients 26 patients underwent PET/CT for staging and 47 for restaging. 266 metastases could be detected in 60 patients. Contrast-enhanced PET/CT had a lesion-based sensitivity of 100%, contrast-enhanced CT of 91% and PET of 85%. PET/CT identified 2 lesions as false positive. PET/CT could also reach a patient-based sensitivity of 100%, which was superior to contrast-enhanced CT and PET.

Conclusion

Our study clearly demonstrated the added value of contrast-enhanced PET/CT in staging and restaging patients with colorectal cancer over CT and PET alone.     

The Clinical Usefulness of 18F-FDG PET/CT in Patients with Systemic Autoimmune Disease

Purpose

Individuals with systemic autoimmune disease have an increased susceptibility to both inflammation and malignancy. The aim of this study was to evaluate the clinical usefulness of ¹⁸F-FDG PET/CT in patients with systemic autoimmune disease.

Methods

Forty patients diagnosed with systemic autoimmune disease were enrolled. Diagnostic accuracy of FDG PET/CT for detecting malignancy was assessed. FDG PET/CT findings, including maximum standardized uptake (SUVmax) of lymphadenopathy (LAP), liver, bone marrow, spleen, joint and muscles, were considered for the characterization of LAPs.

Results

FDG PET/CT could detect metabolically activated lesions in 36 out of 40 patients (90%) including inflammatory lesions in 28 out of 32 patients (88%). The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of FDG PET/CT for the detection of malignancy were 100, 67, 70, 25, and 100%, respectively. Multiple LAPs were found in 25 of 40 patients (63%), and comprised three malignancies, four cases of tuberculosis, and 18 reactive changes. A SUVmax ratio of bone marrow to liver below 0.78 could distinguish malignancy from tuberculosis + reactive change (AUC = 1.000, sensitivity: 100%, specificity: 100%). The SUVmax ratio of spleen to liver in the reactive group was also significantly higher than that in the malignancy group (P = 0.014). SUVmax of LAP in the TB group was significantly higher than that in the reactive group (P = 0.040).

Conclusions

PET/CT is useful in detecting and differentiating inflammation and malignancy in patients with systemic autoimmune disease. Frequent false-positive interpretations can be minimized by consideration of FDG uptake in bone marrow and spleen.     

Dual-time-point FDG PET/CT imaging in prosthetic heart valve endocarditis

Purpose

FDG PET/CT has been of increasing interest in the diagnostic workup of prosthetic heart valve endocarditis (PVE). Some reports advocate later imaging time points to improve the diagnostic accuracy for PVE. In this study, we compared standard and late FDG PET/CT images in patients with a clinical suspicion of PVE.

Materials and Methods

Fourteen scans in 13 patients referred for FDG PET/CT for suspicion of PVE performed at standard (60 min post injection) and late (150 min post injection) time points were scored based on visual interpretation and semi-quantitatively with SUVmax and target-to-background ratio (TBR, defined as [SUVmax valve/SUVmean blood pool]). Final diagnosis was based on surgical findings in all cases of infection (n = 6) and unremarkable follow-up in all others (n = 8).

Results

Late images were more prone to false positive interpretation for both visual and semi-quantitative analyses. Visual analysis of the standard images yielded 1 false negative and 1 false positive result. On the late images, no scans were false negative but 5 scans were false positive.

Conclusion

Late FDG PET/CT imaging for PVE seems prone to false positive results. Therefore, late imaging should be interpreted with caution.

     

Role of FDG-PET and PET/CT in the diagnosis and management of vasculitis

Purpose

to investigate the role of FDG-PET and PET/CT in the evaluation of vasculitis.

Materials and methods

a systematic revision of the papers published in PubMed/Medline until December 2009 was done.

Results

FDG-PET and PET/CT have been proven to be valuable in the diagnosis of large-vessel vasculitis, especially giant cells arteritis with sensitivity values ranging 77% to 92%, and specificity values ranging 89% to 100%. In particular, FDG-PET/CT has demonstrated the potential to non-invasively diagnose the onset of the vasculitis earlier than traditional anatomical imaging techniques, thus enabling prompt treatment. False positive results mainly occur in the differential diagnosis between vasculitis and atherosclerotic vessels in elderly patients. Another area where FDG-PET/CT is gaining wider acceptance is in monitoring response to therapy; it can reliably detect the earliest changes of disease improvement post-therapy, and persistent activity is an indicator of non-responders to therapy. A few data have been reported about medium/small vessel vasculitis.

Discussion

FDG-PET and PET/CT have proven utility: (a) in the initial diagnosis of patients suspected of having vasculitis particularly in those who present with non-specific symptoms; (b) in the identification of areas of increased FDG uptake in which a biopsy should be done for obtaining a diagnosis; (c) in evaluating the extent of the disease; (d) in assessing response to treatment.     

Bone metastasis in patients with non-small cell lung cancer: The diagnostic role of F-18 FDG PET/CT

Purpose

To evaluate the performance of F-18 FDG PET/CT in the detection of bone metastasis in non-small cell lung cancer (NSCLC) patients.

Materials and methods

Three hundred and sixty-two consecutive NSCLC patients who underwent F-18 FDG PET/CT scanning were retrospectively analyzed. Each image of PET/CT, combined CT, and PET was performed at 10 separate areas and interpreted blindly and separately. The sensitivity, specificity and accuracy of F-18 FDG PET/CT, combined CT and F-18 FDG PET were calculated and the results were statistically analyzed.

Results

Bone metastasis was confirmed in 82 patients with 331 positive segments based on the image findings and clinical follow-up. On patient-based analysis, the sensitivity of F-18 FDG PET/CT (93.9%) was significantly higher than those of combined CT (74.4%) and F-18 FDG PET (84.1%), respectively (p < 0.05). The overall specificity and accuracy of combined CT, F-18 FDG PET, and F-18 FDG PET/CT were 90.7%, 93.2%, 98.9% and 87.0%, 91.2%, and 97.8%, respectively (compared with PET/CT, p < 0.05). On segment-based analysis, the sensitivity of the three modalities were 79.5%, 94.3%, and 98.8%, respectively (compared with PET/CT, p < 0.05). The overall specificity and accuracy of the three modalities were 87.9%, 89.2%, 98.6% and 84.5%, 91.2%, 98.7%, respectively (compared with PET/CT, p < 0.05).

Conclusion

F-18 FDG PET/CT is superior to F-18 FDG PET or combined CT in detecting bone metastasis of NSCLC patients because of the complementation of CT and PET. It is worth noting that the added value of F-18 FDG PET/CT may beneficially impact the clinical management of NSCLC.     

PET/CT in initial staging and therapy response assessment of early mediastinal lymphoma

Objective

To detect accuracy of PET/CT in the initial staging, response after the first line and end of treatment in early mediastinal lymphoma patients compared to contrast CT.

Materials and methods

We studied 50 patients with pathologically proven lymphoma with a mean age = 27.5. All patients were at early stage. All patients performed CT and PET/CT for initial staging, after the first course of chemotherapy (after 4–6 weeks) and at the end of treatment (after 2–4 months).

Results

PET/CT upstaged 5 cases. At first line of treatment, PET/CT and CECT were agreeable in 32% of cases. PET/CT showed 100% sensitivity, 96.7% specificity, 95% positive predictive value and 100% negative predictive value. At the end of treatment both methods showed a 46% agreement. PET/CT was statistically significant in the follow up of hilar and axillary lymph nodes. PET/CT showed 100% sensitivity and specificity; compared to 62.5% sensitivity and 97.6% specificity for CECT in detection of extra-nodal disease sites.

Conclusion

PET/CT proved higher sensitivity and specificity over CECT. The major strength of PET/CT over CECT was its higher ability for detection of extra-nodal sites of lymphoma and excluding active disease in residual nodal mass lesions on follow up.     

FDG PET/CT and Mediastinal Nodal Metastasis Detection in Stage T1 Non-Small Cell Lung Cancer: Prognostic Implications

Objective

We aimed to compare the prognoses of patients with pathologically true negative (P-TN) N2 and PET/CT false negative (FN) results in stage T1 non-small cell lung cancer (NSCLC).

Materials and Methods

Our institutional review board approved this retrospective study with a waiver of informed consent. The study included 184 patients (124 men and 60 women; mean age, 59 years) with stage T1 NSCLC who underwent an integrated PET/CT and surgery. After estimating the efficacy of PET/CT for detecting N2 disease, we determined and compared disease-free survival (DFS) rates in three groups (P-TN [n = 161], PET/CT FN [n = 12], and PET/CT true positive [TP, n = 11]) using the Kaplan-Meier analysis and log-rank test.

Results

Pathologic N2 disease was observed in 23 (12%) patients. PET/CT had an N2 disease detection sensitivity of 48% (11 of 23 patients), a specificity of 95% (153 of 161), and an accuracy of 89% (164 of 184). The 3-year DFS rate in the PET/CT FN group (31%, 95% confidence interval [CI]; 13.6-48.0%) was similar to that of the TP group (16%, 95% CI; 1.7-29.5%) (p = 0.649), but both groups had significantly shorter DFS rates than the P-TN group (77%, 95% CI; 72.0-81.2%) (p < 0.001).

Conclusion

The PET/CT shows a high specificity, but low sensitivity for detecting N2 disease in stage T1 NSCLC. Patients with PET/CT FN N2 disease have survival rates similar to PET/CT TP N2 disease patients, which are both substantially shorter than the survival rate of P-TN patients.     

Thin-section CT of the mediastinum in preoperative N-staging of non-small cell lung cancer: Comparison with FDG PET

Purpose

To compare diagnostic capability of preoperative N-staging of lung cancer between thin-section CT of the mediastinum and FDG PET, and 5 mm slice thickness CT.

Materials and methods

The subjects were 34 patients with lung carcinoma who were examined by both CT and PET, and subsequently underwent surgery between May 2005 and January 2007. CT was carried out with a 16 detector row helical CT scanner. The raw data were reconstructed into 5 mm slice thickness and 1 mm slice thickness (thin-section CT). A total of 251 lymph node stations were retrospectively assessed for the presence of lymph node metastasis with thin-section CT, 5 mm CT and PET. In the interpretations of thin-section CT and 5 mm CT, we employed multi-criteria as follows: nodular calcification and intranodal fat as benign criteria, and short-axis diameter more than 10 mm (size criterion), focal low density other than fat, surrounding fat infiltration and convex margin in hilar lymph nodes, as malignant criteria. On PET, maximum standardized uptake value (SUVmax) of 2.5 or more was used as the criterion of malignancy. Sensitivity and specificity were compared between these examinations using McNemar test.

Results

Sensitivities and specificities of thin-section CT, 5 mm CT and PET were 25%, 25%, 25%, and 97%, 94%, 98%, respectively. The statistical analysis revealed that the specificity of 5 mm CT was significantly lower than those of thin-section CT (p = 0.039) and PET (p = 0.006), while no difference was present between thin-section CT and PET.

Conclusion

Thin-section CT of the mediastinum using multiple criteria was comparable to PET in preoperative N-staging of lung cancer.     

FDG-PET/CT in advanced ovarian cancer staging: Value and pitfalls in detecting lesions in different abdominal and pelvic quadrants compared with laparoscopy

Introduction and aim

Ovarian carcinoma (OC) is a common cancer in the Western Countries, and an important cause of death in patients suffering with gynaecologic malignancies. The majority of patients present with advanced disease at the time of diagnosis. Treatment with debulking surgery followed by chemotherapy is the standard approach while chemotherapy is contemplated when surgery is not possible. A correct pre-operative staging is important to ensure a most appropriate management. Laparoscopy (LPS) is the standard diagnostic tool for the assessment of intraperitoneal infiltration but is invasive and requires general anaesthesia. FDG-PET/CT is increasingly used for staging different types of cancer, and the aim of this study is to assess the value of FDG-PET/CT in staging advanced OC and its sensitivity to detect lesions in different quadrants of the abdominal-pelvic area compared to laparoscopy.

Materials and methods

From September 2004 till April 2008, 40 patients with high suspicion of OC were referred to our hospital for diagnostic LPS to explore the possibility of optimal debulking surgery. Those who were not suitable for surgery were referred for chemotherapy. Before chemotherapy, the patients underwent an FDG-PET/CT scan. The findings in 9 quadrants of abdominal-pelvic area (total 360 quadrants) for PET/CT and LPS were recorded and compared.

Results

In 14/360 areas (3.8%), surgical evaluation was not possible because of presence of adhesions, thus the number of areas explored by laparoscopy was 346. Tumour was found in 308 quadrants (38 quadrants free of disease). PET/CT was positive in all 40 patients with true negative results in 26/346 quadrants (7.5%), and true positives results in 243/346 quadrants (70.2%). False positive and negative PET/CT results were found in 12/346 and 65/346 quadrants, respectively. False positive PET/CT findings were evenly present in all quadrants. False negative PET/CT findings were present in 31/109 (28.4%) upper abdominal quadrants (epigastrium and diaphragmatic areas). Final analysis showed a sensitivity and specificity for PET/TC of 78.9 and 68.4% respectively with a positive predictive value of 95.3%. A significant difference was noted between mean SUVmax associated with lesions smaller or larger than 0.5 cm (p = 0.006).

Conclusion

Our results suggest that PET/CT may prove a useful tool for pre-surgical staging of ovarian cancer with a sensitivity and specificity of 78 and 68%, respectively. However, it may be used in combination with laparoscopy for better results. PET/CT showed an adequate correlation between SUVmax values and laparoscopy findings of lesions >5 mm, but a high rate of false negative results in lesions <5 mm such as in carcinomatosis. PET/CT should be used carefully in early stage disease, with low risk of peritoneal infiltration, because of high rate of false positive results, to avoid unnecessary therapy procedures.     

Usefulness of F-18 FDG PET/CT in Assessment of Recurrence of Cervical Cancer After Treatment

Objective

Until now, serum tumor markers, physical examination, and conventional imaging modalities, such as CT or MRI, have been used in assessment of recurrence of cervical cancer after treatment. However, CT and MRI provide only anatomical data, which makes analysis of post-treatment change difficult. This study aims to explore the effectiveness of PET/CT, a new scanning device that combines PET and CT, in evaluation of cervical cancer lesions in patients with suspected recurrence.

Methods

We studied 51 patients suspected of recurrence among those who underwent F-18 FDG PET/CT for cervical cancer follow-up at Gachon University Gil Hospital between June 2006 and August 2009. Patients were considered to be at risk for recurrence if they reported symptoms that were clinically suggestive of recurrence, or if physical examination showed abnormalities, serum tumor marker levels rose, or follow-up images revealed changes, such as new lesions or swelling of previous sites. Sensitivity, accuracy, specificity, and positive and negative predictive values of PET/CT were measured.

Results

A total of 37 patients were confirmed with recurrence or metastasis, 13 of whom were diagnosed histologically. Measured across all patients, PET/CT scored 97.3% on sensitivity, 71.4% on specificity, a positive predictive value of 90%, a negative predictive value of 90.9%, and an accuracy of 90.2%. PET/CT yielded only one false negative diagnosis and four false positives.

Conclusion

As F-18 FDG PET/CT has high sensitivity and negative predictive value in diagnosis of recurrent cervical cancers, it is expected that it will be useful for clinical determination of recurrence and prevention of unnecessary additional treatments. The hope is that a future study on a larger scale will contribute further to determination of the efficacy of PET/CT.     

No correlation between glucose metabolism and apparent diffusion coefficient in diffuse large B-cell lymphoma: a PET/CT and DW-MRI study

Purpose

Both positron emission tomography/computed tomography (PET/CT) and diffusion-weighted magnetic resonance imaging (DW-MRI) are oncologic feasible techniques for evaluating the malignancy of tumors. Standardized uptake value (SUV) is a marker of tumor glucose metabolism detected by PET/CT. Apparent diffusion coefficient (ADC) measured by DWI can provide information about tissue cellularity. The aim of the study was to evaluate the correlation between SUV and ADC in untreated diffuse large B-cell lymphoma (DLBCL).

Materials and methods

Fifteen pre-therapy patients with histologically proven DLBCL underwent PET/CT and DWI examinations within two days. Tumor glucose metabolism was evaluated by the maximum and mean SUV (SUV_max and SUV_mean) on the PET/CT images. The mean ADC value was measured directly on the parametric ADC maps.

Results

In total, 28 lymphoma lesions with best match PET/CT and DWI were identified and evaluated. The mean SUV_max and SUV_mean were 16.8 and 11.1, respectively; the mean ADC was 0.74 × 10⁻³ mm²/s. There was no correlation between the mean ADC and the SUV_max or SUV_mean.

Conclusion

SUV determined from PET/CT and ADC value measured from DWI are different indices for the diagnosis of tumor malignancy, they may provide complimentary functional information of tumor tissue.     

18F-FDG PET or PET/CT for detecting extrahepatic metastases or recurrent hepatocellular carcinoma: a systematic review and meta-analysis

Aim

Positron emission tomography (PET) using F18-flurodeoxy-glucose (FDG) has been widely used for reflecting cellular metabolism. However, the feasibility of FDG PET in the diagnosis of hepatocellular carcinoma (HCC) is limited. The aim of the study was to assess the ability of FDG PET (PET/CT) in the detection of extrahepatic metastases or recurrent HCC.

Materials and methods

We conducted MEDLINE, EMBASE and COCHRANE searches (last update, April 2011). Eight eligible articles were identified evaluating F18-FDG PET (PET/CT) in extrahepatic metastases or recurrent HCC. Two authors independently evaluated the methodological quality of each study. We estimated pooled sensitivities, specificities, summary receiver-operating-characteristic (SROC) curves, and summary likelihood ratios.

Results

Eight eligible studies were enrolled in this study. The pooled estimates of sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of FDG PET (PET/CT) in the detection of metastatic HCC were 76.6%, 98.0%, 14.68, and 0.28, respectively. The pooled estimates of sensitivity, specificity, LR+ and LR− of FDG PET (PET/CT) in the detection of recurrent HCC were 81.7%, 88.9%, 4.72, and 0.19, respectively.

Conclusion

Based on the results of this systematic review, F-18 FDG PET (PET/CT) was useful in ruling in extrahepatic metastases of HCC and valuable for ruling out the recurrent HCC.     

FDG PET scan strategies and long-term outcomes after first-line therapy in Hodgkin's disease

Background

The use of positron emission tomography with fluoro-deoxy-glucose (FDG PET) in Hodgkin's disease (HD) is continuing to expand worldwide, with response assessment after completion of therapy being its most widely utilized application. A positive scan has been associated with high relapse rates and disease progression.

Methods

A decision analysis was performed to determine the long-term impact of FDG PET restaging both with and without computed tomography (CT) in terms of the 5-year progression-free survival (5yrPFS). Outcomes and utilities were based on published data. The first strategy involved CT restaging after first-line therapy, with or without subsequent FDG PET, while the second strategy used FDG PET scan alone. All positive test required histological examination. Upon histological confirmation of active lymphoma, patients were considered candidates for autologous transplantation and long-term outcomes were retrieved. The expected clinical benefit of the two strategies was calculated and depicted, along with the mean costs. One-way and two-way sensitivity analyses were performed to ensure the validity of the results.

Results

CT restaging plus FDG PET when residual mass is detected, results in a 2% benefit at 5yrPFS at baseline compared to FDG PET-alone restaging and remains positive for a wide range of probabilities. This strategy reduces the average cost by €1863 per patient, including costs of biopsy and autologous transplantation.

Conclusion

A more conservative approach that includes CT restaging after first-line therapy and FDG PET scan only on residual mass, is the preferred strategy in HD. Furthermore it appears to confer the maximal diagnostic yield along with a substantial reduction in the mean cost.     

Comparison of whole-body PET/CT and PET/MRI in breast cancer patients: Lesion detection and quantitation of 18F-deoxyglucose uptake in lesions and in normal organ tissues

Purpose

To compare the performance of PET/MRI imaging using MR attenuation correction (MRAC) (DIXON-based 4-segment -map) in breast cancer patients with that of PET/CT using CT-based attenuation correction and to compare the quantification accuracy in lesions and in normal organ tissues.

Methods

A total of 36 patients underwent a whole-body PET/CT scan 1 h after injection and an average of 62 min later a second scan using a hybrid PET/MRI system. PET/MRI and PET/CT were compared visually by rating anatomic allocation and image contrast. Regional tracer uptake in lesions was quantified using volumes of interest, and maximal and mean standardized uptake values (SUVmax and SUVmean, respectively) were calculated. Metabolic tumor volume (MTV) of each lesion was computed on PET/MRI and PET/CT. Tracer uptake in normal organ tissue was assessed as SUVmax and SUVmean in liver, spleen, left ventricular myocardium, lung, and muscle.

Results

Overall 74 FDG positive lesions were visualized by both PET/CT and PET/MRI. No significant differences in anatomic allocation scores were found between PET/CT and PERT/MRI, while contrast score of lesions on PET/MRI was significantly higher. Both SUVmax and SUVmean of lesions were significantly higher on PET/MRI than on PET/CT, with strong correlations between PET/MRI and PET/CT data (ρ = 0.71–0.88). MTVs of all lesions were 4% lower on PET/MRI than on PET/CT, but no statistically significant difference was observed, and an excellent correlation between measurements of MTV with PET/MRI and PET/CT was found (ρ = 0.95–0.97; p < 0.0001). Both SUVmax and SUVmean were significantly lower by PET/MRI than by PET/CT for lung, liver and muscle, no significant difference was observed for spleen, while either SUVmax and SUVmean of myocardium were significantly higher by PET/MRI. High correlations were found between PET/MRI and PET/CT for both SUVmax and SUVmean of the left ventricular myocardium (ρ = 0.91; p < 0.0001), while moderate correlations were found for the other normal organ tissues (ρ = 0.36–0.61; p < 0.05).

Conclusions

PET/MRI showed equivalent performance in terms of qualitative lesion detection to PET/CT. Despite significant differences in tracer uptake quantification, due to either methodological and biological factors, PET/MRI and PET/CT measurements in lesions and normal organ tissues correlated well. This study demonstrates that integrated whole-body PET/MRI is feasible in a clinical setting with high quality and in a short examination time.     

Present and future of PET and PET/CT in gynaecologic malignancies

Objectives

To review the published data in literature on patients affected by gynaecological malignancies to establish the role of ¹⁸F-FDG positron emission tomography (PET) and PET/CT in comparison to conventional imaging (CI).

Materials and methods

All papers specifically addressed to the role of ¹⁸F-FDG PET and PET/CT in gynaecological malignancies published on PubMed/Medline, in abstracts from the principal international congresses, in the guidelines from national Societies that had appeared in literature until November 2009 were considered for the purpose of the present study.

Results and conclusions

The use of ¹⁸F-FDG PET, and even more of ¹⁸F-FDG PET/CT, is increasing in the follow up of patients with gynaecologic malignancies and suspected recurrent disease: there is evidence in the literature that ¹⁸F-FDG PET/CT has a higher sensitivity than CI in depicting occult metastatic spread. An interesting issue is represented by patients with ovarian cancer with an increase of the specific biomarker, CA-125, and negative/inconclusive findings at CI. The use of ¹⁸F-FDG PET in differential diagnosis and staging is more controversial, but there is some evidence that a baseline PET examination performed before commencing therapy, for staging purpose, is also useful to evaluate the response to chemoradiation treatment. In several papers it has been suggested a relevant role of ¹⁸F-FDG PET/CT in evaluating the entity of response to treatment and therefore to plan the subsequent therapeutic strategy.     

Is There Any Additional Benefit of Contrast-Enhanced CT as Part of Routine PET/CT Protocols for the Differentiation of Suspicious Incidental Gastrointestinal 2-Deoxy-18F-FDG Uptake?

Objective

Suspicious incidental gastrointestinal FDG uptake during positron-emission tomography/computed tomography (PET/CT) examinations can be caused by different diseases, including malignancies. However, differentiation with PET alone is difficult. The aim of this study was to investigate the potential of PET alone, contrast-enhanced CT (ceCT), and low-dose CT (ldCT) in routine PET/CT protocols for differentiation of incidental gastrointestinal lesions.

Materials and Methods

Sixty patients with incidental gastrointestinal lesions who underwent a routine PET/CT protocol with ldCT and ceCT were retrospectively analysed. The PET lesions were evaluated regarding their FDG uptake patterns and the standard uptake value. The anatomical correlates in both CT protocols were compared in regard to the correct lesion classification with the reference standard endoscopy.

Results

Sixty-two lesions were found in 60 patients (17 malignant, 10 premalignant, 5 benign, 13 inflammatory, 17 physiological). The differentiation of the FDG uptake patterns did not enable reliable lesion classification. The positive predictive value for pathology was 0.81 for ceCT in PET/CT and 0.70 for ldCT. Malignancies were detected in 100% of the patients by ceCT vs. 29.4% by ldCT. The false negative rate of ceCT for all pathologies was 31.1%, vs. 68.9% for ldCT. False positive results (17/62) could not be excluded sufficiently by either CT protocol.

Conclusion

PET/ceCT protocols provide additional benefit especially in detecting gastrointestinal malignancies as a cause of suspicious incidental gastrointestinal FDG uptake. However, since follow-up endoscopy cannot be forgone due to the considerable false negative rate even with ceCT, the addition of ceCT to a routine PET/ldCT protocol cannot be recommended for this purpose.     

FDG avidity and PET/CT patterns in primary gastric lymphoma

PURPOSE: The use of 18F-fluoro-deoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in primary gastric lymphoma (PGL) is challenging due to physiologic FDG activity in the stomach and variability in the degree of uptake in various histologic subtypes. This study assesses FDG avidity and PET/CT patterns in newly diagnosed PGL. METHODS: Sixty-two PET/CT studies of newly diagnosed PGL were reviewed (24 low-grade mucosa-associated lymphoid tissue [MALT], 38 aggressive non-Hodgkin's lymphoma [AGNHL]). FDG avidity, patterns (focal/diffuse), and intensity (visually vs. the liver and SUVmax) were assessed and compared to 27 controls. Gastric CT abnormalities and extragastric sites were recorded. RESULTS: Gastric FDG uptake was found in 55/62 (89%) PGL (71% MALT vs. 100% AGNHL, p < 0.001) and 63% controls. A diffuse pattern was found in 60% PGL (76% MALT vs. 53% AGNHL, p = NS) and 47% controls. FDG uptake higher than liver was found in 82% PGL (58% MALT vs. 97% AGNHL, p < 0.05) and 63% controls. SUVmax in FDG-avid PGLs was 15.3 +/- 11.7 (5.4 +/- 2.9 MALT vs. 19.7 +/- 11.5 AGNHL, p < 0.001) and 4.6 +/- 1.4 in controls. CT abnormalities were found in 79% PGL (thickening, n = 49; ulcerations, n = 22). Extra-gastric FDG-avid sites were seen in none of MALT, but 61% of AGNHL (nodal, n = 18; nodal and extranodal, n = 5). CONCLUSIONS: FDG avidity was present in 89% of PGLs, including all patients with AGNHL but only 71% of MALT. FDG uptake can be differentiated, in particular in AGNHL-PGL, from physiologic tracer activity by intensity but not by pattern. Extragastric foci on PET and structural CT abnormalities are additional parameters that can improve PET/CT assessment of PGL. Defining FDG avidity and PET/CT patterns in AGNHL and a subgroup of MALT-PGL before treatment may be important for further monitoring therapy response.     

Metabolic volume performs better than SUVmax in the detection of left ventricular assist device driveline infection

Purpose

A continuous-flow left ventricular assist device (LVAD) is a new and highly promising therapy in supporting end-stage heart failure patients, either bridging them to heart transplantation or as a destination therapy. Infection is one of the major complications associated with LVAD implants. ¹⁸F–FDG PET/CT has already been shown to be useful in the detection of LVAD infection. The goal of this study was to compare the diagnostic accuracy of different PET analysis techniques (visual grading versus SUVmax and metabolic volume).

Methods

We retrospectively analyzed 48 patients with implanted LVAD who underwent an ¹⁸F–FDG PET/CT that were either suspected to have a driveline or device infection or inflammation of unknown origin. PET/CT was analyzed qualitatively (visual grading) and quantitatively (SUVmax and metabolic volume) and matched to the final clinical diagnosis concerning driveline infection. The final diagnosis (standard of reference) was made at the end of clinically recorded follow-up or transplantation and included microbiological cultures of the driveline exit site and/or surgical samples, and clinical signs of infection despite negative cultures as well as recurrence of symptoms.

Results

Sensitivity, specificity, positive and negative predictive value were 87.5%, 79%, 81% and 86% for visual score, 87.5%, 87.5%, 87.5% and 87.5% for SUVmax and 96%, 87.5%, 88.5%, 95.5% for metabolic volume, respectively. ROC analysis revealed an AUC of .929 for SUVmax and .969 for metabolic volume. Both SUVmax and metabolic volume had a high detection rate of patients with driveline infection (21/24 = 91.5% true positive vs. 23/26 = 88.5% true positive, respectively). However, metabolic volume detected more patients without any infection correctly (1/22 = 4.5% false negative vs. 3/24 = 12.5% false negative).

Conclusions

¹⁸F–FDG PET/CT is a valuable tool for the diagnosis of LVAD driveline infection with high diagnostic accuracy. Particularly the use of the metabolic volume yields very high accuracy and performs slightly better than SUVmax.

     

The role of F-18 positron emission tomography/computed tomography in evaluation of extranodal lymphoma

Aim and objectives

To assess the added value of hybrid FDG PET/CT in evaluation of extranodal lymphoma.