Incidental focal F-18 FDG accumulation in lung parenchyma without abnormal CT findings

F-18 fluorodeoxyglucose (FDG) PET/CT that simultaneously offers anatomic and metabolic information is widely used and has become an effective modality in many clinical fields, especially oncology. For accurate interpretation, it is necessary to understand false-positive findings in the F-18 FDG PET image, such as physiologic conditions, findings related to patients’ medical and surgical histories, normal variants, and artificial conditions. We report three cases of incidental focal F-18 FDG accumulation in lung parenchyma without abnormal CT findings in the PET/CT images. In the primary PET/CT studies, two cases showed single and one case showed multiple FDG foci in the lung without any CT abnormalities. All FDG accumulations disappeared in PET/CT studies repeated 1–3 days after the primary scannings. These artifacts are probably related to microembolisms attributable to the intravenous injection of F-18 FDG. Therefore, a cautious interpretation of the correspondence between anatomic and metabolic images is required and repeated PET/CT is helpful.     

F-18 FDG PET demonstration of a thyroid metastasis in a patient with colon cancer

A 51-year-old man with a history of surgical removal of sigmoid colon cancer underwent F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) to search for distant metastases and/or local recurrence because the carcinoembryonic antigen level was elevated. F-18 FDG PET images showed increased focal FDG uptake in the left lobe of the thyroid. Computed tomography images showed thyroid tumor in the left lobe as well as F-18 FDG PET images. Thereafter he underwent thyroidectomy and the resected specimen was histopathlogically shown to have thyroid metastasis from colon cancer. F-18 FDG PET was useful to detect thyroid metastasis from colon cancer as well as the most frequently seen metastatic sites such as liver, lungs, and lymph nodes.     

F-18 fluorodeoxyglucose chest uptake in lung inflammation and infection

PURPOSE: F-18 fluorodeoxyglucose (FDG) may accumulate at sites of inflammation or infection, making interpretation of whole-body scans difficult in patients with cancer. METHODS: More than 650 whole-body positron emission tomographic (PET) scans performed to examine patients with cancer were reviewed to identify uptake in pulmonary infection or inflammation based on the appearance of F-18 FDG chest uptake, chest radiographs, computed tomography, or all of these. RESULTS: Ten patients had uptake in benign lung disease. Eight patients had head and neck tumors and two patients had breast cancer. Intense focal or multifocal F-18 FDG chest uptake was seen in 6 of 10 scans. This was difficult to distinguish from pulmonary metastases based on the scan appearance. However, in the remaining patients, the uptake was atypical for malignancy and displayed an apical, segmental, or lobar pattern. In all patients, the F-18 FDG lung uptake corresponded to benign radiologic changes (infiltration, consolidation, or atelectasis), and the final diagnosis was pulmonary inflammation or infection. Nine patients were asymptomatic and one patient had clinical aspiration pneumonia. Follow-up PET scans were performed in five patients to evaluate their conditions. Chest uptake disappeared completely in three patients and partially in two patients, and there were no new findings. Variable degrees of F-18 FDG chest uptake have been reported with more than 40 different benign causes. They can be classified based on the underlying mechanism into four major categories: 1) Inflammation or infection, 2) benign tumor, 3) physiologic activity, and 4) iatrogenic. Most of these false-positive cases are included in the first category. CONCLUSIONS: Pulmonary infection or inflammation might predispose patients to localized F-18 FDG chest uptake mimicking pulmonary metastases and limiting the specificity of whole-body scans performed in patients with cancer.     

F-18 FDG PET Images of the Cervix at Various Time Points after the Loop Electrosurgical Excision Procedure

F-18 FDG PET is useful for monitoring residual or recurrent tumors after surgical resection. We describe five F-18 FDG PET images of three patients who had cervical carcinoma and then underwent a loop electrosurgical excision procedure (LEEP). Two of the images were taken within 15 days and three at least 2 months after LEEP. The earlier F-18 FDG PET images revealed linear hypermetabolic lesions in the cervix that were produced by inflammation. This was confirmed by pathological analysis. The later F-18 FDG PET images did not reveal any remarkable hypermetabolism in the cervix without any treatment. These observations suggest that, to determine the response to LEEP therapy, F-18 FDG PET should not be performed within 15 days of the procedure.     

Differentiation of residual or recurrent tumors from post-treatment changes with F-18 FDG PET.

Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) was used to differentiate recurrent or residual malignant disease from the effects of cancer treatment. Transaxial images were obtained after injection of 5-10 mCi (185-370 MBq) of F-18 FDG in 68 patients (including 33 with brain tumors) whose posttreatment computed tomographic (CT) or magnetic resonance (MR) imaging findings had been suggestive of malignant disease. PET findings were correlated with surgical results in 18 patients and with the outcomes of CT, MR imaging, clinical, and laboratory 9-month follow-up studies in 50 patients. There was good agreement between F-18 FDG uptake and presence or absence of malignant disease except in four cases of brain tumors in which histologic findings could not be correlated with biologic behavior. The putative sensitivity and specificity in the 33 cases of brain tumors were 80% and 94%, respectively. The authors conclude that PET with F-18 FDG is useful in detection of previously treated metabolically active tumors but is limited in diagnosis of recurrent microscopic or metabolically inactive tumors.     

The clinical usefulness of F-18 FDG coincidence PET without attenuation correction and without whole-body scanning mode in pulmonary lesions comparison with CT, MRI, and clinical findings

PURPOSE: This study was undertaken to assess the clinical usefulness of fluorine-18 flurodeoxyglucose (F-18 FDG) coincidence detection (CoDe) positron emission tomography (PET) of various lung lesions by comparing it with CT, MRI, and clinical findings. MATERIALS AND METHODS: Forty-two patients with pulmonary lesions underwent CoDe PET using a dual-head gamma camera equipped with a 5/8 inch thick NaI (Tl) crystals. The patients were prepared for the study by overnight fasting. Data was acquired at approximately 1 hour after the intravenous injection of 111 to 370 MBq (3 to 10 mCi) of F-18 FDG. A spinal scan of the thorax was performed using a slip ring gantry for 30 minutes. After rebinning, routine tomographic slices were reconstructed without attenuation correction and the images were analyzed visually. RESULTS: Pathologic diagnoses and staging were obtained at surgery in nine patients; in the remaining 33 patients, aspiration cytology was available. CoDe PET detected all 35 pathologically proved malignant lesions. In nine patients who underwent surgery, seven CoDe PET studies corresponded with pathologic staging, whereas in six of the nine patients, CT and MRI corresponded with the pathologic findings. Seven patients also had benign lesions that showed FDG uptake. CONCLUSIONS: F-18 FDG CoDe PET was sensitive in the evaluation of lung lesions but was not specific for malignancy. F-18 FDG CoDe PET was more sensitive than CT and MRI in nodal staging in the limited number of patients studied thus far.     

Incidental detection of bilateral elastofibroma dorsi with F-18 FDG PET/CT

An 83-year-old asymptomatic woman with a history of breast cancer treated with resection, radiation, and chemotherapy was studied with F-18 FDG positron emission tomography/computed tomography (PET/CT) for staging purposes. The whole-body F-18 FDG PET/CT images revealed poorly circumscribed, bilateral soft tissue masses between the inferior tips of the scapulae and chest wall with a moderate degree of F-18 FDG accumulation. The maximum standardized uptake values were 2.8 for both the left and right lesions. A biopsy or further imaging was not recommended because the lesions were asymptomatic, bilateral, and their imaging features were diagnostic for elastofibroma dorsi. Comparison to a CT scan performed 2 years earlier demonstrated stability of the lesions, further supporting our diagnosis. Recognition of this moderately metabolic benign entity in oncologic patients will avoid unnecessary medical, radiologic, or surgical interventions.     

FDG PET evaluation of residual masses and regrowth of abdominal lymph node metastases from colon cancer compared with CT during chemotherapy.

Fluorine-18-2-deoxy-2-fluoro-D-glucose (F-18 FDG) PET may be more suitable for follow-up after cancer treatment than other morphologic approaches, because it reflects tumor viability. A patient with abdominal lymph node metastases from colon cancer was followed by CT and F-18 FDG PET during chemotherapy. F-18 FDG PET tumor images changed in accordance with the clinical progress, whereas CT findings were relatively unchanged. This case clearly shows the utility of F-18 FDG PET for follow-up during cancer chemotherapy.     

Positron-emission tomography/computed tomography: artifacts and pitfalls in cancer patients

Diagnostic accuracy and correct initial staging (or restaging) are fundamental in the management of oncological patients and can directly influence therapeutic decisions. The combination of positron-emission tomography (PET) and computed tomography (CT) in a single scanner (PET/TC) represents an important achievement in the fields of oncology, nuclear medicine, and radiology. These scanners allow morphologic images (obtained by CT) to be fused and correlated with metabolic images (obtained by PET) to a high degree of accuracy. In addition to an understanding of the physiopathology of cancer and the behavior of the different types of neoplasms, the correct interpretation of PET/CT images requires in-depth knowledge of the physiological distribution of the F-18 fluorodeoxyglucose molecule (FDG, currently the most widely used marker in oncology), of the frequent physiological variations in its distribution, and of the possible causes of non-malignant pathological FDG uptake. Furthermore, the use of CT data to correct attenuation and reconstruct PET images in PET/CT scanners can generate some characteristic artifacts specific to this new diagnostic tool, and these can lead to misinterpretation with potential therapeutic implications. This article reviews and illustrates some of the most common artifacts and pitfalls that can appear in PET/CT studies. The detection and correct interpretation of these findings are essential for the appropriate management of oncologic patients.     

Limited value of interictal brain perfusion SPECT for detection of epileptic foci: High resolution SPECT studies in comparison with FDG-PET

Accurate localization of epileptic foci is important for pre-surgical evaluation of patients with medically intractable epilepsy, and F-18 FDG PET has been proved to be a valuable method for this purpose. To examine the clinical value with interictal brain perfusion SPECT, we performed brain perfusion SPECT of Tc-99m HMPAO by means of a high resolution SPECT camera, and compared the results with F-18 FDG PET images and MRI in 10 patients with medically intractable epilepsy. In 9 of 10 patients (90%), FDG PET images showed focal hypo-metabolism in the area corresponding with the results of electroencephalography (EEG). SPECT images, however, demonstrated hypo-perfused lesions which corresponded with hypo-metabolic lesions on FDG PET images in only 6 cases (60%). Although MRI showed abnormal findings in 8 cases, the lesions were not directly related to epileptic foci in 2 cases. In conclusion, FDG PET is a valuable tool for accurate localization of epileptic foci. Brain perfusion SPECT, however, may not always be paralleled to metabolism visualized on FDG PET images.     

Metastatic thyroid cancer occurring as an unknown primary lesion: the role of F-18 FDG positron emission tomography

Thyroid cancer can appear as metastatic disease of an unknown primary origin, and fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomographic (PET) studies are helpful in the workup evaluation of these patients. The authors describe two patients who had metastatic disease from an unknown primary lesion. F-18 FDG PET studies played an important role in localizing the primary malignant site in the thyroid gland. The utility of F-18 FDG imaging in decreasing the number of procedures, cost, and inconvenience to patients is shown clearly in both cases.     

PET/CT imaging of thyroid cancer

Positron emission tomography (PET) is a highly sensitive, low invasive technology for cancer biology imaging. The role of F-18 FDG PET/CT in differentiated thyroid cancer (DTC) is well established, particularly in patients presenting with elevated Tg levels and negative radioactive iodine WBS. It has been demonstrated that F-18 FDG uptake represents less differentiated thyroid cancer cells or dedifferentiated cells and PET positive lesions are more likely to be resistant to I treatment. The uptake of F-18 FDG is related to tumor size, thyroid capsule invasion and histological variants with a poor prognosis. As in other cancers, early detection of recurrences improves outcomes and survival. I PET/CT can also be used to image the patients with DTC, similarly to I WBS. Compared with F-18 FDG PET/CT, its spatial resolution is only slightly degraded but increasing the imaging time reduces this difference. In addition, F-18 FDG PET/CT has been found helpful in the management of patients with anaplastic and medullary thyroid cancer. Other radiopharmaceuticals such as Ga-DOTATOC and F-18 DOPA may provide complimentary information to F-18 FDG PET/CT in the detection of recurrent thyroid cancer.     

Use of 2-deoxy-2-[F-18]-fluoro-D-glucose positron emission tomography to monitor therapeutic response by rhabdomyosarcoma in children: report of a retrospective case study

PURPOSE: The purpose of this study was to study the use of 2-deoxy-2-[F-18]-fluoro-D-glucose positron emission tomography (F-18 FDG PET) for monitoring therapeutic response by rhabdomyosarcoma (RMSA) in children. PATIENTS AND METHODS: A retrospective case study was performed by searching a computer database for the patients with RMSA in whom F-18 FDG PET studies were performed pre- and posttreatment. The data of the PET studies from these patients were analyzed in conjunction with clinical treatment and other imaging studies to determine whether interval changes of F-18 FDG uptake by the RMSA reflect response of RMSA to treatment. RESULTS: Four patients with RMSA who received both pretreatment and posttreatment F-18 FDG PET studies were identified from the database and included in this study. A dramatic decrease of F-18 FDG uptake by the tumor was evident in the patients who had a favorable response to the therapy and prolonged remission of the disease. In contrast, persistent abnormal FDG uptake in one patient was associated with early relapse of the RMSA. CONCLUSIONS: F-18 FDG PET may be useful for monitoring therapeutic response by RMSA in children, which needs to be verified with a prospective study in a larger patient population.     

18F-FDG PET显像在胰腺癌诊断中的临床应用

目的：探讨^18F-FDG PET显像在胰腺癌诊断中的应用价值。方法：54例临床怀疑为胰腺癌的患者均行^18F-FDG PET显像,对显像结果进行目测法及半定量分析,并与CT、手术、腹腔镜取病理等进行对比研究。结果：^18F-FDG PET显像对胰腺癌诊断的敏感度为93％(38／41),特异度为85g(11／13)。CT对胰腺癌诊断的敏感度为76N(31／41),特异度为69％(9／13)。^18F-FDG PET显像发现7例CT检查未能确定的肝、肺及淋巴结转移,同时PET诊断结果使15例(28％)患者的临床治疗方案得到修正。结论：^18F-FDG PET显像对胰腺癌的诊断及临床分期具有较好的临床应用价值。     

Patterns of papillary muscle ischemia in myocardial PET

PURPOSE: Conventional nuclear medicine equipment lacks sufficient spatial resolution to reliably visualize the papillary muscles (PM). Positron emission tomography (PET), however, can adequately visualize these structures using various positron emitters. METHODS AND PATIENTS: We present various patterns of PM observed on myocardial PET imaging in 4 patients. These patterns demonstrate different pathologic conditions such as PM ischemia of varying severity, as well as hibernation, using both N-13 NH3 and F-18 FDG as perfusion and metabolic agents, respectively. These patterns of infarction, stress-induced myocardial ischemia, or hibernation can be identified in one or both PM using PET scanning. Normal PM visualization on chest F-18 FDG PET images is also presented. CONCLUSION: This report illustrates the potential ability of myocardial PET as a noninvasive modality to study the perfusion and metabolic abnormalities of the PM.     

~(18)F-FDG PET显像在胰腺癌诊断中的临床应用

目的 :探讨18F FDGPET显像在胰腺癌诊断中的应用价值。方法 :5 4例临床怀疑为胰腺癌的患者均行18F FDGPET显像 ,对显像结果进行目测法及半定量分析 ,并与CT、手术、腹腔镜取病理等进行对比研究。结果 :18F FDGPET显像对胰腺癌诊断的敏感度为 93 % ( 3 8/4 1) ,特异度为 85 % ( 11/13 )。CT对胰腺癌诊断的敏感度为 76% ( 3 1/4 1) ,特异度为 69% ( 9/13 )。18F FDGPET显像发现 7例CT检查未能确定的肝、肺及淋巴结转移 ,同时PET诊断结果使 15例( 2 8% )患者的临床治疗方案得到修正。结论 :18F FDGPET显像对胰腺癌的诊断及临床分期具有较好的临床应用价值。     

Radiation-induced myositis mimicking chest wall tumor invasion in two patients with lung cancer: a PET/CT study

Two patients with lung cancer who had undergone stereotactic body radiation therapy (SBRT) exhibited increased F-18 FDG uptake in the chest wall after 6 months and 18 months, respectively, after SBRT. The prescribed dose of 50 Gy to the planning target volume was delivered on 4 consecutive days in each patient. It is important for nuclear medicine physicians to be familiar with F-18 FDG PET/CT findings ascribed to radiation-induced myositis in lung cancer patients treated with SBRT so that an appropriate differential diagnosis can be established.     

PET/CT显像联合融合图像纹理特征分析在肺癌鉴别诊断中的应用价值探讨

目的:探讨~(18)F-FDG PET/CT显像医师先验知识、PET/CT融合图像纹理特征参数联合应用对肺癌的诊断价值.方法:130例患者行PET/CT检查,分别由医师先验知识和4项融合图像纹理特征参数(粗糙度、对比度、频度、角二阶矩)判断肺部病灶的良恶性.经病理检查或治疗后影像学随访确诊肺部良恶性病变.计算每种方法及联合应用诊断肺癌的灵敏度和特异性.结果:130例中,77例诊断为肺癌.医师先验知识诊断肺癌的灵敏度为87.0%、特异性为81.1%,纹理特征参数诊断肺癌的灵敏度为80.5%、特异性为71.7%,两者联合的灵敏度为97.4%、特异性为60.4%.结论:基于PET/CT,两者联合应用在判断肺部病灶良恶性中起到积极作用.     

F-18 FDG PET-CT findings of intraperitoneal carbon particles-induced granulomas mimicking peritoneal carcinomatosis

F-18 FDG PET-CT is a useful modality for monitoring residual or recurrent tumors after surgical resection. We report on 3 patients with intraperitoneal charcoal-induced granulomas mimicking peritoneal carcinomatosis on PET-CT images. Two of them underwent a radical gastrectomy because of advanced gastric cancer, and the other underwent a hemicolectomy because of sigmoid colon cancer. All 3 patients had a history of intraperitoneal chemotherapy using mitomycin C bound to activated carbon particles during surgery. Follow-up PET-CT studies demonstrated increased FDG uptake mimicking peritoneal carcinomatosis on PET images alone. However, the accompanying noncontrast CT showed variously shaped hyperdense nodules in the dependent positions of the peritoneal cavity, including the paracolic gutter and rectovesical space, indicating charcoal-induced granulomas rather than peritoneal carcinomatosis.     

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.