FDG-PET and CT characterization of adrenal lesions in cancer patients

Purpose Fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) may differentiate benign from malignant adrenal lesions. In this study, standardized uptake values (SUVs), visual interpretation, and computed tomography (CT) data were correlated with the final diagnosis to determine the contribution of adrenal FDG-PET in patients with known non-adrenal cancer.Methods Ninety-two patients with adrenal lesions on CT underwent FDG-PET. Eighty adrenals in 74 patients met the inclusion criteria (PET scan within 4 weeks of CT plus >1 year of follow-up after PET scan with repeat CT or biopsy for final diagnosis). CT was considered positive for metastases (CT+) based on two of the following three criteria: >4 cm, Hounsfield units (HU) >30, and delayed contrast enhancement. Lesions with <2 cm, with HU <20, and showing no enhancement were considered benign (CT–). Remaining lesions were considered indeterminate (CT-Ind). Visually, adrenal uptake exceeding liver uptake was considered PET positive (PET+). Diagnosis of metastases was based on biopsy or interval CT growth (unchanged >1 year=benign). SUV_max and SUV_avg were calculated from a 4×4 pixel region of interest drawn from CT, PET, and fused images. A receiver operator curve (ROC) determined the SUV with the best sensitivity and specificity.Results Overall, PET was 93% sensitive and 96% specific for metastases. A SUV_max of 3.4 was 95% sensitive and 86% specific. A SUV_avg of 3.1 was 95% sensitive and 90% specific. There was no significant difference between visual interpretation and SUV (SUV_max or SUV_avg). Among CT+ and CT– lesions, PET was 100% sensitive and 96% specific; CT was 86% sensitive and 100% specific. In the CT-Ind group, PET was 88% sensitive and 96% specific.Conclusion PET accurately characterized adrenal lesions. Visual interpretation was as accurate as SUV. FDG-PET was most useful in the 52.5% of cancer patients with inconclusive adrenal lesions on CT.     

Differentiation of adrenal incidentalomas by qualitative and quantitative analytical data obtained by 18F-FDG positron emission tomography/computed tomography in cancer patients

Aim of the work

To evaluate the diagnostic reliability of qualitative and quantitative data of 18F-FDG PET/CT scanning in the identification and differentiation of adrenal incidentalomas discovered in cancer patients.

Dual-time point PET/CT with F-18 FDG for the differentiation of malignant and benign bone lesions

Purpose  The purpose of the present study was to evaluate whether 2-fluoro[fluorine-18]-2-deoxy-d-glucose (F-18 FDG) positron emission tomography (PET) could differentiate malignant and benign bone lesions and whether obtaining delayed F-18 FDG PET images could improve the accuracy of the technique. Methods  In a prospective study, 67 patients with bone lesions detected by computed tomography (CT) or magnetic resonance imaging were included. Whole body PET/CT imaging was performed at 1 h (early) after the F-18 FDG injection and delayed imaging at 2 h post injection was performed only in the abnormal region. Semiquantitative analysis was performed using maximum standardized uptake value (SUV_max), obtained from early and delayed images (SUV_maxE and SUV_maxD, respectively). The retention index (RI) was calculated according to the equation: RI = (SUV_maxD − SUV_maxE) × 100/SUV_maxE. Histopathology of surgical specimens and follow-up data were used as reference criteria. The SUV_maxE and RI were compared between benign and malignant lesions. Results  The final diagnoses revealed 53 malignant bone lesions in 37 patients and 45 benign lesions in 30 patients. There were statistically significant differences in the SUV_maxE between the malignant and benign lesions (P = 0.03). The mean SUV_maxE was 6.8 ± 4.7 for malignant lesions and 4.5 ± 3.3 for benign lesions. However, a considerable overlap in the SUV_maxE was observed between some benign and malignant tumors. With a cutoff value of 2.5 for the SUV_maxE, the sensitivity, specificity, and accuracy were 96.0%, 44.0%, and 72.4%, respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 67.1% and 90.9%, respectively. There were significant differences in the RI between the malignant and benign lesions (P = 0.004). But there was overlap between the two groups. The mean RI was 7 ± 11 for the benign lesions and 18 ± 11 for the malignant lesions. When an RI of 10 was used as the cutoff point, the sensitivity, specificity, and accuracy were 90.6%, 76.0%, and 83.7.0%, respectively. The PPV and NPV were 81.4% and 87.1%, respectively. Conclusions  The results of this study indicate that dual-time point F-18 FDG PET may provide more help in the differentiation of malignant tumors from benign ones.     

Evaluation of Adrenal Masses in Lung Cancer Patients Using F-18 FDG PET/CT

Purpose

The aim of this study was to assess the diagnostic efficacy of PET/CT using various parameters for the characterization of adrenal nodules in lung cancer patients.

Methods

Sixty-one adrenal nodules in 51 lung cancer patients were evaluated. The final diagnosis was based on histology (n = 2) or imaging follow-up (n = 59, range of follow-up: 7–57 months, median 27 months). Each adrenal nodule was analyzed using four parameters of PET/CT: the maximum standardized uptake value (SUV_max), the adrenal nodule/liver ratio of the SUV (SUV ratio), Hounsfield units (HU) and size. The optimal cutoff of each parameter for the identification of metastatic nodule was determined by ROC analysis and then the diagnostic efficacy was compared among the parameters.

Results

Of the 61 adrenal nodules, 45 (73%) were considered metastasis. The optimal cutoff values of the parameters were SUV_max >2.7, SUV ratio >1.3, HU >18 and size >20 mm, respectively. The sensitivity, specificity and accuracy by SUV_max >2.7 were 88.9%, 87.5% and 88.5%, and those by SUV ratio >1.3 were 84.4%, 100% and 88.5%, respectively. The combination of SUV ratio >1.3 and HU >18 had sensitivity of 97.7%, specificity of 81.2% and accuracy of 93.4% to predict adrenal metastasis in patients with lung cancer.

Conclusion

SUV ratio from F-18 FDG PET/CT could identify the adrenal metastasis in lung cancer patients. The combination of SUV ratio and HU can improve the accuracy of differentiating benign and metastatic adrenal lesions in lung cancer patients.     

Nonionic intravenous contrast agent does not cause clinically significant artifacts to <Superscript>18</Superscript>F-FDG PET/CT in patients with lung cancer

Objective This study was performed to evaluate the effects of intravenous (i.v.) contrast agent on semi-quantitative values and lymph node (LN) staging of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) in patients with lung cancer. Methods Thirty-five patients with lung cancer were prospectively included. Whole-body PET and nonenhanced CT images were acquired 60 min following the i.v. injection of 370 MBq ¹⁸F-FDG and subsequently, enhanced-CT images were acquired with the i.v. administration of 400 mg iodinated contrast agent without positional change. PET images were reconstructed with both nonenhanced and enhanced CTs, and the maximum and average standardized uptake values (SUV_max and SUV_ave) calculated from lung masses, LNs, metastatic lesions, and normal structures were compared. To evaluate the effects of the i.v. contrast agent on LN staging, we compared the LN status on the basis of SUVs (cut-offs; SUV_max = 3.5, SUV_ave = 3.0). Results The mean differences of SUV_max in normal structures between enhanced and nonenhanced PET/CT were 15.23% ± 13.19% for contralateral lung, 8.53% ± 6.11% for aorta, 5.85% ± 4.99% for liver, 5.47% ± 6.81% for muscle, and 2.81% ± 3.05% for bone marrow, and those of SUV_ave were 10.17% ± 9.00%, 10.51% ± 7.89%, 4.95% ± 3.89%, 5.66% ± 9.12%, and 2.49% ± 2.50%, respectively. The mean differences of SUV_max between enhanced and nonenhanced PET/CT were 5.89% ± 3.92% for lung lesions (n = 41), 6.27% ± 3.79% for LNs (n = 76), and 3.55% ± 3.38% for metastatic lesions (n = 35), and those of SUV_ave were 3.22% ± 3.01%, 2.86% ± 1.71%, and 2.33% ± 3.95%, respectively. Although one LN status changed from benign to malignant because of contrast-related artifact, there was no up- or down-staging in any of the patients after contrast enhancement. Conclusions An i.v. contrast agent may be used in PET/CT without producing any clinically significant artifact.     

Usefulness of a breath-holding acquisition method in PET/CT for pulmonary lesions

Objective  To evaluate the usefulness of a breath-holding (BH) ¹⁸F-2-fluoro-2-deoxy-D-glucose positron emission tomography (¹⁸F-FDG-PET) technique for PET/computed tomography (CT) scanning of pulmonary lesions near the diaphragm, where image quality is influenced by respiratory motion. Methods  In a basic study, simulated breath-holding PET (sBH-PET) data were acquired by repeating image acquisition eight times with fixation of a phantom at 15 s/bed. Free-breathing PET (FB-PET) was simulated by acquiring data even as moving the phantom at 120 s/bed (sFB-PET). Images with total acquisition times of 15 s, 30 s, 45 s, 60 s, and 120 s were generated for sBHPET. Receiver-operating characteristic (ROC) analyses and determination of the statistical significance of differences between sFB-PET images and sBH-PET images were performed. A total of 22 pulmonary lesions in 21 patients (12 men and 9 women, mean age 61.3 ± 10.6 years, 10 benign lesions in 9 patients and 12 malignant lesions in 12 patients) were examined by FB-PET and BH-PET). For evaluation of these two acquisition methods, displacement of the lesion between CT and PET was considered to be a translation, and the statistical significance of differences in maximum standardized uptake value (SUV_max) of the lesion was assessed using the paired t test. Results  In the basic study, sBH-PET images with acquisition times of 45 s, 60 s, and 120 s had significantly higher diagnostic accuracy than 120-s sFB-PET images (P < 0.05). In clinical cases, translation of the BH-PET images was significantly lower than that of the FB-PET images (benign: 5.29 ± 4.02 mm vs. 11.79 ± 8.27 mm, P = 0.005; malignant: 4.29 ± 3.36 mm vs. 18.26 ± 12.31 mm, P = 0.003). The SUV_max of the lesions in the BH-PET images was significantly higher than that in the FB-PET images (benign: 2.40 ± 0.86 vs. 2.20 ± 0.85, P = 0.005; malignant: 4.84 ± 2.16 vs. 3.75 ± 2.11, P = 0.001). Conclusions  BH-PET provides images with better diagnostic accuracy, avoids image degradation owing to respiratory motion, and yields more accurate attenuation correction. This method is very useful for overcoming the problem of respiratory motion.     

Prospective evaluation of solitary thyroid nodule on 18F-FDG PET/CT and high-resolution ultrasonography

Purpose

The utility of 18F-FDG PET/CT in the assessment of thyroid nodules is unclear as there are several conflicting reports on the usefulness of SUV as an indicator to distinguish benign from malignant thyroid lesions. This study incorporated an additional parameter, namely dual time point imaging, to determine the diagnostic accuracy of PET/CT imaging. The performance of 18F-FDG PET/CT was compared to that of high-resolution ultrasound which is routinely used for the evaluation of thyroid nodules.

Methods

Two hundred patients with incidentally detected solitary thyroid nodules were included in the study. Each patient underwent ultrasound and PET/CT evaluation within 7 days of each other, reported by an experienced radiologist and nuclear medicine specialist, respectively, in a blinded manner. The PET/CT criteria employed were maximum SUV (SUV_max) at 60 min and change in SUV_max at delayed (120 min) imaging. Final diagnosis was based on pathological evaluation and follow-up.

Results

Of the 200 patients, 26 had malignant and 174 had benign nodules. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of ultrasound were 80.8, 81.6, 39.6, 96.6 and 81.5%, respectively. Using SUV_max at 60 min as the diagnostic criterion, the above indices were 80.8, 84.5, 43.8, 96.7 and 84%, respectively, for PET/CT. The SUV_max of malignant thyroid lesions was significantly higher than benign lesions (16.2 ± 10.6 vs. 4.5 ± 3.1, respectively; p = 0.0001). Incorporation of percentage change in SUV_max at delayed imaging as the diagnostic criterion yielded a slightly improved sensitivity, specificity, PPV, NPV and accuracy of 84.6, 85.6, 46.8, 97.4 and 85.5%, respectively. There was a significant difference in percentage change in SUV_max between malignant and benign thyroid lesions (14.9 ± 11.4 vs. ?1.6 ± 13.7, respectively; p = 0.0001). However, there was no statistically significant difference (95% confidence interval) between the diagnostic performance of PET/CT and ultrasound.

Conclusions

Routine use of 18F-FDG PET/CT with SUV_max at 60 min as the sole diagnostic criterion does not appear to have a significant advantage over high-resolution ultrasound in the evaluation of thyroid nodules. Incorporation of dual time point imaging enhances image interpretation, and yields a higher diagnostic performance, yet it is not statistically significant. Bearing in mind the cost, limited availability and radiation exposure, routine use of 18F-FDG PET/CT for distinguishing benign from malignant thyroid nodules cannot be recommended.     

The additional value of CT images interpretation in the differential diagnosis of benign vs. malignant primary bone lesions with 18F-FDG-PET/CT

Objective  To evaluate the value of a dedicated interpretation of the CT images in the differential diagnosis of benign vs. malignant primary bone lesions with 18fluorodeoxyglucose-positron emission tomography/computed tomography (18F-FDG-PET/CT). Materials and methods  In 50 consecutive patients (21 women, 29 men, mean age 36.9, age range 11–72) with suspected primary bone neoplasm conventional radiographs and 18F-FDG-PET/CT were performed. Differentiation of benign and malignant lesions was separately performed on conventional radiographs, PET alone (PET), and PET/CT with specific evaluation of the CT part. Histology served as the standard of reference in 46 cases, clinical, and imaging follow-up in four cases. Results  According to the standard of reference, conventional 17 lesions were benign and 33 malignant. Sensitivity, specificity, and accuracy in assessment of malignancy was 85%, 65% and 78% for conventional radiographs, 85%, 35% and 68% for PET alone and 91%, 77% and 86% for combined PET/CT. Median SUV_max was 3.5 for benign lesions (range 1.6–8.0) and 5.7 (range 0.8–41.7) for malignant lesions. In eight patients with bone lesions with high FDG-uptake (SUV_max ≥ 2.5) dedicated CT interpretation led to the correct diagnosis of a benign lesion (three fibrous dysplasias, two osteomyelitis, one aneurysmatic bone cyst, one fibrous cortical defect, 1 phosphaturic mesenchymal tumor). In four patients with lesions with low FDG-uptake (SUV_max < 2.5) dedicated CT interpretation led to the correct diagnosis of a malignant lesion (three chondrosarcomas and one leiomyosarcoma). Combined PET/CT was significantly more accurate in the differentiation of benign and malignant lesions than PET alone (p = .039). There was no significant difference between PET/CT and conventional radiographs (p = .625). Conclusion  Dedicated interpretation of the CT part significantly improved the performance of FDG-PET/CT in differentiation of benign and malignant primary bone lesions compared to PET alone. PET/CT more commonly differentiated benign from malignant primary bone lesions compared with conventional radiographs, but this difference was not significant.     

The clinical efficacy of <Superscript>18</Superscript>F-FDG-PET/CT in benign and malignant musculoskeletal tumors

Objective  Most of the current clinical data on the role of 2-[¹⁸F]fluoro-2-deoxy-d-glucose positron emission tomography (¹⁸F-FDG-PET) in musculoskeletal tumors come from patients studied with PET and less frequently with hardware fusion PET/computed tomography (CT). And the number of cases in each report is too small to clarify the exact clinical efficacy of PET or PET/CT. This prompted us to analyze our experience with ¹⁸F-FDG-PET/CT in a relatively large group of patients with musculoskeletal tumors. Methods   ¹⁸F-FDG-PET/CT was performed on 91 patients from May 2004 to June 2007. The final diagnosis was obtained from surgical biopsy in 83 patients (91%) and clinical follow-up in 8 (9%). We analyzed the characteristics and amount of ¹⁸F-FDG uptake in soft tissue and bone tumors, and investigated the ability of ¹⁸F-FDG-PET/CT to differentiate malignant from benign tumors. The cutoff maximum standardized uptake value (SUV_max) was calculated using the receiver-operation characteristic curve method. Sensitivity, specificity, and diagnostic accuracy were calculated with cutoff SUV_max and the final diagnosis. Unpaired t test was used for the statistical analysis. Results  Final diagnosis revealed 19 benign soft tissue tumors (mean SUV_max 4.7), 27 benign bone tumors (5.1), 25 malignant soft tissue tumors (8.8), and 20 malignant bone tumors (10.8). There was a significant difference in SUV_max between benign and malignant musculoskeletal tumors in total (P < 0.002), soft tissue tumors (P < 0.05), and bone tumors (P < 0.02). Sensitivity, specificity, and diagnostic accuracy were 80%, 65.2%, and 73% in total with cutoff SUV_max 3.8, 80%, 68.4%, and 75% in the soft tissue tumors with cutoff SUV_max 3.8, and 80%, 63%, and 70% in the bone tumors with cutoff SUV_max 3.7. Conclusions   ¹⁸F-FDG-PET/CT reliably differentiated malignant soft tissue and bone tumors from benign ones, although there were many false-positive and falsenegative lesions. Further studies with all kinds of musculoskeletal tumors in large numbers are needed to improve the diagnostic accuracy of ¹⁸F-FDG-PET/CT.     

Utilisation of combined 18F-FDG PET/CT scan for differential diagnosis between benign and malignant adrenal enlargement

Objective:

To assess the properties of adrenal lesions with and without known primary cancer and investigate predictors for differential diagnosis between benign and malignant adrenal enlargement.

Methods:

This retrospective study used fluorine-18 fludeoxyglucose positron emission tomography (PET)/CT in 325 patients with adrenal lesions (229 with known primary cancer and 96 without primary cancer). Age, sex, the presence of right and left masses, nodules or hyperplasia, unenhanced attenuation, maximum standardised uptake value (SUV_max) ratio, and the presence of metastasis in other body parts and locations of the primary cancer were assessed. Univariate and multivariate analyses were used to assess variables associated with risk of adrenal metastasis.

Results:

Patients with adrenal metastasis vs those without had a higher frequency of primary lung cancer (52.3% vs 30.7%) but a lower frequency of gastrointestinal cancer (7.9% vs 16.6%). The frequency of other abnormalities, including adenoma and hyperplasia, was similar between patients with and without known primary cancer. A higher proportion of patients with adrenal metastasis regardless of primary cancer site were younger, had a nodule or a mass, had an unenhanced attenuation of >10 HU, had an SUV_max ratio of >2.5, and had metastasis in other body parts. Analysis found independent associations of age, unenhanced attenuation of >10 HU, SUV_max ratio of >2.5 and the presence of metastasis in other body parts with adrenal metastasis. The combination of the four variables was strongly associated with adrenal metastasis.

Conclusion:

PET/CT was useful in characterising adrenal lesions as benign or malignant and helpful in identifying adrenal metastasis and cancer severity.

Advances in knowledge:

PET/CT can help in the differential diagnosis between benign and malignant adrenal enlargement.The adrenal gland is a common site of metastasis in patients with cancer. Up to 50% of adrenal lesions in patients with known primary non-adrenal cancers are malignant disease [1–4]. The most common malignant lesions that metastasise to the adrenal gland include lung, liver, colon, lymphoma, melanoma, breast, kidney, oesophagus, pancreas and stomach cancer [4–6]. However, diagnosis of an adrenal lesion as malignant or benign can be problematic. Characterisation of these adrenal lesions is therefore critical to stage the primary disease, direct therapy and predict prognosis. Although CT and MRI are typically used to characterise a lesion, a small but important number of adrenal lesions are found to be indeterminate on cross-sectional images [7–9].Several reports have documented the effectiveness of stand-alone fluorine-18 fludeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) to differentiate benign from malignant adrenal lesions [8–10]. Interest has focused on the ability of integrated in-line PET/CT to definitively characterise these lesions given that this technique combines the anatomical and densitometrical applications of CT and the functional and metabolic advantages of PET. Several studies have reported PET/CT''s high sensitivity, specificity and accuracy for detecting adrenal metastatic lesions [7–10].PET/CT can also be used as a non-invasive method to help assess the lesion, facilitating diagnosis and treatment decisions. The purpose of our study was to investigate whether PET/CT can reliably detect differences between malignant and benign lesions, tumour characteristics associated with the location of the primary cancer and predictors for adrenal metastasis.     

Current generation time-of-flight <Superscript>18</Superscript>F-FDG PET/CT provides higher SUVs for normal adrenal glands,while maintaining an accurate characterization of benign and malignant glands

Objective

Modern PET/CT scanners have significantly improved detectors and fast time-of-flight (TOF) performance and this may improve clinical performance. The aim of this study was to analyze the impact of a current generation TOF PET/CT scanner on standardized uptake values (SUV), lesion-background contrast and characterization of the adrenal glands in patients with suspected lung cancer, in comparison with literature data and commonly used SUV cut-off levels.

Methods

We included 149 adrenal glands from 88 patients with suspected lung cancer, who underwent ¹⁸F-FDG PET/CT. We measured the SUV_max in the adrenal gland and compared this with liver SUV_mean to calculate the adrenal-to-liver ratio (AL ratio). Results were compared with literature derived with older scanners, with SUV_max values of 1.0 and 1.8 for normal glands [1, 2]. Final diagnosis was based on histological proof or follow-up imaging. We proposed cut-off values for optimal separation of benign from malignant glands.

Results

In 127 benign and 22 malignant adrenal glands, SUV_max values were 2.3 ± 0.7 (mean ± SD) and 7.8 ± 3.2 respectively (p < 0.01). Corresponding AL ratios were 1.0 ± 0.3 and 3.5 ± 1.4 respectively (p < 0.01). With a SUV_max cut-off value of 3.7, 96 % sensitivity and 96 % specificity was reached. An AL ratio cut-off value of 1.8 resulted in 91 % sensitivity and 97 % specificity. The ability of both SUV_max and AL ratio to separate benign from malignant glands was similar (AUC 0.989 vs. 0.993, p = 0.22).

Conclusions

Compared with literature based on the previous generation of PET scanners, current generation TOF ¹⁸F-FDG PET/CT imaging provides higher SUVs for benign adrenal glands, while it maintains a highly accurate distinction between benign and malignant glands. Clinical implementation of current generation TOF PET/CT requires not only the use of higher cut-off levels but also visual adaptation by PET readers.

     

18F-FDG-PET of musculoskeletal tumors: a correlation with the expression of glucose transporter 1 and hexokinase II

Objective  It remains controversial whether positron emission tomography (PET) with 2-deoxy-2-[F-18]fluoro-d-glucose (F-18-FDG) can differentiate between benign and malignant musculoskeletal tumors. To uncover the mechanism of F-18-FDG accumulations, we analyzed the correlation between the F-18-FDG accumulation and the expression of glucose transporter 1 (Glut-1) and hexokinase II (HK-II) in benign and malignant musculoskeletal tumors. Methods  The maximum standardized uptake values (SUV_max) of F-18-FDG in 24 benign and 26 malignant musculoskeletal tumors were compared with the histologic malignancies, and the expression of Glut-1 and HK-II was analyzed by immunohistochemistry. Results  The SUV_max for malignant tumors (6.33 ± 4.79) was significantly higher than those with benign tumors (3.47 ± 3.12, P < 0.01). The expression of Glut-1 was high in 12 patients (all malignant) and low in 38 patients (24 benign and 14 malignant), and the expression of HK-II was high in 36 patients (11 benign and 25 malignant) and low in 14 patients (13 benign and 1 malignant). Cases with high expression of Glut-1 and HK-II at immunohistochemistry showed a higher SUV_max than those with low expression (Glut-1 8.03 ± 5.10 and 3.98 ± 3.53, P < 0.01; HK-II 5.73 ± 4.49 and 2.99 ± 3.02, P < 0.01). No significant dividing threshold of the SUV_max of F-18 FDG was found for the differential diagnosis between benign and malignant tumors or for the expression of Glut-1 and HK-II. Conclusions  The limited capability of F-18 FDG-PET in the differential diagnosis of musculoskeletal tumors is owing partly to the various levels of Glut-1 and HK-II expression in individual tumors.     

Usefulness of FDG-PET/CT in the detection of pancreatic metastases from lung cancer

Objective  The objective of this study was to assess the ability to detect pancreatic metastasis of lung cancer and to clarify the degree of fluorodeoxyglucose (FDG) accumulation and computed tomography (CT) characteristics of pancreatic metastasis from lung cancer. Methods  A total of 573 patients (415 men and 158 women) with lung cancer were retrospectively evaluated. All patients underwent FDG-positron emission tomography (PET)/CT with contrast-enhanced CT for first=stage (313 patients; initial study group) or follow-up study (260 patients; follow-up study group). A lesion was regarded as positive for metastasis on the basis of visual judgment of the degree of increased metabolism by two experienced and independent interpreters, supported by semiquantitative evaluation on the basis of calculation of the maximum standardized uptake value (SUV_max). Results  Abnormal accumulations in the pancreas were detected in 5 of 313 patients (1.60%) in the initial study group, and 6 of 260 patients (2.31%) in the follow-up study group. Seven of these patients had adenocarcinoma, three had small cell carcinoma, and the rest had large cell endocrine carcinoma. Tumor sizes (longitudinal diameter), measured by CT, of these 11 patients ranged from 6 mm to 52 mm (mean ± SD 8.3 mm ± 11.9 mm), and SUV_max for 1 h ranged from 3.37 to 11.1 (mean ± SD 6.12 ± 2.43). Three of these pancreatic lesions were difficult to determine by routine transaxial images, and detection was obvious only by thin-slice images or multiplanar reconstruction images. Contrast-enhanced CT showed gradual fill-in from the peripheral portion to the center. In addition, 10 of 11 cases did not show main pancreatic duct dilatation even if the tumor size was large. Conclusions  Metastases to the pancreas in lung cancer patients are not so rare and radiologists first have an important role to detect the pancreatic mass and then suggest to metastasis as the likely diagnosis. For this purpose, FDG-PET/CT has an advantage in depicting unsuspected pancreatic metastasis from lung cancer, particularly that which is not detected by CT alone.     

FDG uptake heterogeneity evaluated by fractal analysis improves the differential diagnosis of pulmonary nodules

Purpose

The present study aimed to determine whether fractal analysis of morphological complexity and intratumoral heterogeneity of FDG uptake can help to differentiate malignant from benign pulmonary nodules.

Materials and methods

We retrospectively analyzed data from 54 patients with suspected non-small cell lung cancer (NSCLC) who were examined by FDG PET/CT. Pathological assessments of biopsy specimens confirmed 35 and 19 nodules as NSCLC and inflammatory lesions, respectively. The morphological fractal dimension (m-FD), maximum standardized uptake value (SUV_max) and density fractal dimension (d-FD) of target nodules were calculated from CT and PET images. Fractal dimension is a quantitative index of morphological complexity and tracer uptake heterogeneity; higher values indicate increased complexity and heterogeneity.

Results

The m-FD, SUV_max and d-FD significantly differed between malignant and benign pulmonary nodules (p < 0.05). Although the diagnostic ability was better for d-FD than m-FD and SUV_max, the difference did not reach statistical significance. Tumor size correlated significantly with SUV_max (r = 0.51, p < 0.05), but not with either m-FD or d-FD. Furthermore, m-FD combined with either SUV_max or d-FD improved diagnostic accuracy to 92.6% and 94.4%, respectively.

Conclusion

The d-FD of intratumoral heterogeneity of FDG uptake can help to differentially diagnose malignant and benign pulmonary nodules. The SUV_max and d-FD obtained from FDG-PET images provide different types of information that are equally useful for differential diagnoses. Furthermore, the morphological complexity determined by CT combined with heterogeneous FDG uptake determined by PET improved diagnostic accuracy.     

Diagnostic impact of 18F-FDG PET–CT evaluating solid pancreatic lesions versus endosonography, endoscopic retrograde cholangio-pancreatography with intraductal ultrasonography and abdominal ultrasound

Purpose  This prospective single-centre phase II trial assessed the diagnostic impact of ¹⁸F-FDG PET–CT in the evaluation of solid pancreatic lesions (∅ ≥10 mm) compared to endosonography (EUS), endoscopic retrograde cholangio-pancreatography (ERCP) with intraductal ultrasound (IDUS), abdominal ultrasound (US) and histopathological reference. Methods  Forty-six patients (32 men/14 women, ∅ 61.7 years) with suspected pancreatic neoplasms underwent PET–CT with contrast-enhanced biphasic multi-detector CT of the upper abdomen followed by a diagnostic work-up with EUS, ERCP with IDUS and US within 3 weeks. PET–CT data sets were analysed by two expert readers in a consensus reading. Histology from surgery, biopsy/fine-needle aspiration and/or clinical follow-up ≥12 months served as standard of reference. Results  Twenty-seven pancreatic malignancies were histopathologically proven; 19 patients had benign diseases: 36/46 lesions (78%) were detected in the head of the pancreas, 7/46 and 3/46 in the body and tail region, respectively. Sensitivity and specificity of PET–CT were 89% and 74%, respectively; positive predictive value (PPV) and negative predictive value (NPV) were 83% and 82%, respectively. Sensitivity (81–89%), specificity (74–88%), PPV (83–90%) and NPV (77–82%) achieved by EUS, ERCP and US were not significantly different. PET analysis revealed significantly higher maximum mean standardised uptake values (SUV_max 6.5 ± 4.6) in patients with pancreatic malignancy (benign lesions: SUV_max 4.2 ± 1.5; p < 0.05). PET–CT revealed cervical lymphonodal metastasis from occult bronchogenic carcinoma and a tubular colon adenoma with intermediate dysplasia on polypectomy, respectively. Conclusions   ¹⁸F-FDG PET–CT achieves a comparably high diagnostic impact evaluating small solid pancreatic lesions versus conventional reference imaging modalities. Additional clinical diagnoses are derived from concomitant whole-body PET–CT imaging. Verena Schick and Christiane Franzius contributed equally to this work.     

Does chemotherapy influence the quantification of SUV when contrast-enhanced CT is used in PET/CT in lymphoma?

Purpose In patients with lymphoma, we investigated the impact of contrast-enhanced CT on PET attenuation correction in lesions and normal tissues, particularly when PET/CT was performed after chemotherapy. Methods Fifty patients (51±18 years) with Hodgkin’s disease (n=17) or non-Hodgkin lymphomas (n=33) were studied before and after chemotherapy. PET/CT scans were performed 60 min after injection of FDG. Iopamiron 300 (iopamidol, 1.5 cc/kg) was injected immediately afterwards, followed 50 s later by a second craniocaudal CT (CT+). PET images were successively reconstructed using the unenhanced CT (PET−) and the CT+ (PET+) for attenuation correction, using iterative reconstruction (4 iterations, 8 subsets, 5 mm post-filtering). HU_mean, SUV_max and SUV_mean were measured before and after chemotherapy in ten non-tumoural ROIs [aorta, femur, kidney, lung, iliopsoas muscle, occipital cortex, T12 vertebra, liver, spleen and inferior vena cava (IVC)] and in tumoural lymphadenopathies or malignant tissues (n=397 and 51 VOIs respectively before and after chemotherapy) using a 3D-thresholding method (identical threshold for PET− and PET+). ROIs were defined on the PET− and automatically applied on the unenhanced CT (CT−), the CT+ and the PET+. Results In the non-tumoural tissues, HU_mean increased significantly in the CT+ compared with the CT− in the vessels and the highly vascularised organs, and slight increases were observed in the occipital cortex (+11%), the iliopsoas muscle (+6%) and the femur (+3%). SUV_max increased significantly in the PET+ compared with the PET− in the aorta (+14%), the liver (+10%), the spleen (+10%) and the IVC (+12%). SUV_mean increased significantly in the PET+ compared with the PET− in the aorta (+15%), the kidney (+13%), the liver (+11%), the spleen (10%) and the IVC (+12%). In the lesions, HU_mean was not significantly different before and after chemotherapy, whatever the normal region considered. SUV_max increased significantly after treatment in the T12 vertebra (+12%). SUV_mean increased significantly after treatment in the T12 vertebra (+13%) and in the liver (+12%). HU_mean increased significantly in the CT+ compared with the CT− in the lesions (+55%) before chemotherapy. SUV_max and SUV_mean increased significantly in the PET+ compared with the PET− in the lesions (+4%) only before chemotherapy. No significant difference was seen in measurements (HU_mean, SUV_max and SUV_mean) after chemotherapy. Conclusion Our study demonstrates that use of enhanced CT for attenuation correction has a negligible effect on quantification at staging and after chemotherapy. A “single-shot” enhanced PET/CT may thus be performed in the evaluation of patients with lymphoma at staging, during treatment and at follow-up.     

18F-FDG PET/CT in the characterization and surgical decision concerning adrenal masses: a prospective multicentre evaluation

Purpose

This prospective multicentre study assesses the usefulness of FDG PET/CT in characterizing and making the therapeutic decision concerning adrenal tumours that are suspicious or indeterminate in nature after conventional examinations (CE).

Methods

Seventy-eight patients (37 men, 41 women, 81 adrenal lesions) underwent FDG PET/CT after CE including CT scan, biological tests and optionally ¹³¹I-metaiodobenzylguanidine (MIBG) and/or ¹³¹I-norcholesterol scans. FDG adrenal uptake exceeding that of the liver was considered positive. PET results were not decisive. Surgery was discussed when at least one of the following criteria was found during CE: size >3 cm, spontaneous attenuation value >10 HU, heterogeneous aspect, abnormal MIBG or norcholesterol scan or hormonal hypersecretion.

Results

Following the gold standard (histology analysis or ≥9 months follow-up), 49 lesions potentially qualified for surgery (malignant = 27, benign secreting = 22) and 32 benign non-secreting lesions did not. PET was negative in 97% of non-surgical lesions and positive in 73% of potentially surgical ones which included all the malignant lesions, except 3 renal cell metastases, and 12 of 22 benign secreting lesions. The negative predictive value for malignancy was 93% (41/44) and positive predictive value for detecting surgical lesions was 97% (36/37). A high FDG uptake (maximum standardized uptake value?≥?10) was highly predictive of malignancy.

Conclusion

Adrenal FDG uptake is a good indicator of malignancy and/or of secreting lesions and should lead one to discuss surgery. If there is no prior history of poorly FDG-avid cancer, the absence of FDG uptake should avoid unnecessary removal of benign adrenal lesions.     

Differentiation of tumor recurrence from radiation-induced pulmonary fibrosis after stereotactic ablative radiotherapy for lung cancer: characterization of 18F-FDG PET/CT findings

Objective

Stereotactic ablative radiotherapy (SABR), also known as stereotactic body radiotherapy (SBRT), is now a standard treatment option for patients with stage I non-small cell lung cancer or oligometastatic lung tumor who are medically inoperable or medically operable but refuse surgery. When mass-like consolidation is observed on follow-up CT after SABR, it is sometimes difficult to differentiate tumor recurrence from SABR-induced pulmonary fibrosis. In this study, we evaluated the role of ¹⁸F-fluorodeoxyglucose positron emission tomography combined with computed tomography (FDG-PET/CT) in differentiating tumor recurrence from radiation fibrosis after SABR.

Methods

Between June 2006 and June 2009, 130 patients received SABR for stage I non-small cell lung cancer or metastatic lung cancer at our institution. Fifty-nine patients of them were imaged with FDG-PET/CT after SABR. There were a total of 137 FDG-PET/CT scans for retrospective analysis. The FDG uptake in the pulmonary region was assessed qualitatively using a 3-point scale (0, none or faint; 1, mild; or 2, moderate to intense), and the shape (mass-like or non mass-like) was evaluated. For semi-quantitative analysis, the maximum standardized uptake value (SUV_max) was calculated.

Results

Sixteen of 59 patients had local failure. In recurrent tumor, the combination of intensity grade 2 and mass-like shape was most common (21/23; 91 %). By contrast, in cases of radiation fibrosis, the combination of intensity grade 0 or 1 and non mass-like shape was most common (48/59; 81 %). The SUV_max of tumor recurrence after 12 months was significantly higher than that of radiation fibrosis (8.0 ± 3.2 vs. 2.1 ± 0.9, p < 0.001), and all tumor recurrence showed the SUV_max > 4.5 at diagnosis of local failure. At ≥12 months after SABR, these two variables, the combination of intensity 2 and mass-like FDG uptake or SUV_max > 4.5 acquired a significant high predictive value of local recurrence, finding sensitivity 100 % and specificity 100 % for both of them.

Conclusions

The combination of FDG uptake patterns and SUV_max was useful for distinguishing tumor recurrence from radiation fibrosis after SABR.     

Does <Superscript>18</Superscript>F-FDG PET/CT add diagnostic accuracy in incidentally identified non-secreting adrenal tumours?

Purpose  The widespread use of high-resolution cross-sectional imaging such as computed tomography (CT) and magnetic resonance imaging (MRI) for the investigation of the abdomen is associated with an increasing detection of incidental adrenal masses. We evaluated the ability of ¹⁸F-fluorodeoxyglucose positron emission tomography to distinguish benign from malignant adrenal masses when CT or MRI results had been inconclusive. Methods  We included only patients with no evidence of hormonal hypersecretion and no personal history of cancer or in whom previously diagnosed cancer was in prolonged remission. PET/CT scans were acquired after 90 min (mean, range 60–140 min) after FDG injection. The visual interpretation, maximum standardised uptake values (SUVmax) and adrenal compared to liver uptake ratio were correlated with the final histological diagnosis or clinico-radiological follow-up when surgery had not been performed. Results  Thirty-seven patients with 41 adrenal masses were prospectively evaluated. The final diagnosis was 12 malignant, 17 benign tumours, and 12 tumours classified as benign on follow-up. The visual interpretation was more accurate than SUVmax alone, tumour diameter or unenhanced density, with a sensitivity of 100% (12/12), a specificity of 86% (25/29) and a negative predictive value of 100% (25/25). The use of 1.8 as the threshold for tumour/liver SUVmax ratio, retrospectively established, demonstrated 100% sensitivity and specificity. Conclusion  FDG PET/CT accurately characterises adrenal tumours, with an excellent sensitivity and negative predictive values. Thus, a negative PET may predict a benign tumour that would potentially prevent the need for surgery of adrenal tumours with inconclusive conventional imaging.     

Diagnostic accuracy of 68Ga-DOTANOC PET/CT imaging in pheochromocytoma

Purpose

The purpose of the present study was to evaluate the diagnostic accuracy of ⁶⁸Ga-DOTANOC positron emission tomography (PET)/CT in patients with suspicion of pheochromocytoma.

Methods

Data of 62 patients [age 34.3?±?16.1 years, 14 with multiple endocrine neoplasia type 2 (MEN2)] with clinical/biochemical suspicion of pheochromocytoma and suspicious adrenal lesion on contrast CT (n?=?70), who had undergone ⁶⁸Ga-DOTANOC PET/CT, were retrospectively analyzed. PET/CT images were analyzed visually as well as semiquantitatively, with measurement of maximum standardized uptake value (SUV_max), SUV_mean, SUV_max/SUV_liver, and SUV_mean/SUV_liver. Results of PET/CT were compared with ¹³¹I-metaiodobenzylguanidine (MIBG) imaging, which was available in 40 patients (45 lesions). Histopathology and/or imaging/clinical/biochemical follow-up (minimum 6 months) was used as reference standard.

Results

The sensitivity, specificity, and accuracy of ⁶⁸Ga-DOTANOC PET/CT was 90.4, 85, and 88.7 %, respectively, on patient-based analysis and 92, 85, and 90 %, respectively, on lesion-based analysis. ⁶⁸Ga-DOTANOC PET/CT showed 100 % accuracy in patients with MEN2 syndrome and malignant pheochromocytoma. On direct comparison, lesion-based accuracy of ⁶⁸Ga-DOTANOC PET/CT for pheochromocytoma was significantly higher than ¹³¹I-MIBG imaging (91.1 vs 66.6 %, p?=?0.035). SUV_max was higher for pheochromocytomas than other adrenal lesions (p?=?0.005), MEN2-associated vs sporadic pheochromocytoma (p?=?0.012), but no difference was seen between benign vs malignant pheochromocytoma (p?=?0.269).

Conclusion

⁶⁸Ga-DOTANOC PET/CT shows high diagnostic accuracy in patients with suspicion of pheochromocytoma and is superior to ¹³¹I-MIBG imaging for this purpose. Best results of ⁶⁸Ga-DOTANOC PET/CT are seen in patients with MEN2-associated and malignant pheochromocytoma.