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

Catheter-Related Thrombosis With Extremely High FDG Uptake on 18 F-FDG PET

ABSTRACT

A 38-year-old woman with exertional dyspnea and decreased ejection fraction underwent 18 F-FDG PET/CT, which showed extraordinarily high FDG uptake in a catheter-related thrombus formed along a central venous catheter. The thrombus's uptake (SUV max , 127.3) was comparable to or greater than uptake seen in the bladder's urine. This abnormal uptake was unusual for thrombi, suggesting additional factors like undiluted FDG solution stasis due to a fibrin sheath formation around the catheter and first-pass effect. A new peripheral venous route should be secured to administer FDG in case of suspected catheter-related thrombus to avoid potential complications including a pulmonary embolism.

The Diagnostic Value of FDG PET/CT and Thin-Slice High-Resolution Chest CT in Pulmonary Intravascular Metastasis

OBJECTIVE. Pulmonary intravascular metastasis is a special type of pulmonary metastasis of malignancies; however, few relevant studies have been performed. This study aimed to determine the characteristics of pulmonary intravascular metastasis and improve understanding of the disease by retrospective analysis of FDG PET/CT and thin-layer high-resolution CT (HRCT) imaging of the chest in patients with tumors. MATERIALS AND METHODS. We identified all patients who underwent FDG PET/CT at two hospitals between January 2016 and February 2019 and conducted a comparative analysis of HRCT and PET/CT images. In total, 84 patients (38 women and 46 men) ranging in age from 35 to 82 years old (mean age, 54.7 ± 14.5 [SD] years) participated in the study. Patient characteristics were summarized, and diagnosis was confirmed by chest CT or PET/CT follow-up. RESULTS. A total of 260 pulmonary intravascular metastases were found, which were classified as type I (no significant abnormality, n = 5), type II (abrupt and uneven thickening of the pulmonary vessel, n = 118), type III (simultaneous invasion of adjacent pulmonary vessel, n = 121), and type IV (large strip-shaped high-density mass, n = 16). The majority were located in peripheral pulmonary vessels (94.2% [245/260]). FDG up-take was increased in 252 lesions, and the mean SUV_max was 4.6 ± 2.5. CONCLUSION. The combination of PET/CT and chest HRCT is an effective approach for detecting pulmonary intravascular metastasis. The linear pattern of FDG uptake, abnormal pulmonary blood vessel morphology, and location (below the lung segment) are specific indicators for the diagnosis of pulmonary intravascular metastasis and should be recognized by clinicians and radiologists.

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.

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.

Tumour thrombus of the inferior vena cava extending into the right atrium in the setting of colon cancer

Tumour thrombus is seen in renal cell and hepatocellular carcinoma, but is rarely reported in colorectal cancer. A woman aged 46 years, with metastatic colonic adenocarcinoma, was found to have a large mass in the inferior vena cava (IVC) extending into the right atrium. Although this lesion was initially thought to be bland thrombus, imaging with contrast-enhanced CT scan and contrast-enhanced ultrasound supported the diagnosis of tumour thrombus. Despite the large size of the lesion, the patient was asymptomatic. Her lack of symptoms, and poor overall prognosis from her cancer led to the decision to avoid aggressive surgical or radiological interventions. Several months later, the patient passed away. At autopsy, there was no evidence of fatal embolisation from the pre-existing thrombus. Diagnosis of tumour thrombus in the IVC is difficult and management can be challenging due to the significant risks associated with treatment options.

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.

Adrenal metastasis of breast cancer with involvement of the inferior vena cava

Tumour thrombosis of the inferior cava vein is usually associated with primary renal cell cancer. To our knowledge, this is the first case reported of adrenal metastasis of breast cancer extending into the inferior vena cava. There are few references in the literature documenting this extension with positron emission tomography (PET) and enhanced computed tomography (CT). The authors focus on the role of combined PET-CT imaging in the accurate detection of malignant thrombus.

Role of modern imaging techniques for diagnosis of infection in the era of 18F-fluorodeoxyglucose positron emission tomography

During the past several years, it has become quite evident that positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) imaging can play a major role in the management of patients with suspected infection. Particularly, several groups have demonstrated that this powerful imaging methodology is very effective in the evaluation of osteomyelitis, infected prostheses, fever of unknown origin, and AIDS. In view of its extraordinary sensitivity in detecting disease activity and the ability to quantitate the degree of FDG uptake, PET might prove to be an appropriate modality for monitoring disease activity and evaluating response to therapy. FDG-PET has many advantages over existing imaging techniques for the diagnosis of infectious diseases. These include feasibility of securing diagnostic results within 1.5 to 2 h, excellent spatial resolution, and accurate anatomical localization of sites of abnormality. The availability of PET/computed tomography as a practical tool has further enhanced the role of metabolic imaging in many settings. In the future, this modality is very likely to be employed on a routine basis for detecting, characterizing, and monitoring patients with suspected and proven infection.

Acute intramural hematoma of the aorta as a cause of positive FDG PET/CT

Type A acute intramural hematoma (IMH) of the ascending aorta is defined as hemorrhage in the aortic wall in the absence of intimal disruption. Proximity to the adventitia may explain the higher incidence of rupture in IMH. We present a case of IMH, diagnosed by the presence of linear intense uptake of FDG on PET/CT, in a 70-year-old woman undergoing staging for colorectal cancer. There is no current role for FDG-PET in the diagnosis of IMH. This case demonstrates that incidental focal FDG activity in the wall of the aorta may indicate the life-threatening diagnosis of IMH.

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.

Extrathoracic PET/CT Findings in Thoracic Malignancies

The routine use of integrated positron emission tomography computed tomography in the staging and follow-up of patients diagnosed with non-small-cell lung cancer has improved diagnostic accuracy but many incidental extrathoracic findings are routinely encountered. These include physiologic fluorodeoxy glucose avid foci, normal computed tomography variants, and second primary malignancies, all of which have to be differentiated from extrathoracic metastatic disease. Knowledge of these findings is important for correct staging and identification of second primaries.

Utility of FDG-PET/CT in follow-up of children treated for Hodgkin and non-Hodgkin lymphoma

Positron emission tomography using F-flurodeoxyglucose (FDG-PET) is considered an excellent tool for staging and monitoring disease status in adults with lymphoma. We retrospectively reviewed results of PET/CT and diagnostic computed tomography (CT) scans performed during follow-up after completion of therapy in 41 children <18 years of age with Hodgkin lymphoma and non-Hodgkin lymphoma. PET/CT scan with uptake greater than that of the liver was considered positive. Uptake that increased over the background but less than in the liver was equivocal. Clinical outcomes were obtained from medical records. Thirteen (32%) had a positive PET/CT scan and an equal number had equivocal scans in a median follow-up of 2.3 years. Diagnostic CT scans revealed new findings in 13 (32%) and persistent abnormalities in 21 (51%) of the children. Five children developed recurrent disease, and one developed a second cancer. No children with equivocal positivity developed recurrent disease. PET/CT scan was 95% sensitive, with a positive predictive value (PPV) of 53%. Diagnostic CT was 79% sensitive, with a PPV of 52%. We conclude that a negative PET/CT scan during routine follow-up for lymphoma in children strongly suggests absence of recurrence but a positive PET/CT and diagnostic CT scans have low PPV and should be interpreted with caution in this setting.