Catheter-Related Focal FDG Activity on Whole Body PET Imaging

Septic Pulmonary Emboli Detected by 18F-FDG PET/CT in a Patient with Central Venous Catheter-Related Staphylococcus aureus Bacteremia

We describe a case of ¹⁸F-FDG PET/CT detecting septic pulmonary emboli in a patient with Staphylococcus aureus catheter-related bloodstream infection (CRBSI). The patient, who had an implantable venous access port for chemotherapy, underwent ¹⁸F-FDG PET/CT to diagnose unsuspected infectious foci. The PET/CT examination made it possible to offer a suggestive diagnosis and yielded metastatic infectious foci.

Human Radiation Dosimetry for Orally and Intravenously Administered 18F-FDG

Intravenous access is difficult in some patients referred for ¹⁸F-FDG PET imaging. Extravasation at the injection site and accumulation in central catheters can lead to limited tumor ¹⁸F-FDG uptake, erroneous quantitation, and significant image artifacts. In this study, we compared the human biodistribution and dosimetry for ¹⁸F-FDG after oral and intravenous administrations sequentially in the same subjects to ascertain the dosimetry and potential suitability of orally administered ¹⁸F-FDG as an alternative to intravenous administration. We also compared our detailed intravenous ¹⁸F-FDG dosimetry with older dosimetry data. Methods: Nine healthy volunteers (6 male and 3 female; aged 19-32 y) underwent PET/CT imaging after oral and intravenous administration of ¹⁸F-FDG. Identical preparation and imaging protocols (except administration route) were used for oral and intravenous studies. During each imaging session, 9 whole-body PET scans were obtained at 5, 10, 20, 30, 40, 50, 60, 120, and 240 min after ¹⁸F-FDG administration (370 ± 16 MBq). Source organ contours drawn using CT were overlaid onto registered PET images to extract time-activity curves. Time-integrated activity coefficients derived from time-activity curves were given as input to OLINDA/EXM for dose calculations. Results: Blood uptake after orally administered ¹⁸F-FDG peaked at 45-50 min after ingestion. The oral-to-intravenous ratios of ¹⁸F-FDG uptake for major organs at 45 min were 1.07 ± 0.24 for blood, 0.94 ± 0.39 for heart wall, 0.47 ± 0.12 for brain, 1.25 ± 0.18 for liver, and 0.84 ± 0.24 for kidneys. The highest organ-absorbed doses (μGy/MBq) after oral ¹⁸F-FDG administration were observed for urinary bladder (75.9 ± 17.2), stomach (48.4 ± 14.3), and brain (29.4 ± 5.1), and the effective dose was significantly higher (20%) than after intravenous administration (P = 0.002). Conclusion: ¹⁸F-FDG has excellent bioavailability after oral administration, but peak organ activities occur later than after intravenous injection. These data suggest PET at 2 h after oral ¹⁸F-FDG administration should yield images that are comparable in biodistribution to conventional clinical images acquired 1 h after injection. Oral ¹⁸F-FDG is a palatable alternative to intravenous ¹⁸F-FDG when venous access is problematic.

The Incidence of Totally Implantable Venous Access Devices Insertion and the Associated Abnormalities in Patients With Cancer Revealed in 18F-FDG PET-CT Imaging

RATIONALE AND OBJECTIVES

The purpose of this retrospective study was to evaluate the incidence of totally implantable venous access devices, also called ports, implantation and the associated abnormalities in 2-[¹⁸F]-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography-computed tomography (PET-CT) images for patients with cancer, and to determine the percentage of abnormalities identified in the original reports.

MATERIALS AND METHODS

The study aimed to perform a retrospective review of all FDG PET-CT imaging in a 3-year period. Cases of port-associated abnormalities found on the FDG PET-CT images were identified and then correlated with X-ray reports and clinical treatment or follow-up.

RESULTS

In total, 2442 FDG PET-CT scans were retrospectively reviewed. Among them, 897 (897 of 2442, 36.7%) demonstrated port implantation. Abnormalities, including 22 port fractures (22 of 897, 2.45%), 14 malposition (1.56%), one infection (0.11%), and one embraced by a fibrin sheath or tumor (0.11%) were found. Only the infectious one had clinical symptoms. Among the 22 fractured ports, eight fractured catheters migrated and became dislodged. All of the malpositioned ports, except two in the contralateral subclavian vein, were found in the ipsilateral jugular vein. Both the port infection and the port embraced by a fibrin sheath or tumor occurred at the tips of the devices, which demonstrated FDG uptake in the mediastinal region. Only seven of the 38 (18.42%) images of port abnormalities had been identified in the original reports.

CONCLUSIONS

Based on this study, we recommend that the interpretation of FDG PET-CT scans should include a checklist to record all metallic device implantations and to interpret the whole-body X-ray topography as a standard part of PET-CT image report.

Assessment of radiopharmaceutical retention for vascular access ports using positron emission tomography imaging

Purpose

The purpose of this study was to resolve the issue of whether various generations of CR Bard peripheral vascular access ports and catheters are prone to retain PET radiopharmaceuticals. The study evaluates the residual radioactivity remaining following injection for two PET radiopharmaceuticals currently used extensively in the clinic, FDG and Na¹⁸F.

Methods

FDG was purchased from a local cyclotron facility and Na¹⁸F was prepared in‐house. Three generations of currently marketed vascular access ports were tested. A total of five (n = 5) of each model was tested. Radiopharmaceutical of 2–3 mCi of each was injected into each port and flushed with 10, 30, 60, and 120 ml of saline. MicroPET scans were performed after each flush to detect the residual radioactivity on each port. A dose calibrator was used to detect the retention of radioactivity after each flush.

Results

Radioactivity retention for all vascular port models measured by microPET imaging was similar for both FDG and Na¹⁸F, with less than 1% residual activity following a 10 ml saline flush. Based on the microPET images, all the subsequent flushes of 30, 60, and 120 ml were also considered. Dose calibrator activity measurements validated microPET measurements as negligible for all the ports, even with the first 10 ml flush.

Conclusions

MicroPET imaging was more sensitive than the dose calibrator in determining the radioactivity retention of the vascular access ports from CR Bard. These ports may be used for the injection of FDG and Na¹⁸F to track glucose metabolism and bone uptake with PET imaging. It is recommended to apply at least a 10 ml flush after radiopharmaceutical administration, to reduce residual activity to baseline levels.

Challenges in Interpretation of Staging PET/CT in Thoracic Malignancies

¹⁸F-fluorodeoxryglucose (¹⁸F-FDG) PET/CT imaging is routinely performed in the evaluation of patients with known or suspected thoracic malignancy. Indications for its use include staging of malignancy, assessment of response to therapy, evaluation of suspected disease recurrence, and evaluation of a solitary pulmonary nodule. In this article, we will discuss specific technical artifacts and also review potential pitfalls in the interpretation of PET/CT in thoracic malignancies including normal variations in physiologic uptake of FDG, benign conditions (such as infection, inflammation, posttreatment changes, and iatrogenic factors) that can result in increased FDG uptake, and malignancies that demonstrate scarce to no FDG uptake.

18F-FDG-PET/CT in unexplained elevated inflammatory markers. Joining entities

The diagnostic strategy in patients with fever or inflammation of unknown origin remains a major clinical challenge. The aim of this study was to evaluate the role of ¹⁸F-FDG-PET/CT in patients with unexplained elevated C-reactive protein with or without fever. Contribution of ¹⁸F-FDG-PET/CT to the final diagnosis was evaluated. In addition we determined whether a differentiation between patients with or without fever is clinically reasonable.

PATIENTS, METHODS

We retrospectively analysed 72 consecutive patients with unexplained elevated C-reactive protein levels (above 8mg/l) that underwent ¹⁸F-FDG-PET/CT in our facility between 10/2009 and 11/2012. ¹⁸F-FDG-PET/CT was considered a so-called diagnostic scan when results decisively led to a final diagnosis and adequate therapy with a response of symptoms was initiated due to the PET/CT result.

RESULTS

In 60/72 patients (83%) a final diagnosis was established. Diagnoses included infections (58%), non-infectious inflammatory diseases (29%) and malignancies (8%). ¹⁸F-FDG-PET/CT was true positive in 47 cases (65%) and the diagnostic scan in 29 patients (40%). Sensitivity of ¹⁸F-FDG-PET/CT was 81% and specificity was 86%. Diagnostics, final diagnoses, ¹⁸F-FDG-PET/CT results, SUVmax, C-reactive protein levels and the diagnostic scan did not differ significantly between patients with fever and patients without fever.

CONCLUSION

¹⁸F-FDG-PET/CT is a useful method in the diagnostic workup of patients with inflammation of unknown origin. In our series there was no significant difference between patients with or without fever. Regarding ¹⁸F-FDG-PET/CT-imaging inflammation of unknown origin and unexplained fever can be joined to one entity.

Cardiac Magnetic Resonance for Evaluating Catheter Related FDG Avidity

A 53-year-old female with a history of metastatic left arm melanoma presented for F(18) fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) which showed a moderately FDG avid focus at her port catheter tip near the cavoatrial junction. Although catheter tip related FDG avidity has previously been suggested to be bland thrombus or infection, melanoma can metastasize to unusual locations including the superior vena cava. In addition, the patient had an elevated risk of anticoagulation due to a history of hemorrhagic brain metastases. Therefore, confirmatory cardiac magnetic resonance (CMR) was obtained and findings were consistent with bland catheter-related thrombus.

Focal FDG Activity in the Region of Right Atrium: Coregistered CT Identifies Three Benign Etiologies

We present the whole body FDG PET-CT images on 3 different patients with benign focal activity in the region of the right atrium. Co-registered CT correctly identified the cause of focal FDG activity as: right atrial appendage, lipomatous hypertrophy of the interatrial septum, and catheter-related activity. Although all these have been reported separately in the literature, we are presenting them together to emphasize the importance of recognizing the benign causes of FDG uptake in the region of right atrium and the role of co-registered CT in improving the accuracy and specificity of the FDG PET.

Imaging findings of pelvic tumor thrombosis extending from sacral bone metastasis of adrenocortical carcinoma

We report the imaging findings of a patient with adrenocortical carcinoma who showed pelvic tumor thrombosis extending from sacral bone metastasis. Contrast-enhanced computed tomography demonstrated extensive intraluminal filling defects in the pelvic veins. A lytic lesion in the sacrum was also noted and continuity between the sacral lesion and the filling defect in the branch of pelvic veins was indicated. The filling defects showed increased uptake on positron emission tomography with (18)F-fluorodeoxyglucose and single-photon emission computed tomography with (131)I-iodomethylnorcholesterol, and fusion images with computed tomography aided the localization of the increased uptake areas. Multimodality imaging may be beneficial for the characterization and localization of lesions in patients suspected of having metastatic adrenocortical carcinoma.

Intense FDG Uptake around the Inguinal Surgical Mesh 5 Years after Operation: Case Report and Review of the Literature

We present the case of a 40-year-old man who underwent a FDG PET/CT study for restaging of renal cell carcinoma treated with left nephrectomy, for suspected metastasis in lung and retroperitoneal lymph nodes. The patient had a history of left inguinal hernia repair with implantation of mesh prosthesis 5 years ago. PET/CT image revealed linear intense FDG uptake in left inguinal region most likely corresponding to a persistent foreign body reaction. In this article, a case with an intense FDG uptake around mesh prosthesis after many years was reported, and a summary of the literature about surgical mesh and foreign body reaction causing FDG uptake was reviewed.

CONFLICT OF INTEREST

None declared.

[¹⁸F]FDG-PET/CT in patients affected by retroperitoneal fibrosis: a bicentric experience

PURPOSE

The aim of our study was to assess the feasibility and usefulness of 2-[(18)F]-fluoro-2-deoxy-D: -glucose positron emission tomography computed tomography ([(18)F]FDG-PET/CT) in patients affected by retroperitoneal fibrosis.

MATERIALS AND METHODS

We retrospectively evaluated 25 patients studied in two centers: 18 underwent [(18)F]FDG-PET/CT as initial evaluation, three during follow-up, three during steroid therapy, and one to re-evaluate the disease. Among the group who underwent initial evaluation, ten underwent a second [(18)F]FDG-PET/CT after steroid therapy.

RESULTS

[(18)F]FDG-PET/CT was positive in 18 patients and negative in seven. Among the ten patients who underwent a second study after steroid therapy, six showed complete metabolic response, three partial response, and one no significant maximum standardized uptake value (SUV(max)) reduction.

CONCLUSION

Our preliminary results show that [(18)F]FDG-PET/CT is feasible and suitable for evaluating retroperitoneal fibrosis and is useful in assessing therapy response. Larger studies are desirable to confirm these findings and to determine the appropriate position of [(18)F]FDG-PET/CT in the diagnostic flow chart for this disease.

Functional imaging of inflammatory diseases using nuclear medicine techniques

Molecular imaging with positron emission tomography (PET) and single-photon emission computed tomography (SPECT) is increasingly used to diagnose, characterize, and monitor disease activity in the setting of inflammatory disorders of known and unknown etiology. These disorders include sarcoidosis, atherosclerosis, vasculitis, inflammatory bowel disease (IBD), rheumatoid arthritis (RA), and degenerative joint disease. Gallium-67 ((67)Ga) citrate, labeled leukocytes with technetium-99m ((99m)Tc) or indium-111 ((111)In), and (18)F-fluorodeoxyglucose (FDG) represent the most widely used radiopharmaceutical agents. However, other preparations, such as labeled murine monoclonal antigranulocyte antibodies and labeled human polyclonal nonspecific immunoglobulin G, chemotactic peptides, interleukins, chemokines, and liposomes, have been used to image inflammation. Also, (99m)Tc nanocolloid scintigraphy has been found to be suitable for bone and joint diseases, especially RA. Among the single photon emitting imaging agents, the recommended radiotracer for abdominal inflammation has been (99m)Tc-hexamethylpropylene amine oxime (HMPAO)-labeled leukocytes. During the last several years, FDG-PET imaging has been shown to have great value for the detection of inflammation and has become the centerpiece of such initiatives. This very powerful technique will play an increasingly important role in the management of patients with inflammatory conditions. FDG-PET can provide valuable information in patients with pulmonary and extrapulmonary sarcoidosis, and is a useful tool for testing the efficacy of various treatments. FDG-PET combined with computed tomography holds great promise for assessing atherosclerosis of the large arteries. This modality is very sensitive in detecting large-vessel vasculitis and can be used to monitor the disease course. FDG-PET is also being used to study the inflamed synovial joints both in the experimental and clinical settings, especially for the investigation and management of RA and degenerative joint disease. This technique also has the potential to become the imaging modality of choice in assessing IBD, replacing radiolabeled autologous leukocyte imaging in this setting. Detection of inflammation in the lungs and airways may improve our knowledge about a multitude of disorders that affect these structures. Therefore, functional imaging, led by FDG-PET imaging, is likely to play an increasingly critical role in assessing inflammatory disorders of known and unknown etiologies, and will improve their management immensely in the future.

Tumor thrombus in the inferior vena cava from colon cancer detected by 18F-FDG-PET

We present a case of inferior vena cava (IVC) tumor thrombus detected by fluorine- 18 fluorodeoxyglucose positron emission tomography (18F-FDG-PET). A man underwent operations for the treatment of sigmoid colon cancer at the age of 63. Because tumor markers [carcinoembryonic antigen (CEA) and CA19-9] were increased at the age of 67, abdominal contrast-enhanced computed tomography (CT) was performed. CT revealed IVC dilatation, including a low-attenuation area. 18F-FDG-PET was performed to make the differential diagnosis between tumor thrombus and clot. 18F-FDG-PET showed that 18F-FDG had accumulated in the IVC region. We considered the IVC tumor thrombus because of the 18F-FDG uptake in the IVC region and the patient's clinical course. To our knowledge, there are a few reports concerning 18F-FDG-PET and IVC tumor thrombus. 18F-FDG-PET may be useful in diagnosing tumor thrombus.

Unsuspected FDG–PET findings in the follow-up of patients with lymphoma

18F-Fluorodeoxyglucose-positron emission tomography (FDG-PET) plays an increasing role in the management of patients with lymphoma, for which it is successfully used for staging and treatment monitoring. We report seven patients with a history of lymphoma who presented a positive FDG-PET suggestive of lymphoma relapse and for which FDG-PET oriented biopsies revealed alternative diagnoses. Early in lymphoma follow-up, persistence of focal increased FDG activity corresponded to inflammatory or infectious lesions in two patients: one aspergillosis and one sarcoidosis. Later in the follow-up, five cases of secondary malignancies were identified (three lung cancers, one epidermoid carcinoma, and one villous tumor) in this particularly exposed population. The routine use of FDG PET to evaluate lymphoma significantly increases the probability of detecting unexpected diseases. These cases illustrate the potential pitfalls in PET follow-up. Because FDG is not lymphoma-specific, a relapse suspected only on FDG-PET imaging requires biopsy, as alternative diagnoses--infectious or malignant--are possible. Our data draws clinician's attention to potential false-positive FDG-PET findings, which may lead to therapeutic mistakes. Our data also suggests that FDG-PET might be a new imaging modality for long-term monitoring of late effects, especially second cancer occurrence.

FDG Uptake in Tumor Thrombus in Inferior Vena Cava From Rectal Cancer on Positron Emission Tomography

A 74-year-old woman with a history of rectal carcinoma underwent whole body combined positron emission tomography/computed tomography (PET/CT) scanning for staging. Diffuse intense FDG uptake was seen in the distended infrarenal inferior vena cava (IVC) extending to the bilateral common iliac and left external as well as internal iliac veins. Heterogeneous hyperdense material was seen on the corresponding CT scan, suggesting tumor thrombus. Tumor thrombus shows increased FDG uptake resulting from the increased glycolytic rate in malignant cells.

FDG Uptake in a Catheter-Related Thrombus Simulating Relapse of Lymphoma

FDG-PET imaging was performed because of suspected recurrence of lymphoma of the chest. There was an area of increased activity posterior to the left sternoclavicular joint, suspected of being a relapse. Workup showed a thrombus at the tip of a central venous line corresponding to the FDG uptake. This is explained by the inflammatory process involving and surrounding chronic thrombus. Focal activity in relation to the tip of a venous catheter is very likely to have a benign etiology. It is important to recognize this not to overdiagnose a malignancy. For a correct interpretation, it is necessary to know the patient's history and having access to current radiologic examinations.

Evolving role of positron emission tomography in the management of patients with inflammatory and other benign disorders

Fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) has evolved from a research imaging modality assessing brain function in physiologic and pathologic states to a pure clinical necessity. It has been successfully used for diagnosing, staging, and monitoring a variety of malignancies. FDG-PET imaging also is evolving into a powerful imaging modality that can be effectively used for the diagnosis and monitoring of a certain nononcological diseases. PET has been shown to be very useful in the diagnosis of osteomyelitis, painful prostheses, sarcoidosis, fever of unknown etiology, and acquired immunodeficiency syndrome. Based on recent observations, several other disorders, such as environment-induced lung diseases, atherosclerosis, vasculitis, back pain, transplantation, and blood clot, can be successfully assessed with this technique. With the development and the introduction of several new PET radiotracers, it is expected that PET will secure a major role in the management of patients with inflammatory and other benign disorders.

PET: a revolution in medical imaging

FDG-PET has had remarkable influence on the assessment of physiologic and pathologic states. The authors predict that FDG-PET imaging could soon become the most common procedure used by nuclear medicine laboratories and could remain so for an extended period of time. The power of molecular imaging lies in the vast potential for using biochemical and pharmacologic probes to extend applications arising from an understanding of cell biology to a large number of well-characterized pathologic states. Molecular imaging based upon tracer kinetics with positron-emitting radiopharmaceuticals could become the main source of information for the management of cancer patients. In that case, nuclear medicine procedures might become the most common imaging studies performed in the practice of medicine. This speculation is not farfetched when one realizes the enormous change that a single biologically important compound, FDG, has brought to the medical arena. The major challenge today is to attract the highly qualified individuals and to secure the resources needed to harness the opportunities in the specialty of molecular imaging.