淋巴瘤骨髓浸润的18F-FDG PET显像研究

目的 用^18F-脱氧葡萄糖（FDG）PET显像研究淋巴瘤细胞骨髓浸润。方法 恶性淋巴癌患者30例，其中非霍奇金淋巴瘤（NHL）20例、霍奇金病（HD）10例，进行全身^18F-FDG PET显像。局灶性边缘清楚的淋巴结相应区域^18F-FDG浓聚视为恶性淋巴结显影。利用灰度色标，视觉分析骨髓及肝脏内^18F-FDG浓聚情况。骨髓的^18F-FDG分布不均，摄取高于肝脏，判断为骨髓^18F-FDG摄取异常；骨髓的^18F-FDG分布均匀，摄取低于或等于肝脏，判断为骨髓^18F-FDG摄取正常。所有患者均行髂棘的骨髓活组织检查。结果 30例中18例有淋巴结摄取^18F-FDG；12例淋巴结摄取^18F-FDG阴性患者中，8例NHL，4例HD。有26例患者的骨髓^18F-FDG摄取情况与骨髓组织学检查结果一致，其中骨髓有淋巴细胞浸润7例，无淋巴细胞浸润19例。有3例骨髓组织学检查阴性的患者，^18F-FDG PET示骨髓^18F-FDG摄取异常、骨髓有淋巴细胞浸润；1例NHL患者，骨髓组织学检查阳性但^18F-FDG PET示骨髓^18F-FDG摄取正常。结论 ^18F-DG PET全身显像能正确评价骨髓淋巴细胞浸润情况，减少对淋巴瘤分期所进行的骨髓组织学检查。     

Enhanced myocardial fluorodeoxyglucose uptake following Adriamycin-based therapy: Evidence of early chemotherapeutic cardiotoxicity?

AIM: To analyze changes in myocardial glucose metabolism using fluorodeoxyglucose (FDG)-positron emission tomography (PET) in patients treated with adriamycin and to investigate the clinical significance of these changes.METHODS: Considering that FDG-PET scanning has the ability to show changes in glucose metabolism in the myocardium, we retrospectively analyzed the FDGPET studies of 18 lymphoma patients treated with adriamycin-based chemotherapy in both the preand posttherapy setting. Cardiac contractile parameters such as left ventricular ejection fraction were not available for correlation in all patients due to the short duration and the level of cumulative dose administered in these patients during the time of the follow-up FDG-PET study. The change in myocardial glucose utilization was estimated by change in standard uptake values (SUV) in the myocardium.RESULTS: We observed a significant change in SUVmean values in the myocardium (defined as more than change in cardiac SUVmean between pre-and post-chemotherapy PET) in 1 patients, whereas 6 patients did not show any significant cardiac FDG uptake in both preand post-therapy PET scans. Patients were divided into three groups based on the changes observed in myocardial tracer uptake on the followup 18 F-FDG-PET study. Group A (n = 8): showed an increase in cardiac 18 F-FDG uptake in the post-therapy scan compared to the baseline scan carried out prior to starting adriamycin-based chemotherapy. Group B (n = 6): showed no significant cardiac 18 F-FDG uptake in post-therapy and baseline PET scans, and group C (n = 4): showed a fall in cardiac 18 F-FDG uptake in the posttherapy scan compared to the baseline scan. Mean cumulative adriamycin dose (in mg/m 2 ) received during the time of the follow-up FDG-PET study was 256. 25, 250 and 137.5, respectively.CONCLUSION: Our study shows three different trends in the change in myocardial glucose metabolism in patients undergoing adriamycin-based chemotherapy. A further prospective study with prolonged follow-up of ventricular function is warranted to explore the significance of enhanced FDG uptake as a marker of early identification of adriamycin-induced cardiotoxicity.     

Value of FDG PET in papillary thyroid carcinoma with negative 131I whole-body scan.

The management of metastatic thyroid carcinoma patients with a negative 131I scan presents considerable problems. Fifty-four athyrotic papillary thyroid carcinoma patients whose 1311 whole-body scans were negative underwent 18F-fluorodeoxyglucose (FDG) PET; the purpose was to determine whether this procedure could localize metastatic sites. We also assessed its usefulness in the management of these patients. METHODS: Whole-body emission scan was performed 60 min after the injection of 370-555 MBq 18F-FDG, and additional regional attenuation-corrected scans were obtained. Metastasis was pathologically confirmed in 12 patients and was confirmed in other patients by overall clinical evaluation of the findings of other imaging studies and of the subsequent clinical course. RESULTS: In 33 patients, tumor had metastasized, whereas 21 patients were in remission. FDG PET revealed metastases in 31 patients (sensitivity 93.9%), whereas thyroglobulin levels were elevated in 18 patients (sensitivity 54.5%). FDG PET was positive in 14 of 15 metastatic cancer patients with normal thyroglobulin levels. In 20 of 21 patients in remission, FDG PET was negative (specificity 95.2%), whereas thyroglobulin levels were normal in 16 patients (specificity 76.1%). The sensitivity and specificity of FDG PET were significantly higher than those of serum thyroglobulin. In patients with negative 1311 scans, FDG PET detected cervical lymph node metastasis in 87.9%, lung metastasis in 27.3%, mediastinal metastasis in 33.3% and bone metastasis in 9.1%. In contrast, among 117 patients with 131I scan-positive functional metastases, 131I scan detected cervical lymph node metastasis in 61.5%, lung metastasis in 56.4%, mediastinal metastasis in 22.2% and bone metastasis in 16.2%. In all 5 patients in whom thyroglobulin was false-negative with negative antithyroglobulin antibody, PET showed increased 18F-FDG uptake in cervical lymph nodes, mediastinal lymph nodes, or both. Among patients with increased 18F-FDG uptake only in the cervical lymph nodes, the nodes were dissected in 11. Metastasis was confirmed in all, even in normal-sized lymph nodes. CONCLUSION: FDG PET scan localized metastatic sites in 131I scan-negative thyroid carcinoma patients with high accuracy. In particular, it was superior to 131I whole-body scan and serum thyroglobulin measurement for detecting metastases to cervical lymph nodes. FDG PET was helpful for determining the surgical management of these patients.     

18F-FDG PET of pulmonary embolism

OBJECTIVE: The purpose of this study was to describe the manifestations of pulmonary embolism on 18F-FDG PET scans in 13 patients. CONCLUSION: The activity of acute pulmonary embolism on FDG PET scans was significantly higher than the activity of vessels not containing thrombi. The shape of the abnormal FDG uptake may be focal or curvilinear.     

Intra-individual variability of cardiac uptake on serial whole-body 18F-FDG PET

OBJECTIVE: To measure the variability of cardiac uptake on serial whole-body F-FDG PET scans. METHODS: Two hundred and eighteen whole-body PET scans were performed in 47 patients with different primary malignancies between October 1996 and April 2003 on a dedicated PET system. The number of scans per patient ranged between four and nine. Two experienced nuclear medicine physicians reviewed the scans retrospectively using the non-attenuation corrected images to assess the cardiac FDG uptake. Patients with cardiac uptake less or equal to lung uptake were assigned in the "low" uptake group, and those with cardiac uptake more than the lung uptake were assigned to the "high" uptake group. The reproducibility of cardiac uptake on serial whole-body PET scans and the effect of age, sex, weight, diabetes and primary diagnosis on cardiac uptake was evaluated. RESULTS: There was very good reproducibility (intra-class correlation coefficient=0.77) of individual cardiac FDG uptake on serial whole-body PET scans. Diabetics (n=6) in comparison to non-diabetics were less likely to have high cardiac uptake (odds ratio (OR)=0.24, P<0.05). Patients with lymphoma (n=12) in comparison to patients with other primary diagnoses were more likely to have high cardiac uptake (OR=8.6, P<0.05). There was no association between cardiac uptake and age, sex or weight. CONCLUSION: Cardiac FDG uptake on whole-body PET does not appear to change significantly over time. It is likely that uptake is determined by individual characteristics; these likely include diabetes and primary diagnosis of lymphoma.     

Follow-up FDG PET in the evaluation of unexplained focal activity in the abdomen

PURPOSE: This study assessed the value of a follow-up FDG PET scan when the initial PET demonstrated unexplained findings of focal FDG uptake in the abdomen. METHOD: The records of 3634 patients with PET scans were retrospectively reviewed. Those patients who had follow-up PET scans after the initial PET scan showed unexplained FDG activity in the abdomen were further analyzed. The results from the second PET scan were compared with the follow-up data, which included the findings from other imaging modalities, clinical course, and biopsy or surgical pathology interpretations. RESULTS: A total of 59 patients were included in the final analysis. The average time interval between the initial and the follow-up PET scans was 4.2 + 2.3 months. The follow-up PET provided a clear-cut diagnosis in 55 (93.2%) of these patients, whereas diagnoses in only 4 patients remained indeterminate. Follow-up PET scans were negative for abdominal malignancy in 38 patients. Thirty-five of these 38 patients with negative follow-up PET were proven to be without abdominal malignancy, with a negative predictive value of 92.1% (35 of 38). The follow-up PET was positive in 17 patients. Fifteen of these 17 patients with a positive follow-up PET scans were found to have malignancy in the abdomen with a positive predicative value of 88.2% (15 of 17). All 4 patients with indeterminate follow-up scans were proven not to have malignancy. CONCLUSION: Follow-up FDG PET scan provides an effective means for diagnosing unexplained findings in the abdomen that were previously detected on initial PET scan.     

Spontaneous regression of follicular, mantle cell, and diffuse large B-cell non-Hodgkin's lymphomas detected by FDG-PET imaging

Spontaneous regression of non-Hodgkin lymphoma (NHL) has been reported in low-grade tumors but is an extremely rare event in intermediate- and high-grade disease. Documentation of spontaneous regression by serial fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging has not been reported in the literature. We present 3 cases of spontaneous regression, 1 each of follicular lymphoma (FL), mantle cell lymphoma (MCL), and diffuse large B-cell lymphoma (DLBCL), which showed spontaneous regression on serial FDG-PET imaging. All patients underwent serial whole-body FDG-PET scans 60 minutes after intravenous injection of 9-11 mCi of this radiotracer. None of them had any chemotherapy, radiotherapy, or surgery after the baseline PET scan. Spontaneous regression of disease in all 3 cases was correlated with conventional imaging and clinical course. All 3 patients had positive FDG-PET results on their baseline scan. There was complete disappearance of FDG uptake on a follow-up PET scan for the patient with follicular lymphoma. These results suggest complete regression. The patients with MCL and DLBCL both showed a significant reduction in FDG uptake on serial whole-body PET scans, suggesting partial regression in both cases. Although spontaneous regression of lymphoma is uncommon, this phenomenon can be successfully demonstrated by FDG-PET imaging. Therefore, serial PET imaging may play an important role in detecting this unusual event and may further enhance our understanding of the biologic behavior of this malignancy.     

18F-FDG PET in malignant lymphoma: significance of positive findings

Purpose The aim of this study was to evaluate the significance of increased uptake of ¹⁸F-fluorodeoxyglucose (FDG) in patients with malignant lymphoma (ML) studied by positron emission tomography (PET).Methods A total of 1,120 consecutive scans carried out in 848 patients were reviewed; all patients had a diagnosis of ML [574 non-Hodgkins lymphoma (NHL) and 274 Hodgkins disease (HD)] and were studied at completion of therapy, for suspected recurrence or during follow-up. PET was carried out after intravenous injection of 370 MBq of ¹⁸F-FDG; images were recorded after 60–90 min. Patients were selected whose reports indicated areas of increased FDG uptake. PET findings were considered positive for lymphomatous localisation when uptake occurred at sites of previous disease, in asymmetrical lymph nodes or in nodes unlikely to be affected by inflammation (mediastinal, except for hilar, and abdominal). PET findings were adjudged negative for neoplastic localisations in the following instances: physiological uptake (urinary, muscular, thymic or gastrointestinal in patients without MALT), symmetrical nodal uptake, uptake in lesions unrelated to lymphoma that had already been identified by other imaging methods at the time of PET scan, uptake at sites atypical for lymphoma, very low uptake and non-focal uptake. PET findings were compared with the results of other diagnostic procedures (including CT and ultrasound), biopsy findings and follow-up data.Results Overall, 354 scans (in 256 patients) showed increased FDG uptake (244 scans in NHL and 110 in HD): in 286 cases, FDG uptake was considered pathological and indicative of ML, in 41 cases the findings were described as uncertain or equivocal and in 37 cases, FDG uptake was considered unrelated to ML (in ten scans, concurrent findings of abnormal FDG uptake attributed to ML and uptake assigned to other causes were obtained) . Of the 286 patients with positive PET findings, 274 (95.8%) were found to have residual or recurrent ML (i.e. true positives). Four of the 41 patients with inconclusive findings turned out to have ML, while in 13 patients, pathological processes other than ML could be identified as the cause of FDG uptake. ML was excluded in all patients with findings reported as non-pathological (100% true-negative rate). Therefore, the false-positive rate in our series was about 5%. The main cause of increased FDG uptake mimicking ML was inflammation.Conclusion Our data confirm that ¹⁸F-FDG-PET has very high but not absolute specificity for ML. As already suggested, increased FDG uptake may also be observed in patients without active disease; in most cases, however, non-pathological FDG accumulation is properly identified. Less frequently, inconclusive scans are encountered; these cases are usually caused by inflammation, which subsequently resolves.     

Comparison of 11C-methionine PET and 18F-fluorodeoxyglucose PET in differentiated thyroid cancer

BACKGROUND: The purpose of this prospective study is to evaluate the possibility of 11C-methionine (Met) PET compared with 18F-fluorodeoxyglucose (FDG) PET for the detection of recurrent or metastatic disease in patients with differentiated thyroid cancer (DTC). MATERIALS AND METHODS: Twenty patients with clinical suspicion of recurrent DTC but negative posttreatment 131I-whole body scans were included in the study. Both 11C-Met PET and 18F-FDG PET were performed within 1 week. PET images were analyzed by two independent and blinded physicians using visual and standardized uptake value analysis. PET results were also correlated with radiologic and/or cytological investigations. RESULTS: Thirteen patients showed concordant findings on both PET scans: six patients showed uptake and in seven no uptake was observed. In six of the seven patients without Met and FDG uptake, additional MRI and ultrasound-guided fine needle aspiration cytology of the lymph nodes revealed inconclusive or negative results. Six patients showed discordant findings on the PET scans: in three patients uptake was only observed on the Met PET, confirmed by MRI in one. In three patients lesions were seen on the FDG PET, confirmed by computed tomography or ultrasound-guided fine needle aspiration cytology. However, those lesions were not compatible with the lesions seen on the Met PET. In general, FDG uptake appeared to be higher than Met uptake, but was not significant (P=0.075). CONCLUSION: This study shows that imaging using radiolabeled amino acids is feasible in DTC. For now, 11C-Met PET has not proven to be superior to 18F-FDG PET in the detection of recurrent disease in DTC. Complementary uptake of Met and FDG has, however, been observed, which has to be further clarified and long-term follow-up is needed to define the true clinical value of the 11C-Met PET, and possible other amino acids tracers.     

FDG positron emission tomography in the surveillance of hepatic tumors treated with radiofrequency ablation

PURPOSE: Radiofrequency thermal ablation (RFA) is an emerging technique in the treatment of focal hepatic tumors. Magnetic resonance imaging (MRI) and computed tomography (CT) are currently used to monitor hepatic tumors after RFA for residual disease and recurrence. Fluorodeoxyglucose (FDG) positron emission tomography (PET) is an excellent imaging method for the detection of liver metastases, but it has not been thoroughly evaluated as an alternative to anatomic imaging in the surveillance of liver tumors treated with RFA. The purpose of this investigation was to determine the role of FDG-PET imaging in the surveillance of liver tumors treated with RFA. METHODS: Thirteen patients with histories of malignant tumors of the liver treated with RFA and who had received post-treatment FDG-PET scans were assessed retrospectively. One patient had two post-RFA FDG-PET scans, eight patients had concurrent MRI scans, and six patients had concurrent CT scans. Imaging findings were compared with the results of clinical follow-up. RESULTS: There were either recurrent tumors at the ablation site (8 patients) or new metastases (3 patients) in 11 patients. FDG-PET identified all 11 cases and did not misidentify any cases. Of the seven patients with positive PET findings who received an MRI scan, three were also positive on MRI (42.9%); the other four cases were either negative or equivocal. Of the four patients with positive PET findings who received a CT scan, only two had positive CT scan findings (50%). All recurrences diagnosed by PET were confirmed on clinical follow-up. CONCLUSION: In this preliminary study, FDG-PET was superior to anatomic imaging in the surveillance of patients treated with RFA for malignant hepatic tumors.     

Gallium-67 imaging in lymphoma: tricks of the trade

Objective: Although the use of 18F-fluorodeoxyglucose (FDG) PET for evaluating lymphoma is gaining in popularity, PET is not yet universally available and large prospective comparisons between 67Ga and 18F-FDG PET scans in predicting the long-term outcome after treatment are lacking. Scintigraphic imaging with 67Ga remains an important tool in evaluating the response of lymphoma to therapy. There are a variety of challenges and pitfalls inherent in 67Ga imaging for lymphoma. These are discussed and problem cases are illustrated. After reading this article, the nuclear medicine professional should be able to: (a) optimize the technical approach to and (b) maximize the diagnostic accuracy of 67Ga scintigraphy in assessing the response of lymphoma to therapy.     

Focal FDG uptake in mediastinal brown fat mimicking malignancy: a potential pitfall resolved on PET/CT

OBJECTIVE: A potential source of false-positive FDG PET interpretations in oncologic imaging is FDG uptake in brown fat. The purpose of this study was to determine the prevalence, location, and appearance of hypermetabolic brown fat in the mediastinum. MATERIALS AND METHODS: All PET/CT scans obtained at our cancer institution from August to October 2003 were retrospectively reviewed for increased FDG uptake in the mediastinum localized to fat on CT. The following features were recorded: location, appearance, maximal standard uptake value (SUV(max)) of hypermetabolic mediastinal brown fat, and presence of extramediastinal brown fat. RESULTS: PET/CT scans were obtained in 845 oncologic patients. Fifteen patients (1.8%) with focal hypermetabolic mediastinal brown fat were identified: nine women and two men (age range, 27-79; mean, 55.1 years) and four children (age range, 5-16 years; mean, 10 years). Hypermetabolic mediastinal brown fat (mean SUV(max), 5.7) was more common in children (4/8) than in adults (11/837) and more common in women (9/372) than in men (2/465). Foci of hypermetabolic brown fat were localized to the paratracheal, paraesophageal, prevascular, and pericardial regions; interatrial septum; and azygoesophageal recess. Five patients had focal hypermetabolic brown fat isolated to the mediastinum. Ten patients also had extramediastinal hypermetabolic brown fat in the neck, thorax, and abdomen. There was no difference in the body weight (p = 0.876) or body mass index (p = 0.538) of patients with hypermetabolic brown fat compared with age- and sex-matched control subjects. CONCLUSION: Hypermetabolic brown fat can be localized to the mediastinum and manifests as focal increased FDG uptake. Knowledge of this potential pitfall and precise localization with fusion PET/CT are important in preventing misinterpretation as malignancy.     

Nonossifying fibroma can mimic residual lymphoma in FDG PET: additional value of combined PET/CT

A 12-year-old girl was diagnosed with Hodgkin's lymphoma and underwent conventional cross-sectional imaging for initial staging. Chemotherapy was given according to standard pediatric protocols. At the end of therapy, an F-18 FDG PET/CT examination was performed to evaluate the therapeutic response. The scan demonstrated focal uptake of FDG in the right distal femur and residual lymphoma was taken into consideration. However, findings in the coregistered CT scan were consistent with nonossfiying fibroma, a common benign skeletal lesion. Combined PET/CT imaging can be helpful to identify benign bone lesions mimicking metastatic or residual disease in F-18 FDG PET as illustrated by this case.     

Prevalence and patterns of physiologic muscle uptake detected with whole-body 18F-FDG PET

Recently, the use of 18F-FDG PET has progressed rapidly as a standard diagnostic imaging tool in many types of cancer. The purpose of this study was to evaluate the patterns and prevalence of muscle uptake as a result of muscle activity shortly before the 18F-FDG injection or during the uptake phase. METHODS: From October 2002 to October 2003, whole-body 18F-FDG PET scans (4-min emission and 3-min transmission per bed position) were performed on 1,164 patients with known or suspected malignancy. Images were acquired on a dedicated PET scanner 45-60 min after an intravenous injection of a weight-adjusted dose of 7.4 MBq/kg (0.2 mCi/kg) with a maximum of 925 MBq (25 mCi) 18F-FDG. A log of any nonphysiologic muscle activity during the uptake phase or reported excessive muscle activity the day before scanning was kept by the technologists. In addition, PET scans were reviewed retrospectively to evaluate any undesirably increased muscle uptake. RESULTS: A total of 146 of 1,164 patients (12.5%) had excessively increased muscle uptake detected on the PET scan that corresponded to the technologists' notes of muscle activity during the uptake phase or before 18F-FDG injection. Encountered patterns of muscle uptake due to muscle activity included uptake in neck, secondary to neck strain from being on a stretcher; masseter, secondary to chewing gum; vocal cords, secondary to speaking; chest wall, secondary to labored breathing; forearms and hands, secondary to reading; and lower extremities, secondary to nervous tapping of the feet. CONCLUSION: Undesirably increased physiologic muscle uptake is frequently encountered on 18F-FDG PET scans. In this study, 12.5% of patients were affected. It is prudent to instruct the patient to avoid any excessive physical activity at least 48 h before injection as well as to not exert muscle activity during the uptake phase. Furthermore, a record should be kept by the technologist of any observed excessive muscle activity during the uptake phase and reported to the reading physician-thus, eliminating a potential source of false-positive findings on interpreting PET scans.     

Whole-body (18)F-FDG PET identifies high-risk myeloma.

The purpose of this study was to evaluate the clinical utility of whole-body PET with (18)F-FDG in patients with multiple myeloma and related monoclonal diseases. METHODS: Between July 1, 1996, and July 2000, 98 (18)F-FDG PET scans were obtained for 66 patients, with 25 patients having 2 or more scans. The results were compared with routine clinical and staging information, including CT and MRI scans, as indicated. Of the 66 patients, 16 had previously untreated active myeloma, 14 had monoclonal gammopathy of undetermined significance (MGUS), 10 had disease in remission, and 26 had relapsing disease. RESULTS: Negative whole-body (18)F-FDG PET findings reliably predicted stable MGUS. Of the 14 MGUS patients with follow-up of 3-43+ mo, myeloma has developed in only 1 (7%), at 8 mo. Conversely, the 16 previously untreated patients with active myeloma all had focal or diffusely positive scan findings. Four (25%) of 16 previously untreated patients with positive (18)F-FDG PET findings had negative full radiologic surveys. Another 4 (25%) of 16 patients had focal extramedullary disease. This was confirmed by biopsy or other imaging techniques. Extramedullary uptake also occurred in 6 (23%) of 26 patients with relapse. This extramedullary uptake was a very poor prognostic factor both before treatment and at relapse. For example, median survival was 7 mo for patients with disease relapse. Persistent positive (18)F-FDG PET findings after induction therapy predicted early relapse. In 13 (81%) of 16 patients with relapsing disease, new sites of disease were identified. The (18)F-FDG PET results were especially helpful in identifying focal recurrent disease in patients with nonsecretory or hyposecretory disease amenable to local irradiation therapy, which was used in 6 patients. CONCLUSION: Whole-body (18)F-FDG PET provides important prognostic information, which is clinically useful and complementary to conventional methods of evaluating plasma cell disorders. (18)F-FDG PET is a unique tool for evaluation of nonsecretory myeloma. Residual or recurrent disease after therapy, especially extramedullary disease, is a poor prognostic factor.     

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.     

The use of [18 F]fluorodeoxyglucose positron emission tomography to differentiate between synovitis,loosening and infection of hip and knee prostheses

Pain is a common unspecific symptom in orthopaedic prosthetics. The accurate differentiation between synovitis, loosening or infection is often difficult with conventional X-rays, arthrography or bone scintigraphy. Because of the high glucose uptake of inflammatory cells, [18F]fluorodeoxyglucose (18F-FDG) is an appropriate tracer for the evaluation of suspected inflammation or infection. In this preliminary study we describe 18F-FDG PET findings in patients referred for evaluation of painful hip or knee prostheses. We studied 23 patients with 28 prostheses, 14 hip and 14 knee prostheses, who had a complete operative or clinical follow-up. 18F-FDG PET scans were obtained with an ECAT EXACT HR+ PET scanner. High glucose uptake in the bone prostheses interface was considered as positive for infection, an intermediate uptake as suspect for loosening, and uptake only in the synovia was considered as synovitis. The imaging results were compared with operative findings or clinical outcome. PET correctly identified three hip and one knee prostheses as infected, two hip and two knee prostheses as loosening, four hip and nine knee prostheses as synovitis, and two hip and one knee prostheses as unsuspected for loosening or infection. In three patients covered with an expander after explantation of an infected prosthesis PET revealed no further evidence of infection in concordance with the clinical follow-up. PET was false negative for loosening in one case. Our preliminary results suggest that FDG PET could be a useful tool for differentiating between infected and loose orthopaedic prostheses as well as for detecting only inflammatory tissue such as synovitis.     

Detection of bone metastases in thyroid cancer patients: bone scintigraphy or 18F-FDG PET?

BACKGROUND: Similar to the situation in other tumour types, it is currently unclear whether fluorodeoxyglucose (FDG) positron emission tomography (PET) is adequate in the detection of bone metastases of thyroid cancer. The purpose of this retrospective study was to evaluate the performance of bone scans in comparison with FDG PET in the detection of bone metastases in patients with differentiated thyroid cancer (DTC). MATERIALS AND METHODS: Twenty-four patients had undergone both FDG PET and bone scans within 6 months because of suspected bone metastases. All scans were re-evaluated using all available additional imaging and clinical data for verification. Scan findings were scored as positive, negative or doubtful. RESULTS: Bone metastases were present in eight of 24 (33%) patients. Only bone scintigraphy but not FDG PET suggested the presence of bone metastases in three patients, all confirmed with magnetic resonance imaging (MRI)/X-ray. Five patients were identified with bone metastases on both bone scan and FDG PET, which was confirmed by computed tomography (CT)/MRI/X-ray in four. Five patients had doubtful findings on bone scans whereas FDG PET scans were negative. MRI showed degenerative disorders in two of five and was normal in two. Eleven patients had both a negative bone scan and FDG PET scan. CONCLUSION: In three of eight (38%) thyroid cancer patients bone metastases were only identified on bone scans. Therefore, bone scans are still valuable in detecting bone metastases in patients with DTC and can not be replaced by FDG PET.     

The clinical impact of18F-FDG PET in papillary thyroid carcinoma with a negative131I whole body scan: A single-center study of 108 patients

OBJECTIVE: To assess whether FDG PET could localize the recurrent or metastatic lesions in papillary thyroid cancer patients with negative radioiodine scan. METHODS: Whole body PET was performed after injecting 370-555 MBq of 18F-FDG in 108 patients, who were suspected of having recurrence or metastasis and whose 131I whole body scans were negative. Recurrence or metastasis occurred in 63 patients by pathology or clinical assessment, whereas 45 patients remained in remission. RESULTS: FDG PET revealed recurrence or metastases in 59 patients (sensitivity 93.7%), whereas thyroglobulin (Tg) levels were elevated in 41 (sensitivity 65.1%). In 35 of 45 patients in remission, FDG PET was negative (specificity 77.8%). When patients positive for antithyroglobulin antibody were excluded, the sensitivity and specificity of serum Tg became 84.8% and 46.9%, respectively. Compared to Tg measurement, FDG PET detected more metastatic lesions in cervical lymph nodes. Of 40 patients with a negative radioiodine scan showing diffuse hepatic uptake, metastases occurred in 23 patients and remission in 17. FDG PET showed 100% sensitivity and 76.5% specificity in the detection of recurrence in these 40 patients. CONCLUSION: FDG PET is useful for localizing recurrent or metastatic lesions in 131I scan-negative thyroid cancer patients. In particular, it is superior to serum Tg measurement for identifying metastases to cervical lymph nodes. We recommend its use in cases of negative radioiodine scan with diffuse hepatic uptake.     

Comparison of imaging with FDG PET/CT with other imaging modalities in myeloma

Objective To determine the usefulness of FDG PET/CT scanning in the management and staging of myeloma and to assess its strengths and limitations.Design FDG PET/CT scans and all other available imaging studies were reviewed retrospectively from 16 consecutive patients by two experienced musculoskeletal radiologists and two nuclear medicine physicians working in consensus.Patients The 16 patients had undergone a total of 19 FDG PET/CT scans. Radiographs were available in all cases, including 13 skeletal surveys; 25 CT scans (16 chest, three abdominal, four pelvic, one spine, one neck) and 22 MR imaging studies (17 spine, three pelvic, two extremity) also were reviewed. Patients’ records were examined for relevant clinical information. All focal areas of abnormal FDG uptake were correlated with the other imaging studies to determine clinical significance. FDG PET/CT scans also were reviewed to see if small lesions shown on the other imaging studies could be identified in retrospect.Results The 12 men and four women had an average age of 58 years (range 30–69 years). All 16 patients had an established diagnosis of multiple myeloma, with average duration of disease, from time of initial diagnosis to review, of 30 months (range 6 months to 11+ years). The FDG PET/CT scans revealed a total of 104 sites (90 in bone, 14 soft tissue) that were suspicious for neoplastic activity based on a standardized uptake value (SUV) greater than 2.5. Fifty-seven of these sites (55%) were new or previously undetected. The other imaging studies (X-ray, CT, MR) and clinical information confirmed the other 47 areas but also revealed 133 other small skeletal lesions. Six of these 133 additional lesions showed mild FDG uptake on re-review of the PET/CT scans. The FDG PET/CT findings led to management changes in 9/16 patients. MR imaging revealed five cases of diffuse bone involvement (four spine, one scapula) that were not evident by FDG PET/CT.Conclusion FDG PET/CT scans are useful for the management and staging of myeloma. However, if PET/CT were the sole imaging study done, it would miss many additional small lytic skeletal lesions and could miss diffuse spine involvement.