Incidental colonic focal lesions detected by FDG PET/CT

OBJECTIVE: The aim of this study was to assess the performance of FDG PET/CT for the detection of colonic lesions, especially advanced neoplasms (villous or >10-mm adenomas, carcinomas). Because of 18F FDG accumulation in adenomatous polyps, PET using FDG can detect early premalignant colorectal lesions. MATERIALS AND METHODS: FDG PET/CT studies performed for a 1-year period in 1,716 consecutive patients with various malignant diseases, except colorectal cancer, were retrospectively reviewed. PET images obtained 1 hr after FDG injection and non-contrast CT images used for attenuation correction were fused for analysis. Of 45 patients showing intense focal colonic FDG uptake, 20 patients (with 21 foci) underwent a colonoscopic investigation, and, when necessary, polyp resection. The intensity of FDG uptake was quantified using the standardized uptake value (SUV(max)). RESULTS: The FDG colonic foci were associated with 18 colonoscopic abnormalities in 15 patients, with no colonic abnormality detected in five patients (false-positive [FP] results). Histopathologic findings revealed advanced neoplasms in 13 patients (13 villous adenomas and three carcinomas) and two cases of hyperplastic polyps. A difference in the mean SUV(max) was found between FP and true-positive colonic FDG foci but was not statistically significant (p = 0.14). CONCLUSION: Presence of a focal colonic FDG uptake incidental finding on a PET/CT scan justifies a colonoscopy to detect (pre-)malignant lesions. The fusion of PET and CT images allows an accurate localization of the lesions. PET/CT is a useful tool to differentiate pathologic from physiologic FDG uptake.     

Focal uptake of fluorodeoxyglucose by the thyroid in patients undergoing initial disease staging with combined PET/CT for non-small cell lung cancer

PURPOSE: To retrospectively evaluate the prevalence of focal fluorodeoxyglucose (FDG) uptake by the thyroid gland on combined positron emission tomographic (PET) and computed tomographic (CT) scans in patients undergoing staging of newly diagnosed non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: Institutional review board approval was obtained, informed consent was waived, and the study was Health Insurance Portability and Accountability Act-compliant. Whole-body PET/CT scans and medical records of 140 consecutive patients with newly diagnosed NSCLC (80 men, 60 women; mean age, 66 years; range, 39-89 years) were retrospectively reviewed by two experienced PET/CT scan readers. Maximum standardized uptake value (SUV) was calculated for FDG-avid thyroid foci. Corresponding thyroid CT findings were recorded in patients with focal increased FDG thyroid uptake. RESULTS: PET results showed that six patients (4.3%) had seven foci of increased FDG uptake in the thyroid. Five of the seven foci (in four patients) corresponded to a low-attenuation thyroid lesion on the non-enhanced CT scan. Lesions ranged in diameter from 0.8 to 2.5 cm. Four of the lesions were found to be papillary thyroid cancers at fine-needle aspiration biopsy. The fifth lesion was found to be benign at thyroidectomy. The remaining two patients did not have histologic confirmation of their thyroid lesion because no specific biopsy site was visualized on CT or sonographic images and lesions were considered benign. Maximum SUV of the thyroid cancers ranged from 3.0 to 32.9 (mean, 13.7). Maximum SUV of benign thyroid lesions ranged from 4.6 to 6.2 (mean, 5.4). CONCLUSION: Focal thyroid FDG uptake found during the initial staging of NSCLC at PET/CT indicates a high likelihood of primary thyroid cancer.     

Diagnostic accuracy of FDG PET imaging for the detection of recurrent or metastatic gynecologic cancer

PURPOSE: This study evaluated the diagnostic role and accuracy of positron emission tomography (PET) using 2-[F-18]fluoro-2-deoxy-D-glucose (FDG) for the detection of tumor foci in patients with suspected recurrent or metastatic lesions of gynecologic cancers. MATERIALS AND METHODS: FDG PET imaging was performed on 51 patients with a previous history of gynecologic cancer who were referred for a clinical suspicion of recurrent disease. PET acquisition was started 50-60 min after the intravenous injection of 5-6 MBq/kg FDG in all patients. The PET images were interpreted visually, and tracer uptake was quantitated as the standardized uptake value adjusted to body weight (SUV) in the lesions showing FDG uptake. The accuracy of the PET results was assessed by a consensual verdict based on histology, cytology, other imaging and clinical follow-up. RESULTS: FDG PET correctly diagnosed 33 of 36 patients with recurrent disease and 12 of 15 patients without recurrence. On patient-based analysis, the sensitivity, specificity and accuracy of FDG PET were 91.7%, 80.0% and 88.2%, respectively, depending on the selected scheme for visual scoring of the lesions. The area index in receiver-operating characteristic analysis was 0.95 for patient detection. Malignant lesions accumulated significantly more FDG than the benign ones (the mean SUVs were 3.7 +/- 1.9 and 1.6 +/- 1.1, respectively, p = 0.004). The sensitivity and specificity in correct identification of tumor recurrence or metastases using a threshold SUV 1.9 were 88.8% and 66.7% in contrast to the visual analysis (sensitivity 96.4%, specificity 50%) on a lesion-based analysis. The partial volume effect of SUV in a few small lesions and the presence of bone lesions in which FDG uptake was relatively low might be the reason for the lower sensitivity in SUV analysis. FDG PET was valuable when CT/MRI was negative or inconclusive, and in patients with elevated tumor marker levels as well as with normal tumor marker levels when recurrence was suspected clinically. However, PET failed to visualize some small metastatic lesions in lung and bone, and showed falsely high FDG uptake in some benign lesions. CONCLUSION: The results indicated that FDG PET is a reliable and accurate diagnostic method for detecting recurrent or metastatic gynecologic cancer particularly lymph node metastases. Although the sensitivity of PET for detecting small metastases was relatively limited, the overall sensitivity of FDG PET was significantly higher than morphologic imaging.     

Optimal interpretation of FDG PET in the diagnosis, staging and management of pancreatic carcinoma.

This study had two purposes: to optimize the semiquantitative interpretation of 18F-fluorodeoxyglucose (FDG) PET scans in the diagnosis of pancreatic carcinoma by analyzing different cutoff levels for the standardized uptake value (SUV), with and without correction for serum glucose level (SUV(gluc)); and to evaluate the usefulness of FDG PET when used in addition to CT for the staging and management of patients with pancreatic cancer. METHODS: Sixty-five patients who presented with suspected pancreatic carcinoma underwent whole-body FDG PET in addition to CT imaging. The PET images were analyzed visually and semiquantitatively using the SUV and SUV(gluc). The final diagnosis was obtained by pathologic (n = 56) or clinical and radiologic follow-up (n = 9). The performance of CT and PET at different cutoff levels of SUV was determined, and the impact of FDG PET in addition to CT on patient management was reviewed retrospectively. RESULTS: Fifty-two patients had proven pancreatic carcinoma, whereas 13 had benign lesions, including chronic pancreatitis (n = 10), benign biliary stricture (n = 1), pancreatic complex cyst (n = 1) and no pancreatic pathology (n = 1). Areas under receiver operating characteristic curves were not significantly different for SUV and SUV(gluc). Using a cutoff level of 3.0 for the SUV, FDG PET had higher sensitivity and specificity than CT in correctly diagnosing pancreatic carcinoma (92% and 85% versus 65% and 61%). There were 2 false-positive PET (chronic pancreatitis, also false-positive with CT) and 4 false-negative PET (all with true-positive CT, abnormal but nondiagnostic) examinations. There were 5 false-positive CT (4 chronic pancreatitis and 1 pancreatic cyst) and 18 false-negative CT (all with true-positive FDG PET scans) examinations. FDG PET clarified indeterminate hepatic lesions or identified additional distant metastases (or both) in 7 patients compared with CT. Overall, FDG PET altered the management of 28 of 65 patients (43%). CONCLUSION: FDG PET is more accurate than CT in the detection of primary tumors and in the clarification and identification of hepatic and distant metastases. The optimal cutoff value of FDG uptake to differentiate benign from malignant pancreatic lesions was 2.0. Correction for serum glucose did not significantly improve the accuracy of FDG PET. Although FDG PET cannot replace CT in defining local tumor extension, the application of FDG PET in addition to CT alters the management in up to 43% of patients with suspected pancreatic cancer.     

(18)F-FDG PET versus (18)F-FDG PET/CT for adrenal gland lesion characterization: a comparison of diagnostic efficacy in lung cancer patients.

OBJECTIVE: The aim of this study was to assess the diagnostic efficacy of integrated PET/CT using fluorodeoxyglucose (FDG) for the differentiation of benign and metastatic adrenal gland lesions in patients with lung cancer and to compare the diagnostic efficacy with the use of PET alone. MATERIALS AND METHODS: Sixty-one adrenal lesions (size range, 5-104 mm; mean size, 16 mm) were evaluated retrospectively in 42 lung cancer patients. Both PET images alone and integrated PET/CT images were assessed, respectively, at two-month intervals. PET findings were interpreted as positive if the FDG uptake of adrenal lesions was greater than or equal to that of the liver, and the PET/CT findings were interpreted as positive if an adrenal lesion show attenuation > 10 HU and showed increased FDG uptake. Final diagnoses of adrenal gland lesions were made at clinical follow-up (n = 52) or by a biopsy (n = 9) when available. The diagnostic accuracies of PET and PET/CT for the characterization of adrenal lesions were compared using the McNemar test. RESULTS: Thirty-five (57%) of the 61 adrenal lesions were metastatic and the remaining 26 lesions were benign. For the depiction of adrenal gland metastasis, the sensitivity, specificity, and accuracy of PET were 74%, 73%, and 74%, respectively, whereas those of integrated PET/CT were 80%, 89%, and 84%, respectively (p values; 0.5, 0.125, and 0.031, respectively). CONCLUSION: The use of integrated PET/CT is more accurate than the use of PET alone for differentiating benign and metastatic adrenal gland lesions in lung cancer patients.     

Bone invasion in patients with oral cavity cancer: comparison of conventional CT with PET/CT and SPECT/CT

PURPOSE: To prospectively compare the accuracy of helical contrast material-enhanced computed tomography (CT) with that of CT and positron emission tomography (PET) combined and CT and single photon emission CT (SPECT) combined in the detection of bone invasion in patients scheduled to undergo surgery for clinically suspected oral cavity carcinoma with possible bone invasion, with surgical results as the reference standard. MATERIALS AND METHODS: This study had local ethical committee approval, and all patients gave written informed consent. Thirty-four consecutive patients (17 men, 17 women; mean age, 64.2 years; age range, 46.0-84.6 years) who were clinically suspected of having bone invasion from oral cavity carcinoma prospectively underwent helical contrast-enhanced CT, coregistered PET/CT, and coregistered SPECT/CT. Two radiologists assessed the contrast-enhanced CT images and two nuclear medicine physicians separately assessed the PET/CT and SPECT/CT images in consensus and without knowledge of the results of other imaging tests. The presence of bone involvement as suggested with an imaging modality was compared with histologic findings in the surgical specimen. RESULTS: With histologic findings as the standard of reference, the accuracy of SPECT/CT (88% [30 of 34 patients]) was lower than that of PET/CT and contrast-enhanced CT (94% [32 of 34 patients] and 97% [33 of 34 patients], respectively). Sensitivity was highest with PET/CT (100% [12 of 12 patients]), and specificity was highest with contrast-enhanced CT (100% [22 of 22 patients]). Fluorine 18 fluorodeoxyglucose (FDG) uptake seen on two sides of the same cortical bone was not a helpful imaging pattern for better identifying bone invasion in patients without evident cortical erosion on CT scans. CONCLUSION: The assessment of cortical erosion with contrast-enhanced CT and the CT information from PET/CT are the most reliable methods for detecting bone invasion in patients with oral cavity carcinoma. FDG uptake seen on PET/CT images does not improve identification of bone infiltration.     

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.     

Head and neck cancer: clinical usefulness and accuracy of PET/CT image fusion

PURPOSE: To compare diagnostic accuracy of attenuation-corrected positron emission tomography (PET) with fused PET and computed tomography (CT) in patients with head and neck cancer and to evaluate the effect of PET/CT findings on patient care. MATERIALS AND METHODS: Studies of 68 patients were reviewed by two physicians in consensus. Focal fluorodeoxyglucose (FDG) uptake in the head and neck on attenuation-corrected PET images was graded as benign, equivocal, or malignant. CT and PET/CT images were then reviewed, and initial findings were amended if necessary. Comparison was performed on a lesion-by-lesion basis. Accuracy was evaluated on the basis of follow-up and histopathologic findings. Potential effects on patient care were assessed by a head and neck surgeon. PET and PET/CT accuracy was compared with a McNemar test adjusted for clustering. RESULTS: A total of 157 foci with abnormal FDG uptake were noted, two of which were seen only on PET/CT images. PET/CT images were essential in determining the exact anatomic location for 100 lesions (74% better localization in regions previously treated surgically or with irradiation vs 58% in untreated areas; P =.06). On the basis of PET findings alone, 45 lesions were considered benign; 39, equivocal; and 71, malignant. With PET/CT, the fraction of equivocal lesions decreased by 53%, from 39 of 155 to 18 of 157 (P <.01). PET/CT had a higher accuracy of depicting cancer than did PET (96% vs 90%, P =.03). Six proved malignancies were missed with PET, but only one was missed with PET/CT. PET/CT findings altered the care for 12 (18%) of 68 patients. CONCLUSION: PET/CT is more accurate than PET alone in the detection and anatomic localization of head and neck cancer and has the clear potential to affect patient care.     

90Y microsphere treatment of unresectable liver metastases: changes in 18F-FDG uptake and tumour size on PET/CT

Purpose The intra-arterial administration of ⁹⁰Y microspheres is a new palliative treatment option for unresectable liver metastases. The aim of this study was to quantitatively assess changes in FDG uptake and tumour size following ⁹⁰Y microsphere treatment (SIR-Spheres) using ¹⁸F-fluorodeoxyglucose (FDG) PET/CT imaging.Methods Five patients with unresectable liver metastases who had failed multiple prior chemotherapy regimens received seven ⁹⁰Y microsphere treatments to a single liver lobe. All patients underwent a baseline PET/CT scan prior to treatment, as well as up to four follow-up PET/CT scans. The tumour area of 30 liver metastases was measured on CT and the FDG uptake was semiquantitatively assessed by calculation of standardised uptake values (SUVs). A total of 18 FDG-PET/CT scans were performed.Results The SUVs in the 30 treated liver metastases decreased from 6.5±2.3 at baseline to 4.2±1.8 after the first follow-up PET/CT scan (p=0.001). In contrast, the SUVs of untreated metastases increased slightly from 7.2±2.3 to 8.0±0.8. There was no difference in FDG uptake in treated versus untreated normal liver tissue. Using a previously defined threshold of 20% decrease in SUV from baseline to determine response, 20 out of 30 liver metastases were considered to have responded at the first follow-up PET/CT scan approximately 1 month after treatment. In these metastases, the SUV decreased by 47±12%, compared with a slight increase by 5.9±19% in ten non-responding metastases (p=0.0001). The changes in tumour size did not correlate with changes in FDG uptake. On the first follow-up PET/CT scan, the tumour area on CT increased by 3.1±57% in treated metastases compared with 23.3±32% in untreated metastases. A wide range of post-treatment changes of target lesions was observed on CT, including an increase in the size of hypodense lesions, necrotic features and complete resolution of CT abnormalities.Conclusion The metabolic information obtained from FDG-PET/CT seems to provide a more accurate and earlier assessment of therapy response following ⁹⁰Y microsphere treatment than does the anatomical CT information.     

Detection of liver metastases from pancreatic cancer using FDG PET.

We evaluated the potential of the glucose analog [18F]fluorodeoxyglucose (FDG) as a PET tracer for the hepatic staging in 168 patients designated for resective pancreatic surgery. METHODS: Metastatic liver disease was confirmed or excluded during surgery or with CT follow-up for at least 6 mo. Proven metastases were then retrospectively identified on preoperative CT (gold standard). Hepatic PET scans of all patients were interpreted blindly. Any focal FDG uptake was considered malignant. Both proven hepatic metastases and suspicious hepatic PET lesions were then compared, lesion by lesion, with CT. Standardized uptake values (SUV) and tumor-to-liver ratios (T/L) were determined for the most intense lesion of each patient. RESULTS: Sensitivity of FDG PET was 68% (15 of 22 patients). The lesion detection rate was 97% (28 of 29 metastases) for lesions >1 cm and 43% (16 of 37 metastases) for lesions < or = 1 cm. Specificity was 95% (138 of 146 patients). Six of eight patients with false-positive results had marked intrahepatic cholestasis (versus 3 of 15 patients with true-positive lesions), one had an infrahepatic abscess and one had a right basal pulmonary metastasis. The SUV and T/L were 4.6+/-1.4 and 2.3+/-1.1, respectively, for malignant lesions and 4.1+/-1.5 and 1.9+/-0.3, respectively, for false-positive lesions and therefore are of limited value. CONCLUSION: FDG PET provides reliable hepatic staging for lesions >1 cm. False-positive results are associated with the presence of marked intrahepatic cholestasis. For lesions < or = 1 cm, FDG PET can define malignancy in 43% of suspicious CT lesions in the absence of dilated bile ducts.     

Metastatic eccrine porocarcinoma detected on FDG PET/CT

Eccrine porocarcinoma is an uncommon neoplasm of the sweat gland duct and poses a significant risk of cutaneous, regional lymph node, or visceral metastases. A 62-year-old woman with a history of eccrine porocarcinoma in the left flank area underwent an F-18 FDG PET/CT scan, which revealed increased FDG uptake in left pelvic (SUV 6.34) and left axillary regions (SUV 4.02). Wide excision of left axillary and left pelvic lymph nodes was performed, and histopathologic findings were consistent with eccrine porocarcinoma. PET/CT detects metastases accurately and is helpful in the management of patients with eccrine porocarcinoma.     

Unexpected finding of elevated glucose uptake in fibrous dysplasia mimicking malignancy: contradicting metabolism and morphology in combined PET/CT

Fibrous dysplasia is a common benign disorder of bone in which fibro-osseous tissue replaces bone spongiosa. Lesions have a typical appearance on computed tomography (CT) images and regularly show a markedly increased uptake in bone scintigraphy using ^99mTc-labelled methylene diphosphonate (^99mTc-MDP) as radiotracer. The glucose avidity of these lesions depicted by positron emission tomography (PET) using the radiolabelled glucose derivative ¹⁸F-fluoro-2-deoxy-glucose (FDG) is less well known since FDG-PET does not have a role in the assessment of this disease. However, single cases have been reported in which fibrous dysplasia was present in patients undergoing FDG-PET scanning for oncological reasons, and no significant FDG uptake was observed for lesions identified as fibrous dysplasia. We report on a 24-year-old man with known fibrous dysplasia who underwent combined FDG-PET/CT scanning because of suspected recurrence of testicular cancer. In contrast to prior reports, a markedly elevated uptake of FDG was seen in numerous locations that were identified as fibrous dysplasia by CT. Based on this result, we conclude that fibrous dysplasia may mimick malignancy in FDG-PET and that coregistered CT may help to resolve these equivocal findings.     

Role of 18F-FDG PET/CT in differentiation of a benign lesion and metastasis on the ribs of cancer patients

ObjectiveIncidental 18-Fluoro-2-deoxyglucose positron emission tomography (¹⁸F-FDG) uptake in the ribs is a relatively common finding on positron emission tomography/computed tomography (PET/CT) images of cancer patients. This study examined the role of ¹⁸F-FDG PET/CT in differentiating between benign lesions and metastases on the ribs.MethodsThis study included 264 lesions in 172 PET/CT cases with underlying malignancy showing newly developed indeterminate ¹⁸F-FDG rib uptake between June 2009 and May 2010. Patients with more than five FDG rib uptakes or hematologic malignancy were excluded. Malignancy was confirmed either histologically or by imaging studies, and clinical follow-up with serial images was at least 6 months. The maximum standardized uptake value (SUVmax) of the rib lesion was recorded. The FDG uptake patterns (focal or segmental; discrete or non-discrete) and CT findings (evidence of fracture, soft tissue lesions, osteoblastic and/or osteolytic lesions) were recorded.ResultsThere were 206 benign lesions and 58 metastases. The SUVmax was significantly higher in the metastatic group (3.0±1.8) than in the benign group (2.5±1.1), (P= .014). For the differential diagnosis between benign and metastatic lesions, the best SUVmax cut-off was determined to be 2.4. Significant indicators for metastasis were a segmental FDG uptake pattern (OR=10.262, 95% CI 4.151–25.371), presence of an osteoblastic/-lytic lesion (OR=22.903, 95% CI 10.468 to 50.108) and the absence of fractures on CT (OR=291.629, 95% CI 39.09–2175.666).ConclusionSUVmax alone is not sufficient to differentiate benign and metastatic rib lesions in cancer patients. The diagnostic accuracy can be further increased when findings of the CT part of PET/CT are considered.     

Contribution of PET in the detection of liver metastases from pancreatic tumours

AIM: Although uptake of 2-deoxy-2-[fluorine-18]fluoro-D-glucose (FDG) in the liver is basically high, metastatic liver tumours are known to be positive on positron emission tomography (PET). The purpose of this study is to evaluate the diagnostic accuracy of FDG-PET in detecting hepatic metastases from pancreatic cancer. METHODS: Thirty-four patients with histologically proven malignant tumours of the pancreas underwent FDG-PET, computed tomography (CT) and transabdominal ultrasound (US). The findings of PET, CT and US were compared with the histopathologic findings at surgery or with clinical follow-up and the diagnostic accuracy of PET was evaluated. RESULTS: PET showed 28 regions of high FDG uptake (SUV = 3.3-9.1) in 13 patients. Twenty-six foci were metastatic lesions confirmed by surgery (n = 11), clinical follow-up (n = 10) or autopsy (n = 5). FDG-PET accurately differentiated seven metastatic lesions from cysts when the diagnosis by US or CT was unreliable because of the small size of the lesion. In two patients who had areas of high uptake in the liver, no metastases were detected by surgery. FDG-PET showed no areas of increased uptake in 21 patients. Surgery revealed no metastatic lesions in the liver in 20 of 21 patients, but a liver metastasis was found at surgery in one patient. The diagnostic accuracy of FDG-PET was 90%, which was comparable with that of US or CT. CONCLUSION: Our data suggest that PET is reliable in detecting liver, metastases from pancreatic cancer.     

FDG-PET and CT patterns of bone metastases and their relationship to previously administered anti-cancer therapy

Purpose To assess ¹⁸F-fluorodeoxyglucose (FDG) uptake in bone metastases in patients with and without previous treatment, and compare positive positron emission tomography (PET) with osteolytic or osteoblastic changes on computed tomography (CT).Methods One hundred and thirty-one FDG-PET/CT studies were reviewed for bone metastases. A total of 294 lesions were found in 76 patients, 81 in untreated patients and 213 in previously treated patients. PET was assessed for abnormal FDG uptake localised by PET/CT to the skeleton. CT was evaluated for bone metastases and for blastic or lytic pattern. The relationship between the presence and pattern of bone metastases on PET and CT, and prior treatment was statistically analysed using the chi-square test.Results PET identified 174 (59%) metastases, while CT detected 280 (95%). FDG-avid metastases included 74/81 (91%) untreated and 100/213 (47%) treated lesions (p<0.001). On CT there were 76/81 (94%) untreated and 204/213 (96%) treated metastases (p NS). In untreated patients, 85% of lesions were seen on both PET and CT (26 blastic, 43 lytic). In treated patients, 53% of lesions were seen only on CT (95 blastic, 18 lytic). Of the osteoblastic metastases, 65/174 (37%) were PET positive and 98/120 (82%), PET negative (p<0.001).Conclusion The results of the present study indicate that when imaging bone metastases, prior treatment can alter the relationship between PET and CT findings. Most untreated bone metastases are PET positive and lytic on CT, while in previously treated patients most lesions are PET negative and blastic on CT. PET and CT therefore appear to be complementary in the assessment of bone metastases.     

Indeterminate pleural metastasis on contrast-enhanced chest CT in non-small cell lung cancer: improved differential diagnosis with 18F-FDG PET/CT

Purpose

To evaluate the diagnostic performance of ¹⁸F-fluorodeoxyglucose (FDG) PET/CT (PET/CT) for determining the presence of pleural metastasis in patients with indeterminate findings on a contrast-enhanced chest CT (CECT) for non-small cell lung cancer (NSCLC).

Materials and methods

This is a retrospective study. NSCLC patients (n?=?63) who underwent thoracentesis and/or pleural biopsy were enrolled. CECT and PET/CT reports of pleural metastasis were analyzed based on comparison with cytological or histological confirmation. Negative cytologic results were re-confirmed with follow-up study prior to cancer-related therapy. CECT results were classified into 3 categories: negative, indeterminate, and positive for pleural metastasis. PET/CT results were classified into 2 categories (negative and positive for pleural metastasis) based on FDG uptake visual grading. The level of max SUV of pleura was also analyzed. ROC analysis was done for establishing the max SUV cut-off value.

Result

PET/CT could differentiate pleural metastasis with 70.8% diagnostic accuracy when the CECT finding was indeterminate (n?=?24). Optimal cut-off value to predict pleural metastasis was 2.8 for max SUV. Diagnosis by max SUV 2.8 had lower sensitivity (86.3 vs. 92.2%), but higher specificity (66.7 vs. 58.3%) than PET/CT by FDG visual grading criteria.

Conclusion

PET/CT showed better diagnostic performance than CECT for detecting pleural metastasis in NSCLC patients. When the finding of CECT is controversial, PET/CT can differentiate the metastatic pleural lesion. Both FDG uptake visual grading and max SUG cut-off value can be used as diagnostic criteria for pleural metastasis.     

FDG-PET/CT in the evaluation of epithelioid hemangioendothelioma of the liver: the role of dual-time-point imaging. A case presentation and review of the literature

A 46-year-old man with liver lesions referred to us as having “metastases of a malignant mesenchymal tumor” underwent PET/computerized tomography (CT) imaging for the localization of the primary tumor and determination of the extent of disease. No pathological FDG uptake was observed in PET/CT images obtained after 60 min, following FDG injection but delayed PET/CT images demonstrated intense FDG uptake at the liver masses. Since the PET/CT findings were discordant with the initial diagnosis, the pathology specimen was reevaluated and with certain immunohistochemical examinations, the final histopathological decision was changed to epithelioid hemangioendothelioma (EHE). In this report, we discuss the FDG uptake pattern in a patient with hepatic EHE and emphasize the importance of dual-time-point hepatic FDG-PET/CT imaging.     

F-18 FDG PET/CT in the management of thyroid cancer

PURPOSE: There are approximately 32,000 new cases of thyroid carcinoma annually in the United States. F-18 FDG PET/CT has an established role in cancer management, including thyroid cancer, usually in patients who are thyroglobulin (Tg) positive/iodine negative. We reviewed our experience with F-18 FDG PET/CT in thyroid cancer, with an emphasis on correlation with Tg, and maximum standardized uptake values (SUV). We also analyzed the role of thyroid stimulating hormone (TSH) on PET/CT results. MATERIALS AND METHODS: This is a retrospective study (January 2003 to December 2006) of 76 patients with differentiated thyroid cancer, who had F-18 FDG PET/CT scans. There were 44 women and 32 men, with age range of 20 to 81 years (average, 51.1 +/- 18.1). The administered doses of F-18 FDG ranged from 396 to 717 MBq (15.8-19.4 mCi) (average, 566 +/- 74.8) (15.3 +/- 2). Reinterpretation of the imaging studies for accuracy and data analysis from medical records were performed. RESULTS: A total of 98 PET/CT scans were analyzed (59 patients had 1 scan, 12 patients had 2, and 5 patients had 3). PET/CT was 88.6% sensitive (95% CI: 78.-94.3) and 89.3% specific (95% CI: 71.9-97.1). Mean Tg level was 1203 ng/mL (range, 0.5-28,357) in patients with positive PET/CT and 9.72 ng/mL (range, 0.5-123.0) in patients with negative PET/CT scans (P = 0.0389). Mean SUV max was 10.8 (range, 2.5-32) in the thyroid bed recurrence/residual disease and 7.53 (range, 2.5-26.2) in metastatic lesions (P = 0.0114). Mean SUV max in recurrent/residual disease in patients with TSH 30 mIU/L was 8.1 (range, 2.6-32) (P = 0.2994). CONCLUSION: F-18 FDG PET/CT had excellent sensitivity (88.6%) and specificity (89.3%) in this patient population. Metastatic lesions were reliably identified, but were less F-18 FDG avid than recurrence/residual disease in the thyroid bed. TSH levels at the time of PET/CT did not appear to impact the FDG uptake in the lesions or the ability to detect disease. In the setting of high or rising levels of Tg, our study confirms that it is indicated to include PET/CT in the management of patients with differentiated thyroid cancer.     

Adrenal-to-liver SUV ratio is the best parameter for differentiation of adrenal metastases from adenomas using 18F-FDG PET/CT

Purpose

To investigate the best standardized uptake value (SUV) index for differentiation of adrenal metastases from adrenocortical adenomas using 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT).

Materials and methods

A total of 129 patients (82 males and 47 females; mean age 65.4 years) with extra-adrenal primary malignancies who had known or suspected adrenal lesions underwent FDG PET/CT examinations for detection, staging, re-staging, or recurrence of tumor. Among these patients, 45 adrenal lesions (22 adenomas and 23 metastases) in 41 patients were evaluated. The maximum SUVs for adrenal lesions (adrenal SUVmax) and mean liver and spleen SUVs were recorded, and the ratio of the adrenal SUVmax to the mean liver SUV (adrenal-to-liver SUV ratio) and that of the adrenal SUVmax to the mean spleen SUV (adrenal-to-spleen SUV ratio) were obtained. Diagnostic performances for the adrenal SUVmax, adrenal-to-liver SUV ratio, and adrenal-to-spleen SUV ratio were compared.

Results

The mean adrenal SUVmax, adrenal-to-liver SUV ratio, and adrenal-to-spleen SUV ratio were higher for adrenal metastases (8.4 ± 3.8, 3.0 ± 1.3, and 4.0 ± 1.9, respectively) than for adrenocortical adenomas (2.9 ± 1.0, 0.9 ± 0.3, and 1.3 ± 0.3, respectively) (P < 0.001). The area under the curve was higher for the adrenal-to-liver SUV ratio (0.99) than for the adrenal SUVmax (0.96) and adrenal-to-spleen SUV ratio (0.98). In the differentiation of adrenocortical adenomas and adrenal metastases, an adrenal-to-liver SUV ratio cutoff value of 1.37 yielded a sensitivity of 96 % and specificity of 100 %.

Conclusion

In FDG PET/CT analysis, the adrenal-to-liver SUV ratio had a greater ability to differentiate adrenocortical adenomas and adrenal metastases than did the adrenal SUVmax or adrenal-to-spleen SUV ratio.     

Dual-time-point [18F]-FDG PET/CT in the diagnostic evaluation of suspicious breast lesions

Purpose

The authors sought to evaluate whether the reacquisition of images 3 h after administration of radiotracer improves the sensitivity of fluorine-18 fluorodeoxyglucose positron emission tomography computed tomography ([¹⁸F]-FDG PET/CT) in patients with suspicious breast lesions.

Materials and methods

Forty-eight patients with 59 breast lesions underwent an [¹⁸F]-FDG PET/CT study in the prone position with a dual-time-point acquisition performed in the early phase 1 h after FDG administration (PET-1) and in the delayed phase 3 h after FDG administration (PET-2). Both examinations were evaluated qualitatively and semiquantitatively with calculation of the mean percentage variation of the standard uptake values (Δ% SUV_max) between PET-1 and PET-2. All lesions with an SUV_max ≥2.5 at PET-1 or a reduction in SUV between PET-1 and PET-2 were considered benign. The definitive histopathological diagnosis was available for all patients included in the study.

Results

The dual-time-point acquisition of [¹⁸F]-FDG PET/CT displayed an accuracy of 85% for lesions with an SUV_max ≥2.5 and/or positive Δ% SUV_max, with sensitivity and specificity values of 81% and 100% compared with 69%, 63% (both p<0.001) and 100% (p=n.s.), respectively, for the single-time-point acquisition. Malignant lesions showed an increase in FDG uptake between PET-1 and PET-2, with a Δ% SUV_max of 10±7 (p<0.04). In contrast, benign lesions showed a decrease in SUV between PET-1 and PET-2, with aΔ% SUV_max of ?21±7 (p<0.001).

Conclusions

The delayed repeat acquisition of PET images improves the accuracy of [¹⁸F]-FDG PET/CT in patients with suspicious breast lesions with respect to the single-time-point acquisition. In addition, malignant breast lesions displayed an increase in FDG uptake over time, whereas benign lesions showed a reduction. These variations in FDG uptake between PET-1 and PET-2 are a reliable parameter that can be used for differentiating between benign and malignant breast lesions.